A kind of phosphorus-free biodegradable scale inhibitor and its preparation method and application

Abstract

The present invention relates to the technical field of chemical products, and specifically discloses a class of phosphorus-free biodegradable scale inhibitors and their preparation methods and applications. The scale inhibitor is shown in Formula I. Bis maleamic acid (Intermediate 1) is prepared by reacting maleic anhydride with a polyamino compound, and then salt is formed with an alkali compound to prepare bis maleamate salt (Intermediate 2). Finally, it reacts with the polyamino compound to prepare a high molecular weight poly bis maleamic acid-amine scale inhibitor. The scale inhibitor provided by the present invention has excellent scale inhibition performance. The scale inhibition rate of CaCO3 is greater than 98%, and the scale inhibition rate of CaSO4 can reach 100%. Moreover, it is biodegradable, and the degradation rate in 28 days is greater than 60%. It is a new type of scale inhibitor that is phosphorus-free, non-toxic, green and environmentally friendly, and has broad application prospects in industrial water treatment systems. #imgabs0#

Description

Technical Field

[0001] The present invention relates to the technical field of chemical products, and particularly to a class of phosphorus-free biodegradable scale inhibitors and their preparation methods and applications. Background Art

[0002] In the mid-20th century, industrial circulating cooling water systems were put into use. In order to alleviate the shortage of water resources, countries began to adopt industrial circulating cooling water systems instead of once-through cooling water systems. However, due to the repeated use of industrial circulating cooling water systems, the concentration ratio increases, resulting in an increase in the hardness of water (such as Ca 2+ , Mg 2+ etc.) and alkalinity (such as OH - , HCO3 - etc.), causing consequences such as scaling and corrosion of cooling towers, heat exchangers, and metal pipes, bringing potential production safety hazards and economic losses.

[0003] Chemical scale inhibitors are simple to use, convenient in price, and excellent in scale inhibition effect, and are widely used in circulating cooling water. Generally, scale inhibitor molecules contain phosphate groups, carboxyl groups, hydroxyl groups, amide groups, sulfonic acid groups, etc., which can chelate, adsorb, and disperse with Ca 2+ , Mg 2+ etc., bind to the active growth sites of crystals, and promote the irregular growth of crystals, thereby softening the water scale.

[0004] Currently, industrial scale inhibitors are mostly phosphorus-based or compound products formed by their combination with polymer scale inhibitors. Such phosphorus-containing scale inhibitors may pose potential hazards to aquatic organisms and the water environment. In view of the problems of easy hydrolysis at high temperatures, easy eutrophication of water bodies, and calcium phosphate deposition of phosphorus-containing scale inhibitors, domestic and foreign scholars have developed various environmentally friendly phosphorus-free scale inhibitors. Among them, new biodegradable scale inhibitors mainly based on polyepoxysuccinic acid and polyaspartic acid have been widely studied. However, the relative molecular weight of polyepoxysuccinic acid is relatively small (generally 400 - 1300). Although its scale inhibition performance improves with the increase in dosage, when reaching a certain dosage (threshold), its scale inhibition rate no longer increases (the maximum can reach about 90%). The molecular weight of industrial polyaspartic acid ranges from 4000 to 8000, and its scale inhibition ability generally increases with the increase in molecular weight and the increase in the carboxyl group content on the molecular chain. However, due to the limitation of the synthesis process conditions, it is difficult to increase the molecular weight of traditional polyaspartic acid, so its scale inhibition rate is also difficult to further increase, generally below 90%. Although modifying polyaspartic acid can improve its scale inhibition rate to a certain extent, the reagents used for modified polyaspartic acid are generally expensive and not suitable for large-scale industrial production applications. Therefore, researching and developing a new type of scale inhibitor with good economy, high scale inhibition rate, and environmental friendliness is of great significance for saving water resources and extending the service life of industrial circulating cooling water systems. Summary of the Invention

[0005] In view of the problems of poor scale inhibition performance and high price of scale inhibitors in the prior art, the present invention provides a class of phosphorus-free biodegradable scale inhibitors, their preparation methods and applications.

[0006] To solve the above technical problems, the technical solution provided by the present invention is:

[0007] A class of phosphorus-free biodegradable scale inhibitors, the structure of the scale inhibitor is shown in Formula I:

[0008]

[0009] Wherein, R1, R2 are -(CH2) x -, -(CH2) y CH(CH3)-, -CH2CH2CH(CH2CH3)-,

[0010] -CH2CH(CH3)CH2CH2CH2-, -CH2CH2(NHCH2CH2) i - or

[0011] -CH2CH(OH)CH2-;

[0012] x = 2, 3, 4, 5 or 6; y = 1 or 3; i = 1, 2 or 3;

[0013] M is Li, Na or K.

[0014] In the above molecular formula, n is the number of repeating units.

[0015] It should be noted that R1 and R2 may be the same or different.

[0016] Compared with the prior art, the novel scale inhibitor provided by the present invention has good solubility in water, good chemical stability, and contains a large number of amide groups on the main chain and carboxyl groups on the side chain of the molecule, which can attract and stably chelate Ca 2+ , Ba 2+ , Mg 2+ and other poorly soluble metal ions, thereby reducing the growth rate of poorly soluble substances; at the same time, a large number of amino and carboxyl groups in the molecule are also conducive to the stable adsorption and spreading of the scale inhibitor on the surface of the scaling body and the metal container surface, so that the scaling bodies and the metal container surface are all charged with the same charge, and the charge repulsion effect will effectively hinder the possibility of forming large scaling bodies due to molecular collision, and also hinder the possibility of collision between tiny scale crystals and the heat transfer surface of the metal container to form a scale layer; in addition, the scale inhibitor provided by the present invention can also bind to the active growth sites of crystals, interfere with the directional growth of scale crystals, make the scale crystals distorted during scaling, become loose and porous, and thus disperse in water or be washed away by water, further avoiding the formation of scaling bodies.

[0017] The scale inhibitor provided by the present invention has excellent scale inhibition performance, with a scale inhibition rate greater than 98%, and is biodegradable, with a degradation rate greater than 60%. It is a new type of scale inhibitor that is phosphorus-free, non-toxic, and environmentally friendly, and has broad application prospects in industrial water treatment systems.

[0018] Preferably, the average molecular weight of the scale inhibitor is between 17443 and 36542.

[0019] The scale inhibitor provided by the present invention is a high-molecular-weight phosphorus-free scale inhibitor with an average molecular weight between 17443 and 36542. It has a higher content of amino groups and side-chain carboxyl groups in its main chain structure, has more excellent scale inhibition performance, and is easily degradable. It is a type of environmentally friendly scale inhibitor.

[0020] The present invention also provides a preparation method for a class of phosphorus-free biodegradable scale inhibitors, which includes the following steps:

[0021] Step a, in a solvent, maleic anhydride and a polyamino compound a shown in formula (II) undergo a ring-opening reaction to obtain intermediate 1 shown in formula (III);

[0022]

[0023] Step b, adding the intermediate 1 and an alkali compound to water to carry out a salt-forming reaction to obtain a reaction solution containing intermediate 2 shown in formula (IV); the alkali compound is a hydroxide, bicarbonate, or carbonate of Li, Na, or K element;

[0024]

[0025] Step c, adding a polyamino compound b shown in formula (V) to the reaction solution of intermediate 2 to carry out a chain extension reaction to obtain a phosphorus-free biodegradable scale inhibitor shown in formula I;

[0026]

[0027] Among them, R1 and R2 are -(CH2) x -, -(CH2) y CH(CH3)-, -CH2CH2CH(CH2CH3)-,

[0028] -CH2CH(CH3)CH2CH2CH2-, -CH2CH2(NHCH2CH2) i - or

[0029] -CH2CH(OH)CH2-;

[0030] x = 2, 3, 4, 5 or 6; y = 1 or 3; i = 1, 2 or 3;

[0031] M is Li, Na or K.

[0032] The equation of the above reaction is as follows:

[0033] Step a:

[0034]

[0035] Step b:

[0036]

[0037] Step c:

[0038]

[0039] The preparation method of the scale inhibitor provided by the present invention prepares bis maleamic acid (intermediate 1) by reacting maleic anhydride with a polyamino compound, then salts it with an alkali compound to prepare bis maleamate (intermediate 2), and finally reacts it with a polyamino compound, and the amino group attacks the double bond on bis maleamic acid to obtain a high molecular weight poly bis maleamic acid-amine scale inhibitor.

[0040] The high molecular weight poly bis maleamic acid-amine scale inhibitor prepared by the above method has excellent scale inhibition performance and biodegradability, and the reaction raw materials are easy to obtain, the price is low, the operation is simple, the reaction conditions are mild, the energy consumption is low, it is suitable for industrial scale production, and the potential application value is high.

[0041] Preferably, in step a, the polyamino compound a is ethylenediamine, 1,3-propanediamine, 1,2-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,4-pentanediamine, 1,3-pentanediamine, 2-methylpentanediamine, 1,6-hexanediamine, 1,4-cyclohexanediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine or 1,3-diamino-2-propanol.

[0042] More preferably, in step a, the polyamino compound a is ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, 1,4-pentanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,4-cyclohexanediamine, diethylenetriamine, triethylenetetramine or 1,3-diamino-2-propanol.

[0043] Even more preferably, in step a, the polyamino compound a is ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine or 1,6-hexanediamine.

[0044] The preferred polyamino compound is inexpensive, and the scale inhibitor prepared has excellent scale inhibition performance.

[0045] Preferably, in step a, the solvent is at least one of water, methanol, ethanol, propanol, isopropanol, acetone, glacial acetic acid, ethyl acetate, ether, petroleum ether, dichloromethane, dimethyl sulfoxide or N,N-dimethylformamide.

[0046] More preferably, in step a, the solvent is at least one of water, ethanol, acetone or glacial acetic acid.

[0047] Preferably, in step a, the molar ratio of maleic anhydride to polyamino compound a is 2-4:1.

[0048] More preferably, in step a, the molar ratio of maleic anhydride to polyamino compound a is 2-2.3:1.

[0049] Preferably, in step a, the mass ratio of maleic anhydride to the solvent is 1:2-10.

[0050] More preferably, in step a, the mass ratio of maleic anhydride to the solvent is 1:3-9.

[0051] Preferably, in step a, the temperature of the ring-opening reaction is -30°C to 100°C, and the reaction time is not less than 40 min.

[0052] More preferably, in step a, the temperature of the ring-opening reaction is -15°C to 60°C, and the reaction time is not less than 40 min.

[0053] The preferred reaction conditions are conducive to the ring-opening of maleic anhydride and the reaction with polyamino compound a, thereby improving the conversion rate of raw materials.

[0054] Preferably, in step b, the base compound is at least one of NaHCO3, KHCO3, NaOH, KOH, LiOH, Li2CO3, Na2CO3 or K2CO3; the molar ratio of intermediate 1 to the metal element in the base compound is 1:2-2.4.

[0055] Further preferably, in step b, the base compound is at least one of NaHCO3, KHCO3, NaOH, KOH, Na2CO3, K2CO3.

[0056] Even more preferably, in step b, the base compound is at least one of NaOH or KOH.

[0057] Preferably, in step b, the mass ratio of the total mass of intermediate 1 and the base compound to the mass of water is 1:1-3.

[0058] Preferably, the temperature of the salt-forming reaction is 10°C to 40°C, and the reaction time of the salt-forming reaction is not less than 10 min.

[0059] The above preferred reaction conditions are conducive to the full progress of the salt formation reaction and improve the yield of intermediate 2.

[0060] Preferably, in step c, the polyamine compound b is ethylenediamine, 1,3-propanediamine, 1,2-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,4-pentanediamine, 1,3-pentanediamine, 2-methylpentanediamine, 1,6-hexanediamine, 1,4-cyclohexanediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine or 1,3-diamino-2-propanol.

[0061] More preferably, in step c, the polyamine compound b is ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, 1,4-pentanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,4-cyclohexanediamine, diethylenetriamine, triethylenetetramine or 1,3-diamino-2-propanol.

[0062] Even more preferably, in step c, the polyamine compound b is ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine or 1,6-hexanediamine.

[0063] The preferred polyamine compound is inexpensive, and the prepared scale inhibitor has excellent scale inhibition performance.

[0064] Preferably, in step c, the molar ratio of the polyamine compound b to the intermediate 1 in step a is 1:1 to 1.2.

[0065] Preferably, in step c, the reaction temperature of the chain extension reaction is 0°C to 100°C, and the reaction time is not less than 1 h.

[0066] More preferably, in step c, the reaction temperature of the chain extension reaction is 20°C to 100°C.

[0067] The preferred molar ratio of the polyamine compound b to the intermediate 1, as well as the reaction temperature and reaction time, can increase the molecular weight of the prepared scale inhibitor, thereby increasing the scale inhibition rate.

[0068] The present invention also provides a class of scale inhibitor compositions, comprising the above scale inhibitor composition.

[0069] This scale inhibitor can be used in combination with conventional water treatment scale inhibitors in the art, and there is no adverse effect between the components.

[0070] The present invention also provides the application of the above phosphorus-free biodegradable scale inhibitor in circulating cooling water treatment.

[0071] Compared with the prior art, the scale inhibitor provided by the present invention has the following advantages:

[0072] (1) The raw materials for preparation are bulk chemicals maleic anhydride, inorganic bases (salts) and polyamines, which are inexpensive and have good prospects for large-scale industrial production applications;

[0073] (2) The preparation method is simple, the synthesis conditions are mild, no special reaction equipment is required, and the energy consumption is low;

[0074] (3) Based on the conjugated double bond-heteroatom polymerization reaction mechanism, a new type of high molecular weight phosphorus-free biodegradable polybismaleamic acid-amine scale inhibitor is prepared. Its scale inhibition rate for CaCO3 is greater than 98%, the scale inhibition rate for CaSO4 can reach 100%, and the degradation rate in 28 days is greater than 60%. It belongs to biodegradable materials. The present invention provides new ideas and methods for the research and development of phosphorus-free scale inhibitors;

[0075] (4) It has excellent scale inhibition performance and can be applied to circulating cooling systems with different concentration multiples. It can keep the circulating water at a high concentration ratio without scaling, protect the safe operation of circulating water equipment, extend the service life of the equipment, help alleviate the water resource crisis, and realize the organic unity of economic, environmental and social benefits. Description of the Drawings

[0076] Figure 1 It is the infrared spectrum diagram of the scale inhibitor prepared in Example 1 of the present invention;

[0077] Figure 2 It is the 1H nuclear magnetic resonance spectrum diagram of the scale inhibitor prepared in Example 1 of the present invention. Detailed Embodiments

[0078] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0079] To better illustrate the present invention, further examples are given below through embodiments.

[0080] The test standards for scale inhibition performance and degradation performance in the following embodiments are as follows:

[0081] Referring to the calcium carbonate deposition method in "GB / T 16632-2019 Determination of Scale Inhibition Performance of Water Treatment Agents", the scale inhibition performance of CaCO3 was tested for the high molecular weight phosphorus-free biodegradable polybismaleamic acid-amine scale inhibitors prepared in Examples 1 to 16.

[0082] Referring to the determination of the scale inhibition rate of CaSO4 scale in "SY / T 5673-2020 General Technical Conditions for Scale Inhibitors for Oil Fields", the scale inhibition performance of CaSO4 was tested for the high molecular weight phosphorus-free biodegradable polybismaleamic acid-amine scale inhibitors prepared in Examples 1 to 16.

[0083] Referring to the permanganate index method in "Determination of Chemical Oxygen Demand (COD) in Industrial Circulating Cooling Water - GB / T 15456-2019", the degradation performance of the high molecular weight phosphorus-free biodegradable polybismaleamic acid-amine scale inhibitors obtained in Examples 1 to 16 was determined. The degradation rate calculation formula is as follows:

[0084]

[0085] In the formula:

[0086] C (1 / 2Na2C2O4) : represents the concentration of the sodium oxalate standard solution;

[0087] 10.00: both refer to the volume of the sodium oxalate standard solution;

[0088] 10.00 / V2: represents the calibration coefficient of the potassium permanganate standard solution;

[0089]

[0090] In the formula:

[0091] C 0白 : refers to the COD of the blank solution Mn (mg / L);

[0092] C0: refers to the COD of the sample solution to be measured Mn (mg / L);

[0093] C n白 : refers to the COD of the blank solution Mn (mg / L);

[0094] C n : refers to the COD of the sample solution to be measured Mn (mg / L).

[0095] Example 1

[0096] A preparation method of a scale inhibitor, comprising the following steps:

[0097] Step a, control the reaction temperature at 0-5°C, add 10.79 g of maleic anhydride and 25.36 g of distilled water to a three-necked flask, stir and disperse evenly; dissolve 3.01 g of ethylenediamine in 7.01 g of distilled water, and use a constant pressure dropping funnel to slowly add the ethylenediamine solution to the above three-necked flask at a constant speed. The dropping time is 30 min. After the dropping is completed, continue the reaction for 10 min, filter, wash with distilled water, and dry to obtain Intermediate 1 shown in formula (III), with a yield of 96.50%; R1 is -CH2CH2-;

[0098]

[0099] Step b, at room temperature, add 5.56 g of the above intermediate 1 and 8 g of distilled water into a three-necked flask, stir and disperse evenly, then add 1.79 g of NaOH, stir and react for 20 min to obtain a reaction solution containing intermediate 2 shown in formula (IV); M is Na;

[0100]

[0101] Step c, add 1.20 g of ethylenediamine to the reaction solution of intermediate 2, react at 100 °C for 6 h, and dry to obtain the phosphorus-free biodegradable scale inhibitor shown in formula I, with a molecular weight of 36542; R2 is -CH2CH2-;

[0102]

[0103] The Fourier transform infrared spectrum of the phosphorus-free biodegradable scale inhibitor shown in formula I is as Figure 1 shown. It can be seen from the figure that the stretching vibration absorption peak of the N-H bond is at 3280 cm -1 ; the asymmetric and symmetric stretching vibration absorption peaks of the carboxylate ion are at 1582 cm -1 and 1398 cm -1 respectively; the stretching vibration absorption peak of the newly formed C-N bond in the addition reaction is at 1241 cm -1 .

[0104] The nuclear magnetic resonance hydrogen spectrum of the phosphorus-free biodegradable scale inhibitor shown in formula I is as Figure 2 shown. The deuterated reagent is D2O. It can be seen from the figure that the absorption peak of -CH2-CH2- in the molecular main chain -NH-CH2-CH2-NH- is at 3.24 ppm to 3.43 ppm, the absorption peak of -CH- in the molecular main chain -NH-CH(COO - )-CH2-CONH- is at 2.50 ppm to 2.61 ppm, the absorption peak of -CH2- in the molecular main chain -NH-CH(COO - )-CH2-CONH- is at 2.45 ppm to 2.50 ppm, and the absorption peak of the terminal double bond group of the polybismaleamic acid-amine scale inhibitor is at 6.59 ppm to 6.70 ppm.

[0105] According to the calcium carbonate deposition method in "GB / T 16632-2019 Determination of Scale Inhibition Performance of Water Treatment Agents", when the concentration of the scale inhibitor is 10 mg / L, the scale inhibition rate of CaCO3 is 99.92%.

[0106] According to the determination of the scale inhibition rate of CaSO4 scale in "SY / T 5673-2020 General Technical Conditions for Scale Inhibitors Used in Oilfields", when the concentration of the scale inhibitor is 8 mg / L, the scale inhibition rate of CaSO4 can reach 100%.

[0107] According to the permanganate index method in "Determination of Chemical Oxygen Demand (COD) in Industrial Circulating Cooling Water - GB / T 15456 - 2019", ensure that the scale inhibitor concentration is greater than 0.05 mg / L, and its maximum measured oxygen consumption is not higher than 5.0 mg / L. At 28 days, its degradation rate is 63.26%.

[0108] Example 2

[0109] A preparation method of a scale inhibitor includes the following steps:

[0110] Step a, control the reaction temperature at 5 - 10 °C, add 10.30 g of maleic anhydride and 46.23 g of absolute ethanol to a three - necked flask, and stir to disperse evenly; dissolve 3.01 g of ethylenediamine in 13.52 g of absolute ethanol, and use a constant - pressure dropping funnel to slowly add the ethylenediamine solution to the above - mentioned three - necked flask at a uniform speed. The dropping time is 30 min. After the dropping is completed, continue the reaction for 10 min, filter, wash with absolute ethanol, and dry to obtain intermediate 1 shown in formula (Ⅲ), with a yield of 95.34%; R1 is -CH2CH2-;

[0111]

[0112] Step b, at room temperature, add 5.12 g of the above intermediate 1 and 13 g of distilled water to a three - necked flask, stir to disperse evenly, then add 4.03 g of NaHCO3, and stir and react for 10 min to obtain a reaction solution containing intermediate 2 shown in formula (Ⅳ); M is Na;

[0113]

[0114] Step c, add 2.32 g of 1,6 - hexanediamine to the reaction solution of intermediate 2, react at 90 °C for 3 h, and dry to obtain the phosphorus - free biodegradable scale inhibitor shown in formula Ⅰ, with a molecular weight of 25683; R2 is -(CH2)6-;

[0115]

[0116] According to the calcium carbonate deposition method in "Determination of Scale Inhibition Performance of Water Treatment Agents - GB / T 16632 - 2019", when the scale inhibitor concentration is 10 mg / L, the scale inhibition rate of CaCO3 is 98.50%.

[0117] According to the determination of the scale inhibition rate of CaSO4 scale in "General Technical Conditions for Scale Inhibitors for Oil Fields - SY / T 5673 - 2020", when the scale inhibitor concentration is 8 mg / L, the scale inhibition rate of CaSO4 can reach 100%.

[0118] According to the permanganate index method in "Determination of Chemical Oxygen Demand (COD) in Industrial Circulating Cooling Water - GB / T 15456-2019", ensure that the scale inhibitor concentration is greater than 0.05 mg / L, and its maximum measured oxygen consumption is not higher than 5.0 mg / L. At 28 days, its degradation rate is 65.47%.

[0119] Example 3

[0120] A preparation method of a scale inhibitor includes the following steps:

[0121] Step a, control the reaction temperature at 10 - 15 °C, add 10.30 g of maleic anhydride and 51.48 g of dichloromethane to a three-necked flask, and stir to disperse evenly; dissolve 3.71 g of 1,3-propanediamine in 18.53 g of dichloromethane, and use a constant-pressure dropping funnel to slowly add the 1,3-propanediamine solution to the above three-necked flask at a uniform speed. The dropping time is 30 min. After the dropping is completed, continue to react for 20 min, filter, wash with dichloromethane, and dry to obtain intermediate 1 shown in formula (Ⅲ), with a yield of 95.83%; R1 is -(CH2)3-;

[0122]

[0123] Step b, at room temperature, add 5.89 g of the above intermediate 1 and 21 g of distilled water to a three-necked flask, stir to disperse evenly, then add 2.51 g of Na2CO3, and stir and react for 20 min to obtain a reaction solution containing intermediate 2 shown in formula (Ⅳ); M is Na;

[0124]

[0125] Step c, add 1.48 g of 1,3-propanediamine to the reaction solution of intermediate 2, react at 50 °C for 25 h, and dry to obtain the phosphorus-free biodegradable scale inhibitor shown in formula Ⅰ, with a molecular weight of 21287; R2 is -(CH2)3-;

[0126]

[0127] According to the calcium carbonate deposition method in "Determination of Scale Inhibition Performance of Water Treatment Agents - GB / T 16632-2019", when the scale inhibitor concentration is 10 mg / L, the scale inhibition rate of CaCO3 is 99.10%.

[0128] According to the determination of the scale inhibition rate of CaSO4 scale in "General Technical Conditions for Scale Inhibitors for Oilfields - SY / T 5673-2020", when the scale inhibitor concentration is 8 mg / L, the scale inhibition rate of CaSO4 can reach 100%.

[0129] According to the permanganate index method in "GB / T 15456-2019 Determination of Chemical Oxygen Demand (COD) in Industrial Recirculating Cooling Water", ensure that the concentration of the scale inhibitor is greater than 0.05 mg / L, and its maximum measured oxygen consumption is not higher than 5.0 mg / L. At 28 days, its degradation rate is 67.37%.

[0130] Example 4

[0131] A preparation method of a scale inhibitor includes the following steps:

[0132] Step a, control the reaction temperature at -5 to 0 °C, add 10.79 g of maleic anhydride and 64.72 g of ethyl acetate to a three-necked flask, and stir to disperse evenly; dissolve 3.71 g of 1,2-propanediamine in 22.24 g of ethyl acetate, and use a constant-pressure dropping funnel to slowly add the 1,3-propanediamine solution to the above three-necked flask at a constant speed. The dropping time is 30 min. After the dropping is completed, continue to react for 20 min, filter, wash with ethyl acetate, and dry to obtain intermediate 1 shown in formula (Ⅲ), with a yield of 92.56%; R1 is -CH2CH(CH3)-;

[0133]

[0134] Step b, at room temperature, add 5.54 g of the above intermediate 1 and 25 g of distilled water to a three-necked flask, stir to disperse evenly, then add 3.03 g of K2CO3, and stir and react for 15 min to obtain a reaction solution containing intermediate 2 shown in formula (Ⅳ); M is K;

[0135]

[0136] Step c, add 2.04 g of 1,3-pentanediamine to the reaction solution of intermediate 2, react at 70 °C for 18 h, and dry to obtain the phosphorus-free biodegradable scale inhibitor shown in formula I, with a molecular weight of 28945; R2 is -CH2CH2CH(CH2CH3)-;

[0137]

[0138] According to the calcium carbonate deposition method in "GB / T 16632-2019 Determination of Scale Inhibition Performance of Water Treatment Agents", when the concentration of the scale inhibitor is 10 mg / L, the scale inhibition rate of CaCO3 is 98.76%.

[0139] According to the determination of the scale inhibition rate of CaSO4 scale in "SY / T 5673-2020 General Technical Conditions for Scale Inhibitors for Oil Fields", when the concentration of the scale inhibitor is 8 mg / L, the scale inhibition rate of CaSO4 can reach 100%.

[0140] According to the permanganate index method in "Determination of Chemical Oxygen Demand (COD) in Industrial Circulating Cooling Water - GB / T 15456-2019", ensure that the scale inhibitor concentration is greater than 0.05 mg / L, and its maximum measured oxygen consumption is not higher than 5.0 mg / L. At 28 days, its degradation rate is 64.31%.

[0141] Example 5

[0142] A preparation method of a scale inhibitor, comprising the following steps:

[0143] Step a, control the reaction temperature at -5 to 0 °C, add 10.30 g of maleic anhydride and 52.50 g of isopropanol to a three-necked flask, and stir to disperse evenly; dissolve 5.71 g of 1,4-cyclohexanediamine in 40.2 g of isopropanol, and use a constant-pressure dropping funnel to slowly add the 1,4-cyclohexanediamine solution to the above three-necked flask at a uniform speed. The dropping time is 30 min. After the dropping is completed, continue to react for 4 h, filter, wash with isopropanol, and dry to obtain Intermediate 1 shown in formula (Ⅲ), with a yield of 96.14%; R1 is

[0144]

[0145] Step b, at room temperature, add 7.45 g of the above Intermediate 1 and 29 g of distilled water to a three-necked flask, stir to disperse evenly, then add 4.56 g of NaHCO3, and stir and react for 25 min to obtain a reaction solution containing Intermediate 2 shown in formula (Ⅳ); M is Na;

[0146]

[0147] Step c, add 1.20 g of ethylenediamine to the reaction solution of Intermediate 2, react at 70 °C for 20 h, and dry to obtain the phosphorus-free biodegradable scale inhibitor shown in formula Ⅰ, with a molecular weight of 26548; R2 is -CH2CH2-;

[0148]

[0149] According to the calcium carbonate deposition method in "Determination of Scale Inhibition Performance of Water Treatment Agents - GB / T 16632-2019", when the scale inhibitor concentration is 10 mg / L, the scale inhibition rate of CaCO3 is 99.05%.

[0150] According to the determination of the scale inhibition rate of CaSO4 scale in "General Technical Conditions for Scale Inhibitors for Oilfields - SY / T 5673-2020", when the scale inhibitor concentration is 8 mg / L, the scale inhibition rate of CaSO4 can reach 100%.

[0151] According to the permanganate index method in "Determination of Chemical Oxygen Demand (COD) in Industrial Circulating Cooling Water - GB / T 15456 - 2019", ensure that the scale inhibitor concentration is greater than 0.05 mg / L, and its maximum measured oxygen consumption is not higher than 5.0 mg / L. At 28 days, its degradation rate is 63.41%.

[0152] Example 6

[0153] A preparation method of a scale inhibitor, comprising the following steps:

[0154] Step a, control the reaction temperature at -15 to -10 °C, add 11.28 g of maleic anhydride and 50.74 g of absolute ethanol to a three-necked flask, stir and disperse evenly; dissolve 4.41 g of 1,4-butanediamine in 19.83 g of absolute ethanol, and use a constant-pressure dropping funnel to uniformly drop the 1,4-butanediamine solution into the above three-necked flask. The dropping time is 30 min. After the dropping is completed, continue to react for 2 h, filter, wash with absolute ethanol, and dry to obtain intermediate 1 shown in formula (Ⅲ), with a yield of 94.04%; R1 is -(CH2)4-;

[0155]

[0156] Step b, at room temperature, add 5.80 g of the above intermediate 1 and 7 g of distilled water to a three-necked flask, stir and disperse evenly, then add 0.98 g of LiOH, and stir and react for 15 min to obtain a reaction solution containing intermediate 2 shown in formula (Ⅳ); M is Li;

[0157]

[0158] Step c, add 1.76 g of 1,4-butanediamine to the reaction solution of intermediate 2, react at 20 °C for 120 h, and dry to obtain the phosphorus-free biodegradable scale inhibitor shown in formula Ⅰ, with a molecular weight of 19651; R2 is -(CH2)4-;

[0159]

[0160] According to the calcium carbonate deposition method in "Determination of Scale Inhibition Performance of Water Treatment Agents - GB / T 16632 - 2019", when the scale inhibitor concentration is 10 mg / L, the scale inhibition rate of CaCO3 is 99.73%.

[0161] According to the determination of the scale inhibition rate of CaSO4 scale in "General Technical Conditions for Scale Inhibitors for Oil Fields - SY / T 5673 - 2020", when the scale inhibitor concentration is 8 mg / L, the scale inhibition rate of CaSO4 can reach 100%.

[0162] According to the permanganate index method in "Determination of Chemical Oxygen Demand (COD) in Industrial Circulating Cooling Water - GB / T 15456-2019", ensure that the concentration of the scale inhibitor is greater than 0.05 mg / L, and its maximum measured oxygen consumption is not higher than 5.0 mg / L. At 28 days, its degradation rate is 61.17%.

[0163] Example 7

[0164] A preparation method of a scale inhibitor, comprising the following steps:

[0165] Step a, control the reaction temperature at 0 - 5 °C, add 10.79 g of maleic anhydride and 53.93 g of dichloromethane into a three-necked flask, and stir to disperse evenly; dissolve 4.41 g of 1,4-butanediamine in 22.04 g of dichloromethane, and use a constant pressure dropping funnel to drop the 1,4-butanediamine solution into the above three-necked flask at a constant speed. The dropping time is 30 min. After the dropping is completed, continue to react for 1 h, filter, wash with dichloromethane, and dry to obtain intermediate 1 shown in formula (Ⅲ), with a yield of 97.46%; R1 is -(CH2)4-;

[0166]

[0167] Step b, at room temperature, add 6.45 g of the above intermediate 1 and 10 g of distilled water into a three-necked flask, stir to disperse evenly, then add 2.57 g of KOH, and stir and react for 20 min to obtain a reaction solution containing intermediate 2 shown in formula (Ⅳ); M is K;

[0168]

[0169] Step c, add 2.06 g of diethylenetriamine to the reaction solution of intermediate 2, react at 60 °C for 30 h, and dry to obtain the phosphorus-free biodegradable scale inhibitor shown in formula Ⅰ, with a molecular weight of 23689; R2 is -CH2CH2 NHCH2CH2-;

[0170]

[0171] According to the calcium carbonate deposition method in "Determination of Scale Inhibition Performance of Water Treatment Agents - GB / T 16632-2019", when the concentration of the scale inhibitor is 10 mg / L, the scale inhibition rate of CaCO3 is 98.52%.

[0172] According to the determination of the scale inhibition rate of CaSO4 scale in "General Technical Conditions for Scale Inhibitors for Oil Fields - SY / T 5673-2020", when the concentration of the scale inhibitor is 8 mg / L, the scale inhibition rate of CaSO4 can reach 100%.

[0173] According to the permanganate index method in "Determination of Chemical Oxygen Demand (COD) in Industrial Circulating Cooling Water - GB / T 15456-2019", ensure that the scale inhibitor concentration is greater than 0.05 mg / L, and its maximum measured oxygen consumption is not higher than 5.0 mg / L. At 28 days, its degradation rate is 65.38%.

[0174] Example 8

[0175] A preparation method of a scale inhibitor, comprising the following steps:

[0176] Step a, control the reaction temperature at 20 - 25 °C, add 11.28 g of maleic anhydride and 62.02 g of glacial acetic acid to a three-necked flask, stir and disperse evenly; dissolve 5.11 g of 1,5-pentanediamine in 28.10 g of glacial acetic acid, and use a constant-pressure dropping funnel to uniformly drop the pentanediamine solution into the above three-necked flask. The dropping time is 30 min. After the dropping is completed, continue to react for 30 min, filter, wash with glacial acetic acid, and dry to obtain intermediate 1 shown in formula (Ⅲ), with a yield of 96.74%; R1 is -(CH2)5-;

[0177]

[0178] Step b, at room temperature, add 6.38 g of the above intermediate 1 and 17 g of distilled water to a three-necked flask, stir and disperse evenly, then add 5.08 g of KHCO3, and stir and react for 20 min to obtain a reaction solution containing intermediate 2 shown in formula (Ⅳ); M is K;

[0179]

[0180] Step c, add 1.80 g of 1,3-diamino-2-propanol to the reaction solution of intermediate 2, react at 90 °C for 8 h, and dry to obtain the phosphorus-free biodegradable scale inhibitor shown in formula Ⅰ, with a molecular weight of 25582; R2 is -CH2CH(OH)CH2-;

[0181]

[0182] According to the calcium carbonate deposition method in "Determination of Scale Inhibition Performance of Water Treatment Agents - GB / T 16632-2019", when the scale inhibitor concentration is 10 mg / L, the scale inhibition rate of CaCO3 is 98.58%.

[0183] According to the determination of the scale inhibition rate of CaSO4 scale in "General Technical Conditions for Scale Inhibitors for Oil Fields - SY / T 5673-2020", when the scale inhibitor concentration is 8 mg / L, the scale inhibition rate of CaSO4 can reach 100%.

[0184] According to the permanganate index method in "Determination of Chemical Oxygen Demand (COD) in Industrial Circulating Cooling Water - GB / T 15456-2019", ensure that the scale inhibitor concentration is greater than 0.05 mg / L, and its maximum measured oxygen consumption is not higher than 5.0 mg / L. At 28 days, its degradation rate is 69.59%.

[0185] Example 9

[0186] A preparation method of a scale inhibitor includes the following steps:

[0187] Step a: Control the reaction temperature at 0 - 5°C. Add 10.30 g of maleic anhydride and 61.78 g of acetone into a three-necked flask, and stir to disperse evenly. Another 5.11 g of 1,5-pentanediamine is dissolved in 30.65 g of acetone, and the pentanediamine solution is evenly added dropwise to the above three-necked flask using a constant-pressure dropping funnel. The dropping time is 30 min. After the dropping is completed, continue the reaction for 1 h, filter, wash with acetone, and dry to obtain intermediate 1 shown in formula (Ⅲ) with a yield of 95.57%; R1 is -(CH2)5-;

[0188]

[0189] Step b: At room temperature, add 6.41 g of the above intermediate 1 and 12 g of distilled water into a three-necked flask, stir to disperse evenly, then add 2.42 g of KOH, and stir and react for 15 min to obtain a reaction solution containing intermediate 2 shown in formula (Ⅳ); M is K;

[0190]

[0191] Step c: Add 1.20 g of ethylenediamine to the reaction solution of intermediate 2, react at 90°C for 4 h, and dry to obtain the phosphorus-free biodegradable scale inhibitor shown in formula Ⅰ with a molecular weight of 30536; R2 is -CH2CH2-;

[0192]

[0193] According to the calcium carbonate deposition method in "Determination of Scale Inhibition Performance of Water Treatment Agents - GB / T 16632-2019", when the scale inhibitor concentration is 10 mg / L, the scale inhibition rate of CaCO3 is 99.71%.

[0194] According to the determination of the scale inhibition rate of CaSO4 scale in "General Technical Conditions for Scale Inhibitors for Oilfields - SY / T 5673-2020", when the scale inhibitor concentration is 8 mg / L, the scale inhibition rate of CaSO4 can reach 100%.

[0195] According to the permanganate index method in "Determination of Chemical Oxygen Demand (COD) in Industrial Circulating Cooling Water - GB / T 15456-2019", ensure that the concentration of the scale inhibitor is greater than 0.05 mg / L, and its maximum measured oxygen consumption is not higher than 5.0 mg / L. At 28 days, its degradation rate is 66.57%.

[0196] Example 10

[0197] A preparation method of a scale inhibitor, comprising the following steps:

[0198] Step a, control the reaction temperature at -10 to -5 °C, add 9.81 g of maleic anhydride and 34.32 g of ether to a three-necked flask, and stir to disperse evenly; dissolve 5.81 g of 2-methylpentanediamine in 20.34 g of ether, and use a constant-pressure dropping funnel to evenly drop the hexanediamine solution into the above three-necked flask. The dropping time is 30 min. After the dropping is completed, continue to react for 3 h, filter, wash with ether, and dry to obtain intermediate 1 shown in formula (Ⅲ), with a yield of 96.94%; R1 is -CH2CH(CH3)CH2CH2CH2-;

[0199]

[0200] Step b, at room temperature, add 7.31 g of the above intermediate 1 and 25 g of distilled water to a three-necked flask, stir to disperse evenly, then add 1.89 g of NaOH, and stir and react for 20 min to obtain a reaction solution containing intermediate 2 shown in formula (Ⅳ); M is Na;

[0201]

[0202] Step c, add 2.28 g of 1,4-cyclohexanediamine to the reaction solution of intermediate 2, react at 70 °C for 20 h, and dry to obtain the phosphorus-free biodegradable scale inhibitor shown in formula Ⅰ, with a molecular weight of 24788; R2 is

[0203]

[0204] According to the calcium carbonate deposition method in "Determination of Scale Inhibition Performance of Water Treatment Agents - GB / T 16632-2019", when the concentration of the scale inhibitor is 10 mg / L, the scale inhibition rate of CaCO3 is 98.11%.

[0205] According to the determination of the scale inhibition rate of CaSO4 scale in "General Technical Conditions for Scale Inhibitors for Oil Fields - SY / T 5673-2020", when the concentration of the scale inhibitor is 8 mg / L, the scale inhibition rate of CaSO4 can reach 100%.

[0206] According to the permanganate index method in "Determination of Chemical Oxygen Demand (COD) in Industrial Circulating Cooling Water - GB / T 15456-2019", ensure that the concentration of the scale inhibitor is greater than 0.05 mg / L, and its maximum measured oxygen consumption is not higher than 5.0 mg / L. At 28 days, its degradation rate is 68.42%.

[0207] Example 11

[0208] A preparation method of a scale inhibitor includes the following steps:

[0209] Step a, control the reaction temperature at 5 - 10 °C, add 10.79 g of maleic anhydride and 53.92 g of distilled water to a three-necked flask, and stir to disperse evenly; dissolve 5.81 g of 1,6-hexanediamine in 31.96 g of distilled water, and use a constant-pressure dropping funnel to uniformly drop the hexanediamine solution into the above three-necked flask. The dropping time is 30 min. After the dropping is completed, continue to react for 2 h, filter, wash with distilled water, and dry to obtain intermediate 1 shown in formula (Ⅲ), with a yield of 97.32%; R1 is -(CH2)6-;

[0210]

[0211] Step b, at room temperature, add 6.96 g of the above intermediate 1 and 20 g of distilled water to a three-necked flask, stir to disperse evenly, then add 1.65 g of Li2CO3, and stir and react for 30 min to obtain a reaction solution containing intermediate 2 shown in formula (Ⅳ); M is Li;

[0212]

[0213] Step c, add 1.80 g of 1,3-diamino-2-propanol to the reaction solution of intermediate 2, react at 100 °C for 1 h, and dry to obtain the phosphorus-free biodegradable scale inhibitor shown in formula I, with a molecular weight of 17443; R2 is -CH2CH(OH)CH2-;

[0214]

[0215] According to the calcium carbonate deposition method in "Determination of Scale Inhibition Performance of Water Treatment Agents - GB / T 16632-2019", when the concentration of the scale inhibitor is 10 mg / L, the scale inhibition rate of CaCO3 is 98.38%.

[0216] According to the determination of the scale inhibition rate of CaSO4 scale in "General Technical Conditions for Scale Inhibitors for Oilfields - SY / T 5673-2020", when the concentration of the scale inhibitor is 8 mg / L, the scale inhibition rate of CaSO4 can reach 100%.

[0217] According to the permanganate index method in "Determination of Chemical Oxygen Demand (COD) in Industrial Circulating Cooling Water - GB / T 15456-2019", ensure that the concentration of the scale inhibitor is greater than 0.05 mg / L, and its maximum measured oxygen consumption is not higher than 5.0 mg / L. At 28 days, its degradation rate is 68.72%.

[0218] Example 12

[0219] A preparation method of a scale inhibitor, comprising the following steps:

[0220] Step a, control the reaction temperature at 5 - 10 °C, add 10.30 g of maleic anhydride and 41.18 g of isopropanol to a three-necked flask, and stir to disperse evenly; dissolve 4.51 g of 1,3-diamino-2-propanol in 18.04 g of isopropanol, and use a constant-pressure dropping funnel to uniformly drop the 1,3-diamino-2-propanol solution into the above three-necked flask. The dropping time is 30 min. After the dropping is completed, continue to react for 5 h, filter, wash with isopropanol, and dry to obtain intermediate 1 shown in formula (Ⅲ), with a yield of 95.15%; R1 is -CH2CH(OH)CH2-;

[0221]

[0222] Step b, at room temperature, add 6.73 g of the above intermediate 1 and 17 g of distilled water to a three-necked flask, stir to disperse evenly, then add 1.93 g of NaOH, and stir and react for 35 min to obtain a reaction solution containing intermediate 2 shown in formula (Ⅳ); M is Na;

[0223]

[0224] Step c, add 2.06 g of diethylenetriamine to the reaction solution of intermediate 2, react at 100 °C for 2 h, and dry to obtain the phosphorus-free biodegradable scale inhibitor shown in formula Ⅰ, with a molecular weight of 18464; R2 is -CH2CH2NHCH2CH2-;

[0225]

[0226] According to the calcium carbonate deposition method in "Determination of Scale Inhibition Performance of Water Treatment Agents - GB / T 16632-2019", when the concentration of the scale inhibitor is 10 mg / L, the scale inhibition rate of CaCO3 is 98.44%.

[0227] According to the determination of the scale inhibition rate of CaSO4 scale in "General Technical Conditions for Scale Inhibitors for Oilfields - SY / T 5673-2020", when the concentration of the scale inhibitor is 8 mg / L, the scale inhibition rate of CaSO4 can reach 100%.

[0228] According to the permanganate index method in "Determination of Chemical Oxygen Demand (COD) in Industrial Circulating Cooling Water - GB / T 15456-2019", ensure that the scale inhibitor concentration is greater than 0.05 mg / L, and its maximum measured oxygen consumption is not higher than 5.0 mg / L. At 28 days, its degradation rate is 65.11%.

[0229] Example 13

[0230] A preparation method of a scale inhibitor includes the following steps:

[0231] Step a, control the reaction temperature at 55 - 60 °C, add 9.81 g of maleic anhydride and 34.32 g of N,N-dimethylformamide into a three-necked flask, and stir to disperse evenly. Another 4.51 g of 1,3-diamino-2-propanol is dissolved in 15.79 g of N,N-dimethylformamide, and the 1,3-diamino-2-propanol solution is evenly added dropwise to the above three-necked flask using a constant-pressure dropping funnel. The dropping time is 30 min. After the dropping is completed, continue to react for 1 h, filter, wash with N,N-dimethylformamide, and dry to obtain intermediate 1 shown in formula (Ⅲ), with a yield of 93.33%; R1 is -CH2CH(OH)CH2-;

[0232]

[0233] Step b, at room temperature, add 6.15 g of the above intermediate 1 and 26 g of distilled water into a three-necked flask, stir to disperse evenly, then add 2.56 g of KOH, and stir and react for 40 min to obtain a reaction solution containing intermediate 2 shown in formula (Ⅳ); M is K;

[0234]

[0235] Step c, add 1.76 g of 1,4-butanediamine to the reaction solution of intermediate 2, react at 50 °C for 24 h, and dry to obtain the phosphorus-free biodegradable scale inhibitor shown in formula Ⅰ, with a molecular weight of 20161; R2 is -(CH2)4-;

[0236]

[0237] According to the calcium carbonate deposition method in "Determination of Scale Inhibition Performance of Water Treatment Agents - GB / T 16632-2019", when the scale inhibitor concentration is 10 mg / L, the scale inhibition rate of CaCO3 is 98.71%.

[0238] According to the determination of the scale inhibition rate of CaSO4 scale in "General Technical Conditions for Scale Inhibitors for Oil Fields - SY / T 5673-2020", when the scale inhibitor concentration is 8 mg / L, the scale inhibition rate of CaSO4 can reach 100%.

[0239] According to the permanganate index method in "Determination of Chemical Oxygen Demand (COD) in Industrial Circulating Cooling Water - GB / T 15456-2019", ensure that the scale inhibitor concentration is greater than 0.05 mg / L, and its maximum measured oxygen consumption is not higher than 5.0 mg / L. At 28 days, its degradation rate is 67.88%.

[0240] Example 14

[0241] A preparation method of a scale inhibitor includes the following steps:

[0242] Step a: Control the reaction temperature at 40 - 45 °C. Add 10.30 g of maleic anhydride and 30.89 g of absolute ethanol into a three-necked flask, and stir to disperse evenly. Separately dissolve 5.11 g of 1,3-pentanediamine in 15.33 g of absolute ethanol, and use a constant-pressure dropping funnel to uniformly drop the 1,3-pentanediamine solution into the above three-necked flask. The dropping time is 30 min. After the dropping is completed, continue the reaction for 2 h. Filter, wash with absolute ethanol, and dry to obtain intermediate 1 shown in formula (Ⅲ), with a yield of 96.86%; R1 is -CH2CH2CH(CH2CH3)-;

[0243]

[0244] Step b: At room temperature, add 6.11 g of the above intermediate 1 and 10 g of distilled water into a three-necked flask, stir to disperse evenly, then add 3.34 g of K2CO3, and stir and react for 20 min to obtain a reaction solution containing intermediate 2 shown in formula (Ⅳ); M is K;

[0245]

[0246] Step c: Add 2.32 g of 1,6-hexanediamine to the reaction solution of intermediate 2, react at 80 °C for 6 h, and dry to obtain the phosphorus-free biodegradable scale inhibitor shown in formula Ⅰ, with a molecular weight of 23342; R2 is -(CH2)6-;

[0247]

[0248] According to the calcium carbonate deposition method in "Determination of Scale Inhibition Performance of Water Treatment Agents - GB / T 16632-2019", when the scale inhibitor concentration is 10 mg / L, the scale inhibition rate of CaCO3 is 98.52%.

[0249] According to the determination of the scale inhibition rate of CaSO4 scale in "General Technical Conditions for Scale Inhibitors for Oilfields - SY / T 5673-2020", when the scale inhibitor concentration is 8 mg / L, the scale inhibition rate of CaSO4 can reach 100%.

[0250] According to the permanganate index method in "Determination of Chemical Oxygen Demand (COD) in Industrial Circulating Cooling Water - GB / T 15456 - 2019", ensure that the scale inhibitor concentration is greater than 0.05 mg / L, and its maximum measured oxygen consumption is not higher than 5.0 mg / L. At 28 days, its degradation rate is 62.15%.

[0251] Example 15

[0252] A preparation method of a scale inhibitor, comprising the following steps:

[0253] Step a, control the reaction temperature at 15 - 20 °C, add 10.79 g of maleic anhydride and 53.39 g of ethyl acetate to a three - necked flask, stir and disperse evenly; dissolve 5.16 g of diethylenetriamine in 25.79 g of ethyl acetate, and use a constant - pressure dropping funnel to slowly add the diethylenetriamine solution to the above - mentioned three - necked flask at a uniform speed. The dropping time is 30 min. After the dropping is completed, continue the reaction for 4 h, filter, wash with ethyl acetate, and dry to obtain intermediate 1 shown in formula (Ⅲ), with a yield of 93.49%; R1 is -CH2CH2NHCH2CH2-;

[0254]

[0255] Step b, at room temperature, add 6.34 g of the above intermediate 1 and 17 g of distilled water to a three - necked flask, stir and disperse evenly, then add 4.99 g of KHCO3, and stir and react for 15 min to obtain a reaction solution containing intermediate 2 shown in formula (Ⅳ); M is K;

[0256]

[0257] Step c, add 1.48 g of 1,3 - propanediamine to the reaction solution of intermediate 2, react at 60 °C for 12 h, and dry to obtain the phosphorus - free biodegradable scale inhibitor shown in formula Ⅰ, with a molecular weight of 20054; R2 is -(CH2)3-;

[0258]

[0259] According to the calcium carbonate deposition method in "Determination of Scale Inhibition Performance of Water Treatment Agents - GB / T 16632 - 2019", when the scale inhibitor concentration is 10 mg / L, the scale inhibition rate of CaCO3 is 99.11%.

[0260] According to the determination of the scale inhibition rate of CaSO4 scale in "General Technical Conditions for Scale Inhibitors for Oil Fields - SY / T 5673 - 2020", when the scale inhibitor concentration is 8 mg / L, the scale inhibition rate of CaSO4 can reach 100%.

[0261] According to the permanganate index method in "Determination of Chemical Oxygen Demand (COD) in Industrial Recirculating Cooling Water - GB / T 15456-2019", ensure that the scale inhibitor concentration is greater than 0.05 mg / L, and its maximum measured oxygen consumption is not higher than 5.0 mg / L. At 28 days, its degradation rate is 62.93%.

[0262] Example 16

[0263] A preparation method of a scale inhibitor includes the following steps:

[0264] Step a, control the reaction temperature at 35 - 40 °C, add 11.28 g of maleic anhydride and 39.47 g of glacial acetic acid to a three-necked flask, stir and disperse evenly; dissolve 5.16 g of diethylenetriamine in 18.05 g of glacial acetic acid, and use a constant pressure dropping funnel to slowly add the diethylenetriamine solution to the above three-necked flask at a uniform speed. The dropping time is 30 min. After the dropping is completed, continue the reaction for 2.5 h, filter, wash with glacial acetic acid, and dry to obtain intermediate 1 shown in formula (Ⅲ), with a yield of 92.58%; R1 is -CH2CH2 NHCH2CH2-;

[0265]

[0266] Step b, at room temperature, add 6.58 g of the above intermediate 1 and 20 g of distilled water to a three-necked flask, stir and disperse evenly, then add 2.80 g of Na2CO3, and stir and react for 10 min to obtain a reaction solution containing intermediate 2 shown in formula (Ⅳ); M is Na;

[0267]

[0268] Step c, add 2.04 g of 1,5-pentanediamine to the reaction solution of intermediate 2, react at 90 °C for 10 h, and dry to obtain the phosphorus-free biodegradable scale inhibitor shown in formula Ⅰ, with a molecular weight of 27467; R2 is -(CH2)5-;

[0269]

[0270] According to the calcium carbonate deposition method in "Determination of Scale Inhibition Performance of Water Treatment Agents - GB / T 16632-2019", when the scale inhibitor concentration is 10 mg / L, the scale inhibition rate of CaCO3 is 98.56%.

[0271] According to the determination of the scale inhibition rate of CaSO4 scale in "General Technical Conditions for Scale Inhibitors for Oilfields - SY / T 5673-2020", when the scale inhibitor concentration is 8 mg / L, the scale inhibition rate of CaSO4 can reach 100%.

[0272] According to the permanganate index method in "Determination of Chemical Oxygen Demand (COD) in Industrial Circulating Cooling Water - GB / T 15456 - 2019", ensure that the concentration of the scale inhibitor is greater than 0.05 mg / L, and its maximum measured oxygen consumption is not higher than 5.0 mg / L. At 28 days, its degradation rate is 65.28%.

[0273] In summary, the scale inhibitor provided by the present invention has excellent scale inhibition performance and is biodegradable. It can be applied to circulating cooling with different concentration multiples, enabling the circulating water to maintain a very high concentration ratio without scaling, protecting the safe operation of circulating water equipment, facilitating the alleviation of the water resource crisis, promoting economic development, and also helping to extend the service life of the equipment, achieving the organic unity of economic, environmental, and social benefits.

[0274] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, or improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A class of phosphorus-free biodegradable scale inhibitors, characterized in that, The structure of the scale inhibitor is shown in Formula I: wherein, R1 and R2 are -(CH2) x -, -(CH2) y CH(CH3)-, -CH2CH2CH(CH2CH3)-, -CH2CH(CH3)CH2CH2CH2- -CH2CH2(NHCH2CH2) i - or -CH2CH(OH)CH2-; x = 2, 3, 4, 5 or 6; y = 1 or 3; i = 1, 2 or 3; M is Li, Na or K.

2. The phosphorus-free biodegradable scale inhibitor according to claim 1, wherein The average molecular weight of the scale inhibitor is between 17443 and 36542.

3. The preparation method of the phosphorus-free biodegradable scale inhibitor according to claim 1 or 2, characterized in that, It includes the following steps: Step a, in a solvent, maleic anhydride and the polyamino compound a shown in Formula (II) carry out a ring-opening reaction to obtain Intermediate 1 shown in Formula (III); Step b, adding the Intermediate 1 and an alkali compound into water to carry out a salt-forming reaction to obtain a reaction solution containing Intermediate 2 shown in Formula (IV); the alkali compound is a hydroxide, bicarbonate or carbonate of Li, Na or K element; Step c, adding the polyamino compound b shown in Formula (V) to the reaction solution of Intermediate 2 to carry out a chain extension reaction to obtain the phosphorus-free biodegradable scale inhibitor shown in Formula I; wherein, R1 and R2 are -(CH2) x -, -(CH2) y CH(CH3)-, -CH2CH2CH(CH2CH3)-, -CH2CH(CH3)CH2CH2CH2- -CH2CH2(NHCH2CH2) i - or -CH2CH(OH)CH2-; x = 2, 3, 4, 5 or 6; y = 1 or 3; i = 1, 2 or 3; M is Li, Na or K.

4. The preparation method of the phosphorus-free biodegradable scale inhibitor according to claim 3, characterized in that, In Step a, the solvent is at least one of water, methanol, ethanol, propanol, isopropanol, acetone, glacial acetic acid, ethyl acetate, ether, petroleum ether, dichloromethane, dimethyl sulfoxide or N,N-dimethylformamide; and / or In Step a, the molar ratio of maleic anhydride to the polyamino compound a is 2 - 4:1; and / or In Step a, the mass ratio of maleic anhydride to the solvent is 1:2 - 10; and / or In Step a, the temperature of the ring-opening reaction is -30°C to 100°C, and the reaction time is not less than 40 min.

5. The preparation method of the phosphorus-free biodegradable scale inhibitor according to claim 4, characterized in that, In Step a, the solvent is at least one of water, ethanol, acetone or glacial acetic acid; and / or In Step a, the molar ratio of maleic anhydride to the polyamino compound a is 2 - 2.3:1; and / or In Step a, the mass ratio of maleic anhydride to the solvent is 1:3 - 9; and / or In Step a, the temperature of the ring-opening reaction is -15°C to 60°C, and the reaction time is not less than 40 min.

6. The preparation method of the phosphorus-free biodegradable scale inhibitor according to claim 3, characterized in that, In Step b, the alkali compound is at least one of NaHCO3, KHCO3, NaOH, KOH, LiOH, Li2CO3, Na2CO3 or K2CO3; the molar ratio of the metal element in Intermediate 1 to the alkali compound is 1:2 - 2.

4.

7. The preparation method of the phosphorus-free biodegradable scale inhibitor according to claim 3, characterized in that, In Step b, the mass ratio of the total mass of Intermediate 1 and the alkali compound to the mass of water is 1:1 - 3; and / or In Step b, the temperature of the salt-forming reaction is 10°C to 40°C, and the reaction time of the salt-forming reaction is not less than 10 min; and / or The molar ratio of the polyamino compound b to Intermediate 1 in Step a is 1:1 - 1.2; and / or In Step c, the reaction temperature of the chain extension reaction is 0°C to 100°C, and the reaction time is not less than 1 h.

8. The preparation method of the phosphorus-free biodegradable scale inhibitor according to claim 7, characterized in that, In Step c, the reaction temperature of the chain extension reaction is 20°C to 100°C.

9. A kind of scale inhibitor composition, characterized in that, It contains the phosphorus-free biodegradable scale inhibitor described in Claim 1 or 2.

10. Application of the phosphorus-free biodegradable scale inhibitor described in Claim 1 or 2 in circulating cooling water treatment.

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