CN113087903B - High-temperature-resistant modified polyaspartic acid scale inhibitor and preparation method and use method thereof - Google Patents

Abstract

The invention discloses a high-temperature-resistant modified polyaspartic acid scale inhibitor, a preparation method and a use method thereof, belonging to the technical field of chemical synthesis.A maleic anhydride and urea are used as raw materials and react in a mixed acid solution to obtain polysuccinimide; the polysuccinimide and prolinamide are subjected to ring-opening grafting reaction to prepare the high-temperature-resistant modified polyaspartic acid scale inhibitor. The nitrogen heterocyclic ring micromolecule modified polyaspartic acid prepared by the invention belongs to a phosphorus-free environment-friendly scale inhibitor, overcomes the defect of poor scale inhibition effect of the existing polyaspartic acid at high temperature, has excellent scale inhibition performance on a calcium carbonate type scale formation system, and is suitable for a water circulation system with local high temperature in an urban geothermal heating system, oil well exploitation production and the like.

Description

A kind of high temperature-resistant modified polyaspartic acid scale inhibitor and its preparation method and use method

technical field

The invention belongs to the technical field of chemical synthesis, and relates to a high temperature-resistant polyaspartic acid scale inhibitor and a preparation method and use method thereof.

Background technique

A large amount of anions and cations are often dissolved in industrial water systems. When pressure, temperature and concentration changes in the process of water use, the concentration of inorganic salt ions in the system will be supersaturated, which will precipitate and form scale. The heat transfer efficiency brings safety hazards and economic losses to industrial production. In many industrial processes, such as the application of geothermal resources, reverse osmosis, multi-stage flash evaporation, multi-effect distillation, etc., the scaling phenomenon is extremely common in industrial water circulation cooling applications. The types of scale generated are mainly calcium carbonate, calcium sulfate, calcium phosphate, and barium sulfate. , iron oxide, etc., of which calcium carbonate scale is the most common. Regarding the calcium carbonate scaling problem that is most likely to occur in the industrial water circulation system, the most common treatment method is to add a scale inhibitor to inhibit the scale. It has anti-corrosion and bacteriostatic effect. At present, common industrial scale inhibitors include inorganic phosphates, organic phosphonic acids and other phosphorus-rich scale inhibitors. Although they have excellent scale inhibition properties, they cannot meet increasingly stringent environmental protection requirements due to the presence of phosphorus. Therefore, the development of green, non-toxic, biodegradable and environmentally friendly scale inhibitors is an inevitable trend in the development of this field.

Polyaspartic acid (PASP) and polyepoxysuccinic acid (PESA) are regarded as the most promising new environmentally friendly scale inhibitors. Among them, polyaspartic acid has excellent scale inhibition effect on calcium carbonate or calcium sulfate scale, but when the local temperature of the water system is too high, the linear polyaspartic acid is prone to break bonds and lose effective functional groups. Then the scale inhibitory activity is obviously lost, so the polyaspartic acid scale inhibitor has the disadvantage of poor thermal stability. In order to improve the thermal stability of polyaspartic acid, it can be chemically modified to improve its temperature resistance. Some existing invention patents (CN 105645606A: a preparation method of a special scale inhibitor for a heating network; CN 102515373 A: a green corrosion and scale inhibitor for a hot water boiler; CN 108726693A: a winter heating hot water High-temperature corrosion and scale inhibitor for pipe network and its preparation method), a method of applying polyaspartic acid scale inhibitor to high-temperature system is tried. However, in these patents, the method of physical compounding of polyaspartic acid and other compounds is adopted, which is cumbersome in actual use.

SUMMARY OF THE INVENTION

In order to overcome the defective problem of poor thermal stability of the existing polyaspartic acid scale inhibitor, the purpose of the present invention is to provide a high temperature-resistant modified polyaspartic acid scale inhibitor and its preparation method and use method.

In order to achieve the above object, the present invention adopts the following technical solutions to be realized:

The preparation method of a high temperature-resistant modified polyaspartic acid scale inhibitor disclosed in the invention comprises:

Take maleic anhydride and urea as raw materials, react in mixed acid solution to obtain polysuccinimide;

A high temperature-resistant modified polyaspartic acid scale inhibitor is prepared by subjecting polysuccinimide and prolineamide to a ring-opening graft reaction.

Preferably, the preparation method of the high temperature-resistant modified polyaspartic acid scale inhibitor is characterized in that, comprising the following steps:

1) Preparation of ammonium hydrogen maleate

Fully dissolving maleic anhydride in water to prepare an aqueous maleic anhydride solution, adding urea powder to the aqueous maleic anhydride solution, and generating ammonium hydrogen maleate through a ring-opening reaction;

2) Preparation of polysuccinimide

Under reflux conditions, the reaction solution containing ammonium hydrogen maleate in step 1) is heated to 160±5°C, then a mixed acid solution is added, the temperature is raised to 180±5°C, and the reaction is performed for 1.5 to 3 hours to obtain polysuccinimide;

3) Preparation of modified polyaspartic acid

Under the condition of water bath at 40～60℃, the polysuccinimide and prolineamide are subjected to ring-opening grafting reaction in water, then alkali solution is added to open the ungrafted part of the polysuccinimide segment, and the reaction is 12 After ~24, the pH value of the reaction system was adjusted to neutrality, the product was precipitated with alcohol, and dried to obtain modified polyaspartic acid, that is, a high temperature-resistant modified polyaspartic acid scale inhibitor.

Further, in step 1), an aqueous solution of ammonium hydrogen maleate is prepared: maleic anhydride and deionized water are added to a three-necked flask with a condensing device, and magnetic stirring is performed in an oil bath to fully dissolve them. The urea powder is uniformly added to the maleic anhydride aqueous solution to react, and in the process, the maleic anhydride and the ammonia donor urea undergo a ring-opening reaction to generate ammonium hydrogen maleate.

Preferably, in step 1), the dissolving temperature of maleic anhydride is 60-80°C, the molar ratio of maleic anhydride and urea is 1:0.5-1:0.7, and the temperature of the ring-opening reaction is 80-110°C.

Further, in step 2), polysuccinimide (PSI) synthesis: the condensation pipe is passed into 5 ℃ of cold water to condense and reflux, the temperature of the generated ammonium hydrogen maleate solution is raised to 160 ± 5 ℃, and sulfuric acid is added to the system. mixed acid with phosphoric acid. After that, the temperature was raised to 180±5°C to continue the reaction, and the ammonium hydrogen maleate monomer was polymerized to form orange-red polysuccinimide.

Further, in step 3), modification of polyaspartic acid: ring-opening grafting of polysuccinimide and light yellow prolineamide in deionized water in a water bath of 40-60° C., and then adding sodium hydroxide alkali The ungrafted part of the polysuccinimide segment is ring-opened, and after reacting for a period of time, the pH is adjusted to neutrality, and anhydrous ethanol is used to separate out and dry to obtain a light yellow brittle solid cyclic small molecule modified polymer. Aspartic acid (PASP-Pro).

In addition, similarly, polyaspartic acid can be synthesized by: in a water bath environment of 40-60 °C, the ring-opening of polysuccinimide is hydrolyzed in sodium hydroxide lye to obtain polyaspartic acid. Water ethanol precipitation. After separation and drying, light yellow viscous polyaspartic acid (PASP) was obtained.

Preferably, in step 2), the added mixed acid solution is made of sulfuric acid and phosphoric acid in a volume ratio of 1:1. More preferably, the amount of mixed acid of sulfuric acid and phosphoric acid is 1.6-2 mL.

Preferably, in step 3), the molar ratio of polysuccinimide and prolineamide is 1:0.5-1:0.75; the reaction time of ring-opening grafting is 4-8h.

Preferably, in step 3), the lye solution used for hydrolyzing the meeting adopts a sodium hydroxide solution with a concentration of 2.5～3 mol/L, wherein the volume of the sodium hydroxide solution added per g of polysuccinimide is 5～3 mol/L 6mL.

Preferably, before step 3), the operation of purifying the polysuccinimide obtained in step 2) is also included, which specifically includes:

The obtained crude polysuccinimide is taken out and dried, and is completely dissolved by N-N-dimethylformamide, then filtered, and the filtrate is collected by absolute ethanol, and after the product is precipitated, suction filtration separation, and drying;

After repeating the purification operation twice, the product was ground to obtain the purified polysuccinimide.

Specifically, the orange-red solid polysuccinimide crude product attached to the wall of the flask was taken out and dried, completely dissolved by N-N-dimethylformamide (DMF), poured into a funnel with qualitative analysis filter paper and filtered to contain The filtrate was collected in a beaker with absolute ethanol. The polysuccinimide was precipitated in anhydrous ethanol in the form of pink flocs. After separation by suction filtration, the obtained product was placed in a vacuum oven to dry. Repeat the purification step 2 times and grind, and finally obtain the deep red purified polysuccinimide.

Further preferably, the volume ratio of absolute ethanol to N-N-dimethylformamide used for collecting the filtrate is greater than 5.

The invention also discloses a high temperature-resistant modified polyaspartic acid scale inhibitor prepared by the above preparation method.

The present invention also discloses a method of using the above-mentioned high temperature-resistant modified polyaspartic acid scale inhibitor, which can maintain the temperature when the high temperature-resistant modified polyaspartic acid scale inhibitor is used in water system treatment below 90°C Long-term anti-scaling effect;

When the high temperature-resistant modified polyaspartic acid scale inhibitor is treated in a water system where the local temperature reaches 170°C, the scale inhibitory effect can be maintained for 3.5 hours;

When in use, it is suitable for water system with pH value of 6.0-8.5 and calcium ion concentration lower than 700mg/L;

The concentration of the high temperature-resistant modified polyaspartic acid scale inhibitor when used is 10-20 mg/L.

Compared with the prior art, the present invention has the following beneficial effects:

The preparation method of the high temperature-resistant modified polyaspartic acid scale inhibitor disclosed in the present invention utilizes the maleic anhydride method to synthesize the polysuccinimide precursor, the synthesis conditions are mild, and the nitrogen-containing heterocyclic small molecule prolineamide is utilized. Modified polyaspartic acid is used to synthesize a new type of environmentally friendly high temperature resistant calcium carbonate scale inhibitor. The reaction conditions are mild and the reaction raw materials are readily available, which is suitable for large-scale production.

The modified polyaspartic acid scale inhibitor prepared by the above method of the present invention is a nitrogen-containing heterocyclic small molecule modified polyaspartic acid, which belongs to a phosphorus-free environment-friendly scale inhibitor, and is a kind of polyaspartic acid. In the process of amino acid modification, a structurally stable heterocyclic group is selected to undergo amidation reaction with polyaspartic acid. Since a rigid prolineamide molecule is grafted on the linear polyaspartic acid, on the one hand, it increases The steric hindrance of the original polyaspartic acid chain is enlarged, so that the chain segment is not easy to move. On the other hand, new hydrogen bonds are generated, which is beneficial to maintain the stability of the polymer structure. Under these effects, the modified polyaspartic acid scale inhibitor has a stable structure at high temperature and maintains high-efficiency scale inhibition effect. It overcomes the disadvantage of poor scale inhibition effect of existing polyaspartic acid at high temperature, and has excellent scale inhibition performance for calcium carbonate type scaling systems, and is suitable for urban geothermal heating systems, oil well mining and production and other water circulation systems with local high temperature .

The modified polyaspartic acid scale inhibitor of the present invention is obviously different from the traditional organic phosphoric acid system while realizing the scale inhibition effect at high temperature, and achieves the goal of green scale inhibition. Therefore, the modified polyaspartic acid prepared by the present invention Partic acid scale inhibitor can be used in industrial circulating water, boiler water, geothermal water, urban heating water, oil field exploitation and other water fields.

Description of drawings

Fig. 1 is the infrared spectrum of modified molecule prolineamide (Pro), polyaspartic acid (PASP) and modified polyaspartic acid (PASP-Pro);

Figure 2 is a graph showing the effect of constant temperature water bath temperature on calcium carbonate scale inhibition performance of aspartic acid (PASP) and modified polyaspartic acid (PASP-Pro);

Figure 3 is a graph showing the effect of polyaspartic acid (PASP) and modified polyaspartic acid (PASP-Pro) on the scale inhibition performance of calcium carbonate scale under different constant temperature durations;

Figure 4 is a graph showing the effect of different pretreatment temperatures on the calcium carbonate scale inhibition performance of polyaspartic acid (PASP) and modified polyaspartic acid (PASP-Pro) on calcium carbonate scale;

Figure 5 is a graph showing the effect of Ca ²⁺ concentration in solution on the calcium carbonate scale inhibition performance of polyaspartic acid (PASP) and modified polyaspartic acid (PASP-Pro) on calcium carbonate scale.

Detailed ways

In order to make those skilled in the art better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only Embodiments are part of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

It should be noted that the terms "first", "second" and the like in the description and claims of the present invention and the above drawings are used to distinguish similar objects, and are not necessarily used to describe a specific sequence or sequence. It is to be understood that the data so used may be interchanged under appropriate circumstances such that the embodiments of the invention described herein can be practiced in sequences other than those illustrated or described herein. Furthermore, the terms "comprising" and "having", and any variations thereof, are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those expressly listed Rather, those steps or units may include other steps or units not expressly listed or inherent to these processes, methods, products or devices.

Below in conjunction with accompanying drawing, the present invention is described in further detail:

The preparation method of the nitrogen-containing heterocyclic small molecule modified and modified to synthesize a high temperature resistant polyaspartic acid scale inhibitor disclosed in the invention adopts the following steps:

(A) Preparation of polysuccinimide (PSI) by maleic anhydride method

Add 20～30g solid maleic anhydride and 20～30ml deionized water to a 500ml three-necked flask with a condensing device, stir magnetically, control the temperature of the oil bath to 80±5℃, and the heating time is 60～90min to completely dissolve the maleic anhydride .

The molar ratio of maleic anhydride and urea is controlled to be 1:0.5～1:0.7, the urea powder is evenly added to the homogeneous maleic anhydride solution obtained in the above, the oil bath temperature is controlled to 80±5℃, and the heating time is 60～90min , so that maleic anhydride and ammonia donor urea can fully generate ammonium hydrogen maleate through ring-opening reaction.

Pour cold water at 5°C into the condenser tube of the above-mentioned three-necked flask to start condensation, and continue to heat up to 160±5°C. After maintaining for a period of time, the colorless ammonium hydrogen maleate solution boils and gradually becomes turbid. It can be found that in the three-necked flask A small amount of orange solid formed on the bottle wall. Slowly add to the three-necked flask (pay attention to the rate of dripping to prevent bumping) 1.6-2 ml of a mixed acid solution with a volume ratio of phosphoric acid and sulfuric acid of 1:1 as a dehydrating agent to promote the polymerization reaction. After adding the mixed acid, increase the temperature to 180 ±5℃, the reaction was maintained for 1.5～3h.

(B) Purified polysuccinimide (PSI)

The orange-red polysuccinimide solid obtained in (A) was taken out and dried, and 20 ml of N-N-dimethylformamide (DMF) was added and dissolved into an orange-red solution, filtered with No. 102 qualitative filter paper, and the filtrate was dried with anhydrous Ethanol is collected, wherein the volume of ethanol used is at least greater than 100 ml. The polysuccinimide was precipitated in pink flocculent form at the bottom of absolute ethanol. After separation by suction filtration, the obtained pink filter cake was placed in a vacuum drying oven at 60°C to 80°C for complete drying.

The above steps are repeated twice, the obtained product is dried and ground, and the dark red precursor polysuccinimide can be obtained.

(C) Preparation of polyaspartic acid (PASP) and modified polyaspartic acid (PASP-Pro)

(C1) Place 2g of the purified polysuccinimide powder in (B) in 10ml of 2.5mol/L sodium hydroxide lye solution in a 60°C water bath environment to conduct hydrolysis and ring-opening, and the orange-red polysuccinimide The imine solution gradually turned pale yellow, and after 12-24 hours of hydrolysis, a polyaspartic acid solution of suitable molecular weight was obtained. After adding an appropriate amount of hydrochloric acid to adjust the pH to neutrality, anhydrous ethanol with a volume of more than 50ml was added dropwise, and then the polyaspartic acid was precipitated at the bottom of the anhydrous ethanol as a pale yellow mucus. After separation and drying, light yellow viscous polyaspartic acid can be obtained.

(C2) In a 60°C water bath, put 2g of the purified polysuccinimide powder in (B) into 10ml of deionized water to dissolve completely, and slowly add 1.2-1.8g of goose yellow prolineamide powder to it to open the ring Grafting, after reacting for 4-8 hours, add 5ml of 2.5mol/L sodium hydroxide lye to it, and the ungrafted monomer part in the polysuccinimide segment is hydrolyzed and ring-opened in an alkaline environment, and the reaction is performed for 12-18 hours Then, an appropriate amount of hydrochloric acid was added to adjust the pH to neutrality, and then anhydrous ethanol with a volume greater than 75 ml was added dropwise, and the modified polyaspartic acid was precipitated at the bottom of the anhydrous ethanol, and after separation and drying, a pale yellow brittle solid ring was obtained. Small molecule modified polyaspartic acid.

Example 1 (Prolineamide-modified polyaspartic acid)

Step 1: Add 20g maleic anhydride and 20ml distilled water into a 250ml three-necked round-bottomed flask with a condensing device, and dissolve with magnetic stirring for 1 hour in an oil bath at 80°C. 9 g of urea powder was slowly added to the solution, and the mixture was magnetically stirred for 1 h until the mixture was uniform. After the start of the experiment, turn on the condensed water at 5°C, raise the temperature of the oil bath to 160°C, add 2 ml of mixed acid of sulfuric acid and phosphoric acid with a volume ratio of 1:1, continue to heat up to 180°C, continue the reaction for 3 hours, and generate on the inner wall of the beaker. Orange-red polysuccinimide solid (PSI).

Step 2: The orange-red polysuccinimide solid obtained in Step 1 was taken out and dried, and 20 ml of N-N-dimethylformamide was added to dissolve it into an orange-red solution, filtered, and the filtrate was collected with sufficient absolute ethanol. The pink flocculent precipitate separated from absolute ethanol was separated by suction filtration, and the obtained filter cake was dried in a vacuum oven at 80° C. for 24 hours.

The purification step was repeated twice, and a dark red polysuccinimide powder was obtained by grinding.

Step 3: In a 60°C water bath, dissolve 2 g of the purified polysuccinimide powder obtained in step 2 in 10 ml of deionized water completely, add 1.5 g of prolineamide powder, and conduct a ring-opening grafting reaction for 4-8 hours. Add 5 ml of 2.5 mol/L sodium hydroxide lye, hydrolyze for 12 to 18 hours, adjust the pH to neutrality with hydrochloric acid, drop into 100 ml of absolute ethanol, separate and dry the precipitate, and purify 1 to 2 times to obtain prolineamide Modified polyaspartic acid.

The infrared spectrum of the prepared prolineamide-modified polyaspartic acid is shown in FIG. 1 . Figure 1 contains the infrared spectra of modified molecules prolineamide (Pro), polyaspartic acid (PASP) and modified polyaspartic acid (PASP-Pro).

Comparative Example 1 (polyaspartic acid)

Step 1 and Step 2 are the same as in the embodiment.

Step 3: In a 60°C water bath, hydrolyze 2g of the purified polysuccinimide powder obtained in step 2 in 10ml of 2.5mol/L sodium hydroxide lye for ring-opening for 24h, and adjust the pH to neutrality with hydrochloric acid , drop into 100ml of absolute ethanol, separate and dry the precipitation, and purify 1 to 2 times to obtain polyaspartic acid. The prepared polyaspartic acid was prepared as a dilute solution with ultrapure water.

Comparative Example 2 (blank group)

An equal volume of ultrapure water was used as a blank instead of the antiscalant solution.

Scale inhibition performance test: In accordance with GB/T 16632 2008 Determination of scale inhibition performance of water treatment agents, calcium carbonate deposition method was used to test the scale inhibition performance of polyaspartic acid and prolineamide modified polyaspartic acid.

Preparation of test solution: add 100ml of calcium chloride solution to a 250ml volumetric flask, so that the amount of calcium ions added is 60mg; add a certain volume of scale inhibitor solution with a pipette, in which polyaspartic acid or prolineamide are modified Add 5 mg of polyaspartic acid, shake well; then slowly add 100 ml of sodium bicarbonate solution so that the amount of bicarbonate ions added is 183 mg, and add ultrapure water to a volume of 250 ml.

Application Experiment 1: Take 15 250ml round-bottomed flasks and label them No. 1-15. According to the preparation steps of the test solution, accurately add Ca ²⁺ concentration to 240mg/L and HCO ₃ ^- concentration to 732mg/L to No. 1 to No. 15 flasks , wherein the No. 1-5 flasks are added with the prolineamide-modified polyaspartic acid prepared in Example 1 of the present invention, and the concentration is 20 mg/L; the No. 6-10 flasks are added with the polyaspartic acid prepared in Comparative Example 1 of the present invention. , the concentration was 20mg/L; the same volume of ultrapure water was added to flasks No. 11-15 as blank control group. The pH was adjusted to 7, and each group was placed in a constant temperature water bath at 50, 60, 70, 80, and 90 °C, and the water bath time was 10 h. After the experiment, the test solution was cooled to room temperature, and the filtrate was taken to measure Ca ² by ion chromatography. ⁺ Concentration, calculate the scale inhibition rate. The results of the assay are shown in Table 1, and are drawn as Figure 2.

Table 1: The duration of the controlled constant temperature water bath is 10h, and the constant temperature temperature affects the calcium carbonate scale inhibition performance of the polyaspartic acid and the modified polyaspartic acid of the present invention.

Table 1

Example 1 1(50℃) 2(60℃) 3(70℃) 4(80℃) 5(90℃) Scale inhibition rate 96.0 94.1 95.6 95.3 88.2 Comparative Example 1 6(50℃) 7(60℃) 8(70℃) 9(80℃) 10(90℃) Scale inhibition rate 94.1 93.0 96.1 92.2 86.9

From the results in Table 1 and Figure 2, it can be seen that when the water bath temperature of the static experiment is low, the scale inhibition effect of polyaspartic acid and modified polyaspartic acid is not much different, and when the water bath temperature is high, the modified The scale inhibition effect of polyaspartic acid is higher than that of the unmodified one.

Application Experiment 2: Take 15 250ml round-bottomed flasks and label them No. 1-15. According to the test solution preparation steps, accurately add Ca ²⁺ to the flasks with a concentration of 240 mg/L and HCO ₃ ^- with a concentration of 732 mg/L. , wherein the No. 1-5 flasks are added with the prolineamide-modified polyaspartic acid prepared in Example 1 of the present invention, and the concentration is 20 mg/L; the No. 6-10 flasks are added with the polyaspartic acid prepared in Comparative Example 1 of the present invention. , the concentration was 20mg/L; the same volume of ultrapure water was added to flasks No. 11-15 as blank control group. The pH was adjusted to 7, and each group was placed in a constant temperature water bath at 80 °C, and the water bath time was 6, 8, 10, 15, and 20 h. After the experiment, the test solution was cooled to room temperature, and the filtrate was taken and tested by ion chromatography. Ca ²⁺ concentration, the scale inhibition rate was calculated. The results of the assay are shown in Table 2, and are drawn as Figure 3.

Table 2: The temperature of the constant temperature water bath is controlled to be 80°C, and the effects of different constant temperature durations on the calcium carbonate scale inhibition performance of the polyaspartic acid and the modified polyaspartic acid of the present invention.

Table 2

Example 1 1(6h) 2(8h) 3(10h) 4(15h) 5(20h) Scale inhibition rate 93.9 95.3 97.3 96.9 85.2 Comparative Example 1 6(6h) 7(8h) 8(10h) 9(15h) 10(20h) Scale inhibition rate 94.1 92.2 94.6 84.7 74.4

From the results in Table 2 and Figure 3, it can be seen that when the temperature of the water bath is controlled to be 80 °C, with the prolongation of the water bath time, the scale inhibition effect of polyaspartic acid and modified polyaspartic acid decreases, but the same The scale inhibition effect of time-modified polyaspartic acid was significantly higher than that of unmodified polyaspartic acid.

Application Experiment 3: Take 8 hydrothermal kettles marked 1 to 8, add the prolineamide modified polyaspartic acid solution prepared in Example 1 to No. 1 to No. 4 hydrothermal kettles, and add No. 5 to No. 8 hydrothermal kettles for Comparative Example 1 The prepared polyaspartic acid was placed in a high-temperature oven at 110, 130, 150, and 170 °C for pretreatment for 3.5 hours, and then taken out and cooled to room temperature. Take nine 250ml round-bottomed flasks and label them No. 1 to No. 9. According to the test solution preparation steps, accurately add Ca ²⁺ concentration to 240 mg/L and HCO ₃ ^- concentration to 732 mg/L in No. 1 to No. 9 flasks, of which 1- Flask No. 4 was added with pretreated prolineamide-modified polyaspartic acid at a concentration of 20 mg/L; flasks No. 5 to 8 were added with polyaspartic acid prepared in Comparative Example 1 of the present invention at a concentration of 20 mg/L; 9 An equal volume of ultrapure water was added to the flask as a blank control group. The pH was adjusted to 7, and each group was placed in a constant temperature water bath at 80 °C, and the water bath time was 10 h. After the experiment, the test solution was ^cooled to room temperature. fouling rate. The results of the assay are shown in Table 3 and drawn as Figure 4 . Table 3: After high temperature pretreatment for 3.5h, 80°C constant temperature water bath for 10h, the effect of pretreatment temperature on the calcium carbonate scale inhibition performance of polyaspartic acid and modified polyaspartic acid of the present invention.

table 3

Example 1 1(110℃) 2(130℃) 3(150℃) 4(170℃) Scale inhibition rate 94.6 90.8 87.1 61.7 Comparative Example 1 5(110℃) 6(130℃) 7(150℃) 8(170℃) Scale inhibition rate 85.7 82.1 73.6 43.0

From the results in Table 3 and Figure 4, it can be seen that with the increase of pretreatment temperature, the scale inhibition effect of polyaspartic acid and modified polyaspartic acid decreased in static experiments, but modified polyaspartic acid decreased. The scale inhibition effect of aspartic acid is significantly higher than that of the unmodified one.

Application Experiment 4: Take 18 250ml round-bottomed flasks, label No. 1-18, follow the test solution preparation steps, in which flasks No. 1-6, 7-12, 13-18 respectively control the Ca ²⁺ concentration to be 120, 240 , 360, 480, 600, 720 mg/L, the No. 1-6 flasks were added with the prolineamide-modified polyaspartic acid prepared in Example 1 of the present invention, and the concentration was 20 mg/L; The concentration of polyaspartic acid prepared in the ratio 1 was 20 mg/L; an equal volume of ultrapure water was added to the flasks of Nos. 13 to 18 as a blank control group. Accurately add HCO ₃ -concentration ^of 732 mg/L to the flasks No. 1 to No. 18, adjust the pH to 7, put each group in a constant temperature water bath at 80°C, and the water bath time is 10h. The concentration of Ca ²⁺ was tested by ion chromatography, and the scale inhibition rate was calculated. The results of the assay are shown in Table 4, and are drawn as Figure 5.

Table 4: Controlling the constant temperature water bath for 10h, the Ca ²⁺ concentration in the solution affects the calcium carbonate scale inhibition performance of the polyaspartic acid and the modified polyaspartic acid of the present invention

Table 4

Example 1 1 (120) 2(240) 3(360) 4(480) 5(600) 6(720) Scale inhibition rate 95.2 95.3 93.2 79.3 77.1 70.2 Comparative Example 1 7(120) 8(240) 9(360) 10 (480) 11(600) 12 (720) Scale inhibition rate 96.4 92.2 94.7 81.9 80.7 74.6

From the results in Table 4 and Figure 5, it can be seen that: with the increase of calcium ion concentration in the solution, the scale inhibition effect of polyaspartic acid and modified polyaspartic acid decreases slowly, and the modified polyaspartic acid inhibits The scaling effect is slightly lower than that of unmodified polyaspartic acid, but the overall effect is similar.

The above disclosures are only specific examples and comparative examples of the present invention. The results of the specific implementation methods show that under the temperature change of the water bath, under the constant temperature water bath for a long time, and after high temperature pretreatment, the modified prolineamide prepared in the examples The scale inhibition effect of polyaspartic acid on calcium carbonate was significantly higher than that of unmodified polyaspartic acid in the comparative example, indicating that prolineamide modified polyaspartic acid significantly improved the effect of polyaspartic acid on calcium carbonate. The high temperature scale inhibition performance of the system. In addition, under the conditions of high mineralization and high calcium water, prolineamide-modified polyaspartic acid showed similar scale inhibition performance as polyaspartic acid, indicating that prolineamide-modified polyaspartic acid can be used in high water quality. Mineralization and high calcium water system can stably inhibit calcium carbonate scale.

The above content is only to illustrate the technical idea of the present invention, and cannot limit the protection scope of the present invention. Any modification made on the basis of the technical solution proposed in accordance with the technical idea of the present invention falls within the scope of the claims of the present invention. within the scope of protection.

Claims (7)

1. A preparation method of a high-temperature-resistant modified polyaspartic acid scale inhibitor is characterized by comprising the following steps:

1) preparation of ammonium hydrogen maleate

Fully dissolving maleic anhydride in water to prepare a maleic anhydride aqueous solution, adding urea powder into the maleic anhydride aqueous solution, and generating ammonium hydrogen maleate through a ring-opening reaction;

the molar ratio of maleic anhydride to urea is 1: 0.5-1: 0.7, wherein the temperature of the ring opening reaction is 80-110 ℃;

2) preparation of polysuccinimide

Under the reflux condition, heating the reaction solution containing ammonium hydrogen maleate in the step 1) to 160 +/-5 ℃, then adding the mixed acid solution, heating to 180 +/-5 ℃, and reacting for 1.5-3 h to obtain polysuccinimide;

the added mixed acid solution is prepared by sulfuric acid and phosphoric acid according to the volume ratio of 1: 1;

3) preparation of modified polyaspartic acid

Under the condition of water bath at 40-60 ℃, polysuccinimide and prolinamide are subjected to ring-opening grafting reaction in water, then alkali liquor is added to open the ring of the ungrafted part in a polysuccinimide chain segment, after the reaction is carried out for 12-24 ℃, the pH value of a reaction system is adjusted to be neutral, and a product is precipitated by alcohol and dried to prepare modified polyaspartic acid, namely the high-temperature-resistant modified polyaspartic acid scale inhibitor;

the molar ratio of polysuccinimide to prolinamide is 1: 0.5-1: 0.75; the open-loop grafting reaction time is 4-8 h.

2. The preparation method of the high-temperature-resistant modified polyaspartic acid scale inhibitor according to claim 1, wherein in the step 1), the temperature of the dissolved maleic anhydride is 60-80 ℃.

3. The preparation method of the high-temperature-resistant modified polyaspartic acid scale inhibitor according to claim 1, wherein in the step 3), the alkali solution for hydrolytic ring opening is a sodium hydroxide solution with a concentration of 2.5-3 mol/L, wherein the volume of the sodium hydroxide solution added per g of the polysuccinimide is 5-6 mL.

4. The preparation method of the high-temperature-resistant modified polyaspartic acid scale inhibitor according to any one of claims 1 to 3, characterized by further comprising an operation of purifying the polysuccinimide prepared in the step 2) before the step 3), and specifically comprising the following steps:

taking out the prepared crude polysuccinimide product, drying, completely dissolving the crude polysuccinimide product by adopting N, N-dimethylformamide, filtering, collecting filtrate by adopting absolute ethyl alcohol, filtering, separating by suction after a product is separated out, and drying;

after repeating the purification operation 2 times, the product was ground to obtain purified polysuccinimide.

5. The method for preparing the high-temperature-resistant modified polyaspartic acid scale inhibitor according to claim 4, wherein the volume ratio of absolute ethyl alcohol to N, N-dimethylformamide used for collecting the filtrate is more than 5.

6. The high-temperature-resistant modified polyaspartic acid scale inhibitor prepared by the preparation method of any one of claims 1-5.

7. The method for using the high-temperature-resistant modified polyaspartic acid scale inhibitor according to claim 6, wherein the high-temperature-resistant modified polyaspartic acid scale inhibitor can maintain a long-acting scale inhibition effect when used for treating water systems at 90 ℃ or below;

when the high-temperature-resistant modified polyaspartic acid scale inhibitor is treated in a water system with local temperature reaching 170 ℃, the scale inhibition effect can be maintained for 3.5 h;

when in use, the water system with the pH value of 6.0-8.5 and the calcium ion concentration lower than 700mg/L is suitable;

the concentration of the high-temperature-resistant modified polyaspartic acid scale inhibitor in use is 10-20 mg/L.

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