A slow-release scale inhibitor and a preparation method thereof

Abstract

The application belongs to the technical field of scale inhibitors, and particularly relates to a slow-release scale inhibitor and a preparation method thereof. Allyl 3,4,5-trihydroxybenzoate, itaconic acid, sodium bisulfite, methyl acryloyl-oxyethyl-n-hexadecyl-dimethyl ammonium bromide and deionized water are mixed, an ammonium persulfate aqueous solution is slowly added after water bath warming, and the scale inhibitor is obtained after reaction. Agar is dissolved in deionized water, polyethylene glycol modified sodium alginate and the scale inhibitor are added into the agar, and the gel microspheres are obtained by dropwise adding the mixture into edible oil after stirring. The gel microspheres are added into a calcium chloride aqueous solution, crosslinked by slow stirring, and the slow-release scale inhibitor is obtained after washing and drying. The hydrogel microspheres slowly release the scale inhibitor by swelling, and the released scale inhibitor is hydrolyzed in water, the ester group is slowly broken, and polycarboxylic acid, 3,4,5-trihydroxybenzoic acid and hydroxyethyl-n-hexadecyl-dimethyl ammonium bromide are slowly released, thereby achieving good scale inhibition and corrosion inhibition.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of scale inhibitors, and particularly relates to a slow-release scale inhibitor and a preparation method thereof. BACKGROUND

[0002] In the process of oil and gas exploitation, the produced formation water usually contains various soluble salts, such as carbonates, sulfates and silicates. When the solutes in the water exceed a certain solubility, the minerals originally dissolved in the water will precipitate to form scale under the influence of temperature, pressure change or pH change. Scale causes serious harm to oil and gas field production, which may lead to uneven heat transfer of equipment, accelerated corrosion of oil and gas pipelines, and even blockage of oil pipelines and damage to equipment. Since scale is mostly a dense crystal with high crystallinity, the removal process is time-consuming and laborious, and is relatively difficult.

[0003] Therefore, developing efficient corrosion and scale inhibitors can not only prolong the service life of equipment, but also improve production efficiency and reduce operating costs.

[0004] At present, there are corresponding mature treatment technologies for carbonic acid scale and sulfuric acid scale in mixed scale, but the inhibition technology for silicic acid scale still needs to be developed. Silicate scale is dense and hard, and its causes are complex, and it is insoluble in ordinary acid and alkali, which has become the most difficult scale to deal with at present. The existing scale inhibitors have poor scale inhibition performance for mixed scale. SUMMARY

[0005] The application aims to provide a slow-release scale inhibitor and a preparation method thereof to solve the above technical problems.

[0006] To achieve the above technical purposes, the technical scheme of the application is as follows:

[0007] A preparation method of a slow-release scale inhibitor, comprising the following steps:

[0008] S1, mixing 3,4,5-trihydroxybenzoic acid allyl ester, itaconic acid, sodium bisulfite, methacryloyloxyethyl-n-hexadecyl-dimethyl ammonium bromide and deionized water, water bath heating to 80-85℃, slowly adding ammonium persulfate aqueous solution thereto, 30min dropwise addition, incubation reaction for 4h, natural cooling to room temperature after reaction, adjusting the pH of the product to neutral, to obtain a scale inhibitor;

[0009] The molar ratio of the 3,4,5-trihydroxybenzoic acid allyl ester, itaconic acid and methacryloyloxyethyl-n-hexadecyl-dimethyl ammonium bromide is 1.2-1.5:2.0-2.2:1;

[0010] S2, dissolve agar in deionized water at 90℃, cool to 45℃, then add polyethylene glycol modified sodium alginate to it, then add scale inhibitor to it, stir to get a uniform solution, after 1h, drop the uniform solution into edible oil drop by drop, after 30min, take out the gel microspheres, wash the gel microspheres with 1% Tween-80 aqueous solution, then add the gel microspheres to a 3% calcium chloride aqueous solution, slowly stir to crosslink for 1h to get crosslinked hydrogel microspheres, after washing and drying, get the slow-release scale inhibitor;

[0011] The amount of scale inhibitor added is 25-28% of the mass of polyethylene glycol modified sodium alginate.

[0012] As a further improvement, in step S1, the preparation method of 3,4,5-trihydroxybenzoic acid allyl ester is: mix 3,4,5-trihydroxybenzoic acid and allyl alcohol, then dissolve in tetrahydrofuran, slowly add N,N-dicyclohexyl carbodiimide solution to it at 0℃, then stir at room temperature for 18-20h, after the reaction is completed, wash, dry, and purify to get 3,4,5-trihydroxybenzoic acid allyl ester.

[0013] As a further improvement, in step S1, the preparation method of methacryloyloxyethyl-n-hexadecyl-dimethyl ammonium bromide is: take acetone as the solvent, add dimethylaminoethyl methacrylate and bromohexadecane in a molar ratio of 1:1, and add a polymerization inhibitor at the same time, heat to reflux at 56-58℃ for 18-20h, after the reaction is completed, naturally cool to precipitate crystals, then filter, wash, and dry to get.

[0014] As a further improvement, in step S2, the preparation method of polyethylene glycol modified sodium alginate is: add oxidized sodium alginate to a phosphate buffer solution, stir at room temperature until it is completely dissolved to get an oxidized sodium alginate solution;

[0015] Dissolve amino polyethylene glycol in deionized water, adjust the pH to 7-8 with 1mol / L sodium hydroxide to get an amino polyethylene glycol solution;

[0016] Mix the oxidized sodium alginate solution and the amino polyethylene glycol solution, react at room temperature under a nitrogen atmosphere for 8-10h, then dialyze, freeze-dry to get polyethylene glycol modified sodium alginate.

[0017] As a further improvement, the mass ratio of amino polyethylene glycol to oxidized sodium alginate is 1.5-1.8:1.

[0018] As a further improvement, the preparation method of the amino polyethylene glycol is: polyethylene glycol is dissolved in dichloromethane, a triethylamine solution of p-toluenesulfonyl chloride is added, reacted for 12 hours, after the reaction is completed, extracted with hydrochloric acid for 3 times, the organic phase is combined, sodium bicarbonate is added, stirred until no bubbles are generated, filtered and concentrated to obtain a concentrated solution, ether is added, a precipitate is separated out, filtered, dried to obtain polyethylene glycol p-toluenesulfonate;

[0019] The polyethylene glycol p-toluenesulfonate is mixed with ammonia water, reacted at 140 DEG C for 6 hours, cooled to room temperature, extracted with dichloromethane for 3 times, the organic phase is combined, sodium hydroxide solution is added, stirred at room temperature for 4-6 hours, the organic phase is separated, washed until neutral, dried, filtered, and rotary evaporated to obtain amino polyethylene glycol.

[0020] As a further improvement, the molar ratio of the polyethylene glycol and p-toluenesulfonyl chloride is 1:3, and the mass-volume ratio of the polyethylene glycol p-toluenesulfonate and the ammonia water is 23-25 g:80 mL.

[0021] As a further improvement, in step S1, the mass of ammonium persulfate in the ammonium persulfate aqueous solution is 4% of the total mass of 3,4,5-trihydroxybenzoic acid allyl ester, itaconic acid and methyl acryloyloxyethyl-n-hexadecyl-dimethyl ammonium bromide.

[0022] As a further improvement, in step S2, the mass ratio of the agar and the polyethylene glycol modified sodium alginate is 5-8:15.

[0023] The application also provides a slow-release scale inhibitor.

[0024] Due to the adoption of the above technical solutions, the application has the following beneficial effects:

[0025] The slow-release scale inhibitor and the preparation method thereof provided by the application have the following advantages: in the process of use, the hydrogel microspheres swell slowly to release the scale inhibitor, meanwhile, the released scale inhibitor is hydrolyzed in water, the ester groups are slowly broken, and polycarboxylic acid, 3,4,5-trihydroxybenzoic acid and hydroxyethyl-n-hexadecyl-dimethyl ammonium bromide are slowly released, thereby achieving a good scale inhibition and corrosion inhibition effect.

[0026] In the application, 3,4,5-trihydroxybenzoic acid is connected to the scale inhibitor through an ester group, and after the release of 3,4,5-trihydroxybenzoic acid, the scale inhibitor has a good scale inhibition effect on silicate scale, and the released polycarboxylic acid has a good scale inhibition effect on carbonate scale and sulfate scale, and the scale inhibition effect of the scale inhibitor of the application is wider.

[0027] In the present application, the amino group in the amino polyethylene glycol and the aldehyde group in the oxidized sodium alginate undergo Schiff base reaction, the mechanical properties of the sodium alginate hydrogel are improved, and the agar and the ion cross-linked polyethylene glycol modified sodium alginate form the hydrogel microspheres, the branched chains of the agar penetrate the polyethylene glycol modified sodium alginate gel network, the mechanical strength of the hydrogel microspheres is further improved, the swelling performance of the hydrogel microspheres can be improved, the burst release of the scale inhibitor is prevented, and the long-term scale inhibition effect is affected. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 Table 1 is the slow-release performance test results of Example 1 and Comparative Examples 1-3. DETAILED DESCRIPTION

[0029] The technical solutions of the present application will be described clearly and completely in combination with the specific embodiments, but those skilled in the art will understand that the following described embodiments are part of the embodiments of the present application, not all the embodiments, and are only used to illustrate the present application, and should not be regarded as limiting the scope of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. The specific conditions are not specified in the embodiments, and are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not specified by the manufacturer, and are conventional products that can be purchased on the market.

[0030] In the present application, the molecular weight of the polyethylene glycol is 2000 Da.

[0031] Example 1, a preparation method of a slow-release scale inhibitor, specifically includes the following steps:

[0032] S1, 15 mL of acetone is used as a solvent, 10 mmol of dimethylaminoethyl methacrylate and 10 mmol of bromohexadecane are added, 0.38 g of hydroquinone is added as a polymerization inhibitor, and the reaction is heated to reflux at 56℃ for 20 h, the crystal is naturally cooled and precipitated after the reaction is completed, and the crystal is extracted, washed and dried to obtain methacryloyloxyethyl-n-hexadecyl-dimethyl ammonium bromide;

[0033] S2, 1 mmol of 3,4,5-trihydroxybenzoic acid and 1 mmol of allyl alcohol were mixed and dissolved in 15 mL of tetrahydrofuran, 72.73 mL of 16.5 mmol / L N,N-dicyclohexyl carbodiimide solution was slowly added at 0℃, and then stirred at room temperature for 20 h. After the reaction was completed, the reaction liquid was washed with ethyl acetate, and after standing, the aqueous phase was removed. The obtained substance was washed with 5% citric acid aqueous solution, saturated sodium bicarbonate aqueous solution and distilled water in turn, and then dried with magnesium sulfate. After that, 3,4,5-trihydroxybenzoic acid allyl ester was purified by silica gel column chromatography, and the eluent was a mixture of chloroform and methanol with a volume ratio of 95:2;

[0034] S3, 1.26 g (6 mmol) of 3,4,5-trihydroxybenzoic acid allyl ester, 1.3 g (10 mmol) of itaconic acid, 62.44 mg (0.6 mmol) of sodium bisulfite, 2.31 g (5 mmol) of methacryloyloxyethyl-n-hexadecyl-dimethyl ammonium bromide and 20 mL of deionized water were mixed, and the water bath was heated to 85℃. An aqueous solution of ammonium persulfate was slowly added, and the dropwise addition was completed in 30 min. The reaction was kept for 4 h. After the reaction was completed, it was naturally cooled to room temperature. Then, 30% sodium hydroxide aqueous solution was used to adjust the pH of the reaction product to neutral, and a scale inhibitor was obtained. The aqueous solution of ammonium persulfate was obtained by dissolving 0.19 g of ammonium persulfate in 15 mL of water;

[0035] S4, 40 g of polyethylene glycol was dissolved in 200 mL of dichloromethane, and 100 mL of triethylamine solution containing 11.4 g of p-toluenesulfonyl chloride was added. The reaction was carried out for 12 h. After the reaction was completed, 3 mol / L hydrochloric acid was extracted 3 times, and the organic phase was combined. Sodium bicarbonate was added, stirred until no bubbles were generated, and then filtered and concentrated to obtain a concentrated solution. Ethyl ether was added to precipitate, filtered and dried at 30℃ to obtain polyethylene glycol p-toluenesulfonate;

[0036] 23.1 g of polyethylene glycol p-toluenesulfonate was mixed with 80 mL of ammonia water, and reacted at 140℃ for 6 h. After cooling to room temperature, it was extracted with dichloromethane 3 times, and the organic phase was combined. 100 mL of 1 mol / L sodium hydroxide solution was added, stirred at room temperature for 4 h, and then the organic phase was separated. It was washed with saturated brine until neutral, dried with anhydrous sodium sulfate, filtered, and the filtrate was rotary evaporated to obtain amino polyethylene glycol;

[0037] S5, 2.0 g of oxidized sodium alginate was added to 50 mL of pH 7.4 phosphate buffer solution, and stirred at room temperature until completely dissolved to obtain an oxidized sodium alginate solution;

[0038] 3.0 g of amino polyethylene glycol was dissolved in deionized water, and the pH was adjusted to 7 with 1 mol / L sodium hydroxide to obtain an amino polyethylene glycol solution;

[0039] Mix the two solutions above, react at room temperature under nitrogen atmosphere for 8h, and then dialyze the aqueous solution and freeze-dry to obtain the polyethylene glycol modified sodium alginate;

[0040] The oxidized sodium alginate is obtained by oxidizing sodium alginate with sodium periodate, and the specific method is a prior art;

[0041] S6, 5g of agar is dissolved in 50mL of deionized water at 90℃, and then cooled to 45℃, 15g of polyethylene glycol modified sodium alginate is added, then 3.75g of scale inhibitor is added, and stirred uniformly to obtain a uniform solution, after 1h, the uniform solution is added dropwise into edible oil, and after 30min, the gel microspheres are taken out, washed with 1% Tween-80 aqueous solution, and then added into 3% calcium chloride aqueous solution, and then slowly stirred for crosslinking for 1h to obtain crosslinked hydrogel microspheres, which are washed with deionized water for 3 times, naturally dried, and then vacuum dried at 40℃ to obtain a slow-release scale inhibitor.

[0042] Example 2, a preparation method of a slow-release scale inhibitor, specifically comprising the following steps:

[0043] S1, 15mL of acetone is used as a solvent, 10mmol of dimethylaminoethyl methacrylate and 10mmol of bromohexadecane are added, 0.38g of hydroquinone is added as a polymerization inhibitor, and the mixture is heated to reflux at 58℃ for 18h, then naturally cooled to precipitate crystals, and then filtered, washed and dried to obtain methacryloyloxyethyl-n-hexadecyl-dimethyl ammonium bromide;

[0044] S2, 1mmol of 3,4,5-trihydroxybenzoic acid and 1mmol of allyl alcohol are mixed and dissolved in 15mL of tetrahydrofuran, 72.73mL of 16.5mmol / L N,N-dicyclohexyl carbodiimide solution is slowly added at 0℃, and then stirred at room temperature for 20h, then washed with ethyl acetate, and then removed the water phase after standing, and then washed with 5% citric acid aqueous solution, saturated sodium bicarbonate aqueous solution and distilled water, and then dried with magnesium sulfate, and then purified by silica gel column chromatography to obtain 3,4,5-trihydroxybenzoic acid allyl ester, and the eluent is a mixture of 95:2 of chloroform and methanol by volume;

[0045] S3, 1.58 g (7.5 mmol) of 3,4,5-trihydroxybenzoic acid allyl ester, 1.3 g (10 mmol) of itaconic acid, 62.44 mg (0.6 mmol) of sodium bisulfite, 2.31 g (5 mmol) of methacryloyloxyethyl-n-hexadecyl-dimethyl ammonium bromide and 25 mL of deionized water were mixed, and the water bath was warmed to 80°C, and an aqueous ammonium persulfate solution was slowly added thereto, and the dropwise addition was completed in 30 min, and the reaction was maintained for 4 h, and after the reaction was completed, the reaction product was naturally cooled to room temperature, and then a 30% aqueous sodium hydroxide solution was used to adjust the pH of the reaction product to neutral, to obtain a scale inhibitor, wherein the aqueous ammonium persulfate solution was obtained by dissolving 0.21 g of ammonium persulfate in 20 mL of water;

[0046] S4, 40 g of polyethylene glycol was dissolved in 200 mL of dichloromethane, and 100 mL of a triethylamine solution containing 11.4 g of p-toluenesulfonyl chloride was added thereto, and the reaction was maintained for 12 h, and after the reaction was completed, a 3 mol / L hydrochloric acid solution was used to extract 3 times, and the combined organic phase was added with sodium bicarbonate, and stirred until no bubbles were generated, and then filtered and concentrated to obtain a concentrated solution, and then ether was added thereto, and a precipitate was separated out, and after filtration, drying was performed at 30°C to obtain polyethylene glycol p-toluenesulfonate;

[0047] After 25 g of polyethylene glycol p-toluenesulfonate was mixed with 80 mL of an aqueous ammonia solution, the mixture was reacted at 140°C for 6 h, and then cooled to room temperature, and extracted 3 times with dichloromethane, and the combined organic phase was added with 100 mL of a 1 mol / L sodium hydroxide solution, and stirred at room temperature for 6 h, and then the organic phase was separated, and washed with saturated brine until neutral, and dried with anhydrous sodium sulfate, and filtered, and the filtrate was rotary evaporated to obtain amino polyethylene glycol;

[0048] S5, 2.0 g of oxidized sodium alginate was added to 50 mL of a pH 7.4 phosphate buffer solution, and stirred at room temperature until completely dissolved, to obtain an oxidized sodium alginate solution;

[0049] 3.6 g of amino polyethylene glycol was dissolved in deionized water, and a 1 mol / L sodium hydroxide solution was used to adjust the pH to 8, to obtain an amino polyethylene glycol solution;

[0050] The above two solutions were mixed, and reacted at room temperature under a nitrogen atmosphere for 10 h, and the aqueous solution was dialyzed, and freeze-dried to obtain polyethylene glycol modified sodium alginate;

[0051] S6, 8g agar is dissolved in 50mL, 90℃ deionized water, after cooling to 45℃, 15g polyethylene glycol modified sodium alginate is added, then 4.2g scale inhibitor is added, stirring to get a uniform solution, 1h after the above uniform solution is added dropwise into the edible oil, 30min after taking out the gel microspheres, the gel microspheres are washed with 1% tween-80 aqueous solution, then the gel microspheres are added to the 3% calcium chloride aqueous solution, slowly stirring crosslinking 1h to get the crosslinked hydrogel microspheres, the hydrogel microspheres are washed with deionized water for 3 times, and then naturally air dried at 40℃ to get the slow-release scale inhibitor.

[0052] Example 3, a preparation method of a slow-release scale inhibitor, specifically comprising the following steps:

[0053] S1, 15mL acetone is used as a solvent, 10mmol dimethylaminoethyl methacrylate and 10mmol bromohexadecane are added, 0.38g hydroquinone is added as a polymerization inhibitor, and the mixture is heated to reflux at 57℃ for 19h. After the reaction is completed, the crystals are naturally cooled and separated, and then filtered, washed and dried to obtain methyl methacryloyloxyethyl-n-hexadecyl-dimethyl ammonium bromide;

[0054] S2, 1mmol of 3,4,5-trihydroxybenzoic acid and 1mmol of allyl alcohol are mixed and dissolved in 15mL of tetrahydrofuran. 72.73mL of 16.5mmol / L N,N-dicyclohexyl carbodiimide solution is slowly added at 0℃, and then stirred at room temperature for 19h. After the reaction is completed, the reaction liquid is washed with ethyl acetate, and the water phase is removed after standing. The obtained substance is washed with 5% citric acid aqueous solution, saturated sodium bicarbonate aqueous solution and distilled water in sequence, and then dried with magnesium sulfate. After drying, 3,4,5-trihydroxybenzoic acid allyl ester is purified by silica gel column chromatography, and the eluent is a mixture of 95:2 trichloromethane and methanol by volume;

[0055] S3, 1.26g (6mmol) of 3,4,5-trihydroxybenzoic acid allyl ester, 1.43g (11mmol) of itaconic acid, 62.44mg (0.6mmol) of sodium bisulfite, 2.31g (5mmol) of methyl methacryloyloxyethyl-n-hexadecyl-dimethyl ammonium bromide and 20mL of deionized water are mixed, and the water bath is heated to 83℃. An ammonium persulfate aqueous solution is slowly added, and the dropwise addition is completed in 30min. The reaction is kept for 4h, and then naturally cooled to room temperature. The pH of the reaction product is adjusted to neutral with 30% sodium hydroxide aqueous solution to obtain the scale inhibitor. The ammonium persulfate aqueous solution is obtained by dissolving 0.20g of ammonium persulfate in 15mL of water;

[0056] S4, 40 g of polyethylene glycol was dissolved in 200 mL of dichloromethane, 100 mL of triethylamine solution containing 11.4 g of p-toluenesulfonyl chloride was added, and the reaction was carried out for 12 h. After the reaction, the organic phase was extracted with 3 mol / L hydrochloric acid for 3 times, and then sodium bicarbonate was added to the combined organic phase. After stirring until no bubbles were generated, the mixture was filtered and concentrated to obtain a concentrated solution. Ethyl ether was added to the concentrated solution to precipitate a precipitate. The precipitate was filtered and dried at 30°C to obtain polyethylene glycol p-toluenesulfonate;

[0057] 23 g of polyethylene glycol p-toluenesulfonate was mixed with 80 mL of ammonia water, and then the mixture was reacted at 140°C for 6 h. After cooling to room temperature, the mixture was extracted with dichloromethane for 3 times. The organic phase was combined, and then 100 mL of 1 mol / L sodium hydroxide solution was added. The mixture was stirred at room temperature for 5 h, and then the organic phase was separated. The organic phase was washed with saturated brine until neutral, and then dried with anhydrous sodium sulfate. The mixture was filtered, and then the filtrate was rotary evaporated to obtain amino polyethylene glycol;

[0058] S5, 2.0 g of oxidized sodium alginate was added to 50 mL of pH 7.4 phosphate buffer solution, and then the mixture was stirred at room temperature until the oxidized sodium alginate was completely dissolved to obtain an oxidized sodium alginate solution;

[0059] 3.4 g of amino polyethylene glycol was dissolved in deionized water, and then the pH of the solution was adjusted to 7 with 1 mol / L sodium hydroxide to obtain an amino polyethylene glycol solution;

[0060] The two solutions were mixed, and then the mixture was reacted at room temperature under nitrogen atmosphere for 9 h. The aqueous solution was dialyzed and freeze-dried to obtain polyethylene glycol modified sodium alginate;

[0061] S6, 7 g of agar was dissolved in 50 mL of deionized water at 90°C, and then the mixture was cooled to 45°C. Then, 15 g of polyethylene glycol modified sodium alginate was added to the mixture, and then 4.05 g of scale inhibitor was added. The mixture was stirred to obtain a uniform solution. After 1 h, the uniform solution was added dropwise into edible oil. After 30 min, the gel microspheres were taken out, and then the gel microspheres were washed with 1% Tween-80 aqueous solution. Then, the gel microspheres were added to 3% calcium chloride aqueous solution, and then the mixture was slowly stirred for 1 h to obtain crosslinked hydrogel microspheres. The hydrogel microspheres were washed with deionized water for 3 times, and then the mixture was naturally air-dried and vacuum dried at 40°C to obtain a slow-release scale inhibitor.

[0062] The preparation method of the slow-release scale inhibitor specifically comprises the following steps:

[0063] S1, 10 mmol of dimethylaminoethyl methacrylate and 10 mmol of bromohexadecane were added to 15 mL of acetone as a solvent, and 0.38 g of hydroquinone was added as a polymerization inhibitor. The mixture was heated to reflux at 56°C for 20 h. After the reaction was completed, the mixture was naturally cooled to precipitate crystals. The crystals were filtered, washed, and dried to obtain methacryloyloxyethyl-n-hexadecyl-dimethyl ammonium bromide;

[0064] S2, 1 mmol of 3,4,5-trihydroxybenzoic acid and 1 mmol of allyl alcohol were mixed and dissolved in 15 mL of tetrahydrofuran, 72.73 mL of 16.5 mmol / L N,N-dicyclohexyl carbodiimide solution was slowly added at 0°C, and then stirred at room temperature for 20 h. After the reaction was completed, the reaction liquid was washed with ethyl acetate, and after standing, the aqueous phase was removed. The obtained substance was washed with 5% citric acid aqueous solution, saturated sodium bicarbonate aqueous solution and distilled water in turn, and then dried with magnesium sulfate. After that, 3,4,5-trihydroxybenzoic acid allyl ester was purified by silica gel column chromatography, and the eluent was a mixture of chloroform and methanol with a volume ratio of 95:2;

[0065] S3, 1.58 g (7.5 mmol) of 3,4,5-trihydroxybenzoic acid allyl ester, 1.43 g (11 mmol) of itaconic acid, 62.44 mg (0.6 mmol) of sodium bisulfite, 2.31 g (5 mmol) of methyl acryloyloxyethyl-n-hexadecyl-dimethyl ammonium bromide and 25 mL of deionized water were mixed, and the water bath was heated to 85°C. An aqueous solution of ammonium persulfate was slowly added, and the dropwise addition was completed in 30 min. The reaction was kept for 4 h. After the reaction was completed, it was naturally cooled to room temperature. Then, the pH of the reaction product was adjusted to neutral with 30% sodium hydroxide aqueous solution to obtain a scale inhibitor. The aqueous solution of ammonium persulfate was obtained by dissolving 0.21 g of ammonium persulfate in 15 mL of water;

[0066] S4, 40 g of polyethylene glycol was dissolved in 200 mL of dichloromethane, and 100 mL of triethylamine solution containing 11.4 g of p-toluenesulfonyl chloride was added. The reaction was carried out for 12 h. After the reaction was completed, the organic phase was extracted with 3 mol / L hydrochloric acid for 3 times. Then, sodium bicarbonate was added to the combined organic phase. After stirring until no bubbles were generated, the mixture was filtered and concentrated to obtain a concentrated solution. Ethyl ether was added to the concentrated solution to precipitate a precipitate. After filtration, the precipitate was dried at 30°C to obtain polyethylene glycol p-toluenesulfonate;

[0067] 23.1 g of polyethylene glycol p-toluenesulfonate was mixed with 80 mL of ammonia water, and the mixture was reacted at 140°C for 6 h. After cooling to room temperature, the mixture was extracted with dichloromethane for 3 times. The combined organic phase was added with 100 mL of 1 mol / L sodium hydroxide solution. The mixture was stirred at room temperature for 4 h. After standing, the organic phase was separated. The separated organic phase was washed with saturated brine until neutral. The mixture was dried with anhydrous sodium sulfate, filtered, and the filtrate was rotary evaporated to obtain amino polyethylene glycol;

[0068] S5, 2.0 g of oxidized sodium alginate was added to 50 mL of pH 7.4 phosphate buffer solution, and stirred at room temperature until completely dissolved to obtain an oxidized sodium alginate solution;

[0069] 3.0 g of the amino polyethylene glycol is dissolved in deionized water, and the pH is adjusted to 7 with 1 mol / L sodium hydroxide to obtain an amino polyethylene glycol solution;

[0070] The two solutions are mixed, and the reaction is carried out at room temperature under a nitrogen atmosphere for 8 h. The aqueous solution is subjected to dialysis and freeze-drying to obtain the polyethylene glycol-modified sodium alginate;

[0071] The oxidized sodium alginate is obtained by oxidizing sodium alginate with sodium periodate, and the specific method is a prior art;

[0072] S6. 5 g of agar is dissolved in 50 mL of deionized water at 90°C, and then cooled to 45°C. Then, 15 g of the polyethylene glycol-modified sodium alginate is added, followed by 3.75 g of the scale inhibitor. After stirring, a uniform solution is obtained. After 1 h, the uniform solution is added dropwise into edible oil, and then the gel microspheres are taken out after 30 min. The gel microspheres are washed with a 1% Tween-80 aqueous solution, and then added into a 3% calcium chloride aqueous solution. After slow stirring for 1 h, the crosslinked hydrogel microspheres are obtained. The hydrogel microspheres are washed with deionized water for 3 times, and then naturally air-dried and vacuum-dried at 40°C to obtain the slow-release scale inhibitor.

[0073] The preparation method of the slow-release scale inhibitor specifically includes the following steps:

[0074] S1. 10 mmol of dimethylaminoethyl methacrylate and 10 mmol of bromohexadecane are added to 15 mL of acetone as a solvent, and 0.38 g of hydroquinone is added as a polymerization inhibitor. The reaction is carried out at 56°C under reflux for 20 h. After the reaction is completed, the crystals are naturally cooled and precipitated. After filtration, washing and drying, methyl methacryloyloxyethyl-n-hexadecyl-dimethyl ammonium bromide is obtained.

[0075] S2. 1 mmol of 3,4,5-trihydroxybenzoic acid and 1 mmol of allyl alcohol are mixed and dissolved in 15 mL of tetrahydrofuran. At 0°C, 72.73 mL of a 16.5 mmol / L N,N-dicyclohexyl carbodiimide solution is slowly added. After being placed at room temperature, the reaction is stirred for 20 h. After the reaction is completed, the reaction liquid is washed with ethyl acetate, and the water phase is removed after standing. The obtained substance is sequentially washed with 5% citric acid aqueous solution, saturated sodium bicarbonate aqueous solution and distilled water, and then dried with magnesium sulfate. After purification by silica gel column chromatography, 3,4,5-trihydroxybenzoic acid allyl ester is obtained. The eluent is a mixture of 95:2 chloroform and methanol by volume.

[0076] S3, 1.47 g (7 mmol) of 3,4,5-trihydroxybenzoic acid allyl ester, 1.37 g (10.5 mmol) of itaconic acid, 62.44 mg (0.6 mmol) of sodium bisulfite, 2.31 g (5 mmol) of methacryloyloxyethyl-n-hexadecyl-dimethyl ammonium bromide and 25 mL of deionized water are mixed, the water bath is warmed to 85°C, and an aqueous ammonium persulfate solution is slowly added thereto, dropwise over 30 min, and the reaction is maintained for 4 h. After the reaction is completed, the reaction product is naturally cooled to room temperature, and then a 30% aqueous sodium hydroxide solution is used to adjust the pH of the reaction product to neutral, to obtain a scale inhibitor. The aqueous ammonium persulfate solution is obtained by dissolving 0.21 g of ammonium persulfate in 15 mL of water;

[0077] S4, 40 g of polyethylene glycol is dissolved in 200 mL of dichloromethane, 100 mL of a triethylamine solution containing 11.4 g of p-toluenesulfonyl chloride is added thereto, and the reaction is maintained for 12 h. After the reaction is completed, the organic phase is extracted with 3 mol / L hydrochloric acid three times, and then sodium bicarbonate is added to the combined organic phase. After stirring until no gas bubbles are generated, the mixture is filtered and concentrated to obtain a concentrated solution. Ethyl ether is added thereto, a precipitate is separated out, and the mixture is filtered and dried at 30°C to obtain polyethylene glycol p-toluenesulfonate;

[0078] After 23.1 g of polyethylene glycol p-toluenesulfonate is mixed with 80 mL of aqueous ammonia, the mixture is reacted at 140°C for 6 h, cooled to room temperature, extracted with dichloromethane three times, and the combined organic phase is added to 100 mL of a 1 mol / L sodium hydroxide solution. The mixture is stirred at room temperature for 4 h, and then the organic phase is separated and washed with saturated brine until neutral. The mixture is dried with anhydrous sodium sulfate, filtered, and the filtrate is rotary evaporated to obtain amino polyethylene glycol;

[0079] S5, 2.0 g of oxidized sodium alginate is added to 50 mL of a pH 7.4 phosphate buffer solution, and the mixture is stirred at room temperature until the oxidized sodium alginate is completely dissolved, to obtain an oxidized sodium alginate solution;

[0080] 3.0 g of amino polyethylene glycol is dissolved in deionized water, and the pH is adjusted to 7 with a 1 mol / L sodium hydroxide solution, to obtain an amino polyethylene glycol solution;

[0081] The two solutions are mixed, and the mixture is reacted at room temperature under a nitrogen atmosphere for 8 h. The aqueous solution is dialyzed, and then freeze-dried to obtain polyethylene glycol-modified sodium alginate;

[0082] The oxidized sodium alginate is obtained by oxidizing sodium alginate with sodium periodate, and the specific method is a prior art;

[0083] S6, 5g agar was dissolved in 50mL, 90℃ deionized water, cooled to 45℃, then 15g polyethylene glycol modified sodium alginate was added, then 3.75g scale inhibitor was added, stirred uniformly to obtain a uniform solution, 1h later, the above uniform solution was added dropwise into edible oil, 30min later, the gel microspheres were taken out, washed with 1% tween-80 aqueous solution, then the gel microspheres were added to 3% calcium chloride aqueous solution, slowly stirred and crosslinked for 1h to obtain crosslinked hydrogel microspheres, the hydrogel microspheres were washed with deionized water for 3 times, naturally air-dried and vacuum dried at 40℃ to obtain a sustained-release scale inhibitor.

[0084] The present example provides a method for preparing a sustained-release scale inhibitor, and the specific preparation method is as follows:

[0085] S1, 15mL of acetone was used as a solvent, 10mmol of dimethylaminoethyl methacrylate and 10mmol of bromohexadecane were added, 0.38g of hydroquinone was added as a polymerization inhibitor, and the mixture was heated to reflux at 56℃ for 20h. After the reaction was completed, the crystals were naturally cooled and precipitated, and then filtered, washed and dried to obtain methyl methacryloyloxyethyl-n-hexadecyl-dimethyl ammonium bromide;

[0086] S2, 1mmol of 3,4,5-trihydroxybenzoic acid and 1mmol of allyl alcohol were mixed and dissolved in 15mL of tetrahydrofuran, 72.73mL of 16.5mmol / L N,N-dicyclohexyl carbodiimide solution was slowly added at 0℃, and then the mixture was stirred at room temperature for 20h. After the reaction was completed, the reaction liquid was washed with ethyl acetate, and the water phase was removed after standing. The obtained substance was washed with 5% citric acid aqueous solution, saturated sodium bicarbonate aqueous solution and distilled water in turn, then dried with magnesium sulfate, and then purified by silica gel column chromatography to obtain 3,4,5-trihydroxybenzoic acid allyl ester, and the eluent was a mixture of chloroform and methanol with a volume ratio of 95:2;

[0087] S3, 1.26g (6mmol) of 3,4,5-trihydroxybenzoic acid allyl ester, 1.3g (10mmol) of itaconic acid, 62.44mg (0.6mmol) of sodium bisulfite, 2.31g (5mmol) of methyl methacryloyloxyethyl-n-hexadecyl-dimethyl ammonium bromide and 20mL of deionized water were mixed, and the water bath was heated to 85℃. An ammonium persulfate aqueous solution was slowly added, and the dropwise addition was completed in 30min. The reaction was kept for 4h, and then naturally cooled to room temperature. Then, the pH of the reaction product was adjusted to neutral with 30% sodium hydroxide aqueous solution to obtain a scale inhibitor. The ammonium persulfate aqueous solution was prepared by dissolving 0.19g of ammonium persulfate in 15mL of water;

[0088] S4, 5g agar was dissolved in 50mL, 90℃ deionized water, cooled to 45℃, then 15g sodium alginate was added, then 3.75g scale inhibitor was added, stirred uniformly to obtain a uniform solution, after 1h, the above uniform solution was added dropwise into edible oil, after 30min, the gel microspheres were taken out, washed with 1% tween-80 aqueous solution, then the gel microspheres were added into 3% calcium chloride aqueous solution, slowly stirred and crosslinked for 1h to obtain crosslinked hydrogel microspheres, the hydrogel microspheres were washed with deionized water for 3 times, naturally air-dried and vacuum dried at 40℃ to obtain a slow-release scale inhibitor.

[0089] The present example provides a preparation method of a slow-release scale inhibitor, specifically comprising the following steps:

[0090] S1, 15mL acetone was used as a solvent, 10mmol dimethylaminoethyl methacrylate and 10mmol bromohexadecane were added, 0.38g hydroquinone was added as a polymerization inhibitor, heated to reflux at 56℃ for 20h, after the reaction was completed, the crystals were naturally cooled and precipitated, filtered, washed and dried to obtain methacryloyloxyethyl-n-hexadecyl-dimethyl ammonium bromide;

[0091] S2, 1mmol 3,4,5-trihydroxybenzoic acid and 1mmol allyl alcohol were mixed and dissolved in 15mL tetrahydrofuran, 72.73mL, 16.5mmol / L N,N-dicyclohexyl carbodiimide solution was slowly added at 0℃, then placed at room temperature and stirred for 20h, after the reaction was completed, the reaction liquid was washed with ethyl acetate, the water phase was removed after standing, the obtained substance was washed with 5% citric acid aqueous solution, saturated sodium bicarbonate aqueous solution and distilled water in turn, then dried with magnesium sulfate, and then purified by silica gel column chromatography to obtain 3,4,5-trihydroxybenzoic acid allyl ester, and the eluent was a mixture of 95:2 trichloromethane and methanol by volume;

[0092] S3, 1.26g (6mmol) 3,4,5-trihydroxybenzoic acid allyl ester, 1.3g (10mmol) itaconic acid, 62.44mg (0.6mmol) sodium bisulfite, 2.31g (5mmol) methacryloyloxyethyl-n-hexadecyl-dimethyl ammonium bromide and 20mL deionized water were mixed, the water bath was heated to 85℃, and an ammonium persulfate aqueous solution was slowly added, and the dropwise addition was completed in 30min, and the reaction was kept for 4h, after the reaction was completed, the temperature was naturally cooled to room temperature, then 30% sodium hydroxide aqueous solution was used to adjust the pH of the reaction product to neutral, to obtain a scale inhibitor, wherein the ammonium persulfate aqueous solution was obtained by dissolving 0.19g ammonium persulfate in 15mL water;

[0093] S4, 40 g of polyethylene glycol was dissolved in 200 mL of dichloromethane, 100 mL of triethylamine solution containing 11.4 g of p-toluenesulfonyl chloride was added thereto, and the reaction was carried out for 12 h. After the reaction was completed, the organic phase was extracted with 3 mol / L hydrochloric acid for 3 times, and then sodium bicarbonate was added to the combined organic phase. After stirring until no bubbles were generated, the mixture was filtered and concentrated to obtain a concentrated solution. Ethyl ether was added to the concentrated solution, and a precipitate was separated. After filtration, the precipitate was dried at 30°C to obtain polyethylene glycol p-toluenesulfonate;

[0094] After 23.1 g of polyethylene glycol p-toluenesulfonate was mixed with 80 mL of ammonia water and reacted at 140°C for 6 h, the reaction mixture was cooled to room temperature, extracted with dichloromethane for 3 times, and then the organic phase was combined. 100 mL of 1 mol / L sodium hydroxide solution was added to the combined organic phase, and the mixture was stirred at room temperature for 4 h. After separation, the organic phase was washed with saturated brine until neutral, dried with anhydrous sodium sulfate, filtered, and then the filtrate was rotary evaporated to obtain amino polyethylene glycol.

[0095] S5, 2.0 g of oxidized sodium alginate was added to 50 mL of a phosphate buffer solution having a pH of 7.4, and then the mixture was stirred at room temperature until the oxidized sodium alginate was completely dissolved to obtain an oxidized sodium alginate solution;

[0096] 3.0 g of amino polyethylene glycol was dissolved in deionized water, and then the pH of the solution was adjusted to 7 with 1 mol / L sodium hydroxide to obtain an amino polyethylene glycol solution;

[0097] The above two solutions were mixed, and then the mixture was reacted at room temperature under a nitrogen atmosphere for 8 h. The aqueous solution was dialyzed, and then freeze-dried to obtain polyethylene glycol-modified sodium alginate.

[0098] The oxidized sodium alginate was obtained by oxidizing sodium alginate with sodium periodate, and the specific method was a prior art.

[0099] S6, 15 g of polyethylene glycol-modified sodium alginate was dissolved in 50 mL of deionized water, and then 3.75 g of a scale inhibitor was added to the solution. After stirring, a uniform solution was obtained. After 1 h, the uniform solution was added dropwise to edible oil, and then the mixture was stirred for 30 min. The gel microspheres were removed, washed with 1% Tween-80 aqueous solution, and then added to a 3% calcium chloride aqueous solution. After crosslinking at room temperature for 1 h, the crosslinked hydrogel microspheres were washed with deionized water for 3 times, naturally air-dried, and then vacuum-dried at 40°C to obtain a slow-release scale inhibitor.

[0100] Comparative Example 3

[0101] S1, 10 mmol of dimethylaminoethyl methacrylate and 10 mmol of bromohexadecane were added to 15 mL of acetone as a solvent, 0.38 g of hydroquinone was added as a polymerization inhibitor, and the reaction was heated to reflux at 56°C for 20 h. After the reaction was completed, the crystals were naturally cooled and precipitated, and then filtered, washed and dried to obtain methyl methacryloyloxyethyl-n-hexadecyl-dimethyl ammonium bromide;

[0102] S2, 1 mmol of 3,4,5-trihydroxybenzoic acid and 1 mmol of allyl alcohol were mixed and dissolved in 15 mL of tetrahydrofuran. At 0°C, 72.73 mL of 16.5 mmol / L N,N-dicyclohexyl carbodiimide solution was slowly added, and then the reaction was stirred at room temperature for 20 h. After the reaction was completed, the reaction solution was washed with ethyl acetate, and the water phase was removed after standing. The obtained substance was washed with 5% citric acid aqueous solution, saturated sodium bicarbonate aqueous solution and distilled water in turn, and then dried with magnesium sulfate. After that, 3,4,5-trihydroxybenzoic acid allyl ester was obtained by silica gel column chromatography purification, and the eluent was a mixture of 95:2 of chloroform and methanol by volume.

[0103] S3, 1.26 g (6 mmol) of 3,4,5-trihydroxybenzoic acid allyl ester, 1.3 g (10 mmol) of itaconic acid, 62.44 mg (0.6 mmol) of sodium bisulfite, 2.31 g (5 mmol) of methyl methacryloyloxyethyl-n-hexadecyl-dimethyl ammonium bromide and 20 mL of deionized water were mixed, and the water bath was heated to 85°C. An aqueous solution of ammonium persulfate was slowly added, and the dropwise addition was completed in 30 min. The reaction was kept for 4 h, and then the reaction product was naturally cooled to room temperature. The pH of the reaction product was adjusted to neutral with 30% sodium hydroxide aqueous solution to obtain a scale inhibitor. The aqueous solution of ammonium persulfate was obtained by dissolving 0.19 g of ammonium persulfate in 15 mL of water.

[0104] S4, 15 g of sodium alginate was added to 50 mL of deionized water, and then 3.75 g of the scale inhibitor was added and stirred uniformly to obtain a uniform solution. After 1 h, the uniform solution was added dropwise into edible oil, and after 30 min, the gel microspheres were taken out and washed with 1% Tween-80 aqueous solution. Then, the gel microspheres were added to a 3% calcium chloride aqueous solution, and crosslinked for 1 h by slow stirring to obtain crosslinked hydrogel microspheres. The hydrogel microspheres were washed with deionized water for 3 times, naturally air-dried and vacuum dried at 40°C to obtain a slow-release scale inhibitor.

[0105] The slow-release scale inhibitors prepared in Example 1 and Comparative Examples 1-3 were tested for slow-release performance. The specific test method is as follows: 5g of slow-release scale inhibitor was weighed and placed in a gauze bag, which was then placed in a pre-prepared calcium carbonate scale simulation solution. The bag was then placed in a constant temperature water bath and kept warm until the same time the next day. 25mL of the supernatant was taken, and the scale inhibition rate was used as the release study object. Finally, the gauze bag was removed and placed back into the newly prepared calcium carbonate scale simulation solution. The test was repeated until the 91st day.

[0106] Preparation of calcium chloride standard solution: Dissolve 8.35g of anhydrous calcium chloride in 30mL of deionized water, cool, transfer to a 500mL volumetric flask and dilute to volume to obtain calcium chloride standard solution;

[0107] Preparation of sodium bicarbonate standard solution: Accurately weigh 12.6g of sodium bicarbonate into a 100mL beaker, add 45mL of deionized water and let it dissolve, transfer it to a 500mL volumetric flask, add deionized water to make up to volume, and obtain sodium bicarbonate standard solution.

[0108] Preparation of calcium carbonate scale simulation solution: Mix calcium chloride standard solution and sodium bicarbonate standard solution to obtain calcium carbonate scale simulation solution, wherein Ca... 2+ The concentration was 120 mg / L, HCO3 - The concentration was 366 mg / L.

[0109] The results of the slow-release performance tests of the slow-release scale inhibitors in Examples 1 and Comparative Examples 1-3 are as follows: Figure 1 As shown.

[0110] pass Figure 1 It can be seen that comparative examples 1-3 all experienced burst release at different times and to different degrees, while the scale inhibition effect of the slow-release scale inhibitor in Example 1 could still reach more than 50% after 91 days.

[0111] The scale inhibition performance of the slow-release scale inhibitor in Example 1 on silica scale and mixed scale was tested.

[0112] A 250 mL sodium silicate solution with a concentration of 400 mg / L was placed in a 250 mL conical flask, the pH of the solution was adjusted to 8.0 ± 0.3, 0.0375 g of the slow-release scale inhibitor was added to make the concentration of the slow-release scale inhibitor 150 mg / L, the conical flask was sealed, and the conical flask was placed in a constant temperature oscillator at 40°C and 140 r / min. Every 4 h, 5 mL of the sample was taken from the middle part of the solution with a disposable syringe and filtered through a 0.45 μm filter membrane, and the silicon acid concentration in the filtrate was determined by the silicon molybdenum yellow colorimetric method. Under the same silicon acid concentration conditions, no slow-release scale inhibitor was added as a blank control, the slow-release scale inhibitor and the blank control were added according to the same steps, the initial silicon acid concentration was based on the concentration before the experiment started, the scale inhibition rate was calculated, and the test results showed that the scale inhibition rate of the slow-release scale inhibitor of Example 1 on silicon acid scale was 88.64%, and the slow-release scale inhibitor had good scale inhibition performance on silicon acid scale.

[0113] A Ca 2+ , HCO3 - , and H4SiO4 mixed system with three different ion concentration ratios was designed, and the scale inhibition performance of the slow-release scale inhibitor of Example 1 on mixed scale was tested.

[0114] The first group: according to GB / T 16632-2008 and GB / T 50050-2017, the mixed system was set to C(Ca 2+ ) = 240 mg / L, C(HCO3 - ) = 732 mg / L, C(Si) = 81.80 mg / L, and the addition amount of the slow-release scale inhibitor was 150 mg / L.

[0115] The second group: the concentration multiple N = 5 was set, so that the mixed system was C(Ca 2+ ) = 500 mg / L, C(HCO3 - ) = 1375 mg / L, C(Si) = 175 mg / L, and the addition amount of the slow-release scale inhibitor was 400 mg / L.

[0116] The third group: the concentration multiple N = 8 was set, so that the mixed system was C(Ca 2+ ) = 800 mg / L, C(HCO3 - ) = 2200 mg / L, C(Si) = 280 mg / L, and the addition amount of the slow-release scale inhibitor was 1000 mg / L.

[0117] According to the designed ion concentration, test solution was prepared by taking calcium chloride, sodium bicarbonate and sodium silicate as solute respectively, test solution was taken into conical flask respectively, slow-release scale inhibitor was added into the conical flask, the adding amount of slow-release scale inhibitor was 400 mg / L, the conical flask was sealed, the conical flask was placed in a constant temperature oscillator at 40℃ and 140 r / min, 10 mL sample was taken from the middle part of the solution after 24 days, the sample was filtered through 0.45 μm filter membrane, the scale inhibition rate of carbonate scale and the scale inhibition rate of silicate scale were tested and calculated, and the test results are shown in Table 1.

[0118] Table 1: Scale inhibition rate results of slow-release scale inhibitor of example 1 on test solution with different ion concentrations

[0119]

[0120] As can be seen from Table 1, the scale inhibition performance of the slow-release scale inhibitor of example 1 on mixed water scale is also high.

[0121] The specific embodiments of the application described above do not constitute a limitation on the protection scope of the application. Any various other corresponding changes and modifications made according to the technical concept of the application shall be included in the protection scope of the claims of the application.

Claims

1. A method for preparing a slow release scale and soil inhibitor, characterized in that, Comprising the following steps: S1, 3, 4, 5-allyl 3, 4, 5-trihydroxybenzoic acid, itaconic acid, sodium bisulfite, methyl methacryloyl ethyl-n-hexadecyl-dimethyl ammonium bromide and deionized water are mixed, the water bath is warmed to 80~85℃, ammonium persulfate aqueous solution is slowly added, 30min is added dropwise, and the reaction is kept for 4h, after the reaction is completed, it is naturally cooled to room temperature, the pH of the product is adjusted to neutral, and the scale inhibitor is obtained; The molar ratio of the 3, 4, 5-allyl 3, 4, 5-trihydroxybenzoic acid, itaconic acid and methyl methacryloyl ethyl-n-hexadecyl-dimethyl ammonium bromide is 1.2~1.5:2.0~2.2:1; The preparation method of the 3, 4, 5-allyl 3, 4, 5-trihydroxybenzoic acid is as follows: 3, 4, 5-trihydroxybenzoic acid and allyl alcohol are mixed and dissolved in tetrahydrofuran, N, N-dicyclohexyl carbodiimide solution is slowly added at 0℃, and then the reaction is stirred at room temperature for 18~20h, after the reaction is completed, washing, drying and purification are carried out to obtain 3, 4, 5-allyl 3, 4, 5-trihydroxybenzoic acid; The preparation method of the methyl methacryloyl ethyl-n-hexadecyl-dimethyl ammonium bromide is as follows: dimethylaminoethyl methacrylate and bromohexadecane with a molar ratio of 1:1 are added in acetone as solvent, a polymerization inhibitor is added, and the reaction is carried out at 56~58℃ under reflux for 18~20h, after the reaction is completed, the crystal is naturally cooled and precipitated, and the gel microspheres are obtained by filtration, washing and drying; S2, agar is dissolved in deionized water at 90℃, cooled to 45℃, then polyethylene glycol modified sodium alginate is added, then the scale inhibitor is added, stirred to obtain a uniform solution, and then the uniform solution is added dropwise into edible oil, after 30min, the gel microspheres are taken out, washed with 1% Tween-80 aqueous solution, then the gel microspheres are added into 3% calcium chloride aqueous solution, slowly stirred and crosslinked for 1h to obtain crosslinked hydrogel microspheres, and after washing and drying, the slow-release scale inhibitor is obtained; The amount of the scale inhibitor is 25~28% of the mass of the polyethylene glycol modified sodium alginate; The preparation method of the polyethylene glycol modified sodium alginate is as follows: oxidized sodium alginate is added into a phosphate buffer solution, stirred at room temperature until completely dissolved to obtain an oxidized sodium alginate solution; amino polyethylene glycol is dissolved in deionized water, and the pH is adjusted to 7~8 with 1mol / L sodium hydroxide to obtain an amino polyethylene glycol solution; the oxidized sodium alginate solution and the amino polyethylene glycol solution are mixed, and the reaction is carried out at room temperature under nitrogen atmosphere for 8~10h, and then the polyethylene glycol modified sodium alginate is obtained by dialysis and freeze-drying.

2. The method of claim 1, wherein the slow release scale inhibitor is prepared by the process of: The mass ratio of the amino polyethylene glycol and the oxidized sodium alginate is 1.5~1.8:

1.

3. The method of claim 1, wherein the slow release scale inhibitor is prepared by the steps of: The preparation method of the amino polyethylene glycol is as follows: polyethylene glycol is dissolved in dichloromethane, triethylamine solution of p-toluenesulfonyl chloride is added, the reaction is carried out for 12h, after the reaction is completed, the organic phase is extracted with hydrochloric acid for 3 times, then sodium bicarbonate is added, stirred until no bubbles are generated, filtered and concentrated to obtain a concentrated solution, then ether is added, the precipitate is separated by filtration and dried to obtain polyethylene glycol p-toluenesulfonate. Polyethylene glycol p-toluenesulfonate is mixed with ammonia water, reacted at 140℃ for 6h, cooled to room temperature, extracted with dichloromethane for 3 times, combined organic phase, added sodium hydroxide solution, stirred at room temperature for 4-6h, separated organic phase, washed to neutral, dried, filtered, rotary evaporated to obtain amino polyethylene glycol.

4. The method for preparing the slow-release scale inhibitor according to claim 3, characterized in that, The molar ratio of the polyethylene glycol and p-toluenesulfonyl chloride is 1:3, and the mass-volume ratio of the polyethylene glycol p-toluenesulfonate and the ammonia water is 23-25g:80mL.

5. The method of claim 1, wherein the slow release scale inhibitor is prepared by the steps of: In step S1, the mass of ammonium persulfate in the ammonium persulfate aqueous solution is 4% of the total mass of 3,4,5-trihydroxybenzoic acid allyl ester, itaconic acid and methyl acryloyloxyethyl-n-hexadecyl-dimethyl ammonium bromide.

6. The method of claim 1, wherein the slow release scale inhibitor is prepared by the steps of: In step S2, the mass ratio of the agar and the polyethylene glycol modified sodium alginate is 5-8:

15.

7. The slow-release scale inhibitor prepared by the preparation method of the slow-release scale inhibitor in claim 1.

Images