Alkali-resistant resin coated sand, its preparation method and application in the field of co2 flooding

Abstract

This invention discloses an alkali-resistant resin-coated sand, its preparation method, and its application in CO2 flooding, relating to the field of oilfield coated sand technology. The alkali-resistant resin-coated sand comprises the following raw materials in parts by weight: quartz sand: 1000 parts, modified composite resin: 100 parts, gold powder: 5-15 parts, nickel powder: 10-20 parts, titanium powder: 5-10 parts, zinc powder: 3-8 parts, silane coupling agent: 1-3 parts, curing agent: 5-15 parts, and dodecyl stearic acid: 0.5-2 parts. The modified composite resin is prepared by blending modified epoxy resin and modified polyurethane resin. The alkali-resistant resin-coated sand prepared by this invention exhibits good alkali resistance, self-healing properties, and a low breakage rate, showing promising application prospects in the CO2 flooding field.

Description

Technical Field

[0001] This invention relates to the field of oilfield coated sand technology, specifically to an alkali-resistant resin coated sand, its preparation method, and its application in the field of CO2 flooding. Background Technology

[0002] CO2 flooding is an important technology for enhancing oil recovery. It involves injecting CO2 into the reservoir to reduce crude oil viscosity and expand its volume. This technology is both environmentally friendly (CO2 sequestration reduces emissions) and economical, but it faces several challenges in practical application: CO2 dissolves in formation water to form carbonic acid, which, over time, can lead to the dissolution of reservoir rocks (such as quartz sand), causing sand production and wellbore blockage. In loose sandstone reservoirs, traditional proppants (such as bare sand) are prone to failure under alkaline conditions, requiring corrosion-resistant, high-strength sand-fixing materials to ensure long-term stability. While traditional resin-coated sand (such as phenolic resin-coated sand) can improve proppant strength, it still suffers from insufficient high-temperature resistance, alkali corrosion resistance, and self-healing capabilities in CO2 flooding environments, severely limiting its application.

[0003] Chinese invention patent CN108997989A discloses a resin-coated sand for achieving directional fracturing, its preparation method, and its application. This resin-coated sand is made from raw materials containing the following components: 100 parts of main material, 0.1-1 parts of silane coupling agent, 10-15 parts of polyetheramine resin or sulfonated polyetheramine resin, 1-3 parts of polyvinyl alcohol, 1-10 parts of hyaluronic acid-modified polysulfide ketone, and 0.1-2 parts of chitosan. This resin-coated sand is a high-strength sealing material that does not produce backflow, but its alkali resistance and corrosion resistance are poor, and it lacks self-healing ability. Therefore, developing a novel resin-coated sand that combines alkali resistance, corrosion resistance, high mechanical strength, and self-healing function is particularly important. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide an alkali-resistant resin-coated sand, its preparation method, and its application in the field of CO2 flooding.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] An alkali-resistant resin-coated sand comprises the following raw materials in parts by weight:

[0007] Quartz sand: 1000 parts

[0008] Modified composite resin: 90-110 parts,

[0009] Gold powder: 5-15 parts

[0010] Nickel powder: 10-20 parts

[0011] Titanium powder: 5-10 parts

[0012] Zinc powder: 3-8 parts

[0013] Silane coupling agent: 1-3 parts,

[0014] Hardener: 5-15 parts

[0015] Dodecyl stearic acid: 0.5-2 parts,

[0016] The modified composite resin is prepared by blending modified epoxy resin and modified polyurethane resin; the modified epoxy resin is prepared by reacting 2,2'-diallylhexafluorobisphenol A with 4-carboxyphenylboronic acid pinacol ester to generate intermediate 1, intermediate 1 is reacted with m-chloroperoxybenzoic acid to generate intermediate 2, and intermediate 2 is reacted with ethylenediamine; the modified polyurethane is prepared by reacting polycaprolactone diol, isophorone diisocyanate and 4,4'-dithiodiphenylamine.

[0017] The modified composite resin is prepared by the following method:

[0018] S1: Add 2,2'-diallylhexafluorobisphenol A and 4-carboxyphenylboronic acid pinacol ester to anhydrous toluene, stir and mix well, add p-toluenesulfonic acid, and react for 7-9 hours to obtain intermediate 1.

[0019] S2: Add intermediate 1 to anhydrous dichloromethane, stir and mix well, then add m-chloroperoxybenzoic acid to react and obtain intermediate 2.

[0020] S3: Mix intermediate 2, ethylenediamine and acetone, add curing accelerator 2,4,6-tris(dimethylaminomethyl)phenol to obtain modified epoxy resin;

[0021] S4: Under nitrogen protection, polycaprolactone diol, isophorone diisocyanate, and dibutyltin dilaurate are added to DMF. After the reaction, 4,4'-dithiodiphenylamine is added to react and a modified polyurethane solution is obtained.

[0022] S5: Mix modified epoxy resin, modified polyurethane solution and DMF, stir at room temperature, heat to cure and dry to obtain modified composite resin.

[0023] In step S1, the molar ratio of 2,2'-diallyl hexafluorobisphenol A and 4-carboxyphenylboronic acid pinacol ester is 1:(2-2.2).

[0024] In step S2, the molar ratio of intermediate 1 to m-chloroperoxybenzoic acid is 1:(2.1-2.3).

[0025] In step S3, the molar ratio of intermediate 2 to ethylenediamine is 1:(1.5-2.5).

[0026] In step S4, the molar ratio of polycaprolactone diol, isophorone diisocyanate, and 4,4'-dithiodiphenylamine is 1:(2.1-2.5):1.

[0027] In step S5, the mass ratio of the modified epoxy resin to the modified polyurethane solution is (1-2.5):5.

[0028] The silane coupling agent is KH-550 silane coupling agent; the curing agent is one of diethylenetriamine, triethylenetetraamine, and tetraethylenepentamine.

[0029] A method for preparing alkali-resistant resin-coated sand includes the following steps:

[0030] (1) The gold powder, nickel powder, titanium powder and zinc powder were ultrasonically cleaned with 5wt% dilute hydrochloric acid in sequence, filtered and washed with deionized water until neutral, and dried at 80℃ for 2h. The gold powder, nickel powder, titanium powder and zinc powder were mixed evenly to obtain metal powder. Then, the silane coupling agent was dissolved in anhydrous ethanol to prepare a dilution solution, which was evenly sprayed onto the surface of the dried metal powder and dried for later use.

[0031] (2) Add the modified composite resin, curing agent and dodecyl stearic acid to a high-speed mixer and mix evenly. Then add metal powder and continue stirring. Control the stirring temperature at 40-50℃ throughout the process to obtain a mixed resin.

[0032] (3) Turn on the sand mixer, add quartz sand, heat to 130°C, inject the mixed resin into the sand mixer, stir at high speed for 10 minutes for coating; cool down to 80°C and keep warm for 2 hours, keep warm at 100°C for 10 hours, use a crusher to break the material into particles, pass through 15 mesh and 40 mesh sieves, and you will get alkali-resistant resin coated sand.

[0033] Due to the adoption of the above technical solutions, the beneficial effects of the present invention include:

[0034] The modified composite resin prepared in this invention comprises an epoxy resin rigid network modified with perfluoroalkyl and phenylboronic acid ester functional groups and a polyurethane network with flexible chains. The rigid network of epoxy resin and the flexible chain segments of polyurethane work synergistically to reduce the breakage rate of coated sand. The introduction of perfluoroalkyl groups further improves the alkali resistance of the resin, and the introduction of flexible chains improves the toughness of the resin. The boronic acid ester structure of epoxy resin and the disulfide bond structure of polyurethane endow the resin with self-healing properties.

[0035] (2) The present invention uses gold powder and nickel powder to enhance the conductivity of the coated sand, and uses nickel powder and titanium powder to enhance the wear resistance of the coated sand. At the same time, the use of zinc powder can further improve the interface bonding. Detailed Implementation

[0036] The following description, in conjunction with specific embodiments, provides further details, but the present invention is not limited to these embodiments.

[0037] Example 1: Preparation of modified composite resin:

[0038] S1: 0.1 mol of 2,2'-diallyl hexafluorobisphenol A and 0.2 mol of 4-carboxyphenylboronic acid pinacol ester were added to 400 mL of anhydrous toluene, followed by 0.01 mol of p-toluenesulfonic acid. The mixture was stirred for 10 min and reacted at 100 °C for 9 h. After cooling to room temperature, the reaction solution was washed with 200 mL of saturated sodium bicarbonate solution. After separation, the organic phase was dried over 15 g of anhydrous magnesium sulfate and rotary evaporated at 60 °C for 2 h to obtain intermediate 1. The reaction equation is shown below:

[0039] .

[0040] Its 1H NMR data are as follows:

[0041] 1 H NMR (500 MHz, Chloroform-d) δ 8.01-7.95 (m, 4H), 7.66-7.60 (m,4H), 7.45 (d, J = 1.8 Hz, 2H), 7.34-7.25 (m, 4H), 5.92 (s, 2H), 5.14-4.95 (m,4H), 3.44 (s, 4H), 1.38 (s, 24H).

[0042] S2: Dissolve 0.1 mol of intermediate 1 in 350 ml of anhydrous dichloromethane. Under ice bath conditions, add 0.21 mol of m-chloroperoxybenzoic acid, stir for 30 min, then heat to 25 °C and react for 4 h. Wash the reaction solution successively with 250 ml of saturated sodium sulfite solution and 350 ml of saturated sodium bicarbonate solution, dry with 15 g of anhydrous magnesium sulfate, and rotary evaporate at 50 °C for 2 h to obtain intermediate 2. The reaction equation is shown below:

[0043] .

[0044] Its 1H NMR data are as follows:

[0045] 1 H NMR (500 MHz, Chloroform-d) δ 8.01-7.95 (m, 4H), 7.66-7.60 (m,4H), 7.39-7.34 (m, 2H), 7.34-7.14 (m, 4H), 3.71 (s, 2H), 3.12-2.95 (m, 8H),1.38 (d, J = 25.1 Hz, 24H).

[0046] S3: Add 0.1 mol of intermediate 2 to 350 ml of acetone, stir, heat in an oil bath at 90 °C for 1 h, add 0.15 mol of ethylenediamine and 0.017 mol of 2,4,6-tris(dimethylaminomethyl)phenol, stir for 10 min, degas under vacuum at 40 °C for 20 min, pre-cur at 60 °C for 2 h, heat to 80 °C for 4 h, and finally cure at 100 °C for 2 h. Allow to cool naturally to room temperature to obtain the modified epoxy resin. In this reaction, the epoxy group of intermediate 2 undergoes ring-opening and reacts with the amino group of ethylenediamine to generate a modified epoxy resin with a cross-linked structure.

[0047] S4: Under nitrogen protection, 500 ml DMF and 0.21 mol isophorone diisocyanate were added sequentially to the reactor and stirred for 10 min. The temperature was raised to 75 °C, and then 0.1 mol polycaprolactone diol was slowly added dropwise over 20 min. After the addition was complete, 1.8 g dibutyltin dilaurate was added, and the reaction was allowed to proceed for 4 h. Then the temperature was lowered to 50 °C, and a DMF solution of 4,4'-dithiodiphenylamine (0.1 mol 4,4'-dithiodiphenylamine dissolved in 300 ml DMF) was slowly added dropwise over 15 min. After the addition was complete, the reaction was allowed to proceed for 4 h to obtain a modified polyurethane solution (number average molecular weight of 8940). In this reaction, the isocyanate group of isophorone diisocyanate first reacts with the hydroxyl group of polycaprolactone diol to form a urethane compound, and then reacts with the amino group of 4,4'-dithiodiphenylamine to form an isocyanate-terminated modified polyurethane solution.

[0048] S5: Mix 20g DMF, 25g modified polyurethane solution and 5g modified epoxy resin, add 1g triethylenetetramine, stir at room temperature for 1h, transfer to a rotary evaporator (60℃ / -0.1 MPa) for 45min of reduced evaporation, cure at 60℃ for 2h, and cure at 80℃ for 10h to obtain modified composite resin.

[0049] Example 2: Preparation of modified composite resin:

[0050] S1: 0.1 mol of 2,2'-diallyl hexafluorobisphenol A and 0.21 mol of 4-carboxyphenylboronic acid pinacol ester were added to 400 ml of anhydrous toluene, and 0.01 mol of p-toluenesulfonic acid was added. The mixture was stirred for 10 min and reacted at 105 °C for 8 h. After cooling to room temperature, the reaction solution was washed with 200 ml of saturated sodium bicarbonate solution. After separation, the organic phase was dried with 15 g of anhydrous magnesium sulfate and rotary evaporated at 60 °C for 2 h to obtain intermediate 1.

[0051] S2: Dissolve 0.1 mol of intermediate 1 in 350 ml of anhydrous dichloromethane. Under ice bath conditions, add 0.22 mol of m-chloroperoxybenzoic acid. Stir for 30 min and then heat to 35 °C for 2 h. Wash the reaction solution successively with 250 ml of saturated sodium sulfite solution and 350 ml of saturated sodium bicarbonate solution. Dry with 15 g of anhydrous magnesium sulfate and rotary evaporate at 50 °C for 2 h to obtain intermediate 2.

[0052] S3: Add 0.1 mol of intermediate 2 to 350 ml of acetone, stir, heat in an oil bath at 90°C for 1 h, add 0.2 mol of ethylenediamine and 0.017 mol of 2,4,6-tris(dimethylaminomethyl)phenol, stir for 10 min, vacuum degas at 40°C for 15 min, pre-cur at 66°C for 1.5 h, heat to 85°C for 3.5 h, and finally cure at 105°C for 1.5 h. Allow to cool naturally to room temperature to obtain the modified epoxy resin.

[0053] S4: Under nitrogen protection, 500 ml DMF and 0.23 mol isophorone diisocyanate were added sequentially to the reactor and stirred for 10 min. The temperature was raised to 75 °C, and then 0.1 mol polycaprolactone diol was slowly added dropwise over 20 min. After the addition was complete, 1.8 g dibutyltin dilaurate was added, and the reaction was allowed to proceed for 4 h. Then the temperature was lowered to 50 °C, and a DMF solution of 4,4'-dithiodiphenylamine (0.1 mol 4,4'-dithiodiphenylamine dissolved in 300 ml DMF) was slowly added dropwise over 15 min. After the addition was complete, the reaction was allowed to proceed for 4 h to obtain a modified polyurethane solution (number average molecular weight of 7864).

[0054] S5: Mix 20g DMF, 25g modified polyurethane solution and 10g modified epoxy resin, add 1g triethylenetetramine, stir at room temperature for 1h, transfer to a rotary evaporator (60℃ / -0.1 MPa) for 45min of reduced evaporation, cure at 60℃ for 2h, and cure at 80℃ for 10h to obtain modified composite resin.

[0055] Example 3: Preparation of modified composite resin:

[0056] S1: 0.1 mol of 2,2'-diallyl hexafluorobisphenol A and 0.22 mol of 4-carboxyphenylboronic acid pinacol ester were added to 400 ml of anhydrous toluene, and 0.01 mol of p-toluenesulfonic acid was added. The mixture was stirred for 10 min and reacted at 110 °C for 7 h. After cooling to room temperature, the reaction solution was washed with 200 ml of saturated sodium bicarbonate solution. After separation, the organic phase was dried with 15 g of anhydrous magnesium sulfate and rotary evaporated at 60 °C for 2 h to obtain intermediate 1.

[0057] S2: Dissolve 0.1 mol of intermediate 1 in 350 ml of anhydrous dichloromethane. Under ice bath conditions, add 0.23 mol of m-chloroperoxybenzoic acid. Stir for 30 min and then heat to 30 °C for 3 h. Wash the reaction solution successively with 250 ml of saturated sodium sulfite solution and 350 ml of saturated sodium bicarbonate solution. Dry with 15 g of anhydrous magnesium sulfate and rotary evaporate at 50 °C for 2 h to obtain intermediate 2.

[0058] S3: Add 0.1 mol of intermediate 2 to 350 ml of acetone, stir, heat in an oil bath at 90°C for 1 h, add 0.25 mol of ethylenediamine and 0.017 mol of 2,4,6-tris(dimethylaminomethyl)phenol, stir for 10 min, vacuum degas at 40°C for 15 min, pre-cur at 70°C for 1 h, heat to 90°C for 3 h, finally cure at 110°C for 1 h, and cool naturally to room temperature to obtain modified epoxy resin;

[0059] S4: Under nitrogen protection, 500 ml DMF and 0.25 mol isophorone diisocyanate were added sequentially to the reactor and stirred for 10 min. The temperature was raised to 80 °C, and then 0.1 mol polycaprolactone diol was slowly added dropwise over 20 min. After the addition was complete, 2 g dibutyltin dilaurate was added, and the reaction was carried out for 4 h. Then the temperature was lowered to 50 °C, and a DMF solution of 4,4'-dithiodiphenylamine (0.1 mol 4,4'-dithiodiphenylamine dissolved in 300 ml DMF) was slowly added dropwise over 15 min. After the addition was complete, the reaction was carried out for 4 h to obtain a modified polyurethane solution (number average molecular weight of 7180).

[0060] S5: Mix 20g DMF, 25g modified polyurethane solution and 12.5g modified epoxy resin, add 1g triethylenetetramine, stir at room temperature for 1h, transfer to a rotary evaporator (60℃ / -0.1 MPa) for 45min of reduced evaporation, cure at 60℃ for 2h, and cure at 80℃ for 10h to obtain modified composite resin.

[0061] Example 4: Preparation of alkali-resistant resin-coated sand:

[0062] Weigh the following by weight: 10,000g of quartz sand, 900g of modified composite resin (prepared in Example 1), 50g of gold powder, 100g of nickel powder, 50g of titanium powder, 30g of zinc powder, 10g of silane coupling agent (KH-550 silane coupling agent), 50g of curing agent (diethylenetriamine), and 5g of dodecyl hydroxystearic acid.

[0063] (1) The gold powder, nickel powder, titanium powder and zinc powder were ultrasonically cleaned with 5wt% dilute hydrochloric acid for 10 min in sequence, filtered and washed with deionized water until neutral, and dried at 80℃ for 2 h. The gold powder, nickel powder, titanium powder and zinc powder were mixed evenly to obtain metal powder. 10g of silane coupling agent was added to 90g of anhydrous ethanol to prepare a dilution solution, which was evenly sprayed onto the surface of the metal powder and dried at 60℃ for later use.

[0064] (2) Add 900g of modified composite resin, 50g of curing agent and 5g of dodecyl stearic acid to a high-speed mixer and premix at 500rpm for 10min; add the dried metal powder from step (1) and continue stirring for 10min. The stirring temperature is controlled at 40℃ throughout the process to obtain the mixed resin.

[0065] (3) Turn on the sand mixer, add 10,000 g of quartz sand, heat to 130°C, inject 500 g of mixed resin into the sand mixer, stir at high speed for 10 min for coating; cool down to 80°C and keep warm for 2 h, keep warm at 100°C for 10 h, use a crusher to break the material into particles, pass through 15 mesh and 40 mesh sieves, and you will get alkali-resistant resin coated sand.

[0066] Example 5: Preparation of alkali-resistant resin-coated sand:

[0067] Weigh the following by weight: 10,000g of quartz sand, 1,000g of modified composite resin (prepared in Example 2), 100g of gold powder, 150g of nickel powder, 80g of titanium powder, 50g of zinc powder, 20g of silane coupling agent (KH-550 silane coupling agent), 100g of curing agent (triethylenetetramine), and 10g of dodecyl hydroxystearic acid;

[0068] (1) The gold powder, nickel powder, titanium powder and zinc powder were ultrasonically cleaned with 5wt% dilute hydrochloric acid for 10 min in sequence, filtered and washed with deionized water until neutral, and dried at 80℃ for 2 h. The gold powder, nickel powder, titanium powder and zinc powder were mixed evenly to obtain metal powder. 20g of silane coupling agent was added to 150g of anhydrous ethanol to prepare a dilution solution, which was evenly sprayed onto the surface of the metal powder and dried at 60℃ for later use.

[0069] (2) Add 1000g of modified composite resin, 100g of curing agent and 10g of dodecyl stearic acid to a high-speed mixer and premix at 500rpm for 10min; add the dried metal powder from step (1) and continue stirring for 10min. The stirring temperature is controlled at 45℃ throughout the process to obtain the mixed resin.

[0070] (3) Turn on the sand mixer, add 10,000 g of quartz sand, heat to 130°C, inject 500 g of mixed resin into the sand mixer, stir at high speed for 10 min for coating; cool down to 80°C and keep warm for 2 h, keep warm at 100°C for 10 h, use a crusher to break the material into particles, pass through 15 mesh and 40 mesh sieves, and you will get alkali-resistant resin coated sand.

[0071] Example 6 Preparation of alkali-resistant resin coated sand:

[0072] Weigh the following by weight: 10,000g of quartz sand, 1,100g of modified composite resin (prepared in Example 3), 150g of gold powder, 200g of nickel powder, 100g of titanium powder, 80g of zinc powder, 30g of silane coupling agent (KH-550 silane coupling agent), 150g of curing agent (tetraethylenepentamine), and 20g of dodecyl stearic acid.

[0073] (1) The gold powder, nickel powder, titanium powder and zinc powder were ultrasonically cleaned with 5wt% dilute hydrochloric acid for 10 min in sequence, filtered and washed with deionized water until neutral, and dried at 80℃ for 2 h. The gold powder, nickel powder, titanium powder and zinc powder were mixed evenly to obtain metal powder. 30g of silane coupling agent was added to 250g of anhydrous ethanol to prepare a dilution solution, which was evenly sprayed onto the surface of the metal powder and dried at 60℃ for later use.

[0074] (2) Add 1100g of modified composite resin, 150g of curing agent and 20g of dodecyl stearic acid to a high-speed mixer and premix at 500rpm for 10min; add the dried metal powder from step (1) and continue stirring for 10min. The stirring temperature is controlled at 50℃ throughout the process to obtain the mixed resin.

[0075] (3) Turn on the sand mixer, add 10,000 g of quartz sand, heat to 130°C, inject 500 g of mixed resin into the sand mixer, stir at high speed for 10 min for coating; cool down to 80°C and keep warm for 2 h, keep warm at 100°C for 10 h, use a crusher to break the material into particles, pass through 15 mesh and 40 mesh sieves, and you will get alkali-resistant resin coated sand.

[0076] Comparative Example 1

[0077] The raw material composition and process of the alkali-resistant resin coated sand are basically the same as those in Example 5, except that titanium powder is not added to the components.

[0078] Comparative Example 2

[0079] The raw material composition and process of the alkali-resistant resin coated sand are basically the same as those in Example 5, except that the modified composite resin is replaced with an equal weight of the modified composite resin prepared by the following method:

[0080] The preparation method of the modified composite resin is basically the same as that in Example 2, except that 2,2'-diallylhexafluorobisphenol A in step S1 is replaced with an equimolar amount of 2-(3-allyl-4-hydroxyphenyl)-2-(4-allyloxyphenyl)-1,1,1-trifluoropropane (CAS: 107839-91-8).

[0081] Comparative Example 3

[0082] The raw material composition and process of the alkali-resistant resin coated sand are basically the same as those in Example 5, except that the modified composite resin is replaced with an equal weight of the modified composite resin prepared by the following method:

[0083] The preparation method of the modified composite resin is basically the same as that in Example 2, except that 4,4'-dithiodiphenylamine in step S4 is replaced with an equimolar amount of 4,4'-diaminodiphenyl sulfide.

[0084] Comparative Example 4

[0085] The raw material composition and process of the alkali-resistant resin coated sand are basically the same as those in Example 5, except that the modified composite resin is replaced with an equal weight of the modified composite resin prepared by the following method:

[0086] The preparation method of the modified composite resin is basically the same as that in Example 2, except that 4,4'-dithiodiphenylamine in step S4 is replaced with an equimolar amount of cystamine.

[0087] Comparative Example 5

[0088] The raw material composition and process of the alkali-resistant resin coated sand are basically the same as those in Example 5, except that the modified composite resin is replaced with an equal weight of the modified composite resin prepared by the following method:

[0089] The preparation method of the modified composite resin is basically the same as that in Example 2, except that the polycaprolactone diol in step S4 is replaced with an equimolar amount of 1,4-butanediol.

[0090] The quartz sand used in the embodiments and comparative examples of this application is 20-40 mesh and comes from Yongshun Mineral Products Processing Plant in Lingshou County; the gold powder is 1500 mesh and comes from Shenzhen Hangcai Chemical Co., Ltd.; the nickel powder is 400 mesh and comes from Huizhou Tenghui Technology Co., Ltd.; the titanium powder is 325 mesh and comes from Changsha Xinkang New Materials Co., Ltd.; and the zinc powder is 1200 mesh and comes from Guangdong Daxiao Chemical Co., Ltd. 2,2'-Dearly allyl hexafluorobisphenol A is also known as compound T27537, CAS number 128481-73-2.

[0091] Self-healing performance test: The compressive strength of the initial specimen and the repaired specimen was tested using a material compression testing machine according to SY / T5276-2000. The compressive strength of the initial specimen and the repaired specimen was recorded. Self-healing rate = compressive strength after repair / initial compressive strength × 100%. The test results are shown in Table 1.

[0092] Sample preparation: Pour 200g of resin-coated sand into a 500ml beaker, add 4wt% dilute hydrochloric acid solution, stir for 1min, remove the resin sand and put it into a stainless steel cylinder with a copper mesh at one end, and cover the other end with a copper mesh as well. Tighten the stainless steel cylinder with a screw with a hole in the center. After completion, immerse one end of the steel cylinder with the screw into 3wt% hydrochloric acid solution, and use a suction bulb to draw the hydrochloric acid solution into the stainless steel cylinder at the other end. After sealing, place it in a water bath and cure at 40℃ for 48h to prepare the sample (sample diameter 25mm, length 25mm).

[0093] Sample repair test: Use a blade to make three parallel scratches with a length of 10 mm, a depth of 0.5 mm, and a width of 150 μm in the middle of the sample. The three scratches are spaced at the same distance. Then, place the sample in an 80℃ oven for 3 hours and leave it at room temperature for 24 hours to prepare the repaired sample.

[0094] Alkali resistance test: The sample was cured at a constant temperature of 20℃ for 1 day, and then immersed in 200ml of 2wt% sodium hydroxide solution for 48h. The state of the resin-coated sand surface was observed. The test results are shown in Table 1.

[0095] The breakage rate of resin-coated sand was determined and calculated according to SY / T5108-2014 "Test Method for Performance of Proppants Used in Hydraulic Fracturing and Gravel Packing Operations". The test results are shown in Table 1.

[0096] Table 1

[0097]

[0098] As can be seen from Table 1, the coated sand prepared in Examples 4-6 of this application has excellent alkali resistance, self-healing properties and anti-breakage properties.

[0099] Comparative Example 1 is a comparative example without the addition of titanium powder. The breakage rate of the coated sand prepared in it is worse than that of the example. This is because the addition of titanium powder can work synergistically with nickel powder to improve wear resistance, thereby reducing the breakage rate.

[0100] The alkali resistance of the coated sand prepared in Comparative Example 2 was worse than that of the Example, mainly because the modified composite resin prepared using 2-(3-allyl-4-hydroxyphenyl)-2-(4-allyloxyphenyl)-1,1,1-trifluoropropane had fewer fluorine groups introduced. The introduction of fluorine groups can significantly improve the alkali resistance of the resin-coated sand.

[0101] The self-healing performance of the coated sand prepared in Comparative Example 3 was worse than that of the Example. This was mainly because the raw materials used to prepare the modified composite resin lacked the dynamic reversibility of disulfide bonds. The resin crosslinking network changed from dynamic reversibility to static, and the molecular chain segments could not fill the scratches through bond breakage and recombination, resulting in a significant reduction in self-healing performance.

[0102] The breakage rate of the coated sand prepared in Comparative Example 4 was worse than that of the Example. This was mainly because the flexible segments of cystamine increased, the crosslinking density decreased, and the interfacial bonding weakened, causing the polyurethane crosslinking network to change from rigid and dense to flexible and loose. This reduced the rigidity of the crosslinking network, and when the coated sand was subjected to force, the flexible network was more likely to undergo plastic deformation rather than elastic support, resulting in an increased breakage rate.

[0103] The fracture rate of the coated sand prepared in Comparative Example 5 was worse than that in the Example. This is mainly because 1,4-butanediol lacks a long-chain flexible soft segment structure. After reacting with isophorone diisocyanate, it forms highly cross-linked hard segments. The network rigidity increases but the brittleness increases significantly, making the coated sand more prone to breakage when squeezed.

[0104] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. However, any modifications, alterations, and variations made by those skilled in the art without departing from the scope of the present invention based on the disclosed technical content are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. An alkali-resistant resin-coated sand, characterized in that, The raw materials include the following parts by weight: Quartz sand: 1000 parts Modified composite resin: 90-110 parts, Gold powder: 5-15 parts Nickel powder: 10-20 parts Titanium powder: 5-10 parts Zinc powder: 3-8 parts Silane coupling agent: 1-3 parts, Hardener: 5-15 parts Dodecyl stearic acid: 0.5-2 parts, The modified composite resin is prepared by blending modified epoxy resin and modified polyurethane resin; the modified epoxy resin is prepared by reacting 2,2'-diallylhexafluorobisphenol A with 4-carboxyphenylboronic acid pinacol ester to generate intermediate 1, intermediate 1 is reacted with m-chloroperoxybenzoic acid to generate intermediate 2, and intermediate 2 is reacted with ethylenediamine; the modified polyurethane is prepared by reacting polycaprolactone diol, isophorone diisocyanate and 4,4'-dithiodiphenylamine. The gold powder is 1500 mesh and is produced by Shenzhen Hangcai Chemical Co., Ltd.

2. The alkali-resistant resin-coated sand according to claim 1, characterized in that, The modified composite resin is prepared by the following method: S1: Add 2,2'-diallylhexafluorobisphenol A and 4-carboxyphenylboronic acid pinacol ester to anhydrous toluene, stir and mix well, add p-toluenesulfonic acid, and react for 7-9 hours to obtain intermediate 1. S2: Add intermediate 1 to anhydrous dichloromethane, stir and mix well, then add m-chloroperoxybenzoic acid to react and obtain intermediate 2. S3: Mix intermediate 2, ethylenediamine and acetone, add curing accelerator 2,4,6-tris(dimethylaminomethyl)phenol to obtain modified epoxy resin; S4: Under nitrogen protection, polycaprolactone diol, isophorone diisocyanate, and dibutyltin dilaurate are added to DMF. After the reaction, 4,4'-dithiodiphenylamine is added to react and a modified polyurethane solution is obtained. S5: Mix modified epoxy resin, modified polyurethane solution and DMF, stir at room temperature, heat to cure and dry to obtain modified composite resin.

3. The alkali-resistant resin-coated sand according to claim 2, characterized in that, In step S1, the molar ratio of 2,2'-diallyl hexafluorobisphenol A and 4-carboxyphenylboronic acid pinacol ester is 1:(2-2.2).

4. The alkali-resistant resin-coated sand according to claim 2, characterized in that, In step S2, the molar ratio of intermediate 1 to m-chloroperoxybenzoic acid is 1:(2.1-2.3).

5. The alkali-resistant resin-coated sand according to claim 2, characterized in that, In step S3, the molar ratio of intermediate 2 to ethylenediamine is 1:(1.5-2.5).

6. The alkali-resistant resin-coated sand according to claim 2, characterized in that, In step S4, the molar ratio of polycaprolactone diol, isophorone diisocyanate, and 4,4'-dithiodiphenylamine is 1:(2.1-2.5):

1.

7. The alkali-resistant resin-coated sand according to claim 2, characterized in that, In step S5, the mass ratio of the modified epoxy resin to the modified polyurethane solution is (1-2.5):

5.

8. The alkali-resistant resin-coated sand according to claim 1, characterized in that, The silane coupling agent is KH-550 silane coupling agent; the curing agent is one of diethylenetriamine, triethylenetetraamine, and tetraethylenepentamine.

9. A method for preparing alkali-resistant resin-coated sand according to any one of claims 1-8, characterized in that, Includes the following steps: (1) The gold powder, nickel powder, titanium powder and zinc powder were ultrasonically cleaned with 5wt% dilute hydrochloric acid in sequence, filtered and washed with deionized water until neutral, and dried at 80℃ for 2h. The gold powder, nickel powder, titanium powder and zinc powder were mixed to obtain metal powder. Then, the silane coupling agent was dissolved in anhydrous ethanol to prepare a dilution solution, which was evenly sprayed onto the surface of the metal powder and dried for later use. (2) Add the modified composite resin, curing agent and dodecyl stearic acid to a high-speed mixer and mix evenly. Then add metal powder and continue stirring. Control the stirring temperature at 40-50℃ throughout the process to obtain a mixed resin. (3) Turn on the sand mixer, add quartz sand, heat to 130°C, inject the mixed resin into the sand mixer, stir at high speed for 10 minutes for coating; cool down to 80°C and keep warm for 2 hours, keep warm at 100°C for 10 hours, use a crusher to break the material into particles, pass through 15 mesh and 40 mesh sieves, and you will get alkali-resistant resin coated sand.

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