Quick heat-conducting coated sand and its preparation process

Abstract

This invention discloses a rapid thermally conductive coated sand and its preparation process, relating to the field of coated sand technology. The raw materials include the following parts by weight: 100-105 parts raw sand, 6-8 parts modified resin prepolymer, 2-4 parts modified POE, 3.5-4.5 parts lubricant, and 3-5 parts nano-silicon nitride. The modified POE has a strong high-temperature toughening effect on the modified resin prepolymer and can also form chemical crosslinks with it, exhibiting strong compatibility with other raw materials in the coated sand. The modified resin prepolymer is obtained by heating and ring-opening polymerization of benzoxazine monomers obtained from the reaction of 5-nitrosalicylic acid, ethyl 2,4-ditrifluoromethyl-5-pyrimidinecarboxylate, paraformaldehyde, and furfurylamine. The modified resin prepolymer has a lower curing temperature and improved thermal stability, which helps to improve the high-temperature resistance of the coated sand.

Description

A rapid thermally conductive coated sand and its preparation process Technical Field

[0001] This invention relates to the field of coated sand technology, specifically to a rapid thermally conductive coated sand and its preparation process. Background Technology

[0002] Rapidly conductive coated sand is a special material used for temperature control in rapid packaging, ensuring that electronic products, pharmaceuticals, food, and other products are kept at a suitable temperature during transportation. It is typically prepared by coating a natural quartz sand substrate with a resin film, and adding curing agents, lubricants, and reinforcing and toughening additives.

[0003] In thermally conductive coated sand, the resin needs to possess good mechanical properties and high-temperature resistance to ensure the stability and reliability of the coated sand under high-temperature environments. However, the increased brittleness of polybenzoxazine resin at high temperatures may lead to cracking and breakage of the coated sand, thus affecting its performance and lifespan. POE can be used for toughening modification of polybenzoxazine resin; however, POE's insufficient heat resistance limits its high-temperature toughening effect on polybenzoxazine resin, thus restricting its use in coated sand. Furthermore, the significant polarity difference between POE and polybenzoxazine resin necessitates improvement in their compatibility. Polybenzoxazine resin can be obtained by thermally activated ring-opening polymerization of benzoxazine monomers. The six-membered heterocyclic oxazine ring in the benzoxazine monomer has high stability, resulting in a curing temperature of up to 250°C for traditional polybenzoxazine resin. However, this temperature may cause the benzoxazine monomer to evaporate or the resin to degrade. Although the use of catalysts can reduce the curing temperature of benzoxazine resin, it will have a negative impact on the high temperature resistance, which limits the use of traditional polybenzoxazine resin in coated sand.

[0004] Therefore, suitable modification methods are needed to improve the heat resistance of POE materials, enhance the compatibility of POE materials with polybenzoxazine resins, etc., reduce the curing temperature of polybenzoxazine resins while ensuring high temperature resistance, and apply them to the preparation of coated sand to obtain fast thermally conductive coated sand with better mechanical strength, high temperature resistance and other properties. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a rapid thermally conductive coated sand and its preparation process.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A rapid thermally conductive coated sand comprises the following raw materials in parts by weight: 100-105 parts raw sand, 6-8 parts modified resin prepolymer, 2-4 parts modified POE, 3.5-4.5 parts lubricant, and 3-5 parts nano-silicon nitride;

[0008] Furthermore, the raw sand is obtained by mixing quartz sand and ceramsite sand in a mass ratio of 1-1.5:0.5-1, and the particle size of both quartz sand and ceramsite sand is 50-70 mesh; the lubricant is obtained by mixing zinc stearate and calcium stearate in a mass ratio of 1:1.5-2.

[0009] The preparation of the rapid thermally conductive coated sand includes the following steps:

[0010] Dry the raw sand to obtain dry raw sand for later use; heat and stir the modified resin prepolymer and modified POE together, add nano silicon nitride, continue stirring, cool down and add raw sand and half of the lubricant, continue mixing, reduce the speed and heat up to solidify, add the remaining lubricant, continue mixing, cool, and sieve to obtain fast thermally conductive coated sand.

[0011] The preparation of the rapid thermally conductive coated sand includes the following specific steps:

[0012] Dry the raw sand at 100-110℃ for 3-4 hours to obtain dried raw sand for later use; mix the modified resin prepolymer and modified POE at 90-100℃ and 1000-1200rpm for 0.5-1 hours, add nano-silicon nitride, continue stirring for 20-30 minutes, cool to 60-80℃, add the raw sand and half of the lubricant, continue mixing for 25-35 minutes, reduce the speed to 500-600rpm, raise the temperature to 155-165℃, stir for 4-4.5 hours, add the remaining lubricant, continue mixing for 10-15 minutes, cool, and pass through a 90-110 mesh sieve to obtain rapidly thermally conductive coated sand;

[0013] The modified POE is prepared by the following steps:

[0014] Step A1: Mix vinylsiloxane and toluene, add m-chloroperoxybenzoic acid, heat and stir to obtain product a1; mix azirospirocarboxylic acid, toluene and DMF in a protective gas atmosphere, heat and stir, add product a1 and 4-dimethylaminopyridine while stirring, heat and stir again to obtain product a2.

[0015] Step A2: Mix vinylbenzoic acid and DMAC and stir, then place in an ice-water bath and add oxaloyl chloride dropwise. After the addition is complete, heat and stir to obtain product a3. Add product a2, potassium carbonate and pyridine to DMSO and stir. Then add the solution of product a3 dropwise in an ice-water bath and heat and stir to obtain product a4.

[0016] Step A3: Mix product a4, toluene, and ethyl acetate, add sodium hydrosulfite and sodium bicarbonate, heat and reflux with stirring to obtain product a5; mix product a5, triphosgene, toluene, and cyclohexane, introduce protective gas, stir and heat, and reflux with stirring to obtain product a6.

[0017] Step A4: After mixing and stirring POE and toluene, add product a6, ethyl acetate and initiator, continue stirring, and then heat and reflux to obtain modified POE.

[0018] The preparation of the modified POE includes the following specific steps:

[0019] Step A1: Mix vinylsiloxane and toluene and stir for 20-25 min, add m-chloroperoxybenzoic acid, heat to 70-80℃, and stir for 8-8.5 h to obtain product a1; Mix azirospirocarboxylic acid, toluene, and DMF in a protective gas atmosphere and stir for 30-40 min, heat to 55-65℃, add product a1 and 4-dimethylaminopyridine while stirring, stir for 6-6.5 h, then heat to 100-105℃ and stir for 1.5-2 h to obtain product a2;

[0020] Further, the ratio of vinylsiloxane, toluene, and m-chloroperoxybenzoic acid is 28-30g: 115-125mL: 25-27g; the vinylsiloxane is 1,5-divinylhexamethyltrisiloxane; the ratio of azirospirocarboxylic acid, toluene, DMF, product a1, and 4-dimethylaminopyridine is 18-20g: 75-85mL: 40-50mL: 31-33g: 2.8-3.2g; the azirospirocarboxylic acid is 2-methyl-2-azirospiro[3.3]heptane-6-carboxylic acid;

[0021] In step A1, the carbon-carbon double bond of vinylsiloxane is oxidized to an epoxy group to obtain product a1; the azeotropic carboxylic acid reacts with the epoxy group of product a1 in a ring-opening reaction to obtain product a2 containing a hydroxyl group.

[0022] Step A2: Mix vinylbenzoic acid and DMAC and stir for 15-20 min. Place the mixture in an ice-water bath and add oxaloyl chloride dropwise. After the addition is complete, heat the mixture to 55-65℃ and stir for 1.5-2 h to obtain product a3. Add product a2, potassium carbonate, and pyridine to DMSO and stir for 30-40 min. Add the solution of product a3 dropwise in an ice-water bath, then heat the mixture to 50-55℃ and stir for 8.5-9 h to obtain product a4.

[0023] Further, the ratio of vinylbenzoic acid, DMAC, and oxaloyl chloride is 23-25g:90-100mL:19-21g; the vinylbenzoic acid is 3-nitro-4-vinylbenzoic acid; the ratio of product a2, potassium carbonate, pyridine, DMSO, and product a3 solution is 35-37g:14.5-15.5g:0.2-0.4g:100-110mL:85-95mL; the product a3 solution is obtained by adding 26-28g of product a3 to 55-65mL of DMAC and stirring.

[0024] In step A2, vinylbenzoic acid reacts with oxaloyl chloride to give product a3 containing acyl chloride; product a3 reacts with the hydroxyl group of product a2 to give an esterified product containing nitro group, namely product a4.

[0025] Step A3: Mix product a4, toluene, and ethyl acetate and stir for 15-25 min. Add sodium hydrosulfite and sodium bicarbonate, heat to 70-80℃, and reflux and stir for 6.5-7 h to obtain product a5. Mix product a5, triphosgene, toluene, and cyclohexane, introduce a protective gas, stir and heat to 100-110℃, and reflux and stir for 4.5-5 h to obtain product a6.

[0026] Furthermore, the ratio of product a4, toluene, ethyl acetate, sodium hydrosulfite, and sodium bicarbonate is 54-56g: 90-100mL: 70-80mL: 27-29g: 0.9-1.1g; the ratio of product a5, triphosgene, toluene, and cyclohexane is 51-53g: 45-47g: 110-120mL: 90-100mL.

[0027] During step A3, the nitro group of product a4 is selectively reduced to an amino group, retaining the terminal carbon-carbon double bond, to obtain product a5; the amino group in product a5 reacts with triphosgene to generate chloroamide, which is then dechlorinated by heating to generate isocyanate group, which is product a6.

[0028] Step A4: Mix POE and toluene and stir for 40-50 min. Add product a6, ethyl acetate and initiator, and continue stirring for 30-40 min. Reflux and stir at 125-135℃ for 6.5-7 h to obtain modified POE.

[0029] Furthermore, the ratio of POE, toluene, product a6, ethyl acetate, and initiator is 100-110g: 210-220mL: 10.5-11.5g: 25-35mL: 0.65-0.75g; the initiator is a mixture of benzoyl peroxide and azobisisobutyronitrile in a mass ratio of 1.5-2: 1-1.5; POE is an ethylene-1-butene copolymer.

[0030] During step A4, product a6 is grafted onto POE to obtain modified POE containing siloxane segments, azaspirocyclic rings, and isocyanate groups.

[0031] The modified resin prepolymer is prepared by the following steps:

[0032] Step B1: After mixing and stirring salicylaldehyde, hydroxylamine-O-sulfonic acid, and acetic acid, deionized water is added, and the mixture is heated under reflux and stirred to obtain product b1. Under a protective gas atmosphere, product b1, toluene, and acetonitrile are mixed and stirred, and then heated. Sodium bisulfite and sodium carbonate are added and stirred to obtain product b2.

[0033] Step B2: Under a protective gas atmosphere, pyrimidine carbamate and DMF are mixed and stirred, then product b2 and ammonium chloride are added after heating. After stirring and reacting, the pH is adjusted to obtain product b3.

[0034] Step B3: Mix product b3, paraformaldehyde, and 2-furfuralamine, heat and stir to react, then heat and continue stirring, cool to room temperature, wash with ethyl acetate to obtain the modified resin prepolymer;

[0035] The preparation of the modified resin prepolymer includes the following specific steps:

[0036] Step B1: Mix salicylaldehyde, hydroxylamine-O-sulfonic acid, and acetic acid and stir for 10-15 min. Add deionized water and reflux at 50-60℃ for 24-25 h. After post-treatment, obtain product b1. Under a protective gas atmosphere, mix product b1, toluene, and acetonitrile and stir for 35-45 min. Heat to 40-45℃, add sodium bisulfite and sodium carbonate, and stir to react, obtaining product b2.

[0037] Further, the ratio of salicylaldehyde, hydroxylamine-O-sulfonic acid, acetic acid, and deionized water is 18-20g: 14-16g: 6.5-7g: 500-520mL; the salicylaldehyde is 5-nitrosalicylic acid; the post-treatment involves adding a 10-15% sodium bicarbonate solution to the reaction solution obtained by heating and reflux until no bubbles are generated, followed by extraction with chloroform, rotary evaporation of the obtained organic phase, and washing with diethyl ether; the ratio of product b1, toluene, acetonitrile, sodium bisulfite, and sodium carbonate is 21-23g: 60-70mL: 40-50mL: 16-18g: 1.5-2.5g;

[0038] In step B1, the aldehyde group of salicylaldehyde reacts with hydroxylamine-O-sulfonic acid to convert the aldehyde group into a cyano group, yielding product b1; the nitro group of product b1 is selectively reduced to an amino group, while retaining the cyano group, yielding product b2.

[0039] Step B2: Under a protective gas atmosphere, mix and stir pyrimidine carbamate and DMF for 35-45 min, add product b2 and ammonium chloride at 80-85℃, stir and react for 8-8.5 h, adjust pH to neutral, and obtain product b3;

[0040] Furthermore, the ratio of pyrimidine carbamate, DMF, product b2, and ammonium chloride is 33-35g: 110-120mL: 18-20g: 1-3g; the pyrimidine carbamate is ethyl 2,4-ditrifluoromethyl-5-pyrimidine carbamate.

[0041] During step B2, the amino group of product b2 reacts with the ester group of pyrimidine carbamate to give product b3 containing trifluoromethyl, pyrimidine, cyano, etc.

[0042] Step B3: Mix product b3, paraformaldehyde, and 2-furfuralamine, heat to 100-105℃ and stir for 4.5-5 hours, then heat to 125-135℃ and continue stirring for 1-1.5 hours. Cool to room temperature and wash with ethyl acetate to obtain the modified resin prepolymer.

[0043] Furthermore, the ratio of product b3, paraformaldehyde, and 2-furfural is 53-55g: 6.5-7.5g: 11-13g;

[0044] In step B3, product b3, paraformaldehyde, and 2-furfurylamine react to obtain benzoxazine resin prepolymer, i.e., modified resin prepolymer.

[0045] Beneficial effects of the present invention: The present invention discloses a rapid thermally conductive coated sand and its preparation process. The rapid thermally conductive coated sand is prepared from raw sand, modified resin prepolymer, modified POE, lubricant, nano silicon nitride and other raw materials.

[0046] The modified POE is obtained by grafting POE with the product obtained from the reaction of 1,5-divinylhexamethyltrisiloxane, 2-methyl-2-azaspirocyclic[3.3]heptane-6-carboxylic acid, and 3-nitro-4-vinylbenzoic acid. The combined use of 1,5-divinylhexamethyltrisiloxane and 2-methyl-2-azaspirocyclic[3.3]heptane-6-carboxylic acid in the modified POE, along with the thermally stable siloxane and the rigid azaspirocyclic compound, endows the modified POE with strong heat resistance. This enhances the temperature adaptability of the modified POE in coated sand, improves the high-temperature toughening effect of the modified POE on the modified resin prepolymer, and thus improves the thermal tensile strength and thermal flexural strength of the rapidly thermally conductive coated sand. The modified POE uses 3-nitro-4-vinylbenzoic acid in the reaction, which introduces isocyanate groups into the modified POE. This helps the modified POE to form chemical crosslinks with the modified resin prepolymer, and also helps to enhance the compatibility of the modified POE with other raw materials in the coated sand, thereby improving the overall performance of the coated sand.

[0047] The modified resin prepolymer is obtained by heating and ring-opening polymerization of benzoxazine monomers obtained from the reaction of 5-nitrosalicylic acid, ethyl 2,4-ditrifluoromethyl-5-pyrimidinecarboxylate, paraformaldehyde, and 2-furfurylamine. The combined use of 5-nitrosalicylic acid and ethyl 2,4-ditrifluoromethyl-5-pyrimidinecarboxylate results in a phenolic source product containing electron-withdrawing trifluoromethyl, pyrimidine, and cyano groups. This facilitates the formation of more acidic phenolic substances, thereby generating a stronger intramolecular synergistic catalytic ring-opening effect. This lowers the curing temperature of the modified resin prepolymer and improves its thermal stability, contributing to the enhanced high-temperature resistance of the coated sand. Furthermore, the cyano group transforms into a triazine ring during the curing process, synergistically enhancing the flame retardancy of the modified resin prepolymer with the pyrimidine ring. Detailed Implementation

[0048] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] Example 1

[0050] A modified POE, the preparation of which includes the following steps:

[0051] Step A1: Mix 1,5-divinylhexamethyltrisiloxane and toluene and stir for 20 min, add m-chloroperoxybenzoic acid, heat to 70℃, and stir for 8 h to obtain product a1; mix 2-methyl-2-azaspirocyclic[3.3]heptane-6-carboxylic acid, toluene, and DMF in a nitrogen atmosphere and stir for 30 min, heat to 55℃, add product a1 and 4-dimethylaminopyridine while stirring, stir for 6 h, then heat to 100℃ and stir for 1.5 h to obtain product a2; the ratio of 1,5-divinylhexamethyltrisiloxane, toluene, and m-chloroperoxybenzoic acid is 28 g: 115 mL: 25 g; the ratio of 2-methyl-2-azaspirocyclic[3.3]heptane-6-carboxylic acid, toluene, DMF, product a1, and 4-dimethylaminopyridine is 18 g: 75 mL: 40 mL: 31 g: 2.8 g;

[0052] Step A2: Mix 3-nitro-4-vinylbenzoic acid and DMAC and stir for 15 min. Place the mixture in an ice-water bath and add oxaloyl chloride dropwise. After the addition is complete, heat to 55℃ and stir for 1.5 h to obtain product a3. Add product a2, potassium carbonate, and pyridine to DMSO and stir for 30 min. Add the solution of product a3 dropwise in an ice-water bath, then heat to 50℃ and stir for 8.5 h to obtain product a4. The molar ratio of 3-nitro-4-vinylbenzoic acid, DMAC, and oxaloyl chloride is 23 g: 90 mL: 19 g. The molar ratio of product a2, potassium carbonate, pyridine, DMSO, and the solution of product a3 is 35 g: 14.5 g: 0.2 g: 100 mL: 85 mL. The solution of product a3 is obtained by adding 26 g of product a3 to 55 mL of DMAC and stirring.

[0053] Step A3: Mix product a4, toluene, and ethyl acetate and stir for 15 min. Add sodium hydrosulfite and sodium bicarbonate, heat to 70°C, and reflux for 6.5 h to obtain product a5. Mix product a5, triphosgene, toluene, and cyclohexane, purge with nitrogen, stir and heat to 100°C, and reflux for 4.5 h to obtain product a6. The ratio of product a4, toluene, ethyl acetate, sodium hydrosulfite, and sodium bicarbonate is 54 g: 90 mL: 70 mL: 27 g: 0.9 g; the ratio of product a5, triphosgene, toluene, and cyclohexane is 51 g: 45 g: 110 mL: 90 mL.

[0054] Step A4: Mix POE and toluene and stir for 40 min. Add product a6, ethyl acetate, and initiator, and continue stirring for 30 min. Reflux and stir at 125℃ for 6.5 h to obtain modified POE. The ratio of POE, toluene, product a6, ethyl acetate, and initiator is 100 g: 210 mL: 10.5 g: 25 mL: 0.65 g. The initiator is a mixture of benzoyl peroxide and azobisisobutyronitrile in a mass ratio of 1.5:1. POE is an ethylene-1-butene copolymer (supplier: Jiangsu Loujiang New Materials Co., Ltd.).

[0055] Example 2

[0056] A modified POE, the preparation of which includes the following steps:

[0057] Step A1: Mix 1,5-divinylhexamethyltrisiloxane and toluene and stir for 23 min, add m-chloroperoxybenzoic acid, heat to 75℃, and stir for 8.3 h to obtain product a1; mix 2-methyl-2-azaspirocyclic[3.3]heptane-6-carboxylic acid, toluene, and DMF in a nitrogen atmosphere and stir for 35 min, heat to 60℃, add product a1 and 4-dimethylaminopyridine while stirring, stir for 6.3 h, then heat to 103℃ and stir for 1.8 h to obtain product a2; the ratio of 1,5-divinylhexamethyltrisiloxane, toluene, and m-chloroperoxybenzoic acid is 29 g: 120 mL: 26 g; the ratio of 2-methyl-2-azaspirocyclic[3.3]heptane-6-carboxylic acid, toluene, DMF, product a1, and 4-dimethylaminopyridine is 19 g: 80 mL: 45 mL: 32 g: 3.0 g;

[0058] Step A2: Mix 3-nitro-4-vinylbenzoic acid and DMAC and stir for 18 min. Place the mixture in an ice-water bath and add oxaloyl chloride dropwise. After the addition is complete, heat to 60℃ and stir for 1.8 h to obtain product a3. Add product a2, potassium carbonate, and pyridine to DMSO and stir for 35 min. Add the solution of product a3 dropwise in an ice-water bath, then heat to 53℃ and stir for 8.8 h to obtain product a4. The molar ratio of 3-nitro-4-vinylbenzoic acid, DMAC, and oxaloyl chloride is 24 g: 95 mL: 20 g. The molar ratio of product a2, potassium carbonate, pyridine, DMSO, and the solution of product a3 is 36 g: 15.0 g: 0.3 g: 105 mL: 90 mL. The solution of product a3 is obtained by adding 27 g of product a3 to 60 mL of DMAC and stirring.

[0059] Step A3: Mix product a4, toluene, and ethyl acetate and stir for 20 min. Add sodium hydrosulfite and sodium bicarbonate, heat to 75℃, and reflux for 6.8 h to obtain product a5. Mix product a5, triphosgene, toluene, and cyclohexane, purge with nitrogen, stir and heat to 105℃, and reflux for 4.8 h to obtain product a6. The ratio of product a4, toluene, ethyl acetate, sodium hydrosulfite, and sodium bicarbonate is 55 g: 95 mL: 75 mL: 28 g: 1.0 g; the ratio of product a5, triphosgene, toluene, and cyclohexane is 52 g: 46 g: 115 mL: 95 mL.

[0060] Step A4: Mix POE and toluene and stir for 45 min. Add product a6, ethyl acetate, and initiator, and continue stirring for 35 min. Reflux and stir at 130℃ for 6.8 h to obtain modified POE. The ratio of POE, toluene, product a6, ethyl acetate, and initiator is 105 g: 215 mL: 11.0 g: 30 mL: 0.70 g. The initiator is a mixture of benzoyl peroxide and azobisisobutyronitrile in a mass ratio of 1.8:1.3. POE is an ethylene-1-butene copolymer (supplier: Jiangsu Loujiang New Materials Co., Ltd.).

[0061] Example 3

[0062] A modified POE, the preparation of which includes the following steps:

[0063] Step A1: Mix 1,5-divinylhexamethyltrisiloxane and toluene and stir for 25 min, add m-chloroperoxybenzoic acid, heat to 80℃, and stir for 8.5 h to obtain product a1; Mix 2-methyl-2-azaspirocyclic[3.3]heptane-6-carboxylic acid, toluene, and DMF in a nitrogen atmosphere and stir for 40 min, heat to 65℃, add product a1 and 4-dimethylaminopyridine while stirring, stir for 6.5 h, then heat to 105℃ and stir for 2 h to obtain product a2; The ratio of 1,5-divinylhexamethyltrisiloxane, toluene, and m-chloroperoxybenzoic acid is 30 g: 125 mL: 27 g; The ratio of 2-methyl-2-azaspirocyclic[3.3]heptane-6-carboxylic acid, toluene, DMF, product a1, and 4-dimethylaminopyridine is 20 g: 85 mL: 50 mL: 33 g: 3.2 g;

[0064] Step A2: Mix 3-nitro-4-vinylbenzoic acid and DMAC and stir for 20 min. Place the mixture in an ice-water bath and add oxaloyl chloride dropwise. After the addition is complete, heat to 65℃ and stir for 2 h to obtain product a3. Add product a2, potassium carbonate, and pyridine to DMSO and stir for 40 min. Add the solution of product a3 dropwise in an ice-water bath, then heat to 55℃ and stir for 9 h to obtain product a4. The ratio of 3-nitro-4-vinylbenzoic acid, DMAC, and oxaloyl chloride is 25 g: 100 mL: 21 g. The ratio of the solution of product a2, potassium carbonate, pyridine, DMSO, and product a3 is 37 g: 15.5 g: 0.4 g: 110 mL: 95 mL. The solution of product a3 is obtained by adding 28 g of product a3 to 65 mL of DMAC and stirring.

[0065] Step A3: Mix product a4, toluene, and ethyl acetate and stir for 25 min. Add sodium hydrosulfite and sodium bicarbonate, heat to 80℃, and reflux for 7 h to obtain product a5. Mix product a5, triphosgene, toluene, and cyclohexane, purge with nitrogen, stir and heat to 110℃, and reflux for 5 h to obtain product a6. The ratio of product a4, toluene, ethyl acetate, sodium hydrosulfite, and sodium bicarbonate is 56 g: 100 mL: 80 mL: 29 g: 1.1 g; the ratio of product a5, triphosgene, toluene, and cyclohexane is 53 g: 47 g: 120 mL: 100 mL.

[0066] Step A4: Mix POE and toluene and stir for 50 min. Add product a6, ethyl acetate, and initiator, and continue stirring for 40 min. Reflux and stir at 135℃ for 7 h to obtain modified POE. The ratio of POE, toluene, product a6, ethyl acetate, and initiator is 110 g: 220 mL: 11.5 g: 35 mL: 0.75 g. The initiator is a mixture of benzoyl peroxide and azobisisobutyronitrile in a mass ratio of 2:1.5. POE is an ethylene-1-butene copolymer (supplier: Jiangsu Loujiang New Materials Co., Ltd.).

[0067] Example 4

[0068] A modified resin prepolymer, the preparation of which includes the following steps:

[0069] Step B1: Mix 5-nitrosalicylic acid, hydroxylamine-O-sulfonic acid, and acetic acid and stir for 10 min. Add deionized water and reflux at 50 °C for 24 h. Post-treatment yields product b1. Under a nitrogen atmosphere, mix product b1, toluene, and acetonitrile and stir for 35 min. Heat to 40 °C, add sodium bisulfite and sodium carbonate, and stir to react, yielding product b2. The ratio of 5-nitrosalicylic acid, hydroxylamine-O-sulfonic acid, acetic acid, and deionized water is 18 g: 14 g: 6.5 g: 500 mL. Post-treatment involves adding a 10% sodium bicarbonate solution to the refluxed reaction solution until no bubbles are generated, followed by chloroform extraction. The resulting organic phase is then rotary evaporated and washed with ether. The ratio of product b1, toluene, acetonitrile, sodium bisulfite, and sodium carbonate is 21 g: 60 mL: 40 mL: 16 g: 1.5 g.

[0070] Step B2: Under a nitrogen atmosphere, ethyl 2,4-ditrifluoromethyl-5-pyrimidinecarboxylate and DMF were mixed and stirred for 35 min. Product b2 and ammonium chloride were added at 80 °C, and the mixture was stirred and reacted for 8 h. The pH was adjusted to neutral to obtain product b3. The ratio of ethyl 2,4-ditrifluoromethyl-5-pyrimidinecarboxylate, DMF, product b2, and ammonium chloride was 33 g: 110 mL: 18 g: 1 g.

[0071] Step B3: Mix product b3, paraformaldehyde, and 2-furfurylamine, heat to 100℃ and stir for 4.5 h, then heat to 125℃ and continue stirring for 1 h, cool to room temperature, wash with ethyl acetate to obtain the modified resin prepolymer; the ratio of product b3, paraformaldehyde, and 2-furfurylamine is 53 g: 6.5 g: 11 g.

[0072] Example 5

[0073] A modified resin prepolymer, the preparation of which includes the following steps:

[0074] Step B1: Mix 5-nitrosalicylic acid, hydroxylamine-O-sulfonic acid, and acetic acid and stir for 13 min. Add deionized water and reflux at 55 °C for 24.5 h. Post-treatment yields product b1. Under a nitrogen atmosphere, mix product b1, toluene, and acetonitrile and stir for 40 min. Heat to 43 °C, add sodium bisulfite and sodium carbonate, and stir to react, yielding product b2. The ratio of 5-nitrosalicylic acid, hydroxylamine-O-sulfonic acid, acetic acid, and deionized water is 19 g: 15 g: 6.8 g: 510 mL. Post-treatment involves adding a 13% sodium bicarbonate solution to the refluxed reaction solution until no more bubbles are generated, followed by chloroform extraction. The resulting organic phase is then rotary evaporated and washed with diethyl ether. The ratio of product b1, toluene, acetonitrile, sodium bisulfite, and sodium carbonate is 22 g: 65 mL: 45 mL: 17 g: 2.0 g.

[0075] Step B2: Under a nitrogen atmosphere, ethyl 2,4-ditrifluoromethyl-5-pyrimidinecarboxylate and DMF were mixed and stirred for 40 min. Product b2 and ammonium chloride were added at 83 °C, and the mixture was stirred for 8.3 h. The pH was adjusted to neutral to obtain product b3. The ratio of ethyl 2,4-ditrifluoromethyl-5-pyrimidinecarboxylate, DMF, product b2, and ammonium chloride was 34 g: 115 mL: 19 g: 2 g.

[0076] Step B3: Mix product b3, paraformaldehyde, and 2-furfurylamine, heat to 103℃ and stir for 4.8 h, then heat to 130℃ and continue stirring for 1.3 h, cool to room temperature, wash with ethyl acetate to obtain the modified resin prepolymer; the ratio of product b3, paraformaldehyde, and 2-furfurylamine is 54 g: 7.0 g: 12 g.

[0077] Example 6

[0078] A modified resin prepolymer, the preparation of which includes the following steps:

[0079] Step B1: Mix 5-nitrosalicylic acid, hydroxylamine-O-sulfonic acid, and acetic acid and stir for 15 min. Add deionized water and reflux at 60 °C for 25 h. Post-treatment yields product b1. Under a nitrogen atmosphere, mix product b1, toluene, and acetonitrile and stir for 45 min. Heat to 45 °C, add sodium bisulfite and sodium carbonate, and stir to react, yielding product b2. The ratio of 5-nitrosalicylic acid, hydroxylamine-O-sulfonic acid, acetic acid, and deionized water is 20 g: 16 g: 7 g: 520 mL. Post-treatment involves adding a 15% sodium bicarbonate solution to the refluxed reaction solution until no bubbles are generated, followed by chloroform extraction. The resulting organic phase is then rotary evaporated and washed with ether. The ratio of product b1, toluene, acetonitrile, sodium bisulfite, and sodium carbonate is 23 g: 70 mL: 50 mL: 18 g: 2.5 g.

[0080] Step B2: Under a nitrogen atmosphere, ethyl 2,4-ditrifluoromethyl-5-pyrimidinecarboxylate and DMF were mixed and stirred for 45 min. Product b2 and ammonium chloride were added at 85 °C, and the mixture was stirred and reacted for 8.5 h. The pH was adjusted to neutral to obtain product b3. The ratio of ethyl 2,4-ditrifluoromethyl-5-pyrimidinecarboxylate, DMF, product b2, and ammonium chloride was 35 g: 120 mL: 20 g: 3 g.

[0081] Step B3: Mix product b3, paraformaldehyde, and 2-furfurylamine, heat to 105℃ and stir for 5 hours, then heat to 135℃ and continue stirring for 1.5 hours. Cool to room temperature and wash with ethyl acetate to obtain the modified resin prepolymer. The ratio of product b3, paraformaldehyde, and 2-furfurylamine is 55g:7.5g:13g.

[0082] Example 7

[0083] A rapid thermally conductive coated sand comprises the following raw materials in parts by weight: 100 parts raw sand, 6 parts modified resin prepolymer, 2 parts modified POE, 3.5 parts lubricant, and 3 parts nano-silicon nitride; the raw sand is obtained by mixing quartz sand and ceramsite sand in a mass ratio of 1:0.5, and both quartz sand and ceramsite sand have a particle size of 50 mesh; the lubricant is obtained by mixing zinc stearate and calcium stearate in a mass ratio of 1:1.5.

[0084] The preparation of the rapid thermally conductive coated sand includes the following steps:

[0085] The raw sand was dried at 100°C for 3 hours to obtain dried raw sand for later use. The modified resin prepolymer obtained in Example 4 and the modified POE obtained in Example 1 were stirred and mixed at 90°C and 1000 rpm for 0.5 hours. Nano silicon nitride was added, and stirring was continued for 20 minutes. The temperature was lowered to 60°C, the raw sand and half of the lubricant were added, and mixing was continued for 25 minutes. The speed was reduced to 500 rpm, the temperature was raised to 155°C, and stirring was carried out for 4 hours. The remaining lubricant was added, and mixing was continued for 10 minutes. The mixture was cooled and passed through a 90-mesh sieve to obtain rapidly thermally conductive coated sand.

[0086] Example 8

[0087] A rapid thermally conductive coated sand comprises the following raw materials in parts by weight: 103 parts raw sand, 7 parts modified resin prepolymer, 3 parts modified POE, 4.0 parts lubricant, and 4 parts nano-silicon nitride; the raw sand is obtained by mixing quartz sand and ceramsite sand in a mass ratio of 1.3:0.8, and the particle size of both quartz sand and ceramsite sand is 60 mesh; the lubricant is obtained by mixing zinc stearate and calcium stearate in a mass ratio of 1:1.8.

[0088] The preparation of the rapid thermally conductive coated sand includes the following steps:

[0089] The raw sand was dried at 105°C for 3.5 hours to obtain dried raw sand for later use. The modified resin prepolymer obtained in Example 5 and the modified POE obtained in Example 2 were stirred and mixed at 95°C and 1100 rpm for 0.8 hours. Nano-silicon nitride was added, and stirring was continued for 25 minutes. The temperature was lowered to 70°C, the raw sand and half of the lubricant were added, and mixing was continued for 30 minutes. The speed was reduced to 550 rpm, the temperature was raised to 160°C, and stirring was carried out for 4.3 hours. The remaining lubricant was added, and mixing was continued for 13 minutes. The mixture was cooled and passed through a 100-mesh sieve to obtain rapidly thermally conductive coated sand.

[0090] Example 9

[0091] A rapid thermally conductive coated sand comprises the following raw materials in parts by weight: 105 parts raw sand, 8 parts modified resin prepolymer, 4 parts modified POE, 4.5 parts lubricant, and 5 parts nano-silicon nitride; the raw sand is obtained by mixing quartz sand and ceramsite sand in a mass ratio of 1.5:1, and the particle size of both quartz sand and ceramsite sand is 70 mesh; the lubricant is obtained by mixing zinc stearate and calcium stearate in a mass ratio of 1:2.

[0092] The preparation of the rapid thermally conductive coated sand includes the following steps:

[0093] The raw sand was dried at 110°C for 4 hours to obtain dried raw sand for later use. The modified resin prepolymer obtained in Example 6 and the modified POE obtained in Example 3 were stirred and mixed at 100°C and 1200 rpm for 1 hour. Nano-silicon nitride was added, and stirring was continued for 30 minutes. The temperature was lowered to 80°C, the raw sand and half of the lubricant were added, and mixing was continued for 35 minutes. The speed was reduced to 600 rpm, the temperature was raised to 165°C, and stirring was carried out for 4.5 hours. The remaining lubricant was added, and mixing was continued for 15 minutes. The mixture was cooled and passed through a 110-mesh sieve to obtain rapidly thermally conductive coated sand.

[0094] Comparative Example 1

[0095] Compared with Example 9, the 2-methyl-2-azaspirocyclic[3.3]heptane-6-carboxylic acid in the modified POE preparation process was replaced with 3-succinimide propionic acid, and the rest was exactly the same as in Example 9, to obtain a fast thermally conductive coated sand.

[0096] Comparative Example 2

[0097] Compared with Example 9, the 1,5-divinylhexamethyltrisiloxane in the modified POE preparation process was replaced with ethylene glycol diethylene ether, and the rest was exactly the same as in Example 9, to obtain a fast thermally conductive coated sand.

[0098] Comparative Example 3

[0099] Compared with Example 9, product a6 grafted with POE during the preparation of modified POE was replaced with product a5, and the rest was exactly the same as in Example 9, to obtain fast thermally conductive coated sand.

[0100] Comparative Example 4

[0101] Compared with Example 9, the ethyl 2,4-ditrifluoromethyl-5-pyrimidinecarboxylate in the modified resin prepolymer preparation process was replaced with methyl 2-cyanopyrimidine-5-carboxylate, and the rest was exactly the same as in Example 9, to obtain a fast thermally conductive coated sand.

[0102] Example 5

[0103] Compared with Example 9, ethyl 2,4-ditrifluoromethyl-5-pyrimidinecarboxylate in the preparation process of modified resin prepolymer was replaced with methyl 4-(trifluoromethyl)benzoate, and the rest was exactly the same as in Example 9, to obtain rapid thermally conductive coated sand.

[0104] The following is a further performance test of the rapid thermally conductive coated sand prepared according to the present invention, and the test results are as follows.

[0105] Hot tensile strength and hot flexural strength: The obtained rapid thermal conductivity coated sand was tested according to JB / T 8583-2008;

[0106] High temperature resistance time: The obtained rapid thermal conductivity coated sand was tested according to T / CFA 010604.1;

[0107] The results are recorded in Table 1;

[0108] Table 1: Test Results

[0109]

[0110] According to the data in Table 1, the rapid thermally conductive coated sand of the present invention has strong mechanical strength and high temperature resistance. Comparing Example 9 with Comparative Example 1, it can be seen that replacing 2-methyl-2-azaspirocyclic[3.3]heptane-6-carboxylic acid in the modified POE preparation process with 3-succinimide propionic acid reduces the heat resistance of the modified POE and decreases its high-temperature toughening effect on the modified resin prepolymer, resulting in a decrease in both the hot tensile strength and hot flexural strength of the coated sand, and a reduction in the high-temperature resistance time of the coated sand. Comparing Example 9 with Comparative Example 2, it can be seen that replacing 1,5-divinylhexamethyltrisiloxane in the modified POE preparation process with ethylene glycol divinyl ether reduces the heat resistance of the modified POE and decreases its high-temperature toughening effect on the modified resin prepolymer, resulting in a decrease in both the hot tensile strength and hot flexural strength of the coated sand, and a reduction in the high-temperature resistance time of the coated sand. Comparing Example 9 with Comparative Example 3, it can be seen that replacing product a6, which is grafted onto POE during the preparation of modified POE, with product a5 weakens the compatibility between modified POE and modified resin prepolymers, resulting in a decrease in the hot tensile strength, hot flexural strength, and high-temperature resistance time of the coated sand. Comparing Example 9 with Comparative Example 4, it can be seen that replacing ethyl 2,4-ditrifluoromethyl-5-pyrimidinecarboxylate in the preparation of modified resin prepolymer with methyl 2-cyanopyrimidine-5-carboxylate reduces the catalytic ring-opening effect, decreases the high-temperature resistance of the modified resin prepolymer, and significantly reduces the hot tensile strength, room temperature tensile strength, hot flexural strength, and high-temperature resistance time of the coated sand. Comparing Example 9 with Comparative Example 5, it can be seen that replacing ethyl 2,4-ditrifluoromethyl-5-pyrimidinecarboxylate in the preparation process of the modified resin prepolymer with methyl 4-(trifluoromethyl)benzoate reduces the catalytic ring-opening effect, decreases the high-temperature resistance of the modified resin prepolymer, and significantly reduces the hot tensile strength, room temperature tensile strength, hot flexural strength, and high-temperature resistance time of the coated sand.

[0111] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A rapid thermally conductive coated sand, characterized in that: The raw materials include the following parts by weight: 100-105 parts raw sand, 6-8 parts modified resin prepolymer, 2-4 parts modified POE, 3.5-4.5 parts lubricant, and 3-5 parts nano-silicon nitride; the modified POE is prepared by the following steps: Step A1, vinylsiloxane and toluene are mixed and stirred, then m-chloroperoxybenzoic acid is added, and the mixture is heated and stirred to obtain product a1; azirospirocarboxylic acid, toluene, and DMF are mixed and stirred in a protective gas atmosphere, then heated, and product a1 and 4-dimethylaminopyridine are added while stirring, and the mixture is heated again to obtain product a2; Step A2, vinylbenzoic acid and DMAC are mixed and stirred, then placed in an ice-water bath, and oxaloyl chloride is added dropwise. After the addition is complete, the mixture is heated and stirred to obtain product a2. Product a3; After adding product a2, potassium carbonate, and pyridine to DMSO and stirring, a solution of product a3 is added dropwise under an ice-water bath, and then heated and stirred to obtain product a4; Step A3: After mixing and stirring product a4, toluene, and ethyl acetate, sodium hydrosulfite and sodium bicarbonate are added, and the mixture is heated and refluxed to obtain product a5; Product a5, triphosgene, toluene, and cyclohexane are mixed, a protective gas is introduced, and the mixture is stirred, heated, and refluxed to obtain product a6; Step A4: After mixing and stirring POE and toluene, product a6, ethyl acetate, and an initiator are added, and the mixture is stirred and heated and refluxed to obtain modified POE.

2. The rapid thermally conductive coated sand according to claim 1, characterized in that: The raw sand is obtained by mixing quartz sand and ceramsite sand in a mass ratio of 1-1.5:0.5-1, and the particle size of both quartz sand and ceramsite sand is 50-70 mesh; the lubricant is obtained by mixing zinc stearate and calcium stearate in a mass ratio of 1:1.5-2.

3. The rapid thermally conductive coated sand according to claim 1, characterized in that: In step A1, the vinylsiloxane is 1,5-divinylhexamethyltrisiloxane; the azirocyclocarboxylic acid is 2-methyl-2-azirocyclo[3.3]heptane-6-carboxylic acid.

4. The rapid thermally conductive coated sand according to claim 1, characterized in that: In step A2, vinylbenzoic acid is 3-nitro-4-vinylbenzoic acid.

5. The rapid thermally conductive coated sand according to claim 1, characterized in that: In step A2, the solution of product a3 is obtained by adding 26-28g of product a3 to 55-65mL of DMAC and stirring to mix.

6. The rapid thermally conductive coated sand according to claim 1, characterized in that: The modified resin prepolymer is prepared by the following steps: Step B1, after mixing and stirring salicylaldehyde, hydroxylamine-O-sulfonic acid, and acetic acid, deionized water is added, and the mixture is heated under reflux and stirred to obtain product b1; under a protective gas atmosphere, product b1, toluene, and acetonitrile are mixed and stirred, and then heated to obtain product b2 by adding sodium bisulfite and sodium carbonate; Step B2, under a protective gas atmosphere, pyrimidine carbamate and DMF are mixed and stirred, and then product b2 and ammonium chloride are added to the mixture by heating and stirring. After the reaction is carried out, the pH is adjusted to obtain product b3. Step B3: Mix product b3, paraformaldehyde, and 2-furfuralamine, heat and stir to react, then heat and continue stirring, cool to room temperature, wash with ethyl acetate to obtain the modified resin prepolymer.

7. The rapid thermally conductive coated sand according to claim 6, characterized in that: In step B1, salicylaldehyde is 5-nitrosalicylic aldehyde.

8. The rapid thermally conductive coated sand according to claim 6, characterized in that: In step B2, the pyrimidine carbamate is ethyl 2,4-ditrifluoromethyl-5-pyrimidine carbamate; after the reaction, the pH is adjusted to neutral.

9. A method for preparing the rapid thermally conductive coated sand according to any one of claims 1-8, characterized in that: The process includes the following steps: drying the raw sand to obtain dry raw sand for later use; heating and stirring the modified resin prepolymer and modified POE together, adding nano-silicon nitride, continuing to stir, cooling down and adding the raw sand and half of the lubricant, continuing to mix, reducing the rotation speed and then heating up to solidify, adding the remaining lubricant, continuing to mix, cooling, and sieving to obtain fast thermally conductive coated sand.

10. The method for preparing a rapid thermally conductive coated sand according to claim 9, characterized in that: The curing temperature is 155-165℃.

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