Modified methyl silicone resin and preparation method thereof

Abstract

The invention discloses modified methyl silicone resin and a preparation method thereof, and belongs to the technical field of silicone resin, nano silicon dioxide is deposited on the surface of ferroferric oxide to obtain composite microspheres, and the thermal stability of the modified methyl silicone resin is improved by using the composite microspheres wrapped by amorphous carbon generated by pyrolysis and carbonization of glucose; hydroxyl on the surface of polycaprolactone is bonded with carboxyl on the surface of the carbon-coated composite microsphere, agglomeration of the carbon-coated composite microsphere is avoided, gamma-glycidyl ether oxypropyl trimethoxy silane is used for modification treatment, the surface of the carbon-coated composite microsphere is provided with an epoxy group, and the epoxy group and a methyl silicone resin monomer are used for copolymerization modification, so that the carbon-coated composite microsphere is prepared. The polycaprolactone is decomposed into carbon dioxide in the curing process, so that the porosity of the material is improved, the crack propagation is delayed, the toughness of the material is improved, and the cracking caused by insufficient toughness when the material is used as insulating paint is avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of silicone resins, and particularly relates to a modified methyl silicone resin and a preparation method thereof. Background Art

[0002] Silicone resins are thermosetting polysiloxane systems with a highly cross-linked structure, usually prepared by hydrolysis condensation and thickening rearrangement of organochlorosilanes or alkoxysilanes. Currently, there are mainly several types such as methyl silicone resins, phenyl silicone resins, and methylphenyl silicone resins. Methyl silicone resins have advantages such as high hardness and good wear resistance, but they have poor thermal elasticity and compatibility; for the current general-purpose methylphenyl silicone resins of existing brands at home and abroad, their curing temperature needs to be greater than 200°C. Currently, there are also silicone resins with low-temperature curing characteristics, mainly relying on adding cross-linking agents, catalysts and other components to strengthen the curing reaction, and the result is that the heat resistance of the cured silicone resin decreases.

[0003] Chinese Patent Publication No. CN101508776B discloses a preparation method of methylphenyl silicone resin. The methylphenyl silicone resin prepared by this method has characteristics such as low curing temperature, non-sticking back, clarity and transparency, resistance to high and low temperatures, weather resistance, and insulation. It is particularly suitable for impregnating varnishes above H grade, for formulating insulating varnishes, weather-resistant varnishes, and high-temperature resistant varnishes above H grade, and for high-temperature resistant release agents. However, in this scheme, the cross-linking density of the methyl silicone resin after curing at low temperature is usually low, and the strength is insufficient when used as a paint, and the paint film is prone to cracking. Summary of the Invention

[0004] The purpose of the present invention is to provide a modified methyl silicone resin and a preparation method thereof. By depositing nano-silica on the surface of iron tetroxide to obtain composite microspheres, and using amorphous carbon wrapped composite microspheres generated by the pyrolytic carbonization of glucose to increase the thermal stability of the modified methyl silicone resin, the hydroxyl groups on the surface of polycaprolactone are bonded to the carboxyl groups on the surface of the carbon-coated composite microspheres to avoid the aggregation of the carbon-coated composite microspheres. Then, through the modification treatment with γ-glycidoxypropyltrimethoxysilane, epoxy groups are introduced on its surface, and the epoxy groups and methyl silicone resin monomers are copolymerized and modified. And by the decomposition of polycaprolactone into carbon dioxide during the curing process, the porosity of the material is increased, thereby delaying the crack propagation and improving the toughness of the material, and avoiding cracking caused by insufficient toughness when used as an insulating paint.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A preparation method of a modified methyl silicone resin is prepared by the following steps:

[0007] Step 1: Modify the polycaprolactone-modified composite microspheres with γ-glycidoxypropyltrimethoxysilane and retain the epoxy groups to obtain modified composite microspheres; Add diphenyldichlorosilane, phenyltrichlorosilane, dimethyldichlorosilane, methyltrichlorosilane, toluene and deionized water into the reaction kettle, stir at 40-45 °C and 500-600 r / min for 1-2 h, let it stand for stratification, remove the lower acidic water layer, continue to stir for 30-60 min, and concentrate under reduced pressure to obtain a prepolymer with a solid content of 12-15%.

[0008] Step 2: Add the prepolymer, modified composite microspheres and tetraethylammonium hydroxide butanol solution with a mass fraction of 10-12% as a catalyst into the reaction kettle, stir and react at 60-70 °C and 500-600 r / min for 1-2 h, then add acetic anhydride as a stabilizer, heat to 200-220 °C for curing for 1-1.2 h, and cool naturally to obtain a modified methyl silicone resin.

[0009] Furthermore, the dosage ratio of diphenyldichlorosilane, phenyltrichlorosilane, dimethyldichlorosilane, methyltrichlorosilane, toluene and deionized water in Step 1 is 30-40 mL: 32-35 mL: 35-38 mL: 28-35 mL: 100-120 mL: 120-140 mL.

[0010] Furthermore, the dosage ratio of the prepolymer, modified composite microspheres, tetraethylammonium hydroxide butanol solution and acetic anhydride in Step 2 is 150-180 mL: 38-40 mL: 0.5-0.8 mL: 0.12-0.2 mL.

[0011] Furthermore, the modified composite microspheres in Step 1 are specifically prepared by the following steps:

[0012] Add the polycaprolactone-modified composite microspheres, γ-glycidoxypropyltrimethoxysilane, absolute ethanol and deionized water into the reaction kettle, stir at 20-25 °C and 500-600 r / min for 1-2 h, filter, wash the filter cake with deionized water and absolute ethanol respectively for 2-3 times, and dry in vacuum at 60-80 °C for 1-2 h to obtain modified composite microspheres.

[0013] Furthermore, the dosage ratio of the polycaprolactone-modified composite microspheres, γ-glycidoxypropyltrimethoxysilane, absolute ethanol and deionized water is 40-45 g: 50-60 mL: 120-140 mL: 180-200 mL.

[0014] Furthermore, the polycaprolactone-modified composite microspheres are prepared by the following steps:

[0015] ε-Caprolactone and stannous octoate as a catalyst were heated in an oil bath to 95 - 100 °C and reacted for 2 - 3 h under the condition of 500 - 600 r / min. Then, carbon-coated composite microspheres were added and stirring was continued for 1 - 2 h. Sodium dodecylbenzenesulfonate and polyethylene glycol with a molecular weight of 500 were added to the reaction kettle and stirring was continued for 3 - 4 h. Centrifugation was carried out at 3000 - 3500 r / min for 5 - 6 min, and the supernatant was discarded. The product was washed 2 - 3 times with deionized water and anhydrous ethanol respectively, and vacuum dried at 60 - 80 °C for 1 - 2 h to obtain polycaprolactone-modified composite microspheres.

[0016] Furthermore, the dosage ratio of ε-caprolactone, stannous octoate, carbon-coated composite microspheres, sodium dodecylbenzenesulfonate and polyethylene glycol is 80 - 90 mL : 0.2 - 0.4 g : 50 - 60 g : 1 - 2 g : 2 - 4 mL.

[0017] Furthermore, the carbon-coated composite microspheres were prepared by the following steps:

[0018] The composite microspheres, glucose, acrylic acid and deionized water were added to the reaction kettle, ultrasonically dispersed for 30 - 40 min, heated to 170 - 180 °C and stirred for 6 - 7 h under the condition of 500 - 600 r / min, cooled naturally, filtered, and the filter cake was washed 2 - 3 times with deionized water and anhydrous ethanol respectively, and vacuum dried at 60 - 80 °C for 1 - 2 h to obtain carbon-coated composite microspheres.

[0019] Furthermore, the dosage ratio of the composite microspheres, glucose, acrylic acid and deionized water is 50 - 60 g : 70 - 80 g : 80 - 90 mL : 500 - 600 mL.

[0020] Furthermore, the composite microspheres were prepared by the following steps:

[0021] Ferric chloride hexahydrate and deionized water were added to the reaction kettle and stirred for 20 - 30 min under the condition of 20 - 25 °C and 500 - 600 r / min. Under a nitrogen atmosphere, ferrous sulfate tetrahydrate and an ammonia water solution with a mass fraction of 20 - 30% were added, and stirring was continued for 1.5 - 2 h. Then, tetraethyl orthosilicate and anhydrous ethanol were added and stirred for 12 - 14 h under the condition of 40 - 45 °C and 500 - 600 r / min. Filtration was carried out, and the filter cake was washed 2 - 3 times with deionized water and anhydrous ethanol respectively, and vacuum dried at 60 - 80 °C for 1 - 2 h. It was transferred to a muffle furnace and calcined at 750 - 800 °C for 12 - 14 h under a nitrogen atmosphere, and cooled naturally to obtain composite microspheres.

[0022] Further, the dosage ratio of ferric chloride hexahydrate, deionized water, ferrous sulfate tetrahydrate, ammonia water solution, tetraethyl orthosilicate and absolute ethanol is 80-90 g: 300-400 mL: 40-60 g: 200-300 mL: 40-50 mL: 120-180 mL.

[0023] Advantages of the present invention:

[0024] 1. The modified methyl silicone resin prepared by the present invention obtains composite microspheres by depositing nano-silica on the surface of iron tetroxide, and uses amorphous carbon wrapped composite microspheres generated by pyrolytic carbonization of glucose. The hydroxyl groups on the surface of polycaprolactone are bonded to the carboxyl groups on the surface of the carbon-coated composite microspheres, and then modified by γ-glycidyletheroxypropyltrimethoxysilane. When applied in insulating paint, it has good heat resistance, hardness, toughness, adhesion and heat insulation.

[0025] 2. The modified composite microspheres of the present invention are obtained by modifying composite microspheres with polycaprolactone and then modifying them with γ-glycidyletheroxypropyltrimethoxysilane, so that the surface of the polycaprolactone-modified composite microspheres is provided with epoxy groups, and the epoxy groups are used to copolymerize and modify methyl silicone resin, which can improve the hardness, tensile strength and wear resistance of methyl silicone resin, and make up for the deficiency of the mechanical properties of methyl silicone resin; the polycaprolactone-modified composite microspheres of the present invention are modified by polycaprolactone on the carbon-coated composite microspheres. Polycaprolactone is a polymer material with rich groups on its surface, which can avoid the aggregation of composite microspheres, thereby improving the uniform dispersion in the methyl silicone resin matrix; and polycaprolactone will decompose into carbon dioxide during the curing process, which can reverse the decrease of porosity to a certain extent, thereby increasing the porosity of the material. Porosity can absorb energy through pore collapse and local plastic deformation around pores, delay crack propagation, and improve heat insulation and toughness.

[0026] 3. For the carbon-coated composite microspheres of the present invention, silica is deposited on the surface of iron tetroxide. Using silica as a transition layer, the surface of silica is rich in hydroxyl groups, which can form hydrogen bonds with the carbon precursor of glucose, promote the uniform adsorption of carbon sources, and avoid the aggregation of carbon layers. The silica layer acts as an inert barrier, which can disperse stress synergistically with the carbon layer, improve the strength and toughness of methyl silicone resin after curing. This synergistic effect can also effectively prevent iron tetroxide from being oxidized and extend the service life of methyl silicone resin as insulating paint. Specific embodiments

[0027] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0028] Embodiment 1: A preparation method of a modified methyl silicone resin is prepared through the following steps:

[0029] S1: Add 80 g of ferric chloride hexahydrate and 300 mL of deionized water into a reaction kettle, stir for 20 min under the conditions of 20 °C and 500 r / min. Under a nitrogen atmosphere, add 40 g of ferrous sulfate tetrahydrate and 200 mL of ammonia water with a mass fraction of 20%, continue to stir for 1.5 h, then add 40 mL of tetraethyl orthosilicate and 120 mL of absolute ethanol, stir for 12 h under the conditions of 40 °C and 500 r / min, filter, wash the filter cake with deionized water and absolute ethanol twice respectively, dry in vacuum at 60 °C for 1 h, transfer to a muffle furnace, and calcine at 750 °C for 12 h under a nitrogen atmosphere, and cool naturally to obtain composite microspheres.

[0030] Coating a layer of silica on the surface of the magnetite microspheres by the coprecipitation method can improve the adhesion, prevent the magnetite from being oxidized, increase the thermal stability of the material. The coating layer can reduce the thermal conductivity of the material, delay the heat transfer, and improve the heat resistance at the same time; the surface of silica is rich in hydroxyl groups, which can form hydrogen bonds with the carbon precursor of glucose, promote the uniform adsorption of the carbon source, and avoid the aggregation of the carbon layer.

[0031] S2: Add 50 g of composite microspheres, 70 g of glucose, 80 mL of acrylic acid and 500 mL of deionized water into a reaction kettle, ultrasonically disperse for 30 min, heat to 170 °C and stir at 500 r / min for 6 h, cool naturally, filter, wash the filter cake with deionized water and absolute ethanol twice respectively, dry in vacuum at 60 °C for 1 h to obtain carbon-coated composite microspheres.

[0032] During the synthesis of magnetite, due to hydroxylation, the surface has incompletely shed hydroxyl groups. The nitric acid solution can remove the impurities on the surface of the magnetite and expose the original hydroxyl groups. Glucose is carbonized at high temperature to form an amorphous carbon layer, which tightly wraps the composite microspheres and isolates oxygen to prevent oxidation. The carbon-carbon double bond (C=C) of acrylic acid undergoes an addition reaction with the free radicals generated by the pyrolysis of glucose under high-temperature hydrothermal conditions, and fixes the carboxyl group on the surface of the microspheres. On the one hand, the carbon layer generated by glucose can prevent the magnetite from being oxidized, and on the other hand, the carbon layer can further improve the hardness of the modified methyl silicone resin as an insulating paint.

[0033] S3: Heat 80 mL of ε-caprolactone and 0.2 g of stannous octoate catalyst in an oil bath to 95 °C, react for 2 h under the condition of 500 r / min, then add 50 g of carbon-coated composite microspheres, continue stirring for 1 h, add 1 g of sodium dodecylbenzenesulfonate and 2 mL of polyethylene glycol with a molecular weight of 500 to the reaction kettle, continue stirring for 3 h, centrifuge at 3000 r / min for 5 min, discard the supernatant, wash the product twice with deionized water and absolute ethanol respectively, and dry in vacuum at 60 °C for 1 h to obtain polycaprolactone-modified composite microspheres.

[0034] Polycaprolactone is a kind of polymer material with rich groups on its surface. Using polycaprolactone to wrap carbon-coated composite microspheres can avoid agglomeration, thereby improving the uniform dispersion in the methyl silicone resin matrix.

[0035] S4: Add 40 g of polycaprolactone-modified composite microspheres, 50 mL of γ-glycidoxypropyltrimethoxysilane, 120 mL of absolute ethanol and 180 mL of deionized water to the reaction kettle, stir at 20 °C and 500 r / min for 1 h, filter, wash the filter cake twice with deionized water and absolute ethanol respectively, and dry in vacuum at 60 °C for 1 h to obtain modified composite microspheres.

[0036] S5: Add 30 mL of diphenyldichlorosilane, 32 mL of phenyltrichlorosilane, 35 mL of dimethyldichlorosilane, 28 mL of methyltrichlorosilane, 100 mL of toluene and 120 mL of deionized water to the reaction kettle, stir at 40 °C and 500 r / min for 1 h, let it stand for layer separation, remove the lower acidic water layer, continue stirring for 30 min, concentrate under reduced pressure to obtain a prepolymer with a solid content of 12%; add 150 mL of prepolymer, 38 mL of modified composite microspheres and 0.5 mL of tetraethylammonium hydroxide butanol solution with a mass fraction of 10% as a catalyst to the reaction kettle, stir and react at 60 °C and 500 r / min for 1 h, then add 0.12 mL of acetic anhydride as a stabilizer, heat to 200 °C for curing for 1 h, and cool naturally to obtain a modified methyl silicone resin.

[0037] By copolymerizing and modifying methyl silicone resin with epoxy groups, epoxy modification can improve the hardness, tensile strength and wear resistance of methyl silicone resin, making up for the deficiency of its mechanical properties. However, the active groups on its surface gradually embed the unreacted groups of methyl silicone resin, resulting in difficulties in the growth of the molecular chain of methyl silicone resin, and the generated spherical particles become smaller and smaller. At the same time, it also makes the connection between molecules closer, and the particles gradually fill the pore part, and the density of the material gradually increases. With the increase in density, the structure becomes more compact, increasing the mechanical strength of the material, but the porosity will decrease. When the porosity decreases, the energy absorption path decreases, and stress concentration is more likely to cause brittle fracture and lead to a decrease in heat insulation ability; by wrapping carbon-coated composite microspheres with polycaprolactone, during the curing process of methyl silicone resin, the epoxy groups of γ-glycidoxypropyltrimethoxysilane grafted on its surface ring open under the action of the alkaline catalyst tetraethylammonium hydroxide butanol solution to form hydroxyl groups and copolymerize with methyl silicone resin monomers to obtain epoxy group-modified methyl silicone resin. And polycaprolactone will decompose to generate carbon dioxide during the curing process, reversing the decrease in porosity to a certain extent, thereby increasing the porosity of the material. Porosity can absorb energy through pore collapse and local plastic deformation around pores, delay crack propagation, and improve heat insulation and toughness.

[0038] Example 2: A preparation method of modified methyl silicone resin is prepared by the following steps:

[0039] S1: Add 85 g of ferric chloride hexahydrate and 350 mL of deionized water into the reaction kettle, stir at 22.5 °C and 550 r / min for 25 min. Under a nitrogen atmosphere, add 50 g of ferrous sulfate tetrahydrate and 250 mL of 25% ammonia water solution by mass, continue to stir for 1.75 h, then add 45 mL of tetraethyl orthosilicate and 150 mL of absolute ethanol, stir at 42.5 °C and 550 r / min for 13 h, filter, wash the filter cake with deionized water and absolute ethanol twice respectively, vacuum dry at 70 °C for 1.5 h, transfer to a muffle furnace, and calcine at 775 °C for 13 h under a nitrogen atmosphere, and cool naturally to obtain composite microspheres.

[0040] S2: Add 55 g of composite microspheres, 75 g of glucose, 85 mL of acrylic acid and 550 mL of deionized water into the reaction kettle, ultrasonically disperse for 35 min, heat to 175 °C and stir at 550 r / min for 6.5 h, cool naturally, filter, wash the filter cake with deionized water and absolute ethanol twice respectively, vacuum dry at 70 °C for 1.5 h to obtain carbon-coated composite microspheres.

[0041] S3: Add 85 mL of ε-caprolactone and 0.3 g of stannous octanoate as a catalyst, heat it in an oil bath to 97.5 °C, react for 2.5 h under the condition of 550 r / min, then add 55 g of carbon-coated composite microspheres, continue stirring for 1.5 h, add 1.5 g of sodium dodecylbenzenesulfonate and 3 mL of polyethylene glycol with a molecular weight of 500 into the reaction kettle, continue stirring for 3.5 h, centrifuge at 3250 r / min for 5.5 min, discard the supernatant, wash the product twice with deionized water and absolute ethanol respectively, and dry it in vacuum at 70 °C for 1.5 h to obtain polycaprolactone-modified composite microspheres.

[0042] S4: Add 42.5 g of polycaprolactone-modified composite microspheres, 55 mL of γ-glycidoxypropyltrimethoxysilane, 130 mL of absolute ethanol and 190 mL of deionized water into the reaction kettle, stir at 22.5 °C and 550 r / min for 1.5 h, filter, wash the filter cake twice with deionized water and absolute ethanol respectively, and dry it in vacuum at 70 °C for 1.5 h to obtain modified composite microspheres.

[0043] S5: Add 35 mL of diphenyldichlorosilane, 33.5 mL of phenyltrichlorosilane, 36.5 mL of dimethyldichlorosilane, 31.5 mL of methyltrichlorosilane, 110 mL of toluene and 130 mL of deionized water into the reaction kettle, stir at 42.5 °C and 550 r / min for 1.5 h, let it stand for liquid separation, remove the lower acidic water layer, continue stirring for 45 min, concentrate under reduced pressure to obtain a prepolymer with a solid content of 13.5%; add 165 mL of the prepolymer, 39 mL of modified composite microspheres and 0.65 mL of a butanol solution of tetraethylammonium hydroxide with a mass fraction of 11% as a catalyst into the reaction kettle, stir and react at 65 °C and 550 r / min for 1.5 h, then add 0.16 mL of acetic anhydride as a stabilizer, heat to 210 °C for curing for 1.1 h, and cool naturally to obtain a modified methyl silicone resin.

[0044] Example 3: A preparation method of a modified methyl silicone resin is prepared by the following steps:

[0045] S1: Add 90 g of ferric chloride hexahydrate and 400 mL of deionized water into the reaction kettle, stir at 25 °C and 600 r / min for 30 min, under a nitrogen atmosphere, add 60 g of ferrous sulfate tetrahydrate and 300 mL of an ammonia water solution with a mass fraction of 30%, continue stirring for 2 h, then add 50 mL of tetraethyl orthosilicate and 180 mL of absolute ethanol, stir at 45 °C and 600 r / min for 14 h, filter, wash the filter cake three times with deionized water and absolute ethanol respectively, dry it in vacuum at 80 °C for 2 h, transfer it to a muffle furnace, and calcine it at 800 °C for 14 h under a nitrogen atmosphere, and cool naturally to obtain composite microspheres.

[0046] S2: Add 60 g of composite microspheres, 80 g of glucose, 90 mL of acrylic acid, and 600 mL of deionized water into a reaction kettle, ultrasonically disperse for 40 min, heat to 180 °C and stir at 600 r / min for 7 h, cool naturally, filter, wash the filter cake with deionized water and absolute ethanol three times respectively, and dry in vacuum at 80 °C for 2 h to obtain carbon-coated composite microspheres.

[0047] S3: Heat 90 mL of ε-caprolactone and 0.4 g of catalyst stannous octanoate in an oil bath to 100 °C, react at 600 r / min for 3 h, then add 60 g of carbon-coated composite microspheres and continue stirring for 2 h. Add 2 g of sodium dodecylbenzenesulfonate and 4 mL of polyethylene glycol with a molecular weight of 500 into the reaction kettle, continue stirring for 4 h, centrifuge at 3500 r / min for 6 min, discard the supernatant, wash the product with deionized water and absolute ethanol three times respectively, and dry in vacuum at 80 °C for 2 h to obtain polycaprolactone-modified composite microspheres.

[0048] S4: Add 45 g of polycaprolactone-modified composite microspheres, 60 mL of γ-glycidoxypropyltrimethoxysilane, 140 mL of absolute ethanol, and 200 mL of deionized water into a reaction kettle, stir at 25 °C and 600 r / min for 2 h, filter, wash the filter cake with deionized water and absolute ethanol three times respectively, and dry in vacuum at 80 °C for 2 h to obtain modified composite microspheres.

[0049] S5: Add 40 mL of diphenyldichlorosilane, 35 mL of phenyltrichlorosilane, 38 mL of dimethyldichlorosilane, 35 mL of methyltrichlorosilane, 120 mL of toluene, and 140 mL of deionized water into a reaction kettle, stir at 45 °C and 600 r / min for 2 h, let it stand for layer separation, remove the lower acidic water layer, continue stirring for 60 min, and concentrate under reduced pressure to obtain a prepolymer with a solid content of 15%. Add 180 mL of the prepolymer, 40 mL of modified composite microspheres, and 0.8 mL of a butanol solution of tetraethylammonium hydroxide with a mass fraction of 12% as a catalyst into the reaction kettle, stir and react at 70 °C and 600 r / min for 2 h, then add 0.2 mL of acetic anhydride as a stabilizer, heat to 220 °C for curing for 1.2 h, and cool naturally to obtain a modified methyl silicone resin.

[0050] Comparative Example 1: On the basis of Example 3, replace the composite microspheres in step S2 with commercially available iron oxide with the same mass, and keep the other steps unchanged to prepare a modified methyl silicone resin.

[0051] Comparative Example 2: On the basis of Example 3, directly use the composite microspheres in step S2 as the carbon-coated composite microspheres in step S3, and keep the other steps unchanged to prepare a modified methyl silicone resin.

[0052] Comparative Example 3: Based on Example 3, the polycaprolactone-modified composite microspheres in step S4 are replaced by carbon-coated composite microspheres in step S2, and the remaining steps remain unchanged to prepare modified methyl silicone resin.

[0053] The modified methyl silicone resin prepared in Examples 1 to 3 and Comparative Examples 1 to 3 was prepared into an insulating paint for performance testing; 55 g of modified methyl silicone resin, 3 g of polyether defoamer BYK-019, 2 g of modified silicone leveling agent BYK-306, 3 g of polyacrylic acid thickener VISCOLAM330 and 500 mL of deionized water were stirred and mixed for 3.5 hours, and the fineness was ground to 20 μm. The results are shown in Table 1:

[0054] 1. Heat resistance test: Refer to the standard of "GB / T1735-2009 Determination of Heat Resistance of Paints and Varnishes" for testing. Spray the insulating paint on a 30cm×30cm wooden board, place the board horizontally in a high-temperature furnace, heat it to the target value according to the set temperature and keep it for the specified time of 2h, observe whether the paint layer changes or is damaged, and record the temperature at this time. The higher the temperature, the better the heat resistance.

[0055] 2. Flexibility test The test is carried out according to the standard of "GB / T1731-1993 Determination of paint film flexibility". A 120mm×25mm×0.2mm tinplate is used as the base plate to ensure that it is flat, without distortion and cracks. Seven steel shafts with different diameters (diameter range 0.5mm-15mm) are used, each shaft is 35mm long. The paint film is facing up and close to the shaft of the specified diameter. Use both hands to evenly bend the test plate 180° within 2-3 seconds, ensuring that the thumbs are symmetrical to the center line of the shaft. Use a 4x magnifying glass to check whether the paint film has any reticulation, cracks or peeling. The minimum shaft diameter that does not cause damage to the paint film indicates the flexibility of the paint film.

[0056] 3. Hardness test GB / T 6739-2006 "Determination of film hardness of paint and varnish by pencil method" is tested by applying pressure on the surface of the material with pencils of different hardness and scratching it. The hardness level is judged by observing whether scratches are produced. The hardness of the pencil is determined by the ratio of graphite to clay. The higher the hardness (the larger the H value), the harder the pencil lead and the lighter the color.

[0057] 4. Adhesion test: The test is carried out according to the standard of "Determination Method for Adhesion of Paint Films GB / T 1720 - 1979(1989)". Spray the insulating paint on a tinplate with dimensions of 120mm × 25mm × 0.2mm, dry and cure it. Fix the tinplate on the platform of the measuring instrument, adjust the turning radius of the stylus to 5.25mm, and the stylus draws continuous overlapping circular rolling lines at a speed of 80 - 100r / min, penetrating through the paint film to the substrate. Observe the damage of the paint film in the scratched area with a four - fold magnifying glass. The scratch is divided into 7 parts, corresponding to 7 grades (grade 1 is the best, grade 7 is the worst). If more than 70% of the area does not peel off, it is regarded as intact, and the lowest grade with an intact paint film is used as the final adhesion rating.

[0058] 5. Heat insulation test: Refer to the standard of JG / T235 - 2014 (WQ type) to test the heat insulation. Spray the insulating paint on a metal plate with dimensions of 150mm × 200mm × 5mm, place the metal plate on the test platform of the instrument to ensure that the surface of the paint layer is perpendicular to the incident light, and conduct continuous scanning in the full solar wavelength band (300 - 2500nm). Record the reflectivity data at each wavelength respectively, which is represented by the heat insulation temperature difference. The larger the heat insulation temperature difference, the better the heat insulation performance of the coating.

[0059] Table 1 Performance test results of insulating paint

[0060]

[0061]

[0062] The insulating paints prepared from the modified methyl silicone resins prepared in Examples 1 - 3 and Comparative Examples 1 - 3 were subjected to performance tests. The heat - resistant temperature, minimum shaft diameter, hardness, and heat insulation temperature difference were significantly better than those of the comparative examples, and the adhesion grade was significantly lower than that of the comparative examples. This shows that when the modified methyl silicone resin prepared by the present invention is used as an insulating paint, it has good heat resistance, hardness, toughness, adhesion, and heat insulation.

[0063] In Comparative Example 1, the composite microspheres were replaced with commercially available iron oxide black of the same mass, and a layer of silica was coated on the surface of the iron oxide black microspheres, which can improve the adhesion, prevent the iron oxide black from being oxidized, increase the thermal stability of the material. The coating layer can reduce the thermal conductivity of the material, delay the heat transfer, and improve the heat resistance at the same time.

[0064] In Comparative Example 2, the composite microspheres were directly used as carbon-coated composite microspheres. Glucose was carbonized at high temperature to form an amorphous carbon layer, which tightly wrapped the composite microspheres, isolated oxygen to prevent oxidation. The carbon-carbon double bond (C=C) of acrylic acid underwent an addition reaction with the free radicals generated by the pyrolysis of glucose under high-temperature hydrothermal conditions, fixing the carboxyl group on the surface of the microspheres. The carbon layer generated by glucose could further prevent the oxidation of iron tetroxide. The carbon layer could disperse stress through a relative slip mechanism, thereby improving the impact resistance of the modified methyl silicone resin as an insulating paint.

[0065] In Comparative Example 3, the polycaprolactone-modified composite microspheres were replaced with carbon-coated composite microspheres. Using polycaprolactone to wrap the carbon-coated composite microspheres could avoid agglomeration, thereby improving the uniform dispersion in the methyl silicone resin matrix. And polycaprolactone would decompose thermally to generate carbon dioxide during the curing process, reversing the decrease in porosity to a certain extent, thereby increasing the porosity of the material. The porosity could absorb energy through pore collapse and local plastic deformation around the pores, delaying crack propagation and improving heat insulation or toughness.

[0066] It should be noted that in this article, terms such as "including", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such process, method, article or device.

[0067] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention.

Claims

1. A method for preparing a modified methyl silicone resin, characterized in that: Prepared by the following steps: Step 1: Modify the polycaprolactone modified composite microspheres by γ-glycidyloxypropyltrimethoxysilane and retain the epoxy group to obtain modified composite microspheres; add diphenyldichlorosilane, phenyltrichlorosilane, dimethyldichlorosilane, methyltrichlorosilane, toluene and deionized water into a reaction kettle, stir at 40-45° C. and 500-600 r / min for 1-2 hours, stand for stratification, remove the lower layer, continue stirring for 30-60 minutes, and concentrate under reduced pressure to obtain a prepolymer; Step 2: Add the prepolymer, modified composite microspheres and 10-12wt% tetraethylammonium hydroxide butanol solution into a reactor, stir and react for 1-2h at 60-70°C and 500-600r / min, then add acetic anhydride as a stabilizer, heat to 200-220°C and cure for 1-1.2h, and cool naturally to obtain a modified methyl silicone resin.

2. The method for preparing a modified methyl silicone resin according to claim 1, characterized in that: The dosage ratio of phenyldichlorosilane, phenyltrichlorosilane, dimethyldichlorosilane, methyltrichlorosilane, toluene and deionized water in step 1 is 30-40 mL: 32-35 mL: 35-38 mL: 28-35 mL: 100-120 mL: 120-140 mL.

3. The method for preparing a modified methyl silicone resin according to claim 1, characterized in that: The dosage ratio of the prepolymer, modified composite microspheres, tetraethylammonium hydroxide butanol solution and acetic anhydride in step 2 is 150-180 mL: 38-40 mL: 0.5-0.8 mL: 0.12-0.2 mL.

4. The method for preparing a modified methyl silicone resin according to claim 1, characterized in that: The modified composite microspheres described in step 1 are specifically prepared by the following steps: Add polycaprolactone modified composite microspheres, γ-glycidyloxypropyltrimethoxysilane, anhydrous ethanol and deionized water into a reaction kettle, stir at 20-25° C. and 500-600 r / min for 1-2 hours, filter, wash and vacuum dry to obtain modified composite microspheres; The dosage ratio of the polycaprolactone modified composite microspheres, gamma-glycidyloxypropyltrimethoxysilane, anhydrous ethanol and deionized water is 40-45 g: 50-60 mL: 120-140 mL: 180-200 mL.

5. The method for preparing a modified methyl silicone resin according to claim 1, characterized in that: The polycaprolactone modified composite microspheres are prepared by the following steps: Heat ε-caprolactone and catalyst stannous octoate in an oil bath to 95-100°C, react at 500-600 r / min for 2-3 hours, then add carbon-coated composite microspheres, continue stirring for 1-2 hours, add sodium dodecylbenzene sulfonate and polyethylene glycol into the reaction kettle, continue stirring for 3-4 hours, centrifuge at 3000-3500 r / min for 5-6 minutes, discard the supernatant, wash the product with deionized water and anhydrous ethanol for 2-3 times respectively, and vacuum dry to obtain polycaprolactone modified composite microspheres.

6. The method for preparing a modified methyl silicone resin according to claim 5, characterized in that: The usage ratio of the ε-caprolactone, stannous octoate, carbon-coated composite microspheres, sodium dodecylbenzene sulfonate and polyethylene glycol is 80-90 mL: 0.2-0.4 g: 50-60 g: 1-2 g: 2-4 mL.

7. The method for preparing a modified methyl silicone resin according to claim 5, characterized in that: The carbon-coated composite microspheres are prepared by the following steps: Add composite microspheres, glucose, acrylic acid and deionized water into a reaction kettle, perform ultrasonic dispersion for 30-40 minutes, heat to 170-180°C, stir at 500-600 r / min for 6-7 hours, cool naturally, filter, wash and vacuum dry to obtain carbon-coated composite microspheres; The usage ratio of the composite microspheres, glucose, acrylic acid and deionized water is 50-60 g: 70-80 g: 80-90 mL: 500-600 mL.

8. The method for preparing a modified methyl silicone resin according to claim 7, characterized in that: The composite microspheres are prepared by the following steps: Add ferric chloride hexahydrate and deionized water into a reaction kettle, stir at 20-25°C and 500-600r / min for 20-30min, add ferrous sulfate tetrahydrate and 20-30wt% ammonia solution under a nitrogen atmosphere, continue stirring for 1.5-2h, then add tetraethyl orthosilicate and anhydrous ethanol, stir at 40-45°C and 500-600r / min for 12-14h, filter, wash, vacuum dry, transfer to a muffle furnace, calcine at 750-800°C for 12-14h under a nitrogen atmosphere, and cool naturally to obtain composite microspheres.

9. The method for preparing a modified methyl silicone resin according to claim 8, characterized in that: The usage ratio of the ferric chloride hexahydrate, deionized water, ferrous sulfate tetrahydrate, ammonia solution, tetraethyl orthosilicate and anhydrous ethanol is 80-90g: 300-400mL: 40-60g: 200-300mL: 40-50mL: 120-180mL.

10. A modified methyl silicone resin, characterized in that: It is prepared by the preparation method described in any one of claims 1 to 9.

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