Organic silicon modified polyacrylate engine coating and preparation method thereof

Abstract

The invention relates to the technical field of high-temperature-resistant and corrosion-resistant coatings, in particular to an organic silicon modified polyacrylate engine coating and a preparation method thereof. The coating is prepared by mixing the following components in parts by weight: 65-75 parts of organic silicon modified polyacrylate copolymer, 15-25 parts of inorganic filler and 3-8 parts of curing agent, the organic silicon modified polyacrylate copolymer is prepared from the following components in parts by weight: 55-75 parts of a main monomer, 15-23 parts of a functional monomer, 5-10 parts of an organic silicon modifier and 5-15 parts of an initiator. The inorganic filler is obtained by carrying out surface modification treatment on one or more of titanium dioxide, silicon carbide, aluminum nitride, aluminum oxide and silicate through a silane coupling agent KH550; the curing agent comprises a mixture of hexamethylene diisocyanate tripolymer and dibutyltin dilaurate. The coating has the effects of excellent high temperature resistance, corrosion resistance, strong adhesive force and the like, and can effectively prolong the service life of key parts of an engine.

Description

Technical Field

[0001] The present invention relates to the technical field of high-temperature resistant and corrosion-resistant coatings, and particularly to an organosilicon-modified polyacrylate engine coating and a preparation method thereof.

Background Art

[0002] With the popularization of internal combustion engine turbocharging technology and high-temperature exhaust gas recirculation systems, key engine components (such as cylinder blocks, exhaust manifolds, turbocharger housings, etc.) are exposed to extreme environments of 300 - 500 °C high temperature, strong vibration, and corrosive gases (SOx, NOx) for a long time. Traditional protective coatings are prone to problems such as thermal degradation, interfacial peeling, and microcrack propagation, leading to increased oxidation corrosion of the metal matrix, seriously threatening the service life and operation safety of equipment.

[0003] Currently, commercial engine coatings mainly adopt epoxy resins, organosilicon resins, and polyimide systems. Although epoxy resins have excellent adhesion, their glass transition temperature (Tg < 150 °C) limits their high-temperature applications; although organosilicon coatings have outstanding heat resistance (can withstand 300 - 400 °C), they have defects such as low mechanical strength and large curing shrinkage rate; although polyimides have both heat resistance and mechanical properties, their synthesis process is complex and costly. Polyacrylate coatings have been widely studied due to their low cost and good film-forming properties, but their linear molecular structure has poor heat stability (decomposition temperature < 250 °C), and their brittle characteristics result in insufficient impact resistance.

[0004] Therefore, there is an urgent need to develop a coating with high temperature resistance and corrosion resistance, suitable for use in engines.

Summary of the Invention

[0005] The object of the present invention is to provide an organosilicon-modified polyacrylate engine coating and a preparation method thereof to solve the technical problems that existing engine coatings are prone to cracks, interfacial peeling, etc. in high-temperature and corrosive gas environments. The present invention has excellent effects such as high temperature resistance, corrosion resistance, and strong adhesion, and can effectively extend the service life of key engine components.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] An organosilicon-modified polyacrylate engine coating is composed of the following components: in parts by weight, 65 - 75 parts of an organosilicon-modified polyacrylate copolymer, 15 - 25 parts of an inorganic filler, and 3 - 8 parts of a curing agent are mixed;

[0008] The organosilicon-modified polyacrylate copolymer is prepared from 55 - 75 parts of a main monomer, 15 - 23 parts of a functional monomer, 5 - 10 parts of an organosilicon modifier, and 5 - 15 parts of an initiator in parts by weight;

[0009] The inorganic filler is obtained by surface modification of one or several of titanium dioxide, silicon carbide, aluminum nitride, aluminum oxide, and silicate with silane coupling agent KH550;

[0010] The curing agent comprises a mixture of hexamethylene diisocyanate trimer and dibutyltin dilaurate.

[0011] Further optimized, the main monomer is one or several of acrylic acid, methyl acrylate, butyl acrylate, 2-hydroxyethyl acrylate, methyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxyethyl methacrylate, lauryl acrylate, isobornyl acrylate, isobornyl methacrylate or its homologues; the functional monomer is one or several of hexafluorobutyl methacrylate, epoxy acrylate, 1,6-hexanediol diacrylate, diethylene glycol diacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate or its homologues; the organosilicon modifier is one or several of epoxy group silane, amino silane, methacryloxy silane, isocyanate group silane; the initiator is azobisisobutyronitrile or benzoyl peroxide.

[0012] Further optimized, the main monomer is composed of isobornyl methacrylate, 2-hydroxyethyl acrylate and glycidyl methacrylate in a mass ratio of 5-7:1-2:1-3; the functional monomer is composed of hexafluorobutyl methacrylate (DFHMA), trimethylolpropane triacrylate (TMPTA) and γ-methacryloxypropyltrimethoxysilane (KH570) in a mass ratio of 3-5:1-2:0.5-1; the modifier is an organosilicon modifier composed of epoxy group silane and isocyanate group silane in a mass ratio of 4-6:1-2; the initiator is azobisisobutyronitrile.

[0013] Further optimized, the mass ratio of hexamethylene diisocyanate trimer to dibutyltin dilaurate in the curing agent is 10-15:1.

[0014] Further optimized, the inorganic filler needs to be modified before use. The modification steps are: dispersing the inorganic filler powder in ethanol with a mass percentage of 75-95%, adding KH550 with a mass percentage of 1-2%, then performing ultrasonic treatment for 1-4 h, and drying at 75-85 °C until the water content is below 10%. The mass ratio of the inorganic filler powder to ethanol is 1:5-10.

[0015] A preparation method of the above-mentioned organosilicon-modified polyacrylate engine coating, comprising:

[0016] Mix the main monomer and the functional monomer in proportion and prepare a solution, ensuring that the solid content of the solution is 40-50%, stir at 30-40 °C for 30-60 min, and the stirring speed is 300-500 r / min;

[0017] Add the modifier and the initiator, and under nitrogen protection, heat up to 60-90 °C at a rate of 3-5 °C / min and react for 6-12 h to obtain a prepolymer solution;

[0018] Slowly add deionized water dropwise, adjust the pH to 3-6, and continue to react at 70-90 °C for 2-5 h to obtain a silicone-modified polyacrylate copolymer, where the dropping rate of deionized water is 1-2 mL / min;

[0019] Mix the silicone-modified polyacrylate copolymer, inorganic filler, curing agent and antioxidant evenly to obtain the coating. The vacuum degree during mixing is -0.08 MPa---0.09 MPa, and the mixing time is 1-2 h.

[0020] In a further optimized preparation method, mix the main monomer and the functional monomer in proportion and prepare a solution, ensuring that the solid content of the solution is 40-50%, stir at 30-40 °C for 30-60 min, and the stirring speed is 300-500 r / min;

[0021] Add the modifier and the initiator, and under nitrogen protection, heat up to 70-80 °C at a rate of 3-5 °C / min and react for 8-10 h to obtain a prepolymer solution;

[0022] Slowly add deionized water dropwise, adjust the pH to 3-6, and continue to react at 75-85 °C for 3-4 h to obtain a silicone-modified polyacrylate copolymer, where the dropping rate of deionized water is 1-2 mL / min;

[0023] Mix the silicone-modified polyacrylate copolymer, inorganic filler, curing agent and antioxidant evenly to obtain the coating. The vacuum degree during mixing is -0.08 MPa---0.09 MPa, and the mixing time is 1-2 h.

[0024] Further optimized, after step 4, it also includes a step of curing at 50-60 °C for 12-24 h.

[0025] An application method of the above silicone-modified polyacrylate engine coating, spray the coating onto the surface of the engine block substrate, and the gradient curing process is: pre-bake at 70 °C - 90 °C for 10-15 min → cure at 130 °C - 150 °C for 50-65 min → cure at 180 °C - 200 °C for 35-50 min, and the heating rate ≤ 5 °C / min.

[0026] Further optimized, before spraying, the surface of the engine cylinder block is polished to make the surface roughness reach 1.5 - 2.5 μm, and the spraying thickness is 100 - 200 μm.

[0027] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are as follows:

[0028] 1. By reasonably proportioning the organosilicon-modified polyacrylate copolymer, inorganic filler and curing agent, the coating achieves a balance in terms of high temperature resistance, corrosion resistance, adhesion, etc. The organosilicon-modified polyacrylate copolymer provides excellent high temperature resistance and corrosion resistance. After the inorganic filler is modified with the silane coupling agent KH550, the bonding force with the matrix is enhanced, and the wear resistance and thermal stability of the coating are improved. The curing agent ensures rapid curing and good adhesion of the coating at high temperatures. After baking at 450°C for 24 hours, there is no cracking, and the thermal weight loss < 5%, which is better than the temperature resistance limit of traditional polyacrylate coatings (decomposition temperature < 250°C). It blocks the penetration of SOx / NOx corrosive media, and there is no blistering or failure after more than 1000 hours of salt spray testing. Overall, this coating can effectively solve the protection problem of key engine components in high temperature, strong vibration and corrosive gas environments, extend the service life of equipment, and improve operation safety.

[0029] 2. In the main monomers of the organosilicon-modified polyacrylate copolymer of the present invention, the specific mass ratio of isobornyl methacrylate, 2-hydroxyethyl acrylate and glycidyl methacrylate enables the thermal decomposition temperature of the coating to be > 450°C through chemical cross-linking of the rigid skeleton and epoxy groups, which is significantly better than that of traditional two-component systems. In the functional monomers, hexafluorobutyl methacrylate (DFHMA), trimethylolpropane triacrylate (TMPTA) and γ-methacryloxypropyltrimethoxysilane (KH570) construct a fluorine-silicon composite barrier layer, and the impact strength ≥ 50 kg·cm. In the organosilicon modifier, the compounding ratio of epoxy group silane and isocyanate group silane forms a double interfacial bond of Si-O-C and urethane bonds, and the interfacial shear strength is significantly enhanced, breaking through the performance bottleneck of a single silane system.

[0030] 3. The mass ratio of hexamethylene diisocyanate trimer to dibutyltin dilaurate in the curing agent is 10 - 15:1, which can effectively improve the curing efficiency and curing effect of the coating. Hexamethylene diisocyanate trimer provides good cross-linking performance, while dibutyltin dilaurate, as a catalyst, accelerates the curing reaction, enabling the coating to meet the expected performance requirements in a shorter time, avoiding brittleness caused by over-crosslinking, making the elongation at break > 20%, significantly improving the toughness of the coating, and at the same time improving the chemical corrosion resistance and thermal stability of the coating.

[0031] 4. The inorganic filler is finely modified. By controlling parameters such as the concentration of ethanol, the dosage of KH550, the ultrasonic treatment time, and the drying temperature, the efficient dispersion and stable combination of the inorganic filler in the matrix of the silicone-modified polyacrylate copolymer are ensured. The modified inorganic filler can fully exert its functional advantages such as strengthening, toughening, and high-temperature resistance, effectively improving the hardness, wear resistance, and thermal conductivity of the coating. At the same time, the surface quality of the coating is improved, and the adhesion between the coating and the matrix is enhanced.

[0032] 5. The stepwise polymerization process controls the molecular weight distribution in the prepolymerization stage, inhibits the pre-hydrolysis of silane in the pH regulation stage, and reduces the generation of by-products; vacuum mixing eliminates residual bubbles, and the surface roughness Ra < 0.1 μm; the curing process eliminates internal stress, enabling the coating to have no cracking after 90 thermal shock cycles, and improving the long-term stability.

Specific Embodiments

[0033] The technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0035] Example 1

[0036] A silicone-modified polyacrylate engine coating contains the following components: mixed by weight ratio, 65 parts of silicone-modified polyacrylate copolymer, 15 parts of inorganic filler, and 3 parts of curing agent;

[0037] The silicone-modified polyacrylate copolymer is prepared from 55 parts of main monomer, 15 parts of functional monomer, 5 parts of silicone modifier, and 5 parts of initiator by weight ratio;

[0038] The inorganic filler is obtained by surface modification of one or more of titanium dioxide, silicon carbide, aluminum nitride, aluminum oxide, and silicate with the silane coupling agent KH550; Aluminum nitride is used in this example.

[0039] The curing agent contains a mixture of hexamethylene diisocyanate trimer and dibutyltin dilaurate.

[0040] Furthermore, the monomer in this embodiment is composed of isobornyl methacrylate, 2-hydroxyethyl acrylate, and glycidyl methacrylate with a mass ratio of 5:1:1; the functional monomer is composed of 2,2,3,3,4,4,4-heptafluorobutyl methacrylate (DFHMA), trimethylolpropane triacrylate (TMPTA), and γ-methacryloxypropyltrimethoxysilane (KH570) with a mass ratio of 3:1:0.5; the modifier is an organosilicon modifier composed of epoxy group silane and isocyanate group silane with a mass ratio of 4:1; the initiator is azobisisobutyronitrile.

[0041] In the curing agent, the mass ratio of hexamethylene diisocyanate trimer to dibutyltin dilaurate is 10:1.

[0042] The inorganic filler needs to be modified before use. The modification steps are as follows: Disperse the inorganic filler powder in ethanol with a mass percentage of 75%, add KH550 with a mass percentage of 2%, then after ultrasonic treatment for 1 h, dry it at 75 °C until the water content is below 10%. The mass ratio of the inorganic filler powder to ethanol is 1:5.

[0043] A preparation method of the above-mentioned organosilicon-modified polyacrylate engine coating includes:

[0044] Mix the main monomer and the functional monomer in proportion and configure them into a solution to ensure that the solid content of the solution is 40%. Stir at 30 °C for 60 min, and the stirring speed is 300 r / min;

[0045] Add the modifier and the initiator, and under nitrogen protection, heat it to 60 °C at a rate of 3 - 5 °C / min and react for 12 h to obtain a prepolymer solution;

[0046] Slowly dropwise add deionized water to adjust the pH to 3, and continue to react at 90 °C for 4 h to obtain an organosilicon-modified polyacrylate copolymer. The dropping rate of deionized water is 1 - 2 mL / min;

[0047] Mix the organosilicon-modified polyacrylate copolymer, inorganic filler, curing agent, and antioxidant evenly to obtain the coating. The vacuum degree during mixing is -0.08 MPa, and the mixing time is 2 h.

[0048] Further optimized, after step 4, it also includes a step of curing at 50 °C for 24 h.

[0049] Example 2

[0050] An organosilicon-modified polyacrylate engine coating contains the following components: Mixed by weight ratio, 75 parts of organosilicon-modified polyacrylate copolymer, 25 parts of inorganic filler, and 8 parts of curing agent;

[0051] The organosilicon-modified polyacrylate copolymer is prepared from 75 parts of main monomers, 23 parts of functional monomers, 10 parts of organosilicon modifier and 15 parts of initiator by weight ratio.

[0052] The inorganic filler is obtained by surface modification of one or several of titanium dioxide, silicon carbide, aluminum nitride, aluminum oxide, and silicate with silane coupling agent KH550; silicon carbide is used in this example.

[0053] The curing agent contains a mixture of hexamethylene diisocyanate trimer and dibutyltin dilaurate.

[0054] Furthermore, the monomers in this example are composed of isobornyl methacrylate, 2-hydroxyethyl acrylate, and glycidyl methacrylate with a mass ratio of 7:2:3; the functional monomers are composed of 2,2,3,3,4,4,4-heptafluorobutyl methacrylate (DFHMA), trimethylolpropane triacrylate (TMPTA), and γ-methacryloxypropyltrimethoxysilane (KH570) with a mass ratio of 5:2:1; the modifier is an organosilicon modifier composed of epoxy group silane and isocyanate group silane with a mass ratio of 6:2; the initiator is azobisisobutyronitrile.

[0055] In the curing agent, the mass ratio of hexamethylene diisocyanate trimer to dibutyltin dilaurate is 15:1.

[0056] The inorganic filler needs to be modified before use. The modification steps are as follows: disperse the inorganic filler powder in ethanol with a mass percentage of 95%, add KH550 with a mass percentage of 1%, then perform ultrasonic treatment for 4 h, and dry at 85 °C until the water content is below 10%. The mass ratio of the inorganic filler powder to ethanol is 1:10.

[0057] A preparation method of the above organosilicon-modified polyacrylate engine coating includes:

[0058] Mix the main monomers and functional monomers in proportion and configure them into a solution to ensure that the solid content of the solution is 50%. Stir at 40 °C for 30 min, and the stirring speed is 500 r / min.

[0059] Add the modifier and initiator, and heat up to 90 °C at a rate of 4-5 °C / min under nitrogen protection, and react for 6 h to obtain a prepolymer solution.

[0060] Slowly dropwise add deionized water to adjust the pH to 5-6, and continue to react at 70 °C for 3 h to obtain an organosilicon-modified polyacrylate copolymer, where the dropping rate of deionized water is 1-2 mL / min.

[0061] Mix the silicone-modified polyacrylate copolymer, inorganic filler, curing agent and antioxidant evenly to obtain the coating. The vacuum degree during mixing is -0.09 MPa, and the mixing time is 1 h.

[0062] Further optimized, after step 4, it also includes a step of curing at 60 °C for 12 h.

[0063] Example 3

[0064] A silicone-modified polyacrylate engine coating contains the following components: calculated by weight ratio, it is composed of 70 parts of silicone-modified polyacrylate copolymer, 18 parts of inorganic filler and 5 parts of curing agent;

[0065] The silicone-modified polyacrylate copolymer is prepared from 60 parts of main monomer, 18 parts of functional monomer, 7.5 parts of silicone modifier and 10 parts of initiator by weight ratio;

[0066] The inorganic filler is obtained by surface modification treatment of one or several of titanium dioxide, silicon carbide, aluminum nitride, aluminum oxide, silicate with silane coupling agent KH550; The inorganic filler used in the present invention is: the weight ratio of silicon carbide to aluminum nitride is 3:1;

[0067] The curing agent contains a mixture of hexamethylene diisocyanate trimer and dibutyltin dilaurate.

[0068] Further, the monomers in this example are composed of isobornyl methacrylate, hydroxyethyl acrylate and glycidyl methacrylate with a mass ratio of 6:1.5:2; The functional monomers are composed of hexafluorobutyl methacrylate (DFHMA), trimethylolpropane triacrylate (TMPTA) and γ-methacryloxypropyltrimethoxysilane (KH570) with a mass ratio of 4:1.2:0.6; The modifier is a silicone modifier, which is composed of epoxy group silane and isocyanate group silane with a mass ratio of 5:1.5; The initiator is azobisisobutyronitrile.

[0069] The mass ratio of hexamethylene diisocyanate trimer to dibutyltin dilaurate in the curing agent is 12:1.

[0070] The inorganic filler needs to be modified before use. The modification treatment steps are: disperse the inorganic filler powder in ethanol with a mass percentage of 90%, add KH550 with a mass percentage of 1.5%, then after ultrasonic treatment for 2 h, dry it at 80 °C until the water content is below 8%, and the mass ratio of the inorganic filler powder to ethanol is 1:7.5.

[0071] A preparation method of the above silicone-modified polyacrylate engine coating includes:

[0072] Mix the main monomer and the functional monomer in proportion and prepare a solution, ensuring that the solid content of the solution is 45%, stir at 35 °C for 45 min, and the stirring speed is 400 r / min;

[0073] Add the modifier and the initiator, and heat up to 70 °C at a rate of 4 °C / min under nitrogen protection, and react for 10 h to obtain a prepolymer solution;

[0074] Slowly add deionized water, adjust the pH to 4.5, and continue to react at 75 °C for 4 h to obtain a silicone-modified polyacrylate copolymer, where the rate of adding deionized water is 1 - 2 mL / min;

[0075] Mix the silicone-modified polyacrylate copolymer, inorganic filler, curing agent and antioxidant evenly to obtain the coating. The vacuum degree during mixing is -0.08 MPa, and the mixing time is 1.5 h.

[0076] Further optimized, after step 4, it also includes a step of curing at 55 °C for 16 h.

[0077] Example 4

[0078] A silicone-modified polyacrylate engine coating contains the following components: calculated by weight ratio, it is composed of 72 parts of silicone-modified polyacrylate copolymer, 23 parts of inorganic filler and 6.5 parts of curing agent;

[0079] The silicone-modified polyacrylate copolymer is prepared from 68 parts of main monomer, 19 parts of functional monomer, 8 parts of silicone modifier and 11 parts of initiator calculated by weight ratio;

[0080] The inorganic filler is obtained by surface modification treatment of one or several of titanium dioxide, silicon carbide, aluminum nitride, aluminum oxide, and silicate with silane coupling agent KH550; the inorganic filler used in the present invention is: the weight ratio of silicon carbide to aluminum nitride is 2:1;

[0081] The curing agent contains a mixture of hexamethylene diisocyanate trimer and dibutyltin dilaurate.

[0082] Further, the monomers in this example are composed of isobornyl methacrylate, 2-hydroxyethyl acrylate and glycidyl methacrylate with a mass ratio of 6.5:1.8:2; the functional monomers are composed of 2,2,3,3,4,4,4-heptafluorobutyl methacrylate (DFHMA), trimethylolpropane triacrylate (TMPTA) and γ-methacryloxypropyltrimethoxysilane (KH570) with a mass ratio of 3.5:1.8:0.7; the modifier is a silicone modifier, which is composed of epoxy group silane and isocyanate group silane with a mass ratio of 5:1.5; the initiator is azobisisobutyronitrile.

[0083] In the curing agent, the mass ratio of hexamethylene diisocyanate trimer to dibutyltin dilaurate is 12:1.

[0084] The inorganic filler needs to be modified before use. The modification steps are as follows: Disperse the inorganic filler powder in ethanol with a mass percentage of 85%, add KH550 with a mass percentage of 1.6%, then perform ultrasonic treatment for 2.5 h, and dry at 85 °C until the water content is below 10%. The mass ratio of the inorganic filler powder to ethanol is 1:7.

[0085] A preparation method of the above-mentioned organosilicon-modified polyacrylate engine coating includes:

[0086] Mix the main monomer and the functional monomer in proportion and configure them into a solution to ensure that the solid content of the solution is 45%. Stir at 35 °C for 50 min, and the stirring speed is 400 r / min;

[0087] Add the modifier and the initiator, and under nitrogen protection, heat up to 80 °C at a rate of 3-5 °C / min and react for 8 h to obtain a prepolymer solution;

[0088] Slowly dropwise add deionized water to adjust the pH to 3-6, and continue to react at 85 °C for 3 h to obtain an organosilicon-modified polyacrylate copolymer. The dropping rate of deionized water is 1-2 mL / min;

[0089] Mix the organosilicon-modified polyacrylate copolymer, the inorganic filler, the curing agent and the antioxidant evenly to obtain the coating. The vacuum degree during mixing is -0.08 MPa, and the mixing time is 1.5 h.

[0090] Further optimized, after step 4, it also includes a step of curing at 55 °C for 14 h.

[0091] Example 5

[0092] A using method of the organosilicon-modified polyacrylate engine coating prepared in Example 4. Spray the coating onto the surface of the engine cylinder block substrate. The gradient curing process is: pre-bake at 70 °C for 15 min → cure at 130 °C for 50 min → cure at 180 °C for 50 min, and the heating rate ≤ 5 °C / min.

[0093] Further optimized, before spraying, grind the surface of the engine cylinder block to make the surface roughness reach 1.5-2.5 μm, and the spraying thickness is 100-200 μm.

[0094] Example 6

[0095] A method of using an organosilicon-modified polyacrylate engine coating prepared in Example 4. The coating is sprayed onto the surface of the engine block substrate. The gradient curing process is as follows: pre-bake at 90 °C for 10 min → cure at 150 °C for 50 min → cure at 200 °C for 35 min, and the heating rate ≤ 5 °C / min.

[0096] Further optimized, before spraying, the surface of the engine block is polished to make the surface roughness reach 1.5 - 2.5 μm, and the spraying thickness is 100 - 200 μm.

[0097] Coating performance test and effect verification in Example 7

[0098] (1) Test samples

[0099] Samples of Examples 1 - 4: Prepare the coatings according to Examples 1 - 4, without optimizing the spraying process (substrate roughness 1.5 μm, spraying thickness 150 μm, and the curing process is conventional curing: 150 °C / 2 h).

[0100] Samples of Examples 5 - 6: Prepare the coatings according to Examples 5 - 6, using the gradient curing process (substrate roughness 1.5 μm, thickness 150 μm).

[0101] Comparative Example 1: Traditional silicone-acrylic coating (refer to the method of Patent CN202210275691), (substrate roughness 1.5 μm, spraying thickness 150 μm, and the curing process is conventional curing: 150 °C / 2 h);

[0102] Comparative Example 2: Single silane-modified coating (refer to the method of Patent CN202410829814.X), (substrate roughness 1.5 μm, spraying thickness 150 μm, and the curing process is conventional curing: 150 °C / 2 h).

[0103] (2) Test methods

[0104] High-temperature resistance test (GB / T 1735 - 2009): Place the coated sample in a muffle furnace, heat it to 450 °C at a rate of 10 °C / min, keep it at a constant temperature for 24 h, and calculate the thermal weight loss rate after cooling and weighing.

[0105] Salt spray test (ASTM B117): 5% NaCl solution, continuous spraying at 35 °C, and check the coating for blistering and peeling every 240 h.

[0106] Adhesion test (GB / T 5210 - 2006): Use the cross-cut method (1 mm × 1 mm grid), calculate the percentage of the remaining area after peeling with 3M tape, and convert it to the adhesion value.

[0107] Impact resistance test (ASTM D2794): A 1-kg steel ball is freely dropped from a height of 50 cm onto the coating surface, and the maximum impact energy without cracks is recorded.

[0108] Thermal shock cycle test: The sample is placed in an oven at 300 °C for 30 min and then immediately immersed in water at 25 °C for rapid cooling, and the cycle is repeated until the coating cracks.

[0109] Porosity test: The surface and cross-section morphologies of the coating are observed using a scanning electron microscope (SEM), and the porosity is calculated.

[0110] Electrochemical impedance spectroscopy (EIS): The impedance value of the coating in a 5% H2SO4 solution is measured using an electrochemical workstation (frequency range 10 5 -10 -2 Hz, amplitude 10 mV).

[0111] (3) Test results

[0112] The test results are shown in the following table.

[0113] Table 1 Test results of sample properties

[0114]

[0115] As can be seen from the above, all examples are significantly better than the comparative examples.

[0116] Examples 3-4 have the best thermal stability due to the optimized filler compounding (silicon carbide: aluminum nitride = 3:1) and the main monomer ratio (6:1.5:2); Examples 5-6 have the lowest thermal weight loss rate (<4%) due to the gradient curing process that further reduces the porosity.

[0117] The gradient curing process of Examples 5-6 makes the coating more dense, extends the penetration path of the corrosive medium, and there is no failure in the salt spray test for >1200 h; Examples 3-4 have better corrosion resistance than Examples 1-2 due to the synergistic effect of KH570 and DFHMA.

[0118] Examples 5-6 have an adhesion force >9 MPa due to gradient curing; Examples 3-4 have an adhesion force above 8.5 MPa due to more sufficient surface modification of the filler (ultrasonic treatment for 2 h + 1.5% KH550). In Examples 3-4, the crosslinking density of TMPTA is higher (functional monomer ratio 4:1.2:0.6), and the impact resistance strength >60 kg·cm. The gradient curing process of Examples 5-6 significantly reduces the internal stress, and there is no cracking in the thermal shock cycle for >100 times.

[0119] Comparative Example 1 (traditional silicon-acrylic coating) has a thermal weight loss rate >12% and a salt spray test <500 h due to unmodified filler and a single curing agent;

[0120] Comparative Example 2 (single silane system) cracked after 30 thermal shock cycles due to weak interfacial bonding (shear strength 3.5 MPa).

[0121] The above description is a detailed description of the preferred and feasible embodiments of the present invention. However, the embodiments are not intended to limit the scope of the patent application of the present invention. Any equivalent changes or modifications made under the technical spirit disclosed by the present invention shall fall within the scope of the patent covered by the present invention.

Claims

1. A silicone-modified polyacrylate engine coating, characterized in that, It comprises the following components: mixed by weight ratio, 65 - 75 parts of silicone-modified polyacrylate copolymer, 15 - 25 parts of inorganic filler, and 3 - 8 parts of curing agent; The silicone-modified polyacrylate copolymer is prepared by weight ratio from 55 - 75 parts of main monomer, 15 - 23 parts of functional monomer, 5 - 10 parts of silicone modifier, and 5 - 15 parts of initiator; The inorganic filler is obtained by surface modification treatment of one or several of titanium dioxide, silicon carbide, aluminum nitride, alumina, silicate with silane coupling agent KH550; The curing agent contains a mixture of hexamethylene diisocyanate trimer and dibutyltin dilaurate.

2. The organosilicon-modified polyacrylate engine coating according to claim 1, characterized in that The main monomer is one or several of acrylic acid, methyl acrylate, butyl acrylate, hydroxyethyl acrylate, methyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl methacrylate, lauryl acrylate, isobornyl acrylate, isobornyl methacrylate or their homologues; the functional monomer is one or several of hexafluorobutyl methacrylate, epoxy acrylate, 1,6 - hexanediol diacrylate, diethylene glycol diacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate or their homologues; the silicone modifier is one or several of epoxy group silane, amino silane, methacryloxy silane, isocyanate group silane; the initiator is azobisisobutyronitrile or benzoyl peroxide.

3. An organosilicon-modified polyacrylate engine coating according to claim 2, characterized in that The main monomer is composed of isobornyl methacrylate, hydroxyethyl acrylate, and glycidyl methacrylate in a mass ratio of 5 - 7:1 - 2:1 - 3; the functional monomer is composed of hexafluorobutyl methacrylate, trimethylolpropane triacrylate, and γ - methacryloxypropyltrimethoxysilane in a mass ratio of 3 - 5:1 - 2:0.5 - 1; the modifier is a silicone modifier composed of epoxy group silane and isocyanate group silane in a mass ratio of 4 - 6:1 - 2; the initiator is azobisisobutyronitrile.

4. The organosilicon-modified polyacrylate engine coating according to claim 1, wherein, In the curing agent, the mass ratio of hexamethylene diisocyanate trimer to dibutyltin dilaurate is 10 - 15:

1.

5. An organosilicon-modified polyacrylate engine coating according to claim 1, characterized in that, Before use, the inorganic filler needs to be modified. The modification steps are: dispersing the inorganic filler powder in ethanol with a mass percentage of 75 - 95%, adding KH550 with a mass percentage of 1 - 2%, then performing ultrasonic treatment for 1 - 4 h, and drying at 75 - 85 °C until the water content is below 10%. The mass ratio of the inorganic filler powder to ethanol is 1:5 - 10.

6. A preparation method of the organosilicon-modified polyacrylate engine coating as claimed in claim 1, characterized in that, It includes: Mix the main monomer and functional monomer in proportion to form a solution, ensure that the solid content of the solution is 40 - 50%, stir at 30 - 40 °C for 30 - 60 min, and the stirring speed is 300 - 500 r / min; Add the modifier and initiator, heat up to 60 - 90 °C at a rate of 3 - 5 °C / min under nitrogen protection, and react for 6 - 12 h to obtain a prepolymer solution; Slowly add deionized water dropwise, adjust the pH to 3 - 6, and continue the reaction at 70 - 90 °C for 2 - 5 h to obtain the organosilicon-modified polyacrylate copolymer, where the dropping rate of deionized water is 1 - 2 mL / min; Mix the organosilicon-modified polyacrylate copolymer, inorganic filler, curing agent and antioxidant evenly to obtain the coating. The vacuum degree during mixing is -0.08 MPa - 0.09 MPa, and the mixing time is 1 - 2 h.

7. The preparation method of an organosilicon-modified polyacrylate engine coating according to claim 6, characterized in that, After step 4, it also includes a step of curing at 50 - 60 °C for 12 - 24 h.

8. A method for applying the organosilicon-modified polyacrylate engine coating according to claim 1, characterized in that, Spray the coating onto the surface of the engine block substrate. The gradient curing process is: pre-bake at 70 °C - 90 °C for 10 - 15 min → cure at 130 °C - 150 °C for 50 - 65 min → cure at 180 °C - 200 °C for 35 - 50 min, and the heating rate ≤ 5 °C / min.

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