Modified polyurethane photocureable coating and preparation method thereof

Abstract

The invention discloses a modified polyurethane photocureable coating and a preparation method thereof. The preparation method comprises the following steps: firstly, introducing modified BNNS into castor oil to prepare a modified chain extender; the preparation method comprises the following steps: reacting dihydric alcohol with isocyanate to obtain a prepolymer; sequentially reacting the prepolymer with modified castor oil and a modified chain extender to prepare modified polyurethane resin; stirring and mixing the modified polyurethane resin, the reactive diluent, the dispersing agent and the flatting agent; adding a defoaming agent, stirring and mixing, grinding, filtering and discharging, and adding a photoinitiator for stirring and dispersing during use, so as to obtain the modified polyurethane photocureable coating. The ink has a dielectric property and a self-repairing property, and also has relatively strong adhesive force, relatively good water resistance and solvent resistance.

Description

Technical Field

[0001] The invention relates to the field of protective coating materials, and in particular to a modified polyurethane light-curing coating and a preparation method thereof. Background Art

[0002] As a protective coating, modified polyurethane photocuring coating is widely used in the anti-corrosion protection of circuit boards of electronic and electrical equipment, such as smart home appliances, automotive electronics, power supply / frequency conversion, intelligent industrial control, military ships, outdoor precision equipment, etc. It can protect circuit boards and related equipment from environmental erosion, thereby improving and extending the service life of circuit boards and ensuring the safety and reliability of circuit boards.

[0003] As the requirements for the reliability of electronic components become higher and higher, coating materials are not only required to have advantages such as solvent resistance, salt spray corrosion resistance and good adhesion, but also excellent thermal conductivity and dielectric properties. However, the commonly used coating materials such as acrylic, epoxy, and polyurethane do not have excellent thermal conductivity and dielectric properties. Moreover, during the use of these material coatings, due to the influence of external environments such as collision, corrosion, and light degradation, the coatings will produce micro cracks, resulting in a decrease in the mechanical properties of the material and affecting the functional effects of the coating. Summary of the invention

[0004] The purpose of the present invention is to provide a modified polyurethane photocuring coating and a preparation method thereof in view of the deficiencies in the prior art. Firstly, the modified polyurethane is synthesized by a step-by-step method, and -Si-O-CH3-, -BNNS and UPy groups are introduced into the polyurethane side chain, thereby maintaining a large degree of freedom of the silicone structure, the BNNS structure and the UPy group. Then, a network-structured polyurethane is obtained by cross-linking modification and photocuring technology, so that it has good adhesion performance, water resistance and solvent resistance, and at the same time, its dielectric properties, thermal conductivity and self-healing properties are improved.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A modified polyurethane light-curing coating is prepared by the following process:

[0007] Preparation of modified castor oil:

[0008] Under N2 atmosphere, 15-30 parts by weight of castor oil, 1-3 parts by weight of succinic anhydride and 0.15-0.3 parts by weight of SnCl2 are placed in a reaction container, the temperature is slowly raised to 80-120°C, and the reaction is stirred for 1-5 hours; when the temperature drops to 70-90°C, 10-15 parts by weight of modified BNNS and 0.01-0.1 parts by weight of triethylamine are added, and the reaction is continued with stirring for 2-6 hours to obtain modified castor oil;

[0009] Preparation of chain extender:

[0010] Under a nitrogen atmosphere, 5 to 15 parts by weight of hexamethylene diisocyanate and 0.5 to 1 part by weight of 2-amino-6-methyl-4-pyrimidone are placed in a reaction container, the temperature is raised to 90 to 100° C., and the reaction is stirred for 15 to 30 hours. After the temperature drops to room temperature, the reaction is filtered, washed, and vacuum dried to obtain NCO-terminated UPy;

[0011] Under a nitrogen atmosphere, 25 to 30 parts by weight of UPy, 12 to 16 parts by weight of 2-amino-2-methyl-1,3-propanediol and an appropriate amount of dimethyl sulfoxide are placed in a reaction container, the temperature is raised to 40 to 60° C., and the mixture is stirred for reaction for 3 to 8 hours. After the temperature drops to room temperature, the mixture is centrifuged, washed and dried to obtain a chain extender;

[0012] Preparation of modified polyurethane resin:

[0013] In a nitrogen atmosphere, diisocyanate and part of the polymerization inhibitor are placed in a reaction container, the temperature is raised to 60-80°C, diol and catalyst are added, stirring and heat-keeping reaction is carried out for 1-4 hours, modified castor oil is added, stirring and heat-keeping reaction is carried out for 3-8 hours, the temperature is raised to 70-100°C, the remaining polymerization inhibitor and chain extender are added, stirring and heat-keeping reaction is carried out for 2-3 hours, and a modified polyurethane resin is obtained;

[0014] Preparation of modified polyurethane light-curing coating:

[0015] 80-100 parts by weight of modified polyurethane resin, 30-40 parts by weight of active diluent, 0.5-2 parts by weight of dispersant and 1-3 parts by weight of leveling agent are put into a reactor and stirred to make them evenly mixed; then 0.5-1.5 parts by weight of defoamer are added and stirred to make them evenly dispersed and mixed, the material is ground and filtered, and when used, 3-10 parts by weight of photoinitiator is added and stirred to disperse, so as to prepare the modified polyurethane light-curing coating.

[0016] Furthermore, the modified BNNS is prepared by the following method:

[0017] 1 to 2 parts by weight of γ-glycidyloxypropyltrimethoxysilane and 10 to 15 parts by weight of BNNS are added to an ethanol / H2O solution, the temperature is raised to 60 to 80°C, and the solution is stirred for reaction for 6 to 10 hours. After the temperature drops to room temperature, the solution is filtered, washed, and dried to obtain modified BNNS.

[0018] Further, in the preparation of modified polyurethane resin:

[0019] The molar ratio of the diol, modified castor oil, chain extender and diisocyanate is 3-5:2-3:0.5-1.5:8-10;

[0020] The dosage of the polymerization inhibitor is 0.1-0.5% of the weight of the diisocyanate.

[0021] The amount of the catalyst used is 0.01-0.1% by weight of the diisocyanate.

[0022] Furthermore, the diisocyanate compound is selected from at least one of hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, tetramethyl-m-xylylene diisocyanate and toluene diisocyanate.

[0023] Further, the diol is selected from at least one of polypropylene glycol (PPG2000), polyethylene glycol (PEG 800), polycaprolactone diol (PCL1000) and polybutadiene diol (HTPB1000), and the average molecular weight of the diol is 500-3000;

[0024] Furthermore, the polymerization inhibitor is p-hydroxyanisole, hydroquinone or 2,6-di-tert-butyl-p-cresol;

[0025] The catalyst is stannous octoate, dibutyltin dilaurate or tetrabutyl titanate.

[0026] Further, the photoinitiator is selected from ethyl 2,4,6-trimethylbenzoylphenylphosphonate, 2,4-diethylthioxanthone, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methyl-1-propanone, 2-isopropylthioxanthone, 2-methyl-1-(4-methylthiophenyl)-2-morpholine-1-propanone, 2,4,6-trimethylbenzoyldiphenylphosphonate ...1-hydroxycyclohexylphenyl ketone, 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methyl-1-propanone, 2-isopropylthioxanthone, 1-hydroxycyclohexylphenyl ketone, 1-hydroxycyclohexylphenyl ketone, 1-hydroxycyclohexylphenyl ketone, 1-hydroxycyclohexylphenyl ketone, 1-hydroxycyclohexylphenyl ketone, 1-hydroxycyclohexylphenyl ketone, 1-hydroxycyclohexylphenyl ketone, 1-hydroxycyclohexylphenyl ketone, 1-hydroxycyclohexylphenyl ketone, 1-hydroxycyclohexylphenyl ketone, 1-hydroxycyclohexylphenyl ketone, 1-hydroxycyclohexylphenyl ketone, 1-hydroxycyclohexylphenyl At least one of phenylphosphine oxide, methyl o-benzoylbenzoate, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, benzophenone, benzoin diethyl ether, benzoin dimethyl ether, biphenylbenzophenone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and 2-(4-methylbenzyl)-2-(dimethylamino)-1-(4-morpholinophenyl)-1-butanone.

[0027] Furthermore, the active diluent is at least one of lauryl methacrylate, lauryl acrylate, isobornyl acrylate, isobornyl methacrylate, isodecyl acrylate, isooctyl acrylate, 2-phenoxyethyl acrylate, and ethoxylated trimethylolpropane triacrylate.

[0028] In the synthesis of polyurethane, the chain length, content, and end group type of the chain extender will affect the crystallinity of PU, and thus its thermal stability. The chain extender contains a branched structure. If the branched structure in the chain extender cannot participate in hydrogen bond assembly, it will hinder the aggregation of the hard segment and affect the formation of hydrogen bonds between PU molecules, thereby reducing the thermal stability of PU.

[0029] Vegetable oil is an ideal renewable chemical raw material with abundant reserves, little impact on the environment, and relatively low cost, and is not easily affected by the fluctuations of the global oil market. Several common vegetable oils, such as castor oil (CO), soybean oil, rapeseed oil, palm oil, linseed oil, etc., all contain active groups such as double bonds and ester groups, and can be used as the starting materials of bio-based polymers after chemical modification. The castor oil structure of the present invention comprises 3 fatty acid carbon chains, each fatty acid carbon chain is composed of 19 carbon atoms, and there are ester groups, unsaturated carbon-carbon double bonds and 3 active reaction sites of hydroxyl groups, which provide possibilities for the reaction and modification of castor oil, such as the ester group can be hydrolyzed, alcoholysed, amidated and other modifications, double bonds are utilized to carry out polymerization, hydrogenation, epoxidation and other reactions, hydroxyl groups are utilized to carry out esterification, etherification and other reactions, this special structure provides a theoretical basis for its synthesis of polyurethane, so that castor oil can be used instead of polyols or chain extenders, and the long-chain non-polar fatty acid chains in its components can improve the water resistance and elasticity of polyurethane, so that the modified polyurethane has good softness and flex resistance.

[0030] The structure of boron nitride nanosheets (BNNS) is similar to the two-dimensional nanostructure of graphene, and has excellent mechanical properties and thermal conductivity. However, unlike conductive materials such as graphene, BNNS, as an insulating material, is filled in the resin. While improving the mechanical properties of the base material, it can also prepare a composite material with good insulating properties. However, the single-component BNNS has few surface functional groups, and the interaction with the base polymer is weak, making it difficult to form a strong interaction, resulting in poor dispersion uniformity of BNNS in the base polymer material, resulting in poor performance.

[0031] The present invention firstly modifies the surface of BNNS with a silane coupling agent by a surface grafting method, and the silane coupling agent modified on the surface of BNNS increases a large number of polymer segments on the surface of the nanosheet, and also loads epoxy groups on the surface of BNNS; then, succinic anhydride is reacted with biomass raw material castor oil to obtain carboxyl-containing castor oil; finally, the epoxy group and the carboxyl group on the modified castor oil undergo a ring-opening addition reaction, thereby introducing silane and BNNS into the polyol. On the one hand, the dispersion performance of BNNS in the polymer substrate is improved, and the interaction between BNNS and the substrate polymer is improved through the interaction between the surface functional groups and the polymer molecular chains, thereby improving the mechanical properties, insulation properties and thermal conductivity of the composite material; on the other hand, the introduction of modified BNNS into castor oil can participate in hydrogen bond assembly, thereby enhancing the thermal stability and friction resistance of PU.

[0032] Compared with traditional anticorrosion coatings, self-healing coatings represent a shift in the field of corrosion protection. Compared with traditional coatings, self-healing coatings can repair damage autonomously. By continuously reducing vulnerabilities, self-healing coatings ensure long-lasting durability and higher performance, extending the service life of the protective layer. In general, self-healing cross-linked networks are mainly through dynamic and reversible reactions without the introduction of external substances, and non-covalent bonds are easier to break and rebuild than reversible covalent bonds. Hydrogen bonds, as an important non-covalent bond, are directional, highly reversible, and responsive to various stimuli. However, the binding energy of hydrogen bonds is usually between 25 and 65 kJ / mol. Compared with covalent bonds, this is a weaker interaction. It is difficult to obtain materials with good repair performance by constructing a cross-linked network only through hydrogen bonds formed between -C=O in the PU structure and -NH- in the BNNS structure. Therefore, it is usually necessary to construct multiple hydrogen bond interactions in the PU system to give polyurethane excellent properties.

[0033] The chemical structure of urea-4-pyrimidinone (UPy) containing urea and pyrimidine groups makes it easy to form strong quadruple hydrogen bonds. Due to the large number of hydrogen bonds formed between -NH- and -C=O in the PU structure and -NH- and -C=O of UPy, the synergistic effect with the dynamically reversible BNNS group in the PU structure and the thermal conductivity of BNNS improves the internal thermal conductivity of the material and increases the movement effect of the polymer molecular chain segments, the modified polyurethane resin of the present invention has good self-healing properties.

[0034] The polyurethane of the present invention is synthesized by a three-step method: the first step is to react a macromolecular diol (polyester or polyether diol) with an excess of diisocyanate to generate a prepolymer with an NCO terminal chain; the second step is to obtain a modified castor oil-based diol by introducing a Si-O-CH3 structure and BNNS into castor oil, and then through copolymerization modification, the diol containing silicon and BNNS is reacted with the previous prepolymer as a soft segment and connected to the main chain structure to obtain a modified prepolymer containing a C=C double bond; the third step is to introduce a UPy group into a small molecule diol to form a modified chain extender, and then the modified chain extender is reacted with the modified prepolymer to obtain a long TPU chain. The present invention utilizes a step-by-step synthesis method, and by adjusting the structure and molar mass of the diol and the type of diisocyanate, the final main chain and side chain structure are designed and finely controlled, and the desired PU structure is finally obtained.

[0035] The present invention introduces Si-O-CH3 structure, BNNS structure and UPy group into the polyurethane side chain, and maintains a large degree of freedom of the organosilicon structure, BNNS structure and UPy group. On the one hand, the dispersibility of BNNS in the polymer substrate is improved, and the interaction between BNNS and the substrate polymer is improved through the action between the surface functional group and the polymer molecular chain, thereby improving the mechanical properties and thermal conductivity of the composite material, and making the material have excellent dielectric properties; on the other hand, the ability of siloxane to migrate to the surface when it is located in the side chain is higher than that when it is located in the main chain, and the organosilicon segment will be enriched on the coating surface, and the surface free energy of the polyurethane material can be significantly reduced after film formation, and it is used as a soft segment to prepare a composite coating, showing better mechanical strength and viscoelastic properties, because it has good lubricity, can effectively reduce the friction resistance of the coating, thereby contributing to the improvement of the wear resistance of the coating; on the other hand, the main chain and side chain structure of the polyurethane are designed, BNNS and UPy groups are introduced into the PU side chain to form multiple hydrogen bonds, and rich hydrogen bonds are introduced into the polymer to construct a multiple cross-linked network, so that it has a rapid self-repairing ability, and greatly improves the self-repairing performance of the material.

[0036] The modified polyurethane light-curing coating of the present invention is further added with an active diluent, a defoamer, a leveling agent and a dispersant. The active diluent adjusts the viscosity and curing speed of the coating, and improves the hardness, abrasion resistance, adhesion performance, etc. of the cured film. The defoamer of the present invention is a silicone defoamer, the leveling agent is a solvent-free non-ionic leveling agent, and the dispersant is a polyester wetting dispersant. The defoamer coating forms bubbles and pinholes during stirring and construction. The leveling agent can control and improve the fluidity and leveling of the surface of the coating during construction, reduce the occurrence of shrinkage holes in the coating, and does not affect the gloss and transparency of the coating. The dispersant in the coating can stabilize the viscosity of the coating and improve its storage stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1The schematic diagram of the preparation route of the modified castor oil of the present invention;

[0038] Figure 2 Schematic diagram of the preparation route of the chain extender of the present invention. DETAILED DESCRIPTION

[0039] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0040] The reagents or instruments used in the present invention without indicating the manufacturer are all conventional products that can be purchased from the market.

[0041] The following is a specific embodiment:

[0042] Example 1

[0043] The preparation process of the modified polyurethane light-curing coating of this embodiment is as follows:

[0044] (1) Preparation of modified castor oil

[0045] 3 parts by weight of γ-glycidyloxypropyltrimethoxysilane (KH560) and 10 parts by weight of two-dimensional nanosheet structured boron nitride (BNNS, 500 nm) were added to an ethanol / H2O solution (ethanol:H2O=1:1, weight / weight), the temperature was raised to 70°C, and the mixture was stirred at 800 rpm for 8 hours. After the temperature was lowered to room temperature, the mixture was filtered, washed with ethanol, and dried at 60°C for 24 hours to obtain a modified BNNS.

[0046] Under N2 atmosphere, 25 parts by weight of castor oil, 1.5 parts by weight of succinic anhydride (SA) and 0.1 parts by weight of SnCl2 were placed in a reaction vessel, slowly heated to 100°C, stirred at 400 rpm for 3 hours, and when the temperature dropped to 80°C, 12 parts by weight of modified BNNS and 0.03 parts by weight of triethylamine were added, and the stirring reaction was continued for 4 hours to obtain modified castor oil.

[0047] (2) Preparation of chain extender

[0048] Under a nitrogen atmosphere, 13 parts by weight of hexamethylene diisocyanate (HDI) and 1 part by weight of 2-amino-6-methyl-4-pyrimidone were placed in a reaction vessel, heated to 90°C, stirred at 300 rpm for 26 hours, and after the temperature dropped to room temperature, filtered, washed, and vacuum dried at 60°C for 24 hours to obtain NCO-terminated UPy;

[0049] Under a nitrogen atmosphere, 30 parts by weight of UPy, 12 to 15 parts by weight of 2-amino-2-methyl-1,3-propanediol (AMPD) and 300 parts by weight of dimethyl sulfoxide (DMSO) were placed in a reaction container, heated to 60°C, stirred for reaction for 6 hours, and after the temperature dropped to room temperature, DMF was added to the reaction system to wash away the residual solvent DMSO, centrifuged and freeze-dried to obtain the chain extender UPy-OH.

[0050] (3) Preparation of modified polyurethane photocurable coating

[0051] Under a nitrogen atmosphere, 18 parts by weight of HDI and 0.04 parts by weight of p-hydroxyanisole are placed in a reaction container, mixed evenly and heated to 85° C., 50 parts by weight of polybutadiene glycol (HTPB-1000) and 0.01 parts by weight of a catalyst are added, stirred and kept warm for 3 hours, 40 parts by weight of modified castor oil are added, stirred and kept warm for 5 hours, the temperature is raised to 75° C., 4.1 parts by weight of a chain extender UPy-OH and 0.01 parts by weight of p-hydroxyanisole are added, stirred and kept warm for 3 hours, and a modified polyurethane resin is obtained; the stirring speed in this process is 400 rpm;

[0052] According to weight, 80 parts of modified polyurethane resin, 30 parts of lauryl methacrylate, 5 parts of 1-hydroxycyclohexyl phenyl ketone, 2 parts of leveling agent, 1 part of defoaming agent and 1 part of dispersant are weighed, and the modified polyurethane resin, lauryl methacrylate, dispersant and leveling agent are put into a reactor and dispersed at a rotation speed of 900 rpm for 10 minutes; then the defoaming agent is added, and the mixture is dispersed at a rotation speed of 1300 rpm for 15 minutes, and the material is ground and filtered. When used, 1-hydroxycyclohexyl phenyl ketone is added and dispersed at a rotation speed of 700 rpm for 10 minutes to obtain a modified polyurethane light-curing coating.

[0053] The implementation methods of Example 2 and Example 3 are the same as those of Example 1, except that the raw materials and their contents are different in the process of preparing the modified polyurethane light-curing coating. In each example, the specific raw materials and their contents are shown in Table 1, in parts by weight.

[0054] Table 1

[0055]

[0056]

[0057] Comparative Example 1

[0058] Under a nitrogen atmosphere, 18 parts by weight of HDI and 0.04 parts by weight of p-hydroxyanisole are placed in a reaction container, mixed evenly and heated to 85° C., 50 parts by weight of polybutadiene glycol (HTPB-1000) and 0.01 parts by weight of a catalyst are added, stirred and kept warm for 3 hours, 40 parts by weight of castor oil are added, stirred and kept warm for 5 hours, the temperature is raised to 75° C., 4.1 parts by weight of 2-amino-2-methyl-1,3-propanediol and 0.01 parts by weight of p-hydroxyanisole are added, stirred and kept warm for 3 hours, and a polyurethane acrylic resin is prepared; the stirring speed in this process is 400 rpm;

[0059] According to weight, 80 parts of polyurethane acrylic resin, 30 parts of lauryl methacrylate, 5 parts of 1-hydroxycyclohexyl phenyl ketone, 2 parts of leveling agent, 1 part of defoaming agent and 1 part of dispersant are weighed, and the modified polyurethane resin, lauryl methacrylate, dispersant and leveling agent are put into a reactor and dispersed at a speed of 900 rpm for 10 minutes; then the defoaming agent is added, and the mixture is dispersed at a speed of 1300 rpm for 15 minutes, and the material is ground and filtered. When used, 1-hydroxycyclohexyl phenyl ketone is added and dispersed at a speed of 700 rpm for 10 minutes to obtain a modified polyurethane light-curing coating.

[0060] Comparative Example 2

[0061] Under a nitrogen atmosphere, 18 parts by weight of HDI and 0.04 parts by weight of p-hydroxyanisole are placed in a reaction container, mixed evenly and heated to 85° C., 50 parts by weight of polybutadiene glycol (HTPB-1000) and 0.01 parts by weight of a catalyst are added, stirred and kept warm for 3 hours, 40 parts by weight of castor oil are added, stirred and kept warm for 5 hours, the temperature is raised to 75° C., 4.1 parts by weight of 2-amino-2-methyl-1,3-propanediol and 0.01 parts by weight of p-hydroxyanisole are added, stirred and kept warm for 3 hours, and a polyurethane acrylic resin is prepared; the stirring speed in this process is 400 rpm;

[0062] 3 parts by weight of γ-glycidyloxypropyltrimethoxysilane (KH560) and 10 parts by weight of two-dimensional nanosheet structured boron nitride (BNNS, 500 nm) were added to an ethanol / H2O solution (ethanol:H2O=1:1, weight / weight), the temperature was raised to 70°C, and the mixture was stirred at 800 rpm for 8 hours. After the temperature was lowered to room temperature, the mixture was filtered, washed with ethanol, and dried at 60°C for 24 hours to obtain a modified BNNS.

[0063] According to weight, 80 parts of polyurethane acrylic resin, 30 parts of lauryl methacrylate, 15 parts of epoxy acrylate, 12 parts of modified BNNS, 5 parts of 1-hydroxycyclohexyl phenyl ketone, 2 parts of leveling agent, 1 part of defoaming agent and 1 part of dispersant are weighed; the modified polyurethane resin, lauryl methacrylate, modified BNNS, dispersant and leveling agent are put into a reactor and dispersed at a speed of 900 rpm for 10 minutes; then the defoaming agent is added, dispersed at a speed of 1300 rpm for 15 minutes, ground and filtered, and when used, 1-hydroxycyclohexyl phenyl ketone is added and dispersed at a speed of 700 rpm for 10 minutes to obtain a modified polyurethane light-curing coating.

[0064] Comparative Example 3

[0065] The difference between Comparative Example 3 and Example 1 is that:

[0066] (3) Preparation of modified polyurethane photocurable coating

[0067] Under a nitrogen atmosphere, 18 parts by weight of HDI and 0.04 parts by weight of p-hydroxyanisole are placed in a reaction container, mixed evenly and heated to 85° C., 50 parts by weight of polybutadiene glycol (HTPB-1000) and 0.01 parts by weight of a catalyst are added, stirred and kept warm for 3 hours, 40 parts by weight of modified castor oil are added, stirred and kept warm for 5 hours, the temperature is raised to 75° C., 4.1 parts by weight of 2-amino-2-methyl-1,3-propanediol and 0.01 parts by weight of p-hydroxyanisole are added, stirred and kept warm for 3 hours, and a modified polyurethane resin is obtained; the stirring speed in this process is 400 rpm;

[0068] According to weight, 80 parts of modified polyurethane resin, 30 parts of lauryl methacrylate, 5 parts of 1-hydroxycyclohexyl phenyl ketone, 2 parts of leveling agent, 1 part of defoaming agent and 1 part of dispersant are weighed, and the modified polyurethane resin, lauryl methacrylate, dispersant and leveling agent are put into a reactor and dispersed at a rotation speed of 900 rpm for 10 minutes; then the defoaming agent is added, and the mixture is dispersed at a rotation speed of 1300 rpm for 15 minutes, and the material is ground and filtered. When used, 1-hydroxycyclohexyl phenyl ketone is added and dispersed at a rotation speed of 700 rpm for 10 minutes to obtain a modified polyurethane light-curing coating.

[0069] Comparative Example 4

[0070] The difference between Comparative Example 4 and Example 1 is that:

[0071] (1) Castor oil is not modified;

[0072] (3) Preparation of modified polyurethane photocurable coating

[0073] Under nitrogen atmosphere, 18 parts by weight of HDI and 0.04 parts by weight of polymerization inhibitor were placed in a reaction container, mixed evenly and heated to 85° C., 50 parts by weight of polybutadiene glycol (HTPB-1000) and 0.01 parts by weight of catalyst were added, stirred and kept warm for 3 hours, 40 parts by weight of castor oil were added, stirred and kept warm for 5 hours, heated to 75° C., 4.1 parts by weight of chain extender UPy-OH and 0.01 parts by weight of polymerization inhibitor were added, stirred and kept warm for 3 hours, and a modified polyurethane resin was obtained; the stirring speed in this process was 400 rpm;

[0074] The modified polyurethane resin, lauryl methacrylate, modified BNNS, 12 parts, 1-hydroxycyclohexyl phenyl ketone, 5 parts, leveling agent, defoamer and dispersant were weighed in parts by weight. The modified polyurethane resin, lauryl methacrylate, modified BNNS, dispersant and leveling agent were put into a reactor and dispersed at a speed of 900 rpm for 10 minutes. Then, the defoamer was added and dispersed at a speed of 1300 rpm for 15 minutes. The material was ground and filtered. When used, 1-hydroxycyclohexyl phenyl ketone was added and dispersed at a speed of 700 rpm for 10 minutes to obtain a modified polyurethane light-curing coating.

[0075] In the above, the defoaming agent used in Examples 1-3 and Comparative Examples 1-4 is a silicone defoaming agent, the leveling agent is a solvent-free nonionic leveling agent, and the dispersant is a polyester wetting dispersant, which are conventional reagents used in coatings and can be purchased.

[0076] The finished coatings obtained in Examples 1-3 and Comparative Examples 1-4 were applied on 50 mm × 50 mm ITO glass, and then placed under a UV curing machine and irradiated with 365 nm wavelength UV light for 3 min to obtain a cured film with a controlled thickness of 20 μm. The film was then dried at room temperature for 24 h, and the following tests were performed:

[0077] (1) Water absorption rate: ITO glass coated with a cured film was immersed in distilled water at room temperature for 24 h, and the mass of the sample before and after immersion was weighed.

[0078] (2) Alkali and alcohol resistance test: At room temperature, soak the sample in 10% NaOH aqueous solution and ethanol for 24 hours respectively, rub it with your hands to see the degree of discoloration. The number of "+" indicates the degree of discoloration, +: slight discoloration; ++: moderate discoloration; +++: severe discoloration.

[0079] (3) The water contact angle was measured on the top of the cured coating using the sessile drop method. The droplet was set to 3 μL / droplet and the measurement temperature was about 20°C.

[0080] (4) Adhesion test: GB / T9286-1998 Cross-cut test for paint and varnish films.

[0081] (5) Dielectric constant test: Use "GB / T1409-2006 Permittivity and Dielectric Dissipation Factor".

[0082] (6) Thermal conductivity: The test method used is ASTM D 5470-01, Characterization of thermal conductivity of thin thermally conductive solid electrical insulating materials.

[0083] (7) Storage stability: Weigh 50 g of each sample of Examples 1 to 3 and Comparative Examples 1 to 4, seal them in a can, and place them at 60° C. for 30 days. Observe whether the system shows any gel or precipitation. If not, record it as stable; otherwise, record it as unstable.

[0084] (8) Self-healing performance: A line was scratched on the ITO glass coated with the cured film using a utility knife. The sample was then kept at 40 °C for different periods of time and the healing condition was observed using an optical microscope.

[0085] The test results are shown in Table 1.

[0086] Table 1

[0087]

[0088] According to the disclosure of the above description, those skilled in the art to which the present invention belongs may also make appropriate changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the scope of protection of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. A method for preparing a modified polyurethane light-curing coating, characterized in that: Preparation of modified castor oil: Under N2 atmosphere, 15-30 parts by weight of castor oil, 1-3 parts by weight of succinic anhydride and 0.15-0.3 parts by weight of SnCl2 are placed in a reaction container, the temperature is slowly raised to 80-120°C, and the reaction is stirred for 1-5 hours; when the temperature drops to 70-90°C, 10-15 parts by weight of modified BNNS and 0.01-0.1 parts by weight of triethylamine are added, and the reaction is continued with stirring for 2-6 hours to obtain modified castor oil; Preparation of chain extender: Under a nitrogen atmosphere, 5 to 15 parts by weight of hexamethylene diisocyanate and 0.5 to 1 part by weight of 2-amino-6-methyl-4-pyrimidone are placed in a reaction container, the temperature is raised to 90 to 100° C., and the reaction is stirred for 15 to 30 hours. After the temperature drops to room temperature, the reaction is filtered, washed, and vacuum dried to obtain NCO-terminated UPy; Under a nitrogen atmosphere, 25 to 30 parts by weight of UPy, 12 to 16 parts by weight of 2-amino-2-methyl-1,3-propanediol and an appropriate amount of dimethyl sulfoxide are placed in a reaction container, the temperature is raised to 40 to 60° C., and the mixture is stirred for reaction for 3 to 8 hours. After the temperature drops to room temperature, the mixture is centrifuged, washed and dried to obtain a chain extender; Preparation of modified polyurethane resin: In a nitrogen atmosphere, diisocyanate and part of the polymerization inhibitor are placed in a reaction container, the temperature is raised to 60-80°C, diol and catalyst are added, stirring and heat-keeping reaction is carried out for 1-4 hours, modified castor oil is added, stirring and heat-keeping reaction is carried out for 3-8 hours, the temperature is raised to 70-100°C, the remaining polymerization inhibitor and chain extender are added, stirring and heat-keeping reaction is carried out for 2-3 hours, and a modified polyurethane resin is obtained; Preparation of modified polyurethane light-curing coating: 80-100 parts by weight of modified polyurethane resin, 30-40 parts by weight of active diluent, 0.5-2 parts by weight of dispersant and 1-3 parts by weight of leveling agent are put into a reactor and stirred to make them evenly mixed; then 0.5-1.5 parts by weight of defoamer are added and stirred to make them evenly dispersed and mixed, the material is ground and filtered, and when used, 3-10 parts by weight of photoinitiator is added and stirred to disperse, so as to prepare the modified polyurethane light-curing coating.

2. The method for preparing the modified polyurethane light-curing coating according to claim 1, characterized in that: The modified BNNS is prepared by the following method: 1 to 2 parts by weight of γ-glycidyloxypropyltrimethoxysilane and 10 to 15 parts by weight of BNNS are added to an ethanol / H2O solution, the temperature is raised to 60 to 80°C, and the solution is stirred for reaction for 6 to 10 hours. After the temperature drops to room temperature, the solution is filtered, washed, and dried to obtain modified BNNS.

3. The method for preparing the modified polyurethane light-curing coating according to claim 1, characterized in that: In the preparation of modified polyurethane resin: The molar ratio of the diol, modified castor oil, chain extender and diisocyanate is 3-5:2-3:0.5-1.5:8-10; The dosage of the polymerization inhibitor is 0.1-0.5% of the weight of the diisocyanate. The amount of the catalyst used is 0.01-0.1% by weight of the diisocyanate.

4. The method for preparing the modified polyurethane light-curing coating according to claim 3, characterized in that: The diisocyanate compound is at least one selected from hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, tetramethyl-m-xylylene diisocyanate and toluene diisocyanate.

5. The method for preparing the modified polyurethane light-curing coating according to claim 3, characterized in that: The diol is selected from at least one of polypropylene glycol, polyethylene glycol, polycaprolactone glycol and polybutadiene glycol, and the average molecular weight of the diol is 500-3000.

6. The method for preparing the modified polyurethane light-curing coating according to claim 3, characterized in that: The polymerization inhibitor is p-hydroxyanisole, hydroquinone or 2,6-di-tert-butyl-p-cresol.

7. The method for preparing the modified polyurethane light-curing coating according to claim 3, characterized in that: The catalyst is stannous octoate, dibutyltin dilaurate or tetrabutyl titanate.

8. The method for preparing the modified polyurethane light-curing coating according to claim 1, characterized in that: The photoinitiator is selected from ethyl 2,4,6-trimethylbenzoylphenylphosphonate, 2,4-diethylthioxanthone, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methyl-1-propanone, 2-isopropylthioxanthone, 2-methyl-1-(4-methylthiophenyl)-2-morpholine-1-propanone, 2,4,6-trimethylbenzoyldiphenyl At least one of phosphine oxide, methyl o-benzoylbenzoate, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, benzophenone, benzoin diethyl ether, benzoin dimethyl ether, biphenyl benzophenone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and 2-(4-methylbenzyl)-2-(dimethylamino)-1-(4-morpholinophenyl)-1-butanone.

9. The method for preparing the modified polyurethane light-curing coating according to claim 1, characterized in that: The active diluent is at least one of lauryl methacrylate, lauryl acrylate, isobornyl acrylate, isobornyl methacrylate, isodecyl acrylate, isooctyl acrylate, 2-phenoxyethyl acrylate, and ethoxylated trimethylolpropane triacrylate.

10. A modified polyurethane photocurable coating, prepared by the preparation method of the modified polyurethane photocurable coating according to any one of claims 1 to 9.

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