High-adhesion varnished wire priming paint and preparation method thereof

Abstract

The invention discloses a high-adhesion varnished wire primer and a preparation method thereof, belongs to the technical field of primer processing, and aims to solve the technical problem that the adhesion and the electrical insulation property of the varnished wire primer on a conductor need to be further improved in the prior art. The varnished wire priming paint comprises the following components in parts by weight: 10 parts of composite polyurethane emulsion and 2-3 parts of a curing agent, modified polyurethane prepared by taking silane modified PEG as a base material, modified styrene-butadiene latex modified by benzyl ammonia and epoxy groups and a cross-linking agent form composite polyurethane, and then the composite polyurethane is matched with the curing agent to prepare the varnished wire priming paint. The adhesion performance and flexibility of the paint film are effectively improved, and the electrical insulation performance of the enameled wire is also improved.

Description

Technical Field

[0001] The present invention relates to the technical field of primer processing, and particularly relates to a primer for enameled wire with high adhesion and a preparation method thereof. Background Art

[0002] As a core component of electrical equipment such as motors and transformers, the performance of the insulating layer of enameled wire directly affects the reliability and service life of the equipment. Among them, the primer, as the first layer of the enameled wire insulation system, mainly functions to enhance the adhesion between the conductor (such as copper wire or aluminum wire) and the topcoat, and at the same time provides basic insulation performance and mechanical protection.

[0003] In the prior art, the primers for enameled wire mostly use acetal, epoxy or ordinary polyester resin as the matrix material. Although these materials have a certain adhesion, the flexibility of these matrix materials is poor. When applying the primer, it is difficult for the primer to quickly infiltrate and spread on the surface of the matrix. Under high mechanical stress or thermal cycling conditions, problems such as paint shrinkage and peeling are likely to occur in the paint film. In order to improve production efficiency, the running speed of the winding equipment of manufacturers of electrical equipment such as motors and transformers is getting faster and faster, resulting in a larger winding tension and a larger elongation rate of the enameled wire during the winding process. The adhesion between the traditional primer for enameled wire and the conductor is poor, resulting in easy cracking of the paint film of the enameled wire during winding. Moreover, the electrical insulation performance of the existing primer also needs to be further improved.

[0004] In view of the technical defects in this regard, a solution is proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a primer for enameled wire with high adhesion and a preparation method thereof, which are used to solve the technical problems that the adhesion and electrical insulation performance of the primer for enameled wire on the conductor in the prior art need to be further improved.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A primer for enameled wire with high adhesion includes 10 parts by weight of a composite polyurethane emulsion and 2 - 3 parts by weight of a curing agent;

[0008] The curing agent is composed of polyetheramine and N,N - dimethylformamide in a ratio of 1 g:1 mL;

[0009] The preparation method of the composite polyurethane emulsion is as follows: Under the protection of inert gas, silane - modified PEG, tetrahydrofuran and a catalyst are mixed and stirred until dissolved, the temperature of the reaction system is raised to 50 - 60 °C, diisocyanate is added to the reaction system, and the reaction is carried out under insulation for 80 - 100 min. Then glycidyl is added to the reaction system, and the reaction is carried out under insulation for 50 - 60 min, and then post - treatment is carried out to obtain the modified polyurethane;

[0010] The synthesis reaction formula of the modified polyurethane is as follows:

[0011]

[0012] In the formula:

[0013]

[0014] .

[0015] The synthesis reaction mechanism of the modified polyurethane is as follows:

[0016] During the reaction process, the catalyst catalyzes the reaction between the hydroxyl groups on the silane-modified PEG molecules and the isocyanate groups on the diisocyanate molecules. By controlling the dosage ratio of the reactants, a polyurethane prepolymer with multiple silane-modified PEG co-embedded and end-capped with isocyanate groups is formed. Then, taking the isocyanate groups on the polyurethane prepolymer molecules as the active reaction sites, they react with the hydroxyl groups on the glycidyl molecules to form epoxy group end-capping on the polyurethane prepolymer molecular chains, and the modified polyurethane is prepared.

[0017] The modified styrene-butadiene latex, modified polyurethane, and DMF solution are stirred and mixed. The temperature of the reaction system is raised to 95 - 115 °C, and high-speed shear dispersion is carried out for 80 - 100 min. Then the temperature of the reaction system is lowered to 70 - 80 °C. A cross-linking agent is added to the reaction system, and heat preservation reaction is carried out for 2 - 3 h, followed by post-treatment to obtain the composite polyurethane emulsion.

[0018] The synthesis reaction mechanism of the composite polyurethane emulsion is as follows:

[0019] During the reaction process, through high-speed shear dispersion, the modified styrene-butadiene latex and the modified polyurethane are promoted to be uniformly dispersed in the DMF solution. Then, taking the isocyanate groups on the cross-linking agent molecules as the reactive groups, they react with the active reaction sites such as phenolic hydroxyl groups and imino groups on the modified styrene-butadiene latex or modified polyurethane molecules to promote the chemical cross-linking between the modified styrene-butadiene latex and the modified polyurethane molecules. Then, through temperature-controlled vacuum distillation, the low-boiling substances are removed to prepare the composite polyurethane emulsion containing DMF.

[0020] Furthermore, during the preparation process of the composite polyurethane emulsion, the dosage ratio of the modified styrene-butadiene latex, modified polyurethane, DMF solution, and cross-linking agent is 2 - 3 g: 7 - 8 g: 50 mL: 1.2 - 1.8 g. The DMF solution is composed of N,N-dimethylformamide, xylene, Tween 80, and sodium dodecyl sulfate in a ratio of 7 mL: 4 mL: 0.3 g: 0.2 g. The post-treatment includes: after the reaction is completed, the reaction system is kept at 75 °C, and the low-boiling substances are removed by vacuum distillation to obtain the composite polyurethane emulsion.

[0021] Further, in the preparation process of the modified polyurethane, the dosage ratio of the silane-modified PEG, tetrahydrofuran, catalyst and glycidyl is 5 g: 30 mL: 0.2 g: 3 g, and the dosage of the diisocyanate is calculated from N 二异氰酸酯-NCO / N 硅烷改性PEG-OH = 1.1: 1. The diisocyanate is toluene diisocyanate. The post-treatment includes: after the reaction is completed, the temperature of the reaction system is kept at 50 - 60 °C, and the low-boiling substances are removed by reduced pressure distillation to obtain the modified polyurethane.

[0022] Further, the preparation method of the silane-modified PEG is as follows: under the protection of an inert gas, polyethylene glycol, tetrahydrofuran and a catalyst are mixed and stirred until the system is dissolved. The temperature of the reaction system is lowered to 3 - 8 °C, and a dichlorosilane solution is added dropwise to the reaction system. After the addition is completed, the reaction is kept warm for 6 - 8 h, and then post-treated to obtain the silane-modified PEG.

[0023] The synthesis reaction formula of the silane-modified PEG is:

[0024]

[0025] The synthesis reaction mechanism of the silane-modified PEG is:

[0026] In the reaction process, triethylamine, as a strong nucleophilic organic base, the lone pair electrons in its molecule form a hydrogen bond with the chlorine atom in 1,5-dichlorohexamethyltrisiloxane, activating the C-Cl bond and reducing the energy barrier of nucleophilic substitution. Subsequently, the hydroxyl group of the polyol acts as a nucleophile to replace the chloride ion, completing the substitution reaction to form the silane-modified PEG with a polysiloxane chain segment embedded. During the reaction process, by keeping the temperature low, the side reaction of siloxane self-polymerization is reduced, and the reaction selectivity is improved.

[0027] Further, the dosage ratio of the polyethylene glycol and dichlorosilane is 1.1 mol: 1 mol, the dosage ratio of the polyethylene glycol, tetrahydrofuran and catalyst is 1 g: 10 mL: 0.6 g. The polyethylene glycol is PEG400, the catalyst is triethylamine, and the dichlorosilane solution is composed of 1,5-dichlorohexamethyltrisiloxane and tetrahydrofuran in a ratio of 1 g: 2 mL. The post-treatment includes: after the reaction is completed, the temperature of the reaction system is raised to 40 - 60 °C, and the low-boiling substances are removed by reduced pressure distillation to obtain the silane-modified PEG.

[0028] Further, the preparation method of the modified styrene-butadiene latex is as follows: the styrene-butadiene latex and the emulsion are stirred and mixed. The temperature of the reaction system is raised to 70 - 80 °C, and an initiator solution is added dropwise to the reaction system for 30 - 50 min continuously. Then a modified liquid is added to the reaction system, and the reaction is kept warm for 3 - 5 h, and then post-treated to obtain the modified styrene-butadiene latex.

[0029] The synthesis reaction mechanism of the modified styrene-butadiene latex is:

[0030] During the reaction process, styrene-butadiene latex provides the elastic skeleton of polystyrene-polybutadiene. The isobutyronitrile radicals generated by the decomposition of the free radical initiator azobisisobutyronitrile attack the unsaturated double bonds on the molecular chain of the styrene-polybutadiene elastic skeleton or the modified liquid molecules, forming the macromolecular radicals of styrene-polybutadiene and the modified monomers containing radicals. Then, through free radical polymerization reaction, epoxy groups and benzylamine modifications are introduced onto the styrene-polybutadiene skeleton to prepare the modified styrene-butadiene latex.

[0031] Furthermore, the dosage ratio of the styrene-butadiene latex, emulsion, initiator solution and modified liquid is 10 g: 30 mL: 5 mL: 5 g. The emulsion consists of deionized water, tetrahydrofuran, sodium dodecyl sulfate, and OP-10 in a ratio of 60 mL: 40 mL: 3 g: 1 g. The initiator solution consists of azobisisobutyronitrile and tetrahydrofuran in a ratio of 1 g: 8 mL. The modified liquid consists of glycidyl methacrylate, 4-vinylbenzylamine and tetrahydrofuran in a ratio of 3 g: 1 g: 8 mL. The post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, calcium chloride is added to the reaction system, demulsification is carried out, filtration is performed by suction, the filter cake is washed three times with purified water and ethanol respectively and then dried by suction, the filter cake is transferred to a drying oven at 70-80 °C, and vacuum dried to constant weight to obtain the modified styrene-butadiene latex.

[0032] Furthermore, the preparation method of the crosslinking agent is as follows: under the protection of inert gas, polyethylene glycol, tetrahydrofuran and a catalyst are mixed and stirred, the temperature of the reaction system is raised to 55-60 °C, isophorone diisocyanate is added to the reaction system, and the reaction is carried out under insulation for 60-80 min. 2-(Aminomethyl)-2-methyl-1,3-propanediamine is added to the reaction system, and the reaction is carried out under insulation for 40-60 min, followed by post-treatment to obtain the crosslinking agent.

[0033] The synthesis reaction formula of the crosslinking agent is:

[0034]

[0035] In the formula:

[0036] ;

[0037] .

[0038] The synthesis reaction mechanism of the crosslinking agent is:

[0039] During the reaction process, the catalyst catalyzes the condensation reaction between the hydroxyl groups on the polyethylene glycol molecules and the isocyanate groups on the isophorone diisocyanate molecules. By controlling the dosage ratio of the reactants, isocyanate group-terminated modification is formed at both ends of the polyethylene glycol molecular chain. Then, 2-(aminomethyl)-2-methyl-1,3-propanediamine is used as the crosslinking agent, and the isocyanate groups modified on the polyethylene glycol molecular chain react with the amino groups on the 2-(aminomethyl)-2-methyl-1,3-propanediamine molecules to form a multi-crosslinked network terminated with isocyanate groups, and the crosslinking agent is prepared.

[0040] Further, the dosage ratio of the polyethylene glycol, isophorone diisocyanate, and 2-(aminomethyl)-2-methyl-1,3-propanediamine is 3 mol: 6 mol: 1 mol, the dosage ratio of the polyethylene glycol, tetrahydrofuran, and the catalyst is 5 g: 50 mL: 0.2 g, the catalyst is dibutyltin dilaurate, the polyethylene glycol is PEG-400, and the post-treatment includes: after the reaction is completed, the reaction system is kept at 55-60 °C, and the low-boiling substances are removed by reduced pressure distillation to obtain the crosslinking agent.

[0041] A preparation method of an enameled wire primer with high adhesion, the preparation method of the enameled wire primer with high adhesion is: mixing a composite polyurethane emulsion and a curing agent, and stirring and dispersing for 20-30 min to obtain the primer.

[0042] The present invention has the following beneficial effects:

[0043] 1. For the enameled wire primer with high adhesion proposed by the present invention, the polyethylene glycol is co-embedded and modified by dichlorosilane to form a silane-modified PEG with a long straight-chain structure. Then, based on it, a highly flexible epoxy-terminated modified polyurethane is prepared. By enhancing the intermolecular compatibility between the modified styrene-butadiene latex and the modified polyurethane, after preparing the composite polyurethane emulsion, through mixing with polyetheramine, the flexibility of the primer material is improved, and the adhesion strength between the primer and the metal substrate is improved by the mutual cooperation between the modified polyurethane and the modified styrene-butadiene latex. The dielectric gradient formed by the styrene-butadiene latex and the polyurethane makes the electric field distribution more uniform, reduces the ionization channel, and reduces the activation energy of ion migration, thereby improving the surface resistance and breakdown voltage resistance of the paint film.

[0044] 2. The primer paint for enameled wire with high adhesion proposed by the present invention modifies polyethylene glycol with dichlorosilane to synthesize silane-modified PEG with a polysiloxane block. Then, using the silane-modified PEG as the base material, a condensation reaction occurs with toluene diisocyanate to form a modified polyurethane capped with an epoxy group. By pre-synthesizing the silane-modified PEG with a polysiloxane block to prepare the modified polyurethane, the dosage of toluene diisocyanate is effectively reduced, that is, the content of the hard segment in the modified polyurethane is reduced, enhancing the flexibility of the modified polyurethane. The high bond energy of the Si-O-Si segment in the modified polyurethane forms a molecular barrier to inhibit electron migration. The dipole moment of the ether bond in polyethylene glycol is evenly distributed in the electric field, reducing the local field strength concentration, lowering the conductivity, and increasing the breakdown voltage. The molecular chain of the modified polyurethane contains a large number of urethane groups. The carbonyl oxygen and amino nitrogen in this group have strong polarity and can generate strong van der Waals forces and hydrogen bond interactions with the surfaces of substrates such as metals and plastics. Moreover, the flexibility of the ether bond and the Si-O-Si segment helps to improve the wettability of the coating, enabling the coating to spread better on the substrate surface, increasing the contact area, and thus enhancing the adhesion.

[0045] 3. The primer paint for enameled wire with high adhesion proposed by the present invention is modified using styrene-butadiene latex as the raw material to prepare a modified styrene-butadiene latex modified with benzylamine and epoxy groups. The polar groups modified on its molecules increase its compatibility with the modified polyurethane, and then promote its uniform dispersion and mixing under high-speed shearing. Moreover, the modified isocyanate group on the crosslinking agent molecule will react preferentially with the modified benzylamine on the modified styrene-butadiene latex to form a chemical graft modification, and then react with the active reaction sites on the modified polyurethane molecule to form a crosslinking bond, thereby promoting the homogeneous mixing performance between the modified styrene-butadiene latex and the modified polyurethane molecule. The polymer system of the modified polyurethane and the modified styrene-butadiene latex with good compatibility forms a coating with good elasticity, enhancing the flexibility and recovery of the coating. The curing agent promotes the intermolecular crosslinking between the polymers. The crosslinking structure and the flexibility of the molecular chain in the coating enable the coating to undergo large deformations without being damaged when stressed, thereby improving the flexibility. The styrene-butadiene rubber segment has good adhesion performance and can generate physical adsorption with the substrate surface, improving the adhesion of the material. The conjugated structure of the benzene ring can capture high-energy electrons. The non-polar benzene rings of the styrene units in the styrene-butadiene latex form a continuous phase to inhibit electron migration and reduce ionization damage. Under the action of the curing agent, the epoxy groups on the modified styrene-butadiene rubber and the modified polyurethane molecule undergo ring-opening condensation to form a crosslinked network, making the coating adhere more tightly to the substrate surface while increasing the density of the material, restricting the migration of carriers, and increasing the volume resistivity coefficient and breakdown voltage of the material. Detailed implementation mode

[0046] The technical solutions of the present invention will be clearly and completely described below in conjunction with embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0047] In the present invention, polyethylene glycol 400 is selected from Jinan Yunuo Chemical Co., Ltd., with an active ingredient content of 99%, model number PEG400, density 1.27 g / mL (25 °C), and CAS number 25322-68-3;

[0048] In the present invention, styrene-butadiene latex is selected from Dongguan Jiaqing Plastic Raw Materials Co., Ltd., with a solids content of 45-50%;

[0049] In the present invention, polyetheramine is selected from Shanghai Yushicheng Chemical Technology Co., Ltd., with the product name BASF polyetheramine D230 (Bassoul EC301), and model number polyetheramine D230;

[0050] In the present invention, the CAS number of hydroxypropyl-terminated polydimethylsiloxane is 104780-66-7;

[0051] In the present invention, OP-10 is an OP-10 emulsifier, with an active ingredient content of 99%, a pH value of 6-7 (1% aqueous solution), an HLB value of 14.5, and a cloud point of 61-67 °C.

[0052] Example 1

[0053] This example provides a preparation method for an enameled wire primer with high adhesion, including the following steps:

[0054] S1. Prepare modified polyurethane

[0055] Weigh: 27.7 g of 1,5-dichlorohexamethyltrisiloxane and 55.4 mL of tetrahydrofuran to form a homogeneous mixture to obtain a dichlorosilane solution for standby;

[0056] Weigh: 88 g of polyethylene glycol 400, 880 mL of tetrahydrofuran, and 52.8 g of catalyst triethylamine and add them to a reaction flask protected by nitrogen and stir until the system dissolves. The temperature of the reaction flask is reduced to 3 °C, and the above-prepared dichlorosilane solution is added dropwise to the reaction flask. After the addition is complete, keep the reaction at a constant temperature for 6 h, raise the temperature of the reaction flask to 40 °C, and evacuate the reaction flask to a negative pressure of 0.1 MPa to distill off the low-boiling substances to obtain silane-modified PEG;

[0057] Weigh: 100 g of silane-modified PEG, 600 mL of tetrahydrofuran, and 4 g of catalyst dibutyltin dilaurate and add them to a reaction flask protected by nitrogen and stir until dissolved. Raise the temperature of the reaction flask to 50 °C, and according to N二异氰酸酯-NCO / N 硅烷改性PEG-OH Calculate the feeding mass of toluene - 2,3 - diisocyanate in a ratio of 1.1:1 and add it to the reaction flask. Keep the temperature for reaction for 80 min. Add 60 g of glycidyl alcohol to the reaction flask and keep the temperature for reaction for 50 min. Keep the temperature of the reaction flask at 50 °C, evacuate the reaction flask to a negative pressure of 0.1 MPa, and distill off the low - boiling substances under reduced pressure to obtain the modified polyurethane, N 二异氰酸酯-NCO is the molar amount of isocyanate groups in toluene diisocyanate, N 硅烷改性PEG-OH is the molar amount of hydroxyl groups in silane - modified PEG.

[0058] S2. Preparation of modified styrene - butadiene latex

[0059] Mix deionized water, tetrahydrofuran, sodium dodecyl sulfate, and OP - 10 evenly in a ratio of 60 mL:40 mL:3 g:1 g to obtain an emulsion;

[0060] Mix azobisisobutyronitrile and tetrahydrofuran evenly in a ratio of 1 g:8 mL to obtain an initiator solution;

[0061] Mix glycidyl methacrylate, 4 - vinylbenzylamine, and tetrahydrofuran evenly in a ratio of 3 g:1 g:8 mL to obtain a modified solution;

[0062] Weigh: Add 200 g of styrene - butadiene latex and 600 mL of the emulsion to the reaction flask and stir. Raise the temperature of the reaction flask to 70 °C. Add 100 mL of the initiator solution drop - by - drop to the reaction flask over a dropping time of 30 min. After the dropping is completed, add 100 g of the modified solution to the reaction flask. Keep the temperature for reaction for 3 h. Lower the temperature of the reaction flask to room temperature. Add 30 g of anhydrous calcium chloride to the reaction flask to break the emulsion. Filter by suction. Wash the filter cake three times with purified water and ethanol respectively, and then dry by suction. Transfer the filter cake to a drying oven at 70 °C, evacuate to a negative pressure of 0.1 MPa, and dry under vacuum until constant weight to obtain the modified styrene - butadiene latex.

[0063] S3. Preparation of cross - linker

[0064] Weigh: Add 120 g of polyethylene glycol 400, 1200 mL of tetrahydrofuran, and 4.8 g of the catalyst dibutyltin dilaurate to a reaction flask under nitrogen protection and stir. Raise the temperature of the reaction flask to 55 °C. Add 133.4 g of isophorone diisocyanate to the reaction flask. Keep the temperature for reaction for 60 min. Add 11.7 g of 2 - (aminomethyl) - 2 - methyl - 1,3 - propanediamine to the reaction system. Keep the temperature for reaction for 40 min. Keep the temperature of the reaction flask at 55 °C, evacuate the reaction flask to a negative pressure of 0.1 MPa, and distill off the low - boiling substances under reduced pressure to obtain the cross - linker.

[0065] S4. Preparation of composite polyurethane emulsion

[0066] Mix 7 mL of N,N-dimethylformamide, 4 mL of xylene, 0.3 g of Tween 80, and 0.2 g of sodium dodecyl sulfate uniformly to obtain a DMF solution;

[0067] Weigh: 40 g of modified styrene-butadiene latex, 140 g of modified polyurethane, and 1000 mL of DMF solution and add them to a high-speed disperser for stirring. The temperature of the high-speed disperser is raised to 95 °C, the rotation speed of the disperser is set to 10,000 r / min, and high-speed shear dispersion is carried out for 80 min. The temperature of the high-speed disperser is lowered to 70 °C, 24 g of cross-linking agent is added to the high-speed disperser, and the reaction is carried out under insulation for 2 h. The reaction solution is transferred to a rotary evaporator with a water bath temperature of 75 °C, and the negative pressure is pumped to 0.1 MPa to distill off low-boiling substances under reduced pressure to obtain a composite polyurethane emulsion.

[0068] S5. Prepare the primer

[0069] Mix polyetheramine and N,N-dimethylformamide in a ratio of 1 g:1 mL uniformly to obtain a curing agent;

[0070] Weigh by weight: 10 parts of composite polyurethane emulsion and 2 parts of curing agent and add them to a high-speed dispersant. Set the stirring speed to 3000 r / min and stir and disperse for 20 min to obtain a primer.

[0071] Example 2

[0072] This example provides a method for preparing a high-adhesion enameled wire primer, including the following steps:

[0073] S1. Prepare modified polyurethane

[0074] Weigh: 27.7 g of 1,5-dichlorohexamethyltrisiloxane and 55.4 mL of tetrahydrofuran and mix them uniformly to obtain a dichlorosilane solution for standby;

[0075] Weigh: 88 g of polyethylene glycol 400, 880 mL of tetrahydrofuran, and 52.8 g of catalyst triethylamine and add them to a reaction flask under nitrogen protection and stir until the system dissolves. The temperature of the reaction flask is lowered to 5 °C, and the above-prepared dichlorosilane solution is added dropwise to the reaction flask. After the addition is complete, the reaction is carried out under insulation for 7 h. The temperature of the reaction flask is raised to 50 °C, and the reaction flask is evacuated to 0.1 MPa to distill off low-boiling substances under reduced pressure to obtain silane-modified PEG;

[0076] Weigh: 100 g of silane-modified PEG, 600 mL of tetrahydrofuran, and 4 g of catalyst dibutyltin dilaurate and add them to a reaction flask under nitrogen protection and stir until dissolved. The temperature of the reaction flask is raised to 55 °C, according to N 二异氰酸酯-NCO / N 硅烷改性PEG-OHCalculate the feeding mass of toluene-2,4-diisocyanate at a ratio of 1.1:1, add it to the reaction flask, keep the temperature for 90 min, add 60 g of glycidyl alcohol to the reaction flask, keep the temperature for 55 min, keep the temperature of the reaction flask at 55 °C, evacuate the reaction flask to a negative pressure of 0.1 MPa, and distill off the low-boiling substances under reduced pressure to obtain the modified polyurethane, N 二异氰酸酯-NCO is the molar amount of isocyanate groups in toluene diisocyanate, N 硅烷改性PEG-OH is the molar amount of hydroxyl groups in the silane-modified PEG.

[0077] S2. Preparation of modified styrene-butadiene latex

[0078] Mix deionized water, tetrahydrofuran, sodium dodecyl sulfate, and OP-10 evenly at a ratio of 60 mL:40 mL:3 g:1 g to obtain an emulsion;

[0079] Mix azobisisobutyronitrile and tetrahydrofuran evenly at a ratio of 1 g:8 mL to obtain an initiator solution;

[0080] Mix glycidyl methacrylate, 4-vinylbenzylamine, and tetrahydrofuran evenly at a ratio of 3 g:1 g:8 mL to obtain a modified solution;

[0081] Weigh: Add 200 g of styrene-butadiene latex and 600 mL of the emulsion to the reaction flask and stir. Raise the temperature of the reaction flask to 75 °C. Add 100 mL of the initiator solution dropwise to the reaction flask continuously over a dropping time of 40 min. After the dropping is complete, add 100 g of the modified solution to the reaction flask, keep the temperature for 4 h, lower the temperature of the reaction flask to room temperature, add 30 g of anhydrous calcium chloride to the reaction flask to break the emulsion, filter by suction, wash the filter cake three times with purified water and ethanol respectively, and then dry by suction. Transfer the filter cake to a drying oven at 75 °C, evacuate to a negative pressure of 0.1 MPa, and vacuum dry to constant weight to obtain the modified styrene-butadiene latex.

[0082] S3. Preparation of crosslinking agent

[0083] Weigh: Add 120 g of polyethylene glycol 400, 1200 mL of tetrahydrofuran, and 4.8 g of the catalyst dibutyltin dilaurate to a reaction flask under nitrogen protection and stir. Raise the temperature of the reaction flask to 57 °C. Add 133.4 g of isophorone diisocyanate to the reaction flask, keep the temperature for 70 min. Add 11.7 g of 2-(aminomethyl)-2-methyl-1,3-propanediamine to the reaction system, keep the temperature for 50 min, keep the temperature of the reaction flask at 58 °C, evacuate the reaction flask to a negative pressure of 0.1 MPa, and distill off the low-boiling substances under reduced pressure to obtain the crosslinking agent.

[0084] S4. Preparation of composite polyurethane emulsion

[0085] Mix 7 mL of N,N-dimethylformamide, 4 mL of xylene, 0.3 g of Tween 80, and 0.2 g of sodium dodecyl sulfate evenly to obtain a DMF solution;

[0086] Weigh: 50 g of modified styrene-butadiene latex, 160 g of modified polyurethane, and 1000 mL of the DMF solution, add them to a high-speed disperser and stir. The temperature of the high-speed disperser rises to 105 °C, set the rotation speed of the disperser to 20000 r / min, carry out high-speed shear dispersion for 90 min, the temperature of the high-speed disperser drops to 75 °C, add 30 g of cross-linking agent to the high-speed disperser, keep the temperature for reaction for 2.5 h, transfer the reaction solution to a rotary evaporator with a water bath temperature of 75 °C, pump to a negative pressure of 0.1 MPa, and distill off low-boiling substances under reduced pressure to obtain a composite polyurethane emulsion.

[0087] S5. Prepare the primer

[0088] Mix polyetheramine and N,N-dimethylformamide evenly at a ratio of 1 g:1 mL to obtain a curing agent;

[0089] Weigh by weight: 10 parts of the composite polyurethane emulsion and 2.5 parts of the curing agent, add them to a high-speed dispersant, set the stirring speed to 4000 r / min, and stir and disperse for 25 min to obtain a primer.

[0090] Example 3

[0091] This example provides a preparation method of a high-adhesion enameled wire primer, including the following steps:

[0092] S1. Prepare modified polyurethane

[0093] Weigh: 27.7 g of 1,5-dichlorohexamethyltrisiloxane and 55.4 mL of tetrahydrofuran to form a homogeneous mixture to obtain a dichlorosilane solution for standby;

[0094] Weigh: 88 g of polyethylene glycol 400, 880 mL of tetrahydrofuran, and 52.8 g of catalyst triethylamine, add them to a reaction flask under nitrogen protection and stir until the system dissolves. The temperature of the reaction flask drops to 8 °C, add the above-prepared dichlorosilane solution dropwise to the reaction flask. After the dropwise addition, keep the temperature for reaction for 8 h, raise the temperature of the reaction flask to 60 °C, pump the reaction flask to a negative pressure of 0.1 MPa, and distill off low-boiling substances under reduced pressure to obtain silane-modified PEG;

[0095] Weigh: 100 g of silane-modified PEG, 600 mL of tetrahydrofuran, and 4 g of catalyst dibutyltin dilaurate, add them to a reaction flask under nitrogen protection and stir until dissolved. The temperature of the reaction flask rises to 60 °C, according to N 二异氰酸酯-NCO / N 硅烷改性PEG-OHCalculate the feeding mass of toluene-3,5-diisocyanate at a ratio of 1.1:1 and add it to the reaction flask. Keep the temperature for reaction for 100 min. Add 60 g of glycidyl alcohol to the reaction flask and keep the temperature for reaction for 60 min. Keep the temperature of the reaction flask at 60 °C. Draw a negative pressure in the reaction flask to 0.1 MPa and distill off the low-boiling substances under reduced pressure to obtain the modified polyurethane, N 二异氰酸酯-NCO is the molar amount of isocyanate groups in toluene diisocyanate, N 硅烷改性PEG-OH is the molar amount of hydroxyl groups in the silane-modified PEG.

[0096] S2. Preparation of modified styrene-butadiene latex

[0097] Mix deionized water, tetrahydrofuran, sodium dodecyl sulfate, and OP-10 evenly at a ratio of 60 mL:40 mL:3 g:1 g to obtain an emulsion;

[0098] Mix azobisisobutyronitrile and tetrahydrofuran evenly at a ratio of 1 g:8 mL to obtain an initiator solution;

[0099] Mix glycidyl methacrylate, 4-vinylbenzylamine, and tetrahydrofuran evenly at a ratio of 3 g:1 g:8 mL to obtain a modified solution;

[0100] Weigh: Add 200 g of styrene-butadiene latex and 600 mL of the emulsion to the reaction flask and stir. Raise the temperature of the reaction flask to 80 °C. Add 100 mL of the initiator solution dropwise to the reaction flask continuously over a dropping time of 50 min. After the dropping is complete, add 100 g of the modified solution to the reaction flask and keep the temperature for reaction for 5 h. Lower the temperature of the reaction flask to room temperature. Add 30 g of anhydrous calcium chloride to the reaction flask to break the emulsion. Filter by suction. Wash the filter cake three times with purified water and ethanol respectively and then drain it by suction. Transfer the filter cake to a drying oven at 80 °C, draw a negative pressure to 0.1 MPa, and dry it under vacuum to constant weight to obtain the modified styrene-butadiene latex.

[0101] S3. Preparation of crosslinking agent

[0102] Weigh: Add 120 g of polyethylene glycol 400, 1200 mL of tetrahydrofuran, and 4.8 g of the catalyst dibutyltin dilaurate to the reaction flask protected by nitrogen and stir. Raise the temperature of the reaction flask to 60 °C. Add 133.4 g of isophorone diisocyanate to the reaction flask and keep the temperature for reaction for 80 min. Add 11.7 g of 2-(aminomethyl)-2-methyl-1,3-propanediamine to the reaction system and keep the temperature for reaction for 60 min. Keep the temperature of the reaction flask at 60 °C. Draw a negative pressure in the reaction flask to 0.1 MPa and distill off the low-boiling substances under reduced pressure to obtain the crosslinking agent.

[0103] S4. Preparation of composite polyurethane emulsion

[0104] Mix 7 mL of N,N-dimethylformamide, 4 mL of xylene, 0.3 g of Tween 80, and 0.2 g of sodium dodecyl sulfate uniformly to obtain a DMF solution;

[0105] Weigh: 60 g of modified styrene-butadiene latex, 180 g of modified polyurethane, and 1000 mL of DMF solution, add them to a high-speed disperser and stir. Raise the temperature of the high-speed disperser to 115 °C, set the rotation speed of the disperser to 30000 r / min, perform high-speed shear dispersion for 100 min, lower the temperature of the high-speed disperser to 80 °C, add 36 g of cross-linking agent to the high-speed disperser, keep the temperature for reaction for 3 h, transfer the reaction solution to a rotary evaporator with a water bath temperature of 75 °C, draw a negative pressure to 0.1 MPa, and distill off low-boiling substances under reduced pressure to obtain a composite polyurethane emulsion.

[0106] S5. Prepare the primer

[0107] Mix polyetheramine and N,N-dimethylformamide uniformly at a ratio of 1 g:1 mL to obtain a curing agent;

[0108] Weigh by weight: 10 parts of the composite polyurethane emulsion and 3 parts of the curing agent, add them to a high-speed disperser, set the stirring speed to 5000 r / min, and stir and disperse for 30 min to obtain the primer.

[0109] Comparative Example 1

[0110] The difference between this comparative example and Example 3 is that in step S1, hydroxypropyl-terminated polydimethylsiloxane is used to replace 1,5-dichlorohexamethyltrisiloxane in an equimolar amount.

[0111] Comparative Example 2

[0112] The difference between this comparative example and Example 3 is that in step S2, 4-vinylbenzylamine is not added.

[0113] Comparative Example 3

[0114] The difference between this comparative example and Example 3 is that step S3 is cancelled and no cross-linking agent is added in step S4.

[0115] Comparative Example 4

[0116] The difference between this comparative example and Example 3 is that in step S4, modified styrene-butadiene latex is not added.

[0117] Performance test:

[0118] Apply the primers prepared in Examples 1-3 and Comparative Examples 1-4 to a round aluminum wire with a diameter of 3 mm on a Meda vertical enameling machine to form a primer layer with a thickness of 0.1 ± 0.02 mm on the round aluminum wire, and prepare the enameled wire specimens to be tested;

[0119] The flexibility of the test sample was determined with reference to the standard GB / T 1731-2020 "Determination method for flexibility of paint films and putty films".

[0120] The breakdown voltage of the test sample was determined with reference to the standard GB / T 23312.1-2009 "Enameled round aluminium winding wires - Part 1: General requirements".

[0121] The surface resistivity of the test sample was determined with reference to the standard HG / T 3331-2012 "Determination method for volume resistivity and surface resistivity of insulating paint films".

[0122] With reference to the standard GB / T 5210-2006 "Pull-off adhesion test for paints and varnishes", the primer paints prepared in Examples 1-3 and Comparative Examples 1-4 were coated on an aluminium substrate to form a primer film with a thickness of 0.1 ± 0.02 mm, and the failure strength of the paint film was determined.

[0123] The specific test results are shown in Table 1 below.

[0124] Table 1 - Data sheet for performance detection of samples

[0125]

[0126] Data analysis:

[0127] By comparing and analyzing the data in Table 1 above, the failure strength of the primer paint sample prepared in the present invention reached 6.5 MPa, the breakdown voltage reached 7.1 kV, and the volume resistivity reached 2.6×10 15 Ω·cm. The flexibility test passed the roller bar 7 test. All the performance test data are superior to those of the comparative examples. It shows that after the modified polyurethane prepared with silane-modified PEG as the base material is combined with the modified styrene-butadiene latex modified with benzylamine and epoxy groups and the crosslinking agent to form a composite polyurethane, and then cooperated with the curing agent, the primer paint for enameled wires is prepared, which not only effectively improves the adhesion performance and flexibility of the paint film, but also improves the electrical insulation performance of the enameled wire.

[0128] The above content is only an example and illustration of the structure of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the described specific embodiments or use similar methods for substitution, as long as they do not deviate from the structure of the invention or exceed the scope defined by this claim book, they should all fall within the protection scope of the present invention.

[0129] In the description of this specification, the descriptions referring to the terms "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0130] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the present invention to only the specific embodiments. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A high-adhesion enameled wire primer, characterized in that: The invention comprises 10 parts by weight of a composite polyurethane emulsion and 2-3 parts by weight of a curing agent; Wherein, the curing agent is composed of polyetheramine and N,N-dimethylformamide at a ratio of 1g:1mL; The preparation method of the composite polyurethane emulsion is as follows: under the protection of inert gas, silane-modified PEG, tetrahydrofuran and a catalyst are mixed and stirred until dissolved, the temperature of the reaction system is increased to 50-60°C, diisocyanate is added to the reaction system, the reaction is kept warm for 80-100 minutes, glycidol is added to the reaction system, the reaction is kept warm for 50-60 minutes, and post-treatment is performed to obtain modified polyurethane; modified styrene-butadiene latex, modified polyurethane and DMF solution are stirred and mixed, the temperature of the reaction system is increased to 95-115°C, high-speed shear dispersion is performed for 80-100 minutes, the temperature of the reaction system is reduced to 70-80°C, a cross-linking agent is added to the reaction system, the reaction is kept warm for 2-3 hours, and post-treatment is performed to obtain the composite polyurethane emulsion.

2. The high-adhesion enameled wire primer according to claim 1, characterized in that: In the preparation process of the composite polyurethane emulsion, the usage ratio of the modified styrene-butadiene latex, the modified polyurethane, the DMF solution and the crosslinking agent is 2-3g:7-8g:50mL:1.2-1.8g, and the DMF solution is composed of N,N-dimethylformamide, xylene, Tween 80 and sodium dodecyl sulfate in the ratio of 7mL:4mL:0.3g:0.2g.

3. The high-adhesion enameled wire primer according to claim 1, characterized in that: In the preparation process of modified polyurethane, the dosage ratio of silane-modified PEG, tetrahydrofuran, catalyst and glycidol is 5g:30mL:0.2g:3g, and the dosage of diisocyanate is N 二异氰酸酯-NCO / N 硅烷改性PEG-OH =1.1:1, the diisocyanate is toluene diisocyanate.

4. The high-adhesion enameled wire primer according to claim 1, characterized in that: The preparation method of silane-modified PEG is as follows: under the protection of inert gas, polyethylene glycol, tetrahydrofuran and a catalyst are mixed and stirred until the system is dissolved, the temperature of the reaction system is lowered to 3-8°C, and a dichlorosilane solution is added dropwise to the reaction system. After the addition is completed, the reaction is kept warm for 6-8 hours, and post-processed to obtain the silane-modified PEG.

5. The high-adhesion enameled wire primer according to claim 4, characterized in that: The dosage ratio of the polyethylene glycol and dichlorosilane is 1.1 mol:1 mol, the dosage ratio of the polyethylene glycol, tetrahydrofuran and the catalyst is 1 g:10 mL:0.6 g, the polyethylene glycol is PEG400, the catalyst is triethylamine, and the dichlorosilane solution is composed of 1,5-dichlorohexamethyltrisiloxane and tetrahydrofuran at a ratio of 1 g:2 mL.

6. The high-adhesion enameled wire primer according to claim 1, characterized in that: The preparation method of modified styrene butadiene latex is as follows: styrene butadiene latex and emulsion are stirred and mixed, the temperature of the reaction system is increased to 70-80°C, an initiator solution is added dropwise to the reaction system, the addition is continued for 30-50 minutes, a modification liquid is added to the reaction system, the reaction is kept warm for 3-5 hours, and post-processed to obtain modified styrene butadiene latex.

7. The high-adhesion enameled wire primer according to claim 6, characterized in that: The dosage ratio of the styrene-butadiene latex, emulsion, initiator solution and modifying liquid is 10g:30mL:5mL:5g, the emulsion is composed of deionized water, tetrahydrofuran, sodium dodecyl sulfate and OP-10 in the ratio of 60mL:40mL:3g:1g, the initiator solution is composed of azobisisobutyronitrile and tetrahydrofuran in the ratio of 1g:8mL, and the modifying liquid is composed of glycidyl methacrylate, 4-vinylbenzylamine and tetrahydrofuran in the ratio of 3g:1g:8mL.

8. The high-adhesion enameled wire primer according to claim 1, characterized in that: The preparation method of the crosslinking agent is as follows: under the protection of inert gas, polyethylene glycol, tetrahydrofuran and a catalyst are mixed and stirred, the temperature of the reaction system is increased to 55-60°C, isophorone diisocyanate is added to the reaction system, the reaction is kept warm for 60-80 minutes, 2-(aminomethyl)-2-methyl-1,3-propylenediamine is added to the reaction system, the reaction is kept warm for 40-60 minutes, and post-processing is performed to obtain the crosslinking agent.

9. The high-adhesion enameled wire primer according to claim 8, characterized in that: The dosage ratio of the polyethylene glycol, isophorone diisocyanate and 2-(aminomethyl)-2-methyl-1,3-propylenediamine is 3 mol:6 mol:1 mol, the dosage ratio of the polyethylene glycol, tetrahydrofuran and the catalyst is 5 g:50 mL:0.2 g, the catalyst is dibutyltin dilaurate, and the polyethylene glycol is PEG-400.

10. A method for preparing a primer for enameled wire with high adhesion according to any one of claims 1 to 9, characterized in that: The composite polyurethane emulsion and the curing agent are mixed, and stirred and dispersed for 20-30 minutes to obtain a high-adhesion enameled wire primer.

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