A primer paint for enameled wire with high adhesion and its preparation method

Abstract

The present invention discloses a primer paint for enameled wire with high adhesion and its preparation method, belonging to the technical field of primer processing, and is used to solve the technical problem that the adhesion and electrical insulation performance of the primer paint for enameled wire on the conductor need to be further improved in the prior art; the present invention includes 10 parts of a composite polyurethane emulsion and 2-3 parts of a curing agent by weight. After preparing a modified polyurethane based on silane-modified PEG, a modified styrene-butadiene latex containing benzylamine and epoxy group modification and a cross-linking agent are used to form a composite polyurethane, and then it is combined with the curing agent to prepare the primer paint for enameled wire, 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.

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 polyvinyl formal, epoxy or ordinary polyester resin as the matrix material. Although these materials have 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 lacquer shrinkage and peeling are likely to occur in the paint film. 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, leading to 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 now. 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 comprises 10 parts by weight of a composite polyurethane emulsion and 2 - 3 parts by weight of a curing agent;

[0008] The curing agent consists 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, mix silane - modified PEG, tetrahydrofuran and a catalyst and stir until dissolved. Raise the temperature of the reaction system to 50 - 60 °C, add diisocyanate to the reaction system, keep the temperature for reaction for 80 - 100 min, add glycidyl to the reaction system, keep the temperature for reaction for 50 - 60 min, and perform post - treatment to obtain 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 PEGs co-embedded and 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 capping on the polyurethane prepolymer molecular chains, and the modified polyurethane is prepared.

[0017] Stir and mix the modified styrene-butadiene latex, modified polyurethane, and DMF solution. Raise the temperature of the reaction system to 95 - 115 °C, perform high-speed shear dispersion for 80 - 100 min, lower the temperature of the reaction system to 70 - 80 °C, add a crosslinking agent to the reaction system, carry out heat preservation reaction for 2 - 3 h, and perform 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, it promotes the uniform dispersion of the modified styrene-butadiene latex and the modified polyurethane in the DMF solution. Then, taking the isocyanate groups on the crosslinking agent molecules as the reactive groups, they react with the reactive sites such as phenolic hydroxyl groups and imino groups on the modified styrene-butadiene latex or modified polyurethane molecules, promoting the chemical crosslinking between the modified styrene-butadiene latex and the modified polyurethane molecules. Then, through temperature-controlled reduced-pressure distillation, low-boiling substances are removed, and the composite polyurethane emulsion containing DMF is prepared.

[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 crosslinking 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, keep the reaction system at 75 °C and distill off the low-boiling substances under reduced pressure to obtain the composite polyurethane emulsion.

[0021] Furthermore, 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 by 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] Furthermore, the preparation method of the silane-modified PEG is as follows: under the protection of inert gas, polyethylene glycol, tetrahydrofuran, and catalyst are mixed and stirred until the system is dissolved. The temperature of the reaction system is reduced to 3 - 8 °C, and the dichlorosilane solution is added dropwise to the reaction system. After the addition is completed, the reaction is carried out under insulation for 6 - 8 h, and then post-treatment is carried out 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 nucleophilic reagent to replace the chloride ion, completing the substitution reaction and forming the silane-modified PEG with polyoxosilane chain segments embedded. During the reaction process, by keeping the temperature low, the side reaction of self-polymerization of siloxane is reduced, and the reaction selectivity is improved.

[0027] Furthermore, 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] Furthermore, the preparation method of the modified styrene-butadiene latex is as follows: stir and mix the styrene-butadiene latex and the emulsion. The temperature of the reaction system is raised to 70 - 80 °C, and the initiator solution is added dropwise to the reaction system for 30 - 50 min continuously. Then the modified liquid is added to the reaction system, and the reaction is carried out under insulation for 3 - 5 h, and then post-treatment is carried out 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. 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 macromolecular radicals of styrene-polybutadiene and modified monomers containing free 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 composition of 60 mL: 40 mL: 3 g: 1 g. The initiator solution consists of azobisisobutyronitrile and tetrahydrofuran in a composition of 1 g: 8 mL. The modified liquid consists of glycidyl methacrylate, 4-vinylbenzylamine and tetrahydrofuran in a composition 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 a temperature of 70 - 80 °C, and vacuum dried to a 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 constant temperature for 60 - 80 min. 2-(Aminomethyl)-2-methyl-1,3-propanediamine is added to the reaction system, and the reaction is carried out under constant temperature 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 a 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 polyisocyanate-terminated multi-crosslinked network, and a 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 low-boiling substances are removed by vacuum distillation to obtain a crosslinking agent.

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

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

[0043] 1. The high-adhesion enameled wire primer proposed by the present invention conducts co-embedding modification of polyethylene glycol through dichlorosilane to form a silane-modified PEG with a long straight-chain structure. Then, based on it, a high-flexibility epoxy-terminated modified polyurethane is prepared. By enhancing the intermolecular compatibility between the modified styrene-butadiene latex and the modified polyurethane, after preparing a composite polyurethane emulsion, through mixing with polyetheramine, the flexibility of the primer material is improved, and the bonding and adhesion strength between the primer and the metal substrate is improved by the cooperative action 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 ion migration activation energy, thereby improving the surface resistance and breakdown voltage resistance of the paint film.

[0044] 2. The high-adhesion enameled wire primer proposed by the present invention is to modify polyethylene glycol with dichlorosilane to synthesize silane-modified PEG with polysiloxane blocks, and then use the silane-modified PEG as a base material to react with toluene diisocyanate to form an epoxy-terminated modified polyurethane. By pre-synthesizing the silane-modified PEG with polysiloxane blocks to prepare the modified polyurethane, the amount of toluene diisocyanate used is effectively reduced, that is, the content of hard segments in the modified polyurethane is reduced, the flexibility of the modified polyurethane is enhanced, and the Si-O-Si segments in the modified polyurethane are improved. The high bond energy forms a molecular barrier to inhibit electron migration. The dipole moment of the ether bond in polyethylene glycol evenly distributes the electric field, reduces local field concentration, reduces conductivity, and improves breakdown voltage. The modified polyurethane molecular chain contains a large number of carbamate groups. The carbonyl oxygen and amino nitrogen in this group have strong polarity and can produce strong van der Waals forces and hydrogen bonds with the surfaces of metal, plastic and other substrates. In addition, the ether bond and Si-O-Si chain segment have good flexibility, which helps to improve the wettability of the coating, so that the coating can be better spread on the substrate surface, increase the contact area, and thus improve adhesion.

[0045] 3. The high-adhesion enameled wire primer proposed by the present invention is prepared by modifying styrene-butadiene latex as a raw material to obtain a modified styrene-butadiene latex modified with benzylamine and epoxy groups. The modified polar groups on the molecules increase its compatibility with the modified polyurethane, thereby promoting their uniform dispersion and mixing under high-speed shearing. The modified isocyanate groups on the cross-linking agent molecules will preferentially react 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 molecules to form cross-linking bonds, thereby promoting the uniform mixing performance between the modified styrene-butadiene latex and the modified polyurethane molecules. The polymer system of the modified polyurethane with good compatibility and the modified styrene-butadiene latex forms a coating with good elasticity, thereby enhancing the flexibility and resilience of the coating and solidifying it. The curing agent promotes intermolecular cross-linking between polymers, and utilizes the cross-linking structure and the flexibility of the molecular chain in the coating to enable the coating to undergo large deformation without being destroyed when subjected to force, thereby improving flexibility. The styrene-butadiene rubber segment has good adhesion properties and can produce physical adsorption with the substrate surface to improve the adhesion of the material. The conjugated structure of the benzene ring can capture high-energy electrons. The non-polar benzene ring of the styrene unit in the styrene-butadiene latex forms a continuous phase, inhibits electron migration, and reduces ionization damage. Under the action of the curing agent, the epoxy groups on the modified styrene-butadiene rubber and modified polyurethane molecules undergo ring-opening condensation to form a cross-linking network, which makes the coating more closely adhere to the substrate surface while increasing the density of the material, limiting the migration of carriers, and improving the material's volume resistivity and breakdown voltage. DETAILED DESCRIPTION

[0046] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of 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 fall within the protection scope 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., the product name is BASF polyetheramine D230 (Bassoul EC301), and the model number is 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 a high-adhesion enameled wire primer, 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 lowered to 3 °C, and the above-prepared dichlorosilane solution is added dropwise to the reaction flask. After the dropwise addition is completed, 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 at a ratio of 1.1:1 and add it to the reaction flask. Keep the reaction at a certain temperature for 80 min. Then add 60 g of glycidyl alcohol to the reaction flask and keep the reaction at a certain temperature 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 60 mL of deionized water, 40 mL of tetrahydrofuran, 3 g of sodium dodecyl sulfate, and 1 g of OP-10 evenly to obtain an emulsion;

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

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

[0062] Weigh: Add 200 g of styrene-butadiene latex and 600 mL of emulsion to the reaction flask and stir. Raise the temperature of the reaction flask to 70 °C. Add 100 mL of the initiator solution dropwise to the reaction flask over a 30-min period. After the dropwise addition is complete, add 100 g of the modified solution to the reaction flask and keep the reaction at a certain temperature 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 crosslinking agent

[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 and keep the reaction at a certain temperature for 60 min. Add 11.7 g of 2-(aminomethyl)-2-methyl-1,3-propanediamine to the reaction system and keep the reaction at a certain temperature 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 crosslinking agent.

[0065] S4. Preparation of composite polyurethane emulsion

[0066] N,N-dimethylformamide, xylene, Tween 80, and sodium lauryl sulfate were mixed in a ratio of 7 mL:4 mL:0.3 g:0.2 g 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, add them to a high-speed disperser and stir, raise the temperature of the high-speed disperser to 95 ° C, set the disperser speed to 10000 r / min, high-speed shear dispersion for 80 min, lower the temperature of the high-speed disperser to 70 ° C, add 24 g of cross-linking agent to the high-speed disperser, keep warm and react for 2 h, transfer the reaction solution to a rotary evaporator with a water bath temperature of 75 ° C, pump the negative pressure to 0.1 MPa, and remove low-boiling substances under reduced pressure to obtain a composite polyurethane emulsion.

[0068] S5. Preparation of primer

[0069] Polyetheramine and N,N-dimethylformamide were mixed uniformly at a ratio of 1 g:1 mL to obtain a curing agent;

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

[0071] Example 2

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

[0073] S1. Preparation of modified polyurethane

[0074] Weigh 27.7 g of 1,5-dichlorohexamethyltrisiloxane and 55.4 mL of tetrahydrofuran and mix them evenly to obtain a dichlorosilane solution, which is set aside.

[0075] Weigh 88 g of polyethylene glycol 400, 880 mL of tetrahydrofuran, and 52.8 g of triethylamine catalyst into a nitrogen-protected reaction flask and stir until the system is dissolved. The temperature of the reaction flask is lowered to 5°C. The dichlorosilane solution is added dropwise to the reaction flask. After the addition is complete, the reaction is kept warm for 7 h. The temperature of the reaction flask is raised to 50°C, the reaction flask is evacuated to 0.1 MPa, and low-boiling substances are evaporated under reduced pressure to obtain silane-modified PEG.

[0076] Weigh: 100g of silane-modified PEG, 600mL of tetrahydrofuran and 4g of dibutyltin dilaurate catalyst, add them into a nitrogen-protected reaction flask and stir until dissolved. The temperature of the reaction flask is raised to 55°C and heated under 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, and carry out a heat-preserving reaction for 90 min. Add 60 g of glycidyl alcohol to the reaction flask, carry out a heat-preserving reaction 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 low-boiling substances under reduced pressure to obtain a 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 60 mL of deionized water, 40 mL of tetrahydrofuran, 3 g of sodium dodecyl sulfate, and 1 g of OP-10 evenly to obtain an emulsion;

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

[0080] Mix glycidyl methacrylate, 4-vinylbenzylamine, and tetrahydrofuran at a ratio of 3 g:1 g:8 mL evenly 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 completed, add 100 g of the modified solution to the reaction flask, carry out a heat-preserving reaction 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, carry out suction filtration, wash the filter cake three times with purified water and ethanol respectively, and then drain it. Transfer the filter cake to a drying oven at 75 °C, evacuate to a negative pressure of 0.1 MPa, and carry out vacuum drying to constant weight to obtain a 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, carry out a heat-preserving reaction for 70 min. Add 11.7 g of 2-(aminomethyl)-2-methyl-1,3-propanediamine to the reaction system, carry out a heat-preserving reaction 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 low-boiling substances under reduced pressure to obtain a 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 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, perform high-speed shear dispersion for 90 min, the temperature of the high-speed disperser drops to 75 °C, add 30 g of crosslinking 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, draw a negative pressure to 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 composite polyurethane emulsion and 2.5 parts of 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, dropwise add the above-prepared dichlorosilane solution 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, draw a negative pressure of 0.1 MPa in the reaction flask, 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 100 min. Add 60 g of glycidyl alcohol to the reaction flask and keep the temperature 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. Prepare the modified styrene-butadiene latex

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

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

[0099] Mix glycidyl methacrylate, 4-vinylbenzylamine, and tetrahydrofuran evenly at 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 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 by suction. Transfer the filter cake to a drying oven at 80 °C. Draw a negative pressure to 0.1 MPa and dry under vacuum until a constant weight is obtained to obtain the modified styrene-butadiene latex.

[0101] S3. Prepare the 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 under nitrogen protection 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 80 min. Add 11.7 g of 2-(aminomethyl)-2-methyl-1,3-propanediamine to the reaction system and keep the temperature 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. Prepare the composite polyurethane emulsion

[0104] N,N-dimethylformamide, xylene, Tween 80, and sodium lauryl sulfate were mixed in a ratio of 7 mL:4 mL:0.3 g:0.2 g 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 disperser speed to 30000 r / min, 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 warm and react for 3 hours, transfer the reaction solution to a rotary evaporator with a water bath temperature of 75 ° C, pump the negative pressure to 0.1 MPa, and remove low-boiling substances under reduced pressure to obtain a composite polyurethane emulsion.

[0106] S5. Preparation of primer

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

[0108] Weigh by weight: 10 parts of composite polyurethane emulsion and 3 parts of curing agent are added to the high-speed dispersant, the stirring speed is set to 5000 r / min, and the mixture is stirred and dispersed for 30 minutes to obtain a primer.

[0109] Comparative Example 1

[0110] The difference between this comparative example and Example 3 is that in step S1, 1,5-dichlorohexamethyltrisiloxane is replaced by hydroxypropyl-terminated polydimethylsiloxane in an equal molar amount.

[0111] Comparative Example 2

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

[0113] Comparative Example 3

[0114] The difference between this comparative example and Example 3 is that step S3 is omitted 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 testing:

[0118] The primer prepared in Examples 1-3 and Comparative Examples 1-4 was applied to a round aluminum wire with a diameter of 3 mm on a Meida vertical enameling machine to form a primer layer with a thickness of 0.1±0.02 mm on the round aluminum wire to prepare an enameled wire sample to be tested;

[0119] The flexibility of the test sample was determined according 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 according to the standard GB / T 23312.1-2009 "Enamelled round aluminium winding wires - Part 1: General requirements".

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

[0122] According 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 damage 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 damage strength of the primer paint sample prepared by 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 were better than 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 cooperates with the curing agent, the primer paint for enameled wire 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 explanation of the structure of the present invention. Those skilled in the art of the present 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 the claims of the present invention, they should 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 a suitable manner in any one or more embodiments or examples.

[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 invention to only the specific implementation manners. 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 high-adhesion enameled wire primer comprises 10 parts by weight of a composite polyurethane emulsion and 2-3 parts by weight of a curing agent; 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 comprises the following steps: under the protection of inert gas, mixing and stirring silane-modified PEG, tetrahydrofuran and a catalyst until dissolved, raising the temperature of the reaction system to 50-60° C., adding diisocyanate to the reaction system, keeping the temperature for reaction for 80-100 minutes, adding glycidol to the reaction system, keeping the temperature for reaction for 50-60 minutes, and post-treating to obtain modified polyurethane; and stirring and mixing modified styrene-butadiene latex, modified polyurethane and DMF solution, raising the temperature of the reaction system to 95-115° C., high-speed shear dispersion for 80-100 minutes, lowering the temperature of the reaction system to 70-80° C., adding a crosslinking agent to the reaction system, keeping the temperature for reaction for 2-3 hours, and post-treating to obtain the composite polyurethane emulsion. The preparation method of silane-modified PEG comprises: under the protection of inert gas, mixing polyethylene glycol, tetrahydrofuran and a catalyst and stirring until the system is dissolved, lowering the temperature of the reaction system to 3-8°C, adding a dichlorosilane solution dropwise to the reaction system, and keeping the temperature for 6-8 hours after the addition is complete, and post-treating to obtain the silane-modified PEG, wherein the dichlorosilane solution is composed of 1,5-dichlorohexamethyltrisiloxane and tetrahydrofuran at a ratio of 1g:2mL; The modified styrene-butadiene latex is a styrene-butadiene latex modified with benzylamine and epoxy groups; The preparation method of the cross-linking agent comprises the following steps: 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, the reaction is carried out by heat preservation for 60-80 minutes, 2-(aminomethyl)-2-methyl-1,3-propylenediamine is added to the reaction system, the reaction is carried out by heat preservation for 40-60 minutes, and post-processing is performed to obtain the cross-linking agent.

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

4. The high-adhesion enameled wire primer according to claim 1, characterized in that: In the preparation process of silane-modified PEG, the usage ratio of polyethylene glycol and dichlorosilane is 1.1 mol:1 mol, the usage ratio of polyethylene glycol, tetrahydrofuran and catalyst is 1 g:10 mL:0.6 g, the polyethylene glycol is PEG400, and the catalyst is triethylamine.

5. 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 the modified styrene butadiene latex.

6. The high-adhesion enameled wire primer according to claim 5, 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 lauryl sulfate and OP-10 in a ratio of 60mL:40mL:3g:1g, the initiator solution is composed of azobisisobutyronitrile and tetrahydrofuran in a ratio of 1g:8mL, and the modifying liquid is composed of glycidyl methacrylate, 4-vinylbenzylamine and tetrahydrofuran in a ratio of 3g:1g:8mL.

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

8. A method for preparing a high-adhesion enameled wire primer according to any one of claims 1 to 7, characterized in that: The preparation method of the high-adhesion enameled wire primer comprises the following steps: mixing a composite polyurethane emulsion and a curing agent, and stirring and dispersing the mixture for 20-30 minutes to obtain the primer.

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