Paper-covered copper rectangular wire and its preparation method and application

Abstract

The present invention discloses a paper-wrapped copper flat wire and its preparation method and application, belonging to the field of insulated wire technology, and is used to solve the technical problem in the prior art that the insulation performance, flame retardancy, and high-temperature resistance of paper-wrapped copper flat wire need to be further improved. The invention specifically comprises the following steps: dissociating and evacuating a wood pulp board to prepare wood pulp fiber, adding the wood pulp fiber, pretreated PI fiber, and purified water to a dissociator for dissociation to obtain a dissociated slurry. The present invention is to coat a crude insulating paper product prepared with a polysiloxane emulsion, pretreated PI fiber, and wood pulp fiber as a base material with a phosphorus aluminum gel to prepare a highly insulating, high-tensile-strength, flame-retardant, and high-temperature-resistant insulating paper, and tightly wrap it around the copper flat wire with an adhesive, forming a stable insulating paper coating on the copper flat wire, effectively improving its insulation performance and high-temperature aging resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of insulated wire processing, and in particular to a paper-covered copper rectangular wire and a preparation method and application thereof. Background Art

[0002] As a key equipment in the power system, dry-type transformers have been widely used in places with high fire protection requirements, such as subways, high-rise buildings, workshops, and power stations, due to their advantages such as no need for oil immersion, good fire resistance, and environmental safety. Compared with oil-immersed transformers, dry-type transformers use air as insulation and cooling medium, but their insulation performance and heat dissipation capacity are relatively poor, resulting in greater consumption of effective materials.

[0003] Copper flat wire is a key material for transformer windings. Its performance directly affects the efficiency, safety and service life of the transformer. Traditional copper flat wire mostly uses ordinary insulating varnish or synthetic resin coating as the insulation layer, which has problems such as poor environmental protection, insufficient high-temperature resistance and complex process. Paper-wrapped insulation is a new way to insulate copper flat wire.

[0004] However, in the prior art, when preparing paper-wrapped copper flat wire, insulating paper is usually directly wrapped on the outside of the copper flat wire. The adhesion between the insulating paper and the copper conductor is poor. During the operation of the transformer, delamination is easily generated due to electromagnetic vibration, thermal expansion and contraction, etc., resulting in partial discharge and even insulation failure. Although common insulating paper has good insulating properties, it is essentially a fiber material with poor flame retardant properties. It is difficult to effectively suppress the spread of flames in the event of a short circuit or overload, and there is a fire hazard. In addition, the insulating paper is prone to thermal aging in a high temperature environment, resulting in a decrease in the insulation performance of the paper-wrapped copper flat wire. Summary of the Invention

[0005] The object of the present invention is to provide a paper-covered copper rectangular wire and a preparation method and application thereof, so as to solve the technical problem in the prior art that the insulation performance, flame retardancy and high temperature resistance of the paper-covered copper rectangular wire need to be further improved.

[0006] The object of the present invention can be achieved by the following technical solution: A method for preparing paper-covered copper rectangular wire comprises the following steps:

[0007] S1. Dissociate and evacuate a wood pulp board to prepare wood pulp fibers, and add the wood pulp fibers, pretreated PI fibers, and purified water into a dissociator for dissociation to obtain a dissociated slurry;

[0008] S2. Mix the dissociated slurry and the polysiloxane emulsion, stir and mix for 20-30 minutes to obtain a papermaking slurry, and sheet the papermaking slurry to obtain a crude insulating paper with a thickness of 0.9-1.1 mm;

[0009] S3, after evenly coating the insulating paper crude product with silica-alumina gel, hot rolling it in a hot rolling mill at a temperature of 110-120° C. to obtain insulating paper;

[0010] S4. After coating the epoxy resin adhesive on the insulating paper, evenly wrap it on the copper flat wire, and then perform heat curing treatment on it to prepare the paper-wrapped copper flat wire.

[0011] Furthermore, in step S1, the usage ratio of the wood pulp fiber, pretreated PI fiber and purified water is 2g:1g:150mL; in step S2, the volume ratio of the dissociated slurry and polysiloxane emulsion is 7:1; in step S3, the coating amount of the silica-alumina gel is 10g / m2; in step S4, the epoxy resin adhesive is composed of epoxy resin E-42 and 4-aminobutyltriethoxysilane in a weight ratio of 5:1.

[0012] Furthermore, the pretreated PI fibers are obtained by processing the following steps:

[0013] A1. Mix and stir the polyimide staple fibers and the activation solution, raise the temperature of the reaction system to 50-60°C, keep the mixture warm for 40-60 minutes, and perform post-treatment to obtain activated PI fibers.

[0014] A2. Mix and stir the activated PI fiber and acetic acid solution, react at room temperature for 90-120 minutes, and post-treat to obtain pretreated PI fiber.

[0015] The synthetic reaction mechanism of pretreated PI fiber is:

[0016] During the reaction, hydroxide ions combine with carbonyl carbon atoms to form a tetrahedral intermediate, and then the proton on the imide nitrogen atom in the intermediate is captured by the alkaline environment to form a negative ion. Subsequently, an elimination reaction occurs, the imide ring opens, and a molecular fragment with a carboxylate ion (or its precursor) and an amino group is generated. N,N-dimethylacetamide is a polar aprotic solvent that can dissolve the intermediates and products generated by the reaction, promote the reaction, and stabilize the negative ion intermediates in the reaction process, reducing the activation energy of the reaction. The amino group on the PI fiber is a basic group that easily accepts hydrogen ions to form ammonium ions. At the same time, the carboxylate ion precursor or unstable intermediate generated after the imide ring is opened on the activated PI fiber will further undergo a protonation reaction under acidic conditions to form a stable carboxyl group, thereby preparing a pretreated PI fiber with modified carboxyl reaction active sites.

[0017] Furthermore, in step A1, the solid-liquid ratio of the polyimide staple fiber and the activation solution is 1:10, and the activation solution is composed of sodium hydroxide, purified water and N,N-dimethylacetamide at a ratio of 1g:10mL:15mL. The post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, filtered, the filter cake is washed with purified water until neutral and then dried, the filter cake is transferred to a drying oven at a temperature of 70°C, and dried to constant weight to obtain activated PI fiber; in step A2, the solid-liquid ratio of the activated PI fiber and the acetic acid solution is 1:8, and the acetic acid solution is composed of glacial acetic acid and purified water at a ratio of 1g:5mL. The post-treatment includes: after the reaction is completed, filtered, the filter cake is washed with purified water until neutral and then dried, the filter cake is transferred to a drying oven at a temperature of 70°C, and dried to constant weight to obtain pretreated PI fiber.

[0018] Further, the polysiloxane emulsion is processed by the following steps:

[0019] B1, mixing diethoxysilane-modified DOPO, tetramethyltetravinylcyclotetrasiloxane, octamethylcyclotetrasiloxane, and methacrylic acid trioxycyclosiloxane to obtain a mixed siloxane solution;

[0020] B2. Under stirring, add the mixed siloxane solution dropwise to the emulsion at a temperature of 60-80°C. After the addition is complete, keep the temperature for 60-80 minutes, lower the temperature of the reaction system to room temperature, and adjust the pH of the reaction system to 7 to obtain a polysiloxane emulsion.

[0021] The synthetic reaction mechanism of polysiloxane emulsion is:

[0022] During the reaction, the mixed siloxane solution is emulsified and dispersed in the emulsion. At the same time, the protonic acid in the emulsion catalyzes the hydrolysis of the cyclic siloxane monomers or siloxyethane bonds in the mixed siloxane solution to form siloxane segments with silanol activity. Then, silanols condense with silanols to form a polysiloxane emulsion with multi-side chain modified polysiloxane segments having epoxy groups, unsaturated olefin double bonds and DOPO.

[0023] Furthermore, in step B1, the weight ratio of diethoxysilane-modified DOPO, tetramethyltetravinylcyclotetrasiloxane, octamethylcyclotetrasiloxane, and methyl acrylate trioxycyclosiloxane is 3-4:2-3:8-9:1-2; in step B2, the volume ratio of the mixed siloxane solution and the emulsion is 1:20, and the emulsion is composed of anhydrous ethanol, purified water, 80wt% sulfuric acid, sodium lauryl sulfate, Tween-80, and polyethylene glycol-400 in the ratio of 30mL:90mL:8mL:1g:2g:2g.

[0024] Furthermore, the preparation method of diethoxysilane-modified DOPO is as follows: under an inert atmosphere, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-methanol-10-oxide, 3-isocyanatepropylmethyldiethoxysilane and 1,4-dioxane are mixed and stirred, the reaction system temperature is increased to 50-60°C, the reaction is kept warm for 80-90 minutes, and post-processed to obtain diethoxysilane-modified DOPO.

[0025] The synthetic reaction mechanism of diethoxysilane-modified DOPO is:

[0026] During the reaction, the hydroxyl group on the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-methanol-10-oxide molecule reacted with the isocyanate group on the 3-isocyanatopropylmethyldiethoxysilane molecule to form diisocyanate-modified DOPO. The mass spectrometry analysis data were: m / z: 463.15800 (100.0%), 464.16136 (23.8%), 464.15757 (5.1%), 465.15484 (3.3%), 465.16471 (2.7%), 465.16225 (1.2%), 465.16092 (1.2%).

[0027] Furthermore, the amount ratio of the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-methanol-10-oxide and 3-isocyanatepropylmethyldiethoxysilane is 1 mol:1 mol, and the amount ratio of the 3-isocyanatepropylmethyldiethoxysilane and 1,4-dioxane is 1 g:6 mL. The post-treatment includes: after the reaction is completed, the temperature of the reaction system is raised to 70-80 ° C, and low-boiling substances are removed under reduced pressure to obtain diethoxysilane-modified DOPO.

[0028] Furthermore, the preparation method of the phosphate aluminum gel is: heating phosphoric acid to 80-90°C, adding aluminum hydroxide to the phosphoric acid in batches, keeping the temperature for reaction for 2-3 hours, cooling the reaction system to room temperature, adding 5-hexenyltriethoxysilane and an initiator to the reaction system, and reacting for 40-60 minutes to obtain the phosphate aluminum gel.

[0029] The synthetic reaction mechanism of phosphate aluminum gel is:

[0030] During the reaction, phosphoric acid and aluminum hydroxide undergo a neutralization reaction to generate amorphous aluminum phosphate and water. The surface of the generated amorphous aluminum phosphate contains unreacted P-OH and Al-OH, which further condense under heating to form a porous gel with a three-dimensional network. In an acidic environment, the ethoxy group of 5-hexenyltriethoxysilane is hydrolyzed to silanol, which undergoes chemical cross-linking with the surface of the porous gel. Ammonium persulfate acts as a free radical initiator and is dissolved in the aqueous solution and uniformly dispersed to prepare a phosphate aluminum gel.

[0031] Furthermore, the molar ratio of the phosphoric acid to aluminum hydroxide is 3:2, the weight ratio of the aluminum hydroxide, 5-hexenyltriethoxysilane and initiator is 3:1:0.1, the initiator is ammonium persulfate, and the mass fraction of the phosphoric acid is 50%.

[0032] The present invention also provides a paper-covered copper flat wire, which is prepared by using the above-mentioned method for preparing a paper-covered copper flat wire.

[0033] An application of a paper-covered copper flat wire is to apply the paper-covered copper flat wire prepared by the above-mentioned method for preparing a paper-covered copper flat wire to a dry-type transformer.

[0034] The present invention has the following beneficial effects:

[0035] 1. The present invention uses an adhesive to bond insulating paper to the outside of the copper flat wire to form an insulating coating. Under high temperature, the adhesive is cured and cross-linked, and at the same time, it promotes cross-linking between the adhesive and the insulating paper and the surface layer of the copper flat wire, forming a stable insulating paper coating on the outside of the copper flat wire, reducing the porosity of the paper-wrapped insulation layer outside the paper-wrapped copper flat wire, thereby effectively reducing the penetration of moisture and improving the insulation performance of the paper-wrapped copper flat wire. When preparing the insulating paper, the mixed slurry of PI fiber and pulp fiber is reinforced with a polysiloxane emulsion, and then diluted to make paper. The PI fiber retains the rigid aromatic ring structure of polyimide, and the high modulus of its molecular chain provides a skeleton support for the paper base, inhibits the slip of the molecular chain under external force, and improves the tensile strength of the paper. The PI fiber has a low dielectric constant, and the main chain contains a five-membered imide ring and an aromatic ring, and has a high decomposition temperature. It cooperates with the high stability of polysiloxane to further improve the high temperature resistance and electrical insulation performance of the material.

[0036] 2. The present invention further activates the polyimide fiber and then re-treats it with acetic acid to form a large number of carboxyl groups on the PI fiber, thereby improving its reaction activity and promoting the uniform dispersion and mixing of the pretreated PI fiber in the papermaking pulp and wood pulp fiber. The polysiloxane molecules in the polysiloxane emulsion form a polysiloxane network between the fibers, and the epoxy groups on the polysiloxane molecular chain can condense with the oxygen-containing active sites on the surface of the pretreated PI fiber or wood pulp fiber, thereby promoting the mutual cross-linking and bonding between the PI fiber and the wood pulp fiber in the insulating paper, thereby further improving the tensile strength of the insulating paper. The Si-O bond energy of the polysiloxane main chain is high and the electron trap is deep, thereby suppressing the conductive current. The phosphaphenanthrene ring in the DOPO modified on the polysiloxane molecule contains a large π conjugated system and a P=O polar bond, which can capture high-energy electrons and scatter electron paths, thereby improving local voltage resistance and further improving the insulating properties of the material.

[0037] 3. The present invention also prepares a gel with phosphoric acid and aluminum hydroxide, and then mixes it with 5-hexenyltriethoxysilane and an initiator to form a phosphate aluminum gel, which is coated on the insulating paper. After high temperature and high pressure treatment, the initiator triggers the unsaturated double bonds on the phosphate aluminum gel to undergo free radical polymerization with the unsaturated olefins on the crude insulating paper. The phosphate aluminum gel is stably attached to the crude insulating paper in the form of a CC covalent bond network, thereby enhancing the van der Waals force and mechanical interlocking. The siloxane-coated amorphous aluminum phosphate structure of the phosphate aluminum gel improves the electron tunneling barrier, and then undergoes hot rolling to promote the phosphorus Aluminum gel fills the pores between fibers, eliminates interface energy level defects, forms a densification effect, and improves the tensile strength and insulation properties of the insulating paper material. The phosphate aluminum gel is pyrolyzed under high temperature, catalyzed into carbon by the condensed phase and quenched by gas-phase free radicals, thereby increasing the flame retardant properties of the insulating paper. In addition, a synergistic effect is constructed between the phosphate aluminum gel and the polysiloxane, further improving its flame retardant properties. In the insulating paper, the phosphate aluminum gel and the polysiloxane undergo intermolecular recombination at high temperature, forming Si-O-Al bonds to replace organic bonds, resisting thermal cracking and further improving its heat stability. DETAILED DESCRIPTION

[0038] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0039] In the present invention, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-methanol-10-oxide, CAS No. 35948-26-6;

[0040] In the present invention, the polyimide staple fiber is selected from Jiangsu Xiannuo New Material Technology Co., Ltd., the brand is Shilon, and the model is S0T-S;

[0041] In the present invention, the wood pulp board is selected from Henan Huining Paper Co., Ltd., using perennial northern softwood as raw material, and the fiber length is 1-2.95mm;

[0042] In the present invention, the epoxy value of the epoxy resin E-42 is 0.38-0.45 eq / 100 g.

[0043] Example 1

[0044] This embodiment provides a method for preparing a polysiloxane emulsion, comprising the following steps:

[0045] Step 1: Preparation of diethoxysilane-modified DOPO

[0046] Weigh 24.6 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-methanol-10-oxide, 21.7 g of 3-isocyanatepropylmethyldiethoxysilane, and 130.2 mL of 1,4-dioxane, add them into an argon-protected reaction flask and mix and stir. The temperature of the reaction flask is raised to 50° C. and the reaction is kept warm for 80 min. The temperature of the reaction flask is raised to 70° C. and low-boiling substances are evaporated under reduced pressure to obtain diethoxysilane-modified DOPO.

[0047] Step 2: Prepare mixed siloxane solution

[0048] Diethoxysilane-modified DOPO, tetramethyltetravinylcyclotetrasiloxane, octamethylcyclotetrasiloxane, and methyl acrylate trioxycyclosiloxane were uniformly mixed in a weight ratio of 3:2:8:1 to obtain a mixed siloxane solution.

[0049] Step 3: Preparation of polysiloxane emulsion

[0050] Anhydrous ethanol, purified water, 80 wt% sulfuric acid, sodium lauryl sulfate, Tween-80, and polyethylene glycol-400 were mixed in a ratio of 30 mL:90 mL:8 mL:1 g:2 g:2 g to obtain an emulsion;

[0051] Weigh: 2 L of emulsion was added to the reaction flask and stirred at a stirring rate of 800 rpm. The temperature of the reaction flask was raised to 60°C. 100 mL of the mixed siloxane solution was added dropwise to the reaction flask. After the addition was complete, the mixture was kept warm for 60 minutes. The temperature of the reaction flask was lowered to room temperature and the pH of the reaction system was adjusted to 7 to obtain a polysiloxane emulsion.

[0052] Example 2

[0053] This embodiment provides a method for preparing a polysiloxane emulsion, comprising the following steps:

[0054] Step 1: Preparation of diethoxysilane-modified DOPO

[0055] Weigh 24.6 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-methanol-10-oxide, 21.7 g of 3-isocyanatepropylmethyldiethoxysilane, and 130.2 mL of 1,4-dioxane, add them into a reaction flask protected by argon and mix with stirring. The temperature of the reaction flask is raised to 55° C. and the reaction is kept warm for 85 minutes. The temperature of the reaction flask is raised to 75° C. and low-boiling substances are evaporated under reduced pressure to obtain diethoxysilane-modified DOPO.

[0056] Step 2: Prepare mixed siloxane solution

[0057] Diethoxysilane-modified DOPO, tetramethyltetravinylcyclotetrasiloxane, octamethylcyclotetrasiloxane, and methacrylic acid trioxycyclosiloxane were uniformly mixed in a weight ratio of 3.5:2.5:8.5:1.5 to obtain a mixed siloxane solution.

[0058] Step 3: Preparation of polysiloxane emulsion

[0059] Anhydrous ethanol, purified water, 80 wt% sulfuric acid, sodium lauryl sulfate, Tween-80, and polyethylene glycol-400 were mixed in a ratio of 30 mL:90 mL:8 mL:1 g:2 g:2 g to obtain an emulsion;

[0060] Weigh: 2 L of emulsion was added to the reaction flask and stirred at a stirring rate of 800 rpm. The temperature of the reaction flask was raised to 70°C. 100 mL of the mixed siloxane solution was added dropwise to the reaction flask. After the addition was complete, the mixture was kept warm for 70 minutes. The temperature of the reaction flask was lowered to room temperature and the pH of the reaction system was adjusted to 7 to obtain a polysiloxane emulsion.

[0061] Example 3

[0062] This embodiment provides a method for preparing a polysiloxane emulsion, comprising the following steps:

[0063] Step 1: Preparation of diethoxysilane-modified DOPO

[0064] Weigh 24.6 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-methanol-10-oxide, 21.7 g of 3-isocyanatepropylmethyldiethoxysilane, and 130.2 mL of 1,4-dioxane, add them into a reaction flask protected by argon and mix and stir. The temperature of the reaction flask is raised to 60°C, and the reaction is kept warm for 90 minutes. The temperature of the reaction flask is raised to 80°C, and low-boiling substances are evaporated under reduced pressure to obtain diethoxysilane-modified DOPO.

[0065] Step 2: Prepare mixed siloxane solution

[0066] Diethoxysilane-modified DOPO, tetramethyltetravinylcyclotetrasiloxane, octamethylcyclotetrasiloxane, and methyl acrylate trioxycyclosiloxane were uniformly mixed in a weight ratio of 4:3:9:2 to obtain a mixed siloxane solution.

[0067] Step 3: Preparation of polysiloxane emulsion

[0068] Anhydrous ethanol, purified water, 80 wt% sulfuric acid, sodium lauryl sulfate, Tween-80, and polyethylene glycol-400 were mixed in a ratio of 30 mL:90 mL:8 mL:1 g:2 g:2 g to obtain an emulsion;

[0069] Weigh: 2 L of emulsion was added to the reaction flask and stirred. The stirring rate was set to 800 rpm. The temperature of the reaction flask was raised to 80°C. 100 mL of the mixed siloxane solution was added dropwise to the reaction flask. After the addition was complete, the mixture was kept warm for 80 minutes. The temperature of the reaction flask was lowered to room temperature and the pH of the reaction system was adjusted to 7 to obtain a polysiloxane emulsion.

[0070] Example 4

[0071] This embodiment provides a method for preparing a paper-covered rectangular copper wire, comprising the following steps:

[0072] S1. Preparation of pretreated PI fibers

[0073] Mix sodium hydroxide, purified water, and N,N-dimethylacetamide at a ratio of 1 g:10 mL:15 mL to obtain an activation solution.

[0074] Weigh: polyimide staple fibers and activation solution at a solid-liquid ratio of 1:10, add them to a reaction flask and mix and stir. Raise the temperature of the reaction flask to 50°C and keep it warm for 40 minutes. Lower the temperature of the reaction flask to room temperature, filter, wash the filter cake with purified water until it is neutral, and then drain it. Transfer the filter cake to a drying oven at 70°C and dry it to constant weight to obtain activated PI fibers.

[0075] Mix glacial acetic acid and purified water at a ratio of 1 g:5 mL to obtain an acetic acid solution;

[0076] Weigh: activated PI fiber and acetic acid solution are added to the reaction bottle in a solid-liquid ratio of 1:8 and mixed and stirred. Stir at room temperature for 90 minutes, filter, wash the filter cake with purified water until neutral and then dry. Transfer the filter cake to a drying oven at a temperature of 70°C and dry to constant weight to obtain pretreated PI fiber.

[0077] S2. Preparation of dissociation slurry

[0078] The wood pulp board and deionized water were mixed at a ratio of 1 g:100 mL, soaked at room temperature for 6 h, transferred to a beater, set the speed to 2000 rpm, and beat for 6 min. Then, it was transferred to a high-frequency deflaker to obtain a beating degree of 43°SR, filtered, and dried to obtain wood pulp fiber;

[0079] Wood pulp fiber, pretreated PI fiber and purified water are added into the high-frequency disintegrator at a ratio of 2g:1g:150mL, the power is turned on, the revolution counter of the disintegrator is reset to zero, and then the pulp is dissociated. When the counter shows 1000 revolutions, the power is disconnected. After 1 minute, the power is turned on again until the revolution reaches 10,000 revolutions, and the power is disconnected. After 1 minute, the power is turned on again until the revolution reaches 30,000 revolutions, and the power is disconnected to obtain the dissociated pulp.

[0080] S3. Preparation of crude insulating paper

[0081] The dissociated slurry and the polysiloxane emulsion prepared in Example 1 were added to a stirrer at a volume ratio of 7:1 and mixed. The stirring speed was set to 300 rpm and the mixture was stirred for 20 minutes to obtain a papermaking slurry.

[0082] The papermaking pulp was transferred to a paper sheet former, diluted with water to obtain a suspension with a concentration of 0.02 wt%, and then dried after oil pressure to obtain a crude insulating paper with a thickness of 0.9 mm.

[0083] S4. Preparation of insulating paper

[0084] Weigh: 500 mL of 50 wt% phosphoric acid solution was added to a reaction flask and stirred. The temperature of the reaction flask was raised to 80°C. 132.7 g of nano-aluminum hydroxide was added to the reaction flask in batches. The reaction was kept warm for 2 h. The reaction flask was cooled to room temperature. 44.2 g of 5-hexenyltriethoxysilane and 4.4 g of initiator ammonium persulfate were added to the reaction flask and reacted for 40 min to obtain a phosphoaluminum gel.

[0085] The coating amount is 10g / m 2 Coat the two sides of the insulating paper with silica-alumina gel, and heat it at 110℃ and 60N / mm 2 , hot rolling on a hot rolling mill with a rolling speed of 3m / min to obtain insulating paper.

[0086] S5. Preparation of paper-covered copper rectangular wire

[0087] Epoxy resin E-42 and 4-aminobutyltriethoxysilane are mixed in a weight ratio of 5:1 to obtain an epoxy resin adhesive for later use;

[0088] Apply epoxy resin adhesive at 20g / m 2 The coating amount is applied on one side of the insulating paper, and after it is evenly wound on the copper rectangular wire, it is transferred to an environment with a temperature of 150°C, kept warm and cured for 30 minutes to obtain a paper-wrapped copper rectangular wire.

[0089] Example 5

[0090] This embodiment provides a method for preparing a paper-covered rectangular copper wire, comprising the following steps:

[0091] S1. Preparation of pretreated PI fibers

[0092] Mix sodium hydroxide, purified water, and N,N-dimethylacetamide at a ratio of 1 g:10 mL:15 mL to obtain an activation solution.

[0093] Weigh: polyimide staple fibers and activation solution at a solid-liquid ratio of 1:10, add them to a reaction flask and mix and stir. Raise the temperature of the reaction flask to 55°C and keep it warm for 50 minutes. Lower the temperature of the reaction flask to room temperature and filter. Wash the filter cake with purified water until it is neutral and then drain it. Transfer the filter cake to a drying oven at 70°C and dry it to constant weight to obtain activated PI fibers.

[0094] Mix glacial acetic acid and purified water at a ratio of 1 g:5 mL to obtain an acetic acid solution;

[0095] Weigh: activated PI fiber and acetic acid solution are added to the reaction bottle in a solid-liquid ratio of 1:8 and mixed and stirred. Stir at room temperature for 105 minutes, filter, wash the filter cake with purified water until neutral and then dry. Transfer the filter cake to a drying oven at a temperature of 70°C and dry to constant weight to obtain pretreated PI fiber.

[0096] S2. Preparation of dissociation slurry

[0097] The wood pulp board and deionized water were mixed at a ratio of 1 g: 100 mL, soaked at room temperature for 7 h, transferred to a beater, set the speed to 2000 rpm, and beat for 7 min. Then, it was transferred to a high-frequency deflaker to obtain a beating degree of 45° SR, filtered, and dried to obtain wood pulp fiber;

[0098] Wood pulp fiber, pretreated PI fiber and purified water are added into the high-frequency disintegrator at a ratio of 2g:1g:150mL, the power is turned on, the revolution counter of the disintegrator is reset to zero, and then the pulp is dissociated. When the counter shows 1000 revolutions, the power is disconnected. After 1 minute, the power is turned on again until the revolution reaches 10,000 revolutions, and the power is disconnected. After 1 minute, the power is turned on again until the revolution reaches 30,000 revolutions, and the power is disconnected to obtain the dissociated pulp.

[0099] S3. Preparation of crude insulating paper

[0100] The dissociated slurry and the polysiloxane emulsion prepared in Example 2 were added to a stirrer at a volume ratio of 7:1 and mixed. The stirring speed was set to 350 rpm and the mixture was stirred for 25 minutes to obtain a papermaking slurry.

[0101] The papermaking pulp was transferred to a paper sheet former, diluted with water to obtain a suspension with a concentration of 0.02 wt%, and then dried after oil pressure to obtain a crude insulating paper with a thickness of 1.0 mm.

[0102] S4. Preparation of insulating paper

[0103] Weigh: 500 mL of 50 wt% phosphoric acid solution was added to a reaction flask and stirred. The temperature of the reaction flask was raised to 85°C. 132.7 g of nano-aluminum hydroxide was added to the reaction flask in batches. The reaction was kept warm for 2.5 hours. The reaction flask was cooled to room temperature. 44.2 g of 5-hexenyltriethoxysilane and 4.4 g of initiator ammonium persulfate were added to the reaction flask and reacted for 50 minutes to obtain a phosphoaluminum gel.

[0104] The coating amount is 10g / m 2 Coat the two sides of the insulating paper with silica-alumina gel, and heat it at 115℃ and 70N / mm 2 , and hot rolling on a hot rolling mill with a rolling speed of 4m / min to obtain insulating paper.

[0105] S5. Preparation of paper-covered copper rectangular wire

[0106] Epoxy resin E-42 and 4-aminobutyltriethoxysilane are mixed in a weight ratio of 5:1 to obtain an epoxy resin adhesive for later use;

[0107] Apply epoxy resin adhesive at 20g / m 2 The coating amount is applied on one side of the insulating paper, and after it is evenly wound on the copper rectangular wire, it is transferred to an environment with a temperature of 160°C, kept warm and cured for 40 minutes to obtain a paper-wrapped copper rectangular wire.

[0108] Example 6

[0109] This embodiment provides a method for preparing a paper-covered rectangular copper wire, comprising the following steps:

[0110] S1. Preparation of pretreated PI fibers

[0111] Mix sodium hydroxide, purified water, and N,N-dimethylacetamide at a ratio of 1 g:10 mL:15 mL to obtain an activation solution.

[0112] Weigh: polyimide staple fibers and activation solution at a solid-liquid ratio of 1:10, add them to a reaction flask and mix and stir. Raise the temperature of the reaction flask to 60°C and keep it warm for 60 minutes. Lower the temperature of the reaction flask to room temperature and filter. Wash the filter cake with purified water until it is neutral and then drain it. Transfer the filter cake to a drying oven at 70°C and dry it to constant weight to obtain activated PI fibers.

[0113] Mix glacial acetic acid and purified water at a ratio of 1 g:5 mL to obtain an acetic acid solution;

[0114] Weigh: activated PI fiber and acetic acid solution are added to the reaction bottle in a solid-liquid ratio of 1:8 and mixed and stirred. Stir at room temperature for 120 minutes, filter, wash the filter cake with purified water until neutral and then dry. Transfer the filter cake to a drying oven at a temperature of 70°C and dry to constant weight to obtain pretreated PI fiber.

[0115] S2. Preparation of dissociation slurry

[0116] The wood pulp board and deionized water were mixed at a ratio of 1 g:100 mL, soaked at room temperature for 8 h, transferred to a beater, set the speed to 2000 rpm, and beat for 8 min. Then, the wood pulp board was transferred to a high-frequency deflaker to obtain a beating degree of 46°SR, filtered, and dried to obtain wood pulp fiber.

[0117] Wood pulp fiber, pretreated PI fiber and purified water are added into the high-frequency disintegrator at a ratio of 2g:1g:150mL, the power is turned on, the revolution counter of the disintegrator is reset to zero, and then the pulp is dissociated. When the counter shows 1000 revolutions, the power is disconnected. After 1 minute, the power is turned on again until the revolution reaches 10,000 revolutions, and the power is disconnected. After 1 minute, the power is turned on again until the revolution reaches 30,000 revolutions, and the power is disconnected to obtain the dissociated pulp.

[0118] S3. Preparation of crude insulating paper

[0119] The dissociated slurry and the polysiloxane emulsion prepared in Example 3 were added to a stirrer at a volume ratio of 7:1 and mixed. The stirring speed was set to 400 rpm and the mixture was stirred for 30 minutes to obtain a papermaking slurry.

[0120] The papermaking pulp was transferred to a paper sheet former, diluted with water to obtain a suspension with a concentration of 0.02 wt%, and then dried after oil pressure to obtain a crude insulating paper with a thickness of 1.1 mm.

[0121] S4. Preparation of insulating paper

[0122] Weigh: 500 mL of 50 wt% phosphoric acid solution was added to a reaction flask and stirred. The temperature of the reaction flask was raised to 90°C. 132.7 g of nano-aluminum hydroxide was added to the reaction flask in batches. The reaction was kept warm for 3 hours. The reaction flask was cooled to room temperature. 44.2 g of 5-hexenyltriethoxysilane and 4.4 g of initiator ammonium persulfate were added to the reaction flask and reacted for 60 minutes to obtain a phosphoaluminum gel.

[0123] The coating amount is 10g / m 2 Coat the two sides of the insulating paper with silica-alumina gel, and heat it at 120℃ and 80N / mm 2 , hot rolling on a hot rolling mill with a rolling speed of 5m / min to obtain insulating paper.

[0124] S5. Preparation of paper-covered copper rectangular wire

[0125] Epoxy resin E-42 and 4-aminobutyltriethoxysilane are mixed in a weight ratio of 5:1 to obtain an epoxy resin adhesive for later use;

[0126] Apply epoxy resin adhesive at 20g / m 2The coating amount is applied on one side of the insulating paper, and after it is evenly wound on the copper rectangular wire, it is transferred to an environment with a temperature of 170°C, kept warm and cured for 50 minutes to obtain a paper-wrapped copper rectangular wire.

[0127] Comparative Example 1

[0128] The difference between this comparative example and Example 6 is that, in the preparation process of the polysiloxane emulsion used, in step 2, no diethoxysilane-modified DOPO is added.

[0129] Comparative Example 2

[0130] The difference between this comparative example and Example 6 is that step S1 is omitted and the pretreated PI fiber in step 2 is replaced by polyimide staple fibers.

[0131] Comparative Example 3

[0132] The difference between this comparative example and Example 6 is that in step S3, no polysiloxane emulsion is added.

[0133] Comparative Example 4

[0134] The difference between this comparative example and Example 6 is that in step S4, no 5-hexenyltriethoxysilane and initiator were added.

[0135] Performance testing:

[0136] The longitudinal tensile strength and power frequency breakdown voltage of the insulating paper samples prepared in Examples 1-3 and Comparative Examples 1-4 were measured with reference to the standard QB / T 4250-2011 "500 kV transformer interturn insulation paper";

[0137] The average afterflame time of the insulating paper samples prepared in Examples 1-3 and Comparative Examples 1-4 was measured with reference to the standard GB / T 14656-2009 "Test method for burning performance of flame-retardant paper and paperboard";

[0138] The insulating paper samples prepared in Examples 1-3 and Comparative Examples 1-4 were placed in an environment at a temperature of 200° C. and heat aged for 60 days. The tensile strength, power frequency breakdown voltage and average afterflaming time thereof were measured. The specific test results are shown in Table 1 below.

[0139] Table 1-Performance test data of the sample

[0140]

[0141] Data Analysis:

[0142] A comparative analysis of the data in Table 1 above shows that the longitudinal tensile strength of the insulating paper sample prepared by the present invention reaches 1013 kN / m, the power frequency breakdown voltage reaches 10.921 kV / mm, and the average afterflaming time is reduced to 2.0 s. After heat aging treatment, the longitudinal tensile strength of the insulating paper sample reaches 9.58 kN / m, the power frequency breakdown voltage reaches 10.723 kV / mm, and the average afterflaming time is maintained at 2.6 s. All performance test data are better than those of the comparative example, indicating that the present invention not only effectively improves the insulating performance and tensile strength of the insulating paper by coating the phosphoaluminum gel on the insulating paper crude product prepared by reinforcing the pretreated PI fiber and wood pulp fiber with a polysiloxane emulsion, but also improves its flame retardant performance and heat aging resistance. The prepared insulating paper is then tightly wrapped on the copper flat wire with an adhesive to form a stable insulating paper coating on the copper flat wire, thereby improving its insulating performance and high temperature aging resistance.

[0143] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Obviously, many modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing paper-covered rectangular copper wire, characterized in that: The following steps are involved: S1. Dissociate and evacuate a wood pulp board to prepare wood pulp fibers, and add the wood pulp fibers, pretreated PI fibers, and purified water into a dissociator for dissociation to obtain a dissociated slurry; S2. Mix the dissociated slurry and the polysiloxane emulsion, stir and mix for 20-30 minutes to obtain a papermaking slurry, and sheet the papermaking slurry to obtain a crude insulating paper with a thickness of 0.9-1.1 mm; S3, after uniformly coating the aluminum-phosphorus gel on the crude insulating paper, hot rolling it in a hot rolling mill at a temperature of 110-120° C. to obtain insulating paper; S4, coating the insulating paper with epoxy resin adhesive, evenly winding the insulating paper on the copper rectangular wire, and then heat-curing the insulating paper to prepare a paper-wrapped copper rectangular wire; The pretreated PI fibers are processed by the following steps: A1. Mix and stir the polyimide staple fibers and the activation solution, raise the temperature of the reaction system to 50-60°C, keep the mixture warm for 40-60 minutes, and perform post-treatment to obtain activated PI fibers. A2. Mixing the activated PI fiber and the acetic acid solution, stirring, reacting at room temperature for 90-120 min, and post-treating to obtain pretreated PI fiber; The preparation method of the phosphate aluminum gel is as follows: heating phosphoric acid to 80-90°C, adding aluminum hydroxide to the phosphoric acid in batches, keeping the temperature for reaction for 2-3 hours, cooling the reaction system to room temperature, adding 5-hexenyltriethoxysilane and an initiator to the reaction system, and reacting for 40-60 minutes to obtain the phosphate aluminum gel; The polysiloxane emulsion includes diethoxysilane-modified DOPO, tetramethyltetravinylcyclotetrasiloxane, octamethylcyclotetrasiloxane, and methylacrylate trioxycyclosiloxane; The preparation method of diethoxysilane-modified DOPO is as follows: under an inert atmosphere, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-methanol-10-oxide, 3-isocyanatepropylmethyldiethoxysilane and 1,4-dioxane are mixed and stirred, the temperature of the reaction system is increased to 50-60° C., the reaction is kept warm for 80-90 minutes, and post-processed to obtain diethoxysilane-modified DOPO.

2. The method for preparing a paper-covered rectangular copper wire according to claim 1, wherein: In step S1, the ratio of the wood pulp fiber, pretreated PI fiber and purified water is 2g:1g:150mL; in step S2, the volume ratio of the dissociated slurry and polysiloxane emulsion is 7:1; in step S3, the coating amount of the phosphate aluminum gel is 10g / m 2 ; In step S4, the epoxy resin adhesive is composed of epoxy resin E-42 and 4-aminobutyltriethoxysilane in a weight ratio of 5:

1.

3. The method for preparing a paper-covered rectangular copper wire according to claim 1, wherein: In step A1, the solid-liquid ratio of the polyimide staple fiber and the activation solution is 1:10, and the activation solution is composed of sodium hydroxide, purified water and N,N-dimethylacetamide at a ratio of 1 g:10 mL:15 mL; in step A2, the solid-liquid ratio of the activated PI fiber and the acetic acid solution is 1:8, and the acetic acid solution is composed of glacial acetic acid and purified water at a ratio of 1 g:5 mL.

4. The method for preparing a paper-covered rectangular copper wire according to claim 1, wherein: The polysiloxane emulsion is processed by the following steps: B1, mixing diethoxysilane-modified DOPO, tetramethyltetravinylcyclotetrasiloxane, octamethylcyclotetrasiloxane, and methacrylic acid trioxycyclosiloxane to obtain a mixed siloxane solution; B2. Under stirring, add the mixed siloxane solution dropwise to the emulsion at a temperature of 60-80°C. After the addition is complete, keep the temperature for 60-80 minutes, lower the temperature of the reaction system to room temperature, and adjust the pH of the reaction system to 7 to obtain a polysiloxane emulsion.

5. The method for preparing a paper-covered rectangular copper wire according to claim 4, characterized in that: In step B1, the weight ratio of diethoxysilane-modified DOPO, tetramethyltetravinylcyclotetrasiloxane, octamethylcyclotetrasiloxane, and methyl methacrylate trioxycyclosiloxane is 3-4:2-3:8-9:1-2; in step B2, the volume ratio of the mixed siloxane solution and the emulsion is 1:20, and the emulsion is composed of anhydrous ethanol, purified water, 80wt% sulfuric acid, sodium lauryl sulfate, Tween-80, and polyethylene glycol-400 at 30mL:90mL:8mL:1g:2g:2g.

6. A paper-covered rectangular copper wire, characterized in that: The paper-covered copper rectangular wire is prepared by the method for preparing a paper-covered copper rectangular wire according to any one of claims 1 to 5.

7. An application of paper-covered rectangular copper wire, characterized in that: The paper-covered copper flat wire prepared by the method for preparing a paper-covered copper flat wire according to any one of claims 1 to 5 is applied to a dry-type transformer.

Images