Foaming epoxy resin composition for motor slot insulation, foaming material and preparation method of foaming epoxy resin composition

Abstract

The invention belongs to the field of electrical insulating materials, and discloses a foaming epoxy resin composition for motor slot insulation, a foaming material and a preparation method of the foaming material. The foaming epoxy resin composition for motor slot insulation comprises a component A, a component B and a component C, the component A comprises bisphenol A epoxy resin, novolac epoxy resin and a solvent, the component B comprises epoxy resin and a foaming agent, and the component C comprises a latent curing agent, a solvent and an accelerant. The component A and the component C are uniformly mixed with the solvent to obtain an epoxy resin premixed solution, and then the epoxy resin premixed solution is uniformly mixed with the component B and the solvent. The viscosity of the epoxy resin polystyrene foam composition for motor slot insulation is 200-1000 mPa.s, the foaming multiple of a foaming material is 3-5 times, the bonding strength reaches up to 5 MPa or above at the normal temperature and still reaches 1.5 MPa or above at the high temperature of 200 DEG C, and the storage period at the normal temperature is long.

Description

Technical Field

[0001] This invention relates to the field of electrical insulation materials, specifically to a foamed epoxy resin composition and foaming material for motor slot insulation, and a method for preparing the same. Background Technology

[0002] Under the national policy background of energy conservation, emission reduction, and vigorous development of new energy sources, strong insulation performance, good economic efficiency, energy saving, emission reduction, and low carbon environmental protection have become the key development directions for insulation materials. As we all know, slot insulation materials for motors require long service life, high reliability, and excellent hydrolysis resistance.

[0003] Existing motors use slot insulation, which inevitably creates gaps between the insulation and the copper wire, requiring additional slot wedges, under-wedge spacers, and other components for tightening. If the existing slot paper is not tightly bonded to the coil, air gaps will exist. Under a high-voltage alternating electric field, the air in these gaps is prone to partial discharge (corona discharge), which over time corrodes the insulation material, leading to insulation failure. The heat generated by the motor coils in existing slot paper motors needs to pass through these air gaps to be conducted to the stator core and then dissipated through the casing. Air is a poor conductor of heat, severely hindering heat dissipation. Furthermore, existing slot paper requires impregnation with insulating varnish, which generates a significant amount of volatile organic compounds during the process, and the high-temperature curing time of the insulating varnish is long, resulting in high energy consumption.

[0004] During the insulation impregnation and baking process, the foamed material used for motor slot insulation expands due to heat, forming an "airbag" that actively fills all gaps between the copper wire and the iron core slot wall. This firmly fixes the coil within the slot, preventing insulation wear (corona corrosion) and coil loosening caused by vibration, significantly improving slot fill factor and enhancing the mechanical stability and reliability of the equipment. The foamed material eliminates air gaps, forming a dense, solid insulation unit. Because the dielectric constant of the foamed resin is much higher than that of air, the electric field distribution is more uniform, greatly suppressing partial discharge and significantly improving the equipment's corona resistance life and overall dielectric strength. The foamed material also fills the air gaps and establishes a direct heat conduction path from the copper wire to the iron core. Although the foamed material itself may not have high thermal conductivity, it replaces the poorly conductive air, greatly reducing thermal resistance and significantly improving the motor's heat dissipation efficiency. This can lower the winding operating temperature (typically by 5-15°C), thereby extending the life of the insulation system. The foamed material for motor slot insulation is rapidly foamed in the motor through short-time heating, which significantly reduces volatile organic compounds and energy consumption, achieving the effect of energy saving and emission reduction. Summary of the Invention

[0005] The present invention addresses the development needs of existing technologies by providing a foamed epoxy resin composition and foaming material for motor slot insulation, and a method for preparing the same. The foaming material has the characteristics of moderate foaming ratio, high bonding strength, and long storage period at room temperature.

[0006] To achieve the objective of this invention, the foamed epoxy resin composition for motor slot insulation of this invention comprises component A, component B, and component C. Component A comprises bisphenol A epoxy resin, phenolic epoxy resin, and solvent. Component B comprises epoxy resin and foaming agent. Component C comprises latent curing agent, solvent, and accelerator. Component A and component C are mixed uniformly with solvent to obtain epoxy resin premix, and then mixed uniformly with component B and solvent.

[0007] Furthermore, in some embodiments of the present invention, components A and C are mixed uniformly with solvent at a mass ratio of 100:5-20:80-90; preferably, the epoxy resin premix is ​​mixed uniformly with component B at a mass ratio of 100:17-35.

[0008] Furthermore, in some embodiments of the present invention, the epoxy equivalent of the bisphenol A epoxy resin ranges from 500 to 1800 g / eq; preferably, the epoxy equivalent of the phenolic epoxy resin ranges from 150 to 200 g / eq.

[0009] Further, in some embodiments of the present invention, the solvent in component A is selected from one or more of acetone, ethyl acetate, butyl acetate, butanone, toluene, and xylene; preferably, the solvent in component A is ethyl acetate and butyl acetate; preferably, the mass ratio of ethyl acetate to butyl acetate is 20-35:25-40; preferably, the bisphenol A epoxy resin and phenolic epoxy resin in component A are stirred evenly with ethyl acetate and butyl acetate in a mass ratio of 18-22:28-32:23-32:28-38.

[0010] Furthermore, in some embodiments of the present invention, the epoxy resin and foaming agent in component B are stirred evenly at a mass ratio of 25-35:8-12; preferably, the epoxy resin in component B is one or two of bisphenol F epoxy resin and alicyclic epoxy resin; preferably, the epoxy equivalent of the bisphenol F epoxy resin is 140-200 g / eq; preferably, the epoxy equivalent of the alicyclic epoxy resin is 140-250 g / eq.

[0011] Furthermore, in some embodiments of the present invention, the latent curing agent is selected from amine curing agents and / or imidazole curing agents, or a pre-dispersion mixture of liquid epoxy and dicyandiamide; preferably, the solvent in component C is one or more of N,N-dimethylformamide, butanone, and butyl acetate, preferably N,N-dimethylformamide; preferably, the latent curing agent and solvent in component C are stirred evenly at a mass ratio of 0.8-1.2:2-4.

[0012] Furthermore, in some embodiments of the present invention, the amount of accelerator in component C is 15-35% (parts by mass) of the latent curing agent.

[0013] Furthermore, in some embodiments of the present invention, the accelerator is selected from imidazole and / or urea derivatives, which can maintain the stability of the coating for a long time.

[0014] Furthermore, in some embodiments of the present invention, the foaming agent is selected from thermally expandable microcapsules and / or inorganic foaming agents; preferably, the inorganic foaming agent is selected from one or more of ammonium bicarbonate, ammonium borohydride and azides.

[0015] Furthermore, in some embodiments of the present invention, the solvent in the uniform mixing of component A and component C with the solvent, and the uniform mixing of epoxy resin premix with component B and solvent, is selected from one or more of acetone, ethyl acetate, methyl acetate, butanone, toluene, and xylene.

[0016] On the other hand, the present invention also provides a method for preparing the aforementioned foamed epoxy resin composition for motor slot insulation, comprising the following steps:

[0017] (a) Mix component A and component C at the required mass ratio and then mix them with solvent to obtain epoxy resin premix;

[0018] (b) Mix component B with the epoxy resin premix obtained in step (a) above, dilute with solvent, and mix evenly to obtain a foamed epoxy resin composition for motor slot insulation.

[0019] Furthermore, in some embodiments of the present invention, in step (b), component B is first heated to 45-55°C and kept at that temperature for 0.4-0.6 hours, and then mixed evenly with the epoxy resin premix obtained in step (a).

[0020] In another aspect, the present invention also provides a foamed material for insulating motor slots, the foamed material for insulating motor slots comprising an insulating layer and a foamed epoxy resin composition coated on the insulating layer, wherein the foamed epoxy resin composition is the aforementioned foamed epoxy resin composition of the present invention.

[0021] Furthermore, in some embodiments of the present invention, the insulating layer is any one of polyphenylene sulfide film, polynatrimethylene film, polyimide film, composite material of polyaramid fiber and polyphenylene sulfide film, or composite material of polyaramid fiber and polynatrimethylene film.

[0022] Furthermore, the present invention also provides a method for preparing the aforementioned foamed material for motor slot insulation, comprising the following steps:

[0023] The prepared foamed epoxy resin composition is placed into a glue tank, and the upper and lower surfaces of the insulation layer are applied with glue through a comma-shaped scraper or slit extrusion. The foamed epoxy resin composition is then transferred to the surface of the insulation layer. After the surface of the insulation layer undergoes a drying process and a cooling process, it is wound up to obtain foamed insulating paper.

[0024] Furthermore, in some embodiments of the present invention, the amount of adhesive applied is 30-50 g / m² on one side. 2 .

[0025] Furthermore, in some embodiments of the present invention, the drying process and cooling process include: the drying tunnel has 3 to 9 sections, and the temperature is designed from low to high, with a minimum of 35°C and a maximum of 100°C, wherein the temperature of each section is allowed to have a tolerance of ±10°C, and a protective film is applied after the drying process.

[0026] The epoxy resin foam composition for motor slot insulation of the present invention has a viscosity of 200-1000 mPa·s, a foaming ratio of 3-5 times, a bonding strength of up to 5 MPa or more at room temperature, a bonding strength of up to 1.5 MPa or more at a high temperature of 200°C, and a long storage period at room temperature. Attached Figure Description

[0027] Figure 1 A simplified structural diagram of the foamed material used for motor slot insulation according to an embodiment of the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. It should be understood that the following description is merely illustrative and not intended to limit the invention.

[0029] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1 to 5” is disclosed, the described range should be interpreted as including the ranges “1 to 4”, “1 to 3”, “1 to 2”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0030] The singular form includes the plural objects of discussion unless the context clearly indicates otherwise. "Optional" or "any one" means that the matter or event described thereafter may or may not occur, and the description includes both the possibility that the event occurs and the possibility that the event does not occur.

[0031] Approximate terms used in the specification and claims to modify quantities indicate that the invention is not limited to that specific quantity, but also includes acceptable modifications close to that quantity that do not alter the relevant essential function. Correspondingly, the use of "about," "approximately," etc., to modify a numerical value means that the invention is not limited to that precise value. In some instances, approximate terms may correspond to the precision of the instrument used to measure the value. In this application's specification and claims, scope definitions can be combined and / or interchanged, unless otherwise stated, these scopes include all subscopes contained therein.

[0032] The indefinite articles “a” and “an” preceding an element or component of this invention do not impose any limitation on the quantity (i.e., number of times) of the element or component. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers only to the singular form.

[0033] Furthermore, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., described below refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms are not necessarily directed at the same embodiment or example. Moreover, the technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0034] Example 1

[0035] The insulation foam material for motor slots is prepared as follows:

[0036] (a) Bisphenol A epoxy resin (epoxy equivalent 500-700 g / eq) and phenolic epoxy resin (epoxy equivalent 150-200 g / eq) are mixed with ethyl acetate and butyl acetate in a mass ratio of 20:30:25:35 to form component A;

[0037] (b) Bisphenol F epoxy resin (epoxy equivalent 150-180 g / eq) and foaming agent (AkzoNobel foaming microspheres, foaming ratio range 2.0-6.0) are mixed evenly at a mass ratio of 30:10 to form component B;

[0038] (c) Soluble dicyandiamide and polar solvent N,N-dimethylformamide are stirred evenly at a mass ratio of 1:3, and then an accelerator, imidazole 2E4MZ, is added. The amount of accelerator is 25% (by mass) of soluble dicyandiamide. The mixture is stirred evenly to form component C.

[0039] (d) Mix component A, component C and ethyl acetate at a mass ratio of 100:20:85 until homogeneous, and stir at high speed to obtain epoxy resin premix.

[0040] The viscosity of the epoxy resin prepreg obtained in step (d) above is 350 mPa·s;

[0041] (e) Heat component B to about 50°C and keep it warm for 0.5 h. Mix it with the epoxy resin premix obtained in step d above and component B at a mass ratio of 100:25. Add the third type of solvent for dilution and mix evenly under stirring for 30 to 60 min. The viscosity of the resulting foaming epoxy resin composition is 320 mPa·s.

[0042] Example 2

[0043] The epoxy resin foaming composition prepared in Example 1 was placed into a glue tank, and the polyphenylene sulfide film was coated on both sides using a comma-shaped doctor blade. After the polyphenylene sulfide film surface underwent drying and cooling processes, a protective film was attached, and the film was then wound up to obtain polyphenylene sulfide foaming material for groove insulation.

[0044] In this embodiment, the drying tunnel consists of 7 sections, each with a temperature of 40–50–60–65–75–85–95°C. A cooling process is then performed at a temperature of 15–20°C. Finally, a protective film is laminated and the material is rolled up to obtain the groove-insulating polyphenylene sulfide foam material.

[0045] The coating amount of this foam material is 35g / m² on one side. 2 The foaming ratio is 4.1 times, and the adhesion strength at room temperature after curing is 6.3 MPa. When the adhesion strength is tested after keeping it at 200℃ for 30-60 minutes, the adhesion strength is 1.8 MPa.

[0046] Example 3

[0047] The insulation foam material for motor slots is prepared as follows:

[0048] (a) Bisphenol A epoxy resin (epoxy equivalent 700-900 g / eq) and phenolic epoxy resin (epoxy equivalent 150-200 g / eq) are mixed with ethyl acetate and butyl acetate in a mass ratio of 20:30:25:35 to form component A;

[0049] (b) Mix alicyclic epoxy resin (epoxy equivalent 140-200 g / eq) and foaming agent (Matsumoto foaming microspheres, foaming ratio 3.0-7.0) at a mass ratio of 30:10 to form component B;

[0050] (c) Soluble dicyandiamide and polar solvent N,N-dimethylformamide are stirred evenly at a mass ratio of 1:3, and then an accelerator, imidazole 2E4MZ, is added. The amount of accelerator is 25% (by mass) of soluble dicyandiamide. The mixture is stirred evenly to form component C.

[0051] (d) Mix component A, component C and ethyl acetate at a mass ratio of 100:20:85 until homogeneous, and stir at high speed to obtain epoxy resin premix.

[0052] The viscosity of the epoxy resin prepreg obtained in step (d) above is 470 mPa·s;

[0053] (e) Heat component B to about 50°C and keep it warm for 0.5 h. Mix it with the epoxy resin premix obtained in step d above and component B at a mass ratio of 100:20. Add the third type of solvent for dilution and mix evenly under stirring for 30 to 60 min. The viscosity of the resulting foaming epoxy resin composition is 340 mPa·s.

[0054] Example 4

[0055] The epoxy resin foaming composition prepared in Example 3 was placed into a glue tank, and the polynatamine film was coated on both sides using a comma-shaped doctor blade. After the polynatamine film surface underwent drying and cooling processes, a protective film was attached, and the film was then wound up to obtain polynatamine foaming material for groove insulation.

[0056] In this embodiment, the drying tunnel consists of 7 sections, each with a temperature of 40–50–60–65–75–85–95°C. A cooling process is then performed at a temperature of 15–20°C. Finally, a protective film is laminated and the material is rolled up to obtain the groove-insulating polynaphthalene foam material.

[0057] The coating amount of this foam material is 38g / m² on one side. 2 The foaming ratio is 3.9 times, and the adhesion strength at room temperature after curing is 5.9 MPa. When the adhesion strength is tested after keeping it at 200℃ for 30-60 minutes, the adhesion strength is 1.6 MPa.

[0058] Example 5

[0059] The insulation foam material for motor slots is prepared as follows:

[0060] (a) Bisphenol A epoxy resin (epoxy equivalent 550-650 g / eq) and phenolic epoxy resin (epoxy equivalent 150-200 g / eq) are mixed with ethyl acetate and butyl acetate in a mass ratio of 20:30:30:30 to form component A;

[0061] (b) Bisphenol F epoxy resin (epoxy equivalent 140-200 g / eq) and foaming agent (Wu Yu Chemical foaming microspheres, foaming ratio 2.5-6.0) are mixed evenly at a mass ratio of 30:12 to form component B;

[0062] (c) Soluble dicyandiamide and polar solvent N,N-dimethylformamide are stirred evenly at a mass ratio of 1:3, and then an accelerator, imidazole 2E4MZ, is added. The amount of accelerator is 30% (by mass) of soluble dicyandiamide. The mixture is stirred evenly to form component C.

[0063] (d) Mix component A, component C and ethyl acetate at a mass ratio of 100:20:85 until homogeneous, and stir at high speed to obtain epoxy resin premix.

[0064] The viscosity of the epoxy resin prepreg obtained in step (d) above is 420 mPa·s;

[0065] (e) Heat component B to about 50°C, preheat for 0.5 h, and mix it with the epoxy resin premix obtained in step d above and component B at a mass ratio of 100:30. Add the third type of solvent for dilution, and mix evenly under stirring for 30 to 60 min. The viscosity of the resulting foaming epoxy resin composition is 380 mPa·s.

[0066] Example 6

[0067] The epoxy resin foam composition prepared in Example 5 was placed into a glue tank, and the polyimide film was coated on both sides using a comma-shaped doctor blade. After the polyimide film surface underwent drying and cooling processes, a protective film was attached, and the film was then wound up to obtain polyimide foam material for groove insulation.

[0068] In this embodiment, the drying tunnel consists of 7 sections, each with a temperature of 40–50–60–65–75–85–95°C. A cooling process is then performed at a temperature of 15–20°C. Finally, a protective film is laminated and the material is rolled up to obtain the groove-insulating polyimide foam material.

[0069] The coating amount of this foam material is 35g / m² on one side. 2 The foaming ratio is 4.0 times. After curing, the adhesion strength at room temperature is 6.1 MPa. When the adhesion strength is tested after keeping it at 200℃ for 30-60 minutes, the adhesion strength is 2.1 MPa.

[0070] Example 7

[0071] The insulation foam material for motor slots is prepared as follows:

[0072] (a) Bisphenol A epoxy resin (epoxy equivalent 900-1800 g / eq) and phenolic epoxy resin (epoxy equivalent 150-200 g / eq) are mixed with ethyl acetate and butyl acetate in a mass ratio of 20:30:30:30 to form component A;

[0073] (b) Mix aliphatic epoxy resin (epoxy equivalent 140-250 g / eq) and foaming agent (Akzo foaming microspheres, foaming ratio range 2.0-6.0) at a mass ratio of 30:8 to form component B;

[0074] (c) Mix the amine curing agent and the polar solvent N,N-dimethylformamide at a mass ratio of 1:3, then add the accelerator MY-24 (imidazolium-based), the amount of accelerator being 30% (by mass) of the soluble dicyandiamide, and mix well to form component C.

[0075] (d) Mix component A, component C and ethyl acetate in a mass ratio of 100:15:85 until homogeneous, and stir at high speed to obtain epoxy resin premix.

[0076] The viscosity of the epoxy resin prepreg obtained in step (d) above is 450 mPa·s;

[0077] (e) Heat component B to about 50°C and keep it warm for 0.5 h. Mix it with the epoxy resin premix obtained in step d above and component B at a mass ratio of 100:25. Add the third type of solvent for dilution and mix evenly under stirring for 30 to 60 min. The viscosity of the resulting foaming epoxy resin composition is 380 mPa·s.

[0078] Example 8

[0079] The epoxy resin foam composition prepared in Example 7 was placed into a glue tank, and the polyimide film was coated on both sides using a comma-shaped doctor blade. After the polyimide film underwent drying and cooling processes, a protective film was attached, and the film was wound up to obtain polyimide foam material for groove insulation.

[0080] In this embodiment, the drying tunnel consists of 7 sections, each with a temperature of 40–50–60–65–75–85–95°C. A cooling process is then performed at a temperature of 15–20°C. Finally, a protective film is laminated and the material is rolled up to obtain the groove-insulating polyimide foam material.

[0081] The coating amount of this foam material is 35g / m² on one side. 2The foaming ratio is 4.5 times. After curing, the adhesion strength at room temperature is 6.6 MPa. When the adhesion strength is tested after keeping it at 200℃ for 30-60 minutes, the adhesion strength is 2.2 MPa.

[0082] The foaming material coating applied in this case can be stored at room temperature (30°C) for at least one month, maintaining the stability of the pre-coated film and not affecting subsequent foaming.

[0083] Example 9

[0084] The insulation foam material for motor slots is prepared as follows:

[0085] (a) Bisphenol A epoxy resin (epoxy equivalent 900-1800 g / eq) and phenolic epoxy resin (epoxy equivalent 150-200 g / eq) are mixed with ethyl acetate and butyl acetate in a mass ratio of 20:30:30:30 to form component A;

[0086] (b) Mix aliphatic epoxy resin (epoxy equivalent 150-250 g / eq) and foaming agent (AkzoNobel foaming microspheres, foaming ratio range 2.0-6.0) at a mass ratio of 30:10 to form component B;

[0087] (c) The pre-dispersed mixture of liquid epoxy and dicyandiamide curing agent and polar solvent N,N-dimethylformamide are stirred evenly at a mass ratio of 1:3. Then, microcapsule-form imidazole accelerators are added. The amount of accelerator is 20% (by mass) of the mixture of dicyandiamide, epoxy resin and dispersion. The mixture is stirred evenly to form component C.

[0088] (d) Mix component A, component C and ethyl acetate in a mass ratio of 100:6:85 until homogeneous, and stir at low speed to obtain epoxy resin premix.

[0089] The viscosity of the epoxy resin prepreg obtained in step (d) above is 430 mPa·s;

[0090] (e) Heat component B to about 50°C, preheat for 0.5 h, and mix it with the epoxy resin premix obtained in step d above and component B at a mass ratio of 100:30. Add the third type of solvent for dilution, and mix evenly under stirring for 30 to 60 min. The viscosity of the resulting foaming epoxy resin composition is 380 mPa·s.

[0091] Example 10

[0092] The epoxy resin foam composition prepared in Example 9 was placed into a glue tank, and the polyimide film was coated on both sides using a comma-shaped doctor blade. After the polyimide film underwent drying and cooling processes, a protective film was attached, and the film was wound up to obtain polyimide foam material for groove insulation.

[0093] In this embodiment, the drying tunnel consists of 7 sections, each with a temperature of 40–50–60–65–75–85–95°C. A cooling process is then performed at a temperature of 15–20°C. Finally, a protective film is laminated and the material is rolled up to obtain the groove-insulating polyimide foam material.

[0094] The coating amount of this foam material is 35g / m² on one side. 2 The foaming ratio is 4.3 times, and the adhesion strength at room temperature after curing is 6.5 MPa. When the adhesion strength is tested after keeping it at 200℃ for 30-60 minutes, the adhesion strength is 2.3 MPa.

[0095] The foaming material coating applied in this case can be stored at room temperature (30℃) for at least one month, maintaining the stability of the pre-coated film and not affecting subsequent foaming.

[0096] Comparative Example 1

[0097] The insulation foam material for motor slots is prepared as follows:

[0098] (a) Bisphenol A epoxy resin (epoxy equivalent 500-700 g / eq) and phenolic epoxy resin (epoxy equivalent 150-200 g / eq) are mixed with ethyl acetate and butyl acetate in a mass ratio of 20:30:25:35 to form component A;

[0099] (b) Bisphenol F epoxy resin (epoxy equivalent 150-180 g / eq) and foaming agent (AkzoNobel foaming microspheres, foaming ratio range 2.0-6.0) are mixed evenly at a mass ratio of 30:10 to form component B;

[0100] (c) Soluble dicyandiamide and polar solvent N,N-dimethylformamide are stirred evenly at a mass ratio of 1:3, and then an accelerator, imidazole 2E4MZ, is added. The amount of accelerator is 25% (by mass) of soluble dicyandiamide. The mixture is stirred evenly to form component C.

[0101] (d) Mix component A, component C and ethyl acetate at a mass ratio of 100:20:85 until homogeneous, and stir at high speed to obtain epoxy resin premix.

[0102] The viscosity of the epoxy resin prepreg obtained in step (d) above is 350 mPa·s;

[0103] (e) Heat component B to about 50°C and preheat for 0.5 h. Mix it with the epoxy resin premix obtained in step d above and component B at a mass ratio of 100:5. Add the third type of solvent for dilution and mix evenly under stirring for 30 to 60 min. The viscosity of the resulting foaming epoxy resin composition is 290 mPa·s.

[0104] Comparative Example 2

[0105] The epoxy resin foam composition prepared in Comparative Example 1 was placed into a glue tank, and the polyphenylene sulfide film was coated on both sides using a comma-shaped doctor blade. After the polyphenylene sulfide film surface underwent drying and cooling processes, a protective film was attached, and the film was then wound up to obtain polyphenylene sulfide foam material for groove insulation.

[0106] In this embodiment, the drying tunnel consists of 7 sections, each with a temperature of 40–50–60–65–75–85–95°C. A cooling process is then performed at a temperature of 15–20°C. Finally, a protective film is laminated and the material is rolled up to obtain the groove-insulating polyphenylene sulfide foam material.

[0107] The coating amount of this foam material is 35g / m² on one side. 2 The foaming ratio is 1.9 times, and the adhesion strength at room temperature after curing is 6.3 MPa. When the adhesion strength is tested after keeping it at 200℃ for 30-60 minutes, the adhesion strength is 1.5 MPa.

[0108] Compared with Examples 1 and 2, the foaming ratio of Component B, i.e. the foaming agent, was significantly insufficient after the amount of Component B was reduced, decreasing from 4.1 times in Example 2 to 1.9 times, which did not meet the foaming ratio requirement.

[0109] Comparative Example 3

[0110] (a) Bisphenol A epoxy resin (epoxy equivalent 230-270 g / eq) and phenolic epoxy resin (epoxy equivalent 150-200 g / eq) are mixed with ethyl acetate and butyl acetate in a mass ratio of 20:30:30:30 to form component A;

[0111] (b) Bisphenol F epoxy resin (epoxy equivalent 140-200 g / eq) and foaming agent (Wu Yu Chemical foaming microspheres, foaming ratio 2.5-6.0) are mixed evenly at a mass ratio of 30:12 to form component B;

[0112] (c) Soluble dicyandiamide and polar solvent N,N-dimethylformamide are stirred evenly at a mass ratio of 1:3, and then an accelerator, imidazole 2E4MZ, is added. The amount of accelerator is 30% (by mass) of soluble dicyandiamide. The mixture is stirred evenly to form component C.

[0113] (d) Mix component A, component C and ethyl acetate at a mass ratio of 100:20:85 until homogeneous, and stir at high speed to obtain epoxy resin premix.

[0114] The viscosity of the epoxy resin prepreg obtained in step (d) above is 310 mPa·s;

[0115] (e) Heat component B to about 50°C, preheat for 0.5 h, and mix it with the epoxy resin premix obtained in step d above and component B at a mass ratio of 100:30. Add the third type of solvent for dilution, and mix evenly under stirring for 30 to 60 min. The resulting foaming epoxy resin composition has a viscosity of 280 mPa·s.

[0116] Comparative Example 4

[0117] The epoxy resin foam composition prepared in Comparative Example 3 was placed into a glue tank, and the polyimide film was coated on both sides using a comma-shaped doctor blade. After the polyimide film surface underwent drying and cooling processes, a protective film was attached, and the film was then wound up to obtain polyimide foam material for groove insulation.

[0118] In this embodiment, the drying tunnel consists of 7 sections, each with a temperature of 40–50–60–65–75–85–95°C. A cooling process is then performed at a temperature of 15–20°C. Finally, a protective film is laminated and the material is rolled up to obtain the groove-insulating polyimide foam material.

[0119] The coating amount of the foam material is 35g / m² on one side. 2 The foaming ratio is 4.1 times, and the adhesion at room temperature after curing is 1.1 MPa. The adhesion to the substrate is reduced, and it is easy to crack and fall off.

[0120] Compared with Examples 5 and 6, the epoxy equivalent of bisphenol A in Component A decreased from the initial 550-650 g / eq to 230-270 g / eq in Examples 3 and 4. The bonding strength at room temperature decreased significantly, from 6.1 MPa in Example 6 to 1.1 MPa, which did not meet the bonding strength requirements.

[0121] Comparative Example 5

[0122] (a) Bisphenol A epoxy resin (epoxy equivalent 550-650 g / eq) and aliphatic epoxy resin (epoxy equivalent 15-200 g / eq) are mixed with ethyl acetate and butyl acetate in a mass ratio of 20:30:30:30 to form component A;

[0123] (b) Bisphenol F epoxy resin (epoxy equivalent 140-200 g / eq) and foaming agent (Wu Yu Chemical foaming microspheres, foaming ratio 2.5-6.0) are mixed evenly at a mass ratio of 30:12 to form component B;

[0124] (c) Soluble dicyandiamide and polar solvent N,N-dimethylformamide are stirred evenly at a mass ratio of 1:3, and then an accelerator, imidazole 2E4MZ, is added. The amount of accelerator is 30% (by mass) of soluble dicyandiamide. The mixture is stirred evenly to form component C.

[0125] (d) Mix component A, component C and ethyl acetate at a mass ratio of 100:20:85 until homogeneous, and stir at high speed to obtain epoxy resin premix.

[0126] The viscosity of the epoxy resin prepreg obtained in step (d) above is 450 mPa·s;

[0127] (e) Heat component B to about 50°C, preheat for 0.5 h, and mix it with the epoxy resin premix obtained in step d above and component B at a mass ratio of 100:30. Add the third type of solvent for dilution, and mix evenly under stirring for 30 to 60 min. The viscosity of the resulting foaming epoxy resin composition is 360 mPa·s.

[0128] Comparative Example 6

[0129] The epoxy resin foam composition prepared in Comparative Example 5 was placed into a glue tank, and the polyimide was coated on both sides using a comma-shaped doctor blade. After the polyimide film surface underwent drying and cooling processes, a protective film was attached, and the film was then wound up to obtain polyimide film foam material for groove insulation.

[0130] In this embodiment, the drying tunnel consists of 7 sections, each with a temperature of 40–50–60–65–75–85–95°C. A cooling process is then performed at a temperature of 15–20°C. Finally, a protective film is laminated and the material is rolled up to obtain the groove-insulating polyimide film foam material.

[0131] The coating amount of the foam material is 35g / m² on one side. 2 It has a foaming ratio of 2.9 times, and after curing, the adhesion strength is 5.3 MPa at room temperature and 0.4 MPa at 200℃. It is not heat resistant.

[0132] Compared with Examples 5 and 6, the change in the epoxy system ratio in component A resulted in excessively rapid foaming and curing, insufficient foaming ratio, and a decrease in adhesion to 0.4 MPa at high temperature, which did not meet the requirements for foaming ratio and adhesion at high temperature.

[0133] Comparative Example 7

[0134] (a) Bisphenol A epoxy resin (epoxy equivalent 900-1800 g / eq) and phenolic epoxy resin (epoxy equivalent 150-200 g / eq) are mixed with ethyl acetate and butyl acetate in a mass ratio of 20:30:30:30 to form component A;

[0135] (b) Mix aliphatic epoxy resin (epoxy equivalent 140-250 g / eq) and foaming agent (Akzo foaming microspheres, foaming ratio range 2.0-6.0) at a mass ratio of 30:8 to form component B;

[0136] (c) Mix the amine curing agent and the polar solvent N,N-dimethylformamide at a mass ratio of 1:3, then add the accelerator MY-24 (imidazolium-based), the amount of accelerator being 30% (by mass) of the soluble dicyandiamide, and mix well to form component C.

[0137] (d) Mix component A, component C and ethyl acetate at a mass ratio of 100:30:85 until homogeneous, and stir at high speed to obtain epoxy resin premix.

[0138] The viscosity of the epoxy resin prepreg obtained in step (d) above is 410 mPa·s;

[0139] (e) Heat component B to about 50°C, preheat for 0.5 h, and mix it with the epoxy resin premix obtained in step d above and component B at a mass ratio of 100:25. Add the third type of solvent for dilution, and mix evenly under stirring for 30 to 60 min. The viscosity of the resulting foaming epoxy resin composition is 320 mPa·s.

[0140] Comparative Example 8

[0141] The epoxy resin foam composition prepared in Comparative Example 7 was placed into a glue tank, and the polyimide film was coated on both sides using a comma-shaped doctor blade. After the polyimide film surface underwent drying and cooling processes, a protective film was attached, and the film was then wound up to obtain polyimide foam material for groove insulation.

[0142] In this embodiment, the drying tunnel consists of 7 sections, each with a temperature of 40–50–60–65–75–85–95°C. A cooling process is then performed at a temperature of 15–20°C. Finally, a protective film is laminated and the material is rolled up to obtain the groove-insulating polyimide foam material.

[0143] The coating amount of this foam material is 35g / m² on one side. 2 It has a foaming ratio of 3.5 times, and after curing, the adhesion strength is 5.3 MPa at room temperature and 0.4 MPa at 200℃. It is not heat resistant.

[0144] In this case, the pre-coated film, when left at room temperature (30℃) for 2-3 days, becomes hard, brittle, and unstable. It is easy to fall off when folded, which greatly affects the subsequent foaming process.

[0145] In Comparative Examples 7 and 8, compared with Examples 7-8, the increased proportion of component C in the curing system caused the pre-coated film to become brittle in a short period of time, affecting the storage period. In addition, the foaming ratio was insufficient, and the adhesion at high temperature dropped to 0.4 MPa. These comparative examples did not meet the requirements for both foaming ratio and adhesion at high temperature.

[0146] Comparative Example 9

[0147] The insulation foam material for motor slots is prepared as follows:

[0148] (a) Bisphenol A epoxy resin (epoxy equivalent 900-1800 g / eq) and phenolic epoxy resin (epoxy equivalent 150-200 g / eq) are mixed with ethyl acetate and butyl acetate in a mass ratio of 20:30:30:30 to form component A;

[0149] (b) Mix aliphatic epoxy resin (epoxy equivalent 150-250 g / eq) and foaming agent (Akzo foaming microspheres, foaming ratio range 2.0-6.0) at a mass ratio of 30:10 to form component B;

[0150] (c) The pre-dispersed mixture of liquid epoxy and dicyandiamide curing agent and polar solvent N,N-dimethylformamide are stirred evenly at a mass ratio of 1:3. Then, microcapsule-form imidazole accelerators are added. The amount of accelerator is 20% (by mass) of the mixture of dicyandiamide, epoxy resin and dispersion. The mixture is stirred evenly to form component C.

[0151] (d) Mix component A, component C and ethyl acetate at a mass ratio of 100:3:85 until homogeneous, and stir at low speed to obtain epoxy resin premix.

[0152] The viscosity of the epoxy resin prepreg obtained in step (d) above is 425 mPa·s;

[0153] (e) Heat component B to about 50°C, preheat for 0.5 h, and mix it with the epoxy resin pre-prepared liquid obtained in step d above and component B at a mass ratio of 100:30. After diluting with the third type of solvent, mix the mixture evenly under the condition of stirring for 30 to 60 min. The viscosity of the resulting foaming epoxy resin composition is 390 mPa·s.

[0154] Comparative Example 10

[0155] The epoxy resin foam composition prepared in Comparative Example 9 was placed into a glue tank, and the polyimide film was coated on both sides using a comma-shaped doctor blade. After the polyimide film surface underwent drying and cooling processes, a protective film was attached, and the film was then wound up to obtain polyimide foam material for groove insulation.

[0156] In this embodiment, the drying tunnel consists of 7 sections, each with a temperature of 40–50–60–65–75–85–95°C. A cooling process is then performed at a temperature of 15–20°C. Finally, a protective film is laminated and the material is rolled up to obtain the groove-insulating polyimide foam material.

[0157] The coating amount of the foam material is 35g / m² on one side. 2 The foaming ratio is 7.3 times, and the adhesion strength at room temperature after curing is 1.5 MPa. When the adhesion strength is tested after keeping it at 200℃ for 30-60 minutes, the adhesion strength is 0.3 MPa.

[0158] In Comparative Examples 9 and 10, compared with Examples 9-10, the proportion of component C in the curing system is reduced, resulting in the pre-coated film not reaching a fully cured state, leading to an excessive foaming ratio and insufficient adhesion. These comparative examples do not meet the requirements for either foaming ratio or adhesion.

[0159] Those skilled in the art will readily understand that the above description is only a part of the embodiments of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A foamed epoxy resin composition for motor slot insulation, characterized in that, The foamed epoxy resin composition for motor slot insulation includes component A, component B, and component C. Component A includes bisphenol A epoxy resin, phenolic epoxy resin, and solvent. Component B includes epoxy resin and foaming agent. Component C includes latent curing agent, solvent, and accelerator. Component A and component C are mixed evenly with solvent to obtain epoxy resin premix, and then mixed evenly with component B and solvent.

2. The foamed epoxy resin composition for motor slot insulation according to claim 1, characterized in that, The components A and C are mixed with the solvent at a mass ratio of 100:5-20:80-90 until homogeneous; preferably, the epoxy resin premix is ​​mixed with component B at a mass ratio of 100:17-35 until homogeneous; preferably, the epoxy equivalent of the bisphenol A epoxy resin is 500-1800 g / eq; preferably, the epoxy equivalent of the phenolic epoxy resin is 150-200 g / eq.

3. The foamed epoxy resin composition for motor slot insulation according to claim 1, characterized in that, The solvent in component A is selected from one or more of acetone, ethyl acetate, butyl acetate, butanone, toluene, and xylene; preferably, the solvent in component A is ethyl acetate and butyl acetate; preferably, the mass ratio of ethyl acetate to butyl acetate is 20-35:25-40; preferably, the bisphenol A epoxy resin and phenolic epoxy resin in component A are mixed with ethyl acetate and butyl acetate in a mass ratio of 18-22:28-32:23-32:28-38 until homogeneous.

4. The foamed epoxy resin composition for motor slot insulation according to claim 1, characterized in that, The epoxy resin and foaming agent in component B are stirred evenly at a mass ratio of 25-35:8-12; preferably, the epoxy resin in component B is one or two of bisphenol F epoxy resin and alicyclic epoxy resin; preferably, the epoxy equivalent of the bisphenol F epoxy resin is 140-200 g / eq; preferably, the epoxy equivalent of the alicyclic epoxy resin is 140-250 g / eq.

5. The foamed epoxy resin composition for motor slot insulation according to claim 1, characterized in that, The latent curing agent is selected from amine curing agents and / or imidazole curing agents, or a pre-dispersion mixture of liquid epoxy and dicyandiamide; preferably, the solvent in component C is one or more of N,N-dimethylformamide, butanone, and butyl acetate, preferably N,N-dimethylformamide; preferably, the latent curing agent and solvent in component C are stirred evenly at a mass ratio of 0.8-1.2:2-4; preferably, the amount of accelerator in component C is 15-35% of the latent curing agent; preferably, the accelerator is selected from imidazole and / or urea derivatives; preferably, the foaming agent is selected from thermally expandable microcapsules and / or inorganic foaming agents; preferably, the inorganic foaming agent is selected from one or more of ammonium bicarbonate, ammonium borohydride, and azides.

6. The foamed epoxy resin composition for motor slot insulation according to claim 1, characterized in that, The solvents used in the uniform mixing of components A and C with the solvent, and the uniform mixing of the epoxy resin premix with component B and the solvent, are selected from one or more of acetone, ethyl acetate, methyl acetate, butanone, toluene, and xylene.

7. A method for preparing the foamed epoxy resin composition for motor slot insulation according to any one of claims 1-6, characterized in that, The method includes the following steps: (a) Mix component A and component C at the required mass ratio and then mix them with solvent to obtain epoxy resin premix; (b) Mix component B with the epoxy resin premix obtained in step (a) above, dilute with solvent, and mix evenly to obtain a foamed epoxy resin composition for motor slot insulation.

8. The method for preparing the foamed epoxy resin composition for motor slot insulation according to claim 7, characterized in that, In step (b), component B is first heated to 45-55°C and kept at that temperature for 0.4-0.6 hours, and then mixed evenly with the epoxy resin premix obtained in step (a).

9. A foamed material for insulating motor slots, characterized in that, The foamed material for motor slot insulation includes an insulating layer and a foamed epoxy resin composition coated on the insulating layer. The foamed epoxy resin composition is the foamed epoxy resin composition for motor slot insulation according to any one of claims 1-6. Preferably, the insulating layer is any one of polyphenylene sulfide film, polynatrimethylene film, polyimide film, a composite material of polyaramid fiber and polyphenylene sulfide film, or a composite material of polyaramid fiber and polynatrimethylene film.

10. The method for preparing the foamed material for motor slot insulation according to claim 9, characterized in that, The method includes the following steps: The prepared foamed epoxy resin composition is placed into a glue tank, and the resin is applied to the upper and lower surfaces of the insulating layer using a comma-shaped scraper or slit extrusion. The foamed epoxy resin composition is then transferred to the surface of the insulating layer. After the insulating layer surface undergoes drying and cooling processes, it is wound up to obtain foamed insulating paper. Preferably, the resin application amount is 30-50 g / m² on one side. 2 Preferably, the drying and cooling processes include: the drying tunnel has 3 to 9 sections, with the temperature designed from low to high, ranging from a minimum of 35°C to a maximum of 100°C, wherein the temperature of each section is allowed to have a tolerance of ±10°C, and a protective film is applied after the drying process.

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