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CN-121975474-A - High-temperature-shearing-resistant epoxy structural adhesive and preparation method thereof

CN121975474ACN 121975474 ACN121975474 ACN 121975474ACN-121975474-A

Abstract

The invention discloses high-temperature-shearing-resistant epoxy structural adhesive and a preparation method thereof, and belongs to the technical field of high-performance composite materials. The invention is applicable to rigid oxazolidone modified epoxy resin, and solves the problems of the epoxy resin matrix that the modulus is reduced and the cohesive force is insufficient at high temperature by introducing rigid oxazolidone five-membered heterocycle, cooperating with bisphenol A epoxy resin, bisphenol F epoxy resin and core-shell modified epoxy resin and cooperating with other components, the tensile shear strength at 80 ℃ is more than or equal to 30MPa, the cohesive failure rate is more than or equal to 95%, the normal temperature impact strength is more than or equal to 44N/mm, and the moisture-heat resistance is excellent, thus being applicable to the bonding of high temperature key parts such as automobile engine cabins, three-electric systems and the like.

Inventors

  • Cen Shangxu
  • LIU LINA
  • MEI XI
  • LI XIAOYUE
  • WANG YACHAO
  • XU LI
  • Dai Xiaoshuai

Assignees

  • 保光(天津)汽车零部件有限公司

Dates

Publication Date
20260505
Application Date
20260408

Claims (8)

  1. 1. The high-temperature-shearing-resistant epoxy structural adhesive is characterized by comprising the following components in parts by weight: 10-20 parts of bisphenol A type epoxy resin, 10-15 parts of bisphenol F type epoxy resin, 10-20 parts of core-shell modified epoxy resin, 15-25 parts of oxazolidone modified epoxy resin, 1-5 parts of curing agent, 0.1-0.5 part of curing accelerator, 10-30 parts of filler, 10-15 parts of toughening agent, 3-5 parts of moisture absorbent, 2-5 parts of thixotropic agent and 0.1-0.5 part of silane coupling agent; the oxazolidone modified epoxy resin is prepared by cycloaddition reaction of isocyanate compound and epoxy group of epoxy resin, and the oxazolidone five-membered ring is chemically bonded and embedded into the main chain of the epoxy resin; The number average molecular weight Mn of the oxazolidone modified epoxy resin is 700-900 Da, and the molecular weight distribution Mw/Mn is 1.6-2.5; the toughening agent comprises a polyurethane toughening agent, and the mass ratio of the polyurethane toughening agent to the oxazolidone modified epoxy resin is 1:1.25-2; the filler comprises heavy calcium carbonate and fibrous wollastonite with a mass ratio of 2-4:1.
  2. 2. The epoxy structural adhesive of claim 1, wherein the method for preparing the oxazolidone modified epoxy resin comprises the following steps: S1, adding 4,4 '-diaminodiphenylmethane and diethyl carbonate in a molar ratio of 1:12, adding a catalyst accounting for 0.5-1.0% of the mass of the 4,4' -diaminodiphenylmethane, and under the protection of nitrogen, adopting a gradient heating mode, namely heating to 110 ℃ for 2 hours, heating to 125-130 ℃ for violent stirring reaction for 5 hours, cooling to room temperature, and removing excessive diethyl carbonate to obtain a carbamate intermediate; S2, sectionally cracking the carbamate intermediate under the conditions of vacuum degree of-0.098 MPa and 180-230 ℃, namely, firstly carrying out preliminary cracking at 180 ℃ for 1h, then carrying out deep cracking at 220-230 ℃ for 2h, then collecting a crude product through a condensing tube at 10-15 ℃, carrying out reduced pressure rectification on the crude product at-0.098 MPa and 120 ℃, and then carrying out recrystallization and drying to obtain 4,4' -diphenylmethane diisocyanate; s3, adding 4,4' -diphenylmethane diisocyanate and epoxy resin according to the mol ratio of isocyanate groups to epoxy groups of 0.9:1.0, adding a catalyst accounting for 0.3-0.5% of the mass of the epoxy resin and a dehydrating agent accounting for 2-3% of the total mass of the system, dehydrating and drying for 1h under the vacuum condition of 100-0.09 MPa, reacting for 4-6 h under the protection of nitrogen at 80-140 ℃, and washing with ethyl acetate after the reaction is finished, and removing the solvent in vacuum to obtain the oxazolidone modified epoxy resin.
  3. 3. The epoxy structural adhesive according to claim 1, wherein the core-shell modified epoxy resin is an epoxy resin modified by using core-shell particles, the core-shell particles are formed by taking polybutadiene rubber as a core and methyl methacrylate as a shell, and the average particle size of the core-shell particles is 100-200 nm.
  4. 4. The epoxy structural adhesive of claim 1, wherein the particle size of the heavy calcium carbonate is 1-10 μm, and the purity is more than or equal to 98%; The length-diameter ratio of the fibrous wollastonite is 10-15:1, and the particle size is 600-1250 meshes.
  5. 5. The epoxy structural adhesive according to claim 1, wherein the thixotropic agent comprises fumed silica and quaternary ammonium salt modified bentonite, and the mass ratio of the fumed silica to the quaternary ammonium salt modified bentonite is 1.5-3:1; the specific surface area of the gas-phase white carbon black is 140-220 m 2 /g; The quaternary ammonium salt modified bentonite is hexadecyl trimethyl ammonium chloride, octadecyl trimethyl ammonium chloride or dioctadecyl dimethyl ammonium chloride modified organic bentonite, the activation degree is more than or equal to 95%, and the particle size is 1-8 mu m.
  6. 6. The epoxy structural adhesive according to claim 1, wherein the silane coupling agent comprises KH560 and KH590, wherein the amount of KH560 is 0.05-0.3 part, and the amount of KH590 is 0.05-0.2 part; The curing accelerator comprises an organic urea accelerator; the curing agent comprises one or more of dicyandiamide, sebacic dihydrazide or adipic dihydrazide.
  7. 7. The epoxy structural adhesive of any one of claims 1-6, further comprising 0.01-0.05 parts by weight of a pigment comprising carbon black; The moisture absorbent comprises a calcium oxide moisture absorbent.
  8. 8. The method of preparing an epoxy structural adhesive according to any one of claims 1 to 7, comprising: a, raw material pretreatment: respectively placing the moisture absorbent, the filler and the thixotropic agent in a 110-120 ℃ vacuum drying oven, drying for 2-3 hours, and cooling to room temperature for standby; pre-dispersing pigment and 0.5-1 part by weight of bisphenol A epoxy resin to prepare pigment master batch for standby, so as to avoid pigment agglomeration; b, mixing the substrates: adding the rest bisphenol A type epoxy resin, bisphenol F type epoxy resin, core-shell modified epoxy resin and oxazolidone modified epoxy resin into a planetary stirrer, introducing nitrogen to replace the air of the system for 3 times, controlling the stirring rotation speed to be 500-600 r/min and the temperature to be 40-50 ℃, and stirring for 20-30 min until the system is uniform and transparent; Then, keeping nitrogen protection, the temperature and the rotating speed, slowly adding the toughening agent and the silane coupling agent, and continuously stirring for 30-40 min; Then sequentially adding the pretreated thixotropic agent, filler and moisture absorbent into the system, adjusting the stirring rotation speed to 800-1000 r/min and the temperature to 50-60 ℃, dispersing at a high speed for 40-60 min, and stopping the machine for scraping the wall 1 time every 15min during the high-speed dispersion; c, vacuum defoaming Switching the planetary stirrer to a vacuum mode, controlling the vacuum degree to be-0.09 to-0.095 MPa and the temperature to be 45-55 ℃, and keeping the rotating speed to be 300-400 r/min for defoaming for 30-40 min; d, mixing a curing system: Closing vacuum, cooling to 30-40 ℃, adding a curing agent, a curing accelerator and the pretreated pigment master batch, adjusting the stirring rotation speed to 500-600 r/min, and stirring for 20-30 min; And e, post-treatment: defoaming for 10-15 min at normal temperature under the vacuum degree of-0.09 to-0.095 MPa, detecting the viscosity of the system, and controlling the viscosity at 8000-20000 mPas at 25 ℃ to obtain the high-temperature-resistant shearing epoxy structural adhesive.

Description

High-temperature-shearing-resistant epoxy structural adhesive and preparation method thereof Technical Field The invention relates to the technical field of high-performance composite materials, in particular to high-temperature-shearing-resistant epoxy structural adhesive and a preparation method thereof. Background With the rapid development of the automobile industry towards light weight, high performance and new energy, the integration of a vehicle body structure, the improvement of the thermal efficiency of an engine and the wide application of a three-electric system (battery, motor and electric control) of a new energy automobile, more stringent requirements are put forward on the high temperature resistance, mechanical reliability and environmental protection safety of the structural adhesive for the automobile. The epoxy structural adhesive has the core advantages of high bonding strength, excellent chemical corrosion resistance, good compatibility with metal/composite materials and the like, and is a core material for key scenes such as welding reinforcement of automobile bodies, fixing of peripheral parts of engines, bonding of chassis structures, sealing of three-electric systems and the like, and the performance of the epoxy structural adhesive directly influences the structural stability, service life and safety redundancy of automobiles. In the actual service process of the automobile, the working temperature of the engine room, the periphery of the exhaust pipe and other core areas often reaches 80 ℃ or more, and even approaches 120 ℃ under partial extreme working conditions. However, the molecular network of the traditional epoxy structural adhesive is mainly composed of flexible ether bonds (C-O-C) and methylene chains, has low glass transition temperature (Tg), is easy to enter a high-elastic state in a high-temperature environment, and causes the problems of aggravation of molecular chain segment movement, reduction of cohesive energy density, rapid attenuation of shear strength, failure of an adhesive interface and the like, so that the traditional epoxy structural adhesive becomes a core bottleneck for restricting the large-scale application of the traditional epoxy structural adhesive to high-temperature key parts of automobiles. In order to improve the high temperature resistance of the epoxy structural adhesive, various technical researches have been carried out in the industry. The common improvement path in the prior art comprises the steps of optimizing an epoxy resin matrix (such as multi-functionality epoxy, bisphenol F/S epoxy and the like), enhancing the thermal stability by improving the crosslinking density, adding a rigid filler (such as gas-phase white carbon black and modified ceramic powder) or a heat-resistant auxiliary agent (such as polyimide micro powder), inhibiting molecular chain movement by utilizing a physical filling effect, adopting elastomer modification (such as CTBN rubber and core-shell rubber), balancing high-temperature rigidity and normal-temperature toughness, optimizing a curing system (such as a latent curing agent and a composite curing accelerator), and improving the thermal stability of a crosslinked network. However, the prior art still has obvious limitations that firstly, the brittleness of a glue layer is easily increased and the normal-temperature impact resistance is reduced due to the simple modification of polyfunctional epoxy or rigid filler, secondly, the toughness can be improved due to the modification of an elastomer, but the heat resistance of the elastomer is limited, the elastomer is easily softened at high temperature, the cohesive strength of the glue layer can be weakened, the improvement of the high-temperature shearing performance is not obvious, thirdly, the existing modification scheme is mainly physical blending or simple chemical grafting, and the core problems of slippage of a molecular chain segment and insufficient cohesive force at high temperature are difficult to fundamentally solve. In addition, the existing scheme of the special epoxy structural adhesive for the automobile focuses on the wide-temperature-range adhesive performance, but the shear strength optimization aiming at the high-temperature working condition of 80 ℃ and above is insufficient. Therefore, developing an epoxy structural adhesive for automobiles, which combines high-temperature shear strength and comprehensive mechanical properties, becomes a technical problem to be solved urgently in the current industry. Disclosure of Invention In order to solve the technical problems in the prior art, the invention aims to provide high-temperature-shearing-resistant epoxy structural adhesive and a preparation method thereof. The invention aims to provide high-temperature-shearing-resistant epoxy structural adhesive, which comprises the following components in parts by weight: 10-20 parts of bisphenol A type epoxy resin, 10-15 parts of bisphenol F type epoxy