Thermal shrinkage epoxy resin thermal breaking adhesive film and preparation method thereof

Abstract

The invention discloses a thermal shrinkage epoxy resin thermal breaking adhesive film and a preparation method thereof, and belongs to the technical field of epoxy resin adhesive films. A thermal shrinkage polyurethane prepolymer reacts with epoxy resin to prepare polyurethane modified epoxy resin; adding the modified epoxy resin, the unmodified epoxy resin, the solid toughening powder, an amine curing agent and a urea compound into a reaction device, blending to obtain an adhesive film blend, calendering the adhesive film blend twice at high and low temperatures according to the thermophysical property difference of polyol and isocyanate components forming a polyurethane prepolymer, and then quenching and shaping to obtain the adhesive film. Preparing a thermal gel breaking film; according to the technical scheme, the hot breaking process of the adhesive film is accurately controlled within the accurate temperature range, the technological process is greatly simplified, the application effect of the adhesive film is improved, and the method is particularly suitable for manufacturing of aerospace honeycomb structural components.

Description

Technical Field

[0001] The present application belongs to the technical field of epoxy resin films, and in particular, relates to a heat-shrinkable epoxy resin thermal breakable film and a preparation method thereof. Background Art

[0002] The bonded honeycomb sandwich structure is a layered composite material structure formed by bonding the face sheet to the honeycomb core material with an adhesive. It is widely used in the aerospace field because of its high specific strength, specific stiffness, and good thermal insulation, vibration isolation, and impact resistance. The bonding position of the bonded honeycomb sandwich structure is at the junction of the edge of the honeycomb core and the surface skin. The effective adhesive application area is small, and the use of conventional adhesive film will cause material waste and increase the weight of the structure. However, when using thermal break adhesive film, the adhesive film can be thermally broken by the combined action of heating and hot air. The thermal break colloid gathers at the edge of the honeycomb core, which increases the bonding area and the thickness of the adhesive layer, which is beneficial to improving the bonding strength. In addition, the amount of adhesive film used can be reduced, and the production efficiency can be significantly improved. According to the literature "Development of Thermal Breaking Machine for Composite Material Structural Plate Adhesive Film" and "Research on Thermal Breaking Process of Adhesive Film for Spacecraft Honeycomb Sandwich Structure", the thermal break type adhesive film needs to be combined with a special thermal break process device and can only be actually used under the set preheating temperature, wind pressure, and hot air scanning rate process conditions. Therefore, it brings great restrictions to the large-scale application of thermal break adhesive film. In addition, it has been reported that the response relationship between the rheological state of the thermal break adhesive film and the heating temperature and heating time is difficult to quantitatively analyze, resulting in a low pore rate in the adhesive film during the thermal break process and premature solidification of the colloid, which has an adverse effect on the use of the thermal break adhesive film. Summary of the invention

[0003] The purpose of the present application is to provide a heat-shrinkable epoxy resin thermal break adhesive film and a preparation method thereof, so as to solve the problems in the prior art that the thermal break process of the epoxy thermal break adhesive film has high process requirements and the thermal break rate is difficult to accurately control.

[0004] To achieve the above-mentioned purpose, the technical solution adopted in the present application is: to provide a heat-shrinkable epoxy resin thermal breakable adhesive film, wherein the raw materials include, by weight: 40-70 parts of modified epoxy resin, 30-60 parts of unmodified epoxy resin, 5-10 parts of solid toughening powder, 3-8 parts of amine curing agent and 1-3 parts of urea compound;

[0005] The modified epoxy resin consists of unmodified epoxy resin and polyurethane prepolymer in a mass ratio of 60-100:5-40.

[0006] In one embodiment,

[0007] The polyurethane prepolymer is composed of polyol and isocyanate; the molar ratio of polyol to isocyanate is 1:2-5;

[0008] The polyol is one or more of polyoxypropylene diol, polycarbonate diol, polycarbonate triol or polyether urethane-based polyol, and the isocyanate is one or more of fluorinated toluene diisocyanate, diphenylmethane diisocyanate, p-phenylene diisocyanate or dicyclohexylmethane diisocyanate.

[0009] In one embodiment,

[0010] The polyurethane prepolymer further includes a diluent and a stabilizer. The dosage of the diluent is 5-10% of the total amount of the polyurethane prepolymer; the dosage of the stabilizer is 0.1-1% of the total amount of the polyurethane prepolymer.

[0011] The diluent is one or more of dimethyl phthalate, di-n-butyl phthalate or butyl acetate; the stabilizer is one or more of tert-butylhydroquinone, diisopropylbenzene peroxide or tetrabutyltin.

[0012] In one embodiment,

[0013] The unmodified epoxy resin is one of bisphenol A epoxy resin, aliphatic epoxy resin, polybutadiene epoxy resin, a blend of bisphenol A epoxy resin and polybutadiene epoxy resin, a blend of polybutadiene epoxy resin and aliphatic epoxy resin, or a blend of bisphenol A epoxy resin with polybutadiene epoxy resin and aliphatic epoxy resin.

[0014] In one embodiment,

[0015] The bisphenol A epoxy resin is one or more of E-54 epoxy resin, E-51 epoxy resin, E-44 epoxy resin or 601 epoxy resin; the aliphatic epoxy resin is one or more of polypropylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether or n-butyl glycidyl ether.

[0016] In one embodiment,

[0017] The solid toughening powder is one or more of nitrile rubber powder, PES powder, PEEK powder or PA powder, the amine curing agent is one or more of dicyandiamide, 4,4'-diaminodiphenylmethane, 4,4-diaminodiphenyl sulfone, m-phenylenediamine, 4,4'-diaminodiphenyl ether, bis-N,N'-(methyl-butylmethylene)-diethylenetriamine or 1,2-diaminocyclohexane, and the urea compound is one or more of 3-phenyl-1,1-dimethylurea, 3-(4-chlorophenyl)-1,1-dimethylurea, 3-ethyl-1,1-dimethylurea, 3-p-nitrophenyl-1,1-dimethylurea, N,N-(1,4-phenylene)bis(N',N'-dimethylurea).

[0018] The present application also provides a method for preparing a heat-shrinkable epoxy resin thermal breaker film, which specifically includes the following steps:

[0019] (1) Weigh polyol, unmodified epoxy resin, isocyanate, diluent, stabilizer, solid toughening powder, amine curing agent and urea compound by weight parts;

[0020] (2) Heat up the polyol and unmodified epoxy resin. After the heating is completed, evacuate the air, take it out and cool it down to obtain pretreated polyol and pretreated unmodified epoxy resin. Heat up the isocyanate to obtain pretreated isocyanate;

[0021] (3) Stir the pretreated polyol evenly, introduce nitrogen to remove air, dropwise add the pretreated isocyanate, add the diluent and stabilizer, and react to obtain a polyurethane prepolymer; add the pretreated unmodified epoxy resin into the polyurethane prepolymer and stir evenly, and react under nitrogen to obtain a modified epoxy resin;

[0022] (4) Mix the modified epoxy resin with unmodified epoxy resin, solid toughening powder, amine curing agent and urea compound to obtain a rubber compound;

[0023] (5) Add the rubber compound into a film-making machine, perform primary calendering and shaping under the condition that the roll temperature is -3 - 5°C, then use the film-making machine to perform secondary pressing to form a film at 80°C, and then perform rapid cooling and shaping to obtain a heat-shrinkable epoxy resin thermal breaker film.

[0024] In one embodiment,

[0025] The specific steps for heating the polyol and unmodified epoxy resin in step (2) are: put the polyol and unmodified epoxy resin into a vacuum oven and heat them up to 110°C at a heating rate of 2°C / min, keep the temperature for 30 min, and the evacuation time is 120 min; the specific steps for heating the isocyanate are: put the isocyanate into a vacuum oven and heat it up to 60°C, keep the temperature for 60 min.

[0026] In one embodiment,

[0027] The conditions for evenly stirring the pretreated polyol in step (3) are: place the pretreated polyol in a three-necked flask, and use a cantilever stirrer to drive the stirrer paddle to stir evenly at a speed of 150 - 600 r / min under the condition of an oil bath at 70°C; the dropping speed of the pretreated isocyanate is 1 g / min; the reaction time for preparing the polyurethane prepolymer is 1 - 5 h; the conditions for evenly stirring the pretreated unmodified epoxy resin are: stir evenly at a speed of 180 - 600 r / min under the condition of an oil bath at 120°C; the reaction time for preparing the modified epoxy resin is 1 - 4 h; the mixing time in step (4) is 30 min and the temperature is 70°C; the temperature for rapid cooling and shaping in step (4) is 0 - 5°C.

[0028] In one embodiment,

[0029] The thickness of the thermal fracturing film is 0.1 - 0.5 mm, and the storage temperature is below -20 °C.

[0030] The present application provides a heat-shrinkable epoxy resin thermal fracturing film and a preparation method thereof, and the effective effects are as follows:

[0031] 1. By introducing a polyurethane prepolymer as a modification component of the epoxy resin, the present application successfully solves the problems of high process requirements and difficult accurate control of the thermal fracturing rate in the thermal fracturing process of the existing epoxy thermal fracturing film. The polyurethane prepolymer not only has good heat-shrinkage performance, but also its soft and hard segment multiphase structure can effectively respond to temperature changes and generate controllable shape changes; after heating to an appropriate temperature, the film deforms under the action of external force and is secondarily shaped by rapid cooling. This process freezes the uncompleted reversible strain in the macromolecular chains, ensuring the stability and controllability of the thermal fracturing process. By this method, the thermal fracturing behavior of the film can be precisely triggered within a specific temperature range, greatly improving the controllability and accuracy of the thermal fracturing rate and meeting the requirements of different application scenarios for thermal fracturing performance;

[0032] 2. The heat-shrinkable epoxy resin thermal fracturing film has good thermal response characteristics. When the film is shaped, it can release the internal stress of the material by heating at a specific temperature and then return to the initial shaped state; this reversible deformation process enables precise temperature control management of the thermal fracturing behavior of the film. Especially when heated to the recovery temperature by external force, the internal stress of the material is released and drives the film to return to its original state, ensuring the controllability and efficiency of the thermal fracturing behavior; in addition, due to the stress concentration generated at the position of the toughening particles inside the film caused by the difference in the thermal deformation coefficient from the colloidal resin, the uniformity and stability of the thermal fracturing process are further optimized, providing excellent temperature adaptability and performance reliability in its practical application and greatly enhancing the practicality and applicable range of the thermal fracturing film;

[0033] 3. After adopting the polyurethane modification component, the heat-shrinkable epoxy resin thermal fracturing film forms a soft and hard segment multiphase structure with thermal stress incompatibility, which can effectively improve the strength and toughness of the film; when the film is heated to the heat-shrinkage temperature and deformed, the heat-shrinkage deformation will generate stress concentration at the toughening particles inside the film, thereby promoting the thermal fracturing behavior of the film at a controllable temperature; in this way, the mechanical properties of the film are significantly enhanced, and it can withstand higher external forces during the thermal fracturing process. At the same time, when the thermal fracturing behavior occurs, the film does not undergo brittle fracture but shows a controllable thermal fracturing process, thus improving the reliability and durability of the material. Especially in applications under high-temperature or stress environments, it demonstrates excellent anti-destruction performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the accompanying drawings required in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0035] Figure 1 It is the reaction principle diagram of the polyurethane prepolymer in Example 1;

[0036] Figure 2 It is the reaction principle diagram of the modified epoxy resin in Example 1;

[0037] Figure 3 It is the microscopic schematic diagram of the secondary forming process in Example 1;

[0038] Figure 4 It is the physical diagram of the heat-shrinkable epoxy resin heat-breaking film prepared in Example 1 covering the aluminum honeycomb surface;

[0039] Figure 5 It is the physical diagram of the heat-shrinkable epoxy resin heat-breaking film prepared in Example 1 during the heat-breaking process on the aluminum honeycomb surface;

[0040] Figure 6 It is the physical diagram of the heat-shrinkable epoxy resin heat-breaking film prepared in Example 1 after heat-breaking on the aluminum honeycomb surface;

[0041] Figure 7 It is the infrared spectrum diagram of Example 1. Detailed implementation manners

[0042] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clear and understandable, the present application will be further described in detail. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0043] Example 1

[0044] A heat-shrinkable epoxy resin heat-breaking film, by weight, the raw materials include: 40 parts of modified epoxy resin, 60 parts of E-51 epoxy resin, 5 parts of PES powder, 5 parts of dicyandiamide and 2 parts of 3-ethyl-1,1-dimethylurea; the modified epoxy resin is composed of E-51 epoxy resin and polyurethane prepolymer with a mass ratio of 80:20;

[0045] The preparation method of the heat-shrinkable epoxy resin heat-breaking film specifically includes the following steps:

[0046] (1). Weigh each raw material by weight;

[0047] (2). Polyoxypropylene diol (PPG-2000) with a molecular weight of 2000 and E-51 epoxy resin were placed in a vacuum oven and heated to 110°C at a heating rate of 2°C / min, held for 30 min. After the holding period, air extraction was carried out to create a vacuum environment, and vacuum dehydration and degassing were performed for more than 120 min. Then, it was taken out and cooled to obtain pretreated PPG-2000 and pretreated E-51 epoxy resin, which were used immediately. Diphenylmethane diisocyanate (MDI) was placed in a vacuum oven and held at 60°C for more than 60 min to obtain pretreated MDI;

[0048] (3). 50 g of pretreated PPG-2000 was placed in a three-necked flask, and under the condition of an oil bath at 70°C, a cantilever stirrer was used to drive the stirrer paddle to stir evenly at a speed of 150 r / min. At the same time, nitrogen was introduced to remove air, and 15 g of pretreated MDI was added dropwise evenly at a dropping rate of 1 g / min. After the addition of raw materials was completed and the reaction temperature was stable, timing was started, and the reaction continued for 2.5 h to obtain a polyurethane prepolymer. The reaction principle is as Figure 1 shown; 260 g of pretreated E-51 epoxy resin was stirred evenly at a speed of 180 r / min under the condition of an oil bath at 120°C, and nitrogen protection was introduced. After the addition of raw materials was completed and the reaction temperature was stable, timing was started, and the reaction continued for 2.5 h to obtain a modified epoxy resin. The reaction principle of the modified epoxy is as Figure 2 shown;

[0049] (4). The modified epoxy resin, E-51 epoxy resin, PES powder, dicyandiamide, and 3-ethyl-1,1-dimethylurea were mixed for 30 min at a mixing temperature of 70°C to obtain a rubber compound;

[0050] (5). The rubber compound was added to a film-making machine and subjected to primary calendering and shaping under the condition of a roll temperature of 0°C, and then secondary pressed into a rubber film by the film-making machine under the condition of a roll temperature of 80°C. Subsequently, it was rapidly cooled and shaped at 0 - 5°C to obtain an epoxy resin thermal fracturing film with heat shrinkage performance; the thickness of the thermal fracturing film is 0.1 - 0.2 mm, and the storage temperature is below -20°C. The schematic diagram of the secondary forming process is as Figure 3 shown;

[0051] The epoxy resin forming and cooling device includes a cooling roller and an inlet and outlet water pipe component; the rubber film after secondary forming is heat-transferred and cooled by being attached and conveyed on the cooling roller, and this device can improve the heat exchange effect by setting the conveying speed and the water temperature in the cooling roller.

[0052] Example 2

[0053] A heat-shrinkable epoxy resin thermal breaker film, by weight, the raw materials include: 40 parts of modified epoxy resin, 60 parts of polypropylene glycol diglycidyl ether, 5 parts of PES powder, 5 parts of dicyandiamide, and 2 parts of 3-ethyl-1,1-dimethylurea; the modified epoxy resin is composed of polypropylene glycol diglycidyl ether and polyurethane prepolymer with a mass ratio of 75.2:20;

[0054] A preparation method of the heat-shrinkable epoxy resin thermal breaker film specifically includes the following steps:

[0055] (1) Weigh each raw material by weight;

[0056] (2) Place polyoxypropylene diol (PPG-2000) with a molecular weight of 2000 and polypropylene glycol diglycidyl ether into a vacuum oven and heat it to 110°C at a heating rate of 2°C / min, keep it warm for 30 min. After the heat preservation ends, evacuate to create a vacuum environment and perform vacuum dehydration and degassing for more than 120 min, then take it out and cool it down to obtain pretreated PPG-2000 and pretreated polypropylene glycol diglycidyl ether, and use it immediately. Place MDI into a vacuum oven and keep it at 60°C for more than 60 min to obtain pretreated MDI;

[0057] (3) Place 50 g of pretreated PPG-2000 in a three-necked flask, use a cantilever stirrer to drive the stirrer paddle to stir evenly at a speed of 150 r / min under an oil bath condition of 70°C, and at the same time introduce nitrogen to exclude air. Drop 15 g of pretreated MDI at a dropping rate of 1 g / min evenly, add 3.5 g of dibutyl phthalate (DBP) and 0.6 g of tert-butylhydroquinone (BHT). Start timing after the raw materials are added and the reaction temperature is stable, and continue the reaction for 2.5 h to obtain a polyurethane prepolymer; Stir 260 g of pretreated polypropylene glycol diglycidyl ether evenly at a speed of 180 r / min under an oil bath condition of 120°C, and introduce nitrogen for protection. Start timing after the raw materials are added and the reaction temperature is stable, and continue the reaction for 2.5 h to obtain a modified epoxy resin;

[0058] (4) Mix the modified epoxy resin, polypropylene glycol diglycidyl ether, PES powder, dicyandiamide, and 3-ethyl-1,1-dimethylurea for 30 min at a mixing temperature of 70°C to obtain a sizing material;

[0059] (5) Add the sizing material to a film-making machine, perform primary calendering and shaping under the condition that the roll temperature is 0°C, then use the film-making machine to perform secondary pressing to form a film under the condition that the roll temperature is 80°C, and then perform rapid cooling and shaping at 0 - 5°C to obtain an epoxy resin thermal breaker film with heat-shrinkable properties; the thickness of the thermal breaker film is 0.1 - 0.2 mm, and the storage temperature is lower than -20°C.

[0060] Example 3

[0061] A heat-shrinkable epoxy resin thermal fracturing film, by weight, the raw materials include: 40 parts of modified epoxy resin, 60 parts of E-51 epoxy resin, 5 parts of PES powder, 5 parts of dicyandiamide and 2 parts of 3-ethyl-1,1-dimethylurea; the modified epoxy resin is composed of E-51 epoxy resin and polyurethane prepolymer with a mass ratio of 76.3:20;

[0062] A preparation method of a heat-shrinkable epoxy resin thermal fracturing film specifically includes the following steps:

[0063] (1). Weigh each raw material according to the parts by weight;

[0064] (2). Put polycarbonate diol (PCD) and E-51 epoxy resin into a vacuum oven and heat it up to 110°C at a heating rate of 2°C / min, keep it warm for 30 min. After the heat preservation is over, evacuate the air to create a vacuum environment, carry out vacuum dehydration and degassing for more than 120 min, take it out and cool it down to obtain pretreated PCD and pretreated E-51 epoxy resin, and use it immediately. Put p-phenylene diisocyanate (PPDI) into a vacuum oven and keep it at 60°C for more than 60 min to obtain pretreated PPDI;

[0065] (3). Place 40 g of pretreated PCD in a three-necked flask, use a cantilever stirrer to drive the stirrer paddle to stir evenly at a speed of 150 r / min under the condition of an oil bath at 70°C, and at the same time introduce nitrogen to exclude air. Drop 24 g of pretreated PPDI at a dropping rate of 1 g / min evenly, add 3.5 g of DBP and 0.6 g of BHT. Start timing after the raw materials are added and the reaction temperature is stable, and continue to react for 2.5 h to obtain a polyurethane prepolymer; stir 260 g of pretreated E-51 epoxy resin evenly at a speed of 180 r / min under the condition of an oil bath at 120°C, introduce nitrogen for protection, start timing after the raw materials are added and the reaction temperature is stable, and continue to react for 2.5 h to obtain a modified epoxy resin;

[0066] (4). Mix the modified epoxy resin, E-51 epoxy resin, PES powder, dicyandiamide and 3-ethyl-1,1-dimethylurea for 30 min at a mixing temperature of 70°C to obtain a rubber compound;

[0067] (5). Add the rubber compound to a film-making machine, carry out primary calendering and shaping under the condition that the roll temperature is 0°C, then use the film-making machine to carry out secondary pressing to form a rubber film under the condition that the roll temperature is 80°C, and then carry out rapid cooling and shaping at 0 - 5°C to obtain an epoxy resin thermal fracturing film with heat-shrinkable performance; the thickness of the thermal fracturing film is 0.1 - 0.2 mm, and the storage temperature is lower than -20°C.

[0068] Example 4

[0069] A heat-shrinkable epoxy resin thermal fracturing film, by weight, the raw materials include: 40 parts of modified epoxy resin, 60 parts of E-51 epoxy resin, 5 parts of PEEK powder, 5 parts of dicyandiamide, and 2 parts of 3-ethyl-1,1-dimethylurea; the modified epoxy resin is composed of E-51 epoxy resin and polyurethane prepolymer with a mass ratio of 75.2:20;

[0070] Preparation method of heat-shrinkable epoxy resin thermal fracturing film, specifically including the following steps:

[0071] (1). Weigh each raw material by weight;

[0072] (2). Put polyoxypropylene diol with a molecular weight of 2000 (PPG-2000) and E-51 epoxy resin into a vacuum oven, heat it up to 110°C at a heating rate of 2°C / min, keep it warm for 30 min, after the heat preservation is over, evacuate to give it a vacuum environment, carry out vacuum dehydration and degassing for more than 120 min, take it out and cool it down to obtain pretreated PPG-2000 and pretreated E-51 epoxy resin, and use it immediately. Put diphenylmethane diisocyanate (MDI) into a vacuum oven and keep it at 60°C for more than 60 min to obtain pretreated MDI;

[0073] (3). Put 50 g of pretreated PPG-2000 into a three-necked flask, use a cantilever stirrer to drive the stirrer paddle to stir evenly at a speed of 150 r / min under the condition of an oil bath at 70°C, and at the same time introduce nitrogen to remove air, and drop 15 g of pretreated MDI evenly at a dropping rate of 1 g / min. Add 3.5 g of DBP and 0.6 g of tetrabutyltin (TBT). Start timing after the raw materials are added and the reaction temperature is stable, and continue to react for 2.5 h to obtain a polyurethane prepolymer; stir 260 g of pretreated E-51 epoxy resin evenly at a speed of 180 r / min under the condition of an oil bath at 120°C, introduce nitrogen for protection, start timing after the raw materials are added and the reaction temperature is stable, and continue to react for 2.5 h to obtain a modified epoxy resin;

[0074] (4). Mix the modified epoxy resin, E-51 epoxy resin, PEEK powder, dicyandiamide, and 3-ethyl-1,1-dimethylurea for 30 min, and the mixing temperature is 70°C to obtain a rubber compound;

[0075] (5). Add the rubber compound to a film-making machine, carry out primary calendering and shaping under the condition that the roll temperature is 0°C, then use the film-making machine to press it into a film again under the condition that the roll temperature is 80°C, and then rapidly cool and shape it at 0 - 5°C to obtain an epoxy resin thermal fracturing film with heat-shrinkable properties; the thickness of the thermal fracturing film is 0.1 - 0.2 mm, and the storage temperature is below -20°C.

[0076] Example 5

[0077] A heat-shrinkable epoxy resin thermal fracturing film, by weight, the raw materials include: 40 parts of modified epoxy resin, 60 parts of E-51 epoxy resin, 5 parts of PES powder, 5 parts of m-phenylenediamine, and 2 parts of 3-ethyl-1,1-dimethylurea; the modified epoxy resin is composed of E-51 epoxy resin and polyurethane prepolymer with a mass ratio of 75.2:20;

[0078] A preparation method of a heat-shrinkable epoxy resin thermal fracturing film specifically includes the following steps:

[0079] (1) Weigh each raw material by weight;

[0080] (2) Place polyoxypropylene diol with a molecular weight of 2000 (PPG-2000) and E-51 epoxy resin into a vacuum oven and heat it up to 110°C at a heating rate of 2°C / min, keep it warm for 30 min. After the heat preservation ends, evacuate to create a vacuum environment, and carry out vacuum dehydration and degassing for more than 120 min. Take it out and cool it down to obtain pretreated PPG-2000 and pretreated E-51 epoxy resin, and use it immediately. Place diphenylmethane diisocyanate (MDI) into a vacuum oven and keep it at 60°C for more than 60 min to obtain pretreated MDI;

[0081] (3) Place 50 g of pretreated PPG-2000 in a three-necked flask, use a cantilever stirrer to drive the stirrer paddle to stir evenly at a speed of 150 r / min under the condition of an oil bath at 70°C, and at the same time introduce nitrogen to remove air. Drop 15 g of pretreated MDI at a dropping rate of 1 g / min evenly, add 3.5 g of DBP and 0.6 g of TBT. After the raw materials are added and the reaction temperature is stable, start timing and continue the reaction for 2.5 h to obtain a polyurethane prepolymer; stir 260 g of pretreated E-51 epoxy resin evenly at a speed of 180 r / min under the condition of an oil bath at 120°C, introduce nitrogen for protection. After the raw materials are added and the reaction temperature is stable, start timing and continue the reaction for 2.5 h to obtain a modified epoxy resin;

[0082] (4) Mix the modified epoxy resin, E-51 epoxy resin, PES powder, m-phenylenediamine, and 3-ethyl-1,1-dimethylurea for 30 min, and the mixing temperature is 70°C to obtain a rubber compound;

[0083] (5) Add the rubber compound to a film-making machine, carry out primary calendering and shaping under the condition that the roll temperature is 0°C, and then use the film-making machine to carry out secondary pressing to form a rubber film under the condition that the roll temperature is 80°C. Subsequently, carry out rapid cooling and shaping at 0 - 5°C to obtain an epoxy resin thermal fracturing film with heat-shrinkable properties; the thickness of the thermal fracturing film is 0.1 - 0.2 mm, and the storage temperature is lower than -20°C.

[0084] Example 6

[0085] In this example, different from Example 1, there are 70 parts of modified epoxy resin, 30 parts of E-51 epoxy resin, 10 parts of PES powder, 3 parts of m-phenylenediamine and 3 parts of 3-ethyl-1,1-dimethylurea; the modified epoxy resin is composed of E-51 epoxy resin and polyurethane prepolymer with a mass ratio of 60:40, and other conditions remain unchanged.

[0086] Example 7

[0087] In this example, different from Example 1, there are 55 parts of modified epoxy resin, 45 parts of E-51 epoxy resin, 7.5 parts of PES powder, 8 parts of m-phenylenediamine and 1 part of 3-ethyl-1,1-dimethylurea; the modified epoxy resin is composed of E-51 epoxy resin and polyurethane prepolymer with a mass ratio of 100:5, and other conditions remain unchanged.

[0088] Example 8

[0089] In this example, different from Example 1, E-51 epoxy resin is replaced with E-54 epoxy resin, PES powder is replaced with nitrile rubber powder, dicyandiamide is replaced with 4,4'-diaminodiphenylmethane, and 3-ethyl-1,1-dimethylurea is replaced with 3-phenyl-1,1-dimethylurea, and other conditions remain unchanged.

[0090] Example 9

[0091] In this example, different from Example 1, E-51 epoxy resin is replaced with E-44 epoxy resin, PES powder is replaced with PA powder, dicyandiamide is replaced with 4,4-diaminodiphenyl sulfone, and 3-ethyl-1,1-dimethylurea is replaced with 3-p-nitrophenyl-1,1-dimethylurea, and other conditions remain unchanged.

[0092] Example 10

[0093] In this example, different from Example 1, E-51 epoxy resin is replaced with 601 epoxy resin, dicyandiamide is replaced with 4,4'-diaminodiphenyl ether, and 3-ethyl-1,1-dimethylurea is replaced with 3-(4-chlorophenyl)-1,1-dimethylurea, and other conditions remain unchanged.

[0094] Example 11

[0095] In this example, different from Example 1, E-51 epoxy resin is replaced with polybutadiene epoxy resin, dicyandiamide is replaced with bis-N,N'-(methyl-butylmethylene)-diethylenetriamine, and 3-ethyl-1,1-dimethylurea is replaced with N,N-(1,4-phenylene)bis(N',N'-dimethylurea), and other conditions remain unchanged.

[0096] Example 12

[0097] The difference between this example and Example 1 is that E-51 epoxy resin is replaced with polyethylene glycol diglycidyl ether, and dicyandiamide is replaced with 1,2-diaminocyclohexane, with other conditions remaining unchanged.

[0098] Example 13

[0099] The difference between this example and Example 1 is that E-51 epoxy resin is replaced with n-butyl glycidyl ether, with other conditions remaining unchanged.

[0100] Example 14

[0101] The difference between this example and Example 1 is that E-51 epoxy resin is replaced with a blend of E-51 epoxy resin and polybutadiene epoxy resin, and the mass ratio of E-51 epoxy resin to polybutadiene epoxy resin is 1:1, with other conditions remaining unchanged.

[0102] Example 15

[0103] The difference between this example and Example 1 is that E-51 epoxy resin is replaced with a blend of polypropylene glycol diglycidyl ether and polybutadiene epoxy resin, and the mass ratio of polypropylene glycol diglycidyl ether to polybutadiene epoxy resin is 1:1, with other conditions remaining unchanged.

[0104] Example 16

[0105] The difference between this example and Example 1 is that E-51 epoxy resin is replaced with a blend of E-51 epoxy resin, polypropylene glycol diglycidyl ether and polybutadiene epoxy resin, and the mass ratio of E-51 epoxy resin, polypropylene glycol diglycidyl ether to polybutadiene epoxy resin is 1:1:1, with other conditions remaining unchanged.

[0106] Example 17

[0107] The difference between this example and Example 1 is that polyoxypropylene diol is replaced with polycarbonate triol, diphenylmethane diisocyanate is replaced with dicyclohexylmethane diisocyanate, 2.5 g of dimethyl phthalate and 0.6 g of diisopropylbenzene peroxide are added, with other conditions remaining unchanged.

[0108] Example 18

[0109] The difference between this example and Example 1 is that polyoxypropylene diol is replaced with polyether urethane-based polyol, diphenylmethane diisocyanate is replaced with fluorinated toluene diisocyanate, 2.5 g of butyl acetate and 0.6 g of diisopropylbenzene peroxide are added, with other conditions remaining unchanged.

[0110] Example 19

[0111] The difference between this example and Example 1 is that the molar ratio of PPG-2000 to MDI is 1:5, with other conditions remaining unchanged.

[0112] Example 20

[0113] The difference between this example and Example 2 is that the dosage of dibutyl phthalate is 10% of the total amount of the polyurethane prepolymer, and the dosage of tert-butylhydroquinone is 0.1% of the total amount of the polyurethane prepolymer, and other conditions remain unchanged.

[0114] Example 21

[0115] The difference between this example and Example 1 is that in the preparation method of the heat-shrinkable epoxy resin thermal breaker film, in step (five), the roll temperature of the primary calendering is -3°C, and the thickness of the thermal breaker film is 0.2 - 0.3 mm, and other conditions remain unchanged.

[0116] Example 22

[0117] The difference between this example and Example 1 is that in the preparation method of the heat-shrinkable epoxy resin thermal breaker film, in step (five), the roll temperature of the primary calendering is 5°C, and the thickness of the thermal breaker film is 0.4 - 0.5 mm, and other conditions remain unchanged.

[0118] Example 23

[0119] The difference between this example and Example 1 is that in the preparation method of the heat-shrinkable epoxy resin thermal breaker film, in step (three), the speed of the stirring paddle for pretreating the polyol is 160 r / min, the reaction time for preparing the polyurethane prepolymer is 1 h, the stirring speed for pretreating the unmodified epoxy resin is 600 r / min, and the reaction time for preparing the modified epoxy resin is 1 h, and other conditions remain unchanged.

[0120] Example 24

[0121] The difference between this example and Example 1 is that in the preparation method of the heat-shrinkable epoxy resin thermal breaker film, in step (three), the reaction time for preparing the polyurethane prepolymer is 5 h, and the reaction time for preparing the modified epoxy resin is 4 h, and other conditions remain unchanged.

[0122] Example 25

[0123] The difference between this example and Example 1 is that the polyoxypropylene diol is replaced with a mixture of polyoxypropylene diol and polycarbonate diol, and the diphenylmethane diisocyanate is replaced with a mixture of diphenylmethane diisocyanate and p-phenylene diisocyanate, and 2.5 g of a mixture of dimethyl phthalate and butyl acetate, and 0.6 g of a mixture of diisopropylbenzene peroxide and tert-butylhydroquinone are added, and the mixing ratios of the above mixtures are all 1:1 by mass ratio, and other conditions remain unchanged.

[0124] Example 26

[0125] The difference between this example and Example 1 is that the E-51 epoxy resin is replaced with a mixture of E-51 epoxy resin and E-54 epoxy resin, the PES powder is replaced with a mixture of PES powder and nitrile rubber powder, the dicyandiamide is replaced with a mixture of dicyandiamide and 4,4'-diaminodiphenylmethane, and the 3-ethyl-1,1-dimethylurea is replaced with a mixture of 3-ethyl-1,1-dimethylurea and 3-phenyl-1,1-dimethylurea. The mixing ratio of the above mixtures is 1:1 by mass, and other conditions remain unchanged.

[0126] Example 27

[0127] The difference between this example and Example 12 is that the polyethylene glycol diglycidyl ether is replaced with a mixture of polyethylene glycol diglycidyl ether and polypropylene glycol diglycidyl ether, and the mixing ratio is 1:1 by mass, and other conditions remain unchanged.

[0128] Performance test methods and data

[0129] The thermally shrinkable epoxy resin hot break film prepared in Examples 1-5 was subjected to mechanical property tests at 23°C ± 2°C according to the method in GB / T7123.2-02 "Determination of the Storage Life of Adhesives". The test results are shown in Table 1; the physical diagram of the thermally shrinkable epoxy resin hot break film prepared in Example 1 laid on the surface of the paper honeycomb is shown in Figure 4 , the physical diagram of the hot break process is shown in Figure 5 , the physical diagram after hot break is shown in Figure 6 .

[0130] Table 1 Mechanical property data table of Examples 1-5

[0131]

[0132] From Table 1, Figures 4 - 6 it can be seen that the epoxy hot break film prepared in this application has good laying properties and hot break properties, is easy to peel off and can be completely laid on the surface of the honeycomb core, without phenomena such as glue flow, collapse and stacking. The hot break film will condense into glue nodules at the ends of the honeycomb core cells and will not block the micropores on the panel. There are no phenomena such as glue film splashing, flowing and drawing during the hot break process. By forming stress concentration with toughening particles inside the glue film, the uniformity and stability of the hot break are optimized, the strength, toughness and anti-destruction performance of the glue film are significantly improved, and its practicability and reliability in different application scenarios are enhanced.

[0133] Example 1 Infrared characterization: Take a small amount of E-51 epoxy resin, polyurethane prepolymer and modified epoxy resin respectively, mix them with anhydrous potassium bromide at a volume ratio of 1:200 and grind them thoroughly, then use a sample making machine to compress them into tablets, and then perform FTIR testing to analyze the chemical groups of E-51 epoxy resin, polyurethane prepolymer and modified epoxy resin. The scanning range of the test is 4000-400cm -1 , with a resolution of 4cm -1 , used to determine the characteristic functional groups contained in E-51 epoxy resin, polyurethane prepolymer and modified epoxy resin. The test data are listed in Figure 7 middle.

[0134] Depend on Figure 7 It can be seen that E-51 epoxy resin has a peak at 3470 cm -1 There is a -OH stretching vibration peak at 2265cm -1 The nearby -NCO characteristic peak no longer exists in the modified epoxy resin, proving that the -NCO in the polyurethane prepolymer has reacted with the -OH in the resin system and has been completely consumed.

[0135] The present application provides a heat-shrinkable epoxy resin thermal break adhesive film and a preparation method thereof, wherein a polyol, an isocyanate, a diluent and a stabilizer are mixed and reacted to prepare a polyurethane prepolymer composed of a soft segment and a hard segment to form a heat-shrinkable polyurethane prepolymer, and then the polyurethane prepolymer is grafted with an epoxy resin to prepare a polyurethane-modified epoxy resin, and then the modified epoxy resin, an unmodified epoxy resin, a solid toughening powder, an amine curing agent and a urea compound are added to a reaction device for blending to obtain an adhesive film blend, and a calendering shaping is performed once below the glass transition temperature of the soft segment phase in the polyurethane component, and then a secondary calendering is performed between the glass transition temperatures of the soft segment phase and the hard segment phase, and then rapid cooling is performed to shape the film; the present application selects a heat-shrinkable epoxy resin having a heat-shrinkable A polyurethane prepolymer with good shrinkage performance and improved bonding strength is used as an epoxy resin modified component to prepare a heat-shrinkable epoxy resin thermal breakable adhesive film. During the use of the film, when the temperature rises to above the glass transition temperature of the soft segment phase, the film will shrink and deform, and the solid toughening particles will break, pushing the film to evenly gather at the edges and corners of the honeycomb structure during the shrinkage process to form a glue nodule; this process enables the film to be used efficiently and reasonably, and is particularly suitable for the high performance requirements of thermal breakable adhesive films in the fields of aerospace and aviation. The present application achieves precise control of the heat shrinkage function under relatively low temperature conditions, greatly simplifies the process flow, and improves the application effect of the film, and is particularly suitable for the manufacture of aerospace honeycomb structure components.

[0136] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of this application, "a plurality of" means two or more unless otherwise specifically defined.

[0137] The above are only the preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application shall be included within the protection scope of this application.

Claims

1. A heat-shrinkable epoxy resin thermal break adhesive film, characterized in that: The raw materials include, by weight: 40-70 parts of modified epoxy resin, 30-60 parts of unmodified epoxy resin, 5-10 parts of solid toughening powder, 3-8 parts of amine curing agent and 1-3 parts of urea compound; The modified epoxy resin is composed of the unmodified epoxy resin and the polyurethane prepolymer in a mass ratio of 60-100:5-40.

2. A heat-shrinkable epoxy resin thermal break adhesive film according to claim 1, characterized in that, The polyurethane prepolymer is composed of polyol and isocyanate; the molar ratio of the polyol to the isocyanate is 1:2-5; The polyol is one or more of polyoxypropylene diol, polycarbonate diol, polycarbonate triol or polyether urethane polyol, and the isocyanate is one or more of fluorinated toluene diisocyanate, diphenylmethane diisocyanate, p-phenylene diisocyanate or dicyclohexylmethane diisocyanate.

3. A heat-shrinkable epoxy resin thermal break adhesive film according to claim 2, characterized in that, The polyurethane prepolymer further comprises a diluent and a stabilizer, wherein the diluent is used in an amount of 5-10% of the total amount of the polyurethane prepolymer; the stabilizer is used in an amount of 0.1-1% of the total amount of the polyurethane prepolymer; The diluent is one or more of dimethyl phthalate, di-n-butyl phthalate or butyl acetate; the stabilizer is one or more of tert-butylhydroquinone, diisophorone peroxide or tetrabutyltin.

4. A heat-shrinkable epoxy resin thermal break adhesive film according to claim 1, characterized in that, The unmodified epoxy resin is one of bisphenol A epoxy resin, aliphatic epoxy resin, polybutadiene epoxy resin, a blend of bisphenol A epoxy resin and polybutadiene epoxy resin, a blend of polybutadiene epoxy resin and aliphatic epoxy resin, or a blend of bisphenol A epoxy resin, polybutadiene epoxy resin and aliphatic epoxy resin.

5. A heat-shrinkable epoxy resin thermal break adhesive film according to claim 4, characterized in that, The bisphenol A type epoxy resin is one or more of E-54 epoxy resin, E-51 epoxy resin, E-44 epoxy resin or 601 epoxy resin; the aliphatic epoxy resin is one or more of polypropylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether or n-butyl glycidyl ether.

6. A heat-shrinkable epoxy resin thermal break adhesive film according to claim 1, characterized in that, The solid toughening powder is one or more of nitrile rubber powder, PES powder, PEEK powder or PA powder; the amine curing agent is one or more of dicyandiamide, 4,4'-diaminodiphenylmethane, 4,4-diaminodiphenyl sulfone, m-phenylenediamine, 4,4'-diaminodiphenyl ether, bis-N,N'-(methyl-butylmethylene)-diethylenetriamine or 1,2-diaminocyclohexane; the urea compound is one or more of 3-phenyl-1,1-dimethylurea, 3-(4-chlorophenyl)-1,1-dimethylurea, 3-ethyl-1,1-dimethylurea, 3-p-nitrophenyl-1,1-dimethylurea, N,N-(1,4-phenylene)bis(N',N'-dimethylurea).

7. A method for preparing a heat-shrinkable epoxy resin thermal breakable adhesive film, characterized in that: The specific steps include: (i) Weigh polyol, unmodified epoxy resin, isocyanate, diluent, stabilizer, solid toughening powder, amine curing agent and urea compound according to weight proportion; (ii) heating the polyol and the unmodified epoxy resin, evacuating the air after the heating is completed, taking out and cooling, thereby obtaining a pretreated polyol and a pretreated unmodified epoxy resin, and heating the isocyanate, thereby obtaining a pretreated isocyanate; (iii) stirring the pretreated polyol at a uniform speed, introducing nitrogen to remove air, adding the pretreated isocyanate dropwise, adding a diluent and a stabilizer, and reacting to obtain a polyurethane prepolymer; adding the pretreated unmodified epoxy resin to the polyurethane prepolymer, stirring at a uniform speed, and introducing nitrogen to react to obtain a modified epoxy resin; (iv) mixing the modified epoxy resin with the unmodified epoxy resin, solid toughening powder, amine curing agent and urea compound to prepare a rubber material; (V) Add the rubber material into a film-making machine, perform calendering and shaping once at a roller temperature of -3-5°C, and then perform secondary pressing into a rubber film using a film-making machine at a roller temperature of 80°C, and then rapidly cool and shape to obtain an epoxy resin thermal breakable rubber film with heat shrinkage performance.

8. The method for preparing a heat-shrinkable epoxy resin thermal breakable adhesive film according to claim 7, wherein: The specific steps of heating the polyol and the unmodified epoxy resin in step (ii) are as follows: placing the polyol and the unmodified epoxy resin in a vacuum oven and heating them to 110°C at a heating rate of 2°C / min, and keeping them warm for 30 minutes, during which the evacuation time is 120 minutes; the specific steps of heating the isocyanate are as follows: placing the isocyanate in a vacuum oven and heating it to 60°C, and keeping it warm for 60 minutes.

9. The method for preparing a heat-shrinkable epoxy resin thermally ruptured adhesive film according to claim 7, wherein: The conditions for uniform stirring of the pretreated polyol in step (iii) are as follows: placing the pretreated polyol in a three-necked flask, and using a cantilever stirrer to drive a stirring paddle to uniformly stir at a speed of 150-600r / min under an oil bath at 70°C; the rate of dripping the pretreated isocyanate is 1g / min; the reaction time for preparing the polyurethane prepolymer is 1-5h; the conditions for uniform stirring of the pretreated unmodified epoxy resin are as follows: uniform stirring at a speed of 180-600r / min under an oil bath at 120°C; the reaction time for preparing the modified epoxy resin is 1-4h; the mixing time in step (iv) is 30min and the temperature is 70°C; the temperature for rapid cooling and shaping in step (iv) is 0-5°C.

10. The method for preparing a heat-shrinkable epoxy resin thermally ruptured adhesive film according to claim 7, wherein: The thickness of the thermally ruptured film is 0.1-0.5 mm, and the storage temperature is lower than -20°C.

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