Two-component epoxy resin structural adhesive for thick adhesive layer and preparation method of two-component epoxy resin structural adhesive

Abstract

The invention relates to a bi-component epoxy structural adhesive for thick adhesive layer bonding. The bi-component epoxy structural adhesive comprises a component A and a component B, the component A comprises epoxy resin, a self-made epoxy toughening agent, a coupling agent, a diluent, a defoaming agent A, black paste, a thixotropic agent and filler; and the component B comprises a self-made epoxy curing agent, an epoxy accelerator, a thixotropic agent, a defoaming agent B and a filler. The bi-component epoxy structural adhesive for thick adhesive layer bonding has the advantages of good adhesive flexibility, excellent bonding performance, good adaptability to a base material, excellent temperature resistance, long pot life, good storage stability and excellent aging performance, and is a high-performance epoxy structural adhesive for thick adhesive layer bonding.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesive preparation, and particularly relates to a two-component epoxy structural adhesive for thick adhesive layer bonding and a preparation method thereof. Technical Background

[0002] With the introduction of the "Action Plan for Carbon Peaking Before 2030", clean energy has increasingly become the key energy for national development. As a clean energy source, wind energy has received encouragement and support from the policies of various countries and is currently in continuous development. As of 2024, the total installed capacity of wind turbines in China continues to show an increasing trend. According to data from the National Energy Administration, the newly installed wind power capacity globally reached a record 117GW in 2023, and the newly installed capacity in China reached 75GW, accounting for nearly 65% of the global newly installed capacity. As of the end of June 2024, the installed wind power capacity in China had reached 467 million kilowatts. This data reflects the rapid development of China in the wind power field. The total installed capacity of wind power and solar power has exceeded the installed capacity of coal-fired power, indicating that renewable energy occupies an increasingly important position in China's energy structure. In the continuous pursuit of efficient utilization of wind energy, the length of wind turbine blades has been increasing and has now reached 80 meters. As a key component of wind turbines, wind turbine blades bear huge aerodynamic and inertial loads when converting wind energy into mechanical energy of the impeller rotor, and have high requirements for blade reliability. Modern large wind turbine blades are mainly composed of composite materials. In the existing blade manufacturing process, there are usually large bonding areas. The leading and trailing edges of the suction surface and pressure surface (upper and lower aerodynamic shells), and between the web and the aerodynamic shell are mainly connected by adhesive bonding. Generally, the thickness of the adhesive layer is required to be controlled within 1-8mm. Controlling the thickness of the adhesive layer is a key and difficult point in the production process. Usually, wind farms are located in sparsely populated, mountainous, and coastal areas with harsh environments. The maintenance cost of blades is very high and difficult. The adhesive bonding manufacturing process of blades usually has poor reassembly performance. Therefore, the bonding strength and reliability of blades are very important for the safe operation of wind turbines.

[0003] In most bonded structures, the typical value of the adhesive layer thickness range is between 0.2 and several millimeters. In some applications in civil industries such as wind turbine blades and automobiles, the adhesive layer thickness is generally several millimeters and may even reach 20mm. The main advantage of using a thick adhesive layer is that it reduces the requirements for the dimensional accuracy of the structural components, thereby reducing the difficulty of the manufacturing process. In some cases, this is almost impossible to achieve with a thin adhesive layer. However, the lack of research on thick adhesive layer bonded joints leads to a conservative strength design when designing joints. Usually, the costly trial-and-error method is used, consuming a large amount of time and materials.

[0004] At present, the market of adhesives for thick adhesive layer bonding is mostly occupied by imported brands such as Henkel and 3M. The prices are relatively high, and there are also problems such as low mechanical properties, uneven stress distribution, which easily lead to damage at the joint, being more sensitive to the environment, and the performance being affected by temperature, humidity, etc. Some thick adhesive layer adhesives have problems such as exceeding the VOCs standard and are not environmentally friendly. Therefore, it has become an urgent task to develop a two-component epoxy structural adhesive for thick adhesive layer bonding. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention provides a two-component epoxy structural adhesive for thick adhesive layer bonding and its preparation method. It has good flexibility of the colloid, excellent bonding performance, good adaptability to the substrate, excellent heat resistance, long pot life, good storage stability, and excellent aging performance. It is a high-performance epoxy structural adhesive for thick adhesive layer bonding.

[0006] A two-component epoxy structural adhesive for thick adhesive layer bonding comprises component A and component B. Component A comprises epoxy resin, self-made epoxy toughening agent, coupling agent, diluent, defoaming agent A, black paste, thixotropic agent, filler; component B comprises self-made epoxy curing agent, epoxy accelerator, thixotropic agent, defoaming agent B, filler.

[0007] Further, the epoxy resin is bisphenol A epoxy resin with a molecular weight of 185-195 g / eq.

[0008] Further, the preparation process of the self-made epoxy toughening agent is as follows:

[0009] At room temperature, 176 g of bisphenol A epoxy resin E51 is added to a three-necked flask, and 24 g of special polyurethane is added. Then the temperature is raised to 90 °C, and it is stirred at a constant temperature of 90 °C for 30 min. Then the temperature of the heating jacket is adjusted, and the material temperature is raised to 110-120 °C while vacuum stirring for 1 h. After 12 h, the temperature is lowered to 25 °C to stop the reaction and discharge the material; the structural formula of the special polyurethane is as follows:

[0010]

[0011] Further, the coupling agent in component A is one or a compound of several of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, 3-(2-aminoethyl)-aminopropyltrimethoxysilane.

[0012] Further, the diluent in component A is one or a compound of several of polypropylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, etc.

[0013] Further, the defoaming agent A in component A is a solvent-free polyether silicone defoaming agent.

[0014] Furthermore, the thixotropic agent in the component A is hydrophobic fumed silica.

[0015] Furthermore, the filler in the component A is silicon micropowder treated with a coupling agent. The specific method is to weigh silicon micropowders with different particle sizes, and at the same time weigh 0.5 - 3% of the total amount of silane coupling agent and place it in the liquid storage tank of the spraying equipment. Heat the silicon micropowder to 70 - 120°C, turn on the switch of the spraying equipment, spray the atomized coupling agent, stir while spraying. After spraying is completed, dry it in an oven at 110°C for 15 - 18 h for standby.

[0016] Furthermore, the preparation process of the self-made epoxy curing agent in the component B is as follows:

[0017] According to the molar ratio n(dicyclic carbonate) : n(pentamethylenediamine) = 1:2, in ethylene glycol monoethyl ether solvent, control the temperature at 30 - 40°C and react until a constant amine value is reached. The dicyclic carbonate is prepared from commercially available carbon dioxide and bisphenol A epoxy resin. The amine value of the finally obtained self-made epoxy curing agent is 65 - 70 mgKOH / g.

[0018] The reaction equation is as follows:

[0019]

[0020] The self-made epoxy curing agent of formula II, where R is the structure other than the epoxy group of the epoxy resin

[0021] Furthermore, the epoxy accelerator in the component B is 2,4,6-tris(dimethylaminomethyl)phenol.

[0022] Furthermore, the thixotropic agent in the component B is hydrophobic fumed silica.

[0023] Furthermore, the defoaming agent B in the component B is an organosilicon polymer defoaming agent.

[0024] Furthermore, the filler in the component B is silicon micropowder treated with a coupling agent. The specific method is to weigh silicon micropowders with different particle sizes, and at the same time weigh 0.5 - 3% of the total amount of silane coupling agent and place it in the liquid storage tank of the spraying equipment. Heat the silicon micropowder to 70 - 120°C, turn on the switch of the spraying equipment, spray the atomized coupling agent, stir while spraying. After spraying is completed, dry it in an oven at 110°C for 15 - 18 h for standby.

[0025] Furthermore, the preparation method of the component A is as follows:

[0026] (1) Pretreat all fillers, set the oven temperature at 110°C, and bake for 15 - 18 h;

[0027] (2) Add epoxy resin, self-made epoxy toughening agent, diluent, black paste, and coupling agent into the reaction kettle, and stir at room temperature for 30 min;

[0028] (3) Add filler and thixotropic agent, continue to stir at room temperature for 30 min. After the filler is stirred in, scrape the material;

[0029] (4) Add defoaming agent A and stir at room temperature for 10 min,

[0030] (5) Continue to stir under vacuum at room temperature for 1.5 h, and discharge the material into a tube.

[0031] Furthermore, the preparation method of the B component is as follows:

[0032] (1) Add self-made epoxy curing agent and accelerator into the reaction kettle, and stir at room temperature for 30 min;

[0033] (2) Add filler and thixotropic agent, continue to stir at room temperature for 30 min. After the filler is stirred in, scrape the material;

[0034] (3) Add defoaming agent B, continue to stir under vacuum at room temperature for 30 min, and discharge the material into a tube.

[0035] Furthermore, the mixing mass ratio of the A component to the B component is 2:(0.8 - 1.2); after the A and B components are mixed and cured, the cured body has good colloidal flexibility, excellent bonding performance, good adaptability to the substrate, excellent heat resistance, long pot life, good storage stability, and excellent aging performance. It is a high-performance epoxy structural adhesive for thick adhesive layer bonding.

[0036] When using double-tube packaging, simply insert the tube into the application gun, discharge a small amount of glue to ensure uniform and free flow on both sides. If automatic mixing of the resin and curing agent is required, connect the mixing nozzle to the automatic mixer and start dispensing the adhesive. When mixing manually, discharge the required amount of adhesive and mix thoroughly for 15 seconds. When using bulk container packaging, mix well in accordance with the above weight ratio for about 15 seconds. When used for bonding substrates, it includes the following steps:

[0037] Apply the two-component epoxy structural adhesive for thick adhesive layer bonding evenly on the surface of one substrate or two substrates to be joined; the application should be completed within the pot life, and the two substrates are in contact with each other.

[0038] Prevent the parts from moving during the curing process. Apply contact pressure if necessary; complete the curing at room temperature.

[0039] For high-strength structural parts, remove the surface contamination of the substrate, such as paint, oxide film, oil, dust, release agent, and all other surface contaminants.

[0040] The A component and the B component have no volatile substances and low odor, which are beneficial to the use environment and the operator.

[0041] The two-component epoxy structural adhesive for thick adhesive layer bonding described in the present invention is applied to the bonding of the wind turbine blade mold closing structure, and is used for sleeve bonding, such as the sleeve bonding at the connection of the three transmission shafts between the helicopter main reducer and the tail reducer, etc.

[0042] The self-made epoxy toughening agent in the A component is polymerized by special polyurethane and epoxy resin. There is a chemical grafting reaction between the molecular chains of polyurethane (PU) and epoxy resin (EP), which can effectively improve the compatibility and interpenetration between PU and EP molecules in the PU / EP system. The polyurethane-modified epoxy resin forms an interpenetrating polymer network structure, which improves the mechanical properties of the material. This structure increases the number of permanent entanglements between the two networks and the degree of interpenetration. Therefore, when subjected to external forces, cracks and shear bands are formed inside to consume energy, enhancing the toughness of the material and increasing the flexural strength. The polyurethane molecular structure has both flexible C—C chains and C—O—C chains, as well as active amide groups, which are compatible with epoxy resin, thus improving the toughness of the material. This structure endows polyurethane with excellent flexibility and heat resistance. The polyurethane and epoxy resin form a two-phase interpenetrating network structure, greatly enhancing its thermal stability. The self-made epoxy curing agent in the B component is a curing agent with urethane groups in the molecule synthesized by reacting pentamethylenediamine with bicyclic carbonate. The molecular structure contains urethane groups and has a relatively high cohesive energy, so the prepared adhesive has a high breaking strength. The presence of the urethane flexible chain segment reduces the internal stress of the adhesive itself and improves the flexibility of the cross-linked product after curing. At the same time, this type of curing agent itself contains carbonate groups, and the carbonate groups can react with hydroxyl groups or other active groups in the resin to form a stable cross-linked network. The curing agent has at least two reactive functional groups, which can be hydroxyl groups, amino groups or other groups capable of reacting with the resin, ensuring good chemical bonding between the curing agent and the resin, and improving the adhesion and durability of the adhesive to plastics and metals. The beneficial effects of the present invention are as follows: By polymerizing special polyurethane and epoxy resin, and at the same time using a curing agent with urethane groups in the molecule with the reaction performance of pentamethylenediamine and bicyclic carbonate, the structural adhesive of the present invention has good flexibility, high bonding strength, excellent heat resistance, especially high bonding strength to metal and plastic substrates; the formed colloid has high flexibility, overcomes the high internal stress of the thick adhesive layer, and the high toughness absorbs part of the non-shear stress with good micro-deformation, realizing the idea of high shear strength under the thick adhesive layer. It is a reliable two-component epoxy structural adhesive that can be used for thick adhesive layer bonding such as wind turbine blade bonding. Detailed implementation mode

[0043] 1. Preparation of the A component

[0044] (1) Pre-treat all fillers. Set the oven temperature to 110 °C and bake for 15 - 18 h;

[0045] (2) Add epoxy resin, self-made epoxy toughening agent, diluent, black paste, and coupling agent to the reaction kettle and stir at room temperature for 30 min;

[0046] (3) Add fillers and thixotropic agent, continue to stir at room temperature for 30 min. After the fillers are stirred in, scrape the material;

[0047] (4) Add defoaming agent A and stir at room temperature for 10 min,

[0048] (5) Continue to stir under vacuum at room temperature for 1.5 h, then discharge and fill into tubes.

[0049] 2. Preparation of Component B

[0050] (1) Add self-made epoxy curing agent and accelerator to the reaction kettle and stir at room temperature for 30 min;

[0051] (2) Add fillers and thixotropic agent, continue to stir at room temperature for 30 min. After the fillers are stirred in, scrape the material;

[0052] (3) Add defoaming agent B, continue to stir under vacuum at room temperature for 30 min, then discharge and fill into tubes.

[0053] Post-treatment: With the help of a centrifuge, centrifuge the epoxy adhesive in double-tube packaging at 1200 rpm for 5 min at room temperature to remove air bubbles. Store the finished product at room temperature.

[0054] 2. Detection

[0055] According to the above usage method of the two-component epoxy structural adhesive for thick adhesive layer bonding, detect by means of discharging and applying glue with a mixing glue gun:

[0056] Operating time: The time from the preparation of the multi-component adhesive to the time when the adhesive can maintain its use performance. Under standard conditions, apply 2 g of the mixed glue solution in a tart cup and slide it with a toothpick until the scratch cannot be restored. The duration is the operating time.

[0057] Hardness: The ability of a material to locally resist the indentation of a hard object into its surface is called hardness. Prepare a fully cured test piece for testing: The thickness is at least 6 mm, and it can be stacked with 3 layers of 2-mm specimens or 2 layers of 3-mm specimens; the area is at least 100 mm * 100 mm, and the test point is at least 15 mm away from the edge; the surface near the test point is flat and parallel up and down. According to the operation guide of the hardness tester, cure the sample at room temperature for 7 days and test the surface hardness at room temperature: The maximum indentation speed is 3.2 mm / s, keep the indentation for 3 s, and take at least 5 groups of data from at least 5 different places and take the average.

[0058] Shear strength: Apply longitudinal tensile shear force to the lap joint surface of the specimen and measure the maximum load that the specimen can withstand. Under standard environmental conditions, for carbon steel after grinding treatment, with a gap of 1 mm, apply adhesive evenly for lap joint and fix it. After 24 hours of timing, start the testing machine and load at a stable speed within 10 mm / min. Record the maximum load at which the specimen undergoes shear failure, measure the length and width of the lap joint surface of the specimen with a measuring tool, and calculate the tensile shear strength.

[0059] Peel strength: Use 3003Al sheet, T-peel (N / cm), with the thickness of the thin sheet being 0.4 mm, the test temperature being room temperature, and the number of test specimens being at least 3, and calculate the peel strength.

[0060] Tensile strength and elongation at break: Tensile strength is the maximum stress that a material can withstand during the tensile process. Elongation at break is the ratio of the maximum deformation before fracture to the original length during the tensile process of the material. Prepare an adhesive cured sample sheet with a thickness of 2 mm, ensuring that the surface is flat, smooth, and free of contamination. After the sample is completely cured, let it stand in the laboratory environment for 3 hours, and then cut out standard specimens with a Type I dumbbell cutter. The number of specimens is at least 3.

[0061] Thermal shock: To test the ability to withstand thermal shock conditions. Use a thermal shock testing machine, expose it continuously at -40 °C for 30 minutes, and quickly switch to expose it at 85 °C for 30 minutes. Repeat this cycle 100 times.

[0062] Humid heat aging: According to "GB / T 2423.3 Environmental testing - Part 2: Test methods - Test Cab: Damp heat, steady state", put the sample into a thermostatic and humid cabinet with the temperature set at 85 ± 3 °C and the humidity set at 82%-88%RH for 1000 hours, then take it out and place it at room temperature for another 2 hours. Conduct performance testing according to the standard test method.

[0063] The results are listed in Table 1 below.

[0064]

[0065]

[0066] It can be seen from the above table data that for the two-component epoxy structural adhesive for thick adhesive layer bonding in Examples 1 to 4, the shear strength at a 1 mm gap after curing is ≥20 MPa, the bulk strength is ≥30 MPa, the peel strength is >50 N / cm, and the shear strength decay rate is relatively low after thermal shock and humid heat aging, and the strength retention rate is >90%; while the shear strength, bulk strength, and peel strength of Comparative Example 1 and Comparative Example 2 are lower than those of the examples, and the shear strength decay rate after aging is higher than that of the examples.

[0067] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as falling within the scope described in this specification.

[0068] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A two-component epoxy structural adhesive for bonding thick adhesive layers, comprising component A and component B; in parts by weight, the component A comprises 45-74 parts of epoxy resin, 10-30 parts of homemade epoxy toughening agent, 1-3 parts of coupling agent, 1-5 parts of diluent, 0.01-0.5 parts of defoamer A, 0.5-2 parts of black paste, 1-5 parts of thixotropic agent, and 15-40 parts of filler; the component B comprises 45-80 parts of homemade epoxy curing agent, 1-5 parts of epoxy accelerator, 1-5 parts of thixotropic agent, 0.01-0.5 parts of defoamer B, and 15-65 parts of filler.

2. The two-component epoxy structural adhesive for thick adhesive layer bonding according to claim 1, characterized in that: The epoxy resin is 185-195 g / eq bisphenol A epoxy resin.

3. The two-component epoxy structural adhesive for thick adhesive layer bonding according to claim 1, characterized in that: The homemade epoxy toughening agent has the following preparation process: 176g of bisphenol A epoxy resin E51 and 24g of special polyurethane are added to a three-necked flask at room temperature, and then the temperature is raised to 90°C, and the mixture is stirred at a constant temperature of 90°C for 30 minutes, and then the temperature of the heating jacket is adjusted to raise the material temperature to 110-120°C while vacuuming and stirring for 1 hour, and then the temperature is lowered to 25°C after 12 hours to stop the reaction and discharge the material; the structural formula of the special polyurethane is as follows: 。 4. The two-component epoxy structural adhesive for thick adhesive layer bonding according to claim 1, characterized in that: The coupling agent in the component A is one or a combination of γ-aminopropyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and 3-(2-aminoethyl)-aminopropyltrimethoxysilane.

5. The two-component epoxy structural adhesive for thick adhesive layer bonding according to claim 1, characterized in that: The diluent in component A is one or a combination of polypropylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, etc.; the defoamer A in component A is a solvent-free polyether silicone defoamer; and the thixotropic agent in component A is hydrophobic fumed silica.

6. The two-component epoxy structural adhesive for thick adhesive layer bonding according to claim 1, characterized in that: The filler in component A is silicon micropowder treated with a coupling agent. The specific method is to weigh silicon micropowders of different particle sizes, and at the same time weigh 0.5-3% of the total silane coupling agent and place them in a liquid storage tank of a spray device, heat the silicon micropowder to 70-120°C, turn on the spray device switch, spray the atomized coupling agent, stir while spraying, and after spraying is completed, place it in a 110°C oven for drying for 15-18 hours for use.

7. The two-component epoxy structural adhesive for thick adhesive layer bonding according to claim 1, characterized in that: The preparation process of the homemade epoxy curing agent in the B component is as follows: According to the molar ratio of n (bicyclic carbonate): n (pentanediamine) = 1:2, the temperature was controlled at 30-40°C in ethylene glycol ether solvent to achieve a constant amine value, wherein the bicyclic carbonate was prepared from commercially available carbon dioxide and bisphenol A epoxy resin, and the final self-made epoxy curing agent had an amine value of 65-70 mgKOH / g; the reaction equation is as follows: Wherein R is a structure other than the epoxy group of the epoxy resin.

8. The two-component epoxy structural adhesive for thick adhesive layer bonding according to claim 1, characterized in that: The epoxy accelerator in the B component is 2, 4, 6-tris(dimethylaminomethyl)phenol; the thixotropic agent in the B component is hydrophobic fumed silica; the defoamer B in the B component is an organosilicon polymer defoamer; the filler in the B component is silicon micropowder treated with a coupling agent. The specific method is to weigh silicon micropowders of different particle sizes, and at the same time weigh 0.5-3% of the total silane coupling agent and place them in a liquid storage tank of a spray device, heat the silicon micropowder to 70-120° C., turn on the spray device switch, spray the atomized coupling agent, stir while spraying, and after spraying, place it in a 110° C. oven for drying for 15-18 hours for standby use.

9. The two-component epoxy structural adhesive for thick adhesive layer bonding according to claim 1, wherein the mixing mass ratio of component A to component B is 2:(0.8-1.2).

10. The two-component epoxy structural adhesive for thick adhesive layer bonding according to claim 1 is used for bonding of wind turbine blade mold structures and sleeve-type bonding of three transmission shafts connecting the main reducer and tail reducer of a helicopter.

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