Single-component epoxy structural adhesive as well as preparation method and application thereof

Abstract

The invention discloses a single-component epoxy structural adhesive as well as a preparation method and application thereof. The single-component epoxy structural adhesive is characterized by comprising the following components in parts by weight: A, an epoxy resin composition: 20-40 parts of liquid bisphenol A epoxy resin, 5-10 parts of solid bisphenol A epoxy resin, 5-15 parts of CTBN modified epoxy resin and 10-30 parts of PU modified epoxy resin; b, a latent curing system: 1-5 parts of a curing agent and 0.1-4 parts of an accelerant; c, 0.1 to 4 parts of a catalysis-interface reinforcing agent TPTS; d, 0-30 parts of functional filler; and E, other auxiliary agents: 0.1-4 parts of cardanol glycidyl ether and 0-1 part of an antioxidant. The technical problem that an existing epoxy resin structural adhesive is insufficient in corrosion resistance in a salt mist environment can be solved.

Description

Technical Field

[0001] This invention relates to an epoxy structural adhesive, and more particularly to a one-component epoxy structural adhesive, its preparation method, and its application, belonging to the field of polymer materials technology. Background Technology

[0002] Epoxy structural adhesives are high-performance engineering adhesives widely used in aerospace, automotive manufacturing, electronics, electrical engineering, and construction engineering. With the development of industrial technology, the performance requirements for epoxy structural adhesives are increasing, especially in terms of durability and reliability in harsh environments.

[0003] Currently, epoxy structural adhesives on the market are mainly divided into two categories: single-component and two-component. Single-component epoxy structural adhesives occupy an important position in industrial applications due to their advantages such as ease of use and storage stability. CN112646523A discloses a high-performance, medium-temperature curing single-component epoxy structural adhesive, which contains epoxy resin, diluent, latent curing agent, toughening agent, accelerator, thixotropic reinforcing agent, coupling agent, and filler, and features high toughness, high bond strength, and long shelf life. CN118048122B proposes a single-component epoxy structural adhesive that uses a combination of bisphenol A type epoxy resin and polyurethane modified epoxy resin, along with two curing agents, dicyandiamide and hydrazide composite, resulting in a structural adhesive with a low curing temperature and excellent storage stability.

[0004] Regarding the selection of epoxy resin systems, CN119410317A discloses a wide-temperature-range epoxy structural adhesive for automotive manufacturing. This structural adhesive uses a combination of solid bisphenol A epoxy resin, liquid bisphenol A epoxy resin, elastomer-modified epoxy resin, and CTBN-modified epoxy resin, exhibiting high strength and 100% cohesive failure within a temperature range of -40℃ to 80℃. CN107722900A proposes a two-component structural adhesive. Component A includes bisphenol A type epoxy resin, solid epoxy resin, polybutadiene, and PU-modified epoxy resin, while component B includes modified polyetheramine and amino-terminated liquid nitrile rubber.

[0005] In terms of curing systems, latent curing agents are a key component of one-component epoxy structural adhesives. CN118048122B uses a combination of dicyandiamide and hydrazide composite curing agents, supplemented by imidazole adducts and urea-based accelerators, to achieve a one-component epoxy structural adhesive with a low curing temperature and excellent storage stability. CN118064088A proposes a two-component epoxy structural adhesive that cures at medium to low temperatures, achieving even lower curing temperatures and a longer shelf life through a specific curing agent composition.

[0006] However, existing epoxy structural adhesives still face several unresolved issues. First, the curing process of current epoxy structural adhesives exhibits poor reaction uniformity, leading to uneven crosslinking density and a tendency to generate micro-defects, providing opportunities for salt spray corrosion. Second, the bonding between epoxy structural adhesives and the metal interface relies primarily on physical adsorption and a small amount of chemical bonding, resulting in poor stability under salt spray conditions and a susceptibility to interfacial failure. Furthermore, current technologies lack sufficient research on optimizing the internal crosslinking network of epoxy resin structural adhesives and their interaction mechanisms with the metal interface, resulting in a lack of effective interfacial reinforcement strategies. These problems lead to insufficient corrosion resistance of epoxy structural adhesives under salt spray conditions, limiting their application in harsh environments.

[0007] In particular, existing technologies lack research on the application of triazinepropyltrimethoxysilane (TPTS) as a catalyst-interface enhancer in epoxy structural adhesives, and there are no reports on the synergistic effect of TPTS with cashew phenol glycidyl ether to improve the salt spray corrosion resistance of epoxy structural adhesives. Therefore, developing a one-component epoxy structural adhesive with excellent salt spray corrosion resistance is of great significance for expanding the application of epoxy structural adhesives in harsh environments. Summary of the Invention

[0008] To address the technical problem of insufficient corrosion resistance of existing epoxy structural adhesives in salt spray environments and to improve the bonding strength and environmental durability of epoxy structural adhesives to metals, this invention first provides a one-component epoxy structural adhesive, secondly, a method for preparing the one-component epoxy structural adhesive, and thirdly, an application of the one-component epoxy structural adhesive in industrial adhesives.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A one-component epoxy structural adhesive, comprising the following components in parts by weight:

[0011] A. Epoxy resin composition: 20-40 parts of liquid bisphenol A epoxy resin, 5-10 parts of solid bisphenol A epoxy resin, 5-15 parts of CTBN modified epoxy resin, and 10-30 parts of PU modified epoxy resin.

[0012] B. Latent curing system: 1-5 parts curing agent, 0.1-4 parts accelerator;

[0013] C. Catalyst-interface enhancer TPTS: 0.1-4 parts;

[0014] D. Functional fillers: 0-30 parts;

[0015] E. Other additives: 0.1-4 parts of cashew phenol glycidyl ether, 0-1 part of antioxidant.

[0016] Preferably, the viscosity of the liquid bisphenol A epoxy resin is 2000-20000 mPa·s@25℃, and the epoxy equivalent is 170-230 g / mol. It is preferably one or a mixture of Gadida NPEL-128, Gadida NPEL-128S, Gadida NPEF-127, and Dow DER331.

[0017] Preferably, the epoxy equivalent of the solid bisphenol A epoxy resin is 300-900 g / mol, and more preferably one or more of NPES-901, NPES-904H, E-12, and Huntsman PY307.

[0018] Preferably, the CTBN-modified epoxy resin is an adduct of bisphenol A glycidyl ether and nitrile rubber CTBN elastomer, wherein the CTBN content in the adduct is 20-40% by mass; the CTBN-modified epoxy resin is preferably one or more of Huntsman HyPoxRA 95, Hypox RA 1340, HyPox RK 84L, CTBN 1300X13, and complexed high-tech ER8101 and ER8104.

[0019] Preferably, the PU-modified epoxy resin is a polyurethane-modified epoxy resin, wherein the PU content is 15-30% by mass and the epoxy equivalent is 150-700 g / mol; the PU-modified epoxy resin is preferably one or more of the following: Celway EU8000, Nanya 133L, Complex EPU-300s, Adico EPU-73B, and Adico EPU-7N.

[0020] Preferably, the curing agent is a dicyandiamide curing agent with a melting point of 180℃-215℃ and D50 < 10μm, preferably one or more of DDA-10, DDA-5, ABL3002, and AH154; the accelerator is a substituted urea accelerator with a melting point of 125℃-180℃ and D50 < 10μm, preferably one or more of UR101, UR201, UR410, OMICURE U-24M, and U-52M.

[0021] Preferably, the catalyst-interface enhancer TPTS is synthesized through the following steps:

[0022] a) Cyanuryl chloride reacts with KH550 at 0-25℃ to obtain an intermediate;

[0023] b. Mix the intermediate, methanol and MgCl2 catalyst, and react at high temperature for 5-12 hours to obtain TPTS.

[0024] Preferably, in step a, the molar ratio of cyanuric chloride to KH550 is 1:(1.05-1.2).

[0025] Preferably, in step b, the mass ratio of the intermediate to methanol is 1:(8-15); the amount of the MgCl2 catalyst is 0.5-1.5% of the mass of the intermediate.

[0026] Preferably, the reaction temperature in step b is 100-150℃.

[0027] Preferably, the mass ratio of cashew phenol glycidyl ether to TPTS is 1:(0.04-1.0).

[0028] Preferably, the functional filler is one or more of silica, wollastonite, and calcium oxide.

[0029] Preferably, the antioxidant is a hindered phenolic antioxidant, preferably one or more of KY616, KY1310, antioxidant 1010, antioxidant 235, and TH1520.

[0030] A method for preparing a one-component epoxy structural adhesive as described above, characterized by comprising the following steps:

[0031] The epoxy resin composition was mixed in a planetary mixer and vacuum dehydrated to a moisture content of <0.03%; optional functional fillers were added, the temperature was lowered to below 40°C, TPTS, latent curing system, and other additives were added, and the mixture was thoroughly mixed; the mixture was then vacuum degassed, packed into glue buckets, and sealed with nitrogen.

[0032] Preferably, the mixing conditions for the epoxy resin composition are: mixing and stirring at 80-120°C for 30-100 min at a speed of 50-200 rpm.

[0033] An application of a single-component epoxy structural adhesive as described above in industrial adhesives, particularly as an adhesive for aerospace, automotive manufacturing, electronics and electrical engineering, ship decking, and construction engineering.

[0034] This invention, through the synergistic effect of TPTS, not only promotes the formation of a more complete cross-linking network, giving the adhesive higher initial mechanical properties, but more importantly, the stable cross-linking structure enhances the compactness of the structural adhesive and its adhesion to the metal substrate. At the same time, the cross-linking structure formed by TPTS is chemically stable and not easily degraded, effectively resisting the erosion of environmental aging factors (such as water molecules and chloride ions), thereby greatly extending the service life of the adhesive structure in harsh environments. It solves the technical problem of insufficient corrosion resistance of epoxy resin structural adhesives in salt spray environments in the prior art, and improves the resistance of epoxy structural adhesives to damp heat, acid aging and solvent aging, so that the structural adhesive exhibits excellent stability in various harsh environments. Detailed Implementation

[0035] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0036] Unless otherwise specified, the raw materials and reagents used in the following embodiments of the present invention can be purchased from commercially available finished products; wherein,

[0037] Liquid bisphenol A epoxy resin: NPEL-128 (Jiadida), epoxy equivalent is 190 g / mol, viscosity is 12000 mPa·s (25℃);

[0038] Liquid bisphenol A epoxy resin: NPEL-128S, epoxy equivalent is 225 g / mol, viscosity is 20000 mPa·s (25℃);

[0039] Liquid bisphenol A epoxy resin: NPEL-127, epoxy equivalent is 175 g / mol, viscosity is 8000 mPa·s (25℃);

[0040] Solid bisphenol A epoxy resin: E-12 (Nanya), epoxy equivalent is 800 g / mol, softening point is 100℃;

[0041] Solid bisphenol A epoxy resin: NPES-901 (Nanya), epoxy equivalent is 475 g / mol, softening point is 70℃;

[0042] Solid bisphenol A epoxy resin: NPES-904H (Nanya), epoxy equivalent is 900 g / mol, softening point is 110℃;

[0043] CTBN-modified epoxy resin: HyPox RA 95 (Huntsman), CTBN content 20%, epoxy equivalent 200 g / mol;

[0044] CTBN-modified epoxy resin: Hypox RA 1340 (Huntsman), CTBN content 40%, epoxy equivalent 350 g / mol;

[0045] CTBN-modified epoxy resin: HyPox RK 84L (Huntsman), CTBN content is 30%, epoxy equivalent is 1350 g / mol;

[0046] PU modified epoxy resin: EU8000 (Selvey), PU content is 15%, epoxy equivalent is 680g / mol;

[0047] PU-modified epoxy resin: 133L (Nanya), PU content is 20%, epoxy equivalent is 190g / mol;

[0048] PU-modified epoxy resin: EPU-7N (Aidi Ke), PU content is 30%, epoxy equivalent is 230g / mol;

[0049] Silica: H18 (Wacker)

[0050] Wollastonite: Ordinary wollastonite powder (Jiangxi Kete Fine Powder)

[0051] Hardener: Dicyandiamide 110 (Serox)

[0052] Accelerator: UR101 (Serox)

[0053] Cashew phenol glycidyl ether: XY710 (Senfeda Chemical)

[0054] Antioxidants: KY616, KY1310 (Dongfang Ruichuang)

[0055] Coupling agents: KH550, McLean

[0056] Cyanuryl chloride: Wuhan Jixin Yibang Biotechnology

[0057] The performance testing methods involved in the following embodiments of the present invention are as follows:

[0058] <Tensive Shear Strength Test>

[0059] The tensile shear strength of epoxy structural adhesive was tested using a universal testing machine.

[0060] <Salt spray aging test>

[0061] The test sample was suspended in a salt spray aging chamber with a salt concentration of 50 g / L, a pH value of 6.5-7.2, and an ambient temperature of 35°C. After the treatment was completed according to the set time, the tensile shear strength was tested.

[0062] <Damp Heat Aging Test>

[0063] The test sample was suspended in a high-temperature and high-humidity oven at 80°C and 80% RH. After the set time was completed, the tensile shear strength was tested.

[0064] <Acid and Alkali Aging Test>

[0065] An acidic solution with a pH of 5.5 ± 0.5 was prepared using aluminum chloride hexahydrate (AlCl3·6H2O) and NaOH, and stored in a sealed PP container at a controlled ambient temperature of 25°C. The test sample was then immersed in the acidic solution for the set time, and the tensile shear strength was tested.

[0066] Solvent Resistance Aging Test

[0067] Using machine oil as a solvent, the sample was placed in a sealed PP container at an ambient temperature of 45°C and a humidity of 50%RH. The test sample was then immersed in the machine oil for the set time, and the tensile shear strength was tested.

[0068] <Storage Stability Test>

[0069] The initial viscosity of the structural adhesive was tested using a BROOKFIELD DV2T viscometer at 45°C and 0.1 rpm / min. The structural adhesive was then sealed and stored in a 40°C oven to track viscosity changes. The test frequency was once a week. The test was terminated when the viscosity of the structural adhesive doubled, and the test duration was recorded as the product's stable storage period.

[0070] [Preparation Example] Preparation of the Catalyst-Interface Enhancer TPTS

[0071] TPTS-1: 1 mol of cyanuric chloride was dissolved in 500 mL of anhydrous THF at 0℃, and a THF solution containing 1.05 mol KH550 was added dropwise while maintaining the temperature ≤5℃. After the addition was complete, the temperature was raised to 25℃ and reacted for 4 h. The mixture was filtered to remove impurities, and then distilled under reduced pressure to obtain the intermediate. The intermediate, methanol, and MgCl2 catalyst were added to an autoclave at a mass ratio of 1:10:0.01, and reacted at 120℃ for 6 h. The solvent was removed by rotary evaporation to obtain TPTS-1.

[0072] TPTS-2: 1 mol of cyanuric chloride was dissolved in 500 mL of anhydrous THF at 0℃. A THF solution containing 1.2 mol KH550 was added dropwise, with the temperature controlled at ≤5℃. After the addition was complete, the temperature was raised to 25℃ and reacted for 4 h. The mixture was filtered to remove impurities, and then distilled under reduced pressure to obtain the intermediate. The intermediate, methanol, and MgCl2 catalyst were added to an autoclave at a mass ratio of 1:10:0.01, and reacted at 120℃ for 6 h. The solvent was removed by rotary evaporation to obtain TPTS-2.

[0073] TPTS-3: 1 mol of cyanuric chloride was dissolved in 500 mL of anhydrous THF at 0℃. A THF solution containing 1.05 mol KH550 was added dropwise, with the temperature controlled at ≤5℃. After the addition was complete, the temperature was raised to 25℃ and reacted for 4 h. The mixture was filtered to remove impurities, and then distilled under reduced pressure to obtain the intermediate. The intermediate, methanol, and MgCl2 catalyst were added to an autoclave at a mass ratio of 1:8:0.005, and reacted at 100℃ for 12 h. The solvent was removed by rotary evaporation to obtain TPTS-3.

[0074] TPTS-4: 1 mol of cyanuric chloride was dissolved in 500 mL of anhydrous THF at 0℃. A THF solution containing 1.05 mol KH550 was added dropwise, with the temperature controlled at ≤5℃. After the addition was complete, the temperature was raised to 25℃ and reacted for 4 h. The mixture was filtered to remove impurities, and then distilled under reduced pressure to obtain the intermediate. The intermediate, methanol, and MgCl2 catalyst were added to an autoclave at a mass ratio of 1:15:0.015 and reacted at 150℃ for 5 h. The solvent was removed by rotary evaporation to obtain TPTS-4.

[0075]

Examples 1-7

[0076] Prepare the epoxy structural adhesive formulations for each example according to the formulations in Table 1, by weight, and uniformly prepare the mixtures according to the following method:

[0077] Liquid bisphenol A epoxy resin, solid bisphenol A epoxy resin, CTBN modified epoxy resin, and PU modified epoxy resin were mixed in a planetary mixer at 100°C for 60 minutes at 100 rpm to obtain an epoxy resin composition. The mixture was then vacuum dehydrated until the moisture content was <0.03%. Functional fillers were added, and the mixture was cooled to below 40°C. TPTS, curing agent, accelerator, cashew phenol glycidyl ether, and antioxidant were then added and mixed thoroughly. The mixture was then vacuum degassed, placed into a glue container, and sealed with nitrogen to obtain the epoxy structural adhesive composition.

[0078] Table 1

[0079]

[0080]

[0081] Comparative Example 1

[0082] The epoxy structural adhesive composition was prepared according to the formulation and method of Example 1 in Table 1, except that TPTS-1 was not added.

[0083] Comparative Example 2

[0084] The epoxy structural adhesive composition was prepared according to the formulation and method of Example 1 in Table 1, except that TPTS-1 was replaced with an equal amount of KH550.

[0085] Comparative Example 3

[0086] The epoxy structural adhesive composition was prepared according to the formulation and method of Example 1 in Table 1, except that TPTS-1 was replaced with an equal amount of cyanuric chloride.

[0087] Comparative Example 4

[0088] The epoxy structural adhesive composition was prepared according to the formulation and method of Example 1 in Table 1, except that TPTS-1 was replaced with an equal amount of cyanuric chloride and KH550 (molar ratio 1:1.05).

[0089] The applicability and stability of the epoxy structural adhesive compositions provided in each embodiment and comparative example were tested under various harsh environments, and the results are shown in Tables 2-4.

[0090] Table 2. Salt spray aging resistance and high temperature and humidity resistance

[0091]

[0092] Table 3. Acid resistance and solvent aging resistance

[0093]

[0094]

[0095] Table 4. Storage Stability

[0096]

[0097] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A one-component epoxy structural adhesive, characterized in that, The composition comprises the following components by weight: A, epoxy resin composition: liquid bisphenol A epoxy resin 20-40 parts, solid bisphenol A epoxy resin 5-10 parts, CTBN modified epoxy resin 5-15 parts, PU modified epoxy resin 10-30 parts; B, latent curing system: curing agent 1-5 parts, accelerator 0.1-4 parts; C, catalytic-interfacial enhancer TPTS: 0.1-4 parts; D, functional filler: 0-30 parts; E, other auxiliaries: cashew phenol glycidyl ether 0.1-4 parts, antioxidant 0-1 part.

2. The one-part epoxy structural adhesive of claim 1, wherein, The viscosity of the liquid bisphenol A epoxy resin is 2000-20000 mPa·s@25℃, and the epoxy equivalent weight is 170-230 g / mol, preferably one or more mixtures of NPEL-128, NPEL-128S, NPEF-127, and DER331 of Dow Chemical; Preferably, the epoxy equivalent weight of the solid bisphenol A epoxy resin is 300-900 g / mol, preferably one or more of NPES-901, NPES-904H, E-12, and PY307 of Huntsman; Preferably, the CTBN modified epoxy resin is an adduct of bisphenol A glycidyl ether and butyl nitrile rubber CTBN elastomer, wherein the mass content of CTBN in the adduct is 20-40%, and preferably one or more of HyPox RA 95, Hypox RA 1340, HyPox RK 84L, CTBN 1300X13, and ER8101, ER8104 of Luxi High-tech; Preferably, the PU modified epoxy resin is a polyurethane modified epoxy resin, wherein the mass content of PU is 15-30%, and the epoxy equivalent weight is 150-700 g / mol, preferably one or more of EU8000 of Seli, 133L of Nanya, EPU-300s of Luxi, EPU-73B of Aikick, and EPU-7N of Aikick.

3. The one-part epoxy structural adhesive of claim 1, wherein, The curing agent is a dicyandiamide curing agent with a melting point of 180℃-215℃ and a D50 of less than 10μm, preferably one or more of DDA-10, DDA-5, ABL3002, and AH154; the accelerator is a substituted urea accelerator with a melting point of 125℃-180℃ and a D50 of less than 10μm, preferably one or more of UR101, UR201, UR410, OMICURE U-24M, and U-52M.

4. The one-part epoxy structural adhesive of claim 1, wherein, The catalytic-interfacial enhancer TPTS is synthesized by the following steps: a. Mixing cyanuric chloride and KH550 at 0-25℃ to obtain an intermediate; b. Mixing the intermediate, methanol, and MgCl2 catalyst and reacting at high temperature for 5-12h to obtain TPTS.

5. The one-part epoxy structural adhesive of claim 4, wherein, In step a, the molar ratio of cyanuric chloride to KH550 is 1:(1.05-1.2).

6. The one-part epoxy structural adhesive of claim 4, wherein, In step b, the mass ratio of the intermediate to methanol is 1:(8-15); the amount of MgCl2 catalyst used is 0.5-1.5% of the mass of the intermediate; Preferably, the reaction temperature in step b is 100-150℃.

7. The one-part epoxy structural adhesive according to any one of claims 1 to 6, characterized in that The mass ratio of the cardanol glycidyl ether to TPTS is 1:(0.04-1.0).

8. The one-part epoxy structural adhesive according to any one of claims 1 to 7, characterized in that The functional filler is one or a combination of silica, wollastonite, calcium oxide; Preferably, the antioxidant is a hindered phenol antioxidant.

9. A method of preparing a one-part epoxy structural adhesive according to any one of claims 1 to 8, characterized in that, The method comprises the following steps: The epoxy resin composition is mixed in a planetary mixer and vacuum dewatered to a water content of <0.03%; optionally, the functional filler is added, the temperature is lowered to below 40°C, TPTS, a latent curing system, and other additives are added, and mixed uniformly; vacuum defoaming is performed, the mixture is loaded into a glue barrel, and is sealed with nitrogen filling; Preferably, the mixing conditions of the epoxy resin composition are mixing and stirring at 80-120°C for 30-100min at a rotation speed of 50-200rpm.

10. Use of the one-component epoxy structural adhesive according to any one of claims 1-8 in industrial adhesives.

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