High-strength stripping-resistant single-component epoxy structural adhesive and preparation method thereof

Abstract

The invention discloses a high-strength stripping-resistant one-component epoxy structural adhesive and a manufacturing method thereof, and belongs to the technical field of vehicle body adhesives. The epoxy structural adhesive comprises epoxy resin, core-shell rubber, modified nitrile rubber, a flexibilizer, a thixotropic agent, a filler, a coupling agent, a curing agent and a curing accelerator. The adhesive is simple in preparation process, has excellent adhesive performance, stripping resistance and oil resistance, the curing temperature meets the requirements of an automobile production line, and the storage stability is good. The T peel strength of the cured epoxy material is improved by regulating and controlling the ratio of the resin to the powder and the ratio of the epoxy resin to the toughened resin in the system, and in addition, the damage form of a T peel test is converted into cohesive damage by regulating and controlling the particle size of the filler. The single-component epoxy structural adhesive disclosed by the invention can be applied to adhesion of a vehicle body chassis / power transmission part, an aluminum sealing part and a vehicle roof, integration of a cockpit, a composite material vehicle body part and the like, is specially developed for a vehicle body workshop, and improves the rigidity and collision stability of a vehicle body.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of automobile body adhesives, and particularly relates to a high-strength anti-peeling one-component epoxy structural adhesive and a preparation method thereof. BACKGROUND

[0002] With the continuous development of new energy vehicles, to adapt to the core needs of lightweight, high safety and long endurance, substrates are increasingly diversified and widely distributed in key modules such as vehicle body, battery pack, motor and electrical control. Different types of substrates have their own characteristics and adaptation scenarios, and also bring new challenges to production and manufacturing. DC01 low-carbon cold-rolled steel sheet becomes one of the most widely used base materials in automobile bodies due to its controllable cost and good formability.

[0003] Epoxy adhesives are widely used in the automobile manufacturing industry due to their excellent mechanical properties and chemical stability. To adapt to the development of the times, the performance requirements are constantly upgraded, and they are required to have excellent bonding performance and anti-peeling performance for a variety of heterogeneous substrates. Although epoxy adhesives have high shear strength for a variety of substrates, their peeling performance is poor, especially for DC01 cold-rolled steel, the peeling strength is low, and the interface is often damaged. However, in actual application, there is a tendency of peeling to varying degrees. Therefore, epoxy adhesives replace traditional welding technology, and one of the important performance indicators of the cured product is T-peeling strength. In addition to meeting certain T-peeling strength, the failure mode generally requires cohesive failure, that is, there is residual cured material on the surface of the substrate.

[0004] In recent years, adhesive workers have done a lot of work to improve the shear strength and peeling strength of epoxy adhesives, but often the shear strength and peeling strength are acceptable, but the failure mode is poor, and there is no or little cured residue on the surface of the substrate after bonding failure. The existing technology mostly uses low-molecular-weight polyamide and other toughening agents, adds polyvinyl butyral, polysulfone or hydroxymethyl nylon and other thermoplastic resins, or increases the content of coupling agents in the system, which not only increases the cost of the adhesive, but also the effect is not very obvious.

[0005] Therefore, the present application is proposed. SUMMARY

[0006] The purpose of the present application is to provide a high-strength anti-peeling one-component epoxy structural adhesive and a preparation method thereof, which can have high shear strength and peeling strength while ensuring that the T-peeling interface failure type is cohesive failure, thus meeting the increasingly high requirements for the shear and peeling performance of bonding adhesives in the development of the automobile manufacturing industry, and solving the problems existing in the prior art.

[0007] The purpose of the present application is achieved by the following technical solutions: A high-strength peel-resistant one-component epoxy structural adhesive, comprising raw materials in the following mass parts: epoxy resin 25-40 parts, core-shell rubber 15-20 parts, modified nitrile rubber 4-8 parts, toughening agent 10-18 parts, thixotropic agent 3-8 parts, filler 10-20 parts, coupling agent 0.5-1.5 parts, curing agent 3-8 parts and curing accelerator 0.1-0.5 parts.

[0008] Preferably, in the above structural adhesive, the epoxy resin uses any one or a combination of glycidyl ether epoxy resin, glycidyl ester epoxy resin, alicyclic epoxy resin.

[0009] Preferably, in the above structural adhesive, the core-shell rubber uses a resin-rubber particle masterbatch system formed by a core-shell double-layer structure and an epoxy resin as a carrier with core-shell rubber particles; The epoxy equivalent weight of the masterbatch system is 250-350 g / eq; The inner core of the core-shell rubber particle is a butadiene and styrene copolymer, and the shell material is a homopolymer or copolymer of (meth)acrylate, and the average particle size of the core-shell rubber particle is less than 400 nm.

[0010] Preferably, in the above structural adhesive, the modified nitrile rubber is a high-viscosity adduct of bisphenol A glycidyl ether and nitrile rubber elastomer.

[0011] Preferably, in the above structural adhesive, the toughening agent uses a high-viscosity polyurethane toughening agent.

[0012] Preferably, in the above structural adhesive, the high-viscosity polyurethane toughening agent uses a reactive polyurethane elastomer prepolymer with a viscosity of 150,000-250,000 mPa·s.

[0013] Preferably, in the above structural adhesive, the thixotropic agent uses hydrophobic fumed silica; The filler uses an inorganic filler; The coupling agent uses one or more of γ-glycidoxypropyltrimethoxysilane, epoxy-functional silane oligomer, γ-methacryloyloxypropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

[0014] Preferably, in the above structural adhesive, the inorganic filler uses one or more of calcium carbonate, calcium oxide, wollastonite, talc powder, mica, bentonite, quartz powder, carbon black and glass microbeads.

[0015] Preferably, in the above structural adhesive, the curing agent uses a heat-activated latent curing agent; The accelerator uses one or more of imidazole, imidazole derivatives, substituted urea and its derivatives.

[0016] A preparation method of the high-strength peel-resistant single-component epoxy structural adhesive is characterized in that it comprises the following steps: The raw materials are taken according to the formula of the single-component epoxy structural adhesive. Step 1, the core-shell rubber, modified nitrile rubber, toughening agent and thixotropic agent are added into the raw material epoxy resin and uniformly dispersed; Step 2, the fillers are further added and uniformly dispersed by stirring, and then the coupling agent is added and uniformly dispersed by stirring; Step 3, finally, the curing agent and curing accelerator are added, uniformly dispersed by stirring, and vacuum degassed, thereby obtaining the high-strength peel-resistant single-component epoxy structural adhesive.

[0017] Compared with the prior art, the high-strength peel-resistant single-component epoxy structural adhesive and the preparation method thereof have the following beneficial effects: Without adding additional new toughening agent or coupling agent, the T-peel strength of the cured product can be improved by adjusting the ratio of the powder to the resin and the ratio of the epoxy resin to the toughening resin; on this basis, by adjusting the particle size of the filler, the T-peel failure mode is improved from interfacial failure to cohesive failure; the raw material cost of the adhesive can be effectively controlled, and the epoxy single-component structural adhesive has high shear strength and T-peel strength on the metal substrate. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the specific contents of the present application; obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments, which do not constitute a limitation on the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0019] Firstly, the terms possibly used in the present application are explained as follows:

[0020] The term "and / or" means either one or both, for example, X and / or Y means three cases including "X", "Y" or "X and Y".

[0021] The terms "include", "contain", "have", "possess" or other similar semantic descriptions should be interpreted as non-exclusive inclusion. For example, including a technical feature element (such as raw materials, components, ingredients, carriers, dosage forms, materials, sizes, parts, components, mechanisms, devices, steps, processes, methods, reaction conditions, processing conditions, parameters, algorithms, signals, data, products or articles, etc.) should be interpreted as not only including the explicitly listed technical feature element, but also including other technical feature elements not explicitly listed in the art.

[0022] The term "consisting of" denotes an exclusion of any element, not explicitly listed. If the term is used in the claims, the term "consisting of" shall mean that the only technology features of the claims are those that are explicitly listed. If the term is used in the description, then the term "consisting of" limits the claims only to the technology features that are explicitly listed.

[0023] The term "mass parts" is used to express the mass ratio relationship between components, for example: if it is described that X component is x mass parts, Y component is y mass parts, it means that the mass ratio of X component to Y component is x:y; 1 mass part can represent any mass, for example: 1 mass part can represent 1 kg, 3.1415926 kg, etc. The sum of the mass parts of all components does not necessarily equal 100 parts, and can be greater than 100 parts, less than 100 parts, or equal to 100 parts. Unless otherwise specified, the parts, proportions, and percentages described herein are by mass.

[0024] When a concentration, temperature, pressure, size, or other parameter is expressed as a numerical range, the numerical range should be understood to specifically disclose all ranges formed from any pair of an upper limit value, a lower limit value, and a preferred value within the numerical range, regardless of whether the range is explicitly recited; for example, if a numerical range "2-8" is recited, the numerical range should be interpreted to include ranges such as "2-7", "2-6", "5-7", "3-4 and 6-7", "3-5 and 7", "2 and 5-7", etc. Unless otherwise specified, the numerical ranges recited herein include all integers and fractions within the range.

[0025] The schemes provided by the present application are described in detail below. The content not described in detail in the embodiments of the present application belongs to the prior art known to those skilled in the art. Unless otherwise specified, the specific conditions in the embodiments of the present application are carried out according to the conventional conditions in the art or the conditions recommended by the manufacturer. Unless otherwise specified, the reagents or instruments used in the embodiments of the present application are conventional products that can be obtained by commercial purchase.

[0026] The embodiment of the present application provides a high-strength peel-resistant single-component epoxy structural adhesive, which comprises raw materials in the following mass parts: 25-40 mass parts of an epoxy resin; 15-20 mass parts of a core-shell rubber; 4-8 mass parts of a modified nitrile rubber; 10-18 mass parts of a toughening agent; 3-8 mass parts of a thixotropic agent; 10-20 mass parts of a filler; 0.5-1.5 mass parts of a coupling agent; 3-8 mass parts of a curing agent; and 0.1-0.5 mass parts of a curing accelerator.

[0027] In some embodiments of the present application, the epoxy resin in the structural adhesive is selected from any one or a combination of at least two of glycidyl ether epoxy resin, glycidyl ester epoxy resin or alicyclic epoxy resin. The epoxy resin is preferably bisphenol A type epoxy resin E-51.

[0028] In some embodiments of the present application, the core-shell rubber in the structural adhesive is selected from a resin-rubber particle masterbatch system with a double-layer core-shell structure, with epoxy resin as the carrier. The resin-rubber particle masterbatch system is preferably one or several of MX-154, MX-150, MX-160, XA-542;

[0029] In some embodiments of the present application, the modified nitrile rubber in the structural adhesive is selected from a high-viscosity adduct of bisphenol A glycidyl ether (DGEBA) and nitrile rubber (CTBN) elastomer addition reaction. The modified nitrile rubber is selected from one or both of CTBN 1300X13 and 861340;

[0030] In some embodiments of the present application, the coupling agent in the structural adhesive is selected from one or a mixture of several of γ-glycidyl ether propyl trimethoxysilane (KH560), epoxy functional silane oligomer (MP200), γ-methacryloyl propyl trimethoxysilane (KH570), N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane (KHU792).

[0031] In some embodiments of the present application, the curing agent in the structural adhesive is selected from a heat-activated latent curing agent. The heat-activated latent curing agent is preferably dicyandiamide (DICY).

[0032] In some embodiments of the present application, the curing accelerator in the structural adhesive is selected from one or a mixture of several of imidazole, imidazole derivatives, substituted urea and derivatives thereof. The curing accelerator is preferably a modified urea latent accelerator.

[0033] The present application also provides a preparation method of the above-mentioned high-strength peel-resistant one-component epoxy structural adhesive. The raw materials are taken according to the formula of the structural adhesive, and the preparation method comprises the following steps: Step 1: The core-shell rubber, modified nitrile rubber, toughening agent and thixotropic agent are added to the epoxy resin in proportion and uniformly dispersed; Step 2: The filler is further added and uniformly dispersed by stirring, and then the coupling agent is added and uniformly dispersed by stirring; Step 3: Finally, the curing agent and the curing accelerator are added and uniformly dispersed by stirring, and vacuum degassing is performed, thereby obtaining the one-component epoxy structural adhesive.

[0034] The one-component epoxy structural adhesive of the present application can be applied to the bonding of vehicle body chassis / power transmission components, aluminum closures and roofs, driver cabins, composite vehicle body components integration, etc., and is developed for vehicle body workshops to improve the stiffness and collision stability of the vehicle body.

[0035] In order to more clearly show the technical solutions provided by the present application and the technical effects produced thereby, the schemes provided by the embodiments of the present application are described in detail below with specific examples.

[0036] (1) The raw material ratios in the embodiments are shown in Table 1: Table 1 is the raw material ratios in the embodiments ; Note: The substrates for shear and T-peeling tests are DC01 cold-rolled steel; the interface failure modes are: Type A is interface failure, Type B is cohesive failure, and Type C is mixed failure.

[0037] (2) The preparation methods of the embodiments are as follows: Step 1) Add core-shell rubber, modified nitrile rubber, toughening agent and thixotropic agent into the epoxy resin in the proportions of the above-mentioned formulations of the embodiments and disperse uniformly; Step 2) Then add fillers and stir to disperse uniformly, and then add coupling agents and stir to disperse uniformly; Step 3) Finally, add curing agent and curing accelerator, stir to disperse, and vacuum degassing to obtain the one-component epoxy structural adhesive.

[0038] (3) Performance test methods: The sample preparation method for tensile shear strength test and the test reference standard are GB / T 7124-2008 Adhesives-Determination of tensile shear strength (rigid material against rigid material); the test rate is 10 mm / min; The sample preparation method for T-peeling strength and the test reference standard are ISO 11339:2010; the test rate is 100 mm / min.

[0039] The results of Table 1 are discussed: Examples A1-A3 are intended to study the influence of the size of the ratio of filler to epoxy resin on the performance. From Table 1, it can be seen that as the content of epoxy resin gradually increases, the T-peeling strength shows a trend of first increasing and then decreasing, and the interface failure mode also changes from mixed failure to interface failure; the shear strength also shows a similar trend. To some extent, it shows that the ratio of powder to epoxy resin directly affects the density, phase distribution and interface action of the cross-linked network after curing, and then affects the mechanical properties of the adhesive layer. This is mainly because when the content of epoxy resin is too low and the content of powder is too high, the powder particles are excessively accumulated, which is easy to form agglomerates, and the cross-linking reaction is hindered, the uniformity and density of the network will decrease sharply, resulting in the decrease of the mechanical properties of the system; however, when the content of epoxy resin is too high, it is also not conducive to the improvement of the performance of the system. When the content of resin is too high, the curing shrinkage of the adhesive is large, and there is not enough filler to offset the curing shrinkage, so that the internal stress generated during the shrinkage process exceeds the bearing limit of the interface bonding strength and the toughness of the adhesive layer itself, resulting in the decrease of the mechanical properties of the cured adhesive and the interface failure (debonding) of the failure mode. Examples A2, B1-B3 are to study the influence of the ratio of epoxy resin to toughener resin on the performance of the system under the condition that the amount of powder added is the same. From Table 1, it can be seen that as the content of epoxy resin in the system increases, the performance of the cured system also shows a trend of first increasing and then decreasing, which is mainly because the content of active groups epoxy group in the system is continuously increased, which makes the density and structure of the cross-linked network of the system change continuously, resulting in the change of the mechanical properties and failure mode of the cured system.

[0040] Table 2 is the ratio of Examples C1-C3 and Comparative Example B2 ; Discussion of Table 2: On the basis of optimizing the ratio of powder to resin and the ratio of epoxy resin to toughener resin, Examples C1-C3 change the mesh number of the filler, i.e. the particle size of the filler, so that the T-peeling failure mode of the cured product changes from mixed failure to cohesive failure, and the shear strength and T-peeling strength are also improved to some extent.

[0041] The above description is only a preferred embodiment of the present application, but the protection scope of the present application is not limited to this. Any changes or replacements within the technical range disclosed in the present application can be easily thought of by those skilled in the art, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims. The information disclosed in the background section of this document is only intended to deepen the understanding of the overall background of the present application, and should not be regarded as acknowledging or implying in any form that the information constitutes prior art known to those skilled in the art.

Claims

1. A high-strength, peel-resistant, one-component epoxy structural adhesive, characterized in that, The epoxy structural adhesive comprises the following raw materials in parts by weight: 25-40 parts epoxy resin, 15-20 parts core-shell rubber, 4-8 parts modified nitrile rubber, 10-18 parts toughening agent, 3-8 parts thixotropic agent, 10-20 parts filler, 0.5-1.5 parts coupling agent, 3-8 parts curing agent, and 0.1-0.5 parts curing accelerator.

2. The single-component epoxy structural adhesive according to claim 1, characterized in that, The epoxy resin is any one or a combination of glycidyl ether epoxy resin, glycidyl ester epoxy resin, and alicyclic epoxy resin.

3. The single-component epoxy structural adhesive according to claim 1 or 2, characterized in that, The core-shell rubber adopts a resin-rubber particle masterbatch system with a core-shell double-layer structure, using epoxy resin as a carrier and core-shell rubber particles as a carrier. The epoxy equivalent of the masterbatch system is 250-350 g / eq; The core of the core-shell rubber particles is a copolymer of butadiene and styrene, and the shell material is a homogeneous material or copolymer of (meth)acrylate. The average particle size of the core-shell rubber particles is less than 400 nm.

4. The single-component epoxy structural adhesive according to claim 1 or 2, characterized in that, The modified nitrile rubber is a high-viscosity adduct formed by the addition reaction of bisphenol A glycidyl ether and nitrile rubber elastomer.

5. The single-component epoxy structural adhesive according to claim 1 or 2, characterized in that, The toughening agent is a high-viscosity polyurethane toughening agent.

6. The one-component epoxy structural adhesive according to claim 5, characterized in that, The high-viscosity polyurethane toughening agent is a reactive polyurethane elastic prepolymer with a viscosity of 150,000 to 250,000 mPa·s.

7. The one-component epoxy structural adhesive according to claim 1 or 2, characterized in that, The thixotropic agent is hydrophobic fumed silica; The packing material is an inorganic packing material; The coupling agent is one or a mixture of γ-glycidoxypropyltrimethoxysilane, epoxy functional silane oligomer, γ-methacryloyloxypropyltrimethoxysilane, and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

8. The one-component epoxy structural adhesive according to claim 1 or 2, characterized in that, The inorganic filler is one or more of the following: calcium carbonate, calcium oxide, wollastonite, talc, mica, bentonite, quartz powder, carbon black, and glass microspheres.

9. The one-component epoxy structural adhesive according to claim 1 or 2, characterized in that, The curing agent is a thermally activated latent curing agent; The promoter is one or a mixture of several of imidazole, imidazole derivatives, substituted urea and their derivatives.

10. A method for preparing the high-strength, peel-resistant, single-component epoxy structural adhesive according to any one of claims 1-9, characterized in that, include: The raw materials are prepared according to the formulation of the single-component epoxy structural adhesive according to any one of claims 1-9; Step 1: Add core-shell rubber, modified nitrile rubber, toughening agent and thixotropic agent to the epoxy resin of the raw material and disperse them evenly; Step 2: Add filler and stir to disperse evenly, then add coupling agent and stir to disperse evenly. Step 3: Finally, add the curing agent and curing accelerator, stir and disperse, and vacuum degas to obtain a high-strength peel-resistant single-component epoxy structural adhesive.