Epoxy structural adhesive, preparation method and application thereof

Abstract

This invention discloses an epoxy structural adhesive, its preparation method, and its applications, belonging to the field of polymer materials. The epoxy structural adhesive comprises an epoxy structural adhesive portion and a curing agent portion; the mass ratio of the epoxy structural adhesive portion to the curing agent portion is 100:15-40; the epoxy structural adhesive portion contains bisphenol A type epoxy resin, bisphenol F type epoxy resin, nitrile rubber, and calcium carbonate; the curing agent portion contains phenolic amine curing agent and alicyclic amine curing agent. The epoxy structural adhesive provided by this invention, based on the synergistic effect between its components, not only achieves high adhesion performance and can quickly form high bond strength, but also exhibits excellent high and low temperature performance and excellent fatigue resistance after bonding, reducing the risk of debonding in repetitive operations, and has a wider range of applications.

Description

Technical Field

[0001] This invention relates to an epoxy structural adhesive, its preparation method, and its application, belonging to the field of polymer materials. Background Technology

[0002] Epoxy structural adhesives are widely used in construction, automotive and other fields. They can be used to bond metals, wood and composite materials.

[0003] The epoxy structural adhesives commonly used in the present technology have high stiffness but poor fatigue resistance, and generally have low heat resistance and too fast curing speed, which cannot properly wet the substrate surface. Their cured products have poor durability and cannot be used in oil well operations with repeated high-temperature environments. They are also prone to debonding during operations and cannot be used in the field of sucker rod bonding.

[0004] Chinese Patent (Publication No. CN 117659613 A) discloses an epoxy resin system composition and its application. The epoxy resin system composition of this invention consists of an epoxy resin component and a curing agent component. The epoxy resin component is prepared by mixing hydrogenated bisphenol A diglycidyl ether epoxy resin, bisphenol A diglycidyl ether epoxy resin, diluent, and mixing additives in a specific ratio. The curing agent component is prepared by reacting an acid anhydride curing agent, toughening agent, and accelerator in a specific ratio. However, the adhesive obtained by this method has low bonding strength and cannot be used in the field of sucker rod bonding.

[0005] Chinese Patent (Publication No. CN 113337234 A) discloses a room-temperature curing epoxy resin-based Vitrimer adhesive, which is composed of component A (epoxy resin) and component B (epoxy curing agent) mixed in a weight ratio of 1:(0.80-1.20). Component A contains 100 parts of bisphenol A type epoxy resin, 5-15 parts of bisphenol F type epoxy resin, 5-20 parts of reactive diluent, and 0.5-20 parts of terminal epoxy group liquid nitrile rubber. Component B contains 55-70 parts of amine curing agent, 15-30 parts of toughening agent, and 15-25 parts of curing accelerator. The amine curing agent is a mixture of long-chain aliphatic amine curing agent, alicyclic amine curing agent, and polyether amine curing agent. The toughening agent is terminal amino, terminal carboxyl, or terminal hydroxyl group liquid nitrile rubber or any mixture thereof. However, the adhesive prepared by this method cannot be used at high temperatures and has low bonding strength, making it unsuitable for use in sucker rod bonding. Summary of the Invention

[0006] To address the problems existing in the prior art, one of the objectives of this invention is to provide an epoxy structural adhesive. Based on the synergistic effect between its components, this structural adhesive not only achieves high adhesion performance and reaches a heat resistance of 100°C after curing for 2 hours, enabling it to quickly form high bonding strength, but also exhibits excellent high and low temperature performance, excellent fatigue resistance, and reduces the risk of debonding during repeated operations, thus having a wider range of applications.

[0007] The second objective of this invention is to provide a method for preparing epoxy structural adhesives. This method is simple, mild, environmentally friendly, requires no solvents during the entire preparation process, and yields products with high purity.

[0008] The third objective of this invention is to provide a method for applying epoxy structural adhesive in sucker rod bonding. This method is simple to apply, using epoxy structural adhesive to bond metal bushings to pultruded glass fiber composite sucker rods. After curing, it can achieve high bonding strength, with a tensile shear strength of up to 30 MPa, good fatigue resistance, and reduced risk of debonding.

[0009] To achieve the above objectives, a first aspect of the present invention is to provide an epoxy structural adhesive, comprising an epoxy structural adhesive portion and a curing agent portion; wherein the content-to-mass ratio of the epoxy structural adhesive portion to the curing agent portion is 100:15-40;

[0010] The epoxy structural adhesive portion contains bisphenol A type epoxy resin, bisphenol F type epoxy resin, nitrile rubber, and calcium carbonate; based on the total weight of the epoxy structural adhesive portion as 100%, the content of bisphenol A type epoxy resin is 40-70%, the content of bisphenol F type epoxy resin is 5-30%, the content of nitrile rubber is 5-25%, and the content of calcium carbonate is 15-40%.

[0011] The curing agent portion contains phenolic amine curing agent and alicyclic amine curing agent; based on the total weight of the curing agent portion as 100%, the content of phenolic amine curing agent is 50-90%, and the content of alicyclic amine curing agent is 10-50%.

[0012] The innovation of this invention lies in using bisphenol A epoxy resin, bisphenol F epoxy resin, nitrile rubber, and calcium carbonate as raw materials in the epoxy structural adhesive portion. Bisphenol F epoxy resin is used to adjust the viscosity of the epoxy resin. Viscosity is a crucial parameter for structural adhesives, significantly impacting processability and defoaming properties. Excessive viscosity leads to poor flowability and affects the bonding performance of the material. Therefore, conventional epoxy structural adhesives typically require the addition of large amounts of diluents and solvents to reduce the viscosity. However, excessive diluent addition can affect the heat resistance and mechanical properties of the cured product. This invention, by mixing bisphenol F epoxy resin with bisphenol A epoxy resin, effectively reduces the viscosity of the structural adhesive. Furthermore, the introduction of nitrile rubber improves the toughness and fatigue resistance of the structural adhesive. In addition, this invention introduces calcium carbonate into the composition. Compared to other inorganic fillers, the addition of calcium carbonate to this system effectively enhances the bonding strength with metals.

[0013] Furthermore, the curing agent of this invention contains phenolic amine curing agent and alicyclic amine curing agent. The two amine curing agents have a synergistic effect, which can ensure that the epoxy resin achieves high bonding strength after curing, and can improve the comprehensive performance of epoxy structural adhesive. At the same time, it can also give the cured product good weather resistance, heat resistance and toughness, and low toxicity.

[0014] At the same time, when the epoxy structural adhesive and curing agent are used together, the adhesive can be given better fatigue resistance and the bonding stability between metal and composite materials can be increased.

[0015] In a preferred embodiment, the epoxy equivalent of the bisphenol A type epoxy resin is 170-230, and the epoxy equivalent of the bisphenol F type epoxy resin is 160-180.

[0016] In a preferred embodiment, the bisphenol F epoxy resin has an epoxy equivalent of 160-170. Under these preferred conditions, the bisphenol F epoxy resin itself has a low viscosity and good compatibility with nitrile rubber, allowing the viscosity to be further adjusted to an appropriate range while avoiding the use of diluents and solvents. Furthermore, under these preferred conditions, the bisphenol F epoxy resin has relatively low viscosity, is easy to level, and has good wettability to the substrate.

[0017] In a preferred embodiment, the average particle size of the calcium carbonate is 2–10 μm. If the filler particle size is too small, the system viscosity will increase significantly, resulting in poor colloidal flowability, poor processability, and poor wettability, leading to a decrease in bond strength. If the filler particle size is too large, the impact of filler agglomeration will be amplified, which will also lead to a decrease in bond strength.

[0018] In a preferred embodiment, the nitrile rubber is selected from at least one of carboxyl-terminated liquid nitrile rubber, hydroxyl-terminated liquid nitrile rubber, and epoxy-terminated liquid nitrile rubber. Introducing the preferred nitrile rubber into the epoxy structural adhesive can impart higher toughness, fatigue resistance, and better adhesive strength to the epoxy structural adhesive.

[0019] In a more preferred embodiment, the nitrile rubber is an epoxy-terminated liquid nitrile rubber. This nitrile rubber can avoid the prepolymerization process and directly participate in the resin curing reaction to form a cross-linked network, which can improve the toughness and bonding strength of the structural adhesive. The resulting cross-linked product has excellent wear resistance, low-temperature resistance, oil resistance, water resistance, and acid and alkali resistance, while also having excellent mechanical properties and good electrical insulation properties.

[0020] In a preferred embodiment, the amine value of the phenolic amine curing agent is 430–520 mg KOH / g, and the alicyclic amine curing agent is IPDA and / or DDM. The phenolic amine curing agent has high heat resistance, and the phenolic hydroxyl groups in its structure promote the reactivity of the curing agent, enabling it to cure completely with epoxy resin at relatively low temperatures. Mixing the two curing agents can improve the heat resistance and adhesive strength of the system.

[0021] In a preferred embodiment, the mass ratio of the epoxy structural adhesive portion to the curing agent portion is 100:15-25.

[0022] In a more preferred embodiment, the content of bisphenol A epoxy resin is 45-60%, the content of bisphenol F epoxy resin is 10-20%, the content of nitrile rubber is 10-20%, and the content of calcium carbonate is 18-30%, with the total weight of the epoxy structural adhesive portion being 100%; the content of phenolic amine curing agent is 70-90%, and the content of alicyclic amine curing agent is 10-30%, with the total weight of the curing agent portion being 100%. In the epoxy structural adhesive section, using two epoxy resins in combination can effectively adjust the viscosity of the structural adhesive, improve the bonding strength and heat resistance of the system, etc. If the proportion of bisphenol A epoxy resin is too high, the overall viscosity of the system is low, resulting in a low adhesive volume and poor bonding effect. If the proportion of epoxy equivalent bisphenol F epoxy resin is too low, the overall viscosity of the system is high, making it difficult to spread evenly during bonding. Excessive addition of nitrile rubber makes it difficult to disperse evenly within the system, leading to product instability. Conversely, insufficient addition of nitrile rubber affects the bonding strength of the product. When the addition of nitrile rubber in the epoxy resin system reaches an optimal ratio, it can effectively improve the toughness and bonding strength of the system, making it more suitable for bonding metal bushings and fiberglass sucker rods, and also helping to extend the product's service life. In the curing agent section, if the proportion of alicyclic amine curing agent is too high, although it can increase the system's heat resistance, the viscosity is too low and the curing speed is too fast, which is not conducive to the system's bonding. Therefore, using both in an appropriate ratio provides good heat resistance while maintaining good bonding performance.

[0023] The present invention also provides a method for preparing epoxy structural adhesive, the method comprising: preparing epoxy adhesive and curing agent separately, for later use;

[0024] The method for preparing epoxy resin includes: mixing bisphenol A type epoxy resin, bisphenol F type epoxy resin, nitrile rubber and calcium carbonate in the epoxy structural adhesive part to obtain epoxy resin.

[0025] The method for preparing the curing agent includes: mixing the phenolic amine curing agent and the alicyclic amine curing agent in the curing agent part to obtain the curing agent.

[0026] The preparation method provided by this invention does not require solvent-assisted reaction throughout the entire process, has no waste gas or waste liquid emissions, and also avoids the impact of solvent on product purity.

[0027] In a preferred embodiment, the conditions for preparing the epoxy compound include: a temperature of 40–80°C and a time of 100–500 min.

[0028] In a preferred embodiment, the conditions for preparing the epoxy compound also include a stirring rate of 1000–5000 r / min.

[0029] In a more preferred embodiment, the conditions for preparing the epoxy compound include: a temperature of 60–70°C, a time of 200–300 min, and a stirring rate of 2000–4000 r / min.

[0030] In a preferred embodiment, the conditions for preparing the curing agent include: a temperature of 40–60°C and a time of 40–80 min.

[0031] In a preferred embodiment, the conditions for preparing the curing agent also include a stirring rate of 1000–5000 r / min.

[0032] In a more preferred embodiment, the conditions for preparing the curing agent include: a temperature of 45–55°C, a time of 50–70 min, and a stirring rate of 2000–3000 r / min.

[0033] This invention also provides the application of epoxy structural adhesive in sucker rod bonding. When the epoxy structural adhesive prepared according to this invention is used to bond metal bushings to pultruded glass fiber composite sucker rods, high bond strength is achieved after curing, with a maximum tensile shear strength of 30 MPa. It also exhibits good fatigue resistance and reduces the risk of debonding.

[0034] This invention also provides a method for applying epoxy structural adhesive in sucker rod bonding. The method includes:

[0035] The epoxy structural adhesive is injected into the metal sleeve, and then either end of the sucker rod is placed inside the metal sleeve. Heating completes the curing process. This method is simple and convenient.

[0036] In a preferred embodiment, the curing conditions include a temperature of 60–120°C and a time of 2–6 hours.

[0037] Compared with the prior art, the present invention has at least the following advantages:

[0038] (1) The epoxy resin structural adhesive for bonding metal sleeves of sucker rods provided by this invention achieves high impact toughness and high bonding strength based on the synergistic effect of its components, and can be used for bonding metals and composite materials. Tests show that the glass transition temperature of this structural adhesive can reach over 100℃, the tensile-shear strength can reach 26MPa, and the maximum can reach 30.1MPa. It also exhibits good high and low temperature stability, reducing the risk of debonding during repeated operations.

[0039] (2) The preparation method provided by the present invention is simple, mild, green and environmentally friendly, and no solvent needs to be added during the preparation process, and the resulting product has high purity.

[0040] (3) The curing agent of the present invention contains phenolic amine curing agent and alicyclic amine curing agent. The two amine curing agents have a synergistic effect, which can ensure that the epoxy resin achieves high bonding strength after curing, and can improve the comprehensive performance of epoxy structural adhesive. At the same time, it can also give the cured material good weather resistance, heat resistance and toughness, and low toxicity. Detailed Implementation

[0041] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0042] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments. Obviously, the embodiments described below are only a part of the embodiments, and all other embodiments obtained by those skilled in the art without creative effort are still within the scope of protection of the present invention.

[0043] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0044] Example 1

[0045] The epoxy equivalent of bisphenol A type epoxy resin is 180; the epoxy equivalent of bisphenol F type epoxy resin is 170; the average particle size of calcium carbonate is 2μm; and the nitrile rubber is a liquid nitrile rubber with terminal epoxy groups.

[0046] The amine value of the phenolic amine curing agent is 480 mg KOH / g; the alicyclic amine curing agent is IPDA.

[0047] Preparation of epoxy compound: Take 50g of bisphenol A type epoxy resin, 12.5g of bisphenol F type epoxy resin, 12.5g of nitrile rubber and 25g of calcium carbonate and mix them. Stir mechanically at 60℃ for 200min at a stirring speed of 4000r / min to obtain epoxy compound for later use.

[0048] Preparation of curing agent: Mix 16.6g of phenolic amine curing agent and 3.4g of alicyclic amine curing agent, and mechanically stir at 50℃ for 60min at a stirring speed of 2500r / min to obtain the curing agent, which is ready for use.

[0049] Example 2

[0050] The epoxy equivalent of bisphenol A type epoxy resin is 180; the epoxy equivalent of bisphenol F type epoxy resin is 170; the average particle size of calcium carbonate is 5μm; and the nitrile rubber is a liquid nitrile rubber with terminal epoxy groups.

[0051] The amine value of the phenolic amine curing agent is 480 mg KOH / g; the alicyclic amine curing agent is IPDA.

[0052] Preparation of epoxy compound: Take 50g of bisphenol A type epoxy resin, 16.7g of bisphenol F type epoxy resin, 11.1g of nitrile rubber and 22.2g of calcium carbonate and mix them. Stir mechanically at 60℃ for 200min at a stirring speed of 4000r / min to obtain epoxy compound for later use.

[0053] Preparation of curing agent: Mix 13.6g of phenolic amine curing agent and 3.4g of alicyclic amine curing agent, and mechanically stir at 50℃ for 60min at a stirring speed of 2500r / min to obtain the curing agent, which is ready for use.

[0054] Example 3

[0055] The epoxy equivalent of bisphenol A type epoxy resin is 210; the epoxy equivalent of bisphenol F type epoxy resin is 170; the average particle size of calcium carbonate is 5μm; and the nitrile rubber is a liquid nitrile rubber with terminal epoxy groups.

[0056] The amine value of the phenolic amine curing agent is 480 mg KOH / g; the alicyclic amine curing agent is IPDA.

[0057] Preparation of epoxy compound: Take 45g of bisphenol A type epoxy resin, 18g of bisphenol F type epoxy resin, 17g of nitrile rubber and 20g of calcium carbonate and mix them. Stir mechanically at 60℃ for 200min at a stirring speed of 4000r / min to obtain epoxy compound for later use.

[0058] Preparation of curing agent: Mix 15.2g of phenolic amine curing agent and 3.8g of alicyclic amine curing agent, and mechanically stir at 50℃ for 60min at a stirring speed of 2500r / min to obtain the curing agent, which is ready for use.

[0059] Example 4

[0060] This embodiment is carried out using a similar method to Example 1, except that the calcium carbonate in Example 1 is replaced with an equal mass of calcium carbonate with an average particle size of 15 μm.

[0061] Comparative Example 1

[0062] This comparative example was conducted using a method similar to that of Example 1. The types of raw materials used in this comparative example are the same as in Example 1, except that the amounts of raw materials used are different. Specifically:

[0063] The amount of bisphenol A epoxy resin used is 60g, the amount of bisphenol F epoxy resin and nitrile rubber used is 0g, and the amount of calcium carbonate used is 40g.

[0064] The amount of phenolic amine curing agent used is 15g, and the amount of alicyclic amine curing agent used is 0g.

[0065] Comparative Example 2

[0066] This comparative example was conducted using a method similar to that of Example 1. The types of raw materials used in this comparative example are the same as in Example 1, except that the amounts of raw materials used are different. Specifically:

[0067] The amount of bisphenol A epoxy resin used is 80g, the amount of bisphenol F epoxy resin and nitrile rubber used is 0g, and the amount of calcium carbonate used is 20g.

[0068] The amount of phenolic amine curing agent used is 20g, and the amount of alicyclic amine curing agent used is 0g.

[0069] Comparative Example 3

[0070] This comparative example was conducted using a similar method to Example 1, except that the amount of bisphenol A epoxy resin was adjusted to 61g and the amount of calcium carbonate was adjusted to 14g.

[0071] Comparative Example 4

[0072] This comparative example was carried out using a similar method to Example 1, except that calcium carbonate was replaced with an equal mass of silicon dioxide.

[0073] Comparative Example 5

[0074] This comparative example was conducted using a similar method to Example 1, except that the types and amounts of raw materials used to prepare the curing agent were different. Specifically:

[0075] The amount of phenolic amine curing agent used is 10g, the amount of alicyclic amine curing agent used is 5g, and the amount of polyether amine curing agent (D230) used is 6g.

[0076] Test case

[0077] After the epoxy resin and curing agent prepared in the above examples are mixed evenly, epoxy structural adhesive is obtained. After curing, tensile strength, glass transition temperature and lap test are performed. The curing conditions are: 80℃, 2h. The test method is based on GB / T7124-2008. The test results are shown in Table 1.

[0078] The epoxy structural adhesive provided in Example 1 was tested for sucker rod bonding. After more than 7.5 million fatigue tests, its pull-out strength was still greater than 30 tons. The epoxy structural adhesive provided by the present invention has good high and low temperature stability and good fatigue resistance.

[0079] Table 1

[0080] Glass transition temperature / °C Tensile-shear strength / MPa Example 1 111 30.1 Example 2 105 29.4 Example 3 115 28.7 Example 4 110 26.9 Comparative Example 1 90 16.9 Comparative Example 2 81 15.5 Comparative Example 3 106 17.8 Comparative Example 4 110 12.3 Comparative Example 5 95 16.8

[0081] As can be seen from the results in Table 1, the epoxy structural adhesive system provided by this invention can achieve heat resistance of over 100℃, and its glass transition temperature is also much higher than that of the comparative examples. The tensile shear strength of Examples 1 and 2 can reach over 29 MPa, and the tensile shear strength of Examples 3, 4 and 5 can reach over 26 MPa, showing a significant enhancement in tensile-shear strength.

[0082] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An epoxy structural adhesive, characterized in that: This includes the epoxy structural adhesive component and the curing agent component; The mass ratio of the epoxy structural adhesive portion to the curing agent portion is 100:15~40; The epoxy structural adhesive portion contains bisphenol A type epoxy resin, bisphenol F type epoxy resin, nitrile rubber, and calcium carbonate; based on the total weight of the epoxy structural adhesive portion as 100%, the content of bisphenol A type epoxy resin is 40-70%, the content of bisphenol F type epoxy resin is 5-30%, the content of nitrile rubber is 5-25%, and the content of calcium carbonate is 15-40%. The curing agent portion contains phenolic amine curing agent and alicyclic amine curing agent; based on the total weight of the curing agent portion as 100%, the content of phenolic amine curing agent is 50-90%, and the content of alicyclic amine curing agent is 10-50%.

2. The epoxy structural adhesive according to claim 1, characterized in that: The amine value of the phenolic amine curing agent is 430~520 mgKOH / g, and the alicyclic amine curing agent is IPDA and / or DDM.

3. An epoxy structural adhesive according to claim 1 or 2, characterized in that: The epoxy equivalent of the bisphenol A type epoxy resin is 170~230, and the epoxy equivalent of the bisphenol F type epoxy resin is 160~180.

4. The epoxy structural adhesive according to claim 3, characterized in that: The epoxy equivalent of the bisphenol F type epoxy resin is 160~170.

5. An epoxy structural adhesive according to claim 1 or 2, characterized in that: The average particle size of the calcium carbonate is 2~10μm.

6. An epoxy structural adhesive according to claim 1 or 2, characterized in that: The nitrile rubber is selected from at least one of carboxyl-terminated liquid nitrile rubber, hydroxyl-terminated liquid nitrile rubber, and epoxy-terminated liquid nitrile rubber.

7. An epoxy structural adhesive according to claim 1 or 2, characterized in that: The mass ratio of the epoxy structural adhesive portion to the curing agent portion is 100:15~25.

8. An epoxy structural adhesive according to claim 1 or 2, characterized in that: The total weight of the epoxy structural adhesive portion is taken as 100%, the content of bisphenol A type epoxy resin is 45~60%, the content of bisphenol F type epoxy resin is 10~20%, the content of nitrile rubber is 10~20%, and the content of calcium carbonate is 18~30%. The curing agent content is 70-90% based on the total weight of the curing agent portion, and the content of the phenolic amine curing agent is 10-30%.

9. The method for preparing the epoxy structural adhesive according to any one of claims 1 to 8, characterized in that: The method includes: preparing epoxy resin and curing agent separately, for later use; The method for preparing epoxy resin includes: mixing bisphenol A type epoxy resin, bisphenol F type epoxy resin, nitrile rubber and calcium carbonate in the epoxy structural adhesive part to obtain epoxy resin. The method for preparing the curing agent includes: mixing the phenolic amine curing agent and the alicyclic amine curing agent in the curing agent part to obtain the curing agent.

10. The method for preparing the epoxy structural adhesive according to claim 9, characterized in that: The conditions for preparing epoxy resins include: temperature of 40~80℃ and time of 100~500min; And / or, the conditions for preparing the curing agent include: a temperature of 40~60℃ and a time of 40~80min.

11. The application of the epoxy structural adhesive according to any one of claims 1 to 8 in sucker rod bonding.

12. A method for applying epoxy structural adhesive in sucker rod bonding, characterized in that: The method includes: The epoxy resin and curing agent in any one of the epoxy structural adhesives according to claims 1 to 8 are mixed and injected into a metal sleeve. Then, either end of the sucker rod is placed in the metal sleeve and heated to complete the curing.

13. The application method of the epoxy structural adhesive according to claim 12 in the bonding of pultruded sucker rod metal sleeves, characterized in that: The curing conditions include a temperature of 60~120℃ and a time of 2~6h.