High-strength epoxy resin film with ultra-high toughness before curing and preparation method thereof

Abstract

The present invention relates to the technical field of adhesive materials, and in particular to a high-strength epoxy resin film with ultra-high toughness before curing and a preparation method thereof, wherein the film is composed of an epoxy resin, a curing agent, an accelerator, and a toughening agent; the weight ratio between the components is: per 100 parts of epoxy resin, the curing agent is 5-20 parts; the accelerator is 3-10 parts; and the toughening agent is 5-15 parts. By adjusting the ratio between the components, the present invention not only has good fluidity and operability before curing, but also facilitates the control of the thickness and shape of the film, and can be used in metal bonding specimens of various shapes, to a certain extent reducing waste, saving costs, and expanding the scope of use of the film; after curing, it shows higher bonding strength, improves the adhesion effect of the epoxy resin film on the surface of the metal material, and increases the bonding strength of the epoxy resin film to the metal material.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesive materials, and in particular to a high-strength epoxy resin film with ultra-high toughness before curing and a preparation method thereof. Background Art

[0002] With the rapid development of technologies in aerospace, automobiles, electronics and other fields, the demand for high-performance hot melt adhesive films is increasing. Epoxy resin film is a thermosetting hot melt adhesive film containing a latent curing agent. When heated to a certain temperature, the latent curing agent and epoxy resin cross-link and polymerize, the degree of cross-linking gradually increases, and it is finally fully cured and formed, playing the role of bonding and protection. Because epoxy resin film has the inherent advantages of epoxy adhesives such as low curing shrinkage, dimensional stability, excellent electrical properties, and excellent resistance to chemical media, and compared with liquid adhesives, epoxy resin film also has unique advantages in ease of use. It has very broad application prospects in many fields such as electronics, communications, automobiles, aerospace, machinery, ships, rail transportation, wind power generation and construction, and is highly favored by the industry. At present, there are many varieties of epoxy resin films available, but they often have problems such as difficulty in achieving both strength and toughness, insufficient initial adhesion or toughness at room temperature, and the need for high-temperature attachment.

[0003] This is in response to emerging market demands for epoxy resin films, specifically when used as a bonding and fixing component between two device test pieces. These films must exhibit good viscosity and elasticity at room temperature, along with excellent shape retention and stability. They can be directly applied to one device test piece, with the other naturally pressed on top, and then post-cured. Furthermore, they must exhibit high bond strength after curing to meet the requirements of the bonded test pieces. Summary of the Invention

[0004] To address the problems of current epoxy resin films, such as difficulty achieving both strength and toughness, insufficient initial tack or toughness at room temperature, and the need for high-temperature attachment, the present invention provides a high-strength epoxy resin film with ultra-high toughness before curing and a method for preparing the same. The present invention discloses an epoxy resin film with a simple preparation process, high strength, a certain initial tack and excellent toughness at room temperature, and exhibits high bonding strength after curing, improving the adhesion of the epoxy resin film to the surface of metal materials and increasing the bonding strength of the epoxy resin film to the metal material, thereby meeting the current market demand for epoxy resin films.

[0005] The present invention is achieved through the following technical solution: a high-strength epoxy resin film with ultra-high toughness before curing, wherein the film is composed of an epoxy resin, a curing agent, an accelerator and a toughening agent; the weight ratio between the components is: per 100 parts of epoxy resin, the amount of curing agent is 5-20 parts; the amount of accelerator is 3-10 parts; and the amount of toughening agent is 5-15 parts.

[0006] As a further improvement of the technical solution of the present invention, the epoxy resin is selected from one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, hydrogenated bisphenol A epoxy resin, bisphenol AF epoxy resin, naphthalene-containing epoxy resin, and novolac epoxy resin.

[0007] As a further improvement of the technical solution of the present invention, the curing agent is selected from one or more of modified aliphatic amine curing agents, aromatic diamine curing agents, dicyandiamide curing agents, imidazole curing agents, and organic acid anhydride curing agents.

[0008] As a further improvement of the technical solution of the present invention, the accelerator includes a first accelerator and a second accelerator, and the first accelerator and the second accelerator are selected from any two of imidazole accelerators and their derivatives, organic phosphorus compounds, amine accelerators, quaternary ammonium salt accelerators, and organic urea accelerators.

[0009] As a further improvement to the technical solution of the present invention, the weight ratio of the first accelerator to the second accelerator is 1:1-3:1.

[0010] As a further improvement of the technical solution of the present invention, the toughening agent is obtained by a mercapto-ene click chemical reaction between a modifier and an allyl epoxy resin.

[0011] As a further improvement of the technical solution of the present invention, the modifier is one or more of 4-fluorothiophenol, 2,3,5,6-tetrafluorothiophenol, pentafluorothiophenol, 2-amino-3-fluorothiophenol, 2-(trifluoromethoxy)thiophenol, and 4-bromo-2-fluorothiophenol.

[0012] As a further improvement of the technical solution of the present invention, the weight ratio of the modifier to the allyl epoxy resin is 1:9-3:7.

[0013] As a further improvement of the technical solution of the present invention, the specific preparation method of the toughening agent is: utilizing the principle of thiol-ene click chemistry reaction, the modifier is reacted with the double bond in the allyl epoxy resin, the temperature is controlled to 80°C, under the condition of magnetic stirring, assisted by ultraviolet light, and the reaction is carried out for 1-2 hours to obtain the final product.

[0014] The present invention further provides a method for preparing a high-strength epoxy resin film having ultra-high toughness before curing, comprising the following steps:

[0015] 1) adding a toughening agent to an epoxy resin in parts by weight, and stirring the mixture at a high speed under a temperature of ≥140° C. to obtain a prepolymer resin;

[0016] 2) slowly adding a curing agent to the prepolymer resin obtained in step 1), and stirring at high speed to mix evenly under the condition of controlling the temperature to be ≤ 60° C.;

[0017] 3) Slowly adding an accelerator to the mixture obtained in step 2), and stirring at high speed to mix evenly under the condition of controlling the temperature to ≤ 60° C.;

[0018] 4) The mixture obtained in step 3) is placed in the glue tank of the glue coating machine, transferred to the corresponding release paper by a roller, and then the finished film is cooled and coated by a cooling device.

[0019] The high-strength epoxy resin film with ultra-high toughness before curing and the preparation method thereof provided by the present invention have the following advantages over the prior art:

[0020] 1) The present invention adopts thiol-ene click chemistry to synthesize the toughening agent, which has a simple process, does not require solvent, is green and environmentally friendly, has high yield, and does not require post-processing;

[0021] 2) By adding a toughening agent and blending it with the epoxy resin, the film has excellent elongation and initial adhesion at room temperature before curing;

[0022] 3) By adjusting the ratio between the components, not only does it have good fluidity and workability before curing, but it also facilitates the control of film thickness and shape, and can be used in metal bonding specimens of various shapes, which can reduce waste to a certain extent, save costs, and expand the scope of application of the film; after curing, it shows higher bonding strength, improves the adhesion effect of the epoxy resin film on the surface of the metal material, and increases the bonding strength of the epoxy resin film to the metal material;

[0023] 4) During the preparation of the epoxy resin film, the mixture is mixed with the curing agent and toughening agent at a temperature below 70°C. Under this condition, the components have good fluidity and are ensured to be fully mixed;

[0024] 5) In addition, the preparation method has the advantages of simplicity and short preparation cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0027] Figure 1 Schematic diagram of the synthesis of the toughening agent in the present invention.

[0028] Figure 2 This is the viscosity-temperature curve of the epoxy resin film prepared in Example 2 of the present invention.

[0029] Figure 3 This is the isothermal curing kinetics curve of the epoxy resin film prepared in Example 1 of the present invention.

[0030] Figure 4 This is the loss tangent-temperature curve of the epoxy resin film prepared in Example 3 of the present invention after curing. DETAILED DESCRIPTION

[0031] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features therein can be combined with each other.

[0032] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all the embodiments.

[0033] The present invention provides a specific embodiment of a high-strength epoxy resin film having ultra-high toughness before curing. The film is composed of an epoxy resin, a curing agent, an accelerator, and a toughening agent. The weight ratio of the components is as follows: per 100 parts of epoxy resin, the curing agent is used in an amount of 5-20 parts; the accelerator is used in an amount of 3-10 parts; and the toughening agent is used in an amount of 5-15 parts.

[0034] In the weight ratio of the above components, preferably, based on 100 parts of epoxy resin, the amount of curing agent is 10 parts; the amount of accelerator is 4 parts; and the amount of toughening agent is 10 parts.

[0035] In one example provided by the present invention, the epoxy resin is selected from one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, hydrogenated bisphenol A epoxy resin, bisphenol AF epoxy resin, naphthalene-containing epoxy resin, and novolac epoxy resin. Preferably, the epoxy resin is bisphenol S epoxy resin.

[0036] In another example provided by the present invention, the curing agent is selected from one or more of a modified aliphatic amine curing agent, an aromatic diamine curing agent, a dicyandiamide curing agent, an imidazole curing agent, and an organic acid anhydride curing agent. Among them, the modified aliphatic amine curing agent can be selected from ketimine, etc.; the aromatic diamine curing agent can be selected from diaminodiphenyl sulfone (DDS), diaminodiphenylmethane (DDM), m-phenylenediamine (mPDA), etc.; the dicyandiamide curing agent can be selected from dicyandiamide, 1-o-tolylbiguanide, phenylbiguanide, etc.; the imidazole curing agent can be selected from 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, etc.; the organic acid anhydride curing agent can be selected from phthalic anhydride, maleic anhydride, hexahydrophthalic anhydride, etc.

[0037] Preferably, the curing agent is diaminodiphenyl sulfone (DDS).

[0038] In one example provided by the present invention, the accelerator includes a first accelerator and a second accelerator, and the first accelerator and the second accelerator are selected from any two of imidazole accelerators and their derivatives, organophosphorus compounds, amine accelerators, quaternary ammonium salt accelerators, and organic urea accelerators. Preferably, the first accelerator and the second accelerator are different types of accelerators, such as the first accelerator is an imidazole accelerator and its derivatives, and the second accelerator is another type of accelerator. Among them, imidazole accelerators and their derivatives can be selected from 2-phenylimidazole, 2-ethyl-4-methylimidazole, etc.; organophosphorus compounds can be selected from triphenylphosphine, diphosphomethane, etc.; amine accelerators can be selected from N-methyldiethanolamine, triethylamine, diethylenetriamine, etc.; quaternary ammonium salt accelerators can be selected from benzyltriethylammonium chloride; organic urea accelerators can be selected from N,N'-dimethylurea, 3-phenyl-1,1-dimethylurea, 3, 3'-(4-methyl-1,3-phenylene)bis(1,1-dimethylurea), etc.

[0039] Preferably, the first accelerator is 2-phenylimidazole, and the second accelerator is N,N'-dimethylurea.

[0040] In another example provided by the present invention, the weight ratio of the first accelerator to the second accelerator is 1:1-3:1.

[0041] In one example provided by the present invention, the toughening agent is obtained by a mercapto-ene click chemical reaction between a modifier and an allyl epoxy resin.

[0042] In another example provided by the present invention, the modifier is one or more of 4-fluorothiophenol, 2,3,5,6-tetrafluorothiophenol, pentafluorothiophenol, 2-amino-3-fluorothiophenol, 2-(trifluoromethoxy)thiophenol, and 4-bromo-2-fluorothiophenol. Preferably, the modifier is pentafluorothiophenol.

[0043] In an example provided by the present invention, the weight ratio of the modifier to the allyl epoxy resin is 1:9-3:7.

[0044] In another example provided by the present invention, the specific preparation method of the toughening agent is: utilizing the principle of thiol-ene click chemistry reaction, the modifier is reacted with the double bond in the allyl epoxy resin, the temperature is controlled at 80°C, under the condition of magnetic stirring, assisted by ultraviolet light, and the reaction is carried out for 1-2 hours to obtain the final product.

[0045] The present invention also provides a method for preparing a high-strength epoxy resin film having ultra-high toughness before curing, comprising the following steps:

[0046] 1) Add toughening agent to epoxy resin by weight, and stir at high speed to mix evenly under the condition of controlling the temperature to ≥140°C;

[0047] 2) Slowly add the curing agent to the mixture obtained in the previous step, and stir at high speed to mix evenly under the condition of controlling the temperature to ≤ 60°C;

[0048] 3) Slowly add the accelerator to the mixture obtained in the previous step, and stir at high speed to mix evenly under the condition of controlling the temperature to ≤ 60°C;

[0049] 4) The mixture obtained in the previous step is placed in the glue tank of the glue coating machine, transferred to the corresponding release paper by a roller, and then the finished film is cooled and coated by a cooling device.

[0050] The following are specific examples of the present invention. All raw materials used in the examples are commercially available. Example 1

[0051] A high-strength epoxy resin film with ultra-high toughness before curing, comprising an epoxy resin, a curing agent, an accelerator, and a toughening agent; the preparation method thereof is as follows:

[0052] ① Add 1 part of pentafluorobenzenethiol to 9 parts of allyl epoxy resin by weight, control the temperature to 80°C, and react for 1 hour under magnetic stirring and UV irradiation to obtain a toughening agent;

[0053] ② Add 10 parts of toughening agent to 100 parts of bisphenol S epoxy resin by weight, and stir mechanically at 450 rpm at 150° C. until the mixture is completely mixed to obtain a prepolymer resin;

[0054] ③ Place the prepolymer resin in a torque rheometer, set the initial speed to 20 rpm, slowly add 10 parts of diaminodiphenyl sulfone (DDS), and mix evenly at 50°C and 80 rpm;

[0055] ④ Slowly add 3 parts of 2-phenylimidazole and 1 part of N,N'-dimethylurea to the mixture in step ③ and mix well at 50°C and 80 rpm;

[0056] ⑤Put the mixture obtained in step ④ into the glue tank of the glue coating machine, transfer it to the corresponding release paper through a roller, and then cool and coat the finished film through a cooling device.

[0057] The resulting epoxy resin film had an elongation of 500% when tested on a universal testing machine before curing, which is much higher than other epoxy resin films on the market. For example, the elongation at break of J351 film before curing is 200%, and the elongation at break of HY-JM-05-40 epoxy resin film before curing is 50%.

[0058] The isothermal curing kinetic curves of the epoxy resin film of this embodiment at different temperatures (80, 85, 90 and 100°C) are shown in FIG. Figure 3 The curve shown in Figure 1 is derived from differential scanning calorimetry testing. This curve demonstrates that the epoxy resin film begins to cure when the curing temperature is above 80°C, and the curing rate significantly increases with increasing curing temperature. To ensure that the epoxy resin film cures quickly while maintaining its excellent properties, the preferred curing process is to first cure at 80°C for one hour, followed by curing at 125°C for four hours.

[0059] The preparation method of Example 1 was repeated, and the prepared epoxy resin film was cured (curing conditions: curing at 80°C for 1 hour, followed by curing at 125°C for 4 hours). The glass transition temperature of the epoxy resin film of this example was tested using a dynamic thermal mechanical analyzer, and the glass transition temperature was found to be 128°C. Referring to GB / T 7124-2008, the epoxy resin film was cut into corresponding sizes and then adhered to a 6061 aluminum alloy (the aluminum alloy was pretreated according to phosphoric acid anodizing in accordance with HB / Z197-1991) adhesive to obtain a single lap shear specimen. The tensile shear strength of the specimen was tested using a universal testing machine and was found to be 24 MPa. Example 2

[0060] A high-strength epoxy resin film with ultra-high toughness before curing, comprising an epoxy resin, a curing agent, an accelerator, and a toughening agent; the preparation method thereof is as follows:

[0061] ① Add 3 parts of 4-fluorobenzenethiol to 12 parts of allyl epoxy resin by weight, control the temperature to 80°C, and react for 1.5 hours under magnetic stirring and UV irradiation to obtain a toughening agent;

[0062] ② Add 15 parts of toughening agent to 100 parts of bisphenol A epoxy resin by weight, and mix thoroughly with mechanical stirring at 140°C and 500 rpm to obtain a prepolymer resin;

[0063] ③ Place the prepolymer resin in a speed rheometer, set the initial speed to 10 rpm, slowly add 15 parts of triethylenetetramine, and mix evenly at 60°C and 60 rpm;

[0064] ④ Slowly add 4 parts of N-methyldiethanolamine and 2 parts of triethylamine to the mixture in step ③ and mix well at 60°C and 60rpm;

[0065] ⑤Put the mixture obtained in step ④ into the glue tank of the glue coating machine, transfer it to the corresponding release paper through a roller, and then cool and coat the finished film through a cooling device.

[0066] The resulting epoxy resin film had an elongation of 700% when tested on a universal testing machine before curing, which is much higher than other epoxy resin films on the market. For example, the elongation at break of J351 film before curing is 200%, and the elongation at break of HY-JM-05-40 epoxy resin film before curing is 50%.

[0067] The viscosity-temperature curve of the epoxy resin film obtained (such as Figure 2 The results show that the film has ultra-high viscosity at room temperature, so it can maintain its solid form at room temperature. As the temperature increases, the viscosity of the epoxy resin film decreases continuously, showing better processability.

[0068] After curing (curing conditions: curing at 80°C for 1 hour, followed by curing at 125°C for 4 hours), the glass transition temperature of the epoxy resin film of this example was tested using a dynamic thermal mechanical analyzer and found to be 130°C. Referring to GB / T 7124-2008, the epoxy resin film was cut into corresponding sizes and then bonded to a 6061 aluminum alloy (the aluminum alloy was pretreated according to phosphoric acid anodizing in accordance with HB / Z 197-1991) to obtain a single lap shear specimen. The tensile shear strength of the specimen was tested using a universal testing machine and was found to be 21 MPa. Example 3

[0069] A high-strength epoxy resin film with ultra-high toughness before curing, comprising an epoxy resin, a curing agent, an accelerator, and a toughening agent; the preparation method thereof is as follows:

[0070] ① Add 1.5 parts of 4-fluorobenzenethiol to 3.5 parts of allyl epoxy resin by weight, control the temperature to 80°C, and react for 2 hours under magnetic stirring and UV irradiation to obtain a toughening agent;

[0071] ② Add 5 parts of toughening agent to 100 parts of phenolic epoxy resin by weight, and stir mechanically at 400 rpm at 145°C until completely mixed to obtain a prepolymer resin;

[0072] ③ Place the prepolymer resin in a speed rheometer, set the initial speed to 20 rpm, slowly add 8 parts of dicyandiamide, and mix evenly at room temperature and 40 rpm;

[0073] ④ Slowly add 6 parts of diethylenetriamine and 2 parts of 2-ethyl-4-methylimidazole to the mixture in step ③ and mix well at room temperature and 40 rpm;

[0074] ⑤Put the mixture obtained in the previous step into the glue tank of the glue coating machine, transfer it to the corresponding release paper through a roller, and then cool and coat the finished film through a cooling device.

[0075] The resulting epoxy resin film had an elongation of 800% when tested on a universal testing machine before curing, which is much higher than other epoxy resin films on the market. For example, the elongation at break of J351 film before curing is 200%, and the elongation at break of HY-JM-05-40 epoxy resin film before curing is 50%.

[0076] After curing (curing conditions: curing at 80°C for 1 hour and then curing at 125°C for 4 hours), the glass transition temperature of the epoxy resin film of this embodiment was tested by dynamic thermal mechanical analyzer, and the glass transition temperature was found to be 133°C (as shown in FIG. Figure 4 ), indicating that the epoxy resin film of this embodiment has excellent temperature resistance and has the potential for long-term use at this temperature. Referring to GB / T 7124-2008, the epoxy resin film was cut into corresponding sizes and then adhered to a 6061 aluminum alloy (the aluminum alloy pretreatment method was phosphoric acid anodizing according to HB / Z 197-1991) adhesive member to obtain a single lap shear specimen. The tensile shear strength of the specimen tested using a universal testing machine was 20 MPa.

[0077] The above description is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Although detailed descriptions have been made with reference to the aforementioned embodiments, those skilled in the art should understand that they may still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents; and such modifications or replacements do not deviate from the essence of the corresponding technical solutions within the scope of the technical solutions of the embodiments, and they should all be included in the scope of protection of the claims.

Claims

1. A method for preparing a high-strength epoxy resin film having ultra-high toughness before curing, characterized in that: The following steps are involved: 1) adding a toughening agent to an epoxy resin in parts by weight, and stirring the mixture at a high speed under a temperature of ≥140° C. to obtain a prepolymer resin; 2) slowly adding a curing agent to the prepolymer resin obtained in step 1), and stirring at high speed to mix evenly under the condition of controlling the temperature to be ≤ 60° C.; 3) Slowly adding an accelerator to the mixture obtained in step 2), and stirring at high speed to mix evenly under the condition of controlling the temperature to ≤ 60° C.; 4) placing the mixture obtained in step 3) into the glue tank of the glue coating machine, transferring it to the corresponding release paper by a roller, and then cooling and laminating the finished film by a cooling device; The adhesive film is composed of an epoxy resin, a curing agent, an accelerator and a toughening agent; the weight ratio between the components is: per 100 parts of epoxy resin, the curing agent is used in an amount of 5-20 parts; the accelerator is used in an amount of 3-10 parts; and the toughening agent is used in an amount of 5-15 parts; the toughening agent is obtained by a thiol-ene click chemical reaction between a modifier and an allyl epoxy resin, and the modifier is one or more of 4-fluorothiophenol, 2,3,5,6-tetrafluorothiophenol, pentafluorothiophenol, 2-amino-3-fluorothiophenol, 2-(trifluoromethoxy)thiophenol, and 4-bromo-2-fluorothiophenol.

2. The method for preparing a high-strength epoxy resin film having ultra-high toughness before curing according to claim 1, characterized in that: The epoxy resin is selected from one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, hydrogenated bisphenol A epoxy resin, bisphenol AF epoxy resin, naphthalene-containing epoxy resin, and novolac epoxy resin.

3. The method for preparing a high-strength epoxy resin film having ultra-high toughness before curing according to claim 1, characterized in that: The curing agent is selected from one or more of modified aliphatic amine curing agents, aromatic diamine curing agents, dicyandiamide curing agents, imidazole curing agents, and organic acid anhydride curing agents.

4. The method for preparing a high-strength epoxy resin film having ultra-high toughness before curing according to claim 1, characterized in that: The accelerator includes a first accelerator and a second accelerator, and the first accelerator and the second accelerator are selected from any two of imidazole accelerators and their derivatives, organic phosphorus compounds, amine accelerators, quaternary ammonium salt accelerators, and organic urea accelerators.

5. The method for preparing a high-strength epoxy resin film having ultra-high toughness before curing according to claim 4, characterized in that: The weight ratio of the first accelerator to the second accelerator is 1:1-3:

1.

6. The method for preparing a high-strength epoxy resin film having ultra-high toughness before curing according to claim 1, characterized in that: The weight ratio of the modifier to the allyl epoxy resin is 1:9-3:

7.

7. The method for preparing a high-strength epoxy resin film having ultra-high toughness before curing according to claim 1, characterized in that: The specific preparation method of the toughening agent is: using the principle of mercapto-ene click chemistry reaction, the modifier reacts with the double bond in the allyl epoxy resin, controlling the temperature to 80°C, under magnetic stirring conditions, assisted by ultraviolet light, and reacting for 1-2 hours to obtain the final product.

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