Toughened modified epoxy adhesive with both heat resistance and toughness

Abstract

The present invention discloses a toughened modified epoxy adhesive that combines heat resistance with toughness. The epoxy adhesive comprises the following components by weight: 88-94 parts of a modified epoxy resin, 5-10 parts of a methacrylate compound, 0.002 parts of a polymerization inhibitor, and 1.0-2.0 parts of an initiator. The epoxy adhesive is a single component and offers the advantages of high bonding strength and toughness while also offering heat resistance and excellent flame retardancy.

Description

Technical Field

[0001] The present invention specifically relates to the technical field of adhesives, specifically a toughened modified epoxy glue that takes into account heat resistance, and in particular relates to a one-component epoxy glue with good heat resistance, high bonding strength, high toughness and high flame retardancy. The present invention is suitable for the technical field of one-component epoxy glue that has requirements for heat resistance, bonding, toughness and flame retardancy. Background Art

[0002] Epoxy resin is an organic polymer containing two or more epoxy groups in its molecule. These epoxy groups react with a curing agent through a ring-opening reaction to form a thermosetting polymer with a three-dimensional structure. Currently, the most widely used epoxy resin in the world is bisphenol A. However, due to the presence of multiple rigid benzene rings in the molecular structure of bisphenol A, epoxy resin is inherently brittle. Furthermore, due to its high degree of chemical crosslinking, it exhibits poor impact resistance and crack growth resistance. Therefore, toughening epoxy resin has long been a challenging topic in academia and industry. Chemists and materials scientists have conducted extensive research on toughening and modifying epoxy resins, such as by adding liquid rubbers, block polymers, and nano-toughening particles. Liquid rubbers and block polymers are excellent toughening and modification components, but their uniform mixing with epoxy resins requires compatibility between the materials. Typically, the end groups of the rubber are designed to react with the reactive groups of the epoxy resin. After the epoxy resin cures, the rubber block precipitates to form a microphase structure, achieving toughening. Alternatively, one block of the block polymer can be designed to be compatible with the epoxy resin. Before and after the epoxy resin cure reaction, the block polymer self-assembles within the epoxy resin to form a microphase structure, which provides toughening. However, some of the chain segments of both the liquid rubber and the block polymer are compatible with the epoxy resin cross-linked network, resulting in a decrease in the glass transition temperature or heat deformation temperature of the epoxy resin after curing. This lowers the material's operating temperature, resulting in a heat resistance of only 60-80°C (up to around 90°C before toughening modification), leading to problems such as glue failure and deformation at high temperatures.

[0003] Epoxidized soybean oil is a renewable and sustainable bio-based material. It is produced by oxidizing soybean oil with peroxides. Its low cost and readily available availability make it ideal for toughening and modifying rigid bisphenol A epoxy resins. However, the molecular chains of epoxidized soybean oil are long, non-polar alkyl chains, which impart high flexibility, a low melting point (-10°C to -3°C), and hydrophobicity. Meanwhile, the molecular structure of bisphenol A epoxy resins contains multiple ether bonds, making them highly polar. Direct mixing of bisphenol A epoxy resins and epoxidized soybean oil results in rapid phase separation due to the significant difference in their molecular polarity. Therefore, epoxidized soybean oil cannot be used directly as a toughening modifier to modify bisphenol A epoxy resins.

[0004] Therefore, how to take into account the heat resistance while toughening the epoxy adhesive is one of the technical problems that need to be solved urgently. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention proposes a toughened modified epoxy adhesive with both heat resistance and toughness.

[0006] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is as follows:

[0007] The toughened modified epoxy adhesive taking into account heat resistance comprises, by weight:

[0008] 88-94 parts of modified epoxy resin

[0009] 5-10 parts of methacrylate compound;

[0010] 0.002 parts of polymerization inhibitor;

[0011] 1.0-2.0 parts of initiator;

[0012] Wherein, the modified epoxy resin comprises, by weight:

[0013] 40-50 parts of bisphenol A epoxy resin,

[0014] Epoxidized soybean oil 5-20 parts,

[0015] 20-40 parts of hydroxyethyl methacrylate phosphate.

[0016] The preparation method of the modified epoxy resin comprises the following steps:

[0017] (1) At room temperature, bisphenol A epoxy resin (Phoenix brand, epoxy value 0.526 eq / 100 g) and epoxidized soybean oil (Shanghai MacLean Reagent Co., Ltd., molecular weight 975.4 g / mol, epoxy value 0.66 eq / 100 g) were mixed according to weight parts;

[0018] (2) Slowly add hydroxyethyl methacrylate phosphate in parts by weight under electric mechanical stirring. Continue stirring the mixture at room temperature for 30 to 90 minutes. Filter to obtain a modified epoxy resin.

[0019] Preferably, the methacrylate compound is at least one of hydroxyethyl methacrylate, hydroxypropyl methacrylate, 2-phenoxyethyl methacrylate, and isobornyl methacrylate.

[0020] Preferably, the polymerization inhibitor is at least one of hydroquinone, p-hydroxyanisole, 2,4,6-trinitrophenol, and benzoquinone.

[0021] Preferably, the initiator is at least one of benzoyl peroxide, tert-butyl perbenzoate, methyl ethyl ketone peroxide, diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, bis(4-tert-butylcyclohexyl) peroxydicarbonate, isopropyl benzene hydroperoxide, and diisopropyl benzene hydroperoxide.

[0022] Beneficial effects:

[0023] The epoxy glue of the present invention is a single component and has the advantages of high bonding strength and good toughness. At the same time, it takes into account heat resistance without reducing heat resistance and has excellent flame retardant effect.

[0024] The present invention can use methacrylate compounds to adjust the viscosity of the epoxy adhesive so as to meet the construction requirements of different application scenarios.

[0025] The methacrylate compound of the present invention is polymerized to obtain linear polymethacrylate, and the crosslinking density and flexibility of the cured glue can be conveniently adjusted by adjusting the type and amount of the methacrylate compound, thereby obtaining an epoxy glue with excellent comprehensive performance suitable for different construction scenarios.

[0026] The epoxy adhesive of the present invention is a single component and can be used directly during construction without the need for additional weighing and mixing, thereby improving construction efficiency and avoiding waste.

[0027] The epoxy adhesive of the present invention takes into account both heat resistance and toughness, and has heat resistance while improving mechanical properties such as toughness. This is due to the following reasons: 1) The modified epoxy resin molecule contains 8 methacrylate functional groups that can undergo free radical polymerization. At the same time, due to the presence of methyl groups in the methacrylate group, the glass transition temperature of the epoxy adhesive and better heat resistance are effectively improved by increasing the cross-linking density and the steric hindrance of the molecular chain rotation formed by the methyl group; 2) The modified epoxy resin molecule contains both a rigid polyphenyl ring structure and a flexible long-chain alkyl group, forming a tough structure that alternates between rigid and flexible at the microscopic level. Therefore, under the action of an initiator, the epoxy adhesive can copolymerize the methacrylate functional groups on the periphery of the modified epoxy resin molecule with the methacrylate compound, fix the tough structure of the modified epoxy resin that alternates between rigid and flexible, and make the epoxy adhesive have high strength and high toughness. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 .Infrared spectrum of modified epoxy resin used in Example 1.

[0029] Figure 2 .Shear strength-strain curves of Examples 1 to 4.

[0030] Figure 3 .Bending strength curves of Examples 1 to 4.

[0031] Figure 4 Critical strength factor K of Example 1-Example 4 IC .

[0032] Figure 5 . Vicat softening temperature of Examples 1 to 4.

[0033] Figure 6 .Oxygen index of Examples 1 to 4. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0035] Example 1

[0036] The toughened modified epoxy adhesive taking into account heat resistance comprises, by weight:

[0037] 88 parts of modified epoxy resin

[0038] 7 parts of hydroxyethyl methacrylate;

[0039] 3 parts of 2-phenoxyethyl methacrylate;

[0040] 0.002 parts of hydroquinone;

[0041] 1 part of tert-butyl perbenzoate;

[0042] 1 part diisopropyl peroxydicarbonate;

[0043] The modified epoxy resin used in Example 1 was prepared as follows:

[0044] (1) At room temperature, bisphenol A epoxy resin and epoxidized soybean oil are mixed;

[0045] (2) Slowly add hydroxyethyl methacrylate phosphate under electric mechanical stirring, wherein the weight ratio of bisphenol A epoxy resin, epoxy soybean oil, and hydroxyethyl methacrylate phosphate is 2:1:2. The mixture is stirred at room temperature for 30 minutes. Filter to obtain a modified epoxy resin.

[0046] Example 2

[0047] The toughened modified epoxy adhesive taking into account heat resistance comprises, by weight:

[0048] 94 parts of modified epoxy resin

[0049] 5 parts of hydroxypropyl methacrylate;

[0050] 0.001 parts of p-hydroxyanisole;

[0051] 0.001 part of benzoquinone;

[0052] 1.0 part of diisopropyl peroxydicarbonate;

[0053] The modified epoxy resin used in Example 2 was prepared as follows:

[0054] (1) At room temperature, bisphenol A epoxy resin and epoxidized soybean oil are mixed;

[0055] (2) Slowly add hydroxyethyl methacrylate phosphate under electric mechanical stirring, wherein the weight ratio of bisphenol A epoxy resin, epoxy soybean oil, and hydroxyethyl methacrylate phosphate is 5:1:3. The mixture is stirred at room temperature for 30 minutes. Filter to obtain a modified epoxy resin.

[0056] Example 3

[0057] The toughened modified epoxy adhesive taking into account heat resistance comprises, by weight:

[0058] 90 parts of modified epoxy resin

[0059] 7.5 parts of hydroxyethyl methacrylate;

[0060] 1.0 part of isobornyl methacrylate;

[0061] 0.002 parts of 2,4,6-trinitrophenol;

[0062] 0.5 part of bis(4-tert-butylcyclohexyl) peroxydicarbonate;

[0063] 1.0 part of diisopropylbenzene hydroperoxide.

[0064] The modified epoxy resin used in Example 3 was prepared as follows:

[0065] (1) At room temperature, bisphenol A epoxy resin and epoxidized soybean oil are mixed;

[0066] (2) Slowly add hydroxyethyl methacrylate phosphate under electric mechanical stirring, wherein the weight ratio of bisphenol A epoxy resin, epoxy soybean oil, and hydroxyethyl methacrylate phosphate is 5:2:2. The mixture is stirred at room temperature for 30 minutes. Filter to obtain a modified epoxy resin.

[0067] Example 4

[0068] The toughened modified epoxy adhesive taking into account heat resistance comprises, by weight:

[0069] 92 parts of modified epoxy resin

[0070] 4.0 parts of hydroxyethyl methacrylate;

[0071] 1.5 parts of 2-phenoxyethyl methacrylate;

[0072] 0.8 parts of isobornyl methacrylate;

[0073] 0.002 parts of hydroquinone;

[0074] 1.2 parts of diisopropyl peroxydicarbonate;

[0075] The modified epoxy resin used in Example 4 was prepared as follows:

[0076] (1) At room temperature, bisphenol A epoxy resin and epoxidized soybean oil are mixed;

[0077] (2) Slowly add hydroxyethyl methacrylate phosphate under electric mechanical stirring, wherein the weight ratio of bisphenol A epoxy resin, epoxy soybean oil, and hydroxyethyl methacrylate phosphate is 10:1:7. The mixture is stirred at room temperature for 30 minutes. Filter to obtain a modified epoxy resin.

[0078] Experimental verification

[0079] (1) Structural characterization of modified epoxy resin:

[0080] The structure of the modified epoxy resin used in Example 1 was characterized by Fourier transform infrared spectroscopy. The results are as follows: Figure 1 As shown. Figure 1 It can be seen that at 829cm -1 The characteristic absorption peak at 1026cm is the absorption peak of epoxy group. After modification with hydroxyethyl methacrylate phosphate, the absorption peak of the product here disappears, indicating that the epoxy group has completely reacted. -1 The characteristic absorption peak at 1634 cm is the stretching vibration absorption peak of POC in phosphate ester, indicating that the product contains the characteristic functional group structure of hydroxyethyl methacrylate phosphate; -1 The characteristic absorption peak of carbon-carbon double bond comes from the double bond of hydroxyethyl methacrylate phosphate; at 3423cm -1 The characteristic peak at is the characteristic absorption peak of the hydroxyl group generated by the addition reaction of phosphoric acid and epoxy group, indicating that hydroxyethyl methacrylate phosphate reacted with epoxidized soybean oil and bisphenol A epoxy resin, proving that the modified epoxy resin of Example 1 was successfully synthesized.

[0081] (2) Epoxy glue tensile test:

[0082] Apply epoxy glue evenly to both ends of the standard carbon steel sheet, and then cure it in a 130℃ forced air oven for 3 hours. Use a WYC-20KN universal electronic testing machine to test the tensile properties of the bonded steel sheet at a tensile speed of 1mm / min. The results are as follows: Figure 2 shown.

[0083] Depend on Figure 2 As can be seen, the tensile shear strengths of the splines of Examples 1-4 were 20.90 MPa, 9.76 MPa, 16.21 MPa, and 10.50 MPa, respectively, and their elongations at break were 4.46%, 2.04%, 2.94%, and 2.26%, respectively. This indicates that the splines of Examples 1-4 have good tensile shear properties, and the prepared epoxy adhesives can be used as structural adhesives.

[0084] (3) Bending properties of epoxy glue:

[0085] Pour the epoxy glue into the polytetrafluoroethylene mold and cure it at 130℃ for 3 hours. Demold it and perform a three-point bending test on it using a WYC-20KN universal electronic testing machine. The crossbeam movement speed is 1mm / min. The results are as follows: Figure 3 shown.

[0086] Depend on Figure 3 It can be seen that the shear strengths of the splines of Examples 1 to 4 are 114.75 MPa, 90.67 MPa, 108.75 MPa, and 104.34 MPa, respectively, indicating that the splines of Examples 1 to 4 have good bending properties.

[0087] Calculate the fracture strength factor K of each spline based on the bending strength and span of the spline IC (Because it is a parameter to measure the toughness of brittle materials, the larger its value is, the better the spline toughness is). The results are as follows Figure 4 As shown. Figure 4 It can be seen that the K of the splines of Examples 1 to 4 is IC The values ​​are 3.292 MPa·m 0.5 、3.215MPa·m 0.5 、3.399MPa·m 0.5 and 3.022 MPa·m 0.5 .

[0088] The K of the cured product of traditional bisphenol A epoxy resin and aromatic amine (such as 4,4'-diaminodiphenyl sulfone) is IC The value is 1.5-1.75MPa·m 0.5 about.

[0089] It shows that the products of Examples 1-4 have very good toughness.

[0090] (4) Vicat softening temperature test

[0091] The Vicat softening point of the cured epoxy adhesive was measured using a Vicat softening temperature tester. The test standard was GB / T1633-2000. The experimental load was 50N and the heating rate was set at 120℃ / h. The test results are as follows: Figure 5 shown.

[0092] Depend on Figure 5 It can be seen that the Vicat softening temperatures of the specimens of Examples 1-4 are 103.5°C, 138.5°C, 104.5°C and 144.4°C, respectively.

[0093] It shows that the products of Examples 1 to 4 have good heat resistance. That is, the products of Examples 1 to 4 of the present invention have very good heat resistance while taking into account mechanical properties.

[0094] In summary, Figures 2 to 5 The experimental results show that the products of Examples 1 to 4 have not reduced the heat resistance of epoxy glue while greatly improving its toughness (the heat resistance of the traditional rigid glue-cured strips is improved by about 45°C). The reason why the epoxy glue of the present invention takes into account both heat resistance and toughness is the addition of the modified epoxy resin synthesized for the first time. On the one hand, the modified epoxy resin molecules contain both a rigid polyphenyl ring structure and a flexible long-chain alkyl group, which can form a tough structure that is both rigid and flexible, so that the epoxy glue has high strength and high toughness; at the same time, the modified epoxy resin molecules contain multiple methacrylate functional groups and methyl groups that can undergo free radical polymerization, which can effectively improve the glass transition temperature and good heat resistance of the epoxy glue by increasing the cross-linking density and the steric hindrance of the molecular chain rotation formed by the methyl group. Therefore, the one-component epoxy glue of the present invention has the advantages of high bonding strength and good toughness while taking into account heat resistance.

[0095] (5) Oxygen index test:

[0096] According to the standard GB / T2406, the oxygen index of the modified epoxy resin was measured using an oxygen index tester from Chengde Testing Machine Co., Ltd. The flame retardancy of the specimens was evaluated by the oxygen index. The results are as follows: Figure 6 shown.

[0097] Depend on Figure 6 It can be seen that the oxygen index values ​​of the blank sample and the samples of Examples 1 to 4 are 24.5, 30.1, 25.3 and 26.7 respectively, indicating that the flame retardancy of the products of Examples 1 to 4 is very good.

[0098] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all fall within the scope of protection of the present invention. It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner unless there is any contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

Claims

1. A toughened modified epoxy adhesive with both heat resistance and heat resistance, characterized in that The following parts by weight are included: 88-94 parts of modified epoxy resin; 5-10 parts of methacrylate compound; 0.002 parts of polymerization inhibitor; 1.0-2.0 parts of initiator; Wherein, the modified epoxy resin comprises, by weight: 40-50 parts of bisphenol A epoxy resin, Epoxidized soybean oil 5-20 parts, 20-40 parts of hydroxyethyl methacrylate phosphate, Furthermore, the modified epoxy resin is prepared as follows: (1) At room temperature, bisphenol A epoxy resin and epoxidized soybean oil are mixed according to weight components; (2) Under stirring conditions, slowly add hydroxyethyl methacrylate phosphate as the weight component, and then continue stirring for 30 to 90 minutes, and then filter to obtain the modified epoxy resin.

2. The toughened modified epoxy adhesive having both heat resistance and heat resistance according to claim 1, characterized in that: The methacrylate compound is at least one of hydroxyethyl methacrylate, hydroxypropyl methacrylate, 2-phenoxyethyl methacrylate, and isobornyl methacrylate.

3. The toughened modified epoxy adhesive with heat resistance according to claim 1, characterized in that: The polymerization inhibitor is at least one of hydroquinone, p-hydroxyanisole, 2,4,6-trinitrophenol and benzoquinone.

4. The toughened modified epoxy adhesive having both heat resistance and heat resistance according to claim 1, characterized in that: The initiator is at least one of benzoyl peroxide, tert-butyl perbenzoate, methyl ethyl ketone peroxide, diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, bis(4-tert-butylcyclohexyl) peroxydicarbonate, cumene hydroperoxide, and diisopropyl peroxide.

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