A transparent, conductive and flame-retardant epoxy glue

Abstract

The application discloses transparent, conductive and flame-retardant epoxy glue. The epoxy glue comprises two components A and B. The component A is epoxy resin (E-51) 100 parts. The component B is modified polyether amine curing agent 40-50 parts, specifically polyether amine compound 30-40 parts, phosphate ester ionic liquid 5-10 parts and 2,4,6-tris(dimethylaminomethyl) phenol (DMP-30) 1-3 parts. The epoxy glue has good transparency, high bonding strength, and obvious improvement in conductivity and flame retardance.

Description

Technical Field

[0001] This invention specifically relates to the field of adhesive technology, and particularly to a transparent, conductive, and flame-retardant epoxy adhesive, suitable for the electronic and electrical industries where transparency, static electricity, and flame retardancy are required. Background Technology

[0002] The rapid development of the automotive, electrical, and electronics industries is driving continuous progress in electronic and circuit control systems, while also raising the bar for their stability. During the operation of electronic devices, static electricity is generated due to friction, electromagnetic field changes, and other factors. This static electricity has a very high voltage, and its discharge can cause short circuits, severely damaging electronic and electrical equipment and affecting its normal operation.

[0003] In industry, antistatic agents are commonly used to eliminate static electricity hazards. Antistatic agents are typically ionic compounds with molecular structures similar to surfactants. Commonly involved polar groups include anions of carboxylic acids, sulfonic acids, sulfuric acids, and phosphoric acids, or cationic amine salts, quaternary ammonium salts, or polyethylene glycol; common nonpolar groups are long-chain alkyl groups. Water, alcohols, or other organic solvents are generally used as solvents or dispersants for antistatic agents, which are then uniformly coated onto the surface of the material requiring antistatic properties. The hydrophilic groups of the antistatic agent absorb trace amounts of moisture from the surrounding environment, forming a conductive layer that conducts static electricity away. Furthermore, antistatic agents can be added internally to the material requiring antistatic properties to obtain long-lasting antistatic materials. However, achieving a long-term antistatic effect depends on the structure and compatibility between the antistatic agent and the added material.

[0004] Because epoxy adhesive is a polar material, the types of antistatic agents that can be added to epoxy adhesives are currently very limited due to the molecular structure and properties of antistatic agents. Traditional conductive adhesives achieve conductivity by adding conductive particles (such as nanoscale silver powder or copper powder) to the base adhesive. However, because the density of the base adhesive differs greatly from that of the conductive metal particles, the particles naturally sink, resulting in a generally low overlap rate of conductive particles in the adhesive layer, leading to increased resistance. Furthermore, the refractive index of the conductive metal particles differs significantly from that of the adhesive matrix, causing the conductive adhesive to become less transparent, or even opaque. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a transparent, conductive, and flame-retardant epoxy adhesive.

[0006] To achieve the above-mentioned objectives, the technical solution of the present invention is as follows:

[0007] A transparent, conductive, and flame-retardant epoxy adhesive, composed of two components, A and B, comprising, by weight:

[0008] Component A: 100 parts of epoxy resin (E-51);

[0009] Component B: 40-50 parts of modified polyetheramine curing agent, wherein the modified polyetheramine curing agent comprises, by weight, the following:

[0010] 30-40 parts of polyetheramine compound,

[0011] 5-10 parts of phosphate ester ionic liquid

[0012] DMP-30 1-3 copies,

[0013] Phosphate ester ionic liquids are shown in Formula I:

[0014]

[0015] The preparation method of phosphate ester ionic liquids includes the following steps:

[0016] (1) Mix diethyl(3-bromopropyl)phosphonate and 1-butylimidazole in a molar ratio of 1:1, add excess toluene to dissolve completely, and then react with stirring at 95°C for 24 h to obtain the product.

[0017] (2) The product was concentrated using a rotary evaporator and then vacuum dried at 50°C for 24 hours to obtain a phosphate ester ionic liquid.

[0018] Preferably, the polyetheramine compound is at least one selected from polyetheramine D230, polyetheramine 403, 3,6-dioxo-1,10-octadecanediamine, 4,7-dioxo-1,10-decanediamine, 3,6,9-trioxo-1,12-undecanediamine, and 4,7,10-trioxo-1,13-tetanediamine.

[0019] Beneficial effects:

[0020] The epoxy adhesive of this invention features good transparency, high bonding strength, and significantly improved conductivity and flame retardant properties. The ionic liquid in the epoxy adhesive exhibits good compatibility with the epoxy-polyetheramine curing system, absorbs trace amounts of moisture from the surrounding environment to eliminate static electricity, and simultaneously displays certain flame retardant properties, making it more suitable for applications in the electronics and electrical industries that require transparency, conductivity, and flame retardancy.

[0021] (1) The ionic liquid has good compatibility with the epoxy-polyetheramine system. The resulting epoxy-modified polyetheramine adhesive is transparent before and after curing, which meets the requirements for good appearance and display of electronic components. In addition, the phosphate ester ionic liquid is dispersed at the molecular level in the epoxy adhesive, and there is no problem of uneven dispersion and unstable conductivity of traditional metal conductive particles in the adhesive. (2) The phosphate ester ionic liquid can absorb water molecules in the environment to form ionic liquid hydrated molecules, which avoids the combination of water molecules with carbon dioxide that has penetrated into the adhesive layer to form carbonic acid (H2CO3). This is because carbonic acid reacts with alkaline organic amines to formamide, causing the epoxy-organic amine adhesive surface to "whiten". (3) Compared with the sample without phosphate ester ionic liquid, the surface resistance and volume resistance of the epoxy-modified polyetheramine cured adhesive block decreased by two orders of magnitude, and the oxygen index increased by about 2%. Attached Figure Description

[0022] Figure 1 Infrared spectrum of phosphate ester ionic liquid.

[0023] Figure 2 Transparency characterization of Examples 1-4.

[0024] Figure 3 Tensile strength of Examples 1-4.

[0025] Figure 4 Shear strength of Examples 1-4.

[0026] Figure 5 Oxygen index of Examples 1-4. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1

[0029] A transparent, conductive, and flame-retardant epoxy adhesive, composed of two components, A and B, comprising, by weight:

[0030] Component A: 100 parts of epoxy resin (E-51);

[0031] Component B: 40 parts of modified polyetheramine curing agent;

[0032] Component B includes:

[0033] 30 parts of 3,6-dioxo-1,10-octadecanediamine

[0034] 7 parts of phosphate ester ionic liquid

[0035] 3 copies of DMP-30.

[0036] Example 2

[0037] A transparent, conductive, and flame-retardant epoxy adhesive, composed of two components, A and B, comprising, by weight:

[0038] Component A: 100 parts of epoxy resin (E-51);

[0039] Component B: 50 parts of modified polyetheramine curing agent;

[0040] Component B includes:

[0041]

[0042]

[0043] Example 3

[0044] A transparent, conductive, and flame-retardant epoxy adhesive, composed of two components, A and B, comprising, by weight:

[0045] Component A: 100 parts of epoxy resin (E-51);

[0046] Component B: 45 parts of modified polyetheramine curing agent;

[0047] Component B includes:

[0048]

[0049] Example 4

[0050] A transparent, conductive, and flame-retardant epoxy adhesive, composed of two components, A and B, comprising, by weight:

[0051] Component A: 100 parts of epoxy resin (E-51);

[0052] Component B: 50 parts of modified polyetheramine curing agent;

[0053] Component B includes:

[0054]

[0055] The phosphate-containing ionic liquid used in the above embodiments is shown in Formula I:

[0056]

[0057] Furthermore, it was prepared according to the following method,

[0058] (1) Accurately weigh 1.0 mol of diethyl(3-bromopropyl)phosphonate and 1.0 mol of 1-butylimidazole into a dry three-necked flask, and add toluene to control the mass percentage concentration of the solution at 25%-33%. React under stirring and at 95℃ for 24 h to obtain the product;

[0059] (2) The product was concentrated using a rotary evaporator and then vacuum dried at 50°C for 24 hours to obtain a phosphate ester ionic liquid.

[0060] Experimental verification

[0061] (1) Structural characterization:

[0062] The structures of the phosphate-containing ionic liquids used in Examples 1-4 were characterized using Fourier transform infrared spectroscopy, and the results are as follows: Figure 1 As shown. By Figure 1 It can be seen that at 635cm -1 The characteristic absorption peak at 1011 cm⁻¹ is the C-Br absorption peak of diethyl(3-bromopropyl)phosphonate; -1 The characteristic absorption peak at 1225 cm⁻¹ is the stretching vibration absorption peak of POC in diethyl(3-bromopropyl)phosphonate; -1 The characteristic absorption peak at 1620 cm⁻¹ is the characteristic absorption peak of P=O in diethyl(3-bromopropyl)phosphonate; -1 The characteristic absorption peak at 3055 cm⁻¹ is the vibrational absorption peak of the C=N ring on the imidazole ring; -1 The characteristic peak at 1496 cm⁻¹ is due to the CH stretching vibration of the imidazole ring side chain. -1 The characteristic absorption peak at the point is the absorption peak of the ammonium salt CN in the phosphate-containing ionic liquid molecule, indicating that the diethyl (3-bromopropyl)phosphonate and 1-butylimidazole completed the quaternization reaction under heating conditions, proving that the phosphate-containing ionic liquid was successfully synthesized.

[0063] (2) Viscosity:

[0064] The epoxy-modified polyetheramine curing agent was weighed according to the mass ratio and mixed for 10 minutes; the viscosity of the mixture was measured using a viscometer. The viscosities of Examples 1-4 were between 800-1000 mPa·s, which are similar to the viscosities of the epoxy-polyetheramine system before the addition of the ionic liquid. This indicates that the presence of ionic liquid in the components does not affect the application performance of the product.

[0065] (3) Sample transparency:

[0066] Weigh and mix the epoxy-modified polyetheramine curing agent according to the mass ratio for 10 minutes; then remove air bubbles from the mixture in a vacuum drying oven at 30℃. Pour into a PTFE mold, degas, and cure at room temperature for 48 hours. After demolding, a transparent sample block with a diameter of approximately 50 mm and a thickness of 6-8 mm is obtained. Figure 2 .

[0067] Depend on Figure 2 As can be seen, the epoxy-modified polyetheramine curing system exhibits excellent transparency, allowing clear visibility of the ink marks on the bottom backing paper. This is because the phosphate-containing ionic liquid of this invention can absorb water molecules from the environment to form hydrated ionic liquid molecules, preventing water molecules from combining with carbon dioxide that has penetrated into the adhesive layer to form carbonic acid (H2CO3). This avoids the formamide reaction that occurs between traditional carbonic acid and alkaline organic amines, which would otherwise cause a "whitening" phenomenon on the surface of the epoxy-organic amine adhesive. In other words, the ionic liquid in this invention exhibits good compatibility with the epoxy-polyetheramine system, resulting in an epoxy-modified polyetheramine adhesive that is transparent both before and after curing, satisfying the requirements for good appearance and display of electronic components.

[0068] (4) Tensile test:

[0069] Weigh the epoxy-modified polyetheramine adhesive according to the formula, mix thoroughly, and then pour it into a PTFE mold. Cure at room temperature for 48 hours, then demold. Test the tensile properties of the prepared specimens using a WYC-20KN universal electronic testing machine at a tensile speed of 1 mm / min. The results are as follows. Figure 3 As shown.

[0070] Depend on Figure 3 It can be seen that the tensile strengths of the specimens in Examples 1-4 are 14.21 MPa, 25.07 MPa, 18.35 MPa, and 20.57 MPa, respectively. This indicates that the specimens in Examples 1-4 have good tensile properties.

[0071] (5) Shear properties:

[0072] Weigh the epoxy-modified polyetheramine adhesive according to the formula and mix thoroughly. Then apply it to both ends of a standard carbon steel sheet and cure at 60℃ for 3 hours. Perform tensile property testing on the sheet using a WYC-20KN universal electronic testing machine at a tensile speed of 1 mm / min. The results are as follows. Figure 4 As shown.

[0073] Depend on Figure 4 It can be seen that the shear strengths of the spline samples in Examples 1-4 are 4.37 MPa, 5.04 MPa, 5.48 MPa, and 3.81 MPa, respectively. This indicates that the spline samples in Examples 1-4 have good shear properties.

[0074] The above tests show that after adding a specific ionic liquid, the adhesive of the present invention still has the excellent mechanical properties of epoxy curing adhesive and does not reduce the relevant properties of the adhesive.

[0075] (6) Oxygen Index Test:

[0076] The oxygen index of modified epoxy resin was determined using an oxygen index tester manufactured by Chengde Testing Machine Co., Ltd., according to standard GB / T 2406. The flame retardancy of the sample was evaluated using the oxygen index, and the results are as follows: Figure 5 As shown.

[0077] Depend on Figure 5 It can be seen that the oxygen index values ​​of the blank sample and the samples from Examples 1-4 are 22.5, 25.9, 27.1, 25.3, and 26.5, respectively. This indicates that the addition of phosphate-based ionic liquid significantly improves the flame retardancy of the samples. To compare the flame retardant effect of phosphate-based ionic liquid with the traditional flame retardant triphenyl phosphate (TPPP), TPPP with the same phosphorus content was added to replace the ionic liquid in Example 2. Its oxygen index was measured to be 26.04, lower than the oxygen index of 27.11 of the sample from Example 2. In addition, the mechanical properties of the epoxy-polyetheramine curing system modified with TPPP also decreased significantly. For example, the tensile strength decreased to 13.84 MPa, and the shear strength decreased to 2.71 MPa. This proves that the epoxy-polyetheramine curing system modified with phosphate-based ionic liquid has better overall performance.

[0078] (7) Surface resistance and volume resistance tests:

[0079] The surface resistance R of the blank sample and the samples from Examples 1, 2 and 3 was measured using a ZC-type high-resistivity meter. S and volume resistivity R V The surface resistivity R of the epoxy system with added ionic liquid (Example 1) S and volume resistivity R V The values ​​decreased by 2 to 3 orders of magnitude compared to the blank sample, from 1.22 × 10⁻⁶ for the blank sample. 14 Ω and 9.16×10 14 Ω decreased to 5.06 × 10 12 Ω and 2.03×10 11 Ω; Surface resistivity R of the sample prepared in Example 2 S and volume resistivity R V The value decreased by 3-4 orders of magnitude compared to the blank sample, dropping to 4.75 × 10⁻⁶. 11 Ω and 7.03×10 10 Ω; Surface resistivity R of the sample prepared in Example 3 S and volume resistivity R VThe value decreased by 2-3 orders of magnitude compared to the blank sample, dropping to 8.13 × 10⁻⁶. 11 Ω and 1.73×10 11 Ω. This demonstrates that the epoxy-polyetheramine curing system modified with phosphate ester ionic liquid has good electrical conductivity.

[0080] The samples prepared in Examples 1-3 were left to stand naturally at room temperature for 60 days. Each day, between 10:00 AM and 12:00 PM, the sample surface was wiped back and forth five times with lens cleaning paper. The surface resistivity R of each sample was then measured. S and volume resistivity R V Their values ​​are 5.31 × 10 12 Ω and 1.99×10 11 Ω (Example 1); 4.01 × 10 11 Ω and 6.82×10 10 Ω (Example 2) and 8.26 × 10 11 Ω and 1.62×10 11 Ω (Example 3). The surface resistance and volume resistance values ​​of the samples prepared in Examples 1-3 illustrate that the conductivity of each sample did not decrease significantly after being placed and wiped for a long time, overcoming the defect of the conductivity of traditional conductive adhesives decreasing over time.

[0081] The conductive and flame-retardant properties of the epoxy adhesive of this invention are achieved by incorporating an ionic liquid containing a phosphate ester. The ionic liquid exhibits good compatibility with the epoxy-polyetheramine curing system and absorbs trace amounts of moisture from the surrounding environment to eliminate static electricity. Simultaneously, the introduction of phosphorus atoms gives the epoxy adhesive certain flame-retardant properties, making it more suitable for applications in the electronics and electrical industries that require transparency, conductivity, and flame retardancy.

[0082] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various equivalent modifications can be made to the technical solutions of the present invention, and all such equivalent modifications fall within the protection scope of the present invention. Furthermore, it should be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe the various possible combinations.

Claims

1. A transparent, conductive, and flame-retardant epoxy adhesive, characterized in that... The epoxy adhesive consists of two components, A and B, which, by weight, comprise: Component A: 100 parts of epoxy resin E-51; Component B: 40-50 parts of modified amine curing agent, wherein the modified amine curing agent comprises, by weight, the following: 30-40 parts of amine compounds, 5-10 parts of phosphate ester ionic liquid DMP-30 1-3 copies, The amine compound is at least one selected from polyetheramine D230, polyetheramine 403, 3,6-dioxo-1,10-octadecanediamine, 4,7-dioxo-1,10-decadecanediamine, 3,6,9-trioxo-1,12-undecanediamine, and 4,7,10-trioxo-1,13-tridecanediamine. The phosphate ester ionic liquid is shown in the following formula: ； Furthermore, the phosphate ester-containing ionic liquid was prepared by the following method: (1) Mix diethyl(3-bromopropyl)phosphonate and 1-butylimidazole in a molar ratio of 1:1, add excess toluene to completely dissolve, and then react under stirring and 95°C for 24 h to obtain the product; (2) The product was concentrated using a rotary evaporator and then vacuum dried at 50°C for 24 h to obtain a phosphate ester ionic liquid.

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