Preparation method of phenolic resin adhesive with heat resistance and high bonding strength

Abstract

The invention relates to the technical field of adhesives, and discloses a preparation method of a phenolic resin adhesive with heat resistance and high bonding strength, phenolic resin is added into a solvent, a dobby polyethylene glycol modifier is added after stirring, and the phenolic resin adhesive with heat resistance and high bonding strength is prepared; the multi-arm polyethylene glycol modifier contains a four-arm flexible polyethylene glycol molecular chain, the end position contains four isocyanate groups, the number of crosslinking sites is more, a three-dimensional flexible crosslinking network is formed in a phenolic resin matrix, and the impact strength, the bending strength and the toughness of the adhesive are remarkably improved. The interaction force between the multi-arm polyethylene glycol modifier and the surfaces of base materials such as wood and steel is very strong, the binding force and the binding performance between the phenolic resin adhesive and the base materials are improved, and higher bonding strength and tensile shear strength are shown.

Description

Technical Field

[0001] The invention relates to the technical field of adhesives, in particular to a method for preparing a phenolic resin adhesive with heat resistance and high bonding strength. Background Art

[0002] Phenolic resin has good mechanical strength, heat resistance, wear resistance, flame retardancy, adhesion and other properties. It can be made into adhesives and is widely used in plywood, particleboard, metal substrates, etc. Traditional phenolic resin adhesives have problems such as poor toughness and poor bonding performance during long-term use. The use of materials such as polyethylene glycol, nitrile rubber, and acrylic rubber can achieve toughening modification of phenolic resin. A Chinese patent with announcement number CN117004172B discloses a method for preparing a high-toughness phenolic resin glue for copper-clad laminates. A flexible compound is prepared by inducing a click reaction between dithiol polyethylene glycol and hydroxyethyl acrylate and maleimide by ultraviolet laser irradiation. The flexible compound is then grafted onto a linear phenolic resin to obtain a modified linear phenolic resin. Terpene phenolic resin, bisphenol A epoxy resin, modified silicon nitride, modified styrene-butadiene rubber, etc. are then mixed to obtain a high-toughness phenolic resin for copper-clad laminates. However, the raw materials and preparation method of the phenolic resin are relatively complicated, and the bonding performance between the phenolic resin and wood and metal substrates is not improved. Summary of the invention

[0003] The present invention solves the problems of poor bonding performance and poor toughness of phenolic resin adhesives, while enabling the adhesive to maintain good heat resistance.

[0004] Technical solution: A method for preparing a phenolic resin adhesive with heat resistance and high bonding strength: Step (1): Add tetrakis(4-formylphenyl)methane and single-terminated amino polyethylene glycol to ethanol, add glacial acetic acid with a mass fraction of ≥98%, stir and react at 30-45°C for 12-24h, rotary evaporate, wash with acetone, and dry to obtain tetrakis(4-polyethylene glycol Schiff base benzene)methane. The reaction formula is as follows:

[0005] Step (2): Add tetra(4-polyethylene glycol Schiff base benzene)methane, diisocyanate, and dibutyltin dilaurate to toluene, heat to 70-80°C in a nitrogen atmosphere, stir and react for 2-3 hours, rotary evaporate, wash with acetone, and dry to obtain a multi-arm polyethylene glycol modifier. The reaction formula is as follows:

[0006] Step (3): Add phenolic resin to the solvent, stir, and then add a multi-arm polyethylene glycol modifier to obtain a phenolic resin adhesive with heat resistance and high bonding strength.

[0007] Preferably, in step (1), the ratio of tetrakis(4-formylphenyl)methane to single-amino-terminated polyethylene glycol is 1 mol:(4.8-6.4) mol.

[0008] Preferably, in step (2), the ratio of tetrakis(4-polyethylene glycol Schiff base benzene)methane, diisocyanate and dibutyltin dilaurate is 1 mol: (5.2-5.6) mol: (0.004-0.005) mol.

[0009] Preferably, the diisocyanate is isophorone diisocyanate, toluene-2,4-diisocyanate or diphenylmethane-4,4'-diisocyanate.

[0010] Preferably, in step (3), the ratio of phenolic resin to multi-arm polyethylene glycol modifier is 100 g:(2-10) g.

[0011] Preferably, the solvent in step (3) is ethyl acetate or butyl acetate.

[0012] Technical effect: The present invention uses phenolic resin as the main agent of the adhesive and adds a multi-arm polyethylene glycol modifier, which contains a four-arm flexible polyethylene glycol molecular chain and four isocyanate groups at the end, with more cross-linking sites, forming a three-dimensional flexible cross-linking network in the phenolic resin matrix, which significantly improves the impact strength, bending strength and toughness of the adhesive.

[0013] The multi-arm polyethylene glycol modifier of the present invention contains multiple isocyanate groups, and has stronger interaction with the surface of substrates such as wood and steel, thereby improving the binding force and bonding performance between the phenolic resin adhesive and the substrate, and showing higher bonding strength and tensile shear strength.

[0014] The multi-arm polyethylene glycol modifier of the invention contains a thermally stable tetraphenylmethane center. After adding a proper amount of the modifier and cross-linking with the phenolic resin, the adhesive can maintain a relatively high thermal decomposition temperature and heat resistance. DETAILED DESCRIPTION

[0015] The phenolic resin of the present invention is a thermosetting phenolic resin with an effective component content of 99%, produced by Jinan Dahui Chemical Technology Co., Ltd.

[0016] According to the method of the literature "Preparation of single-terminal maleimide functionalized polyethylene glycol", single-terminal amino polyethylene glycol was prepared, and the structural formula is .

[0017] Embodiment 1: (1) Add 2 mmol of tetrakis(4-formylphenyl)methane and 10.4 mmol of single-terminated amino polyethylene glycol to 40 mL of ethanol, add 0.13 mL of 98% glacial acetic acid dropwise, stir and react at 30 °C for 24 h, rotary evaporate, wash with acetone, and dry to obtain tetrakis(4-polyethylene glycol Schiff base benzene)methane.

[0018] (2) Add 2 mmol of tetrakis(4-polyethylene glycol Schiff base benzene)methane, 11.2 mmol of isophorone diisocyanate, and 0.008 mmol of dibutyltin dilaurate to 40 mL of toluene, heat to 75 °C in a nitrogen atmosphere, stir and react for 3 h, rotary evaporate, wash with acetone, and dry to obtain a multi-arm polyethylene glycol modifier.

[0019] (3) Add 100 g of phenolic resin to 30 mL of butyl acetate solvent, stir, and then add 2 g of multi-arm polyethylene glycol modifier to prepare a phenolic resin adhesive with heat resistance and high bonding strength. Embodiment 2:

[0020] (1) Add 2 mmol of tetrakis(4-formylphenyl)methane and 12.8 mmol of single-terminated amino polyethylene glycol to 50 mL of ethanol, add 0.12 mL of 99% glacial acetic acid dropwise, stir at 45 °C for 12 h, rotary evaporate, wash with acetone, and dry to obtain tetrakis(4-polyethylene glycol Schiff base benzene)methane.

[0021] (2) Add 2 mmol of tetrakis(4-polyethylene glycol Schiff base benzene)methane, 10.4 mmol of diphenylmethane-4,4'-diisocyanate, and 0.01 mmol of dibutyltin dilaurate to 40 mL of toluene, heat to 80 °C in a nitrogen atmosphere, stir and react for 2 h, rotary evaporate, wash with acetone, and dry to obtain a multi-arm polyethylene glycol modifier.

[0022] (3) Add 100 g of phenolic resin to 30 mL of ethyl acetate solvent, stir, and then add 4 g of multi-arm polyethylene glycol modifier to prepare a phenolic resin adhesive with heat resistance and high bonding strength. Embodiment 3:

[0023] (1) Add 2 mmol of tetrakis(4-formylphenyl)methane and 9.6 mmol of single-terminated amino polyethylene glycol to 40 mL of ethanol, add 0.13 mL of 98% glacial acetic acid dropwise, stir at 35 °C for 24 h, rotary evaporate, wash with acetone, and dry to obtain tetrakis(4-polyethylene glycol Schiff base benzene)methane.

[0024] (2) Add 2 mmol of tetrakis(4-polyethylene glycol Schiff base benzene)methane, 10.4 mmol of toluene-2,4-diisocyanate, and 0.01 mmol of dibutyltin dilaurate to 30 mL of toluene, heat to 70 °C in a nitrogen atmosphere, stir and react for 3 h, rotary evaporate, wash with acetone, and dry to obtain a multi-arm polyethylene glycol modifier.

[0025] (3) Add 100 g of phenolic resin to 40 mL of butyl acetate solvent, stir, and then add 6 g of multi-arm polyethylene glycol modifier to prepare a phenolic resin adhesive with heat resistance and high bonding strength. Embodiment 4:

[0026] (1) Add 100 g of phenolic resin to 30 mL of butyl acetate solvent, stir, and then add 8 g of multi-arm polyethylene glycol modifier (prepared in the same manner as in Example 1) to prepare a phenolic resin adhesive with heat resistance and high bonding strength. Embodiment 5:

[0027] (1) Add 100 g of phenolic resin to 30 mL of butyl acetate solvent, stir, and then add 10 g of multi-arm polyethylene glycol modifier (prepared in the same manner as in Example 1) to prepare a phenolic resin adhesive with heat resistance and high bonding strength.

[0028] Comparative Example 1: (1) Add 100 g of phenolic resin to 30 mL of butyl acetate solvent and stir to obtain a phenolic resin adhesive.

[0029] Comparative Example 2: (1) 2 mmol of polyethylene glycol 2000 was dried under vacuum, mixed with 5.6 mmol of isophorone diisocyanate and 0.008 mmol of dibutyltin dilaurate, heated to 75°C in a nitrogen atmosphere, stirred for reaction for 3 h, rotary evaporated, washed with acetone, and dried to obtain an isocyanate-terminated polyethylene glycol modifier.

[0030] (2) Add 100 g of phenolic resin to 30 mL of butyl acetate solvent, stir, and then add 2 g of terminal isocyanate polyethylene glycol modifier to prepare a phenolic resin adhesive.

[0031] Apply phenolic resin adhesive on both sides of poplar veneer (thickness 1.8mm) with an application amount of 280g / m 2 (double-sided), and then place the other two poplar veneers on the double-sided poplar veneer coated with adhesive, and hot press them at 130℃, with a pressure of 1.2MPa and a hot pressing time of 1min / mm. After cooling, place them at room temperature for 24h to make a three-layer plywood sample. Test the bonding strength according to the national standard GB / T 17657-2022.

[0032] According to the national standard GB / T 7124-2008, the tensile shear strength of the adhesive is tested. The substrate is steel sheet to steel sheet, and the thickness of the adhesive layer is 0.2mm.

[0033] Pour the phenolic resin adhesive into the mold, cure it at 110℃ for 12 hours, and cut it into film specimens. Test the impact performance according to the national standard GB / T 1043.1-2008. Test the bending strength according to the national standard GB / T9341-2008.

[0034] Weigh 6 mg of a phenolic resin film sample, place it in a thermogravimetric analyzer, and test the thermal properties in a nitrogen atmosphere at a heating rate of 10°C / min in a temperature range of 25-700°C.

[0035] Table 1

[0036] After testing, the phenolic resin adhesive of Comparative Example 1 has low bonding strength and tensile shear strength, poor bonding performance, low impact strength and bending strength, and poor toughness.

[0037] Comparative Example 2 has added terminal isocyanate polyethylene glycol properties-correcting agent, and its double-end contains isocyanate groups, can cross-link reaction with the hydroxyl of phenolic resin, makes polyethylene glycol play good toughening effect, can improve the impact strength and bending strength of adhesive.And a plurality of isocyanate groups that the properties-correcting agent contains can interact with substrate surfaces such as timber, steel, etc., is conducive to improving the bonding force and bonding property between phenolic resin adhesive and substrate, and bonding strength and tensile shear strength become large.But after phenolic resin introduces polyethylene glycol, initial thermal decomposition temperature obviously reduces, and heat resistance deteriorates.

[0038] The multi-arm polyethylene glycol modifier added in embodiment 1-5 contains four-arm flexible polyethylene glycol molecular chains, and the end position contains four isocyanate groups, and the cross-linking sites are more, forming a three-dimensional flexible cross-linked network in the phenolic resin matrix, significantly improving the impact strength, bending strength and toughness of the adhesive. The modifier contains multiple isocyanate groups at the same time, and the interaction force with the substrate surfaces such as wood and steel is also stronger, further improving the bonding force and bonding performance between the phenolic resin adhesive and the substrate, showing higher bonding strength and tensile shear strength. The multi-arm polyethylene glycol modifier contains the tetraphenylmethane center of thermal stability, adds an appropriate amount of modifier, and after cross-linking with the phenolic resin, the adhesive can maintain a higher thermal decomposition temperature and heat resistance.

Claims

1. A method for preparing a heat-resistant phenolic resin adhesive with high bonding strength, characterized in that: The preparation method is: Step (1): adding tetrakis(4-formylphenyl)methane and single-terminated amino polyethylene glycol to ethanol, adding glacial acetic acid dropwise, stirring for reaction, and then rotary evaporating, washing, and drying to obtain tetrakis(4-polyethylene glycol Schiff base benzene)methane; Step (2): adding tetrakis(4-polyethylene glycol Schiff base benzene)methane, diisocyanate and dibutyltin dilaurate to toluene, stirring and reacting in a nitrogen atmosphere, rotary evaporation, washing and drying to obtain a multi-arm polyethylene glycol modifier; Step (3): Add phenolic resin to the solvent, stir, and then add a multi-arm polyethylene glycol modifier to obtain a phenolic resin adhesive with heat resistance and high bonding strength.

2. The method for preparing the heat-resistant high-bonding-strength phenolic resin adhesive according to claim 1, characterized in that: In the step (1), the ratio of tetrakis(4-formylphenyl)methane to single-terminated amino polyethylene glycol is 1 mol:(4.8-6.4) mol.

3. The method for preparing the heat-resistant high-bonding-strength phenolic resin adhesive according to claim 1, characterized in that: The mass fraction of glacial acetic acid in step (1) is ≥ 98%.

4. The method for preparing the heat-resistant high-bonding-strength phenolic resin adhesive according to claim 1, characterized in that: The reaction in step (1) is carried out at 30-45° C. for 12-24 hours.

5. The method for preparing the heat-resistant high-bonding-strength phenolic resin adhesive according to claim 1, characterized in that: In the step (2), the ratio of tetrakis(4-polyethylene glycol Schiff base benzene)methane, diisocyanate and dibutyltin dilaurate is 1 mol: (5.2-5.6) mol: (0.004-0.005) mol.

6. The method for preparing the heat-resistant high-bonding-strength phenolic resin adhesive according to claim 5, characterized in that: The diisocyanate is isophorone diisocyanate, toluene-2,4-diisocyanate or diphenylmethane-4,4'-diisocyanate.

7. The method for preparing the heat-resistant high-bonding-strength phenolic resin adhesive according to claim 1, characterized in that: The reaction in step (2) is carried out at 70-80° C. for 2-3 hours.

8. The method for preparing the heat-resistant high-bonding-strength phenolic resin adhesive according to claim 1, characterized in that: In the step (3), the ratio of phenolic resin to multi-arm polyethylene glycol modifier is 100 g: (2-10) g.

9. The method for preparing the heat-resistant high-bonding-strength phenolic resin adhesive according to claim 1, characterized in that: The solvent in step (3) is ethyl acetate or butyl acetate.

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