Preparation Process of Flame Retardant Adhesive for Copper Clad Laminate

Abstract

The present invention relates to the technical field of adhesives, and discloses a preparation process of a flame-retardant adhesive for copper clad laminates. In the present invention, a solvent, an epoxy resin, a phosphorus-containing polyarylether, an antifoaming agent, a curing agent, etc. are mixed to obtain a flame-retardant adhesive for copper clad laminates. The molecular main chain of the phosphorus-containing polyarylether contains DOPO groups and phenylimide ring structures, forming a nitrogen-phosphorus flame-retardant system, which plays a very good condensed-phase flame-retardant role. When burning, an expanded carbon layer is formed in the adhesive matrix, having an excellent flame-retardant effect, significantly reducing the peak value of the heat release rate and the total heat release amount. The phosphorus-containing polyarylether contains a phenylimide ring with a large rigidity and high structural stability, and at the same time, the side chain contains a flexible long-chain alkyl group, having a very good toughening effect, so that while the epoxy resin adhesive maintains good mechanical strength, it also exhibits very good toughness, having higher impact strength and flexural strength.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, and specifically to a preparation process of a flame-retardant adhesive for copper clad laminates. Background Art

[0002] Copper clad laminates mainly consist of insulating base films, conductive copper foils, resin adhesives, etc., and are widely used in PCB boards, computers, automotive electronic instruments, communication equipment, etc. Adhesives have a great influence on the flame retardancy, heat resistance, toughness and other properties of copper clad laminates. There are mainly epoxy resin adhesives, acrylate adhesives, etc. Among them, epoxy resin adhesives have good curing performance, high heat resistance and high strength, and are widely used. However, epoxy resin adhesives have problems such as poor toughness and poor flame retardancy, which are not conducive to their practical applications in copper clad laminates and other aspects.

[0003] 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide DOPO and its derivatives are excellent phosphorus-based flame retardants, which can be made into nitrogen-phosphorus flame retardants, intumescent flame retardants, macromolecular polymer flame retardants, etc., and have wide applications in high molecular materials such as epoxy resins, polyurethanes, and polypropylenes. Chinese Patent CN101880395B discloses a polymer-type phosphorus-containing flame retardant containing DOPO and its preparation method, in which an aromatic-based diol modified with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide reacts with a dichlorinated substituted phosphate ester to obtain a polymer-type phosphorus-containing flame retardant, which improves the flame retardancy of epoxy resins and overcomes the disadvantages of poor compatibility and easy migration between small molecule phosphorus-based flame retardants and polymer matrices. However, this polymer-type phosphorus-containing flame retardant does not improve the toughness and other properties of epoxy resins. Summary of the Invention

[0004] The present invention solves the problems of poor flame retardancy and toughness of epoxy resin adhesives for copper clad laminates.

[0005] The technical solution of the present invention: The preparation process of the flame-retardant adhesive for copper clad laminates is the following steps:

[0006] Step A: Add N-methylpyrrolidone, toluene, 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide, difluorophenylimide monomer, and potassium carbonate into a reaction vessel, carry out azeotropic water removal and polycondensation reaction, pour the solution into an ethanol aqueous solution after cooling, precipitate a precipitate, filter, wash with water and ethanol, and dry to obtain a phosphorus-containing polyarylether. The reaction formula is as follows:

[0007]

[0008] Step B: Add a solvent, 100 parts by weight of epoxy resin, a co-solvent, 10 - 25 parts by weight of phosphorus-containing polyarylether into a container. After stirring, add 0.4 - 0.7 parts by weight of defoamer and 35 - 44 parts by weight of curing agent to obtain a flame-retardant adhesive for copper clad laminates.

[0009] Further, in Step A, the temperature for azeotropic dehydration is 150 - 160 °C and the time is 1 - 2 h; the temperature for polycondensation reaction is 180 - 190 °C and the time is 8 - 12 h.

[0010] Further, in Step A, the molar ratio of 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide (CAS registration number: 99208-50-1), difluorophenylimide monomer, and potassium carbonate is 1:(1 - 1.05):(1.5 - 1.7).

[0011] Further, the solvent includes methyl ethyl ketone, n-butanol, and butyl acetate, and the co-solvent includes N,N-dimethylformamide.

[0012] Further, the curing agent includes 4,4-diaminodiphenyl sulfone and 4,4-diaminodiphenyl methane.

[0013] Further, the preparation process of the difluorophenylimide monomer is as follows:

[0014] (1) Add glacial acetic acid, 3,5-diaminobenzoic acid with a molar ratio of (2 - 2.4):1, and 4-fluorophthalic anhydride (CAS registration number: 319-03-9) into a reaction vessel. Heat to 115 - 125 °C and carry out a condensation reflux reaction for 10 - 15 h. After cooling, pour the solution into water to precipitate a solid. After filtration, the product is recrystallized in isopropanol to obtain a precursor.

[0015] (2) Add toluene, the precursor with a molar ratio of 1:(2.6 - 3.2):(0.05 - 0.07), an alkyl alcohol, and p-toluenesulfonic acid into a reaction vessel. Heat to 100 - 110 °C and carry out a condensation reflux reaction for 6 - 8 h. Rotate to evaporate to remove toluene, wash with petroleum ether, and recrystallize the product in isopropanol to obtain the difluorophenylimide monomer. The reaction formula is as follows:

[0016]

[0017] Preferably, in (2), the molecular formula of the alkyl alcohol is OH-C n H 2n+1 , where n is any integer from 8 to 14.

[0018] Technical effects of the present invention: Using 3,5-diaminobenzoic acid, 4-fluorophthalic anhydride, and alkyl alcohol as reactants, a novel difluorophenylimide monomer is prepared. Then, it undergoes an etherification polycondensation reaction with 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide to obtain a phosphorus-containing polyarylether. Finally, it is mixed with epoxy resin, curing agent, etc. to obtain a flame-retardant adhesive for copper clad laminates. The molecular main chain of this phosphorus-containing polyarylether contains DOPO groups and phenylimide ring structures, forming a nitrogen-phosphorus flame-retardant system, which plays a good condensed-phase flame-retardant role. When burning, an expanded carbon layer is formed in the adhesive matrix, having excellent flame-retardant properties and significantly reducing the peak value of the heat release rate and the total heat release amount.

[0019] The phosphorus-containing polyarylether of the present invention contains a phenylimide ring with large rigidity and high structural stability, and at the same time, the side chain contains a flexible long-chain alkyl group, having a good toughening effect, enabling the epoxy resin adhesive to exhibit good toughness while maintaining good mechanical strength, and having higher impact strength and flexural strength. Specific embodiments

[0020] The technical solution of the present invention is further described below, but the scope of protection is not limited thereto.

[0021] The epoxy resin model of the present invention is E51, and the defoaming agent brand is AGITAN A201. Example 1

[0022] (1) Add 120 mL of glacial acetic acid, 86 mmol of 3,5-diaminobenzoic acid, and 40 mmol of 4-fluorophthalic anhydride to a reaction vessel, heat to 115 °C, and carry out a condensation reflux reaction for 15 h. After cooling, pour the solution into water, precipitate a solid, and after filtration, the product is recrystallized in isopropanol to obtain a precursor.

[0023] (2) Add 30 mL of toluene, 30 mmol of the precursor, 78 mmol of 1-decanol, and 1.9 mmol of p-toluenesulfonic acid to a reaction vessel, heat to 110 °C, and carry out a condensation reflux reaction for 6 h. Rotate and evaporate to remove toluene, wash with petroleum ether, and the product is recrystallized in isopropanol to obtain a difluorophenylimide monomer.

[0024] (3) Add 150 mL of N-methylpyrrolidone, 100 mL of toluene, 40 mmol of 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide, 40 mmol of difluorophenylimide monomer, and 60 mmol of potassium carbonate to a reaction vessel, heat to 150 °C, carry out azeotropic water removal for 2 h, then heat to 190 °C, and carry out a polycondensation reaction for 8 h. After cooling, pour the solution into an ethanol aqueous solution, precipitate a solid, and after filtration, wash with water and ethanol, and dry to obtain a phosphorus-containing polyarylether.

[0025] (4) Add 80 mL of butyl acetate, 100 g of epoxy resin, 10 mL of co-solvent N,N-dimethylformamide, and 10 g of phosphorus-containing polyarylether into a container. After stirring, add 0.4 g of defoamer and 44 g of curing agent 4,4-diaminodiphenyl sulfone to obtain a flame-retardant adhesive for copper clad laminate. Example 2

[0026] (1) Add 100 mL of glacial acetic acid, 80 mmol of 3,5-diaminobenzoic acid, and 40 mmol of 4-fluorophthalic anhydride into a reaction vessel. Heat to 125 °C and carry out a condensation reflux reaction for 10 h. After cooling, pour the solution into water to precipitate a solid. Filter the product and recrystallize it from isopropanol to obtain a precursor.

[0027] (2) Add 40 mL of toluene, 30 mmol of the precursor, 96 mmol of tetradecanol, and 1.5 mmol of p-toluenesulfonic acid into a reaction vessel. Heat to 110 °C and carry out a condensation reflux reaction for 6 h. Rotate to evaporate to remove toluene, wash with petroleum ether, and recrystallize the product from isopropanol to obtain a difluorophenylimide monomer.

[0028] (3) Add 150 mL of N-methylpyrrolidone, 120 mL of toluene, 40 mmol of 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide, 42 mmol of difluorophenylimide monomer, and 68 mmol of potassium carbonate into a reaction vessel. Heat to 160 °C and carry out azeotropic water removal for 1 h, then heat to 190 °C and carry out a polycondensation reaction for 8 h. After cooling, pour the solution into an ethanol-water solution to precipitate a solid. Filter the product and wash it with water and ethanol, then dry to obtain a phosphorus-containing polyarylether.

[0029] (4) Add 80 mL of butanone, 100 g of epoxy resin, 20 mL of co-solvent N,N-dimethylformamide, and 17 g of phosphorus-containing polyarylether into a container. After stirring, add 0.7 g of defoamer and 35 g of curing agent 4,4-diaminodiphenylmethane to obtain a flame-retardant adhesive for copper clad laminate. Example 3

[0030] (1) Add 130 mL of glacial acetic acid, 96 mmol of 3,5-diaminobenzoic acid, and 40 mmol of 4-fluorophthalic anhydride into a reaction vessel. Heat to 120 °C and carry out a condensation reflux reaction for 10 h. After cooling, pour the solution into water to precipitate a solid. Filter the product and recrystallize it from isopropanol to obtain a precursor.

[0031] (2) Add 40 mL of toluene, 30 mmol of the precursor, 84 mmol of 1-octanol, and 2.1 mmol of p-toluenesulfonic acid to the reaction vessel. Heat to 100 °C and reflux for 8 h. Rotate evaporate to remove toluene, wash with petroleum ether, and recrystallize the product from isopropanol to obtain the difluorophenylimide monomer.

[0032] (3) Add 150 mL of N-methylpyrrolidone, 120 mL of toluene, 40 mmol of 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide, 40 mmol of the difluorophenylimide monomer, and 68 mmol of potassium carbonate to the reaction vessel. Heat to 150 °C and azeotropically remove water for 2 h. Then heat to 180 °C and carry out polycondensation for 12 h. After cooling, pour the solution into an ethanol-water solution to precipitate a solid. Filter and wash with water and ethanol, and dry to obtain the phosphorus-containing polyarylether.

[0033] (4) Add 80 mL of n-butanol, 100 g of epoxy resin, 30 mL of the co-solvent N,N-dimethylformamide, and 25 g of the phosphorus-containing polyarylether to the container. After stirring, add 0.7 g of defoamer and 37 g of the curing agent 4,4-diaminodiphenylmethane to obtain the flame-retardant adhesive for copper clad laminates.

[0034] Comparative Example 1

[0035] The difference between Comparative Example 1 and Example 1 is that the phosphorus-containing polyarylether is not added.

[0036] (1) Add 80 mL of butyl acetate, 100 g of epoxy resin, 10 mL of the co-solvent N,N-dimethylformamide to the container. After stirring, add 0.4 g of defoamer and 44 g of the curing agent 4,4-diaminodiphenyl sulfone to obtain the adhesive for copper clad laminates.

[0037] Comparative Example 2

[0038] The difference between Comparative Example 2 and Example 1 is that hydroquinone is used instead of 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide when preparing the polyarylether.

[0039] (1) Add 150 mL of N-methylpyrrolidone, 100 mL of toluene, 40 mmol of hydroquinone, 40 mmol of the difluorophenylimide monomer, and 60 mmol of potassium carbonate to the reaction vessel. Heat to 150 °C and azeotropically remove water for 2 h. Then heat to 190 °C and carry out polycondensation for 8 h. After cooling, pour the solution into an ethanol-water solution to precipitate a solid. Filter and wash with water and ethanol, and dry to obtain the polyarylether.

[0040] (2) Add 80 mL of butyl acetate, 100 g of epoxy resin, 10 mL of co-solvent N,N-dimethylformamide, and 10 g of polyarylether into a container. After stirring, add 0.4 g of defoamer and 44 g of curing agent 4,4-diaminodiphenyl sulfone to obtain an adhesive for copper clad laminate.

[0041] Comparative Example 3

[0042] The difference between Comparative Example 3 and Example 1 is that 4,4'-difluorobenzophenone is used instead of difluorophenylimide monomer when preparing the phosphorus-containing polyarylether.

[0043] (1) Add 150 mL of N-methylpyrrolidone, 100 mL of toluene, 40 mmol of 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide, 40 mmol of 4,4'-difluorobenzophenone, and 60 mmol of potassium carbonate into a reaction vessel. Heat to 150 °C and remove water by azeotropic distillation for 2 h. Then heat to 190 °C and carry out polycondensation reaction for 8 h. After cooling, pour the solution into an ethanol aqueous solution to precipitate a solid. Filter and wash with water and ethanol, and dry to obtain the phosphorus-containing polyarylether.

[0044] (2) Add 80 mL of butyl acetate, 100 g of epoxy resin, 10 mL of co-solvent N,N-dimethylformamide, and 10 g of phosphorus-containing polyarylether into a container. After stirring, add 0.4 g of defoamer and 44 g of curing agent 4,4-diaminodiphenyl sulfone to obtain a flame-retardant adhesive for copper clad laminate.

[0045] Comparative Example 4

[0046] The difference between Comparative Example 4 and Example 1 is that ethanol is used instead of 1-decanol when preparing the difluorophenylimide monomer.

[0047] (1) Add 30 mL of toluene, 30 mmol of precursor, 78 mmol of ethanol, and 1.9 mmol of p-toluenesulfonic acid into a reaction vessel. Heat to 110 °C and carry out reflux condensation reaction for 6 h. Rotate and evaporate to remove toluene, wash with petroleum ether, and recrystallize the product in isopropanol to obtain the difluorophenylimide monomer. The structural formula is:

[0048]

[0049] (2) Add 150 mL of N-methylpyrrolidone, 100 mL of toluene, 40 mmol of 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide, 40 mmol of difluorophenylimide monomer, and 60 mmol of potassium carbonate into the reaction vessel. Heat to 150 °C and remove water by azeotropic distillation for 2 h. Then heat to 190 °C and carry out polycondensation reaction for 8 h. After cooling, pour the solution into an ethanol aqueous solution to precipitate a solid. Filter and wash with water and ethanol, and dry to obtain a phosphorus-containing polyarylether.

[0050] (3) Add 80 mL of butyl acetate, 100 g of epoxy resin, 10 mL of co-solvent N,N-dimethylformamide, and 10 g of phosphorus-containing polyarylether into the container. After stirring, add 0.4 g of defoamer and 44 g of curing agent 4,4-diaminodiphenylsulfone to obtain a flame-retardant adhesive for copper clad laminates.

[0051] Coat the adhesive on the surface of the polyimide film, then laminate the copper foil on the surface of the polyimide film, and press. Cure at 120 °C for 1 h and then at 150 °C for 2 h in sequence to make a copper clad laminate specimen. Use a tensile testing machine to test the peel strength according to the standard of GB / T 7122-1996, and the peeling speed is 50 mm / min.

[0052] Pour the adhesive into a mold, degas it under vacuum, cure at 120 °C for 2 h and then at 150 °C for 4 h in sequence to make a casting specimen, and test the impact strength and flexural strength according to the standard of GB / T 2567-2021.

[0053] Test the combustion properties of the cured adhesive specimen by a cone calorimeter. The heat flux is 35 kW / m 2 .

[0054] Table 1

[0055]

[0056] As can be seen from Table 1, the epoxy resin adhesive in Comparative Example 1 has relatively low impact strength and flexural strength, poor toughness, and relatively large peak heat release rate and total heat release, and its flame retardancy is poor.

[0057] In the epoxy resin adhesives of Examples 1 - 3, a phosphorus-containing polyarylether was added. Its molecular main chain contains DOPO groups and phenylimide ring structures, forming a nitrogen-phosphorus flame retardant system, which plays a very good condensed-phase flame retardant role. During combustion, an expanded carbon layer is formed in the adhesive matrix, having excellent flame retardant properties and significantly reducing the peak heat release rate and the total heat release amount. Moreover, the phenylimide ring has a large rigidity and high structural stability. At the same time, the side chain of the phosphorus-containing polyarylether contains a flexible long-chain alkyl group, having a good toughening effect, so that the epoxy resin adhesive not only maintains good mechanical strength but also exhibits good toughness, with higher impact strength and flexural strength.

[0058] In Comparative Example 2, hydroquinone was used to replace 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide, and the obtained polyarylether does not contain DOPO structure, resulting in very poor flame retardant effect on the epoxy resin adhesive, leading to a large peak heat release rate and total heat release amount of the adhesive. However, the main chain of the polyarylether contains a rigid phenylimide ring and the side chain contains a flexible long-chain alkyl group, having a good toughening effect and can improve the impact strength and flexural strength of the adhesive.

[0059] In Comparative Example 3, 4,4'-difluorobenzophenone was used to replace the difluorophenylimide monomer, and the obtained phosphorus-containing polyarylether contains DOPO structure and has good flame retardant effect, but does not contain phenylimide ring structure and does not form a nitrogen-phosphorus flame retardant system, resulting in a flame retardant effect lower than that of Example 1, and the peak heat release rate and total heat release amount higher than those of Example 1. Moreover, the side chain of the phosphorus-containing polyarylether also does not contain a flexible long-chain alkyl group, with poor toughening effect and lower impact strength and flexural strength of the adhesive.

[0060] In Comparative Example 4, ethanol was used to replace 1-decanol, and the prepared difluorophenylimide monomer and phosphorus-containing polyarylether do not contain flexible long-chain alkyl groups, with poor toughening effect and lower impact strength and flexural strength of the adhesive.

[0061] The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those skilled in the technical field to which the present invention belongs, without departing from the concept of the present invention, several equivalent substitutions or obvious modifications can be made, and if the performance or use is the same, they should all be regarded as belonging to the present invention.

Claims

1. A preparation process of a flame retardant adhesive for copper clad laminates, characterized in that: The preparation process comprises the following steps: Step A, adding N-methylpyrrolidone, toluene, 10-(2,5-dihydroxyphenyl)-10-hydrogen-9-oxa-10-phosphaphenanthrene-10-oxide, difluorophenylimide monomer, and potassium carbonate into a reaction container, performing azeotropic dehydration and polycondensation reaction, and after cooling, pouring the solution into an ethanol aqueous solution to precipitate a precipitate, filtering, washing with water and ethanol, and drying to obtain a phosphorus-containing polyarylether; The structural formula of the difluorophenylimide monomer is , n is any integer between 8 and 14; Step B, adding a solvent, 100 parts by weight of epoxy resin, a cosolvent, and 10-25 parts by weight of phosphorus-containing polyarylether into a container, and adding 0.4-0.7 parts by weight of a defoamer and 35-44 parts by weight of a curing agent after stirring to obtain a flame retardant adhesive for copper clad laminates; The preparation process of the difluorophenylimide monomer is: (1) Add glacial acetic acid, 3,5-diaminobenzoic acid and 4-fluorophthalic anhydride to a reaction vessel, heat to 115-125°C, condense and reflux for 10-15 hours, and after cooling, pour the solution into water to precipitate a precipitate. After filtering, the product is recrystallized in isopropanol to obtain a precursor; (2) Add toluene, precursor, alkyl alcohol and p-toluenesulfonic acid into a reaction vessel, heat to 100-110° C., condense and reflux for 6-8 hours, remove toluene by rotary evaporation, wash with petroleum ether, and recrystallize the product in isopropanol to obtain a difluorophenylimide monomer; The molar ratio of 3,5-diaminobenzoic acid to 4-fluorophthalic anhydride in (1) is (2-2.4):1; The molar ratio of the precursor, alkyl alcohol and p-toluenesulfonic acid in (2) is 1:(2.6-3.2):(0.05-0.07); The molecular formula of the alkyl alcohol in (2) is OH-C n H 2n+1 , n is any integer from 8 to 14.

2. The preparation process of the flame retardant adhesive for copper clad laminate according to claim 1, characterized in that: In the step A, the temperature of azeotropic dehydration is 150-160° C., and the time is 1-2 hours; the temperature of polycondensation reaction is 180-190° C., and the time is 8-12 hours.

3. The preparation process of the flame retardant adhesive for copper clad laminate according to claim 1, characterized in that: In the step A, the molar ratio of 10-(2,5-dihydroxyphenyl)-10-hydrogen-9-oxa-10-phosphaphenanthrene-10-oxide, difluorophenylimide monomer and potassium carbonate is 1:(1-1.05):(1.5-1.7).

4. The preparation process of the flame retardant adhesive for copper clad laminate according to claim 1, characterized in that: The solvent is butanone, n-butanol or butyl acetate, and the co-solvent is N,N-dimethylformamide.

5. The preparation process of the flame retardant adhesive for copper clad laminate according to claim 1, characterized in that: The curing agent includes 4,4-diaminodiphenyl sulfone and 4,4-diaminodiphenylmethane.

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