Preparation method of phosphorus-containing flame-retardant halogen-free copper-clad plate

Abstract

The invention relates to the technical field of preparation of copper-clad plates, and discloses a preparation method of a phosphorus-containing flame-retardant halogen-free copper-clad plate, which comprises the following steps: uniformly stirring and mixing bisphenol A type epoxy resin, linear phenolic resin, phosphorus-containing tetraglycidyl ester and the like, smearing the mixture on E-glass fabric, baking to obtain prepregs, overlapping eight prepregs, coating copper foils on the two surfaces, and drying to obtain the phosphorus-containing flame-retardant halogen-free copper-clad plate. According to the preparation method, bisphenol A type epoxy resin is taken as matrix resin, linear phenolic resin is taken as a curing agent, phosphorus-containing tetraglycidyl ester is added, flame-retardant elements and a heat-resistant structure contained in the phosphorus-containing tetraglycidyl ester are utilized, the flame-retardant halogen-free copper-clad plate is obtained, and the flame-retardant halogen-free copper-clad plate is obtained. The flame retardant property, the heat resistance and the mechanical property of the copper-clad plate material are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of copper clad laminates, and specifically to a preparation method of a phosphorus-containing flame-retardant halogen-free copper clad laminate. Background Art

[0002] Printed circuit boards are currently an indispensable and important component for realizing circuit interconnection in the vast majority of electronic products. As the substrate material of printed circuit boards, copper clad laminates have the functions of conductivity, insulation, and support. A copper clad laminate is a product obtained by impregnating reinforcing materials such as paper and glass cloth with resin, and covering one or both sides with copper foil and then hot pressing. However, its flame-retardant performance cannot meet the requirements of current printed circuit boards. Traditional copper clad laminates are prepared using brominated epoxy resin as raw material. However, brominated epoxy resin generates a large amount of toxic fumes during combustion, causing irreparable damage to the natural environment and human health. Therefore, reducing the application of bromine-containing materials and halogen-free are the trends in the development of copper clad laminates in recent years.

[0003] For example, the Chinese patent application number is CN 108146035 A. This patent discloses a flame-retardant and heat-resistant copper clad laminate. The copper clad laminate prepared by this invention has good flame-retardant performance and heat-resistant performance, but does not improve the mechanical properties of the copper clad laminate material. Summary of the Invention

[0004] (I) Technical Problems to be Solved

[0005] Aiming at the deficiencies of the prior art, the present invention provides a preparation method of a phosphorus-containing flame-retardant halogen-free copper clad laminate. The prepared copper clad laminate has good flame-retardant performance, heat-resistant performance, and mechanical properties.

[0006] (II) Technical Solutions

[0007] A preparation method of a phosphorus-containing flame-retardant halogen-free copper clad laminate, the preparation method comprising the following steps:

[0008] Bisphenol A epoxy resin, linear phenolic resin, and phosphorus-containing tetra-glycidyl ester are added to acetone solvent, stirred and mixed evenly, and then 2-methylimidazole accelerator is added thereto and stirred and mixed evenly to obtain a glue solution; the glue solution is applied on an E-glass fiber cloth and baked in an oven at 170 - 180 °C for 5 - 8 min, and then cooled to room temperature to obtain a semi-cured sheet; 8 semi-cured sheets are taken for lamination, copper foils are laid on both sides, and then put into a vacuum laminator for hot pressing to obtain a phosphorus-containing flame-retardant halogen-free copper clad laminate. During the process of preparing the glue solution, linear phenolic resin is used as the curing agent and bisphenol A epoxy resin is used as the main resin. The epoxy groups contained in the phosphorus-containing tetra-glycidyl ester and the epoxy groups contained in the epoxy resin are used for curing crosslinking with the linear phenolic resin to form a three-dimensional network structure. Due to having more epoxy groups, a larger crosslinking density is generated. This crosslinked network structure with a larger density can effectively improve the heat resistance and mechanical properties of the material.

[0009] Preferably, the mass ratio of bisphenol A epoxy resin, linear phenolic resin, phosphorus-containing tetra-glycidyl ester, and accelerator is 100:30 - 40:10 - 20:0.4 - 0.6.

[0010] Preferably, the preparation method of the phosphorus-containing tetra-glycidyl ester includes the following steps:

[0011] Step (1): p-formylbenzoic acid is added to ethanol, stirred and dispersed, and then an ethanol solution of diethylenetriamine is added thereto, and the temperature is raised to 60 - 70 °C and reacted for 2 - 5 h. After the reaction is completed, it is washed with n-hexane, filtered by suction, and dried. The obtained product is denoted as target product I, where the molar ratio of p-formylbenzoic acid to diethylenetriamine is 2 - 2.2:1. In this reaction, using p-formylbenzoic acid and diethylenetriamine as raw materials, through the Schiff base reaction, target product I is obtained, that is, a Schiff base structure and a benzene ring structure are introduced into target product I. When the Schiff base structure is heated, it can absorb heat, open-ring crosslink to form a network structure, so it has good heat resistance, and the benzene ring is a rigid structure and also has good heat resistance. Its reaction synthesis route is:

[0012] ;

[0013] Step (2): Allyl chloride and target product I are added to ethanol, stirred and mixed evenly, and then sodium bicarbonate is added thereto, and the temperature is controlled at 50 - 60 °C and reacted for 12 - 16 h. After the reaction is completed, it is washed with deionized water, the solvent is removed by rotary evaporation, and dried. The obtained product is denoted as target product II, where the molar ratio of allyl chloride, target product I, and sodium bicarbonate is 1:1.5 - 2:0.8 - 1.2. In this reaction, using allyl chloride and target product I as raw materials, through the substitution reaction, target product II is obtained. Its reaction synthesis route is:

[0014] ;

[0015] Step (3): Under a nitrogen atmosphere, add SPDPC-H to N,N-dimethylformamide, heat up to 60 - 70 °C, stir to dissolve, then add the target product II thereto, stir and react for 24 - 30 h. After the reaction is completed, wash with dichloromethane and dry. The obtained product is denoted as the target product III, where the molar ratio of SPDPC-H to the target product II is 1:2.2 - 2.5. In this reaction, an addition reaction occurs between the C=C in the target product II and the P-H bond in SPDPC-H to obtain the target product III. Through the addition reaction, a phosphorus-containing structure, a nitrogen-containing structure, and a carbon-containing skeleton are introduced into the target product III. During combustion, the carbon-containing skeleton can form a layer of coke protection layer to inhibit the further combustion of the matrix; when the phosphorus-containing structure is heated, the P-O bond breaks, and phosphoric acid substances are generated during the combustion process to promote the system to degrade into carbon in advance, forming a stable carbon layer, and a glassy substance is formed on the surface of the carbide. This layer of structure can effectively inhibit the diffusion of combustible gases generated during the combustion process to the combustion area, isolate oxygen and heat, and thus improve the flame retardancy of the material; the nitrogen-containing structure decomposes endothermically at high temperature to lower the surface temperature of the material, and at the same time, incombustible gases such as NH3 and N2 generated by decomposition dilute the concentration of air and oxygen, playing a role in synergistic flame retardancy. Its reaction synthesis route is:

[0016] ;

[0017] Step (4): Add the target product III and epichlorohydrin to a flask, stir and disperse, heat up to 100 - 110 °C, add tetrabutylammonium bromide thereto, react at a constant temperature for 4 - 6 h. After the reaction is completed, cool to 60 - 65 °C, add a 50% sodium hydroxide aqueous solution thereto, keep warm and react for 3 - 5 h. After the reaction is completed, wash with saturated sodium chloride and dry to obtain a phosphorus-containing tetraglycidyl ester, where the molar ratio of the target product III to epichlorohydrin is 1:8 - 10, and the dosage of tetrabutylammonium bromide is 2 - 4% of the mass of the target product III. In this reaction, under the action of tetrabutylammonium bromide, the carboxylate group of the target product III acts as a nucleophile to attack the epoxy group in epichlorohydrin, undergoing a ring-opening esterification reaction, and then adding sodium hydroxide for a ring-closing reaction to obtain a phosphorus-containing tetraglycidyl ester, that is, a tetra-epoxy group is introduced into the phosphorus-containing tetraglycidyl ester. Its reaction route is:

[0018] ;

[0019] (III) Beneficial technical effects

[0020] The present invention prepares a phosphorus-containing tetraglycidyl ester and uses it as a raw material to jointly prepare a phosphorus-containing flame-retardant halogen-free copper clad laminate with epoxy resin. First, the flame-retardant elements contained in the phosphorus-containing tetraglycidyl ester are used to improve the flame-retardant performance of the copper clad laminate material. Second, the heat-resistant structures (Schiff base structure, benzene ring structure, spiro ring structure) contained in the phosphorus-containing tetraglycidyl ester are used to improve the heat-resistant performance of the copper clad laminate. Further, the heat-resistant performance and mechanical properties of the copper clad laminate material are improved by using the cross-linked network structure with a relatively large density generated during the curing of the phosphorus-containing tetraglycidyl ester. This is because the phosphorus-containing tetraglycidyl ester contains more epoxy groups and can generate a relatively large cross-linking density with the curing agent. On the one hand, the cross-linking density of the cured product is large, and the thermal stability is enhanced. On the other hand, a relatively large cross-linking density can generate relatively large cross-linking sites. When the material is subjected to external force, it can be dispersed to other network chains through the cross-linking sites, thereby improving the mechanical properties. In addition, the copper clad laminate material prepared in the present invention contains more ester groups, ether bonds and other polar structures, which can generate a strong force with the copper foil, effectively improve the adhesion, and thus improve the peel strength. Detailed implementation mode

[0021] The following further describes the present invention in detail through specific examples.

[0022] Preparation method of 2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane-3,9-dioxide (SPDPC-H): At room temperature, 0.4 mol of formic acid was added to 0.2 mol of 3,9-dichloro-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane 3,9-dioxide (SPDPC). The reaction was protected by filling nitrogen during the reaction. After reacting for 2 h, it was washed with diethyl ether and deionized water in sequence and dried to obtain SPDPC-H. The reaction synthesis route is as follows:

[0023] 。

[0024] Example 1

[0025] (1) 0.2 mol of p-formylbenzoic acid was added to ethanol and stirred to disperse. Then, an ethanol solution containing 0.1 mol of diethylenetriamine was added thereto, and the temperature was raised to 65 °C and reacted for 4 h. After the reaction was completed, it was washed with n-hexane, filtered by suction, and dried. The obtained product was denoted as target product I.

[0026] (2) 50 mmol of allyl chloride and 80 mmol of target product I were added to ethanol and stirred and mixed evenly. Then, 50 mmol of sodium bicarbonate was added thereto, and the temperature was controlled at 55 °C and reacted for 15 h. After the reaction was completed, it was washed with deionized water, the solvent was removed by rotary evaporation, and dried. The obtained product was denoted as target product II.

[0027] (3) Under a nitrogen atmosphere, 20 mmol of SPDPC-H was added to N,N-dimethylformamide, and the temperature was raised to 65 °C and stirred until dissolved. Then 50 mmol of target product II was added thereto, and the mixture was stirred and reacted for 26 h. After the reaction was completed, it was washed with dichloromethane and dried. The obtained product was denoted as target product III.

[0028] (4) 20 mmol of target product III and 180 mmol of epichlorohydrin were added to a flask, stirred and dispersed, and the temperature was raised to 105 °C. 0.6 g of tetrabutylammonium bromide was added thereto, and the reaction was carried out at a constant temperature for 6 h. After the reaction was completed, the temperature was lowered to 60 °C, and an aqueous sodium hydroxide solution with a mass fraction of 50% was added thereto, and the mixture was kept warm and reacted for 5 h. After the reaction was completed, it was washed with saturated sodium chloride and dried to obtain phosphorus-containing tetraglycidyl ester.

[0029] (5) 100 g of bisphenol A type epoxy resin, 30 g of linear phenolic resin, and 10 g of phosphorus-containing tetraglycidyl ester were added to acetone solvent, stirred and mixed evenly. Then 0.5 g of 2-methylimidazole accelerator was added thereto, and the mixture was stirred and mixed evenly to obtain a glue solution; the glue solution was applied on an E-glass fiber cloth and baked in an oven at 170 °C for 6 min, and then cooled to room temperature to obtain a prepreg; 8 prepregs were taken for lamination, copper foils were laid on both sides, and then put into a vacuum laminator and hot-pressed at 190 °C and 2.5 MPa for 100 min to obtain a phosphorus-containing flame-retardant halogen-free copper clad laminate.

[0030] Example 2

[0031] (1) 0.22 mol of p-formylbenzoic acid was added to ethanol, stirred and dispersed. Then an ethanol solution containing 0.1 mol of diethylenetriamine was added thereto, and the temperature was raised to 60 °C and reacted for 5 h. After the reaction was completed, it was washed with n-hexane, filtered by suction, and dried. The obtained product was denoted as target product I.

[0032] (2) 50 mmol of allyl chloride and 100 mmol of target product I were added to ethanol, stirred and mixed evenly. Then 60 mmol of sodium bicarbonate was added thereto, and the temperature was controlled at 50 °C and reacted for 16 h. After the reaction was completed, it was washed with deionized water, the solvent was removed by rotary evaporation, and dried. The obtained product was denoted as target product II.

[0033] (3) Under a nitrogen atmosphere, 20 mmol of SPDPC-H was added to N,N-dimethylformamide, and the temperature was raised to 65 °C and stirred until dissolved. Then 45 mmol of target product II was added thereto, and the mixture was stirred and reacted for 30 h. After the reaction was completed, it was washed with dichloromethane and dried. The obtained product was denoted as target product III.

[0034] (4) Add 20 mmol of the target product Ⅲ and 190 mmol of epichlorohydrin into a flask, stir to disperse, heat up to 105 °C, add 0.6 g of tetrabutylammonium bromide thereto, react at a constant temperature for 4 h. After the reaction is completed, cool down to 60 °C, add an aqueous sodium hydroxide solution with a mass fraction of 50%, keep the temperature for reaction for 4 h. After the reaction is completed, wash with saturated sodium chloride, dry to obtain phosphorus-containing tetraglycidyl ester.

[0035] (5) Add 100 g of bisphenol A type epoxy resin, 32 g of linear phenolic resin, and 14 g of phosphorus-containing tetraglycidyl ester into acetone solvent, stir and mix evenly. Then add 0.4 g of 2-methylimidazole accelerator thereto, stir and mix evenly to obtain a glue solution; apply the glue solution on E-glass fiber cloth, bake in an oven at 175 °C for 6 min, cool to room temperature to obtain a semi-cured sheet; take 8 semi-cured sheets for lamination, apply copper foil on both sides, put it into a vacuum laminator, and perform hot pressing at 190 °C and 2.5 MPa for 100 min to obtain a phosphorus-containing flame-retardant halogen-free copper clad laminate.

[0036] Example 3

[0037] (1) Add 0.2 mol of p-formylbenzoic acid into ethanol, stir to disperse, then add an ethanol solution containing 0.1 mol of diethylenetriamine thereto, heat up to 70 °C, react for 2 h. After the reaction is completed, wash with n-hexane, filter by suction, dry, and record the obtained product as target product Ⅰ.

[0038] (2) Add 50 mmol of allyl chloride and 75 mmol of target product Ⅰ into ethanol, stir and mix evenly. Then add 50 mmol of sodium bicarbonate thereto, control the temperature at 55 °C, react for 14 h. After the reaction is completed, wash with deionized water, remove the solvent by rotary evaporation, dry, and record the obtained product as target product Ⅱ.

[0039] (3) Under a nitrogen atmosphere, add 20 mmol of SPDPC-H into N,N-dimethylformamide, heat up to 70 °C, stir to dissolve, then add 44 mmol of target product Ⅱ thereto, stir and react for 25 h. After the reaction is completed, wash with dichloromethane, dry, and record the obtained product as target product Ⅲ.

[0040] (4) Add 20 mmol of target product Ⅲ and 160 mmol of epichlorohydrin into a flask, stir to disperse, heat up to 110 °C, add 0.4 g of tetrabutylammonium bromide thereto, react at a constant temperature for 6 h. After the reaction is completed, cool down to 65 °C, add an aqueous sodium hydroxide solution with a mass fraction of 50%, keep the temperature for reaction for 3 h. After the reaction is completed, wash with saturated sodium chloride, dry to obtain phosphorus-containing tetraglycidyl ester.

[0041] (5) Add 100 g of bisphenol A type epoxy resin, 36 g of linear phenolic resin, and 18 g of phosphorus-containing tetraglycidyl ester to acetone solvent, stir and mix evenly, then add 0.6 g of 2-methylimidazole accelerator thereto, stir and mix evenly to obtain a glue solution; apply the glue solution on E-glass fiber cloth, bake in an oven at 170 °C for 8 min, and cool to room temperature to obtain a prepreg; take 8 prepregs for lamination, apply copper foils on both sides, put them into a vacuum laminator, and perform hot pressing at 190 °C and 2.5 MPa for 100 min to obtain a phosphorus-containing flame-retardant halogen-free copper clad laminate.

[0042] Example 4

[0043] (1) Add 0.22 mol of p-formylbenzoic acid to ethanol, stir and disperse, then add an ethanol solution containing 0.1 mol of diethylenetriamine thereto, heat up to 70 °C, react for 3 h, after the reaction is completed, wash with n-hexane, filter by suction, and dry, and the obtained product is denoted as target product I.

[0044] (2) Add 50 mmol of allyl chloride and 80 mmol of target product I to ethanol, stir and mix evenly, then add 40 mmol of sodium bicarbonate thereto, control the temperature at 60 °C, react for 12 h, after the reaction is completed, wash with deionized water, remove the solvent by rotary evaporation, and dry, and the obtained product is denoted as target product II.

[0045] (3) Under a nitrogen atmosphere, add 20 mmol of SPDPC-H to N,N-dimethylformamide, heat up to 60 °C, stir and dissolve, then add 50 mmol of target product II thereto, stir and react for 24 h, after the reaction is completed, wash with dichloromethane and dry, and the obtained product is denoted as target product III.

[0046] (4) Add 20 mmol of target product III and 200 mmol of epichlorohydrin to a flask, stir and disperse, heat up to 100 °C, add 0.8 g of tetrabutylammonium bromide thereto, react at a constant temperature for 4 h, after the reaction is completed, cool to 60 °C, add a 50% sodium hydroxide aqueous solution by mass thereto, keep warm and react for 5 h, after the reaction is completed, wash with saturated sodium chloride and dry to obtain a phosphorus-containing tetraglycidyl ester.

[0047] (5) Add 100 g of bisphenol A epoxy resin, 40 g of linear phenolic resin, and 20 g of phosphorus-containing tetraglycidyl ester to acetone solvent, stir and mix evenly. Then add 0.4 g of 2-methylimidazole accelerator and stir and mix evenly to obtain a glue solution. Apply the glue solution on E-glass fiber cloth, bake it in an oven at 180 °C for 5 min, and cool it to room temperature to obtain a prepreg. Take 8 prepregs for lamination, apply copper foil on both sides, put them into a vacuum laminator, and perform hot pressing at 190 °C and 2.5 MPa for 100 min to obtain a phosphorus-containing flame-retardant halogen-free copper clad laminate.

[0048] Comparative Example 1

[0049] The preparation method of the copper clad laminate provided in this comparative example is generally the same as that of Example 1, and the main difference is that: in step (5), it does not contain phosphorus-containing tetraglycidyl ester.

[0050] Flame retardancy test: Use a horizontal-vertical burning tester to test the flame retardancy of the copper clad laminate;

[0051] Heat resistance limit test: Judge the heat resistance performance according to the IPC-TM-650-2.4.13.1 method.

[0052] Table 1: Test results of flame retardancy and heat resistance of Examples 1-4 and Comparative Example 1

[0053]

[0054] As can be seen from the table, the flame retardancy and heat resistance of Examples 1-4 are better than those of Comparative Example 1. The difference between the two is that Comparative Example 1 does not contain phosphorus-containing tetraglycidyl ester. This is because the phosphorus-containing tetraglycidyl ester prepared by the present invention is added to the copper clad laminate. On the one hand, the flame retardant elements contained in the phosphorus-containing tetraglycidyl ester are used to improve the flame retardancy of the copper clad laminate; on the other hand, the rigid structure and Schiff base structure contained in the phosphorus-containing tetraglycidyl ester are used to improve the heat resistance of the material. And during its curing process, due to the presence of a tetra-epoxy group structure, more cross-linked structures with a larger density will be generated, and the structure with a large cross-linking density can also improve the heat resistance of the material. Therefore, the flame retardancy and heat resistance of Comparative Example 1 without phosphorus-containing tetraglycidyl ester are inferior to those of Examples 1-4.

[0055] Bending property test: Use a universal testing machine to test the bending property of the copper clad laminate;

[0056] Peeling performance test: Peel the copper foil at one end of the specimen from the substrate by 10 mm, clamp the specimen on the specimen holder of the peeling machine, clamp the peeled copper foil with the specimen clamp, keep the copper foil perpendicular to the substrate, start the peeling machine to apply a uniform tensile force, and keep the tensile force direction perpendicular to the substrate direction. Record the minimum value during the process where the peeling length is not less than 25 mm. The minimum load required per unit width is the peeling strength.

[0057] Table 2: Mechanical property test results of Examples 1-4 and Comparative Example 1

[0058]

[0059] As can be seen from the table, the flexural strength and peeling strength of Examples 1-4 are better than those of Comparative Example 1. In Examples 1-4 containing phosphorus tetraglycidyl ester, since the phosphorus tetraglycidyl ester contains more polar structures that can interact with the copper foil, therefore, it can effectively improve the peeling strength of the copper clad laminate; and in Examples 1-4 containing phosphorus tetraglycidyl ester, a three-dimensional crosslinked network is also generated during the curing process, and the three-dimensional crosslinked network structure can improve the flexural strength of the material.

[0060] Therefore, the copper clad laminate prepared by the present invention has good heat resistance, flame retardancy and mechanical properties.

[0061] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A preparation method of a phosphorus-containing flame-retardant halogen-free copper clad laminate, characterized in that, The preparation method comprises the following steps: Add bisphenol A type epoxy resin, linear phenolic resin, and phosphorus-containing tetraglycidyl ester into acetone solvent, stir and mix evenly, then add 2-methylimidazole accelerator thereto, stir and mix evenly to obtain a glue solution; apply the glue solution on an E-glass cloth, bake it in an oven at 170 - 180 °C for 5 - 8 min, cool it to room temperature to obtain a prepreg; take 8 prepregs for lamination, apply copper foils on both sides, put them into a vacuum laminator, and perform hot pressing to obtain a phosphorus-containing flame-retardant halogen-free copper clad laminate.

2. The preparation method of the phosphorus-containing flame-retardant halogen-free copper clad laminate according to claim 1, characterized in that, The mass ratio of bisphenol A type epoxy resin, linear phenolic resin, phosphorus-containing tetraglycidyl ester, and accelerator is 100:30 - 40:10 - 20:0.4 - 0.

6.

3. The preparation method of the phosphorus-containing flame-retardant halogen-free copper clad laminate according to claim 1, characterized in that, The preparation method of the phosphorus-containing tetraglycidyl ester comprises the following steps: Step (1): Add p-formylbenzoic acid into ethanol, stir and disperse it, then add an ethanol solution of diethylenetriamine thereto, heat up to 60 - 70 °C, react for 2 - 5 h, after the reaction ends, wash with n-hexane, filter by suction, and dry. The obtained product is denoted as target product I; Step (2): Add allyl chloride and target product I into ethanol, stir and mix evenly, then add sodium bicarbonate thereto, control the temperature at 50 - 60 °C, react for 12 - 16 h, after the reaction ends, wash with deionized water, remove the solvent by rotary evaporation, and dry. The obtained product is denoted as target product II; Step (3): Under a nitrogen atmosphere, add SPDPC-H into N,N-dimethylformamide, heat up to 60 - 70 °C, stir to dissolve it, then add target product II thereto, stir and react for 24 - 30 h, after the reaction ends, wash with dichloromethane, and dry. The obtained product is denoted as target product III; Step (4): Add target product III and epichlorohydrin into a flask, stir and disperse them, heat up to 100 - 110 °C, add tetrabutylammonium bromide thereto, react at a constant temperature for 4 - 6 h, after the reaction ends, cool down to 60 - 65 °C, add a 50% sodium hydroxide aqueous solution thereto, keep the temperature and react for 3 - 5 h, after the reaction ends, wash with saturated sodium chloride, and dry. The obtained product is denoted as the phosphorus-containing tetraglycidyl ester.

4. The preparation method of the phosphorus-containing flame-retardant halogen-free copper clad laminate according to claim 3, characterized in that, In step (1), the molar ratio of p-formylbenzoic acid to diethylenetriamine is 2 - 2.2:

1.

5. The preparation method of the phosphorus-containing flame-retardant halogen-free copper clad laminate according to claim 3, wherein, In step (2), the molar ratio of allyl chloride, target product I, and sodium bicarbonate is 1:1.5 - 2:0.8 - 1.

2.

6. The preparation method of the phosphorus-containing flame-retardant halogen-free copper clad laminate according to claim 3, characterized in that, In step (3), the molar ratio of SPDPC-H to target product II is 1:2.2 - 2.

5.

7. The preparation method of the phosphorus-containing flame-retardant halogen-free copper clad laminate according to claim 3, characterized in that, [[ID= 8. The preparation method of the phosphorus-containing flame-retardant halogen-free copper clad laminate according to claim 3, wherein, ​

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