A method for preparing an acetylene-nitrogen-phosphorus benzoxazine resin for copper-clad laminates

Abstract

This invention relates to a method for preparing an acetylene-nitrogen-phosphorus benzoxazine resin for copper-clad laminates, and is a method for preparing polymer materials. The invention uses vanillin (3-methoxy-4-hydroxybenzaldehyde) and 2-aminobenzimidazole as raw materials, and utilizes this intermediate to undergo a substitution reaction with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to synthesize a novel halogen-free phosphorus-based flame retardant. Ring-opening polymerization with aldehydes and phenolic compounds synthesizes a six-membered oxazine ring containing nitrogen and oxygen structures, thereby obtaining an acetylene-containing benzoxazine resin. The synthesized novel phosphorus-containing halogen-free flame retardant is then subjected to a curing reaction with the synthesized acetylene-containing benzoxazine to obtain a cured benzoxazine resin product with an acetylene-nitrogen-phosphorus structure. This significantly improves the heat resistance and flame retardancy of the benzoxazine resin and its cured system. Simultaneously, the cured system exhibits excellent char-forming properties, forming a dense char layer that effectively insulates against heat and combustible gases.

Description

Technical Field

[0001] This invention relates to a method for preparing polymer materials, and more particularly to a method for preparing an acetylene-nitrogen-phosphorus benzoxazine resin for copper-clad laminates. Background Technology

[0002] Copper-clad laminates (CCLs), as a fundamental material for electronic components, are widely used in electronics, medical, aerospace, and other fields. CCLs are made by impregnating fiberglass cloth with a resin solution, drying it, then covering it with copper foil, and finally processing it under high temperature and pressure in a hot press. Industrially, phenolic resins and epoxy resins are commonly used to prepare the resin solution; however, the various resins currently selected have certain drawbacks in terms of processing, heat resistance, and flame retardancy.

[0003] Benzoxazine resin is a novel thermosetting resin that has matured over the past 40 years. It is also a special type of phenolic resin with many advantages, such as simple molding and processing conditions, low melt viscosity, near-zero volume expansion and shrinkage during polymerization, and excellent molecular designability. For specific applications, benzoxazine resins can be synthesized by selecting raw materials containing specific functional groups. Compared to traditional phenolic resins, benzoxazine resins not only retain the advantages of traditional phenolic resins but also compensate for their shortcomings in many aspects. As a base resin for copper-clad laminates, it needs to possess high heat resistance, with a glass transition temperature (Tg) exceeding 250℃. However, the glass transition temperatures of common bifunctional benzoxazine resins are typically between 160-200℃, thus requiring further performance improvements. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing an acetylene-nitrogen-phosphorus benzoxazine resin for copper-clad laminates. This method introduces nitrogen (N) into the components and incorporates vanillin-based halogen-free flame retardants. The system exhibits significantly improved heat resistance and flame retardancy, higher char residue, and excellent char layer continuity and density. This effectively optimizes the performance of the final product.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for preparing an acetylene-nitrogen-phosphorus benzoxazine resin for copper-clad laminates, the method comprising the following steps:

[0007] a. Preparation of phosphorus-containing halogen-free flame retardant: Vanillin (3-methoxy-4-hydroxybenzaldehyde) and 2-aminobenzimidazole were mixed in a molar ratio of 1:1, and then mixed thoroughly with solvent and alkaline solution in a three-necked flask equipped with a magnetic stirrer. The reaction temperature was controlled at 50-70℃, and the mixture was stirred continuously at this temperature for 7-10 hours. Then, a solution of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was added to the system. The system temperature was kept constant, and nitrogen gas was introduced. The mixture was stirred continuously for 7-10 hours under nitrogen protection. After the reaction was completed, the product was obtained by rotary evaporation to obtain a white viscous latex-like liquid. The liquid was then slowly poured into anhydrous ethanol to ensure thorough mixing. Next, the mixed solution was placed in a beaker for recrystallization. After recrystallization, the mixture was vacuum filtered and washed three times with deionized water to ensure thorough purification. The product was then dried in an oven at 70℃ to constant weight to obtain a yellow powder.

[0008] b. Preparation of acetylene-containing benzoxazine resin: 3-aminophenylacetylene and aniline were mixed evenly in a reaction flask, and then aldehydes were added. The reaction system was reacted at 40°C for 1 hour. After the reaction was completed, phenols were added to dissolve the resin, and then the temperature was raised to 120°C and stirred until the system became transparent. The resin was then dried in an oven at 70°C to obtain acetylene-containing benzoxazine resin.

[0009] The method for preparing an acetylene-nitrogen-phosphorus benzoxazine resin for copper-clad laminates, wherein the alkaline solvent includes one or more of pyridine, imidazole, triethylamine, sodium ethoxide, sodium methoxide, diethylamine, potassium hydroxide, sodium hydroxide, and potassium tert-butoxide.

[0010] The method for preparing an acetylene-nitrogen-phosphorus-benzoxazine resin for copper-clad laminates, wherein the organic solvent includes one of methanol, acetonitrile, ethanol, cyclopentanone, dichloromethane, chloroform, carbon tetrachloride, tetrahydrofuran, hexamethylphosphoric triamine, dimethylacetamide, and N-methylpyrrolidone.

[0011] The method for preparing an acetylene-nitrogen-phosphorus benzoxazine resin for copper clad laminates, wherein the molar ratio of 3-aminophenylacetylene to aniline is 0.9:1.

[0012] The method for preparing an acetylene-nitrogen-phosphorus benzoxazine resin for copper clad laminates, wherein the phenolic substance is phenol, bisphenol A, or bisphenol F.

[0013] The method for preparing an acetylene-nitrogen-phosphorus benzoxazine resin for copper clad laminates, wherein the aldehyde is one of paraformaldehyde or formaldehyde aqueous solution.

[0014] The method for preparing an acetylene-nitrogen-phosphorus benzoxazine resin for copper clad laminates, wherein the molar ratio of paraformaldehyde to phenol source is 4:1.

[0015] The beneficial effects of this invention are as follows:

[0016] This invention first utilizes the addition reaction of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide with vanillin to synthesize a phosphorus-containing halogen-free flame retardant. The preparation process is convenient and simple, and the yield is high.

[0017] The incorporation of an acetylene group into the benzoxazine ring significantly improves the heat resistance of benzoxazine.

[0018] The crosslinking density of the curing system using benzoxazine resin containing acetylene groups as a curing agent was significantly improved, and it also had higher residual char content and better continuous and dense char layer. Attached Figure Description

[0019] Figure 1 This is the molecular formula of the phosphorus-containing halogen-free flame retardant of the present invention;

[0020] Figure 2 This is the reaction equation for the acetylene-containing benzoxazine resin of the present invention. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention, but the embodiments are not intended to limit the present invention. Example 1

[0022] Preparation of phosphorus-containing halogen-free flame retardants

[0023] 15.2 g (0.1 mol) of vanillin and 13.3 g (0.1 mol) of 2-aminobenzimidazole were mixed together with methanol and triethylamine solution in a three-necked flask equipped with a magnetic stirrer. The mixture was stirred thoroughly at 50-70 °C for 7-10 h. Then, a solution of 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was added, and the system temperature was kept constant while nitrogen gas was introduced. The mixture was stirred continuously for 7-10 h under nitrogen protection. After the reaction was complete, the product was evaporated by rotary evaporation to obtain a white, viscous, latex-like liquid. This liquid was then slowly poured into anhydrous ethanol to ensure thorough mixing. The mixture was then recrystallized in a beaker. After recrystallization, the solution was vacuum filtered and washed three times with deionized water to ensure complete purification. The product was then dried in an oven at 70 °C to constant weight to obtain a phosphorus-containing halogen-free flame retardant.

[0024] (2) Preparation of resin containing acetylene benzoxazine

[0025] 25.2 g (0.9 mol) of paraformaldehyde and a mixture of 37.2 g of aniline and 3-acetyleneaniline (0.4 mol) were added to a reaction flask, mixed thoroughly, and heated to 40 °C for 1 h. Then, 57 g of bisphenol A (0.25 mol) was added, and the reaction system was heated to 110 °C for 0.5 h. The system became transparent, and the mixture was poured off while hot and cooled to room temperature to obtain an acetylene-containing benzoxazine resin. Example 2

[0026] (1) Preparation of phosphorus-containing halogen-free flame retardants

[0027] 7.6 g (0.05 mol) of vanillin and 6.65 g (0.05 mol) of 2-aminobenzimidazole were mixed. This mixture, along with dichloromethane and an aqueous sodium hydroxide solution, was placed in a three-necked flask equipped with a magnetic stirrer and mixed thoroughly. The reaction temperature was maintained at 50-70 °C, and the mixture was stirred continuously at this temperature for 7-10 hours. Then, a solution of 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was added. The system temperature was kept constant, and nitrogen gas was introduced. The mixture was stirred continuously under nitrogen protection for 7-10 hours. After the reaction was complete, the product was evaporated by rotary evaporation to obtain a white, viscous, latex-like liquid. This liquid was then slowly poured into anhydrous ethanol to ensure thorough mixing. Next, the mixture was recrystallized in a beaker. After recrystallization, the mixture was vacuum filtered and washed three times with deionized water to ensure complete purification. The product was then dried in an oven at 70 °C to constant weight to obtain a phosphorus-containing halogen-free flame retardant.

[0028] (2) Preparation of resin containing acetylene benzoxazine

[0029] 1.23 g (0.04 mol) of paraformaldehyde and 2.34 g (0.02 mol) of 3-acetyleneaniline were added to a reaction flask, mixed thoroughly, and heated to 40 °C for 1 h. Then, 2.002 g (0.01 mol) of bisphenol F was added, and the reaction system was heated to 110 °C for 0.5 h. The system became transparent, and the mixture was poured off while hot and cooled to room temperature to obtain an acetylene-containing benzoxazine resin. Example 3

[0030] (1) Preparation of phosphorus-containing halogen-free flame retardants

[0031] 7.6 g (0.05 mol) of vanillin and 6.65 g (0.05 mol) of 2-aminobenzimidazole were mixed together with dimethylacetamide and potassium tert-butoxide solution in a three-necked flask equipped with a magnetic stirrer. The mixture was stirred continuously at 50-70 °C for 7-10 h. Then, a solution of 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was added, and the system temperature was kept constant while nitrogen gas was introduced. The mixture was stirred continuously for 7-10 h under nitrogen protection. After the reaction was complete, the product was evaporated by rotary evaporation to obtain a white, viscous, latex-like liquid. This liquid was then slowly poured into anhydrous ethanol to ensure thorough mixing. The mixture was then recrystallized in a beaker. After recrystallization, the mixture was vacuum filtered and washed three times with deionized water to ensure complete purification. The product was then dried in an oven at 70 °C to constant weight to obtain a phosphorus-containing halogen-free flame retardant.

[0032] (2) Preparation of resin containing acetylene benzoxazine

[0033] 1.23 g (0.04 mol) of paraformaldehyde and 1.86 g (0.02 mol) of aniline were added to a reaction flask, mixed thoroughly, and heated to 40 °C for 1 h. Then, 1.88 g (0.02 mol) of phenol was added, and the reaction system was heated to 110 °C for 0.5 h. The system became transparent, and the mixture was poured off while hot and cooled to room temperature to obtain a resin containing acetylene-based benzoxazine. Example 4

[0034] (1) Preparation of phosphorus-containing halogen-free flame retardants

[0035] 3.04 g (0.02 mol) of vanillin and 2.66 g (0.02 mol) of 2-aminobenzimidazole were mixed together with ethanol and triethylamine in a three-necked flask equipped with a magnetic stirrer. The mixture was stirred thoroughly at 50-70 °C for 7-10 h. Then, a solution of 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was added, and the system temperature was kept constant while nitrogen gas was introduced. The mixture was stirred continuously for 7-10 h under nitrogen protection. After the reaction was complete, the product was evaporated by rotary evaporation to obtain a white, viscous, latex-like liquid. This liquid was then slowly poured into anhydrous ethanol to ensure thorough mixing. The mixture was then recrystallized in a beaker. After recrystallization, the solution was vacuum filtered and washed three times with deionized water to ensure complete purification. The product was then dried in an oven at 70 °C to constant weight to obtain a phosphorus-containing halogen-free flame retardant.

[0036] (2) Preparation of resin containing acetylene benzoxazine

[0037] 1.23 g (0.04 mol) of paraformaldehyde, 0.93 g (0.01 mol) of aniline, and 1.17 g (0.01 mol) of 3-acetyleneaniline were added to a reaction flask, mixed thoroughly, and heated to 40 °C for 1 h. Then, 2.002 g (0.01 mol) of bisphenol F was added, and the reaction system was heated to 110 °C for 0.5 h. The system became transparent, and the mixture was poured off while hot and cooled to room temperature to obtain an acetylene-containing benzoxazine resin. Example 5

[0038] (1) Preparation of phosphorus-containing halogen-free flame retardants

[0039] 15.2 g (0.1 mol) of vanillin and 13.3 g (0.1 mol) of 2-aminobenzimidazole were mixed and placed in a three-necked flask equipped with a magnetic stirrer along with ethanol and an appropriate amount of imidazole. The mixture was stirred thoroughly at 50-70 °C for 7-10 h. Then, a solution of 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was added, and the system temperature was kept constant while nitrogen gas was introduced. The mixture was stirred continuously for 7-10 h under nitrogen protection. After the reaction was complete, the product was evaporated by rotary evaporation to obtain a white, viscous, latex-like liquid. This liquid was then slowly poured into anhydrous ethanol to ensure thorough mixing. The mixture was then recrystallized in a beaker. After recrystallization, the solution was vacuum filtered and washed three times with deionized water to ensure complete purification. The product was then dried in an oven at 70 °C to constant weight to obtain a phosphorus-containing halogen-free flame retardant.

[0040] (2) Preparation of resin containing acetylene benzoxazine

[0041] 6.06 g (0.2 mol) of paraformaldehyde, 3.73 g (0.04 mol) of aniline, and 7.03 g (0.06 mol) of 3-acetyleneaniline were added to a reaction flask, mixed thoroughly, and heated to 40 °C for 1 h. Then, 10 g (0.05 mol) of bisphenol F was added, and the reaction system was heated to 110 °C for 0.5 h. The system became transparent, and the mixture was poured off while hot and cooled to room temperature to obtain an acetylene-containing benzoxazine resin.

[0042] The benzoxazine resin curing agent obtained in the above examples and comparative examples was mixed evenly with 9% vanillin phosphorus-containing halogen-free flame retardant and epoxy resin through a solvent, and 2-phenylimidazolium curing accelerator was added. After the curing reaction, the limiting oxygen index (LOI) and vertical burning UL-94 tests were performed. The test results are shown in Table 1.

[0043] Table 1. Test Results of Examples and Comparative Examples

[0044]

[0045] The determination of the limiting oxygen index in Table 1 is based on the national standard method GB / T 2406.2-2009, and the UL-94 vertical burning test adopts the standard GB / T 2408-2008.

Claims

1. A method for preparing an acetylene-nitrogen-phosphorus benzoxazine resin for copper-clad laminates, characterized in that, The method includes the following steps: a. Preparation of phosphorus-containing halogen-free flame retardant: Vanillin (3-methoxy-4-hydroxybenzaldehyde) and 2-aminobenzimidazole were mixed in a molar ratio of 1:1, and then mixed thoroughly with solvent and alkaline solution in a three-necked flask equipped with a magnetic stirrer. The reaction temperature was controlled at 50-70℃, and the mixture was stirred continuously at this temperature for 7-10 hours. Then, a solution of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was added to the system. The system temperature was kept constant, and nitrogen gas was introduced. The mixture was stirred continuously for 7-10 hours under nitrogen protection. After the reaction was completed, the product was obtained by rotary evaporation to obtain a white viscous latex-like liquid. The liquid was then slowly poured into anhydrous ethanol to ensure thorough mixing. Next, the mixed solution was placed in a beaker for recrystallization. After recrystallization, the mixture was vacuum filtered and washed three times with deionized water to ensure thorough purification. The product was then dried in an oven at 70℃ to constant weight to obtain a yellow powder. b. Preparation of acetylene-containing benzoxazine resin: 3-aminophenylacetylene and aniline were mixed evenly in a reaction flask, and then aldehydes were added. The reaction system was reacted at 40°C for 1 hour. After the reaction was completed, phenols were added to dissolve the resin, and then the temperature was raised to 120°C and stirred until the system became transparent. The resin was then dried in an oven at 70°C to obtain acetylene-containing benzoxazine resin.

2. The method for preparing an acetylene-nitrogen-phosphorus benzoxazine resin for copper-clad laminates according to claim 1, characterized in that, The alkaline solution includes one or more of pyridine, imidazole, triethylamine, sodium ethoxide, sodium methoxide, diethylamine, potassium hydroxide, sodium hydroxide, and potassium tert-butoxide.

3. The method for preparing an acetylene-nitrogen-phosphorus benzoxazine resin for copper-clad laminates according to claim 1, characterized in that, The solvent includes one of methanol, acetonitrile, ethanol, cyclopentanone, dichloromethane, trichloromethane, carbon tetrachloride, tetrahydrofuran, hexamethylphosphoric triamine, dimethylacetamide, and N-methylpyrrolidone.

4. The method for preparing an acetylene-nitrogen-phosphorus benzoxazine resin for copper-clad laminates according to claim 1, characterized in that, The molar ratio of 3-aminophenylacetylene to aniline is 0.9:

1.

5. The method for preparing an acetylene-nitrogen-phosphorus benzoxazine resin for copper-clad laminates according to claim 1, characterized in that, The phenolic substances are phenol, bisphenol A, and bisphenol F.

6. The method for preparing an acetylene-nitrogen-phosphorus benzoxazine resin for copper-clad laminates according to claim 1, characterized in that, The aldehydes mentioned are paraformaldehyde and formaldehyde aqueous solution.

7. A method for preparing an acetylene-nitrogen-phosphorus benzoxazine resin for copper-clad laminates according to claim 6, characterized in that, The molar ratio of paraformaldehyde to phenol source is 4:1.

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