High-temperature-resistant low-dielectric high-strength benzoxazine intermediate and preparation method of benzoxazine

Abstract

The invention relates to a high-temperature-resistant low-dielectric high-strength benzoxazine intermediate and a preparation method of benzoxazine, and belongs to the field of functional polymer materials. The method comprises the following steps: adding paraformaldehyde, unsaturated bond-containing dihydric phenol, a monohydric phenol compound and a diamine compound into a reactor, adding a solvent, reacting at 85-110 DEG C for 8-12 hours, after the reaction is finished, obtaining a benzoxazine intermediate through a purification process, and fully drying the benzoxazine intermediate for later use; and reacting the benzoxazine intermediate at 120-230 DEG C for 8-20 hours to obtain the polybenzoxazine resin.

Description

Technical Field

[0001] The invention relates to a high temperature resistant, low dielectric and high strength benzoxazine intermediate and a benzoxazine preparation method, belonging to the field of functional polymer materials. Background Art

[0002] With the rapid development of electronic information technology, antenna systems are becoming more and more dense and the accuracy requirements are getting higher and higher in the fields of aerospace and communication equipment. In order to ensure the high-fidelity transmission of electromagnetic waves and protect the antenna system from interference from complex external environments, there is an urgent need for resin-based wave-transmitting composite materials with light weight, low dielectric constant and low dielectric loss tangent, high temperature resistance and excellent mechanical properties. Resin-based wave-transmitting composite materials are composed of a resin matrix and a fiber reinforcement. The dielectric, heat resistance and mechanical properties of the resin matrix directly affect the performance of the final composite material. Benzoxazine is a new type of phenolic structure polymerizable compound containing nitrogen and oxygen six-membered heterocyclic rings synthesized from phenolic compounds, aldehydes and amine compounds as raw materials. It can undergo a ring-opening polymerization reaction under heating or the action of a catalyst to generate a network structure similar to phenolic resin. There is no release of small molecular substances during the curing process of benzoxazine resin, and the curing shrinkage rate is low. It not only has the advantages of high mechanical strength and heat resistance of traditional phenolic resins, but also has low water absorption and flexible molecular structure design. Therefore, its dielectric properties are highly controllable and have broad application prospects in the field of wave-transmitting composite materials.

[0003] CN 115340505A Zhang Chi et al. prepared low-dielectric diamine benzoxazine using 4,4-diaminotriphenylmethane, phenolic compounds and aldehyde compounds. The polybenzoxazine resin obtained after polymerization has a low dielectric constant and loss tangent, and is expected to be used in electronic packaging materials and high-performance resin-based composite materials. However, the molecular structure of the benzoxazine resin synthesized in this patent contains a large number of rigid groups, which leads to poor toughness of the resin. CN112062908 B Guo Kangkang et al. prepared a benzoxazine resin containing high unsaturated functionality by reacting phenols containing unsaturated bonds, amines containing unsaturated bonds and polyformaldehyde. After curing, the resin exhibits high thermal stability, high glass transition temperature, low water absorption and low dielectric properties. Summary of the invention

[0004] Purpose of the invention: Provide a high temperature resistant, low dielectric, high strength benzoxazine intermediate and a method for preparing benzoxazine. Aiming at the problem that the current low dielectric benzoxazine resin cannot take into account the heat resistance, mechanical and dielectric properties, this paper uses bisphenol with unsaturated bonds, aliphatic diamines and formaldehyde as raw materials to prepare benzoxazine polymers with regular molecular structure. The regular molecular structure gives the resin a low dielectric constant and loss tangent. The allyl double bond introduced in this patent has high reactivity, does not require a catalyst, and can fully react and polymerize under heating conditions. The introduction of unsaturated double bonds can increase the crosslinking density of the resin matrix, thereby improving the heat resistance and mechanical strength of the resin. The resin can be used as a resin matrix for wave-transmitting composite materials and electronic potting materials.

[0005] Technical solution:

[0006] In the first aspect, a high temperature resistant, low dielectric and high strength benzoxazine intermediate is provided, and its molecular formula structure is:

[0007]

[0008] In a second aspect, a method for preparing a high temperature resistant, low dielectric and high strength benzoxazine resin is provided, comprising:

[0009] Adding paraformaldehyde, dihydric phenol containing unsaturated bonds, monohydric phenol compounds and diamine compounds into a reactor, adding a solvent, reacting at 85-110° C. for 8-12 hours, and after the reaction is completed, obtaining a benzoxazine intermediate through a purification process, and fully drying it for later use;

[0010] The benzoxazine intermediate is reacted at 120-230° C. for 8-20 hours to obtain a polybenzoxazine resin.

[0011] The molecular formula of the benzoxazine intermediate is:

[0012]

[0013] The molar ratio of the aldehyde group of the formaldehyde polymer, the phenolic hydroxyl group of the phenolic compound, and the amino functional group of the diamine compound is 2:1:1.

[0014] The molar ratio of the dihydric phenol compound to the monohydric phenol compound is preferably 2:1 to 2:5.

[0015] The dihydric phenol compound is 2,2-diallyl bisphenol A or 2,2-diallyl bisphenol AF, and the monohydric phenol compound is p-tert-butylphenol or 3-tert-butylphenol.

[0016] The solvent is any one or more of dioxane, ethanol, toluene and xylene.

[0017] The purification process is:

[0018] The amount of solvent distilled from the reaction solution by low-pressure distillation is not less than 90% of the amount of solvent added, and then the reaction solution is poured into methanol or water to produce precipitation, and the upper clear liquid is removed to obtain the precipitate, and the precipitate is dried in a vacuum drying oven, and the dried precipitate is ground to obtain the benzoxazine intermediate.

[0019] Beneficial effects:

[0020] The benzoxazine resin prepared by the present invention using allyl bisphenol A, aliphatic diamine and polyformaldehyde has the characteristics of high temperature resistance, low dielectric and high strength, can meet the performance requirements of 5G communication antenna covers, PCBs and radar antenna covers for the resin matrix, and will improve the transmittance of electromagnetic waves and reduce the transmission loss of electromagnetic waves. DETAILED DESCRIPTION

[0021] The commonly used methods for preparing benzoxazine resins with low dielectric constant, heat resistance and mechanical properties are as follows: 1. Introducing low polar aliphatic structures, such as selecting octylamine as the raw material amine source and bisphenol B as the phenol source, but the introduction of a large amount of aliphatic structures will cause the resin matrix to exhibit low heat resistance and low mechanical strength. 2. Introducing large volume rigid groups, although the dielectric constant of the resin can be reduced, it also reduces the crosslinking density of the resin and reduces the mechanical properties of the resin.

[0022] The present invention provides a high temperature resistant, low dielectric and high strength benzoxazine intermediate, the molecular formula of which is:

[0023]

[0024] The present invention also provides a method for preparing the above-mentioned benzoxazine intermediate and polybenzoxazine resin, and the specific steps are as follows: add polyformaldehyde, dihydric phenol containing unsaturated bonds, monohydric phenol compounds and diamine compounds into a reactor, add a solvent, react at 85-110° C. for 8-12 hours, and after the reaction is completed, obtain the benzoxazine intermediate through a purification process, and fully dry it for use. The benzoxazine intermediate is reacted at 120-230° C. for 8-20 hours to obtain the polybenzoxazine resin.

[0025] The molar ratio of the aldehyde group of the formaldehyde polymer, the phenolic hydroxyl group of the phenolic compound, and the amino functional group of the diamine compound is 2:1:1.

[0026] According to the above scheme, the molar ratio of the dihydric phenol compound to the monohydric phenol compound is preferably 2:1 to 2:5.

[0027] According to the above scheme, the dihydric phenol compound is 2,2-diallyl bisphenol A or 2,2-diallyl bisphenol AF, and the monohydric phenol compound is p-tert-butylphenol or 3-tert-butylphenol, and their molecular structures are as follows:

[0028]

[0029] According to the above scheme, the solvent is any one or more of dioxane, ethanol, toluene and xylene.

[0030] According to the above scheme, the purification treatment is as follows: by low-pressure distillation, the amount of solvent distilled from the reaction solution is not less than 90% of the amount of solvent added, and then the reaction solution is poured into methanol or water to produce precipitation, the supernatant is removed to obtain a precipitate, the precipitate is dried in a vacuum drying oven, and the dried precipitate is ground to obtain a benzoxazine intermediate.

[0031] Example 1

[0032] 41.6 g (0.1 mol) of 2,2-diallylbisphenol AF, 23.24 g (0.2 mol) of hexamethylenediamine, 30.04 g (0.2 mol) of 3-tert-butylphenol and 24.02 g (0.8 mol) of paraformaldehyde were added into a 1000 mL three-necked flask equipped with a condenser, wherein the molar ratio of the phenolic hydroxyl functional groups in 2,2-diallylbisphenol AF and 3-tert-butylphenol was 1:1. Subsequently, 250 mL of a toluene:ethanol mixed solvent was added, wherein the volume ratio of toluene to ethanol was 3:2. The mixture was reacted at 85°C for 12 h. After the reaction was completed, the solvent was distilled off under reduced pressure using a rotary evaporator until the amount of solvent distilled out was not less than 225 mL. The reaction solution was poured into a water solvent and allowed to stand for 12 h. The upper solution was removed to obtain a precipitate. The precipitate was vacuum dried at 70°C for 48 h. The dried product was ground and pulverized to obtain a benzoxazine intermediate. The benzoxazine intermediate is subjected to the following curing system to obtain a polybenzoxazine resin: 120°C×2h+150°C×2h+180°C×6h+220°C×2h.

[0033] The yield of the benzoxazine intermediate in this example is 78.0%. The obtained polybenzoxazine resin has a glass transition temperature of 235° C., a bending strength of 110 MPa, a dielectric constant of 2.73 at 10 GHz, and a dielectric loss of 0.006.

[0034] Example 2

[0035] 41.6 g (0.1 mol) of 2,2-diallylbisphenol AF, 23.24 g (0.2 mol) of hexamethylenediamine, 30.04 g (0.2 mol) of 3-tert-butylphenol and 24.02 g (0.8 mol) of paraformaldehyde were added into a 1000 mL three-necked flask equipped with a condenser, wherein the molar ratio of the phenolic hydroxyl functional groups in 2,2-diallylbisphenol AF and 3-tert-butylphenol was 1:1, and then 250 mL of a toluene:ethanol mixed solvent was added, wherein the volume ratio of toluene to ethanol was 3:2, and the mixture was reacted at 110°C for 8 h. After the reaction was completed, the solvent was distilled off under reduced pressure using a rotary evaporator until the amount of solvent distilled out was not less than 225 mL. The reaction solution was poured into a water solvent and allowed to stand for 12 h. The upper solution was removed to obtain a precipitate, and the precipitate was dried in a vacuum at 70°C for 48 h. The dried product was ground and pulverized to obtain a benzoxazine intermediate. The benzoxazine intermediate is subjected to the following curing system to obtain a cured resin: 150°C×2h+180°C×2h+220°C×2h+230°C×2h.

[0036] The yield of the benzoxazine intermediate in this example is 78.0%. The obtained polybenzoxazine resin has a glass transition temperature of 239° C., a bending strength of 115 MPa, a dielectric constant of 2.70 at 10 GHz, and a dielectric loss of 0.008.

[0037] Example 3

[0038] 30.8 g (0.1 mol) of 2,2-diallylbisphenol A, 17.43 g (0.15 mol) of hexamethylenediamine, 30.04 g (0.1 mol) of p-tert-butylphenol and 18.0 g (0.6 mol) of paraformaldehyde were added into a 1000 mL three-necked flask equipped with a condenser, wherein the molar ratio of the phenolic hydroxyl functional groups in 2,2-diallylbisphenol A and p-tert-butylphenol was 2:1. Subsequently, 250 mL of a toluene:ethanol mixed solvent was added, wherein the volume ratio of toluene to ethanol was 2:1. The mixture was reacted at 95°C for 12 h. After the reaction was completed, the solvent was distilled under reduced pressure using a rotary evaporator until the amount of solvent distilled out was not less than 225 mL. The reaction solution was poured into a methanol solvent and allowed to stand for 12 h. The upper solution was removed to obtain a precipitate. The precipitate was dried in a vacuum at 70°C for 48 h. The dried product was ground and pulverized to obtain a benzoxazine intermediate. The benzoxazine intermediate is subjected to the following curing system to obtain a cured resin: 120°C×2h+150°C×2h+180°C×2h+220°C×2h.

[0039] The yield of the benzoxazine intermediate in this example is 80.0%. The obtained polybenzoxazine resin has a glass transition temperature of 229° C., a bending strength of 115 MPa, a dielectric constant of 2.81 at 10 GHz, and a dielectric loss of 0.010.

[0040] Example 4

[0041] 30.8 g (0.1 mol) of 2,2-diallylbisphenol A, 40.67 g (0.35 mol) of hexamethylenediamine, 75.1 g (0.5 mol) of p-tert-butylphenol and 21.0 g (0.7 mol) of paraformaldehyde were added into a 1000 mL three-necked flask equipped with a condenser, wherein the molar ratio of the phenolic hydroxyl functional groups in 2,2-diallylbisphenol A and p-tert-butylphenol was 2:5. Subsequently, 250 mL of a mixed solvent of toluene and ethanol was added, wherein the volume ratio of toluene to ethanol was 2:1. The mixture was reacted at 95°C for 12 h. After the reaction, the solvent was distilled under reduced pressure using a rotary evaporator until the amount of solvent distilled out was not less than 225 mL. The reaction solution was poured into a methanol solvent and allowed to stand for 12 h. The upper solution was removed to obtain a precipitate. The precipitate was dried in a vacuum at 70°C for 48 h. The dried product was ground and pulverized to obtain a benzoxazine intermediate. The benzoxazine intermediate is subjected to the following curing system to obtain a cured resin: 150°C×3h+180°C×3h+220°C×4h.

[0042] The yield of the benzoxazine intermediate in this example is 65.0%. The obtained polybenzoxazine resin has a glass transition temperature of 230° C., a bending strength of 106 MPa, a dielectric constant of 2.79 at 10 GHz, and a dielectric loss of 0.010.

[0043] Example 5

[0044] 30.8 g (0.1 mol) of 2,2-diallylbisphenol A, 23.24 g (0.2 mol) of hexamethylenediamine, 30.04 g (0.2 mol) of p-tert-butylphenol and 24.02 g (0.8 mol) of polyformaldehyde were added into a 1000 mL three-necked flask equipped with a condenser, and the molar ratio of aldehyde group, phenolic hydroxyl group and amino functional group was 2:1:1. Then 250 mL of dioxane solvent was added, and the reaction was carried out at 95 °C for 8 h. After the reaction was completed, the solvent was distilled under reduced pressure using a rotary evaporator until the amount of solvent distilled was not less than 225 mL. The reaction solution was poured into methanol solvent and allowed to stand for 12 h. The upper solution was removed to obtain a precipitate. The precipitate was vacuum dried at 70 °C for 48 h. The dried product was ground and pulverized to obtain a benzoxazine intermediate. The benzoxazine intermediate is subjected to the following curing system to obtain a cured resin: 150°C×2h+180°C×2h+210°C×2h+220°C×4h.

[0045] The yield of the benzoxazine intermediate in this example is 73.0%. The obtained polybenzoxazine resin has a glass transition temperature of 220° C., a bending strength of 110 MPa, a dielectric constant of 2.79 at 10 GHz, and a dielectric loss of 0.006.

[0046] Example 6

[0047] 33.6 g (0.1 mol) of 2,2-diallylbisphenol A, 23.24 g (0.2 mol) of hexamethylenediamine, 30.04 g (0.2 mol) of p-tert-butylphenol and 24.02 g (0.8 mol) of paraformaldehyde were added into a 1000 mL three-necked flask equipped with a condenser, the molar ratio of aldehyde, phenolic hydroxyl and amino functional groups was 2:1:1, and the molar ratio of phenolic hydroxyl functional groups in 2,2-diallylbisphenol A and p-tert-butylphenol was 1:1. Then 210 mL of butanone solvent was added, and the mixture was reacted at 95°C on a heat-collecting magnetic stirrer for 8 h. After the reaction, the solvent was distilled under reduced pressure using a rotary evaporator until the amount of solvent distilled was not less than 168 mL. The reaction solution was poured into a methanol solvent and allowed to stand for 12 h. The upper solution was removed to obtain a precipitate. The precipitate was vacuum dried at 70°C for 48 h. The dried product was ground and pulverized to obtain a benzoxazine intermediate. The benzoxazine intermediate is subjected to the following curing system to obtain a cured resin: 120°C×2h+150°C×2h+180°C×2h+210°C×1h+220°C×1h.

[0048] The yield of the benzoxazine intermediate in this example is 76%. The obtained polybenzoxazine resin has a glass transition temperature of 225°C, a compressive strength of 135 MPa, a bending strength of 115 MPa, a dielectric constant of 2.70 at 10 GHz, and a dielectric loss of 0.006.

[0049] Example 7

[0050] 33.6 g (0.1 mol) of 2,2-diallylbisphenol A, 23.24 g (0.2 mol) of hexamethylenediamine, 30.04 g (0.2 mol) of p-tert-butylphenol and 24.02 g (0.8 mol) of paraformaldehyde were added to a 1000 mL three-necked flask equipped with a condenser, the molar ratio of aldehyde, phenolic hydroxyl and amino functional groups was 2:1:1, and the molar ratio of phenolic hydroxyl functional groups in 2,2-diallylbisphenol A and p-tert-butylphenol was 1:1. Subsequently, 210 mL of xylene solvent was added, and the mixture was reacted at 95° C. on a heat-collecting magnetic stirrer for 8 h. After the reaction, the solvent was distilled under reduced pressure using a rotary evaporator until the amount of solvent distilled was not less than 168 mL. The reaction solution was poured into a methanol solvent and allowed to stand for 12 h. The upper solution was removed to obtain a precipitate. The precipitate was vacuum dried at 70° C. for 48 h. The dried product was ground and pulverized to obtain a benzoxazine intermediate. The benzoxazine intermediate is subjected to the following curing system to obtain a cured resin: 120°C×2h+150°C×2h+180°C×2h+210°C×1h+220°C×1h.

[0051] The yield of the benzoxazine intermediate in this example is 60%. The obtained polybenzoxazine resin has a glass transition temperature of 226° C., a bending strength of 110 MPa, a dielectric constant of 2.78 at 10 GHz, and a dielectric loss of 0.007.

Claims

1. A high temperature resistant, low dielectric and high strength benzoxazine intermediate, It is characterized in that Its molecular formula structure is:

2. A method for preparing a high temperature resistant, low dielectric and high strength benzoxazine resin, It is characterized in that include: Adding paraformaldehyde, dihydric phenol containing unsaturated bonds, monohydric phenol compounds and diamine compounds into a reactor, adding a solvent, reacting at 85-110° C. for 8-12 hours, and after the reaction, obtaining the benzoxazine intermediate according to claim 1 through a purification process, and fully drying it for later use; The benzoxazine intermediate is reacted at 120-230° C. for 8-20 hours to obtain a polybenzoxazine resin.

3. The method according to claim 2, It is characterized in that The molecular formula of the benzoxazine intermediate is:

4. The method according to claim 2, It is characterized in that The molar ratio of the aldehyde group of the formaldehyde polymer, the phenolic hydroxyl group of the phenolic compound, and the amino functional group of the diamine compound is 2:1:

1.

5. The method according to claim 2, It is characterized in that The molar ratio of the dihydric phenol compound to the monohydric phenol compound is preferably 2:1 to 2:

5.

6. The method according to claim 2, It is characterized in that The dihydric phenol compound is 2,2-diallyl bisphenol A or 2,2-diallyl bisphenol AF, and the monohydric phenol compound is p-tert-butylphenol or 3-tert-butylphenol.

7. The method according to claim 2, It is characterized in that The solvent is any one or more of dioxane, ethanol, toluene and xylene.

8. The method according to claim 2, It is characterized in that The purification process is: The amount of solvent distilled from the reaction solution by low-pressure distillation is not less than 90% of the amount of solvent added, and then the reaction solution is poured into methanol or water to produce precipitation, and the upper clear liquid is removed to obtain the precipitate, and the precipitate is dried in a vacuum drying oven, and the dried precipitate is ground to obtain the benzoxazine intermediate.

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