Boron-silicon hybrid phenolic resin suitable for hot-melt preimpregnation process and preparation method of boron-silicon hybrid phenolic resin

Abstract

The invention discloses a boron-silicon hybrid phenolic resin suitable for a hot melting preimpregnation process and a preparation method thereof, and belongs to the field of ablation-resistant thermal protection materials, and the preparation method comprises the following steps: uniformly mixing molten phenol with sodium hydroxide and organosiloxane, then adjusting the pH value to 7-10, then adding aldehyde, heating to 60-80 DEG C, reacting for 1-3 hours, and cooling to room temperature to obtain the boron-silicon hybrid phenolic resin. Carrying out reduced pressure dehydration, and then adding boric acid substances to carry out condensation polymerization; and finally carrying out vacuum decompression dehydration to obtain a final product. The hot-melt boron-silicon hybrid phenolic resin prepared by the invention is simple in synthesis method, stable and controllable in reaction, less in wastewater generated in the synthesis process, not lower than 425 DEG C in initial decomposition temperature of a condensate, and not lower than 71.9% in carbon yield; and the hot-melt boron-silicon hybrid phenolic resin has good film-forming property, can keep low viscosity for a long time at a film coating temperature, is suitable for large-scale production of hot-melt prepregs with an environment-friendly process, and particularly has a good application prospect in the fields of ablation heat-proof and refractory materials and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of ablation-resistant thermal protection materials, and in particular, relates to a borosilicate hybrid phenolic resin suitable for a hot-melt prepreg process and a preparation method thereof. Background Art

[0002] The hot melt impregnation method has low volatility, controllable resin content, and good batch stability. It can effectively avoid the environmental pollution caused by the solvent of the solution impregnation method. The prepared composite materials have low porosity, good mechanical properties, and high dimensional accuracy. It has become a research hotspot at home and abroad in recent years. At present, the resin matrix used in the hot melt prepreg method is mainly epoxy resin, while phenolic resin has poor film-forming properties and high bulk viscosity. It is often stored in the form of resin solution, which limits its use in the hot melt prepreg process. At the same time, the heat resistance of phenolic resin is increasingly difficult to meet the use requirements of existing thermal protection materials.

[0003] Boron-containing phenolic resin has a series of excellent properties, such as high temperature resistance, high residual carbon, excellent dimensional stability and low smoke toxicity, and is a commonly used matrix resin for ablative heat-resistant composite materials in the aerospace field. Traditional boron-containing phenolic resin has high viscosity and is brittle, is not easy to form a film, and has a fast viscosity increase at the melting temperature. The mechanical properties of its composite material are poor, and it is difficult to meet the use conditions of hot-melt phenolic resin.

[0004] In view of this, there is an urgent need to seek an improved preparation method for borosilicate phenolic resin suitable for hot melt process, which can improve the thermal properties of phenolic resin and the mechanical properties of composite materials while optimizing the synthesis process and simplifying the synthesis steps, while meeting the requirements of hot melt processing technology. Summary of the invention

[0005] In order to overcome the technical problems in the prior art that boron phenolic resin is brittle, has poor film-forming properties, and is difficult to meet the requirements of the hot-melt prepreg process, the purpose of the present invention is to provide a boron-silicon hybrid phenolic resin suitable for hot-melt prepreg process and a preparation method thereof. The method effectively reduces the brittleness of the resin while being suitable for the hot-melt process, and improves the film-forming properties of the resin as well as the initial decomposition temperature and the charring rate.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A method for preparing a boron-silicon hybrid phenolic resin suitable for a hot melt prepreg process comprises the following steps: The molten phenol is mixed evenly with sodium hydroxide and organosiloxane, and then the pH is adjusted to 7-10 and aldehyde is added, heated to 60-80°C for reaction for 1-3 hours, and then decompressed and dehydrated, and then boric acid substances are added to carry out condensation reaction; finally, vacuum decompression and dehydration are carried out to obtain borosilicate hybrid phenolic resin suitable for hot melt prepreg process.

[0007] Furthermore, the organosiloxane is one or more of γ-aminopropyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane, trisilanolphenylsilsesquioxane and cyclopolydimethylsiloxane.

[0008] Furthermore, one or more of KOH, NaOH, NH3·H2O, Ca(OH)2 and Ba(OH)2 is used to adjust the pH to 7-10.

[0009] Further, the pH is 7-8.

[0010] Furthermore, the aldehyde is one or more of formaldehyde solution, glutaraldehyde and paraformaldehyde.

[0011] Furthermore, the molar ratio of phenol, aldehyde and boron compound is 10-200:12-300:1-40.

[0012] Furthermore, the mass of the organosiloxane is 3-12% of the mass of the phenol.

[0013] Further, the molar ratio of phenol, aldehyde and boron compound is 100:120-150:10-30; Furthermore, the phenol is one or both of monohydric phenol and dihydric phenol; and the boric acid substance is boric acid or a boric acid derivative.

[0014] Further, the monohydric phenol is one or more of phenol, o-cresol, m-cresol, p-cresol, α-naphthol, β-naphthol, and 4-hydroxymethylphenol; The dihydric phenol is one or more of catechol, resorcinol, hydroquinone, bisphenol A and bisphenol F.

[0015] Further, the boric acid derivative is one or more of phenylboric acid, hydroxymethylphenylboric acid, hydroxyphenylboric acid, biphenylboric acid, borax, sodium borate, diphenylboric acid, methylphenylboric acid, dimethylphenylboric acid, methoxyphenylboric acid, isopropylphenylboric acid, ethoxyphenylboric acid, 1,4-phenyldiboric acid, ethylphenylboric acid, butylphenylboric acid, 2,4,6-triphenylboroxine and 3-hydroxyphenylboric acid.

[0016] Furthermore, the polycondensation reaction temperature is 90-120°C and the time is 1-9 h.

[0017] A borosilicate hybrid phenolic resin suitable for hot melt prepreg process, wherein the solid content of the borosilicate hybrid phenolic resin is not less than 94%, the viscosity of the borosilicate hybrid phenolic resin tested at 70°C is 14000-22100 mPa·s, the low viscosity window is 65-120°C, the residual carbon rate is 71.9-77.3%, and the thermal decomposition temperature T 5％ It is 425-473℃.

[0018] Compared with the prior art, the present invention has the following beneficial effects: In the present invention, compared with the synthesis method of hot-melt boron-containing phenolic resin in the prior art, aldehyde is used and hot-melt boron-containing phenolic resin is prepared by salicyl alcohol method, the synthesis temperature is reduced, which is conducive to industrial large-scale production. At the same time, the waste water generated by polyformaldehyde during the reaction process is less, which is more environmentally friendly; by using a mixture of traditional alkaline catalysts and organosilane catalysts, the directional formation of phenolic resin methylene in the synthesis process is regulated, the initial decomposition temperature of phenolic resin is effectively improved, and the application range of new hot-melt borosilicate phenolic resin is broadened; the hot-melt boron phenolic resin described in the present invention does not contain solvent, overcomes the defects of pores generated by the volatilization of solvents in boron phenolic resin solutions in the prior art during the composite material molding process and the quality instability of prepregs; it can achieve the effect of reducing the molding porosity of boron phenolic resin-based composite materials, improving their interlaminar shear strength, and improving their ablation and scouring resistance.

[0019] The borosilicate hybrid phenolic resin prepared by the present invention effectively reduces the brittleness of the resin while being suitable for the hot melt process, improves the film-forming property of the resin as well as the initial decomposition temperature and the charring rate, and has good molding processability, high temperature resistance and ablation resistance. It is a high-performance matrix resin for advanced composite materials, and is expected to be used in high-tech fields such as aerospace, and has good application prospects in the fields of refractory materials, coated sand, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 1 is the TGA and DTG curve of the borosilicate hybrid phenolic resin suitable for hot melt prepreg process in Example 1 of the present invention under a nitrogen atmosphere; Figure 2 The infrared and nuclear magnetic resonance images of the borosilicate hybrid phenolic resin suitable for hot melt prepreg process in Example 1 of the present invention are shown; wherein (a) is the nuclear magnetic hydrogen spectrum of the borosilicate hybrid phenolic resin, (b) is the nuclear magnetic carbon spectrum of the borosilicate hybrid phenolic resin, and (c) is the infrared spectrum of the cured product of the borosilicate hybrid phenolic resin; Figure 3 is an ablation data diagram of a carbon fiber composite material prepared from a boron-silicon hybrid phenolic resin suitable for a hot-melt prepreg process in Example 1 of the present invention; Figure 4 This is a mechanical data diagram of a carbon fiber composite material prepared from the boron-silicon hybrid phenolic resin suitable for hot-melt prepreg process in Example 1 of the present invention. DETAILED DESCRIPTION

[0021] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly and comprehensively understood.

[0022] The preparation method of the boron-silicon hybrid phenolic resin suitable for hot-melt prepreg process of the present invention comprises the following steps: (1) After heating phenol until it is melted, sodium hydroxide and organosiloxane are added under stirring, and the mixture is evenly mixed, and the mixture is stirred until the sodium hydroxide and organosiloxane are dissolved in the phenol to obtain a solution with a pH of 7-10; The phenol is one or both of monohydric phenol and dihydric phenol; the monohydric phenol is one or more of phenol, o-cresol, m-cresol, p-cresol, α-naphthol, β-naphthol and 4-hydroxymethylphenol; the dihydric phenol is one or more of o-catechol, m-cresol, hydroquinone, bisphenol A and bisphenol F. The mass of the organosiloxane is 3-12% of the mass of the phenol. The organosiloxane is one or more of γ-aminopropyl triethoxysilane, γ-glycidyloxypropyl trimethoxysilane, trisilanol phenyl silsesquioxane and cyclopolydimethylsiloxane.

[0023] (2) adding aldehyde to the solution in step (1), heating to 60-80°C for 1-3 h, and performing dehydration under reduced pressure; The aldehyde is one or more of formaldehyde aqueous solution (37% by mass), glutaraldehyde and paraformaldehyde.

[0024] One or more of KOH, NaOH, NH3·H2O, Ca(OH)2 and Ba(OH)2 is used to adjust the pH to 7-10, preferably 7-8.

[0025] (3) adding a boric acid substance to the product obtained in step (2), and heating to 90-120° C. for polycondensation reaction for 1-9 h; Wherein, the aldehyde is one or more of formaldehyde aqueous solution, glutaraldehyde and paraformaldehyde.

[0026] The molar ratio of phenol, aldehyde and boron compound is 10-200:12-300:1-40; preferably, the molar ratio of phenol, aldehyde and boron compound is 100:120-150:10-30; The boric acid substance is boric acid or a boric acid derivative. The boric acid derivative is one or more of phenylboric acid, hydroxymethylphenylboric acid, hydroxyphenylboric acid, biphenylboric acid, borax, sodium borate, diphenylboric acid, methylphenylboric acid, dimethylphenylboric acid, methoxyphenylboric acid, isopropylphenylboric acid, ethoxyphenylboric acid, 1,4-phenyldiboric acid, ethylphenylboric acid, butylphenylboric acid, 2,4,6-triphenylboroxine and 3-hydroxyphenylboric acid.

[0027] (4) The product obtained in step (3) is dehydrated under vacuum until the gel time of the product is 150-300s at 180±1°C, thereby obtaining a borosilicate hybrid phenolic resin suitable for hot melt prepreg process.

[0028] A borosilicate hybrid phenolic resin suitable for hot melt prepreg process prepared according to the method has a solid content of not less than 94%, an initial test viscosity of 14000-22100 mPa·s by a 70°C rotational rheometer, a low viscosity window of 65-120°C, a residual carbon rate of 71.9-77.3%, and a thermal decomposition temperature T 5％ It is 425-473℃.

[0029] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods.

[0030] Unless otherwise specified, the materials, reagents, etc. used in the following embodiments can be obtained from commercial sources.

[0031] Example 1 The boron-silicon hybrid phenolic resin suitable for the hot-melt prepreg process of this embodiment includes the following components, calculated by molar ratio: 10 parts of phenol, 13 parts of aldehyde, and 2 parts of boron compound.

[0032] Wherein, the phenol is monohydric phenol, the monohydric phenol is phenol; the aldehyde is paraformaldehyde; and the boron compound is boric acid.

[0033] The preparation method of the boron-silicon hybrid phenolic resin suitable for hot-melt prepreg process of this embodiment is as follows: (3) adding 9.9 g of boric acid to the product obtained in step (2), heating to 110° C. for polycondensation reaction for 2 h, and then performing reduced pressure distillation to remove water; (4) The product obtained in step (3) is subjected to vacuum decompression dehydration until the gel time of the product is 150-300 s at 180±1°C, thereby obtaining a borosilicate hybrid phenolic resin suitable for hot melt prepreg process, named TBPR, and the solid content, 70°C rotational rheometer test viscosity, residual carbon rate and thermal decomposition temperature T 5％ See Table 1.

[0034] Example 2 The boron-silicon hybrid phenolic resin suitable for the hot-melt prepreg process of this embodiment includes the following components, calculated by molar ratio: 10 parts of phenol, 20 parts of aldehyde, and 2 parts of boron compound.

[0035] Wherein, the phenol is monohydric phenol, the monohydric phenol is phenol; the aldehyde is paraformaldehyde; and the boron compound is boric acid.

[0036] The preparation method of the boron-silicon hybrid phenolic resin suitable for hot-melt prepreg process of this embodiment is as follows: (1) After heating 75.2 g of phenol until it is melted, add 0.4 g of sodium hydroxide and 3 g of γ-aminopropyltriethoxysilane under stirring, mix well, and stir until the sodium hydroxide and the organosiloxane are dissolved in the phenol to obtain a solution with a pH of 7; (2) Add 48.0 g of formaldehyde to the solution in step (1), heat to 65°C for 2 h, and perform decompression dehydration; (3) adding 9.9 g of boric acid to the product obtained in step (2), heating to 110° C. for polycondensation reaction for 2 h, and then performing reduced pressure distillation to remove water; (4) The product obtained in step (3) is dehydrated under vacuum until the gel time of the product is 150-300s at 180±1°C, thereby obtaining a borosilicate hybrid phenolic resin suitable for hot melt prepreg process, and the solid content, 70°C rotational rheometer test viscosity, residual carbon rate and thermal decomposition temperature T 5％ See Table 1.

[0037] Example 3 The boron-silicon hybrid phenolic resin suitable for the hot-melt prepreg process of this embodiment includes the following components, calculated by molar ratio: 10 parts of phenol, 13 parts of aldehyde, and 4 parts of boron compound.

[0038] Wherein, the phenol is monohydric phenol, the monohydric phenol is phenol; the aldehyde is paraformaldehyde; and the boron compound is boric acid.

[0039] The preparation method of the boron-silicon hybrid phenolic resin suitable for hot-melt prepreg process of this embodiment is as follows: (1) After heating 75.2 g of phenol until it is melted, add 0.4 g of sodium hydroxide and 3 g of γ-aminopropyltriethoxysilane under stirring, mix well, and stir until the sodium hydroxide and the organosiloxane are dissolved in the phenol to obtain a solution with a pH of 7; (2) Add 31.2 g of formaldehyde to the solution in step (1), heat to 65°C for 2 h, and perform decompression dehydration; (3) adding 19.8 g of boric acid to the product obtained in step (2), heating to 110° C. for polycondensation reaction for 2 h, and then performing reduced pressure distillation to remove water; (4) The product obtained in step (3) is dehydrated under vacuum until the gel time of the product is 150-300 s at 180±1°C, thereby obtaining a borosilicate hybrid phenolic resin suitable for hot melt prepreg process, and the solid content, 70°C rotational rheometer test viscosity, residual carbon rate and thermal decomposition temperature T 5％ See Table 1.

[0040] Example 4 The boron-silicon hybrid phenolic resin suitable for the hot-melt prepreg process of this embodiment includes the following components, calculated by molar ratio: 10 parts of phenol, 13 parts of aldehyde, and 2 parts of boron compound.

[0041] Wherein, the phenol is monohydric phenol, the monohydric phenol is phenol; the aldehyde is paraformaldehyde; and the boron compound is boric acid.

[0042] The preparation method of the boron-silicon hybrid phenolic resin suitable for hot-melt prepreg process of this embodiment is as follows: (1) After heating 75.2 g of phenol until it is melted, add 0.4 g of sodium hydroxide and 3 g of γ-aminopropyltriethoxysilane under stirring, mix well, and stir until the sodium hydroxide and the organosiloxane are dissolved in the phenol to obtain a solution with a pH of 9; (2) Add 31.2 g of formaldehyde to the solution in step (1), heat to 65°C for 1 h, and perform decompression dehydration; (3) adding 9.9 g of boric acid to the product obtained in step (2), heating to 110° C. for polycondensation reaction for 2 h, and then performing reduced pressure distillation to remove water; (4) The product obtained in step (3) is dehydrated under vacuum until the gel time of the product is 150-300 s at 180±1°C, thereby obtaining a borosilicate hybrid phenolic resin suitable for hot melt prepreg process, and the solid content, 70°C rotational rheometer test viscosity, residual carbon rate and thermal decomposition temperature T 5％ See Table 1.

[0043] Example 5 The boron-silicon hybrid phenolic resin suitable for hot-melt prepreg process of this embodiment includes the following components, calculated by molar ratio: 10 parts of phenol, 20 parts of aldehyde, and 4 parts of boron compound.

[0044] Wherein, the phenol is monohydric phenol, the monohydric phenol is phenol; the aldehyde is paraformaldehyde; and the boron compound is boric acid.

[0045] The preparation method of the boron-silicon hybrid phenolic resin suitable for hot-melt prepreg process of this embodiment is as follows: (1) After heating 75.2 g of phenol until it is melted, add 0.4 g of sodium hydroxide and 3 g of γ-aminopropyltriethoxysilane under stirring, mix well, and stir until the sodium hydroxide and the organosiloxane are dissolved in the phenol to obtain a solution with a pH of 9; (2) Add 48.0 g of formaldehyde to the solution in step (1), heat to 65°C for 3 h, and perform decompression dehydration; (3) adding 19.8 g of boric acid to the product obtained in step (2), heating to 110° C. for polycondensation reaction for 2 h, and then performing reduced pressure distillation to remove water; (4) The product obtained in step (3) is dehydrated under vacuum until the gel time of the product is 150-300s at 180±1°C, thereby obtaining a borosilicate hybrid phenolic resin suitable for hot melt prepreg process, and the solid content, 70°C rotational rheometer test viscosity, residual carbon rate and thermal decomposition temperature T 5％ See Table 1.

[0046] Example 6 The boron-silicon hybrid phenolic resin suitable for the hot-melt prepreg process of this embodiment includes the following components, calculated by molar ratio: 10 parts of phenol, 13 parts of aldehyde, and 1 part of boron compound.

[0047] Wherein, the phenol is monohydric phenol, the monohydric phenol is phenol; the aldehyde is paraformaldehyde; and the boron compound is boric acid.

[0048] The preparation method of the boron-silicon hybrid phenolic resin suitable for hot-melt prepreg process of this embodiment is as follows: (1) After heating 75.2 g of phenol until it is melted, add 0.4 g of sodium hydroxide and 3 g of trisilanolphenylsilsesquioxane under stirring, mix well, and stir until the sodium hydroxide and organosiloxane are dissolved in phenol to obtain a solution with a pH of 7; (2) Add 31.2 g of formaldehyde to the solution in step (1), heat to 65°C for 3 h, and dehydrate under reduced pressure; (3) adding 4.95 g of boric acid to the product obtained in step (2), heating to 120° C. for polycondensation reaction for 2 h, and then performing reduced pressure distillation to remove water; (4) The product obtained in step (3) is dehydrated under vacuum until the gel time of the product is 150-300s at 180±1°C, thereby obtaining a borosilicate hybrid phenolic resin suitable for hot melt prepreg process, and the solid content, 70°C rotational rheometer test viscosity, residual carbon rate and thermal decomposition temperature T 5％ See Table 1.

[0049] Example 7 The boron-silicon hybrid phenolic resin suitable for the hot-melt prepreg process of this embodiment includes the following components, calculated by molar ratio: 10 parts of phenol, 13 parts of aldehyde, and 1 part of boron compound.

[0050] Wherein, the phenol is monohydric phenol, the monohydric phenol is phenol; the aldehyde is paraformaldehyde; and the boron compound is boric acid.

[0051] The preparation method of the boron-silicon hybrid phenolic resin suitable for hot-melt prepreg process of this embodiment is as follows: (1) After heating 75.2 g of phenol until it is melted, add 0.4 g of sodium hydroxide, 3 g of γ-aminopropyltriethoxysilane and 3 g of trisilanolphenylsilsesquioxane under stirring, mix well, and stir until the sodium hydroxide and the organosiloxane are dissolved in the phenol to obtain a solution with a pH of 8; (2) Add 31.2 g of formaldehyde to the solution in step (1), heat to 65°C for 3 h, and dehydrate under reduced pressure; (3) adding 4.95 g of boric acid to the product obtained in step (2), heating to 120° C. for polycondensation reaction for 2 h, and then performing reduced pressure distillation to remove water; (4) The product obtained in step (3) is dehydrated under vacuum until the gel time of the product is 150-300s at 180±1°C, thereby obtaining a borosilicate hybrid phenolic resin suitable for hot melt prepreg process.

[0052] Example 8 The boron-silicon hybrid phenolic resin suitable for hot-melt prepreg process of this embodiment includes the following components, calculated by molar ratio: 10 parts of phenol, 12 parts of aldehyde, 40 parts of boron compound, and the mass of organic siloxane is 12% of the mass of phenol.

[0053] The phenol is monophenol, which is o-benzoyl phenol; the aldehyde is a formaldehyde aqueous solution with a mass fraction of 37%; the boron compound is boric acid, and the organosiloxane is γ-aminopropyltriethoxysilane.

[0054] The preparation method of the boron-silicon hybrid phenolic resin suitable for hot-melt prepreg process of this embodiment is as follows: (1) After heating 75.2 g of o-cresol until it melts, Ba(OH)2 and γ-aminopropyltriethoxysilane are added under stirring, and the mixture is mixed evenly. The mixture is stirred until Ba(OH)2 and the organosiloxane are dissolved in the phenol to obtain a solution with a pH of 8. (2) adding formaldehyde aqueous solution (mass fraction 37%) to the solution in step (1), heating to 60°C for 3 h, and performing decompression dehydration; (3) adding boric acid to the product obtained in step (2), heating to 120° C. for polycondensation reaction for 1 h, and then performing reduced pressure distillation to remove water; (4) The product obtained in step (3) is dehydrated under vacuum until the gel time of the product is 150 s at 180±1° C., thereby obtaining a borosilicate hybrid phenolic resin suitable for hot melt prepreg process.

[0055] Example 9 The boron-silicon hybrid phenolic resin suitable for hot-melt prepreg process of this embodiment includes the following components in terms of molar ratio: 100 parts of phenol, 300 parts of aldehyde, 30 parts of boron compound, and the mass of the organic siloxane is 9% of the mass of the phenol.

[0056] The phenol is monohydric phenol, and the monohydric phenol is α-naphthol; the aldehyde is paraformaldehyde; the boron compound is phenylboric acid, and the organosiloxane is γ-glycidyloxypropyltrimethoxysilane.

[0057] The preparation method of the boron-silicon hybrid phenolic resin suitable for hot-melt prepreg process of this embodiment is as follows: (1) After heating 75.2 g of α-naphthol until it is melted, add Ca(OH)2 and γ-glycidyloxypropyltrimethoxysilane under stirring, mix well, and stir until Ca(OH)2 and organosiloxane are dissolved in phenol to obtain a solution with a pH of 8; (2) Add glutaraldehyde to the solution in step (1), heat to 80°C for 1 h, and dehydrate under reduced pressure; (3) adding boric acid to the product obtained in step (2), heating to 90° C. for polycondensation reaction for 9 h, and then performing reduced pressure distillation to remove water; (4) The product obtained in step (3) is dehydrated under vacuum until the gel time of the product is 300 s at 180±1° C., thereby obtaining a borosilicate hybrid phenolic resin suitable for hot melt prepreg process.

[0058] Example 10 The boron-silicon hybrid phenolic resin suitable for hot-melt prepreg process of this embodiment includes the following components, calculated by molar ratio: 200 parts of phenol, 120 parts of aldehyde, 10 parts of boron compound, and the mass of organic siloxane is 6% of the mass of phenol.

[0059] The phenol is monohydric phenol, which is 4-hydroxymethylphenol; the aldehyde is paraformaldehyde; the boron compound is a mixture of hydroxymethylphenylboric acid and diphenylboric acid in a molar ratio of 1:1; and the organosiloxane is trisilanol phenyl silsesquioxane.

[0060] The preparation method of the boron-silicon hybrid phenolic resin suitable for hot-melt prepreg process of this embodiment is as follows: (1) After heating 75.2 g of 4-hydroxymethylphenol until it melts, add NH3·H2O and trisilanolphenylsilsesquioxane under stirring, mix well, and stir until the organosiloxane is dissolved in the phenol to obtain a solution with a pH of 9; (2) adding paraformaldehyde to the solution in step (1), heating to 70°C for 2 h, and performing decompression dehydration; (3) adding boric acid to the product obtained in step (2), heating to 100° C. for polycondensation reaction for 6 h, and then performing reduced pressure distillation to remove water; (4) The product obtained in step (3) is dehydrated under vacuum until the gel time of the product is 200 s at 180±1° C., thereby obtaining a borosilicate hybrid phenolic resin suitable for hot melt prepreg process.

[0061] Embodiment 11 The boron-silicon hybrid phenolic resin suitable for hot-melt prepreg process of this embodiment includes the following components by molar ratio: 150 parts of phenol, 150 parts of aldehyde, and 1 part of boron compound. The mass of the organosiloxane is 3% of the mass of the phenol.

[0062] The phenol is a dihydric phenol, which is a mixture of hydroquinone and bisphenol A in a molar ratio of 1:1; the aldehyde is paraformaldehyde; the boron compound is a mixture of biphenylboric acid, borax and sodium borate in a molar ratio of 1:1:1; the organosiloxane is a mixture of γ-glycidyloxypropyltrimethoxysilane and cyclopolydimethylsiloxane in a molar ratio of 1:1.

[0063] The preparation method of the boron-silicon hybrid phenolic resin suitable for hot-melt prepreg process of this embodiment is as follows: (1) After heating 75.2 g of a mixture of hydroquinone and bisphenol A in a molar ratio of 1:1 until it melts, KOH and a mixture of γ-glycidyloxypropyltrimethoxysilane and cyclopolydimethylsiloxane in a molar ratio of 1:1 are added under stirring, the mixture is mixed evenly, and the mixture is stirred until KOH and the organosiloxane are dissolved in phenol to obtain a solution with a pH of 10; (2) adding a mixture of glutaraldehyde and paraformaldehyde in a molar ratio of 1:1 to the solution in step (1), heating to 75° C. for 2 h, and performing dehydration under reduced pressure; (3) adding boric acid to the product obtained in step (2), heating to 110° C. for polycondensation reaction for 4 h, and then performing reduced pressure distillation to remove water; (4) The product obtained in step (3) is dehydrated under vacuum until the gel time of the product is 250 s at 180±1° C., thereby obtaining a borosilicate hybrid phenolic resin suitable for hot melt prepreg process.

[0064] Comparative Example 1 The phenolic resin in this comparative example has the same components as those in Example 1, except that only an alkaline catalyst is used in this comparative example, and no boric acid is added. The phenolic resin is prepared by the same method as in Example 1.

[0065] Comparative Example 2 The boron phenolic resin in this comparative example has the same components as those in Example 1, except that this comparative example uses only sodium hydroxide catalyst and no organosiloxane. It is prepared by the same method as in Example 1.

[0066] In order to verify the technical effect of the hot-melt boron-silicon hybrid phenolic resin of the present invention, the following experiment was conducted using Examples 2-6, the phenolic resin PR obtained in Comparative Example 1, and the boron phenolic resin BPR prepared in Comparative Example 2: Take the resin to be tested and measure its viscosity and its change at 70 °C using an SNB-1 digital rotational viscometer; After the resin to be tested is cured, the residual carbon rate of the resin at 800°C is tested using a thermogravimetric analyzer (TG) to simply judge the thermal stability of the resin.

[0067] The boron resin to be tested is taken to compress the carbon fiber composite material according to the national standard GB / T 9341-2008, and the impact strength and interlaminar shear strength of the prepared composite material are tested on a universal testing machine.

[0068] The resins of Example 1, Comparative Example 1 and Comparative Example 2 were used to prepare carbon fiber composite materials through a hot melt process, and the ablation resistance at 4.18 MW was tested according to the GJB 323A-1996 standard.

[0069] The experimental results are shown in Table 1 below: Table 1 Viscosity, residual carbon content, solid content and thermal decomposition temperature T 5％ result

[0070] The thermal stability of the resin was analyzed by thermogravimetric analysis. The thermogravimetric and DTG curves of the residual amount of the resin used in Example 1 under a nitrogen atmosphere as a function of temperature are shown in FIG. Figure 1 As shown, it can be seen that the resin has a higher residual carbon rate and thermal decomposition temperature T at 800 °C. 5％ .

[0071] The structure of the hot-melt borosilicate hybrid phenolic resin was analyzed by infrared and nuclear magnetic resonance. The infrared and nuclear magnetic resonance images of the resin used in Example 1 are as follows: Figure 2 As shown in (a), (b) and (c).

[0072] from Figure 1It can be seen that the cured product of the resin (boric acid and organosiloxane hybrid phenolic resin) obtained in Example 1 has very excellent thermal properties under N2 atmosphere at 40-800°C. The temperature at which the weight loss is 5% is defined as the initial decomposition temperature, and the mass at 800°C represents the carbon yield. Under the condition of 800°C, the carbon yield of the phenolic resin hybridized with boric acid and organosiloxane can reach 75.8%, and the initial decomposition temperature can reach 450.0°C.

[0073] from Figure 2 As can be seen in (a), the chemical shift at 3.5-4.0 ppm can be attributed to the typical methylene group, while the chemical shifts at 6.6-7.2, 4.4-5.2 and 8.2-8.5 ppm are the chemical shifts of the benzene ring hydrogen protons, hydroxymethyl and phenolic hydroxyl groups. Figure 2 In (b), the chemical shift of BOC appears at 58.8 ppm, indicating that the boric acid has successfully incorporated into the polymer network. Figure 2 In (c), at 1375 cm −1 The BOC stretching vibration peak was observed at 946 ~ 1060 cm −1 The peak at BO-Si stretching vibration indicates that boric acid and organosiloxane have chemically reacted. This can explain the successful synthesis of boron-silicon hybrid phenolic resin.

[0074] The resin pressed carbon fiber composite materials prepared by Example 1 (TBPR) of the present invention and Comparative Example 1 (PR) and Comparative Example 2 (BPR) are CF / TBPR, CF / PR, and CF / BPR, respectively, and the ablation performance of the fiber composite materials is tested. The data are as follows: Figure 3 As shown in the figure, it can be seen that the ablation resistance of the composite material of Example 1 is effectively improved.

[0075] The resin pressed carbon fiber composite materials prepared by Example 1 of the present invention and Comparative Examples 1 and 2 were tested for mechanical properties of the composite materials using a universal testing machine. The data are as follows: Figure 4 As shown, it can be seen that the bending strength and interlaminar shear strength of the resin-pressed carbon fiber composite material prepared by Example 1 are better than those of the resin-pressed carbon fiber composite materials prepared by Comparative Examples 1 and 2. Compared with the CF / PR material, the bending strength is increased by 23.6%, and the interlaminar shear strength is increased by 58.3%. The specific preparation method of the resin-pressed carbon fiber composite material is as follows: First, the solvent in the borosilicate hybrid phenolic resin suitable for the hot melt prepreg process is removed by decompression to meet the requirements of the hot melt process.

[0076] Then, a boron-silicon hybrid phenolic resin suitable for a hot-melt prepreg process is coated on the carbon fiber in a hot press according to a certain mass ratio to form a prepreg.

[0077] Finally, the prepregs were laminated and cured in a hot press. The curing schedule was 120◦C / 1h + 160◦C / 2h + 180◦C / 2h + 220◦C / 2h.

[0078] The preparation methods of the composite materials of Comparative Examples 1 and 2 are the same.

[0079] Depend on Figure 3 It can be seen that by adding organosiloxane (γ-aminopropyltriethoxysilane), the flexural strength and interlaminar shear strength of the composite material are significantly improved. The flexural strength of the carbon fiber composite material prepared using the resin of Example 1 is 516.6 MPa, and the interlaminar shear strength is 34.2 MPa, which can be attributed to the introduction of organosilane.

[0080] The boric acid substance in the present invention can also be one or more of methylphenylboronic acid, dimethylphenylboronic acid, methoxyphenylboronic acid, isopropylphenylboronic acid, ethoxyphenylboronic acid, 1,4-phenyldiboronic acid, ethylphenylboronic acid, butylphenylboronic acid, 2,4,6-triphenylboroxine and 3-hydroxyphenylboronic acid.

[0081] The hot-melt borosilicate hybrid phenolic resin prepared by the present invention has a simple synthesis method, a stable and controllable reaction, less wastewater generated during the synthesis process, an initial decomposition temperature of the solidified material of not less than 425°C, and a charcoal yield of not less than 71.9%; and the hot-melt borosilicate hybrid phenolic resin has good film-forming properties and can maintain a low viscosity for a long time at the coating temperature, and is suitable for the production of hot-melt prepregs with environmentally friendly processes and large scale, especially in the fields of ablation heat protection, refractory materials, etc., and has good application prospects.

[0082] The above description is only for the best embodiment of the present invention, but it should not be understood as limiting the claims. The present invention is not limited to the above embodiments, and its specific structure is allowed to be changed. However, all changes made within the protection scope of the independent claims of the present invention are within the protection scope of the present invention.

[0083] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

Claims

1. A method for preparing a boron-silicon hybrid phenolic resin suitable for hot melt prepreg process, characterized in that: The following steps are involved: The molten phenol is mixed evenly with sodium hydroxide and organosiloxane, and then the aldehyde is added after the pH is adjusted to 7-10 with an alkaline catalyst, and the mixture is heated to 60-80°C for reaction for 1-3 hours. After decompression dehydration, boric acid substances are added to carry out polycondensation reaction; finally, vacuum decompression dehydration is carried out to obtain a borosilicate hybrid phenolic resin suitable for hot melt prepreg process. The borosilicate hybrid phenolic resin suitable for hot melt prepreg process has a gel time of 150-300s at 180±1°C.

2. The method for preparing a boron-silicon hybrid phenolic resin suitable for hot melt prepreg process according to claim 1, characterized in that: The organosiloxane is one or more of γ-aminopropyl triethoxysilane, γ-glycidyloxypropyl trimethoxysilane, trisilanol phenyl silsesquioxane and cyclopolydimethylsiloxane.

3. The method for preparing a boron-silicon hybrid phenolic resin suitable for hot melt prepreg process according to claim 1, characterized in that: The aldehyde is one or more of formaldehyde solution, glutaraldehyde and paraformaldehyde.

4. The method for preparing a boron-silicon hybrid phenolic resin suitable for hot melt prepreg process according to claim 1, characterized in that: The molar ratio of phenol, aldehyde and boron compound is 10-200:12-300:1-40.

5. The method for preparing boron-silicon hybrid phenolic resin suitable for hot melt prepreg process according to claim 1, characterized in that: The mass of the organosiloxane is 3-12% of the mass of the phenol.

6. The method for preparing boron-silicon hybrid phenolic resin suitable for hot melt prepreg process according to claim 1, characterized in that: The phenol is one or both of monohydric phenol and dihydric phenol; the boric acid substance is boric acid or a boric acid derivative; the alkaline catalyst is one or more of KOH, NaOH, NH3·H2O, Ca(OH)2 and Ba(OH)2.

7. The method for preparing boron-silicon hybrid phenolic resin suitable for hot melt prepreg process according to claim 6, characterized in that: The monohydric phenol is one or more of phenol, o-cresol, m-cresol, p-cresol, α-naphthol, β-naphthol, and 4-hydroxymethylphenol; The dihydric phenol is one or more of catechol, resorcinol, hydroquinone, bisphenol A and bisphenol F.

8. The method for preparing boron-silicon hybrid phenolic resin suitable for hot melt prepreg process according to claim 6, characterized in that: The boric acid derivative is one or more of phenylboric acid, hydroxymethylphenylboric acid, hydroxyphenylboric acid, biphenylboric acid, borax, sodium borate, diphenylboric acid, methylphenylboric acid, dimethylphenylboric acid, methoxyphenylboric acid, isopropylphenylboric acid, ethoxyphenylboric acid, 1,4-phenyldiboric acid, ethylphenylboric acid, butylphenylboric acid, 2,4,6-triphenylboroxine and 3-hydroxyphenylboric acid.

9. The method for preparing boron-silicon hybrid phenolic resin suitable for hot melt prepreg process according to claim 1, characterized in that: The temperature of the polycondensation reaction is 90-120°C and the time is 1-9 h.

10. A borosilicate hybrid phenolic resin suitable for hot melt prepreg process prepared according to the method of any one of claims 1 to 9, characterized in that: The solid content of the borosilicate hybrid phenolic resin is not less than 94%, the initial viscosity of the 70°C rotational rheometer test is 14000-22100 mPa·s, the low viscosity window is 65-120°C, the residual carbon rate is 71.9-77.3%, and the thermal decomposition temperature T 5％ It is 425-473℃.

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