Preparation method and modification method of poly-salicyl alcohol resin and application of poly-salicyl alcohol resin in ablation-resistant composite material

Abstract

The invention discloses a preparation method and a modification method of poly-salicyl alcohol resin and application of the poly-salicyl alcohol resin in an ablation-resistant composite material. Salicyl alcohol (o-hydroxymethylphenol) is used as a main raw material, and under the protection of nitrogen, melt polymerization is carried out to obtain the poly-salicyl alcohol resin. In the preparation process, no solvent or catalyst needs to be added, the reaction condition is mild, environment-friendly and easy to control, and the poly-salicylol resin with different molecular weights and different viscosities can be prepared by controlling the reaction temperature and the reaction time; therefore, a resin transfer molding forming process of the ablation-resistant composite material and a hot melt adhesive film process for preparing the ablation-resistant composite material prepreg are met. By adding hexamethylenetetramine and other hydroxymethylphenol-containing compounds, the poly-salicyl alcohol resin can be modified, the thermal decomposition temperature and char yield of the poly-salicyl alcohol resin are improved, and the requirements of the ablation-resistant composite material on mechanical properties and ablation resistance are met.

Description

Technical Field

[0001] The present invention belongs to the field of polymer materials, and in particular relates to a polysalicylic alcohol resin, a preparation method and a modification method thereof, and an application thereof in ablation-resistant composite materials. Background Art

[0002] Phenolic resin-based composite materials are used in the manufacture of solid rocket motor nozzle expansion sections due to their high specific strength, ablation resistance, and low cost. Currently, the most commonly used method for manufacturing phenolic resin-based composite expansion sections is the tape winding process, which involves first impregnating carbon fiber cloth (or high-silica glass fiber cloth) with a thermosetting phenolic resin solution or a thermoplastic phenolic resin solution with a curing agent to prepare the required prepreg. The prepreg is then wound or layered and then cured in an autoclave under high temperature and high pressure to produce a composite material product. The solution-impregnation-based prepreg preparation process requires a large amount of organic solvents. In addition to causing environmental pollution, it also has problems such as cumbersome procedures and low production efficiency. In particular, the residual solvent and prepreg resin content in the prepreg are difficult to accurately control, which seriously affects the performance and quality of the composite material product.

[0003] In order to overcome the various shortcomings of the solution impregnation method, a hot melt adhesive film method prepreg preparation process has been developed in recent years. The hot melt adhesive film method prepreg preparation process requires the use of a solvent-free resin with appropriate viscosity, first heating the resin to prepare a film, and then heating the resin film and carbon fiber cloth to obtain a prepreg. Therefore, the prepreg prepared by the hot melt adhesive film method has very little volatile matter, and the resin content and thickness of the prepreg are precisely controllable, thereby significantly improving the quality of the composite material and improving the performance of the composite material, which is an important development direction of the ablation-resistant composite material manufacturing process. However, the hot melt adhesive film method prepreg preparation process puts forward new and higher requirements for the resin. In addition to requiring a high carbonization rate of the cured resin, it also requires the resin to have good processability, such as a wide process window and applicability period, specifically the viscosity is maintained at 0.1-2.5 Pa.s for more than 1h, and a moderate viscosity at room temperature (10 4 ~10 5 Pa.s), low curing weight loss (≤10%) and mild curing temperature (around 165°C).

[0004] Another advanced manufacturing process for high-performance ablation-resistant composite materials is the resin transfer molding (RTM) process. The RTM process is a closed-mold molding process for composite materials. A low-viscosity resin is injected into a closed mold to impregnate pre-placed reinforcement materials (i.e., preforms), and composite parts are obtained after high-temperature curing. The RTM process is characterized by precise molding, high production efficiency, strong designability, and stable and reliable quality. In particular, the interlaminar shear strength of the composite material is significantly improved. However, the RTM process usually requires that the viscosity of the resin at the injection temperature be between 250 and 500 mPa·s and maintained for a long time (more than 1 hour) in order to quickly impregnate the fibers and avoid damage to the ply or fabric structure. The process also requires that the resin curing process should have no or as little volatile components as possible to reduce product defects and improve the mechanical properties and ablation properties of the composite material.

[0005] Based on the synthesis reaction conditions and molecular structure, traditional phenolic resins can be divided into thermosetting phenolic resins (i.e., resole) and thermoplastic phenolic resins (i.e., novolac). Their inherent defects limit their application in solvent-free molding processes. Thermosetting phenolic resins are produced by alkali-catalyzed reaction of phenol with excess formaldehyde to form a prepolymer containing hydroxyl groups. Curing can be completed by heating alone without adding a curing agent. Thermosetting phenolic resins inevitably contain up to 10% free phenol (phenol), and the curing process releases a large amount of water or formaldehyde. Therefore, traditional thermosetting phenolic resins are difficult to meet the requirements of hot melt adhesive film processes and RTM processes. Thermoplastic phenolic resins are oligomers that do not contain hydroxyl groups and are synthesized by acid-catalyzed reaction of excess phenol with formaldehyde. They require the addition of a curing agent (commonly used is hexamethylenetetramine) to complete the curing and preparation of composite materials. Because thermoplastic phenolic resins are high-molecular-weight oligomers, their high viscosity cannot meet the requirements of hot melt adhesive film processes and RTM processes. At the same time, traditional thermosetting phenolic resins and traditional thermoplastic phenolic resins are both synthesized using phenol as a monomer. The presence of a large number of terminal phenols in their cured cross-linked networks is one of the reasons that affect the thermal stability and carbonization rate of the cured resins.

[0006] Therefore, it is necessary to develop an ablation-resistant composite matrix resin with a high charring rate and good processability to meet the requirements of the RTM process of composite materials and the hot melt adhesive film process of composite prepregs, and to adapt to the needs of composite materials for the nozzle expansion section of solid rocket engines. Summary of the Invention

[0007] The object of the present invention is to provide a method for preparing a polysalicylic alcohol resin that can be prepared without adding any solvent or catalyst, has mild reaction conditions, is environmentally friendly and easy to control, and can prepare polysalicylic alcohol resins of different molecular weights and viscosities by controlling the reaction temperature and reaction time, thereby meeting the RTM molding process of ablation-resistant composite materials and the hot melt adhesive film process for preparing ablation-resistant composite material prepregs, a modification method, and application in ablation-resistant composite materials.

[0008] To achieve the above object, the preparation method of the polysalicylol resin of the present invention is as follows: salicylol, salicylol isomers or salicylol derivatives are added to a flask, and stirred at 90-140° C. for 1-60 hours under an inert atmosphere to obtain the polysalicylol resin.

[0009] The salicyl alcohol isomer is 4-hydroxymethylphenol.

[0010] The salicyl alcohol derivative is 2-hydroxymethyl-4-methylphenol, 2-hydroxymethyl-6-methylphenol or 4-hydroxymethyl-2-methylphenol.

[0011] The inert atmosphere is nitrogen, helium or argon.

[0012] The modification method of the polysalicylol resin prepared according to the above preparation method is: adding 0.1-50.0% by weight of additives of salicylol, salicylol isomers or salicylol derivatives during the synthesis process of the polysalicylol resin or after the synthesis is completed to change the processability, curing structure and performance of the polysalicylol resin.

[0013] The additive is a dihydroxymethylphenol compound, a trihydroxymethylphenol compound, hexamethylenetetramine, a silsesquioxane compound, graphene or phenylboric acid.

[0014] The dihydroxymethylphenol compound is 2,4-dihydroxymethylphenol, 2,4-dihydroxymethyl-6-methylphenol, 2,6-dihydroxymethylphenol or 2,6-dihydroxymethyl-4-methylphenol.

[0015] The trimethylolphenol compound is 2,4,6-trimethylolphenol.

[0016] The silsesquioxane compound is trisilanol phenyl-cage polysilsesquioxane, methyl silsesquioxane, phenyl silsesquioxane or vinyl silsesquioxane.

[0017] The polysalicylic alcohol resin prepared by the preparation method or modification method of the present invention has a viscosity of 0.01-1.00 Pa·s within a processing range of 60-90° C. and is suitable for use in RTM technology.

[0018] The polysalicylic alcohol resin prepared by the preparation method or modification method of the present invention has a viscosity of 10 at room temperature (25°C). 4 ~10 5 Pa·s is suitable for hot melt adhesive film process.

[0019] The present invention controls its molecular weight by controlling the reaction time or reaction temperature. Products with different molecular weights are suitable for different processes. The polysalicylic alcohol resin prepared by the preparation method or modification method of the present invention has a viscosity greater than 10 at room temperature (25°C). 5 Pa·s liquid or solid, suitable for solution impregnation process.

[0020] The polysalicylic alcohol resin prepared by the preparation method or modification method of the present invention is used as a matrix resin in preparing fiber-reinforced ablation-resistant phenolic resin-based composite materials.

[0021] The present invention uses industrially mature salicyl alcohol (i.e., o-hydroxymethylphenol) as a raw material. Without the addition of any solvent or catalyst, a bulk polymerization reaction of salicyl alcohol under heating is performed to synthesize a polysalicylic alcohol resin with a specific molecular weight. By regulating the polymerization temperature and time, polysalicylic alcohol resins with varying molecular weights and viscosities can be prepared.

[0022] The polysalicylic alcohol resin prepared by the present invention has a chemical structure similar to that of traditional phenolic resins, but has obvious differences. That is, it is different from both traditional thermosetting phenolic resins and traditional thermoplastic phenolic resins, and is a new type of resin with a chemical structure similar to that of phenolic resins.

[0023] 202410266446.2 Bio-derived polymers for aerospace applications and methods thereof disclose a self-condensation reaction of salicyl alcohol (SA) (2-hydroxybenzyl alcohol) (2-HBA). In the presence of unreacted SA in the reactor during plant-based resin synthesis, monomeric SA undergoes self-condensation. This unreacted SA is the first reaction product, which further self-condenses into the self-condensation product shown at a temperature of 50 to 100°C in the presence of a base or acid. Since formaldehyde is not used, the complexity of the reaction is reduced compared to conventional phenolic resin synthesis. However, para-para condensation or di- or trifunctional hydroxymethyl monomers as in conventional synthesis does not occur, although dimers and / or trimers may still form during the self-condensation of SA. The polysalicyl alcohol resin described in the present invention is also obtained by the self-condensation of salicyl alcohol, but no solvent or catalyst is used in the reaction process. The polysalicyl alcohol resin contains a large amount of hydroxymethyl groups, which react slowly above 60°C, making the removal of the solvent and catalyst very difficult. Residual solvent can volatilize during the curing process, causing defects in the material. Residual catalyst can increase the activity of the methylol reaction and reduce the reaction temperature of the methylol. This not only reduces the shelf life of the resin, but also has a serious impact on the use of the resin in the RTM process and hot-melt adhesive film process. This is also one of the important reasons why thermosetting phenolic resins are difficult to use in the RTM process and hot-melt adhesive film process. The preparation process of the polysalicylic alcohol resin of the present invention does not use solvents and catalysts, which solves the problem of solvent and catalyst residues from the source, and has better processability and longer storage period.

[0024] The present invention is similar to conventional thermosetting phenolic resins in that the polysalicyl alcohol resin contains a certain amount of unreacted monomers, namely salicyl alcohol. However, unlike the residual monomer phenol in thermosetting phenolic resins, the salicyl alcohol monomer is nonvolatile and can actively participate in the curing reaction to become part of the cross-linked network of the cured resin, thus overcoming the inherent defects of conventional thermosetting phenolic resins. However, the polysalicyl alcohol resin has a limited number of methylol groups, which is insufficient to form a complete cross-linked network through the existing methylol curing. Therefore, it is necessary to further introduce a curing agent to achieve complete curing of the resin.

[0025] By further introducing a modifier or a curing agent into the polysalicylic alcohol resin of the present invention, an ablation-resistant resin that meets the requirements of RTM process and hot melt adhesive film process can be prepared.

[0026] Compared with traditional thermoplastic phenolic resins, the present invention is similar in that: (1) neither will cure under mild conditions, and has a longer storage period; (2) both require the addition of a certain amount of curing agent for complete curing. The difference is that (1) each benzene ring in the polysalicylic alcohol resin is connected to a methylene group or a reactive hydroxymethyl group, so no monomer remains after the resin is cured, and the cross-linked network contains fewer terminal phenols, which is beneficial for improving the char formation rate of the cured resin; (2) compared with thermoplastic phenolic resins, the amount of curing agent required to achieve complete curing is relatively small, and about 0 to 8 parts (relative to 100 parts of polysalicylic alcohol resin) can achieve complete curing.

[0027] Although polysalicylol resin molecules contain methylol groups, these are insufficient to fully cure the resin. Therefore, polysalicylol resins require the addition of a curing agent for curing. These curing agents can be polymethylol compounds or hexamethylenetetramine. Without compromising the good processability of polysalicylol resins, the use of appropriate modifiers and curing agents can yield cured resins with excellent processability, high char yields, and composite materials with superior mechanical properties and ablation resistance.

[0028] Compared with the prior art, the present invention has at least the following beneficial effects:

[0029] (1) Polysalicyl alcohol resin is formed by direct bulk polymerization of salicyl alcohol and its derivatives. Each phenol ring of the reactant is connected to at least one hydroxymethyl group. All phenol rings are added to the cross-linked network during the curing process, eliminating the free phenol that may exist in the resin from the source. This is beneficial to the environment and can reduce the volatile matter during the resin curing process.

[0030] (2) The raw materials used in polysalicylic alcohol resin have a defined structure, which avoids the stringent requirements on the formaldehyde / phenol molar ratio in the synthesis of traditional phenolic resins. The structure of the resin can be more accurately controlled and optimized, thereby improving the batch stability and repeatability of resin production.

[0031] (3) The hydroxymethylphenol compound used in the present invention to modify the polysalicylic alcohol resin has a high melting point and boiling point and can be polymerized by heating in the absence of solvents and catalysts without any post-treatment, such as distillation or washing. Therefore, the molecular weight of the polysalicylic alcohol resin can be more accurately controlled by the polymerization temperature and reaction time. By varying the molecular weight, the processability of the resin can be controlled. Low molecular weight resins are suitable for RTM processes; medium molecular weight resins are suitable for hot melt adhesive film processes; and high molecular weight resins are suitable for solution impregnation processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the differential scanning calorimetry (DSC) curve of the polymerization process of salicyl alcohol.

[0033] Figure 2 This is the thermogravimetric analysis (TG) curve of the polymerization process of salicyl alcohol.

[0034] Figure 3 This is the H-NMR spectrum of the polysalicylic alcohol resin prepared in Example 1, Example 2 and Example 3.

[0035] Figure 4 Gel permeation chromatography (GPC) of the polysalicylic alcohol resins prepared in Example 1, Example 2, and Example 3. DETAILED DESCRIPTION

[0036] The present invention discloses methods for preparing and modifying polysalicylic alcohol resins, as well as their application in ablation-resistant composite materials. The salicyl alcohol used in the present invention was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. Other reagents or instruments, whose manufacturers are not indicated, are commercially available conventional products. The use of raw materials from different manufacturers and types does not affect the implementation of the present invention's technical solutions or the achievement of its technical effects.

[0037] The first aspect of the present invention discloses a method for preparing polysalicylic alcohol resin.

[0038] 1) Preparation method of polysalicylic alcohol resin

[0039] In an inert atmosphere, the structure shown in Formula 1 is subjected to a heating condensation reaction to prepare a polysalicylic alcohol resin;

[0040]

[0041] In Formula 1, R is selected from H or methyl.

[0042] Specifically, the inert atmosphere is selected from nitrogen, helium or argon.

[0043] Specifically, the formula 1 is selected from salicyl alcohol and its isomers or derivatives.

[0044] Specifically, the salicyl alcohol and its isomers or derivatives are selected from hydroxymethyl (methyl)phenol.

[0045] More specifically, specific examples of the salicyl alcohol and its isomers or derivatives include, but are not limited to, 2-hydroxymethylphenol 2-Hydroxymethyl-4-methylphenol 2-Hydroxymethyl-6-methylphenol 4-Hydroxymethylphenol and 4-hydroxymethyl-2-methylphenol

[0046] Specifically, the reaction temperature of the heating condensation reaction is 90 to 140° C., and the reaction time is 1 to 60 hours.

[0047] In the present invention, the prepared polysalicylic alcohol resin is a liquid or solid with a viscosity greater than 10 Pa·s at room temperature.

[0048] Specifically, the degree of polymerization can be controlled by regulating the reaction temperature and reaction time to produce polysalicylic alcohol resins of varying molecular weights. Polysalicylic alcohol resins of varying viscosities can meet the needs of different composite material or prepreg preparation processes.

[0049] Specifically, when the reaction conditions are 90°C / 20h or 120°C / 1h or therebetween, the viscosity at room temperature (about 25°C) is 10-300 Pa·s, which is a low-viscosity polysalicylic alcohol resin suitable for RTM process; when the reaction conditions are 90°C / 40h or 120°C / 4h or therebetween, the viscosity at room temperature (about 25°C) is 10-300 Pa·s. 4 ~10 5 Pa·s, it is a medium viscosity polysalicylic alcohol resin, which is suitable for the hot melt adhesive film method prepreg preparation process, and then the preparation of composite materials; when the reaction conditions are 90℃ / 60h or 140℃ / 1h or between the two, its viscosity at room temperature (about 25℃) is greater than 10 5 When the viscosity is less than 0.05 Pa·s in liquid or solid form, it is a high-viscosity polysalicylic alcohol resin, which is more suitable for the solution impregnation method prepreg preparation process and further preparation of composite materials.

[0050] The second aspect of the present invention discloses a modified polysalicylic alcohol resin and a preparation method thereof.

[0051] (1) Modification method of polysalicylic alcohol resin

[0052] Introducing polyhydroxymethylphenol compounds during the synthesis process of polysalicyl alcohol resin or after the synthesis is completed can adjust the processability of polysalicyl alcohol resin and the structure and performance of the cured resin.

[0053] Preparation method of modified polysalicylic alcohol resin:

[0054] Method 1: In an inert atmosphere, 100 parts of the structure shown in Formula 1 and 0.1 to 50.0 parts of a polyhydroxymethylphenol compound are mixed and polymerized to obtain a modified polysalicylic alcohol resin.

[0055]

[0056] In Formula 1, R is selected from H or methyl.

[0057] Specifically, the inert atmosphere is selected from nitrogen, helium or argon.

[0058] Specifically, the formula 1 is selected from salicyl alcohol and its isomers or derivatives.

[0059] Specifically, the salicyl alcohol and its isomers or derivatives are selected from hydroxymethyl (methyl)phenol.

[0060] More specifically, specific examples of the salicyl alcohol and its isomers or derivatives include, but are not limited to, 2-hydroxymethylphenol 2-Hydroxymethyl-4-methylphenol 2-Hydroxymethyl-6-methylphenol 4-Hydroxymethylphenol and 4-hydroxymethyl-2-methylphenol

[0061] Specifically, the reaction temperature of the heating condensation reaction is 90 to 140° C., and the reaction time is 1 to 60 hours.

[0062] Specifically, the polyhydroxymethylphenol compound is selected from one or more of dihydroxymethylphenol compounds and trihydroxymethylphenol compounds.

[0063] More specifically, specific examples of the dihydroxymethylphenol compounds include but are not limited to: 2,4-dihydroxymethylphenol 2,4-Dihydroxymethyl-6-methylphenol 2,6-Dihydroxymethylphenol

[0064] and 2,6-dihydroxymethyl-4-methylphenol

[0065] More specifically, specific examples of the trishydroxymethylphenol compounds include but are not limited to: 2,4,6-trishydroxymethylphenol

[0066] In the present invention, the modified polysalicylic alcohol resin prepared by method 1 is a liquid or solid having a viscosity greater than 10 Pa·s at room temperature.

[0067] Specifically, the degree of polymerization can be controlled by regulating the reaction temperature and reaction time to produce modified polysalicylic alcohol resins of varying molecular weights. Modified polysalicylic alcohol resins of varying viscosities can meet the needs of different composite material or prepreg preparation processes.

[0068] Method 2: In an inert atmosphere, 100 parts of the polysalicylic alcohol resin prepared in the first aspect of the present invention are mixed with 0.1 to 50.0 parts of a polyhydroxymethylphenol compound, and then heated and stirred to disperse uniformly to obtain a modified polysalicylic alcohol resin.

[0069] Specifically, the inert atmosphere is selected from nitrogen, helium or argon.

[0070] Specifically, the viscosity of the polysalicylic alcohol resin prepared in the first aspect is greater than 10 Pa·s.

[0071] Specifically, the heating and stirring temperature is 25 to 120° C., and the stirring time is 0.5 to 100 minutes.

[0072] Specifically, the polyhydroxymethylphenol compound is selected from one or more of dihydroxymethylphenol compounds and trihydroxymethylphenol compounds.

[0073] More specifically, specific examples of the dihydroxymethylphenol compounds include but are not limited to: 2,4-dihydroxymethylphenol 2,4-Dihydroxymethyl-6-methylphenol 2,6-Dihydroxymethylphenol and 2,6-dihydroxymethyl-4-methylphenol

[0074] More specifically, specific examples of the trishydroxymethylphenol compounds include but are not limited to: 2,4,6-trishydroxymethylphenol

[0075] In the present invention, the modified polysalicylic alcohol resin prepared by the second method is a liquid or solid with a viscosity greater than 10 Pa·s at room temperature.

[0076] Specifically, the viscosity of the polysalicylic alcohol resin prepared in the first aspect and the ratio of the polyhydroxymethylphenol compound are adjusted to prepare modified polysalicylic alcohol resins with different molecular weights. Modified polysalicylic alcohol resins with different viscosities can meet different composite material or prepreg preparation processes.

[0077] Specifically, when the reaction conditions are 90°C / 20h or 120°C / 1h or therebetween, the viscosity at room temperature (about 25°C) is 10-300 Pa·s, which is a low-viscosity polysalicylic alcohol resin suitable for RTM process; when the reaction conditions are 90°C / 40h or 120°C / 4h or therebetween, the viscosity at room temperature (about 25°C) is 10-300 Pa·s. 4 ~10 5 Pa·s, it is a medium viscosity polysalicylic alcohol resin, which is suitable for the hot melt adhesive film method prepreg preparation process, and then the preparation of composite materials; when the reaction conditions are 90℃ / 60h or 140℃ / 1h or between the two, its viscosity at room temperature (about 25℃) is greater than 10 5 When the viscosity is less than 0.05 Pa·s in liquid or solid form, it is a high-viscosity polysalicylic alcohol resin, which is more suitable for the solution impregnation method prepreg preparation process and further preparation of composite materials.

[0078] The third aspect of the present invention discloses a thermosetting polysalicylic alcohol-based composition and a preparation method thereof.

[0079] (1) Preparation method of thermosetting polysalicylic alcohol-based composition

[0080] The additives are mixed with the polysalicylic alcohol resin described in the first aspect of the present invention and / or the modified polysalicylic alcohol resin described in the second aspect, and then dispersed uniformly to obtain a thermosetting polysalicylic alcohol-based composition.

[0081] The polysalicylic alcohol resin described in the first aspect of the present invention and / or the modified polysalicylic alcohol resin described in the second aspect and the curing agent are mixed in a ratio of 100 parts by mass of the polysalicylic alcohol resin described in the first aspect of the present invention and / or the modified polysalicylic alcohol resin described in the second aspect, and / or 0 to 8 parts by mass of hexamethylenetetramine, and / or 0 to 10 parts by mass of silsesquioxane (such as trisilanolphenyl-cage polysilsesquioxane), and / or 0 to 2 parts by mass of graphene (CAS No.: 1034343-98-0), and / or 0 to 10 parts by mass of phenylboronic acid, and are uniformly dispersed by stirring or ultrasonic dispersion at 70 to 100° C. to obtain a thermosetting polysalicylic alcohol composition.

[0082] The mass fractions of hexamethylenetetramine, silsesquioxane, graphene, and phenylboric acid are not all 0.

[0083] Preferably, the stirring time is 0.5 to 20 minutes.

[0084] Preferably, the ultrasonic dispersion time is 0 to 20 minutes.

[0085] The fourth aspect of the present invention discloses the use of the polysalicylic alcohol resin described in the first aspect of the present invention and the modified polysalicylic alcohol resin described in the second aspect of the present invention in an RTM process.

[0086] In some embodiments of the present invention, 100 parts of the polysalicylic alcohol resin described in the first aspect of the present invention or the modified polysalicylic alcohol resin described in the second aspect having a room temperature viscosity of 10 to 300 Pa·s, 0 to 8 parts of hexamethylenetetramine, 0 to 10 parts of silsesquioxane, 0 to 2 parts of graphene, and 0 to 10 parts of phenylboric acid are mixed and stirred or ultrasonically dispersed at 70 to 100° C. to obtain an RTM polysalicylic alcohol resin.

[0087] The mass fractions of hexamethylenetetramine, silsesquioxane, graphene, and phenylboric acid are not all 0.

[0088] Preferably, the stirring time is 0.5 to 20 minutes.

[0089] Preferably, the ultrasonic dispersion time is 0.5 to 20 minutes.

[0090] The RTM-type polysalicylic alcohol resin has a viscosity of 0.1 to 0.5 Pa·s at an injection temperature of 60 to 90°C. After curing at 170°C for 2 hours, the resulting cured resin has a char yield greater than 61.0%. The carbon fiber preform composite material produced using the RTM process exhibits excellent mechanical properties and ablation resistance.

[0091] The fifth aspect of the present invention discloses the use of the polysalicylic alcohol resin described in the first aspect of the present invention and the modified polysalicylic alcohol resin described in the second aspect of the present invention in a hot melt adhesive film process.

[0092] In some embodiments of the present invention, the viscosity is adjusted to 10 4 ~10 5 100 parts of the polysalicylic alcohol resin described in the first aspect of the present invention or the modified polysalicylic alcohol resin described in the second aspect of the present invention with a Pa·s, 0-8 parts of hexamethylenetetramine, 0-10 parts of silsesquioxane, 0-2 parts of graphene, and 0-10 parts of phenylboric acid are mixed, and the mixture is stirred or ultrasonically dispersed at 70-100° C. to obtain a film-type polysalicylic alcohol resin.

[0093] The mass fractions of hexamethylenetetramine, silsesquioxane, graphene, and phenylboric acid are not all 0.

[0094] Preferably, the stirring time is 0.5 to 20 minutes.

[0095] Preferably, the ultrasonic dispersion time is 0.5 to 20 minutes.

[0096] The film-type polysalicylic alcohol resin has a viscosity of 0.5 to 2.5 Pa·s at a processing temperature of 60 to 90°C. After curing at 170°C for 2 hours, the resulting cured resin has a char yield exceeding 61.0%. The prepreg prepared using the hot-melt adhesive film process exhibits excellent mechanical properties and ablation resistance after pressurized curing.

[0097] The sixth aspect of the present invention discloses the use of the polysalicylic alcohol resin described in the first aspect of the present invention and the modified polysalicylic alcohol resin described in the second aspect of the present invention in a solution impregnation process.

[0098] In some embodiments of the present invention, the viscosity is greater than 10 5 100 parts of the polysalicylic alcohol resin described in the first aspect of the present invention or the modified polysalicylic alcohol resin described in the second aspect of the present invention with a Pa·s, 0-8 parts of hexamethylenetetramine, 0-10 parts of silsesquioxane, 0-2 parts of graphene, 0-10 parts of phenylboric acid, and 100 parts of anhydrous ethanol are mixed and stirred at room temperature until completely dissolved to obtain a solution-impregnated polysalicylic alcohol resin.

[0099] The mass fractions of hexamethylenetetramine, silsesquioxane, graphene, and phenylboric acid are not all 0.

[0100] The solution-impregnated polysalicylic alcohol resin has a char yield greater than 61.0% after being cured at 170° C. for 2 hours. The carbon fiber preform composite material prepared by the solution-impregnation-molding process has good mechanical properties and ablation resistance.

[0101] Example 1:

[0102] Add 100 parts of salicyl alcohol to a flask under nitrogen protection. Heat to 90°C to melt the salicyl alcohol. Stir and maintain for 4 hours before cooling to room temperature. The resulting liquid resin is polysalicylic alcohol resin. Gel permeation chromatography and rotational rheology measurements show a number-average molecular weight of 350 g / mol, a viscosity of 102.2 Pa·s at 25°C, and a viscosity of 0.015 Pa·s at 80°C. This low-viscosity resin meets the requirements of the RTM process.

[0103] Take 100 parts of the above resin and 6 parts of hexamethylenetetramine, mix them, heat to 80-90°C, and stir under nitrogen. After the hexamethylenetetramine is completely dissolved, cool to room temperature and set aside. Remove 1-2g of the resin and keep it at 170°C for 2 hours to completely cure the resin. Thermogravimetric analysis (nitrogen atmosphere, heating rate of 10°C / min) shows a char yield of 61.4%.

[0104] Example 2:

[0105] Add 100 parts of salicyl alcohol to a flask under nitrogen protection. Heat to 120°C to melt the salicyl alcohol. Stir and maintain for 4 hours before cooling to room temperature. The resulting resin is polysalicylic alcohol resin. Gel permeation chromatography and rotational rheometry measurements show a number-average molecular weight of 690 g / mol, a viscosity of 47,500 Pa·s at 25°C, and a viscosity of 1.06 Pa·s at 80°C. This resin is suitable for preparing prepregs using the hot-melt adhesive film method.

[0106] Take 100 parts of the above resin and 6 parts of hexamethylenetetramine, mix them, heat to 80-90°C, and stir under nitrogen. After the hexamethylenetetramine is completely dissolved, cool to room temperature and set aside. Remove 1-2g of the resin and keep it at 170°C for 2 hours to completely cure the resin. The char yield of the cured resin was determined by thermogravimetric analysis (nitrogen atmosphere, heating rate of 10°C / min) to be 61.3%.

[0107] Example 3

[0108] Add 100 parts of salicyl alcohol to a flask, purge with nitrogen, heat to 140°C to melt the salicyl alcohol, stir and maintain for 2 hours, then cool to room temperature. The resulting solid resin is polysalicylic alcohol resin. Gel permeation chromatography and rotational rheometer measurements show a number average molecular weight of 1441 g / mol and a viscosity of 970,000 Pa·s at 25°C. This resin can be used to prepare prepregs using the solution impregnation method.

[0109] Take 100 parts of the above resin and 6 parts of hexamethylenetetramine, mix them, heat to 80-90°C, and stir under nitrogen. After the hexamethylenetetramine is completely dissolved, cool to room temperature and set aside. Remove 1-2g of the resin and keep it at 170°C for 2 hours to completely cure the resin. Thermogravimetric analysis (nitrogen atmosphere, heating rate of 10°C / min) shows a char yield of 61.9%.

[0110] Depend on Figure 1 It can be seen that salicylic alcohol has an obvious exothermic peak in the DSC with constant temperature increase, which proves that salicylic alcohol can undergo self-polymerization reaction under melting conditions.

[0111] Depend on Figure 2 It can be seen that salicylic alcohol has an obvious weight loss peak in the TG with constant temperature increase, which proves that salicylic alcohol can undergo self-polymerization reaction under melting conditions and water molecules are released.

[0112] Depend on Figure 3 It can be seen that polysalicylic alcohol has structures such as benzene ring, methylene and hydroxymethyl, and has the structural characteristics of both thermosetting phenolic resin and thermoplastic phenolic resin.

[0113] Depend on Figure 4 It can be seen that polysalicyl alcohol resins with different molecular weights can be obtained by controlling the reaction conditions of salicyl alcohol.

[0114] Example 4

[0115] Add 100 parts of salicyl alcohol and 5 parts of 2,6-dihydroxymethyl-4-methylphenol to a flask under nitrogen. Heat to 90°C to melt the salicyl alcohol. Stir and maintain for 4 hours before cooling to room temperature. The resulting liquid resin is a modified polysalicylic alcohol resin. Gel permeation chromatography and rotational rheology measurements show a number-average molecular weight of 370 g / mol, a viscosity of 107 Pa·s at 25°C, and a viscosity of 0.023 Pa·s at 80°C. This low-viscosity resin meets the requirements of the RTM process.

[0116] Take 100 parts of the above resin and 4 parts of hexamethylenetetramine, mix them, heat to 80-90°C, and stir under nitrogen. After the hexamethylenetetramine is completely dissolved, cool to room temperature and set aside. Remove 1-2g of the resin and keep it at 170°C for 2 hours to completely cure the resin. Thermogravimetric analysis (nitrogen atmosphere, heating rate of 10°C / min) shows a char yield of 62.9%.

[0117] Example 5

[0118] Add 100 parts of salicyl alcohol and 5 parts of 2,6-dihydroxymethyl-4-methylphenol to a flask under nitrogen protection. Heat to 90°C to melt the salicyl alcohol. Stir and maintain for 4 hours before cooling to room temperature. The resulting liquid resin is a modified polysalicylic alcohol resin. Gel permeation chromatography and rotational rheology measurements show a number-average molecular weight of 370 g / mol, a viscosity of 109 Pa·s at 25°C, and a viscosity of 0.021 Pa·s at 80°C. This low-viscosity resin meets the requirements of the RTM process.

[0119] Take 100 parts of the above resin, 4 parts of hexamethylenetetramine, and 5 parts of phenylboric acid, mix them, heat to 80-90°C, and stir under nitrogen. After the hexamethylenetetramine and phenylboric acid are completely dissolved, cool to room temperature and set aside. Take 1-2g of it and keep it at 170°C for 2 hours to completely cure the resin. The char yield of the cured resin was determined by thermogravimetric analysis (nitrogen atmosphere, heating rate of 10°C / min) to be 64.1%.

[0120] The above resin and carbon fiber preform were prepared into a composite material using the RTM process. The injection temperature was 90°C and the injection pressure was 0.7 MPa. The obtained composite material had an interlaminar shear strength of 37.6 MPa, a linear ablation rate of 0.026 mm / s, and a mass ablation rate of 0.0621 g / s.

[0121] Example 6

[0122] Add 100 parts of salicyl alcohol and 5 parts of 2,6-dihydroxymethyl-4-methylphenol to a flask under nitrogen. Heat to 120°C to melt the salicyl alcohol. Stir and maintain for 4 hours before cooling to room temperature. The resulting resin is a modified polysalicylic alcohol resin. Gel permeation chromatography and rotational rheometry measurements indicate a number-average molecular weight of 690 g / mol, a viscosity of 49,700 Pa·s at 25°C, and a viscosity of 1.01 Pa·s at 80°C. This resin is suitable for preparing prepregs using the hot-melt adhesive film method.

[0123] Take 100 parts of the above resin, 6 parts of hexamethylenetetramine, and 5 parts of trisilanolphenyl-cage polysilsesquioxane, mix them, heat to 80-90°C, and stir under nitrogen. After the hexamethylenetetramine and silsesquioxane are completely dissolved, cool to room temperature and set aside. Take 1-2g of it and keep it at 170°C for 2 hours to completely cure the resin. The char yield of the cured resin was determined by thermogravimetric analysis (nitrogen atmosphere, heating rate of 10°C / min) to be 64.3%.

[0124] The resin and carbon fiber preform were combined using a hot melt adhesive process to form a prepreg, which was then heat-pressed into a composite material. The resulting composite material exhibited an interlaminar shear strength of 38.4 MPa, a linear ablation rate of 0.024 mm / s, and a mass ablation rate of 0.0574 g / s.

[0125] Example 7

[0126] Add 100 parts of salicyl alcohol and 5 parts of 2,6-dihydroxymethyl-4-methylphenol to a flask under nitrogen. Heat to 120°C to melt the salicyl alcohol. Stir and maintain for 4 hours before cooling to room temperature. The resulting resin is a modified polysalicylic alcohol resin. Gel permeation chromatography and rotational rheometry measurements indicate a number-average molecular weight of 690 g / mol, a viscosity of 48,400 Pa·s at 25°C, and a viscosity of 1.02 Pa·s at 80°C. This resin is suitable for preparing prepregs using the hot-melt adhesive film method.

[0127] Take 100 parts of the above resin, 6 parts of hexamethylenetetramine, and 2 parts of graphene, mix them, heat them to 80-90°C, stir them under nitrogen protection, and cool them to room temperature after the hexamethylenetetramine and graphene are completely dissolved. Take 1-2g of it and keep it at 170°C for 2 hours to completely cure the resin. The char yield of the cured resin was determined by thermogravimetric analysis (nitrogen atmosphere, heating rate of 10°C / min) to be 64.0%.

[0128] The resin and carbon fiber preform were combined using a hot melt adhesive process to form a prepreg, which was then heat-pressed into a composite material. The resulting composite material exhibited an interlaminar shear strength of 37.5 MPa, a linear ablation rate of 0.026 mm / s, and a mass ablation rate of 0.0607 g / s.

[0129] Example 8

[0130] Add 100 parts of 4-hydroxymethylphenol to a flask under nitrogen atmosphere. Heat to 120°C to melt the 4-hydroxymethylphenol. Stir and maintain for 4 hours before cooling to room temperature. The resulting resin is polysalicylic alcohol resin. Gel permeation chromatography and rotational rheometry measurements indicate a number-average molecular weight of 630 g / mol, a viscosity of 37,500 Pa·s at 25°C, and a viscosity of 0.94 Pa·s at 80°C. This resin is suitable for preparing prepregs using the hot-melt adhesive film method.

[0131] Take 100 parts of the above resin and 6 parts of hexamethylenetetramine, mix them, heat to 80-90°C, and stir under nitrogen. After the hexamethylenetetramine is completely dissolved, cool to room temperature and set aside. Remove 1-2g of the resin and keep it at 170°C for 2 hours to completely cure the resin. The char yield of the cured resin was determined by thermogravimetric analysis (nitrogen atmosphere, heating rate of 10°C / min) to be 60.7%.

[0132] Example 9

[0133] Add 50 parts of salicyl alcohol and 50 parts of 4-hydroxymethylphenol to a flask under nitrogen. Heat to 120°C to melt the salicyl alcohol. Stir and maintain for 4 hours before cooling to room temperature. The resulting resin is polysalicylic alcohol resin. Gel permeation chromatography and rotational rheometry measurements indicate a number-average molecular weight of 660 g / mol, a viscosity of 42,500 Pa·s at 25°C, and a viscosity of 1.01 Pa·s at 80°C. This resin is suitable for preparing prepregs using the hot-melt adhesive film method.

[0134] Take 100 parts of the above resin and 6 parts of hexamethylenetetramine, mix them, heat to 80-90°C, and stir under nitrogen. After the hexamethylenetetramine is completely dissolved, cool to room temperature and set aside. Take 1-2g of the resin and keep it at 170°C for 2 hours to completely cure the resin. The char yield of the cured resin was determined by thermogravimetric analysis (nitrogen atmosphere, heating rate of 10°C / min) to be 60.9%.

Claims

1. A method for preparing a polysalicylic alcohol resin, characterized in that: Salicyl alcohol, salicyl alcohol isomers or salicyl alcohol derivatives are added into a flask, and stirred at 90-140° C. for 1-60 hours under an inert atmosphere to obtain a polysalicyl alcohol resin.

2. The method for preparing a polysalicylic alcohol resin according to claim 1, wherein: The salicyl alcohol isomer is 4-hydroxymethylphenol.

3. The method for preparing a polysalicylic alcohol resin according to claim 1, wherein: The salicyl alcohol derivative is 2-hydroxymethyl-4-methylphenol, 2-hydroxymethyl-6-methylphenol or 4-hydroxymethyl-2-methylphenol.

4. The method for preparing a polysalicylic alcohol resin according to claim 1, wherein: The inert atmosphere is nitrogen, helium or argon.

5. A method for modifying a polysalicylic alcohol resin prepared by the method according to any one of claims 1 to 4, characterized in that: During the synthesis process of the polysalicylol resin or after the synthesis, 0.1-50% of the mass of salicylol, salicylol isomers or salicylol derivatives are added to the polysalicylol resin to change the processability, curing structure and performance of the polysalicylol resin.

6. The method for modifying the polysalicylic alcohol resin according to claim 5, wherein: The additive is a dihydroxymethylphenol compound, a trihydroxymethylphenol compound, hexamethylenetetramine, a silsesquioxane compound, graphene or phenylboric acid.

7. The method for modifying the polysalicylic alcohol resin according to claim 6, wherein: The dihydroxymethylphenol compound is 2,4-dihydroxymethylphenol, 2,4-dihydroxymethyl-6-methylphenol, 2,6-dihydroxymethylphenol or 2,6-dihydroxymethyl-4-methylphenol.

8. The method for modifying the polysalicylic alcohol resin according to claim 6, wherein: The trimethylolphenol compound is 2,4,6-trimethylolphenol.

9. The method for modifying the polysalicylic alcohol resin according to claim 6, wherein: The silsesquioxane compound is trisilanol phenyl-cage polysilsesquioxane, methyl silsesquioxane, phenyl silsesquioxane or vinyl silsesquioxane.

10. The polysalicylic alcohol resin prepared by the preparation method or modification method according to any one of claims 1 to 9, characterized in that: The polysalicylic alcohol resin has a viscosity of 0.01 to 1.00 Pa·s within a processing range of 60 to 90° C. and is suitable for use in an RTM process.

11. A polysalicylic alcohol resin prepared by the preparation method or modification method according to any one of claims 1 to 9, characterized in that: The viscosity of the polysalicylic alcohol resin at room temperature (25°C) is 10 4 ~10 5 Pa·s is suitable for hot melt adhesive film process.

12. The polysalicylic alcohol resin prepared by the preparation method or modification method according to any one of claims 1 to 9, characterized in that: The polysalicylic alcohol resin has a viscosity greater than 10 at room temperature (25°C). 5 Pa·s liquid or solid, suitable for solution impregnation process.

13. Use of the polysalicylic alcohol resin prepared by the preparation method or modification method according to any one of claims 1 to 9 as a matrix resin in the preparation of fiber-reinforced ablation-resistant phenolic resin-based composite materials.

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