Process for the preparation of a cyanate ester resin and its use in wet winding processes
By blending phenolic cyanate resin with bisphenol A cyanate resin and compounding thiazole accelerators with sulfur-containing catalysts, combined with a gradient temperature curing process, the problems of maintaining the performance of cyanate resin at medium and low temperatures and the applicability of wet winding process were solved, realizing the application of cyanate resin that maintains excellent performance at medium and low temperatures.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HARBIN INST OF TECH
- Filing Date
- 2023-11-27
- Publication Date
- 2026-05-19
AI Technical Summary
Existing cyanate ester resins are difficult to maintain excellent mechanical and heat resistance properties under medium and low temperature curing conditions, and are not suitable for wet winding processes.
A cyanate resin capable of curing at medium and low temperatures was prepared by blending phenolic cyanate resin with bisphenol A cyanate resin, and by compounding thiazole accelerators with sulfur-containing catalysts and combining them with a gradient temperature curing process.
It maintains the excellent properties of cyanate ester resin at medium and low temperatures and meets the requirements of wet winding process, making it suitable for the preparation of solid rocket motor shells.
Smart Images
Figure CN117430948B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of cyanate ester resin technology, specifically relating to a method for preparing cyanate ester resin and its application in wet winding process. Background Technology
[0002] Cyanate ester resin is a high-performance composite resin matrix with advantages such as excellent mechanical properties, high thermal stability, good dielectric properties, excellent hydrophobicity, good adhesion to fiber interfaces, and processing properties similar to epoxy resin. It is widely used in aerospace, electrical insulation, stealth materials, adhesives, and coatings.
[0003] Under the combined action of heating and a catalyst, the cyanate functional groups in cyanate ester resin undergo a trimerization reaction to form a cross-linked network structure with a triazine ring structure, thereby endowing the cyanate ester resin with extremely high heat resistance. However, the activation energy for the cross-linking of cyanate ester groups (-OCN) to form a triazine ring structure is as high as 118.4 kJ / mol, requiring high-temperature curing and cross-linking reactions. Furthermore, the high cross-linking density of the triazine ring structure results in high brittleness, which limits its practical applications. Current research on the modification of cyanate ester resins both domestically and internationally is quite in-depth, but some problems remain unresolved: how to maintain the excellent mechanical and heat resistance properties of cyanate ester resins under medium- and low-temperature curing conditions; and how to make cyanate ester resins meet the requirements of wet winding processes. Summary of the Invention
[0004] To address the technical challenges of maintaining the excellent mechanical and heat resistance properties of cyanate ester resins under medium- and low-temperature curing conditions, and ensuring that cyanate ester resins meet the requirements of wet winding processes, this invention provides a method for preparing cyanate ester resins and their application in wet winding processes.
[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:
[0006] A method for preparing a cyanate ester resin, the method comprising the following steps:
[0007] Step 1: Preparation of resin prepolymer:
[0008] A resin prepolymer was prepared by uniformly mixing phenolic cyanate resin and bisphenol A cyanate resin.
[0009] Step 2: Preparation of high-efficiency composite curing catalyst:
[0010] A highly efficient composite curing catalyst was prepared by mixing thiazole accelerators and sulfur-containing catalysts together.
[0011] Step 3: Establishment of the medium-low temperature curing process:
[0012] The resin prepolymer was mixed and stirred with a high-efficiency composite curing catalyst to obtain a resin prepolymer-composite catalyst system. The resin prepolymer-composite catalyst system was cured using a medium-low temperature curing process to obtain a fully cured cyanate ester resin.
[0013] Furthermore, the mass ratio of the resin prepolymer to the highly efficient composite curing catalyst is 100:(1.0~5.0).
[0014] Furthermore, in step 1, the mass ratio of phenolic cyanate resin to bisphenol A cyanate resin is 1:(3-5), and the mixing temperature is 85-110℃.
[0015] Furthermore, in step 2, the mass ratio of thiazole promoter to sulfur-containing catalyst in the high-efficiency compound curing catalyst is 1:(1-6), and the mixing temperature is 85-110℃.
[0016] Furthermore, in step 2, the thiazole accelerator accounts for 0.5% to 2% of the total mass of the cyanate ester resin by mass fraction, and the thiazole accelerator is any one of 2,2'-dithiodibenzothiazole, benzothiazole, 2-thiol-benzothiazole octyl salt, 2-mercaptobenzothiazole, and 3-methyl-2-thiazothione.
[0017] Furthermore, in step 2, the sulfur-containing catalyst accounts for 0.5% to 3% of the total mass of the cyanate ester resin by mass fraction, and the sulfur-containing catalyst is any one of dimethyl disulfide, 1,2-ethylene sulfur, bis(dodecylthio)dimethyltin, N,N'-diphenylthiourea, and sulfur.
[0018] Furthermore, in step 3, the resin prepolymer-composite catalyst system is cured using a medium-low temperature curing process to obtain a fully cured cyanate ester resin. Specifically, the mixed resin prepolymer-composite catalyst system is kept at a constant temperature in a vacuum oven for 0.5–1 h, and then kept at a constant temperature of 100–120 °C, 130–140 °C, and 150–155 °C for 2–3 h, 1–2 h, and 3–5 h respectively to achieve full curing of the resin system.
[0019] Based on the same inventive concept, the present invention also provides a cyanate ester resin prepared by the method for preparing the cyanate ester resin described above.
[0020] Based on the same inventive concept, the present invention also provides an application of the cyanate ester resin in a wet winding process.
[0021] Furthermore, the specific process for applying the cyanate ester resin in the wet winding process is as follows: the pretreated fiber is immersed in the resin matrix adhesive to fully wet it; the impregnated fiber is wound onto a mold or tooling, and the relative movement between the nozzle and the core mold is controlled to wind in different directions according to the product shape and requirements, and finally the wound fiber product is cured; wherein the temperature of the adhesive tank holding the resin adhesive during wet winding is 20-85℃.
[0022] Compared with the prior art, the beneficial technical effects of the present invention are as follows:
[0023] This invention employs a co-curing process using a blend of phenolic cyanate resin and bisphenol A cyanate resin. While maintaining the heat-resistant structure of the cured product, a catalyst enhances the toughness of the co-cured product. The phenolic cyanate resin improves the system's heat resistance without compromising the mechanical properties of the bisphenol A cyanate resin.
[0024] This invention combines a thiazole accelerator with a sulfur-containing catalyst. The combined catalyst catalyzes the formation of the triazine ring during the curing of cyanate ester resin, effectively lowering the activation energy of the curing reaction, thus allowing the cyanate ester resin system to cure at medium to low temperatures. Furthermore, gradient temperature curing ensures complete curing of the phenolic cyanate ester / bisphenol A cyanate ester resin system, enabling its application in many fields requiring medium to low temperature curing while maintaining the excellent properties of cyanate ester resin.
[0025] Using the curing characteristics, heat resistance, and mechanical properties of the casting as evaluation indicators, this invention ultimately determined a cyanate ester resin formulation that meets the requirements of solid rocket motor casings and wet winding processes. Attached Figure Description
[0026] Figure 1 Example 1: Infrared spectrum analysis of the cyanate ester resin prepolymer-composite catalyst system after curing, where a is the infrared spectrum of the blended resin before curing and b is the infrared spectrum after curing.
[0027] Figure 2 Example 1: Viscosity change curve of cyanate ester resin prepolymer-composite catalyst system upon heating.
[0028] Figure 3 Example 1: Viscosity change curve of cyanate ester resin prepolymer-composite catalyst system at constant temperature.
[0029] Figure 4 Example 1: Differential scanning calorimetry (DSC) curve of cyanate ester resin cured product.
[0030] Figure 5 Example 1: Bending strength of cyanate ester resin casting.
[0031] Figure 6 Example 1: Tensile strength of cyanate ester resin casting. Detailed Implementation
[0032] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below.
[0033] A method for preparing a cyanate ester resin, the method comprising the following steps:
[0034] Step 1: Preparation of resin prepolymer:
[0035] This invention employs a co-curing process using a blend of phenolic cyanate resin and bisphenol A cyanate resin. While maintaining the heat-resistant structure of the cured product, a catalyst enhances the toughness of the co-cured product. The phenolic cyanate resin improves the system's heat resistance without compromising the mechanical properties of the bisphenol A cyanate resin.
[0036] The specific steps for preparing the resin prepolymer are as follows: phenolic cyanate resin and bisphenol A cyanate resin are mixed evenly to prepare the resin prepolymer.
[0037] Preferably, a phenolic cyanate resin and a bisphenol A cyanate resin are melt-mixed uniformly at 85-110°C in a mass ratio of 1:(3-5) to achieve the preparation of a co-cured high-performance cyanate resin.
[0038] Step 2: Preparation of high-efficiency composite curing catalyst:
[0039] Because cyanate ester resins have high curing temperatures and high activation energies in the curing reaction, this invention designs and prepares a novel, highly efficient catalyst that can effectively reduce the activation energy of the curing reaction, thereby enabling the cyanate ester resin system to maintain excellent heat resistance while curing at medium and low temperatures. This invention synthesizes a novel, highly efficient catalyst by compounding a thiazole accelerator with a sulfur-containing catalyst, significantly reducing the activation energy of the curing reaction of cyanate ester resins, thus achieving medium and low temperature curing. The compounded catalyst has a certain catalytic effect on the formation of triazine rings during the curing of cyanate ester resins, and is therefore used as a catalyst in the co-curing system to lower the reaction activation energy, thereby achieving medium and low temperature curing.
[0040] The specific steps for preparing a high-efficiency composite curing catalyst are as follows: a thiazole promoter and a sulfur-containing catalyst are mixed together to prepare a high-efficiency composite curing catalyst.
[0041] The mass ratio of thiazole accelerator to sulfur-containing catalyst in the high-efficiency compound curing catalyst is 1:(1-6), and the preparation temperature is 85-110℃. The thiazole accelerator accounts for 0.5%-2% of the total mass of the cyanate ester resin, and the thiazole accelerator is selected from any one of 2,2'-dithiodibenzothiazole, benzothiazole, 2-thiol-benzothiazole octyl salt, 2-mercaptobenzothiazole, and 3-methyl-2-thiazothione. The sulfur-containing catalyst accounts for 0.5%-3% of the total mass of the cyanate ester resin, and the sulfur-containing catalyst is selected from any one of dimethyl disulfide, 1,2-ethylene sulfur, bis(dodecylthio)dimethyltin, N,N'-diphenylthiourea, and sulfur.
[0042] Step 3: Establishment of the medium-low temperature curing process:
[0043] The curing temperature of cyanate ester resins is generally between 200 and 280°C; only at this temperature can the cured product achieve the required performance. When the curing temperature is lower than this, the cyanate ester resin does not cure completely and cannot maintain its excellent heat resistance. To ensure that cyanate ester resins retain their excellent performance under medium- and low-temperature curing conditions, new curing processes need to be developed. This invention employs gradient temperature curing to ensure complete curing of the phenolic cyanate ester / bisphenol A cyanate ester resin system. This allows for application in many fields requiring medium- and low-temperature curing while maintaining the excellent performance of the cyanate ester resin.
[0044] The specific steps for establishing the medium-low temperature curing process are as follows: the resin prepolymer and the high-efficiency composite curing catalyst are mixed and stirred at a certain temperature to ensure uniform mixing, thereby obtaining a resin prepolymer-composite catalyst system, wherein the ratio of resin prepolymer to high-efficiency composite curing catalyst is 100:(1.0~5.0); the mixed resin prepolymer-composite catalyst system is kept at a constant temperature in a vacuum oven for 0.5~1h, and then kept at a constant temperature of 100~120℃, 130~140℃, and 150~155℃ for 2~3h, 1~2h, and 3~5h respectively to achieve full curing of the resin system.
[0045] Based on the same inventive concept, the present invention also provides a cyanate ester resin prepared by the method for preparing the cyanate ester resin described above.
[0046] Based on the same inventive concept, the present invention also provides an application of the cyanate ester resin in a wet winding process.
[0047] Using the curing characteristics, heat resistance, and mechanical properties of the casting as evaluation indicators, a resin formulation that meets the requirements of the wet winding process was finally determined; the application of this cyanate ester resin in the wet winding process can be used to prepare solid rocket motor casings.
[0048] The specific process for applying cyanate ester resin in wet winding is as follows: Pre-treated fibers are immersed in a resin matrix solution to ensure thorough wetting; the impregnated fibers are wound onto a mold or tooling, and the relative movement between the nozzle and the core mold is controlled to achieve different winding directions according to the product shape and requirements; finally, the wound fiber product is cured. The temperature of the resin bath used for wet winding is 20–85℃.
[0049] The prepared cyanate ester resin meets the requirements of the wet winding process. The viscosity of the resin solution can be maintained at 0.3-0.8 Pa·s for more than 140 minutes, which provides a sufficiently long process window for the wet winding process.
[0050] The specific implementation methods are described and verified below with reference to the embodiments.
[0051] Example 1
[0052] The curing process for cyanate ester resin is as follows:
[0053] Step 1: Preparation of resin prepolymer
[0054] Mix 30g of phenolic cyanate resin and 120g of bisphenol A cyanate resin at 100℃ until homogeneous, stirring constantly during the mixing process to ensure uniform mixing of the two resins.
[0055] Step 2: Preparation of high-efficiency composite curing catalyst
[0056] The high-efficiency compound curing catalyst is composed of 0.6% by mass of 2-mercaptobenzothiazole and 0.7% by mass of sulfur, mixed at a mixing temperature of 100℃.
[0057] Step 3: Establishment of the medium-low temperature curing process
[0058] The high-efficiency compounded curing catalyst and the resin prepolymer were mixed at 90°C with continuous stirring to ensure uniform mixing. The mixed resin prepolymer-compounded catalyst system was then kept at 85°C in a vacuum oven for 1 hour to completely remove air bubbles. The system was then heated to 120°C and kept at that temperature for 2 hours, followed by 140°C and kept at that temperature for 1 hour to allow the resin system to fully gel. Finally, the system was heated to 150°C and kept at that temperature for 4 hours to allow the resin system to fully cure.
[0059] Figures 1-6 The relevant parameter diagrams for the cyanate ester resin curing process in Example 1 are provided.
[0060] Figure 1 The images show the infrared spectra of the cyanate ester resin system before and after curing in Example 1. a) is the infrared spectrum of the blended resin before curing, and b) is the infrared spectrum after curing. (2273-2235 cm⁻¹) -1The characteristic peak at 1560-1510 cm⁻¹ is due to the cyanate ester functional group. -1 The peak at this location is characteristic of the triazine ring. As the curing reaction proceeds, the cyanate functional groups gradually disappear, forming the triazine ring.
[0061] Figure 2 The figure shows the temperature-viscosity change curve of the cyanate ester resin prepolymer-composite catalyst system in Example 1. The temperature range was 70-150℃, and each temperature was held for 15 minutes. The viscosity was counted every 5 minutes. As shown in the figure, the overall trend of the curve is that the viscosity first decreases and then increases.
[0062] Figure 3 The isothermal viscosity change curves of the cyanate ester resin prepolymer-composite catalyst system in Example 1 are shown in the figure. Three temperatures, 75℃, 80℃, and 85℃, were selected. As shown in the figure, the viscosity of the resin system was maintained at 0.3-0.8 Pa·s for 150 min at 75℃, 155 min at 80℃, and 140 min at 85℃.
[0063] Figure 4 The differential scanning calorimetry (DSC) curve of the cyanate ester resin cured product in Example 1 is shown in the figure. The glass transition temperature of the resin system can reach 280.3℃.
[0064] Figure 5 The bending strength of the cyanate ester resin casting in Example 1 is shown in the figure. The bending strength can reach up to 145.0 MPa.
[0065] Figure 6 The tensile strength of the cyanate ester resin casting in Example 1 is shown in the figure. The maximum tensile strength can reach 70.0 MPa.
[0066] Example 2
[0067] Step 1: Preparation of resin prepolymer
[0068] Mix 30g of phenolic cyanate resin and 120g of bisphenol A cyanate resin at 110℃ until homogeneous, stirring constantly during the mixing process to ensure uniform mixing of the two resins.
[0069] Step 2: Preparation of high-efficiency composite curing catalyst
[0070] The high-efficiency compound curing catalyst is composed of 1.5% by mass of 2,2'-dithiodibenzothiazole and 1.8% by mass of bis(dodecylthio)dimethyltin, mixed at a mixing temperature of 110℃.
[0071] Step 3: Establishment of the medium-low temperature curing process
[0072] The high-efficiency compounded curing catalyst and the resin prepolymer were mixed at 100℃ with continuous stirring to ensure uniform mixing. The mixed resin prepolymer-compounded catalyst system was then kept at 85℃ in a vacuum oven for 1 hour to completely remove air bubbles. The system was then heated to 115℃ and kept at that temperature for 2 hours, followed by 140℃ and kept at that temperature for 2 hours to allow the resin system to fully gel. Finally, the system was heated to 150℃ and kept at that temperature for 3 hours to allow the resin system to fully cure.
[0073] Example 3
[0074] The curing process for cyanate ester resin is as follows:
[0075] Step 1: Preparation of resin prepolymer
[0076] Mix 30g of phenolic cyanate resin and 150g of bisphenol A cyanate resin at 110℃ until homogeneous, stirring constantly during the mixing process to ensure uniform mixing of the two resins.
[0077] Step 2: Preparation of high-efficiency composite curing catalyst
[0078] The high-efficiency compound curing catalyst is composed of 1% by mass of 3-methyl-2-thiazothione and 1.2% by mass of N,N'-diphenylthiourea, mixed at a mixing temperature of 110℃.
[0079] Step 3: Establishment of the medium-low temperature curing process
[0080] The high-efficiency compounded curing catalyst and the resin prepolymer were mixed at 95°C with continuous stirring to ensure uniform mixing. The mixed resin prepolymer-compounded catalyst system was then heated in a vacuum oven at 85°C for 45 minutes to completely remove air bubbles. The system was then heated to 120°C and held for 1 hour, followed by a heating to 130°C and held for 2 hours to allow the resin system to fully gel. Finally, the system was heated to 150°C and held for 4 hours to allow the resin system to fully cure.
[0081] Example 4
[0082] The curing process for cyanate ester resin is as follows:
[0083] Step 1: Preparation of resin prepolymer
[0084] Mix 30g of phenolic cyanate resin and 90g of bisphenol A cyanate resin at 110℃ until homogeneous, stirring constantly during the mixing process to ensure uniform mixing of the two resins.
[0085] Step 2: Preparation of high-efficiency composite curing catalyst
[0086] The high-efficiency compound curing catalyst is composed of 0.8% benzothiazole and 1% 1,2-ethylidene sulfur by mass, mixed at a mixing temperature of 105℃.
[0087] Step 3: Establishment of the medium-low temperature curing process
[0088] The high-efficiency compounded curing catalyst and the resin prepolymer were mixed at 90°C with continuous stirring to ensure uniform mixing. The mixed resin prepolymer-compounded catalyst system was then kept at 85°C in a vacuum oven for 1 hour to completely remove air bubbles. The system was then heated to 115°C and kept at that temperature for 2 hours, followed by a further increase to 130°C and a 1-hour holding period to allow the resin system to fully gel. Finally, the system was heated to 150°C and kept at that temperature for 5 hours to allow the resin system to fully cure.
[0089] Examples 1 to 4 all meet the requirements for wet winding processes. This resin system maintains a viscosity of 0.3–0.8 Pa·s for over 140 minutes at 70–85°C, providing a sufficiently long process window for wet winding. This is a resin formulation that meets the requirements for solid rocket motor casings and wet winding processes.
[0090] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing a cyanate ester resin, characterized in that, The preparation method is carried out according to the following steps: Step 1: Preparation of resin prepolymer: A resin prepolymer was prepared by uniformly mixing phenolic cyanate resin and bisphenol A cyanate resin. The mass ratio of the phenolic cyanate resin to the bisphenol A cyanate resin is 1:(3~5), and the mixing temperature is 85~110℃. Step 2: Preparation of high-efficiency composite curing catalyst: A highly efficient composite curing catalyst was prepared by mixing thiazole accelerators and sulfur-containing catalysts together. The thiazole accelerator accounts for 0.5% to 2% of the total mass of the cyanate ester resin by mass fraction, and the thiazole accelerator is any one of 2,2'-dithiodibenzothiazole, benzothiazole, 2-thiol-benzothiazole octyl salt, 2-mercaptobenzothiazole and 3-methyl-2-thiazothione. The sulfur-containing catalyst accounts for 0.5% to 3% of the total mass of the cyanate ester resin by mass fraction, and the sulfur-containing catalyst is any one of dimethyl disulfide, bis(dodecylthio)dimethyltin, N,N'-diphenylthiourea and sulfur. Step 3: Establishment of the medium-low temperature curing process: The resin prepolymer was mixed and stirred with a high-efficiency composite curing catalyst to obtain a resin prepolymer-composite catalyst system. The resin prepolymer-composite catalyst system was cured using a medium-low temperature curing process to obtain a fully cured cyanate ester resin.
2. The method for preparing cyanate ester resin according to claim 1, characterized in that, In step 2, the mass ratio of thiazole promoter to sulfur-containing catalyst in the high-efficiency compound curing catalyst is 1:(1~6), and the mixing temperature is 85~110℃.
3. The method for preparing cyanate ester resin according to claim 1, characterized in that, In step 3, the resin prepolymer-composite catalyst system is cured using a medium-low temperature curing process to obtain a fully cured cyanate ester resin. Specifically, the mixed resin prepolymer-composite catalyst system is kept at a constant temperature in a vacuum oven for 0.5-1 h, and then kept at a constant temperature of 100-120℃, 130-140℃, and 150-155℃ for 2-3 h, 1-2 h, and 3-5 h respectively to achieve full curing of the resin system.
4. A cyanate ester resin prepared by the method for preparing cyanate ester resin according to any one of claims 1-3.
5. The application of the cyanate ester resin according to claim 4 in a wet winding process.
6. The application of the cyanate ester resin according to claim 5 in the wet winding process, characterized in that, The specific process of applying the cyanate ester resin in the wet winding process is as follows: the pretreated fiber is soaked in the resin matrix adhesive to fully wet it; the impregnated fiber is wound on the mold or tooling, and the relative movement between the nozzle and the core mold is controlled to wind in different directions according to the product shape and requirements; finally, the wound fiber product is cured. The temperature of the glue tank containing the resin solution during wet winding is 20~85℃.