Preparation method of cyanate ester impregnating resin, prepreg and preparation method and application thereof

Abstract

The invention discloses a preparation method of cyanate ester impregnating resin, a prepreg and a preparation method and application of the prepreg. The preparation method of the cyanate impregnating resin comprises the following steps: carrying out prepolymerization reaction on bisphenol A dicyanate and dihydric alcohol in the presence of a first catalyst to obtain a first bisphenol A cyanate prepolymer; carrying out chain extension reaction on diamine and the first bisphenol A type cyanate ester prepolymer to obtain a second bisphenol A type cyanate ester prepolymer; and mixing the second bisphenol A cyanate ester prepolymer with polyether amine and a second catalyst. The cyanate impregnating resin prepared by the method has excellent dielectric properties, strength, toughness and high temperature resistance, can be used as an impregnating material of prepregs, has high impregnating solid content, has good wettability to glass fibers and copper foils, and has excellent processability. The invention also provides application of the method in preparation of prepregs, copper-clad plates or PCBs (printed circuit boards).

Description

Technical Field

[0001] This application relates to, but is not limited to, the field of polymer materials technology, and particularly relates to a preparation method of a cyanate ester impregnated resin, a prepreg and its preparation method and application. Background Art

[0002] With the continuous improvement of the demand for high-speed and high-frequency performance in 5G networks, the wiring density of printed circuit boards (PCBs) is gradually developing towards high density and high integration, posing more stringent requirements on material properties. For example, materials are required to have lower dielectric constants, smaller dielectric losses, lower thermal expansion coefficients, low water absorption, as well as excellent heat resistance and mechanical properties to ensure reliability and stability under high-speed and high-frequency operating conditions. At present, the prepregs (also known as bonding sheets, or simply PP sheets) used in PCB boards are mainly epoxy resin-based fiberglass boards. However, traditional epoxy resin materials are difficult to meet the performance requirements of high-speed, high-frequency, and high-temperature resistant PCB boards in terms of heat resistance, mechanical properties, hygroscopicity, and dielectric properties.

[0003] As a high-performance material, cyanate ester resin has developed rapidly in the past few decades and has received much attention in the fields of high-performance resins and composites. The general formula of common cyanate ester monomers is N≡C-O-Ar-O-C≡N, where Ar is a group containing an aromatic ring. The cyanate group (-O-C≡N) will polymerize to form a triazine ring under the action of heat and a catalyst, forming a highly cross-linked network structure. Its molecular structure also contains ether bonds that can rotate freely. This unique structure endows cyanate ester resin with various excellent properties, including excellent dielectric properties (such as low dielectric constant and low dielectric loss), good heat resistance and mechanical properties, excellent bonding properties, as well as low shrinkage rate and low water absorption. With these performance advantages, cyanate ester resin has been successfully applied in the field of composites (such as PCB boards) and can be used in fields such as aerospace and electronic equipment.

[0004] However, the application of cyanate ester resin still has significant limitations and is difficult to meet the extensive industrial demands. First of all, the processing technology of cyanate ester resin is relatively complex and the laying performance is poor. The commonly used bisphenol A cyanate ester monomer is in the form of powdery crystals at room temperature and needs to be heated above the melting temperature (80 °C) for impregnation coating. If coating is carried out by dissolving in a solvent, a large amount of solvent is required, resulting in a low solid content of the impregnating material (for example, about 50%), making it difficult to accurately control the sizing amount, or multiple coatings are needed, increasing the process complexity. In addition, after the solvent volatilizes, the monomer is prone to recrystallize into solid particles, resulting in chipping or powdering of the prepared prepreg, seriously affecting the final use performance. Secondly, the brittleness of cyanate ester resin is relatively large. Existing modification methods, such as chemical modification or physical blending modification, although can improve the toughness to a certain extent, often lead to a reduction in dielectric properties or heat resistance, and it is difficult to achieve a balance among various properties.

[0005] Therefore, it is necessary to develop a cyanate ester resin material with excellent dielectric properties, heat resistance, mechanical properties and process applicability to meet the requirements of higher performance applications. Summary of the Invention

[0006] The present application proposes a preparation method of a cyanate ester impregnating resin. The prepared cyanate ester impregnating resin has excellent dielectric properties, strength, toughness and high temperature resistance, can be used as an impregnating material for prepreg, has a high impregnation solid content, good wettability to glass fiber and copper foil, and has excellent processability.

[0007] The present application also proposes an impregnating material.

[0008] The present application also proposes a prepreg.

[0009] The present application also proposes a method for preparing the above prepreg.

[0010] The present application also proposes the application of the above preparation method of cyanate ester impregnating resin, impregnating material, prepreg or method for preparing prepreg.

[0011] Specifically, the first aspect embodiment of the present invention relates to a preparation method of a cyanate ester impregnating resin, including the following steps:

[0012] Bisphenol A dicyanate ester is subjected to a prepolymerization reaction with a diol in the presence of a first catalyst to obtain a first bisphenol A type cyanate ester prepolymer; a diamine is subjected to a chain extension reaction with the first bisphenol A type cyanate ester prepolymer to obtain a second bisphenol A type cyanate ester prepolymer; wherein, the bisphenol A dicyanate ester is in excess relative to the diol, and the first bisphenol A type cyanate ester prepolymer is in excess relative to the diamine, and the temperatures of the prepolymerization reaction and the chain extension reaction are both 80-140 °C; the second bisphenol A type cyanate ester prepolymer is mixed with a polyetheramine and a second catalyst to obtain the cyanate ester impregnating resin.

[0013] The preparation reaction principle of the cyanate ester impregnating resin is speculated as follows:

[0014] A prepolymerization and chain extension reaction are sequentially carried out on bisphenol A dicyanate ester (monomer) using a diol and a diamine. First, prepolymerization is carried out using a diol to make the reaction more stable and controllable. When the monomer is in excess relative to the diol, it is easier to form a prepolymer structure bridged by the diol (i.e., the first bisphenol A type cyanate ester prepolymer). After the prepolymerization is completed, the reaction activity of the remaining cyanate groups is lower than that of the monomer. At this time, a diamine with higher activity is introduced for chain extension, which can effectively increase the number of chain link units. When the first bisphenol A type cyanate ester prepolymer is in excess relative to the diamine, the chain extension reaction tends to preferentially react with the cyanate groups at one end of the first bisphenol A type cyanate ester prepolymer, thereby forming a prepolymer structure capped with cyanate groups (i.e., the second bisphenol A type cyanate ester prepolymer).

[0015] The curing reaction principle of the cyanate ester impregnating resin is as follows:

[0016] In the later curing stage, the second bisphenol A type cyanate ester prepolymer reacts to form a triazine ring crosslinked network, and diamine and diol are released during the process. At the same time, the polyetheramine can react with the cyanate groups and enter the crosslinked network. Since the temperatures of the prepolymerization and chain extension reactions do not exceed 140 °C (above the melting point of the monomer and far lower than the cyanate ester curing temperature, the latter is usually above 180 °C), at this stage, the cyanate groups mainly react with amino or hydroxyl groups. At a higher curing temperature, the cyanate groups are prone to self-polymerize to form triazine rings. At this time, the reaction between the cyanate groups and amino or hydroxyl groups shows a certain reversibility. Since diamine and diol are usually short-chain molecules, the structures formed by their reaction with cyanate groups are vulnerable to attack by cyanate groups, thereby promoting the formation of triazine rings and releasing diamine or diol. At the same time, diamine or diol is volatile at high temperatures, and its escape further promotes the progress of this reaction. In contrast, the polyetheramine has a longer chain segment and a more stable overall structure. Among them, the flexible polyether chain segment can reduce the local stress of the crosslinked network, improve stability, and has less competitive reaction with adjacent cyanate groups and is not prone to reverse reaction. In addition, the polyetheramine is difficult to volatilize, making it more stably retained in the crosslinked network.

[0017] The schematic chemical reaction formulas of the preparation reaction and the curing reaction of the cyanate ester impregnating resin are as follows:

[0018]

[0019] The above reaction formula is a schematic expression, showing the reaction process of adding diol and diamine, as well as the curing process of the self-polymerization of cyanate ester to form a triazine ring. Where * represents the connection site, and the structure with is the cured product (the raw material for the third-step curing reaction also includes polyetheramine, which is not shown in the reaction formula). represents other structures not shown, such as polyetheramine segments, other triazine ring structures, and OR 1 chain segments, etc. The degree of polymerization of the product of the reaction of adding diol and diamine can be regulated according to the feeding ratio. For example, in the prepolymerization reaction, when the molar ratio of diol (A) to bisphenol A dicyanate (R) is 1:2, the RAR structure may be mainly formed; when the molar ratio of diol (A) to bisphenol A dicyanate (R) is 2:3, the RARAR structure is the main one. The control of the degree of polymerization in the chain extension reaction can be inferred by analogy.

[0020] The preparation method of the cyanate ester impregnated resin according to the first aspect embodiment of the present invention has at least the following beneficial effects:

[0021] Through the prepolymerization and chain extension reactions of diol and diamine, and the copolymer modification of polyetheramine, the liquefaction of cyanate ester monomers is realized, significantly improving the wettability, contributing to improving the electrical properties of the resin material, while ensuring the high-temperature resistance and mechanical properties of the material.

[0022] Specifically, by introducing diol segments through the prepolymerization reaction, the high regularity and crystallization properties of bisphenol A dicyanate are effectively destroyed, the melting point can be reduced, making it liquid at room temperature and improving the processing convenience. Using diamine for chain extension, the movement ability of the segments is enhanced, the fluidity of the resin is improved, and its wettability to reinforcing materials (such as fiberglass cloth) or copper foil during the molding process is better, effectively enhancing the interlayer bonding performance.

[0023] The cyanate group capping can ensure the efficient progress of the subsequent curing. During the curing process, the second bisphenol A type cyanate ester prepolymer polymerizes to form a triazine ring, while releasing diamine and diol. Since the boiling points of common diols are generally higher than those of diamines, the combination of the two can construct a step-by-step volatilization system, enabling small molecule products to gradually escape in different temperature ranges, thereby reducing small molecule residues and bubble defects, and improving the densification, dielectric properties, and thermal stability of the cured material.

[0024] After traditional cyanate ester resin is cured, due to the highly symmetric triazine ring structure in its molecular structure, the crosslinking density is high and the brittleness is relatively large. In this application, in-situ copolymerization modification with polyetheramine is carried out to introduce flexible polyether segments into the curing network, enhancing the movement ability of molecular chains, thereby significantly improving the toughness of the resin. At the same time, by controlling the dosage of polyetheramine, the influence on heat resistance can be reduced, and an optimized balance of overall properties such as toughness and heat resistance can be achieved.

[0025] The cyanate ester impregnated resin prepared by the method of this application has high heat resistance (Tg reaches above 230 °C), high mechanical properties (flexural strength reaches above 108 MPa, impact toughness reaches above 14 kJ / m 2 above), low moisture absorption (moisture absorption rate ≤ 0.5%), and low dielectric constant and dielectric loss (at 10 GHz: Dk ≤ 2.7, Df ≤ 0.006). This resin can be used to prepare prepregs and is applied to the preparation of copper clad laminates or their substrates, and can better meet the requirements of high speed, high frequency, high heat resistance and high dielectric properties required for the operation of 5G communication networks.

[0026] According to some embodiments of the present invention, the diol is selected from ethylene glycol, which has no branched structure and small steric hindrance, and is more likely to contact with cyanate groups during the later curing process, promoting the formation of triazine rings. In addition, the boiling point of ethylene glycol is 195 °C, which is close to the curing temperature range of cyanate ester, enabling it to volatilize sufficiently during the later curing stage to ensure the mechanical properties, temperature resistance and dielectric properties of the cured product.

[0027] According to some embodiments of the present invention, the molar ratio of the diol to bisphenol A dicyanate is 1:2 to 2:3. By controlling the molar ratio, the degree of polymerization can be adjusted to achieve room temperature liquefaction, enhance the movement ability of molecular chains, improve the wettability of the resin system, and optimize the processing performance and interlayer bonding effect.

[0028] According to some embodiments of the present invention, the diamine is selected from at least one of ethylenediamine, 1,3-propanediamine, 1,2-propanediamine, and 1,4-butanediamine. A diamine with a straight-chain or short-chain structure is selected, and its boiling point is relatively low, making it easier to escape during the resin curing stage.

[0029] According to some embodiments of the present invention, the molar ratio of the diamine to the first bisphenol A cyanate prepolymer is 1:2 to 2:3. Among them, the molar amount of the first bisphenol A cyanate prepolymer is calculated according to the theoretical molar amount. For example, when the molar ratio of diol (A) to bisphenol A dicyanate (R) is 1:2, based on the formation of the RAR structure, the theoretical molar amount is calculated, and it can be calculated according to the molar amount of the diol. By controlling the molar ratio of reaction raw materials, the degree of polymerization can be adjusted to form a molecular structure with isocyanate group-terminated ends, so as to further enhance the movement ability of molecular chains and improve the wettability while maintaining the room temperature liquefaction characteristics.

[0030] According to some embodiments of the present invention, the polyetheramine is polyoxypropylene diamine with a molecular weight of 200 to 500. Polyoxypropylene diamine contains methyl side groups, which can reduce the intermolecular force, lower the brittleness of the resin, and enhance the toughness. In addition, it can effectively optimize the toughness at a relatively low dosage and reduce the impact on the heat resistance of the resin. The presence of methyl side groups can also improve the stability of the reaction structure with cyanate groups, contributing to the stable embedding of polyetheramine segments in the crosslinked network.

[0031] The molecular weight of the polyetheramine is not too high, and its reaction activity is higher, which helps to form flexible bridge chains during the resin curing process and improve the toughness of the resin.

[0032] According to some embodiments of the present invention, the mole number of the polyetheramine accounts for 2% to 5% of the mole number of bisphenol A dicyanate. The mole number of the polyetheramine is not too high, which can reduce the impact on heat resistance.

[0033] According to some embodiments of the present invention, both the first catalyst and the second catalyst are selected from dibutyltin dilaurate. Selecting dibutyltin dilaurate as the catalyst, its high catalytic activity and excellent solubility in the resin system can effectively promote the chain extension reaction and the smooth progress of the curing process, improve the reaction rate and the uniformity of the system, thereby optimizing the final properties of the resin.

[0034] According to some embodiments of the present invention, the mass of the first catalyst accounts for 0.01% to 0.05% of the mass of bisphenol A dicyanate, and for example, it can be about 0.01%, 0.02%, 0.03%, 0.04% or 0.05%.

[0035] According to some embodiments of the present invention, the mass of the second catalyst accounts for 0.01% to 0.05% of the mass of bisphenol A dicyanate, and for example, it can be about 0.01%, 0.02%, 0.03%, 0.04% or 0.05%.

[0036] Controlling the dosage of the catalyst can ensure that the reaction rate and conversion rate are moderate, making the reaction process neither too fast nor too slow. If the reaction rate is too fast, it may lead to uneven reaction or incomplete reaction in some parts, affecting the final properties; if the reaction rate is too slow, it will affect the production efficiency.

[0037] According to some embodiments of the present invention, the temperature of the prepolymerization reaction is 90 to 100 °C, and the prepolymerization reaction time is 0.5 to 1 h.

[0038] According to some embodiments of the present invention, the temperature of the chain extension reaction is 110 to 120 °C, and the chain extension reaction time is 1 to 2 h.

[0039] By controlling the temperature and time of the prepolymerization reaction and the chain extension reaction, it can ensure sufficient reaction and reduce side reactions.

[0040] According to some embodiments of the present invention, before the prepolymerization reaction and / or the chain extension reaction, it further includes the step of heating and mixing the reaction raw materials. The heating temperature should be higher than the melting point of bisphenol A dicyanate to liquefy it, facilitating the full mixing of the raw materials. The present invention places no limitation on the mixing time, which can be selected according to the actual situation. For the prepolymerization reaction, first heat to mix bisphenol A dicyanate with the diol, and then add the first catalyst for mixing. During the heating and mixing process, the temperature can be appropriately lower than the reaction temperature. After the raw materials are fully and evenly mixed, then raise the temperature to the reaction temperature for the reaction.

[0041] Considering the volatility of the diol or diamine, reflux operation can be carried out during the reaction or heating process to ensure the ratio of the raw materials.

[0042] According to some embodiments of the present invention, mixing the second bisphenol A cyanate prepolymer with polyetheramine and the second catalyst includes the following steps: mixing the second bisphenol A cyanate prepolymer with polyetheramine under heating conditions, then cooling down, and adding the second catalyst for mixing. Heating can reduce the viscosity and improve the mixing uniformity. After adding polyetheramine for mixing, the fluidity of the system is enhanced. Therefore, the temperature can be appropriately reduced for catalyst mixing. The present invention places no limitation on the heating and cooling temperatures, and appropriate temperatures can be selected according to the system viscosity and process requirements. For example, the heating temperature can be 110 - 120 °C, and the heating and mixing time is 0.5 - 1 h; after adding polyetheramine for mixing, the viscosity is reduced, and the temperature can be cooled down to 70 - 80 °C, and then the second catalyst is added for mixing.

[0043] According to some embodiments of the present invention, the dielectric properties of the cyanate ester impregnating resin satisfy: Dk ≤ 2.6, Df ≤ 0.006, and the test frequency is 10 GHz.

[0044] The second aspect embodiment of the present invention relates to an impregnating material, including a solvent and a cyanate ester impregnating resin, and the cyanate ester impregnating resin is prepared by the above preparation method.

[0045] The impregnating material includes the cyanate ester impregnating resin prepared by the above method, and thus at least has all the beneficial effects brought by the embodiments of the above preparation method of the cyanate ester impregnating resin. Specifically, the impregnating material of the present application not only has excellent dielectric properties, mechanical properties and high temperature resistance, but also realizes the room temperature liquefaction modification of bisphenol A dicyanate due to the cyanate ester impregnating resin, has good wettability to glass fiber and copper foil, can achieve a high impregnation solid content, and has excellent processability.

[0046] According to some embodiments of the present invention, the mass percentage content of the cyanate ester impregnating resin is 75% - 90%, and it has a relatively high impregnation solid content.

[0047] According to some embodiments of the present invention, the solvent is selected from ketone solvents, specifically at least one of acetone and butanone. Such solvents have good solubility and fast drying rate, which helps to improve production efficiency.

[0048] A third aspect of the present invention relates to a method for preparing the above-mentioned impregnating material, comprising the following steps: mixing the cyanate impregnating resin with the solvent.

[0049] The method has simple process and is easy to implement, and can prepare a high-performance impregnated material.

[0050] The mixing process may be heated, for example, mixing near the boiling point of the solvent, to improve the mixing uniformity. The heating time may be 15 to 45 minutes, or other suitable temperatures and times may be selected for mixing according to the viscosity of the system. Reflux may be performed during the heating process to stabilize the solvent content.

[0051] A fourth aspect of the present invention relates to a prepreg, comprising a reinforcing material and a cyanate impregnated resin attached to the reinforcing material, wherein the cyanate impregnated resin is prepared by the above-mentioned preparation method.

[0052] The prepreg includes the cyanate impregnated resin prepared by the above method, and therefore has at least all the beneficial effects brought by the above-mentioned embodiment of the method for preparing the cyanate impregnated resin. Specifically, the prepreg of the present application has excellent dielectric properties (10GHz: Dk≤2.8, Df≤0.008), mechanical properties (bending strength≥250MPa), high temperature resistance (Tg≥230℃), low hygroscopicity (moisture absorption rate≤0.5%), low expansion coefficient (thermal expansion coefficient≤50ppm / ℃), good adhesion (peel strength to copper foil≥1N / mm) and processability, solving the problems of complex processing technology, poor draping performance and high brittleness of cyanate materials.

[0053] According to some embodiments of the present invention, the mass percentage of the cyanate impregnating resin is 55% to 65%. An appropriate amount of resin content can improve the interface bonding strength, ensure the firm bonding between layers, and optimize the later processing performance.

[0054] According to some embodiments of the present invention, the reinforcing material is glass fiber fabric, usually E glass fiber cloth (alkali-free glass fiber cloth).

[0055] According to some embodiments of the present invention, the weight of the reinforcing material is 100 to 200 g / m 2 .

[0056] Glass fiber has excellent dimensional stability, heat resistance and mechanical strength. Its lower weight is conducive to full penetration of resin, and it is suitable for small-size processing, which can improve processing accuracy.

[0057] According to some embodiments of the present invention, the reinforcing material is a glass fiber fabric, and the dielectric properties of the cured prepreg satisfy: Dk ≤ 2.8, Df ≤ 0.0075, at a test frequency of 10 GHz; and / or, Tg ≥ 250 °C, tested by the DMA method.

[0058] The fifth aspect embodiment of the present invention relates to a method for preparing the above prepreg, comprising the following steps:

[0059] Providing an impregnating material containing the cyanate ester impregnating resin;

[0060] After impregnating the reinforcing material with the impregnating material, drying to obtain the prepreg.

[0061] This method has a simple process and is easy for industrial production. The prepreg obtained has excellent comprehensive properties, with good mechanical properties, heat resistance, dielectric properties and processing adaptability, meeting the application requirements of high-performance electronic materials.

[0062] Among them, the preparation process of the impregnating material is as described above, and the impregnation process is a conventional process in the art.

[0063] According to some embodiments of the present invention, the drying temperature is not lower than the boiling point of the solvent used.

[0064] According to some embodiments of the present invention, the drying time is 10 - 30 min.

[0065] The sixth aspect embodiment of the present invention relates to the application of the above-mentioned method for preparing the cyanate ester impregnating resin, impregnating material, prepreg or prepreg, specifically for the preparation of copper clad laminates or PCB boards.

[0066] In view of the excellent properties of the prepared cyanate ester impregnating resin, it ensures a high impregnation solid content, good adhesion and processing performance of the prepreg, thus better meeting the strict requirements of copper clad laminates or PCB boards for material properties under high-speed, high-frequency and high-temperature conditions.

[0067] According to some embodiments of the present invention, the curing process of the cyanate ester impregnating resin comprises the following steps: successively heating at 150 - 160 °C for 0.5 - 1.5 h, reacting at 0.5 - 1 MPa and 165 - 175 °C for 0.5 - 1 h, reacting at 185 - 195 °C for 1 - 1.5 h, and reacting at 205 - 210 °C for 0.5 - 1 h.

[0068] The curing process is divided into four stages, where the first two stages are primary curing and the last two stages are post-curing.

[0069] The reaction temperature of the first-stage initial curing is relatively low, forming partial triazine rings and releasing a small amount of diamine and diol. Due to the relatively low boiling point of the diamine, a gradient volatilization effect is formed, which helps to remove bubbles and resin flow, ensures sufficient infiltration of the reinforcing material, and reduces the forming bubble defects.

[0070] In the second-stage initial curing, pressure is applied and the temperature is raised, but the reaction temperature is still lower than the post-curing temperature, further promoting the formation of triazine rings and removing a certain amount of diamine and diol. The initial curing reaction is relatively mild. Based on the gradient volatilization effect, small molecule diamine and diol can be well removed. At the same time, polyetheramine may participate in the cross-linking reaction, introducing a cross-linking network.

[0071] In the post-curing stage, based on the infiltration effect of the resin on the reinforcing material in the initial curing stage, through two-stage temperature-rising reactions, the participation of cyanate groups in the reaction is further promoted. Driven by temperature and resin flow, the forming defects can be reduced and the overall performance of the material can be improved.

[0072] In practical applications, according to the specification requirements of prepregs or PCB boards, curing is usually carried out after laying multiple prepregs in a stack. The present invention does not limit the number of stacked layers, which can be adjusted according to specific requirements, such as 5 to 8 layers or other numbers of layers.

[0073] In this application, the resin refers to a prepolymer or a high molecular material with a higher molecular weight, and these materials can be solid, viscous liquid (semi-solid) or liquid at room temperature. For example, the cyanate ester impregnated resin of the present invention contains a semi-solid bisphenol A type cyanate ester prepolymer, which can undergo a cross-linking reaction under the action of heat and a catalyst to form a solid high molecular material with a three-dimensional network structure.

[0074] In the description of this application, terms such as "first", "second", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0075] Room temperature refers to 23 ± 2 °C.

[0076] The numerical ranges involved all include the endpoint values and cover any sub-ranges within the range, such as the ranges obtained by any combination of the specifically listed numerical values. In addition, "above" or "below" both include the numerical value itself.

[0077] "About" means an error range of ±5%.

[0078] Other features and advantages of the present invention will be described in the subsequent specification, and part of them will become obvious from the specification or be understood by implementing the present invention. Brief Description of the Drawings

[0079] Figure 1 Appearance of the cyanate ester impregnated resin prepared for Example 1

[0080] Figure 2 Appearance of the impregnating material prepared in Example 1;

[0081] Figure 3 Appearance of the prepreg prepared in Example 1;

[0082] Figure 4 Appearance of the cured product prepared in Example 1. Detailed Description of the Embodiments

[0083] The embodiments of the present invention will be described in detail below. The following described embodiments are exemplary and are only used to explain the present invention, and should not be construed as a limitation of the present invention.

[0084] In the following embodiments, some raw materials are described as follows:

[0085] Bisphenol A dicyanate, CAS No.: 1156 - 51 - 0.

[0086] Diol: Ethylene glycol.

[0087] Diamine: 1,3 - Propanediamine.

[0088] Catalyst: Dibutyltin dilaurate, CAS No.: 77 - 58 - 7.

[0089] Polyetheramine: Polyoxypropylene diamine, Huntsman D400, D4000.

[0090] Glass fiber cloth: Specification EWPC95 (GB / T18373 - 2013), grammage 108 g / m 2 .

[0091] For those not specified in the detailed description of the embodiments, they are carried out under conventional conditions. For raw materials or equipment not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase or prepared according to general conditions.

[0092] Example 1

[0093] 1. Preparation of the first bisphenol A cyanate prepolymer

[0094] (1) Add bisphenol A dicyanate to a three - necked flask equipped with a reflux device and an electric stirring device, and heat it to melt at a constant temperature in an oil bath at 80 °C;

[0095] (2) Drop ethylene glycol into the three - necked flask, control the molar ratio of ethylene glycol to bisphenol A dicyanate to be 1:2. After the addition is completed, stir at 80 °C for 20 min;

[0096] (3) Add dibutyltin dilaurate in an amount of 0.02% of the mass of bisphenol A dicyanate, stir at a constant temperature for 8 min, raise the temperature to 95 °C, and carry out a constant-temperature prepolymerization reaction for 1 h to obtain a light yellow transparent solution, namely the first bisphenol A type cyanate prepolymer.

[0097] 2. Preparation of the second bisphenol A type cyanate prepolymer

[0098] (1) Add 1,3-propanediamine to the first bisphenol A type cyanate prepolymer, and control the molar ratio of 1,3-propanediamine to the first bisphenol A type cyanate prepolymer (calculated based on the molar amount of ethylene glycol according to the theoretical molar amount) to be 1:2. Stir at a constant temperature of 95 °C for 8 min to make it evenly mixed;

[0099] (2) Raise the temperature to 115 °C and carry out a constant-temperature chain extension reaction for 1.5 h to obtain a yellow transparent viscous liquid, namely the second bisphenol A type cyanate prepolymer.

[0100] 3. Preparation of cyanate impregnating resin

[0101] (1) Add polyetheramine D400 (accounting for 3% of the molar amount of bisphenol A dicyanate) to the second bisphenol A type cyanate prepolymer, and stir at a constant temperature of 115 °C for 0.5 h to reduce its viscosity;

[0102] (2) Cool down to 75 °C, add dibutyltin dilaurate again in an amount of 0.01% of the mass of bisphenol A dicyanate, and stir evenly to obtain the cyanate impregnating resin, the appearance of which is as Figure 1 shown.

[0103] 4. Preparation of impregnating material

[0104] Add methyl ethyl ketone to the cyanate impregnating resin, wherein the mass percentage content of the cyanate impregnating resin is 80%. After mixing evenly, heat to 80 °C and reflux and stir for 30 min to obtain the impregnating material, the appearance of which is as Figure 2 shown.

[0105] 5. Preparation of prepreg

[0106] (1) Add an appropriate amount of impregnating material to the impregnation tank, immerse the cut fiberglass cloth into the impregnating material for 1 min, then take it out and roll it with a coating rod to drive away the excess impregnating material;

[0107] (2) Hang the impregnated fiberglass cloth in an oven at 80 °C and bake for 20 min to allow the solvent to fully volatilize, thus obtaining the prepreg (resin content 60%). The appearance is light yellow, close to white, and the surface shows a non-sticky state, as Figure 3 shown.

[0108] 6. Curing of prepreg

[0109] Take several prepregs, stack them neatly, place them in an oven at 150 °C for pre-curing for 1 h, then place them on a flat vulcanizing machine, heat and press them for curing at 0.5 MPa and 170 °C for 30 min, and then transfer them to the oven for post-curing: post-cure at 190 °C for 1 h and then at 210 °C for 0.5 h in sequence to obtain a cured product with an appearance as Figure 4 shown (the result of laminating and curing 5 prepregs).

[0110] Example 2

[0111] Compared with Example 1, the difference lies in that in Step 3, the molar amount of polyetheramine D400 is 5% of the molar amount of bisphenol A dicyanate.

[0112] Example 3

[0113] Compared with Example 1, the difference lies in that in Step 3, polyetheramine D400 is replaced with D4000 of the same mass.

[0114] Example 4

[0115] Compared with Example 1, the difference lies in that the curing process of the prepreg does not include the step of pre-curing in an oven at 150 °C for 1 h, and the remaining steps remain unchanged.

[0116] Comparative Example 1

[0117] Compared with Example 1, the difference lies in that Step 2 is omitted, and in Step 3, the first bisphenol A type cyanate ester prepolymer is used.

[0118] Test Example

[0119] The test method is as follows:

[0120] 1. Viscosity: GB / T 9751.1-2008, general conditions.

[0121] 2. Flexural strength:

[0122] (1) Impregnating material: GB / T 2567-2021. The specimen thickness is 4 mm, width is 15 mm, length is 100 mm, span is 30 mm, test speed is 0.5 mm / min, and 5 test strips are tested for each data, and the average value is taken;

[0123] (2) Cured product: GB / T 1449-2005. The specimen thickness is 2 mm, width is 15 mm, length is 100 mm, test speed is 10 mm / min, span is 32 mm, and 5 test strips are tested for each data, and the average value is taken;

[0124] The test instrument is an Instron1195 universal material testing machine.

[0125] 3. Impact Strength: GB / T 2571-1995. Using an XJU-5.5 cantilever beam impact testing machine, without notched test, specimen thickness 4 mm, width 10 mm, length 80 mm, test 5 test strips for each data, and take the average value.

[0126] 4. Fracture Toughness: GB / T 41932-2022. SENB specimen, thickness 1 mm, width 2 mm, crack length 1 mm, RS notch, test 5 test strips for each data, and take the average value.

[0127] 5. Tg: Using dynamic mechanical analysis (DMA), heating rate 3 °C / min, temperature range 100 - 350 °C.

[0128] 6. Dielectric Constant (Dk) and Dielectric Loss (Df): Test instrument is Agilent N5230C, impregnating material is made into a cured film (20 μm), surface is sputtered with gold; cured product thickness 6 mm.

[0129] 7. Moisture Absorption Rate: GB / T 1034-2008, specimen size 100 mm × 100 mm × 2 mm, test the water absorption rate after soaking at 23 °C for 24 h, test in parallel 3 times, and take the average value.

[0130] 8. Thermal Decomposition Temperature: Determined by thermogravimetric analyzer, sample 5 mg, atmosphere nitrogen, flow rate 20 mL / min, heating rate: 10 °C / min, test range: 25 - 800 °C, record the temperature at 5% mass loss rate, denoted as the initial thermal decomposition temperature.

[0131] 9. Coefficient of Thermal Expansion: GB / T 2572-2005. Specimen length 100 mm, cross-section is a square with side length 6 mm, test temperature range starts from room temperature and rises to 100 °C and 200 °C in turn.

[0132] 10. Peel Strength: GB / T 2791-1995.

[0133] The test results of the impregnating material are shown in Table 1. Among them, the curing conditions are as follows: cure at 150 °C for 1 h, 170 °C for 2 h, and 190 °C for 1 h in turn.

[0134] Table 1

[0135]

[0136] As can be seen from Table 1, there are differences in multiple properties between Example 2 and Example 3 and Example 1. In Example 2, due to the higher molar amount of D400, it can react with more cyanate groups, reducing the proportion of triazine rings in the crosslinked structure, resulting in a decrease in the flexural strength, Tg, and initial thermal decomposition temperature of the material. At the same time, the dielectric properties, toughness, and impact strength are improved. In contrast, in Example 3, the molecular weight of D4000 is larger, and the consumption of cyanate groups is reduced under the same mass. Therefore, the proportion of triazine rings is higher, enhancing the rigidity of the material and improving the flexural strength, Tg, and thermal decomposition temperature, but the toughness and impact strength decrease, and the dielectric properties are slightly reduced. In addition, the structure formed after the reaction of amino groups with cyanate groups has certain hydrophilicity, so the moisture absorption rate of Example 2 is higher.

[0137] The test results of the cured products of Example 1, Example 4, and Comparative Example 1 are shown in Table 2.

[0138] Table 2

[0139]

[0140]

[0141] From the results in Table 2, it can be seen that compared with Example 1, the flexural strength, Tg, peel strength, and dielectric properties of Example 4 decrease, and the coefficient of thermal expansion and moisture absorption rate increase. The reason is that Example 4 lacks the pre-curing step, resulting in difficulty for small molecule diols and diamines to fully overflow, affecting the full wetting of the resin on the glass fiber, and then generating local defects, reducing the strength and rigidity of the material. In addition, the presence of residual diamines and diols or defect areas will increase the mobility and polarization ability of molecular chains, and at the same time make water molecules more likely to penetrate, thus affecting the dielectric properties and hygroscopicity.

[0142] In summary, the cyanate ester impregnated resin prepared in this application realizes the room temperature liquefaction modification of bisphenol A dicyanate ester, has excellent dielectric properties, mechanical properties, and high temperature resistance. At the same time, it has good wettability to glass fiber and copper foil, can achieve a high impregnation solid content, has excellent processability, and is suitable for preparing high-performance prepregs. Applying this prepreg to the manufacture of copper clad laminates or their substrates can meet the strict requirements of 5G communication networks for high speed, high frequency, high heat resistance, and high dielectric properties. Existing prepregs usually have difficulty in simultaneously achieving the above excellent properties. Especially in terms of dielectric properties, the dielectric constant of commercially available glass fiber-based copper clad laminates is usually higher than 3 (10 GHz), and it is difficult to simultaneously achieve comprehensive properties such as high strength, high toughness, and high heat resistance.

[0143] The above has described the embodiments of the present invention in detail, but the present invention is not limited to the above embodiments. Within the knowledge scope of those of ordinary skill in the art to which the present invention pertains, various changes can be made without departing from the gist of the present invention.

Claims

1. A method for preparing a cyanate ester impregnated resin, characterized in that: The steps include: The bisphenol A dicyanate and the diol are subjected to a prepolymerization reaction in the presence of a first catalyst to obtain a first bisphenol A type cyanate prepolymer; wherein the bisphenol A dicyanate is in excess relative to the diol, and the prepolymerization reaction temperature is 80 to 140° C.; The diamine and the first bisphenol A cyanate prepolymer are subjected to a chain extension reaction to obtain a second bisphenol A cyanate prepolymer; wherein the first bisphenol A cyanate prepolymer is in excess relative to the diamine, and the chain extension reaction temperature is 80 to 140° C.; The second bisphenol A cyanate prepolymer is mixed with polyetheramine and a second catalyst to obtain the cyanate impregnated resin.

2. The preparation method according to claim 1, characterized in that: The first catalyst and the second catalyst are both selected from dibutyltin dilaurate; and / or, the mass of the first catalyst accounts for 0.01% to 0.05% of the mass of the bisphenol A dicyanate; and / or, the temperature of the prepolymerization reaction is 90 to 100°C, and the prepolymerization reaction time is 0.5 to 1h; and / or, the mass of the second catalyst accounts for 0.01% to 0.05% of the mass of the bisphenol A dicyanate; and / or, the temperature of the chain extension reaction is 110 to 120°C, and the chain extension reaction time is 1 to 2h.

3. The preparation method according to claim 1, characterized in that: The diol is selected from ethylene glycol; and / or the molar ratio of the diol to bisphenol A dicyanate is 1:2 to 2:3; and / or, the diamine is selected from at least one of ethylenediamine, 1,3-propylenediamine, 1,2-propylenediamine, and 1,4-butylenediamine; and / or, the molar ratio of the diamine to the first bisphenol A cyanate prepolymer is 1:2 to 2:3; And / or, the polyetheramine is polyoxypropylene diamine with a molecular weight of 200 to 500; and / or, the molar number of the polyetheramine accounts for 2% to 5% of the molar number of the bisphenol A dicyanate.

4. A impregnation material, characterized in that: The invention comprises a solvent and a cyanate impregnated resin, wherein the cyanate impregnated resin is prepared by the preparation method according to any one of claims 1 to 3.

5. The impregnation material according to claim 4, characterized in that in, The mass percentage of the cyanate impregnated resin is 75% to 90%; and / or the solvent is selected from at least one of acetone and butanone.

6. A prepreg, characterized in that: It comprises a reinforcing material and a cyanate impregnated resin attached to the reinforcing material, wherein the cyanate impregnated resin is prepared by the preparation method according to any one of claims 1 to 3.

7. The prepreg according to claim 6, characterized in that: in, The mass percentage of the cyanate impregnated resin is 55% to 65%; and / or the reinforcing material is glass fiber fabric; and / or the gram weight of the reinforcing material is 100 to 200 g / m 2 .

8. A method for preparing a prepreg as claimed in claim 6 or 7, characterized in that: The following steps are involved: Providing an impregnation material comprising the cyanate impregnation resin; The reinforcing material is impregnated with the impregnating material and then dried to obtain the prepreg.

9. Use of the preparation method according to any one of claims 1 to 3, or the impregnating material according to any one of claims 4 to 5, or the prepreg according to any one of claims 6 to 7, or the method according to claim 8 in the preparation of copper-clad laminates or PCBs.

10. The use according to claim 9, characterized in that: The curing process of the cyanate impregnated resin comprises the following steps: The mixture was heated at 150-160°C for 0.5-1.5 h, reacted at 0.5-1 MPa and 165-175°C for 0.5-1 h, reacted at 185-195°C for 1-1.5 h, and reacted at 205-210°C for 0.5-1 h.

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