Indene-containing vinylic monomers, indene-containing vinylic resins, and methods for making the same

Abstract

The application provides an indenyl ethylene monomer, an indenyl ethylene resin and a preparation method thereof, relates to the technical fields of high polymer materials and organic synthesis, and provides an indenyl ethylene monomer, a preparation method of the indenyl ethylene monomer, an indenyl ethylene resin and a preparation method of the indenyl ethylene resin. The indenyl ethylene monomer has the characteristics of multi-functionality, mild preparation condition and low raw material cost, is easy to prepare, and the indenyl ethylene monomer is formed into an indenyl styrene resin through pre-polymerization. The resin has high cross-linking density and large steric hindrance, is excellent in heat resistance, and has extremely low dielectric loss.

Description

Technical Field

[0001] This invention relates to the fields of polymer materials and organic synthesis technology, and in particular to an indene-containing monomer and its preparation method, and an indene-containing resin and its preparation method. Background Technology

[0002] Indene-containing resins are an important class of thermosetting hydrocarbon resins, whose molecular structure contains both rigid indene rings and crosslinkable vinyl groups. These resins do not release small molecule byproducts during thermosetting, and the cured products exhibit excellent thermal stability, high mechanical strength, and extremely low moisture absorption, making them promising candidates for applications in specialty adhesives, inks, electronic packaging underfill materials, and copper-clad laminate manufacturing.

[0003] However, existing thermosetting hydrocarbon resins (such as polystyrene and polybutadiene) still face bottlenecks in terms of dielectric loss, coefficient of thermal expansion, and processing performance. While polystyrene and polybutadiene resins offer relatively good processing performance, their cured products exhibit high dielectric loss, making it difficult to meet the low-loss requirements of high-frequency signal transmission. Furthermore, their high coefficient of thermal expansion can easily lead to warping or delamination of copper-clad laminates during high-temperature processes. Although polyphenylene ether resins have relatively low dielectric loss, their complex synthesis processes and high raw material costs limit their large-scale application in high-end copper-clad laminates.

[0004] Therefore, developing a novel indene-containing monomer and its resin with multiple functions, mild synthesis conditions, low raw material costs, and the ability to impart extremely low dielectric loss, excellent heat resistance, and low coefficient of thermal expansion to the resin is of significant technical and economic value. Summary of the Invention

[0005] The purpose of this invention is to provide an indene-containing monomer, an indene-containing resin, and a method for preparing the same, wherein the indene-containing monomer can impart extremely low dielectric loss, excellent heat resistance, and a low coefficient of thermal expansion to the resin.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of this invention provides an indene-containing monomer, wherein the structural formula of the indene-containing monomer is as follows: (1), Among them, R1 is independently selected from any one of hydrogen atom, methyl, methoxy, ethyl, and ester group; R2 is selected from any one of hydrogen atom, methyl, methoxy, ethyl, or ester group; R3 is selected from any one of phenyl, naphthyl, biphenyl, aromatic alkyl, or aliphatic chains containing 1-10 carbon atoms; R4 is selected from any one of hydrogen atom, methoxy group, ester group, or aliphatic chain containing 1-10 carbon atoms; R5 is selected from any one of hydrogen atoms, methoxy groups, or aliphatic chains containing 1 to 10 carbon atoms; R6 is selected from any one of the following: phenyl, naphthyl, biphenyl, aromatic alkyl, aliphatic chain containing 1-10 carbon atoms, or a substituent containing halogen atoms.

[0007] A second aspect of the present invention provides a method for preparing an indene-containing monomer, comprising the following steps: A1. Under an inert atmosphere, a compound containing two chloromethyl groups and indene are dissolved in toluene, and tetrabutylammonium bromide and phenothiazine are added. A first alkali solution is added, and the reaction is carried out at 25℃-80℃ for 1-20 hours. After the reaction is completed, the reaction solution is obtained. A2. Add an aromatic compound containing monochloromethyl to the reaction solution obtained in step A1, add a second alkaline solution, and react at 25℃-80℃ for 1-20h to obtain an indene-containing monomer with the structural formula shown in formula (1): , Among them, the two R1s are independently selected from hydrogen atoms, methyl, methoxy, ethyl, and ester groups, respectively; R2 is selected from hydrogen atom, methyl, methoxy, ethyl, ester group; R3 is selected from phenyl, naphthyl, biphenyl, aromatic alkyl, and aliphatic chains containing 1-10 carbon atoms; R4 is selected from hydrogen atoms, methoxy groups, ester groups, and aliphatic chains containing 1-10 carbon atoms; R5 is selected from hydrogen atoms, methoxy groups, and aliphatic chains containing 1-10 carbon atoms; R6 is selected from phenyl, naphthyl, biphenyl, aromatic alkyl, aliphatic chain containing 1-10 carbon atoms, or substituents containing halogen atoms.

[0008] Optionally, in step A1, the molar ratio of the compound containing two chloromethyl groups to indene is (0.45-0.55):1, the molar ratio of tetrabutylammonium bromide to indene is (0.01-0.1):1, the molar ratio of phenothiazine to indene is (0.001-0.01):1, and the molar ratio of alkali to indene in the first alkaline solution is (3-4.5):1. In step A2, the molar ratio of the aromatic compound containing monochloromethyl to indene is (0.9-1.3):1, and the molar ratio of the alkali to indene in the second alkaline solution is (3-4.5):1. The alkali in the first alkaline solution and the second alkaline solution is selected from one or two of lithium hydroxide, potassium hydroxide, and sodium hydroxide.

[0009] A third aspect of the present invention provides an indene-containing resin, wherein the structural formula of the indene-containing resin is as follows: (2) or (3), In structural formulas (2) and (3), CO represents the polymerization of monomer (1) and monomer M2: The two R1s are each independently selected from hydrogen atom, methyl, methoxy, ethyl, and ester group; R2 is selected from any one of hydrogen atom, methyl, methoxy, ethyl, or ester group; R3 is selected from any one of phenyl, naphthyl, biphenyl, aromatic alkyl, or aliphatic chains containing 1-10 carbon atoms; R4 is selected from any one of hydrogen atom, methoxy group, ester group, or aliphatic chain containing 1-10 carbon atoms; R5 is selected from any one of hydrogen atoms, methoxy groups, ester groups, and aliphatic chains containing 1 to 10 carbon atoms; R6 is selected from any one of phenyl, naphthyl, biphenyl, aromatic alkyl, aliphatic chain containing 1-10 carbon atoms, or a substituent containing halogen atoms; n is selected from integers ≥1 and ≤1000; m is selected from integers ≥ 0 and ≤ 1000; m' is selected from integers ≥0 and ≤1000; And m+n+m'≥2; When the indene-containing resins with structural formulas (2) and (3) are polymerized using an initiator, R7 is an independent terminus or hydrogen atom of the initiator; When the indene-containing resin is not polymerized, R7 is independent of each other. Or hydrogen atoms.

[0010] Optionally, in structural formulas (2) and (3), M2 is selected from at least one of styrene, methylstyrene, bistyrene, naphthalene, divinylbenzene, divinylbiphenyl, methacrylate, acrylate, maleimide, maleic anhydride, butadiene, isoprene, ethylene, propylene, norbornene, and ethylidene norbornene.

[0011] Optionally, n is selected from integers ≥2 and ≤200, and m is selected from integers ≥0 and ≤100.

[0012] Optionally, the initiator is terminated in a naphthalene ring, n-butyl, tert-butyl, benzoyloxy, phenyl, isopropylphenoxy, or tert-butoxy.

[0013] A fourth aspect of this invention provides a method for preparing an indene-containing resin, comprising the following steps: Indene-containing monomers are polymerized or copolymerized with other monomers to form prepolymers, thus obtaining indene-containing resins.

[0014] Optionally, when the polymerization is thermally initiated polymerization, the polymerization is either thermally initiated polymerization or free radical polymerization; the reaction temperature of the thermally initiated polymerization is 40℃-100℃, and the reaction time is 1-20h; the reaction temperature of the free radical polymerization is 40℃-100℃, and the reaction time is 1-20h.

[0015] Optionally, the other monomers are selected from at least one monomer selected from styrene, methylstyrene, bistyrene, naphthalene, divinylbenzene, divinylbiphenyl, methacrylates, acrylates, maleic anhydride, maleimide, butadiene, isoprene, ethylene, propylene, norbornene, and ethylene-imide norbornene.

[0016] Compared with the prior art, the present invention has the following technical effects: 1. By introducing a rigid aromatic conjugated backbone containing indene groups into the structure of indene-containing monomers, the rigid structure and large steric hindrance effect of the indene group can effectively suppress the dipole turning motion of polymer chains under high-frequency alternating electric fields, thereby endowing indene-containing resins with extremely low dielectric constants and ultra-low dielectric losses. Simultaneously, the indene-containing monomers possess multifunctional polymerizable double bond sites, which, after polymerization and curing, can form a rigid three-dimensional network backbone with high crosslinking density. This allows the indene-containing resins to maintain excellent dielectric properties while exhibiting extremely high glass transition temperatures and thermal stability.

[0017] 2. The synthesis conditions of indene-containing monomers are mild, the raw material costs are low, and there are few by-products. Furthermore, the process of preparing indene-containing resins from indene-containing monomers is simple, which solves the technical problem of large-scale production of high-performance low-dielectric resins.

[0018] 3. Indene-containing monomers can be flexibly prepared into prepolymers (i.e., indene-containing resins) with adjustable molecular weight and viscosity by controlling polymerization reaction conditions, exhibiting excellent processing adaptability. Furthermore, indene-containing monomers can not only undergo thermal initiation or free radical curing alone, but also copolymerize with other monomers. This excellent formulation compatibility and processing flexibility allows indene-containing resins to meet diverse process requirements such as copper-clad laminates, prepregs, and advanced semiconductor packaging. Attached Figure Description

[0019] Figure 1 The 1H NMR spectrum of an indene-containing monomer according to Example 1 of the present invention; Figure 2 This is the carbon NMR spectrum of an indene-containing monomer according to Example 1 of the present invention. Detailed Implementation

[0020] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0021] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0022] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of the invention. Various modifications and variations to the specific embodiments described in this specification are apparent to those skilled in the art without departing from the scope or spirit of the invention. Other embodiments derived from this specification will be apparent to those skilled in the art. This application specification and embodiments are merely exemplary.

[0023] The structural formula of indene-containing monomers is as follows: (1), Among them, the two R1s are independently selected from hydrogen atoms, methyl, methoxy, ethyl, and ester groups, respectively; R2 is selected from hydrogen atom, methyl, methoxy, ethyl, ester group; R3 is selected from phenyl, naphthyl, biphenyl, aromatic alkyl, and aliphatic chains containing 1-10 carbon atoms; R4 is selected from hydrogen atoms, methoxy groups, ester groups, and aliphatic chains containing 1-10 carbon atoms; R5 is selected from hydrogen atoms, methoxy groups, and aliphatic chains containing 1-10 carbon atoms; R6 is selected from phenyl, naphthyl, biphenyl, aromatic alkyl, aliphatic chain containing 1-10 carbon atoms, or substituents containing halogen atoms.

[0024] Indene-containing monomers have multiple functionalities, and their preparation conditions are mild, easy to prepare, and low in cost.

[0025] When R1, R2, R4, and R5 in structural formula (1) are all hydrogen atoms, R3 is a phenyl group, R6 is a biphenyl group, and the indene-containing monomer is 4,4'-bis((1-(vinylbenzyl)-1H-inden-1-yl)methyl)-1,1'-biphenyl, the structural formula is: (1-A).

[0026] When R1, R2, R4, and R5 in structural formula (1) are all hydrogen atoms, R3 is naphthyl, R6 is biphenyl, and the indene-containing monomer is 4,4'-bis((1-((vinylnaphthyl-1-yl)methyl)-1H-inden-1-yl)methyl)-1,1'-biphenyl, the structural formula is: (1-B).

[0027] When R1, R2, R4, and R5 in structural formula (1) are all hydrogen atoms, R3 is phenyl, R6 is phenyl, and the indene-containing monomer is 1,4-bis((1-(vinylbenzyl)-1H-inden-1-yl)methyl)benzene, the structural formula is: (1-C).

[0028] When R1, R2, R4, and R5 in structural formula (1) are all hydrogen atoms, R3 is a phenyl group, and R6 is a naphthyl group, then the indene-containing monomer is bis((1-(vinylbenzyl)-1H-inden-1-yl)methyl)naphthalene, with the structural formula: (1-D).

[0029] This application also provides a method for preparing indene-containing monomers, comprising the following steps: A1. Under an inert atmosphere, a compound containing two chloromethyl groups and indene are dissolved in toluene, and tetrabutylammonium bromide and phenothiazine are added. A first alkali solution is added, and the reaction is carried out at 25℃-80℃ for 1-20 hours. After the reaction is completed, the reaction solution is obtained. A2. Add an aromatic compound containing monochloromethyl to the reaction solution obtained in step A1, add a second alkaline solution, and react at 25℃-80℃ for 1-20h to obtain an indene-containing monomer with the structural formula shown in formula (1): , Among them, the two R1s are independently selected from hydrogen atoms, methyl, methoxy, ethyl, and ester groups, respectively; R2 is selected from hydrogen atom, methyl, methoxy, ethyl, ester group; R3 is selected from phenyl, naphthyl, biphenyl, aromatic alkyl, and aliphatic chains containing 1-10 carbon atoms; R4 is selected from hydrogen atoms, methoxy groups, ester groups, and aliphatic chains containing 1-10 carbon atoms; R5 is selected from hydrogen atoms, methoxy groups, and aliphatic chains containing 1-10 carbon atoms; R6 is selected from phenyl, naphthyl, biphenyl, aromatic alkyl, aliphatic chain containing 1-10 carbon atoms, or substituents containing halogen atoms.

[0030] In step A1, under alkaline and phase-transfer catalytic conditions, indene forms a nucleophilic active center, undergoing bimolecular nucleophilic substitution of a compound containing two chloromethyl groups to obtain a diindene skeleton intermediate bridged by R6. In step A2, a second alkaline solution induces the terminal indene ring of the diindene skeleton intermediate to undergo deprotonation again, and the resulting carbanion undergoes nucleophilic substitution with a monochloromethyl aromatic compound, thereby introducing a vinyl aromatic end group composed of R1, R2, and R3, thus preparing an indene-containing vinyl monomer.

[0031] In step A1, the molar ratio of the compound containing two chloromethyl groups to indene is (0.45-0.55):1, the molar ratio of tetrabutylammonium bromide to indene is (0.01-0.1):1, the molar ratio of phenothiazine to indene is (0.001-0.01):1, and the molar ratio of the first alkaline solution to indene is (3-4.5):1. By limiting the molar ratio of the first alkaline solution to indene, a sufficiently alkaline environment can be provided to ensure complete deprotonation of the indene methylene group, while simultaneously neutralizing the hydrochloric acid generated in the reaction. Limiting the molar ratio of tetrabutylammonium bromide to indene allows tetrabutylammonium bromide, as a phase transfer catalyst, to promote efficient mass transfer between the first alkaline solution and indene, increasing the reaction rate. Limiting the molar ratio of the compound containing two chloromethyl groups to indene ensures that the monomolecule of the compound containing two chloromethyl groups undergoes sufficient disubstituted reaction with the two indene carbanions, avoiding monosubstituted byproducts or excessive polymerization. As a polymerization inhibitor, phenothiazine limits the molar ratio of phenothiazine to indene, inhibiting premature free radical polymerization of unsaturated groups in the system and preventing gelation of the reaction solution in step A1.

[0032] In step A2, the molar ratio of the aromatic compound containing monochloromethyl groups to indene is (0.9-1.3):1, and the molar ratio of the second alkaline solution to indene is (3-4.5):1. By limiting the molar ratio of the second alkaline solution to indene, a sufficiently alkaline environment can be provided to promote the deprotonation of the terminal indene ring of the diindene skeleton intermediate in the reaction solution, thereby accelerating the substitution reaction process. At the same time, the by-product acid generated by the reaction is neutralized, and finally, high-yield, high-purity indene-containing monomers are obtained.

[0033] This application also provides an indene-containing resin, which is a prepolymer formed by polymerization of the indene-containing monomer of the above-mentioned structural formula (1) or copolymerization of the indene-containing monomer of structural formula (1) with other monomers. The structural formula of the indene-containing resin is: (2) or (3), In structural formulas (2) and (3), CO represents the polymerization of monomer (1) and monomer M2: The two R1 groups are independently selected from hydrogen atoms, methyl, methoxy, ethyl, and ester groups, respectively; R2 is selected from hydrogen atom, methyl, methoxy, ethyl, ester group; R3 is selected from phenyl, naphthyl, biphenyl, aromatic alkyl, and aliphatic chains containing 1-10 carbon atoms; R4 is selected from hydrogen atoms, methoxy groups, ester groups, and aliphatic chains containing 1-10 carbon atoms; R5 is selected from hydrogen atoms, methoxy groups, ester groups, and aliphatic chains containing 1-10 carbon atoms; R6 is selected from phenyl, naphthyl, biphenyl, aromatic alkyl, aliphatic chain containing 1-10 carbon atoms, aliphatic chain containing 1-10 carbon atoms, or a substituent of halogen atoms. n is selected from integers ≥1 and ≤1000; m is selected from integers ≥ 0 and ≤ 1000; m' is selected from integers ≥0 and ≤1000; And m+n+m'≥2; When the indene-containing resins with structural formulas (2) and (3) are polymerized using an initiator, one of the two R7s is the end of the initiator and the other is a hydrogen atom; When the indene-containing resins with structural formulas (2) and (3) are polymerized without an initiator, one of the two R7s is... The other is a hydrogen atom.

[0034] In the embodiments of this application, M2 in structural formulas (2) and (3) is selected from at least one of styrene, methylstyrene, bistyrene, naphthalene, divinylbenzene, divinylbiphenyl, methacrylate, acrylate, maleimide, maleic anhydride, butadiene, isoprene, ethylene, propylene, norbornene, and ethylidene norbornene.

[0035] Preferably, n is selected from integers ≥2 and ≤200, and m is selected from integers ≥0 and ≤100.

[0036] When indene-containing resins with structural formulas (2) and (3) are polymerized without an initiator, one of the two R7s is an indene-containing monomer residue as shown in formula (1), and the other is a hydrogen atom. The indene-containing monomer residues bond to the main chain of the indene-containing resin through the carbon atom connection points formed after their vinyl double bonds are opened.

[0037] When m = 0, the indene-containing resin of structural formula (2) is a prepolymer product of the polymerization of indene-containing monomers of structural formula (1).

[0038] When m=0 and m'=0, the indene-containing resin of structural formula (3) is a prepolymer product of the polymerization of indene-containing monomers of structural formula (1).

[0039] When M1 represents the monomer to the left of CO in structural formula (2), when monomer M1 and monomer M2 are randomly copolymerized, that is, n M1s and m M2s are randomly arranged on the molecular chain, which is a random distribution. For example, when n and m are both equal to 2, when monomer M1 and monomer M2 are randomly copolymerized in structural formula (2), the arrangement on the molecular chain can be various random arrangements such as M1M2M2M1, M1M2M1M2, etc.

[0040] When M1 represents the monomer between the two COs in structural formula (3), when monomer M1 and monomer M2 are randomly copolymerized, that is, n M1s and m M2s are randomly arranged on the molecular chain, which is a random distribution. For example, when n and m are both equal to 2, when monomer M1 and monomer M2 are randomly copolymerized in structural formula (3), the arrangement on the molecular chain can be various random arrangements such as M1M2M2M1, M1M2M1M2, etc.

[0041] This indene-containing resin has multiple crosslinking sites, and the product obtained by curing it has a large volume steric hindrance. Therefore, it has excellent heat resistance, mechanical properties and low coefficient of thermal expansion. At the same time, it has low dielectric constant and dielectric loss in terms of electrical properties, making it an excellent electrical material.

[0042] The prepolymer (containing indene-based resin) of this application offers excellent flexibility in molecular weight control, allowing for adaptation to filler rheological requirements in copper-clad laminate (CCL) fabrication. Furthermore, the cured product of the indene-based resin exhibits extremely low dielectric loss (0.00095-0.0011@10GHz), a low coefficient of thermal expansion, and excellent heat resistance, effectively reducing signal insertion loss on circuit boards. In addition, its total halogen content is below 100ppm, further ensuring the comprehensive reliability and performance advantages of the indene-based resin in high-frequency, high-speed applications. Based on these characteristics, the indene-based resin can simultaneously improve system electrical performance and enhance reliability while supporting the development of low-dielectric-loss, high-reliability circuit boards.

[0043] This application also provides a method for preparing an indene-containing resin, comprising the following steps: polymerizing an indene-containing monomer or copolymerizing it with other monomers to form a prepolymer, thereby obtaining an indene-containing resin.

[0044] In this application, the indene-containing monomers are obtained from the aforementioned steps A1 and A2.

[0045] The indene-containing monomers obtained in step B1 undergo chain growth reactions via thermal initiation or free radical initiation, or are copolymerized with other monomers, to obtain prepolymers (i.e., indene-containing resins) with adjustable molecular weight and viscosity. While retaining the subsequent crosslinkable unsaturated double bonds, the rheological properties and degree of polymerization of this prepolymer can be flexibly controlled by reaction conditions (such as temperature, time, and initiator dosage). Therefore, it can effectively meet the filling and processing rheological requirements in the preparation of copper-clad laminates and prepregs, and can also form a high-crosslink density three-dimensional network structure through subsequent curing, providing a key molecular structural basis for the final cured product to possess both extremely low dielectric loss and excellent heat resistance.

[0046] The following detailed description uses specific embodiments and comparative examples.

[0047] Example 1 A method for preparing indene-containing monomers includes the following steps: A1. Under nitrogen protection, 4,4'-dichloromethylbiphenyl (12.56 g, 0.05 mol) and indene (11.62 g, 0.1 mol) were dissolved in 80 mL of toluene, and tetrabutylammonium bromide (1.61 g, 0.005 mol) and phenothiazine (0.1 g, 0.0005 mol) were added. After stirring until the solids dissolved, a first alkaline solution prepared by dissolving sodium hydroxide solid (16 g, 0.4 mol) in an appropriate amount of deionized water (about 30 mL) was slowly added dropwise. After the addition was completed, the reaction was carried out at 60 °C for 8 h to obtain the reaction solution. A2. Add 15.26 g (0.1 mol) of 4-vinylbenzyl chloride to the reaction solution obtained in step A1, and then slowly add a second alkaline solution prepared by dissolving 16 g (0.4 mol) of sodium hydroxide solid in an appropriate amount of deionized water (about 30 mL). After the addition is complete, react at 70 °C for 9 h. After the reaction is completed, lower the temperature to 25 °C, add deionized water to remove excess sodium hydroxide, and then add sodium bisulfate to adjust the pH to 4.5. Then wash the organic phase with deionized water (shake and let it stand to separate the layers, remove the aqueous layer) until neutral (pH≈7). Finally, remove the toluene solvent by vacuum distillation of the organic phase to obtain an indene-containing monomer with the structural formula shown in formula (1-A): (1-A).

[0048] Depend on Figure 1It can be seen that the multiple resonance peaks in the chemical shift range of 6.5-7.8 ppm are attributed to aromatic protons on the biphenyl skeleton, indene ring, and vinyl benzyl group, as well as olefin protons on the indene ring. The characteristic multiple peaks appearing in the 5.2-6.5 ppm region correspond to olefin protons of the terminal vinyl group (-CH=CH2), and the multiple peaks in the 3.6-4.2 ppm range correspond to the methylene (-CH2-) protons connecting biphenyl to the indene ring, and between the indene ring and the vinyl benzyl group. Figure 2 It can be seen that the dense absorption peaks in the 120-150 ppm range are attributed to aromatic rings and unsaturated olefin carbon atoms, while multiple signals in the 30-50 ppm range correspond to methylene carbon atoms in the molecule. The characteristic signals and peak shapes of all characteristic signals in the proton and carbon NMR spectra are consistent with the structure of the indene-containing monomer of formula (1-A), and the symmetrical distribution characteristics of the spectral signals are consistent with the centrosymmetric skeleton structure of the indene-containing monomer, confirming that the indene-containing monomer obtained in Example 1 is the target compound.

[0049] The indene-containing monomers shown in Formula (1-A) have a rigid central skeleton of biphenyl and styrene groups at both ends, resulting in a symmetrical molecular structure. The rigid structure of the biphenyl skeleton and indene ring ensures excellent heat resistance and dimensional stability of the cured product. Simultaneously, multiple vinyl unsaturated sites in the indene-containing monomer molecule can form a highly crosslinked three-dimensional network after thermosetting, endowing the indene-containing resin with excellent dielectric properties and low dielectric loss. Furthermore, the introduction of styrene end groups in this monomer allows for the availability of widely sourced raw materials and lower synthesis costs. The cured product exhibits less brittleness, providing good flexibility in toughness control and processing adaptability, fully meeting the comprehensive performance requirements of high-frequency, high-speed copper-clad laminates and electronic packaging materials.

[0050] Example 2 A method for preparing indene-containing monomers includes the following steps: A1. Under nitrogen protection, 3,3'-dichloromethylbiphenyl (27.63 g, 0.11 mol) and indene (23.24 g, 0.2 mol) were dissolved in 150 mL of toluene, and tetrabutylammonium bromide (5.16 g, 0.016 mol) and phenothiazine (0.28 g, 0.0014 mol) were added. After stirring until the solids dissolved, a first alkaline solution prepared by dissolving sodium hydroxide solid (36 g, 0.9 mol) in an appropriate amount of deionized water (about 60 mL) was slowly added dropwise. After the addition was completed, the reaction was carried out at 55 °C for 12 h. During this period, the reaction degree was monitored by thin-layer chromatography (TLC) until the raw material indene was basically reacted, and the reaction solution was obtained. A2. 1-(chloromethyl)-4-vinylnaphthalene (48.64 g, 0.24 mol) was added to the reaction solution obtained in step A1. Then, a second alkaline solution prepared by dissolving 28 g, 0.7 mol of solid sodium hydroxide in an appropriate amount of deionized water (approximately 45 mL) was slowly added dropwise. After the addition was complete, the reaction was carried out at 80 °C for 8 h, during which the reaction degree was monitored by thin-layer chromatography (TLC) until the reaction was complete. After the reaction was completed, the temperature was lowered to 25 °C. Deionized water was added first to remove excess sodium hydroxide, and then sodium bisulfate was added to adjust the pH to 4. The organic phase was then washed with deionized water (after shaking and allowing it to stand to separate into layers, removing the aqueous layer) until neutral (pH≈7). Finally, the organic phase was subjected to vacuum distillation to remove the toluene solvent, yielding an indene-containing monomer with the structural formula shown in formula (1-B). (1-B).

[0051] The indene-containing monomer shown in formula (1-B) has a biphenyl-based central backbone with naphthyl vinyl structures at both ends. This structural design helps reduce dielectric loss and improves the rigidity and heat resistance of the cured product. Multiple reactive vinyl groups in the indene-containing monomer form a tightly cross-linked structure after curing, thereby enhancing the heat resistance and dimensional stability of the indene-containing resin. Furthermore, the polymerization process of this indene-containing monomer is easy to control, allowing for adjustment of the viscosity and molecular weight of the prepolymer, and exhibiting good processing adaptability. The resulting cured product combines extremely low dielectric loss, excellent heat resistance, and low moisture absorption, meeting the comprehensive performance requirements of high-frequency, high-speed copper-clad laminates and advanced electronic packaging materials.

[0052] Example 3 A method for preparing indene-containing resins includes the following steps: B1. Under nitrogen protection, add the indene-containing monomer (13.2 g, about 0.025 mol) of formula (1-A) prepared in Example 1 to a 50 mL three-necked flask and cover with a rubber stopper. B2. Under nitrogen protection, 20 mL of toluene was added, and a thermally initiated polymerization reaction was carried out at 100 °C for 10 h. After the reaction was completed, the mixture was cooled to room temperature, and then the reaction solution was slowly added dropwise to a large amount of methanol for precipitation. The precipitate was collected by filtration, and the resulting solid product was washed repeatedly with methanol three times and dried to obtain an indene-containing resin with the structural formula shown in formula (2). (2), Where m=0, CO represents the indene-containing monomer unit of formula (1-A) in Example 1, R1, R2, R4, and R5 are all hydrogen atoms, R3 is phenyl, R6 is biphenyl, and one of the two R7s is... The other is a hydrogen atom.

[0053] The self-polymerization method in Example 3 allows for easy control of reaction conditions, enabling flexible acquisition of prepolymers with different molecular weights and viscosities. It also exhibits good processing rheology and filler adaptability in copper-clad laminate (CCL) manufacturing processes. The molecular chains of indene-containing resins are rich in biphenyl and indene ring rigid frameworks, while retaining thermosetting unsaturated double bonds. During subsequent curing, these bonds form a high-crosslink density network, endowing the final cured material with excellent heat resistance and dimensional stability. Furthermore, the resulting cured product possesses extremely low dielectric loss and a low coefficient of thermal expansion, fully meeting the comprehensive requirements of high-frequency, high-speed CCLs and advanced electronic packaging for low-dielectric, high-reliability materials.

[0054] Example 4 A method for preparing indene-containing resins includes the following steps: B1. Under nitrogen protection, add the indene-containing monomer (13.2 g, about 0.025 mol) and styrene (5.2 g, about 0.05 mol) of formula (1-A) obtained in Example 1, and stopper the flask with a rubber stopper. B2. Under nitrogen protection, 25 mL of toluene was added, and a thermally initiated polymerization reaction was carried out at 100 °C for 11 h. After the reaction was completed, the mixture was cooled to room temperature, and then the reaction solution was slowly added dropwise to a large amount of methanol for precipitation. The precipitate was collected by filtration, and the resulting solid product was washed repeatedly with methanol three times and dried to obtain an indene-containing resin with the structural formula shown in formula (2). (2), Where m represents the degree of polymerization of the styrene segment unit, CO represents the copolymerization point between the indene-containing monomer unit and the styrene unit in formula (1-A) of Example 1, R1, R2, R4, and R5 are all hydrogen atoms, R3 is phenyl, R6 is biphenyl, M2 is styrene, and one of the two R7s is... The other is a hydrogen atom.

[0055] The indene-containing resin prepared in Example 4 effectively achieved a structural balance between rigidity and flexibility of the molecular chain by introducing styrene copolymer segments into the rigid indene-biphenyl-containing backbone. This not only improved the solubility, melt flowability, and processing rheological behavior of the indene-containing copolymer resin, giving it superior wettability and filler adaptability during copper-clad laminate impregnation and hot pressing, but also, the long-range flexibility of the styrene segments effectively relaxed the internal stress of the cured product and reduced resin brittleness, improving the toughness, adhesion, and processing yield of the indene-containing resin while maintaining extremely low dielectric loss. In summary, Example 4, while retaining excellent dielectric properties and heat resistance, broadened the processing window of indene-containing resins and took into account cost advantages, providing a structured resin with good processability and comprehensive performance for high-frequency, high-speed copper-clad laminates and advanced electronic packaging materials.

[0056] Example 5 A method for preparing indene-containing resins includes the following steps: B1. Under nitrogen protection, add the indene-containing monomer (13.2 g, about 0.025 mol) and styrene (10.4 g, about 0.1 mol) of formula (1-A) obtained in Example 1, and stopper the flask with a rubber stopper. B2. Under nitrogen protection, 25 mL of toluene was added, and the thermally initiated polymerization reaction was carried out at 85 °C for 12 h. After the reaction was completed, the mixture was cooled to room temperature, and then the reaction solution was slowly added dropwise to a large amount of methanol for precipitation. The precipitate was collected by filtration, and the obtained solid product was washed repeatedly with methanol 3 times and dried to obtain an indene-containing resin with the structural formula shown in formula (3): (3), Where m and m' represent the average degree of polymerization of the styrene segment, R1, R2, R4, and R5 are all hydrogen atoms, R3 is phenyl, R6 is biphenyl, M2 is styrene, and one of the two R7s is... The other is a hydrogen atom.

[0057] The indene-containing resin prepared in Example 5, through the symmetrical introduction of long polystyrene chains at both ends of the molecular chain, endows the resin with excellent intramolecular toughening effect, effectively overcoming the inherent brittleness of the rigid indene skeleton and significantly improving the impact resistance and peel strength of the cured product. Simultaneously, the good thermoplasticity of the polystyrene segments broadens the processing temperature window of the prepolymer, and the synergistic effect of the non-polar polystyrene segments and the rigid skeleton ensures a more balanced stress distribution in the three-dimensional network formed by thermosetting, while maintaining extremely low dielectric loss. This, in turn, simultaneously improves the dimensional stability and long-term reliability of the material while maintaining high heat resistance.

[0058] The technical solution of the present invention will be further explained and illustrated below through specific application examples.

[0059] Application Example 1 A low-dielectric material, said low-dielectric material comprising the following raw materials in parts by weight: Contains 40 parts of indene monomers; Contains 10 parts of indene-based resin; Benzoyl peroxide 0.8 parts; 50 parts of spherical silica.

[0060] The indene-containing monomers were prepared in Example 1, and the indene-containing resins were prepared in Example 3.

[0061] Preparation of a prepreg: An indene-containing monomer, an indene-containing resin, benzoyl peroxide, and spherical silica are mixed, and an appropriate amount of butanone solvent is added and stirred to dissolve, forming a homogeneous adhesive solution with a solid content of 70 wt%. E-glass fiber cloth is impregnated in the above adhesive solution and baked in an oven at 140°C for 4 minutes to allow the adhesive solution to reach a semi-cured state, thus obtaining the prepreg.

[0062] Preparation of a laminate: Two prepreg sheets are stacked one on top of the above, copper foil is attached to their opposite sides, and the laminate is placed in a press and hot-pressed for 1 hour at a temperature of 210°C and a pressure of 2.0 MPa to obtain the laminate.

[0063] Application Example 2 A low-dielectric material, said low-dielectric material comprising the following raw materials in parts by weight: Contains 20 parts of indene monomers; Contains 15 parts of indene-based resin; Benzoyl peroxide 0.5 parts; 60 parts of spherical silica.

[0064] The indene-containing monomers were prepared in Example 2, and the indene-containing resins were prepared in Example 4.

[0065] The preparation of the prepreg and laminate is the same as in Application Example 1.

[0066] Application Example 3 A low-dielectric material, said low-dielectric material comprising the following raw materials in parts by weight: Contains 30 parts of indene monomers; Contains 20 parts of indene-based resin; 1 part benzoyl peroxide; 80 parts of spherical silica.

[0067] The indene-containing monomers were prepared in Example 1, and the indene-containing resins were prepared in Example 5.

[0068] The preparation of the prepreg and laminate is the same as in Application Example 1.

[0069] Comparative Example 1 Comparative Example 1 provides a semi-cured sheet and laminate, which differs from Application Example 2 in that the mass of 3,3'-dichloromethylbiphenyl is adjusted to 20.1g during the preparation of the indene-containing monomer.

[0070] Comparative Example 2 Comparative Example 2 provides a semi-cured sheet and laminate, which differs from Application Example 2 in that the mass of 4-vinylbenzyl chloride is adjusted to 31g during the preparation of the indene-containing monomer.

[0071] Comparative Example 3 Comparative Example 3 provides a prepreg and laminate, which differs from Application Example 2 in that phenothiazine is not added in step A1.

[0072] Comparative Example 4 Comparative Example 4 provides a prepreg and laminate, which differs from Application Example 2 in that the sodium hydroxide in steps A1 and A2 is replaced with an equimolar amount of sodium carbonate.

[0073] Comparative Example 5 Comparative Example 5 provides a prepreg and laminate, which differs from Application Example 2 in that the indene-containing monomer is replaced with an equimolar amount of 1,4-bis(vinylbenzyl)benzene.

[0074] Total halogen content test: Determined using oxygen bomb combustion-ion chromatography according to IPC-TM-650 2.3.41 standard. After removing the copper foil from the laminate, the sample is crushed and burned in an oxygen bomb to convert organic halogens into hydrogen halides. The hydrogen halides are then absorbed by an alkaline absorbent, and the chloride ions (Cl-) in the absorbent are analyzed using an ion chromatograph. - ) and bromide ions (Br - Quantitative analysis was performed, and the total halogen content was the sum of the contents of the two. Three samples were taken for each sample for parallel testing, and the average value was taken as the final result (Table 1).

[0075] Table 1

[0076] As shown in Table 1, the average total halogen content of Application Examples 1-3 is 50ppm, 40ppm and 57ppm respectively, all of which are less than 100ppm, meeting the stringent requirements of high-frequency and high-speed copper-clad laminates for low halogen content.

[0077] This application presents the following performance tests on the laminates prepared for various application examples and comparative examples: Dielectric constant (Dk) and dielectric loss (Df) were tested using the splice post dielectric resonator (SPDR) method at a frequency of 10 GHz according to IPC-TM-650 2.5.5.9. Glass transition temperature (Tg) was tested using differential scanning calorimetry (DSC), and the coefficient of thermal expansion (CTE) was determined according to IPC-TM-650 2.4.41 in thermomechanical analysis mode. Copper foil peel strength was tested according to IPC-TM-6502.4.8 standard, while heat resistance was evaluated by 288℃ immersion tin test (floating solder test). According to IPC-TM-6502.4.13 standard, the laminate sample was immersed in a tin bath at 288℃ for a specified time, and the presence of blistering or delamination on the sample surface was observed and recorded to comprehensively determine its heat resistance reliability.

[0078] Table 2 shows the test results of the laminates for each application example and comparative example.

[0079] Table 2

[0080] As shown in Table 2, the laminates prepared in Application Examples 1-3 all exhibit excellent overall performance. In Application Example 2, the low-dielectric material exhibits a strong molecular skeleton, and steric hindrance effectively suppresses molecular polarization, thus achieving low dielectric loss while also possessing a high glass transition temperature and a low coefficient of thermal expansion. Application Examples 1 and 3 both achieved extremely low dielectric losses below 0.001 N / mm, and none of the three showed delamination or blistering during tin immersion testing at 288°C, with peel strength remaining between 0.48 and 0.6 N / mm. This demonstrates that the symmetrical rigid skeleton and multifunctional cross-linked structure of the indene-based monomers and their resins in this application endow the cured products with excellent dielectric properties, heat resistance, dimensional stability, and good interlayer adhesion.

[0081] In contrast, Comparative Examples 1 and 2 increased the amounts of 3,3'-dichloromethylbiphenyl and 4-vinylbenzyl chloride in the synthesis steps of indene-containing monomers, leading to intensified side reactions during nucleophilic substitution, decreased product purity, a significant increase in dielectric loss to approximately 0.004, and delamination and blistering during tin immersion testing at 288°C. Comparative Example 3 omitted the polymerization inhibitor phenothiazine in the preparation of indene-containing monomers, causing gelation of the reaction system, severe internal defects in the laminate, an increased dielectric loss to 0.0058, and poor heat resistance. Comparative Example 4 replaced the strong base sodium hydroxide with the weak base sodium carbonate, resulting in the indene-containing monomer yield being extremely low, incomplete curing, a glass transition temperature as low as 185°C, a dielectric loss of 0.01150, and severe delamination and blistering during tin immersion testing. Comparative Example 5 uses a single benzene ring monomer without a rigid biphenyl-indene framework, which weakens the steric hindrance effect, resulting in a significant deterioration in dielectric loss, heat resistance and dimensional stability.

[0082] Therefore, those skilled in the art should recognize that although numerous exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Thus, the scope of the present invention should be understood and construed as covering all such other variations or modifications.

Claims

1. A monomer containing indene, characterized in that, The structural formula of the indene-containing monomer is: （1）， R1 is independently selected from any one of hydrogen atom, methyl, methoxy, ethyl, and ester group; R2 is selected from any one of hydrogen atom, methyl, methoxy, ethyl, or ester group; R3 is selected from any one of phenyl, naphthyl, biphenyl, aromatic alkyl, or aliphatic chains containing 1-10 carbon atoms; R4 is selected from any one of hydrogen atom, methoxy group, ester group, or aliphatic chain containing 1-10 carbon atoms; R5 is selected from any one of hydrogen atoms, methoxy groups, or aliphatic chains containing 1 to 10 carbon atoms; R6 is selected from any one of the following: phenyl, naphthyl, biphenyl, aromatic alkyl, aliphatic chain containing 1-10 carbon atoms, or a substituent containing halogen atoms.

2. A method for preparing an indene-containing monomer as described in claim 1, characterized in that, Includes the following steps: A1. Under an inert atmosphere, a compound containing two chloromethyl groups and indene are dissolved in toluene, and tetrabutylammonium bromide and phenothiazine are added. A first alkali solution is added, and the reaction is carried out at 25℃-80℃ for 1-20 hours. After the reaction is completed, the reaction solution is obtained. A2. Add an aromatic compound containing monochloromethyl to the reaction solution obtained in step A1, add a second alkali solution, and react at 25℃-80℃ for 1-20h to obtain an indene-containing monomer with the structural formula shown in formula (1).

3. The preparation method according to claim 2, characterized in that, In step A1, the molar ratio of the compound containing two chloromethyl groups to indene is (0.45-0.55):1, the molar ratio of tetrabutylammonium bromide to indene is (0.01-0.1):1, the molar ratio of phenothiazine to indene is (0.001-0.01):1, and the molar ratio of alkali to indene in the first alkaline solution is (3-4.5):

1. In step A2, the molar ratio of the aromatic compound containing monochloromethyl to indene is (0.9-1.3):1, and the molar ratio of the alkali to indene in the second alkaline solution is (3-4.5):

1. The alkali in the first alkaline solution and the second alkaline solution is selected from one or two of lithium hydroxide, potassium hydroxide, and sodium hydroxide.

4. A resin containing indene, characterized in that, The structural formula of the indene-containing resin is: （2） or （3）， In structural formulas (2) and (3), CO represents the polymerization of monomer (1) and monomer M2: R1 is independently selected from any one of hydrogen atom, methyl, methoxy, ethyl, and ester group; R2 is selected from any one of hydrogen atom, methyl, methoxy, ethyl, or ester group; R3 is selected from any one of phenyl, naphthyl, biphenyl, aromatic alkyl, or aliphatic chains containing 1-10 carbon atoms; R4 is selected from any one of hydrogen atom, methoxy group, ester group, or aliphatic chain containing 1-10 carbon atoms; R5 is selected from any one of hydrogen atoms, methoxy groups, or aliphatic chains containing 1 to 10 carbon atoms; R6 is selected from any one of phenyl, naphthyl, biphenyl, aromatic alkyl, aliphatic chain containing 1-10 carbon atoms, or a substituent containing halogen atoms; n is selected from integers ≥1 and ≤1000; m is selected from integers ≥ 0 and ≤ 1000; m' is selected from integers ≥0 and ≤1000; And m+n+m'≥2; When the indene-containing resin is polymerized, R7 is an independent terminal or hydrogen atom of the initiator; When the indene-containing resin is not polymerized, R7 is independent of each other. Or hydrogen atoms.

5. The indene-containing resin according to claim 4, characterized in that, The M2 is selected from at least one of styrene, methylstyrene, bistyrene, naphthalene, divinylbenzene, divinylbiphenyl, methacrylate, acrylate, maleimide, maleic anhydride, butadiene, isoprene, ethylene, propylene, norbornene, and ethylene-imide norbornene.

6. The indene-containing resin according to claim 4, characterized in that, Preferably, n is selected from integers ≥2 and ≤200, and m is selected from integers ≥0 and ≤100.

7. The indene-containing resin according to claim 4, characterized in that, The initiator is terminated in one of the following: naphthalene ring, n-butyl, tert-butyl, benzoyloxy, phenyl, isopropylphenoxy, and tert-butoxy.

8. A method for preparing an indene-containing resin, characterized in that, Includes the following steps: Indene-containing monomers are polymerized or copolymerized with other monomers to form prepolymers, thus obtaining indene-containing resins.

9. The preparation method according to claim 8, characterized in that, The polymerization is either thermally initiated polymerization or free radical polymerization; the reaction temperature of the thermally initiated polymerization is 40℃-100℃, and the reaction time is 1-20h; the reaction temperature of the free radical polymerization is 40℃-100℃, and the reaction time is 1-20h.

10. The preparation method according to claim 9, characterized in that, The other monomers are selected from at least one of styrene, methylstyrene, bistyrene, naphthalene, divinylbenzene, divinylbiphenyl, methacrylates, acrylates, maleic anhydride, maleimide, butadiene, isoprene, ethylene, propylene, norbornene, and ethylene-imide norbornene.

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