A polydivinylbenzene flame retardant resin, a method for preparing the same, and a cured product thereof

Abstract

This invention relates to the field of flame-retardant resin technology, and provides a polyvinylbenzene flame-retardant resin, its preparation method, and the cured product. The polyvinylbenzene flame-retardant resin provided by this invention is copolymerized from divinylbenzene, ethylvinylbenzene, a silicon-containing monomer, and benzofuran. Divinylbenzene provides the unsaturated side-chain groups required for crosslinking and gives the cured resin an excellent rigid skeleton. The ethylstyrene monomer regularly inserts flexible alkyl side chains into the main chain, improving the material's impact resistance. The addition of the silicon-containing monomer reduces the material's flammability and improves its high-temperature resistance and tensile strength. The benzofuran enables effective control of the polymer's molecular weight, reducing the molecular weight distribution of the product. In summary, the polyvinylbenzene flame-retardant resin provided by this invention possesses excellent flame retardancy, along with advantages such as high temperature resistance, high toughness, and low dielectric loss, meeting the application requirements of electronic packaging, high-end copper-clad laminates, and other fields.

Description

Technical Field

[0001] This invention relates to the field of flame retardant resin technology, and in particular to a polyvinylbenzene flame retardant resin, its preparation method, and the cured product. Background Technology

[0002] To meet the demand for low dielectric loss and high thermal stability electrical insulation materials in the high-frequency communication field, existing technologies focus on developing curable resin systems based on vinyl aromatic copolymers to achieve properties such as low dielectric properties, high temperature resistance, and easy processing.

[0003] Conventional divinylbenzene resin is difficult to modify due to its inherent chemical structure. Existing technologies that introduce halogenated or phosphorus-containing modifiers to improve flame retardancy have poor compatibility with divinylbenzene resin, easily inducing resin phase separation. This not only reduces material homogeneity but also deteriorates mechanical and dielectric properties. When applied to copper-clad laminate manufacturing, these defects can further lead to reduced interlayer adhesion and poor bonding of copper foil to via walls.

[0004] In related technologies, a modified vinyl aromatic polymer with characteristics such as heat resistance, transparency, miscibility, and easy processing is prepared by copolymerizing divinylbenzene, vinyl ethylbenzene, styrene, and methyl methacrylate. This technology uses methyl methacrylate to copolymerize and modify polydivinylbenzene resin, but the resulting resin has a tensile strength of only 3.05 kgf / mm². 2 With an elongation at break of 4.2%, the resin strength is relatively low among engineering plastics, making it suitable only for environments with low load-bearing requirements.

[0005] In another related technology, a divinylbenzene resin with enhanced solubility in solvents such as toluene is prepared by copolymerization of divinylbenzene, vinyl ethylbenzene, and 1-chloro-1-phenylethane. The addition of 1-chloro-1-phenylethane not only improves the solubility and compatibility of the divinylbenzene resin by introducing polar groups, but also increases the glass transition temperature Tg of the resin. g The temperature was increased from 278℃ to 291℃. However, due to the copolymerization of 1-chloro-1-phenylethane, organic chlorine components were introduced into the resin, which limited its application in fields such as electronic packaging and high-end copper-clad laminates.

[0006] In another related technology, a vinyl aromatic polymer with improved heat resistance, compatibility, and heat-induced color change was prepared by copolymerizing divinylbenzene, vinyl ethylbenzene, and 2-phenoxyethyl methacrylate. The resin modified by this method did not exhibit significant Tg. g This means that it cannot be formed through conventional melt processing, severely affecting the material's applicability. Furthermore, due to the introduction of numerous polar groups, the material loses the low dielectric loss advantage of polyvinylbenzene resin.

[0007] In summary, current polyvinylbenzene resins struggle to balance flame retardancy, mechanical properties, and low dielectric loss, making it difficult to meet the application requirements of fields such as electronic packaging and high-end copper-clad laminates. Summary of the Invention

[0008] In view of this, the present invention provides a polyvinylbenzene flame-retardant resin, its preparation method, and the cured product. The polyvinylbenzene flame-retardant resin provided by the present invention possesses excellent flame retardancy, as well as advantages such as high temperature resistance, high toughness, and low dielectric loss, and can meet the application requirements of electronic packaging, high-end copper-clad laminates, and other fields.

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0010] A polyvinylbenzene flame retardant resin having the structure shown in Formula I:

[0011] Formula I;

[0012] In formula I: a: b = (0.7~9): 1, c: (a+b) = (0.02~0.2): 1, d: (a+b) = (0.01~0.05): 1;

[0013] R is a silicon-containing group, and the structure of the silicon-containing group is shown in Formula II:

[0014] Formula II;

[0015] In Formula II: R1, R2, and R3 are independently alkenyl-substituted phenyl groups or C2-C6 unsaturated hydrocarbons.

[0016] Preferably, the silicon-containing group has the following structure:

[0017] .

[0018] The present invention also provides a method for preparing the polyvinylbenzene flame retardant resin described above, comprising the following steps: mixing divinylbenzene, ethylvinylbenzene, a silicon-containing monomer, benzofuran, a solvent, and a catalyst to react and obtain the polyvinylbenzene flame retardant resin; wherein the molar ratio of divinylbenzene to ethylvinylbenzene is 0.7~9:1; the molar amount of the silicon-containing monomer is 0.02~0.2 times the sum of the molar amounts of divinylbenzene and ethylvinylbenzene; and the molar amount of the benzofuran is 0.01~0.5 times the sum of the molar amounts of divinylbenzene and ethylvinylbenzene.

[0019] The structure of the silicon-containing monomer is shown in Formula III:

[0020] Formula III.

[0021] Preferably, the solvent is an aprotic solvent.

[0022] Preferably, the aprotic polar solvent includes one or more of toluene, benzene, chlorobenzene, xylene, dichlorobenzene, chloroform, and carbon tetrachloride; the mass of the solvent is 2 to 10 times the sum of the masses of divinylbenzene, ethylvinylbenzene, silicon-containing monomers, and benzofuran.

[0023] Preferably, the catalyst is a protic acid.

[0024] Preferably, the protic acid includes one or more of methanesulfonic acid, trifluoromethanesulfonic acid, sulfuric acid, and hydrogen chloride.

[0025] Preferably, the molar amount of the catalyst is 0.001 to 0.1 times the molar amount of divinylbenzene and ethylvinylbenzene.

[0026] Preferably, the reaction temperature is -30~20℃ and the time is 1~12h.

[0027] This invention also provides a cured polyvinylbenzene flame-retardant resin, obtained by curing the polyvinylbenzene flame-retardant resin described in the above-described scheme or the polyvinylbenzene flame-retardant resin prepared by the preparation method described in the above-described scheme. This invention provides a polyvinylbenzene flame-retardant resin having the structure shown in Formula I. This invention grafts a silicon-containing monomer with flame-retardant groups onto the polyvinylbenzene backbone to form a chemically bonded modified resin. Through the introduction of the silicon-containing monomer, polar groups are firmly anchored to the polymer backbone through covalent bonds, thereby constructing an ordered polar micro-region structure in the resin matrix. This significantly reduces the difference in solubility parameters between the polyvinylbenzene resin and polar materials, thereby improving their thermodynamic compatibility. The polar groups in the polar micro-regions have high dipole moments and can establish dipole-dipole interactions with polar groups on the surface of other substances, enhancing the solubility and carrying capacity of small polar molecules in the system, enabling the mixed resin system to maintain excellent homogeneous stability over a long period. Furthermore, the introduction of silicon-containing monomers further improves the overall performance of the material while maintaining the excellent properties of polyvinylbenzene resin: the addition of silane monomers with rigid aromatic ring structures enhances the rigidity of the molecular chain, restricts the mobility of polymer chain segments, and significantly increases the energy required for chain relaxation, manifested in the glass transition temperature (T). g The polar groups shift towards higher temperatures. Furthermore, the introduced polar groups enhance intermolecular forces through dipole-dipole interactions, increasing tensile strength and inhibiting crack propagation; the introduction of silane groups also increases the contact angle of the resin surface, giving the material significant hydrophobic properties.

[0028] The polyvinylbenzene flame-retardant resin provided by this invention also includes a benzofuran structure. Benzofuran, as a functional comonomer participating in the copolymerization reaction, has a rigid molecular structure and its copolymerization reactivity is slightly lower than that of the divinylbenzene monomer. This difference in reactivity leads to the divinylbenzene monomer tending to react with lower molecular weight segments after the benzofuran is inserted into the growing macromolecular chain, thereby achieving effective control over the polymer molecular weight. This mechanism can suppress the formation of excessively high molecular weight polymers, avoiding explosive polymerization caused by concentrated exothermic reactions and uncontrolled chain growth, thus preventing a sharp increase in system viscosity. Simultaneously, the introduction of benzofuran helps reduce the molecular weight distribution of the product, making the viscosity of the polymerization system easier to control, reducing side reactions caused by localized overheating or uneven reaction, and thus avoiding product coloring problems. The final polymer exhibits higher consistency and stability in terms of viscosity and appearance color.

[0029] The polyvinylbenzene flame retardant resin provided by this invention can be used to prepare a cross-linked thermosetting resin after curing treatment. The divinylbenzene resin forms a rigid three-dimensional network structure through cross-linking and curing, which gives the material excellent mechanical strength. The introduction of ethyl vinylbenzene monomer effectively improves the impact resistance of the material through the toughening effect of its ethyl side chain.

[0030] In addition, the polyvinylbenzene flame retardant resin provided by the present invention is easy to prepare and does not easily undergo gelation during the polymerization process.

[0031] In summary, the polyvinylbenzene flame retardant resin provided by this invention has excellent flame retardancy, as well as the advantages of high temperature resistance, high toughness, and low dielectric loss, which can meet the application requirements of electronic packaging, high-end copper clad laminates and other fields.

[0032] The present invention also provides a method for preparing the polyvinylbenzene flame retardant resin described above. The preparation method provided by the present invention is simple to operate and has a high product yield (reaching more than 82%). Detailed Implementation

[0033] This invention provides a polyvinylbenzene flame retardant resin having the structure shown in Formula I:

[0034] Formula I;

[0035] In formula I: a: b = (0.7~9): 1, c: (a+b) = (0.02~0.2): 1, d: (a+b) = (0.01~0.05): 1;

[0036] R is a silicon-containing group, and the structure of the silicon-containing group is shown in Formula II:

[0037] Formula II;

[0038] In Formula II: R1, R2, and R3 are independently alkenyl-substituted phenyl groups or C2-C6 unsaturated hydrocarbons.

[0039] In this invention, in formula I: a:b=(0.7~9):1, specifically it can be 0.7:0.3, 0.8:0.2, 0.9:0.1, 0.5:0.5 or 0.4:0.6; c:(a+b)=(0.02~0.2):1, specifically it can be 0.02:1, 0.05:1, 0.1:1 or 0.2:1; d:(a+b)=(0.01~0.05):1, specifically it can be 0.01:1, 0.02:1 or 0.05:1.

[0040] In this invention, the alkenyl-substituted phenyl group in Formula II is preferably vinylphenyl, specifically 4-vinylphenyl; the C2-C6 unsaturated hydrocarbon is preferably phenyl, vinyl, propenyl, butenyl, or pentenyl. In specific embodiments of this invention, R1, R2, and R3 are independently preferably vinylphenyl or phenyl.

[0041] In this invention, the silicon-containing group preferably has the following structure:

[0042] .

[0043] In this invention, the weight-average molecular weight (M) of the polyvinylbenzene flame retardant resin is... w The preferred value is 10,000 to 12,000.

[0044] The molecular weight distribution coefficient (PDI) is preferably 4~10, the double bond content (DBC) is preferably 5~7.5 mmol / g, the silicon content is preferably 2~23‰, and the flame retardant rating is V-1.

[0045] The present invention also provides a method for preparing the polyvinylbenzene flame retardant resin described above, comprising the following steps: mixing divinylbenzene, ethylvinylbenzene, a silicon-containing monomer, benzofuran, a solvent, and a catalyst to react and obtain the polyvinylbenzene flame retardant resin; wherein the molar ratio of divinylbenzene to ethylvinylbenzene is 0.7~9:1; the molar amount of the silicon-containing monomer is 0.02~0.2 times the sum of the molar amounts of divinylbenzene and ethylvinylbenzene; and the molar amount of the benzofuran is 0.01~0.5 times the sum of the molar amounts of divinylbenzene and ethylvinylbenzene.

[0046] The structure of the silicon-containing monomer is shown in Formula III:

[0047] Formula III.

[0048] In this invention, the silicon-containing monomer is preferably tetra(4-vinylphenyl)silane. The silicon-containing monomer used in this invention contains double bonds, has large steric hindrance, and can be grafted onto the polyvinylbenzene backbone to form a chemically bonded modified resin, thereby improving the flame retardant properties, high temperature resistance, and mechanical properties of the resin.

[0049] In this invention, the molar ratio of divinylbenzene to ethylvinylbenzene is 0.7 to 9:1, specifically 0.7:0.3, 0.8:0.2, 0.9:0.1, 0.5:0.5, or 0.4:0.6; the molar amount of the silicon-containing monomer is 0.02 to 0.2 times the sum of the molar amounts of divinylbenzene and ethylvinylbenzene, specifically 0.02, 0.05, 0.1, or 0.2 times; the molar amount of benzofuran is 0.01 to 0.5 times the sum of the molar amounts of divinylbenzene and ethylvinylbenzene, specifically 0.01, 0.02, 0.03, or 0.05 times.

[0050] In this invention, the solvent is preferably an aprotic solvent; the aprotic polar solvent preferably includes one or more of toluene, benzene, chlorobenzene, xylene, dichlorobenzene, chloroform and carbon tetrachloride, more preferably toluene; the mass of the solvent is 2 to 10 times the sum of the masses of divinylbenzene, ethylvinylbenzene, silicon-containing monomer and benzofuran, preferably 3 to 5 times.

[0051] In this invention, the catalyst is preferably a protic acid; the protic acid preferably includes one or more of methanesulfonic acid, trifluoromethanesulfonic acid, sulfuric acid and hydrogen chloride, more preferably methanesulfonic acid; the molar amount of the catalyst is 0.001 to 0.1 times the sum of the molar amounts of divinylbenzene and ethylvinylbenzene, specifically 0.015, 0.02 or 0.03 times.

[0052] In this invention, the reaction temperature is preferably -30~20℃, specifically -15, -10, or -5℃, and the reaction time is preferably 1~12 hours, specifically 4 or 6 hours. In a specific embodiment of this invention, it is preferable to first mix divinylbenzene, ethylvinylbenzene, the silicon-containing monomer, and the solvent, then cool to the reaction temperature, and then add the catalyst dropwise to the reaction system. After the addition is complete, the system is kept at the temperature for further reaction. The reaction time is counted from the completion of the catalyst addition.

[0053] After the reaction is completed, the present invention preferably adds anhydrous calcium hydroxide powder to the reaction solution to quench the reaction, and then uses diatomaceous earth for pressure filtration to obtain a filtrate; then the filtrate is subjected to vacuum distillation to obtain a distillation residue; the distillation residue is added to pre-cooled methanol to precipitate the resin, and then filtered, washed and dried to obtain the polyvinylbenzene flame retardant resin; the pre-cooling temperature of the pre-cooled methanol is preferably 0~5℃, and the washing agent is preferably a methanol solution of 2,6-di-tert-butyl-p-cresol (BHT), wherein the concentration of BHT in the methanol solution is preferably 0.1wt%.

[0054] The present invention also provides a cured polyvinylbenzene flame retardant resin, which is obtained by curing the polyvinylbenzene flame retardant resin described in the above scheme or the polyvinylbenzene flame retardant resin prepared by the preparation method described in the above scheme.

[0055] In this invention, the curing method preferably includes: mixing the polyvinylbenzene flame retardant resin, an initiator, and a solvent to obtain a resin solution; coating the resin solution onto the surface of a substrate and then performing heat curing to obtain the cured product; the initiator is preferably azobisisobutyronitrile; the mass of the initiator is preferably 2% to 3% of the mass of the polyvinylbenzene flame retardant resin, more preferably 2.5%; the solvent is preferably toluene; in this invention, the polyvinylbenzene flame retardant resin is first dissolved in toluene under a water bath heating condition of 60°C, and then the initiator is added and stirred evenly; the heat curing is preferably performed by first heating and crosslinking at 80°C for 30 min, and then raising the temperature to 160~180°C and continuing to heat for 20 min to remove the solvent.

[0056] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0057] Preparation Example 1: Preparation of tetra(4-vinylphenyl)silane

[0058] Under nitrogen protection, triphenylphosphine (314.7 g, 1.2 mol, 262.3 Da) and 150 mL of anhydrous tetrahydrofuran were added to a dry three-necked flask. The mixture was cooled to 0°C in an ice bath, and methyl bromoethane (123.4 g, 1.3 mol, 94.9 Da) was slowly added dropwise. After the addition was complete, the mixture was brought to room temperature and stirred for 6 hours, yielding an orange-red phosphorus ylide solution. p-Bromobenzaldehyde (222.0 g, 1.2 mol, 185 Da) was dissolved in 50 mL of anhydrous THF and added dropwise to the above phosphorus ylide solution. The mixture was stirred at room temperature for 12 hours. The reaction solution was quenched with 100 mL of saturated sodium bicarbonate solution. After extraction with diethyl ether, the organic phases were combined, dried over anhydrous sodium sulfate, and the solvent was removed by vacuum distillation. The crude product was purified by silica gel column chromatography (petroleum ether / ethyl acetate = 20:1) to give 186.7 g of yellow p-bromostyrene, with a yield of 85.1%. 1 H NMR (CDCl3, 400 MHz) δ 7.40 (d, J=8.4 Hz, 2H), 7.28 (d, J=8.4Hz, 2H), 6.67 (dd, J=17.6, 10.8 Hz, 1H), 5.76 (d, J=17.6 Hz, 1H), 5.25 (d, J=10.8 Hz, 1H).

[0059] Under nitrogen protection, magnesium shavings (4.1 g, 0.17 mol, 24.3 Da) and a small amount of elemental iodine were added to a dried three-necked flask. A mixture of p-bromostyrene (29.3 g, 0.16 mol, 183 Da) and 100 mL of anhydrous diethyl ether was slowly added dropwise to the flask to initiate the reaction. Heating was then stopped, and the reaction temperature was maintained at 35-40 °C. The mixture was stirred until the magnesium shavings were completely dissolved to prepare a 4-vinylphenyl magnesium bromide solution for later use.

[0060] Silicon tetrachloride (6.8 g, 0.04 mol, 169.9 Da) was dissolved in 50 mL of anhydrous diethyl ether and cooled to -5°C in an ice bath. A solution of 4-vinylphenyl magnesium bromide was slowly added dropwise to the system, and after the addition was complete, the mixture was heated to room temperature and stirred for 4 hours. The reaction mixture was poured into ice water, and 10 wt% dilute hydrochloric acid was added dropwise until the pH reached 3. The combined organic phases were extracted with diethyl ether and washed successively with saturated sodium bicarbonate solution and saturated brine. The mixture was dried over anhydrous magnesium sulfate. The solvent was removed by vacuum distillation, and the crude product was recrystallized from toluene to give 13.7 g of a pale yellow solid, tetra(4-vinylphenyl)silane (440.7 Da), in 78% yield. 1H NMR (CDCl3, 400 MHz): δ7.52 (d, J=7.7 Hz, 8H), 7.38 (d, J=8.4 Hz, 8H), 6.75 (dd, J=10.6, 16.8 Hz, 4H), 5.72 (d, J=17.6 Hz, 4H), 5.30 (d, J=10.8 Hz, 4H).

[0061] Preparation Example 2: Preparation of phenyltris(4-vinylphenyl)silane

[0062] Magnesium 4-vinylphenyl bromide was prepared according to the same scheme as in Preparation Example 1, and phenyltrichlorosilane was prepared and purified by reaction with phenyltrichlorosilane under the same conditions. The product was a yellow solid powder. 1 H NMR (CDCl3, 400 MHz): δ 7.65 (t, J=6.4 Hz, 2H), δ 7.52 (m, J=7.6 Hz, 9H), 7.38 (d, J=8.2 Hz, 6H), 6.75 (dd, J=10.7, 16.7 Hz, 3H), 5.72 (d, J=17.4 Hz, 3H), 5.30 (d, J=10.6 Hz, 3H).

[0063] Example 1

[0064] In a polymerization reactor, 182.3 g (1.4 mol, 130.2 Da) of divinylbenzene, 79.3 g (0.6 mol, 132.2 Da) of ethylvinylbenzene, 44.1 g (0.1 mol, 0.05 eq, 440.7 Da) of tetrakis(4-vinylphenyl)silane, 4.7 g (0.04 mol, 0.02 eq, 118.1 Da) of benzofuran, and 1.2 kg of toluene solvent were added sequentially. After stirring and mixing until completely dissolved, the reaction system was cooled to -10 °C. Then, 3.8 g (0.04 mol, 0.02 eq, 96.1 Da) of methanesulfonic acid was added dropwise to the reaction system, and the reaction temperature was maintained at -10 °C for 6 hours. After the reaction was completed, 4.4 g (0.06 mol, 0.03 eq, 74 Da) of anhydrous calcium hydroxide powder was added to the system to quench the reaction. 30 g of diatomaceous earth was added, stirred evenly, and filtered under pressure to remove insoluble impurities from the material.

[0065] The filtrate was transferred to a vacuum distillation apparatus to remove 900g of solvent toluene at 50°C and 0.05 bar. The concentrated viscous polymer solution was added to 900g of pre-cooled (0-5°C) methanol, and stirred for 30 min to allow the resin to fully precipitate. The solid was filtered and washed with a 0.1% methanol solution of 150g of 2,6-di-tert-butyl-p-cresol (BHT). The solid was then dried in a vacuum drying oven at 40°C for 4 hours to obtain 251g of copolymer, with a reaction yield of 82%.

[0066] The product was sampled, and the molecular weight and molecular weight distribution were determined by gel permeation chromatography (GPC) according to the national standard GB / T 1632.1-2024; the content of unsaturated double bonds was determined according to GB / T 34247.1-2017; and the silicon content was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) according to GB / T 30902-2014. The results showed that the weight-average molecular weight M of the product was... w =10542, molecular weight distribution coefficient PDI=5.71, double bond content DBC=5.42mmol / g, silicon content 7.4‰.

[0067] Examples 2-6

[0068] Polyvinylbenzene flame-retardant resin was prepared according to the same scheme as in Example 1. During the feeding stage into the reaction vessel, the molar ratio of divinylbenzene to vinyl ethylbenzene monomers was changed from 0.7:0.3 in Example 1 to 0.8:0.2 in Example 2; 0.9:0.1 in Example 3; 0.6:0.4 in Example 4; 0.5:0.5 in Example 5; and 0.4:0.6 in Example 6. Except for the change in the ratio of divinylbenzene to vinyl ethylbenzene during feeding, the amounts of other materials and the operation steps of the polymerization reaction were consistent with Example 1. After the polymerization reaction was completed, each example underwent post-processing in the same manner as in Example 1 to obtain copolymer solids. Samples of the copolymer products obtained in each example were taken, and the molecular weight and molecular weight distribution, unsaturated double bond content, and silicon content of the products were tested according to the same scheme as in Example 1.

[0069] Examples 7-9

[0070] Polyvinylbenzene flame-retardant resin was prepared according to the same scheme as in Example 1. During the feeding stage into the reaction flask, the amount of tetra(4-vinylphenyl)silane was changed from 44.1 g (0.1 mol, 0.05 eq, 440.7 Da) in Example 1 to 17.6 g (0.04 mol, 0.02 eq, 440.7 Da) in Example 7; 88.1 g (0.2 mol, 0.1 eq, 440.7 Da) in Example 8; and 176.3 g (0.4 mol, 0.2 eq, 440.7 Da) in Example 9. Except for the change in the amount of tetra(4-vinylphenyl)silane during feeding, the amounts of other materials and the operation steps of the polymerization reaction were consistent with Example 1. After the polymerization reaction was completed, each example underwent post-processing in the same manner as in Example 1 to obtain copolymer solids. Samples of the copolymer products obtained in each example were taken, and the molecular weight and molecular weight distribution, unsaturated double bond content, and silicon content of the products were tested according to the same scheme as in Example 1.

[0071] Examples 10-11

[0072] Divinylbenzene resin was prepared according to the same scheme as in Example 1. During the feeding stage into the reaction flask, the amount of benzofuran was changed from 4.7 g (0.04 mol, 0.02 eq, 118.1 Da) in Example 10 to 11.8 g (0.1 mol, 0.05 eq, 118.1 Da) in Example 10 and 2.4 g (0.02 mol, 0.01 eq, 118.1 Da) in Example 11. Except for the change in the amount of benzofuran during feeding, the amounts of other materials and the operation steps of the polymerization reaction were consistent with Example 1. After the polymerization reaction was completed, each example underwent post-processing in the same manner as in Example 1 to obtain copolymer solids. Samples of the copolymer products obtained in each example were taken, and the molecular weight and molecular weight distribution, unsaturated double bond content, and silicon content of the products were tested according to the same scheme as in Example 1.

[0073] Example 12

[0074] Divinylbenzene resin was prepared according to the same procedure as in Example 1. During the feeding stage into the reaction flask, tetra(4-vinylphenyl)silane in Example 1 was replaced with phenyltris(4-vinylphenyl)silane, and the amount of silicon monomer used was 0.1 mol. Except for the change in the type of silicon monomer used, the amounts of other materials and the operation steps of the polymerization reaction were consistent with Example 1. After the polymerization reaction was completed, post-processing was performed in the same manner as in Example 1 to obtain a copolymer solid. Samples of the product were taken, and the molecular weight and molecular weight distribution, unsaturated double bond content, and silicon content were tested according to the same procedure as in Example 1.

[0075] Comparative Example 1

[0076] Divinylbenzene resin was prepared according to the same procedure as in Example 1. However, during the feeding stage into the reaction flask, the amount of tetrakis(4-vinylphenyl)silane used in Example 1 was changed from 44.1 g (0.1 mol, 0.05 eq, 440.7 Da) to 0, meaning no tetrakis(4-vinylphenyl)silane was added. Except for the change in the amount of tetrakis(4-vinylphenyl)silane during feeding, the amounts of other materials and the operating steps of the polymerization reaction were consistent with Example 1. After the polymerization reaction was completed, post-processing was performed in the same manner as in Example 1 to obtain a copolymer solid. Samples of the product were taken, and the molecular weight and molecular weight distribution, unsaturated double bond content, and silicon content were tested according to the same procedure as in Example 1.

[0077] Comparative Example 2

[0078] Divinylbenzene resin was prepared according to the same procedure as in Example 1. During the feeding stage into the reaction flask, tetra(4-vinylphenyl)silane in Example 1 was replaced with triphenylvinylsilane, and the amount of silicon monomer used was 0.1 mol. Except for the change in the type of silicon monomer used, the amounts of other materials and the operation steps of the polymerization reaction were consistent with Example 1. After the polymerization reaction was completed, post-processing was performed in the same manner as in Example 1 to obtain a copolymer solid. Samples of the product were taken, and the molecular weight and molecular weight distribution, unsaturated double bond content, and silicon content were tested according to the same procedure as in Example 1.

[0079] Comparative Example 3

[0080] Divinylbenzene resin was prepared according to the same procedure as in Example 1. During the feeding stage into the reaction flask, tetra(4-vinylphenyl)silane in Example 1 was replaced with (4-vinylphenyl)trimethoxysilane, and the amount of silicon monomer used was 0.1 mol. Except for the change in the type of silicon monomer used, the amounts of other materials and the operation steps of the polymerization reaction were consistent with Example 1. After the polymerization reaction was completed, post-processing was performed in the same manner as in Example 1 to obtain a copolymer solid. Samples of the product were taken, and the molecular weight and molecular weight distribution, unsaturated double bond content, and silicon content were tested according to the same procedure as in Example 1.

[0081] Comparative Example 4

[0082] Divinylbenzene resin was prepared according to the same procedure as in Example 1. During the feeding stage into the reaction flask, tetra(4-vinylphenyl)silane in Example 1 was replaced with trimethoxyvinylsilane, and the amount of silicon monomer used was 0.1 mol. Except for the change in the type of silicon monomer used, the amounts of other materials and the operation steps of the polymerization reaction were consistent with Example 1. After the polymerization reaction was completed, post-processing was performed in the same manner as in Example 1 to obtain a copolymer solid. Samples of the product were taken, and the molecular weight and molecular weight distribution, unsaturated double bond content, and silicon content were tested according to the same procedure as in Example 1.

[0083] Comparative Example 5

[0084] Divinylbenzene resin was prepared according to the same procedure as in Example 1. During the feeding stage into the reaction flask, tetra(4-vinylphenyl)silane in Example 1 was replaced with tetra(4-vinylphenyl)methane, and the amount of tetra(4-vinylphenyl)methane was 0.1 mol. Except for the change in the type of silicon-containing monomer during feeding, the amounts of other materials and the operation steps of the polymerization reaction were consistent with Example 1. After the polymerization reaction was completed, post-processing was performed in the same manner as in Example 1 to obtain a copolymer solid. Samples of the product were taken, and the molecular weight and molecular weight distribution, unsaturated double bond content, and silicon content were tested according to the same procedure as in Example 1.

[0085] Comparative Example 6

[0086] In a polymerization reactor, 182.3 g (1.4 mol, 130.2 Da) of divinylbenzene, 79.3 g (0.6 mol, 132.2 Da) of ethylvinylbenzene, and 1.2 kg of toluene solvent were added sequentially. After stirring and mixing until completely dissolved, the reaction system was cooled to -10°C. Then, 3.8 g (0.04 mol, 0.02 eq, 96.1 Da) of methanesulfonic acid was added dropwise to the reaction system. The reaction temperature was maintained at -10°C for 4 hours. Then, 44.1 g (0.1 mol, 0.05 eq, 440.7 Da) of tetrakis(4-vinylphenyl)silane was added to the reaction, and the reaction was continued at -10°C for 2 hours. After the reaction was completed, the reaction was treated in the same manner as in Example 1 to obtain a copolymer solid. Samples of the product were taken, and the molecular weight and molecular weight distribution, unsaturated double bond content, and silicon content of the product were tested according to the same procedure as in Example 1.

[0087] Comparative Example 7

[0088] Divinylbenzene resin was prepared according to the same procedure as in Example 1. During the feeding stage into the reaction flask, the molar ratio of divinylbenzene to vinyl ethylbenzene monomers was changed from 0.7:0.3 to 0.35:0.65. Except for the change in the divinylbenzene to vinyl ethylbenzene ratio, the amounts of other materials and the operational steps of the polymerization reaction were consistent with Example 1. After the polymerization reaction was completed, post-processing was performed in the same manner as in Example 1 to obtain a copolymer solid. Samples of the product were taken, and the molecular weight and molecular weight distribution, unsaturated double bond content, and silicon content were tested according to the same procedure as in Example 1.

[0089] Comparative Example 8

[0090] Divinylbenzene resin was prepared according to the same procedure as in Example 1. During the feeding stage into the reaction flask, the molar ratio of divinylbenzene to vinyl ethylbenzene monomers was changed from 0.7:0.3 to 0.93:0.07. Except for the change in the divinylbenzene to vinyl ethylbenzene ratio, the amounts of other materials and the operational steps of the polymerization reaction were consistent with Example 1. After the polymerization reaction was completed, post-processing was performed in the same manner as in Example 1 to obtain a copolymer solid. Samples of the product were taken, and the molecular weight and molecular weight distribution, unsaturated double bond content, and silicon content were tested according to the same procedure as in Example 1.

[0091] Comparative Example 9

[0092] Divinylbenzene resin was prepared according to the same procedure as in Example 1. During the feeding stage into the reaction flask, the amount of benzofuran was changed from 4.7 g (0.04 mol, 0.02 eq, 118.1 Da) in Example 1 to 0, i.e., no benzofuran was added. The amounts of other materials and the operation steps of the polymerization reaction were consistent with Example 1. After the polymerization reaction was completed, each example underwent post-processing in the same manner as in Example 1 to obtain copolymer solids. Samples of the copolymer products obtained from each example were taken, and the molecular weight and molecular weight distribution, unsaturated double bond content, and silicon content of the products were tested according to the same procedure as in Example 1.

[0093] Comparative Example 10

[0094] Divinylbenzene resin was prepared according to the same procedure as in Example 1. During the feeding stage into the reaction flask, the amount of tetra(4-vinylphenyl)silane was changed from 44.1 g (0.1 mol, 0.05 eq, 440.7 Da) in Example 1 to 13.2 g (0.03 mol, 0.0015 eq, 440.7 Da) in Comparative Example 10. Except for the change in the amount of tetra(4-vinylphenyl)silane during feeding, the amounts and ratios of divinylbenzene and vinylethylbenzene, the amount of toluene solvent, and the operational steps of the polymerization reaction were all consistent with Example 1. After the polymerization reaction was completed, each example underwent post-processing in the same manner as in Example 1 to obtain copolymer solids. Samples of the product were taken, and the molecular weight and molecular weight distribution, unsaturated double bond content, and silicon content were tested according to the same procedure as in Example 1.

[0095] The test data of the variables and product resins in the above embodiments and comparative examples were compiled, and the results are shown in Table 1.

[0096] Table 1 Test Results

[0097]

[0098] In the above examples and comparative examples, Examples 1-6 prepared polyvinylbenzene resins with different unsaturated double bond contents by changing the molar ratio of the two monomers, divinylbenzene and vinylethylbenzene. Examples 7-9 prepared resin systems with different silicon contents by changing the amount of tetra(4-vinylphenyl)silane.

[0099] During copolymerization, the modified monomer participates in the main chain extension reaction. Under cationic polymerization conditions, the reactivity ratio of the modified monomer is close to that of divinylbenzene. It is uniformly inserted into the styrene unit of the main chain, and due to steric hindrance, the rigidity of the main chain is enhanced, reducing the degree of freedom of chain segment conformation. This makes it difficult for the double bonds in the side chains to cross the critical reaction distance after initiation, reducing the possibility of intermolecular crosslinking reactions and ensuring the production of linear polyvinylbenzene resin products. The polar groups construct an ordered polar microdomain structure in the resin matrix, possessing a high dipole moment. The solvation effect of the polar microdomains increases the activation energy of the double bonds on the side chains, further reducing side chain crosslinking and avoiding gelation caused by uncontrolled crosslinking.

[0100] In Comparative Examples 1, 3, 4, 5, 6, 8, and 9, after the polymerization reaction was completed, gels appeared in the solution. The resin underwent a certain degree of cross-linking during the reaction. After the gel system was broken up, post-processing was carried out to obtain the resin products of each batch.

[0101] Comparative Examples 2 and 4 experimented with different silicon-containing monomers, but the silicon content in the product resin was low, and the monomers participated poorly in copolymerization.

[0102] Application examples

[0103] For the polymer resin products prepared in each example and comparative example, 20 g of resin was added to 50 g of toluene and stirred in a 60°C constant temperature water bath until completely dissolved. Then, 0.5 g of initiator AIBN was added and stirring continued for 5 minutes to ensure uniform dispersion. Different batches of the resulting resin solutions were coated onto the surface of a glass substrate using a doctor blade. After standing at room temperature for 5 minutes, the substrate was transferred to an 80°C forced-air oven for crosslinking for 30 minutes. The temperature was then increased to 160-180°C and heated for another 20 minutes to remove the solvent. The cured resin sheets were peeled off the substrate and dried under vacuum at 60°C to remove residual solvent until constant weight. The resin sheets were then cut into samples of the required specifications for each test.

[0104] The glass transition temperature of the samples was determined according to the test method in standard GB / T 19466.2-2004; the heat distortion temperature was determined according to the test method in standard GB / T 1634.2-2019; the tensile strength was determined according to the test method in standard GB / T 1040.2-2018; the dielectric constant was determined according to the test method in standard GB / T 31838.8-2024; the notched impact strength was determined according to the test method in standard GB / T 1843-2008; and the flame retardant properties were determined according to the test method in standard GB / T 2408-2021. The test results are shown in Table 2.

[0105] Table 2 Test Results

[0106]

[0107] In the polydivinylbenzene resin proposed in this invention, divinylbenzene provides the unsaturated side chain groups required for crosslinking and gives the cured resin an excellent rigid skeleton; ethyl styrene monomers regularly insert flexible alkyl side chains into the main chain to regulate and improve the thermal processing performance of the material; silicon-containing monomers participate in copolymerization, so that functional groups are bonded to the polymer molecules, reducing the combustion performance of the material. When the temperature reaches the critical threshold, the resin matrix partially decomposes to form a continuous expansion carbonized layer, which physically shields and isolates gas phase heat conduction, while inhibiting the chain reaction of oxidative free radicals, thus achieving flame retardancy.

[0108] Comparative Examples 1-4 explored the effects of different types of silicon-containing monomers. In Comparative Example 1, the polydivinylbenzene resin prepared solely through crosslinking polymerization of divinylbenzene and vinyl ethylbenzene, after curing, showed that the addition of silicon-containing monomers reduced the resin's heat resistance to some extent, resulting in a decrease in its heat distortion temperature; it also improved the resin's mechanical properties, manifested as an increase in tensile strength; the dielectric properties remained largely unchanged. The cured sample of the resin from Example 1 exhibited superior flame retardancy, achieving a V-1 rating, when tested using the vertical method.

[0109] In Comparative Examples 2-4, the polymerization effects of different silicon-containing monomers varied due to differences in their polymerization reactivity and steric hindrance during the reaction. Comparative Examples 2 and 4 experimented with different silicon-containing monomers, but the resulting resins had low silicon content, resulting in poor monomer participation in copolymerization. After curing, the flame retardant properties of the materials were also poor. In Comparative Example 3, the silicon-containing monomer participated in the copolymerization reaction to a higher degree, but due to the low steric hindrance of the monomer molecules, the rigid structure of the material was damaged. The mechanical properties of the resin decreased significantly after curing, and the flame exhibited significant dripping during the combustion test, resulting in a flame retardant performance of only V-2 level.

[0110] In Comparative Example 5, the silicon-containing monomer was replaced with a silicon-free structure with a similar structure. The product had a similar molecular weight and degree of unsaturation as the product of Example 1. However, after cross-linking and curing, it did not show obvious flame retardancy. Based on the phenomena in Comparative Examples 2 to 4, it can be seen that the flame retardant modification ability of the silicon-containing monomer is provided by both steric hindrance and silicon element.

[0111] In Comparative Example 6, after polymerization of divinylbenzene and ethylvinylbenzene, the addition of silicon-containing monomers disrupted the uniform structure of the copolymer. Tests on the product showed that silicon-containing monomers could not be modified for flame retardant properties simply by blending with polyvinylbenzene resin.

[0112] Comparative Examples 7 and 8 demonstrate the performance differences of resins prepared when the ratio of divinylbenzene to vinylethylbenzene monomers is too low or too high. The resin in Comparative Example 7, due to its low DBC value, exhibits poor flame retardancy after crosslinking, reaching only a V-2 rating, with noticeable flame dripping in the corresponding combustion test. The resins in Comparative Examples 8 and 9 show significant crosslinking during copolymerization, generating a large amount of gel. The downstream application of hydrocarbon resins is in the preparation of circuit board substrates, typically involving impregnating fiberglass cloth with a resin solution, followed by curing and drying to prepare the board material. The resins prepared in Comparative Examples 8 and 9 contain a large number of insoluble gel particles, resulting in poor solution fluidity. When used for coating, they exhibit problems such as inability to level and uneven curing, thus failing to meet the requirements of downstream processes.

[0113] In Comparative Example 10, due to the low amount of silicon-containing monomers added, the functional groups had limited effect on optimizing the flame retardant properties of the resin. During the combustion test, the material had a long afterflame time, obvious dripping, and could briefly ignite cotton wool, only reaching the V-2 level.

[0114] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A polydivinylbenzene flame retardant resin characterized in that, It has the structure shown in Equation I: Formula I; In formula I: a: b = (0.7~9): 1, c: (a+b) = (0.02~0.2): 1, d: (a+b) = (0.01~0.05): 1; R is a silicon-containing group, and the structure of the silicon-containing group is shown in Formula II: Formula II; In Formula II: R1, R2, and R3 are independently alkenyl-substituted phenyl groups; The preparation method of the polyvinylbenzene flame retardant resin includes the following steps: mixing divinylbenzene, ethylvinylbenzene, silicon-containing monomer, benzofuran, solvent and catalyst to react and obtain the polyvinylbenzene flame retardant resin.

2. The polyvinylbenzene flame retardant resin according to claim 1, characterized in that, The silicon-containing group has the following structure: 。 3. The method for preparing the polyvinylbenzene flame-retardant resin according to any one of claims 1 to 2, characterized in that, Includes the following steps: Divinylbenzene, ethylvinylbenzene, a silicon-containing monomer, benzofuran, a solvent, and a catalyst are mixed and reacted to obtain the polyvinylbenzene flame-retardant resin; the molar ratio of divinylbenzene to ethylvinylbenzene is (0.7~9):1; the molar amount of the silicon-containing monomer is 0.02~0.2 times the sum of the molar amounts of divinylbenzene and ethylvinylbenzene; the molar amount of the benzofuran is 0.01~0.5 times the sum of the molar amounts of divinylbenzene and ethylvinylbenzene. The structure of the silicon-containing monomer is shown in Formula III: Formula III; In Formula III, R1, R2, and R3 are independently alkenyl-substituted phenyl groups.

4. The preparation method according to claim 3, characterized in that, The solvent is an aprotic solvent.

5. The preparation method according to claim 4, characterized in that, The aprotic solvent includes one or more of toluene, benzene, chlorobenzene, xylene, dichlorobenzene, chloroform, and carbon tetrachloride; the mass of the solvent is 2 to 10 times the sum of the masses of divinylbenzene, ethylvinylbenzene, silicon-containing monomers, and benzofuran.

6. The preparation method according to claim 3, characterized in that, The catalyst is a protic acid.

7. The preparation method according to claim 6, characterized in that, The protic acid includes one or more of methanesulfonic acid, trifluoromethanesulfonic acid, sulfuric acid, and hydrogen chloride.

8. The preparation method according to claim 3, 6 or 7, characterized in that, The molar amount of the catalyst is 0.001 to 0.1 times the sum of the molar amounts of divinylbenzene and ethylvinylbenzene.

9. The preparation method according to claim 3, characterized in that, The reaction temperature is -30~20℃, and the time is 1~12h.

10. A cured polyvinylbenzene flame-retardant resin, characterized in that, It is obtained by curing the polydivinylbenzene flame retardant resin according to claim 1 or 2 or the polydivinylbenzene flame retardant resin prepared by any one of claims 3 to 9.

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