Preparation method of titanium dioxide-based synergistic flame-retardant filler and application thereof in environment-friendly copper-clad plate

Abstract

The application discloses a preparation method of a titanium dioxide-based synergistic flame-retardant filler and application of the titanium dioxide-based synergistic flame-retardant filler in an environmentally-friendly copper-clad plate, and belongs to the technical field of copper-clad plate materials. In order to solve the technical problems that the existing titanium dioxide flame-retardant filler has low flame-retardant efficiency, poor compatibility with resin, weak synergistic effect, and the environmentally-friendly copper-clad plate is difficult to have multiple performances, the following technical scheme is adopted: firstly, titanium dioxide powder is surface-activated through a silane coupling agent; then, phosphorus-based flame-retardant monomers, nitrogen-based flame-retardant monomers and an aluminum source are added; through in-situ compounding and chemical grafting reaction, a titanium dioxide-based synergistic flame-retardant filler loaded with phosphorus, nitrogen and aluminum elements is prepared; the filler is mixed with an environmentally-friendly resin, a curing agent and an accelerator to prepare a resin glue solution; a prepreg is prepared through impregnation of a reinforcing material and drying; and the environmentally-friendly copper-clad plate is obtained through lamination and hot pressing of a copper foil.

Description

Technical Field

[0001] This invention belongs to the technical field of copper clad laminate materials, specifically relating to a method for preparing a titanium dioxide-based synergistic flame-retardant filler and its application in environmentally friendly copper clad laminates. Background Technology

[0002] Environmentally friendly copper-clad laminates (CCLs) are a core material in the electronics and information industry, widely used in various electronic terminal products such as smartphones, computers, and communication equipment. Their flame-retardant properties, environmental friendliness, mechanical properties, and dielectric properties directly determine the safety and reliability of electronic devices. With the miniaturization, high-frequency operation, and high-power development of electronic devices, and the increasingly stringent global environmental regulations, halogen-free, low-smoke, low-toxicity, highly flame-retardant, and highly heat-resistant environmentally friendly CCLs have become a core trend in the industry.

[0003] Flame-retardant fillers are key components for improving the flame-retardant performance of environmentally friendly copper-clad laminates. Currently, commonly used halogen-free flame-retardant fillers in the industry mainly include phosphorus-based, nitrogen-based, and metal oxide-based fillers. Among them, titanium dioxide (TiO2), as an environmentally friendly metal oxide, has the characteristics of being non-toxic, high-temperature resistant, and having excellent mechanical properties. At the same time, it can catalyze polymers to form char and form a heat insulation barrier during combustion, thus possessing certain flame-retardant potential and attracting widespread attention.

[0004] For example, patent CN116656111A discloses a resin composition with excellent compatibility and its application, which uses titanium dioxide as one of the inorganic fillers. However, it is simply added without flame-retardant modification, thus failing to exert a synergistic flame-retardant effect. Furthermore, it requires the addition of other flame retardants to achieve the desired flame-retardant effect, resulting in low flame-retardant efficiency and high addition amounts. Patent CN202410315592.X discloses a halogen-free flame-retardant black epoxy resin composition and a light-shielding copper-clad laminate, which adds titanium dioxide as one of its components. However, the titanium dioxide mainly serves a light-shielding function and is not designed for synergistic flame-retardant modification. The flame-retardant performance depends on the individual action of phosphorus-containing flame retardants, resulting in poor synergistic effect. Patent CN111021077A discloses a flame-retardant textile fabric coating, which adds titanium dioxide and antimony trioxide, etc., but this is merely a physical mixture. Titanium dioxide has poor compatibility with other flame retardants, and its application is limited to textile fabrics, making it unsuitable for use in environmentally friendly copper-clad laminates due to poor compatibility with the resin system of copper-clad laminates.

[0005] However, the application of titanium dioxide in environmentally friendly copper-clad laminates has significant shortcomings in the current technology: First, titanium dioxide alone has low flame retardant efficiency, requiring high addition levels to achieve the expected flame retardant effect. However, high addition levels can easily lead to filler agglomeration, damaging the mechanical strength, processing performance, and dielectric properties of the copper-clad laminate. Second, the surface of titanium dioxide is inert, resulting in poor compatibility with environmentally friendly resins such as epoxy resin and phenolic resin used in copper-clad laminates. This can easily lead to problems such as precipitation and delamination, affecting the long-term stability of the copper-clad laminate. Third, existing modified titanium dioxide flame retardant fillers mostly use single-element modification (such as only phosphorus-based or silicon-based modification) or simple physical mixing and synergy. The synergistic effect between flame retardant elements is weak, making it difficult to simultaneously meet the requirements of high flame retardancy, high heat resistance, and high dielectric properties. Fourth, some modification processes are complex and easily generate waste during preparation, which does not meet the requirements of green production.

[0006] Furthermore, existing modified titanium dioxide for plastics aims to improve thermal stability and dispersibility, but it is not specifically designed to adapt to the resin system and flame retardant requirements of copper clad laminates, making it difficult to meet the stringent requirements of environmentally friendly copper clad laminates for high flame retardancy and low dielectric loss.

[0007] Therefore, developing a titanium dioxide-based synergistic flame-retardant filler that is simple to process, environmentally friendly, and can achieve efficient synergy of flame-retardant elements while improving compatibility with the resin matrix, as well as its application method for environmentally friendly copper-clad laminates, to overcome the shortcomings of existing technologies, has important practical significance and industrial application value. Summary of the Invention

[0008] To address the shortcomings of existing technologies, such as low flame retardant efficiency, poor compatibility with resins, weak synergistic effect of titanium dioxide flame retardant fillers, and the difficulty in achieving high flame retardancy, high heat resistance, and high dielectric properties in environmentally friendly copper clad laminates, this invention provides a method for preparing a titanium dioxide-based synergistic flame retardant filler and its application in environmentally friendly copper clad laminates. This preparation method is simple, green, and controllable. The resulting flame retardant filler has high flame retardant efficiency and good compatibility. When applied to environmentally friendly copper clad laminates, it can achieve a synergistic improvement in flame retardancy, heat resistance, mechanical properties, and dielectric properties, while meeting halogen-free environmental protection requirements. This method is significantly different from existing technologies and possesses outstanding inventiveness and practicality.

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

[0010] A method for preparing a titanium dioxide-based synergistic flame-retardant filler includes the following steps:

[0011] (1) Surface activation treatment: Titanium dioxide powder is dispersed in a solvent, and a silane coupling agent is added for surface activation treatment to obtain activated titanium dioxide dispersion.

[0012] In this step, nano-sized titanium dioxide (particle size 50-200 nm) is selected as the titanium dioxide powder. Nano-sized titanium dioxide has a large specific surface area and strong catalytic carbonization ability, which can enhance the flame retardant synergistic effect. Anhydrous ethanol, deionized water, or an ethanol-water mixture are selected as the solvent, with an ethanol-water mixture being preferred. This ensures uniform dispersion of titanium dioxide and promotes the hydrolysis of the silane coupling agent. An aminosilane coupling agent (such as KH550 or KH792) is selected as the silane coupling agent. The aminosilane coupling agent can introduce amino active groups onto the surface of titanium dioxide, improving its surface activity and providing reaction sites for subsequent chemical grafting of phosphorus, nitrogen, and aluminum elements, thus solving the problems of surface inertness and poor compatibility of existing titanium dioxide. The mass ratio of silane coupling agent to titanium dioxide powder is 1:10-50. This ratio ensures sufficient activation of the titanium dioxide surface while avoiding agglomeration caused by excessive silane coupling agent. The activation conditions are: stirring at room temperature for 1-3 hours at a stirring speed of 300-800 r / min to ensure that the silane coupling agent reacts fully with the surface of titanium dioxide.

[0013] (2) In-situ composite and chemical grafting: Phosphorus-based flame retardant monomers, nitrogen-based flame retardant monomers and aluminum source are added to the activated titanium dioxide dispersion, the pH value of the system is adjusted, the temperature is raised to the reaction temperature and kept at the temperature to achieve chemical grafting and in-situ composite of phosphorus, nitrogen and aluminum elements on the surface of titanium dioxide.

[0014] This step is the core innovation step, breaking the traditional single-element modification or physical mixing synergy mode, and constructing a quaternary synergistic system of "TiO2 (catalytic char formation + heat insulation) - phosphorus (flame retardant main effect) - nitrogen (smoke suppression + synergistic effect) - aluminum (heat resistance + enhanced char layer)" to improve flame retardant efficiency and heat resistance performance by utilizing the synergistic effect of each element. Among them, phosphorus-based flame retardant monomers are selected from phosphate ester monomers (such as ethyl dihydrogen phosphate and triphenyl phosphate) or phosphonic acid monomers (such as methylphosphonic acid and phenylphosphonic acid). During combustion, they can release flame retardant substances such as phosphoric acid and polyphosphoric acid, catalyze the polymer to form char and form a char layer barrier, and inhibit the release of combustible gases. Nitrogen-based flame retardant monomers are selected from melamine derivatives (such as melamine-formaldehyde resin and melamine cyanurate) or urea-formaldehyde monomers. During combustion, they can release inert gases such as ammonia and nitrogen, dilute the concentration of combustible gases, absorb heat, inhibit the combustion chain reaction, and form a phosphorus-nitrogen synergistic flame retardant effect with phosphorus elements, improve flame retardant efficiency and reduce smoke and toxic release. The aluminum source is selected from inorganic aluminum salts (such as aluminum chloride and aluminum sulfate) or aluminum hydroxide. Aluminum elements can form an aluminum oxide or aluminum hydroxide protective layer on the surface of titanium dioxide, improve the heat resistance and thermal stability of the filler, and enhance the density of the char layer during combustion, reduce char layer cracking, and further improve the heat insulation and oxygen barrier effects.

[0015] The total mass ratio of phosphorus-based flame retardant monomers, nitrogen-based flame retardant monomers, aluminum source, and titanium dioxide powder is 1:0.5-2:0.3-1:1-3. This ratio ensures full composite formation of each flame retardant element, maximizing synergistic effects while avoiding compatibility degradation or performance imbalance caused by excessive amounts of any single element. The pH of the system is adjusted to 4-8, preferably 5-7. This pH range promotes the hydrolysis and grafting reactions of the phosphorus-based and nitrogen-based flame retardant monomers, while ensuring uniform dispersion and reaction of the aluminum source. The reaction temperature is 60-120℃, and the reaction time is 2-8 hours. The reaction temperature and time can be adjusted according to the type of monomer and the degree of reaction to ensure sufficient chemical grafting and uniform in-situ composite formation. Compared with existing physical mixing methods, chemical grafting and in-situ composite formation enable each flame retardant element to form a stable chemical bond structure with titanium dioxide, preventing the precipitation of flame retardant elements and improving long-term stability.

[0016] (3) Post-processing: After the reaction is completed, the product is separated, washed, dried and pulverized to obtain titanium dioxide-based synergistic flame retardant filler.

[0017] In this step, centrifugal separation or filtration separation is selected as the separation method, with centrifugal separation being preferred due to its high separation efficiency and reduced product loss. Washing involves alternating between deionized water and anhydrous ethanol 2-3 times to remove unreacted monomers, silane coupling agents, and impurities, ensuring the purity of the packing material. The drying temperature is 80-120℃, and the drying time is 4-12 hours, which removes moisture and residual solvents from the product. Pulverization is performed using air jet milling, resulting in a packing material particle size of 100-500 nm after pulverization, ensuring good dispersibility and preventing agglomeration.

[0018] Furthermore, the present invention also provides a titanium dioxide-based synergistic flame retardant filler obtained by the above preparation method. The filler uses titanium dioxide as a matrix, and phosphorus, nitrogen and aluminum flame retardant elements are loaded on the surface through chemical grafting and in-situ composite method to form a stable quaternary synergistic flame retardant system. It has the characteristics of high flame retardant efficiency, good thermal stability, excellent compatibility with resin, halogen-free and environmentally friendly, 1% thermal decomposition temperature ≥300℃, limiting oxygen index ≥35%, which can effectively solve the shortcomings of existing modified titanium dioxide fillers.

[0019] Furthermore, the present invention also provides the application of the above-mentioned titanium dioxide-based synergistic flame-retardant filler in environmentally friendly copper-clad laminates, and the specific application method includes the following steps:

[0020] S1. Preparation of resin solution: The titanium dioxide-based synergistic flame retardant filler is mixed with environmentally friendly resin, curing agent and accelerator, stirred evenly and then ultrasonically dispersed to obtain resin solution.

[0021] In this step, the environmentally friendly resin is selected from one or more of halogen-free epoxy resin, phenolic resin, or polyphenylene ether resin. A blend of halogen-free epoxy resin and polyphenylene ether resin is preferred, balancing mechanical and dielectric properties to meet the halogen-free requirements of environmentally friendly copper-clad laminates. The curing agent is an amine-based curing agent (such as dicyandiamide or diaminodiphenylmethane) or an anhydride-based curing agent, and the accelerator is an imidazole-based accelerator (such as 2-methylimidazole). The mass ratio of curing agent to environmentally friendly resin is 1:5-10, and the amount of accelerator added is 0.5%-2% of the mass of the environmentally friendly resin. This ensures full curing of the resin and improves the mechanical strength and thermal stability of the copper-clad laminate. The titanium dioxide-based synergistic flame-retardant filler has a mass fraction of 10%-30% in the resin solution. This addition amount ensures that the copper-clad laminate meets the UL94 V-0 flame-retardant standard while avoiding the decrease in dielectric properties and processing difficulties caused by high addition amounts. Compared with existing single flame-retardant fillers, the addition amount can be reduced by 20%-30%. The ultrasonic dispersion treatment conditions are: ultrasonic frequency of 40-80kHz and ultrasonic time of 30-60min, to ensure that the filler is uniformly dispersed in the resin solution and to avoid agglomeration.

[0022] S2. Preparation of semi-cured sheet: The reinforcing material is impregnated in the resin solution, the impregnation time and temperature are controlled, and after drying, a semi-cured sheet is obtained.

[0023] In this step, electronic-grade fiberglass cloth (such as E-grade or D-grade fiberglass cloth) is used as the reinforcing material. The impregnation temperature is 25-40℃, and the impregnation time is 5-15 minutes to ensure that the reinforcing material is fully impregnated with the resin. The drying conditions are as follows: first, dry at 80-100℃ for 1-2 hours to remove moisture and low-boiling-point solvents from the resin, and then dry at 120-140℃ for 2-4 hours to allow the resin to initially cure. The gel time of the prepreg is controlled to be 100-300 seconds to ensure the subsequent hot pressing effect. The resin content of the prepreg is 40%-60%, which can balance mechanical strength and dielectric properties.

[0024] S3. Hot pressing: The prepreg sheets are stacked to the required thickness, covered with copper foil on both sides, and placed in a hot press. The hot pressing temperature, hot pressing pressure and heat and pressure holding time are controlled. After hot pressing, the sheets are cooled to room temperature to obtain an environmentally friendly copper-clad laminate.

[0025] In this step, electrolytic copper foil or rolled copper foil is selected, with a thickness of 12-70μm; the hot pressing temperature is 160-220℃, the pressure is 10-30MPa, and the holding time is 1-3h. The hot pressing process adopts a gradient heating method (such as holding at 160℃ for 30min, 180℃ for 30min, and 200℃ for 60min) to ensure that the resin is fully cured, reduce bubbles and defects inside the copper-clad laminate, and improve the density and mechanical properties of the copper-clad laminate.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] Breaking away from the traditional model of single-element modification or physical mixing synergy, a quaternary synergistic flame-retardant system of "TiO2-phosphorus-nitrogen-aluminum" is constructed. Through a combination of chemical grafting and in-situ composite, each flame-retardant element forms a stable chemical bond structure with titanium dioxide, solving the problems of weak synergistic effect and easy precipitation of flame-retardant elements in existing modified titanium dioxide fillers. At the same time, a special adaptation design is made for the resin system of environmentally friendly copper clad laminates, taking into account both flame-retardant performance and dielectric properties. This is different from existing modified titanium dioxide materials used in plastics and textiles, and also different from copper clad laminate flame-retardant solutions that simply add titanium dioxide.

[0028] In the quaternary synergistic system, TiO2 catalyzes polymer char formation and forms a heat insulation barrier, phosphorus plays a major role in flame retardancy, nitrogen has a synergistic effect in smoke suppression and reduces the release of toxic smoke, and aluminum enhances heat resistance and strengthens the density of the char layer. The four components work synergistically and complement each other to achieve a flame retardant effect of "1+1+1+1>4". Compared with existing single modified titanium dioxide fillers, the flame retardant efficiency is improved by more than 30%, and the amount added is reduced by 20%-30%. This allows environmentally friendly copper clad laminates to easily meet the UL94 V-0 flame retardant standard with a limiting oxygen index ≥35%.

[0029] Surface activation treatment of titanium dioxide using aminosilane coupling agents introduces active groups onto its surface. Simultaneously, chemically grafted phosphorus, nitrogen, and aluminum elements improve the oleophilicity of the filler, effectively enhancing its compatibility with environmentally friendly resins (epoxy resin, polyphenylene ether resin, etc.), preventing filler agglomeration and precipitation, and solving the technical pain point of poor compatibility between existing titanium dioxide and resins. This improves the long-term stability and processing performance of copper clad laminates. Attached Figure Description

[0030] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0031] Figure 1 The infrared spectrum of the titanium dioxide-based synergistic flame-retardant filler prepared in this invention is shown. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1

[0034] A method for preparing a titanium dioxide-based synergistic flame-retardant filler, the specific steps of which are as follows:

[0035] (1) Surface activation treatment: Take 10g of nano titanium dioxide powder (particle size of 50-100nm), disperse it in 100mL of ethanol-water mixture (volume ratio of ethanol to water is 1:1), add 1g of aminosilane coupling agent KH550, stir at 500r / min for 2h at room temperature to obtain activated titanium dioxide dispersion.

[0036] (2) In-situ composite and chemical grafting: Add 5g of ethyl dihydrogen phosphate (phosphorus flame retardant monomer), 8g of melamine formaldehyde resin (nitrogen flame retardant monomer) and 3g of aluminum chloride (aluminum source) to the above activated titanium dioxide dispersion. Adjust the pH of the system to 6 with dilute hydrochloric acid, raise the temperature to 80℃, and keep the reaction at this temperature for 4h to achieve chemical grafting and in-situ composite of phosphorus, nitrogen and aluminum elements on the surface of titanium dioxide.

[0037] (3) Post-processing: After the reaction is completed, the product is obtained by centrifugation (5000 r / min for 10 min), washed three times with deionized water and anhydrous ethanol, placed in an oven and dried at 100℃ for 6 h, and then pulverized by air jet to obtain titanium dioxide-based synergistic flame retardant filler with a particle size of 100-300 nm.

[0038] The specific steps for applying the above-mentioned titanium dioxide-based synergistic flame-retardant filler in environmentally friendly copper-clad laminates are as follows:

[0039] S1. Preparation of resin solution: Take 100g of halogen-free epoxy resin (E-51), 20g of dicyandiamide (curing agent), and 1g of 2-methylimidazole (accelerator), mix them evenly, add 20g of the titanium dioxide-based synergistic flame retardant filler prepared above, stir for 30min, and then disperse with 60kHz ultrasound for 40min to obtain resin solution.

[0040] S2. Preparation of semi-cured sheet: E-glass fiber cloth is impregnated in the above resin solution, impregnated at 30°C for 10 min, dried at 90°C for 1.5 h, and then dried at 130°C for 3 h to obtain a semi-cured sheet (resin content is 50%).

[0041] S3. Hot pressing: Four prepreg sheets are stacked together, and 35μm thick electrolytic copper foil is placed on both sides. They are then placed in a hot press and hot pressed using a gradient heating method: 160℃ for 30min, 180℃ for 30min, and 200℃ for 60min. The hot pressing pressure is 20MPa. After hot pressing, the sheets are cooled to room temperature to obtain an environmentally friendly copper-clad laminate.

[0042] Example 2

[0043] A method for preparing a titanium dioxide-based synergistic flame-retardant filler, the specific steps of which are as follows:

[0044] (1) Surface activation treatment: Take 10g of nano titanium dioxide powder (particle size of 100-200nm), disperse it in 120mL of ethanol-water mixture (volume ratio of ethanol to water is 2:1), add 0.5g of aminosilane coupling agent KH792, stir at 300r / min for 3h at room temperature to obtain activated titanium dioxide dispersion.

[0045] (2) In-situ composite and chemical grafting: Add 10g phenylphosphonic acid (phosphorus flame retardant monomer), 5g melamine cyanurate (nitrogen flame retardant monomer) and 5g aluminum hydroxide (aluminum source) to the above activated titanium dioxide dispersion. Adjust the pH of the system to 7 with dilute sodium hydroxide solution, raise the temperature to 100℃, and keep the reaction at this temperature for 3h to achieve chemical grafting and in-situ composite of phosphorus, nitrogen and aluminum elements on the surface of titanium dioxide.

[0046] (3) Post-processing: After the reaction is completed, the product is separated by filtration, washed twice with deionized water and anhydrous ethanol, placed in an oven and dried at 120°C for 4 hours. After air jet pulverization, titanium dioxide-based synergistic flame retardant filler with a particle size of 200-400 nm is obtained.

[0047] The specific steps for applying the above-mentioned titanium dioxide-based synergistic flame-retardant filler in environmentally friendly copper-clad laminates are as follows:

[0048] S1. Preparation of resin solution: Take 80g of halogen-free epoxy resin (E-44), 20g of polyphenylene ether resin, 18g of diaminodiphenylmethane (curing agent), and 1.2g of 2-methylimidazole (accelerator), mix them evenly, add 25g of the titanium dioxide-based synergistic flame retardant filler prepared above, stir for 40min, and then disperse with ultrasonication at 40kHz for 60min to obtain the resin solution.

[0049] S2. Preparation of semi-cured sheet: D glass fiber cloth is impregnated in the above resin solution, impregnated at 25°C for 15 min, dried at 80°C for 2 h, and then dried at 120°C for 4 h to obtain a semi-cured sheet (resin content is 45%).

[0050] S3. Hot pressing: Stack 5 of the above-mentioned semi-cured sheets together, cover both sides with 50μm thick rolled copper foil, put them into a hot press, and hot press using a gradient heating method: 160℃ for 30min, 190℃ for 30min, 210℃ for 60min, hot pressing pressure is 25MPa. After hot pressing, cool to room temperature to obtain environmentally friendly copper-clad laminate.

[0051] Example 3

[0052] A method for preparing a titanium dioxide-based synergistic flame-retardant filler, the specific steps of which are as follows:

[0053] (1) Surface activation treatment: Take 10g of nano titanium dioxide powder (particle size of 80-150nm), disperse it in 80mL of anhydrous ethanol, add 0.2g of aminosilane coupling agent KH550, stir at 800r / min for 1h at room temperature to obtain activated titanium dioxide dispersion.

[0054] (2) In-situ composite and chemical grafting: Add 8g of triphenyl phosphate (phosphorus flame retardant monomer), 10g of urea-formaldehyde resin (nitrogen flame retardant monomer) and 2g of aluminum sulfate (aluminum source) to the above activated titanium dioxide dispersion. Adjust the pH of the system to 5 with dilute hydrochloric acid, raise the temperature to 60℃, and keep the reaction at this temperature for 8h to achieve chemical grafting and in-situ composite of phosphorus, nitrogen and aluminum elements on the surface of titanium dioxide.

[0055] (3) Post-processing: After the reaction is completed, the product is obtained by centrifugation (6000 r / min for 8 min), washed three times with deionized water and anhydrous ethanol, placed in an oven and dried at 80°C for 12 h, and then pulverized by air jet to obtain titanium dioxide-based synergistic flame retardant filler with a particle size of 300-500 nm.

[0056] The specific steps for applying the above-mentioned titanium dioxide-based synergistic flame-retardant filler in environmentally friendly copper-clad laminates are as follows:

[0057] S1. Preparation of resin solution: Take 100g of phenolic resin, 22g of dicyandiamide (curing agent), and 0.8g of 2-methylimidazole (accelerator), mix them evenly, add 15g of the titanium dioxide-based synergistic flame retardant filler prepared above, stir for 20min, and then disperse with ultrasonication at 80kHz for 30min to obtain resin solution.

[0058] S2. Preparation of semi-cured sheet: E-glass fiber cloth is impregnated in the above resin solution, impregnated at 40°C for 5 min, dried at 100°C for 1 h, and then dried at 140°C for 2 h to obtain a semi-cured sheet (resin content is 55%).

[0059] S3. Hot pressing: Stack three prepreg sheets as described above, cover both sides with 12μm thick electrolytic copper foil, place them in a hot press, and hot press using a gradient heating method: hold at 160℃ for 30min, hold at 170℃ for 30min, hold at 190℃ for 60min, and the hot pressing pressure is 15MPa. After hot pressing, cool to room temperature to obtain an environmentally friendly copper-clad laminate.

[0060] Comparative Example 1

[0061] The preparation method differs from that of Example 1: only 5g of ethyl dihydrogen phosphate is added in step (2), and melamine-formaldehyde resin and aluminum chloride are not added. The remaining steps are exactly the same as in Example 1, and a single phosphorus-modified titanium dioxide filler is obtained. The application method is exactly the same as in Example 1, and environmentally friendly copper-clad laminate is prepared.

[0062] Comparative Example 2

[0063] The preparation method differs from Example 1: no surface activation treatment or in-situ composite grafting is performed. 10g of nano titanium dioxide, 5g of ethyl dihydrogen phosphate, 8g of melamine-formaldehyde resin, 3g of aluminum chloride, and 1g of KH550 are directly mixed evenly and then pulverized to obtain a physically mixed synergistic flame-retardant filler. The application method is exactly the same as in Example 1 to prepare environmentally friendly copper-clad laminates.

[0064] Comparative Example 3

[0065] Preparation method: Instead of using the titanium dioxide-based synergistic flame retardant filler of the present invention, conventional titanium dioxide (unmodified) is used as the inorganic filler, combined with 6g of phosphorus-containing flame retardant (triphenyl phosphate), and the remaining resin components are the same as in Example 1; the application method is exactly the same as in Example 1 to prepare environmentally friendly copper-clad laminate.

[0066] Performance testing structure

[0067] As can be seen from the above test results, the titanium dioxide-based synergistic flame-retardant fillers prepared in Examples 1-3 of the present invention have significantly better thermal stability and flame-retardant efficiency than comparative examples 1-3. The 1% thermal decomposition temperature is ≥310℃ and the limiting oxygen index is ≥36%. The environmentally friendly copper-clad laminates using the flame-retardant fillers of the present invention all achieve UL94 V-0 flame retardant rating, flexural strength ≥122MPa, dielectric constant ≤4.4, and dielectric loss ≤0.018. All performance characteristics are better than those of comparative examples 1-3.

[0068] Among them, Comparative Example 1 (single phosphorus-based modification) has poor flame retardant efficiency and thermal stability due to the lack of synergistic effect of nitrogen and aluminum elements; Comparative Example 2 (physical mixing) has weak synergistic effect and poor compatibility due to the lack of chemical bonding between the flame retardant elements, resulting in a decrease in the mechanical and dielectric properties of the copper clad laminate; Comparative Example 3 (existing technology) has low flame retardant efficiency due to the use of unmodified titanium dioxide and a single phosphorus-containing flame retardant, and the poor compatibility between titanium dioxide and resin results in unsatisfactory performance of the copper clad laminate.

[0069] In summary, the titanium dioxide-based synergistic flame-retardant filler prepared by this invention solves many pain points of the prior art through a quaternary synergistic system and chemical grafting modification. When applied to environmentally friendly copper clad laminates, it can achieve synergistic improvement of various properties, and has outstanding inventiveness, practicality and industrial application value.

[0070] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a titanium dioxide-based synergistic flame-retardant filler, characterized in that, Includes the following steps: (1) Disperse titanium dioxide powder in a solvent, add silane coupling agent for surface activation treatment, and obtain activated titanium dioxide dispersion; (2) Add phosphorus-based flame retardant monomer, nitrogen-based flame retardant monomer and aluminum source to the activated titanium dioxide dispersion, adjust the pH value of the system, raise the temperature to the reaction temperature and keep the reaction at the temperature to achieve chemical grafting and in-situ composite of phosphorus, nitrogen and aluminum elements on the surface of titanium dioxide. (3) After the reaction is completed, the product is separated, washed, dried and pulverized to obtain titanium dioxide-based synergistic flame retardant filler.

2. The preparation method according to claim 1, characterized in that, The silane coupling agent is an aminosilane coupling agent, and the mass ratio of the aminosilane coupling agent to titanium dioxide powder is 1:10-50.

3. The preparation method according to claim 1, characterized in that, The phosphorus-based flame retardant monomer is a phosphate ester monomer or a phosphonic acid monomer, the nitrogen-based flame retardant monomer is a melamine derivative or a urea-formaldehyde monomer, and the aluminum source is an inorganic aluminum salt or aluminum hydroxide.

4. The preparation method according to claim 1, characterized in that, In step (2), the total mass ratio of the phosphorus-based flame retardant monomer, the nitrogen-based flame retardant monomer, the aluminum source and the titanium dioxide powder is 1:0.5-2:0.3-1:1-3.

5. The preparation method according to claim 1, characterized in that, In step (2), the reaction temperature is 60-120℃ and the heat preservation reaction time is 2-8h; in step (3), the drying temperature is 80-120℃ and the drying time is 4-12h.

6. A titanium dioxide-based synergistic flame-retardant filler obtained by the preparation method according to any one of claims 1-5.

7. The application of the titanium dioxide-based synergistic flame-retardant filler as described in claim 6 in environmentally friendly copper-clad laminates, characterized in that, The titanium dioxide-based synergistic flame-retardant filler is mixed with environmentally friendly resin, curing agent, and accelerator to prepare a resin solution; the reinforcing material is impregnated in the resin solution and dried to obtain a semi-cured sheet; the semi-cured sheets are stacked, covered with copper foil on both sides, and hot-pressed to obtain an environmentally friendly copper-clad laminate.

8. The application according to claim 7, characterized in that, The environmentally friendly resin is one or more of halogen-free epoxy resin, phenolic resin, or polyphenylene ether resin; the mass fraction of the titanium dioxide-based synergistic flame retardant filler in the resin solution is 10%-30%.

9. The application according to claim 7, characterized in that, The hot pressing temperature is 160-220℃, the pressure is 10-30MPa, and the holding time is 1-3h.

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