Flame-retardant polyphenyl ether foam material and preparation method thereof

Abstract

The invention provides a flame-retardant polyphenyl ether foam material and a preparation method thereof, the flame-retardant polyphenyl ether foam material is prepared by foaming a polyphenyl ether composition, and the polyphenyl ether composition comprises the following raw materials by weight: 30-80 parts of polyphenyl ether, 20-70 parts of polystyrene, 4-12 parts of an aromatic phosphate flame retardant, and 4-12 parts of a high molecular weight brominated flame retardant, the mass ratio of the aromatic phosphate flame retardant to the high-molecular-weight brominated flame retardant is 0.5-2, the thermal decomposition temperature of the aromatic phosphate flame retardant is 320-470 DEG C, the thermal decomposition temperature of the high-molecular-weight brominated flame retardant is 350-530 DEG C, and the aromatic phosphate flame retardant and the high-molecular-weight brominated flame retardant form a compound flame-retardant system with a gas-phase flame-retardant mechanism. The problems that in the prior art, as the foaming ratio is increased and the carbon layer continuity is reduced, the flame retardant property of the PPO composite foam is poor, and as the addition amount is increased, the melt strength is greatly reduced and the foaming property is reduced when a traditional phosphate flame retardant is independently used due to the strong plasticizing effect of the traditional phosphate flame retardant are solved.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a flame-retardant polyphenylene ether foam material and its preparation method. Background Technology

[0002] Polymer foams are widely used in packaging, construction, and electronic equipment industries due to their advantages such as low density, excellent thermal and sound insulation, high energy absorption, and light weight. In construction, cables, and electronic equipment, flame retardancy and mechanical properties have always been important safety factors. Polyphenylene oxide (PPO) is a high-temperature resistant thermoplastic non-crystalline engineering plastic, one of the five major thermoplastic engineering plastics. Its glass transition temperature (T0) is... g The temperature range is 210℃, and it has a high limiting oxygen index (LOI) of approximately 29.8%. It exhibits good self-extinguishing properties, achieving a UL-94 rating of V-0. Although PPO boasts excellent flame retardant properties and controllable cost, its high melt viscosity makes processing difficult. Most commercially available PPO is a blend of PPO and polystyrene (PS). Polystyrene (PS) is a transparent, thermoplastic, non-crystalline general-purpose plastic with a glass transition temperature (T0). g Its temperature is approximately 100℃. Its limiting oxygen index (LOI) is low, around 18.0%, making it highly flammable. In the UL-94 vertical burning test, pure PS typically achieves an HB rating. Blending the two can reduce viscosity and improve the processing properties of PPO, but the flammability of PS significantly reduces the flame retardant properties of the blend. Therefore, flame retardant modification of PPO / PS blends is an essential requirement.

[0003] European Patent EP 0552355B1 discloses a flame-retardant conductive polyphenylene ether-based composition and its preparation method. The method uses polyphenylene ether resin and polystyrene resin as base materials, and combines glass fiber, inorganic non-fiber dimensional stabilizer, carbon-based conductive material and diphosphate / polyphosphate flame retardant. The synergistic effect of each component gives the composition good conductivity, flame retardancy, dimensional stability and mechanical properties.

[0004] European Patent EP 1424356B1 discloses a flame-retardant thermoplastic resin composition and its preparation method. The method uses polyphenylene ether resin and high-impact polystyrene resin as base materials, and combines organophosphates (such as resorcinol diphenyl bisphosphate and bisphenol A diphenyl bisphosphate) and polyols (such as pentaerythritol) as flame-retardant systems. While reducing the amount of organophosphates used, it achieves good flame-retardant properties, flow properties and cantilever beam impact strength, without affecting the heat distortion temperature.

[0005] US Patent 2006 / 0041046A1 discloses a flame-retardant polyphenylene ether composition and its preparation method. The method uses polyphenylene ether (a rubber-modified vinyl aromatic resin that can be compounded) as a base material and adds a low-melting-point glass containing phosphate (containing RO, R2'O and other components, where R is a divalent metal and R' is an alkali metal) as a flame-retardant system. It achieves good flame-retardant performance and low smoke density while maintaining a high heat distortion temperature, without reducing or eliminating the use of traditional phosphate ester flame retardants.

[0006] European Patent EP 0244393A2 discloses a flame-retardant polyphenylene ether molding composition and its preparation method. The method uses polyphenylene ether resin and rubber-modified high-impact polystyrene as the base material, and compounded with polybrominated triphenyl phosphate (bromine-to-phosphorus ratio 3-10) as a flame retardant. Without the need to add antimony or other synergists, V-0 flame retardant performance can be achieved with a low dosage (8-15 parts by weight). It also has excellent processing fluidity, impact strength, high heat distortion temperature and stress cracking resistance, and no smoke or seepage problems during molding.

[0007] The aforementioned studies mostly focus on unfoamed PPO / PS products, using phosphate ester flame retardants and their compounded flame retardants to supplement the thickness of the char layer. However, for foamed materials, due to the introduction of the cell structure and the increase in foaming ratio, the continuity of the char layer formed by the blend will be significantly reduced. Even if the addition of flame retardants supplements the integrity of the char layer to some extent, it is difficult to improve the flame retardant performance of PPO foamed materials. Furthermore, low molecular weight organophosphorus compounds are usually used as flame retardants for PPO. The addition of low molecular weight organophosphorus compounds will cause a sharp drop in PPO viscosity, which will seriously affect the foaming performance of PPO and make it difficult to prepare flame-retardant foamed materials with high foaming ratios. Moreover, from the perspective of flame retardant mechanism, low molecular weight organophosphorus compounds are solid-phase flame retardants. For foamed materials, solid-phase flame retardancy has relatively low flame retardant efficiency, requires a large amount to be added, and will further lead to a sharp drop in viscosity. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a flame-retardant polyphenylene ether foam material and its preparation method, so as to solve the problems in the prior art where the flame-retardant performance of PPO composite foam is poor due to the decrease in the continuity of the char layer as the foaming ratio increases, and the strong plasticizing effect of traditional phosphate ester flame retardants causes the melt strength to drop significantly and the foaming performance to drop as the amount added increases when used alone.

[0009] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: According to one aspect of the present invention, a flame-retardant polyphenylene ether foam material is provided, which is made by foaming a polyphenylene ether composition. The polyphenylene ether composition comprises, by weight, the following raw materials: 30-80 parts polyphenylene ether, 20-70 parts polystyrene, 4-12 parts aromatic phosphate flame retardant, and 4-12 parts high molecular weight brominated flame retardant. The mass ratio of the aromatic phosphate flame retardant to the high molecular weight brominated flame retardant is 0.5-2. The thermal decomposition temperature of the aromatic phosphate flame retardant is between 320°C and 470°C, and the thermal decomposition temperature of the high molecular weight brominated flame retardant is between 350°C and 530°C. The aromatic phosphate flame retardant and the high molecular weight brominated flame retardant constitute a compound flame-retardant system with a gas-phase flame-retardant mechanism.

[0010] Optionally, in the above-mentioned flame-retardant polyphenylene ether foam material, the polyphenylene ether composition has a zero-shear viscosity greater than 5000 Pa·s at 260°C.

[0011] Optionally, in the above-mentioned flame-retardant polyphenylene ether foam material, the aromatic phosphate flame retardant is at least one of resorcinol bis(diphenyl phosphate), hydroquinone bis(diphenyl phosphate), and bisphenol A-bis(diphenyl phosphate).

[0012] Optionally, in the above-mentioned flame-retardant polyphenylene ether foam material, the phosphorus content of the aromatic phosphate flame retardant is greater than 6 wt%.

[0013] Optionally, in the above-mentioned flame-retardant polyphenylene ether foam material, the high molecular weight brominated flame retardant has a molecular weight greater than or equal to 900, a melting point greater than or equal to 300°C, an average particle size less than 10 μm, and a bromine content greater than 60 wt%.

[0014] Optionally, in the above-mentioned flame-retardant polyphenylene ether foam material, the high molecular weight bromine-based flame retardant is at least one of brominated polystyrene, ethyl-bis(tetrabromophthalimide), decabromodiphenyl ethane, and tetradecylbromodiphenoxybenzene.

[0015] According to another aspect of the present invention, a method for preparing the above-mentioned flame-retardant polyphenylene ether foam material is provided, comprising the following steps: S1. Melting and mixing polyphenylene ether, polystyrene, aromatic phosphate flame retardant and high molecular weight brominated flame retardant at 260°C to 300°C in proportion to obtain a polyphenylene ether composition; and S2. Preparing the polyphenylene ether composition into a polyphenylene ether foam material by a foaming process.

[0016] Optionally, in the above-mentioned method for preparing flame-retardant polyphenylene ether foamed material, in step S2, the polyphenylene ether flame-retardant composition obtained in step S1 is added to an extruder for melting and extruded and pelletized through a die head to prepare microparticles to be foamed. Then, the microparticles to be foamed are added to an autoclave, and a physical foaming agent is introduced and saturated at 150°C to 210°C and 10MPa to 20MPa pressure. Then, the pressure is released and foaming is performed to prepare the polyphenylene ether flame-retardant foamed material.

[0017] Optionally, in the above-mentioned method for preparing flame-retardant polyphenylene ether foamed material, in step S2, the polyphenylene ether flame-retardant composition obtained in step S1 is added to an extrusion foaming device and melted at 260°C to 300°C. After adding a physical foaming agent and mixing evenly, the mixture is cooled to between 150°C and 210°C and then extruded to obtain the polyphenylene ether flame-retardant foamed material. The extrusion foaming device is a single-screw extruder or a twin-screw extruder connected in series with a single-screw extruder.

[0018] According to another aspect of the present invention, a method for preparing the above-mentioned flame-retardant polyphenylene ether foam material is provided. A two-stage extrusion foaming device is used, in which polyphenylene ether, polystyrene, aromatic phosphate flame retardant, and high molecular weight brominated flame retardant are added in proportion to a first-stage extruder and melted at 260°C to 300°C. A physical foaming agent is injected through an injection unit installed on the first-stage extruder, and the mixture is uniformly mixed under the action of the screw to obtain a polyphenylene ether composition melt containing the foaming agent. The polyphenylene ether composition melt is then transported to a downstream single-screw extruder and uniformly cooled to 150°C to 210°C, with a die pressure greater than 4 MPa. After depressurization and foaming through the die, the flame-retardant polyphenylene ether foam material is shaped to obtain the foam material.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention relates to a flame-retardant polyphenylene ether foam material and its preparation method. The aromatic phosphate flame retardant and the high molecular weight brominated flame retardant exhibit significant synergistic flame-retardant effects. This compound flame-retardant system is primarily gas-phase flame-retardant, with condensed-phase flame retardancy as a secondary effect. It demonstrates excellent flame-retardant performance in both unfoamed and foamed polyphenylene ether compositions. Under specific ratios and dosages, the two flame retardants in the compound flame-retardant system maintain the viscosity of the polyphenylene ether composition at a good level, resulting in a higher foaming ratio than either flame retardant acting alone. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below.

[0021] Figure 1 This is a flowchart of the preparation method of the flame-retardant polyphenylene ether foam material of the present invention; Figure 2This is a dispersion diagram of aromatic phosphate flame retardants and high molecular weight brominated flame retardants in the matrix; Figure 3 This is the thermogravimetric result of the compound flame retardant system of the present invention; Figure 4 This is a graph showing the heat release rate of the compound flame retardant system of the present invention; Figure 5 The dynamic rheological curves of Embodiments 1, 3, 4, 5 and Comparative Example 1 of the present invention are shown. Figure 6 Images of the char layer after combustion in Examples 1, 4 and Comparative Example 2 of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0023] The flame-retardant polyphenylene ether foam material of the present invention is made by foaming a polyphenylene ether composition. The polyphenylene ether composition comprises, by weight, the following raw materials: 30-80 parts polyphenylene ether, 20-70 parts polystyrene, 4-12 parts aromatic phosphate flame retardant, and 4-12 parts high molecular weight brominated flame retardant. The mass ratio of the aromatic phosphate flame retardant to the high molecular weight brominated flame retardant is 0.5-2. The polyphenylene ether composition has a zero-shear viscosity greater than 5000 Pa·s at 260°C. The polyphenylene ether composition provided by the present invention has a limiting oxygen index ≥34% when unfoamed, a vertical burning rating of V-0, and an apparent density of 0.05 g / cm³ after foaming. 3 ~0.35g / cm 3 It has a limiting oxygen index of ≥27% and a horizontal combustion test rating of HF-1.

[0024] The thermal decomposition temperature of aromatic phosphate flame retardants is between 320℃ and 470℃. They are solid at room temperature and melt at high temperatures. For PPO, aromatic phosphate flame retardants employ a gas-phase flame retardant mechanism. Upon reaching the decomposition temperature, they decompose and release phosphorus oxygen free radicals (PO- and PO2-), which capture hydrogen and hydroxyl groups (-H and -OH) to interrupt the combustion chain reaction. Furthermore, the flame-retardant gases produced during decomposition, such as P, PO, and HPO, can reduce the concentration of combustible gases and delay flame spread. Preferably, the aromatic phosphate flame retardant is at least one of resorcinol bis(diphenyl phosphate), hydroquinone bis(diphenyl phosphate), and bisphenol A-bis(diphenyl phosphate). The phosphorus content of the aromatic phosphate flame retardant is greater than 6 wt%.

[0025] The high molecular weight brominated flame retardant has a molecular weight greater than or equal to 900, a melting point greater than or equal to 300℃, and exists as non-melting solid particles during extrusion processing. Its average particle size is less than or equal to 10 μm, and its thermal decomposition temperature is between 350℃ and 530℃. For the polyphenylene ether / polystyrene composite system, it employs a gas-phase flame retardant mechanism. During thermal decomposition, the C-Br bond breaks, releasing bromine atoms (-Br). These bromine atoms capture hydrogen and hydroxyl groups to generate hydrogen bromide (HBr), interrupting the combustion chain reaction. HBr further captures -H to generate hydrogen gas (H2) and -Br, interrupting the chain reaction, thus cyclically interrupting the combustion chain reaction. The non-melting brominated flame retardant can act as a heterogeneous nucleating agent to refine the cell structure, maintaining the mechanical properties of the foamed material at a good level. Preferably, the high molecular weight brominated flame retardant is at least one of brominated polystyrene, ethyl-bis(tetrabromophthalimide), decabromodiphenyl ethane, and tetradecylbromodiphenoxybenzene. The bromine content of the high molecular weight brominated flame retardant is greater than 60 wt%.

[0026] The thermal decomposition temperature range of aromatic phosphate flame retardants mainly covers that of polyphenylene ether, while the thermal decomposition temperature range of high molecular weight brominated flame retardants mainly covers that of polystyrene. The combined flame retardant system of both fully covers the thermal decomposition temperature range of polyphenylene ether / polystyrene, effectively capturing free radicals formed during polymer decomposition. This allows the combined flame retardant to provide timely and effective flame retardancy, thus exhibiting a significant synergistic flame retardant effect.

[0027] The thermal decomposition temperature was tested using the thermogravimetric method. The specific steps were as follows: 8-10 mg of sample was weighed and placed in an alumina ceramic crucible. The test was conducted under a nitrogen atmosphere. After stabilizing for 10 minutes, the temperature was increased from 50°C to 600°C at a rate of 20°C / min. The thermal decomposition initiation temperature was defined as the temperature at which the weight loss rate reached 5%, and the decomposition termination temperature was the temperature at which the weight loss rate reached 95%.

[0028] like Figure 1 As shown, the preparation method of the flame-retardant polyphenylene ether foam material of the present invention includes the following steps: S1. Polyphenylene ether, polystyrene, aromatic phosphate flame retardant and high molecular weight brominated flame retardant are melt-mixed at 260~300℃ in proportion to obtain a polyphenylene ether composition.

[0029] In this step, 30-80 parts by weight of polyphenylene ether, 20-70 parts by weight of polystyrene, 4-12 parts by weight of aromatic phosphate flame retardant, and 4-12 parts by weight of high molecular weight brominated flame retardant are added to a twin-screw extruder and melt-mixed at 260℃-300℃ to obtain a polyphenylene ether composition with a zero-shear viscosity greater than 5000 Pa·s at 260℃, wherein the mass ratio of aromatic phosphate flame retardant to high molecular weight brominated flame retardant is 0.5-2.

[0030] At the processing temperature, aromatic phosphate flame retardants are completely compatible with polyphenylene ether / polystyrene, while high molecular weight brominated flame retardants are dispersed as rigid particles within the matrix. The "bridging effect" between the aromatic phosphate flame retardants and the high molecular weight brominated flame retardants ensures uniform dispersion of the flame retardants. Figure 2 As shown in Figures A and B, both A and B are compositions of 50 parts polyphenylene ether and 50 parts polystyrene. In A, the flame retardant is 8 parts high molecular weight brominated polystyrene, and in B, it is a compound flame retardant system of 4 parts hydroquinone bis(diphenyl phosphate) and 4 parts high molecular weight brominated polystyrene, further improving flame retardant efficiency and foaming performance. Regarding the weight ratio of aromatic phosphate flame retardant to high molecular weight brominated flame retardant, it is 0.5-2. When this ratio is less than 0.5, on the one hand, it cannot effectively retard polyphenylene ether; on the other hand, the viscosity of the polyphenylene ether flame retardant composition is too high, making it difficult to foam and mold. When the ratio is greater than 2, the synergistic flame retardant performance is poor, and it will cause a sharp decrease in the viscosity of the polyphenylene ether flame retardant composition, affecting the foaming performance.

[0031] S2. The polyphenylene ether composition is prepared into a polyphenylene ether foam material by a foaming process.

[0032] In this step, in a preferred embodiment, the polyphenylene ether flame-retardant composition obtained in step S1 is added to an extruder for melting and then extruded and pelletized through a die to prepare microparticles to be foamed. These microparticles are then added to an autoclave, and a physical foaming agent is introduced to saturate the material at temperature T and pressure P. The pressure is then released for foaming to prepare the polyphenylene ether flame-retardant foam material. The temperature T is a certain temperature between 150°C and 210°C, and the pressure P is greater than or equal to 10 MPa and less than or equal to 20 MPa.

[0033] In another preferred embodiment, the polyphenylene ether flame-retardant composition obtained in step S1 is added to an extrusion foaming device and melted at 260°C to 300°C. Physical foaming agents such as carbon dioxide, cyclopentane, isobutane, fluorinated foaming agents hydrofluoroolefins (HFO), ethanol, and water are added and mixed thoroughly. The mixture is then cooled to between 150°C and 210°C and extruded to obtain the polyphenylene ether flame-retardant foam material. This extrusion foaming device can be a single-screw extruder or a twin-screw extruder connected in series with a single-screw extruder.

[0034] In addition to the above preparation method, the preparation method of the flame-retardant polyphenylene ether foam material of the present invention can also adopt a one-step extrusion method. A two-stage extrusion foaming device is used, in which polyphenylene ether, polystyrene, aromatic phosphate flame retardant, and high molecular weight brominated flame retardant are added to a first-stage extruder in proportion and melted at 260℃~300℃. Physical foaming agents, such as carbon dioxide, cyclopentane, isobutane, fluorinated foaming agents hydrofluoroolefins (HFO), hydrofluorocarbons (HFC), ethanol, and water, are injected through an injection unit installed on the first-stage extruder. Under the action of the screw, the mixture is uniformly mixed to obtain a polyphenylene ether composition melt containing a foaming agent. The polyphenylene ether composition melt is then transported to a downstream single-screw extruder and uniformly cooled to 150℃~210℃ with a die pressure greater than 4MPa. After depressurization and foaming through the die, the flame-retardant polyphenylene ether foam material is shaped to obtain the final product. The two-stage extrusion foaming device is a twin-screw extruder connected in series with a single-screw extruder, a single-screw extruder connected in series with a single-screw extruder, or a three-screw extruder connected in series with a single-screw extruder. Preferably, it is selected from a twin-screw extruder connected in series with a single-screw extruder or a three-screw extruder connected in series with a single-screw extruder. Preferably, a melt pump is arranged between the first-stage and second-stage extruders, or between the second-stage extruder and the die head, to achieve stability and regulation of the die head pressure.

[0035] This invention constructs a compound flame retardant system by selecting suitable aromatic phosphate flame retardants and high molecular weight brominated flame retardants. The results of thermogravimetric analysis show that (…). Figure 3 This system primarily utilizes gas-phase flame retardancy, supplemented by condensed-phase flame retardancy. The thermal decomposition temperature range of the aromatic phosphate flame retardant mainly covers that of polyphenylene ether, while the thermal decomposition temperature range of the high molecular weight brominated flame retardant mainly covers that of polystyrene. The combined flame retardant system of both fully covers the thermal decomposition temperature range of polyphenylene ether / polystyrene, effectively capturing free radicals formed during polymer decomposition. This allows the combined flame retardant to provide timely and effective flame retardancy, thus exhibiting a significant synergistic flame retardant effect. For unfoamed polyphenylene ether compositions, a blend of 100 parts polyphenylene ether / polystyrene, 4 parts aromatic phosphate flame retardant, and 4 parts high molecular weight brominated flame retardant can achieve a limiting oxygen index greater than or equal to 35.0%.

[0036] The char layer generated by the combustion of the gas-phase product blow-molded matrix in the compound flame retardant system of the present invention forms an intumescent char layer, while the compound flame retardant system effectively reduces the heat release rate. Figure 4 The four matrix groups are all compositions of 50 parts polyphenylene ether and 50 parts polystyrene. The aromatic phosphate flame retardant is hydroquinone bis(diphenyl phosphate), and the high molecular weight brominated flame retardant is high molecular weight brominated polystyrene, thus protecting the integrity of the char layer. The intumescent char layer effectively controls the release of smoke from the unfoamed polyphenylene ether composition.

[0037] For the foamed polyphenylene ether composition of the present invention, the large amount of gaseous products released by the compound system can provide timely and effective flame retardancy even in the case of discontinuous char layer, with a density of 0.134 g / cm³. 3 It can still pass the HF-1 level horizontal combustion test.

[0038] The plasticizing effect of the aromatic phosphate flame retardant and the rigid network formed by the high molecular weight brominated flame retardant of this invention jointly regulate the viscosity of the polyphenylene ether (PPE) composition blend. When the ratio of aromatic phosphate flame retardant to high molecular weight brominated flame retardant is between 0.5 and 2, the high molecular weight brominated flame retardant remains solid during processing, preventing a significant decrease in the viscosity of the PPE composition. This allows the PPE composition viscosity to be >5000 Pa·s, meeting the melt strength requirements for foaming. When the ratio is below 0.5, the high content of high molecular weight brominated flame retardant leads to a surge in smoke release; when the ratio is above 2, the high content of aromatic phosphate flame retardant causes a sharp decrease in the viscosity of the PPE composition, making it difficult to meet foaming requirements.

[0039] This invention relates to a flame-retardant polyphenylene ether foam material and its preparation method. The aromatic phosphate flame retardant and the high molecular weight brominated flame retardant exhibit significant synergistic flame-retardant effects. This compound flame-retardant system is primarily gas-phase flame-retardant, with condensed-phase flame retardancy as a secondary effect. It demonstrates excellent flame-retardant performance in both unfoamed and foamed polyphenylene ether compositions. Under specific ratios and dosages, the two flame retardants in the compound flame-retardant system maintain the viscosity of the polyphenylene ether composition at a good level, resulting in a higher foaming ratio than either flame retardant acting alone.

[0040] Example 1: A flame-retardant polyphenylene ether foam material, by weight, comprises the following raw material components: polyphenylene ether LXN040 (Nantong Xingchen), 80 parts; polystyrene 476L (Yangzi BASF), 20 parts; hydroquinone bis(diphenyl phosphate), 4 parts; and ultra-high molecular weight brominated polystyrene, 4 parts. The hydroquinone bis(diphenyl phosphate) has a thermal decomposition temperature between 360 and 470°C and a melting point of 90°C; the ultra-high molecular weight brominated polystyrene has a thermal decomposition temperature between 390 and 500°C, a melting point greater than 320°C, and a bromine content of 65%.

[0041] Preparation method: S1. Polyphenylene ether, polystyrene, hydroquinone bis(diphenyl phosphate), and ultra-high molecular weight brominated polystyrene are weighed according to the proportion and added to a twin-screw extruder. The mixture is melt-mixed at 260℃~300℃ to obtain a flame-retardant polyphenylene ether composition; S2. The flame-retardant polyphenylene ether composition is added to a single-screw extruder (length-to-diameter ratio 48) and 2wt% cyclopentane is injected and mixed evenly. The melt of the polyphenylene ether composition containing cyclopentane is then cooled to 180℃, and the die pressure is 4MPa. After depressurization and foaming through the die, the flame-retardant polyphenylene ether foam material is obtained.

[0042] Performance Characterization: The density (ρ1) and density (ρ2) of the polyphenylene ether composition before foaming were tested using a sponge densitometer according to the water displacement method of GB / T 6343-2023. The foaming ratio (φ) was calculated using the formula φ=ρ1 / ρ2. The limiting oxygen index was tested according to GB / T 2828.1-2003, with a sample size of 80×10×4mm. The vertical burning UL-94 rating was tested according to GB / T2408-2008, with a sample size of 125×13×3mm. The cone calorimetry test was conducted according to GB / T 6172-2007, with a sample size of 100×100×3mm. The melt rheological properties were tested using a Thermos Fisher Scientific Mars III Hacker rotational rheometer. The test procedure was as follows: the granular sample extruded by the twin screw extruder was placed on a 20 mm diameter circular platform and protected with nitrogen gas to prevent contact with air. The rheometer temperature was set to 260 °C. The sample was slowly pressed into a 1 mm thin sheet and the sample overflowing from the circular platform was scraped off. The angular velocity was 0.1-100 rad / s. The viscoelastic data were recorded.

[0043] Example 2 Polyphenylene ether LXN040, Nantong Xingchen, 80 parts; polystyrene 476L, Yangzi BASF, 20 parts; hydroquinone bis(diphenyl phosphate), 8 parts; tetradecylbromodiphenoxybenzene, 4 parts. Hydroquinone bis(diphenyl phosphate) has a thermal decomposition temperature between 360~470℃ and a melting point of 90℃; tetradecylbromodiphenoxybenzene has a thermal decomposition temperature between 390℃~500℃ and a melting point greater than 350℃, with a bromine content of 82%.

[0044] A two-stage extrusion foaming device is used to add polyphenylene ether, polystyrene, aromatic phosphate flame retardant and high molecular weight brominated flame retardant into a first-stage three-screw extruder in proportion. The mixture is melted at 260-300℃, and carbon dioxide and 3% HFO-1233zd composite foaming agent are injected through an injection unit installed on the three-screw extruder. Under the action of the screw, the mixture is uniformly mixed to obtain a flame-retardant polyphenylene ether melt containing foaming agent. The melt is then conveyed to a downstream single-screw extruder and uniformly cooled to 150-210℃ with a die pressure of 5MPa. After depressurization and foaming through the die, the flame-retardant polyphenylene ether foam material is obtained.

[0045] Example 3 The extrusion molding method and process are the same as in Example 2, and the raw materials are the same as in Example 1. The difference is that the composition ratio is different, as shown in Table 1.

[0046] Example 4 The same raw materials and foaming process as in Example 1 were used, except that the content of each component in the raw materials (see Table 1 for raw material component content) and the foaming agent in the manufacturing process were different. In Example 4, the foaming agent was a composite foaming agent of carbon dioxide and ethanol, added at 3 wt%.

[0047] Example 5 The same raw materials and foaming process as in Example 1 were used, except that the content of each component in the raw materials (see Table 1 for raw material component content) and the foaming agent in the manufacturing process were different. In Example 5, the foaming agent was carbon dioxide.

[0048] Example 6 The same manufacturing process as in Example 1 was used, except that the components and contents of the raw materials were different. The raw material components and proportions were as follows: 60 parts of polyphenylene ether, 40 parts of polystyrene, 6 parts of resorcinol bis(diphenyl phosphate), with a thermal decomposition temperature of 320~470℃, and 9 parts of ethyl-bis(tetrabromophthalimide), with a thermal decomposition temperature of 400~530℃ and a molecular weight of 951.

[0049] Example 7 The same manufacturing process as in Example 1 was used, except that the components and contents of the raw materials were different. The raw material components and proportions were as follows: 60 parts of polyphenylene ether, 40 parts of polystyrene, 5 parts of bisphenol A-bis(diphenyl phosphate), with a thermal decomposition temperature of 370~460℃, and 8 parts of decabromodiphenyl ethane, with a thermal decomposition temperature range of 390~500℃ and a molecular weight of 973.

[0050] Comparative Example 1 The same raw materials, foaming agent, and foaming process as in Example 4 were used, except that the content of each component in the raw materials (see Table 1 for the content of raw material components) was different.

[0051] Comparative Example 2 The manufacturing process is the same as that in Example 1, using the same raw materials, foaming agent, and foaming process, except that the content of each component in the raw materials (see Table 1 for the content of raw material components) is different.

[0052] Comparative Example 3 The same manufacturing process as in Example 5 was used, except that the content of each component in the raw materials was different (the content of raw material components is shown in Table 1).

[0053] Comparative Example 4 The same manufacturing process as in Example 1 was used, except that the raw materials were different. By weight, the specific raw materials and proportions are as follows: 80 parts polyphenylene ether, 20 parts polystyrene, and 8 parts resorcinol bis(diphenyl phosphate), with a thermal decomposition temperature of 320~470℃.

[0054] The test results of Examples 1-7 and Comparative Examples 1-4 are shown in Table 1.

[0055] Table 1 In Comparative Example 1, the weight ratio of aromatic phosphate ester to high molecular weight brominated flame retardant was 3. Compared with Example 4, the content of aromatic phosphate ester was too high. The plasticizing effect significantly reduced the viscosity of the composition, making it difficult to prepare high foaming flame retardant materials and also affecting the flame retardant effect, with an oxygen index of only 25%. Comparative Example 2, which only added one aromatic flame retardant, could not achieve an effective flame retardant effect. The horizontal flammability rating of the foamed material did not reach HF-1, and the oxygen index was only 22.4%. In Comparative Example 3, the ratio of aromatic phosphate ester to high molecular weight brominated flame retardant was 0.33. Compared with Example 5, the excessively high ratio of brominated flame retardant resulted in poor flame retardant effect, with a limiting oxygen index of 23.5%, and caused the melt viscosity to be too high, exceeding 10,000 Pas, making it difficult to foam and mold.

[0056] Comparative Example 4, which only added a high molecular weight brominated flame retardant, had a limiting oxygen index (LOI) of 24% in its foamed material, failing the HF-1 rating in the horizontal combustion test, and also exhibited a low expansion ratio. This is attributed to the fact that Comparative Example 4 used only one flame retardant, whose thermal decomposition temperature range could not fully cover the thermal decomposition temperature range of the polyphenylene ether / polystyrene composition. In contrast, Example 1 used a combination of two flame retardants (aromatic phosphate flame retardant to high molecular weight brominated flame retardant in a 1:1 mass ratio), resulting in a limiting oxygen index (LOI) of 27.6% in its foamed material, which passed the HF-1 rating in the horizontal combustion test. This is attributed to the fact that the thermal decomposition temperature range of the combined aromatic phosphate flame retardant and high molecular weight brominated flame retardant system of this invention fully covers the thermal decomposition temperature range of polyphenylene ether / polystyrene, releasing flame-retardant gases over a wider temperature range, and the two exhibiting a significant synergistic flame-retardant effect.

[0057] As shown in Examples 1-7, when the amount of polyphenylene ether added is 30-80 parts and the amount of polystyrene added is 20-70 parts, and the amount of aromatic phosphate flame retardant and high molecular weight brominated flame retardant added are both 4-12 parts with a mass ratio of 0.5-2, flame-retardant polyphenylene ether foamed materials with a density of less than 0.20 kg / cm³ can be prepared well. 3 The limiting oxygen index of the foamed materials was greater than 27.0%, and all passed the HF-1 level horizontal combustion test. Furthermore, the smoke emission in the cone calorimetry test was less than 28 m³. 2At 260℃, the zero-shear viscosity was above 5000 Pa·s. When the mass ratio of aromatic phosphate flame retardant to high molecular weight brominated flame retardant was less than 0.5 (Comparative Example 3), the intumescent char layer had limited ability to capture smoke particles, while excessive bromine atom release led to a surge in smoke release. When the mass ratio of aromatic phosphate flame retardant to high molecular weight brominated flame retardant was greater than 2 (Comparative Example 1), the phosphate flame retardant caused the viscosity to continue to decrease, falling below 5000 Pa·s, resulting in a significant decrease in foaming performance.

[0058] Figure 5 The dynamic rheological curves of Examples 1, 3, 4, 5 and Comparative Example 1 are shown for the preparation method of the polyphenylene ether (PPE) foam material using the phosphorobromine flame-retardant composition of the present invention. Changes in the PPE content and the amount of aromatic phosphate flame retardant added both affect the complex viscosity; a decrease in chain segment entanglement leads to a decrease in complex viscosity. However, with an increase in the amount of high molecular weight brominated flame retardant added, the rigid network formed by the high molecular weight brominated flame retardant increases the viscosity. At different PPE and polystyrene contents, an appropriate ratio of aromatic phosphate flame retardant to high molecular weight brominated flame retardant by mass will achieve a viscosity above 5000 Pa·s, which is beneficial for improving the foaming performance of the PPE composition. In Comparative Example 1, the mass ratio of aromatic phosphate flame retardant to high molecular weight brominated flame retardant is higher than 2, and the phosphate flame retardant causes the viscosity to continue to decrease, falling below 5000 Pa·s, resulting in a significant decrease in foaming performance.

[0059] Figure 6 Images of the cone-shaped calorimetric char layers from Examples 1, 4, and Comparative Example 2 are shown. The combination system of two gas-phase flame retardants provides a timely gas source, allowing the blown polyphenylene ether to burn and form an intumescent char layer. Simultaneously, the timely and effective gas-phase flame retardancy suppresses the heat release rate, protecting the integrity of the intumescent char layer. Comparative Example 2, with only one flame retardant, cannot provide a timely gas source or suppress the heat release rate effectively. This results in difficulty in forming an intumescent char layer or the intumescent char layer burning through, thus failing to suppress smoke release.

[0060] The above embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and are not intended to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or improve the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features, within the scope of the technology disclosed in the present invention; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A flame-retardant polyphenylene ether foam material, characterized in that, The product is made by foaming a polyphenylene ether composition, wherein the polyphenylene ether composition comprises, by weight, the following raw materials: 30-80 parts polyphenylene ether, 20-70 parts polystyrene, 4-12 parts aromatic phosphate flame retardant, and 4-12 parts high molecular weight brominated flame retardant, wherein the mass ratio of the aromatic phosphate flame retardant to the high molecular weight brominated flame retardant is 0.5-2. The aromatic phosphate flame retardant has a thermal decomposition temperature between 320°C and 470°C, and the high molecular weight bromine flame retardant has a thermal decomposition temperature between 350°C and 530°C. The aromatic phosphate flame retardant and the high molecular weight bromine flame retardant constitute a compound flame retardant system with a gas-phase flame retardant mechanism.

2. The flame-retardant polyphenylene ether foam material according to claim 1, characterized in that, The polyphenylene ether composition has a zero-shear viscosity greater than 5000 Pa·s at 260°C.

3. The flame-retardant polyphenylene ether foam material according to claim 1, characterized in that, The aromatic phosphate flame retardant is at least one of resorcinol bis(diphenyl phosphate), hydroquinone bis(diphenyl phosphate), and bisphenol A-bis(diphenyl phosphate).

4. The flame-retardant polyphenylene ether foam material according to claim 1, characterized in that, The aromatic phosphate flame retardant has a phosphorus content greater than 6 wt%.

5. The flame-retardant polyphenylene ether foam material according to claim 1, characterized in that, The high molecular weight brominated flame retardant has a molecular weight greater than or equal to 900, a melting point greater than or equal to 300°C, an average particle size less than 10 μm, and a bromine content greater than 60 wt%.

6. The flame-retardant polyphenylene ether foam material according to claim 1, characterized in that, The high molecular weight brominated flame retardant is at least one of brominated polystyrene, ethyl-bis(tetrabromophthalimide), decabromodiphenyl ethane, and tetradecylbromodiphenoxybenzene.

7. The method for preparing the flame-retardant polyphenylene ether foam material according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Polyphenylene ether, polystyrene, aromatic phosphate flame retardant, and high molecular weight brominated flame retardant are melt-mixed at 260℃~300℃ in a certain proportion to obtain a polyphenylene ether composition; and S2. The polyphenylene ether composition is prepared into a polyphenylene ether foam material by a foaming process.

8. The method for preparing flame-retardant polyphenylene ether foam material according to claim 7, characterized in that, In step S2, the polyphenylene ether flame retardant composition obtained in step S1 is added to an extruder for melting and extruded and pelletized through a die head to prepare microparticles to be foamed. Then, the microparticles to be foamed are added to an autoclave, and a physical foaming agent is introduced and saturated at 150°C to 210°C and 10MPa to 20MPa pressure. Then, the pressure is released and foaming is performed to prepare the polyphenylene ether flame retardant foam material.

9. The method for preparing flame-retardant polyphenylene ether foam material according to claim 7, characterized in that, In step S2, the polyphenylene ether flame retardant composition obtained in step S1 is added to an extrusion foaming device and melted at 260°C to 300°C. After adding a physical foaming agent and mixing evenly, the mixture is cooled to between 150°C and 210°C and extruded to obtain the polyphenylene ether flame retardant foam material. The extrusion foaming device is a single-screw extruder or a twin-screw extruder connected in series with a single-screw extruder.

10. The method for preparing the flame-retardant polyphenylene ether foam material according to any one of claims 1 to 6, characterized in that, A two-stage extrusion foaming device is used to add polyphenylene ether, polystyrene, aromatic phosphate flame retardant, and high molecular weight brominated flame retardant to the first-stage extruder in proportion and melt them at 260℃~300℃. A physical foaming agent is injected through an air injection unit installed on the first-stage extruder. Under the action of the screw, they are mixed evenly to obtain a polyphenylene ether composition melt containing foaming agent. The polyphenylene ether composition melt is transported to a downstream single-screw extruder and uniformly cooled to 150℃~210℃ with a die pressure greater than 4MPa. After depressurization and foaming through the die, the flame-retardant polyphenylene ether foam material is obtained.

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