A halogen-free flame-retardant long-glass-fiber-reinforced polypropylene composite material and a preparation method thereof

Abstract

The application belongs to the technical field of polypropylene materials, and particularly discloses a halogen-free flame-retardant long-glass-fiber reinforced polypropylene composite material and a preparation method thereof, which is prepared from the following components in parts by weight: high-melt-index copolymerized polypropylene resin 35-55 parts, alkali-free long glass fiber 20-30 parts, composite flame-retardant component 20-30 parts, toner 1-1.5 parts, functional additive 0.1-1 part, and compatibilizer 4-8 parts. The halogen-free flame-retardant polypropylene composite material prepared by the application is reinforced by the composite flame-retardant unit and the long glass fiber, and compared with the short-fiber composite material, the notched impact strength can be increased to 10 kJ / m 2 Meanwhile, V0-grade flame retardation can be achieved. In subsequent applications, the material can resist 85% humidity and 85 DEG C high-temperature and high-humidity environment for 1000 hours without precipitation, and can be widely applied in the fields of automotive interiors, electrical appliance housings, municipal engineering, etc.

Description

Technical Field

[0001] This invention relates to the field of polypropylene materials technology, specifically to a halogen-free, flame-retardant, long glass fiber reinforced polypropylene composite material resistant to precipitation and its preparation method. This material can be widely used in automotive interiors, electrical appliance housings, municipal engineering, and other fields. Background Technology

[0002] With the rapid development of industries such as new energy and electronics, the demand for flame-retardant materials for components such as appliance casings and battery casings is increasing. These materials not only require excellent flame-retardant properties but also need to be cost-effective, dimensionally stable, and reliable over long-term use. Currently, most flame-retardant materials used in these components are nylon. While these materials meet basic flame-retardant requirements, they have significant limitations: Firstly, nylon itself has a high production cost, leading to high component manufacturing costs and making it difficult to meet the industry's demand for cost reduction and efficiency improvement. Secondly, nylon has a high water absorption rate, making it prone to dimensional deformation in high-temperature and high-humidity environments, resulting in poor stability and severely affecting the assembly accuracy and service life of components, thus failing to meet the demands of harsh usage scenarios.

[0003] To achieve cost-effective replacement of nylon flame-retardant materials, the industry has attempted to modify polypropylene for flame retardancy. However, polypropylene has relatively low mechanical properties, requiring reinforcement with glass fiber. Short glass fiber reinforcement offers limited improvement in mechanical properties and is insufficient to provide the structural support required for casing components, thus failing to achieve effective cost-effective replacement. Furthermore, the halogen-free flame retardants used in existing short-fiber flame-retardant polypropylene are prone to migration and precipitation under high temperature and humidity conditions, resulting in surface blooming and stickiness. This not only degrades the flame-retardant performance of the material but also affects the appearance quality and safety of components, significantly limiting its widespread application in critical components such as appliance casings and battery casings.

[0004] Long glass fiber reinforced polypropylene (LGF-PP) has become an ideal alternative to nylon flame retardant materials due to its excellent mechanical properties, lightweight nature, and cost advantages. However, the production process of LGF-PP requires high temperatures (typically 260-300℃), at which conventional halogen-free flame retardant components are prone to decomposition, leading to the failure of flame retardant performance. Furthermore, the significant polarity difference between halogen-free flame retardants and the polypropylene matrix results in poor compatibility, further exacerbating the problem of flame retardant precipitation. Therefore, ensuring the mechanical properties of LGF-PP while addressing the issues of high-temperature decomposition and precipitation of halogen-free flame retardants under high temperature and humidity conditions is crucial for its effective replacement of nylon flame retardant materials. Summary of the Invention

[0005] The technical problem this invention aims to solve is the insufficient mechanical properties and high-temperature decomposition and exudation resistance of existing short glass fiber reinforced halogen-free flame-retardant polypropylene materials. Based on this, it provides an halogen-free flame-retardant long glass fiber reinforced polypropylene composite material with exudation resistance and its preparation method. To solve the above technical problems, the material of this invention adopts a bipolar laminate expansion synergistic flame-retardant system blended with MMT, LDHs, PAPP, and MPP. The thermal stability of the micro-laminate structure fully protects the flame-retardant components, reducing the degradation problem of the flame-retardant components during the production of long glass fibers. Simultaneously, through the overall electrical neutrality of the acid-base bipolar structure, and the synergistic effect of coupling agents and compatibilizers, the compatibility of the flame-retardant components in the polypropylene material is greatly improved. The resulting material can simultaneously achieve high mechanical properties, V0 flame retardancy, and long-term exudation resistance.

[0006] The specific technical solution adopted in this invention is as follows:

[0007] In a first aspect, the present invention provides a halogen-free flame-retardant long glass fiber reinforced polypropylene composite material resistant to precipitation, comprising the following components by weight:

[0008] 35-55 parts of polypropylene

[0009] 20-30 parts long glass fiber,

[0010] 20-30 parts of composite flame retardant component,

[0011] 1-1.5 parts of color powder,

[0012] Functional additives 0.1~1 part,

[0013] Compatibilizer 4-8 parts.

[0014] Preferably, the polypropylene (PP) substrate selected in this invention is a high melt flow index copolymer polypropylene resin with a melt flow index MFR ≥ 60 (test conditions: load 2.16 kg, temperature 230℃).

[0015] Preferably, the long glass fibers selected in this invention are continuous alkali-free long glass fibers with a diameter of 10~20μm and a linear density of 1200~3600tex. The difference between long and short glass fibers lies in their aspect ratio; long fibers are mostly continuous fibers with an aspect ratio exceeding 40:1 in the particles.

[0016] Preferably, the composite flame-retardant component selected in this invention is a blend of sodium montmorillonite (Na-MMT), magnesium aluminum hydrotalcite (Mg / Al-LDHs), piperazine pyrophosphate (PAPP), and melamine polyphosphate (MPP); wherein, sodium montmorillonite accounts for 5% to 15%, magnesium aluminum hydrotalcite accounts for 5% to 15%, piperazine pyrophosphate accounts for 50% to 70%, and melamine polyphosphate accounts for 20% to 30%.

[0017] More preferably, the weight ratio of piperazine pyrophosphate (PAPP) to melamine polyphosphate (MPP) is 2:1.

[0018] Preferably, the pigment used in this invention is furnace black, with a specific surface area of ​​125-140 m². 2 / g.

[0019] Preferably, the functional additive is an antioxidant. The antioxidants selected in this invention are at least two of the following: general antioxidants 1010, 1035, and 1076, and auxiliary antioxidants 168, 619F, 3114, and DSTP.

[0020] Preferably, the compatibilizer selected in this invention is at least two of the following: maleic anhydride graft (such as maleic anhydride grafted polypropylene PP-g-MAH, with a grafting rate of 0.6%~1.5%), KH550 silane coupling agent, KH560 silane coupling agent, KH570 silane coupling agent, and acrylic acid grafted PP.

[0021] Secondly, the present invention provides a method for preparing the above-mentioned halogen-free flame-retardant long glass fiber reinforced polypropylene composite material resistant to precipitation, which includes the following steps:

[0022] (1) Preparation of composite flame retardant components:

[0023] ① Add magnesium nitrate and aluminum nitrate solutions dropwise to sodium hydroxide solution, stir at a constant temperature to carry out the reaction, then filter and wash with deionized water until neutral to obtain magnesium aluminum hydrotalcite (Mg / Al-LDHs). Add magnesium aluminum hydrotalcite to formamide solution and sonicate to obtain LDHs single-layer plate solution.

[0024] ② Add Na-MMT to an ethanol solution to swell, then add PAPP and MPP, stir to react, and after the reaction is complete and the supernatant is removed, the flame retardant component-loaded single-layer plate MMT solution is obtained.

[0025] ③ Mix the two single-layer plate solutions, sonicate them, let them stand, wash them with deionized water until neutral, and dry them to constant weight to obtain composite flame retardant component powder.

[0026] (2) After mixing polypropylene, composite flame retardant components, color powder, functional additives and compatibilizers according to the formula, the mixture is first plasticized and melted by an extruder, and then the melt is fed into the impregnation tank.

[0027] (3) Long glass fibers enter the impregnation tank under the action of the transmission device, disperse and be completely impregnated by the melt. The resulting material is pulled out of the impregnation tank and cooled and granulated to obtain a halogen-free flame-retardant long glass fiber reinforced polypropylene composite material resistant to precipitation.

[0028] Preferably, in step (1) ①, the molar ratio of magnesium nitrate and aluminum nitrate is 2:1, and after adding both to sodium hydroxide solution, the mixture is stirred at a constant temperature of 60°C for 12 hours; the conditions for ultrasonic treatment are: temperature 70°C, frequency 200Hz, and time 5 hours.

[0029] Preferably, in step (1) ②, the conditions for the stirring reaction are: temperature 60°C and time 24h.

[0030] Preferably, in step (1) ③, the conditions for ultrasonic treatment are: temperature 70℃, frequency 200Hz, and time 12h.

[0031] Preferably, in step (2), the process parameters for plasticizing and melting the extruder are: processing temperature of 200~250℃, main machine speed of 150~300rpm, and a vacuum pumping system is added during the extrusion process; the temperature of the impregnation tank is set to 250~300℃.

[0032] Preferably, in step (3), the length of the composite material particles is 10~16mm.

[0033] Montmorillonite (MMT), as a natural inorganic mineral material, possesses excellent thermal stability, with a dehydroxylation temperature reaching 550℃-750℃. Within the processing temperature range of long glass fiber reinforced polypropylene, its layered structure remains stable, exhibiting excellent heat resistance. Hydrotalcite (LDHs), as a type of layered bimetallic hydroxide, also possesses good high-temperature stability, maintaining structural integrity even below 400℃. Both have unique lamellar structures and abundant interlayer water content, commonly used as synergists in flame-retardant materials. Similar descriptions of their combination have appeared in other patents, such as CN202411314880.X, which mentions a composite antioxidant primarily composed of nickel-aluminum hydrotalcite combined with montmorillonite and hyperbranched triazine. However, this does not involve the process of self-combining the two layered compounds after lamellar peeling, failing to form a bipolar layered compound and thus not effectively integrating with polypropylene materials, leaving the precipitation problem unresolved. Patent CN202411314880.X also relates to the composite flame-retardant effect of hydrotalcite and montmorillonite, but it uses montmorillonite and hydrotalcite as functional carriers to load bio-based raw materials and flame-retardant components, respectively, and does not verify the energy level enhancement of the processing of flame-retardant components by the layered structure. This invention uses ultrasonic blending to peel off the single-layer plates of the two layered compounds. The montmorillonite and hydrotalcite plates are acidic and alkaline, respectively. A bipolar layer-by-layer self-assembled composite flame-retardant component is prepared using the plate rearrangement effect, exhibiting an overall non-polar nature. The high heat resistance of montmorillonite and hydrotalcite effectively protects the flame-retardant component, preventing its decomposition at high temperatures during the production of long glass fiber reinforced materials. Simultaneously, their synergistic effect significantly improves compatibility with the polypropylene matrix, effectively reducing the migration and precipitation rate of halogen-free flame retardants, addressing the application pain points of existing materials, and providing technical support for the application of reinforced polypropylene composites in fields such as appliance casings and battery casings.

[0034] The present invention has the following beneficial effects:

[0035] 1. By protecting the loaded flame-retardant components through the micro-layered structure of MMT and LDHs, the loss of flame retardants during the production of long glass fibers can be effectively reduced, while also providing some reinforcement to the material properties. Through the synergistic effect of bipolar layered compounds, the overall polarity of the composite flame-retardant components is reduced, and the compatibility with the polypropylene matrix is ​​greatly improved. This effectively inhibits the migration and precipitation of halogen-free flame retardants under high temperature and high humidity environments, completely solving problems such as surface blooming, stickiness, flame retardant performance degradation, and appearance deterioration.

[0036] 2. Long glass fibers easily break the continuous carbon layer in the flame retardant process. The selected composite flame retardant components, under the action of coupling agents and compatibilizers, tend to adhere to the glass fiber surface, which can greatly avoid the wick effect. At the same time, the water in the interlayer structure of the two layered compounds can also consume a large amount of heat in the combustion process, effectively preventing the material from burning.

[0037] 3. The composite flame-retardant system used in this material fully complies with international prohibited substances lists such as REACH. It can be widely applied to other filler systems and has a certain degree of versatility.

[0038] 4. The halogen-free flame-retardant polypropylene composite material prepared by this invention, through composite flame-retardant units and long glass fibers reinforcement, can improve the notched impact strength to 10 kJ / m compared to short fiber composite materials. 2 The above properties also achieve a V0 flame retardant rating. In subsequent applications, it can withstand 85% humidity and 85℃ high temperature and humidity environments for 1000 hours without leaching, making it widely applicable in automotive interiors, electrical appliance housings, municipal engineering, and other fields. Detailed Implementation

[0039] The present invention will be further described below with reference to specific embodiments. Unless otherwise specified, the raw materials used in the following embodiments are all commercially available conventional raw materials, and the experimental operations involved are all conventional operations in the art unless otherwise specified.

[0040] Example 1

[0041] The polypropylene composite material of this embodiment includes the following components (by weight): 48.6 parts high melt polypropylene, 20 parts alkali-free long glass fiber, 25 parts composite flame retardant components (including 15 parts PAPP, 7.5 parts MPP, 1.25 parts MMT, and 1.25 parts LDHs), 1 part colorant, 0.4 parts functional additives (including 0.2 parts each of antioxidants 1010 and 168), and 5 parts compatibilizer (including 1 part KH560 and 4 parts PP-g-MAH).

[0042] Example 2

[0043] The polypropylene composite material of this embodiment includes the following components (by weight): 50.6 parts high melt polypropylene, 20 parts alkali-free long glass fiber, 23 parts composite flame retardant components (including 13.8 parts PAPP, 6.9 parts MPP, 1.15 parts MMT, and 1.15 parts LDHs), 1 part colorant, 0.4 parts functional additives (including 0.2 parts each of antioxidants 1010 and 168), and 5 parts compatibilizer (including 1 part KH560 and 4 parts PP-g-MAH).

[0044] Example 3

[0045] The polypropylene composite material of this embodiment includes the following components (by weight): 53.6 parts high melt polypropylene, 20 parts alkali-free long glass fiber, 20 parts composite flame retardant component (including 12 parts PAPP, 6 parts MPP, 1 part MMT, and 1 part LDHs), 1 part colorant, 0.4 parts functional additives (including 0.2 parts each of antioxidants 1010 and 168), and 5 parts compatibilizer (including 1 part KH560 and 4 parts PP-g-MAH).

[0046] Example 4

[0047] The polypropylene composite material of this embodiment includes the following components (by weight): 38.6 parts high melt polypropylene, 30 parts alkali-free long glass fiber, 25 parts composite flame retardant components (including 15 parts PAPP, 7.5 parts MPP, 1.25 parts MMT, and 1.25 parts LDHs), 1 part colorant, 0.4 parts functional additives (including 0.2 parts each of antioxidants 1010 and 168), and 5 parts compatibilizer (including 1 part KH560 and 4 parts PP-g-MAH).

[0048] Example 5

[0049] The polypropylene composite material of this embodiment includes the following components (by weight): 40.6 parts high melt polypropylene, 30 parts alkali-free long glass fiber, 23 parts composite flame retardant components (including 13.8 parts PAPP, 6.9 parts MPP, 1.15 parts MMT, and 1.15 parts LDHs), 1 part colorant, 0.4 parts functional additives (including 0.2 parts each of antioxidants 1010 and 168), and 5 parts compatibilizer (including 1 part KH560 and 4 parts PP-g-MAH).

[0050] Example 6

[0051] The polypropylene composite material of this embodiment includes the following components (by weight): 43.6 parts high melt polypropylene, 30 parts alkali-free long glass fiber, 20 parts composite flame retardant component (including 12 parts PAPP, 6 parts MPP, 1 part MMT, and 1 part LDHs), 1 part colorant, 0.4 parts functional additives (including 0.2 parts each of antioxidants 1010 and 168), and 5 parts compatibilizer (including 1 part KH560 and 4 parts PP-g-MAH).

[0052] The component formulations of the polypropylene composite materials in the above embodiments are shown in Table 1.

[0053] Table 1. Specific component dosages (parts by weight) in the examples

[0054]

[0055] Comparative Example 1

[0056] This comparative example of polypropylene composite material comprises the following components (by weight): 50.6 parts high melt polypropylene, 20 parts alkali-free long glass fiber, 23 parts composite flame retardant component (of which PAPP 15.3 parts and MPP 7.7 parts), 1 part colorant, 0.4 parts functional additives (of which antioxidants 1010 and 168, 0.2 parts each), and 5 parts compatibilizer (of which KH560 1 part and PP-g-MAH 4 parts).

[0057] Comparative Example 2

[0058] This comparative example of polypropylene composite material comprises the following components (by weight): 50.6 parts high melt polypropylene, 20 parts alkali-free long glass fiber, 23 parts composite flame retardant component (of which PAPP 13.8 parts, MPP 6.9 parts, MMT 2.3 parts), 1 part colorant, 0.4 parts functional additives (of which antioxidants 1010 and 168, 0.2 parts each), and 5 parts compatibilizer (of which KH560 1 part and PP-g-MAH 4 parts).

[0059] Comparative Example 3

[0060] This comparative example of polypropylene composite material comprises the following components (by weight): 50.6 parts high melt polypropylene, 20 parts alkali-free long glass fiber, 23 parts composite flame retardant component (including 13.8 parts PAPP, 6.9 parts MPP, and 2.3 parts LDHs), 1 part colorant, 0.4 parts functional additives (including 0.2 parts each of antioxidants 1010 and 168), and 5 parts compatibilizer (including 1 part KH560 and 4 parts PP-g-MAH).

[0061] Comparative Example 4

[0062] This comparative example of polypropylene composite material comprises the following components (by weight): 40.6 parts high melt polypropylene, 30 parts alkali-free long glass fiber, 23 parts composite flame retardant component (of which PAPP 15.3 parts and MPP 7.7 parts), 1 part colorant, 0.4 parts functional additives (of which antioxidants 1010 and 168, 0.2 parts each), and 5 parts compatibilizer (of which KH560 1 part and PP-g-MAH 4 parts).

[0063] Comparative Example 5

[0064] This comparative example of polypropylene composite material comprises the following components (by weight): 50.6 parts high melt polypropylene, 20 parts alkali-free short glass fiber, 23 parts composite flame retardant component (including 13.8 parts PAPP, 6.9 parts MPP, 1.15 parts MMT, and 1.15 parts LDHs), 1 part colorant, 0.4 parts functional additives (including 0.2 parts each of antioxidants 1010 and 168), and 5 parts compatibilizer (including 1 part KH560 and 4 parts PP-g-MAH).

[0065] Comparative Example 6

[0066] This comparative example of polypropylene composite material comprises the following components (by weight): 40.6 parts high melt polypropylene, 20 parts alkali-free short glass fiber, 23 parts composite flame retardant component (including 13.8 parts PAPP, 6.9 parts MPP, 1.15 parts MMT, and 1.15 parts LDHs), 1 part colorant, 0.4 parts functional additives (including 0.2 parts each of antioxidants 1010 and 168), and 5 parts compatibilizer (including 1 part KH560 and 4 parts PP-g-MAH).

[0067] The formulations of the polypropylene composite materials in the above comparative examples are shown in Table 2.

[0068] Table 2. Specific component dosages (parts by weight) for comparative examples

[0069]

[0070] In the above embodiments and comparative compound formulations:

[0071] The high melt polypropylene is a copolymer polypropylene, specifically ExxonMobil polypropylene BX3900 (MFR 92g / 10min 230℃, 2.16kg), which is commercially available.

[0072] Long glass fiber (alkali-free long glass fiber) is Owens Corning OC4805-2400 (2400 tex) commercially available.

[0073] The composite flame-retardant component is a blend of sodium-based montmorillonite, magnesium aluminum hydrotalcite, piperazine pyrophosphate, and melamine polyphosphate. Among them:

[0074] The sodium-based montmorillonite (Na-MMT) is commercially available. The magnesium aluminum hydrotalcite is prepared by co-precipitation; the raw materials, aluminum nitrate, magnesium nitrate, and sodium hydroxide, are analytical grade and commercially available. The piperazine pyrophosphate (PAPP) is a commercially available product of Connors, brand name HF-800A. The melamine polyphosphate (MPP) is JELS PNA350.

[0075] The pigment is furnace black, with a specific surface area of ​​125-140 m². 2 / g, commercially available.

[0076] The antioxidants are a combination of two commercially available products: Saint-Lecter Antioxidant 168 and 1010.

[0077] The compatibilizer is a mixture of Huawen maleic anhydride graft HW501 (PP-g-MAH) and KH560 silane coupling agent, which are commercially available.

[0078] The polypropylene composite materials of Examples 1-6 above were prepared according to the following steps:

[0079] (1) Preparation of composite flame retardant components:

[0080] ① A solution of magnesium nitrate and aluminum nitrate in a molar ratio of 2:1 was added dropwise to a sodium hydroxide solution. The mixture was stirred at a constant temperature of 60℃ for 12 hours. After filtration and washing with deionized water until neutral, magnesium aluminum hydrotalcite (Mg / Al-LDHs) was obtained. The magnesium aluminum hydrotalcite was then added to a formamide solution and sonicated at 70℃ (200Hz) for 5 hours to obtain a single-layer LDHs plate solution.

[0081] ② Add Na-MMT to an ethanol solution to swell, then add PAPP and MPP, stir at 60℃ for 24 hours, and remove the supernatant after standing to obtain an intumescent flame retardant component-loaded monolayer MMT solution.

[0082] ③ Mix the two single-layer plate solutions, sonicate at 70℃ (200Hz) for 12 hours, let stand, wash with deionized water until neutral, and dry to constant weight to obtain composite flame retardant component powder.

[0083] (2) After mixing polypropylene, composite flame retardant components, color powder, functional additives and compatibilizers according to the formula, the mixture is first plasticized and melted through an extruder at a processing temperature of 200~250℃ and a main machine speed of 150~300rpm. A vacuum pumping system is added during the extrusion process. Then the melt is fed into the impregnation tank, and the impregnation tank temperature is set to 250~300℃.

[0084] (3) Long glass fibers enter the impregnation tank under the action of the transmission device, disperse and be completely impregnated by the melt. The resulting material is pulled out of the impregnation tank and cooled and granulated to obtain a halogen-free flame-retardant long glass fiber reinforced polypropylene composite material with a particle length of 10~16mm.

[0085] The polypropylene composite materials of Comparative Examples 1-4 were prepared according to the following steps:

[0086] (1) According to the formula, MMT, LDHs, PAPP, MPP powder (the specific number depends on the comparative formula), polypropylene, color powder, functional additives, and compatibilizer are mixed evenly and then plasticized and melted in an extruder at a processing temperature of 200~250℃ and a main machine speed of 150~300rpm. A vacuum pumping system is added during the extrusion process. Then the melt is fed into the impregnation tank, and the impregnation tank temperature is set to 250~300℃.

[0087] (2) Continuous long glass fibers enter the impregnation tank under the action of the transmission device, disperse and be completely impregnated by the melt. The resulting material is pulled out of the impregnation tank and cooled and granulated to obtain halogen-free flame-retardant long glass fiber reinforced polypropylene with a particle length of 10~16mm.

[0088] The polypropylene composite materials of Comparative Examples 5-6 were prepared according to the following steps:

[0089] (1) Preparation of composite flame retardant components:

[0090] ① A solution of magnesium nitrate and aluminum nitrate in a molar ratio of 2:1 was added dropwise to a sodium hydroxide solution. The mixture was stirred at a constant temperature of 60℃ for 12 hours. After filtration and washing with deionized water until neutral, magnesium aluminum hydrotalcite (Mg / Al-LDHs) was obtained. The magnesium aluminum hydrotalcite was then added to a formamide solution and sonicated at 70℃ (200Hz) for 5 hours to obtain a single-layer LDHs plate solution.

[0091] ② Add Na-MMT to an ethanol solution to swell, then add PAPP and MPP, stir at 60℃ for 24 hours, and remove the supernatant after standing to obtain an intumescent flame retardant component-loaded monolayer MMT solution.

[0092] ③ Mix the two single-layer plate solutions, sonicate at 70℃ (200Hz) for 12 hours, let stand, wash with deionized water until neutral, and dry to constant weight to obtain composite flame retardant component powder.

[0093] (2) Mix the raw materials polypropylene, functional additives, compatibilizers and color powder at high speed in proportion.

[0094] (3) After the materials from step (2) are mixed evenly, they are fed into the main feed port of the twin-screw extruder. The main machine speed is 300~500 rpm. Short glass fibers and composite flame retardant components are added to the side feed port located in the middle section. A vacuum pumping system is added during the stirring process. The process is as follows: Zone 1 150~170℃, Zone 2 160~180℃, Zone 3 160~180℃, Zone 4 170~190℃. Cooling water tank 20~60℃. Pelletizer pellet length is 2~4mm.

[0095] Performance testing:

[0096] According to common plastic mechanical property testing standards ISO 179-1, UL94 material flame retardancy standard, and T / CPCIF 0194-2022 piperazine pyrophosphate precipitation standard, the composite material was subjected to injection molding test, and the results are compared in Table 3 below.

[0097] Table 3 Performance test results of the examples and comparative examples

[0098]

[0099] As can be seen from the results table, the new flame-retardant system can achieve flame retardancy when the long glass fiber filling amount is 20% to 30%. When the addition amount is more than 23 parts, the combustion test result of the material is V0. When the addition amount is 20%, the glass fiber filling amount ≥30% cannot reach V0 (at this time, when the addition amount is less than 23%, it is impossible to form a sufficient carbon layer to insulate heat). Comparing Example 2 and Comparative Examples 1, 2, 3, and 4, it can be found that when the halogen-free chemical flame-retardant system is added alone, the material cannot be flame-retardant. This is because the temperature during the production process of long glass fibers is too high, which has a certain destructive effect on the halogen-free flame-retardant system without the protection of the laminate. The laminate composed of montmorillonite and hydrotalcite protects the halogen-free flame retardant in the form of a heat insulation layer, which plays a role in preventing the high-temperature decomposition of the flame retardant (for example, in Comparative Example 4, the flame retardant rating drops to HB when the halogen-free flame retardant is added directly without the protection of the heat insulation layer). Observing Comparative Examples 5 and 6, it can be found that the mechanical properties of the long fiber reinforced material are higher than those of the short fiber reinforced material in the same proportion under the same flame-retardant system. Each individual flame retardant system requires an addition of more than 25% to achieve a significant flame retardant effect. Comparing Examples 1-6 and Comparative Examples 1-4, it can be found that the exudation performance of materials using composite flame retardant systems is significantly improved. From a microscopic perspective, the layers of montmorillonite and hydrotalcite exhibit acidity and alkalinity, respectively. By utilizing the layer rearrangement effect, a bipolar layer-by-layer self-assembled composite flame retardant component was prepared, which is generally non-polar. The synergistic effect of the two can significantly improve the compatibility with the polypropylene matrix, effectively reduce the migration and exudation rate of halogen-free flame retardants, and solve the application pain points of existing materials.

[0100] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A halogen-free, flame-retardant, long glass fiber reinforced polypropylene composite material resistant to precipitation, characterized in that, It contains the following components in parts by weight: 35-55 parts of polypropylene 20-30 parts long glass fiber, 20-30 parts of composite flame retardant component, 1-1.5 parts of color powder, Functional additives 0.1~1 part, 4-8 parts compatibilizer; The composite flame retardant component is a blend of sodium montmorillonite, magnesium aluminum hydrotalcite, piperazine pyrophosphate, and melamine polyphosphate; the functional additive is an antioxidant.

2. The halogen-free flame-retardant long glass fiber reinforced polypropylene composite material resistant to precipitation according to claim 1, characterized in that, The polypropylene is a high melt flow index copolymer polypropylene resin with a melt flow index (MFR) ≥ 60.

3. The halogen-free flame-retardant long glass fiber reinforced polypropylene composite material resistant to precipitation according to claim 1, characterized in that, The long glass fiber is a continuous alkali-free long glass fiber with a diameter of 10~20μm and a linear density of 1200~3600tex.

4. The halogen-free flame-retardant long glass fiber reinforced polypropylene composite material resistant to precipitation according to claim 1, characterized in that, In the composite flame retardant component, sodium montmorillonite accounts for 5% to 15%, magnesium aluminum hydrotalcite accounts for 5% to 15%, piperazine pyrophosphate accounts for 50% to 70%, and melamine polyphosphate accounts for 20% to 30%.

5. The halogen-free flame-retardant long glass fiber reinforced polypropylene composite material resistant to precipitation according to claim 4, characterized in that, The weight ratio of piperazine pyrophosphate to melamine polyphosphate is 2:

1.

6. The halogen-free flame-retardant long glass fiber reinforced polypropylene composite material resistant to precipitation according to claim 1, characterized in that, The pigment is furnace black, with a specific surface area of ​​125~140m². 2 / g.

7. The halogen-free flame-retardant long glass fiber reinforced polypropylene composite material resistant to precipitation according to claim 1, characterized in that, The antioxidant is at least two of the following: general-purpose antioxidants 1010, 1035, and 1076, and auxiliary antioxidants 168, 619F, 3114, and DSTP.

8. The halogen-free flame-retardant long glass fiber reinforced polypropylene composite material resistant to precipitation according to claim 1, characterized in that, The compatibilizer is at least two of maleic anhydride graft, KH550 silane coupling agent, KH560 silane coupling agent, KH570 silane coupling agent and acrylic acid grafted PP, and the grafting rate of the maleic anhydride graft is 0.6% to 1.5%.

9. The method for preparing the halogen-free flame-retardant long glass fiber reinforced polypropylene composite material resistant to precipitation according to any one of claims 1 to 8, characterized in that, Includes the following steps: (1) Preparation of composite flame retardant components: ① Add magnesium nitrate and aluminum nitrate solutions dropwise to sodium hydroxide solution, stir at a constant temperature to carry out the reaction, then filter and wash with deionized water until neutral to obtain magnesium aluminum hydrotalcite; add magnesium aluminum hydrotalcite to formamide solution and sonicate to obtain LDHs single-layer plate solution; ② Sodium-based montmorillonite was added to an ethanol solution to swell, and piperazine pyrophosphate and melamine polyphosphate were added. The mixture was stirred and reacted. After the reaction was completed and the mixture was allowed to stand, the supernatant was removed to obtain a flame-retardant component-loaded single-layer plate MMT solution. ③ Mix the two single-layer plate solutions, sonicate, let stand, wash with deionized water until neutral, and dry to constant weight to obtain composite flame retardant component powder; (2) After mixing polypropylene, composite flame retardant components, color powder, functional additives and compatibilizers according to the formula, the mixture is first plasticized and melted by an extruder, and then the melt is fed into the impregnation tank. (3) Long glass fibers enter the impregnation tank under the action of the transmission device, disperse and be completely impregnated by the melt. The resulting material is pulled out of the impregnation tank and cooled and granulated to obtain a halogen-free flame-retardant long glass fiber reinforced polypropylene composite material resistant to precipitation.

10. The method for preparing the halogen-free flame-retardant long glass fiber reinforced polypropylene composite material resistant to precipitation according to claim 9, characterized in that, Includes the following steps: (1) Preparation of composite flame retardant components: ① Add magnesium nitrate and aluminum nitrate solutions with a molar ratio of 2:1 dropwise to sodium hydroxide solution, stir at 60℃ for 12 hours, then filter and wash with deionized water until neutral to obtain magnesium aluminum hydrotalcite; add magnesium aluminum hydrotalcite to formamide solution and sonicate at 70℃ and 200Hz for 5 hours to obtain LDHs single-layer plate solution. ② Sodium-based montmorillonite was added to an ethanol solution to swell, and piperazine pyrophosphate and melamine polyphosphate were added. The mixture was stirred at 60°C for 24 hours. After the reaction was completed and the mixture was allowed to stand, the supernatant was removed to obtain a flame-retardant component-loaded single-layer plate MMT solution. ③ Mix the two single-layer plate solutions, sonicate at 70℃ and 200Hz for 12 hours, let stand, wash with deionized water until neutral, and dry to constant weight to obtain composite flame retardant component powder. (2) After mixing polypropylene, composite flame retardant components, color powder, functional additives and compatibilizers according to the formula, the mixture is first plasticized and melted through an extruder. The processing temperature is 200~250℃ and the main machine speed is 150~300rpm. A vacuum pumping system is added during the extrusion process. Then the melt is fed into the impregnation tank and the impregnation tank temperature is set to 250~300℃. (3) Long glass fibers enter the impregnation tank under the action of the transmission device, disperse and be completely impregnated by the melt. The resulting material is pulled out of the impregnation tank and cooled and granulated to obtain a halogen-free flame-retardant long glass fiber reinforced polypropylene composite material with a particle length of 10~16mm.

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