Low-carbon natural fiber flame-retardant reinforced polypropylene composite material and preparation method thereof

Abstract

The application discloses a low-carbon natural fiber flame-retardant reinforced polypropylene composite material and a preparation method thereof, which is prepared from the following components in parts by weight: low-melt-index copolymerized polypropylene resin 65-70 parts, natural coconut fiber master batch 15-20 parts, composite flame-retardant component 10-20 parts, toner 1-1.5 parts, functional additive 1-3 parts and compatibilizer 3-4 parts. The low-carbon natural fiber flame-retardant reinforced polypropylene composite material prepared by the application has a unique appearance and can be widely used in automobile interior decoration, indoor decoration engineering and product packaging fields, and meanwhile, the material can reach V0 level of flame retardation, greatly reduces the use risk of the product in a high-temperature environment, and the filled natural fiber part can effectively reduce carbon emission in the production process.

Description

Technical Field

[0001] This invention relates to the field of polypropylene materials technology, specifically a low-carbon natural fiber flame-retardant reinforced polypropylene composite material and its preparation method. The material is suitable for automotive interiors, interior decoration projects, and product packaging materials, etc. Technical Background

[0002] With the advancement of technology and social development, people are paying increasing attention to the environmental performance and sustainability of materials. Polypropylene, as a lightweight and high-strength plastic material, has been widely used in various fields such as automobiles, construction, and packaging. To achieve low-carbon transformation of polypropylene materials, more and more natural fibers have been used in recent years to fill and modify polypropylene. Coconut fiber, a natural fiber material extracted from coconut shells, has low carbon value, excellent mechanical properties, and high moisture resistance, making it an excellent choice for filler materials. At the same time, coconut fiber-filled polypropylene materials have unique appearance characteristics and a soft visual feel, and are currently widely used in interior decoration, product packaging, and automotive interior decoration. However, the insufficient flame retardancy of traditional coconut fiber-filled polypropylene materials severely limits their application in a wider range of fields. Simply adding halogen-free flame retardant systems often faces two problems: first, low flame retardant efficiency; traditional halogen-free flame retardant systems require an addition of more than 25% to achieve VO flame retardancy, which results in excessively high overall costs and is not conducive to reducing carbon emissions. Second, the fibers in the fiber-filled system do not bond well with the flame retardant components. During combustion, the fiber arrangement can puncture the continuous carbon layer required for flame retardancy, leading to a decrease in the flame retardant effect.

[0003] To address these issues, this invention proposes a low-carbon natural fiber flame-retardant reinforced polypropylene composite material and its preparation method, aiming to provide a novel material that is both environmentally friendly and possesses excellent flame-retardant properties. The composite material involved in this invention improves its flame-retardant properties through the synergistic effect of expanded graphite (EG), montmorillonite (MMT), and piperazine pyrophosphate (PAPP) halogen-free flame retardants by introducing a composite flame retardant. Compared with traditional halogen-free flame-retardant systems, the new flame-retardant system simultaneously possesses both physical and chemical expansion flame retardancy, effectively reducing the amount of flame retardant required. Furthermore, high melt index, low molecular weight polypropylene-based coconut fiber masterbatch is co-extruded with the flame-retardant components. The organically modified MMT and coupling agent in the composite flame retardant readily combine with the fibers to form a heat-insulating layer, effectively improving the flame-retardant and heat-resistant properties of the material. Summary of the Invention

[0004] The technical problem this invention aims to solve is the insufficient flame retardant properties of existing natural coconut fiber reinforced polypropylene materials. This invention provides a low-carbon natural fiber flame-retardant reinforced polypropylene composite material and its preparation method. To address the above technical problem, the material of this invention uses a physicochemical dual-expansion synergistic flame retardant system composed of EG, MMT, and PAPP blends. Simultaneously, utilizing the characteristic that small molecular weight molecules in the microstructure tend to float on the material surface, a high molecular weight masterbatch combined with an extremely low molecular weight matrix is ​​selected. Through coupling, the natural fibers and flame-retardant components are effectively combined, improving the flame retardant rating and heat resistance of the material. The resulting material possesses both the low-carbon advantages of natural fiber filling and flame-retardant properties, thus expanding its application range.

[0005] The present invention adopts the following technical solution:

[0006] A low-carbon natural fiber flame-retardant reinforced polypropylene composite material, comprising the following components by weight:

[0007]

[0008] The low melt flow index homopolymer polypropylene has an MFR ≤ 5 (2.16 kg, 230 °C).

[0009] The natural coconut fiber masterbatch has an effective coconut fiber content of ≥60% and a base material MFR.90.

[0010] The composite flame-retardant unit is a blend of expanded graphite (EG), montmorillonite (MMT), and piperazine pyrophosphate, wherein the expanded graphite is sulfuric acid intercalated EG with an ash content of ≤3% and a proportion of 25% to 50%, the montmorillonite is quaternary ammonium salt organic modified montmorillonite (OMMT) with a proportion of 5% to 10%, and the piperazine pyrophosphate (PAPP) has a proportion of 50% to 70%.

[0011] The pigment is furnace black with a specific surface area of ​​120-145 m². 2 / g.

[0012] The antioxidants mentioned are a combination of several of the general-purpose 168, 619F, 3114, 1076, 1035, DSTP, and 1010.

[0013] The compatibilizer is at least one of maleic anhydride graft (grafting rate 0.5-2%), KH560 silane coupling agent, KH570 silane coupling agent, and acrylic acid grafted PP.

[0014] The above-mentioned natural fiber reinforced polypropylene composite material is characterized by comprising the following steps:

[0015] (1) Add OMMT, EG, and PAPP powders to an ethanol solution containing 5% silane coupling agent in proportion and stir until uniform. After mixing for 1 hour, dry the material to constant weight.

[0016] (2) Mix the raw materials polypropylene, grafted material, antioxidant and color powder at high speed in proportion.

[0017] (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 extruder speed is 300-500 rpm. Coconut fiber masterbatch 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.

[0018] The advantages of this invention are:

[0019] 1. The combined effect of physical expansion of EG and chemical expansion of PAPP is more efficient, effectively reducing the amount of flame retardant needed to achieve cost reduction. Meanwhile, natural fiber fillers have a significant carbon reduction effect compared to traditional materials.

[0020] 2. Coconut fiber itself has low heat resistance and is flammable. The intertwining of the fibers can also easily break the continuous carbon layer, affecting flame retardant performance. High melt flow index coconut fiber masterbatch and flame retardant components are blended. During blending, the coconut fiber tends to distribute along with the high melt flow component on the surface of the material. Through the action of coupling agents and compatibilizers, the coconut fiber and the low molecular weight flame retardant component are linked. During combustion, the expansion of EG (extracorporeal membrane oxygenate) acts as a pillar supporting the MMT (Multi-Layer Metallic Media) layer, forming a multi-layered thermal insulation structure that effectively protects the coconut fiber.

[0021] 3. In recent years, fluorinated flame retardants and anti-dripping agents have been increasingly restricted or banned. The composite flame retardant system used in this material fully complies with international lists of prohibited substances such as REACH. It can be widely applied to other filler systems and has a certain degree of versatility. Detailed Implementation

[0022] The present invention will be further described below by way of examples and comparative examples, but the present invention is not limited to the scope of the examples.

[0023] Example 1: The main components of the polypropylene composite material of the present invention include: 60% low-melting-point polypropylene (MFR≤5), 15% natural coconut fiber masterbatch, 20% composite flame retardant component, 1% colorant, 1% antioxidant (of which antioxidants 1010, 1035, 168, and DSTP each account for 0.25%), and 3% compatibilizer (of which KH560 and PP-g-MAH each account for 1.5%). Detailed proportions of the flame retardant component are shown in Table 1.

[0024] Example 2: The main components of the polypropylene composite material of the present invention include: 60% low-melting-point polypropylene (MFR≤5), 15% natural coconut fiber masterbatch, 20% composite flame retardant component, 1% colorant, 1% antioxidant (of which antioxidants 1010, 1035, 168, and DSTP each account for 0.25%), and 3% compatibilizer (of which KH560 and PP-g-MAH each account for 1.5%). Detailed proportions of the flame retardant component are shown in Table 1.

[0025] Example 3: The main components of the polypropylene composite material of the present invention include: 60% low-melting-point polypropylene (MFR≤5), 15% natural coconut fiber masterbatch, 20% composite flame retardant component, 1% colorant, 1% antioxidant (of which antioxidants 1010, 1035, 168, and DSTP each account for 0.25%), and 3% compatibilizer (of which KH560 and PP-g-MAH each account for 1.5%). Detailed proportions of the flame retardant component are shown in Table 1.

[0026] Example 4: The main components of the polypropylene composite material of the present invention include: 60% low-melting-point polypropylene (MFR≤5), 15% natural coconut fiber masterbatch, 20% composite flame retardant component, 1% colorant, 1% antioxidant (of which antioxidants 1010, 1035, 168, and DSTP each account for 0.25%), and 3% compatibilizer (of which KH560 and PP-g-MAH each account for 1.5%). Detailed proportions of the flame retardant component are shown in Table 1.

[0027] Example 5: The main components of the polypropylene composite material of the present invention include: 70% low-melting-point polypropylene (MFR≤5), 10% natural coconut fiber masterbatch, 15% composite flame retardant component, 1% colorant, 1% antioxidant (of which antioxidants 1010, 1035, 168, and DSTP each account for 0.25%), and 3% compatibilizer (of which KH560 and PP-g-MAH each account for 1.5%). Detailed proportions of the flame retardant component are shown in Table 1.

[0028] Example 6: The main components of the polypropylene composite material of the present invention include: 70% low-melting-point polypropylene (MFR≤5), 10% natural coconut fiber masterbatch, 15% composite flame retardant component, 1% colorant, 1% antioxidant (of which antioxidants 1010, 1035, 168, and DSTP each account for 0.25%), and 3% compatibilizer (of which KH560 and PP-g-MAH each account for 1.5%). Detailed proportions of the flame retardant component are shown in Table 1.

[0029] Table 1 shows the specific weight percentages of the components in the embodiments.

[0030]

[0031]

[0032] Comparative Example 1: The main components of this polypropylene composite material include: 60% high melt flow index polypropylene (MFR≥90), 15% natural coconut fiber masterbatch, 20% composite flame retardant component, 1% colorant, 1% antioxidant (of which antioxidants 1010, 1035, 168, and DSTP each account for 0.25%), and 3% compatibilizer (of which KH560 and PP-g-MAH each account for 1.5%). Detailed proportions of the flame retardant component are shown in Table 2.

[0033] Comparative Example 2: The main components of this polypropylene composite material include: 70% high melt flow index polypropylene (MFR≥90), 10% natural coconut fiber masterbatch, 10% composite flame retardant component, 1% colorant, 1% antioxidant (of which antioxidants 1010, 1035, 168, and DSTP each account for 0.25%), and 3% compatibilizer (of which KH560 and PP-g-MAH each account for 1.5%). Detailed proportions of the flame retardant component are shown in Table 2.

[0034] Comparative Example 3: The main components of this polypropylene composite material include: 60% low-melting-point polypropylene (MFR≤5), 15% natural coconut fiber masterbatch, 20% composite flame retardant component, 1% colorant, 1% antioxidant (of which antioxidants 1010, 1035, 168, and DSTP each account for 0.25%), and 3% compatibilizer (of which KH560 and PP-g-MAH each account for 1.5%). Detailed proportions of the flame retardant component are shown in Table 2.

[0035] Comparative Example 4: The main components of this polypropylene composite material include: 60% low-melting-point polypropylene (MFR≤5), 15% natural coconut fiber masterbatch, 20% composite flame retardant component, 1% colorant, 1% antioxidant (of which antioxidants 1010, 1035, 168, and DSTP each account for 0.25%), and 3% compatibilizer (of which KH560 and PP-g-MAH each account for 1.5%). Detailed proportions of the flame retardant component are shown in Table 2.

[0036] Comparative Example 5: The main components of this polypropylene composite material include: 60% low-melting-point polypropylene (MFR≤5), 15% natural coconut fiber masterbatch, 20% composite flame retardant component, 1% colorant, 1% antioxidant (of which antioxidants 1010, 1035, 168, and DSTP each account for 0.25%), and 3% compatibilizer (of which KH560 and PP-g-MAH each account for 1.5%). Detailed proportions of the flame retardant component are shown in Table 2.

[0037] Comparative Example 6: The main components of this polypropylene composite material include: 48% low-melting-point polypropylene (MFR≤5), 15% natural coconut fiber masterbatch, 30% composite flame retardant component, 1% colorant, 1% antioxidant (of which antioxidants 1010, 1035, 168, and DSTP each account for 0.25%), and 3% compatibilizer (of which KH560 and PP-g-MAH each account for 1.5%). Detailed proportions of the flame retardant component are shown in Table 2.

[0038] Comparative Example 7: The main components of this polypropylene composite material include: 50% low-melting-point polypropylene (MFR≤5), 15% natural coconut fiber masterbatch, 30% composite flame retardant component, 1% colorant, 1% antioxidant (of which antioxidants 1010, 1035, 168, and DSTP each account for 0.25%), and 3% compatibilizer (of which KH560 and PP-g-MAH each account for 1.5%). Detailed proportions of the flame retardant component are shown in Table 2.

[0039] Table 2 Comparative Examples: Specific Component Weight Percentages

[0040]

[0041] In the above embodiments and comparative compound formulations:

[0042] The polypropylene in question is homopolymer polypropylene, specifically Sinopec T300 homopolymer polypropylene (MFR 3g / 10min 230℃, 21.6kg) and LG Chem MH7900 (100g / 10min 230℃, 21.6kg), both commercially available.

[0043] The natural coconut shred masterbatch has an effective coconut shred content of 65%, a base material MFR 95, and is commercially available.

[0044] The expanded graphite (EG) mentioned is sulfuric acid intercalated EG with an ash content of ≤3% and an average particle size of 60μm, and is commercially available.

[0045] The montmorillonite in question is quaternary ammonium salt organic modified montmorillonite (OMMT), which is commercially available.

[0046] The alleged piperazine pyrophosphate (PAPP) is a product of Connors Corporation, brand name HF-800A.

[0047] The pigment used in this invention is furnace black, with a specific surface area of ​​120-145 m². 2 / g, commercially available.

[0048] The antioxidants used in this invention are four commercially available compounds: Tong Sheng Leike Special Type 168, 1035, DSTP, and 1010.

[0049] The compatibilizer used in this invention is a mixture of Huawen maleic anhydride graft HW501 and KH560 silane coupling agent in equal proportions, which is commercially available.

[0050] The above-mentioned embodiments and comparative components are processed according to the following steps:

[0051] (1) Add OMMT, EG, and PAPP powders to an ethanol solution containing 5% silane coupling agent in proportion and stir until uniform. After mixing for 1 hour, dry the material to constant weight.

[0052] (2) Mix the raw materials polypropylene, grafted material, antioxidant and color powder at high speed in proportion.

[0053] (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 extruder speed is 300-500 rpm. Coconut fiber masterbatch 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.

[0054] (4) Injection molding tests were conducted on the composite material according to the UL94 flame retardant standard, and the results are compared below. See Table 3:

[0055] Table 3. Combustion rating results for the examples and comparative examples.

[0056]

[0057] The results table shows that the new flame-retardant system can achieve flame retardancy when the coconut fiber filling content is 10-15%, and the combustion test result of the material is V0. Comparing Examples 1 and 2 with Comparative Examples 4 and 5, it can be found that neither the physically expanding flame-retardant system nor the halogen-free chemical flame-retardant system can retard the material. Observing Comparative Examples 6 and 7, it can be found that each single flame-retardant system needs to be added at a concentration of more than 25% to achieve a significant flame-retardant effect. Comparing Examples 2 and 3, it can be found that both possess a two-component flame-retardant system, and MMT needs to be added for synergistic effect to achieve a relatively good flame-retardant effect. From a microscopic perspective, this is because MMT can be used as a char source in the flame-retardant process, improving char formation efficiency; on the other hand, the polar groups of organically modified MMT are more likely to connect with coconut fiber and adhere to the fiber surface to form a heat-insulating protective layer. Comparing Examples 1 and 5 with Comparative Examples 1 and 2, it can be found that when the melt index of the base polypropylene increases, the flame-retardant grade of the product decreases. This indicates that during the blending process, the coconut fiber in the masterbatch was not distributed primarily on the surface of the material as expected, and did not achieve sufficient contact and coupling with the flame-retardant components. Consequently, some of the coconut fiber ignited and burned during subsequent combustion, leading to a decrease in the overall flame-retardant rating of the material.

[0058] 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 low-carbon natural fiber flame-retardant reinforced polypropylene composite material, characterized in that, It is made from the following components in parts by weight: 60-70 parts of low melt index copolymer polypropylene resin, 10-15 parts of natural coconut fiber masterbatch, 15-20 parts of composite flame retardant unit, 1-1.5 parts of color powder, 1-3 parts of functional additives, and 3-4 parts of compatibilizer. The low melt flow rate copolymer polypropylene resin has an MFR ≤ 5 g / 10 min under the test conditions of 2.16 kg and 230℃; the composite flame retardant unit is a blend of expanded graphite, montmorillonite, and piperazine pyrophosphate, wherein the expanded graphite is sulfuric acid intercalated expanded graphite with an ash content ≤ 3% and a proportion of 25% to 50%, the montmorillonite is quaternary ammonium salt organic modified montmorillonite with a proportion of 5% to 10%, and the piperazine pyrophosphate has a proportion of 50% to 70%; the functional additive is an antioxidant.

2. The low-carbon natural fiber flame-retardant reinforced polypropylene composite material according to claim 1, characterized in that: The natural coconut shred masterbatch has an effective coconut shred content of ≥60%.

3. The low-carbon natural fiber flame-retardant reinforced polypropylene composite material according to claim 1, characterized in that: The pigment is furnace black with a specific surface area of ​​120-145 m². 2 / g.

4. The low-carbon natural fiber flame-retardant reinforced polypropylene composite material according to claim 1, characterized in that: The antioxidants mentioned are a combination of several general-purpose antioxidants, namely 168, 619F, 3114, 1076, 1035, DSTP, and 1010.

5. The low-carbon natural fiber flame-retardant reinforced polypropylene composite material according to claim 1, characterized in that: The compatibilizer is at least one of maleic anhydride graft with a grafting rate of 0.5-2%, KH550 silane coupling agent, KH560 silane coupling agent, and acrylic acid grafted PP.

6. A method for preparing a low-carbon natural fiber flame-retardant reinforced polypropylene composite material according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Add montmorillonite, expanded graphite and piperazine pyrophosphate powder to an ethanol solution containing 5% silane coupling agent in proportion and stir evenly. After mixing for 1 hour, dry the material to constant weight. (2) Mix the raw materials polypropylene, compatibilizer, antioxidant and color powder at high speed in proportion; (3) After the material in step (2) is mixed evenly, it is fed into the main feed port of the twin-screw extruder. The main machine speed is 300-500 rpm. Coconut fiber masterbatch 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.

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