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

Abstract

The invention discloses a low-carbon natural fiber flame-retardant reinforced polypropylene composite material and a preparation method thereof. The low-carbon natural fiber flame-retardant reinforced polypropylene composite material is prepared from the following components in parts by weight: 65-70 parts of low-melt-index co-polypropylene resin, 15-20 parts of natural coconut shred master batch, 10-20 parts of a composite flame-retardant component, 1-1.5 parts of toner, 1-3 parts of a functional aid and 3-4 parts of a compatilizer. The low-carbon natural fiber flame-retardant reinforced polypropylene composite material prepared by the invention has unique appearance, can be widely applied to the fields of automotive trim, indoor decoration engineering and product outer package, can achieve V0-level flame retardance, and greatly reduces the use risk of the product in a high-temperature environment; and the filled natural fiber part can effectively reduce the carbon emission in the production process.

Description

Technical Field

[0001] The present invention relates to the technical field of polypropylene materials, in particular to a low-carbon natural fiber flame retardant reinforced polypropylene composite material and a preparation method thereof. The material is suitable for automobile interior decoration, interior decoration engineering and product outer packaging materials, etc. Technical Background

[0002] With the advancement of science and technology and the development of society, people pay more and more attention to the environmental performance and sustainability of materials. Polypropylene, as a lightweight and high-strength plastic material, has been widely used in many fields such as automobiles, construction and packaging. In order to achieve the low carbonization of polypropylene materials, more and more natural fibers have been used to fill polypropylene modification in recent years. Coconut fiber is a natural fiber material extracted from coconut shells. It has low carbon value, excellent mechanical properties, high moisture resistance and other characteristics, and is an excellent choice for filling materials. At the same time, coconut fiber filled polypropylene material has unique appearance characteristics and soft visual appearance. It has been widely used in interior decoration, product packaging, automotive interior decoration and other aspects. However, the lack of flame retardancy of traditional coconut fiber filled polypropylene materials seriously limits its application in a wider range of fields. The simple addition of halogen-free flame retardant system often faces two problems. One is the low flame retardant efficiency. The traditional halogen-free flame retardant system needs to add more than 25% to achieve VO flame retardancy, which will cause the overall cost to be too high and is not conducive to reducing carbon emissions. The second is that the fibers in the fiber filling system are not well combined with the flame retardant component. During the combustion process, the arrangement of the fibers will form a puncture effect on the continuous carbon layer required for flame retardancy, resulting in a decrease in flame retardant effect.

[0003] In order to solve these problems, the present invention proposes a low-carbon natural fiber flame retardant reinforced polypropylene composite material and a preparation method thereof, aiming to provide a new material that is both environmentally friendly and has excellent flame retardant properties. The composite material involved in the present invention improves the flame retardant properties of the material by introducing a composite flame retardant, and the synergistic effect of expanded graphite (EG), montmorillonite (MMT) and piperazine pyrophosphate (PAPP) halogen-free flame retardants. Compared with the traditional halogen-free flame retardant system, the new flame retardant system has both physical expansion flame retardant and chemical expansion flame retardant systems, which can effectively reduce the amount of flame retardant added. At the same time, coconut silk masterbatch with a high melt index and low molecular weight polypropylene base is selected and blended with flame retardant components for extrusion. The organically modified MMT and coupling agent in the composite flame retardant are easily combined with the fiber to form a heat insulation layer, which has a heat insulation effect on the fiber, and effectively improves the flame retardant and heat resistance of the material. Summary of the invention

[0004] The technical problem to be solved by the present invention is the problem that the flame retardant performance of the existing natural coconut fiber reinforced polypropylene material is insufficient, and a low-carbon natural fiber flame retardant reinforced polypropylene composite material and a preparation method thereof are provided. In order to solve the above technical problems, the material of the present invention uses a physical and chemical double expansion synergistic flame retardant system of EG, MMT, and PAPP blends. At the same time, the characteristics of small molecular weight molecules in the microstructure tend to float on the surface of the material are utilized, and a high molecular weight masterbatch is selected to be combined with an extremely low molecular weight base material. Through coupling, the natural fiber and the flame retardant component are effectively combined, thereby improving the flame retardant grade and heat resistance of the material. The obtained material has the low-carbon advantage of natural fiber filling on the one hand, and has flame retardant properties on the other hand, so that the application range of the material has been expanded to a certain extent.

[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 in parts by weight:

[0007]

[0008] The low melting point homopolymer polypropylene has an MFR of ≤5 (2.16kg, 230°C)

[0009] The natural coconut shreds masterbatch has an effective content of 60% or more of coconut shreds and a base material MFR of 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% accounting for 25% to 50%, the montmorillonite is quaternary ammonium salt organic modified montmorillonite (OMMT) accounting for 5% to 10%, and piperazine pyrophosphate (PAPP) accounting for 50% to 70%.

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

[0012] The antioxidant is a compound of several general antioxidants such as 168, 619F, 3114, 1076, 1035, DSTP and 1010.

[0013] The compatibilizer is at least one of maleic anhydride grafted product (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 in proportion to an ethanol solution containing 5% silane coupling agent and stir evenly. After mixing for 1 hour, dry the material to constant weight.

[0016] (2) The raw material polypropylene, grafted material, antioxidant and color powder are mixed and stirred at high speed according to proportion.

[0017] (3) After the materials in step (2) are mixed evenly, they are fed into the main feed port of the twin-screw extruder, the main engine speed is 300-500rpm, the coconut shreds masterbatch and the composite flame retardant component are added to the side feed port located in the middle section, and a vacuum exhaust system is added during the stirring process. The process is: zone 1 150-170°C, zone 2 160-180°C, zone 3 160-180°C, zone 4 170-190°C. The cooling water tank is 20-60°C. The pelletizer pelletizing length is 2-4mm.

[0018] The advantages of the present invention are:

[0019] 1. The physical expansion of EG and the chemical expansion of PAPP have a higher efficiency, which can effectively reduce the amount of flame retardant added to achieve the purpose of cost reduction. At the same time, natural fiber filling has a significant carbon reduction effect compared to traditional materials.

[0020] 2. Coconut fiber itself has low heat resistance and is flammable. The entanglement of the fiber itself is also easy to break the continuous carbon layer and affect the flame retardant performance. High melt index coconut fiber masterbatch is selected and blended with flame retardant components. During the blending process, coconut fiber tends to be distributed in the surface part of the material along with the high melt component. Through the action of coupling agent and compatibilizer, coconut fiber and small molecular weight flame retardant components are linked. During the combustion process, EG expansion plays a pillar role on the MMT layer board, forming a multi-layer insulation structure, which can effectively protect coconut fiber.

[0021] 3 In recent years, more and more fluorinated flame retardants and anti-drip agents have been restricted and banned. The composite flame retardant system used in this material fully complies with the list of international banned substances such as REACH. It can be widely used in other filling systems and has a certain degree of versatility. DETAILED DESCRIPTION

[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 polypropylene (MFR≤5), 15% natural coconut masterbatch, 20% composite flame retardant component, 1% color powder, 1% antioxidant (including antioxidants 1010, 1035, 168, DSTP, each 0.25%), 3% compatibilizer (including KH560, PP-g-MAH each accounting for 1.5%). The detailed proportions of the flame retardant components are shown in Table 1.

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

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

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

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

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

[0029] Table 1 Specific components by weight

[0030]

[0031]

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

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

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

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

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

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

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

[0039] Table 2 Comparative Examples Specific Component Weight Ratio

[0040]

[0041] In the composite formula of the above embodiments and comparative examples:

[0042] The polypropylenes claimed are homopolymer polypropylenes, namely Sinopec T300 homopolymer polypropylene (MFR 3g / 10min 230°C, 21.6kg) and South Korea's LG Chemical MH7900 (100g / 10min 230°C, 21.6kg), which are commercially available.

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

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

[0045] The montmorillonite mentioned is quaternary ammonium salt organically modified montmorillonite (OMMT), which is commercially available.

[0046] The piperazine pyrophosphate (PAPP) in question is a product of Conrad Corporation with the brand name HF-800A.

[0047] The toner applicable to the present invention is furnace carbon black, which has a specific surface area of ​​120-145m 2 / g, commercially available.

[0048] The antioxidants used in the present invention are compounded with four types of 168, 1035, DSTP and 1010, which are commercially available.

[0049] The compatibilizer applicable to the present invention is a commercially available mixture of Huawen maleic anhydride graft HW501 and KH560 silane coupling agent in equal proportions.

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

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

[0052] (2) The raw material polypropylene, grafted material, antioxidant and color powder are mixed and stirred at high speed according to the proportion.

[0053] (3) After the materials in step (2) are mixed evenly, they are fed into the main feed port of the twin-screw extruder, the main engine speed is 300-500rpm, the coconut shreds masterbatch and the composite flame retardant component are added to the side feed port located in the middle section, and a vacuum exhaust system is added during the stirring process. The process is: zone 1 150-170°C, zone 2 160-180°C, zone 3 160-180°C, zone 4 170-190°C. The cooling water tank is 20-60°C. The pelletizer pelletizing length is 2-4mm.

[0054] (4) The composite materials were tested by injection molding according to the UL94 flame retardant standard, and the results are compared as follows. See Table 3:

[0055] Table 3 Combustion grade evaluation results of the embodiments and comparative examples

[0056]

[0057] It can be seen from the result table that the new flame retardant system can play a flame retardant role when the coconut fiber filling amount is 10-15%, and the combustion test result of the material is V0. Comparing Examples 1, 2 and Comparative Examples 4, 5, it can be found that when the physical expansion flame retardant system and the halogen-free chemical flame retardant system are added separately, the materials cannot be flame retardant; observing Comparative Examples 6 and 7, it can be found that the single flame retardant system needs to be added more than 25% to have a significant flame retardant effect. Comparing Example 2 and Comparative Example 3, it can be found that both have a two-component flame retardant system, and MMT needs to be added for synergy to have a relatively good flame retardant effect. From a microscopic perspective, this is because MMT can be used as a carbon source in the flame retardant process to improve the carbonization 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 insulation protective layer. Comparing Examples 1, 5 and Comparative Examples 1, 2, it can be found that when the base material polypropylene melt index is increased, the flame retardant grade of the product decreases. This shows that during the blending process, the coconut shreds in the masterbatch were not mostly distributed in the surface structure of the material as expected, and did not achieve sufficient contact and coupling with the flame retardant components. In the subsequent combustion process, some coconut shreds caught fire, causing the overall flame retardancy of the material to decrease.

[0058] The embodiments described above are only descriptions of the preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the protection scope determined by the claims of the present invention.

Claims

1. A low-carbon natural fiber flame retardant reinforced polypropylene composite material, characterized in that: Made from the following components by weight:

2. The low-carbon natural fiber flame retardant reinforced polypropylene composite material according to claim 1, characterized in that: The MFR of the low melt index polypropylene resin is ≤5.

3. The low-carbon natural fiber flame retardant reinforced polypropylene composite material according to claim 1, characterized in that: The natural coconut shreds masterbatch has an effective coconut shreds content of ≥60% and a base material MFR of ≥90.

4. The low-carbon natural fiber flame retardant reinforced polypropylene composite material according to claim 1, characterized in that: 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% accounting for 25% to 50%, the montmorillonite is quaternary ammonium salt organic modified montmorillonite (OMMT) accounting for 5% to 10%, and piperazine pyrophosphate (PAPP) accounting for 50% to 70%.

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

6. The low-carbon natural fiber flame retardant reinforced polypropylene composite material according to claim 1, characterized in that: The antioxidant is a compound of several general antioxidants such as 168, 619F, 3114, 1076, 1035, DSTP and 1010.

7. 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 grafted product (grafting rate 0.5-2%), KH550 silane coupling agent, KH560 silane coupling agent and acrylic acid grafted PP.

8. The method for preparing a low-carbon natural fiber flame retardant reinforced polypropylene composite material according to any one of claims 1 to 7, characterized in that: It is characterized by comprising the following steps: (1) Add OMMT, EG, and PAPP powders in proportion to an ethanol solution containing 5% silane coupling agent and stir evenly. After mixing for 1 hour, dry the material to constant weight; (2) mixing the raw material polypropylene, grafted material, antioxidant, and color powder in proportion and at high speed; (3) After the materials in step (2) are mixed evenly, they are fed into the main feed port of the twin-screw extruder, and the main engine speed is 300-500rpm; the coconut shreds masterbatch and the composite flame retardant component are added to the side feed port located in the middle section, and a vacuum exhaust system is added during the stirring process. The process is: zone 1 150-170°C, zone 2 160-180°C, zone 3 160-180°C, zone 4 170-190°C. The cooling water tank is 20-60°C. The pelletizer pelletizing length is 2-4mm.

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