Composite fiber flame retardant, plant fiber filled polypropylene flame retardant composite material and preparation method and application thereof

Abstract

The present invention discloses a composite fiber flame retardant, a plant fiber-filled polypropylene flame-retardant composite material, and a preparation method and application thereof. The composite fiber flame retardant comprises the following raw materials in parts by mass: 5 to 12 parts of red phosphorus, 5 to 15 parts of plant powder, 1 to 5 parts of graphene, 0.1 to 0.4 parts of coupling agent, and 0.5 to 1.5 parts of polyester resin; the length distribution range of the composite fiber flame retardant is 95 to 355 μm, the average length is ≤ 235 μm, and the aspect ratio is 220:1 to 380:1. The flame retardant can not only meet the flame retardant properties required by the material, but also effectively ensure the mechanical properties and appearance of the composite material, while having environmental protection advantages. The present invention also provides a preparation method for the above-mentioned composite fiber flame retardant, a plant fiber-filled polypropylene flame-retardant composite material prepared using the composite fiber flame retardant, and a preparation method and application thereof.

Description

Technical Field

[0001] The invention relates to the technical field of flame retardant materials, and in particular to a composite fiber flame retardant, a plant fiber-filled polypropylene flame retardant composite material, and a preparation method and application thereof. Background Art

[0002] Polypropylene is a thermoplastic with excellent comprehensive properties and is widely used in various products. However, the flammability of polypropylene seriously restricts its application in some key fields, especially in occasions with high requirements for flame retardancy. In addition, polypropylene has a large shrinkage rate, which leads to poor dimensional stability during the molding process, affecting the appearance and processing accuracy of the final product. Therefore, the development of a halogen-free and environmentally friendly flame-retardant polypropylene material that can not only improve its flame retardant properties but also maintain good mechanical properties and low shrinkage rate has become the focus of current technical research and has broad market application prospects.

[0003] Red phosphorus is a highly effective flame retardant that can significantly improve the flame retardant properties of materials. However, red phosphorus easily comes into contact with oxygen and water to produce phosphine, which reduces its flame retardant effect and limits its widespread application. On the other hand, in order to improve the mechanical properties of materials, inorganic fillers are usually used for reinforcement. However, inorganic fillers have poor dispersibility and are difficult to achieve uniform distribution, which limits the improvement of the mechanical properties of materials.

[0004] Therefore, it is urgent to develop a new type of flame retardant material to further improve the mechanical properties and dimensional stability of the material while ensuring excellent flame retardant properties. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a composite fiber flame retardant suitable for preparing a flame retardant composite material (such as a polypropylene-based flame retardant plastic). The flame retardant can not only meet the flame retardant properties required by the material, but also effectively ensure the mechanical properties and appearance of the composite material, while having environmental advantages.

[0006] The invention also provides a method for preparing the composite fiber flame retardant.

[0007] The present invention also provides application of the composite fiber flame retardant in preparing a flame retardant composite material.

[0008] The invention also provides a plant fiber filled polypropylene flame retardant composite material.

[0009] The invention also provides a method for preparing the plant fiber filled polypropylene flame retardant composite material.

[0010] The present invention also provides application of the composite fiber flame retardant or the plant fiber filled polypropylene flame retardant composite material.

[0011] Specifically, the first embodiment of the present invention relates to a composite fiber flame retardant, comprising the following preparation raw materials in parts by mass: 5 to 12 parts of red phosphorus, 5 to 15 parts of plant powder, 1 to 5 parts of graphene, 0.1 to 0.4 parts of coupling agent, and 0.5 to 1.5 parts of polyester resin; the length distribution range of the composite fiber flame retardant is 95 to 355 μm, the average length is ≤235 μm, and the aspect ratio is 220:1 to 380:1.

[0012] The composite fiber flame retardant according to the first aspect of the present invention has at least the following beneficial effects:

[0013] Red phosphorus and graphene show significant synergistic flame retardant effects. Graphene has a high specific surface area and can quickly form a dense carbonized layer during the combustion process, preventing the diffusion of heat and oxygen and reducing the combustion rate. Red phosphorus can form phosphoric acid and polyphosphoric acid structures when heated, has a dehydration carbonization effect, and can form a barrier layer on the surface of the material. The high specific surface area of ​​graphene can adsorb and evenly disperse red phosphorus particles, giving full play to the physical shielding effect of graphene and the chemical flame retardant effect of red phosphorus. When polyester is degraded by heat, red phosphorus and graphene can be exposed, effectively ensuring the realization of the flame retardant effect, so that the material has excellent flame retardant properties in high temperature environments, while meeting halogen-free environmental protection requirements.

[0014] The coupling agent can enhance the interaction between plant powder and red phosphorus and graphene, making graphene and red phosphorus more evenly dispersed on the surface of plant powder. Red phosphorus and graphene are compounded to form a dense protective layer on the surface of plant fibers, and the polyester coating modification effectively solves the problem that red phosphorus is easy to fail in air and humid environments. In addition, the design of the flame retardant can also improve the surface defects of plant fibers and enhance the mechanical reinforcement effect of fibers, thereby significantly improving the mechanical properties of materials prepared using the flame retardant.

[0015] By rationally controlling the length distribution and aspect ratio of the composite fibers, the reinforcement effect of the fibers can be significantly improved, and their processability in subsequent applications can be effectively guaranteed. Appropriate fiber length and aspect ratio can effectively improve the overall mechanical properties of the material and avoid the adverse effects on the performance caused by fibers that are too short or too long. Fibers that are too short will lead to a significant decrease in mechanical properties and make it difficult to improve the dimensional stability of the material; while fibers that are too long may reduce the melt index, resulting in poor high-temperature fluidity, affecting molding processing, and at the same time having an adverse effect on further improvement of mechanical properties, such as difficulty in effectively improving properties such as bending strength and impact strength.

[0016] In summary, the design of this flame retardant can be used to prepare flame-retardant composite materials, which can not only significantly improve the flame retardant properties of the material, but also effectively improve the mechanical properties and processability of the material, optimize melt fluidity, and reduce shrinkage, thereby improving the dimensional stability of the material and better meeting the needs of high-performance applications.

[0017] According to some embodiments of the present invention, the particle size of the red phosphorus is 5 to 18 μm. The smaller the particle size of the red phosphorus, the more significant its flame retardant effect. Within the above particle size range, not only can excellent flame retardant performance be guaranteed, but also large-scale production can be achieved.

[0018] According to some embodiments of the present invention, the graphene has a particle size of 8 to 25 μm.

[0019] According to some embodiments of the present invention, the specific surface area of ​​the graphene is 850 to 1800 m 2 / g.

[0020] By rationally controlling the particle size of graphene and utilizing its high specific surface area, red phosphorus can be effectively adsorbed to form a stable and efficient flame-retardant composite structure.

[0021] According to some embodiments of the present invention, the mass ratio of red phosphorus to graphene is 3:1 to 4:1. This ratio ensures the efficient flame retardant effect of red phosphorus as the main flame retardant component, while being able to give play to the high specific surface area characteristics of graphene, effectively adsorbing and uniformly dispersing red phosphorus. Through this optimized ratio, the flame retardant performance is further improved.

[0022] According to some embodiments of the present invention, the polyester resin is polyethylene succinate (PES). PES has a fast thermal degradation rate and can be rapidly decomposed in a high temperature environment, exposing red phosphorus and graphene more quickly, which helps to improve the flame retardant effect. The present invention does not make specific requirements on the molecular weight of PES, and a common commercially available type can be selected.

[0023] According to some embodiments of the present invention, the plant powder is selected from at least one of straw powder, bamboo powder and wood powder. The present invention has no particular limitation on the type and particle size of the plant powder, and any common plant powder type in the art can be selected.

[0024] According to some embodiments of the present invention, the coupling agent is a silane coupling agent, for example, KH560, KH550, KH570, etc.

[0025] According to some embodiments of the present invention, the mass of the coupling agent is 2% to 2.5% of the mass of the plant powder.

[0026] The second aspect of the present invention relates to a method for preparing the above-mentioned composite fiber flame retardant, comprising the following steps: mixing the plant powder, coupling agent, red phosphorus, and graphene in a solvent and heating, followed by drying to obtain a graphene / red phosphorus composite-coated plant powder filler, wherein the mixing process includes high-speed stirring; blending the graphene / red phosphorus composite-coated plant powder filler with the polyester, spinning and grinding to obtain the composite fiber flame retardant.

[0027] It should be understood that the rotation speed of high-speed stirring is generally above 1000 rpm, for example, between 1000 and 5000 rpm. The plant powder can be refined by high-speed stirring.

[0028] The method for preparing the composite fiber flame retardant according to the second aspect of the present invention has at least the following beneficial effects:

[0029] By mixing plant powder with a coupling agent, red phosphorus and graphene in a solvent and heating the mixture, a uniform red phosphorus / graphene composite coating layer can be formed on the surface of the plant powder. The coating layer not only gives the plant powder flame retardant properties, but also improves its surface defects, which helps to improve the reinforcing effect of the plant powder.

[0030] By blending the plant powder filler coated with graphene / red phosphorus composite with polyester, and then spinning and grinding, a composite fiber flame retardant with a target size can be obtained. The fibers after spinning are longer, and the appropriate fiber length can be easily obtained through subsequent grinding and crushing.

[0031] The use of plant powder and red phosphorus / graphene composite as flame retardant avoids the environmental problems of traditional halogen-containing flame retardants and meets the requirements of green and sustainable development. The method is easy to mass produce and has good economic and market adaptability.

[0032] According to some embodiments of the present invention, the solvent is selected from alcohol solvents, including but not limited to ethanol, n-butanol, isobutanol and the like.

[0033] According to some embodiments of the present invention, the plant powder, coupling agent, red phosphorus, and graphene are mixed in a solvent and heated, specifically: preparing a solution containing the coupling agent, a dispersion 1 containing the red phosphorus, and a dispersion 2 containing the graphene, wherein the dispersed phases of the solution, dispersion 1, and dispersion 2 are selected from the solvent; after the plant powder is mixed with the solution, dispersion 1 and dispersion 2 are added and mixed and heated; wherein both mixing processes include high-speed stirring. The plant powder is first modified with a coupling agent, which is conducive to the surface of the plant powder being evenly coated with graphene and red phosphorus.

[0034] According to some embodiments of the present invention, the plant powder is mixed with the solution, which can be specifically carried out in a high-speed mixer. The present invention does not limit the mixing time of this step, as long as uniform mixing is ensured.

[0035] According to some embodiments of the present invention, in the solution containing the coupling agent, the concentration of the coupling agent is 1 wt % to 3 wt %.

[0036] According to some embodiments of the present invention, in the dispersion 1, the content of red phosphorus is 5 wt% to 8 wt%.

[0037] According to some embodiments of the present invention, the content of graphene in the dispersion 2 is 1 wt % to 3 wt %.

[0038] According to some embodiments of the present invention, the heating temperature is 70-80° C. and the heating time is 30-40 min. Prolonging the heating and stirring time appropriately helps to improve the interfacial compatibility.

[0039] The present invention has no particular limitation on the drying temperature and time, and suitable drying conditions can be selected according to conventional processes.

[0040] According to some embodiments of the present invention, the blending is melt blending. Conventional processes, such as extrusion processes, can be used to perform blending above the melting point of the polyester.

[0041] According to some embodiments of the present invention, the spinning is performed by solution spinning.

[0042] According to some embodiments of the present invention, the solvent used in the solution spinning is N,N-dimethylformamide.

[0043] According to some embodiments of the present invention, the mass ratio of the solvent used in the solution spinning to the polyester resin is 16:3 to 16:5.

[0044] According to some embodiments of the present invention, the average length of the fibers obtained by solution spinning is controlled to be less than 1 mm. Since the fiber length is short, the grinding time is less. Through the grinding and crushing action, it is easy to obtain fibers with a length range of 95 to 235 μm and an average length that meets the requirements.

[0045] The present invention does not limit the solvent and process parameters of solution spinning. According to the length and aspect ratio range of the fiber, the fiber of target thickness can be obtained by selecting a nozzle of appropriate size.

[0046] According to some embodiments of the present invention, the grinding is ball milling. The present invention does not impose any specific restrictions on the specific parameters of ball milling (such as ball-to-material ratio, size or type of ball milling beads, ball milling time and rotation speed, etc.), which can be adjusted according to actual needs and experience to obtain fibers of desired size.

[0047] A third aspect of the present invention relates to the use of the composite fiber flame retardant in the preparation of a flame-retardant composite material.

[0048] Based on the advantages of composite fiber flame retardant, it can significantly improve the flame retardancy and mechanical properties of flame retardant composite materials while ensuring the processability of the materials. In addition, the flame retardant can reduce the shrinkage of the material, improve dimensional stability, and improve the appearance of the material.

[0049] According to some embodiments of the present invention, the flame retardant composite material is a polypropylene-based flame retardant composite material, wherein the polypropylene matrix can be selected from one or both of conventional copolymer polypropylene and homopolypropylene according to actual needs.

[0050] According to some embodiments of the present invention, in the polypropylene-based flame-retardant composite material, the mass percentage of the composite fiber flame retardant is 15% to 25%, for example, 17% to 22%, or 19% to 22%.

[0051] The fourth aspect of the present invention relates to a plant fiber filled polypropylene flame retardant composite material, comprising the following raw materials in parts by mass: 35-65 parts of copolymer polypropylene, 10-20 parts of homopolypropylene, 1-5 parts of elastomer, 0.3-0.6 parts of compatibilizer, and 10-35 parts of the above-mentioned composite fiber flame retardant.

[0052] By rationally combining copolymer polypropylene and homopolymer polypropylene, the strength and toughness of the material can be better balanced. In addition, by optimizing the ratio of copolymer polypropylene, homopolymer polypropylene, composite fiber flame retardant, elastomer and compatibilizer, not only can the flame retardant properties be effectively maintained, but also the mechanical properties, dimensional stability and processing performance of the composite material can be significantly improved.

[0053] The present invention does not require the specific selection of copolymer polypropylene and homopolypropylene, and commercially available conventional products can be selected. For example, homopolypropylene can be selected from the following brands: PPH-MN90B, PPH-MN150 (origin: Sinopec); Taiwan Formosa Chemicals and Chemicals brands K1525, K205, K1108, K1P25; copolymer polypropylene can be selected from Yanshan Petrochemical K8303, Taiwan Formosa Chemicals and Chemicals T8002, South Korea Total BJ300, etc.

[0054] According to some embodiments of the present invention, the plant fiber filled polypropylene flame retardant composite material includes the following preparation raw materials in parts by mass: 55-65 parts of copolymer polypropylene, 14-20 parts of homopolypropylene, 2-5 parts of elastomer, 0.3-0.6 parts of compatibilizer, and 15-25 parts of the above-mentioned composite fiber flame retardant.

[0055] According to some embodiments of the present invention, the elastomer is selected from at least one of POE, EPDM, SBS and SEBS. By adding the elastomer, the elongation at break can be significantly increased.

[0056] According to some embodiments of the present invention, the compatibilizer is selected from at least one of SEBS-g-MAH, PP-g-MAH, and POE-g-MAH.

[0057] According to some embodiments of the present invention, the raw materials for preparing the plant fiber filled polypropylene flame retardant composite material also include an antioxidant. The present invention does not limit the type and amount of the antioxidant. For example, common types such as antioxidant 1010 can be selected, and the amount of the antioxidant can be 0.1% to 0.3% of the total weight of the raw materials.

[0058] A fifth embodiment of the present invention relates to a method for preparing the plant fiber filled polypropylene flame retardant composite material, comprising the following steps: melt-extruding and granulating the raw materials for preparing the plant fiber filled polypropylene flame retardant composite material.

[0059] The method is simple in process and can produce materials with excellent flame retardant properties and mechanical properties, while also having small molding shrinkage, good appearance, and excellent processability.

[0060] The preparation method comprises: physically mixing the copolymerized polypropylene, homopolymerized polypropylene and elastomer, and then melt-extruding and granulating them together with other components. The physical mixing method includes but is not limited to using high-speed stirring to improve mixing uniformity.

[0061] The present invention does not impose any specific restrictions on melt extrusion process parameters, and conventional process conditions can be used for implementation.

[0062] A sixth aspect of the present invention relates to the use of the above-mentioned composite fiber flame retardant or plant fiber-filled polypropylene flame retardant composite material in automobiles or household appliances.

[0063] Based on the performance advantages of composite fiber flame retardant or plant fiber filled polypropylene flame retardant composite materials, it can effectively improve the flame retardancy, mechanical properties and appearance quality of the products, while improving dimensional stability and processing performance, meeting the safety, durability and environmental protection requirements of modern automobiles and home appliances. Specific applications include but are not limited to automotive interior parts (such as dashboards, door panels, etc.) and home appliance housings.

[0064] In the present invention, the numerical ranges involved include the endpoint values ​​and cover any sub-ranges within the range, such as the ranges obtained by any combination of the specifically listed values. In addition, "above" or "below" includes the values ​​themselves.

[0065] In the present invention, when referring to size ranges (such as particle diameter, length, etc.), unless otherwise specified (such as particularly emphasized as distribution range), all size ranges refer to average values.

[0066] The length distribution range is 95-355 μm, which means that the fiber sizes are mainly concentrated in this range, for example, more than 95% (or other error ranges that meet industrial standard requirements) of the fiber lengths are within this range. The actual distribution of the fibers does not necessarily cover all length values ​​within this range, but may only be a subset of the lengths within this range.

[0067] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. DETAILED DESCRIPTION

[0068] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0069] If no specific conditions are specified in the specific implementation mode, the process is carried out under conventional conditions. If no manufacturer is specified for the raw materials or equipment used, they are all conventional products that can be purchased from the market or prepared under general conditions.

[0070] The relevant raw materials are described as follows:

[0071] Homopolymer polypropylene is Sinopec PPH-MN90B;

[0072] The copolymer polypropylene is Yanshan Petrochemical K8303;

[0073] The elastomer is POE;

[0074] The compatibilizer is SEBS-g-MAH;

[0075] The plant powder is commercially available conventional straw powder, with a length distribution range of 15 μm to 105 μm;

[0076] The particle size distribution range of red phosphorus is 5 to 18 μm;

[0077] The graphene particle size distribution range is 8 to 25 μm, and the specific surface area is 850 to 1800 m 2 / g;

[0078] The coupling agent is KH560;

[0079] The antioxidant is 1010.

[0080] Example 1

[0081] This example prepares a plant fiber filled polypropylene flame retardant composite material, and the raw materials for preparation are as follows by weight:

[0082] 62.5 parts of copolymer polypropylene, 14 parts of homopolypropylene, 8 parts of red phosphorus, 8 parts of plant powder, 2.5 parts of graphene, 3 parts of elastomer, 0.4 parts of compatibilizer, 0.2 parts of coupling agent, 0.1 parts of antioxidant, and 1.3 parts of PES resin.

[0083] The preparation method of the material is as follows:

[0084] 1. Preparation of composite fiber flame retardant

[0085] 1.1. Prepare 1wt% to 3wt% coupling agent ethanol solution, 6wt% red phosphorus ethanol dispersion and 2wt% graphene ethanol dispersion;

[0086] 1.2. Add plant powder and coupling agent ethanol solution into a high-speed mixer and mix, gradually add red phosphorus ethanol dispersion and graphene ethanol dispersion, continue high-speed stirring at 80° C. for 30 minutes, and obtain graphene / red phosphorus composite coated plant powder filler after drying, the filler particle size distribution range is 8 μm to 75 μm;

[0087] 1.3. Melt-blending the graphene / red phosphorus composite-coated plant powder filler with PES resin, dissolving the blend with N,N-dimethylformamide (the mass ratio of N,N-dimethylformamide to PES resin is 16:3) to obtain a spinning solution;

[0088] 1.4, solution spinning and drying the spinning solution to form composite fibers;

[0089] 1.5. The composite fiber (average length 0.4 mm) was placed in a ball mill for grinding to obtain a composite fiber flame retardant having a length distribution range of 95 to 355 μm, an average length ≤ 235 μm, and an aspect ratio of 220:1 to 380:1.

[0090] 2. Preparation of plant fiber filled polypropylene flame retardant composite materials

[0091] 2.1. Mix copolymerized polypropylene, homopolymerized polypropylene and elastomer in a high-speed mixer for 3 to 8 minutes at a temperature of 55 to 65°C to obtain a premix;

[0092] 2.2. Place the premix, composite fiber flame retardant, compatibilizer and antioxidant in a twin-screw extruder, and perform melt extrusion and granulation to obtain the product.

[0093] Among them, the extrusion conditions are as follows:

[0094] The screw aspect ratio is 48:1, and the temperature is controlled in nine zones. The processing temperatures of zones one to nine are 180℃, 181℃, 182℃, 180℃, 183℃, 187℃, 182℃, 185℃, 185℃, respectively. The die temperature is 190℃, the main engine frequency is 25~33Hz, the feeding frequency is 20~25Hz, the melt pressure is 2.7~3.7MPa, the vacuum degree is -0.03~-0.06MPa, and the pelletizer speed is 330~420rpm.

[0095] Example 2

[0096] This example prepares a plant fiber filled polypropylene flame retardant composite material, and the raw materials for preparation are as follows by weight:

[0097] 58 parts of copolymer polypropylene, 17 parts of homopolypropylene, 6 parts of red phosphorus, 12 parts of plant powder, 2 parts of graphene, 3 parts of elastomer, 0.5 parts of compatibilizer, 0.3 parts of coupling agent, 0.1 parts of antioxidant and 1.1 parts of PES resin.

[0098] The preparation method of the material is similar to that of Example 1, except that the raw materials used are different.

[0099] Example 3

[0100] This example prepares a plant fiber filled polypropylene flame retardant composite material, and the raw materials for preparation are as follows by weight:

[0101] 56 parts of copolymer polypropylene, 20 parts of homopolypropylene, 10 parts of red phosphorus, 5 parts of plant powder, 3 parts of graphene, 4 parts of elastomer, 0.3 parts of compatibilizer, 0.1 parts of coupling agent, 0.1 parts of antioxidant, and 1.5 parts of PES resin.

[0102] The preparation method of the material is similar to that of Example 1, except that the raw materials used are different.

[0103] Example 4

[0104] In this embodiment, a plant fiber-filled polypropylene flame-retardant composite material is prepared. The preparation method is the same as that in Example 1, except that an equal amount of the PES resin is replaced by polybutylene succinate (PBS).

[0105] Example 5

[0106] This example prepares a plant fiber filled polypropylene flame retardant composite material, and the raw materials for preparation are as follows by weight:

[0107] 62.5 parts of copolymer polypropylene, 14 parts of homopolypropylene, 9 parts of red phosphorus, 8 parts of plant powder, 1.5 parts of graphene, 3 parts of elastomer, 0.4 parts of compatibilizer, 0.2 parts of coupling agent, 0.1 parts of antioxidant and 1.3 parts of PES resin.

[0108] The preparation method of the material is similar to that of Example 1, except that the raw materials used are different.

[0109] Example 6

[0110] This example prepares a plant fiber filled polypropylene flame retardant composite material, and the raw materials for preparation are as follows by weight:

[0111] 62.5 parts of copolymer polypropylene, 14 parts of homopolypropylene, 6 parts of red phosphorus, 8 parts of plant powder, 4.5 parts of graphene, 3 parts of elastomer, 0.4 parts of compatibilizer, 0.2 parts of coupling agent, 0.1 parts of antioxidant, and 1.3 parts of PES resin.

[0112] The preparation method of the material is similar to that of Example 1, except that the raw materials used are different.

[0113] Comparative Example 1

[0114] The plant fiber filled polypropylene flame retardant composite material was prepared by referring to the method of Example 1, except that in step 1.5, the size of the composite fiber flame retardant obtained after grinding was: a length distribution range of 25 to 105 μm, an average length ≤ 70 μm, and an aspect ratio of 70:1 to 230:1.

[0115] Comparative Example 2

[0116] The plant fiber filled polypropylene flame retardant composite material was prepared by referring to the method of Example 1, except that in step 1.5, the size of the composite fiber flame retardant obtained after grinding was: a length distribution range of 285 to 505 μm, an average length ≤330 μm, and an aspect ratio of 355:1 to 450:1.

[0117] Comparative Example 3

[0118] In this comparative example, a plant fiber filled polypropylene flame retardant composite material was prepared, and the raw materials for preparation were the same as those in Example 1.

[0119] The preparation method of the material is as follows:

[0120] 1. Place copolymer polypropylene, homopolypropylene, red phosphorus, plant powder, graphene, elastomer, coupling agent and PES resin in a high-speed mixer and stir at high speed for 30 minutes at 80°C to obtain a premix;

[0121] 2. The premix, the compatibilizer and the antioxidant are placed in a twin-screw extruder, and melt-extruded (the extrusion conditions are the same as those in Example 1) and granulated to obtain the product.

[0122] Test Case

[0123] The test items and methods are as follows:

[0124] Shrinkage (MD): Tested according to ASTM D995 standard;

[0125] Melt index: tested according to ASTM D1238 standard (230℃ / 2.16kg);

[0126] Tensile strength and elongation at break: tested according to ASTM D638 standard;

[0127] Flexural strength and flexural modulus: tested according to ASTM D790 standard;

[0128] Izod notched impact strength: tested according to ASTM D256 standard;

[0129] Heat deformation temperature: tested according to ASTM D648 standard;

[0130] Flame retardancy: tested according to ASTM D3014 standard;

[0131] Oxygen index: tested according to ASTM D2863 standard;

[0132] Fog requirements, odor requirements, aldehyde and ketone requirements and VOC test values: tested in accordance with BT / SGMWJ0872-2016 standards.

[0133] The test results are shown in Table 1.

[0134] Table 1

[0135]

[0136] It can be seen from Examples 1 to 3 that the composite fiber flame retardant obtained by coating and modifying the plant powder with coupling agent, red phosphorus, graphene and PES resin and optimizing the component ratio is used to prepare the plant fiber filled polypropylene flame retardant composite material, which significantly improves the overall performance of the material.

[0137] From the comparison between Example 4 and Example 1, it can be seen that the use of PES to coat and modify the plant powder has better flame retardant properties than PBS. This is because PES degrades faster when heated, and can more quickly expose the red phosphorus / graphene composite layer, thereby achieving a V-0 level flame retardant effect.

[0138] By comparing Example 5 and Example 6 with Example 1, it can be seen that when the mass ratio of red phosphorus to graphene is too high or too low, the flame retardant properties are inferior to those of Example 1. In Example 6, although the graphene content is higher, there is no further improvement on the mechanical properties, indicating that there is an optimal range for the content of graphene, and the more the better.

[0139] From the comparison between Comparative Example 1 and Example 1, it can be seen that the fiber length is too short, and the mechanical properties such as bending strength, bending modulus, notched impact strength are not as good as those of Example 1, and the shrinkage rate is higher and the heat deformation temperature is lower.

[0140] From the comparison between Comparative Example 2 and Example 1, it can be seen that the fiber length is too long, and the mechanical properties such as bending strength, bending modulus, and notched impact strength are not as good as those of Example 1, and the melt index is reduced and the high-temperature fluidity is lost, resulting in difficulty in injection molding.

[0141] Comparative Example 3 does not compound red phosphorus, graphene, PES and plant fiber to form a composite fiber flame retardant, and the compatibility of the composite is not as good as that of Example 1. The composite melt has difficulty in flowing and the melt index is reduced. In addition, the orientation of the fiber is affected by the deterioration of the interface compatibility, which has a greater impact on the flexural strength, flexural modulus and heat deformation temperature.

[0142] The embodiments of the present invention are described in detail above, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A composite fiber flame retardant, characterized in that: The preparation comprises the following raw materials in parts by mass: 5-12 parts of red phosphorus; 5-15 parts of plant powder; 1 to 5 parts of graphene; 0.1-0.4 parts of coupling agent; 0.5-1.5 parts of polyester resin; The composite fiber flame retardant has a length distribution range of 95 to 355 μm, an average length of ≤235 μm, and an aspect ratio of 220:1 to 380:

1.

2. The composite fiber flame retardant according to claim 1, characterized in that: The particle size of the graphene is 8 to 25 μm; and / or the specific surface area of ​​the graphene is 850 to 1800 m 2 / g; and / or, the particle size of the red phosphorus is 5 to 18 μm; and / or, the mass ratio of the red phosphorus to the graphene is 3:1 to 4:1; and / or, the polyester resin is polyethylene succinate; and / or, the plant powder is selected from at least one of straw powder, bamboo powder, and wood powder; and / or, the coupling agent is a silane coupling agent; and / or, the mass of the coupling agent is 2% to 2.5% of the mass of the plant powder.

3. The method for preparing the composite fiber flame retardant according to claim 1 or 2, characterized in that: The following steps are involved: The plant powder, coupling agent, red phosphorus and graphene are mixed in a solvent and heated, and then dried to obtain a graphene / red phosphorus composite coated plant powder filler, wherein the mixing process includes high-speed stirring; The graphene / red phosphorus composite-coated plant powder filler is blended with the polyester, and the mixture is spun and ground to obtain the composite fiber flame retardant.

4. The preparation method according to claim 3, characterized in that: The plant powder, coupling agent, red phosphorus and graphene are mixed in a solvent, specifically: A solution containing the coupling agent, a dispersion 1 containing the red phosphorus, and a dispersion 2 containing the graphene are prepared, wherein the dispersed phases of the solution, the dispersion 1, and the dispersion 2 are selected from the solvent; after mixing the plant powder with the solution, the dispersion 1 and the dispersion 2 are added, mixed, and heated; wherein both mixing processes include high-speed stirring; Optionally, in the solution containing the coupling agent, the concentration of the coupling agent is 1 wt% to 3 wt%; Optionally, in the dispersion 1, the content of red phosphorus is 5wt% to 8wt%; Optionally, in the dispersion 2, the content of graphene is 1 wt% to 3 wt%.

5. The preparation method according to claim 3, characterized in that: The solvent is selected from alcohol solvents; And / or, the heating temperature is 70-80° C., and the heating time is 30-40 min; And / or, the grinding is ball milling; And / or, the particle size of the graphene / red phosphorus composite coated plant powder filler is 8 to 75 μm; And / or, the blending is melt blending; And / or, the spinning is solution spinning; optionally, the solvent used in the solution spinning is N,N-dimethylformamide, and the mass ratio of the solvent to the polyester resin is 16:3 to 16:

5.

6. Use of the composite fiber flame retardant according to claim 1 or 2 in the preparation of flame retardant composite materials.

7. A plant fiber filled polypropylene flame retardant composite material, characterized in that: The preparation comprises the following raw materials in parts by mass: Copolymer polypropylene 35-65 parts; Homopolymer polypropylene 10-20 parts; 1 to 5 parts of elastomer; 0.3-0.6 parts of compatibilizer; The composite fiber flame retardant according to claim 1 or 2, 10 to 35 parts.

8. The plant fiber filled polypropylene flame retardant composite material according to claim 7, characterized in that: The elastomer is selected from at least one of POE, EPDM, SBS, and SEBS; and / or the compatibilizer is selected from at least one of SEBS-g-MAH, PP-g-MAH, and POE-g-MAH; and / or, an antioxidant is also included.

9. The method for preparing the plant fiber filled polypropylene flame retardant composite material according to claim 7 or 8, characterized in that: The following steps are involved: The raw materials for preparing the plant fiber-filled polypropylene flame-retardant composite material are melt-extruded and granulated.

10. Use of the composite fiber flame retardant according to any one of claims 1 to 2 or the plant fiber filled polypropylene flame retardant composite material according to any one of claims 7 to 8 in automobiles or household appliances.

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