Halogen-free flame-retardant polypropylene composite material and preparation method thereof

Abstract

The invention discloses a halogen-free flame-retardant polypropylene composite material and a preparation method thereof, the halogen-free flame-retardant polypropylene composite material is prepared from 77-84.1 parts by weight of polypropylene, 15-20 parts by weight of a halogen-free flame retardant, 0.5-2 parts by weight of a modified carbon nanotube, 0.2-0.6 part by weight of a heat stabilizer and 0.2-0.4 part by weight of a processing aid, and the surface of the modified carbon nanotube is modified by MoS2. On the basis of a traditional halogen-free flame-retardant polypropylene formula, a self-made MoS2 modified carbon nanotube material is added, so that the use ratio of a halogen-free flame retardant can be reduced, meanwhile, the mechanical property of the material can be improved, the smoke density of the flame-retardant material can be reduced, and the flame-retardant efficiency can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and specifically relates to a halogen-free flame-retardant polypropylene composite material and a preparation method thereof. Background Art

[0002] As one of the most common general plastics at present, polypropylene has advantages such as good rigid-flexible balance performance, chemical corrosion resistance, and weather resistance, and is widely used in automotive interior and exterior trims, household appliances, and electronic and electrical appliance housing products. The application in some special fields requires polypropylene materials to have special functions. For example, flame-retardant polypropylene is a type of modified polypropylene with a large usage amount. With people's attention to environmental protection, health, and mineral energy, the use of halogen-free flame-retardant polypropylene is becoming more and more widespread. However, the proportion of flame retardants required for halogen-free flame-retardant polypropylene is relatively high, which has a great impact on the mechanical properties of the product. The price of flame retardants is expensive, and every additional 1% of the addition ratio has a great impact on the material cost. Summary of the Invention

[0003] In view of this, the present invention provides a halogen-free flame-retardant polypropylene composite material and a preparation method thereof to solve the problems raised in the above background art. On the basis of the traditional halogen-free flame-retardant polypropylene formula, a self-made carbon nanotube material modified with MoS2 is added, which can reduce the usage ratio of halogen-free flame retardants, improve the mechanical properties of the material, reduce the smoke density of the flame-retardant material, and improve the flame-retardant efficiency.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] On the one hand, the present invention discloses a halogen-free flame-retardant polypropylene composite material, which is prepared from 77 - 84.1 parts by weight of polypropylene, 15 - 20 parts by weight of halogen-free flame retardant, 0.5 - 2 parts by weight of modified carbon nanotubes, 0.2 - 0.6 parts by weight of heat stabilizer, and 0.2 - 0.4 parts by weight of processing aids. Among them, the surface of the modified carbon nanotubes is modified with MoS2.

[0006] As a further solution of the present invention: The polypropylene is selected from at least one of copolymerized polypropylene and homopolymerized polypropylene.

[0007] As a further solution of the present invention: The halogen-free flame retardant is a phosphorus-nitrogen type intumescent flame retardant.

[0008] As a further solution of the present invention: The modified carbon nanotubes are prepared by the following steps:

[0009] (1) Disperse 5 parts by weight of carbon nanotubes in deionized water to obtain solution A; dissolve 8 - 12 parts by weight of Na2MoO4·H2O in deionized water to obtain solution B; add solution B to solution A and stir well to obtain solution C;

[0010] (2) 4 - 6 parts by weight of CN2H4S was added dropwise to solution C. After sufficient stirring, it was poured into a reaction kettle. After calcination, cooling, centrifugal separation, washing, and drying, the modified carbon nanotubes were obtained. CN2H4S provided a nitrogen source and a sulfur source during the calcination process.

[0011] As a further aspect of the present invention: The heat stabilizer is selected from at least one of phenolic heat stabilizers, phosphite heat stabilizers, and thioester heat stabilizers.

[0012] As a further aspect of the present invention: The processing aid is a macromolecular silicone masterbatch, which helps the dispersion of various additives to ensure that the best effect is achieved with the minimum addition amount.

[0013] As a further aspect of the present invention: In solution B, 1 g of Na2MoO4·H2O is dissolved in 30 - 70 mL of deionized water.

[0014] On the other hand, the present invention discloses a method for preparing the halogen-free flame-retardant polypropylene composite material as described in any one of the above, comprising the following steps:

[0015] Polypropylene, halogen-free flame retardant, modified carbon nanotubes, heat stabilizer, and processing aid were fully mixed according to parts by weight to obtain a mixture;

[0016] The mixture was added to a twin-screw extruder, and after melting, mixing, and dispersion, it was extruded and pelletized to obtain the halogen-free flame-retardant polypropylene composite material.

[0017] As a further aspect of the present invention: The temperature range of the twin-screw extruder from the feeding section to the die head is 185 - 195 °C, 185 - 195 °C, 185 - 200 °C, 190 - 200 °C, 190 - 200 °C, 190 - 205 °C, 195 - 205 °C, 200 - 210 °C, 200 - 205 °C, 190 - 200 °C in sequence.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. The present invention only adds the carbon nanotube material modified with MoS2 on the basis of the traditional formula, and the flame retardancy and mechanical properties of the polypropylene composite material can be improved by using the conventional melt blending method. The preparation process is simple and easy to realize industrial scale production;

[0020] 2. The modified carbon nanotube material itself has strong rigidity. As a nanomaterial dispersed in the polypropylene matrix, it can improve the mechanical properties of the flame-retardant polypropylene; at the same time, its small addition amount can also reduce the use content of the halogen-free flame retardant, and can reduce the loss of the mechanical properties of the material due to the addition of the flame retardant;

[0021] 3. A large number of hydroxyl groups exist on the surface of carbon nanotubes, providing a prerequisite for modification and enabling MoS2 to adhere to the surface of carbon nanotubes. MoS2 itself has a layered structure, formed by two layers of S atoms and Mo atoms sandwiched between the two layers to form a layered structure;

[0022] 4. During the combustion process of the material, MoS2 nanosheets play a role of physical barrier, which can effectively inhibit the transfer of heat and the escape of combustible gases; due to its large specific surface area, the MoS2-modified carbon nanotube material can adsorb decomposition products, such as combustible gases and free radicals, and slow down the thermal decomposition of polymers; the process of MoS2 decomposing into MoO3 can absorb the heat during the combustion process and cool the surface of the polymer; and this further decomposition process promotes the formation of a char layer. The heavier char layer can provide an effective protective layer during the combustion process, which reduces the transfer of heat and mass between the flame and the matrix. This hinders the diffusion of oxygen and prevents the further combustion of the lower matrix. Thereby further improving the flame retardancy of the composite material. Specific Embodiments

[0023] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0025] The specific information of the raw materials used in the following examples and comparative examples is as follows:

[0026] Polypropylene: PP BX3800 (SK Chemicals, South Korea), PP S2040 (Shanghai Secco), PP K9829H (Yanshan Petrochemical), PPK7227H (Wuhan Ethylene);

[0027] Halogen-free flame retardant, FP-2200 (ADK, Japan), WR02B (Suzhou Anhongtai);

[0028] Heat stabilizer, 168 (BASF), 1010 (BASF), DSTDP (Tianmen Hengchang Chemical Co., Ltd.)

[0029] Macromolecular silicone masterbatch, E525 (Evonik Industries AG, Germany).

[0030] It should be understood that the above raw material reagents are only examples of some specific embodiments of the present invention to make the technical solutions of the present invention clearer, and do not represent that the present invention can only use the above reagents. Specifically, it shall be subject to the scope in the claims. In addition, the "parts" mentioned in the examples and comparative examples refer to parts by weight unless otherwise specified.

[0031] Any range recorded in the present invention includes the end values, any numerical value between the end values, and any sub-range constituted by any numerical value between the end values or the end values.

[0032] Example 1

[0033] 80.4 parts of copolymer polypropylene PP BX3800, 18 parts of halogen-free flame retardant FP-2200, 1 part of modified carbon nanotubes, 0.2 part of heat stabilizer 1010, 0.2 part of heat stabilizer 168, and 0.2 part of silicone masterbatch were mixed evenly in a high-speed mixer and then added to a twin-screw extruder with a length-diameter ratio of 38:1 for melt mixing and processing, and then pelletized to obtain a halogen-free flame-retardant polypropylene material. Among them, the temperatures of the twin-screw extruder from the feeding section to the head are 190°C, 190°C, 195°C, 195°C, 200°C, 200°C, 200°C, 205°C, 205°C, and 200°C in sequence.

[0034] The modified carbon nanotubes are prepared according to the following steps:

[0035] a. 0.5 g of carbon nanotubes was dispersed in deionized water and mechanically stirred at room temperature for 2 hours to obtain solution A; another 1.0 g of Na2MoO4·H2O was dissolved in 50 mL of aqueous ionic solution and stirred until fully dissolved to obtain solution B. Subsequently, solution B was added to solution A and mechanically stirred at room temperature for 4 hours to obtain solution C;

[0036] b. 0.5 g of CN2H4S was gradually added dropwise to solution C and mechanically stirred for 1.5 hours to obtain solution D;

[0037] c. Solution D was transferred to a Teflon reactor, calcined at 220°C for 5 hours, cooled to room temperature, the precipitate was filtered by a centrifuge, washed 4 times with absolute ethanol, and dried in a vacuum drying oven at 50°C for 15 hours. The obtained product is the modified carbon nanotubes.

[0038] Example 2

[0039] 80.8 parts of homopolypropylene PP S2040, 17 parts of halogen-free flame retardant, 1.5 parts of modified carbon nanotubes, 0.2 parts of heat stabilizer 1010, 0.2 parts of heat stabilizer 168, and 0.3 parts of silicone masterbatch are mixed evenly in a high-speed mixer and then added to a twin-screw extruder with a length-to-diameter ratio of 38:1 for melt mixing and processing. Extrusion granulation is carried out to obtain a halogen-free flame-retardant polypropylene material. Among them, the temperatures of the twin-screw extruder from the feeding section to the head are 185°C, 185°C, 185°C, 190°C, 190°C, 190°C, 195°C, 200°C, 200°C, 200°C in sequence.

[0040] The modified carbon nanotubes are prepared according to the following ratio and steps:

[0041] a. Disperse 0.5 g of carbon nanotubes in deionized water and mechanically stir for 2 hours at room temperature to obtain solution A; separately dissolve 0.9 g of Na2MoO4·H2O in 54 mL of aqueous ionic solution and stir until fully dissolved to obtain solution B. Subsequently, add solution B to solution A and mechanically stir for 3.5 hours at room temperature to obtain solution C;

[0042] b. Gradually add 0.5 g of CN2H4S dropwise to solution C and mechanically stir and react for 1.2 hours to obtain solution D;

[0043] c. Transfer solution D to a Teflon reactor, calcine at 220°C for 5 hours, cool to room temperature, filter the precipitate with a centrifuge, wash 4 times with absolute ethanol, and dry in a vacuum drying oven at 45°C for 18 hours. The obtained product is the modified carbon nanotubes.

[0044] Example 3

[0045] 81.2 parts of copolymer polypropylene PP K9829H, 17 parts of halogen-free flame retardant FP-2200, 1.2 parts of modified carbon nanotubes, 0.1 part of heat stabilizer 1076, 0.2 parts of heat stabilizer 168, and 0.3 parts of silicone masterbatch are mixed evenly in a high-speed mixer and then added to a twin-screw extruder with a length-to-diameter ratio of 42:1 for melt mixing and processing. Extrusion granulation is carried out to obtain a halogen-free flame-retardant polypropylene material. Among them, the temperatures of the twin-screw extruder from the feeding section to the head are 190°C, 190°C, 195°C, 195°C, 200°C, 200°C, 200°C, 210°C, 205°C, 200°C in sequence.

[0046] The modified carbon nanotubes are prepared according to the following ratio and steps:

[0047] a. Disperse 0.5 g of carbon nanotubes in deionized water and mechanically stir for 2 hours at room temperature to obtain Solution A; separately dissolve 1.1 g of Na2MoO4·H2O in 45 mL of aqueous ionic solution and stir until completely dissolved to obtain Solution B. Subsequently, add Solution B to Solution A and mechanically stir for 4.5 hours at room temperature to obtain Solution C;

[0048] b. Gradually add 0.55 g of CN2H4S dropwise to Solution C and mechanically stir and react for 1 hour to obtain Solution D;

[0049] c. Transfer Solution D to a Teflon reactor, calcine at 223 °C for 6 hours, cool to room temperature, filter the precipitate with a centrifuge, wash 5 times with absolute ethanol, and dry in a vacuum drying oven at 50 °C for 14 hours. The resulting product is the modified carbon nanotubes.

[0050] Example 4

[0051] Mix 84.1 parts of copolymer polypropylene PP K7227H, 15 parts of halogen-free flame retardant FP-2200, 0.5 part of modified carbon nanotubes, 0.2 part of heat stabilizer 168, and 0.2 part of silicone masterbatch evenly in a high-speed mixer, then add them to a twin-screw extruder with a length-diameter ratio of 38:1 for melt mixing and processing, and extrude and pelletize to obtain a halogen-free flame-retardant polypropylene material. Among them, the temperatures of the twin-screw extruder from the feeding section to the die head are 190 °C, 190 °C, 195 °C, 195 °C, 195 °C, 200 °C, 200 °C, 200 °C, 200 °C, 190 °C in sequence.

[0052] The modified carbon nanotubes are prepared according to the following ratio and steps:

[0053] a. Disperse 0.5 g of carbon nanotubes in deionized water and mechanically stir for 2 hours at room temperature to obtain Solution A; separately dissolve 0.8 g of Na2MoO4·H2O in 24 mL of aqueous ionic solution and stir until completely dissolved to obtain Solution B. Subsequently, add Solution B to Solution A and mechanically stir for 3 hours at room temperature to obtain Solution C;

[0054] b. Gradually add 0.4 g of CN2H4S dropwise to Solution C and mechanically stir and react for 1 hour to obtain Solution D;

[0055] c. Transfer Solution D to a Teflon reactor, calcine at 220 °C for 4 hours, cool to room temperature, filter the precipitate with a centrifuge, wash 3 times with absolute ethanol, and dry in a vacuum drying oven at 40 °C for 10 hours. The resulting product is the modified carbon nanotubes.

[0056] Example 5

[0057] 77 parts of copolymer polypropylene PP BX3800, 20 parts of halogen-free flame retardant WR02B, 2 parts of modified carbon nanotubes, 0.3 parts of heat stabilizer 1010, 0.3 parts of heat stabilizer DSTDP, and 0.4 parts of silicone masterbatch were mixed evenly in a high-speed mixer and then added to a twin-screw extruder with a length-to-diameter ratio of 38:1 for melt mixing and processing. Extrusion granulation was carried out to obtain a halogen-free flame-retardant polypropylene material. Among them, the temperatures of the twin-screw extruder from the feeding section to the head were 195°C, 195°C, 200°C, 200°C, 200°C, 205°C, 205°C, 205°C, 205°C, and 200°C in sequence.

[0058] The modified carbon nanotubes were prepared according to the following ratio and steps:

[0059] a. 0.5 g of carbon nanotubes was dispersed in deionized water and mechanically stirred at room temperature for 2 hours to obtain solution A; another 1.2 g of Na2MoO4·H2O was dissolved in 84 mL of aqueous ionic solution and stirred until fully dissolved to obtain solution B. Subsequently, solution B was added to solution A and mechanically stirred at room temperature for 5 hours to obtain solution C;

[0060] b. 0.6 g of CN2H4S was gradually added dropwise to solution C and mechanically stirred and reacted for 2 hours to obtain solution D;

[0061] c. Solution D was transferred to a Teflon reactor, calcined at 225°C for 6 hours, cooled to room temperature, the precipitate was filtered by a centrifuge, washed 5 times with absolute ethanol, and dried in a vacuum drying oven at 60°C for 20 hours. The obtained product was the self-made MoS2-modified carbon nanotubes.

[0062] Comparative Example 1

[0063] 81.4 parts of copolymer polypropylene PP BX3800, 18 parts of halogen-free flame retardant FP-2200, 0.2 parts of heat stabilizer 1010, 0.2 parts of heat stabilizer 168, and 0.2 parts of silicone masterbatch were mixed evenly in a high-speed mixer and then added to a twin-screw extruder with a length-to-diameter ratio of 38:1 for melt mixing and processing. Extrusion granulation was carried out to obtain a halogen-free flame-retardant polypropylene material. Among them, the temperatures of the twin-screw extruder from the feeding section to the head were 190°C, 190°C, 195°C, 195°C, 200°C, 200°C, 200°C, 205°C, 205°C, and 200°C in sequence.

[0064] Comparative Example 2

[0065] 75.4 parts of copolymer polypropylene PP BX3800, 24 parts of halogen-free flame retardant FP-2200, 0.2 parts of heat stabilizer 1010, 0.2 parts of heat stabilizer 168, and 0.2 parts of silicone masterbatch were mixed evenly in a high-speed mixer and then added to a twin-screw extruder with a length-diameter ratio of 38:1 for melt mixing and processing. Extrusion granulation was carried out to obtain a halogen-free flame-retardant polypropylene material. Among them, the temperatures of the twin-screw extruder from the feeding section to the die head were 190°C, 190°C, 195°C, 195°C, 200°C, 200°C, 200°C, 205°C, 205°C, and 200°C in sequence.

[0066] Comparative Example 3

[0067] 80.4 parts of copolymer polypropylene PP BX3800, 18 parts of halogen-free flame retardant FP-2200, 1 part of commercially available carbon nanotubes, 0.2 parts of heat stabilizer 1010, 0.2 parts of heat stabilizer 168, and 0.2 parts of processing aid silicone masterbatch were mixed evenly in a high-speed mixer and then added to a twin-screw extruder with a length-diameter ratio of 38:1 for melt mixing and processing. Extrusion granulation was carried out to obtain a halogen-free flame-retardant polypropylene material. Among them, the temperatures of the twin-screw extruder from the feeding section to the die head were 190°C, 190°C, 195°C, 195°C, 200°C, 200°C, 200°C, 205°C, 205°C, and 200°C in sequence.

[0068] The combustion properties of the materials of Examples 1 - 5 and Comparative Examples 1 - 3 were measured using a cone calorimeter. The specific test conditions are as follows:

[0069] The smoke density was tested according to the GB / T 8627 standard; the flame retardancy was tested according to the UL94 standard; the tensile strength was tested according to ISO527; the flexural strength and flexural modulus were tested according to ISO 178; the Izod notched impact strength was tested according to ISO 180. The test results are shown in Table 1.

[0070] Table 1 Performance test results of halogen-free flame-retardant polypropylene composites

[0071]

[0072]

[0073] As can be seen from Table 1, the halogen-free flame-retardant polypropylene prepared by the present invention can achieve a V-0 flame-retardant effect under the condition of a relatively low flame retardant addition amount (15 - 20%), and the self-prepared MoS2-modified carbon nanotubes have the effect of improving the mechanical properties. The flame-retardant polypropylene prepared by the present invention has better mechanical properties.

[0074] Although this specification is described in terms of embodiments, not every embodiment contains only an independent technical solution. This narrative style of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0075] Therefore, the above description is only a preferred embodiment of the present application and is not used to limit the scope of implementation of the present application; that is, all equivalent transformations made according to the scope of the claims of the present application are within the protection scope of the claims of the present application.

Claims

1. A halogen-free flame-retardant polypropylene composite material, characterized in that, It is prepared from 77 - 84.1 parts by weight of polypropylene, 15 - 20 parts by weight of a halogen-free flame retardant, 0.5 - 2 parts by weight of modified carbon nanotubes, 0.2 - 0.6 parts by weight of a heat stabilizer, and 0.2 - 0.4 parts by weight of a processing aid. Among them, the surface of the modified carbon nanotubes is modified with MoS2.

2. The halogen-free flame-retardant polypropylene composite material according to claim 1, characterized in that The polypropylene is selected from at least one of copolymerized polypropylene and homopolymerized polypropylene.

3. The halogen-free flame-retardant polypropylene composite material according to claim 1, characterized in that, The halogen-free flame retardant is a phosphorus-nitrogen intumescent flame retardant.

4. A halogen-free flame-retardant polypropylene composite material according to claim 1, characterized in that, The modified carbon nanotubes are prepared by the following steps: (1) Disperse 5 parts by weight of carbon nanotubes in deionized water to obtain solution A; dissolve 8 - 12 parts by weight of Na2MoO4·H2O in deionized water to obtain solution B; add solution B to solution A, and stir well to obtain solution C; (2) Dropwise add 4 - 6 parts by weight of CN2H4S to solution C, stir well, pour it into a reaction kettle, and after calcination, cooling, centrifugal separation, washing, and drying, the modified carbon nanotubes are obtained.

5. The halogen-free flame-retardant polypropylene composite material according to claim 1, characterized in that, The heat stabilizer is selected from at least one of phenolic heat stabilizers, phosphite heat stabilizers, and thioester heat stabilizers.

6. The halogen-free flame-retardant polypropylene composite material according to claim 1, wherein The processing aid is a macromolecular silicone masterbatch.

7. An environmentally friendly halogen-free flame-retardant polypropylene composite material according to claim 4, characterized in that, In solution B, every 1 g of Na2MoO4·H2O is dissolved in 30 - 70 mL of deionized water.

8. A method for preparing a halogen-free flame-retardant polypropylene composite material according to any one of claims 1-7, characterized in that, It includes the following steps: Fully mix polypropylene, halogen-free flame retardant, modified carbon nanotubes, heat stabilizer, and processing aid according to parts by weight to obtain a mixture; Add the mixture to a twin-screw extruder, and through melt mixing and dispersion, extrude and pelletize to obtain a halogen-free flame-retardant polypropylene composite material.

9. The preparation method according to claim 8, characterized in that, The temperature range of the twin-screw extruder from the feeding section to the die head is 185 - 195°C, 185 - 195°C, 185 - 200°C, 190 - 200°C, 190 - 200°C, 190 - 205°C, 195 - 205°C, 200 - 210°C, 200 - 205°C, 190 - 200°C in sequence.

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