Flame-retardant polypropylene and preparation method thereof

Abstract

The invention discloses flame-retardant polypropylene and a preparation method thereof, and belongs to the technical field of high polymer materials, the product comprises the following components by weight: 58-79 parts of polypropylene resin, 18-33 parts of a halogen-free flame retardant, 3-8 parts of a dispersant, 0.1-1.5 parts of a char forming catalyst, and 0.1-0.5 part of an interfacial compatibilizer. According to the product, the interfacial compatibilizer and the dispersing agent are added into the flame-retardant polypropylene, so that the dispersity of the halogen-free flame retardant in a polypropylene resin matrix is improved, the compatibility of the halogen-free flame retardant in the polypropylene resin matrix is further improved, and the thermal stability of the obtained polypropylene material is improved; therefore, under the condition of relatively high flame-retardant grade and mechanical property, the thermo-oxidative aging resistance is improved, and the material can be applied to a high-temperature environment for a long time and does not have the appearance problems of precipitation / whitening and the like.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to flame-retardant polypropylene and a preparation method thereof. Background Art

[0002] The flame-retardant polypropylene material prepared by adding flame-retardant components to the polypropylene matrix resin has higher flame-retardant properties than general polypropylene materials. The introduction of halogen-free flame-retardant components can make the prepared product less toxic and more environmentally friendly.

[0003] However, existing flame-retardant polypropylene materials generally use halogen-free substances with a high content of polar groups such as polypiperazine phosphate and piperazine pyrophosphate as flame retardant ingredients. This type of flame retardant has poor compatibility with the non-polar polypropylene matrix resin and low interface strength. In addition, its own group activity is high, so it is very easy to undergo thermal oxidation aging under high temperature conditions, causing a number of indicators including flame retardancy and mechanical properties to drop significantly, and even appearance problems such as precipitation and whitening may occur. It is not suitable for the preparation of products that need to be used in high temperature environments for a long time, such as heaters, new energy battery covers, hot air ducts, etc. Summary of the invention

[0004] Based on the defects of the prior art, the purpose of the present invention is to provide a flame-retardant polypropylene. The present invention adds an interfacial compatibilizer and a dispersant to the flame-retardant polypropylene, thereby improving the dispersibility of the halogen-free flame retardant in the polypropylene resin matrix, and further improving the compatibility of the halogen-free flame retardant in the polypropylene resin matrix, so that the thermal stability of the obtained polypropylene material is improved, so that while having a higher flame retardant grade and mechanical properties, the heat-oxidative aging resistance is improved, and it can be used in high-temperature environments for a long time, and there will be no appearance problems such as precipitation / whitening.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A flame retardant polypropylene comprises the following components in parts by weight:

[0007] 58-79 parts of polypropylene resin, 18-33 parts of halogen-free flame retardant, 3-8 parts of dispersant, 0.1-1.5 parts of carbon-forming catalyst, 0.1-0.5 parts of interface compatibilizer;

[0008] The dispersant includes at least one of ethylene-propylene copolymer and ethylene-butene copolymer;

[0009] The interfacial compatibilizer includes at least one of alkyl phosphonic acid and alkyl phosphate.

[0010] Compared with halogen flame retardants, halogen-free flame retardants have the characteristics of low toxicity, low smoke density, low cost and high environmental protection. However, the market share of halogen-free flame retardant polypropylene is low. The main reason is that halogen-free flame retardants, especially nitrogen-phosphorus halogen-free flame retardants, contain a large number of highly active polar groups such as hydroxyl and amino groups. They have low compatibility with polypropylene, low interface strength after compounding, poor component dispersion, high activity, and the interface is easily destroyed under high-temperature thermal oxidation aging conditions, resulting in rapid performance deterioration. Moreover, this degradation not only affects the flame retardant properties of the product, but also significantly reduces the mechanical properties, especially the toughness, and even causes appearance problems. In order to overcome this problem, the flame-retardant polypropylene of the present invention is compounded with copolymer elastomer as dispersant when introducing halogen-free flame retardant. Such elastomer can act as a coating layer of halogen-free flame retardant in the product, and its amorphous nature has good coating property for halogen-free flame retardant, and olefin segment has good compatibility with polypropylene, which is conducive to improving the uniformity of dispersion of halogen-free flame retardant system in polypropylene resin matrix, so that flame retardant can give full play to flame retardancy, and inhibit its precipitation in hot and humid environment; at the same time, alkyl phosphonic acid and / or alkyl phosphate are also introduced as interface compatibilizer to cooperate with dispersant, based on the compatibility of flexible alkyl molecular chain, the compatibility of halogen-free flame retardant and polypropylene matrix resin is significantly improved, so that the heat oxygen aging resistance of the product is greatly improved. In addition, since the elastomer itself has a certain toughening effect, and the product of the present invention introduces a certain amount of carbonization catalyst, the product has high toughness and flame retardancy, which fully meets the basic index requirements of products such as heater housing, new energy battery cover, hot air duct, etc. that work in high temperature environment.

[0011] Preferably, the flame-retardant polypropylene comprises the following components in parts by weight: 65-75 parts of polypropylene resin, 18-30 parts of halogen-free flame retardant, 4.5-7 parts of dispersant, 0.4-0.7 parts of carbon-forming catalyst, and 0.18-0.4 parts of interface compatibilizer.

[0012] When the above preferred component ratio is selected to prepare the product, the product can still achieve a higher flame retardant grade with a lower addition ratio of halogen-free flame retardant, and the product has higher toughness and better resistance to heat and oxygen aging.

[0013] More preferably, in the flame-retardant polypropylene, the mass content of the polypropylene resin is ≥50wt%.

[0014] Preferably, the polypropylene resin has a melt flow rate of 0.2 to 35 g / 10 min at 230° C. and a load of 2.16 kg according to ISO 1133-1-2011.

[0015] More preferably, the melt flow rate of the polypropylene matrix resin at 230°C and a load of 2.16 kg is in the range of one or any two of 0.2 g / 10 min, 1 g / 10 min, 2 g / 10 min, 5 g / 10 min, 10 g / 10 min, 15 g / 10 min, 20 g / 10 min, 25 g / 10 min, 30 g / 10 min, and 35 g / 10 min.

[0016] Preferably, the halogen-free flame retardant is a halogen-free flame retardant having amino groups and / or hydroxyl groups.

[0017] Preferably, the halogen-free flame retardant includes at least one of ammonium phosphate flame retardant, piperazine flame retardant, melamine flame retardant and triazine flame retardant.

[0018] The halogen-free flame retardant described in the present invention is not limited to the above types. Here, only the types of halogen-free flame retardants commonly used in existing polypropylene products known to those skilled in the art are listed. These types are based on the presence of amino and hydroxyl groups. When combined with other resins, they have a high flame retardant effect, but have poor compatibility with non-polar resins such as polypropylene resins, so they cannot exert the expected flame retardant properties. At the same time, they are prone to failure in high temperature environments and do not have resistance to thermal oxygen aging. In the special synergistic system described in the product of the present invention, as long as the type of halogen-free flame retardant used can exert a flame retardant effect similar to the above-mentioned types, and the product can also achieve similar resistance to thermal oxygen aging, then the type of selection is not limited.

[0019] Further preferably, the halogen-free flame retardant includes a nitrogen-phosphorus flame retardant.

[0020] Further preferably, the halogen-free flame retardant includes at least one of piperazine polyphosphate, piperazine pyrophosphate, melamine polyphosphate, melamine pyrophosphate, triazine carbonizing agent, and melamine cyanurate.

[0021] Preferably, the dispersant has a melt flow rate of 0.5 to 5.5 g / 10 min at 190° C. and a load of 2.16 kg according to ISO 1133-1-2011.

[0022] Further preferably, the dispersant has a melt flow rate at 190°C and a load of 2.16 kg according to ISO1133-1-2011 of 0.5 g / 10 min, 0.8 g / 10 min, 1 g / 10 min, 1.1 g / 10 min, 1.5 g / 10 min, 2 g / 10 min, 2.5 g / 10 min, 3 g / 10 min, 4 g / 10 min, 4.5 g / 10 min, 5 / 10 min, 5.5 g / 10 min or any two of the range values.

[0023] More preferably, the melt flow rate of the dispersant at 190° C. and a load of 2.16 kg is ≥ 2 g / 10 min.

[0024] More preferably, the dispersant has a melt flow rate of 3 to 5 g / 10 min at 190° C. and a load of 2.16 kg.

[0025] Different from the toughening agent component often introduced into the polypropylene resin in the prior art, the elastomer component including ethylene-propylene copolymer and / or ethylene-butene copolymer described in the present invention is mainly used to improve the dispersibility and compatibility of the halogen-free flame retardant. Therefore, if ethylene-octene copolymer, ethylene-vinyl acetate copolymer (EVA) and the like having similar conventional toughening effects are selected for replacement, the same effect cannot be achieved, and thus the product cannot be guaranteed to have sufficient heat-oxidative aging resistance. The inventors have screened and found that when a dispersant in the above-mentioned preferred melt flow rate range is selected, the basic performance of the obtained product remains basically unchanged, but the heat-oxidative aging resistance is better.

[0026] Preferably, the interfacial compatibilizer is at least one of alkyl phosphonic acid and alkyl phosphate.

[0027] More preferably, the number of carbon atoms in the alkyl chain of the alkyl phosphonic acid and / or alkyl phosphate is ≥10;

[0028] More preferably, the number of carbon atoms in the alkyl chain of the alkyl phosphonic acid and / or alkyl phosphate is in the range of 10, 12, 15, 18, 20, 22 or any two of them.

[0029] More preferably, the number of carbon atoms in the alkyl chain of the alkyl phosphonic acid and / or alkyl phosphate is ≥15.

[0030] More preferably, the alkyl chain in the alkyl phosphonic acid and / or alkyl phosphate has 15 to 20 carbon atoms.

[0031] As mentioned above, in the technical solution of the present application, the selection of alkyl phosphonic acid and / or alkyl phosphate is not intended to improve the flame retardant properties of the product by synergistically compounding it with a halogen-free flame retardant, but is based on its flexible alkyl chain and its own amphiphilicity to improve the compatibility of the halogen-free flame retardant in the matrix resin. If substitutes with similar flame-retardant phosphate structures such as phenyl phosphate or melamine phosphate are selected, although similar initial flame retardant properties may be achieved, the same heat-oxidative aging resistance cannot be achieved. After further screening, it was found that when an interfacial compatibilizer with the above-mentioned number of carbon atoms in the alkyl chain is selected, the heat-oxidative aging resistance of the product can be improved.

[0032] Preferably, the carbon-forming catalyst includes at least one of zinc oxide, nickel oxide and nickel formate.

[0033] The carbonization catalyst preferably used in the present invention can improve the combustion carbonization efficiency in the product under the premise of introducing an appropriate amount of halogen-free flame retardant, thereby achieving a higher flame retardant grade, and as mentioned above, based on the effects of the dispersant and the interface compatibilizer, the halogen-free flame retardant is less affected by the external environment, and the thermal oxidation rate is greatly slowed down, so a higher flame retardant grade can still be achieved after high-temperature treatment. In existing products, in order to ensure that the product can still achieve a higher flame retardant grade after high-temperature treatment, some researchers will introduce a high proportion of halogen-free flame retardant ingredients into the product. Although this approach can effectively ensure that the product still has a higher grade after heat treatment, due to the effect of the active groups in the halogen-free flame retardant and the interface defects between the halogen-free flame retardant and the polypropylene matrix, the thermal oxidative aging life of the halogen-free flame retardant polypropylene is seriously deteriorated under thermal oxidative aging conditions, and the attenuation amplitude of the mechanical properties after thermal oxidative aging increases.

[0034] More preferably, the average particle size of the carbon-forming catalyst is 0.1 to 10 μm.

[0035] The method for testing the average particle size of the carbon-forming catalyst of the present invention is: dispersing the carbon-forming catalyst in an insoluble water phase or ethanol phase, and testing the average particle size thereof using a laser particle size analyzer.

[0036] Preferably, the flame retardant polypropylene component also includes 0.1 to 2 parts of functional additives;

[0037] Further preferably, the functional additives include but are not limited to at least one of antistatic agents, antibacterial agents, antioxidants, lubricants, anti-ultraviolet agents, and anti-dripping agents and colorants. Those skilled in the art may add various functional additives according to actual needs without affecting the expected performance of the flame-retardant polypropylene of the present invention. For example, in order to further improve the stability of the product during the processing, those skilled in the art may add an appropriate amount of commonly used antioxidants to the product; in order to make the product have a better demolding effect during the processing, those skilled in the art may add a small amount of lubricant to the product for compounding.

[0038] Further preferably, the flame retardant polypropylene component also includes 0.1 to 1 part of an antioxidant and 0.1 to 1 part of an anti-drip agent.

[0039] More preferably, the anti-drip agent comprises polytetrafluoroethylene.

[0040] More preferably, the antioxidant includes at least one of a hindered phenol antioxidant, a phosphite antioxidant, and a thioester antioxidant.

[0041] More preferably, the antioxidant comprises a mixture of hindered phenol antioxidants, phosphite antioxidants and thioester antioxidants, with a mass ratio of (0.8-1.2):(0.8-1.2):(0.4-0.6).

[0042] More preferably, the hindered phenol antioxidant includes at least one of 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and octadecanol β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; the phosphite antioxidant includes at least one of tris[2,4-di-tert-butylphenyl]phosphite and trisbisphenol A phosphite; and the thioester antioxidant includes at least one of lauryl thiodipropionate, octadecanol thiodipropionate, and didodecanol thiodipropionate.

[0043] Another object of the present invention is to provide a method for preparing the flame retardant polypropylene, comprising the following steps:

[0044] The various components are added into a screw extruder for melt extrusion and granulation to obtain the flame retardant polypropylene.

[0045] Preferably, the temperature zones of the screw extruder are set to 110-130°C in zone 1, 210-230°C in zone 2, 210-230°C in zone 3, 210-230°C in zone 4, 210-230°C in zone 5, 210-230°C in zone 6, 210-230°C in zone 7, 210-230°C in zone 8, 210-230°C in zone 9, and 210-230°C in zone 10, the screw speed is 400-500rpm, and the screw aspect ratio is (38-42):1.

[0046] Another object of the present invention is to provide application of the flame-retardant polypropylene in the preparation of high temperature resistant equipment parts.

[0047] Preferably, the high temperature resistant equipment includes a heater and a new energy battery, and the high temperature resistant equipment parts include a heater housing, a new energy battery cover, a hot air delivery pipeline, and an electronic device protective shell.

[0048] The flame-retardant polypropylene of the present invention has the characteristics of high flame retardancy and high toughness under the premise of high environmental protection based on the reasonable addition of halogen-free flame retardants, and meets the basic use requirements of various equipment parts. Most importantly, based on the introduction and coordinated compounding of special additives, the product can be used in a long-term high-temperature environment and maintain a low degree of thermal oxygen aging. The flame retardancy and toughness can still be maintained at a high level after heat treatment, and there will be no obvious appearance problems. It is very suitable for the preparation of equipment parts used for a long time in a high-temperature environment.

[0049] The beneficial effect of the present invention is that the present invention provides a flame-retardant polypropylene, and the product adds an interfacial compatibilizer and a dispersant to the flame-retardant polypropylene, thereby improving the dispersibility of the halogen-free flame retardant in the polypropylene resin matrix, and then improving the compatibility of the halogen-free flame retardant in the polypropylene resin matrix, so that the thermal stability of the obtained polypropylene material is improved, so that while having a higher flame retardant grade and mechanical properties, the heat-oxidative aging resistance is improved, and it can be used in a high-temperature environment for a long time, and there will be no appearance problems such as precipitation / whitening. DETAILED DESCRIPTION

[0050] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments and comparative examples, the purpose of which is to understand the content of the present invention in detail, rather than to limit the present invention. All other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the protection scope of the present invention. The experimental reagents and instruments involved in the implementation of the present invention, unless otherwise specified, are all commonly used common reagents and instruments.

[0051] Examples 1 to 11

[0052] An embodiment of a flame-retardant polypropylene and a preparation method thereof according to the present invention, the composition of the flame-retardant polypropylene is shown in Table 1.

[0053] The method for preparing the flame retardant polypropylene comprises the following steps:

[0054] The components are mixed uniformly, and then melt-extruded and granulated in a twin-screw extruder to obtain the flame-retardant polypropylene.

[0055] When the components are melt-extruded, the temperature zones of the twin-screw extruder are set to 110-130°C in zone one, 210-230°C in zone two, 210-230°C in zone three, 210-230°C in zone four, 210-230°C in zone five, 210-230°C in zone six, 210-230°C in zone seven, 210-230°C in zone eight, 210-230°C in zone nine, and 210-230°C in zone ten, the screw speed is 450rpm, and the screw aspect ratio is 40:1.

[0056] Comparative Examples 1 to 9

[0057] The difference between the comparative examples and the embodiments is only in the types and proportions of components, as shown in Table 2.

[0058] Among the components described in each embodiment and comparative example,

[0059] Polypropylene 1 is HP500N produced by PetroChina Daqing Refining and Chemical, with a melt flow rate of 12 g / 10 min at 230 °C and 2.16 kg load;

[0060] Polypropylene 2 is EP300M produced by CNOOC and Shell, with a melt flow rate of 10 g / 10 min at 230 °C and a load of 2.16 kg;

[0061] Halogen-free flame retardant 1 is FP-2200 produced by Aidico, a piperazine pyrophosphate flame retardant;

[0062] Halogen-free flame retardant 2 is JLS-PNA260 produced by JLS, a polyphosphate piperazine flame retardant;

[0063] Dispersant 1 is MPOE VL8805 produced by Daelim of South Korea, an ethylene-butene copolymer, with a melt flow rate of 5 g / 10 min at 190 °C and a load of 2.16 kg;

[0064] Dispersant 2 is MPOE VL8803 produced by Daelim of South Korea, an ethylene-butene copolymer, with a melt flow rate of 3 g / 10 min at 190 °C and a load of 2.16 kg;

[0065] Dispersant 3 is MPOE VL8801 produced by Daelim of South Korea, an ethylene-butene copolymer, with a melt flow rate of 1 g / 10 min at 190 °C and a load of 2.16 kg;

[0066] Dispersant 4 is Vistamaxx 3020FL produced by Vistamaxx, an ethylene-propylene copolymer, with a melt flow rate of 1.2 g / 10 min at 190°C and a load of 2.16 kg;

[0067] Dispersant 5 is POE ENGAGE 8842 produced by Dow, an ethylene-octene copolymer, with a melt flow rate of 1 g / 10 min at 190°C and a load of 2.16 kg;

[0068] Dispersant 6 is EVA ELVAX 460 produced by DuPont, ethylene-vinyl acetate copolymer, with a melt flow rate of 2.5 g / 10 min at 190°C and a load of 2.16 kg;

[0069] Interfacial compatibilizer 1 is commercially available octadecyl phosphate, CAS: 39471-52-8, with an alkyl chain carbon number of 18;

[0070] Interfacial compatibilizer 2 is commercially available octadecylphosphonic acid, CAS: 4724-47-4, with an alkyl chain carbon number of 18;

[0071] Interfacial compatibilizer 3 is commercially available dodecyl phosphate, CAS: 12751-23-4, with 12 carbon atoms in the alkyl chain;

[0072] Interfacial compatibilizer 4 is commercially available triisopropylphenyl phosphate, CAS: 26967-76-0;

[0073] Interfacial compatibilizer 5 is commercially available melamine phosphate, CAS: 20208-95-1;

[0074] Carbon-forming catalyst 1 is commercially available zinc oxide with an average particle size of 2.5 μm;

[0075] Carbon-forming catalyst 2 is commercially available nickel oxide with an average particle size of 3.0 μm;

[0076] Anti-dripping agent: X-010, polytetrafluoroethylene, Shandong Dongyue Polymer Materials Co., Ltd.;

[0077] The antioxidant is a mixture of hindered phenol antioxidant 168, phosphite antioxidant 1010 and thioester antioxidant DSTDP produced by BASF in a mass ratio of 1:1:0.5;

[0078] Unless otherwise specified, the components and raw materials used in the embodiments and comparative examples of the present invention are all commercially available raw materials, and the components and raw materials used in each parallel experiment are all of the same kind.

[0079] Table 1

[0080]

[0081] Table 2

[0082]

[0083] In order to verify the performance of the flame-retardant polypropylene of the present invention, the products prepared in each embodiment and comparative example were subjected to the following performance tests, and the test items and test methods are as follows:

[0084] (1) Izod notched impact strength test: According to ISO 180-2019, the test specimens were injection molded into 80*10*4 mm, the impact energy was 2.75 J, and the notch was A-type. The initial Izod notched impact strength was tested and recorded as A0. Then, parallel samples were prepared and placed in an incubator at 150°C for 1000 h. The Izod notched impact strength was tested and recorded as A1. The Izod notched impact strength retention rate of the product after heat treatment (%) was calculated as (A1 / A0)×100%;

[0085] (2) Flame retardant grade test and appearance test: The test is carried out according to UL94-2020. The test specimens are injection molded into 127*13*1.6mm test specimens. The flame retardant grade of each product is tested. Then, parallel samples are prepared and placed in an incubator at 150°C for 1000 hours, and then placed at room temperature for 4 hours to observe whether there are any adverse phenomena such as precipitation / whitening on the surface. Finally, the flame retardant grade of the samples after heat treatment is tested.

[0086] The test results are shown in Tables 3 and 4.

[0087] Table 3

[0088]

[0089] Table 4

[0090]

[0091] It can be seen from Table 3 and Table 4 that the flame retardant polypropylene product of the present invention has good basic performance due to the interaction of various components. It can reach V-0 grade or above in the 1.6mm flame retardant grade test, and the cantilever beam notched impact strength can reach 4KJ / m 2 And above, at the same time, due to the compound use of specific dispersants and interface compatibilizers, the product has good resistance to heat and oxygen aging. After 1000 hours of high-temperature treatment, the flame retardant grade of the product can still be maintained above V-0, without flame retardant failure or appearance problems. In addition, after high-temperature treatment, the cantilever beam notch impact strength of the product can be retained by more than 60% compared with before treatment, and it still has high toughness.

[0092] The product of Comparative Example 1 does not introduce dispersant, interfacial bulking agent and carbon-forming catalyst. It can be seen that the flame retardant level of the product is low in the initial stage. Subsequently, after high-temperature treatment, the flame retardancy fails, and the cantilever beam notched impact strength decreases significantly, and precipitation occurs, indicating that the product does not have resistance to heat-oxidative aging; Comparative Example 2 introduces a carbon-forming catalyst and increases the amount of halogen-free flame retardant added on the basis of the product of Comparative Example 1. This is also a common improved product in the prior art. The initial flame retardant level of the product is high and remains unchanged after high-temperature treatment. However, due to the increase in the introduction of halogen-free flame retardants, the dispersibility and compatibility of the product have not changed. Therefore, the decrease in the cantilever beam notched impact strength of the product after high-temperature treatment increases instead, and the appearance is still poor, and it cannot be used normally.

[0093] It can be seen from Comparative Example 3, Example 1, Examples 3 to 5, and Comparative Examples 5 and 6 that in the product of the present invention, the use of dispersant is very critical, and it works synergistically with the interface compatibilizer to ensure the dispersibility and compatibility of the halogen-free flame retardant in the product. When this component is not contained, the flame retardant in the product of Comparative Example 3 does not play an ideal role, and the product cannot reach the flame retardant grade of V-0 before heat treatment, and the Izod notched impact strength decreases seriously after heat treatment. However, the selection of dispersant types is not arbitrary, because it is not used as a toughening agent like conventional elastomers in the product, so if an unsuitable elastomer is selected as a dispersant, such as ethylene-octene copolymer, or EVA, the product can improve the retention rate of the Izod notched impact strength after heat treatment to a certain extent, but the flame retardant performance of the product is still unsatisfactory; when selecting a dispersant, the inventor has found through optimization that when an ethylene-butene copolymer and / or ethylene-propylene copolymer with a melt flow rate of 2g / 10min or more is selected, the product has better heat oxygen aging resistance and a higher Izod impact strength retention rate.

[0094] According to Comparative Example 4, Example 1, Examples 6 and 7, and Comparative Examples 7 and 8, it can be seen that, similar to the dispersant, the interfacial compatibilizer in the product components of the present invention is also indispensable. The component is not a synergist of the halogen-free flame retardant, but a synergistic compatibilizer between it and the polypropylene resin. Therefore, in the case of such a low addition amount, in the absence of this component, the initial flame retardant performance of the product is reduced, and the flame retardant and mechanical properties of the product are significantly weakened after heat treatment, and precipitation occurs in the appearance; if non-alkyl chain phosphate or phosphoric acid is selected as an interfacial compatibilizer, it will not actually improve the interfacial strength between the halogen-free flame retardant and the polypropylene resin, and the degradation rate of the polymer resin cannot be suppressed. Therefore, although the flame retardant grade of the products of Comparative Examples 7 and 8 before and after heat treatment reaches the V-0 grade, the heat-oxidation aging resistance in toughness is not significantly improved compared to Comparative Example 4, and there is still precipitation in appearance. After selecting a suitable alkyl phosphoric acid / phosphate ester, the inventor preferably found that selecting the type of long alkyl chain can further improve the heat-oxidation aging resistance of the product, so that the mechanical property retention rate of the product is higher. However, as shown in the product of Comparative Example 9, since the interface compatibilizer is a small molecule substance, if it is introduced too much, it will cause the product performance to deteriorate, and even the appearance precipitation phenomenon will reappear.

[0095] It can be seen from Example 1 and Examples 8 to 11 that the content of halogen-free flame retardant will not only change the production cost of the product, but also affect the initial mechanical properties and heat-oxidation aging resistance of the product. By adjusting the carbon-forming catalyst, dispersant and interfacial compatibilizer in the product, the flame retardant performance and heat-oxidation aging resistance of the product can be taken into account at a lower weight of flame retardant addition.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A flame retardant polypropylene, characterized in that: The composition comprises the following components in parts by weight: 58-79 parts of polypropylene resin, 18-33 parts of halogen-free flame retardant, 3-8 parts of dispersant, 0.1-1.5 parts of carbon-forming catalyst, 0.1-0.5 parts of interface compatibilizer; The dispersant includes at least one of ethylene-propylene copolymer and ethylene-butene copolymer; The interfacial compatibilizer includes at least one of alkyl phosphonic acid and alkyl phosphate.

2. The flame retardant polypropylene according to claim 1, characterized in that: The polypropylene resin has a melt flow rate of 0.2 to 35 g / 10 min at 230° C. and a load of 2.16 kg according to ISO1133-1-2011.

3. The flame retardant polypropylene according to claim 1, characterized in that: The halogen-free flame retardant includes at least one of ammonium phosphate flame retardant, piperazine flame retardant, melamine flame retardant and triazine flame retardant.

4. The flame retardant polypropylene according to claim 1, characterized in that: The dispersant has a melt flow rate of 0.5 to 5.5 g / 10 min at 190° C. and a load of 2.16 kg according to ISO 1133-1-2011.

5. The flame retardant polypropylene according to claim 1, characterized in that: The number of carbon atoms in the alkyl chain of the alkyl phosphonic acid and / or alkyl phosphate is ≥10.

6. The flame retardant polypropylene according to claim 1, characterized in that: The carbon-forming catalyst includes at least one of zinc oxide, nickel oxide and nickel formate.

7. The flame retardant polypropylene according to claim 1, characterized in that: The flame retardant polypropylene component also includes 0.1 to 2 parts of functional additives; preferably, the flame retardant polypropylene component also includes 0.1 to 1 parts of antioxidants and 0.1 to 1 parts of lubricants.

8. The method for preparing flame-retardant polypropylene according to any one of claims 1 to 7, characterized in that: The following steps are involved: The various components are added into a screw extruder for melt extrusion and granulation to obtain the flame retardant polypropylene.

9. Use of the flame-retardant polypropylene according to any one of claims 1 to 7 in the preparation of high temperature resistant equipment parts.

10. The use according to claim 9, characterized in that The high temperature resistant equipment includes a heater and a new energy battery; the high temperature resistant equipment parts include a heater housing, a new energy battery cover, a hot air delivery pipeline, and an electronic device protective shell.

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