Flame-retardant polypropylene and preparation method therefor

Abstract

A flame-retardant polypropylene and a preparation method therefor, belonging to the technical field of polymer materials. The product comprises the following components in parts by weight: 58-79 parts of a 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. In the product, the interfacial compatibilizer and the dispersant are added to flame-retardant polypropylene, which enhances the dispersion of the halogen-free flame retardant in the polypropylene resin matrix and further improves the compatibility of the halogen-free flame retardant in the polypropylene resin matrix, thereby enhancing the thermal stability of the obtained polypropylene material. Accordingly, while maintaining high flame-retarding level and mechanical properties, the flame-retardant polypropylene has improved resistance to thermo-oxidative aging, and thus can be applied in high-temperature environments for long time without appearance problems such as blooming / whitening.

Description

A flame-retardant polypropylene and its preparation method Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a flame-retardant polypropylene and its preparation method. Background Technology

[0002] Flame-retardant polypropylene materials prepared by adding flame-retardant components to polypropylene matrix resin have higher flame-retardant properties than ordinary polypropylene materials. Introducing halogen-free flame-retardant components can make the prepared products 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 piperazine polyphosphate and piperazine pyrophosphate, as flame-retardant components. These flame retardants have poor compatibility with non-polar polypropylene matrix resins and low interfacial strength. In addition, their own groups are highly active, so they are prone to thermo-oxidative aging in high-temperature environments. This causes a significant decrease in many indicators, including flame retardancy and mechanical properties, and even appearance problems such as precipitation and whitening. They are not suitable for the manufacture of products that need to be used in high-temperature environments for a long time, such as heaters, new energy battery covers, and hot air ducts. Summary of the Invention

[0004] This invention provides a flame-retardant polypropylene. By adding an interface compatibilizer and a dispersant to the flame-retardant polypropylene, the dispersibility of the halogen-free flame retardant in the polypropylene resin matrix is ​​improved, thereby enhancing the compatibility of the halogen-free flame retardant in the polypropylene resin matrix. This improves the thermal stability of the resulting polypropylene material, resulting in improved heat and oxygen aging resistance while maintaining a high flame retardancy rating and mechanical properties. It can be used in high-temperature environments for extended periods without exhibiting appearance problems such as precipitation or whitening.

[0005] This invention provides a flame-retardant polypropylene, comprising 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 char-forming catalyst, and 0.1-0.5 parts of interface compatibilizer.

[0006] The dispersant includes at least one of ethylene-propylene copolymer and ethylene-butene copolymer;

[0007] The interface compatibilizer includes at least one of alkylphosphonic acid and alkyl phosphate.

[0008] In some embodiments, the polypropylene resin has a melt flow rate of 0.2 to 35 g / 10 min at 230°C and 2.16 kg load, according to ISO 1133-1-2011.

[0009] In some embodiments, the halogen-free flame retardant includes at least one of ammonium phosphate flame retardants, piperazine flame retardants, melamine flame retardants, and triazine flame retardants.

[0010] In some embodiments, the dispersant, according to ISO 1133-1-2011, has a melt flow rate of 0.5 to 5.5 g / 10 min at 190°C and a load of 2.16 kg.

[0011] In some embodiments, the alkyl chain in the alkylphosphonic acid and / or alkyl phosphate has ≥10 carbon atoms.

[0012] In some embodiments, the char-forming catalyst includes at least one of zinc oxide, nickel oxide, and nickel formate.

[0013] In some embodiments, the flame-retardant polypropylene further includes 0.1 to 2 parts by weight of functional additives. In some embodiments, the flame-retardant polypropylene further includes 0.1 to 1 part by weight of antioxidant and 0.1 to 1 part by weight of lubricant.

[0014] The present invention provides a method for preparing the flame-retardant polypropylene, comprising the following steps: adding each component into a screw extruder for melt extrusion granulation to obtain the flame-retardant polypropylene.

[0015] This invention provides the application of the flame-retardant polypropylene in the preparation of high-temperature resistant equipment parts.

[0016] In some embodiments, the high-temperature resistant equipment includes at least one of a heater and a new energy battery; the components of the high-temperature resistant equipment include at least one of a heater housing, a new energy battery cover, a hot air delivery pipe, and a protective shell for electronic components.

[0017] The beneficial effects of this invention are that it provides a flame-retardant polypropylene. This product incorporates an interface compatibilizer and a dispersant into the flame-retardant polypropylene, which improves the dispersibility of the halogen-free flame retardant in the polypropylene resin matrix, thereby improving the compatibility of the halogen-free flame retardant in the polypropylene resin matrix. This enhances the thermal stability of the resulting polypropylene material, resulting in improved heat and oxygen aging resistance while maintaining a high flame retardancy rating and mechanical properties. It can be used in high-temperature environments for extended periods without exhibiting appearance problems such as precipitation or whitening. Detailed Implementation

[0018] The technical solution adopted in this invention is as follows: ：

[0019] A flame-retardant polypropylene comprises the following components in parts by weight:

[0020] The mixture contains 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 char-forming catalyst, and 0.1-0.5 parts of interface compatibilizer.

[0021] The dispersant includes at least one of ethylene-propylene copolymer and ethylene-butene copolymer;

[0022] The interface compatibilizer includes at least one of alkylphosphonic acid and alkyl phosphate.

[0023] Compared to halogenated flame retardants, halogen-free flame retardants have the advantages of low toxicity, low smoke density, low cost, and high environmental friendliness. However, the market share of halogen-free flame-retardant polypropylene is relatively low. The main reason is that halogen-free flame retardants, especially nitrogen-phosphorus halogen-free flame retardants, contain a large number of highly reactive polar groups such as hydroxyl and amino groups. They have low compatibility with polypropylene, resulting in low interfacial strength, poor component dispersibility, and high reactivity after compounding. Under high temperature and oxidative aging conditions, the interface is easily damaged, leading to rapid performance degradation. This degradation not only affects the flame retardant performance of the product, but also significantly reduces mechanical properties, especially toughness, and may even cause appearance problems. To overcome this problem, the flame-retardant polypropylene of this invention, in the presence of a halogen-free flame retardant, is compounded using a copolymer elastomer as a dispersant. This elastomer acts as a coating layer for the halogen-free flame retardant in the product. Its amorphous nature provides good coating properties for the halogen-free flame retardant, and the olefin segments have good compatibility with polypropylene, which helps improve the dispersion uniformity of the halogen-free flame retardant system in the polypropylene resin matrix, allowing the flame retardant to fully exert its flame-retardant properties while inhibiting its precipitation in humid and hot environments. Simultaneously, alkyl phosphonic acids and / or alkyl phosphates are introduced as interfacial compatibilizers to synergistically work with the dispersant. Based on the compatibility of flexible alkyl molecular chains, the compatibility between the halogen-free flame retardant and the polypropylene matrix resin is significantly improved, resulting in a substantial increase in the product's resistance to heat and oxygen aging. Furthermore, since the elastomer itself has a certain toughening effect, and the product of this invention incorporates a certain amount of char-forming catalyst, the product exhibits high toughness and flame retardancy, fully meeting the basic performance requirements of products operating in high-temperature environments, such as heater housings, new energy battery covers, and hot air ducts.

[0024] In some embodiments, the flame-retardant polypropylene comprises the following components in parts by weight: 65-75 parts polypropylene resin, 18-30 parts halogen-free flame retardant, 4.5-7 parts dispersant, 0.4-0.7 parts char-forming catalyst, and 0.18-0.4 parts interface compatibilizer.

[0025] When the above component ratio is selected for product preparation, the product can still achieve a high flame retardancy rating with a relatively low proportion of halogen-free flame retardant, while also exhibiting high toughness and better resistance to heat and oxygen aging.

[0026] In some embodiments, the flame-retardant polypropylene contains ≥50 wt% polypropylene resin.

[0027] In some embodiments, the polypropylene resin has a melt flow rate of 0.2 to 35 g / 10 min at 230°C and 2.16 kg load, according to ISO 1133-1-2011.

[0028] In some embodiments, the melt flow rate of the polypropylene matrix resin at 230°C and 2.16 kg load is one or any two of the following values: 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.

[0029] In some embodiments, the halogen-free flame retardant is a halogen-free flame retardant containing amino and / or hydroxyl groups.

[0030] In some embodiments, the halogen-free flame retardant includes at least one of ammonium phosphate flame retardants, piperazine flame retardants, melamine flame retardants, and triazine flame retardants.

[0031] The halogen-free flame retardants described in this invention are not limited to the types mentioned above. Only commonly used halogen-free flame retardants in existing polypropylene products, known to those skilled in the art, are listed here. These types, based on the presence of amino and hydroxyl groups, exhibit high flame retardant effects when combined with other resins, but have poor compatibility with non-polar resins such as polypropylene resins, thus failing to achieve the expected flame retardant performance. Furthermore, they are prone to failure at high temperatures and lack resistance to heat and oxygen aging. However, in the special synergistic system described in this invention, the choice of halogen-free flame retardant is not limited as long as it can achieve similar flame retardant effects to the types described above and the product can also achieve similar resistance to heat and oxygen aging.

[0032] In some embodiments, the halogen-free flame retardant includes nitrogen-phosphorus flame retardants.

[0033] In some embodiments, the halogen-free flame retardant includes at least one of piperazine polyphosphate flame retardants, piperazine pyrophosphate flame retardants, melamine polyphosphate flame retardants, melamine pyrophosphate flame retardants, triazine charring agents, and melamine cyanuric acid flame retardants.

[0034] In some embodiments, the dispersant, according to ISO 1133-1-2011, has a melt flow rate of 0.5 to 5.5 g / 10 min at 190°C and a load of 2.16 kg.

[0035] In some embodiments, the melt flow rate of the dispersant at 190°C and a load of 2.16 kg is one or any two of the following values: 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 g / 10 min, and 5.5 g / 10 min.

[0036] In some embodiments, the dispersant has a melt flow rate ≥2 g / 10 min at 190°C and a load of 2.16 kg.

[0037] In some embodiments, the dispersant has a melt flow rate of 3 to 5 g / 10 min at 190°C and a load of 2.16 kg.

[0038] Unlike the toughening agents often introduced into polypropylene resins in existing technologies, the elastomer components of this invention, including ethylene-propylene copolymers and / or ethylene-butene copolymers, are primarily used to improve the dispersibility and compatibility of halogen-free flame retardants. Therefore, replacing them with dispersants such as ethylene-octene copolymers or ethylene-vinyl acetate copolymers (EVA), which also have similar conventional toughening effects, cannot achieve the same results, thus failing to guarantee sufficient heat and oxygen aging resistance of the product. Through screening, the inventors discovered that when dispersants within the aforementioned melt flow rate range are selected, the basic properties of the resulting product remain essentially unchanged, but the heat and oxygen aging resistance is superior. This invention does not have special requirements regarding the molar ratio of ethylene to propylene in ethylene-propylene copolymers, or the molar ratio of ethylene to butene in ethylene-butene copolymers; these can be conventionally selected by those skilled in the art.

[0039] In some embodiments, the interface compatibilizer is at least one of alkylphosphonic acid and alkyl phosphate.

[0040] In some embodiments, the alkyl chain in the alkylphosphonic acid and / or alkyl phosphate has ≥10 carbon atoms.

[0041] In some embodiments, the number of carbon atoms in the alkyl chain of the alkylphosphonic acid and / or alkyl phosphate is a range of one or both of 10, 12, 15, 18, 20, and 22.

[0042] In some embodiments, the alkyl chain in the alkylphosphonic acid and / or alkyl phosphate has ≥15 carbon atoms.

[0043] In some embodiments, the alkyl chain in the alkylphosphonic acid and / or alkyl phosphate has 15 to 20 carbon atoms.

[0044] As mentioned above, the selection of alkylphosphonic acid and / or alkyl phosphate in this application is not intended to synergistically enhance the flame retardant performance of the product with halogen-free flame retardants, but rather to improve the compatibility of halogen-free flame retardants in the matrix resin due to their flexible alkyl chains and their amphiphilic nature. If substitutes with similar flame-retardant phosphate ester / salt structures, such as phenyl phosphate ester / salt or melamine phosphate ester / salt, are selected, similar initial flame retardant performance may be achieved, but the same heat and oxygen aging resistance cannot be achieved. After further screening, it was found that selecting the above-mentioned interfacial compatibilizers with the number of carbon atoms in the alkyl chain can make the product's heat and oxygen aging resistance even better.

[0045] In some embodiments, the char-forming catalyst includes at least one of zinc oxide, nickel oxide, and nickel formate.

[0046] The char-forming catalyst used in this invention can improve the combustion char-forming efficiency of the product, thereby achieving a high flame retardant rating, provided that an appropriate amount of halogen-free flame retardant is introduced. Furthermore, as mentioned above, due to the effects of dispersants and interface compatibilizers, the halogen-free flame retardant is less affected by the external environment, and the thermal oxidation rate is significantly slowed down. Therefore, a high flame retardant rating can still be achieved after high-temperature treatment. In existing products, to ensure a high flame retardant rating after high-temperature treatment, some researchers introduce a high proportion of halogen-free flame retardant components. While this effectively ensures a high rating after heat treatment, the active groups in the halogen-free flame retardant and the interfacial defects between them and the polypropylene matrix cause a severe deterioration in the thermo-oxidative aging life of the halogen-free flame-retardant polypropylene under thermo-oxidative aging conditions, and the mechanical properties degrade significantly after thermo-oxidative aging.

[0047] In some embodiments, the average particle size (i.e., D50 particle size) of the carbon-forming catalyst is 0.1 to 10 μm.

[0048] The average particle size (i.e., D50 particle size) of the char-forming catalyst described in this invention can be obtained using conventional methods in the art. For example, the testing method includes the following steps: dispersing the char-forming catalyst in an insoluble aqueous or ethanol phase, and measuring its average particle size using a laser particle size analyzer.

[0049] In some embodiments, the flame-retardant polypropylene further includes 0.1 to 2 parts by weight of functional additives;

[0050] In some embodiments, the functional additives include, but are not limited to, at least one of antistatic agents, antibacterial agents, antioxidants, lubricants, UV stabilizers, anti-dripping agents, and colorants. Those skilled in the art can add various functional additives as needed, without affecting the intended performance of the flame-retardant polypropylene described in this invention. For example, to further improve the stability of the product during processing, those skilled in the art can add an appropriate amount of commonly used antioxidants to the product; to improve the demolding effect during processing, those skilled in the art can add a small amount of lubricant for compound processing.

[0051] In some embodiments, the flame-retardant polypropylene further includes 0.1 to 1 part by weight of an antioxidant and 0.1 to 1 part by weight of an anti-dripping agent.

[0052] In some embodiments, the anti-dripping agent includes polytetrafluoroethylene.

[0053] In some embodiments, the antioxidant includes at least one of hindered phenolic antioxidants, phosphite antioxidants, and thioester antioxidants.

[0054] In some embodiments, the antioxidant comprises a mixture of hindered phenolic antioxidants, phosphite antioxidants, and thioester antioxidants in a mass ratio of (0.8–1.2):(0.8–1.2):(0.4–0.6).

[0055] In some embodiments, the hindered phenolic 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 octadecyl 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 tribisphenol A phosphite; and the thioester antioxidant includes at least one of lauryl thiodipropionate, octadecyl thiodipropionate, and dodecyl thiodipropionate.

[0056] Another object of the present invention is to provide a method for preparing the flame-retardant polypropylene, comprising the following steps:

[0057] The components are added to a screw extruder for melt extrusion and granulation to obtain the flame-retardant polypropylene.

[0058] In some embodiments, the temperature zones of the screw extruder are set as follows: Zone 1: 110–130°C; Zone 2: 210–230°C; Zone 3: 210–230°C; Zone 4: 210–230°C; Zone 5: 210–230°C; Zone 6: 210–230°C; Zone 7: 210–230°C; Zone 8: 210–230°C; Zone 9: 210–230°C; Zone 10: 210–230°C; the screw speed is 400–500 rpm; and the screw length-to-diameter ratio is (38–42):1.

[0059] Another object of the present invention is to provide the application of the flame-retardant polypropylene in the preparation of high-temperature resistant equipment parts.

[0060] In some embodiments, the high-temperature resistant equipment includes at least one of a heater and a new energy battery, and the components of the high-temperature resistant equipment include at least one of a heater housing, a new energy battery cover, a hot air delivery pipe, and a protective shell for electronic components.

[0061] In some embodiments, this application provides a high-temperature resistant equipment component, which is prepared (or derived from, or formed from) the flame-retardant polypropylene. The term "prepared" (or "derived from," or "formed") refers to a process that can be achieved through a variety of processes, including but not limited to one or more selected from: molding, such as injection molding, compression molding, blow molding, rotational molding; extrusion, such as sheet extrusion, film extrusion (e.g., blown-film extrusion); thermoforming; vacuum forming; and melt-blown process.

[0062] In some embodiments, typically, the flame-retardant polypropylene does not undergo a chemical change during the preparation (or derivation, or formation) of the high-temperature resistant equipment component (i.e., the high-temperature resistant equipment component comprises the flame-retardant polypropylene). In other embodiments, a chemical change occurs.

[0063] In some embodiments, the raw materials for preparing the high-temperature resistant equipment parts include, in addition to the flame-retardant polypropylene, other substances (e.g., at least one of colorants, antioxidants, and lubricants). In other embodiments, no other substances are included; that is, the high-temperature resistant equipment parts are prepared using only the flame-retardant polypropylene.

[0064] The flame-retardant polypropylene described in this invention, based on the rational addition of halogen-free flame retardants, possesses high flame retardancy and high toughness under the premise of high environmental protection, meeting the basic usage requirements of various equipment parts. Most importantly, based on the introduction and synergistic compounding of special additives, the product can be used in long-term high-temperature environments and maintain a low degree of thermo-oxidative aging. The flame retardancy and toughness can still maintain a high level after heat treatment, and there will be no obvious appearance problems. It is very suitable for the preparation of equipment parts that are used for a long time in high-temperature environments.

[0065] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments and comparative examples. The purpose of this description is to provide a detailed understanding of the invention, not to limit its scope. All other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this invention. Unless otherwise specified, the experimental reagents and instruments involved in the implementation of this invention are commonly used reagents and instruments.

[0066] Examples 1-11

[0067] An embodiment of the flame-retardant polypropylene and its preparation method described in this invention is shown in Table 1.

[0068] The preparation method of the flame-retardant polypropylene includes the following steps:

[0069] The components are mixed evenly, and then melt-extruded and granulated in a twin-screw extruder to obtain the flame-retardant polypropylene.

[0070] During melt extrusion of the component, the temperature zones of the twin-screw extruder are set as follows: Zone 1: 110–130℃; Zone 2: 210–230℃; Zone 3: 210–230℃; Zone 4: 210–230℃; Zone 5: 210–230℃; Zone 6: 210–230℃; Zone 7: 210–230℃; Zone 8: 210–230℃; Zone 9: 210–230℃; Zone 10: 210–230℃; Screw speed: 450 rpm; Screw length-to-diameter ratio: 40:1.

[0071] Comparative Examples 1-9

[0072] The only difference between each comparative example and the embodiment is the type and ratio of components, as shown in Table 2.

[0073] In the components described in each embodiment and comparative example,

[0074] Polypropylene 1 is HP500N produced by PetroChina Daqing Refining & Chemical Co., Ltd., with a melt flow rate of 12g / 10min at 230℃ and 2.16kg load.

[0075] Polypropylene 2 is EP300M produced by CNOOC Shell, with a melt flow rate of 10g / 10min at 230℃ and 2.16kg load;

[0076] Halogen-free flame retardant 1 is FP-2200 produced by Adico, a piperazine pyrophosphate flame retardant;

[0077] Halogen-free flame retardant 2 is JLS-PNA260, a piperazine polyphosphate flame retardant manufactured by JLS.

[0078] Dispersant 1 is MPOEVL8805, an ethylene-butene copolymer produced by Daelim, South Korea, with a melt flow rate of 5 g / 10 min at 190°C and 2.16 kg load.

[0079] Dispersant 2 is MPOEVL8803, an ethylene-butene copolymer produced by Daelim, South Korea, with a melt flow rate of 3 g / 10 min at 190°C and 2.16 kg load.

[0080] Dispersant 3 is MPOEVL8801, an ethylene-butene copolymer produced by Daelim, South Korea, with a melt flow rate of 1 g / 10 min at 190°C and 2.16 kg load.

[0081] Dispersant 4 is Vistamaxx 3020FL, an ethylene-propylene copolymer produced by Vistamaxx, with a melt flow rate of 1.2 g / 10 min at 190 °C and 2.16 kg load;

[0082] Dispersant 5 is POE ENGAGE 8842, an ethylene-octene copolymer manufactured by Dow, with a melt flow rate of 1 g / 10 min at 190 °C and 2.16 kg load;

[0083] Dispersant 6 is DuPont's EVAELVAX 460, an ethylene-vinyl acetate copolymer, with a melt flow rate of 2.5 g / 10 min at 190°C and 2.16 kg load;

[0084] Interface compatibilizer 1 is a commercially available octadecyl phosphate, CAS: 39471-52-8, with 18 carbon atoms in the alkyl chain;

[0085] Interface compatibilizer 2 is commercially available octadecylphosphonic acid, CAS: 4724-47-4, with 18 carbon atoms in the alkyl chain;

[0086] Interface compatibilizer 3 is a commercially available dodecyl phosphate, CAS: 12751-23-4, with 12 carbon atoms in the alkyl chain;

[0087] Interface compatibilizer 4 is commercially available triisopropylphenyl phosphate, CAS: 26967-76-0;

[0088] Interface compatibilizer 5 is commercially available melamine phosphate, CAS: 20208-95-1;

[0089] The char-forming catalyst 1 is commercially available zinc oxide with an average particle size of 2.5 μm;

[0090] The carbonization catalyst 2 is commercially available nickel oxide with an average particle size of 3.0 μm;

[0091] Anti-dripping agent: X-010, polytetrafluoroethylene, Shandong Dongyue Polymer Materials Co., Ltd.;

[0092] The antioxidant is a mixture of hindered phenolic antioxidant 168, phosphite antioxidant 1010 and thioester antioxidant DSTDP produced by BASF in a mass ratio of 1:1:0.5;

[0093] Unless otherwise specified, all components and raw materials used in the embodiments and comparative examples of this invention are commercially available, and the same type of components and raw materials are used in each parallel experiment.

[0094] Table 1

[0095] Table 2

[0096] To verify the performance of the flame-retardant polypropylene described in this invention, the products prepared in each embodiment and comparative example were subjected to the following performance tests. The test items and methods are as follows:

[0097] (1) Cantilever beam notched impact strength test: According to ISO 180-2019, test strips of 80*10*4mm were injection molded (n=5), impact energy 2.75J, type A notch, the initial cantilever beam notched impact strength was tested and recorded as A0, parallel samples (n=5) were prepared and placed in a heat preservation box at 150℃ for 1000h, the cantilever beam notched impact strength was tested and recorded as A1, the cantilever beam notched impact strength retention rate (%) of the product after heat treatment was calculated as (A1 / A0)×100%;

[0098] (2) Flame retardancy rating test and appearance test: According to UL94-2020, test strips of 127*13*1.6mm were injection molded (n=5) to test the flame retardancy rating of each product. Parallel samples (n=5) were prepared and placed in a 150℃ incubator for 1000h, then placed at room temperature for 4h. The surface was observed (visually) for defects such as precipitation / whitening. Finally, the flame retardancy rating of the samples after heat treatment was tested (at 25℃ and 50RH%).

[0099] The test results are shown in Tables 3 and 4.

[0100] Table 3

[0101] Table 4

[0102] As can be seen from Tables 3 and 4, the flame-retardant polypropylene product of this invention, thanks to the interaction of its components, exhibits excellent basic performance. It achieves a V-0 rating or higher in the 1.6mm flame retardancy test, and its cantilever beam notched impact strength can reach 4KJ / m. 2 Furthermore, due to the combined use of specific dispersants and interface compatibilizers, the product exhibits excellent resistance to heat and oxygen aging. After 1000 hours of high-temperature treatment, the flame retardant rating of the product remains above V-0, without any flame retardant failure or appearance issues. In addition, after high-temperature treatment, the notched impact strength of the cantilever beam retains more than 60% of its pre-treatment strength, maintaining high toughness.

[0103] Comparative Example 1, without the introduction of dispersants, interfacial compatibilizers, and char-forming catalysts, shows a low flame retardant rating from the initial stage. Subsequently, after high-temperature treatment, the flame retardant failed, and the cantilever beam notched impact strength decreased significantly, with precipitation occurring, indicating that the product lacks resistance to heat and oxygen aging. Comparative Example 2, based on Comparative Example 1, introduced a char-forming catalyst and increased the amount of halogen-free flame retardant, a common improvement in existing technology. This product initially had a high flame retardant rating, which remained unchanged after high-temperature treatment. However, due to the increased introduction of halogen-free flame retardant without altering dispersibility and compatibility, the product experienced a greater decrease in cantilever beam notched impact strength after high-temperature treatment, and its appearance remained poor, rendering it unusable.

[0104] As can be seen from Comparative Examples 3, 1, 3-5, and 5 and 6, the use of dispersants is crucial in the products of this invention. Working synergistically with interfacial compatibilizers, they ensure the dispersibility and compatibility of the halogen-free flame retardant in the product. Without this component, the flame retardant in Comparative Example 3 did not perform ideally, and the product could not achieve a V-0 flame retardant rating before heat treatment. However, the choice of dispersant type is not arbitrary. Since it is not used as a toughening agent in the product like conventional elastomers, if an unsuitable elastomer is chosen as the dispersant, such as ethylene-octene copolymer or EVA, although the product can improve the retention rate of cantilever beam notched impact strength to some extent after heat treatment, the flame retardant performance of the product is still not ideal. In selecting dispersants, the inventors found that when ethylene-butene copolymers and / or ethylene-propylene copolymers with melt flow rates of 2 g / 10 min or higher are selected, the product exhibits better heat and oxygen aging resistance and a higher cantilever beam impact strength retention rate.

[0105] As can be seen from Comparative Examples 4, 1, 6, and 7, and Comparative Examples 7 and 8, similar to dispersants, interfacial compatibilizers are also indispensable in the product components of this invention. This component is not a synergist for the halogen-free flame retardant, but rather a co-compatibility agent between it and the polypropylene resin. Therefore, even with such a low addition amount, the initial flame retardant performance of the product is reduced when this component is absent, and precipitation occurs on the surface. If non-alkyl chain phosphates or phosphoric acid are selected as interfacial compatibilizers, they do not actually improve the interfacial strength between the halogen-free flame retardant and the polypropylene resin, and cannot inhibit the degradation rate of the polymer resin. Therefore, although the flame retardant rating of Comparative Examples 7 and 8 reaches V-0 before and after heat treatment, the heat and oxygen aging resistance performance in terms of toughness is not significantly improved compared to Comparative Example 4, and precipitation still occurs on the surface. After selecting suitable alkyl phosphates / phosphates, the inventors found that selecting long alkyl chains can further improve the heat and oxygen aging resistance performance of the product, resulting in a higher retention rate of the product's mechanical properties. However, as shown in Comparative Example 9, since this interface compatibilizer is a small molecule, if too much is introduced, it will cause the product performance to deteriorate, and even cause the appearance to precipitate again.

[0106] As can be seen from Examples 1 and 8-11, the amount of halogen-free flame retardant not only changes the production cost of the product, but also affects the initial mechanical properties and heat and oxygen aging resistance of the product. By adjusting the char-forming catalyst, dispersant and interface compatibilizer in the product, the flame retardant performance and heat and oxygen aging resistance of the product can be taken into account with a lower amount of flame retardant added.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A flame-retardant polypropylene, characterized in that, Includes the following components in parts by weight: The mixture contains 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 char-forming catalyst, and 0.1-0.5 parts of interface compatibilizer. The dispersant includes at least one of ethylene-propylene copolymer and ethylene-butene copolymer; The interface compatibilizer includes at least one of alkylphosphonic acid and alkyl phosphate.

2. The flame retardant polypropylene of claim 1, wherein the flame retardant polypropylene is a flame retardant polypropylene composition. The polypropylene resin, according to ISO 1133-1-2011, has a melt flow rate of 0.2–35 g / 10 min at 230°C and 2.16 kg load.

3. The flame retardant polypropylene of claim 1, wherein the flame retardant polypropylene is a flame retardant polypropylene composition. The halogen-free flame retardant includes at least one of ammonium phosphate flame retardants, piperazine flame retardants, melamine flame retardants, and triazine flame retardants.

4. The flame retardant polypropylene of claim 1, wherein the flame retardant polypropylene has a melt volume rate of at least 3.0 cm3 / 10 min. The dispersant, according to ISO 1133-1-2011, has a melt flow rate of 0.5–5.5 g / 10 min at 190 °C and 2.16 kg load.

5. The flame retardant polypropylene of claim 1, wherein the flame retardant polypropylene has a melt volume rate of at least 3.0 cm3 / 10 min. The alkyl chain in the alkylphosphonic acid and / or alkyl phosphate has ≥10 carbon atoms.

6. The flame retardant polypropylene of claim 1, wherein the flame retardant polypropylene has a melt volume rate of at least 3.0 cm3 / 10 min. The char-forming catalyst includes at least one of zinc oxide, nickel oxide, and nickel formate.

7. The flame retardant polypropylene of claim 1, wherein the flame retardant polypropylene has a melt volume rate of at least 3.0 cm3 / 10 min. The flame-retardant polypropylene further includes 0.1 to 2 parts by weight of functional additives; preferably, the flame-retardant polypropylene further includes 0.1 to 1 parts by weight of antioxidant and 0.1 to 1 parts by weight of lubricant.

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

9. The application of flame-retardant polypropylene as described in any one of claims 1 to 7 in the preparation of high-temperature resistant equipment parts.

10. Use according to claim 9, wherein The high-temperature resistant equipment includes at least one of a heater and a new energy battery; the components of the high-temperature resistant equipment include at least one of a heater housing, a new energy battery cover, a hot air delivery pipe, and a protective shell for electronic components.

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