Flame-retardant polypropylene composition as well as preparation method and application thereof

Abstract

The invention discloses a flame-retardant polypropylene composition as well as a preparation method and application thereof. The flame-retardant polypropylene composition comprises the following components in parts by weight: 70 parts of polypropylene resin; 3-8 parts of a compatilizer; 15 to 25 parts of an aluminum hypophosphite flame retardant; 2-5 parts of an antioxidant aid; 0.5 to 2 parts of a metal deactivator; wherein the molecular weight of the antioxidant additive is not less than 900, and the antioxidant additive contains a benzene ring structure. According to the invention, the polypropylene resin is used as matrix resin, and the antioxidant additive containing a benzene ring with specific molecular weight and the aluminum hypophosphite flame retardant are added, so that the hot water resistance and the copper aging resistance of the composition can be effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of halogen-free flame retardancy, and particularly relates to a flame retardant polypropylene composition, a preparation method and an application thereof. Background Art

[0002] German standard PP-9Y automotive cable is used for low-voltage wiring harnesses within vehicles, for communication signals and low-voltage power transmission. It meets full ISO 6722 performance requirements. However, the challenges are that the polypropylene automotive cable must withstand 45°C flammability, copper aging at 125°C for 3000 hours, no cracking during winding, and no breakdown at 1kV after 35 days in a 10g / L NaCl solution at 85°C (with 48V DC voltage). Compared to halogenated flame retardant systems, halogen-free flame retardants require the addition of large amounts of phosphorus-nitrogen flame retardants, making flame retardancy, copper aging, and salt water resistance more challenging. ISO 6722 has been abolished in favor of ISO 19642, which imposes stricter flame retardancy requirements, with an afterflame time of less than 70 seconds reduced to less than 30 seconds. This poses a greater challenge to the flame retardant system and negatively impacts hot water resistance.

[0003] In the prior art, to meet the 3000-hour copper aging requirement, a large amount of antioxidants is typically added. However, this large amount of antioxidants poses the risk of precipitation during long-term salt water soaking. This precipitation process can create defects in the resin system, which can easily lead to electrical dendrites under an electric field, degrading insulation performance and forming breakdown points, leading to reduced hot water resistance. Therefore, there is a need in the art to develop a polypropylene composition that exhibits excellent copper aging resistance, good hot water resistance, and good flame retardancy. Summary of the Invention

[0004] The object of the present invention is to overcome the defects or shortcomings of the flame retardant polypropylene composition in the prior art, that is, the flame retardant polypropylene composition cannot have both hot water resistance and copper aging resistance, and to provide a flame retardant polypropylene composition.

[0005] Another object of the present invention is to provide a method for preparing the flame retardant polypropylene composition.

[0006] Another object of the present invention is to provide applications of the flame retardant polypropylene composition.

[0007] To achieve the above objectives, the present invention adopts the following technical solutions: A flame retardant polypropylene composition comprising the following components calculated in parts by weight: 70 parts of polypropylene resin; 3~8 parts of compatibilizer; 15-25 parts of aluminum hypophosphite flame retardant; 2~5 parts of antioxidant; 0.5~2 parts of metal passivator; The antioxidant has a molecular weight of not less than 900 and contains a benzene ring structure.

[0008] In the present invention, polypropylene resin is used as a base resin, a benzene ring-containing antioxidant additive with a specific molecular weight is added thereto, and an aluminum hypophosphite flame retardant is used in combination to effectively improve the hot water resistance and copper aging resistance of the polypropylene composition. Specifically, adjusting the molecular weight of the antioxidant additive can reduce its precipitation, and the conjugated structure of the benzene ring contains electrophilic groups compared to the polymer matrix, and has the ability to capture electrons. It can absorb the energy of high-energy electrons during excitation or ionization, reduce the number of high-energy electrons, and suppress the impact of high-energy electrons on polymer molecular chains, thereby improving the hot water resistance and copper aging resistance of the polypropylene composition.

[0009] It should be noted that, in the flame-retardant polypropylene composition of the present invention, the content of the polypropylene resin is preferably not less than 60 wt%.

[0010] It should be noted that the molecular weight of the antioxidant additive in the present invention is not less than 900, for example but not limited to not less than 900, 910, 920, 930, 940, 950, 960, 970, 980, 990, 1000, 1050, 1100, 1150, 1200, 1250, 1300, 1350, 1400, 1450, 1500, 1550, 1600, 1650, 1700, 1750, 1800, 1850, 1900, 1950, 2000, 2050 or 2100, and the specific values ​​between the above points. Due to space limitations and for the sake of simplicity, the specific points included in the range are no longer exhaustively listed in the present invention.

[0011] Furthermore, the molecular weight of the antioxidant is 950-2050.

[0012] It should be noted that the antioxidant additive described in the present invention is 2 to 5 parts, for example, but not limited to 2 parts, 2.2 parts, 2.5 parts, 2.8 parts, 3 parts, 3.2 parts, 3.5 parts, 3.8 parts, 4 parts, 4.2 parts, 4.5 parts, 4.8 parts or 5 parts, as well as specific point values ​​between the above points. Due to space limitations and for the sake of simplicity, the specific point values ​​included in the range are no longer exhaustively listed in the present invention.

[0013] Furthermore, the number of benzene ring structures in the antioxidant auxiliary agent is a positive integer of 1 to 10.

[0014] Furthermore, the number of benzene ring structures in the antioxidant auxiliary agent is a positive integer of 2 to 7.

[0015] Specifically, the number of benzene ring structures in the antioxidant can be determined by testing methods such as nuclear magnetic resonance (NMR) hydrogen spectrum, nuclear magnetic resonance (NMR) carbon spectrum and infrared testing.

[0016] Specifically, the molecular weight of the antioxidant can be obtained by calculating the relative molecular mass of the raw materials, or by GPC testing.

[0017] Furthermore, the polypropylene resin has a melt flow rate of 0.5-12 g / 10 min at 230° C. and a load of 2.16 kg.

[0018] Specifically, the melt flow rate of the polypropylene resin is tested according to ISO 1133-1-2011.

[0019] Specifically, the polypropylene resin may be a homopolymer polypropylene resin and / or a copolymer polypropylene resin.

[0020] Furthermore, the aluminum hypophosphite flame retardant is aluminum hypophosphite and / or coated aluminum hypophosphite.

[0021] Furthermore, the aluminum hypophosphite is coated aluminum hypophosphite.

[0022] Furthermore, the coated aluminum hypophosphite includes organosilicon-coated aluminum hypophosphite and / or melamine resin-coated aluminum hypophosphite.

[0023] It should be noted that the organosilicon-coated aluminum hypophosphite in the present invention can be homemade or commercially available, and its source is not limited.

[0024] In some preferred embodiments, the organosilicon-coated aluminum hypophosphite is prepared by the following preparation method: Aluminum hypophosphite and silane coupling agent are stirred at 75-85°C for 2-6 hours to obtain the product.

[0025] Specifically, the silane coupling agent accounts for 0.5-5 wt % of the aluminum hypophosphite.

[0026] Specifically, the silane coupling agent includes one or more of vinyltriethoxysilane, vinyltrimethoxysilane or aminosilane.

[0027] The melamine resin-coated aluminum hypophosphite in the present invention can be homemade or commercially available, and its source is not limited.

[0028] In some preferred embodiments, the melamine resin-coated aluminum hypophosphite is obtained by in-situ polymerization of an aluminum hypophosphite dispersion and a melamine resin prepolymer.

[0029] Specifically, aluminum hypophosphite is dispersed in a solvent to form an aluminum hypophosphite dispersion, and then a melamine resin prepolymer is added, reacted at 50-90° C. and a pH of 8-11 for 2-6 hours, and then washed, filtered, and dried to obtain the dispersion.

[0030] Specifically, the melamine resin prepolymer is obtained by stirring melamine and formaldehyde at 70° C. for 30 minutes.

[0031] Specifically, the mass ratio of the aluminum hypophosphite, melamine and formaldehyde is 1:(0.1-0.3):(0.2-0.6).

[0032] Specifically, the aluminum hypophosphite flame retardant has a D50 of ≤20 μm.

[0033] Specifically, the D50 of the aluminum hypophosphite flame retardant is 3-20 μm.

[0034] Specifically, the D50 of the aluminum hypophosphite flame retardant is tested by a Malvern laser particle size analyzer.

[0035] Furthermore, the metal deactivator includes a hydrazide metal deactivator and / or an amide metal deactivator.

[0036] Furthermore, the metal passivator is a hydrazide metal passivator.

[0037] Specifically, the hydrazide metal passivator is N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazide.

[0038] The amide metal passivator is 2,2-oxalamido-bis[ethyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)]propionate.

[0039] Specifically, the metal passivator may be Irganox® MD 1024 and / or SONOX 1027.

[0040] Furthermore, the compatibilizer is maleic anhydride grafted polypropylene.

[0041] Specifically, the content of maleic anhydride in the compatibilizer is 0.5-1.5 wt %.

[0042] Specifically, the compatibilizer has a melt flow rate of 0.5-15 g / 10 min at 230° C. and a load of 2.16 kg.

[0043] Specifically, the test standard for the melt flow rate is ISO1133-2011.

[0044] Furthermore, under the premise of not affecting the hot water resistance and copper aging performance of the flame retardant polypropylene composition of the present invention, the flame retardant polypropylene composition of the present invention further comprises 1 to 5 parts of a lubricant.

[0045] Specifically, the lubricant may be a silicone lubricant.

[0046] The present invention also provides a method for preparing the flame retardant polypropylene composition, comprising the following steps: The components are mixed uniformly to obtain a premix, and the premix is ​​subjected to banburying and extrusion granulation to obtain a flame retardant polypropylene composition.

[0047] Furthermore, the mixing rotation speed is 1000-2000 rpm.

[0048] Furthermore, the extrusion temperature is 130-155°C.

[0049] The present invention also protects the use of the flame retardant polypropylene composition in preparing cable materials.

[0050] Compared with the prior art, the present invention has the following beneficial effects: The invention provides a flame-retardant polypropylene composition. By adopting polypropylene resin as a base resin, adding a benzene ring-containing antioxidant auxiliary agent with a specific molecular weight, and cooperating with an aluminum hypophosphite flame retardant, the hot water resistance and copper aging resistance of the polypropylene composition can be effectively improved. DETAILED DESCRIPTION

[0051] The present invention is further described in detail below with reference to specific examples. The examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods used in the following examples are conventional methods unless otherwise specified; the materials and reagents used are commercially available reagents and materials unless otherwise specified.

[0052] 1. Raw materials used in each embodiment and comparative example: Polypropylene resin: Polypropylene resin 1: Moplen EP240H, copolymerized polypropylene, melt flow rate 2 g / 10 min at 230 °C and 2.16 kg load, purchased from Basel, Germany; Polypropylene resin 2: PP FC709M, copolymerized polypropylene, melt flow rate of 10 g / 10 min at 230 °C and 2.16 kg load, purchased from China National Petroleum Corporation; Aluminum hypophosphite flame retardant: Coated aluminum hypophosphite 1: Silicone-coated aluminum hypophosphite, homemade, D50 7 μm, was prepared by stirring aluminum hypophosphite and vinyltriethoxysilane (accounting for 2 wt% of aluminum hypophosphite) at 80°C for 4 h, filtering, and vacuum drying the remaining solids, followed by pulverization and sieving. Coated aluminum hypophosphite 2: Melamine resin-coated aluminum hypophosphite, homemade, with a D50 of 8 μm, was prepared by dispersing the aluminum hypophosphite in an ethanol-water solution (ethanol to water volume ratio of 1:6) and ultrasonicating for 30 minutes to obtain an aluminum hypophosphite dispersion. A melamine resin prepolymer (prepared by stirring melamine and formaldehyde at 70°C for 30 minutes) was then added, and the mixture was reacted at 70°C and a pH of 9 for 4 hours. The mixture was then washed, filtered, dried, crushed, and sieved to obtain a dispersion. The mass ratio of the aluminum hypophosphite, melamine, and formaldehyde was 1:0.2:0.4. Aluminum hypophosphite: purchased from MacLean, 10 μm; Melamine polyphosphate: purchased from Maclean, 10 μm; Antioxidant additives: Antioxidant 1: tetrakis(2,4-di-tert-butylphenol)-4,4′-biphenyl diphosphite, SONGNOX PQ, CAS No.: 119345-01-6, molecular weight 1035, number of benzene rings 6, purchased from Songwon Industrial Co., Ltd. Antioxidant 2: pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), IRGANOX 1010, CAS No.: 6683-19-8, molecular weight 1178, number of benzene rings 4, purchased from BASF; Antioxidant 3: polymer of 2-acetone and N-phenylaniline, CHINOX 1325, CAS number: 34137-09-02, molecular weight 1042, number of benzene rings 3, produced by Double Bond Chemical Co., Ltd. Antioxidant 4: Poly (2,2,4-trimethyl-1,2-dihydroquinoline), Flectol TMQ, poly (2,2,4-trimethyl-1,2-dihydroquinoline), CAS number: 26780-96-1, molecular weight 2150, number of benzene rings 10, purchased from Vanderbilt Corporation, USA; Antioxidant 5: 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, Irganox 1330, CAS No.: 1709-70-2, molecular weight 775, number of benzene rings 3, purchased from BASF; Antioxidant 6: N,N'''-1,2-ethanediylbis[N-[3-[[4,6-di[butyl(1,2,2,6,6-pentamethyl-4-piperidinyl)amino]-1,3,5-triazin-2-yl]amino]propyl]-N,N''-dibutyl-N,N''-bis(1,2,2,6,6-pentamethyl-4-piperidinyl)-1,3,5-triazine-2,4,6-triamine, CHISORB 519, CAS number: 106990-43-6, molecular weight 2286, number of benzene rings 0, purchased from Double Bond Chemical Co., Ltd. Metal passivators: Metal passivator 1: Irganox® MD 1024, bis(3,5-di-tert-butyl-4-hydroxy-phenylpropionyl)hydrazine, purchased from BASF; Metal passivator 2: SONOX 1027, 2,2-oxalamido-bis[ethyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)]propionate, purchased from Sanfeng Chemical Co., Ltd. Compatibilizer: maleic anhydride grafted polypropylene, QB510E, purchased from Mitsui Chemicals, Japan; It should be noted that the parallel experiments in the examples and comparative examples all used the same raw materials.

[0053] 2. In each embodiment and comparative example, a polypropylene composition was prepared according to the formulations in Tables 1 and 2, using the following preparation method: The components are added into a high-speed mixer according to a proportion and mixed evenly at a rotation speed of 1000-2000 rpm, and then put into a twin-screw extruder and extruded and granulated at 150-180° C. to obtain a polypropylene composition.

[0054] 3. Performance testing: (1) Flame retardant performance test: The polypropylene compositions prepared in each embodiment and comparative example were extruded using a wire extruder. The copper conductor was 0.5 mm 2 , wall thickness 0.2mm, outer diameter of wire 1.5mm, the prepared wire is tested according to standard ISO 19642-2019 for burning at a 45° angle, and the afterflame time is required to be less than 30s; (2) Copper aging test: The prepared wire is tested according to the standard ISO 19642-2019 for copper aging until the winding cracks. The copper aging cracking time range can be divided into <3000h, ≥3000h, and >3500h. The longer the time, the better the aging resistance. (3) Hot water resistance: The prepared wires were immersed in a 10g / L sodium chloride solution at 85°C for 35 days according to the standard ISO 19642-2019. During the immersion process, a 48V DC voltage was applied and then the 1KV withstand voltage was tested, requiring no breakdown.

[0055] Examples 1 to 10 and Comparative Examples 1 to 5 Table 1 Amount (unit: parts by weight) and properties of each component in the flame retardant polypropylene composition in Examples 1 to 10

[0056] Table 2 Amount (unit: parts by weight) and properties of each component in the polypropylene composition in each comparative example

[0057] As can be seen from Table 1, the flame-retardant polypropylene composition prepared in the present invention has good hot water resistance and copper aging resistance. Specifically, it is not punctured after being soaked in hot salt water, the afterflame time at an angle of 45° is not higher than 30 seconds, and the copper aging time is not lower than 3000 hours.

[0058] It can be seen from Comparative Example 1 that if the molecular weight of the antioxidant used is too low, it is easy to precipitate. The precipitation of the antioxidant will form channels in the resin matrix. During the soaking process in salt water, salt water can easily enter along the precipitation channels, causing breakdown and failing the hot water resistance test.

[0059] It can be seen from Comparative Example 2 that if the antioxidant additive used does not contain a benzene ring, the kinetic energy of high-energy electrons cannot be effectively reduced, resulting in failure of the hot water resistance after soaking in salt water.

[0060] It can be seen from Comparative Examples 3 and 4 that even if the antioxidant additive of the present invention is used, if the dosage is too low or too high, the obtained polypropylene composition cannot meet the requirements.

[0061] It can be seen from Comparative Example 5 that even if the antioxidant additive of the present invention is used, the hot water resistance and copper aging resistance of the obtained polypropylene composition cannot meet the requirements if other non-aluminum hypophosphite flame retardants are used.

[0062] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A flame retardant polypropylene composition, characterized in that The composition comprises the following components calculated in parts by weight: 70 parts of polypropylene resin; 3~8 parts of compatibilizer; 15-25 parts of aluminum hypophosphite flame retardant; 2~5 parts of antioxidant; 0.5~2 parts of metal passivator; The antioxidant has a molecular weight of not less than 900 and contains a benzene ring structure.

2. The flame retardant polypropylene composition according to claim 1, characterized in that: The molecular weight of the antioxidant is 950-2050.

3. The flame retardant polypropylene composition according to claim 1, characterized in that: The number of benzene rings in the antioxidant is a positive integer of 1 to 10.

4. The flame retardant polypropylene composition according to claim 1, characterized in that: The aluminum hypophosphite flame retardant is aluminum hypophosphite and / or coated aluminum hypophosphite; preferably, the aluminum hypophosphite flame retardant is coated aluminum hypophosphite; more preferably, the coated aluminum hypophosphite includes silicone-coated aluminum hypophosphite and / or melamine resin-coated aluminum hypophosphite.

5. The flame retardant polypropylene composition according to claim 1, characterized in that: The particle size D50 of the aluminum hypophosphite flame retardant is ≤20 μm.

6. The flame retardant polypropylene composition according to claim 1, characterized in that: The metal deactivator includes a hydrazide metal deactivator and / or an amide metal deactivator.

7. The flame retardant polypropylene composition according to claim 1, characterized in that: The compatibilizer is maleic anhydride grafted polypropylene.

8. The flame retardant polypropylene composition according to claim 1, characterized in that: The polypropylene resin has a melt flow rate of 0.5-12 g / 10 min at 230° C. and a load of 2.16 kg.

9. A method for preparing the flame retardant polypropylene composition according to any one of claims 1 to 8, characterized in that: The steps include: The components are mixed uniformly to obtain a premix, and the premix is ​​subjected to banburying and extrusion granulation to obtain a polypropylene composition.

10. Use of the flame retardant polypropylene composition according to any one of claims 1 to 8 in the preparation of cable materials.

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