High temperature and high humidity resistant flame retardant polypropylene composite material and preparation method thereof

Abstract

The invention relates to the technical field of flame-retardant high polymer materials, in particular to a high-temperature-resistant and high-humidity-resistant flame-retardant polypropylene composite material and a preparation method thereof. The invention provides a high-temperature-resistant and high-humidity-resistant flame-retardant polypropylene composite material. The high-temperature-resistant and high-humidity-resistant flame-retardant polypropylene composite material consists of polypropylene, a mixed silane modified intumescent flame retardant, a flame-retardant aid NOR 116 and a compatilizer According to the invention, bis [3-(trimethoxysilyl) propyl] amine / triacetoxyvinyl silane is mixed to modify an intumescent flame retardant, which is composed of piperazine pyrophosphate as a main flame retardant and melamine polyphosphate, aluminum hypophosphite or aluminum diethylphosphinate as a secondary flame retardant; a plurality of active silicon hydroxyl sites after silane hydrolysis are mixed, and single flame retardants are connected together to form a macromolecular intumescent flame retardant, so that the modified intumescent flame retardant is still difficult to migrate or separate out from a polypropylene matrix even under high-temperature and high-humidity conditions, and the weather resistance of flame-retardant polypropylene is greatly improved.

Description

Technical Field

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

[0002] Polypropylene plastic is resistant to bending and corrosion, and can withstand attack by acids, alkalis, salt solutions, and most organic solvents. It also has excellent heat resistance, with a melting point of approximately 160-170°C and long-term use above 100°C. It is easy to process and shape, and has high chemical stability, resisting reactions with most chemicals at room temperature. However, its drawbacks include weak aging resistance, prone to oxidative degradation with long-term exposure to ultraviolet light and oxygen, and poor flame retardancy, making it flammable and prone to burning and dripping. These factors severely limit its application in electronics, electrical appliances, and automotive parts.

[0003] One effective approach to addressing polypropylene's weak flame retardancy is to add intumescent flame retardants, such as piperazine pyrophosphate, ammonium polyphosphate, and melamine polyphosphate. However, the molecular polarity of these intumescent flame retardants differs significantly from that of polypropylene, making uniform dispersion difficult. Furthermore, flame retardants inherently have a certain degree of hydrophilicity. These issues lead to the tendency for polypropylene treated with intumescent flame retardants to precipitate under high temperature and humidity, significantly reducing its flame retardant effectiveness.

[0004] Patent CN 110819009A uniformly mixes piperazine pyrophosphate, surface-modified ammonium polyphosphate, melamine or its salt, a coupling agent, a compatibilizer, an antioxidant, and a light stabilizer, and then kneads the mixture with polypropylene through a twin-screw extruder to produce flame-retardant polypropylene. This modified flame-retardant polypropylene only addresses the high pollution problem of traditional triazine carbonizing agent systems, but the flame-retardant polypropylene still faces the problem of precipitation under high temperature and high humidity. Patent CN 115232404A melt-blends a phosphorus-nitrogen flame retardant with a polypropylene resin impregnated with hydrolyzed (7-octen-1-yl)trimethoxysilane. This only addresses the flame retardant precipitation problem under high-temperature baking for a short period of time, and the flame retardant modified with a single silane is not as effective. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a high-temperature and high-humidity resistant flame-retardant polypropylene composite material and a preparation method thereof. The present invention can solve the problem that under high-temperature and high-humidity conditions (temperature of 85°C and humidity of 85%), the flame retardant in the flame-retardant polypropylene composite material is easily precipitated, resulting in poor flame retardant effect of the flame-retardant polypropylene.

[0006] In order to solve the above technical problems, the present invention provides a high temperature and high humidity resistant flame retardant polypropylene composite material, which is composed, by weight, of 75 to 82 parts of polypropylene, 17.8 to 24.4 parts of a mixed silane-modified intumescent flame retardant, 0.1 to 0.3 parts of a flame retardant additive NOR 116 and 0.1 to 0.3 parts of a compatibilizer.

[0007] As an improvement of the high temperature and high humidity resistant flame retardant polypropylene composite material of the present invention, the mixed silane-modified intumescent flame retardant comprises:

[0008] The mixed silane is composed of bis[3-(trimethoxysilyl)propyl]amine (TSPA) and triacetoxyvinylsilane (VTA), wherein the mass ratio of bis[3-(trimethoxysilyl)propyl]amine to triacetoxyvinylsilane is 5-10:1.

[0009] The intumescent flame retardant is composed of a primary flame retardant and a secondary flame retardant, with the mass ratio of primary flame retardant to secondary flame retardant being 2~4:1.

[0010] As a further improvement of the high temperature and high humidity resistant flame retardant polypropylene composite material of the present invention:

[0011] The main flame retardant is piperazine pyrophosphate (PAPP),

[0012] The secondary flame retardant is any one of the following: melamine polyphosphate (MPP), aluminum hypophosphite (HDP), and aluminum diethylphosphinate (ADP).

[0013] As a further improvement of the high temperature and high humidity resistant flame retardant polypropylene composite material of the present invention, the preparation method of the mixed silane modified intumescent flame retardant is to sequentially perform the following steps:

[0014] 1) Mix bis[3-(trimethoxysilyl)propyl]amine and triacetoxyvinylsilane to obtain a mixed silane modified product;

[0015] 2) Add deionized water to 100 parts by weight of the mixed silane-modified product, mix and stir (stirring time is 20-40 minutes) to obtain a mixed silane hydrolyzate;

[0016] 3) Add the intumescent flame retardant to the mixed silane hydrolyzate and stir (stirring time is 1.5 to 2.5 hours), the mass ratio of intumescent flame retardant to mixed silane hydrolyzate = 19.5 to 20.5% (preferably 20%);

[0017] 4) Separating and drying the solid obtained in step 3) to obtain a mixed silane-modified intumescent flame retardant.

[0018] As a further improvement of the high temperature and high humidity resistant flame retardant polypropylene composite material of the present invention:

[0019] The stirring speed of step 2) and step 3) is 120-180 r / min.

[0020] As a further improvement of the high temperature and high humidity resistant flame retardant polypropylene composite material of the present invention, the step 4) is: after the stirring in step 3) is completed, the filter cake is collected by filtration, and the filter cake is dried by forced air at 100±10°C for 4±0.5h to obtain a mixed silane-modified intumescent flame retardant.

[0021] As a further improvement of the high temperature and high humidity resistant flame retardant polypropylene composite material of the present invention:

[0022] The compatibilizer is polypropylene grafted with maleic anhydride or polyethylene grafted with maleic anhydride.

[0023] The present invention also provides a method for preparing the high temperature and high humidity resistant flame retardant polypropylene composite material, comprising the following steps:

[0024] 1. Premix polypropylene, mixed silane-modified intumescent flame retardant, flame retardant additive and compatibilizer in a mixer at 80±10°C for 5±1 min (rotation speed of 300±50r / min) to obtain a mixed material;

[0025] 2. The mixed materials are melted, sheared and extruded into granules (particle size is about 2~3mm) using a twin-screw extruder. The extrusion temperature is 165~210℃, the rotation speed is 450±50 r / min, and the feed speed is 30±3 r / min.

[0026] The bis[3-(trimethoxysilyl)propyl]amine molecule consists of two trimethoxysilylpropyl groups connected by a nitrogen atom. Trimethoxysilylpropyl groups are highly reactive and hydrolyze in the presence of water to produce the corresponding silanols and methanol. Flame retardants such as piperazine pyrophosphate, melamine polyphosphate, aluminum hypophosphite, and aluminum diethylphosphinate have numerous hydroxyl groups on their surfaces. These hydroxyl groups can condense with the silanol groups formed by the hydrolysis of bis[3-(trimethoxysilyl)propyl]amine molecules, forming a macromolecular network structure that links individual intumescent flame retardants. This makes such macromolecular flame retardants more difficult to migrate within polymer materials. Considering that the silanol groups formed by the hydrolysis of bis[3-(trimethoxysilyl)propyl]amine also condense themselves to form a gel, they are unable to react with hydroxyl-containing flame retardants. Therefore, the present invention also incorporates triacetoxyvinylsilane. The acetic acid generated by the hydrolysis of triacetoxyvinylsilane can regulate the pH of the solution, thereby inhibiting the self-condensation reaction of the silanol groups after the hydrolysis of bis[3-(trimethoxysilyl)propyl]amine and promoting its hydrolysis. Furthermore, because the vinyl group in triacetoxyvinylsilane is structurally similar to polypropylene and is highly hydrophobic, the addition of triacetoxyvinylsilane not only improves the flame retardant's compatibility with polypropylene but also significantly enhances its water resistance. Therefore, the macromolecular intumescent flame retardant modified with the mixed bis[3-(trimethoxysilyl)propyl]amine / triacetoxyvinylsilane exhibits significantly greater precipitation resistance.

[0027] In summary, the present invention modifies an intumescent flame retardant composed of piperazine pyrophosphate as a main flame retardant and melamine polyphosphate, aluminum hypophosphite or diethyl aluminum phosphinate as a secondary flame retardant by mixing bis[3-(trimethoxysilyl)propyl]amine / triacetoxyvinylsilane. By mixing multiple active silanol sites after silane hydrolysis, the individual flame retardants are connected together to form a macromolecular intumescent flame retardant. This makes it difficult for the modified intumescent flame retardant to migrate or precipitate from the polypropylene matrix even under high temperature and high humidity conditions, thereby greatly improving the weather resistance of the flame-retardant polypropylene. DETAILED DESCRIPTION

[0028] The present invention is further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto:

[0029] The raw materials used in the embodiments of the present invention are all commonly used raw materials in the art. For example:

[0030] Polypropylene (model PPH-TH3-S, melt index 3 g / 10 min) was purchased from Sinopec Yangzi Petrochemical Co., Ltd.

[0031] Piperazine pyrophosphate (PAPP) can be purchased from Shaoxing Xingxin New Materials Co., Ltd.

[0032] Melamine polyphosphate (Product No.: M302999), aluminum hypophosphite (Product No.: A759044) and aluminum diethylphosphinate (Product No.: A303123) were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., bis[3-(trimethoxysilyl)propyl]amine (Product No.: B834090) and triacetoxyvinylsilane (Product No.: T828557) were purchased from Shanghai MacLean Biochemical Technology Co., Ltd., NOR 116 (BASF flame retardant NOR116, Germany) was purchased from Dafa Chemical Co., Ltd., polypropylene grafted maleic anhydride (Product No.: P478291) and polyethylene grafted maleic anhydride (Product No.: P304899) were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0033] Example 1: Preparation method of modified intumescent flame retardant prepared by mixing silane.

[0034] (1) Weigh 5 g of bis[3-(trimethoxysilyl)propyl]amine (TSPA) and 1 g of triacetoxyvinylsilane (VTA) and stir them thoroughly to obtain a mixed silane-modified product;

[0035] (2) Weigh 2 g of the above-mentioned mixed silane modified product and add it to a beaker containing 98 g of deionized water. Turn on the magnetic stirring for 30 min (speed of 120 r / min) to obtain a mixed silane hydrolyzate;

[0036] (3) 13.33 g of piperazine pyrophosphate (PAPP, as the main flame retardant) and 6.67 g of melamine polyphosphate (MPP, as the secondary flame retardant) were added to the beaker containing the mixed silane hydrolyzate, and mechanical stirring was switched to 180 r / min for 2 h.

[0037] (4) After the stirring in step (3) is completed, the filter cake is collected by filtration and dried at 100°C for 4 hours (basically dried to constant weight) to obtain a mixed silane-modified intumescent flame retardant, which is recorded as modified intumescent flame retardant-1.

[0038] Examples 2 to 6, relative to Example 1, were prepared by changing the amount of TSPA in step (1) to change the ratio of TSPA to VTA; changing the ratio of the mixed silane-modified liquid to deionized water in step (2); changing the amount of PAPP in step (3), and changing the type and amount of the secondary flame retardant; as described in Table 1 below, the rest were the same as in Example 1; the resulting products were named Modified Intumescent Flame Retardant-1 to Modified Intumescent Flame Retardant-6, respectively.

[0039] Table 1 Specific parameters for the preparation of modified intumescent flame retardants 1 to 6

[0040]

[0041] Example 1: A high-temperature and high-humidity flame-retardant polypropylene composite material, having the following formula: 82 parts of polypropylene, 17.8 parts of an intumescent flame retardant, 0.1 parts of a flame retardant additive NOR 116, and 0.1 parts of a compatibilizer polypropylene grafted maleic anhydride;

[0042] The preparation method is to carry out the following steps in sequence:

[0043] 1) Weigh polypropylene, modified intumescent flame retardant, flame retardant additive, and compatibilizer according to the formula, and premix them in a high-speed mixer at a high speed (speed of 300 r / min). The premixing temperature is 80°C and the premixing time is 5 minutes.

[0044] 2) The mixed material obtained in step 1) was melted, sheared, and extruded into pellets using a twin-screw extruder at an extrusion temperature of 180-210°C, a rotation speed of 450 r / min, and a feed speed of 30 r / min. The resulting pellets had a size of approximately 2-3 mm.

[0045] Examples 2 to 6: Compared with Example 1, the formula is changed (the specific formula is shown in Table 2), and the preparation method is the same as that of Example 1.

[0046] Table 2 Components of flame retardant polypropylene composition

[0047]

[0048] Experiment 1: Evaluation of flame retardant properties of polypropylene composites

[0049] 1. Flame retardant performance test conditions and standards are as follows:

[0050] UL-94 vertical combustion specimen size: 130×13×3.2 mm 3 , test standard: ASTM D3801;

[0051] Limiting oxygen index specimen size: 100×6.5×3.2 mm 3 , test standard: ASTM 2863;

[0052] 2. Double 85 test:

[0053] The modified flame retardant polypropylene particles were pressed into 100×100×3.2 mm at a pressure of 10 MPa. 3The panels were placed in a constant temperature and humidity chamber at 85°C and 85% humidity for 1000 hours. After aging, the flame retardant precipitated on the surface of the panels was wiped clean. The panels were then dried in a forced air drying oven at 80°C for 6 hours (to remove surface moisture) before testing for flame retardancy and mechanical properties. The testing standard is GB / T 2423.50.

[0054] 3. Detection of flame retardant precipitation rate:

[0055] First, record the total amount of flame retardant M contained in the board, and then use an analytical balance to accurately weigh the mass M1 of the board before the double 85 test (temperature 85℃, humidity 85%) and the mass M2 of the board after the double 85 test and drying.

[0056]

[0057] The test results are shown in Table 3 below.

[0058] Table 3 Flame retardant properties and flame retardant precipitation of polypropylene before and after double 85 test

[0059]

[0060] Blank comparative example: that is, pure polypropylene; that is, the difference from Example 1 is that no modified intumescent flame retardant, flame retardant auxiliary agent and compatibilizer are added.

[0061] Comparative Example 1-1: The difference from the modified intumescent flame retardant-1 used in Example 1 is that the intumescent flame retardant PAPP / MPP used is not modified by mixing silane.

[0062] That is, the intumescent flame retardant used was prepared by uniformly mixing 13.33 g of PAPP and 6.67 g of MPP; the intumescent flame retardant was named intumescent flame retardant A1.

[0063] The intumescent flame retardant A1 was used to replace the “modified intumescent flame retardant-1” in Example 1, and the amount used remained unchanged, still 17.8 g; the rest was the same as in Example 1.

[0064] Comparative Example 1-2: The difference from the modified intumescent flame retardant-1 used in Example 1 is that the intumescent flame retardant is modified with a single bis[3-(trimethoxysilyl)propyl]amine (TSPA) without adding triacetoxyvinylsilane (VTA).

[0065] That is, compared with Example 1, step (1) was eliminated, and step (2) was changed from "weighing 2 g of the above-mentioned mixed silane-modified liquid" to "weighing 2 g of TSPA", and the rest was the same as Example 1. The obtained intumescent flame retardant was named intumescent flame retardant A2.

[0066] The intumescent flame retardant A2 was used to replace the “modified intumescent flame retardant-1” in Example 1, and the amount used remained unchanged, still 17.8 g; the rest was the same as in Example 1.

[0067] Comparative Example 1-3: The difference from the modified intumescent flame retardant-1 used in Example 1 is that the intumescent flame retardant is modified with a single triacetoxyvinylsilane (VTA) without the addition of bis[3-(trimethoxysilyl)propyl]amine (TSPA).

[0068] That is, compared with Example 1, step (1) was eliminated, and step (2) was changed from "weighing 2 g of the above-mentioned mixed silane-modified liquid" to "weighing 2 g of VTA", and the rest was the same as Example 1. The obtained intumescent flame retardant was named intumescent flame retardant A3.

[0069] The intumescent flame retardant A3 was used to replace the “modified intumescent flame retardant-1” in Example 1, and the amount used remained unchanged, still 17.8 g; the rest was the same as in Example 1.

[0070] Comparative Example 1-4: The difference from the modified intumescent flame retardant-1 used in Example 1 is that 4 g of TSPA and 1 g of VTA are mixed at a mass ratio of 4:1, while the mass ratio of the two in Example 1 is 5:1.

[0071] That is, relative to Example 1, the amount of "TSPA" in step (1) was changed from 5 g to 4 g, and the rest was the same as Example 1. The obtained intumescent flame retardant was named intumescent flame retardant A4.

[0072] The intumescent flame retardant A4 was used to replace the “modified intumescent flame retardant-1” in Example 1, and the amount used remained unchanged, still 17.8 g; the rest was the same as in Example 1.

[0073] Comparative Example 1-5: The difference between the modified intumescent flame retardant-1 used in Example 1 is that the "mixed silane" in the mixed silane-modified intumescent flame retardant is different;

[0074] The details are as follows:

[0075] Compared to Example 1, the "5 g TSPA, 1 g VTA" in step (1) was changed to "4 g TSPA, 2 g VTA", and the rest was the same as Example 1. That is, the mass ratio of the two was 2:1, while the mass ratio of the two in Example 1 was 5:1. The resulting intumescent flame retardant was named intumescent flame retardant A5.

[0076] The intumescent flame retardant A5 was used to replace the "modified intumescent flame retardant-1" in Example 1, and the amount used remained unchanged, still 17.8 g; the rest was the same as Example 1.

[0077] Comparative Example 1-6: The difference between the modified intumescent flame retardant-1 used in Example 1 is that the "mixed silane" in the mixed silane-modified intumescent flame retardant is different;

[0078] The details are as follows:

[0079] Compared to Example 1, the "5 g TSPA, 1 g VTA" in step (1) was changed to "3 g TSPA, 3 g VTA", and the rest was the same as Example 1. That is, the mass ratio of the two was 1:1, while the mass ratio of the two in Example 1 was 5:1. The resulting intumescent flame retardant was named intumescent flame retardant A6.

[0080] The intumescent flame retardant A6 was used to replace the “modified intumescent flame retardant-1” in Example 1, and the amount used remained unchanged, still 17.8 g; the rest was the same as in Example 1.

[0081] Comparative Example 1-7: The difference between the modified intumescent flame retardant-1 used in Example 1 is that the "mixed silane" in the mixed silane-modified intumescent flame retardant is different;

[0082] The details are as follows:

[0083] Compared with Example 1, "TSPA" in step (1) was replaced with "bis(3-(trimethoxysilyl)propyl)ethylenediamine", and the amount used remained unchanged at 5 g. The rest was the same as in Example 1. The obtained intumescent flame retardant was named intumescent flame retardant A7.

[0084] The intumescent flame retardant A7 was used to replace the "modified intumescent flame retardant-1" in Example 1, and the amount used remained unchanged, still 17.8 g; the rest was the same as Example 1.

[0085] Comparative Example 1-8: The difference between the modified intumescent flame retardant-1 used in Example 1 is that the "mixed silane" in the mixed silane-modified intumescent flame retardant is different;

[0086] The details are as follows:

[0087] Compared with Example 1, the "triacetoxyvinylsilane (VTA)" in step (1) was replaced with "vinyltrimethoxysilane (VTMO)", and the amount remained unchanged at 1 g. The rest was the same as in Example 1. The obtained intumescent flame retardant was named intumescent flame retardant A8.

[0088] The intumescent flame retardant A8 was used to replace the "modified intumescent flame retardant-1" in Example 1, and the amount used remained unchanged, still 17.8 g; the rest was the same as Example 1.

[0089] Comparative Example 2: The difference from the modified intumescent flame retardant-3 used in Example 3 is that the intumescent flame retardant PAPP / HDP used is not modified by mixing silane.

[0090] That is, the intumescent flame retardant used was prepared by uniformly mixing 15.0 g of PAPP and 5.0 g of HDP; the intumescent flame retardant was named intumescent flame retardant B.

[0091] The intumescent flame retardant B was used to replace the “modified intumescent flame retardant-3” in Example 3, and the amount used remained unchanged, still 19.7 g; the rest was the same as Example 3.

[0092] Comparative Example 3: The difference from the modified intumescent flame retardant-5 used in Example 5 is that the intumescent flame retardant PAPP / ADP used is not modified by mixing silane.

[0093] That is, the intumescent flame retardant used was prepared by uniformly mixing 16.0 g of PAPP and 4.0 g of ADP; the intumescent flame retardant was named intumescent flame retardant C.

[0094] The intumescent flame retardant C was substituted for the “modified intumescent flame retardant-5” in Example 5, and the amount used remained unchanged, still 22.5 g; the rest was the same as in Example 5.

[0095] Comparative Example 4: The difference from the modified intumescent flame retardant-4 used in Example 4 is that 6 g of mixed silane-modified solution and 94 g of deionized water are mixed, and the mass fraction of the mixed silane-modified solution is 6%, while the mass fraction of the mixed silane-modified solution in Example 4 is 5%.

[0096] That is, relative to Example 4, "5 g mixed silane modified solution, 95 g deionized water" was changed to "6 g mixed silane modified solution, 94 g deionized water", and the rest was the same as Example 4. The obtained intumescent flame retardant was named intumescent flame retardant D.

[0097] The intumescent flame retardant D was substituted for the “modified intumescent flame retardant-4” in Example 4, and the amount used remained unchanged, still 21.6 g; the rest was the same as Example 4.

[0098] The above examples were tested according to the above experiment, and the results are shown in Table 4 below.

[0099] Table 4

[0100]

[0101] In summary, Examples 1-6 of the present invention use an intumescent flame retardant modified with mixed silane, which can make the flame retardant polypropylene composite material pass the V0 grade before and after the double 85 test.

[0102] Comparative Examples 1-1, 2, and 3, however, did not utilize a mixed silane-modified intumescent flame retardant. After the Double 85 test, under high temperature and high humidity, most of the flame retardant migrated to the material surface and dissolved with prolonged water vapor erosion, resulting in a sharp decline in flame retardancy, from V0 to no flame retardancy. These data comparisons demonstrate that the use of a mixed silane-modified flame retardant can significantly improve the flame retardant's resistance to high temperatures and high humidity.

[0103] Comparative Examples 1-2 and 1-3 respectively used single bis[3-(trimethoxysilyl)propyl]amine and triacetoxyvinylsilane to modify the intumescent flame retardant. The results showed that after the double 85 test, a large amount of flame retardant was precipitated on the surface of the board, and there was no flame retardant grade in the vertical burning test. The results show that the flame retardant effect and precipitation resistance of the mixed silane modified intumescent flame retardant are much greater than those of the single silane system.

[0104] Comparative Examples 1-4, 1-5, and 1-6 adjusted the mass ratio of bis[3-(trimethoxysilyl)propyl]amine / triacetoxyvinylsilane to 4:1, 2:1, and 1:1, respectively. Compared with the mass ratio of 5:1 in Example 1, the proportion of bis[3-(trimethoxysilyl)propyl]amine was reduced. The results of the vertical burning test showed that the polypropylene composite material under this mass ratio could only pass the V2 grade before the double 85 test, and had no flame retardant grade after the double 85 test. This is because when the proportion of bis[3-(trimethoxysilyl)propyl]amine is too low, triacetoxyvinylsilane cannot effectively inhibit the self-condensation reaction of silanol groups, resulting in a significant reduction in the linking sites between the mixed silane and the flame retardant, resulting in a decrease in flame retardant properties.

[0105] Comparative Examples 1-7 tested bis(3-(trimethoxysilyl)propyl)ethylenediamine instead of bis(3-(trimethoxysilyl)propyl)amine. The flame retardancy of the modified bis(3-(trimethoxysilyl)propyl)ethylenediamine dropped from V0 to V2 before the 85% bis(trimethoxysilyl)propyl)amine test and then dropped to zero after the 85% bis(trimethoxysilyl)propyl)ethylenediamine test. This is because the two secondary amines in bis(3-(trimethoxysilyl)propyl)ethylenediamine cannot be fully hydrolyzed, resulting in a more condensation-sensitive reaction and less reactivity with the flame retardant.

[0106] Comparative Examples 1-8 replaced triacetoxyvinylsilane with vinyltrimethoxysilane for experimental testing. The results showed that the flame retardant performance of the modified compound also dropped directly from V0 to V2 before the double 85 test, and directly dropped to no grade after the double 85 test. This is because after hydrolysis of vinyltrimethoxysilane, the three methoxy groups directly become three silanol groups. Excessive silanol groups only exacerbate the self-condensation reaction between the silanol groups, making it difficult to react with the hydroxyl groups on the surface of the flame retardant. The advantage of triacetoxyvinylsilane is that after hydrolysis, the product after the acyloxy bond is broken is acetic acid, which can regulate the pH of the solution and inhibit the self-condensation reaction between the silanol groups.

[0107] Comparative Example 4 adjusts the mass fraction of the mixed silane modified solution to 6%, which is equivalent to increasing the concentration of the mixed modified solution. However, the vertical combustion test results show that the polypropylene composite material under this mass fraction can only pass the V2 grade before the double 85 test, and after the double 85 test, there is no flame retardant grade. This is because the main components of bis[3-(trimethoxysilyl)propyl]amine and triacetoxyvinylsilane are C, H, and O. These are all combustion-supporting elements, and a small amount of addition has little effect on the flame retardant properties of the entire system, because the system also contains silicon, which can improve the quality of the burning carbon layer and play a role in condensed phase flame retardancy. However, when the content of bis[3-(trimethoxysilyl)propyl]amine and triacetoxyvinylsilane is too high, the flame retardant properties will be significantly reduced.

[0108] In summary, the present invention provides a high-temperature and high-humidity resistant flame-retardant polypropylene composite material and a preparation method thereof, which provides a broader space for the application of polypropylene in the fields of electronic appliances and automobile manufacturing.

[0109] Finally, it should be noted that the above examples are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above examples and is subject to numerous variations. All variations that can be directly derived or conceived by a person of ordinary skill in the art from the disclosure of the present invention are considered to be within the scope of protection of the present invention.

Claims

1. A high temperature and high humidity resistant flame retardant polypropylene composite material, characterized in that: The invention comprises, by weight, 75-82 parts of polypropylene, 17.8-24.4 parts of mixed silane-modified intumescent flame retardant, 0.1-0.3 parts of flame retardant additive NOR 116 and 0.1-0.3 parts of compatibilizer.

2. The high temperature and high humidity resistant flame retardant polypropylene composite material according to claim 1, characterized in that: In the mixed silane-modified intumescent flame retardant: The mixed silane is composed of bis[3-(trimethoxysilyl)propyl]amine and triacetoxyvinylsilane, wherein the mass ratio of bis[3-(trimethoxysilyl)propyl]amine to triacetoxyvinylsilane is 5-10:

1. The intumescent flame retardant is composed of a primary flame retardant and a secondary flame retardant, with the mass ratio of primary flame retardant to secondary flame retardant being 2 to 4:

1.

3. The high temperature and high humidity resistant flame retardant polypropylene composite material according to claim 2, characterized in that: The main flame retardant is piperazine pyrophosphate, The secondary flame retardant is any one of the following: melamine polyphosphate, aluminum hypophosphite, and aluminum diethylphosphinate.

4. The high temperature and high humidity resistant flame retardant polypropylene composite material according to claim 3, characterized in that: The preparation method of the mixed silane-modified intumescent flame retardant is to carry out the following steps in sequence: 1) Mix bis[3-(trimethoxysilyl)propyl]amine and triacetoxyvinylsilane to obtain a mixed silane modified product; 2) Add deionized water to 100 parts by weight of the mixed silane-modified product, mix and stir to obtain a mixed silane hydrolyzate; 3) Add the intumescent flame retardant to the mixed silane hydrolyzate and stir, with the mass ratio of intumescent flame retardant to mixed silane hydrolyzate = 19.5~20.5%; 4) Separating and drying the solid obtained in step 3) to obtain a mixed silane-modified intumescent flame retardant.

5. The high temperature and high humidity resistant flame retardant polypropylene composite material according to claim 4, characterized in that: The stirring speed of step 2) and step 3) is 120-180 r / min.

6. The high temperature and high humidity resistant flame retardant polypropylene composite material according to claim 5, characterized in that: The step 4) comprises: after the stirring in step 3) is completed, collecting the filter cake by suction filtration, and drying the filter cake by forced air at 100±10° C. for 4±0.5 h to obtain a mixed silane-modified intumescent flame retardant.

7. The high temperature and high humidity resistant flame retardant polypropylene composite material according to any one of claims 1 to 6, characterized in that: The compatibilizer is polypropylene grafted with maleic anhydride or polyethylene grafted with maleic anhydride.

8. The method for preparing the high temperature and high humidity resistant flame retardant polypropylene composite material according to any one of claims 1 to 7, characterized in that The following steps are involved:

1. Premix polypropylene, mixed silane-modified intumescent flame retardant, flame retardant additive and compatibilizer in a mixer at 80±10°C for 5±1 min to obtain a mixed material; 2. The mixed materials are melted, sheared and extruded into granules using a twin-screw extruder. The extrusion temperature is 165~210℃, the rotation speed is 450±50 r / min, and the feed speed is 30±3 r / min.

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