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

Abstract

The present application relates to a kind of halogen-free flame-retardant polypropylene composite material and its preparation method, belong to polymer material technical field.The halogen-free flame-retardant polypropylene composite material of the present application includes the following mass fraction of each component: polypropylene 45~60 parts, flame retardant 15~25 parts, vinyl trialkoxysilane 1~3 parts, toughening agent 3~9 parts, antioxidant 0.05~1.5 parts.The present application uses the addition reaction of the vinyl group in end-vinyl borosilicon compound and the mercapto group in sodium bentonite modified by mercapto, borosilicon compound is grafted to sodium bentonite by C-S chemical bond, forms composite flame retardant, and the flame retardant does not contain halogen element, and simultaneously contains boron element, silicon element and sodium bentonite with good heat resistance, the synergistic effect of the multiple metal elements and silicon elements in sodium bentonite and the boron element, silicon element in organic matter is generated, and the flame-retardant performance of flame retardant is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a halogen-free flame-retardant polypropylene composite material and a preparation method thereof, and belongs to the technical field of high polymer materials. BACKGROUND

[0002] Polypropylene has become one of the most widely used general-purpose plastics due to its excellent comprehensive performance, good performance-price ratio, and wide processing and molding conditions. However, polypropylene is highly flammable, with a limiting oxygen index less than 18.0%, and cannot be extinguished after burning in air. Therefore, polypropylene is not suitable for facilities and places prone to fire.

[0003] In order to broaden the use of polypropylene and make it suitable for facilities and places prone to fire, it is common practice to modify polypropylene by adding flame retardants that can delay the chemical and physical reaction processes of combustion. The flame retardants used to modify polypropylene currently include halogen-based flame retardants and halogen-free flame retardants. Halogen-based flame retardants, as an important variety of organic flame retardants, are the first type of flame retardant used. Due to their low price, good stability, small addition amount, good compatibility with synthetic resin materials, and the ability to maintain the original physical and chemical properties of flame retardant products, they are the most widely used and largest organic flame retardant in the world. Halogen-based flame retardants decompose to produce hydrogen halide (HX), which eliminates the active free radicals produced during the combustion of high molecular weight materials. For example, HX reacts with the chain-reactive material HO· in the flame to reduce the concentration of the above-mentioned free radicals, thereby slowing down or stopping the chain reaction of combustion and achieving flame retardation. Halogen-based flame retardants, while retarding the combustion of polymers, release toxic smoke and gases, which harm the environment and human health. With the increasing awareness of improving material safety and environmental health, high-efficiency low-halogen or even halogen-free flame-retardant materials are the focus of future development. However, the current halogen-free flame-retardant systems, such as phosphorus-nitrogen intumescent, metal hydroxide, red phosphorus, expanded graphite, and organic silicon-inorganic compounds, all have the defects of large addition amount of flame retardant and significant impact on material performance. SUMMARY

[0004] The purpose of the present application is to provide a halogen-free flame-retardant polypropylene composite material to solve the problem that current halogen-free flame-retardant polypropylene materials cannot simultaneously meet the requirements of flame retardancy and mechanical performance.

[0005] Another purpose of the present application is to provide a preparation method for a halogen-free flame-retardant polypropylene composite material to solve the problem that the flame retardancy and mechanical performance of the currently prepared halogen-free flame-retardant polypropylene composite material cannot simultaneously meet the requirements.

[0006] The application provides a halogen-free flame-retardant polypropylene composite material, which comprises the following components in mass fractions: 45-60 parts of polypropylene, 15-25 parts of a flame retardant, 1-3 parts of a vinyl trialkoxysilane, 3-9 parts of a toughening agent and 0.05-1.5 parts of an antioxidant; the preparation method of the flame retardant comprises the following steps: addition reaction of the vinyl group in a terminal vinyl borosilicon compound and the mercapto group on mercapto-modified sodium bentonite, so as to obtain the flame retardant; the mass ratio of the terminal vinyl borosilicon compound and the mercapto-modified sodium bentonite is (0.9-1.2):1; the terminal vinyl borosilicon compound is prepared by reaction of boric acid and a terminal vinyl silane coupling agent, and the molar ratio of the boric acid and the terminal vinyl silane coupling agent is 1:(3.5-4.5).

[0007] Preferably, the preparation method of the mercapto-modified sodium bentonite is as follows: sodium bentonite, mercapto silane coupling agent and hydrochloric acid are mixed and reacted at 80-95 DEG C for 8-15 h, solid-liquid separation, washing, drying, so as to obtain the mercapto-modified sodium bentonite; the mass ratio of the sodium bentonite, the mercapto silane coupling agent and the hydrochloric acid is 1:(7-10):(50-100).

[0008] Preferably, the mercapto silane coupling agent is 3-mercaptopropyl triethoxysilane or 3-mercaptopropyl trimethoxysilane.

[0009] Preferably, the concentration of the hydrochloric acid is 0.08-0.3 mol / L.

[0010] Preferably, the preparation method of the terminal vinyl borosilicon compound is as follows: boric acid, a terminal vinyl silane coupling agent, ethanol and water are uniformly mixed, the pH is adjusted to 3-4, the mixture is mixed and reacted at room temperature for 6-8 h, then the reaction system is mixed and reacted at 80-90 DEG C for 8-10 h, and the terminal vinyl borosilicon compound is obtained after impurity removal.

[0011] Preferably, the terminal vinyl silane coupling agent is vinyl trimethoxysilane or vinyl triethoxysilane.

[0012] Preferably, the addition reaction method comprises the following steps: under inert gas protection, the terminal vinyl borosilicon compound, the mercapto-modified sodium bentonite, an initiator and an organic solvent are mixed and reacted.

[0013] Preferably, the initiator is azobisisobutyronitrile; the mass ratio of the terminal vinyl borosilicon compound, the mercapto-modified sodium bentonite and the azobisisobutyronitrile is (0.9-1.2):1:(0.02-0.05); the temperature of the mixing reaction is 65-80 DEG C, and the time is 8-12 h.

[0014] Preferably, the toughening agent is ethylene-propylene-diene rubber, ethylene-propylene-diene rubber, styrene-butadiene-styrene synthetic rubber; the antioxidant is 4'4-thio-bis(6-tert-butyl-o-cresol), 4,4'-thio-bis(3-methyl-6-tert-butyl) phenol, thiodipropionic acid di(octadecyl), diphenyl isooctyl phosphite; the vinyl trialkoxysilane is vinyl trimethoxysilane, vinyl triethoxysilane.

[0015] The application provides a preparation method of the halogen-free flame-retardant polypropylene composite material.

[0016] Preferably, the temperature of the melt extrusion is 190-200 DEG C.

[0017] The application has the following beneficial effects:

[0018] (1) The application uses the addition reaction of the vinyl group in the end-vinyl borosilicon compound and the mercapto group in the mercapto-modified sodium bentonite to graft the borosilicon compound to the sodium bentonite through the C-S chemical bond, and forms a composite flame retardant, which does not contain halogen elements, and contains boron elements, silicon elements and sodium bentonite with good heat resistance at the same time, and the synergistic effect of the multiple metal elements and the silicon elements in the sodium bentonite and the boron elements and the silicon elements in the organic matter improves the flame retardant performance of the flame retardant.

[0019] (2) The application uses the bonding reaction of the end-vinyl borosilicon compound and the mercapto-modified sodium bentonite in a specific ratio to ensure that the surface of the flame retardant remains part of the active group mercapto, so that the flame retardant is better combined with the polypropylene, and the strength and toughness of the material are ensured.

[0020] (3) The application uses the vinyl trialkoxysilane to pin the flame retardant on the surface of the polypropylene material, and in the melt extrusion process of the polypropylene material, the epoxy group in the vinyl trialkoxysilane can react with the active group mercapto remaining on the surface of the flame retardant, and at the same time, the vinyl trialkoxysilane is combined on the surface of the flame retardant to form a secondary modification of the flame retardant, and the surface has a large number of alkoxysilane groups, improving the bonding force with the polypropylene material.

[0021] (4) The application uses the new flame retardant and the vinyl trialkoxysilane to modify the polypropylene, which can ensure that the polypropylene has good mechanical properties and flame retardant properties at the same time under the condition of less flame retardant addition, widen the use range of the polypropylene, and meet the health and environmental protection use requirements. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1The tensile strength and impact strength test results of the halogen-free flame-retardant polypropylene composite material in each embodiment and the comparative example of the present application are shown in the following table.

[0023] Figure 2 The flame-retardant performance test results of the halogen-free flame-retardant polypropylene composite material in each embodiment and the comparative example of the present application are shown in the following table. DETAILED DESCRIPTION

[0024] The following examples are intended to further illustrate the present application, but not to limit the scope of protection of the present application.

[0025] Example 1

[0026] The halogen-free flame-retardant polypropylene composite material of the present embodiment is composed of the following components in mass fraction: polypropylene 45 parts, flame retardant 15 parts, vinyl trialkoxysilane 1 part, toughening agent 3 parts, antioxidant 0.05 part; wherein the toughening agent is binary ethylene-propylene rubber; the antioxidant is 4'4-thio-bis(6-tert-butyl-o-cresol); the vinyl trialkoxysilane is vinyl trimethoxysilane;

[0027] The preparation method of the flame retardant is as follows:

[0028] (1) 10 g of boric acid, 35 g of vinyl trimethoxysilane, 80 g of ethanol and 150 g of water are added to a reaction kettle, stirred uniformly, acetic acid is added, the pH of the material in the reaction kettle is adjusted to 3, stirred at room temperature for 6 h, then heated to 80℃, continue to stir for 8 h, cool to room temperature, the material in the reaction kettle is rotary evaporated at 60℃, then dried at 60℃ to constant weight to obtain a vinyl-terminated borosilicon compound;

[0029] (2) 10 g of sodium bentonite, 7 g of 3-mercaptopropyl trimethoxysilane and 50 g of 0.08 mol / L hydrochloric acid are added to a reaction kettle, heated to 80℃, stirred for 8 h, cooled to room temperature, filtered, the filter cake is washed with ethanol and then dried at 60℃ to constant weight to obtain mercapto-modified sodium bentonite;

[0030] (3) 9 g of the vinyl-terminated borosilicon compound obtained in step (1), 10 g of the mercapto-modified sodium bentonite obtained in step (2), 0.2 g of azobisisobutyronitrile and 200 g of ethanol are added to a reaction kettle, then nitrogen is introduced into the reaction kettle to replace the air in the reaction kettle, the material in the reaction kettle is heated to 65℃ under stirring, stirred for 12 h, cooled to room temperature, the material in the reaction kettle is rotary evaporated at 60℃, then dried at 60℃ to constant weight to obtain the flame retardant.

[0031] Example 2

[0032] The halogen-free flame-retardant polypropylene composite material of the embodiment is composed of the following components in mass fraction: 60 parts of polypropylene, 20 parts of flame retardant, 3 parts of vinyl trialkoxysilane, 9 parts of toughening agent, and 1.5 parts of antioxidant; wherein the toughening agent is ethylene-propylene-diene rubber; the antioxidant is 4,4'-thiobis(3-methyl-6-tert-butyl) phenol; and the vinyl trialkoxysilane is vinyl triethoxysilane;

[0033] The preparation method of the flame retardant is as follows:

[0034] (2) 10 g of boric acid, 45 g of vinyl triethoxysilane, 100 g of ethanol, and 180 g of water are added to a reaction kettle, stirred uniformly, acetic acid is added, the pH of the material in the reaction kettle is adjusted to 4, stirred at room temperature for 8 h, then heated to 90℃, and stirred for 10 h, cooled to room temperature, the material in the reaction kettle is rotary evaporated at 60℃, and then dried at 60℃ until constant weight to obtain an end-vinyl borosilicon compound;

[0035] (4) 10 g of sodium bentonite, 10 g of 3-mercaptopropyl triethoxysilane, and 100 g of 0.3 mol / L hydrochloric acid are added to a reaction kettle, heated to 95℃, stirred for 15 h, cooled to room temperature, filtered, and the filter cake is washed with ethanol and dried at 60℃ until constant weight to obtain mercapto-modified sodium bentonite;

[0036] (5) 12 g of the end-vinyl borosilicon compound obtained in step (1), 10 g of the mercapto-modified sodium bentonite obtained in step (2), 0.5 g of azobisisobutyronitrile, and 250 g of ethanol are added to a reaction kettle, then nitrogen is introduced into the reaction kettle to replace the air in the reaction kettle, the material in the reaction kettle is heated to 80℃ under stirring, stirred for 8 h, cooled to room temperature, the material in the reaction kettle is rotary evaporated at 60℃, and then dried at 60℃ until constant weight to obtain the flame retardant.

[0037] Example 3

[0038] The halogen-free flame-retardant polypropylene composite material of the embodiment is composed of the following components in mass fraction: 60 parts of polypropylene, 20 parts of flame retardant, 3 parts of vinyl trialkoxysilane, 9 parts of toughening agent, and 1.5 parts of antioxidant; wherein the toughening agent is ethylene-propylene-diene rubber; the antioxidant is 4,4'-thiobis(3-methyl-6-tert-butyl) phenol; and the vinyl trialkoxysilane is vinyl triethoxysilane;

[0039] The preparation method of the flame retardant is as follows:

[0040] (3) 10 g boric acid, 40 g vinyl triethoxysilane, 90 g ethanol and 160 g water were added into a reaction kettle, stirred uniformly, acetic acid was added, the pH of the material in the reaction kettle was adjusted to 3.5, stirred at room temperature for 7 h, then heated to 85℃, continued to stir for 9 h, cooled to room temperature, the material in the reaction kettle was rotary evaporated at 60℃, then dried at 60℃ until constant weight, to obtain an end-vinyl boron-silicon compound;

[0041] (6) 10 g sodium bentonite, 8 g 3-mercaptopropyl trimethoxysilane and 80 g hydrochloric acid with a concentration of 0.2 mol / L were added into a reaction kettle, heated to 85℃, stirred for 10 h, cooled to room temperature, filtered, the filter cake was washed with ethanol and then dried at 60℃ until constant weight, to obtain a mercapto-modified sodium bentonite;

[0042] (7) 10 g end-vinyl boron-silicon compound obtained in step (1), 10 g mercapto-modified sodium bentonite obtained in step (2), 0.3 g azobisisobutyronitrile and 230 g ethanol were added into a reaction kettle, then nitrogen was introduced into the reaction kettle to replace the air in the reaction kettle, the material in the reaction kettle was heated to 70℃ under stirring, stirred for 10 h, cooled to room temperature, the material in the reaction kettle was rotary evaporated at 60℃, then dried at 60℃ until constant weight, to obtain a flame retardant.

[0043] Comparative Example 1

[0044] The difference between the halogen-free flame-retardant polypropylene composite material of the present comparative example and the halogen-free flame-retardant polypropylene composite material of Example 1 is that the flame retardant in the halogen-free flame-retardant polypropylene composite material of the present comparative example is composed of end-vinyl boron-silicon compound and mercapto-modified sodium bentonite, and the mass ratio of end-vinyl boron-silicon compound to mercapto-modified sodium bentonite is 9:10; the end-vinyl boron-silicon compound is the same as the end-vinyl boron-silicon compound obtained in the preparation method of the flame retardant in Example 1, and the mercapto-modified sodium bentonite is the same as the mercapto-modified sodium bentonite obtained in the preparation method of the flame retardant in Example 1.

[0045] Comparative Example 2

[0046] The difference between the halogen-free flame-retardant polypropylene composite material of the present comparative example and the halogen-free flame-retardant polypropylene composite material of Example 1 is that the vinyl trialkoxysilane in the halogen-free flame-retardant polypropylene composite material of the present comparative example is replaced by 3-mercaptopropyl triethoxysilane.

[0047] Comparative Example 3

[0048] The difference between the halogen-free flame-retardant polypropylene composite material of the present comparative example and the halogen-free flame-retardant polypropylene composite material of Example 1 is that the vinyl trialkoxysilane in the halogen-free flame-retardant polypropylene composite material of the present comparative example is replaced by γ-(2,3-epoxypropoxy) propyl trimethoxysilane.

[0049] Comparative Example 4

[0050] The halogen-free flame-retardant polypropylene composite material of the present comparative example is only different from the halogen-free flame-retardant polypropylene composite material of Example 1 in that the vinyl trialkoxysilane in the halogen-free flame-retardant polypropylene composite material of the present comparative example is replaced by γ-aminopropyl trimethoxysilane.

[0051] Effect Example

[0052] According to the composition ratio of the halogen-free flame-retardant polypropylene composite material of each example and comparative example, each raw material is added into a twin-screw extruder, and is melt-extruded at 190℃ to obtain a halogen-free flame-retardant polypropylene composite material. Then, the tensile strength is tested according to the provisions in standard GB / T1040-92, the impact strength is tested according to the provisions in standard ISO179-1, and the flame-retardant property is tested according to the provisions in standards GB / T2408 and GB / T406-93. The tensile strength, impact strength and flame-retardant property test results of the halogen-free flame-retardant polypropylene composite material of each example and comparative example are shown in Table 1.

[0053] Table 1 Tensile strength, impact strength and flame-retardant property test results of the halogen-free flame-retardant polypropylene composite material of each example and comparative example

[0054]

[0055]

[0056] According to Table 1, the tensile strength and impact strength of the halogen-free flame-retardant polypropylene composite material of each example and comparative example are summarized in Figure 1 , and the flame-retardant property test results are summarized in Figure 2 . From Table 1 and Figures 1-2 , it can be seen that the tensile strength of the halogen-free flame-retardant polypropylene composite material of the present application is not less than 36MPa, the impact strength is not less than 9.1kJ / m 2 , the vertical burning experiment UL94 level is all V-0 level, and the limiting oxygen index is greater than 31, while the tensile strength and impact strength of the halogen-free flame-retardant polypropylene composite material in the comparative examples using other flame retardants or silane coupling agents are all decreased, and the flame-retardant property is deteriorated.

Claims

1. A halogen-free flame-retardant polypropylene composite material, characterized in that, The composition comprises the following components in parts by weight: 45-60 parts polypropylene, 15-25 parts flame retardant, 1-3 parts vinyltrialkoxysilane, 3-9 parts toughening agent, and 0.05-1.5 parts antioxidant. The flame retardant is prepared by the following steps: an addition reaction is performed between the vinyl groups in the terminal vinyl borosilicate compound and the mercapto groups on the mercapto-modified sodium bentonite to obtain the flame retardant; the mass ratio of the terminal vinyl borosilicate compound to the mercapto-modified sodium bentonite is (0.9-1.2):1; the terminal vinyl borosilicate compound is prepared by reacting boric acid and a terminal vinyl silane coupling agent, with a molar ratio of boric acid to the terminal vinyl silane coupling agent of 1:(3.5-4.5).

2. The halogen-free flame-retardant polypropylene composite material as described in claim 1, characterized in that, The preparation method of the mercapto-modified sodium bentonite is as follows: sodium bentonite, mercaptosilane coupling agent and hydrochloric acid are mixed and reacted at 80-95℃ for 8-15h, solid-liquid separation is performed, washing and drying are carried out to obtain mercapto-modified sodium bentonite; the mass ratio of sodium bentonite, mercaptosilane coupling agent and hydrochloric acid is 1:(7-10):(50-100).

3. The halogen-free flame-retardant polypropylene composite material as described in claim 2, characterized in that, The mercaptosilane coupling agent is 3-mercaptopropyltriethoxysilane or 3-mercaptopropyltrimethoxysilane.

4. The halogen-free flame-retardant polypropylene composite material as described in claim 2, characterized in that, The concentration of the hydrochloric acid is 0.08–0.3 mol / L.

5. The halogen-free flame-retardant polypropylene composite material as described in claim 1, characterized in that, The method for preparing the terminal vinyl borosilicate compound is as follows: Boric acid, terminal vinyl silane coupling agent, ethanol and water are mixed and the pH is adjusted to 3-4. The mixture is reacted at room temperature for 6-8 hours, and then the reaction system is reacted at 80-90℃ for 8-10 hours. After removing impurities, the terminal vinyl borosilicate compound is obtained.

6. The halogen-free flame-retardant polypropylene composite material as described in claim 5, characterized in that, The terminal vinyl silane coupling agent is vinyltrimethoxysilane or vinyltriethoxysilane.

7. The halogen-free flame-retardant polypropylene composite material according to any one of claims 1-6, characterized in that, The addition reaction method includes the following steps: under inert gas protection, a terminal vinyl borosilicate compound, mercapto-modified sodium bentonite, an initiator, and an organic solvent are mixed and reacted.

8. The halogen-free flame-retardant polypropylene composite material as described in claim 7, characterized in that, The initiator is azobisisobutyronitrile; the mass ratio of the terminal vinyl borosilicate compound, mercapto-modified sodium bentonite, and azobisisobutyronitrile is (0.9–1.2):1:(0.02–0.05); the temperature of the mixed reaction is 65–80°C, and the time is 8–12 h.

9. The halogen-free flame-retardant polypropylene composite material according to any one of claims 1-6, characterized in that, The toughening agent is ethylene propylene diene monomer (EPDM), ethylene propylene diene monomer (EPDM), or styrene-butadiene-styrene synthetic rubber; the antioxidant is 4',4-thiobis(6-tert-butyl-o-cresol), 4,4'-thiobis(3-methyl-6-tert-butyl)phenol, di(octadecyl)thiodipropionate, or diphenylisooctyl phosphite; the vinyltrialkoxysilane is vinyltrimethoxysilane or vinyltriethoxysilane.

10. A method for preparing a halogen-free flame-retardant polypropylene composite material as described in any one of claims 1-9, characterized in that, The process includes the following steps: melt extruding the components in the specified amounts to obtain a halogen-free flame-retardant polypropylene composite material.

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