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

Abstract

The invention 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. The halogen-free flame-retardant polypropylene composite material is prepared from the following components in parts by mass: 45 to 60 parts of polypropylene, 15 to 25 parts of a flame retardant, 1 to 3 parts of vinyl trialkoxy silane, 3 to 9 parts of a toughening agent and 0.05 to 1.5 parts of an antioxidant. Vinyl in the vinyl-terminated borosilicate compound and sulfydryl in sulfydryl modified sodium bentonite are subjected to an addition reaction, the borosilicate compound is grafted to the sodium bentonite through C-S chemical bonds, the composite flame retardant is formed, halogen elements are not contained in the flame retardant, and the flame retardant is environmentally friendly and free of toxic and side effects. Meanwhile, the flame retardant contains boron, silicon and sodium bentonite with good heat resistance, and various metal elements and silicon in the sodium bentonite and the boron and silicon in the organic matter generate a synergistic effect, so that the flame retardance of the flame retardant is improved.

Description

Technical Field

[0001] The invention relates to a halogen-free flame-retardant polypropylene composite material and a preparation method thereof, belonging to the technical field of polymer materials. Background Art

[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 extremely flammable, with a limiting oxygen index of less than 18.0%. It cannot be extinguished after burning in the air. Polypropylene is not suitable for facilities and places prone to fire.

[0003] In order to broaden the scope of use of polypropylene and enable it to be used in facilities and places prone to fire, a common practice is to perform flame retardant modification on polypropylene. The flame retardant modification of polypropylene can be achieved by adding flame retardants that have the ability to delay the chemical and physical reaction processes of combustion. The flame retardants currently used to modify polypropylene include halogen flame retardants and halogen-free flame retardants. Halogen flame retardants, as an important variety of organic flame retardants, are the earliest type of flame retardants 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 largest organic flame retardants in the world in terms of production and usage. Halogen flame retardants decompose to produce hydrogen halides (HX), which eliminate active free radicals produced by the combustion reaction of polymer materials. For example, HX reacts with the chain reaction active substance HO· in the flame to reduce the concentration of the above-mentioned free radicals, thereby slowing down or terminating the chain reaction of combustion and achieving the purpose of flame retardancy. While halogen flame retardants are flame retardant to polymers, they also emit toxic smoke and gases, which harm the environment and human health. As people's awareness of improving material safety and environmental health increases, high-efficiency, low-halogen, and even halogen-free flame retardant materials are the key development direction in the future. However, the currently used halogen-free flame retardant systems such as phosphorus-nitrogen expandable, metal hydroxide, red phosphorus, expanded graphite, and silicone-inorganic compounds all have defects such as large amount of flame retardant added and great impact on material properties. Summary of the invention

[0004] The purpose of the present invention is to provide a halogen-free flame-retardant polypropylene composite material to solve the problem that the current halogen-free flame-retardant polypropylene material cannot simultaneously take into account the flame retardancy and mechanical properties.

[0005] Another object of the present invention is to provide a method for preparing a halogen-free flame-retardant polypropylene composite material, so as to solve the problem that the flame retardancy and mechanical properties of the currently prepared halogen-free flame-retardant polypropylene composite material cannot meet the requirements at the same time.

[0006] The invention provides a halogen-free flame-retardant polypropylene composite material, comprising the following components in parts by weight: 45-60 parts of polypropylene, 15-25 parts of a flame retardant, 1-3 parts of vinyltrialkoxysilane, 3-9 parts of a toughening agent, and 0.05-1.5 parts of an antioxidant; a preparation method of the flame retardant comprises the following steps: performing addition reaction on a vinyl group in a vinyl-terminated borosilicate compound and a thiol group on thiol-modified sodium bentonite to obtain the flame retardant; the mass ratio of the vinyl-terminated borosilicate compound to the thiol-modified sodium bentonite is (0.9-1.2):1; the vinyl-terminated borosilicate compound is prepared by reacting boric acid and a vinyl-terminated silane coupling agent, and the molar ratio of the boric acid to the vinyl-terminated 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, a mercaptosilane coupling agent and hydrochloric acid are mixed and reacted at 80-95° C. for 8-15 hours, solid-liquid separation, washing, and drying to obtain mercapto-modified sodium bentonite; the mass ratio of sodium bentonite, mercaptosilane coupling agent and hydrochloric acid is 1:(7-10):(50-100).

[0008] Preferably, the mercaptosilane coupling agent is 3-mercaptopropyltriethoxysilane or 3-mercaptopropyltrimethoxysilane.

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

[0010] Preferably, the preparation method of the terminal vinyl borosilicate compound is as follows: mix boric acid, terminal vinyl silane coupling agent, ethanol and water, adjust the pH to 3-4, mix and react at room temperature for 6-8 hours, then mix and react the reacted system at 80-90°C for 8-10 hours, and obtain the terminal vinyl borosilicate compound after impurities removal.

[0011] Preferably, the terminal vinyl silane coupling agent is vinyl trimethoxy silane or vinyl triethoxy silane.

[0012] Preferably, the addition reaction method comprises the following steps: under the protection of an inert gas, mixing and reacting a terminal vinyl borosilicate compound, a mercapto-modified sodium bentonite, an initiator and an organic solvent.

[0013] Preferably, the initiator is azobisisobutyronitrile; the mass ratio of the vinyl-terminated borosilicate compound, the 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 8-12h.

[0014] Preferably, the toughening agent is EPDM rubber, EPDM rubber, 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, dioctadecyl thiodipropionate, diisooctyl phosphite; the vinyltrialkoxysilane is vinyltrimethoxysilane and vinyltriethoxysilane.

[0015] The present invention provides a method for preparing the halogen-free flame-retardant polypropylene composite material as described above, comprising the following steps: melt-extruding each component of the formula to obtain the halogen-free flame-retardant polypropylene composite material.

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

[0017] The beneficial effects of the present invention are as follows:

[0018] (1) The present invention adopts the vinyl group in the terminal vinyl borosilicate compound and the thiol group in the thiol-modified sodium bentonite to undergo an addition reaction, and the borosilicate compound is grafted onto the sodium bentonite through a CS chemical bond to form a composite flame retardant. The flame retardant does not contain halogen elements, and contains boron elements, silicon elements and sodium bentonite with good heat resistance. The various metal elements and silicon elements in the sodium bentonite produce a synergistic effect with the boron elements and silicon elements in the organic matter, thereby improving the flame retardant properties of the flame retardant.

[0019] (2) The present invention uses a specific ratio of terminal vinyl borosilicate compounds and mercapto-modified sodium bentonite for bonding reaction, which can ensure that some active group mercapto groups remain on the surface of the flame retardant, so that the flame retardant can better combine with polypropylene, ensuring the strength and toughness of the material.

[0020] (3) The present invention uses vinyltrialkoxysilane to pin the flame retardant on the surface of the polypropylene material. During the melt extrusion of the polypropylene material, the epoxy group in the vinyltrialkoxysilane can chemically react with the active group thiol remaining on the surface of the flame retardant. At the same time, the vinyltrialkoxysilane is combined with the surface of the flame retardant to form a secondary modification of the flame retardant. The surface has a large number of alkoxysilane groups, which improves the bonding force with the polypropylene material.

[0021] (4) The present invention uses a new flame retardant and vinyltrialkoxysilane to modify polypropylene, which can ensure that the polypropylene has both good mechanical properties and flame retardant properties when a small amount of flame retardant is added, thereby broadening the scope of use of polypropylene and meeting the requirements of healthy and environmentally friendly use. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1It is a schematic diagram of the tensile strength and impact strength test results of the halogen-free flame-retardant polypropylene composite materials of various embodiments and comparative examples of the present invention;

[0023] Figure 2 It is a schematic diagram of the flame retardant performance test results of the halogen-free flame retardant polypropylene composite materials of various embodiments and comparative examples in the present invention. DETAILED DESCRIPTION

[0024] The following examples are intended to further illustrate the present invention rather than to limit the scope of protection of the present invention.

[0025] Example 1

[0026] The halogen-free flame-retardant polypropylene composite material of this embodiment is composed of the following components in parts by mass: 45 parts of polypropylene, 15 parts of flame retardant, 1 part of vinyltrialkoxysilane, 3 parts of toughening agent, and 0.05 parts of antioxidant; wherein the toughening agent is ethylene propylene rubber; the antioxidant is 4'4-thiobis(6-tert-butyl-o-cresol); the vinyltrialkoxysilane is vinyltrimethoxysilane;

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

[0028] (1) 10 g of boric acid, 35 g of vinyltrimethoxysilane, 80 g of ethanol and 150 g of water were added to a reactor, stirred evenly, acetic acid was added, the pH of the material in the reactor was adjusted to 3, the reaction was stirred at room temperature for 6 h, then the temperature was raised to 80 ° C, the reaction was continued to be stirred for 8 h, and the reaction was cooled to room temperature. The material in the reactor was rotary evaporated at 60 ° C, and then dried at 60 ° C to constant weight to obtain a terminal vinyl borosilicate compound;

[0029] (2) adding 10 g of sodium bentonite, 7 g of 3-mercaptopropyltrimethoxysilane and 50 g of hydrochloric acid with a concentration of 0.08 mol / L into a reaction kettle, heating to 80° C., stirring for 8 h, cooling to room temperature, filtering, washing the filter cake with ethanol and drying at 60° C. to constant weight, to obtain mercapto-modified sodium bentonite;

[0030] (3) 9 g of the vinyl-terminated borosilicate compound obtained in step (1), 10 g of the thiol-modified sodium bentonite obtained in step (2), 0.2 g of azobisisobutyronitrile and 200 g of ethanol were added to a reactor, and then nitrogen was introduced into the reactor for replacement to remove the air in the reactor. The materials in the reactor were then heated to 65° C. under stirring conditions, stirred for reaction for 12 h, cooled to room temperature, and the materials in the reactor were rotary evaporated at 60° C. and then dried at 60° C. to constant weight to obtain a flame retardant.

[0031] Example 2

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

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

[0034] (2) Add 10 g of boric acid, 45 g of vinyl triethoxysilane, 100 g of ethanol and 180 g of water to a reactor, stir evenly, add acetic acid, adjust the pH of the material in the reactor to 4, stir and react at room temperature for 8 h, then heat to 90 ° C, continue stirring and reacting for 10 h, cool to room temperature, rotary evaporate the material in the reactor at 60 ° C, and then dry at 60 ° C to constant weight to obtain a terminal vinyl borosilicate compound;

[0035] (4) adding 10 g of sodium bentonite, 10 g of 3-mercaptopropyltriethoxysilane and 100 g of 0.3 mol / L hydrochloric acid into a reaction kettle, heating to 95° C., stirring for 15 h, cooling to room temperature, filtering, washing the filter cake with ethanol and drying at 60° C. to constant weight, to obtain mercapto-modified sodium bentonite;

[0036] (5) 12 g of the vinyl-terminated borosilicate compound obtained in step (1), 10 g of the thiol-modified sodium bentonite obtained in step (2), 0.5 g of azobisisobutyronitrile and 250 g of ethanol were added to a reactor, and nitrogen was introduced into the reactor to replace the air in the reactor. The air in the reactor was removed, and then the materials in the reactor were heated to 80° C. under stirring conditions, stirred for reaction for 8 h, cooled to room temperature, and the materials in the reactor were rotary evaporated at 60° C. and then dried at 60° C. to constant weight to obtain a flame retardant.

[0037] Example 3

[0038] The halogen-free flame-retardant polypropylene composite material of this embodiment is composed of the following components in parts by weight: 50 parts of polypropylene, 25 parts of flame retardant, 2 parts of vinyl trialkoxy silane, 5 parts of toughening agent, and 1.0 part of antioxidant; wherein the toughening agent is styrene-butadiene-styrene synthetic rubber; the antioxidant is diphenyl isooctyl phosphite; the vinyl trialkoxy silane is vinyl triethoxy silane;

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

[0040] (3) Add 10 g of boric acid, 40 g of vinyl triethoxysilane, 90 g of ethanol and 160 g of water to a reactor, stir evenly, add acetic acid, adjust the pH of the material in the reactor to 3.5, stir and react at room temperature for 7 h, then heat to 85 ° C, continue stirring and react for 9 h, cool to room temperature, rotary evaporate the material in the reactor at 60 ° C, and then dry at 60 ° C to constant weight to obtain a terminal vinyl borosilicate compound;

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

[0042] (7) 10 g of the terminal vinyl borosilicate compound obtained in step (1), 10 g of the thiol-modified sodium bentonite obtained in step (2), 0.3 g of azobisisobutyronitrile and 230 g of ethanol were added to a reactor, and then nitrogen was introduced into the reactor for replacement to remove the air in the reactor. The materials in the reactor were then heated to 70° C. under stirring conditions, stirred for reaction for 10 hours, cooled to room temperature, and the materials in the reactor were rotary evaporated at 60° C. and then dried at 60° C. to constant weight to obtain a flame retardant.

[0043] Comparative Example 1

[0044] The difference between the halogen-free flame retardant polypropylene composite material of this 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 this comparative example consists of a terminal vinyl borosilicate compound and a mercapto-modified sodium bentonite, and the mass ratio of the terminal vinyl borosilicate compound to the mercapto-modified sodium bentonite is 9:10; the terminal vinyl borosilicate compound is the same as the terminal vinyl borosilicate compound obtained in the method for preparing the flame retardant in Example 1, and the mercapto-modified sodium bentonite is the same as the mercapto-modified sodium bentonite obtained in the method for preparing the flame retardant in Example 1.

[0045] Comparative Example 2

[0046] The halogen-free flame-retardant polypropylene composite material of this comparative example is different from the halogen-free flame-retardant polypropylene composite material of Example 1 only in that the vinyltrialkoxysilane in the halogen-free flame-retardant polypropylene composite material of this comparative example is replaced by 3-mercaptopropyltriethoxysilane.

[0047] Comparative Example 3

[0048] The halogen-free flame retardant polypropylene composite material of this comparative example is different from the halogen-free flame retardant polypropylene composite material of Example 1 only in that the vinyltrialkoxysilane in the halogen-free flame retardant polypropylene composite material of this comparative example is replaced by γ-(2,3-epoxypropoxy)propyltrimethoxysilane.

[0049] Comparative Example 4

[0050] The halogen-free flame-retardant polypropylene composite material of this comparative example is different from the halogen-free flame-retardant polypropylene composite material of Example 1 only in that the vinyltrialkoxysilane in the halogen-free flame-retardant polypropylene composite material of this comparative example is replaced by γ-aminopropyltrimethoxysilane.

[0051] Effect example

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

[0053] Table 1 Test results of tensile strength, impact strength and flame retardant properties of halogen-free flame retardant polypropylene composite materials of various embodiments and comparative examples

[0054]

[0055]

[0056] According to Table 1, the tensile strength and impact strength of the halogen-free flame retardant polypropylene composite materials of each embodiment and comparative example are summarized in Figure 1 The flame retardant test results are summarized in Figure 2 From Table 1 and Figure 1-2 It can be seen that the tensile strength of the halogen-free flame-retardant polypropylene composite material of the present invention is not less than 36MPa, and the impact strength is not less than 9.1kJ / m 2 The vertical combustion test UL94 level is V-0, and the limiting oxygen index is greater than 31. However, the tensile strength and impact strength of the halogen-free flame retardant polypropylene composite materials using other flame retardants or silane coupling agents in the comparative example are reduced, and the flame retardant performance is deteriorated.

Claims

1. A halogen-free flame-retardant polypropylene composite material, characterized in that: The invention comprises the following components in parts by weight: 45 to 60 parts of polypropylene, 15 to 25 parts of flame retardant, 1 to 3 parts of vinyltrialkoxysilane, 3 to 9 parts of toughening agent and 0.05 to 1.5 parts of antioxidant; the preparation method of the flame retardant comprises the following steps: adding the vinyl group in the vinyl-terminated borosilicate compound and the thiol group on the thiol-modified sodium bentonite to obtain the flame retardant; the mass ratio of the vinyl-terminated borosilicate compound to the thiol-modified sodium bentonite is (0.9 to 1.2):1; the vinyl-terminated borosilicate compound is prepared by reacting boric acid and a vinyl-terminated silane coupling agent, and the molar ratio of the boric acid to the vinyl-terminated silane coupling agent is 1:(3.5 to 4.5).

2. The halogen-free flame-retardant polypropylene composite material according to claim 1, characterized in that: The preparation method of the mercapto-modified sodium bentonite is as follows: sodium bentonite, a mercaptosilane coupling agent and hydrochloric acid are mixed and reacted at 80-95° C. for 8-15 hours, solid-liquid separation, washing and drying 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 according to claim 2, characterized in that: The mercaptosilane coupling agent is 3-mercaptopropyltriethoxysilane or 3-mercaptopropyltrimethoxysilane.

4. The halogen-free flame-retardant polypropylene composite material according to 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 according to claim 1, characterized in that: The preparation method of the terminal vinyl borosilicate compound is as follows: boric acid, terminal vinyl silane coupling agent, ethanol and water are mixed, the pH is adjusted to 3-4, mixed and reacted at room temperature for 6-8 hours, and then the reacted system is mixed and reacted at 80-90° C. for 8-10 hours, and the terminal vinyl borosilicate compound is obtained after impurities are removed.

6. The halogen-free flame-retardant polypropylene composite material according to claim 5, characterized in that: The terminal vinyl silane coupling agent is vinyl trimethoxy silane or vinyl triethoxy silane.

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

8. The halogen-free flame-retardant polypropylene composite material according to 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 hours.

9. The halogen-free flame-retardant polypropylene composite material according to any one of claims 1 to 6, characterized in that: The toughening agent is ethylene propylene diene rubber, ethylene propylene diene rubber, 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, dioctadecyl thiodipropionate, diphenyl isooctyl phosphite; the vinyl trialkoxysilane is vinyl trimethoxysilane and vinyl triethoxysilane.

10. A method for preparing a halogen-free flame-retardant polypropylene composite material according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: melting and extruding each component of the formula to obtain a halogen-free flame-retardant polypropylene composite material.

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