Preparation method of polypropylene composite flame-retardant material

Abstract

The invention discloses a preparation method of a polypropylene composite flame-retardant material, and the method comprises the following steps: S1, preparation of a dispersion liquid: taking magnesium hydroxide as a dispersoid, and ultrasonically dispersing the magnesium hydroxide in an ethanol solution A to prepare the dispersion liquid; s2, preparation of a composite modified liquid: mixing a modifier A and a modifier B in an ethanol solution B to prepare the composite modified liquid; s3, preparation of a composite modified magnesium hydroxide flame retardant: adding the composite modified liquid into the dispersion liquid for reaction, and performing suction filtration, washing, airing and grinding after the reaction to obtain the composite modified magnesium hydroxide flame retardant; s4, preparation of the polypropylene composite flame-retardant material: carrying out melt blending on acetic acid fibers, the composite modified magnesium hydroxide flame retardant and polypropylene, and then pressing and curing to prepare the polypropylene composite flame-retardant material with good flame retardant property and mechanical property.

Description

Technical Field

[0001] The invention relates to the technical field of flame retardant materials, and in particular to a method for preparing a polypropylene composite flame retardant material. Background Art

[0002] Magnesium hydroxide is a general inorganic halogen-free flame retardant, which is usually used to fill polymer materials to reduce fire hazards; when a fire occurs, magnesium hydroxide will be thermally decomposed, and a large amount of heat will be absorbed during the decomposition process, thereby reducing the ambient temperature of the fire scene, and at the same time, it will decompose to produce magnesium oxide with high stability and flame retardant properties to cover the surface of the burning material, blocking the further contact between the material and the air, thereby achieving the purpose of reducing the burning rate of the material. At the same time, since magnesium hydroxide flame retardant does not contain halogen elements, it will not produce harmful gases during the flame retardant process, and it has high safety and good smoke suppression effect. It belongs to a green and environmentally friendly flame retardant, so it is highly favored in the addition and selection of fire safety material flame retardants. However, the surface of magnesium hydroxide contains a large number of hydrophilic groups hydroxyl (-OH), and the surface has strong polarity. Therefore, magnesium hydroxide directly blended with polymers will affect the heat resistance and flame retardant properties of the resulting flame retardant material due to poor compatibility, and even cause the original function of the material to decline. Therefore, magnesium hydroxide needs to be modified to improve the compatibility of magnesium hydroxide with the polymer matrix.

[0003] At present, the method of flame retardant modification of magnesium hydroxide is mainly to modify its surface by physical or chemical methods, changing the surface of magnesium hydroxide from hydrophilic to hydrophobic, thereby improving the compatibility between the flame retardant and the polymer material matrix. For example, the common modifier silane coupling agent (KH550) contains flame retardant elements, and KH550 can bond with magnesium hydroxide to form non-polar groups on the surface of magnesium hydroxide, thereby improving the hydrophobicity of magnesium hydroxide. In addition, sodium oleate (C 17 H 33 COONa) is also an anionic surfactant commonly used in magnesium hydroxide surface modification. Since the surface of magnesium hydroxide carries a positive charge, anionic surface modifiers are beneficial to the modification of the surface of magnesium hydroxide. Sodium oleate will dissociate into anionic C in water. 17 H 33 COO - , then C 17 H 33 COO -It is adsorbed on the surface of magnesium hydroxide with a stable chemical bond, and the long hydrophobic alkane chain is exposed, thereby effectively improving the hydrophobicity of the surface of magnesium hydroxide. However, the modification effect of a single modifier on magnesium hydroxide is limited, which will affect the flame retardant performance of the modified magnesium hydroxide flame retardant in polymer materials. At the same time, the addition of the modified magnesium hydroxide flame retardant to polymer materials will also affect the overall mechanical properties of the material, limiting the application of the material. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a polypropylene composite flame retardant material in view of the problem that the mechanical properties of the material will decrease when the modified magnesium hydroxide is blended in a polymer material, thereby solving the above problem.

[0005] To achieve the above object, the present invention is implemented by the following technical solutions:

[0006] The present invention provides a method for preparing a polypropylene composite flame retardant material, the method comprising the following steps:

[0007] S1. Preparation of dispersion: using magnesium hydroxide as a dispersant and dispersing it in ethanol solution A by ultrasonication to prepare a dispersion;

[0008] S2. Preparation of composite modified liquid: mixing modifier A and modifier B in ethanol solution B to prepare composite modified liquid;

[0009] S3, preparation of composite modified magnesium hydroxide flame retardant: adding the composite modified liquid to the dispersion liquid for reaction, filtering after the reaction, washing, drying, grinding, and obtaining the composite modified magnesium hydroxide flame retardant;

[0010] S4. Preparation of polypropylene composite flame retardant material: Acetate fiber, composite modified magnesium hydroxide flame retardant and polypropylene are melt-blended, and then pressed and cured to obtain a polypropylene composite flame retardant material with good flame retardant and mechanical properties.

[0011] Specifically, the present invention makes composite modification on the surface of magnesium hydroxide by co-acting modifier A (sodium oleate) and modifier B (silane coupling agent KH550) on the surface of magnesium hydroxide, thereby making up for the deficiency of a single modifier and improving the flame retardant effect. At the same time, the present invention also introduces non-flammable and tough acetate fiber while adding the modified magnesium hydroxide flame retardant to the polymer material, thereby achieving the purpose of improving the mechanical properties of the material, thereby obtaining a polypropylene composite flame retardant material with good flame retardant properties and mechanical properties.

[0012] The composite modified magnesium hydroxide flame retardant prepared by the present invention has the characteristics of higher hydrophobicity compared with unmodified magnesium hydroxide, and two organic surface modifiers can produce good wrapping on the surface of magnesium hydroxide, thereby effectively improving the compatibility of the magnesium hydroxide flame retardant in polymer materials, and can effectively improve the heat resistance (thermal stability) and flame retardant properties of the material after blending with the polymer material. The method of the present invention is to first ultrasonically disperse the inorganic flame retardant magnesium hydroxide, then add two modifiers, sodium oleate and silane KH550, to perform composite modification on the surface of magnesium hydroxide, then mix the composite modified magnesium hydroxide flame retardant with acetate fiber, add it to the polypropylene material, melt blend it in an internal mixer, and obtain a polypropylene composite flame retardant material with good flame retardant properties and mechanical properties.

[0013] Furthermore, a method for preparing a polypropylene composite flame retardant material: in step S1, the mass volume ratio of the magnesium hydroxide to the ethanol solution A is 0.1 to 0.3 g / ml.

[0014] Furthermore, a method for preparing a polypropylene composite flame retardant material: the ethanol solution A in step S1 is an ethanol aqueous solution with a mass fraction of 75.0-85.0%; the ultrasonic dispersion time is 5-15 minutes, and the ultrasonic dispersion temperature is 45-55°C.

[0015] Furthermore, a method for preparing a polypropylene composite flame retardant material: the amount of the modifier A used in the composite modified liquid is 0.5-2.5% of the weight of the magnesium hydroxide, and the amount of the modifier B used in the composite modified liquid is 0.5-2.5% of the weight of the magnesium hydroxide.

[0016] Furthermore, a method for preparing a polypropylene composite flame retardant material: in step S2, the modifier A is sodium oleate, and the modifier B is silane coupling agent KH550.

[0017] Furthermore, a method for preparing a polypropylene composite flame retardant material: the ethanol solution B is an ethanol aqueous solution with a mass fraction of 75.0 to 85.0%.

[0018] Furthermore, a method for preparing a polypropylene composite flame retardant material: Step S3, preparation of a composite modified magnesium hydroxide flame retardant: under water bath conditions of 45 to 55°C, dropwise adding the composite modified liquid to the dispersion liquid to react for 15 to 25 minutes, filtering after the reaction, and then washing with deionized water and anhydrous ethanol for 1 to 3 times respectively, drying naturally, grinding into powder, and passing through a 50 to 100 mesh sieve to obtain a composite modified magnesium hydroxide flame retardant.

[0019] Furthermore, a method for preparing a polypropylene composite flame retardant material is provided: S4, preparation of a polypropylene composite flame retardant material: melt-blending cellulose acetate, a composite modified magnesium hydroxide flame retardant and polypropylene at 180-220°C for 5-30 minutes, and then pressing in a flat vulcanizer for 5-15 minutes, setting the pressing temperature to 180-220°C and the pressure to 10-20MPa, and then cold-pressing for 1-5 minutes, and curing at room temperature for 2-4 hours to obtain a polypropylene composite flame retardant material with good flame retardant and mechanical properties; wherein the weight ratio of the cellulose acetate, the composite modified magnesium hydroxide flame retardant and the polypropylene is (0.01-0.05):(0.05-0.4):1.

[0020] Beneficial effects of the present invention:

[0021] (1) The polypropylene composite flame retardant material prepared by the present invention using the composite modified magnesium hydroxide flame retardant and cellulose acetate as additives, wherein the addition of cellulose acetate effectively improves the mechanical properties of the material, thereby solving the problem of decreased mechanical properties of the material due to the addition of modified magnesium hydroxide flame retardant to the previous material.

[0022] (2) The present invention realizes the wet surface modification of magnesium hydroxide by anionic surfactant sodium oleate and neutral surfactant silane alkane agent KH550 under ultrasonic dispersion. The method has the advantages of small dosage of modifier, mild reaction conditions, simple operation and low raw material cost. In addition, the surface of the modified magnesium hydroxide has good hydrophobicity and good flame retardant properties.

[0023] (3) The modification method of the composite modified magnesium hydroxide provided by the present invention is simple, and the modifier directly reacts on the surface of the magnesium hydroxide flame retardant. The entire preparation process of the polypropylene composite flame retardant material has the advantages of no need for inert gas protection, mild reaction conditions (low temperature, not exceeding 55°C), and short reaction time (within 30 minutes). At the same time, the method has low operating difficulty, low economic cost, and a small number of required equipment. The prepared polypropylene composite flame retardant material has good flame retardant properties and mechanical properties, which solves the problem that the addition of magnesium hydroxide flame retardant to polymer materials will affect the mechanical properties of the materials and limit the application of the materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0025] Figure 1The infrared spectra of the composite modified magnesium hydroxide flame retardant and the unmodified magnesium hydroxide flame retardant;

[0026] Figure 2 These are TGA test graphs of the polypropylene composite flame retardant material of Example 1, the polypropylene flame retardant material of Comparative Example 1, and the pure polypropylene material. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Example 1

[0029] This embodiment 1 provides a method for preparing a polypropylene composite flame retardant material, the method comprising the following specific steps:

[0030] S1. Preparation of dispersion: 10.0 g of magnesium hydroxide powder (MH) was weighed and placed in a 100 ml three-necked flask, and then 50.0 ml of 80.0% ethanol aqueous solution (ethanol solution A) was added to the flask, followed by ultrasonic dispersion at 50° C. for 10 minutes to obtain a dispersion;

[0031] S2. Preparation of composite modified liquid: 0.15 g of sodium oleate (modifier A) and 0.15 g of silane coupling agent KH550 (modifier B) were weighed and mixed in an ethanol aqueous solution (ethanol solution B) with a mass fraction of 80.0%, thereby preparing a composite modified liquid;

[0032] S3, preparation of composite modified magnesium hydroxide flame retardant: under the condition of a constant temperature water bath at 50° C., the composite modified liquid was added dropwise into the dispersion liquid to react for 20 minutes, cooled to room temperature after the reaction, and then the product was filtered, and then washed twice with deionized water and anhydrous ethanol respectively, dried in a natural environment, ground into powder, and passed through a 100-mesh sieve to obtain a composite modified magnesium hydroxide flame retardant (MMH);

[0033] S4. Preparation of polypropylene composite flame retardant material: 1.0 g of cellulose acetate, 10.0 g of composite modified magnesium hydroxide flame retardant and 25.0 g of polypropylene were melt-blended at 200°C for 10 minutes, and then pressed in a flat vulcanizer for 10 minutes, with the pressing temperature set to 200°C and the pressure set to 15.0 MPa, and then cold-pressed for 3 minutes and cured at room temperature for 3 hours to obtain a polypropylene composite flame retardant material with good flame retardant and mechanical properties.

[0034] Example 2

[0035] This embodiment 2 provides a method for preparing a polypropylene composite flame retardant material, the method comprising the following specific steps:

[0036] S1. Preparation of dispersion: 10.0 g of magnesium hydroxide powder was weighed and placed in a 100 ml three-necked flask, and then 100.0 ml of 85.0% ethanol aqueous solution (ethanol solution A) was added to the flask, followed by ultrasonic dispersion at 55° C. for 10 minutes to obtain a dispersion;

[0037] S2. Preparation of composite modified liquid: 0.1 g of sodium oleate (modifier A) and 0.2 g of silane coupling agent KH550 (modifier B) were weighed and mixed in an ethanol aqueous solution (ethanol solution B) with a mass fraction of 85.0%, thereby preparing a composite modified liquid;

[0038] S3, preparation of composite modified magnesium hydroxide flame retardant: under the condition of a constant temperature water bath at 45°C, the composite modified liquid was added dropwise into the dispersion liquid to react for 15 minutes, cooled to room temperature after the reaction, and then the product was filtered, and then washed with deionized water and anhydrous ethanol for 3 times respectively, dried in a natural environment, ground into powder, and passed through a 50-mesh sieve to obtain a composite modified magnesium hydroxide flame retardant;

[0039] S4. Preparation of polypropylene composite flame retardant material: 2.0g of cellulose acetate, 10.0g of composite modified magnesium hydroxide flame retardant and 40.0g of polypropylene were melt-blended at 180°C for 15 minutes, and then pressed in a flat vulcanizer for 5 minutes, with the pressing temperature set to 210°C and the pressure set to 10.0MPa, and then cold-pressed for 5 minutes and cured at room temperature for 2 hours to obtain a polypropylene composite flame retardant material with good flame retardant and mechanical properties.

[0040] Example 3

[0041] This embodiment 3 provides a method for preparing a polypropylene composite flame retardant material, the method comprising the following specific steps:

[0042] S1. Preparation of dispersion: 10.0 g of magnesium hydroxide powder was weighed and placed in a 100 ml three-necked flask, and then 40.0 ml of 75.0% ethanol aqueous solution (ethanol solution A) was added to the flask, followed by ultrasonic dispersion at 45° C. for 15 minutes to obtain a dispersion;

[0043] S2. Preparation of composite modified liquid: 0.2 g of sodium oleate (modifier A) and 0.1 g of silane coupling agent KH550 (modifier B) were weighed and mixed in an ethanol aqueous solution (ethanol solution B) with a mass fraction of 75.0%, thereby preparing a composite modified liquid;

[0044] S3, preparation of composite modified magnesium hydroxide flame retardant: under the condition of a constant temperature water bath at 55°C, the composite modified liquid was added dropwise into the dispersion liquid to react for 25 minutes, cooled to room temperature after the reaction, and then the product was filtered, and then washed with deionized water and anhydrous ethanol for 3 times respectively, dried in a natural environment, ground into powder, and passed through an 80-mesh sieve to obtain a composite modified magnesium hydroxide flame retardant;

[0045] S4. Preparation of polypropylene composite flame retardant material: 1.0g of cellulose acetate, 15.0g of composite modified magnesium hydroxide flame retardant and 40.0g of polypropylene were melt-blended at 190°C for 15 minutes, and then pressed in a flat vulcanizer for 12 minutes, with the pressing temperature set to 180°C and the pressure set to 12.0MPa, and then cold-pressed for 3 minutes and cured at room temperature for 2 hours to obtain a polypropylene composite flame retardant material with good flame retardant and mechanical properties.

[0046] Comparative Example 1

[0047] Comparative Example 1 provides a method for preparing a polypropylene flame retardant material, the method comprising the following specific steps:

[0048] S1. Preparation of dispersion: 10.0 g of magnesium hydroxide powder was weighed and placed in a 100 ml three-necked flask, and then 50.0 ml of 80.0% ethanol aqueous solution (ethanol solution A) was added to the flask, followed by ultrasonic dispersion at 50° C. for 10 minutes to obtain a dispersion;

[0049] S2. Preparation of composite modified liquid: 0.15 g of sodium oleate (modifier A) and 0.15 g of silane coupling agent KH550 (modifier B) were weighed and mixed in an ethanol aqueous solution (ethanol solution B) with a mass fraction of 80.0%, thereby preparing a composite modified liquid;

[0050] S3, preparation of composite modified magnesium hydroxide flame retardant: under the condition of a constant temperature water bath at 50°C, the composite modified liquid was added dropwise into the dispersion liquid to react for 20 minutes, cooled to room temperature after the reaction, and then the product was filtered, and then washed twice with deionized water and anhydrous ethanol respectively, dried in a natural environment, ground into powder, and passed through a 100-mesh sieve to obtain a composite modified magnesium hydroxide flame retardant;

[0051] S4. Preparation of polypropylene flame retardant material: 10.0 g of composite modified magnesium hydroxide flame retardant and 25.0 g of polypropylene were melt-blended at 200°C for 10 minutes, and then pressed in a flat vulcanizer for 10 minutes, with the pressing temperature set to 200°C and the pressure set to 15.0 MPa, and then cold-pressed for 3 minutes and cured at room temperature for 3 hours to obtain a polypropylene flame retardant material.

[0052] The difference between Comparative Example 1 and Example 1 is that no acetate fiber is added in Comparative Example 1, and the other conditions are the same as those in Example 1.

[0053] Comparative Example 2

[0054] Comparative Example 2 provides a method for preparing a polypropylene composite flame retardant material B, which comprises the following specific steps:

[0055] S1. Preparation of dispersion: 10.0 g of magnesium hydroxide powder was weighed and placed in a 100 ml three-necked flask, and then 50.0 ml of 80.0% ethanol aqueous solution (ethanol solution A) was added to the flask, followed by ultrasonic dispersion at 50° C. for 10 minutes to obtain a dispersion;

[0056] S2. Preparation of modified liquid B: 0.15 g of silane coupling agent KH550 (modifier B) was added to an ethanol aqueous solution (ethanol solution B) with a mass fraction of 80.0% to prepare modified liquid B;

[0057] S3, preparation of modified magnesium hydroxide flame retardant B: under the condition of a constant temperature water bath at 50° C., the modified liquid B was added dropwise into the dispersion liquid to react for 20 minutes, cooled to room temperature after the reaction, and then the product was filtered, and then washed twice with deionized water and anhydrous ethanol respectively, dried in a natural environment, ground into powder, and passed through a 100-mesh sieve to obtain modified magnesium hydroxide flame retardant B;

[0058] S4. Preparation of polypropylene composite flame retardant material B: 1.0 g of cellulose acetate, 10.0 g of modified magnesium hydroxide flame retardant B and 25.0 g of polypropylene were melt-blended at 200°C for 10 minutes, and then pressed in a flat vulcanizer for 10 minutes, with the pressing temperature set to 200°C and the pressure set to 15.0 MPa, and then cold-pressed for 3 minutes and cured at room temperature for 3 hours to obtain polypropylene composite flame retardant material B.

[0059] The difference between Comparative Example 2 and Example 1 is that in Comparative Example 2, only silane coupling agent KH550 is used to modify magnesium hydroxide, and sodium oleate is not used for modification. The other conditions of Comparative Example 2 are the same as those of Example 1.

[0060] Comparative Example 3

[0061] Comparative Example 3 provides a method for preparing a polypropylene composite flame retardant material A, which comprises the following specific steps:

[0062] S1. Preparation of dispersion: 10.0 g of magnesium hydroxide powder was weighed and placed in a 100 ml three-necked flask, and then 50.0 ml of 80.0% ethanol aqueous solution (ethanol solution A) was added to the flask, followed by ultrasonic dispersion at 50° C. for 10 minutes to obtain a dispersion;

[0063] S2. Preparation of modified liquid A: Weigh 0.15 g of sodium oleate (modifier A) and add it to an ethanol aqueous solution (ethanol solution A) with a mass fraction of 80.0% to prepare modified liquid A;

[0064] S3, preparation of modified magnesium hydroxide flame retardant A: under the condition of a constant temperature water bath at 50°C, the modified liquid A was added dropwise into the dispersion liquid to react for 20 minutes, cooled to room temperature after the reaction, and then the product was filtered, and then washed twice with deionized water and anhydrous ethanol respectively, dried in a natural environment, ground into powder, and passed through a 100-mesh sieve to obtain modified magnesium hydroxide flame retardant A;

[0065] S4. Preparation of polypropylene composite flame retardant material A: 1.0 g of cellulose acetate, 10.0 g of modified magnesium hydroxide flame retardant A and 25.0 g of polypropylene were melt-blended at 200°C for 10 minutes, and then pressed in a flat vulcanizer for 10 minutes, with the pressing temperature set to 200°C and the pressure set to 15.0 MPa, and then cold-pressed for 3 minutes and cured at room temperature for 3 hours to obtain polypropylene composite flame retardant material A.

[0066] The difference between Comparative Example 3 and Example 1 is that in Comparative Example 3, only sodium oleate is used to modify the magnesium hydroxide, and silane coupling agent KH550 is not used for modification. The other conditions of Comparative Example 3 are the same as those of Example 1.

[0067] test:

[0068] (1) The hydrophobic properties of the modified magnesium hydroxide samples obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were tested, and the results were as follows:

[0069] sample Contact angle / ° Activation index / % Example 1 111.5 60.02 Example 2 150.5° 98.32％ Example 3 135.8° 78.54％ Comparative Example 1 150.5° 98.32％ Comparative Example 2 76.2° 42.20％ Comparative Example 3 102.0° 65.75％

[0070] It can be seen from the test results in the above table that the water contact angles of the composite modified magnesium hydroxide flame retardants of Examples 1 to 3 and Comparative Example 1 are significantly larger, indicating that they have good hydrophobicity, which indicates that the composite modified magnesium hydroxide of the present invention has better hydrophobicity and can have better flame retardant properties.

[0071] (2) The raw material magnesium hydroxide used in Example 1 and the composite modified magnesium hydroxide obtained after modification were subjected to infrared spectroscopy measurement, and the results are as follows: Figure 1 As shown in the modified magnesium hydroxide spectrum, Si-O-Mg (1030 cm -1 ) and the C=0 stretching vibration absorption peak of sodium oleate (1555cm -1 )

[0072] (3) The flame retardant properties and mechanical properties of the polypropylene composite flame retardant materials obtained in the above Examples 1 to 3 and Comparative Examples 1 to 3 were compared with pure polypropylene. The test results are as follows:

[0073] sample Oxygen Index Tensile Strength Impact strength Elongation at break Example 1 26.0％ 36.9MPa <![CDATA[10.1kJ.m -2 ]]> 740％ Example 2 27.8％ 38.6MPa <![CDATA[12.7kJ.m -2 ]]> 830％ Example 3 25.9％ 35.7MPa <![CDATA[10.7kJ.m -2 ]]> 793％ Comparative Example 1 25.2％ 24.2MPa <![CDATA[3.6kJ.m -2 ]]> 560％ Comparative Example 2 19.2％ 27.8MPa <![CDATA[7.0kJ.m -2 ]]> 770％ Comparative Example 3 19.6％ 26.3MPa <![CDATA[8.4kJ.m -2 ]]> 690％ Pure Polypropylene 17.4％ 24.7MPa <![CDATA[9.2kJ.m -2 ]]> 670％

[0074] From the test results of oxygen index in the above table, it can be seen that the oxygen index of the polypropylene composite flame retardant material obtained after the composite modification of magnesium hydroxide in Examples 1 to 3 and Comparative Example 1 is significantly higher than the oxygen index of the polypropylene composite flame retardant material obtained after the single modification of magnesium hydroxide in Comparative Example 2 and Comparative Example 3, which shows that the composite modified magnesium hydroxide flame retardant prepared by the present invention has a significant improvement in the flame retardant properties of the polypropylene material. At the same time, compared with the oxygen index of the polypropylene composite flame retardant material in Examples 1 to 3 and the oxygen index of the pure polypropylene material, it can be seen that the oxygen index of Examples 1 to 3 is increased by 8.5-10.4%; and compared with the oxygen index of the polypropylene flame retardant material in Comparative Examples 2 and Comparative Examples 3 and the oxygen index of the pure polypropylene material, it can be seen that the oxygen index of Comparative Example 2 is increased by about 1.8%, and the oxygen index of Comparative Example 3 is increased by about 2.2%, and the oxygen index of the composite modified application can be increased by more than 8.5%, 8.5%>1.8%+2.2%, which shows that the composite modification of the present invention has achieved an outstanding effect of "1+1>2" compared with the single modification.

[0075] The addition of magnesium hydroxide flame retardant will cause the mechanical properties of polypropylene materials to decrease, but the addition of acetate fiber in this application can improve this situation and significantly increase the tensile strength, impact strength and elongation at break of polypropylene materials (see the table above).

[0076] The composite modified magnesium hydroxide flame retardant prepared by the present invention has good flame retardant properties for polypropylene. It is possible that the cellulose acetate and the composite modified magnesium hydroxide can effectively improve the mechanical properties of the polypropylene flame retardant material through synergistic effect.

[0077] (4) The polypropylene flame retardant material obtained in Example 1 and Comparative Example 1 and the pure polypropylene material were subjected to thermal stability tests. The test results are as follows:

[0078] sample <![CDATA[T 5％ / ℃]]> <![CDATA[T max / ℃]]> Carbon residue / % Pure Polypropylene 317 429 0.36 Comparative Example 1 394 464 17.30 Example 1 408 471 27.14

[0079] It can be seen from the test results in the above table that the polypropylene flame retardant material obtained in the present invention has better thermal stability.

[0080] (5) The polypropylene composite flame retardant material obtained in Example 1, the polypropylene flame retardant material obtained in Comparative Example 1 and the pure polypropylene material were subjected to TGA test. The results are as follows: Figure 2 As shown by Figure 2 It can be seen that the flame retardant properties of the polypropylene composite flame retardant material obtained in the present invention are significantly improved compared with pure polypropylene material.

[0081] The above are preferred embodiments of the present invention and are only used to explain the present invention, not to limit the present invention. Any obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing a polypropylene composite flame retardant material, characterized in that: The method comprises the following steps: S1. Preparation of dispersion: using magnesium hydroxide as a dispersant and dispersing it in ethanol solution A by ultrasonication to prepare a dispersion; S2. Preparation of composite modified liquid: mixing modifier A and modifier B in ethanol solution B to prepare composite modified liquid; S3, preparation of composite modified magnesium hydroxide flame retardant: adding the composite modified liquid to the dispersion liquid for reaction, filtering after the reaction, washing, drying, grinding, and obtaining the composite modified magnesium hydroxide flame retardant; S4. Preparation of polypropylene composite flame retardant material: Acetate fiber, composite modified magnesium hydroxide flame retardant and polypropylene are melt-blended, and then pressed and cured to obtain a polypropylene composite flame retardant material with good flame retardant and mechanical properties.

2. The method for preparing a polypropylene composite flame retardant material according to claim 1, characterized in that: The mass volume ratio of the magnesium hydroxide to the ethanol solution A in step S1 is 0.1-0.3 g / ml.

3. The method for preparing a polypropylene composite flame retardant material according to claim 1 or 2, characterized in that: The ethanol solution A in step S1 is an ethanol aqueous solution with a mass fraction of 75.0-85.0%; the ultrasonic dispersion time is 5-15 minutes, and the ultrasonic dispersion temperature is 45-55°C.

4. The method for preparing a polypropylene composite flame retardant material according to claim 1, characterized in that: The usage amount of the modifier A in the composite modifier liquid is 0.5-2.5% of the weight of the magnesium hydroxide, and the usage amount of the modifier B in the composite modifier liquid is 0.5-2.5% of the weight of the magnesium hydroxide.

5. The method for preparing a polypropylene composite flame retardant material according to claim 1 or 4, characterized in that: In step S2, the modifier A is sodium oleate, and the modifier B is silane coupling agent KH550.

6. The method for preparing a polypropylene composite flame retardant material according to claim 1, characterized in that: The ethanol solution B is an ethanol aqueous solution with a mass fraction of 75.0-85.0%.

7. The method for preparing a polypropylene composite flame retardant material according to claim 1, characterized in that: Step S3, preparation of composite modified magnesium hydroxide flame retardant: under the condition of 45-55° C. in a water bath, the composite modified liquid is added dropwise to the dispersion liquid to react for 15-25 minutes, filtered after the reaction, and then washed with deionized water and anhydrous ethanol for 1-3 times respectively, dried naturally, ground into powder, and passed through a 50-100 mesh sieve to obtain a composite modified magnesium hydroxide flame retardant.

8. The method for preparing a polypropylene composite flame retardant material according to claim 1, characterized in that: S4, preparation of polypropylene composite flame retardant material: melt-blending acetate fiber, composite modified magnesium hydroxide flame retardant and polypropylene at 180-220°C for 5-30 minutes, and then pressing in a flat vulcanizer for 5-15 minutes, setting the pressing temperature to 180-220°C and the pressure to 10-20MPa, and then cold pressing for 1-5 minutes, and curing at room temperature for 2-4 hours to obtain a polypropylene composite flame retardant material with good flame retardant and mechanical properties; The weight ratio of the acetate fiber, the composite modified magnesium hydroxide flame retardant and the polypropylene is (0.01-0.05):(0.05-0.4):1.

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