Low-smoke halogen-free flame-retardant polypropylene composition as well as preparation method and application thereof

Abstract

The invention provides a low-smoke halogen-free flame-retardant polypropylene composition as well as a preparation method and application thereof, and belongs to the technical field of polypropylene materials. Comprising the following components in parts by weight: 75 to 84 parts of polypropylene, 7 to 9 parts of chlorinated polyethylene, 0.2 to 0.4 part of an antioxidant, 0.1 to 0.3 part of a lubricant, 0.4 to 0.7 part of a stabilizer, 16 to 18 parts of modified aluminum hydroxide-ammonium polyphosphate, 7 to 8 parts of dipentaerythritol and 3 to 5 parts of melamine. The preparation method of the modified aluminum hydroxide-ammonium polyphosphate comprises the following steps: A1, uniformly dispersing 50g of aluminum hydroxide coated ammonium polyphosphate in 200mL of absolute ethyl alcohol to obtain dispersion liquid I; a2, 1-3 g of a coupling agent is evenly dispersed in 20 mL of absolute ethyl alcohol, stirring and dispersing are conducted for 20 min, and second dispersion liquid is obtained; and A3, adding the dispersion liquid I and the dispersion liquid II into a three-neck flask, keeping the constant temperature of 50 DEG C, stirring for 40 minutes, performing suction filtration, drying at 80 DEG C, and crushing, thereby obtaining the product. According to the invention, it is ensured that the composition can still maintain excellent mechanical properties and flame retardant properties for a long time when being practically applied to a high-humidity environment.

Description

Technical Field

[0001] The invention belongs to the technical field of polypropylene materials, and in particular relates to a low-smoke, halogen-free, flame-retardant polypropylene composition, a preparation method and application thereof. Background Art

[0002] Polypropylene is a general-purpose plastic with a large market demand. It has the characteristics of low density, high strength, good rigidity, chemical corrosion resistance, low processing energy consumption, and easy molding. However, polypropylene also has many shortcomings, such as flammability, oxygen index of only 18.5%, fast burning speed, high heat generation, easy melting and dripping, and it is easy to cause fire. This limits the application of polypropylene in the electronic and electrical, communication equipment, household appliances, automotive appliances, building materials and other industries. In order to meet the requirements of flame retardant properties, polypropylene must be flame-retardant modified. The traditional method of flame-retardant modification of polypropylene is to add halogen-containing flame retardants (such as decabromodiphenyl ether, etc.), but flame-retardant polypropylene made of such halogen-containing flame retardants usually releases corrosive gases that pollute the environment and are harmful to the human body while burning to exert flame retardant performance. Today, with the increasing emphasis on safety and environmental protection, it is increasingly unsatisfactory. Therefore, halogen-free flame-retardant modified polypropylene has become a hot spot for research and development in recent years.

[0003] For example, the Chinese invention patent with publication number CN101293984A discloses an expanded carbon flame-retardant polypropylene composition and a preparation method thereof. The composition comprises the following components: 100 parts by weight of polypropylene; 10-30 parts by weight of ammonium polyphosphate; 2.8-8.3 parts by weight of pentaerythritol; 2.8-8.3 parts by weight of melamine cyanurate; 0.5-5 parts by weight of montmorillonite; the preparation method comprises melt blending, extruding and granulating the components including the polypropylene, ammonium polyphosphate, pentaerythritol, melamine cyanurate and montmorillonite according to the component proportions. The composition of the present invention has both good flame retardant properties and good processing properties and mechanical properties.

[0004] However, due to the hygroscopicity of polypropylene, ammonium polyphosphate, etc., the composition obtained by the above preparation method, in actual applications, if it is made into products such as cables and placed in high-humidity environments such as underground tunnels near canals and lakes for a long time, its mechanical properties and flame retardant properties will decrease rapidly, affecting the use effect and lifespan. Summary of the invention

[0005] In order to solve the problems existing in the background technology, the present invention provides a low-smoke halogen-free flame-retardant polypropylene composition and its preparation method and application, ensuring that the prepared composition can still maintain excellent mechanical properties and flame retardant properties for a long time when actually used in a high-humidity environment.

[0006] In order to achieve the above-mentioned object, in a first aspect, the present invention provides a low-smoke halogen-free flame-retardant polypropylene composition, which comprises the following components by weight: 75-84 parts of polypropylene, 7-9 parts of chlorinated polyethylene, 0.2-0.4 parts of antioxidant, 0.1-0.3 parts of lubricant, 0.4-0.7 parts of stabilizer, 16-18 parts of modified aluminum hydroxide-ammonium polyphosphate, 7-8 parts of dipentaerythritol and 3-5 parts of melamine; The preparation method of the modified aluminum hydroxide-ammonium polyphosphate is as follows: A1. Evenly disperse 50 g of aluminum hydroxide-coated ammonium polyphosphate in 200 mL of anhydrous ethanol to obtain dispersion 1. A2, evenly disperse 1-3g of coupling agent in 20mL of anhydrous ethanol, stir and disperse for 20min to obtain dispersion 2; A3. Add the dispersion 1 obtained from A1 and the dispersion 2 obtained from A2 into a three-necked flask, keep the temperature at 50°C, stir for 40 minutes, filter with suction, dry at 80°C, and grind to obtain modified aluminum hydroxide-ammonium polyphosphate.

[0007] Furthermore, in A1, the preparation method of the aluminum hydroxide coated ammonium polyphosphate is as follows: A11, dissolve 6-10 g of aluminum isopropoxide in 100 mL of anhydrous ethanol, and stir until the aluminum isopropoxide is completely dissolved to obtain an aluminum isopropoxide-ethanol solution; A12, 200g of ammonium polyphosphate was dispersed in 400mL of anhydrous ethanol, and after ultrasonic dispersion for 5min, it was transferred to a 1000mL three-necked flask equipped with a thermometer, a stirring device and a reflux device, and stirred for 10min to obtain an ammonium polyphosphate-ethanol dispersion; A13. Add the aluminum isopropoxide-ethanol solution obtained in A11 to the ammonium polyphosphate-ethanol dispersion obtained in A12, then add 0.3-0.5 g of nanofiller, heat to 80°C, stir for 20 min, then add 6-10 g of distilled water dropwise, stir at 85°C for 2 h until the aluminum isopropoxide is fully hydrolyzed, filter with suction, and dry to obtain aluminum hydroxide-coated ammonium polyphosphate.

[0008] Furthermore, in A13, the nanofiller includes nano-silicon dioxide and / or single-walled carbon nanotubes.

[0009] Furthermore, in A2, the coupling agent includes any one of γ-mercaptopropyltrimethoxysilane, vinyltriethoxysilane, and vinyltrimethoxysilane.

[0010] Furthermore, the lubricant includes one of polyethylene wax, microcrystalline wax, and zinc stearate, or a mixture of at least two of them.

[0011] Furthermore, the stabilizer includes aluminum oxide and / or magnesium oxide.

[0012] Furthermore, the antioxidant includes composite antioxidant B215 or antioxidant 1010.

[0013] In a second aspect, the present invention provides a method for preparing the above-mentioned low-smoke halogen-free flame-retardant polypropylene composition, comprising the following steps: S1. Add polypropylene, chlorinated polyethylene, antioxidant, lubricant, stabilizer, modified aluminum hydroxide-ammonium polyphosphate, dipentaerythritol and melamine into a mixer and mix for 3-5 minutes to obtain a mixture; S2. The mixed material obtained in S1 is put into a twin-screw compounding extruder, compounded and extruded at 180-220° C. to form strips, water-cooled, pelletized, and dried to obtain a low-smoke, halogen-free, flame-retardant polypropylene composition.

[0014] In a third aspect, the present invention provides an application of the low-smoke halogen-free flame-retardant polypropylene composition for preparing a cable.

[0015] This application has the following beneficial effects: 1. The polypropylene of the present invention is used as a base resin to provide the basic framework and physical properties of the material. Chlorinated polyethylene is used as a compatibilizer to improve the compatibility of polypropylene with other non-polar materials. The antioxidant, lubricant and stabilizer work together to protect the stability and durability of the material during processing and use. The modified aluminum hydroxide-ammonium polyphosphate is used as a high-efficiency flame retardant. It can achieve a flame retardant effect alone. Through surface modification, the interface interaction with the polypropylene matrix is ​​improved, thereby further improving the mechanical properties (tensile strength) and flame retardant properties. In addition, the modified aluminum hydroxide-ammonium polyphosphate can also be combined with dipentaerythritol and melamine to form an expanded carbon layer to isolate oxygen and heat, thereby further improving the flame retardant properties. Experimental verification has shown that the addition of nanofillers, the coating of ammonium polyphosphate with aluminum hydroxide, and the modification of coupling agents can respectively improve the mechanical properties (tensile strength), flame retardancy, and moisture resistance of the composite material, and that there is a specific synergistic relationship between the three. The order of participation in the relevant preparation steps cannot be easily changed, ensuring that the composite material can maintain excellent mechanical properties and flame retardancy for a long time when used in a high-humidity environment.

[0016] 2. In the preparation of modified aluminum hydroxide-ammonium polyphosphate, the hydrolysis reaction of aluminum isopropoxide forms an aluminum hydroxide coating layer on the surface of ammonium polyphosphate, which can effectively prevent moisture from penetrating into the flame retardant, which is particularly important in high humidity environments. This inorganic-inorganic composite material structure can improve the thermal stability and hydrolysis resistance of the material; the addition of nanofillers can provide additional reinforcement effects, improve the mechanical properties of the material, and further improve the thermal stability and flame retardant properties of the material; The surface modification of aluminum hydroxide coated ammonium polyphosphate by coupling agent can enhance the interaction between inorganic flame retardant and organic polymer matrix, help improve the dispersibility of flame retardant in polypropylene, so as to more effectively exert its flame retardant effect; it can also reduce the stress concentration between filler and matrix, so that the material can distribute the load more evenly when subjected to external force, thereby achieving the effect of improving the overall mechanical properties (tensile strength) of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 , a comparative trend graph of tensile strength test data and a comparative trend graph of limiting oxygen index test data of the polypropylene compositions obtained in Examples 1-8 of the present invention and Comparative Examples 1-10; Figure 2 , a comparative trend graph of the tensile strength loss rate and the limiting oxygen index loss rate of the polypropylene compositions obtained in Examples 1-8 of the present invention and Comparative Examples 1-10 after being immersed in water at 65° C. for 7 days; Figure 3 , a trend chart comparing smoke density test data of the polypropylene compositions obtained from Examples 1-8 of the present invention and Comparative Examples 1-10. DETAILED DESCRIPTION

[0018] The present application is further described in detail below with reference to the embodiments.

[0019] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are all commercially available.

[0020] Example 1: A low-smoke halogen-free flame-retardant polypropylene composition, comprising the following components in parts by weight: 80 parts of polypropylene, 8 parts of chlorinated polyethylene, 0.3 parts of antioxidant, 0.2 parts of lubricant, 0.5 parts of stabilizer, 17 parts of modified aluminum hydroxide-ammonium polyphosphate, 7.5 parts of dipentaerythritol and 4 parts of melamine.

[0021] Among them, polypropylene (Zhenhai Petrochemical E140) and chlorinated polyethylene (Shandong Yaxing 135A (6000 type)) were purchased from Yuyao Tenggui Plastic Co., Ltd.; antioxidant (BASF B215) was purchased from Shanghai Jingyan Chemical Co., Ltd.; lubricant polyethylene wax (H110) was purchased from Henan Anar Industrial Co., Ltd.; stabilizer heavy magnesium oxide was purchased from Shandong Jiuzhong Chemical Co., Ltd.; dipentaerythritol (industrial grade) was purchased from Jiangsu Liyang Ruiyang Chemical Co., Ltd.; melamine (Zhongyuan Dahua, superior grade) was purchased from Henan Bafos Chemical Products Co., Ltd.

[0022] The preparation method of the low-smoke halogen-free flame-retardant polypropylene composition comprises the following steps: S1. Add polypropylene, chlorinated polyethylene, antioxidant, lubricant, stabilizer, modified aluminum hydroxide-ammonium polyphosphate, dipentaerythritol and melamine into a mixer and mix for 4 minutes to obtain a mixture.

[0023] S2, putting the mixture obtained in S1 into a twin-screw extruder, extruding strands at 180-220°C, water cooling, pelletizing, and drying to obtain a low-smoke, halogen-free, flame-retardant polypropylene composition. Specifically, the temperature of the twin-screw extruder from the feeding section to the die is 180°C, 190°C, 190°C, 205°C, 220°C, 220°C, 210°C, 200°C, and 195°C, respectively.

[0024] The low-smoke halogen-free flame-retardant polypropylene composition can be used for preparing cables.

[0025] The preparation method of modified aluminum hydroxide-ammonium polyphosphate is as follows: A1. Evenly disperse 50 g of aluminum hydroxide-coated ammonium polyphosphate in 200 mL of anhydrous ethanol to obtain dispersion 1.

[0026] A2, 2g of coupling agent was uniformly dispersed in 20mL of anhydrous ethanol, and stirred for 20min to obtain dispersion 2. The coupling agent was vinyltrimethoxysilane.

[0027] A3. Add the dispersion 1 obtained from A1 and the dispersion 2 obtained from A2 into a three-necked flask, stir at a constant temperature of 50°C and a speed of 60r / min for 40 minutes, filter with suction, dry at 80°C, and grind to obtain modified aluminum hydroxide-ammonium polyphosphate.

[0028] In A1, the preparation method of aluminum hydroxide coated ammonium polyphosphate is as follows: A11, 8g of aluminum isopropoxide was dissolved in 100mL of anhydrous ethanol, and stirred until the aluminum isopropoxide was completely dissolved to obtain an aluminum isopropoxide-ethanol solution. The aluminum isopropoxide was purchased from Shandong Suihua Biotechnology Co., Ltd.

[0029] A12, 200g of ammonium polyphosphate was dispersed in 400mL of anhydrous ethanol, and after ultrasonic dispersion for 5min, it was transferred to a 1000mL three-necked flask equipped with a thermometer, a stirring device and a reflux device, and stirred for 10min to obtain an ammonium polyphosphate-ethanol dispersion. Among them, ammonium polyphosphate (industrial grade 323 type) was purchased from Lianxuan Chemical Industry and Commerce Bank, Jinshui District, Zhengzhou City.

[0030] A13, add the aluminum isopropoxide-ethanol solution obtained in A11 to the ammonium polyphosphate-ethanol dispersion obtained in A12, then add 0.4g of nano-silicon dioxide, heat to 80°C, stir at 55r / min for 20min, then add 8g of distilled water dropwise, heat to 85°C, stir at 55r / min for 2h, until the aluminum isopropoxide is fully hydrolyzed, filter, and dry to obtain aluminum hydroxide-coated ammonium polyphosphate. Among them, nano-silicon dioxide was purchased from Hubei Huifu Nanomaterial Co., Ltd.

[0031] Example 2: The difference between this example and Example 1 is that a low-smoke halogen-free flame-retardant polypropylene composition comprises the following components, by weight: 75 parts of polypropylene, 7 parts of chlorinated polyethylene, 0.2 parts of antioxidant, 0.1 parts of lubricant, 0.4 parts of stabilizer, 16 parts of modified aluminum hydroxide-ammonium polyphosphate, 7 parts of dipentaerythritol and 3 parts of melamine.

[0032] Example 3: The difference between this example and Example 1 is that a low-smoke halogen-free flame-retardant polypropylene composition comprises the following components in parts by weight: 84 parts of polypropylene, 9 parts of chlorinated polyethylene, 0.4 parts of antioxidant, 0.3 parts of lubricant, 0.7 parts of stabilizer, 18 parts of modified aluminum hydroxide-ammonium polyphosphate, 8 parts of dipentaerythritol and 5 parts of melamine.

[0033] Example 4: The difference between this example and Example 1 is that: a low-smoke halogen-free flame-retardant polypropylene composition, calculated by weight, includes the following components: 84 parts of polypropylene, 7 parts of chlorinated polyethylene, 0.2 parts of antioxidant, 0.1 parts of lubricant, 0.4 parts of stabilizer, 18 parts of modified aluminum hydroxide-ammonium polyphosphate, 7 parts of dipentaerythritol and 3 parts of melamine.

[0034] Example 5: The difference between this example and Example 1 is that in the preparation of modified aluminum hydroxide-ammonium polyphosphate, the amount of coupling agent vinyltrimethoxysilane used is 1g.

[0035] Example 6: The difference between this example and Example 1 is that in the preparation of modified aluminum hydroxide-ammonium polyphosphate, γ-mercaptopropyltrimethoxysilane is used as a coupling agent.

[0036] Example 7: The difference between this example and Example 1 is that the preparation method of aluminum hydroxide coated ammonium polyphosphate is as follows: A11, 6 g of aluminum isopropoxide was dissolved in 100 mL of anhydrous ethanol, and stirred until the aluminum isopropoxide was completely dissolved to obtain an aluminum isopropoxide-ethanol solution. The aluminum isopropoxide was purchased from Shandong Suihua Biotechnology Co., Ltd.

[0037] A12, 200g of ammonium polyphosphate was dispersed in 400mL of anhydrous ethanol, and after ultrasonic dispersion for 5min, it was transferred to a 1000mL three-necked flask equipped with a thermometer, a stirring device and a reflux device, and stirred for 10min to obtain an ammonium polyphosphate-ethanol dispersion. Among them, ammonium polyphosphate (industrial grade 323 type) was purchased from Lianxuan Chemical Industry and Commerce Bank, Jinshui District, Zhengzhou City.

[0038] A13, add the aluminum isopropoxide-ethanol solution obtained in A11 to the ammonium polyphosphate-ethanol dispersion obtained in A12, then add 0.3g of nano-silicon dioxide, heat to 80°C, stir at 55r / min for 20min, then add 6g of distilled water dropwise, heat to 85°C, stir at 55r / min for 2h, until the aluminum isopropoxide is fully hydrolyzed, filter, and dry to obtain aluminum hydroxide-coated ammonium polyphosphate. Among them, nano-silicon dioxide was purchased from Hubei Huifu Nanomaterial Co., Ltd.

[0039] Example 8: The difference between this example and Example 1 is that the preparation method of aluminum hydroxide coated ammonium polyphosphate is as follows: A11, 10g of aluminum isopropoxide was dissolved in 100mL of anhydrous ethanol, and stirred until the aluminum isopropoxide was completely dissolved to obtain an aluminum isopropoxide-ethanol solution. The aluminum isopropoxide was purchased from Shandong Suihua Biotechnology Co., Ltd.

[0040] A12, 200g of ammonium polyphosphate was dispersed in 400mL of anhydrous ethanol, and after ultrasonic dispersion for 5min, it was transferred to a 1000mL three-necked flask equipped with a thermometer, a stirring device and a reflux device, and stirred for 10min to obtain an ammonium polyphosphate-ethanol dispersion. Among them, ammonium polyphosphate (industrial grade 323 type) was purchased from Lianxuan Chemical Industry and Commerce Bank, Jinshui District, Zhengzhou City.

[0041] A13, add the aluminum isopropoxide-ethanol solution obtained in A11 to the ammonium polyphosphate-ethanol dispersion obtained in A12, then add 0.5g of nano-silicon dioxide, heat to 80°C, stir at 55r / min for 20min, then add 10g of distilled water dropwise, heat to 85°C, stir at 55r / min for 2h, until the aluminum isopropoxide is fully hydrolyzed, filter, and dry to obtain aluminum hydroxide-coated ammonium polyphosphate. Among them, nano-silicon dioxide was purchased from Hubei Huifu Nanomaterial Co., Ltd.

[0042] Comparative Example 1: The difference between this comparative example and Example 1 is that in the preparation of aluminum hydroxide-coated ammonium polyphosphate, nano-silicon dioxide is deleted.

[0043] Specifically, the preparation method of aluminum hydroxide coated ammonium polyphosphate is as follows: A11, 8g of aluminum isopropoxide was dissolved in 100mL of anhydrous ethanol, and stirred sufficiently until the aluminum isopropoxide was completely dissolved to obtain an aluminum isopropoxide-ethanol solution. The aluminum isopropoxide was purchased from Shandong Suihua Biotechnology Co., Ltd.

[0044] A12, 200g of ammonium polyphosphate was dispersed in 400mL of anhydrous ethanol, and after ultrasonic dispersion for 5min, it was transferred to a 1000mL three-necked flask equipped with a thermometer, a stirring device and a reflux device, and stirred for 10min to obtain an ammonium polyphosphate-ethanol dispersion. Among them, ammonium polyphosphate (industrial grade 323 type) was purchased from Lianxuan Chemical Industry and Commerce Bank, Jinshui District, Zhengzhou City.

[0045] A13. Add the aluminum isopropoxide-ethanol solution obtained in A11 to the ammonium polyphosphate-ethanol dispersion obtained in A12, heat to 80°C, stir at 55 r / min for 20 min, then add 8 g of distilled water dropwise, heat to 85°C, stir at 55 r / min for 2 h, until the aluminum isopropoxide is fully hydrolyzed, filter with suction, and dry to obtain aluminum hydroxide-coated ammonium polyphosphate.

[0046] Comparative Example 2: The difference between this comparative example and Example 1 is that the aluminum hydroxide-coated ammonium polyphosphate is replaced by ammonium polyphosphate, that is, the modified aluminum hydroxide-ammonium polyphosphate is replaced by modified ammonium polyphosphate.

[0047] Specifically, a low-smoke halogen-free flame-retardant polypropylene composition includes the following components by weight: 80 parts of polypropylene, 8 parts of chlorinated polyethylene, 0.3 parts of antioxidant, 0.2 parts of lubricant, 0.5 parts of stabilizer, 17 parts of modified ammonium polyphosphate, 7.5 parts of dipentaerythritol and 4 parts of melamine.

[0048] The preparation method of modified ammonium polyphosphate is as follows: A1. Evenly disperse 50 g of ammonium polyphosphate in 200 mL of anhydrous ethanol to obtain dispersion 1.

[0049] A2, 2g of coupling agent was uniformly dispersed in 20mL of anhydrous ethanol, and stirred for 20min to obtain dispersion 2. The coupling agent was vinyltrimethoxysilane.

[0050] A3. Add the dispersion 1 obtained from A1 and the dispersion 2 obtained from A2 into a three-necked flask, stir at a constant temperature of 50°C and a speed of 60r / min for 40 minutes, filter with suction, dry at 80°C, and grind to obtain modified ammonium polyphosphate.

[0051] Comparative Example 3: The difference between this comparative example and Example 1 is that the aluminum hydroxide-coated ammonium polyphosphate is replaced by a mixture of aluminum hydroxide + ammonium polyphosphate + nano-silicon dioxide, that is, the modified aluminum hydroxide-ammonium polyphosphate is replaced by a mixed modified product of aluminum hydroxide + ammonium polyphosphate + nano-silicon dioxide.

[0052] Specifically, a low-smoke halogen-free flame-retardant polypropylene composition includes the following components by weight: 80 parts of polypropylene, 8 parts of chlorinated polyethylene, 0.3 parts of antioxidant, 0.2 parts of lubricant, 0.5 parts of stabilizer, 17 parts of a mixed modified product of aluminum hydroxide + ammonium polyphosphate + nano-silicon dioxide, 7.5 parts of dipentaerythritol and 4 parts of melamine.

[0053] The preparation method of the mixed modified product of aluminum hydroxide + ammonium polyphosphate + nano silicon dioxide is as follows: A1. Evenly disperse 50 g of a mixture of aluminum hydroxide + ammonium polyphosphate + nano-silicon dioxide in 200 mL of anhydrous ethanol to obtain dispersion 1.

[0054] A2, 2g of coupling agent was uniformly dispersed in 20mL of anhydrous ethanol, and stirred for 20min to obtain dispersion 2. The coupling agent was vinyltrimethoxysilane.

[0055] A3. Add the dispersion 1 obtained from A1 and the dispersion 2 obtained from A2 into a three-necked flask, stir at a constant temperature of 50°C and a speed of 60r / min for 40 minutes, filter, dry at 80°C, and grind to obtain a mixed modified product of aluminum hydroxide + ammonium polyphosphate + nano-silicon dioxide.

[0056] In A1, the preparation method of the mixture of aluminum hydroxide + ammonium polyphosphate + nano silicon dioxide is as follows: A11. Dissolve 8 g of aluminum isopropoxide in 100 mL of anhydrous ethanol, stir until the aluminum isopropoxide is completely dissolved, and obtain an aluminum isopropoxide-ethanol solution. The aluminum isopropoxide was purchased from Shandong Suihua Biotechnology Co., Ltd. Add 8 g of distilled water dropwise, heat to 85°C, stir at a speed of 55 r / min for 2 h, until the aluminum isopropoxide is fully hydrolyzed, filter, and dry to obtain aluminum hydroxide.

[0057] A12. Mix the aluminum hydroxide obtained in A11 with 200 g of ammonium polyphosphate and 0.4 g of nano-silicon dioxide to obtain a mixture of aluminum hydroxide+ammonium polyphosphate+nano-silicon dioxide.

[0058] Comparative Example 4: The difference between this comparative example and comparative example 3 is that nano silicon dioxide is deleted.

[0059] Comparative Example 5: The difference between this comparative example and Example 1 is that the modified aluminum hydroxide-ammonium polyphosphate is replaced by aluminum hydroxide-coated ammonium polyphosphate; that is, the aluminum hydroxide-coated ammonium polyphosphate is not modified.

[0060] Specifically, a low-smoke halogen-free flame-retardant polypropylene composition includes the following components, by weight: 80 parts of polypropylene, 8 parts of chlorinated polyethylene, 0.3 parts of antioxidant, 0.2 parts of lubricant, 0.5 parts of stabilizer, 17 parts of aluminum hydroxide-coated ammonium polyphosphate, 7.5 parts of dipentaerythritol and 4 parts of melamine.

[0061] Comparative Example 6: The difference between this comparative example and comparative example 2 is that the modified ammonium polyphosphate is replaced by ammonium polyphosphate, that is, the ammonium polyphosphate is not modified.

[0062] Specifically, a low-smoke halogen-free flame-retardant polypropylene composition includes the following components by weight: 80 parts of polypropylene, 8 parts of chlorinated polyethylene, 0.3 parts of antioxidant, 0.2 parts of lubricant, 0.5 parts of stabilizer, 17 parts of ammonium polyphosphate, 7.5 parts of dipentaerythritol and 4 parts of melamine.

[0063] Comparative Example 7: The difference between this comparative example and comparative example 3 is that the mixed modified product of aluminum hydroxide + ammonium polyphosphate + nano-silicon dioxide is replaced by a mixture of aluminum hydroxide + ammonium polyphosphate + nano-silicon dioxide; that is, the mixture of aluminum hydroxide + ammonium polyphosphate + nano-silicon dioxide is not modified.

[0064] Specifically, a low-smoke halogen-free flame-retardant polypropylene composition includes the following components by weight: 80 parts of polypropylene, 8 parts of chlorinated polyethylene, 0.3 parts of antioxidant, 0.2 parts of lubricant, 0.5 parts of stabilizer, 17 parts of a mixture of aluminum hydroxide + ammonium polyphosphate + nano-silicon dioxide, 7.5 parts of dipentaerythritol and 4 parts of melamine.

[0065] Comparative Example 8: The difference between this comparative example and comparative example 4 is that the mixed modified product of aluminum hydroxide + ammonium polyphosphate is replaced by a mixture of aluminum hydroxide + ammonium polyphosphate; that is, the mixture of aluminum hydroxide + ammonium polyphosphate is not modified.

[0066] Specifically, a low-smoke halogen-free flame-retardant polypropylene composition includes the following components by weight: 80 parts of polypropylene, 8 parts of chlorinated polyethylene, 0.3 parts of antioxidant, 0.2 parts of lubricant, 0.5 parts of stabilizer, 17 parts of a mixture of aluminum hydroxide + ammonium polyphosphate, 7.5 parts of dipentaerythritol and 4 parts of melamine.

[0067] Comparative Example 9: The difference between this comparative example and Example 1 is that the amount of chlorinated polyethylene is replaced by the amount of polypropylene.

[0068] Specifically, a low-smoke halogen-free flame-retardant polypropylene composition includes the following components, by weight: 88 parts of polypropylene, 0.3 parts of antioxidant, 0.2 parts of lubricant, 0.5 parts of stabilizer, 17 parts of modified aluminum hydroxide-ammonium polyphosphate, 7.5 parts of dipentaerythritol and 4 parts of melamine.

[0069] Comparative Example 10: The difference between this comparative example and Example 1 is that the modified aluminum hydroxide-ammonium polyphosphate is replaced by aluminum hydroxide-coated ammonium polyphosphate.

[0070] Specifically, a low-smoke halogen-free flame-retardant polypropylene composition includes the following components, measured by weight: 88 parts of polypropylene, 0.3 parts of antioxidant, 0.2 parts of lubricant, 0.5 parts of stabilizer, 17 parts of aluminum hydroxide-coated ammonium polyphosphate, 7.5 parts of dipentaerythritol and 4 parts of melamine.

[0071] Test example: Test object: Polypropylene compositions were prepared according to Examples 1-8 and Comparative Examples 1-10.

[0072] Test items and basis: tensile strength, ISO527 standard; smoke density, GB8627-2007; limiting oxygen index, GB / T2406; UL-94 vertical burning grade; performance loss rate after 7 days of immersion in 65℃ water. Among them, performance loss rate = test data before immersion - test data after immersion / test data before immersion * 100%.

[0073] Test results: See Table 1.

[0074] Table 1. Test data of the experimental example

[0075] Result analysis: Analyze Examples 1-8 and combine the data in Table 1 and Figure 1-3 It can be seen that the tensile strength of the polypropylene composition prepared by the present invention is as high as 31.1MPa or more, the limiting oxygen index is as high as 33.1% or more, the smoke density is lower than 51, and the UL-94 vertical combustion grade is V-0; after being soaked in water at 65°C for 7 days, the tensile strength loss rate is lower than 4.14%, and the limiting oxygen index loss rate is lower than 5.91%. It shows that the polypropylene composition prepared by the present invention has excellent mechanical properties, flame retardant properties and moisture resistance, and can ensure that when it is used in a high humidity environment, it still maintains excellent mechanical properties and flame retardant properties for a long time.

[0076] Analyze Example 1 and Comparative Examples 1-8 and combine the data in Table 1 and Figure 1-3 It can be seen that the addition of nanofillers, the coating of ammonium polyphosphate with aluminum hydroxide, and the modification of coupling agents can all improve the mechanical properties (tensile strength), flame retardancy, and moisture resistance (as reflected in the tensile strength and limiting oxygen index loss rate after immersion in water at 65°C for 7 days) of the prepared composition, and there is a specific synergistic relationship between the three, which are effective in synergy. The nanofiller (nano-silica) must be added after the aluminum isopropoxide-ethanol solution and the ammonium polyphosphate-ethanol dispersion are mixed, so that the aluminum isopropoxide will be preferentially adsorbed on the surface of the ammonium polyphosphate and then hydrolyzed to form aluminum hydroxide, thereby forming aluminum hydroxide-coated ammonium polyphosphate; the coupling agent modification must be performed after the aluminum hydroxide-coated ammonium polyphosphate is formed; if the nanofiller addition method is changed (direct physical mixing), or the aluminum hydroxide coating structure of the ammonium polyphosphate is changed (direct physical mixing), or the coupling agent modification treatment object is changed (directly modifying the ammonium polyphosphate, aluminum hydroxide, and nano-silica), the results will lead to different degrees of reduction in the tensile strength and limiting oxygen index of the obtained composition, and at the same time, the tensile strength loss rate and limiting oxygen index loss rate of the obtained composition after immersion in water at 65°C for 7 days will increase to different degrees.

[0077] Analyze Example 1 and Comparative Examples 9-10 and combine the data in Table 1 and Figure 1-3 It can be seen that the use of polypropylene as a base resin and chlorinated polyethylene (addition) together, although it will lead to a slight decrease in the tensile strength of the obtained composition, can also increase the limiting oxygen index and improve moisture resistance (reduce the tensile strength loss rate and limiting oxygen index loss rate of the obtained composition after immersion in water at 65°C for 7 days); In addition, there is a synergistic effect between the (addition) co-use of chlorinated polyethylene and the modification treatment of the coupling agent, which can achieve the effect of synergistically improving the tensile strength and limiting oxygen index of the prepared composition, and can also achieve the effect of synergistically improving the moisture resistance of the prepared composition (reducing the tensile strength loss rate and limiting oxygen index loss rate of the prepared composition after immersion in water at 65°C for 7 days).

[0078] The order of participation in the relevant preparation steps cannot be easily changed to ensure that the prepared composite material can maintain excellent mechanical properties and flame retardant properties for a long time when used in a high humidity environment.

[0079] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0080] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A low-smoke, halogen-free, flame-retardant polypropylene composition, characterized in that: The composition comprises the following components by weight: 75-84 parts of polypropylene, 7-9 parts of chlorinated polyethylene, 0.2-0.4 parts of antioxidant, 0.1-0.3 parts of lubricant, 0.4-0.7 parts of stabilizer, 16-18 parts of modified aluminum hydroxide-ammonium polyphosphate, 7-8 parts of dipentaerythritol and 3-5 parts of melamine; The preparation method of the modified aluminum hydroxide-ammonium polyphosphate is as follows: A1. Evenly disperse 50 g of aluminum hydroxide-coated ammonium polyphosphate in 200 mL of anhydrous ethanol to obtain dispersion 1. A2, evenly disperse 1-3g of coupling agent in 20mL of anhydrous ethanol, stir and disperse for 20min to obtain dispersion 2; A3. Add the dispersion 1 obtained from A1 and the dispersion 2 obtained from A2 into a three-necked flask, keep the temperature at 50°C, stir for 40 minutes, filter with suction, dry at 80°C, and grind to obtain modified aluminum hydroxide-ammonium polyphosphate.

2. The low-smoke, halogen-free, flame-retardant polypropylene composition according to claim 1, characterized in that: In A1, the preparation method of the aluminum hydroxide-coated ammonium polyphosphate is as follows: A11, dissolve 6-10 g of aluminum isopropoxide in 100 mL of anhydrous ethanol, and stir until the aluminum isopropoxide is completely dissolved to obtain an aluminum isopropoxide-ethanol solution; A12, 200g of ammonium polyphosphate was dispersed in 400mL of anhydrous ethanol, and after ultrasonic dispersion for 5min, it was transferred to a 1000mL three-necked flask equipped with a thermometer, a stirring device and a reflux device, and stirred for 10min to obtain an ammonium polyphosphate-ethanol dispersion; A13. Add the aluminum isopropoxide-ethanol solution obtained in A11 to the ammonium polyphosphate-ethanol dispersion obtained in A12, then add 0.3-0.5 g of nanofiller, heat to 80°C, stir for 20 min, then add 6-10 g of distilled water dropwise, stir at 85°C for 2 h until the aluminum isopropoxide is fully hydrolyzed, filter with suction, and dry to obtain aluminum hydroxide-coated ammonium polyphosphate.

3. The low-smoke, halogen-free, flame-retardant polypropylene composition according to claim 2, characterized in that: In A13, the nanofiller includes nano-silicon dioxide and / or single-walled carbon nanotubes.

4. The low-smoke, halogen-free, flame-retardant polypropylene composition according to claim 1, characterized in that: In A2, the coupling agent includes any one of γ-mercaptopropyltrimethoxysilane, vinyltriethoxysilane, and vinyltrimethoxysilane.

5. The low-smoke, halogen-free, flame-retardant polypropylene composition according to claim 1, characterized in that: The lubricant includes one of polyethylene wax, microcrystalline wax, and zinc stearate, or a mixture of at least two of them.

6. The low-smoke, halogen-free, flame-retardant polypropylene composition according to claim 1, characterized in that: The stabilizer includes aluminum oxide and / or magnesium oxide.

7. The low-smoke, halogen-free, flame-retardant polypropylene composition according to claim 1, characterized in that: The antioxidant includes compound antioxidant B215 or antioxidant 1010.

8. A method for preparing the low-smoke halogen-free flame-retardant polypropylene composition according to any one of claims 1 to 7, characterized in that: The steps include: S1. Add polypropylene, chlorinated polyethylene, antioxidant, lubricant, stabilizer, modified aluminum hydroxide-ammonium polyphosphate, dipentaerythritol and melamine into a mixer and mix for 3-5 minutes to obtain a mixture; S2. The mixed material obtained in S1 is put into a twin-screw compounding extruder, extruded into strips at 180-220° C., water-cooled, pelletized, and dried to obtain a low-smoke, halogen-free, flame-retardant polypropylene composition.

9. An application of the low-smoke, halogen-free, flame-retardant polypropylene composition according to any one of claims 1 to 7, characterized in that: For preparing cables.

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