Soaking-resistant low-precipitation halogen-free flame-retardant polypropylene composite material and preparation method thereof

Abstract

The invention discloses a soaking-resistant low-precipitation halogen-free flame-retardant polypropylene composite material and a preparation method thereof, and belongs to the technical field of high polymer materials. The soaking-resistant low-precipitation halogen-free flame-retardant polypropylene composite material is prepared from the following raw materials in parts by weight: 35 to 50 parts of polypropylene, 20 to 45 parts of halogen-free flame retardant, 5 to 10 parts of soaking-resistant modifier and 0.2 to 0.5 part of antioxidant, the preparation method comprises the following steps: S1, accurately weighing the polypropylene, the halogen-free flame retardant, the soaking-resistant modifier and the antioxidant, adding the weighed components into a high-speed mixer, and mixing for 3-5 minutes; s2, adding the uniformly mixed raw materials into a twin-screw extruder for melt extrusion, and cooling and pelletizing the extruded material to prepare the halogen-free flame-retardant polypropylene composite material. The polypropylene material prepared by the invention not only meets the requirements of flame retardance and low precipitation, but also has good mechanical properties and environmental friendliness.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to an immersion-resistant, low-precipitation, halogen-free, flame-retardant polypropylene composite material and a preparation method thereof. Background Art

[0002] As the application scope of polymer materials continues to expand, polypropylene (PP) has been widely used in the fields of electronics, automobiles, construction, packaging, etc. due to its excellent mechanical properties, chemical stability, processability and low production cost. However, the molecular structure of polypropylene only contains carbon and hydrogen atoms and lacks other flame retardant elements. Therefore, it is essentially a flammable material. When it encounters fire, it will burn quickly and release a large amount of heat and harmful smoke, which seriously limits its application in fields requiring flame retardant properties. Therefore, in order to improve the flame retardant properties of polypropylene, the development of a variety of flame retardant polypropylene materials has become an important research direction in the current materials field.

[0003] The traditional flame retardant method for polypropylene mainly uses halogen flame retardants, such as halogen compounds such as bromide and chloride. These halogen flame retardants inhibit flame propagation through free radical reactions during combustion. Specifically, halogen flame retardants decompose at high temperatures to produce halogen free radicals, which can capture active hydrogen free radicals and oxygen free radicals in the flame, inhibit the free radical chain reaction, and thus slow down the combustion process. In addition, halogen flame retardants have good flame retardant effects and can effectively improve the flame retardant properties of polypropylene materials at a lower addition amount. However, halogen flame retardants will produce toxic and corrosive hydrogen halide gases, such as hydrogen chloride and hydrogen bromide, during combustion. These gases pose a serious threat to the environment and human health. At the same time, their high smoke density will also lead to reduced visibility during fires, increasing the difficulty of fire rescue. In addition, halogen flame retardants have a greater impact on the mechanical properties of materials, especially when used at high contents, which will significantly reduce the toughness and strength of the materials. These defects have gradually restricted halogen flame retardants, especially in fields with high environmental protection requirements such as electronics, construction, and automobiles, where the application of halogen flame retardants is strictly restricted. Therefore, it has become an urgent need to develop environmentally friendly, safe and high-performance halogen-free flame-retardant polypropylene materials.

[0004] In response to the requirements of environmental protection policies, halogen-free flame-retardant polypropylene materials have gradually become a research hotspot. The main types of halogen-free flame retardants include metal hydroxides (such as magnesium hydroxide, aluminum hydroxide), phosphorus-based flame retardants (such as phosphates, intumescent flame retardants), etc. However, the above flame retardants are also prone to precipitation in a humid environment, thus affecting the appearance and service life of the material.

[0005] In practical applications, polypropylene materials often need to withstand a certain humidity or long-term immersion environment, especially products used in the construction, electronics, automobile and other industries, which may be exposed to moisture or water contact for a long time. Current flame-retardant polypropylene materials often encounter the phenomenon of flame retardant precipitation when used in these environments. This precipitation phenomenon not only affects the appearance of the material (such as white spots on the surface), but also may significantly reduce the flame retardant effect of the material. In addition, the precipitated flame retardant components may pollute the surrounding environment, especially in electronic and electrical equipment, where precipitates may cause electrical short circuits and equipment failures, posing safety hazards. Therefore, the development of immersion-resistant, low-precipitation flame-retardant polypropylene materials to improve their stability in hot and humid environments has become a key task in the current materials field. In this context, immersion-resistant modifiers are introduced into the formulation of flame-retardant polypropylene materials to improve the durability and stability of the materials. These immersion-resistant modifiers are usually materials with good water resistance, chemical resistance or good compatibility with polypropylene, and prevent the precipitation of flame retardants by forming a protective layer on the surface of the material. However, current research focuses on the single application of magnesium hydroxide and phosphorus flame retardants, and there is still a lack of a systematic comprehensive solution for immersion resistance and flame retardancy. Therefore, it is of great significance to explore ways to achieve immersion resistance, low precipitation and high efficiency flame retardant polypropylene materials through the synergistic effect of multiple components. Summary of the invention

[0006] In order to solve the problem that the existing technical research in the background technology is mostly focused on the single application of magnesium hydroxide and phosphorus-based flame retardants, and there is still a lack of a systematic comprehensive solution for immersion resistance and flame retardancy, the purpose of the present invention is to provide an immersion-resistant, low-precipitation, halogen-free, flame-retardant polypropylene composite material and a preparation method thereof.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] In a first aspect, the present invention provides an immersion-resistant, low-precipitation, halogen-free, flame-retardant polypropylene composite material, comprising the following raw materials in parts by weight: 35-50 parts of polypropylene, 20-45 parts of a halogen-free flame retardant, 5-10 parts of an immersion-resistant modifier and 0.2-0.5 parts of an antioxidant.

[0009] Furthermore, the polypropylene is any one or both of homopolypropylene and copolymer polypropylene.

[0010] Furthermore, the halogen-free flame retardant is a composite flame retardant of magnesium hydroxide and phosphate, including 15-30 parts by weight of magnesium hydroxide and 5-15 parts by weight of phosphate.

[0011] Halogen-free flame retardants play a core flame retardant role, and a flame retardant system composed of magnesium hydroxide and phosphate is selected. When magnesium hydroxide decomposes at high temperature, it releases water vapor and absorbs a large amount of heat, thereby reducing the surface temperature of the material and delaying combustion. At the same time, the water vapor produced by decomposition can dilute the combustible gas in the combustion zone, further reducing the propagation speed of the flame. Phosphate flame retardants form a dense carbonized layer through carbonization reaction during the combustion process, thereby isolating external heat sources and oxygen and inhibiting the spread of flames. The two can greatly improve the flame retardant efficiency of the material through synergistic effect.

[0012] Furthermore, the phosphate is expandable phosphate or ammonium polyphosphate.

[0013] Furthermore, the immersion resistance modifier is any one or both of acidified activated carbon and silicate.

[0014] After acidification, the surface of acidified activated carbon has more polar functional groups. After combining with the polypropylene matrix, these functional groups can form a dense interface layer, which effectively prevents the migration of flame retardants. In addition, acidified activated carbon can also improve the thermal stability of the material and help extend the service life of the material. Silicate modifiers, such as natural silicate powder, form a tiny lamellar structure after being dispersed in the polypropylene matrix, which not only improves the flame retardant effect of the material, but also has an inhibitory effect on the precipitation of flame retardants in hot and humid environments.

[0015] Furthermore, the acidified activated carbon is fruit shell-based acidified activated carbon powder, and the silicate is sodium silicate.

[0016] Furthermore, the antioxidant is any one of antioxidant 1010 , DLTP and antioxidant 168 .

[0017] In a second aspect, the present invention provides a method for preparing an immersion-resistant, low-precipitation, halogen-free, flame-retardant polypropylene composite material, comprising the following steps:

[0018] S1. Accurately weigh polypropylene, halogen-free flame retardant, immersion resistance modifier and antioxidant, add the weighed components into a high-speed mixer and mix for 3-5 minutes;

[0019] Mixing ensures that the components are evenly distributed and prevents separation or agglomeration during subsequent processing.

[0020] S2. Add the uniformly mixed raw materials into a twin-screw extruder for melt extrusion. The extruded materials are cooled and pelletized to prepare halogen-free flame-retardant polypropylene composite materials.

[0021] Furthermore, the barrel temperature of the twin-screw extruder in S2 is 170-210° C., the screw speed is 350-500 rpm, and the vacuum degree is controlled at -0.04 to -0.08 MPa.

[0022] Beneficial effects of the present invention:

[0023] 1. The present invention achieves a significant improvement in flame retardancy, immersion resistance, low precipitation and environmental protection of flame retardant polypropylene materials through the above technical solutions and preparation methods. The oxygen index (LO I) of the material of the present invention reaches more than 31.5%, and reaches V0 level in the UL-94 flame retardant test, meeting the flame retardant requirements of electronic appliances, automobiles and other fields; after the polypropylene material prepared by the present invention is soaked in 50°C water for 24 hours, the precipitation rate of the material is controlled within 3.2%, which is much better than the traditional halogen-free flame retardant polypropylene material, and meets the requirements for moisture and heat resistance during long-term use; through scientific formula design and the synergistic effect of each component, the material of the present invention maintains good mechanical properties in high temperature and humid and hot environments. Tests show that the tensile strength, impact strength and other mechanical properties of the material meet the industrial application standards, and are suitable for use in application scenarios requiring high strength and impact resistance; the halogen-free flame retardant and immersion resistance modifier selected by the present invention are environmentally friendly materials, and no harmful gas is released after combustion, which meets the requirements of modern environmental protection regulations. At the same time, there is no precipitation pollution during use and will not affect the surrounding environment; the addition of antioxidants effectively improves the anti-aging properties of the material, allowing the material to maintain good mechanical properties and flame retardant effects during long-term use, thereby extending the service life of the material.

[0024] 2. The present invention provides an excellent immersion-resistant, low-precipitation, halogen-free flame-retardant polypropylene composite material by compounding a polypropylene matrix with a halogen-free flame retardant, an immersion-resistant modifier, and an antioxidant. The material not only meets the requirements of flame retardancy and low precipitation, but also has good mechanical properties and environmental protection. It is suitable for use in electronic appliances, automobiles, construction and other application scenarios with strict requirements on flame retardancy and durability, and provides a new technical solution for the multifunctionality and high efficiency and environmental protection of polymer materials. DETAILED DESCRIPTION

[0025] The following will be combined with 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, not all of the embodiments. 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.

[0026] The reagents or instruments used in the present invention without indicating the manufacturer are all conventional products that can be purchased from the market.

[0027] Example 1

[0028] A halogen-free flame-retardant polypropylene composite material with low precipitation and immersion resistance comprises the following raw materials in parts by weight: 50 parts of homopolymer polypropylene, 15 parts of magnesium hydroxide and 5 parts of ammonium polyphosphate composite flame retardant, 5 parts of fruit shell acidified activated carbon powder, and 0.2 parts of antioxidant 1010.

[0029] The preparation method of the material comprises the following steps:

[0030] S1. Accurately weigh polypropylene, halogen-free flame retardant, immersion resistance modifier and antioxidant, add the weighed components into a high-speed mixer and mix for 3 minutes;

[0031] S2. The uniformly mixed raw materials are added into a twin-screw extruder for melt extrusion. The barrel temperature of the twin-screw extruder is 170°C, the screw speed is 350 rpm, and the vacuum degree is controlled at -0.04 MPa. The extruded material is cooled and pelletized to prepare a halogen-free flame-retardant polypropylene composite material.

[0032] Example 2

[0033] A halogen-free flame-retardant polypropylene composite material with low precipitation and immersion resistance comprises the following raw materials in parts by weight: 45 parts of copolymerized polypropylene, 20 parts of magnesium hydroxide and 10 parts of ammonium polyphosphate composite flame retardant, 8 parts of fruit shell acidified activated carbon powder, and 0.3 parts of antioxidant 168.

[0034] The preparation method of the material comprises the following steps:

[0035] S1. Accurately weigh polypropylene, halogen-free flame retardant, immersion resistance modifier and antioxidant, add the weighed components into a high-speed mixer and mix for 5 minutes;

[0036] S2. The uniformly mixed raw materials are added into a twin-screw extruder for melt extrusion. The barrel temperature of the twin-screw extruder is 210°C, the screw speed is 500 rpm, and the vacuum degree is controlled at -0.04 MPa. The extruded material is cooled and pelletized to prepare a halogen-free flame-retardant polypropylene composite material.

[0037] Example 3

[0038] The invention discloses an immersion-resistant, low-precipitation, halogen-free, flame-retardant polypropylene composite material, comprising the following raw materials in parts by weight: 35 parts of homopolymerized polypropylene, 20 parts of magnesium hydroxide, 15 parts of ammonium polyphosphate composite flame retardant, 8 parts of sodium silicate, and 0.4 parts of antioxidant 1010.

[0039] The preparation method of the material comprises the following steps:

[0040] S1. Accurately weigh polypropylene, halogen-free flame retardant, immersion resistance modifier and antioxidant, add the weighed components into a high-speed mixer and mix for 4 minutes;

[0041] S2. The uniformly mixed raw materials are added into a twin-screw extruder for melt extrusion. The barrel temperature of the twin-screw extruder is 200°C, the screw speed is 400 rpm, and the vacuum degree is controlled at -0.04 MPa. The extruded material is cooled and pelletized to prepare a halogen-free flame-retardant polypropylene composite material.

[0042] Example 4

[0043] The invention discloses an immersion-resistant, low-precipitation, halogen-free, flame-retardant polypropylene composite material, comprising the following raw materials in parts by weight: 35 parts of homopolymer polypropylene, 30 parts of magnesium hydroxide, 10 parts of ammonium polyphosphate composite flame retardant, 10 parts of sodium silicate, and 0.5 parts of antioxidant 1010.

[0044] The preparation method of the material comprises the following steps:

[0045] S1. Accurately weigh polypropylene, halogen-free flame retardant, immersion resistance modifier and antioxidant, add the weighed components into a high-speed mixer and mix for 4 minutes;

[0046] S2. The uniformly mixed raw materials are added into a twin-screw extruder for melt extrusion. The barrel temperature of the twin-screw extruder is 200°C, the screw speed is 400 rpm, and the vacuum degree is controlled at -0.04 MPa. The extruded material is cooled and pelletized to prepare a halogen-free flame-retardant polypropylene composite material.

[0047] Example 5

[0048] The invention discloses an immersion-resistant, low-precipitation, halogen-free, flame-retardant polypropylene composite material, comprising the following raw materials in parts by weight: 35 parts of homopolymer polypropylene, 30 parts of magnesium hydroxide, 15 parts of ammonium polyphosphate composite flame retardant, 6 parts of sodium silicate, 4 parts of fruit shell acidified activated carbon powder, and 0.5 part of antioxidant 1010.

[0049] The preparation method of the material comprises the following steps:

[0050] S1. Accurately weigh polypropylene, halogen-free flame retardant, immersion resistance modifier and antioxidant, add the weighed components into a high-speed mixer and mix for 4 minutes;

[0051] S2. The uniformly mixed raw materials are added into a twin-screw extruder for melt extrusion. The barrel temperature of the twin-screw extruder is 200°C, the screw speed is 400 rpm, and the vacuum degree is controlled at -0.04 MPa. The extruded material is cooled and pelletized to prepare a halogen-free flame-retardant polypropylene composite material.

[0052] Comparative Example 1

[0053] Compared with Example 1, this comparative example is different only in that:

[0054] A immersion-resistant, low-precipitation, halogen-free, flame-retardant polypropylene composite material comprises the following raw materials in parts by weight: 50 parts of homopolymer polypropylene, 20 parts of magnesium hydroxide flame retardant, and 0.2 parts of antioxidant 1010.

[0055] Comparative Example 2

[0056] Compared with Example 1, this comparative example is different only in that:

[0057] A halogen-free flame-retardant polypropylene composite material with low precipitation and immersion resistance comprises the following raw materials in parts by weight: 50 parts of homopolymer polypropylene, 20 parts of ammonium polyphosphate flame retardant, and 0.2 parts of antioxidant 1010.

[0058] The performance tests were conducted on the polypropylene composite materials prepared in Examples 1 to 5 and Comparative Examples 1 to 2. The test items are as follows. The test results are shown in Table 1:

[0059] 1. Oxygen index: The oxygen index is tested using XZT-100A oxygen index tester in accordance with GB / T 2406.2-2009.

[0060] 2. Vertical burning test (UL-94), tested according to GB / T 2048-2008.

[0061] 3. Immersion resistance precipitation rate: Soak the material sample in pure water at 50°C for 24 hours and test its precipitation rate.

[0062] 4. Mechanical properties test: Tensile strength is tested in accordance with GB / T 1040.2-2006; impact performance is tested in accordance with GB / T1843-2008.

[0063] 5. Thermal stability: tested by thermogravimetric analysis (TGA).

[0064] 6. Carbon Residue Rate: The carbon residue rate of the test sample at 500°C.

[0065] Table 1

[0066]

[0067] As can be seen from Table 1, the oxygen index of the polypropylene composite materials prepared in Examples 1 to 5 is 31.5% or more, the UL-94 combustion grade is V-0, the precipitation rate is within 3.2%, the tensile strength is ≥16.8MPa, and the impact strength is ≥2.8kJ / m 2 The initial decomposition temperature can reach up to 339°C, and the residual carbon rate at 500°C is over 30%. It has excellent flame retardant properties, low immersion resistance, mechanical properties and thermal stability.

[0068] Comparative Examples 1 and 2 contain only one flame retardant and no immersion resistance modifier is added, and their comprehensive performances are lower than those of Examples 1 to 5.

[0069] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0070] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A halogen-free flame-retardant polypropylene composite material with low precipitation and immersion resistance, characterized in that The invention comprises the following raw materials in parts by weight: 35-50 parts of polypropylene, 20-45 parts of halogen-free flame retardant, 5-10 parts of immersion resistance modifier and 0.2-0.5 parts of antioxidant.

2. The immersion-resistant, low-precipitation, halogen-free, flame-retardant polypropylene composite material according to claim 1, characterized in that: The polypropylene is any one or both of homopolypropylene and copolymer polypropylene.

3. The immersion-resistant, low-precipitation, halogen-free, flame-retardant polypropylene composite material according to claim 1, characterized in that: The halogen-free flame retardant is a composite flame retardant of magnesium hydroxide and phosphate.

4. The immersion-resistant, low-precipitation, halogen-free, flame-retardant polypropylene composite material according to claim 1, characterized in that: The magnesium hydroxide and phosphate composite flame retardant comprises 15-30 parts by weight of magnesium hydroxide and 5-15 parts by weight of phosphate.

5. The immersion-resistant, low-precipitation, halogen-free, flame-retardant polypropylene composite material according to claim 1, characterized in that: The phosphate is expandable phosphate or ammonium polyphosphate.

6. The immersion-resistant, low-precipitation, halogen-free, flame-retardant polypropylene composite material according to claim 1, characterized in that: The immersion resistance modifier is any one or two of acidified activated carbon and silicate.

7. The immersion-resistant, low-precipitation, halogen-free, flame-retardant polypropylene composite material according to claim 1, characterized in that: The acidified activated carbon is fruit shell-based acidified activated carbon powder, and the silicate is sodium silicate.

8. The immersion-resistant, low-precipitation, halogen-free, flame-retardant polypropylene composite material according to claim 1, characterized in that: The antioxidant is any one of antioxidant 1010, DLTP and antioxidant 168.

9. The method for preparing the immersion-resistant, low-precipitation, halogen-free, flame-retardant polypropylene composite material according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. Accurately weigh polypropylene, halogen-free flame retardant, immersion resistance modifier and antioxidant, add the weighed components into a high-speed mixer and mix for 3-5 minutes; S2. Add the uniformly mixed raw materials into a twin-screw extruder for melt extrusion. The extruded materials are cooled and pelletized to prepare halogen-free flame-retardant polypropylene composite materials.

10. The method for preparing the immersion-resistant, low-precipitation, halogen-free, flame-retardant polypropylene composite material according to claim 9, characterized in that: The barrel temperature of the twin-screw extruder in S2 is 170-210° C., the screw speed is 350-500 rpm, and the vacuum degree is controlled at -0.04 to -0.08 MPa.

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