Sb-containing composite environment-friendly flame retardant for pp and pp flame-retardant plastic

Abstract

The application discloses a kind of PP with antimony-containing composite environment-friendly flame retardant and PP flame-retardant plastic, it is related to flame retardant technical field, the flame retardant adopts microencapsulation structure, core includes antimony trioxide, zinc oxide, magnesium hydroxide, silicon powder, spherical magnesium chloride and ferrocene, shell is low molecular weight polypropylene wax, zinc stearate and silane coupling agent, by microencapsulation treatment, the compatibility of flame retardant and polypropylene matrix, dispersibility and processing performance are significantly improved, while effectively inhibiting the problem of early decomposition and moisture absorption of flame retardant, the flame-retardant plastic has high flame-retardant grade, excellent mechanical properties and good processing stability, suitable for high-performance flame-retardant demand in the field of household appliances, automobile, packaging and the like.

Description

Technical Field

[0001] This invention relates to the field of flame retardant technology, and in particular to an antimony-containing composite environmentally friendly flame retardant for PP and flame-retardant PP plastic. Background Technology

[0002] Polypropylene (PP) is a thermoplastic resin with properties such as low density, non-toxicity, corrosion resistance, and high temperature resistance. It is widely used in home appliances, automobiles, packaging and other fields. Its flame retardant modification needs to be based on its flammability (oxygen index is only 17%-18%), and flame retardants are needed to improve its safety.

[0003] Antimony-containing flame retardants are mainly composed of antimony trioxide (Sb₂O₃) and are often used in conjunction with halogenated flame retardants (such as decabromodiphenyl ether, DBDPE). Their mechanism of action includes: generating SbX₃ (such as SbCl₃), which isolates oxygen and inhibits flame; capturing flammable free radicals; and decomposing to generate SbO· free radicals, which consume active free radicals in the gas phase.

[0004] However, inorganic flame retardants (such as Sb₂O₃, Mg(OH)₂, etc.) have high surface polarity and poor compatibility with non-polar PP resin, making them difficult to disperse uniformly. This can easily lead to: flame retardant particle aggregation, forming stress defect points, poor bonding with the matrix, and affecting the material's mechanical properties; high filler content of inorganic flame retardants will significantly increase melt viscosity, leading to processing difficulties and increased energy consumption; premature decomposition or reaction of flame retardants during processing will reduce their final flame retardant efficiency; and if different types of flame retardants cannot work synergistically at the same time and in the same area, their effectiveness will be greatly reduced. Summary of the Invention

[0005] This application provides an antimony-containing composite environmentally friendly flame retardant for PP and flame-retardant PP plastics, solving the core problems that have long existed in the development of flame-retardant plastics in the prior art, such as poor compatibility, difficult processing, large mechanical loss, low efficiency, and easy moisture absorption. It achieves efficient, stable, and long-lasting flame retardant effects without significantly sacrificing the original processing and mechanical properties of PP resin, thereby preparing high-performance flame-retardant plastics with excellent comprehensive performance.

[0006] This application provides an antimony-containing composite environmentally friendly flame retardant for PP, comprising a microencapsulated composite environmentally friendly flame retardant and decabromodiphenyl ethane; the microencapsulated composite environmentally friendly flame retardant comprises a core material and a shell material; the core material comprises antimony trioxide, zinc oxide, magnesium hydroxide, silica powder, spherical magnesium chloride, and ferrocene; the shell material comprises low molecular weight polypropylene wax, zinc stearate, and a silane coupling agent.

[0007] Furthermore, by weight, the core material contains 40-60 parts of antimony trioxide, 10-20 parts of zinc oxide, 15-35 parts of magnesium hydroxide, 10-15 parts of silica powder, 0-8 parts of spherical magnesium chloride, and 1-3 parts of ferrocene.

[0008] Further, by weight, the shell material contains 15-20 parts of low molecular weight polypropylene wax, 1-1.5 parts of zinc stearate, and 1-2 parts of silane coupling agent.

[0009] Furthermore, magnesium hydroxide includes high specific surface area flake magnesium hydroxide and low specific surface area spherical magnesium hydroxide, with a mass ratio of 3:2.

[0010] The preparation method of the above-mentioned antimony-containing composite environmentally friendly flame retardant includes the following steps:

[0011] (1) Add antimony trioxide, zinc oxide, magnesium hydroxide, silicon flame retardant, spherical magnesium chloride and ferrocene to a high-speed mixer; add silane coupling agent, mix at 90-110℃ and 1000-1200 rpm for 10-30 minutes, cool to 60-80℃, add zinc stearate, continue mixing for 5-10 minutes and discharge to obtain surface-modified composite flame retardant core powder;

[0012] (2) Heat the low molecular weight polypropylene wax to 160-170℃ to completely melt it into a liquid state; slowly and evenly add the composite flame retardant core powder into the molten polypropylene wax, and continue to shear and stir for 20-30 minutes to form a uniform suspension slurry.

[0013] (3) The slurry is quickly transferred to the cooling crystallization kettle, and the stirring is turned on and cooling water is introduced. The resulting block material is coarsely crushed and then sent to the air jet mill for crushing and grading to obtain microencapsulated composite flame retardant powder with uniform particle size distribution.

[0014] This application also provides a PP flame-retardant plastic, comprising, by weight, 70-80 parts of polypropylene resin matrix, 10-20 parts of antimony-containing composite environmentally friendly flame retardant, 5-10 parts of decabromodiphenyl ethane, and 11.8-23.8 parts of additives.

[0015] Furthermore, by weight, the polypropylene resin matrix comprises 35-40 parts of homopolymer polypropylene and 35-40 parts of random copolymer polypropylene.

[0016] Furthermore, the additives include one or more of talc, antioxidants, lubricants, light aging resistant additives, and char-forming catalysts, wherein the char-forming catalyst is sodium polystyrene sulfonate.

[0017] The preparation method of the above-mentioned flame-retardant PP plastic includes the following steps:

[0018] (1) The antimony-containing composite environmentally friendly flame retardant and decabromodiphenyl ethane are premixed in a high-speed mixer for 5-10 minutes to obtain the flame retardant premix;

[0019] (2) Polypropylene resin, flame retardant premix and additives are melt-blended, cooled and pelletized to obtain PP flame retardant plastic.

[0020] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:

[0021] By microencapsulating the composite flame retardant with low molecular weight PP-wax, and through chemical (coupling agent pretreatment) and physical (encapsulation) methods, the long-standing problems of compatibility, processability, stability and synergy in the field of plastic flame retardancy are solved simultaneously. Ultimately, while achieving a high flame retardancy rating, the excellent mechanical properties and good processing characteristics of the matrix resin are maintained to the maximum extent. Attached Figure Description

[0022] Figure 1 Infrared spectrum of composite flame retardant;

[0023] Figure 2 The XRD diffraction pattern of the composite flame retardant is shown.

[0024] Figure 3 SEM images of antimony trioxide and composite flame retardants; Detailed Implementation

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention; the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0026] Example 1: A flame-retardant PP plastic, comprising, by weight: 70-80 parts of polypropylene resin matrix, 10-20 parts of antimony-containing composite environmentally friendly flame retardant, 5-10 parts of decabromodiphenyl ethane, and 11.8-23.8 parts of additives;

[0027] The polypropylene resin matrix includes: 35-40 parts of homopolymer polypropylene and 35-40 parts of random copolymer polypropylene;

[0028] Additives include: talc powder (1250 mesh): 10-20 parts;

[0029] Antioxidant (antioxidant 1010 and antioxidant 168 are mixed in a 1:2 ratio): 0.3-0.8 parts;

[0030] Lubricant (calcium stearate): 0.5-1 part;

[0031] Light aging resistant additive (benzotriazole UV-329 and hindered amine 770 compound): 1-2 parts;

[0032] Carbonization catalyst (sodium polystyrene sulfonate, SPS): 0.5 parts;

[0033] Microencapsulated composite environmentally friendly flame retardants include core materials and shell materials;

[0034] The core material, by weight, includes: antimony trioxide (Sb₂O₃, particle size 1-2 μm): 40-60 parts; zinc oxide (ZnO, nano-sized): 10-20 parts; magnesium hydroxide (Mg(OH)₂, surface-activated, specific surface area 20-25 m²). 2 g): 15-25 parts; Silicon-based flame retardant (silicon micro powder): 10-15 parts; Spherical magnesium chloride (specific surface area 20-25m²): 15-25 parts; 2 / g): 3-8 parts; ferrocene 1-3 parts.

[0035] The shell material comprises, by weight, the following: low molecular weight polypropylene wax (PP-wax, acid value <1mgKOH / g, melting point 140-145℃): 20 parts; zinc stearate: 1.5 parts; silane coupling agent (KH-550): 1 part.

[0036] The preparation method of the above-mentioned flame-retardant PP plastic is as follows:

[0037] S1. Preparation of microencapsulated composite flame retardant: Antimony trioxide, zinc oxide, magnesium hydroxide, silicon-based flame retardant, spherical magnesium chloride, and ferrocene are added to a high-speed mixer; a silane coupling agent (pre-diluted with 90% ethanol to a 1:9 solution) is added, and the mixture is stirred at 1000-1200 rpm for 10 minutes at 90-110℃. The mixture is then cooled to 80℃, zinc stearate is added, and the mixture is stirred for another 5 minutes before being discharged to obtain the surface-modified composite flame retardant core powder; low molecular weight polypropylene wax is heated to 160-170℃ to completely melt it into a liquid state; under high-speed shearing (speed > 2000 rpm), the composite flame retardant core powder is slowly and evenly added to the molten PP wax, and the mixture is continuously sheared and stirred for 20-30 minutes to form a uniform suspension slurry;

[0038] The slurry is quickly transferred to a cooling crystallization vessel, and high-speed stirring (800-1000 rpm) is turned on while cooling water is introduced to rapidly cool the slurry to below 40°C. The resulting block material is coarsely crushed and then sent to an air jet mill for crushing and grading to obtain microencapsulated composite flame retardant powder with uniform particle size distribution.

[0039] S2. Preparation of flame retardant premix: Microencapsulated composite flame retardant powder and decabromodiphenyl ethane are premixed in a high-speed mixer for 5-10 minutes to obtain flame retardant premix;

[0040] Preparation of S3, PP flame-retardant plastic: Polypropylene resin, flame retardant premix, and additives are melt-blended (temperature settings: Zone 1 170℃, Zone 2 185℃, Zone 3 195℃, Zone 4 200℃, die head 195℃; screw speed 400-500rpm); underwater pelletizing, cooling and drying to obtain PP flame-retardant plastic.

[0041] The prepared flame-retardant material was detected by infrared spectroscopy, XRD, and SEM (the specific components are described in Experiment 6 of Example 3). Figure 1 The infrared spectrum shows characteristic absorption wavenumbers for substances such as antimony trioxide (peaks around 700 cm⁻¹ and 950 cm⁻¹), magnesium hydroxide (peak around 3700 cm⁻¹), silica fume (peaks around 900 cm⁻¹ and 1050 cm⁻¹), and zinc stearate (peak around 2850 cm⁻¹), indicating the presence of coating components.

[0042] like Figure 2 As can be seen, the XRD characteristic peaks corresponding to substances such as antimony trioxide, magnesium hydroxide, zinc oxide, and silica powder are...

[0043] like Figure 3 It is evident that the composite flame retardant obtained after treatment has a coating structure.

[0044] Example 2: The above example uses a combination of microcapsules and sodium polystyrene sulfonate to make the flame retardant material release quickly and not easily agglomerate. However, magnesium chloride absorbs moisture at low temperatures and releases water vapor at high temperatures, which impacts the char layer. Therefore, this example is further improved based on Example 1.

[0045] Magnesium chloride is removed, and magnesium hydroxide is used in amounts of 25-35 parts; surface activation treatment (etching) is performed, including high specific surface area flake magnesium hydroxide (Mg(OH)2-H), with deep etching to achieve a specific surface area of ​​20-25 μm². 2 / g and low specific surface area spherical magnesium hydroxide (Mg(OH)2-L), lightly etched, specific surface area 8-10m² 2 / g); the mass ratio of high specific surface area flake magnesium hydroxide to low specific surface area spherical magnesium hydroxide is 3:2.

[0046] Example 3: This example is a specific experimental case for verification. Except for the antimony-containing composite environmentally friendly flame retardant, decabromodiphenyl ethane, and magnesium hydroxide as the experimental group, the polypropylene resin matrix included 40 parts of homopolymer polypropylene and 40 parts of random copolymer polypropylene; the additives included: talc (1250 mesh): 15 parts; antioxidant (antioxidant 1010 and antioxidant 168 compounded in a 1:2 ratio): 0.5 parts; char-forming catalyst: 0.5 parts; lubricant (calcium stearate): 0.5 parts; light aging resistant additive (benzotriazole UV-329 compounded with hindered amine 770): 1.5 parts;

[0047] Testing included UL94 rating (3.2mm) (UL94), LOI (ISO4589-2, %), and pHRR (kW / m²). 2 (ISO5660-1, Cone Calorimeter, 50kW / m³) 2 ), THR (ISO5660-1, MJ / m 2 Carbon residue (ISO 11358, %), tensile strength (ASTM D638, MPa), flexural strength (ISO 178, MPa), impact strength (ASTM D256, kJ / m²) 2 The core formulation of the flame retardant includes a high-antimony formulation: 60 parts Sb₂O₃, 10 parts ZnO, 10 parts silica powder, and 1 part ferrocene; and a low-antimony formulation: 40 parts Sb₂O₃, 20 parts ZnO, 15 parts silica powder, and 3 parts ferrocene. The etching process involves magnesium hydroxide etching, including single etching (using a specific surface area of ​​20-25 μm² in Implementation 1). 2 The experimental groups for g of magnesium hydroxide and etching combination (Mg(OH)2-H / Mg(OH)2-L) are shown in Table 1, and the detection results are shown in Table 2.

[0048] Table 1 Experimental Grouping in Example 1

[0049]

[0050] Table 2. Detection results of Example 1

[0051]

[0052] Comparing the shelled and unshelled forms, the improvement in mechanical properties and flame retardancy after microencapsulation is clearly visible. The interfacial bonding between the flame retardant and the matrix is ​​significantly enhanced, stress is effectively transferred, and the loss of mechanical properties such as impact strength and tensile strength is reduced, while flame retardancy is increased. Replacing magnesium chloride with a mixture of high / low specific surface area magnesium hydroxide in a specific ratio is entirely feasible and superior. The two morphologies of magnesium hydroxide are not simply superimposed but play a key role in functional complementarity and synergistic effect, while simultaneously solving the problems of hygroscopicity, processability, and flame retardant efficiency.

[0053] The reason for this is that by encapsulating the composite flame retardant particles entirely with PP-wax, the surface properties of the flame retardant particles are altered, changing them from hydrophilic and highly polar to hydrophobic and non-polar, thus achieving perfect integration with the PP matrix. The molecular structure of PP-wax is completely identical to that of the PP resin matrix, both being hydrocarbon backbones with extremely low surface energy and non-polarity. It acts as a "shell" encapsulating the flame retardant core, establishing a perfect compatibility transition layer between the flame retardant and the resin, greatly improving interfacial affinity. The complete microcapsule shell forms a physical barrier, separating the flame-retardant components within the core (especially those prone to premature reaction at high temperatures, such as Sb₂O₃ and bromine-based flame retardants) from the external environment. Due to the isolation of factors such as screw shear heat and oxygen, the melting point of PP-wax (140-145℃) is lower than the processing temperature of PP resin (180-210℃). In the early stages of processing (mixing and initial melting), the shell layer remains solid, protecting the core. When it enters the high-temperature zone of the extruder, the shell layer melts, but because of its good compatibility with the resin, it will spread evenly on the surface of the flame retardant particles and integrate into the matrix. At this time, the coated flame retardant core is "released", fully mixed with the resin melt, and ready to play a flame retardant role. The interfacial bonding force between the flame retardant and the matrix is ​​significantly enhanced, stress is effectively transferred, and the loss of mechanical properties such as impact strength and tensile strength of the material is minimized. Macroscopically, this results in a more tough material that is less prone to brittle fracture.

[0054] When heated to a certain temperature (usually above 200℃), the sulfonic acid groups (-SO3Na) of sodium polystyrene sulfonate decompose, releasing acidic substances (such as SO2, SO3, etc.). These acidic substances combine with moisture in the air or moisture produced by polymer degradation to form sulfonic acid (R-SO3H); the resulting sulfonic acid (H + The donor attacks the PP molecular chain, causing it to protonate. The protonated PP chain becomes extremely unstable, and the tertiary carbon atoms on the molecular chain become reactive sites. The unstable PP chains undergo cationic cross-linking reactions to form a network structure connected by C-C bonds, which greatly increases the molecular weight of the polymer and transforms it from a linear structure to a three-dimensional network structure. Under further heating, these cross-linked network structures undergo cyclization and aromatization reactions and lose hydrogen atoms, ultimately forming a highly conjugated aromatic carbon layer with a graphite-like structure.

[0055] Mg(OH)₂-H (high specific surface area flake-like) has a huge polar surface that preferentially and strongly adsorbs any trace water molecules that may invade the environment, firmly fixing them through chemical adsorption; Mg(OH)₂-L (low specific surface area spherical) has a smooth surface and few polar sites, resulting in a very weak water adsorption capacity, mainly serving as a physical barrier and ensuring particle flowability. This ensures an extremely low free water content in the entire core powder, and water molecules that could come into contact with SPS or disrupt the interfacial bonds of the microcapsule are almost eliminated, thus fundamentally solving the processing and storage problems caused by hygroscopicity; the two morphologies of magnesium hydroxide have similar chemical properties, therefore their decomposition temperature ranges are basically the same. At the critical moment of combustion, they simultaneously endothermize and decompose, releasing a large amount of water vapor. The water vapor released by both has a synergistic effect in the early stage of char layer formation, diluting combustible gases, cooling the substrate, and interacting with the char layer generated by SPS catalysis to form a denser and tougher expanded char layer. Because the release occurs at the stage when the char layer is still plastic, it avoids the high-pressure steam violently breaking through the already formed solid char layer, unlike magnesium chloride which damages the char layer structure at an inappropriate time. The active MgO residue generated after decomposition, together with the products of SPS catalysis to char and silica powder, accumulate and cover the surface of the char layer, further strengthening and stabilizing the char layer and improving its ability to isolate oxygen and heat.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An antimony-containing composite environmentally friendly flame retardant for PP, characterized in that, The invention includes a microencapsulated composite environmentally friendly flame retardant, comprising a core material and a shell material. The core material comprises antimony trioxide, zinc oxide, magnesium hydroxide, silica powder, spherical magnesium chloride, and ferrocene. By weight, the core material contains 40-60 parts antimony trioxide, 10-20 parts zinc oxide, 15-35 parts magnesium hydroxide, 10-15 parts silica powder, 0-8 parts spherical magnesium chloride, and 1-3 parts ferrocene. The shell material comprises low molecular weight polypropylene wax, zinc stearate, and a silane coupling agent. The shell material contains 15-20 parts by weight of low molecular weight polypropylene wax, 1-1.5 parts by weight of zinc stearate, and 1-2 parts by weight of silane coupling agent. The preparation method of antimony-containing composite environmentally friendly flame retardant includes the following steps: (1) Add antimony trioxide, zinc oxide, magnesium hydroxide, silica powder, spherical magnesium chloride and ferrocene to a high-speed mixer; add silane coupling agent, mix at 90-110℃ and 1000-1200 rpm for 10-30 minutes, cool to 60-80℃, add zinc stearate, continue mixing for 5-10 minutes and discharge to obtain surface-modified composite flame retardant core powder; (2) Heat the low molecular weight polypropylene wax to 160-170℃ to completely melt it into a liquid state; slowly and evenly add the composite flame retardant core powder into the molten polypropylene wax, and continuously shear and stir for 20-30 minutes to form a uniform suspension slurry. (3) The slurry is quickly transferred to the cooling crystallization kettle, and the stirring is turned on and cooling water is introduced. The resulting block material is coarsely crushed and then sent to the air jet mill for crushing and grading to obtain microencapsulated composite flame retardant powder with uniform particle size distribution. The low molecular weight polypropylene wax has an acid value of <1 mgKOH / g and a melting point of 140-145℃. The magnesium hydroxide comprises substances with a specific surface area of ​​20-25 m². 2 / g of high specific surface area flake magnesium hydroxide and specific surface area of ​​8-10m² 2 / g of low specific surface area spherical magnesium hydroxide, with a mass ratio of 3:

2.

2. A flame-retardant PP plastic, characterized in that, The product comprises, by weight, 70-80 parts of polypropylene resin matrix, 10-20 parts of antimony-containing composite environmentally friendly flame retardant as described in claim 1, 5-10 parts of decabromodiphenyl ethane, and 11.8-23.8 parts of additives.

3. The PP flame-retardant plastic as described in claim 2, characterized in that, By weight, the polypropylene resin matrix comprises 35-40 parts of homopolymer polypropylene and 35-40 parts of random copolymer polypropylene.

4. The PP flame-retardant plastic as described in claim 2, characterized in that, The additives include one or more of talc, antioxidants, lubricants, light aging resistant additives, and char-forming catalysts.

5. The PP flame-retardant plastic as described in claim 4, characterized in that, The char-forming catalyst is sodium polystyrene sulfonate.

6. The PP flame-retardant plastic as described in claim 4, characterized in that, The preparation method includes the following steps: (1) The antimony-containing composite environmentally friendly flame retardant and decabromodiphenyl ethane are premixed in a high-speed mixer for 5-10 minutes to obtain the flame retardant premix; (2) Polypropylene resin, flame retardant premix and additives are melt-blended, cooled and pelletized to obtain PP flame retardant plastic.

Images