Flame-retardant polystyrene and its preparation method

Abstract

This invention provides flame-retardant polystyrene and its preparation method, relating to the field of polymer materials technology. The flame-retardant polystyrene comprises the following components in parts by weight: 60-85 parts polystyrene, 15-25 parts composite flame retardant, 5-15 parts toughening agent, 0.1-0.5 parts antioxidant, and 0.2-1.0 parts lubricant; the composite flame retardant comprises phosphate ester flame retardants, phosphonate flame retardants, and melamine polyphosphate in a mass ratio of 1:1-3:2-5. This polystyrene exhibits excellent flame-retardant properties.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a flame-retardant polystyrene and its preparation method. Background Technology

[0002] High-impact polystyrene (HIPS) is a widely used engineering plastic. It possesses good processability and impact resistance, and its moderate cost makes it widely used in appliance housings, electronic components, and automotive interiors. However, HIPS has a low oxygen index and is classified as flammable. When ordinary HIPS burns, it produces a large number of molten droplets, which can ignite surrounding objects, posing a significant fire hazard.

[0003] Currently, flame-retardant modification of HIPS mainly involves adding flame retardants. For example, adding metal hydroxide systems (such as magnesium hydroxide and aluminum hydroxide) is low-cost and non-toxic, but the dosage is large, typically requiring more than 30% to achieve a flame-retardant effect. Furthermore, after the addition of flame retardant particles, the interface between the particles and the matrix is ​​poor, and interface defects lead to a significant decrease in the material's mechanical properties. For instance, Chinese patent CN104292731A discloses a HIPS composite material using modified magnesium hydroxide and modified aluminum hydroxide as halogen-free flame retardants, with a total composite flame retardant content as high as 30-34%, significantly negatively impacting the material's mechanical properties. Therefore, there is an urgent need to develop a flame-retardant polystyrene material that can achieve highly efficient flame retardancy while maintaining good mechanical properties. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] To address the shortcomings of existing technologies, this invention provides a flame-retardant polystyrene and its preparation method, solving the technical problem that existing flame-retardant modifications of polystyrene cannot simultaneously achieve high-efficiency flame retardancy and good mechanical properties.

[0006] (II) Technical Solution

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] The first aspect of this invention discloses a flame-retardant polystyrene, comprising the following components in parts by weight:

[0009] 60-85 parts of polystyrene

[0010] 15-25 parts of composite flame retardant

[0011] 5-15 parts toughening agent

[0012] Antioxidant 0.1-0.5 parts,

[0013] Lubricant 0.2-1.0 parts;

[0014] The composite flame retardant includes phosphate ester flame retardants, phosphonates, and melamine polyphosphates in a mass ratio of 1:1-3:2-5.

[0015] The second aspect of this invention discloses a method for preparing flame-retardant polystyrene, comprising drying and mixing the components to obtain a premix, and then melting, cooling, and drying the premix to obtain flame-retardant polystyrene.

[0016] (III) Beneficial Effects

[0017] This invention provides a flame-retardant polystyrene. Compared with the prior art, it has the following beneficial effects: This invention discloses a flame-retardant polystyrene, comprising polystyrene, a composite flame retardant, a toughening agent, an antioxidant, and a lubricant. The composite flame retardant comprises a phosphate ester flame retardant, a phosphonate flame retardant, and melamine polyphosphate in a mass ratio of 1:1-3:2-5. Under the synergistic effect of the phosphate ester flame retardant, the phosphonate flame retardant, and the melamine polyphosphate, the flame-retardant performance of the polystyrene material is improved. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] The first aspect of this application discloses a flame-retardant polystyrene, comprising 60-85 parts of polystyrene, 15-25 parts of a composite flame retardant, 5-15 parts of a toughening agent, 0.1-0.5 parts of an antioxidant, and 0.2-1.0 parts of a lubricant; wherein the composite flame retardant comprises phosphate ester flame retardants, phosphonates flame retardants, and melamine polyphosphates in a mass ratio of 1:1-3:2-5.

[0020] In this application, the composite flame retardant includes phosphate ester flame retardants, phosphinate flame retardants, and melamine polyphosphate. Melamine polyphosphate plays a role in the condensed phase, decomposing upon heating to produce polyphosphoric acid and non-combustible gas. The polyphosphoric acid dehydrates to form char, which foams and expands under the action of the non-combustible gas, forming a dense, porous expanded char layer that effectively isolates heat and oxygen. Phosphinate flame retardants release phosphorus-containing free radicals (PO·) in the gas phase, capturing key free radicals (H·, OH·) in the combustion chain reaction, thereby interrupting the combustion reaction, and simultaneously catalyzing char formation in the condensed phase. Phosphate ester flame retardants volatilize at high temperatures, releasing phosphorus-containing free radicals that enter the flame zone to quench the combustion reaction, thus making the gas phase coverage more complete. Therefore, the synergistic effect of melamine polyphosphate, phosphinate flame retardants, and phosphate ester flame retardants improves the flame retardancy of polystyrene.

[0021] In this application, the phosphate ester flame retardant is a halogen-free flame retardant with phosphorus as the core element. Specific examples of the phosphate ester flame retardant include bisphenol A bis(diphenyl phosphate) or resorcinol bis(diphenyl phosphate), but it is not limited to these. When the phosphate ester flame retardant is resorcinol bis(diphenyl phosphate), it not only volatilizes phosphorus-containing free radicals at high temperatures to quench the combustion reaction in the flame zone, resulting in a more complete gas phase coverage, but also participates in carbon layer rearrangement under heating conditions, making the carbon layer denser. This further enhances the synergistic effect of melamine polyphosphate, phosphinate flame retardant, and phosphate ester flame retardant, improving the flame retardancy of polystyrene. In this application, the phosphinate flame retardant is an organophosphorus flame retardant. Specific examples of the phosphinate flame retardant include diethylaluminum phosphinate, but it is not limited to these.

[0022] In some preferred embodiments, the flame-retardant polystyrene further includes polyphenylene ether. By introducing polyphenylene ether, when the melamine polyphosphate in the composite flame retardant decomposes at temperatures above 300°C to generate polyphosphoric acid and simultaneously releases non-flammable ammonia gas, the generated polyphosphoric acid catalyzes the dehydration and cross-linking of the polyphenylene ether to form a carbon layer. Simultaneously, the ammonia gas causes the carbon layer to foam and expand, further forming a dense, expanded carbon layer, which further insulates against heat and oxygen. The flame retardancy of the polystyrene is further improved under the synergistic effect of the composite flame retardant and polyphenylene ether. Additionally, the formed dense, expanded carbon layer prevents molten dripping. The mass fraction of the polyphenylene ether is 10-30 parts; for example, the mass fraction of the polyphenylene ether can be any value among 10 parts, 15 parts, 20 parts, and 30 parts, or any value between two values.

[0023] In some preferred embodiments, the flame-retardant polystyrene further includes an anti-dripping agent. By introducing the anti-dripping agent, when the matrix resin begins to burn and decompose, the anti-dripping agent forms a network structure and a physically cross-linked network within the matrix resin, thereby maintaining the matrix resin's morphology and preventing it from immediately melting and flowing upon heating. This effectively increases the melt viscosity and prevents rapid dripping. Simultaneously, the presence of the anti-dripping agent also provides a supporting framework for the formation of the char layer, making the char layer formed after combustion denser and more continuous, thus improving the flame retardancy of the polystyrene. The anti-dripping agent is present in an amount of 0.2-1.0 parts by weight; for example, the amount of anti-dripping agent can be any value from 0.2 parts, 0.5 parts, 0.8 parts, 1.0 parts, or any value between two such values.

[0024] The toughening agent is selected from styrene-ethylene-butene-styrene block copolymer or styrene-butadiene-styrene block copolymer.

[0025] In some preferred embodiments, the toughening agent is a styrene-ethylene-butene-styrene block copolymer with a number-average molecular weight of 80,000-150,000. The styrene blocks in the styrene-ethylene-butene-styrene block copolymer molecular chain are compatible with polystyrene and can form fine elastomeric particle dispersions within the polystyrene matrix. When the material is subjected to impact, these dispersions can absorb and dissipate a large amount of energy, thereby preventing crack propagation and significantly improving impact strength. Importantly, the styrene-ethylene-butene-styrene block copolymer acts as an interfacial compatibilizer, improving the bonding force between the composite flame retardant and the non-polar polystyrene matrix, resulting in more uniform dispersion of the composite flame retardant and mitigating the decline in mechanical properties caused by interfacial defects. The styrene-ethylene-butene-styrene block copolymer molecular chain with a number-average molecular weight of 80,000-150,000 is saturated, exhibits good thermal stability, and is not easily degraded within the high-temperature processing window of polystyrene (typically around 200°C), thus stably reducing the negative impact of the composite flame retardant on the mechanical properties of the material. The saturated structure of the styrene-ethylene-butene-styrene block copolymer improves its compatibility with composite flame retardants, facilitating flame retardant dispersion and significantly mitigating the decline in mechanical properties of flame-retardant polystyrene caused by interfacial defects. The number-average molecular weight of the styrene-ethylene-butene-styrene block copolymer is 80,000-150,000. As an example, the number-average molecular weight of the styrene-ethylene-butene-styrene block copolymer can be any value among 80,000, 100,000, 120,000, 130,000, and 150,000, or any value in between.

[0026] In this application, the antioxidant is selected from a compound of hindered phenolic antioxidants and phosphite antioxidants.

[0027] In this application, the lubricant is selected from calcium stearate or polyethylene wax, but is not limited thereto.

[0028] To better understand the above technical solution, the following will provide a detailed explanation of the above technical solution in conjunction with specific implementation methods.

[0029] The sources of the raw materials used in the embodiments and comparative examples of this invention are as follows:

[0030] High-impact polystyrene (HIPS): Chi Mei Industrial Co., Ltd., grade PH-88, melt flow index 5.5 g / 10 min (200℃, 5 kg).

[0031] Polyphenylene oxide (PPO): Bluestar Chemical New Materials Co., Ltd., intrinsic viscosity is 0.45 dL / g.

[0032] Resorcinol bis(diphenyl phosphate) RDP: Zhejiang Wansheng Co., Ltd., industrial grade, purity ≥99%.

[0033] Aluminum diethylphosphonate (ADP): Clariant Chemicals (China) Co., Ltd., brand name Exolit OP 1230.

[0034] Melamine polyphosphate (MPP): Shandong Yinglang Chemical Co., Ltd., CAS: 15541-60-3, average particle size (D50) is 15μm.

[0035] Melamine cyanurate (MCA): Hebei Naiang Flame Retardant Materials Co., Ltd., CAS: 37640-57-6.

[0036] Styrene-ethylene-butene-styrene block copolymer (SEBS): Kraton Pharmaceuticals, USA, number average molecular weight 120,000, grade G1654.

[0037] Styrene-butadiene-styrene block copolymer (SBS): Baling Petrochemical, number average molecular weight 60,000, grade YH-792.

[0038] Polytetrafluoroethylene (PTFE): Shanghai Sanai New Materials Co., Ltd., grade TF-9207, SAN-coated type.

[0039] Antioxidants: The hindered phenolic antioxidant is β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate octadecyl ester, selected from BASF GmbH, Germany; the phosphite antioxidant is bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate, selected from BASF GmbH, Germany. The hindered phenolic antioxidant and the phosphite antioxidant are compounded in a mass ratio of 1:1.

[0040] Lubricant: Pentaerythritol stearate is supplied by Zhaoqing Sendeli Chemical Industry Co., Ltd.

[0041] Example 1

[0042] This embodiment provides a flame-retardant, high-impact polystyrene material, comprising the following components in parts by weight:

[0043] 70 HIPS

[0044] 15 PPO copies

[0045] The composite flame retardant consists of 2 parts RDP, 6 parts ADP, and 10 parts MPP.

[0046] SEBS 8 copies,

[0047] 0.5 parts PTFE

[0048] Antioxidant 0.3 parts,

[0049] 0.5 parts of lubricant.

[0050] The preparation method of flame-retardant and high-impact polystyrene material includes the following steps:

[0051] (1) Dry HIPS, PPO and SEBS at 85°C for 5 hours; dry RDP, ADP, MPP, PTFE, antioxidant and lubricant at 70°C for 3 hours.

[0052] (2) Weigh each raw material according to the formula ratio, put them into a high-speed mixer and mix for 8 minutes to obtain a premix.

[0053] (3) Add the premixed material to a twin-screw extruder for melt blending and extrusion. The temperatures of each zone of the extruder are set as follows: Zone 1 185℃, Zone 2 195℃, Zone 3 205℃, Zone 4 215℃, Zone 5 225℃, and the die head temperature 215℃. The screw speed is 400 rpm.

[0054] (4) After the extrudate is cooled with water, granulated and dried, flame-retardant high-impact polystyrene material is obtained.

[0055] Example 2

[0056] The difference between this embodiment and Embodiment 1 is that the composition of the composite flame retardant is different. Specifically, the composition is: 2.6 parts RDP, 5 parts ADP, 10.4 parts MPP, and the rest is the same as in Embodiment 1.

[0057] Example 3

[0058] The difference between this embodiment and Embodiment 1 is that the composition of the composite flame retardant is different. Specifically, the composition is: 3 parts RDP, 6 parts ADP, 9 parts MPP, and the rest is the same as in Embodiment 1.

[0059] Example 4

[0060] The difference between this embodiment and Embodiment 1 is that the composition of the composite flame retardant is different. Specifically, the composition is: 3.6 parts RDP, 7.2 parts ADP, and 7.2 parts MPP. The rest is the same as in Embodiment 1.

[0061] Example 5

[0062] The difference between this embodiment and Embodiment 1 is that the composition of the composite flame retardant is different. Specifically, the composition is: 4.5 parts RDP, 4.5 parts ADP, and 9 parts MPP, with the other components the same as in Embodiment 1.

[0063] Comparative Example 1

[0064] The difference between this comparative example and Example 1 is that the composition of the composite flame retardant is different. Specifically, the composition is: 6.8 parts ADP, 11.2 parts MPP, and the rest is the same as in Example 1.

[0065] Comparative Example 2

[0066] The difference between this comparative example and Example 1 is that the composition of the composite flame retardant is different. Specifically, the composition is: 4.6 parts of RDP and 13.4 parts of ADP, with the other components the same as in Example 1.

[0067] Comparative Example 3

[0068] The difference between this comparative example and Example 1 is that the composition of the composite flame retardant is different. Specifically, the composition is: 3 parts RDP, 15 parts MPP, and the rest is the same as in Example 1.

[0069] Comparative Example 4

[0070] The difference between this comparative example and Example 1 is that it does not include PPO, and the composition of the composite flame retardant is different. The composition of the flame retardant is: 3.7 parts RDP, 11 parts ADP, 18.3 parts MPP, and the rest is the same as in Example 1.

[0071] Comparative Example 5

[0072] The difference between this comparative example and Example 1 is that it does not include the composite flame retardant, and the amount of PPO used is 33 parts, while the rest is the same as in Example 1.

[0073] Comparative Example 6

[0074] The difference between this comparative example and Example 1 lies in the composition of the composite flame retardant. Specifically, the components are: 2 parts RDP, 6 parts ADP, and 10 parts MCA, with the other components being the same as in Example 1. MCA is melamine cyanurate, which exerts its flame-retardant effect by decomposing and absorbing heat and releasing non-flammable gases.

[0075] Comparative Example 7

[0076] The difference between this comparative example and Example 1 is that it does not include PTFE; otherwise, it is the same as Example 1.

[0077] Comparative Example 8

[0078] The difference between this comparative example and Example 1 is that it does not include the toughening agent SEBS; otherwise, it is the same as Example 1.

[0079] Comparative Example 9

[0080] The difference between this comparative example and Example 1 is that the toughening agent is SBS, while the rest is the same as in Example 1.

[0081] Performance testing

[0082] The flame-retardant polystyrene materials prepared in the examples and comparative examples were subjected to the following performance tests:

[0083] 1. Vertical flammability rating: Tested according to UL94 standard, with a sample thickness of 1.6mm, and 5 samples are tested for each formulation.

[0084] 2. Limiting oxygen index: Tested according to ISO 4589-2 standard, with a sample size of 80mm×10mm×4mm.

[0085] 3. Tensile properties: Tested according to ISO 527 standard, tensile speed 50 mm / min, and the specimen size is dumbbell shape.

[0086] 4. Bending performance: Tested according to ISO 178 standard, test speed 2 mm / min, sample size 80mm×10mm×4mm.

[0087] 5. Notched impact strength: Tested according to ISO 179 standard, pendulum energy 4J, spline size 80mm×10mm×4mm, V-notch.

[0088] 6. Heat distortion temperature: Tested according to ISO 75 standard, load 1.8MPa, sample size 80mm×10mm×4mm.

[0089] The performance test results are shown in Tables 1 and 2.

[0090] Table 1. Flame retardant properties of flame-retardant polystyrene prepared in the examples and comparative examples.

[0091]

[0092] Table 2 Mechanical and thermal properties of flame-retardant polystyrene prepared in the examples and comparative examples

[0093]

[0094] As shown in Table 1, comparing Examples 1-5 with Comparative Examples 1-3, the composite flame retardant composition of Examples 1-5 includes RDP, ADP, and MPP, with a mass ratio of 1:(1-3):(2-5). This results in excellent flame retardant performance of the polystyrene material. Flame retardants lacking any one of these three components cannot achieve optimal flame retardant effects. Therefore, RDP, ADP, and MPP in a mass ratio of 1:(1-3):(2-5) have a synergistic effect in improving the flame retardant performance of polystyrene materials.

[0095] Table 1, comparing Examples 1-5 with Comparative Examples 4-5, shows that the composite flame retardant composition of Examples 1-5 includes RDP, ADP, and MPP in a mass ratio of 1:(1-3):(2-5). Furthermore, the polystyrene material exhibits excellent flame retardant properties when PPO is present. The optimal flame retardant effect cannot be achieved when PPO or the composite flame retardant is absent. Therefore, the composite flame retardant RDP / ADP / MPP and PPO have a synergistic effect in improving the flame retardancy of polystyrene materials.

[0096] As shown in Table 1, comparing Examples 1-5 with Comparative Example 6, the composite flame retardant composition of Examples 1-5 includes RDP, ADP, and MPP in a mass ratio of 1:(1-3):(2-5), resulting in excellent flame retardant properties of the polystyrene material. However, in Comparative Example 6, after replacing MPP with MCA, the flame retardant properties of the polystyrene material were poor because MCA mainly exerts its flame retardant effect through decomposition, heat absorption, and release of non-combustible gases, failing to achieve the synergistic charring effect of MPP and PPO.

[0097] Table 1, comparing Example 1 and Comparative Example 7, shows that Example 1 achieved a UL94 rating of V-0, with a limiting oxygen index of 30.8%, and no molten droplets igniting the absorbent cotton were observed during combustion. Conversely, Comparative Example 7 had a UL94 rating of V-1, a limiting oxygen index of 26.5%, produced molten droplets, and ignited the absorbent cotton. The mechanism of PTFE's role in combustion is the formation of a network structure. PTFE has a high melting point and does not immediately melt and flow when heated. When the matrix resin begins to burn and decompose, PTFE particles maintain their shape and form a physically cross-linked network within the material, effectively increasing the viscosity of the melt and preventing rapid dripping. Simultaneously, the presence of PTFE provides a supporting framework for the formation of the char layer, resulting in a denser and more continuous char layer after combustion. Therefore, PTFE can improve the flame retardancy of polystyrene materials.

[0098] As shown in Table 2, comparing Comparative Examples 5 and 8 with Example 1, the addition of toughening agent SEBS in the preparation method of this application significantly reduces the negative impact of the RDP / ADP / MPP composite flame retardant on the mechanical properties of polystyrene materials. According to Comparative Example 9, although toughening agent SBS can reduce the negative impact of the RDP / ADP / MPP composite flame retardant on the mechanical properties of polystyrene materials, its effect is less significant than that of SEBS. This is because the SEBS molecular chain is saturated, has good thermal stability, and is not easily degraded within the high-temperature processing window of PS (typically around 200℃), thus stably reducing the negative impact of the composite flame retardant on the material's mechanical properties. Furthermore, its saturated structure improves its compatibility with the composite flame retardant, facilitating flame retardant dispersion and significantly mitigating the decline in mechanical properties caused by interfacial defects.

[0099] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0100] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0101] The present invention has been illustrated with the above embodiments to describe the detailed process flow of the present invention. However, the present invention is not limited to the above detailed process flow, that is, it does not mean that the present invention must rely on the above detailed process flow to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A flame-retardant polystyrene, characterized in that, The components include the following parts by weight: 60-85 parts of polystyrene 15-25 parts of composite flame retardant 5-15 parts toughening agent Antioxidant 0.1-0.5 parts, Lubricant 0.2-1.0 parts; The composite flame retardant includes phosphate ester flame retardants, phosphonates, and melamine polyphosphates in a mass ratio of 1:1-3:2-5.

2. The flame-retardant polystyrene as described in claim 1, characterized in that, The phosphate ester flame retardant is selected from bisphenol A bis(diphenyl phosphate) or resorcinol bis(diphenyl phosphate), and the phosphonate flame retardant is selected from aluminum diethylphosphonate.

3. The flame-retardant polystyrene as described in claim 1, characterized in that, The flame-retardant polystyrene also includes 10-30 parts of polyphenylene ether.

4. The flame-retardant polystyrene as described in claim 1, characterized in that, The flame-retardant polystyrene also includes 0.2-1.0 parts of an anti-dripping agent.

5. The flame-retardant polystyrene as described in claim 4, characterized in that, The anti-dripping agent is selected from PTFE.

6. The flame-retardant polystyrene as described in claim 1, characterized in that, The toughening agent is selected from styrene-ethylene-butene-styrene block copolymer or styrene-butadiene-styrene block copolymer.

7. The flame-retardant polystyrene as described in claim 1, characterized in that, The number-average molecular weight of the styrene-ethylene-butene-styrene block copolymer is 80,000-150,000.

8. The flame-retardant polystyrene as described in claim 1, characterized in that, The antioxidant is selected from a compound of hindered phenolic antioxidants and phosphite antioxidants.

9. The flame-retardant polystyrene as described in claim 1, characterized in that, The lubricant is selected from calcium stearate or polyethylene wax.

10. A method for preparing flame-retardant polystyrene as described in any one of claims 1-9, characterized in that, The process includes drying and mixing the components to obtain a premix, and then melting, cooling, and drying the premix to obtain flame-retardant polystyrene.

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