High cti halogen-free flame-retardant polycarbonate composite material and preparation method thereof

Abstract

The application provides a high-CTI halogen-free flame-retardant polycarbonate composite material and a preparation method thereof, relates to the technical field of composite materials, and the high-CTI halogen-free flame-retardant polycarbonate composite material comprises the following components in parts by weight: PC resin 70-80 parts, siloxane PC resin 20-30 parts, inorganic filler 1-5 parts, flame retardant 2-8 parts, toughening agent 2-8 parts, antioxidant 0.1-0.5 parts, lubricant 0.3-0.5 parts, and anti-dripping agent 0.5-1 part. The polycarbonate composite material has high flame-retardant grade and high CTI value.

Description

Technical Field

[0001] This invention relates to the field of composite materials technology, specifically to high CTI halogen-free flame-retardant polycarbonate composite materials and their preparation methods. Background Technology

[0002] Polycarbonate (PC), as an engineering plastic with excellent comprehensive performance, has good transparency, excellent impact toughness and good dimensional stability, and is widely used in electronics, automotive, aerospace and other fields.

[0003] As electronic and electrical equipment develops towards miniaturization, integration, and high power, higher requirements are placed on the tracking resistance of materials. The Comparative Tracking Index (CTI) is a crucial indicator for evaluating a material's resistance to surface tracking and electrical breakdown under the combined effects of an electric field and electrolyte. A higher CTI value indicates better insulation safety. Simultaneously, flame retardant requirements in the electronics and electrical field are becoming increasingly stringent, severely restricting the use of halogen-containing flame retardants. The development of halogen-free flame-retardant PC has become an inevitable trend in the industry. Currently, mainstream halogen-free flame retardants, including phosphate esters and sulfonates, all rely on condensed-phase char formation as their core flame-retardant mechanism. By providing additional carbon sources, reducing surface hydrophobicity, and catalyzing carbonization, flame retardants improve the flame retardancy of PC while accelerating the formation of conductive carbon pathways, thus lowering the PC's CTI. This makes it difficult for conventional halogen-free flame-retardant PC to simultaneously achieve high flame retardancy ratings and high CTI values. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a high CTI halogen-free flame-retardant polycarbonate composite material and its preparation method, solving the technical problem that existing halogen-free flame-retardant PCs cannot simultaneously possess both high flame retardancy ratings and high CTI values.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] In a first aspect, the present invention provides a high CTI halogen-free flame-retardant polycarbonate composite material, comprising the following components in parts by weight: 70-80 parts of PC resin, 20-30 parts of siloxane PC resin, 1-5 parts of inorganic filler, 2-8 parts of flame retardant, 2-8 parts of toughening agent, 0.1-0.5 parts of antioxidant, 0.3-0.5 parts of lubricant, and 0.5-1 parts of anti-dripping agent.

[0007] Secondly, the present invention provides a method for preparing the high CTI halogen-free flame-retardant polycarbonate composite material, comprising the following steps:

[0008] (1) Dry the PC resin and the siloxane PC resin at 80-120℃ for 4-8 hours respectively, and set aside for later use;

[0009] (2) Weigh the dried PC resin, siloxane PC resin, inorganic filler, flame retardant, toughening agent, antioxidant, lubricant and anti-dripping agent according to the proportion, put them into a high-speed mixer and mix them evenly to obtain a premix.

[0010] (3) The premixed material is melt-blended and extruded, and the extrudate is cooled, pelletized and dried to obtain the high CTI halogen-free flame-retardant polycarbonate composite material.

[0011] Compared with existing technologies, it has the following beneficial effects:

[0012] This invention provides a high CTI halogen-free flame-retardant polycarbonate composite material, comprising the following components in parts by weight: 70-80 parts PC resin, 20-30 parts siloxane PC resin, 1-5 parts inorganic filler, 2-8 parts flame retardant, 2-8 parts toughening agent, 0.1-0.5 parts antioxidant, 0.3-0.5 parts lubricant, and 0.5-1 parts anti-dripping agent. Under the synergistic effect of siloxane PC resin and inorganic filler, the polycarbonate composite material simultaneously possesses a high flame retardant rating and a high CTI value. Detailed Implementation

[0013] 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.

[0014] This application provides a high CTI halogen-free flame-retardant polycarbonate composite material and its preparation method, which solves the technical problem that existing halogen-free flame-retardant PCs cannot simultaneously have high flame retardant ratings and high CTI values, and achieves the effect of polycarbonate composite materials having both high flame retardant ratings and high CTI values.

[0015] The technical solution in this application is to solve the above-mentioned technical problems, and the general idea is as follows:

[0016] In a first aspect, the present invention provides a high CTI halogen-free flame-retardant polycarbonate composite material, comprising the following components in parts by weight: 70-80 parts of PC resin, 20-30 parts of siloxane PC resin, 1-5 parts of inorganic filler, 2-8 parts of flame retardant, 2-8 parts of toughening agent, 0.1-0.5 parts of antioxidant, 0.3-0.5 parts of lubricant, and 0.5-1 parts of anti-dripping agent.

[0017] As a preferred technical solution, the flame retardant is an inorganic nitrogen-phosphorus flame retardant, and the siloxane PC resin is a polycarbonate-polysiloxane copolymer, wherein the content of polysiloxane segments is 5-25 wt%. The inorganic filler is selected from one or more of modified barium sulfate, modified titanium dioxide, and modified talc; the modified barium sulfate, modified titanium dioxide, and modified talc are obtained by modifying barium sulfate, titanium dioxide, and talc respectively using a silane coupling agent. In the CTI test, the dripping of electrolyte will trigger an instantaneous electric arc with an arc temperature as high as 3000℃~4000℃. Under the high temperature generated by the discharge, the phosphorus component of the inorganic nitrogen-phosphorus flame retardant in the polycarbonate composite material decomposes and releases strong acids such as phosphoric acid and polyphosphoric acid. Under the strong dehydrating effect of the strong acid, the PC matrix undergoes a dehydration and cross-linking reaction, forming carbonaceous residues. The nitrogen component in the inorganic nitrogen-phosphorus flame retardant will decompose and release a large amount of non-combustible gas at high temperature, causing the molten carbides to expand and foam, forming a fluffy and porous carbonaceous foam layer. Furthermore, under the high temperatures generated during CTI testing, the compatibility between siloxane PC resin and PC resin deteriorates. Due to the surface energy difference, siloxane chains spontaneously migrate to the material surface. Simultaneously, under the action of siloxane, PC resin undergoes a Fries rearrangement reaction. The phenolic hydroxyl groups generated by the Fries rearrangement undergo a condensation reaction with the broken siloxane chains at high temperature, forming a chemical bond CO-Si. Through the CO-Si chemical bond, a cross-linking structure is constructed between the molecular chains of PC resin and siloxane PC resin. This cross-linking structure intertwines with the fluffy and porous carbonaceous foam layer at the molecular scale. At the same time, the inorganic filler, through the epoxy group at one end, reacts chemically with the PC molecular chains and embeds itself into this cross-linking structure, thereby reducing the continuity of carbon in the carbonaceous foam layer. This forms a discontinuous insulating carbon layer rich in silicon and carbon on the surface of the polycarbonate composite material. Thus, under the synergistic effect of siloxane PC resin and inorganic filler, the polycarbonate composite material has a high CTI and good flame retardancy.

[0018] Preferably, the inorganic nitrogen-phosphorus flame retardant is selected from one or more of ammonium polyphosphate, phosphazene compounds, and polyphosphates. By capturing free radicals and promoting char formation in the matrix, the material can achieve a UL94V-0 flame retardant rating (1.6mm) even with a low addition amount.

[0019] Preferably, the average particle size of the inorganic filler is 0.5-10.0 μm, for example, it can be 0.5 μm, 0.8 μm, 1.0 μm, 5.0 μm, 10.0 μm or any value between them.

[0020] Preferably, the PC resin is bisphenol A type polycarbonate, and the density of the PC resin is 1.18-1.22 g / cm³. 3 For example, it can be 1.18 g / cm³. 3 1.2g / cm 31.22g / cm 3 The melt flow index is 8-24 g / 10 min, or any value between these values, such as 8 g / 10 min, 15 g / 10 min, 24 g / 10 min, or any value between these values. PC resin, as the matrix resin, provides the material with basic mechanical properties and heat resistance.

[0021] Preferably, the high CTI halogen-free flame-retardant polycarbonate composite material satisfies at least one of the following conditions:

[0022] The toughening agent is selected from one or more of methyl methacrylate-butadiene-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, or organosilicon graft copolymer. The synergistic toughening effect of siloxane PC resin and toughening agent effectively compensates for the embrittlement effect caused by inorganic fillers, while the siloxane segments improve the processing fluidity of the system. The addition of siloxane PC resin can also improve the low-temperature impact resistance of the material.

[0023] The antioxidant is a compound of hindered phenolic antioxidants and phosphite antioxidants, wherein the mass ratio of hindered phenolic antioxidants to phosphite antioxidants is 1:1 to 1:3; the hindered phenolic antioxidant can be, for example, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and the phosphite antioxidant can be, for example, tris[2,4-di-tert-butylphenyl]phosphite.

[0024] The lubricant is selected from one or more of pentaerythritol stearate, polyethylene wax, and silicone powder; the anti-dripping agent is polytetrafluoroethylene powder.

[0025] The hindered phenol / phosphite compound antioxidant system can effectively inhibit the thermal oxidative degradation of PC during high-temperature processing; the addition of lubricant improves the fluidity and release properties of the system; good melt blending can be achieved within a wide processing window of 240-280℃, with strong process adaptability and easy industrial production.

[0026] Secondly, the present invention provides a method for preparing the high CTI halogen-free flame-retardant polycarbonate composite material, comprising the following steps:

[0027] (1) Dry the PC resin and the siloxane PC resin at 80-120℃ for 4-8 hours respectively, and set aside for later use;

[0028] (2) Weigh the dried PC resin, siloxane PC resin, inorganic filler, flame retardant, toughening agent, antioxidant, lubricant and anti-dripping agent according to the proportion, put them into a high-speed mixer and mix them evenly to obtain a premix.

[0029] (3) The premixed material is melt-blended and extruded, and the extrudate is cooled, pelletized and dried to obtain the high CTI halogen-free flame-retardant polycarbonate composite material.

[0030] Preferably, in the melt blending extrusion process described in step (3), the temperatures of each section are set as follows: feeding section 220-240℃, melting section 250-270℃, homogenization section 260-280℃, and die head temperature 260-275℃.

[0031] 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.

[0032] I. Preparation Method

[0033] The reagents or raw materials mentioned in the following examples and comparative examples are of the following types and manufacturers:

[0034] PC resin: Bisphenol A type polycarbonate, density approximately 1.2 g / cm³ 3 Melt index is 15g / 10min, commercially available;

[0035] Siloxane PC resin: Polycarbonate-polysiloxane copolymer, with siloxane segment content of approximately 15 wt%, commercially available;

[0036] Talc: Commercially available;

[0037] Titanium dioxide: average particle size 0.8μm, commercially available;

[0038] Ammonium polyphosphate: Flame retardant, commercially available;

[0039] Phosphazene compounds: flame retardants, commercially available;

[0040] Potassium diphenyl sulfone sulfonate: Flame retardant, commercially available;

[0041] MBS toughening agent: methyl methacrylate-butadiene-styrene copolymer, commercially available;

[0042] Antioxidant 1010: Pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], commercially available;

[0043] Antioxidant 168: Tris[2,4-di-tert-butylphenyl]phosphite, commercially available;

[0044] Lubricant PETS: Pentaerythritol stearate, commercially available;

[0045] Anti-dripping agent: Polytetrafluoroethylene powder, commercially available.

[0046] All materials are commercially available, commonly used products. All raw materials were dried under suitable drying conditions before use. The reagents described above are only for illustrating the source and composition of the reagents used in the experiments of this invention, to ensure full disclosure, and do not imply that the invention cannot be achieved by using other similar reagents or reagents provided by other suppliers.

[0047] Example 1

[0048] This embodiment provides a method for preparing a high CTI halogen-free flame-retardant polycarbonate composite material, comprising the following steps:

[0049] (1) Dry the PC resin and the siloxane PC resin at 100°C for 6 hours respectively;

[0050] (2) Weigh the following raw materials according to the following weight proportions: 75 parts PC resin, 25 parts siloxane PC resin, 3 parts modified talc, 5 parts ammonium polyphosphate, 5 parts MBS toughening agent, 0.1 parts antioxidant 1010, 0.2 parts antioxidant 168, 0.4 parts lubricant PETS, and 0.8 parts anti-dripping agent;

[0051] Preparation method of modified talc: The talc powder is dried to a moisture content of <0.4%. KH-560 is added to the talc powder at a mass of 1.5%, and the mixture is stirred at high speed at 150℃ for 60 minutes to obtain modified talc powder.

[0052] (3) Put each raw material from step (2) into a high-speed mixer and mix for 15 minutes to obtain a premix;

[0053] (4) Add the premixed material to a twin-screw extruder (length-to-diameter ratio 40:1) for melt blending and extrusion. The screw speed is 300 rpm, and the temperature of each section is set as follows: feeding section 230℃, melting section 260℃, homogenization section 270℃, die head temperature 270℃, and vacuum degree -0.08MPa.

[0054] (4) The extrudate is cooled with water, granulated, and dried at 100°C for 4 hours to obtain the product.

[0055] Example 2

[0056] The difference between this embodiment and embodiment 1 is that the weight parts of each raw material in step (2) are different. Specifically, the following raw materials are weighed according to the weight parts: 70 parts of PC resin, 30 parts of siloxane PC resin, 2 parts of modified titanium dioxide, 4 parts of phosphazene compound, 3 parts of MBS toughening agent, 0.1 parts of antioxidant 1010, 0.3 parts of antioxidant 168, 0.5 parts of lubricant PETS, and 0.5 parts of anti-dripping agent.

[0057] The rest is the same as in Example 1.

[0058] Example 3

[0059] The difference between this embodiment and embodiment 1 is that the weight parts of each raw material in step (2) are different. Specifically, the following raw materials are weighed according to the weight parts: 80 parts of PC resin, 20 parts of siloxane PC resin, 4 parts of modified talc, 6 parts of ammonium polyphosphate, 6 parts of MBS toughening agent, 0.15 parts of antioxidant 1010, 0.15 parts of antioxidant 168, 0.3 parts of lubricant PETS, and 1.0 part of anti-dripping agent.

[0060] The rest is the same as in Example 1.

[0061] Example 4

[0062] The difference between this embodiment and embodiment 1 is that the weight parts of each raw material in step (2) are different. Specifically, the following raw materials are weighed according to the weight parts: 72 parts of PC resin, 28 parts of siloxane PC resin, 2 parts of modified talc powder, 1 part of titanium dioxide (compound), 3 parts of phosphazene compound, 2 parts of potassium diphenyl sulfonate (compound), 4 parts of MBS toughening agent, 0.1 parts of antioxidant 1010, 0.2 parts of antioxidant 168, 0.4 parts of lubricant PETS, and 0.6 parts of anti-dripping agent.

[0063] The rest is the same as in Example 1.

[0064] Example 5

[0065] The difference between this embodiment and embodiment 1 is that the weight parts of each raw material in step (2) are different, specifically: 75 parts of PC resin, 25 parts of siloxane PC resin, 5 parts of modified talc, 5 parts of ammonium polyphosphate, 5 parts of MBS toughening agent, 0.1 parts of antioxidant 1010, 0.2 parts of antioxidant 168, 0.4 parts of lubricant PETS, and 0.8 parts of anti-dripping agent.

[0066] The rest is the same as in Example 1.

[0067] Comparative Example 1

[0068] The difference between this comparative example and Example 5 is that the raw materials in step (2) do not include siloxane PC resin, 30 parts of modified talc powder, and the rest are the same as in Example 5.

[0069] Comparative Example 2

[0070] The difference between this comparative example and Example 5 is that the raw materials in step (2) do not include modified talc powder, 30 parts of siloxane PC resin, and the rest are the same as in Example 5.

[0071] II. Testing Methods

[0072] The products obtained in Examples 1-5 and Comparative Examples 1-2 were injection molded into standard test strips according to standard methods, and the following performance tests were conducted:

[0073] 1. CTI value: Tested according to GB / T4207 standard;

[0074] 2. Flame retardant performance: Tested according to UL94 standard (1.6mm);

[0075] 3. Notched impact strength: Tested according to GB / T1843 standard;

[0076] 4. Melt Flow Rate (MFR): Tested according to GB / T3682 standard, 300℃ / 1.2kg;

[0077] 5. Heat distortion temperature (HDT): Tested according to GB / T1634 standard, 1.8MPa.

[0078] The test results are shown in Table 1.

[0079] Table 1. Performance test results of the examples and comparative products.

[0080]

[0081] As can be seen from Examples 1-5, the halogen-free flame-retardant PC materials prepared within the formulation range described in this invention can all achieve a CTI value of over 510V, flame retardant performance reaching UL94V-0 level (1.6mm), and notched impact strength maintained above 50kJ / m², demonstrating excellent overall performance.

[0082] Example 5 uses 25 parts of siloxane PC resin and 5 parts of modified talc as raw materials. The CTI of the prepared polycarbonate composite material is 560V. Comparative Example 1 does not use siloxane PC resin, and Comparative Example 2 does not use modified talc as raw materials. The CTI of the prepared polycarbonate composite materials are 380V and 275V, respectively. This shows that siloxane PC resin and modified talc have a synergistic effect in improving the CTI of polycarbonate composite materials.

[0083] In addition, in Comparative Example 1, which did not contain siloxane PC, the MFR of the polycarbonate composite material decreased, indicating a worsening of processing fluidity; at the same time, the notched impact strength decreased, indicating that the addition of siloxane PC can improve processing fluidity and toughness.

[0084] The above results demonstrate that this invention, through reasonable component selection and ratio optimization, achieves a comprehensive balance of high CTI, halogen-free flame retardancy, good toughness, and processing performance, exhibiting significant industrial application value. The formulation system contains no halogen components, complying with the environmental requirements of EU RoHS and REACH regulations. Furthermore, the inorganic nitrogen-phosphorus flame retardant is added in small amounts, resulting in low smoke emission and low toxicity during combustion.

[0085] It should be noted that, in this document, relational terms such as "first" and "second" are used only 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.

[0086] 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.

[0087] 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 high CTI halogen-free flame-retardant polycarbonate composite material, characterized in that, It includes the following components in parts by weight: 70-80 parts PC resin, 20-30 parts siloxane PC resin, 1-5 parts inorganic filler, 2-8 parts flame retardant, 2-8 parts toughening agent, 0.1-0.5 parts antioxidant, 0.3-0.5 parts lubricant, and 0.5-1 part anti-dripping agent.

2. The high CTI halogen-free flame-retardant polycarbonate composite material as described in claim 1, characterized in that, The flame retardant is an inorganic nitrogen-phosphorus flame retardant.

3. The high CTI halogen-free flame-retardant polycarbonate composite material as described in claim 2, characterized in that, The inorganic nitrogen-phosphorus flame retardant is selected from one or more of ammonium polyphosphate, phosphazene compounds, and polyphosphates.

4. The high CTI halogen-free flame-retardant polycarbonate composite material as described in claim 1, characterized in that, The inorganic filler is selected from one or more of modified barium sulfate, modified titanium dioxide, and modified talc. The modified barium sulfate, modified titanium dioxide, and modified talc were obtained by modifying barium sulfate, titanium dioxide, and talc respectively using silane coupling agents.

5. The high CTI halogen-free flame-retardant polycarbonate composite material as described in claim 1, characterized in that, The inorganic filler has an average particle size of 0.5-10 μm.

6. The high CTI halogen-free flame-retardant polycarbonate composite material as described in claim 1, characterized in that, The siloxane PC resin is a polycarbonate-polysiloxane copolymer, wherein the content of polysiloxane segments is 5-25 wt%.

7. The high CTI halogen-free flame-retardant polycarbonate composite material as described in claim 1, characterized in that, The PC resin is bisphenol A type polycarbonate, and the density of the PC resin is 1.18-1.22 g / cm³. 3 The melt flow index is 8-24 g / 10 min.

8. The high CTI halogen-free flame-retardant polycarbonate composite material as described in claim 1, characterized in that, At least one of the following conditions must be met: The toughening agent is selected from one or more of methyl methacrylate-butadiene-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, or organosilicon graft copolymer; The antioxidant is a compound of hindered phenolic antioxidants and phosphite antioxidants, wherein the mass ratio of hindered phenolic antioxidants to phosphite antioxidants is 1:1 to 1:

3. The lubricant is selected from one or more of pentaerythritol stearate, polyethylene wax, and silicone powder; the anti-dripping agent is polytetrafluoroethylene powder.

9. A method for preparing a high CTI halogen-free flame-retardant polycarbonate composite material as described in any one of claims 1-8, characterized in that, Includes the following steps: (1) Dry the PC resin and the siloxane PC resin at 80-120℃ for 4-8 hours respectively, and set aside for later use; (2) Weigh the dried PC resin, siloxane PC resin, inorganic filler, flame retardant, toughening agent, antioxidant, lubricant and anti-dripping agent according to the proportion, mix them evenly to obtain the premix; (3) The premixed material is melt-blended and extruded, and the extrudate is cooled, pelletized and dried to obtain the high CTI halogen-free flame-retardant polycarbonate composite material.

10. The preparation method according to claim 9, characterized in that, In step (3), the temperature of each section of the melt blending extrusion process is set as follows: feeding section 220-240℃, melting section 250-270℃, homogenization section 260-280℃, and die head temperature 260-275℃.

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