Halogen-free flame-retardant polycarbonate material with high dielectric constant and high voltage resistance and preparation method thereof

Abstract

The invention relates to the technical field of material chemistry and polycarbonate material processing, and particularly discloses a halogen-free flame-retardant polycarbonate material with a high dielectric constant and high voltage resistance and a preparation method of the halogen-free flame-retardant polycarbonate material with the high dielectric constant and the high voltage resistance. Borophosphate glass powder is combined to enhance the high pressure resistance, and a phosphorus-silicon synergistic flame-retardant system is adopted to realize halogen-free flame retardance; according to the invention, the surface modified titanate nanofiller is adopted, a chemical bonding interface is constructed through the silane coupling agent, and the Maxwell-Wagner interface polarization effect is induced, so that the dielectric constant is increased to 5.5-7.2 (1MHz), the dielectric loss is less than or equal to 0.02 in the frequency range of 1kHz-10MHz, and the requirements of high-frequency and high-voltage composite working conditions are met.

Description

Technical Field

[0001] The present invention relates to the technical field of material chemistry and polycarbonate material processing, in particular to a high-dielectric-constant, high-voltage-resistant, halogen-free, flame-retardant polycarbonate material and a preparation method thereof. Background Art

[0002] Polycarbonate (PC), a thermoplastic engineering plastic with excellent comprehensive performance, has long been widely used in electronics, automotive manufacturing, and medical devices due to its high transparency, excellent impact resistance, and good electrical insulation properties. However, with the rapid development of technologies such as 5G communications, new energy high-voltage equipment, and smart grids, traditional PC materials have gradually exposed significant shortcomings in key performance: First, the dielectric constant of pure PC is low (ε≈2.9-3.0, 1MHz), which makes it difficult to meet the high dielectric constant requirements of high-frequency and high-speed signal transmission or high-voltage capacitors (ε>5). Second, it is prone to electrical dendrites or localized breakdown under high-voltage electric fields (>25kV / mm), leading to the risk of insulation failure. Third, while traditional halogenated flame retardants (such as brominated epoxy resins) can improve flame retardancy, they release toxic gases during combustion, violating environmental regulations such as RoHS. Among the existing improvement schemes, patent CN108117693B increases the dielectric constant of polypropylene material by adding barium titanate filler, but its breakdown strength is only 20kV / mm, and the thermal deformation temperature (<100°C) and impact strength of the base polypropylene are difficult to adapt to high-voltage scenarios; another type of scheme uses inorganic fillers (such as Al2O3) to enhance voltage resistance, but the mechanical properties deteriorate due to filler agglomeration. Therefore, to address the above problems, a high dielectric constant, high-voltage resistant, halogen-free, flame-retardant polycarbonate material and its preparation method are proposed. Summary of the Invention

[0003] The object of the present invention is to provide a high dielectric constant and high voltage resistant halogen-free flame retardant polycarbonate material and a preparation method thereof, so as to solve the problems raised in the above background technology.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A high dielectric constant and high voltage resistant halogen-free flame retardant polycarbonate material comprising the following components by weight percentage:

[0006] Bisphenol A polycarbonate (PC) 70-85%, with a molecular weight of 25,000-35,000 g / mol and a glass transition temperature (Tg) ≥ 145°C;

[0007] 5-15% surface-modified titanate ceramic filler, selected from barium titanate (BaTiO3), barium strontium titanate (BST), or calcium copper titanate (CCTO) with a particle size of 50-100 mm, treated with a silane coupling agent KH-550 to form an organic-inorganic interface layer on its surface that is chemically bonded to the PC;

[0008] 2-5% halogen-free flame retardant system, comprising a compound of polysiloxane and phosphate ester, wherein the polysiloxane has a molecular weight of 3000-10000 g / mol and the phosphate ester is resorcinol bis(diphenyl phosphate) (RDP);

[0009] 3-8% borophosphate glass powder, whose chemical composition is B2O3 40-50wt%, P2O5 30-40wt%, ZnO 10-20wt%, and average particle size 1-10μm;

[0010] 0.1-0.5% antioxidant, selected from hindered phenol antioxidants Irganox 1076 or Irganox 1010;

[0011] Lubricant 0.2-0.8%, pentaerythritol stearate (PETS);

[0012] The anti-dripping agent is 0.3-0.5%, which is polytetrafluoroethylene (PTFE) with an average particle size of ≤5 μm.

[0013] Preferably, the treatment process of the surface-modified titanate filler comprises the following steps:

[0014] Step 1: Dry the filler in vacuum at 80°C for 4 hours to remove adsorbed water;

[0015] Step 2: The filler was mixed with a 1 wt% KH-550 silane coupling agent ethanol solution at a mass ratio of 1:3, and treated at an ultrasonic frequency of 40 kHz and a power of 300 W for 30 minutes;

[0016] Step 3: Dry in an oven at 80° C. for 2 hours to obtain a modified filler with surface grafted amino functional groups.

[0017] Preferably, the weight ratio of polysiloxane to phosphate in the halogen-free flame retardant system is 1:0.8-1.2, phosphorus accounts for 0.5-1.2% of the total weight of the material, and silicon accounts for 0.8-2.0%; the combustion carbon residue rate (800°C nitrogen atmosphere) is ≥25%.

[0018] Preferably, the molar ratio of B2O3, P2O5 and ZnO in the composition of the borophosphate glass powder is 1:0.8-1.2:0.3-0.6, and the molar ratio with polysiloxane is 1:0.5-1.5.

[0019] Preferably, the dielectric constant temperature of the material is within the range of -40°C to 120°C, and the dielectric constant change rate is ≤±5%; the dielectric constant of the material is within the frequency range of 1kHz-10MHz, and the dielectric loss is ≤0.02.

[0020] A method for preparing a high-dielectric-constant, high-voltage-resistant, halogen-free, flame-retardant polycarbonate material comprises the following steps:

[0021] Step 1: Pre-treating fillers: Surface modification of titanate fillers and borophosphate glass powder;

[0022] Step 2: Premix preparation: Add PC resin, modified filler, flame retardant and additives into a high-speed mixer and mix at 1200 rpm for 10 minutes;

[0023] Step 3: Melt blending:

[0024] Use a co-rotating twin-screw extruder with a length-to-diameter ratio of 40:1. The zone temperatures are set as follows: feeding zone 220°C, compression zone 250°C, melting zone 260°C, and homogenization zone 270°C.

[0025] Screw speed 350±50rpm, vacuum degassing pressure -0.08MPa, melt residence time 2-3 minutes;

[0026] Step 4: Granulation and drying: The extruded strips are water-cooled and pelletized, and the pellets are air-dried at 100°C for 4 hours, with a moisture content of ≤0.02%;

[0027] Step 5: Injection molding: The barrel temperature is set to 250°C for the front section, 265°C for the middle section, and 270°C for the rear section; the mold temperature is 90±10°C, the injection pressure is 90±10MPa, the holding time is 6±2 seconds, and the cooling time is 18±3 seconds.

[0028] Preferably, during the melt blending process:

[0029] The shear rate is controlled at 500-800s - 1. Filler dispersion index (PDI) ≤ 0.25; PC molecular chain breakage rate ≤ 5%.

[0030] Preferably, in the granulation and drying process in step 4, the water cooling process is controlled at a cooling water temperature of 15-25°C and a flow rate of 5-8m 3 / h granule drying adopts staged temperature control: the first stage is drying at 80℃ for 2 hours to remove surface moisture, and the second stage is drying at 100℃ for 2 hours to remove internal bound water. The final granule moisture content is ≤0.02wt%; the granule size is 2-3mm in diameter and 3-5mm in length, and the length deviation rate is ≤5%.

[0031] Preferably, after the melt blending in step three, a dynamic hot pressing treatment step is added: the extruded melt is passed through a hot pressing mold and maintained at a pressure of 10-15 MPa and a temperature of 200-220°C for 30-60 seconds; the surface roughness of the hot pressing mold Ra is ≤ 0.2 μm, and high-frequency vibration (frequency 50-100 Hz, amplitude 0.1-0.3 mm) is applied to eliminate bubbles inside the melt.

[0032] Preferably, the step 5 further includes post-curing treatment after injection molding: placing the molded part in a nitrogen atmosphere, heating it to 140-150°C at 2-5°C / min, keeping it warm for 2-4 hours, and then slowly cooling it to room temperature at 1-3°C / min; the post-curing treatment increases the crystallinity of the PC molecular chain rearrangement by 3-5%, and increases the heat deformation temperature by 8-10°C.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. In the present invention, surface-modified titanate nanofillers (BaTiO3 / BST / CCTO) are used to construct a chemically bonded interface through a silane coupling agent, inducing the Maxwell-Wagner interface polarization effect, thereby increasing the dielectric constant to 5.5-7.2 (1MHz), and the dielectric loss is ≤0.02 in the frequency range of 1kHz-10MHz, and the dielectric constant fluctuation is ≤±5% at a temperature of -40-120°C, meeting the requirements of high-frequency and high-voltage composite working conditions.

[0035] 2. In the present invention, borophosphate glass powder (B2O3-P2O5-ZnO system) is introduced, and the B 3+ / P 5+ The ions react with the decomposition products of polysiloxane to form a BPO-Si passivation layer with a thickness of 0.5 to 2 μm, which inhibits the growth of electrical dendrites, has a breakdown strength of ≥25 kV / mm, and a performance degradation of ≤8% after 1000 hours of electrical aging.

[0036] 3. In the present invention, the polysiloxane / phosphate compound system generates a Si-OP cross-linked expanded carbon layer (residual carbon rate ≥ 25%) through a gas phase-condensed phase synergistic flame retardant mechanism during combustion, achieving UL94 V-0 flame retardancy (1.6mm), and a halogen content of ≤900ppm. It does not contain harmful substances such as antimony and red phosphorus, and complies with IEC61249-2-21 and RoHS standards.

[0037] 4. In the present invention, through dynamic hot pressing (high-frequency vibration defoaming) and nitrogen post-curing process, the porosity of the material is ≤0.05%, the crystallinity is increased by 3-5%, the heat deformation temperature is above 135°C, and it supports three-time melt regeneration (performance retention rate ≥85%), which significantly reduces production costs and environmental load. DETAILED DESCRIPTION

[0038] Example 1: The present invention provides a technical solution:

[0039] A high dielectric constant, high voltage resistant, halogen-free, flame-retardant polycarbonate material and its preparation method:

[0040] Formula composition (wt%)

[0041]

[0042] Preparation process

[0043] Pretreatment of filler: The filler was vacuum dried at 80° C. for 4 hours, ultrasonically treated with a silane coupling agent (KH-550) in an ethanol solution at a mass ratio of 1:3 for 30 minutes (40 kHz, 300 W), and dried for later use.

[0044] Premixing: Add polycarbonate, MBS toughening agent, barium carbonate and pretreated filler into a high-speed mixer (1200 rpm, 10 minutes).

[0045] Melt blending: using a twin-screw extruder (length-to-diameter ratio 40:1), zone temperature settings: feeding zone 220°C → melting zone 250°C → homogenization zone 270°C, screw speed 350 rpm, vacuum degassing (-0.08 MPa).

[0046] Injection molding: barrel temperature 250-270℃, mold temperature 90℃, injection pressure 90MPa, holding time 6 seconds.

[0047] Performance test results

[0048]

[0049] Example 2: The present invention provides a technical solution:

[0050] A high dielectric constant, high voltage resistant, halogen-free, flame-retardant polycarbonate material and its preparation method:

[0051] Formula adjustment: barium carbonate was changed to barium strontium carbonate.

[0052] Performance Comparison

[0053]

[0054] Example 3: The present invention provides a technical solution:

[0055] A high dielectric constant, high voltage resistant, halogen-free, flame-retardant polycarbonate material and its preparation method:

[0056] Formula adjustment: barium carbonate is changed to copper calcium titanate ceramic powder.

[0057] Performance impact

[0058]

[0059] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method of the present invention and its core ideas. The above is only a preferred implementation method of the present invention. It should be pointed out that due to the limitations of textual expression, there are objectively infinite specific structures. For ordinary technicians in this technical field, without departing from the principles of the present invention, they can make several improvements, modifications or changes, and can also combine the above technical features in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the inventive concept and technical solution to other occasions without improvement, should be regarded as the scope of protection of the present invention.

Claims

1. A high dielectric constant, high voltage resistant, halogen-free, flame-retardant polycarbonate material, characterized by: Contains the following components by weight: Bisphenol A polycarbonate (PC) 70-85%, with a molecular weight of 25,000-35,000 g / mol and a glass transition temperature (Tg) ≥ 145°C; 5-15% surface-modified titanate ceramic filler, selected from barium titanate (BaTiO3), barium strontium titanate (BST), or calcium copper titanate (CCTO) with a particle size of 50-100 nm, treated with a silane coupling agent KH-550 to form an organic-inorganic interface layer on its surface that is chemically bonded to the PC; 2-5% halogen-free flame retardant system, comprising a compound of polysiloxane and phosphate ester, wherein the polysiloxane has a molecular weight of 3000-10000 g / mol and the phosphate ester is resorcinol bis(diphenyl phosphate) (RDP); 3-8% borophosphate glass powder, whose chemical composition is B2O3 40-50wt%, P2O5 30-40wt%, ZnO 10-20wt%, and average particle size 1-10μm; 0.1-0.5% antioxidant, selected from hindered phenol antioxidants Irganox 1076 or Irganox 1010; Lubricant 0.2-0.8%, pentaerythritol stearate (PETS); The anti-dripping agent is 0.3-0.5%, which is polytetrafluoroethylene (PTFE) with an average particle size of ≤5 μm.

2. The high dielectric constant, high voltage resistant, halogen-free, flame-retardant polycarbonate material according to claim 1, characterized in that: The treatment process of the surface-modified titanate filler comprises the following steps: Step 1: Dry the filler in vacuum at 80°C for 4 hours to remove adsorbed water; Step 2: The filler was mixed with a 1 wt% KH-550 silane coupling agent ethanol solution at a mass ratio of 1:3, and treated at an ultrasonic frequency of 40 kHz and a power of 300 W for 30 minutes; Step 3: Dry in an oven at 80° C. for 2 hours to obtain a modified filler with surface grafted amino functional groups.

3. The high dielectric constant, high voltage resistant, halogen-free, flame-retardant polycarbonate material according to claim 1, characterized in that: The weight ratio of polysiloxane to phosphate in the halogen-free flame retardant system is 1:0.8-1.2, phosphorus accounts for 0.5-1.2% of the total weight of the material, and silicon accounts for 0.8-2.0%; the combustion carbon residue rate (800°C nitrogen atmosphere) is ≥25%.

4. The high dielectric constant, high voltage resistant, halogen-free, flame-retardant polycarbonate material according to claim 1, characterized in that: The molar ratio of B2O3, P2O5 and ZnO in the borophosphate glass powder is 1:0.8-1.2:0.3-0.6, and the molar ratio of B2O3, P2O5 and ZnO to polysiloxane is 1:0.5-1.

5.

5. The high dielectric constant and high voltage resistant halogen-free flame retardant polycarbonate material according to claim 1, characterized in that: The dielectric constant temperature of the material is within the range of -40°C to 120°C, and the dielectric constant change rate is ≤±5%; the dielectric constant of the material is within the frequency range of 1kHz-10MHz, and the dielectric loss is ≤0.

02.

6. A method for preparing a high dielectric constant, high voltage resistant, halogen-free, flame-retardant polycarbonate material, characterized by: The following steps are involved: Step 1: Pre-treating fillers: Surface modification of titanate fillers and borophosphate glass powder; Step 2: Premix preparation: Add PC resin, modified filler, flame retardant and additives into a high-speed mixer and mix at 1200 rpm for 10 minutes; Step 3: Melt blending: Use a co-rotating twin-screw extruder with a length-to-diameter ratio of 40:

1. The zone temperatures are set as follows: feeding zone 220°C, compression zone 250°C, melting zone 260°C, and homogenization zone 270°C. Screw speed 350±50rpm, vacuum degassing pressure -0.08MPa, melt residence time 2-3 minutes; Step 4: Granulation and drying: The extruded strips are water-cooled and pelletized, and the pellets are air-dried at 100°C for 4 hours, with a moisture content of ≤0.02%; Step 5: Injection molding: The barrel temperature is set to 250°C for the front section, 265°C for the middle section, and 270°C for the rear section; the mold temperature is 90±10°C, the injection pressure is 90±10MPa, the holding time is 6±2 seconds, and the cooling time is 18±3 seconds.

7. The method for preparing a high dielectric constant and high voltage resistant halogen-free flame retardant polycarbonate material according to claim 6, characterized in that: During the melt blending process: The shear rate is controlled at 500-800s -1 , filler dispersion index (PDI) ≤ 0.25; PC molecular chain breakage rate ≤ 5%.

8. The method for preparing a high dielectric constant and high voltage resistant halogen-free flame retardant polycarbonate material according to claim 6, characterized in that: During the granulation and drying process in step 4, the water cooling process is controlled at a cooling water temperature of 15-25°C and a flow rate of 5-8m 3 / h granule drying adopts staged temperature control: the first stage is drying at 80℃ for 2 hours to remove surface moisture, and the second stage is drying at 100℃ for 2 hours to remove internal bound water. The final granule moisture content is ≤0.02wt%; the granule size is 2-3mm in diameter and 3-5mm in length, and the length deviation rate is ≤5%.

9. The method for preparing a high dielectric constant and high voltage resistant halogen-free flame retardant polycarbonate material according to claim 6, characterized in that: After the melt blending in step 3, a dynamic hot pressing treatment step is added: the extruded melt is passed through a hot pressing mold and maintained at a pressure of 10-15 MPa and a temperature of 200-220°C for 30-60 seconds; the surface roughness of the hot pressing mold Ra is ≤ 0.2 μm, and high-frequency vibration (frequency 50-100 Hz, amplitude 0.1-0.3 mm) is applied to eliminate bubbles inside the melt.

10. The method for preparing a high dielectric constant and high voltage resistant halogen-free flame retardant polycarbonate material according to claim 6, characterized in that: After the injection molding, step 5 further includes a post-curing treatment: placing the molded part in a nitrogen atmosphere, heating it to 140-150°C at a rate of 2-5°C / min, keeping it warm for 2-4 hours, and then slowly cooling it to room temperature at a rate of 1-3°C / min; the post-curing treatment increases the crystallinity of the PC molecular chain rearrangement by 3-5% and the heat deformation temperature by 8-10°C.

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