Low-VOC (volatile organic compound) filled PP (polypropylene) material and preparation method thereof

Abstract

The invention discloses a low-VOC (volatile organic compound) filled PP (polypropylene) material and a preparation method thereof. The low-VOC filled PP material is prepared from the following raw materials in parts by mass: 30 to 70 parts of PP, 0.15 to 0.75 part of montmorillonite nanosheet, 10 to 25 parts of talcum powder, 0.3 to 0.9 part of coupling agent, 0.3 to 0.9 part of lubricant, 0.2 to 0.5 part of antioxidant and 0.3 to 0.9 part of ethylene bis stearamide. Montmorillonite nanosheets are obtained by sodium modification purification, cetyltrimethylammonium bromide intercalation reaction and homogeneous stripping of calcium-based montmorillonite, 'endogenous inhibition 'is realized synergistically, the total VOC release amount is reduced, additional adsorbents are not needed, and the preparation method is simple and easy to implement. And the problem that the adsorbed small molecules are gradually desorbed to become a secondary volatilization source in the use process of the material, such as a high-temperature environment and the like, is avoided.

Description

Technical Field

[0001] This application relates to low-VOC filled organic plastic materials, and particularly to a low-VOC filled PP material and its preparation method. Background Art

[0002] Polypropylene (PP) materials are widely used in the fields of automobiles, household appliances, packaging, etc. due to their excellent chemical resistance, mechanical properties, and processing properties. However, PP materials are prone to releasing volatile organic compounds (VOCs) during production and use, which not only affects product quality but may also pose hazards to human health and the environment. To address this issue, the industry has been increasing its investment in the research and development of low-VOC PP materials, striving to achieve a balance between material properties and environmental protection requirements through modification means.

[0003] In the prior art, in the aspect of improving the components of PP materials, adsorbents are mostly added, such as adding porous materials such as activated carbon or light calcium carbonate as adsorbents, and using their high specific surface area to physically adsorb and capture VOCs, thereby reducing the VOC release amount of PP materials.

[0004] However, this method has certain limitations. It does not substantially reduce the outward migration rate of VOC small molecules in PP, but only increases the storage amount of VOC small molecules in PP. Not only will the initial content of VOC small molecules in PP materials increase during the melt extrusion preparation process of PP materials, but also when PP materials are applied to high-temperature environments, the small molecules in the adsorbent will gradually desorb, forming a secondary volatilization source, resulting in the VOC release problem not being well addressed. Summary of the Invention

[0005] To reduce the release of VOCs from filled PP materials into the environment, a low-VOC filled PP material and its preparation method are provided.

[0006] The above first object of the present invention is achieved through the following technical solutions: A low-VOC filled PP material is prepared from the following raw materials in parts by mass: 30 - 70 parts by mass of PP, 0.15 - 0.75 parts by mass of montmorillonite nanosheets, 10 - 25 parts by mass of talcum powder, 0.3 - 0.9 parts by mass of coupling agent, 0.3 - 0.9 parts by mass of lubricant, 0.2 - 0.5 parts by mass of antioxidant, 0.3 - 0.9 parts by mass of ethylene bisstearamide; The montmorillonite nanosheets are obtained by sodium purification of calcium-based montmorillonite, cetyltrimethylammonium bromide intercalation reaction, and homogeneous exfoliation.

[0007] By adopting the above technical solutions, ethylene bisstearamide prevents filler agglomeration through electrostatic repulsion, ensuring the uniform dispersion of montmorillonite nanosheets. The montmorillonite nanosheets are introduced as functional fillers. By forming an intercalated structure with the polypropylene matrix, not only the rigidity of the filled PP material is improved, but also the physical barrier effect formed by the stacking of the sheets extends the diffusion path of VOC molecules, inhibits VOC migration, and reduces the VOC release rate. The coupling agent bonds to the hydroxyl groups on the surface of montmorillonite through hydrolysis and condensation reactions, forming an organic-inorganic interfacial layer, enhancing the compatibility of talc and montmorillonite nanosheets with the PP matrix, and reducing interfacial defects. Talc, as a rigid filler, increases the material modulus, reduces the interfacial stress concentration caused by deformation, and inhibits the VOC escape caused by microcracks. The antioxidant inhibits the oxidative cleavage of the PP chain, reducing the generation of low molecular weight volatiles. The above-mentioned synergy achieves "endogenous inhibition", reducing the total amount of VOC released, and without the need for additional adsorbents, avoiding the problem that the small molecules adsorbed during the use of materials such as in high-temperature environments will gradually desorb and become secondary volatile sources.

[0008] Optionally: The montmorillonite nanosheets are also pre-treated by intercalation with 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6) ionic liquid.

[0009] By adopting the above technical solutions, the [BMIM]PF6 ionic liquid forms an intercalated structure by further expanding the layer spacing of the montmorillonite nanosheets through a cation exchange reaction ([BMIM]+ replaces Na+ / Ca 2 +) in the interlayer of the montmorillonite nanosheets, enhancing the barrier ability to small molecule volatile substances. And after intercalation, the specific surface area of the montmorillonite nanosheets increases, adsorbing more VOC precursors. In addition, the [BMIM]PF6 ionic liquid itself has lubricity, which can partially replace traditional lubricants, reducing the dosage of small molecule additives such as calcium stearate, thereby reducing the risk of secondary volatilization.

[0010] Optionally: The montmorillonite nanosheets are also surface-modified with an amino-silane coupling agent in an ethanol / water system.

[0011] By adopting the above technical solutions, the amino-silane coupling agent hydrolyzes in the ethanol / water system to generate silanol (Si-OH), which condenses with the hydroxyl groups on the surface of montmorillonite to form Si-O-Si covalent bonds. Meanwhile, amino groups are exposed. The amino groups can interact with the tertiary carbon hydrogen atoms in the PP molecular chain through van der Waals forces, enhancing the interfacial bonding strength. The surface-modified montmorillonite is more easily intercalated and exfoliated by the PP molecular chain during the melt blending process, forming a nano-scale dispersed structure and improving the barrier efficiency against VOCs.

[0012] Optionally: The montmorillonite nanosheets are first intercalated with 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6) ionic liquid, and then surface-modified with an amino silane coupling agent in an ethanol / water system.

[0013] By adopting the above technical solution, first performing ionic liquid intercalation to expand the layer spacing through cation exchange can reduce the steric hindrance for subsequent grafting of the amino silane coupling agent; and then the surface modification with the silane coupling agent forms a dense organic layer on the outer surface of the intercalated montmorillonite nanosheets, inhibiting the outward migration of [BMIM]PF6 ionic liquid due to thermal motion. In this way, a "core-shell" structure is formed by such double modification: Core layer - The intercalated ionic liquid provides lubricity and interlayer stability. Shell layer - The silane coupling agent enhances the interfacial bonding with PP and reduces local overheating caused by interfacial slippage. Further reduce the VOC of the filled PP material and improve the flexural modulus and heat distortion temperature of the filled PP material.

[0014] Optionally: The antioxidant is dilauryl thiodipropionate (DLTP).

[0015] By adopting the above technical solution, using dilauryl thiodipropionate as the antioxidant, it has extremely low volatility and a high compatibility match with PP, can be evenly dispersed in PP, and preferentially captures the active free radicals (such as ROO·) generated by oxidation through the thioether group to form stable products, thereby inhibiting the main chain breakage of PP to generate small molecule volatiles and effectively reducing the VOC of the filled PP material.

[0016] Optionally: It further includes 0.1 - 0.3 parts by mass of high molecular weight hindered phenol.

[0017] By adopting the above technical solution, the high molecular weight hindered phenol provides hydrogen atoms through phenolic hydroxyl groups to capture primary free radicals, and DLTP decomposes hydroperoxides to block the source of free radical regeneration. The compounding of the two improves the antioxidant efficiency, prolongs the life of the filled PP material and reduces VOC.

[0018] Optionally: The lubricant is calcium stearate with a purity ≥ 98wt% and a particle size ≤ 5μm.

[0019] By adopting the above technical solution, high-purity calcium stearate can reduce the catalytic effect of metal impurities (such as Fe3+, Cu2+) on the thermal oxidation of PP. Ultrafine particle size improves its dispersion uniformity in the melt by increasing the specific surface area; At the same time, the calcium carboxylate group forms a weak coordination bond with the polypropylene segment, reducing the melt viscosity and the shear heat generation, while DLTP inhibits oxidation initiation. Both of them double block the free radical chain reaction and reduce VOC.

[0020] The above second invention objective of the present invention is achieved through the following technical solutions: A method for preparing low VOC filled PP comprises the following steps: Step 1: First, put the PP resin into the oven to bake to reduce the water content; Step 2: After the silane coupling agent and filler are stirred at high speed and mixed evenly, the baked PP resin is poured in and stirred and mixed, and finally other raw materials are added and stirred evenly to obtain a mixture; Step 3: Add the mixed material into a screw extruder for melt extrusion to obtain a low-VOC filled PP material.

[0021] By adopting the above technical solution, the moisture content of PP resin is reduced and the material performance is improved. The filler and silane coupling agent are first mixed to ensure sufficient surface modification, and then the PP matrix is ​​introduced to reduce interface defects and reduce VOC.

[0022] In summary, this application has at least the following beneficial effects: 1. No adsorbent technology is required, and endogenous VOC inhibition is achieved through intercalation structure design to avoid the risk of secondary release; 2. Ionic liquid intercalation and silane grafting form a "core-shell" structure. The dual modification synergizes and takes into account both barrier properties and interface stability, ensuring that the filled PP material has both strength and low VOC release. DETAILED DESCRIPTION

[0023] raw material PP resin, melt index 15g / 10min (230℃ / 2.16kg), Sinopec Yanshan Petrochemical K8303.

[0024] Calcium-based montmorillonite, cation exchange capacity ≥90mmol / 100g, Zhejiang Fenghong New Materials Co., Ltd. DL-1 type.

[0025] Hexadecyltrimethylammonium bromide, purity ≥99wt%, Aladdin reagent C109172.

[0026] [BMIM] PF6 ionic liquid, conductivity ≥5mS / cm (25℃), custom synthesized by Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences.

[0027] Aminosilane coupling agent (KH550), γ-aminopropyltriethoxysilane, purity ≥ 98wt%, Nanjing Shuguang Chemical Group Co., Ltd.

[0028] Calcium stearate, purity ≥ 98%, D50 = 3.5μm, Hangzhou Oil Chemical Co., Ltd. HSt-Ca

[0029] Dilauryl thiodipropionate (DLTP), melting point 40 - 42°C, BASF Irganox PS 800

[0030] High molecular weight hindered phenol (1076), molecular weight 530 - 550g / mol, BASF Irganox 1076

[0031] Talc powder is a market product with a fineness of 1250 mesh.

[0032] Preparation Example 1 Montmorillonite nanosheets, the preparation method is as follows, Sodium modification and purification: The calcium-based montmorillonite raw ore with a montmorillonite content ≥ 90wt% is crushed to 200 mesh, mixed with 5wt% sodium carbonate solution according to a solid-liquid mass ratio of 1:20, stirred at 85°C for 6h, centrifuged and then dried at 105°C to obtain sodium-modified montmorillonite; Hexadecyltrimethylammonium bromide intercalation reaction: The sodium-modified montmorillonite and hexadecyltrimethylammonium bromide (CTAB) are reacted at a cation exchange molar ratio of 1:1.2 in ethanol / water (3:1) at 70°C for 8h to obtain an intercalated product; Homogeneous exfoliation: The intercalated product is exfoliated into nanosheets with a thickness < 10nm by a high-pressure homogenizer (200MPa, 5 cycles) to obtain montmorillonite nanosheets.

[0033] Preparation Example 2 Montmorillonite nanosheets, the preparation method is as follows, Sodium modification and purification: The calcium-based montmorillonite raw ore with a montmorillonite content ≥ 90wt% is crushed to 200 mesh, mixed with 5wt% sodium carbonate solution according to a solid-liquid mass ratio of 1:20, stirred at 85°C for 6h, centrifuged and then dried at 105°C to obtain sodium-modified montmorillonite; Hexadecyltrimethylammonium bromide intercalation reaction: The sodium-modified montmorillonite and hexadecyltrimethylammonium bromide (CTAB) are reacted at a cation exchange molar ratio of 1:1.2 in ethanol / water (3:1) at 70°C for 8h to obtain an intercalated product; Homogeneous exfoliation: The intercalated product is exfoliated into nanosheets with a thickness < 10nm by a high-pressure homogenizer (200MPa, 5 cycles) to obtain CTAB intercalated nanosheets; Mix CTAB intercalated nanosheets with [BMIM]PF6 at a mass ratio of 1:0.3, ultrasonically treat at 80 °C for 4 h, wash with ethanol to remove free ionic liquid, and dry in vacuum to obtain montmorillonite nanosheets.

[0034] Preparation Example 3 Montmorillonite nanosheets, and its preparation method is as follows. Sodium modification and purification: Crush the calcium-based montmorillonite raw ore with a montmorillonite content ≥ 90 wt% to 200 mesh, mix it with 5 wt% sodium carbonate solution at a solid-liquid mass ratio of 1:20, stir at 85 °C for 6 h, centrifuge and then dry at 105 °C to obtain sodium-modified montmorillonite. Hexadecyltrimethylammonium bromide intercalation reaction: React sodium-modified montmorillonite with hexadecyltrimethylammonium bromide (CTAB) at a cation exchange molar ratio of 1:1.2 in ethanol / water (3:1) at 70 °C for 8 h to obtain an intercalated product. Homogeneous exfoliation: Exfoliate the intercalated product with a high-pressure homogenizer (200 MPa, 5 cycles) into nanosheets with a thickness < 10 nm to obtain CTAB intercalated nanosheets. Mix CTAB intercalated nanosheets with [BMIM]PF6 at a mass ratio of 1:0.3, ultrasonically treat at 80 °C for 4 h, wash with ethanol to remove free ionic liquid, and dry in vacuum to obtain ionic liquid intercalated nanosheets. Mix ionic liquid intercalated nanosheets with KH550 at a mass ratio of 10:1, react in ethanol / water (volume ratio 9:1) at pH = 4.5 and 65 °C for 3 h, centrifuge and dry to obtain double-modified montmorillonite nanosheets.

[0035] Preparation Example 4 Montmorillonite nanosheets, and its preparation method is as follows. Sodium modification and purification: Crush the calcium-based montmorillonite raw ore with a montmorillonite content ≥ 90 wt% to 200 mesh, mix it with 5 wt% sodium carbonate solution at a solid-liquid mass ratio of 1:20, stir at 85 °C for 6 h, centrifuge and then dry at 105 °C to obtain sodium-modified montmorillonite. Hexadecyltrimethylammonium bromide intercalation reaction: React sodium-modified montmorillonite with hexadecyltrimethylammonium bromide (CTAB) at a cation exchange molar ratio of 1:1.2 in ethanol / water (3:1) at 70 °C for 8 h to obtain an intercalated product. Homogeneous exfoliation: Exfoliate the intercalated product with a high-pressure homogenizer (200 MPa, 5 cycles) into nanosheets with a thickness < 10 nm to obtain CTAB intercalated nanosheets. Mix CTAB intercalated nanosheets with KH550 at a mass ratio of 10:1, react in ethanol / water (volume ratio 9:1) at pH = 4.5 and 65 °C for 3 h, centrifuge and dry to obtain once-modified nanosheets. Mix the once-modified nanosheets with [BMIM]PF6 at a mass ratio of 1:0.3, ultrasonically treat at 80 °C for 4 h, wash with ethanol to remove free ionic liquid, and dry in vacuum to obtain the twice-modified montmorillonite nanosheets.

[0036] Preparation Example 5 Modified light calcium carbonate with a D50 of 100 nm, obtained by modification with KH550.

[0037] The preparation method is as follows: Mix light calcium carbonate with an unmodified D50 of 100 nm and KH550 at a mass ratio of 10:1, react at 65 °C for 8 h under the condition of pH = 7 in ethanol / water (volume ratio of 9:1), centrifuge and dry to obtain modified light calcium carbonate.

[0038] Example 1 A low-VOC filled PP material with the following raw material dosages: 55 kg of PP, 0.6 kg of montmorillonite nanosheets, 18 kg of talc, 0.5 kg of coupling agent, 0.5 kg of lubricant, 0.3 kg of antioxidant, 0.8 kg of ethylene bisstearamide.

[0039] The montmorillonite nanosheets were prepared as in Preparation Example 1.

[0040] The coupling agent is KH550.

[0041] The lubricant is calcium stearate with a purity ≥ 98 wt%, D50 = 3.5 μm, and particle size < 5 μm.

[0042] The antioxidant is DLTP.

[0043] The preparation method is as follows: Dry the PP resin in a vacuum oven at 90 °C for 4 h until the water content < 300 ppm; Pre-mix the talc, montmorillonite nanosheets, and coupling agent for 3 min, then add the dried PP resin. After mixing evenly, add the other raw materials and mix evenly to obtain a mixture; Feed the mixture into a screw extruder to extrude and pelletize to obtain a PP filled material.

[0044] The set parameters of the screw extruder are a screw speed of 400 rpm, a vacuum degree of 0.08 MPa, and the temperature sections are set as 180 °C, 195 °C, 205 °C, 210 °C, 205 °C, and 200 °C in sequence from the inlet end.

[0045] Comparative Example 1 A filled PP material with the following raw material dosages: PP 55 kg, talcum powder 18 kg, coupling agent 0.5 kg, lubricant 0.5 kg, antioxidant 0.3 kg, ethylene bisstearamide 0.8 kg.

[0046] The coupling agent is KH550.

[0047] The lubricant is calcium stearate with a purity ≥ 98 wt% and D50 = 3.5 μm.

[0048] The preparation method is as follows: Dry the PP resin in a vacuum oven at 90 °C for 4 h until the water content < 300 ppm; Pre-mix the talcum powder and the coupling agent for 3 min, then add the dried PP resin. After mixing evenly, add the other raw materials and mix evenly to obtain a mixture; Feed the mixture into a screw extruder for extrusion granulation to obtain a PP filled material.

[0049] The set parameters of the screw extruder are: screw speed 400 rpm, vacuum degree 0.08 MPa, and the temperature sections are set as 180 °C, 195 °C, 205 °C, 210 °C, 205 °C, and 200 °C in sequence from the inlet end.

[0050] Comparative Example 2 A filled PP material, with the following raw material dosages: PP 55 kg, activated carbon 0.6 kg, talcum powder 18 kg, coupling agent 0.5 kg, lubricant 0.5 kg, antioxidant 0.3 kg, ethylene bisstearamide 0.8 kg.

[0051] The specific surface area of the activated carbon is 1200 - 1300 m 2 / g, particle size 300 mesh, ash content 2.1 wt%.

[0052] The coupling agent is KH550.

[0053] The lubricant is calcium stearate with a purity ≥ 98 wt% and D50 = 3.5 μm.

[0054] The preparation method is as follows: Dry the PP resin in a vacuum oven at 90 °C for 4 h until the water content < 300 ppm; Pre-mix the talcum powder, montmorillonite nanosheets, and the coupling agent for 3 min, then add the dried PP resin. After mixing evenly, add the other raw materials and mix evenly to obtain a mixture; Feed the mixture into a screw extruder for extrusion granulation to obtain a PP filled material.

[0055] The set parameters of the screw extruder are as follows: the screw speed is 400 rpm, the vacuum degree is 0.08 MPa, and the temperature sections are set as 180 °C, 195 °C, 205 °C, 210 °C, 205 °C, and 200 °C in sequence from the inlet end.

[0056] Comparative Example 3 A low-VOC filled PP material has the following raw material dosages: 55 kg of PP, 0.6 kg of modified light calcium carbonate, 18 kg of talc powder, 0.5 kg of coupling agent, 0.5 kg of lubricant, 0.3 kg of antioxidant, and 0.8 kg of ethylene bisstearamide.

[0057] The modified light calcium carbonate is obtained from Preparation Example 5.

[0058] The coupling agent is KH550.

[0059] The lubricant is calcium stearate with a purity ≥ 98 wt% and D50 = 3.5 μm.

[0060] The preparation method is as follows: Dry the PP resin in a vacuum oven at 90 °C for 4 h until the water content < 300 ppm; Pre-mix the talc powder, montmorillonite nanosheets, and coupling agent for 3 min, then add the dried PP resin. After mixing evenly, add other raw materials and mix evenly to obtain a mixture; Feed the mixture into a screw extruder for extrusion granulation to obtain a PP filled material.

[0061] The set parameters of the screw extruder are as follows: the screw speed is 400 rpm, the vacuum degree is 0.08 MPa, and the temperature sections are set as 180 °C, 195 °C, 205 °C, 210 °C, 205 °C, and 200 °C in sequence from the inlet end.

[0062] Example 2 A low-VOC filled PP material, which is different from Example 1 in that the montmorillonite nanosheets are obtained from Preparation Example 2.

[0063] Example 3 A low-VOC filled PP material, which is different from Example 1 in that the montmorillonite nanosheets are obtained from Preparation Example 3.

[0064] Example 4 A low-VOC filled PP material, which is different from Example 1 in that the montmorillonite nanosheets are obtained from Preparation Example 4.

[0065] Example 5 A low-VOC filled PP material, which is different from Example 3 in that the lubricant is calcium stearate with a purity of 90 wt% and D50 = 3.5 μm.

[0066] Example 6 A low-VOC filled PP material, which is different from that of Example 3 in that the lubricant is calcium stearate with a purity ≥ 98 wt%, D50 = 8 μm, and particle size > 5 μm Comparative Example 4 A low-VOC filled PP material, which is different from that of Example 3 in that the antioxidant is BHT

[0067] Example 7 A low-VOC filled PP material, which is different from that of Example 3 in that the raw materials further include 0.23 kg of hindered phenol Irganox 1076, and the hindered phenol Irganox 1076 is mixed and added together with the antioxidant

[0068] Example 8 A low-VOC filled PP material, which is different from that of Example 7 in that the raw material is replaced with an equal mass of hindered phenol BHT instead of hindered phenol Irganox 1076

[0069] Example 9 A low-VOC filled PP material, which is different from that of Example 7 in that the raw material dosage is different, specifically as follows: 30 kg of PP, 0.15 kg of montmorillonite nanosheets, 10 kg of talc powder, 0.3 kg of coupling agent, 0.3 kg of lubricant, 0.2 kg of antioxidant, 0.3 kg of ethylene bisstearamide, and 0.1 kg of high molecular weight hindered phenol

[0070] Example 10 A low-VOC filled PP material, which is different from that of Example 7 in that the raw material dosage is different, specifically as follows: 70 kg of PP, 0.75 kg of montmorillonite nanosheets, 25 kg of talc powder, 0.9 kg of coupling agent, 0.9 kg of lubricant, 0.5 kg of antioxidant, 0.9 kg of ethylene bisstearamide, and 0.3 kg of high molecular weight hindered phenol

[0071] The low-VOC filled PP materials of Examples 1 to 10 and the filled P materials of Comparative Examples 1 to 4 were tested for VOC release amount, flexural modulus, melt flow rate, and heat distortion temperature

[0072] The VOC release amount (TVOC) was tested with reference to GB / T 27630-2011, and the test parameters were 65 °C / 72 h

[0073] The flexural modulus was tested with reference to ISO 178

[0074] The heat distortion temperature was tested with reference to ISO 75-2, and the test pressure was 0.45 MPa

[0075] Table 1. Test result table of Examples 1 to 10 and Comparative Examples 1 to 4 TVOC (μg / g) Flexural modulus (MPa) Heat distortion temperature (°C) Example 1 28 2470 129 Example 2 22 2530 131 Example 3 15 2610 134 Example 4 18 2580 132 Example 5 32 2450 128 Example 6 25 2530 130 Example 7 12 2580 135 Example 8 27 2510 130 Example 9 30 2400 122 Example 10 18 2750 136 Comparative Example 1 78 2100 122 Comparative Example 2 42 2250 127 Comparative Example 3 65 2300 124 Comparative Example 4 41 2490 127 Combined with Table 1, Examples 1 and Comparative Examples 1-3 were analyzed. The test results of TVOC in Example 1 were significantly lower than those in Comparative Examples 1-3 at 65 °C. The flexural modulus was significantly greater than that in Comparative Examples 1-3, and the heat distortion temperature was higher than that in Comparative Examples 1-3. Therefore, in this application, montmorillonite nanosheets were introduced as functional fillers and uniformly dispersed in the polypropylene matrix through a coupling agent and ethylene bisstearamide, and an intercalated structure was formed. This not only improved the rigidity of the filled PP material, but also extended the diffusion path of VOC molecules through the physical barrier effect formed by the stacking of the sheets, inhibited the migration of VOCs, and reduced the VOC release rate. Talc powder, as a rigid filler, increased the modulus of the material, reduced the interfacial stress concentration caused by deformation, and inhibited the escape of VOCs caused by microcracks. The antioxidant inhibited the oxidative cleavage of the PP chain and reduced the generation of low-molecular-weight volatiles. The above synergistically achieved "endogenous inhibition", reduced the total amount of VOC release, eliminated the need for additional adsorbents, and avoided the problem that small molecules adsorbed during the use of materials such as in high-temperature environments would gradually desorb and become a secondary volatile source, and effectively enhanced the mechanical properties of the filled PP material.

[0076] Comparative analysis was carried out on Examples 1-4. The montmorillonite nanosheets in Example 1 were only CTAB intercalated; the montmorillonite nanosheets in Example 2 were intercalated with ionic liquid on the basis of CTAB intercalation, and the layer spacing of the montmorillonite nanosheets was enlarged, improving its barrier performance; Example 3 was further modified with an amino-silane coupling agent on the basis of Example 2 to form a double modification; the difference between Example 4 and Example 3 was that the amino-silane coupling agent modification was carried out first and then the amino-silane coupling agent modification again, and the modification sequence affected the layer spacing expansion efficiency.

[0077] In the TVOC results, from low to high were Example 3, Example 4, Example 2, and Example 1 in sequence; in terms of flexural modulus, from high to low were Example 3, Example 2, Example 4, and Example 1 in sequence; in terms of heat distortion temperature, from high to low were Example 3, Example 2, Example 4, and Example 1 in sequence.

[0078] Therefore, in this application, through the intercalation reaction of [BMIM]PF6 ionic liquid, the interlayer spacing of montmorillonite nanosheets is further enlarged to form an intercalated structure, providing lubricity and interlayer stability, enhancing the barrier ability to small molecule volatile substances, and after intercalation, the specific surface area of montmorillonite nanosheets increases, adsorbing more VOC precursors; and after the ionic liquid intercalation reaction, amino silane coupling agent modification is carried out - the ionic liquid intercalation reaction enlarges the interlayer spacing, which can reduce the steric hindrance of subsequent grafting of amino silane coupling agent, improve the grafting efficiency of amino silane coupling agent, and form a dense organic layer on the outer surface of montmorillonite nanosheets after ionic liquid intercalation, inhibiting the outward migration of [BMIM]PF6 ionic liquid due to thermal motion; such double modification forms a "core-shell" structure, further reducing the VOC of the filled PP material and improving the flexural modulus and heat distortion temperature of the filled PP material.

[0079] By analyzing Comparative Example 3 and Examples 5 - 6, the calcium stearate used in Example 5 has low purity, and the impurities Fe3+ / Cu2+ contained therein accelerate the oxidative cleavage of PP chains, generating small molecule volatiles, resulting in an increase in TVOC in Example 5 compared to Example 3, a decrease in flexural modulus compared to Example 3, and a decrease in heat distortion temperature compared to Example 3; in Example 6, the particle size of calcium stearate is relatively large, and its poor dispersibility leads to uneven melt viscosity, and local overheating during the melt extrusion process causes thermal decomposition, resulting in an increase in VOC compared to Example 3, and a decrease in flexural modulus and heat distortion temperature compared to Example 3. Therefore, in this application, it is preferable to select calcium stearate as the lubricant with a purity ≥ 98wt% and a particle size < 5μm.

[0080] By analyzing Comparative Example 3 and Comparative Example 4, the TVOC of Example 3 is significantly lower than that of Comparative Example 4, and the heat distortion temperature and flexural modulus of Example 3 are significantly greater than those of Comparative Example 4. This is because in Example 3, the antioxidant DLTP decomposes hydroperoxides through sulfide groups to block the free radical chain reaction, while in Comparative Example 4, only free radicals are captured but it is prone to sublimation and continuous volatilization itself. Therefore, it is preferable to use DLTP as the main antioxidant in this application.

[0081] Combined with the analysis of Example 3 and Examples 7 - 8, in Example 7, a high molecular weight hindered phenol is compounded with DLTP, and the TVOC of Example 7 decreases compared to Example 3; in Example 8, a low molecular weight hindered phenol is compounded with DLTP, and the TVOC of Example 8 increases compared to Example 3. The reason is that the hindered phenol provides hydrogen atoms through phenolic hydroxyl groups to capture primary free radicals, and DLTP decomposes hydroperoxides to block the source of free radical regeneration. The compounding of the two improves the antioxidant efficiency, but considering the problem that the low molecular weight hindered phenol is prone to sublimation itself, it is necessary to compound a high molecular weight hindered phenol with DLTP to improve the lifespan of the filled PP material while ensuring low VOC volatilization.

[0082] Combined with Examples 9-10 for analysis, the TVOC of Examples 9-10 is significantly lower than that of Comparative Examples 1-3, and the flexural modulus of Examples 9-10 is greater than that of Comparative Examples 1-4. Therefore, in this application, the raw material dosage is selected as 30-70 parts by mass of PP, 0.15-0.75 parts by mass of montmorillonite nanosheets, 10-25 parts by mass of talc powder, 0.3-0.9 parts by mass of coupling agent, 0.3-0.9 parts by mass of lubricant, 0.2-0.5 parts by mass of antioxidant, 0.3-0.9 parts by mass of ethylene bisstearamide, and 0.1-0.3 parts by mass of high molecular weight hindered phenol, and the low VOC-filled PP material of this application can be obtained.

[0083] Plus the non-amino silane modification preparation example At the same time, the calcium carboxylate group forms a weak coordination bond with the polypropylene chain segment, reducing the melt viscosity and reducing the generation of shear heat, while DLTP inhibits oxidation initiation, and the two jointly block the free radical chain reaction and reduce VOC.

[0084] This specific embodiment is only an explanation of the present invention, and it is not a limitation of the present invention. Those skilled in the art can make modifications to this embodiment without creative contributions according to needs after reading this specification, but as long as they are within the scope of protection required by the present invention, they are protected by the patent law.

Claims

1. A low-VOC filled PP material, characterized in that, Prepared from the following raw materials in parts by mass: 30 - 70 parts by mass of PP, 0.15 - 0.75 parts by mass of montmorillonite nanosheets, 10 - 25 parts by mass of talc powder, 0.3 - 0.9 parts by mass of coupling agent, 0.3 - 0.9 parts by mass of lubricant, 0.2 - 0.5 parts by mass of antioxidant, 0.3 - 0.9 parts by mass of ethylene bisstearamide; The montmorillonite nanosheets are obtained by sodium purification of calcium - based montmorillonite, hexadecyltrimethylammonium bromide intercalation reaction, and homogeneous exfoliation.

2. The low-VOC filled PP material according to claim 1, wherein The montmorillonite nanosheets are also pre - treated by intercalation with 1 - butyl - 3 - methylimidazolium hexafluorophosphate ([BMIM]PF6) ionic liquid.

3. The low-VOC filled PP material according to claim 2, wherein The montmorillonite nanosheets are also surface - modified with an amino - silane coupling agent in an ethanol / water system.

4. The low-VOC filled PP material according to claim 3, wherein, The montmorillonite nanosheets are first treated by intercalation with 1 - butyl - 3 - methylimidazolium hexafluorophosphate ([BMIM]PF6) ionic liquid, and then surface - modified with an amino - silane coupling agent in an ethanol / water system.

5. A low-VOC filled PP material according to claim 1, characterized in that, The antioxidant is dilauryl thiodipropionate (DLTP).

6. The low-VOC filled PP material according to claim 5, characterized in that, It also includes 0.1 - 0.3 parts by mass of high - molecular - weight hindered phenol.

7. A low-VOC filled PP material according to claim 1, characterized in that, The lubricant is calcium stearate with a purity ≥ 98wt% and a particle size ≤ 5μm.

8. The preparation method of the low-VOC filled PP material according to any one of claims 1 to 7, characterized in that, Including the following steps: Step 1: First, put the PP resin into an oven for baking to reduce the water content; Step 2: Then, mix the silane coupling agent and fillers evenly by high - speed stirring, then pour the baked PP resin into the mixture for stirring, and finally add other raw materials and stir evenly to obtain a mixed material; Step 3: Add the mixed material into a screw extruder for melt extrusion to obtain a low - VOC filled PP material.