A method for low voc stabilization of pc / abs alloys

Abstract

The application discloses a PC / ABS alloy low-VOC stabilization treatment method and relates to the technical field of high polymer materials, which comprises the following steps: placing emulsion ABS resin in subcritical propane; obtaining compounded ABS resin; adding first reactive eliminating agent and second reactive eliminating agent into the compounded ABS resin; the first reactive eliminating agent is an oligomer containing an azide group; and adjusting the compounding ratio of bulk ABS and pretreated emulsion ABS and the adding amount of the first reactive eliminating agent and the second reactive eliminating agent. The application effectively avoids the defect that new VOC by-products are generated due to thermal oxidative degradation of polymers caused by high-temperature vacuum devolatilization; breaks the seesaw effect in the prior art that low VOC and high mechanical properties are difficult to be considered simultaneously; realizes irreversible chemical elimination of VOC molecules, eliminates the risk of secondary release of VOC after temperature rise existing in the physical adsorption method from the root, is far lower than the dosage of 5-8 wt% of a traditional adsorbent, and further makes up for the negative influence of the adsorbent on the mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a method for stabilizing PC / ABS alloys with low VOCs. Background Technology

[0002] PC / ABS alloys, combining the excellent heat resistance and dimensional stability of polycarbonate with the good processing fluidity and impact resistance of ABS resin, are widely used in automotive interior parts, electronic and electrical housings, and food contact materials. However, the volatile organic compounds (VOCs) released during the processing and use of this alloy, causing in-vehicle air pollution, are increasingly subject to strict control. With the implementation of standards such as GB / T 17729—2023 and the stringent requirements of OEMs for odor levels (≤3.0) and TVOC values, low-VOC stabilization treatment of PC / ABS alloys has become a technical bottleneck in the industry. Existing low-VOC treatment technologies for PC / ABS alloys mainly include physical adsorption methods (adding activated carbon or porous molecular sieves, which pose a risk of secondary VOC release and excessive adsorbent can damage mechanical properties), vacuum devolatilization methods (which can only remove VOCs released on the surface of the melt, have limited efficiency in removing deep VOCs, and high-temperature vacuum may exacerbate polymer degradation), and bulk ABS substitution methods (although bulk methods A...). The residual monomer content of BS is only 1 / 20 of that of emulsion ABS, but complete substitution will lead to a decrease in the impact resistance of the alloy. Supercritical fluid extraction (requires independent high-pressure equipment, complex process flow, and difficulty in determining the endpoint) and deodorizing agent addition (only physically shields or adsorbs, and cannot eliminate VOC sources from the chemical level) have all failed to fundamentally solve the problem of targeted removal of the unique VOC sources (emulsifier decomposition products, residual styrene and acrylonitrile monomers) in emulsion ABS. Furthermore, there is a lack of chemical elimination methods that can irreversibly bond VOC molecules to the polymer matrix through chemical reactions to prevent secondary release.

[0003] However, current common solutions have many drawbacks, including: existing technologies generally treat emulsion ABS and bulk ABS as equivalent, failing to fully recognize that the large amount of emulsifier decomposition products (such as dodecylbenzene sulfonic acid) remaining in emulsion ABS due to the polymerization process are its unique main source of VOCs; and lacking technical means to perform targeted pretreatment of emulsion ABS under mild conditions to reduce VOCs at the source; at the same time, existing solutions are mostly limited to single devolatilization methods in the processing stage, lacking a complete process system design from "resin raw material pretreatment → compatibility and cost reduction → chemical elimination → process linkage", with each link being isolated from the others, resulting in unstable VOC control effects, large batch-to-batch fluctuations, and difficulty in simultaneously meeting the automotive interior industry's requirements of TVOC ≤50 μgC / g, odor level ≤3.0, and notched impact strength ≥40 kJ / m 2 The comprehensive indicator requirements. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0005] In view of the problems existing in the current low-VOC stabilization treatment method for PC / ABS alloy, the present invention is proposed.

[0006] Therefore, the purpose of this invention is to provide a low-VOC stabilization treatment method for PC / ABS alloys. This method addresses the common practice in existing technologies of treating emulsion-processed ABS and bulk-processed ABS interchangeably, failing to fully recognize that the large amount of emulsifier decomposition products (such as dodecylbenzene sulfonic acid) remaining in emulsion-processed ABS due to its polymerization process are its unique main source of VOCs. Furthermore, it lacks technical means to perform targeted pretreatment of emulsion-processed ABS under mild conditions to reduce VOCs at the source. Simultaneously, existing solutions are mostly limited to single devolatilization methods during the processing stage, lacking a comprehensive system design encompassing "resin raw material pretreatment → cost reduction through formulation → chemical elimination → process linkage." The fragmented nature of these processes leads to unstable VOC control effects, large batch-to-batch fluctuations, and difficulty in simultaneously meeting the automotive interior materials requirements of TVOC ≤ 50 μgC / g, odor level ≤ 3.0, and notched impact strength ≥ 40 kJ / m². 2 The issue of comprehensive indicator requirements.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: In a first aspect, embodiments of the present invention provide a method for stabilizing PC / ABS alloys with low VOCs, comprising: placing emulsion ABS resin in subcritical propane and extracting it for 20-40 minutes at a temperature of 70-90°C and a pressure of 3-5 MPa to obtain pretreated emulsion ABS resin; mixing bulk ABS resin with the pretreated emulsion ABS resin at a mass ratio of (60-70):(30-40) to obtain a compound ABS resin; adding a first reactive eliminator and a second reactive eliminator to the compound ABS resin, and melt-blending it with PC resin and extruding and granulating it; wherein the first reactive eliminator is an oligomer containing azide groups, used to undergo a CH insertion reaction with styrene and / or ethylbenzene; and the second reactive eliminator is a hyperbranched polyamide-amine containing epoxy end groups, used to undergo a nucleophilic addition reaction with acrylonitrile; and adjusting the compounding ratio of bulk ABS to pretreated emulsion ABS and the amount of the first and second reactive eliminators added to make the TVOC value of the final PC / ABS alloy material ≤50 μgC / g.

[0008] As a preferred embodiment of the low-VOC stabilization treatment method for PC / ABS alloys described in this invention, the subcritical propane extraction temperature is 75~85℃, the pressure is 3.5~4.5 MPa, and the extraction time is 25~35 minutes; the subcritical propane extraction is carried out under stirring conditions, with a stirring speed of 50~200 rpm; after the subcritical propane extraction is completed, a pressure relief and recovery step is also included: the pressure of the extraction vessel is reduced to atmospheric pressure in stages, and gaseous propane is recovered and recycled.

[0009] As a preferred embodiment of the low-VOC stabilization treatment method for PC / ABS alloy described in this invention, the mass ratio of the bulk ABS resin to the pretreated emulsion ABS resin is (63~67):(33~37); the rubber content of the bulk ABS resin is 5~15 wt%, and the rubber content of the emulsion ABS resin is 40~60 wt%.

[0010] As a preferred embodiment of the low-VOC stabilization treatment method for PC / ABS alloys described in this invention, the first reactive eliminator is a styrene-acrylonitrile oligomer containing azido groups. Its main chain is a styrene-acrylonitrile copolymer segment, and its side chain contains azidomethyl groups. The number average molecular weight is 1500~3000, and the azido group content is 0.5~2.0 mmol / g. In the first reactive eliminator, the molar ratio of styrene to acrylonitrile is (60~80):(20~40), and the azidomethyl groups are grafted onto the benzene ring of the styrene-acrylonitrile copolymer segment through methylene linkers.

[0011] As a preferred embodiment of the low-VOC stabilization treatment method for PC / ABS alloys described in this invention, the second reactive eliminator is an epoxy-terminated hyperbranched polyamide-amine with a branching degree of 15-25, an epoxy value of 0.3-0.6 mol / 100g, a number-average molecular weight of 3000-8000, and an epoxy end-group functionality of 8-16; the epoxy-terminated hyperbranched polyamide-amine is prepared by reacting hyperbranched polyamide-amine with epichlorohydrin, and the hyperbranched polyamide-amine is prepared by diethylenetriamine and methyl acrylate via a Michael addition reaction.

[0012] In a preferred embodiment of the low-VOC stabilization treatment method for PC / ABS alloy described in this invention, the following is specified: the amount of the first reactive eliminator added is 0.4~0.8 wt% of the total weight of the compounded ABS resin, and the amount of the second reactive eliminator added is 0.3~0.5 wt% of the total weight of the compounded ABS resin; the ratio of the amount of the first reactive eliminator to the amount of the second reactive eliminator added is (1.2~2.0):1.

[0013] As a preferred embodiment of the low-VOC stabilization treatment method for PC / ABS alloy described in this invention, the following features are specified: the melt blending temperature is 220~250℃, the screw speed is 200~400 rpm, and the vacuum degree is -0.06~-0.09 MPa; the melt blending is carried out in a twin-screw extruder, which is provided with a feeding section, a melting section, a vacuum devouring section, and a discharge section in sequence along the material conveying direction; the vacuum degree of the vacuum devouring section is -0.08~-0.095 MPa; the length-to-diameter ratio of the twin-screw extruder is (36~48):1, and the number of vacuum devouring sections is at least two.

[0014] As a preferred embodiment of the low-VOC stabilization treatment method for PC / ABS alloy described in this invention, the mass ratio of the PC resin to the compounded ABS resin is (50~80):(20~50); the PC resin is bisphenol A type polycarbonate with a viscosity-average molecular weight of 20000~40000 g / mol.

[0015] As a preferred embodiment of the low-VOC stabilization treatment method for PC / ABS alloy described in this invention, wherein: while adding a first reactive eliminator and a second reactive eliminator to the compounded ABS resin, at least one of an antioxidant, a lubricant, and a heat stabilizer is also added; the antioxidant is a hindered phenolic antioxidant or a phosphite antioxidant, and the lubricant is a silicone lubricant or a stearate lubricant.

[0016] Secondly, to further solve the above-mentioned technical problems, the present invention provides a PC / ABS alloy material, which is prepared by a low-VOC stabilization treatment method for PC / ABS alloys, wherein: the TVOC value of the PC / ABS alloy material is ≤50 μgC / g, the odor level is ≤3.0, and the notched impact strength is ≥40 kJ / m. 2 .

[0017] The beneficial effects of this invention are as follows: Firstly, this invention utilizes the high diffusivity and high solubility of subcritical propane to selectively remove VOC sources such as emulsifier decomposition products and residual monomers unique to emulsion-processed ABS. The processing temperature is much lower than the melt processing temperature, effectively avoiding the defects of high-temperature vacuum devolatilization leading to polymer thermo-oxidative degradation and the generation of new VOC byproducts. Secondly, by differentially combining bulk ABS (low VOC contribution) and pretreated emulsion ABS (high toughness contribution) at a mass ratio of (60~70):(30~40), this invention leverages the low VOC characteristics of bulk ABS while retaining the high rubber content imparted to the alloy by emulsion ABS. Its superior impact resistance breaks the "seesaw" effect of existing technologies where low VOC and high mechanical properties are difficult to achieve simultaneously. Furthermore, during the melt blending stage, a two-component targeted reactive eliminator is added—an azide-containing oligomer covalently bonds styrene / ethylbenzene to the polymer chain via CH insertion, and an epoxy-terminated hyperbranched polyamide-amine converts acrylonitrile into a stable five-membered ring structure via nucleophilic addition. This achieves irreversible chemical elimination of VOC molecules, fundamentally eliminating the risk of secondary VOC release after temperature increases, which is present in physical adsorption methods. Moreover, the total addition amount of the two eliminators is only 0.7~1.3wt%, far lower than the 5~8 wt% of traditional adsorbents. At a dosage of wt%, the three-dimensional network structure of the hyperbranched polymer can also act as a reactive compatibilizer to enhance the interfacial bonding force of PC / ABS, further compensating for the negative impact of the adsorbent on mechanical properties. Simultaneously, by linking the elimination efficiency of the first eliminator with the mass fraction of bulk ABS and the elimination efficiency of the second eliminator with the mass fraction of pretreated emulsion ABS, the type and dosage of eliminators are precisely matched to the VOC types of different ABS components. Combined with the physical removal through multi-stage vacuum devolatilization in a twin-screw extruder, a dual guarantee mechanism of "chemical elimination + physical devolatilization" is formed, ensuring the stability and batch consistency of VOC control. Ultimately, the prepared PC / ABS alloy material simultaneously achieves a TVOC value ≤50 μgC / g, an odor level ≤3.0, and a notched impact strength ≥40 kJ / m². 2 Its comprehensive performance indicators can meet the stringent requirements of low VOC, low odor and high mechanical properties in the fields of automotive interior parts, electronic and electrical housings and food contact materials, and have extremely high industrial application value. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 This is a flowchart illustrating the implementation of the present invention in Example 1. Detailed Implementation

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0020] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0021] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0022] Example 1 Reference Figure 1 This is the first embodiment of the present invention, which provides a method for stabilizing PC / ABS alloy with low VOCs, comprising the following steps: S1: Place the emulsion ABS resin in subcritical propane and extract it for 20-40 minutes at a temperature of 70-90℃ and a pressure of 3-5 MPa to obtain pretreated emulsion ABS resin.

[0023] Specifically, the subcritical propane extraction temperature is 75~85℃, the pressure is 3.5~4.5 MPa, and the extraction time is 25~35 minutes; Subcritical propane extraction was carried out under stirring conditions at a stirring speed of 50-200 rpm; After subcritical propane extraction is completed, a depressurization and recovery step is also included: the pressure of the extraction vessel is reduced to atmospheric pressure in stages to recover gaseous propane and recycle it.

[0024] Furthermore, subcritical propane extraction is carried out in a closed extraction vessel. Before extraction, emulsion ABS resin is placed in the extraction vessel, and the extraction vessel is evacuated to -0.06~-0.09 MPa. Liquid propane is then injected into the extraction vessel using the pressure difference, and the temperature is raised to the extraction temperature to convert the propane into a subcritical state.

[0025] Furthermore, in the subcritical propane extraction process, the mass ratio of emulsion ABS resin to liquid propane is 1:(3~8).

[0026] It should be noted that propane has a critical temperature of 96.8℃ and a critical pressure of 4.25 MPa. This invention controls the extraction temperature at 70~90℃ and the pressure at 3~5 MPa, placing propane in a subcritical state. In this state, propane possesses both high gas diffusivity and high liquid solubility, enabling it to effectively penetrate into the ABS resin and selectively dissolve and remove non-polar VOC sources such as styrene, acrylonitrile, and emulsifier decomposition products remaining in emulsion-processed ABS. Because the processing temperature is much lower than the melt processing temperature of ABS, it effectively avoids polymer thermo-oxidative degradation caused by high-temperature processing.

[0027] Specifically, the staged depressurization includes at least three stages: the first stage reduces the extraction pressure to 2.5~3.0 MPa and holds it for 5~10 minutes; the second stage reduces it to 1.0~1.5 MPa and holds it for 5~10 minutes; and the third stage reduces it to atmospheric pressure. The recovered gaseous propane is compressed and condensed into liquid propane, which is then recycled for the next batch of extraction. The propane recovery rate is ≥95%.

[0028] S2: Mix bulk ABS resin and pretreated emulsion ABS resin at a mass ratio of (60~70):(30~40) to obtain a compound ABS resin.

[0029] Specifically, the mass ratio of bulk ABS resin to pretreated emulsion ABS resin is (63~67):(33~37). The rubber content of bulk ABS resin is 5-15 wt%, while that of emulsion ABS resin is 40-60 wt%.

[0030] Specifically, the volume average particle size of rubber particles in bulk ABS is 0.5~3.0 μm; the volume average particle size of rubber particles in emulsion ABS is 0.1~0.5 μm.

[0031] Furthermore, after mixing bulk ABS and pretreated emulsion ABS at a mass ratio of (60~70):(30~40), the compounded ABS resin is dried at 80~100℃ for 2~4 hours to control its moisture content to ≤0.05%.

[0032] S3: Add a first reactive eliminator and a second reactive eliminator to the compounded ABS resin, and melt-blend with PC resin and extrude granulate; the first reactive eliminator is an oligomer containing azide groups, used to undergo CH insertion reaction with styrene and / or ethylbenzene; the second reactive eliminator is a hyperbranched polyamide-amine containing epoxy end groups, used to undergo nucleophilic addition reaction with acrylonitrile.

[0033] Specifically, the first reactive eliminator is a styrene-acrylonitrile oligomer containing azido groups. Its main chain is a styrene-acrylonitrile copolymer segment, and its side chain contains azidomethyl groups. The number average molecular weight is 1500~3000, and the azido group content is 0.5~2.0 mmol / g. In the first reactive eliminator, the molar ratio of styrene to acrylonitrile is (60~80):(20~40), and the azidomethyl group is grafted onto the benzene ring of the styrene-acrylonitrile copolymer segment through a methylene linker.

[0034] Furthermore, the second reactive eliminator is an epoxy-terminated hyperbranched polyamide-amine with a branching degree of 15-25, an epoxy value of 0.3-0.6 mol / 100g, a number-average molecular weight of 3000-8000, and an epoxy functionality of 8-16. The epoxy-terminated hyperbranched polyamide-amine is prepared by reacting hyperbranched polyamide-amine with epichlorohydrin, and the hyperbranched polyamide-amine is prepared by reacting diethylenetriamine with methyl acrylate via Michael addition reaction.

[0035] Specifically, the amount of the first reactive eliminator added is 0.4~0.8 wt% of the total weight of the compounded ABS resin, and the amount of the second reactive eliminator added is 0.3~0.5 wt% of the total weight of the compounded ABS resin. The ratio of the amount of the first reactive eliminator to the amount of the second reactive eliminator is (1.2~2.0):1.

[0036] Furthermore, the melt blending temperature is 220~250℃, the screw speed is 200~400 rpm, and the vacuum degree is -0.06~-0.09 MPa; Melt blending is carried out in a twin-screw extruder, which is equipped with a feeding section, a melting section, a vacuum devouring section and a discharge section in sequence along the material conveying direction. The vacuum degree of the vacuum devouring section is -0.08 to -0.095 MPa. The length-to-diameter ratio of the twin-screw extruder is (36~48):1, and the number of vacuum devouring sections is at least two.

[0037] Specifically, the mass ratio of PC resin to compounded ABS resin is (50~80):(20~50). PC resin is bisphenol A type polycarbonate with a viscosity-average molecular weight of 20,000~40,000 g / mol.

[0038] Furthermore, while adding the first reactive eliminator and the second reactive eliminator to the compounded ABS resin, at least one of the following is also added: antioxidant, lubricant and heat stabilizer. The antioxidant is a hindered phenolic antioxidant or a phosphite antioxidant, and the lubricant is a silicone lubricant or a stearate lubricant.

[0039] Specifically, the preparation method of the first reactive eliminator is as follows: Styrene and acrylonitrile are used as monomers to prepare styrene-acrylonitrile oligomers with a number-average molecular weight of 1500-3000 via free radical polymerization; the oligomers are dissolved in tetrahydrofuran, and chloromethyl methyl ether and SnCl4 catalyst are added. The reaction is carried out at 0-5℃ for 4-8 hours to introduce chloromethyl groups onto the benzene ring; sodium azide is then added, and the reaction is carried out at 60-80℃ for 12-24 hours to convert the chloromethyl groups into azidomethyl groups (-CH2N3). After precipitation, washing, and drying, the first reactive eliminator is obtained. The azido group content in the first reactive eliminator is 0.5-2.0 mmol / g, which can be determined by proton nuclear magnetic resonance spectroscopy (1H NMR spectroscopy). 1 Quantitative determination is performed using ¹H-NMR or elemental analysis.

[0040] It should be noted that compounds containing azide groups decompose under heating conditions (such as melt processing temperatures of 220~250℃) to produce nitrene reactive intermediates. These intermediates have extremely high reactivity and can insert into the CH bonds of polymer molecular chains and small molecules such as styrene / ethylbenzene, forming stable CN covalent bonds. Since the first reactive eliminator is itself a styrene-acrylonitrile oligomer, its main chain has good compatibility with the ABS matrix. After the reaction, the eliminator becomes part of the alloy matrix, eliminating the risk of migration and precipitation. The covalently bonded styrene and ethylbenzene molecules transform from free small molecules into side groups of the polymer chain, increasing their molecular weight by thousands of times, significantly reducing volatility, and preventing further release.

[0041] Specifically, the preparation method of the second reactive eliminator is as follows: Hyperbranched polyamide-amine is prepared by Michael addition reaction using diethylenetriamine and methyl acrylate as raw materials; the obtained hyperbranched polyamide-amine is dissolved in N,N-dimethylformamide, epichlorohydrin is added, and the reaction is carried out at 50-70℃ for 6-12 hours, allowing the amino groups at the ends of the hyperbranched polyamide-amine to react with epichlorohydrin to generate glycidyl ether end groups. Unreacted epichlorohydrin and solvent are removed by vacuum distillation to obtain epoxy-terminated hyperbranched polyamide-amine. The degree of branching of the second reactive eliminator is 15-25, the epoxy value is 0.3-0.6 mol / 100g, the number average molecular weight is 3000-8000, and the terminal epoxy functionality is 8-16.

[0042] It should be noted that the epoxy group (glycidyl ether group) at the end of the second reactive eliminator exhibits high reactivity, capable of undergoing a nucleophilic addition reaction with the cyano group (-C≡N) in the acrylonitrile molecule at the melt blending temperature, generating a stable five-membered cyclooxazoline structure. This reaction transforms acrylonitrile, a highly toxic VOC with a strong pungent odor, into a chemically stable cyclic structure, embedding it within the three-dimensional network of the hyperbranched polymer, fundamentally eliminating the volatility and toxicity of acrylonitrile. Simultaneously, the three-dimensional network structure of the hyperbranched polymer can act as a reactive compatibilizer, enhancing the interfacial bonding between the PC and ABS phases.

[0043] Specifically, the amount of the first reactive eliminator added is 0.4~0.8 wt% of the total weight of the compounded ABS resin, preferably 0.5~0.7 wt%; the amount of the second reactive eliminator added is 0.3~0.5 wt% of the total weight of the compounded ABS resin, preferably 0.35~0.45 wt%. The total amount of the two eliminators added is only 0.7~1.3 wt%, which is much lower than the 5~8 wt% added amount of traditional physical adsorbents, and can effectively avoid the deterioration of mechanical properties caused by the addition of a large amount of additives.

[0044] Specifically, melt blending takes place in a twin-screw extruder, which is sequentially configured along the material conveying direction with a feeding section, a melting section, a vacuum devolatilization section, and a discharge section. The temperature in the feeding section is 180~200℃, the temperature in the melting section is 220~250℃, the temperature in the vacuum devolatilization section is 230~250℃, and the temperature in the discharge section is 220~240℃. The screw speed is 200~400 rpm.

[0045] Specifically, the twin-screw extruder has at least two vacuum devolatilization sections, each independently equipped with a vacuum inlet and a gas outlet. The vacuum level of the first vacuum devolatilization section is -0.08 to -0.095 MPa, and the vacuum level of the second vacuum devolatilization section is also -0.08 to -0.095 MPa. This multi-stage vacuum devolatilization simultaneously removes trace amounts of propane remaining after subcritical propane extraction and newly generated free small molecules during processing during melt blending, forming a dual-protection mechanism of "chemical elimination + physical devolatilization."

[0046] Specifically, the length-to-diameter ratio of the twin-screw extruder is (36~48):1. When the length-to-diameter ratio is within this range, it can ensure that the material has sufficient residence time in the extruder to complete the chemical bonding reaction of the reactive eliminator and vacuum devolatilization, while avoiding thermal degradation of the PC component due to excessive residence time.

[0047] Specifically, the PC resin is bisphenol A type polycarbonate with a viscosity-average molecular weight of 20,000~40,000 g / mol. Before use, the PC resin needs to be dried at 100~120℃ for 4~6 hours to ensure its moisture content is ≤0.02% to prevent hydrolysis of the ester groups on the PC molecular chain during high-temperature processing.

[0048] Specifically, the antioxidant is a hindered phenolic antioxidant (such as Irganox 1076, Irganox 1010) or a phosphite antioxidant (such as Irgafos 168), added at a rate of 0.1~0.5 wt% of the total weight of the PC / ABS alloy. The lubricant is a silicone lubricant or a stearate lubricant (such as calcium stearate, zinc stearate), added at a rate of 0.1~0.5 wt% of the total weight of the PC / ABS alloy. The heat stabilizer is an organotin heat stabilizer or a phosphorus-based heat stabilizer, added at a rate of 0.1~0.3 wt% of the total weight of the PC / ABS alloy.

[0049] S4: Adjust the mixing ratio of bulk ABS and pretreated emulsion ABS, as well as the amount of the first and second reactive eliminators added, so that the TVOC value of the final PC / ABS alloy material is ≤50 μgC / g.

[0050] Specifically, the method for adjusting the compounding ratio of bulk ABS and pretreated emulsion ABS, as well as the addition amounts of the first and second reactive eliminators, is as follows: First, determine the basic compounding ratio based on the VOC contribution values ​​of bulk ABS and pretreated emulsion ABS. The VOC contribution value per unit mass of bulk ABS is 80~150 μgC / g, and the VOC contribution value per unit mass of pretreated emulsion ABS is 40~80 μgC / g. Then, calculate the theoretical addition amounts of the first and second reactive eliminators based on the target TVOC value (≤50 μgC / g). Finally, verify and fine-tune the theoretical calculation values ​​through small-scale experiments to determine the final compounding ratio and eliminator addition amount.

[0051] Specifically, the first reactive eliminator has an elimination efficiency of 60%~90% for styrene and / or ethylbenzene in bulk ABS, and the second reactive eliminator has an elimination efficiency of 50%~80% for acrylonitrile in pretreated emulsion ABS. The elimination efficiency is defined as: under the same processing conditions, the difference in the content of the corresponding VOC component in the PC / ABS alloy material before and after the addition of the eliminator, divided by the content of that component without the addition of the eliminator, expressed as a percentage.

[0052] Specifically, the TVOC value of the PC / ABS alloy material was determined according to ISO 12219-2 or VDA 277 standards, and the VOC components were qualitatively and quantitatively analyzed using gas chromatography-mass spectrometry (GC-MS). The odor level was assessed according to PV3900 standards. The notched impact strength was tested according to ISO 180 standards at 23°C, using a type A notch specimen.

[0053] In summary, this invention utilizes the high diffusivity and high solubility of subcritical propane to selectively remove VOC sources such as emulsifier decomposition products and residual monomers unique to emulsion-processed ABS. The processing temperature is much lower than the melt processing temperature, effectively avoiding the defects of high-temperature vacuum devolatilization leading to polymer thermo-oxidative degradation and the generation of new VOC byproducts. Secondly, the bulk ABS (low VOC contribution) and pretreated emulsion ABS (high toughness contribution) are differentiated and formulated at a mass ratio of (60~70):(30~40), which not only leverages the low VOC characteristics of bulk ABS but also retains the high rubber content of emulsion ABS. The superior impact resistance of the pre-alloy breaks the "seesaw" effect of the difficulty in achieving both low VOC and high mechanical properties in existing technologies. Furthermore, the addition of a two-component targeted reactive eliminator during the melt blending stage—an azide-containing oligomer covalently bonds styrene / ethylbenzene to the polymer chain via CH insertion, and an epoxy-terminated hyperbranched polyamide-amine converting acrylonitrile into a stable five-membered ring structure via nucleophilic addition—achieves irreversible chemical elimination of VOC molecules. This fundamentally eliminates the risk of secondary VOC release after temperature increases, which is present in physical adsorption methods. Moreover, the total addition amount of the two eliminators is only 0.7~1.3%. The dosage is significantly lower than the 5-8 wt% of traditional adsorbents. The three-dimensional network structure of the hyperbranched polymer can also act as a reactive compatibilizer to enhance the interfacial bonding between PC and ABS, further compensating for the negative impact of adsorbents on mechanical properties. Simultaneously, by linking the elimination efficiency of the first eliminator with the mass fraction of bulk ABS and the elimination efficiency of the second eliminator with the mass fraction of pretreated emulsion ABS, the type and dosage of eliminators are precisely matched to the VOC types of different ABS components. Combined with the physical removal through multi-stage vacuum devolatilization in a twin-screw extruder, a dual guarantee mechanism of "chemical elimination + physical devolatilization" is formed, ensuring the stability and batch consistency of VOC control. Ultimately, the prepared PC / ABS alloy material simultaneously achieves a TVOC value ≤50 μgC / g, an odor level ≤3.0, and a notched impact strength ≥40 kJ / m². 2 Its comprehensive performance indicators can meet the stringent requirements of low VOC, low odor and high mechanical properties in the fields of automotive interior parts, electronic and electrical housings and food contact materials, and have extremely high industrial application value.

[0054] Example 2 is an embodiment of the present invention. This embodiment provides a PC / ABS alloy material, which is prepared using the low-VOC stabilization treatment method for PC / ABS alloys in Example 1. Specifically, the TVOC value of the PC / ABS alloy material is ≤50 μgC / g, the odor level is ≤3.0, and the notched impact strength is ≥40 kJ / m. 2 .

[0055] It should be noted that 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 preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for stabilizing PC / ABS alloy with low VOCs, characterized in that: include: The emulsion ABS resin was placed in subcritical propane and extracted for 20-40 minutes at a temperature of 70-90℃ and a pressure of 3-5 MPa to obtain pretreated emulsion ABS resin. The bulk ABS resin and the pretreated emulsion ABS resin are mixed at a mass ratio of (60~70):(30~40) to obtain a compound ABS resin; A first reactive eliminator and a second reactive eliminator are added to the compounded ABS resin, and then melt-blended with PC resin and extruded and granulated. The first reactive eliminator is an oligomer containing azide groups, which is used to undergo a CH insertion reaction with styrene and / or ethylbenzene. The second reactive eliminator is a hyperbranched polyamide-amine containing epoxy end groups, which is used to undergo a nucleophilic addition reaction with acrylonitrile. The mixing ratio of bulk ABS and pretreated emulsion ABS, as well as the amount of the first and second reactive eliminators added, are adjusted to make the TVOC value of the final PC / ABS alloy material ≤50 μgC / g.

2. The method for low-VOC stabilization treatment of PC / ABS alloy as described in claim 1, characterized in that: The subcritical propane extraction temperature is 75~85℃, the pressure is 3.5~4.5 MPa, and the extraction time is 25~35 minutes. The subcritical propane extraction was carried out under stirring conditions, with a stirring speed of 50~200 rpm; After the subcritical propane extraction is completed, a pressure relief and recovery step is also included: the pressure of the extraction vessel is reduced to atmospheric pressure in stages to recover gaseous propane and recycle it.

3. The method for low-VOC stabilization treatment of PC / ABS alloy as described in claim 1, characterized in that: The mass ratio of bulk ABS resin to pretreated emulsion ABS resin is (63~67):(33~37). The bulk ABS resin has a rubber content of 5-15 wt%, and the emulsion ABS resin has a rubber content of 40-60 wt%.

4. The method for low-VOC stabilization treatment of PC / ABS alloy as described in claim 1, characterized in that: The first reactive eliminator is a styrene-acrylonitrile oligomer containing azido groups. Its main chain is a styrene-acrylonitrile copolymer segment, and its side chain contains azidomethyl groups. The number average molecular weight is 1500~3000, and the azido group content is 0.5~2.0 mmol / g. In the first reactive eliminator, the molar ratio of styrene to acrylonitrile is (60~80):(20~40), and the azidomethyl group is grafted onto the benzene ring of the styrene-acrylonitrile copolymer segment via a methylene linker.

5. The method for low-VOC stabilization treatment of PC / ABS alloy as described in claim 1, characterized in that: The second reactive eliminator is an epoxy-terminated hyperbranched polyamide-amine with a branching degree of 15-25, an epoxy value of 0.3-0.6 mol / 100g, a number-average molecular weight of 3000-8000, and an epoxy end-group functionality of 8-16. The epoxy-terminated hyperbranched polyamide-amine is prepared by reacting hyperbranched polyamide-amine with epichlorohydrin, and the hyperbranched polyamide-amine is prepared by Michael addition reaction of diethylenetriamine and methyl acrylate.

6. The method for low-VOC stabilization treatment of PC / ABS alloy as described in claim 1, characterized in that: The first reactive eliminator is added at a rate of 0.4-0.8 wt% of the total weight of the compounded ABS resin, and the second reactive eliminator is added at a rate of 0.3-0.5 wt% of the total weight of the compounded ABS resin. The ratio of the amount of the first reactive eliminator to the amount of the second reactive eliminator is (1.2~2.0):

1.

7. The method for low-VOC stabilization treatment of PC / ABS alloy as described in claim 1, characterized in that: The melt blending temperature is 220~250℃, the screw speed is 200~400 rpm, and the vacuum degree is -0.06~-0.09 MPa; The melt blending is carried out in a twin-screw extruder, which is provided with a feeding section, a melting section, a vacuum devouring section and a discharge section in sequence along the material conveying direction. The vacuum degree of the vacuum devouring section is -0.08 to -0.095 MPa. The length-to-diameter ratio of the twin-screw extruder is (36~48):1, and the number of vacuum devouring sections is at least two.

8. The method for low-VOC stabilization treatment of PC / ABS alloy as described in claim 1, characterized in that: The mass ratio of the PC resin to the compounded ABS resin is (50~80):(20~50). The PC resin is bisphenol A type polycarbonate with a viscosity-average molecular weight of 20,000~40,000 g / mol.

9. The method for low-VOC stabilization treatment of PC / ABS alloy as described in claim 1, characterized in that: While adding a first reactive eliminator and a second reactive eliminator to the compounded ABS resin, at least one of an antioxidant, a lubricant, and a heat stabilizer is also added. The antioxidant is a hindered phenolic antioxidant or a phosphite antioxidant, and the lubricant is a silicone lubricant or a stearate lubricant.

10. The PC / ABS alloy material prepared by the low-VOC stabilization treatment method for PC / ABS alloy according to any one of claims 1-9, characterized in that: The PC / ABS alloy material has a TVOC value ≤ 50 μgC / g, an odor level ≤ 3.0, and a notched impact strength ≥ 40 kJ / m. 2 .

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