Preparation method of refrigerator HIPS (High Impact Polystyrene) inner container without peculiar smell and refrigerator HIPS inner container

Abstract

According to the preparation method of the odorless refrigerator HIPS inner container and the refrigerator HIPS inner container, four odor removal mechanisms of physical adsorption, chemical decomposition, physical removal and low-temperature migration are creatively fused, an all-directional removal system is formed for multiple sources of odorless odor of the HIPS inner container, such as residual monomers, VOCs and oxidative degradation products, and odor removal is more thorough; and the odor removal process occurs in the material manufacturing stage, the odor source is eliminated through the modified HIPS matrix, the effect can penetrate through the whole life cycle of the inner container and cannot be attenuated or rebounded along with the use time, and the industrial pain point of repeated odor is thoroughly solved. By accurately adding 1-3 parts by weight of compatilizer, the interfacial compatibility of the porous adsorbent and an HIPS organic matrix can be effectively improved, and the adsorbent is ensured to be uniformly dispersed in resin and not agglomerated; the original core performances such as impact resistance and easy forming of the HIPS material are reserved, and the structural strength requirement of the refrigerator liner for long-term use is met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of refrigerators, and particularly relates to a preparation method of a refrigerator HIPS inner container without odor and a refrigerator HIPS inner container. BACKGROUND

[0002] As a food storage device indispensable in modern families and commercial places, the inner container of a refrigerator is a core component directly contacting or closely contacting food storage space, and has extremely high requirements for the safety, stability and use experience of the material. With the improvement of consumers' quality of life and health standards, not only is it required that the refrigerator inner container has excellent physical and mechanical properties to meet the long-term use requirements, but also more stringent requirements are put forward for its odor control; odorless release has become one of the key indicators for measuring the quality of the refrigerator inner container, and directly affects the acceptance and use satisfaction of users to the product. At present, plastic materials have become the mainstream choice for refrigerator inner containers because of their convenient processing and molding, controllable cost and ability to meet the basic use strength requirements, among which hydrogenated styrene-butadiene block copolymer (HIPS) has been widely used in this field due to its unique advantages.

[0003] Hydrogenated styrene-butadiene block copolymer (HIPS) is a modified polystyrene high molecular material, which introduces a butadiene elastomer phase into the polystyrene matrix and is subjected to hydrogenation treatment. This structural modification makes it have both the rigidity and easy processability of polystyrene and the impact resistance of butadiene elastomer, effectively making up for the defects of pure polystyrene such as brittleness and low impact strength. In addition, HIPS material also has the advantages of low cost, good chemical stability and low molding shrinkage, and can be conveniently made into refrigerator inner container parts of different shapes and sizes through conventional plastic processing technologies such as injection molding and suction molding, to meet the structural design requirements of various refrigerator products. Therefore, it has been widely and maturely applied in the fields of refrigerator, food storage box, cabinet and other household appliances and plastic parts of daily necessities that contact or nearly contact food.

[0004] However, the HIPS material has a significant odor release defect when used as a refrigerator liner, which is caused by multiple factors in the material itself and the processing process, seriously affecting its use performance and user experience. Specifically, the main sources of odor include three aspects: first, during the polymerization reaction process of HIPS resin, a small amount of monomers such as styrene cannot be completely converted and will remain inside the material. These residual monomers will slowly volatilize during subsequent processing and use, producing irritating odors; second, solvents, lubricants, antioxidants and other types of additives need to be added during the processing of HIPS material. Some additives may decompose under high-temperature processing conditions, or remain in the material incompletely dispersed, forming volatile organic compounds (VOCs) mainly composed of ethylbenzene, toluene, aldehyde and ketone substances, further exacerbating the odor problem; third, HIPS material is prone to oxidative degradation under the action of heat energy during high-temperature extrusion, injection molding and other processing steps, generating low-molecular-weight aldehydes, ketones, acids and other substances. Such oxidative degradation products also have a distinct odor. The above odors not only directly affect the storage environment inside the refrigerator, causing food to have a peculiar smell and reducing the quality of food storage, but also may cause discomfort to sensitive people, and even pose a potential health risk. In order to solve the odor problem of HIPS liner, various treatment schemes have been proposed in the prior art, such as ventilation and airing, ozone treatment, surface spraying of masking agents, etc. However, these schemes have obvious shortcomings: ventilation and airing can only remove a small amount of volatile odor substances on the surface of the material, and cannot remove the internal residual odor sources. The deodorizing effect is short-term and incomplete, and the odor may rebound over time; ozone treatment can oxidize some odor molecules, but ozone itself is irritating. After treatment, it is necessary to ensure that the ozone residue is completely removed, otherwise it may cause secondary pollution, and the method has limited effect on the removal of deep-layer odor in the material; surface spraying of masking agents only covers a layer of odor substances to mask the original odor, and does not fundamentally eliminate the odor source. Not only can it not solve the actual problem, but it may also introduce new odor risks due to the shedding or migration of the masking agent, and increase the processing procedures and costs. In summary, the existing deodorizing methods generally have problems such as short-term effect, low processing efficiency, easy secondary pollution or high cost, and cannot meet the long-term use requirements of refrigerator liners for no odor and high safety. SUMMARY

[0005] The present application provides a method for preparing an odorless refrigerator HIPS liner and an odorless refrigerator HIPS liner to solve the problems that the existing deodorizing methods in the prior art generally have short-term effect, low processing efficiency, easy secondary pollution or high cost, and cannot meet the long-term use requirements of refrigerator liners for no odor and high safety.

[0006] In a first aspect, the present application provides a method for preparing an odorless refrigerator HIPS liner, which comprises:

[0007] HIPS resin particles, porous adsorbent, reactive deodorizing agent, and compatibilizer are added to a high-speed mixer and mixed for 5-15 minutes at 50-80°C to obtain a mixture. The porous adsorbent is selected from one or more of modified zeolite, activated alumina, diatomaceous earth, and mesoporous silica. The reactive deodorizing agent is selected from zinc compounds, ferrous compounds, or amino compounds, wherein the zinc compound is zinc octanoate or zinc stearate. The compatibilizer is selected from styrene-maleic anhydride copolymer or polyethylene grafted maleic anhydride.

[0008] The mixture is fed into a twin-screw extruder for melt blending and granulation. The twin-screw extruder is equipped with at least one vacuum devouring port. During the extrusion process, the vacuum system is turned on in the middle and rear section of the screw. The melt temperature is controlled at 180-230°C. Free monomers, VOCs and small molecule products generated by the reaction are forcibly extracted from the material in the molten state to obtain modified HIPS granules.

[0009] Modified HIPS granules are fed into a cryogenic device and treated at -30°C to -50°C for 2-6 hours. After that, the granules are restored to room temperature and then the cryogenically treated low-odor HIPS granules are made into HIPS liners through injection molding or thermoforming processes.

[0010] In some possible implementations, the HIPS resin particles, porous adsorbent, reactive deodorizer, and compatibilizer are present in weight parts of 100-150 parts, 3-10 parts, 1-5 parts, and 1-3 parts, respectively.

[0011] In some possible implementations, the specific surface area of ​​the porous adsorbent is 200-800 m². 2 / g, with an average pore size of 2-50nm.

[0012] In some possible implementations, the screw temperature of the twin-screw extruder is set to 190-210℃, and the vacuum degree is controlled between -0.08 and -0.095 MPa.

[0013] In some possible implementations, during the mixing process of the high-speed mixer, an inert gas is simultaneously introduced for protection. The inert gas is nitrogen or argon, and the gas flow rate is controlled at 0.5-2 L / min.

[0014] In some possible implementations, the cryogenic treatment in the method is performed using a gradient cooling approach:

[0015] First, the modified HIPS granules are cooled from room temperature to -10℃ at a rate of 5-10℃ / h and held for 1-2 hours; then cooled to -30℃ to -50℃ at a rate of 3-5℃ / h and held for 2-6 hours; finally, they are restored to room temperature at a rate of 8-12℃ / h.

[0016] In some possible implementations, the porous adsorbent is a mixture of modified zeolite and mesoporous silica in a weight ratio of 1:1-3; wherein the modified zeolite is treated with silane coupling agent KH-550.

[0017] The treatment method is as follows: the modified zeolite is soaked in a 1-3% (w / w) ethanol solution of silane coupling agent KH-550, stirred and reacted at 40-60℃ for 2-4 hours, filtered and dried; the compatibility of the treated porous adsorbent with HIPS resin is further improved, and it can be more uniformly dispersed in the resin matrix, avoiding the decrease in adsorption efficiency caused by agglomeration.

[0018] In some possible implementations, the inner surface of the HIPS liner is treated with plasma at a power of 500-800W for 30-60s, and the treatment gas is a mixture of oxygen and nitrogen in a volume ratio of 1:5-10.

[0019] In some possible implementations, the porous adsorbent is modified zeolite, added in an amount of 5 parts by weight; the reactive deodorizer is zinc stearate, added in an amount of 2 parts by weight; and the compatibilizer is SMA, added in an amount of 2 parts by weight.

[0020] Secondly, this application provides an odorless HIPS refrigerator liner, which is prepared by the method for preparing an odorless HIPS refrigerator liner described in the first aspect.

[0021] The refrigerator's HIPS inner liner is composed of the following components by weight: 100 parts by weight of HIPS resin, 3-10 parts by weight of porous adsorbent, 1-5 parts by weight of reactive deodorizer, and 1-3 parts by weight of compatibilizer; the porous adsorbent is selected from one or more of modified zeolite, activated alumina, diatomaceous earth, and mesoporous silica, and the specific surface area of ​​the porous adsorbent is 200-800 m². 2 / g, with an average pore size of 2-50nm; the reactive deodorizer is selected from zinc compounds, ferrous compounds, or amino compounds, wherein the zinc compound is zinc octanoate or zinc stearate; the compatibilizer is selected from styrene-maleic anhydride copolymer or polyethylene grafted maleic anhydride.

[0022] As can be seen from the above, this application provides a method for preparing an odorless HIPS refrigerator liner and a refrigerator.

[0023] HIPS inner liner: This innovative method integrates four deodorization mechanisms: physical adsorption, chemical decomposition, physical removal, and low-temperature migration. It forms a comprehensive removal system targeting multiple sources of odor in HIPS inner liners, such as residual monomers, VOCs, and oxidative degradation products. Compared to existing single deodorization methods, it removes odors more thoroughly. Furthermore, the deodorization process occurs during the material manufacturing stage, eliminating odor sources by modifying the HIPS matrix itself, rather than simply masking surface odors. Therefore, the effect lasts throughout the entire lifespan of the inner liner, without diminishing or rebounding over time, completely solving the industry pain point of recurring odors. By precisely adding 1-3 parts by weight of compatibilizer, the interfacial compatibility between the porous adsorbent and the HIPS organic matrix is ​​effectively improved, ensuring that the adsorbent is uniformly dispersed in the resin and does not agglomerate. While retaining the original impact resistance and easy molding properties of HIPS material, it meets the structural strength requirements for long-term use of refrigerator inner liners. Attached Figure Description

[0024] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 A flowchart illustrating the preparation method of the odorless HIPS refrigerator liner provided in this application. Detailed Implementation

[0026] The embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described below do not represent all embodiments consistent with this application. They are merely examples of systems and methods consistent with some aspects of this application as detailed in the claims.

[0027] As an indispensable food storage device in modern homes and commercial spaces, refrigerators place extremely high demands on the safety, stability, and user experience of their inner liner, which is the core component that directly contacts or is adjacent to food storage space. With consumers' increasing emphasis on quality of life and health standards, not only are excellent physical and mechanical properties required for refrigerator inner liners to meet long-term usage needs, but also more stringent requirements for odor control. The absence of odor release has become a key indicator of refrigerator inner liner quality, directly impacting user acceptance and satisfaction. Currently, plastic materials are the mainstream choice for refrigerator inner liners due to their ease of processing, controllable cost, and ability to meet basic strength requirements. Among them, hydrogenated styrene-butadiene block copolymer (HIPS) is widely used in this field due to its unique advantages.

[0028] Hydrogenated styrene-butadiene block copolymer (HIPS) is a modified polystyrene polymer material. It incorporates a butadiene elastomer phase into the polystyrene matrix and undergoes hydrogenation. This structural modification endows it with both the rigidity and processability of polystyrene and the impact resistance of butadiene elastomers, effectively compensating for the brittleness and low impact strength of pure polystyrene. Furthermore, HIPS materials offer advantages such as low cost, good chemical stability, and low molding shrinkage. They can be easily manufactured into refrigerator inner liner components of various shapes and sizes using conventional plastic processing techniques such as injection molding and thermoforming, meeting the structural design requirements of various refrigerator products. Therefore, it has found widespread and mature application in the manufacturing of plastic components for household appliances and daily necessities that come into close contact with food, such as refrigerators, food storage boxes, and cabinets.

[0029] However, when used as a refrigerator liner, HIPS material exhibits a significant odor release defect. This defect stems from multiple factors inherent to the material itself and during processing, severely impacting its performance and user experience. Specifically, the main sources of odor include three aspects: First, during the polymerization reaction of HIPS resin, monomers such as styrene cannot be completely converted, leaving a small amount remaining inside the material. These residual monomers slowly volatilize during subsequent processing and use, producing a pungent odor. Second, various additives such as solvents, lubricants, and antioxidants are added during the processing of HIPS material. Some of these additives may decompose under high-temperature processing conditions or remain incompletely dispersed, forming volatile organic compounds (VOCs) mainly composed of ethylbenzene, toluene, aldehydes, and ketones, further exacerbating the odor problem. Third, during high-temperature extrusion and injection molding processes, HIPS material is prone to oxidative degradation under the influence of heat, generating low-molecular-weight aldehydes, ketones, acids, and other substances. These oxidative degradation products also have a noticeable odor. The aforementioned odors not only directly affect the storage environment inside the refrigerator, causing food to absorb other smells and reducing food quality, but may also cause discomfort to sensitive individuals and even pose potential health risks. To address the odor problem of HIPS liners, various solutions have been proposed in existing technologies, such as ventilation and airing, ozone treatment, and surface coating with masking agents. However, these solutions all have significant shortcomings: ventilation and airing can only remove a small amount of volatile odor substances from the material surface and cannot eliminate residual odor sources inside; the deodorization effect is short-lived and incomplete, and the odor tends to rebound over time; while ozone treatment can oxidize some odor molecules, ozone itself is irritating, and it is necessary to ensure complete removal of ozone residue after treatment, otherwise it may cause secondary pollution. Furthermore, this method has limited effectiveness in removing deep-seated odors inside the material; surface coating with masking agents merely covers the original odor by covering it with a layer of odorous material, without fundamentally eliminating the odor source. This not only fails to solve the actual problem but may also introduce new odor risks due to the masking agent peeling off or migrating, while also increasing processing steps and costs. In summary, existing deodorization methods generally suffer from problems such as short-lasting effects, low processing efficiency, easy generation of secondary pollution, or high costs, making it difficult to meet the long-term use requirements of refrigerator linings for odor-free and highly safe products.

[0030] Based on this, such as Figure 1 As shown, this application provides a method for preparing an odorless HIPS refrigerator liner, the method comprising:

[0031] HIPS resin particles, porous adsorbent, reactive deodorizing agent, and compatibilizer are added to a high-speed mixer and mixed for 5-15 minutes at 50-80°C to obtain a mixture. The porous adsorbent is selected from one or more of modified zeolite, activated alumina, diatomaceous earth, and mesoporous silica. The reactive deodorizing agent is selected from zinc compounds, ferrous compounds, or amino compounds, wherein the zinc compound is zinc octanoate or zinc stearate. The compatibilizer is selected from styrene-maleic anhydride copolymer or polyethylene grafted maleic anhydride.

[0032] The mixture is fed into a twin-screw extruder for melt blending and granulation. The twin-screw extruder is equipped with at least one vacuum devouring port. During the extrusion process, the vacuum system is turned on in the middle and rear section of the screw. The melt temperature is controlled at 180-230°C. Free monomers, VOCs and small molecule products generated by the reaction are forcibly extracted from the material in the molten state to obtain modified HIPS granules.

[0033] Modified HIPS granules are fed into a cryogenic device and treated at -30°C to -50°C for 2-6 hours. After that, the granules are restored to room temperature and then the cryogenically treated low-odor HIPS granules are made into HIPS liners through injection molding or thermoforming processes.

[0034] The weight parts of the HIPS resin particles, porous adsorbent, reactive deodorizer, and compatibilizer are 100-150 parts, 3-10 parts, 1-5 parts, and 1-3 parts, respectively.

[0035] The method provided in this application innovatively integrates four deodorization mechanisms: physical adsorption, chemical decomposition, physical removal, and low-temperature migration. It forms a comprehensive removal system targeting multiple sources of odor in HIPS liners (residual monomers, VOCs, and oxidative degradation products). Compared with existing single deodorization methods (such as ventilation and sun exposure, and surface masking), it removes odors more thoroughly. Moreover, the deodorization process occurs during the material manufacturing stage, eliminating odor sources by modifying the HIPS matrix itself, rather than simply masking surface odors. Therefore, the effect can last throughout the entire life cycle of the liner and will not diminish or rebound with the use time, completely solving the industry pain point of "recurring odors".

[0036] The core steps of the method provided in this application are raw material pretreatment and blending, melt extrusion vacuum devolatilization, and cryogenic treatment. It can be seamlessly integrated into existing plastic granulation and inner liner molding production lines. Only a "cryogenic treatment" section needs to be added to the traditional process. There is no need for large-scale modification of the original equipment. The modification cost is low and the debugging cycle is short. At the same time, all process parameters (such as 50-80℃ mixing temperature, 180-230℃ extrusion temperature, and -30℃ to -50℃ cryogenic temperature) are within the normal controllable range of industrial production. The operation is simple and can be directly adapted to the mass production needs of products such as refrigerator inner liners.

[0037] On the one hand, the functional additives (porous adsorbents, reactive deodorizers, and compatibilizers) used in the method provided in this application are all non-toxic and harmless materials (such as modified zeolite, zinc stearate, and SMA), posing no safety risk when in contact with food and meeting the "food-grade" material requirements for refrigerator liners. On the other hand, the VOCs and residual monomers extracted through vacuum volatilization during the melt extrusion stage can be centrally collected and purified through the factory's existing waste gas treatment system, avoiding direct emission of waste gas and environmental pollution. The entire process does not generate any toxic or harmful substances, and there is no problem of "introducing new pollution after deodorization".

[0038] In existing technologies, the addition of inorganic adsorbents often leads to a significant decrease in the mechanical properties of HIPS materials, such as impact strength. However, this method, by precisely adding 1-3 parts by weight of a compatibilizer (SMA or PE-g-MAH), effectively improves the interfacial compatibility between the porous adsorbent and the HIPS organic matrix, ensuring that the adsorbent is uniformly dispersed in the resin and does not agglomerate. As shown in the example data, the HIPS liner prepared using this method achieves an impact strength of 15.5 kJ / m². 2 Compared with untreated ordinary HIPS (16.0 kJ / m³), 2 ), commercially available HIPS (16.1kJ / m 2 The results are basically the same, achieving low odor and low VOCs (85μg / m³). 3 At the same time, it fully retains the original core properties of HIPS material, such as impact resistance and easy molding, to meet the structural strength requirements of refrigerator liner for long-term use.

[0039] In some embodiments, the specific surface area of ​​the porous adsorbent is 200-800 m². 2 / g, with an average pore size of 2-50nm.

[0040] 200-800m 2 The specific surface area of ​​ / g is within the reasonable range for efficient adsorption, which is much higher than that of ordinary inorganic fillers (such as ordinary calcium carbonate, whose specific surface area is only 1-10m²). 2 / g), which can provide a large number of adsorption sites formed by micropores and mesopores, can fully capture small molecule odor substances such as free styrene residual monomers, ethylbenzene, and toluene in HIPS materials, and avoid these substances from volatilizing and producing odors during subsequent processing or use.

[0041] This specific surface area range ensures sufficient adsorption capacity (avoiding incomplete capture of odor molecules due to insufficient adsorption sites) while also preventing excessively large specific surface areas (e.g., exceeding 800 m²). 2 / g) This addresses the problem of adsorbent agglomeration and difficulty in dispersing in the HIPS matrix, balancing adsorption efficiency and processing dispersibility.

[0042] The odor molecules released by HIPS liners are all small molecules, and porous adsorbents with an average pore size of 2-50nm can precisely match the adsorption requirements of these molecules.

[0043] A pore size limit of 2nm can effectively intercept and adsorb target odor molecules. If the pore size is too small (e.g., less than 2nm), the odor molecules will have difficulty entering the micropores inside the adsorbent due to steric hindrance and will not be able to contact the deep adsorption sites, thus greatly reducing the adsorption efficiency.

[0044] The upper limit of pore size is 50nm to avoid "insufficient adsorption force" due to excessively large pore size. If the pore size exceeds 50nm, the van der Waals force and capillary force of the adsorbent on small odor molecules will be significantly weakened, which will easily lead to the problem of "adsorption and desorption" and make it impossible to lock odor molecules stably for a long time.

[0045] The average pore size of 2-50nm allows odor molecules to quickly enter the microporous channels inside the adsorbent. At the same time, the suitable pore structure generates stable adsorption force, achieving the dual effect of "efficient capture + long-term locking", reducing the volatilization of odor molecules to the outside of HIPS material from the source.

[0046] On the one hand, its physical adsorption can temporarily lock in some odor molecules, providing time for reactive deodorizers (such as zinc stearate) to fully catalyze the decomposition of active odor molecules such as aldehydes and ketones, thus preventing the active odor molecules from evaporating prematurely.

[0047] On the other hand, for trace odor molecules that are not completely extracted during the vacuum de-volatilization stage, the porous adsorbent can retain them inside the HIPS matrix through its pore structure, preventing them from being released during subsequent cryogenic treatment or use of the inner liner, further reducing the total VOCs release and odor level, and ultimately achieving a comprehensive odor removal closed loop of "physical adsorption + chemical decomposition + vacuum de-volatilization".

[0048] In some embodiments, the screw temperature of the twin-screw extruder is set to 190-210°C, and the vacuum degree is controlled between -0.08 and -0.095 MPa.

[0049] The melting temperature of HIPS resin is typically between 180-230℃, with 190-210℃ being its optimal melting range. This range allows the HIPS resin particles to fully melt and form a homogeneous melt, while ensuring the melt has a suitable viscosity. This prevents insufficient melting and excessively high melt viscosity due to excessively low temperatures (such as below 190℃), which could hinder the migration and diffusion of odor molecules within the melt. Conversely, excessively high temperatures (such as above 210℃) could result in excessively low melt viscosity, increasing the risk of material slippage and process instability during extrusion. Furthermore, it avoids secondary oxidation and degradation of HIPS resin due to overheating, which could generate new aldehydes and ketones that exacerbate odor problems.

[0050] The residual styrene monomers, ethylbenzene, toluene, and other VOCs and small molecule oxidation products in HIPS materials have boiling points mostly between 80-150℃. A melting temperature of 190-210℃ can significantly increase the saturated vapor pressure of these substances in the HIPS melt, making it easier for them to break free from intermolecular forces inside the melt and volatilize and escape to the surface of the melt, thus creating conditions for extraction in the subsequent vacuum devolatilization process.

[0051] A high vacuum environment (-0.08 to -0.095 MPa) can significantly reduce the pressure inside the extruder barrel, creating a pressure difference of "high vapor pressure inside the melt - low pressure inside the barrel". This pressure difference becomes the "driving force" for odor molecules, causing residual monomers and VOCs that have volatilized from the melt to move rapidly to the vacuum devolve port and be forcibly extracted from the barrel. This greatly reduces the residence time of odor substances in the melt and lowers the probability of them redissolving or being adsorbed back into the melt.

[0052] Compared to low vacuum levels (e.g., -0.05 to -0.07 MPa), high vacuum levels of -0.08 to -0.095 MPa can more thoroughly remove trace amounts of non-volatile odorous substances (such as some high-boiling-point aldehydes and ketones) from the melt. This prevents these substances from being slowly released during subsequent cryogenic treatment or use of the inner liner after the melt cools and granulates, ensuring the low-odor characteristics of the modified HIPS granules. This vacuum range does not use higher absolute vacuum levels (e.g., below -0.095 MPa) to prevent excessive removal of small-molecule plasticizers (if added) or necessary additives from the melt due to excessively high vacuum, thus avoiding a decrease in the mechanical properties (such as toughness) of the HIPS material. It also reduces the requirements for vacuum system equipment selection and energy costs, balancing deodorization effect with process economy.

[0053] In some embodiments, during the mixing process of the high-speed mixer, an inert gas is simultaneously introduced for protection. The inert gas is nitrogen or argon, and the gas flow rate is controlled at 0.5-2 L / min.

[0054] The unsaturated bonds of hydrogenated butadiene and the benzene ring side chains in the HIPS resin molecular structure are prone to thermo-oxidative aging reaction when in direct contact with air (oxygen) under mixed heating conditions of 50-80℃. On the one hand, oxygen attacks the weak sites in the resin molecular chain, causing the molecular chain to break and generate low molecular weight aldehydes, ketones, and acids, which are one of the important sources of odor in HIPS liners. On the other hand, the oxidation reaction may also trigger cross-linking between resin molecules, affecting the fluidity of subsequent melt processing.

[0055] Nitrogen or argon, as inert gases, are chemically stable and do not react with HIPS resin or functional additives (porous adsorbents, reactive deodorizers, etc.). When introduced, they can quickly replace the air in the high-speed mixer, forming an "inert protective layer" on the surface of the raw material particles. This isolates oxygen from contact with the HIPS resin, inhibiting the thermo-oxidative aging reaction at its source. It also prevents the addition of oxidative degradation products during the mixing stage from exacerbating odor problems, ensuring that subsequent deodorization processes only need to treat the original odor sources of the resin (residual monomers, processing aid residues), thus reducing the overall difficulty of deodorization.

[0056] In some embodiments, the cryogenic treatment in the method is performed using a gradient cooling approach:

[0057] First, the modified HIPS granules are cooled from room temperature to -10℃ at a rate of 5-10℃ / h and held for 1-2 hours; then cooled to -30℃ to -50℃ at a rate of 3-5℃ / h and held for 2-6 hours; finally, they are restored to room temperature at a rate of 8-12℃ / h.

[0058] Porous adsorbents in modified HIPS granules (specific surface area 200-800 m²) 2 The adsorbent (with an average pore size of 2-50 nm) is the core component for the physical adsorption of odor molecules, and its uniform dispersion in the resin matrix directly affects the deodorization effect. If the cryogenic treatment involves drastic temperature changes, it will not only damage the granular structure but may also cause the uniformly dispersed porous adsorbent to agglomerate due to thermal stress.

[0059] When adsorbents agglomerate, their microporous structure is blocked, significantly reducing their surface area utilization and making it impossible to effectively capture any trace odor molecules that may subsequently be generated. This leads to odor rebound during long-term use of the inner liner. Gradient cooling / heating avoids severe stress within the granules, ensuring that the porous adsorbent remains uniformly dispersed with its microporous structure intact and fully exposed. This not only assists in adsorbing odor molecules that migrate out during the cryogenic stage but also continuously "intercepts" any trace odor substances that may be slowly released during subsequent use of the inner liner, ensuring the longevity of the odor removal effect.

[0060] In some embodiments, the porous adsorbent is a mixture of modified zeolite and mesoporous silica in a weight ratio of 1:1-3; wherein the modified zeolite is treated with silane coupling agent KH-550.

[0061] The treatment method is as follows: the modified zeolite is soaked in a 1-3% (w / w) ethanol solution of silane coupling agent KH-550, stirred and reacted at 40-60℃ for 2-4 hours, filtered and dried; the compatibility of the treated porous adsorbent with HIPS resin is further improved, and it can be more uniformly dispersed in the resin matrix, avoiding the decrease in adsorption efficiency caused by agglomeration.

[0062] In some embodiments, the inner surface of the HIPS liner is treated with plasma at a power of 500-800W for 30-60s, and the treatment gas is a mixture of oxygen and nitrogen in a volume ratio of 1:5-10.

[0063] During plasma treatment, a power of 500-800W can excite a mixture of oxygen and nitrogen to generate high-energy particles (such as electrons, ions, and free radicals), which can quickly act on the inner surface of the liner.

[0064] On the one hand, it directly oxidizes and decomposes the organic odor molecules remaining on the surface, converting them into odorless small molecules such as CO2 and H2O, thus completely eliminating the "last layer" of odor sources on the surface.

[0065] On the other hand, it destroys the adsorption sites of odor molecules on the surface, reduces the adhesion of volatile odors or food odors in the air to the surface during subsequent use, avoids "secondary odors" caused by surface adsorption, further reduces the overall odor level of the inner liner, and improves the user experience.

[0066] During long-term use, the inner surface of HIPS liners may slowly oxidize due to contact with air and food, or trace amounts of residual odor molecules may migrate to the surface due to changes in ambient humidity. The modified layer formed by plasma treatment has good chemical stability.

[0067] Under the action of high-energy particles, the surface molecular chains undergo cross-linking reaction to form a dense "protective layer" that can block residual odor molecules from migrating to the surface, while also inhibiting the contact between external oxygen and the inner liner, thus slowing down the surface oxidation and aging rate.

[0068] Controlling the ratio of oxygen to nitrogen (1:5-10) can balance surface activity and stability—oxygen provides sufficient oxidative modification, while nitrogen avoids the generation of too many unstable groups on the surface, preventing the decomposition of groups during long-term use and the generation of new odor substances, thereby delaying odor rebound and ensuring that the inner liner is in a low-odor state for a long time.

[0069] In some embodiments, the porous adsorbent is modified zeolite, and the amount added is 5 parts by weight; the reactive deodorizer is zinc stearate, and the amount added is 2 parts by weight; the compatibilizer is SMA, and the amount added is 2 parts by weight.

[0070] In some embodiments, this application provides an odorless HIPS refrigerator liner, which is prepared by the odorless HIPS refrigerator liner preparation method described in the above embodiments;

[0071] The refrigerator's HIPS inner liner is composed of the following components by weight: 100 parts by weight of HIPS resin, 3-10 parts by weight of porous adsorbent, 1-5 parts by weight of reactive deodorizer, and 1-3 parts by weight of compatibilizer; the porous adsorbent is selected from one or more of modified zeolite, activated alumina, diatomaceous earth, and mesoporous silica, and the specific surface area of ​​the porous adsorbent is 200-800 m². 2 / g, average pore size 2-50nm; the reactive deodorizer is selected from zinc compounds, ferrous compounds or amino compounds, wherein the zinc compound is zinc octanoate or zinc stearate; the compatibilizer is selected from styrene-maleic anhydride copolymer or polyethylene grafted maleic anhydride.

[0072] This application innovatively combines four mechanisms: physical adsorption (porous materials), chemical decomposition (reactive agents), physical removal (vacuum devolatilization), and cryogenic migration (deep cryogenic treatment). This comprehensive approach targets multiple sources of odor, achieving results far exceeding those of any single method. The odor removal process occurs during the material manufacturing stage, eliminating the odor source at its core, rather than simply masking it on the surface. Therefore, the effect lasts throughout the product's entire lifecycle and does not diminish or rebound over time.

[0073] This application can be seamlessly integrated into existing plastic granulation and molding production lines, requiring only the addition of a cryogenic treatment section. The modification cost is low, making it ideal for large-scale industrial applications. All deodorizing additives used are non-toxic and harmless, and the vacuum-extracted waste gas can be centrally treated. The entire process does not generate secondary pollution and meets environmental protection requirements. By adding a compatibilizer, good dispersion of the adsorbent is ensured, avoiding a significant decrease in the material's mechanical properties (especially impact strength) caused by the addition of inorganic substances.

[0074] Example 1:

[0075] Ingredients: 100 parts HIPS resin, 5 parts modified zeolite (specific surface area 500 m²) 2 (g), 2 parts zinc stearate, 2 parts SMA compatibilizer.

[0076] Premixing: Put the above raw materials into a high-speed mixer and mix at 60°C for 10 minutes.

[0077] Extrusion devolatilization: The mixture is fed into a co-rotating twin-screw extruder, with the screw temperature set to 190-210℃. A vacuum pump is activated at the sixth section of the barrel, maintaining a vacuum of -0.09 MPa. The melt is extruded, water-cooled, and pelletized to obtain primary pellets.

[0078] Cryogenic treatment: Place the granules in a cryogenic chamber at -40℃ for 4 hours.

[0079] Performance Testing: The treated granules were injection molded into standard samples and cup-shaped samples. Sensory odor evaluation was conducted according to "GB / T XXXX Plastic Odor Evaluation Method" (6-person expert panel, 1-5 level rating, lower score is better), and [the evaluation was then performed using...].

[0080] Total VOCs release was detected by GC-MS (gas chromatography-mass spectrometry).

[0081] Comparative Example 1: The same HIPS raw materials and processing parameters as in Example 1 were used, but no additives were added and no vacuum devolatilization and cryogenic treatment were performed.

[0082] Comparative Example 2: Using the same HIPS raw materials and processing parameters as in Example 1, additives were added and vacuum devolatilization was performed, but no cryogenic treatment was performed.

[0083] Table 1

[0084]

[0085] The results in Table 1 show that the HIPS material (Example 1) prepared using the complete process of this invention has a much lower odor level and VOCs emission than the comparative example and commercially available products, while maintaining good mechanical properties.

[0086] Examples 2-4:

[0087] Changing the type of adsorbent (e.g., using mesoporous silica), the proportion of reactive deodorizing agent (e.g., using 1-5 parts of zinc octanoate), or the cryogenic temperature (e.g., -30℃ or -50℃) can all achieve excellent deodorization effects similar to those in Example 1, demonstrating the universality and adjustability of the present invention.

[0088] As can be seen from the above embodiments, this application provides a method for preparing an odorless HIPS refrigerator liner and a refrigerator.

[0089] HIPS inner liner: This innovative method integrates four deodorization mechanisms: physical adsorption, chemical decomposition, physical removal, and low-temperature migration. It forms a comprehensive removal system targeting multiple sources of odor in HIPS inner liners, such as residual monomers, VOCs, and oxidative degradation products. Compared to existing single deodorization methods, it removes odors more thoroughly. Furthermore, the deodorization process occurs during the material manufacturing stage, eliminating odor sources by modifying the HIPS matrix itself, rather than simply masking surface odors. Therefore, the effect lasts throughout the entire lifespan of the inner liner, without diminishing or rebounding over time, completely solving the industry pain point of recurring odors. By precisely adding 1-3 parts by weight of compatibilizer, the interfacial compatibility between the porous adsorbent and the HIPS organic matrix is ​​effectively improved, ensuring that the adsorbent is uniformly dispersed in the resin and does not agglomerate. While retaining the original impact resistance and easy molding properties of HIPS material, it meets the structural strength requirements for long-term use of refrigerator inner liners.

[0090] Similar parts between the embodiments provided in this application can be referred to mutually. The specific implementation methods provided above are only a few examples under the overall concept of this application and do not constitute a limitation on the scope of protection of this application. For those skilled in the art, any other implementation methods extended from the solution of this application without creative effort shall fall within the scope of protection of this application.

Claims

1. A method for preparing an odorless HIPS refrigerator liner, characterized in that, The method includes: HIPS resin particles, porous adsorbent, reactive deodorizing agent, and compatibilizer are added to a high-speed mixer and mixed for 5-15 minutes at 50-80°C to obtain a mixture. The porous adsorbent is selected from one or more of modified zeolite, activated alumina, diatomaceous earth, and mesoporous silica. The reactive deodorizing agent is selected from zinc compounds, ferrous compounds, or amino compounds, wherein the zinc compound is zinc octanoate or zinc stearate. The compatibilizer is selected from styrene-maleic anhydride copolymer or polyethylene grafted maleic anhydride. The mixture is fed into a twin-screw extruder for melt blending and granulation. The twin-screw extruder is equipped with at least one vacuum devouring port. During the extrusion process, the vacuum system is turned on in the middle and rear section of the screw. The melt temperature is controlled at 180-230°C. Free monomers, VOCs and small molecule products generated by the reaction are forcibly extracted from the material in the molten state to obtain modified HIPS granules. Modified HIPS granules are fed into a cryogenic device and treated at -30°C to -50°C for 2-6 hours. After that, the granules are restored to room temperature and then the cryogenically treated low-odor HIPS granules are made into HIPS liners through injection molding or thermoforming processes.

2. The method for preparing the odorless HIPS refrigerator liner according to claim 1, characterized in that, The weight parts of the HIPS resin particles, porous adsorbent, reactive deodorizer, and compatibilizer are 100-150 parts, 3-10 parts, 1-5 parts, and 1-3 parts, respectively.

3. The method for preparing the odorless HIPS refrigerator liner according to claim 2, characterized in that, The specific surface area of ​​the porous adsorbent is 200-800 m². 2 / g, with an average pore size of 2-50nm.

4. The method for preparing the odorless HIPS refrigerator liner according to claim 1, characterized in that, The screw temperature of the twin-screw extruder is set at 190-210℃, and the vacuum degree is controlled between -0.08 and -0.095MPa.

5. The method for preparing the odorless HIPS refrigerator liner according to claim 1, characterized in that, During the mixing process in the high-speed mixer, an inert gas is simultaneously introduced for protection. The inert gas is nitrogen or argon, and the gas flow rate is controlled at 0.5-2 L / min.

6. The method for preparing the odorless HIPS refrigerator liner according to claim 1, characterized in that, In the method described, cryogenic treatment is performed using a gradient cooling approach. First, the modified HIPS granules are cooled from room temperature to -10℃ at a rate of 5-10℃ / h and held for 1-2 hours; then cooled to -30℃ to -50℃ at a rate of 3-5℃ / h and held for 2-6 hours; finally, they are restored to room temperature at a rate of 8-12℃ / h.

7. The method for preparing the odorless HIPS refrigerator liner according to claim 2, characterized in that, The porous adsorbent is a mixture of modified zeolite and mesoporous silica in a weight ratio of 1:1-3; wherein the modified zeolite is treated with silane coupling agent KH-550.

8. The method for preparing the odorless HIPS refrigerator liner according to claim 1, characterized in that, The inner surface of the HIPS liner is treated with plasma at a power of 500-800W for 30-60 seconds. The treatment gas is a mixture of oxygen and nitrogen in a volume ratio of 1:5-10.

9. The method for preparing the odorless HIPS refrigerator liner according to claim 2, characterized in that, The porous adsorbent is modified zeolite, and the addition amount is 5 parts by weight; the reactive deodorizer is zinc stearate, and the addition amount is 2 parts by weight; the compatibilizer is SMA, and the addition amount is 2 parts by weight.

10. An odorless HIPS refrigerator liner, characterized in that, The inner liner is obtained by the method for preparing the odorless refrigerator HIPS inner liner according to any one of claims 1-9; The refrigerator's HIPS inner liner is composed of the following components by weight: 100 parts by weight of HIPS resin, 3-10 parts by weight of porous adsorbent, 1-5 parts by weight of reactive deodorizer, and 1-3 parts by weight of compatibilizer; the porous adsorbent is selected from one or more of modified zeolite, activated alumina, diatomaceous earth, and mesoporous silica, and the specific surface area of ​​the porous adsorbent is 200-800 m². 2 / g, with an average pore size of 2-50nm; the reactive deodorizer is selected from zinc compounds, ferrous compounds, or amino compounds, wherein the zinc compound is zinc octanoate or zinc stearate; the compatibilizer is selected from styrene-maleic anhydride copolymer or polyethylene grafted maleic anhydride.

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