A method for removing impurities from polymers based on steam distillation.

Abstract

The present invention provides a steam distillation method and apparatus for highly removing VOCs from polymer resins and their products, significantly reducing the odor of the polymer resins and their products. The method also removes inorganic ash remaining in the polymer resin. This method involves continuously contacting the material with saturated steam at a predetermined temperature for a predetermined period of time, concentrating and discharging volatile organic compounds (VOCs) and small inorganic molecules (ash) adsorbed on the surface of the polymer or encapsulated within the polymer into the gas or liquid phase, thereby reducing the VOCs and ash content in the polymer material and significantly reducing the odor of the polymer resin or material.

Description

[Technical Field]

[0001] The present invention is in the field of polymer production and specifically provides a process for efficiently removing impurity molecules, especially VOCs, odor molecules and ash, in polymers. [Background technology]

[0002] In recent years, there has been an increasing demand for lighter automotive products and more eco-friendly plastic products in the manufacturing and daily life sectors, such as home appliances and interior products, plastic toys, food contact materials, and medical materials. Polymer resins have excellent overall performance, such as being non-toxic, low density, easy to process, high impact strength, corrosion and heat resistance, and high cost performance, and are therefore widely used in the interior and exterior of automobiles, home appliances and interior products, toys, food packaging materials, and medical materials.

[0003] Due to the influence of many factors, such as the purity of the polymerization monomer, catalyst residues, the polymerization process, the decomposition of auxiliary agents, and the decomposition of the resin itself, commercially available resins generally emit volatile organic compounds (VOCs) to varying degrees. According to a report by the US International Technology Assessment Center, VOCs are one of the most significant threats to human health in modern society, and poor air quality is directly related to people's health. The harm caused by VOC pollution to people's health has already attracted the attention of countries, manufacturers, and consumers.

[0004] As society becomes more environmentally conscious, environmental laws and regulations have become more stringent. VOC and odor issues in plastics have become a growing concern for consumers, manufacturers, and management departments. Many product manufacturers require VOC indicators for raw materials and finished products, particularly in the automotive industry, requiring a total carbon volatility of less than 80 μg C / g for interior materials. The newly revised national standard GB 4806.1-2016, "Common Safety Requirements for Food Contact Materials and Products," explicitly requires food contact materials and products to have no noticeable odor. Furthermore, existing resins have high VOC content, requiring multiple replacements after the resin enters the packaging tank, making the packaging process more difficult. Furthermore, new air emission laws and regulations have led to frequent replacement gas emissions exceeding the standard. The new "Synthetic Resin Industrial Pollutant Emission Standards" began enforcement on July 1, 2017, setting a limit of 100 mg / m3 for non-methane total hydrocarbon emissions for general enterprises. 3 In areas where development density is already high, environmental load capacity is weak, or the air quality tolerance is low, the ecological environment is fragile, and serious air pollution problems are likely to occur, and therefore protective measures are required, enterprises' pollutant discharge activities will be strictly restricted, and stricter emission limits (60 mg / m3) will be imposed. 3 ) is being implemented, reducing VOC issues in plastics production and processing is already a very pressing issue.

[0005] In response to this situation, several well-known overseas companies and research institutions have conducted various levels of research on low-VOC plastics and have made some progress. In the processing field, the main measures for reducing VOCs and odors in plastic products include: (1) screening and using more effective, compatible, and stable additives. Alternatively, additive systems with synergistic effects can achieve stability at low dosages, effectively reducing VOCs and odors in resins. (2) optimizing the processing process. Granulation by high-temperature extrusion, using vacuum suction during the extrusion process, and heating and drying the granulated particles at high temperatures can all remove some of the residues in polypropylene. (3) adding ingredients with good adsorption properties for low-molecular-weight residues. Research has shown that the addition of inorganic porous materials such as volcanic ash and zeolite molecular sieves can also eliminate VOCs in polypropylene in certain amounts, but the effectiveness depends heavily on the specific surface area, pore structure, surface structure, pore size, and pore size distribution of these materials.

[0006] While these measures have some effect on reducing new VOC emissions during processing, they are insufficient to address the problem of high VOC content in the resin raw materials themselves. Furthermore, the addition of large amounts of adsorbent additives to resin raw materials results in the presence of large amounts of ash. Ash is the metal and non-metal oxides that remain when resin is completely burned at high temperatures. Resins with high ash content have a significant impact on plastic processing, particularly in processes that require elongation, such as film and fiber processing. High ash content not only significantly increases production costs, but also significantly impacts the physical and chemical properties of the product, affecting the mechanical properties of the plastic, resulting in whitening and defects in film materials, thread breakage during the spinning process, and reduced mechanical strength. Taking polypropylene as an example, high-purity PP with a relatively low ash content (generally less than 0.0080% by mass) shows promising applications in fields such as electronics, electrical appliances, medicine, food, and textiles. The National Medical Products Administration's collection of standards for packaging materials and containers that come into direct contact with pharmaceuticals requires that the mass fractions of the metal elements copper, cadmium, chromium, lead, tin, and barium in PP infusion bottles, as measured by atomic absorption spectroscopy, be 0.0003% or less, and that the mass fraction of PP used as capacitor film be 0.0050% or less. Currently, most commercially available resins have an ash content of around 0.03-0.3%, and how to reduce the ash content, improve the stability of plastics during processing and use, and fully utilize their performance are issues that need to be addressed.

[0007] As noted above, the art is lacking a method for efficiently removing VOCs, ash, and reducing odor levels in resins. Summary of the Invention

[0008] It is an object of the present invention to provide a method for removing VOCs and ash and reducing odor levels in polymeric materials. In a first aspect of the present invention, there is provided a method for highly removing volatile organic compounds (VOCs), reducing odors, and removing inorganic ash from polymers, the method comprising the step of continuously contacting water vapor with the polymer to remove the volatile organic compounds (VOCs) and odor-causing components from the polymer.

[0009] In another preferred embodiment, the process is carried out under atmospheric or elevated pressure. In a second aspect of the present invention, there is provided a method for removing inorganic ash from a polymer to a high degree, which further comprises the step of dissolving and removing the inorganic ash from the polymer by continuously contacting water vapor with the polymer.

[0010] In another preferred embodiment, water in phase equilibrium with water vapor contacts the polymer simultaneously. In another preferred embodiment, the process is carried out under atmospheric or elevated pressure.

[0011] In another preferred embodiment, the method comprises the step (a): (a) In the reaction system, water vapor in a phase equilibrium state is continuously brought into contact with the polymer for 0.5 to 6 hours (Example 38), preferably 0.5 to 3 hours.

[0012] In another preferred embodiment, the organic matter is selected from the group consisting of volatile organic compounds (VOCs), odorants, or combinations thereof. In another preferred embodiment, the inorganic ash content is removed by reducing the ash content in the polymer by ≥ 20% relative to the original ash content (concentration), preferably to 110 ppm or less.

[0013] In another preferred embodiment, the high degree of removal of organic matter means that the VOC in the polymer is reduced to ≦100 ppm, preferably ≦50 ppm, more preferably ≦10 ppm, and most preferably ≦1 ppm (based on the VDA277 standard test).

[0014] In another preferred embodiment, the organic matter is removed when the odor level of the polymer material is ≦grade 3, preferably ≦grade 2 (according to the VW50180 test). In another preferred embodiment, the temperature of the steam is 100 to 200°C.

[0015] In another preferred embodiment, the reaction system is isolated from air or oxygen during the contacting process. Preferably, the isolation from air or oxygen means that the oxygen content of the reaction system is less than 5% (v / v) during the entire process, preferably less than 1% (v / v), preferably less than 0.1% (v / v), more preferably less than 100 ppm.

[0016] In another preferred embodiment, the method further comprises, before step (a), a step of replacing the air in the reaction system by first blowing the reaction system with an inert gas or water vapor.

[0017] In another preferred embodiment, the method further comprises continuously introducing steam into the reaction system and simultaneously discharging the steam and / or condensed water from the cooling system, and preferably the steam discharging rate is 1 to 200 kg steam / ton of polymer / hour, preferably 1 to 120 kg steam / ton of polymer / hour, more preferably 5 to 50 kg steam / ton of polymer / hour, and most preferably 5 to 25 kg steam / ton of polymer / hour.

[0018] In another preferred embodiment, the steam and / or cooling condensate is discharged intermittently or continuously. In another preferred embodiment, the polymer is selected from the group consisting of polyethylene (PE), polypropylene (PP), polybutene PB-1, acrylonitrile / butadiene / styrene terpolymer (ABS), ethylene propylene rubber (EPDM, EPM), polyolefin elastomer (POE), olefin block copolymer (OBC), nylon (PA), polycarbonate (PC), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, or polyphenylene sulfide, or a combination thereof.

[0019] In another preferred embodiment, the polymer is polypropylene (PP) or random copolymer polypropylene (PPR), and preferably, the melt index of the polypropylene (PP) or random copolymer polypropylene (PPR) is in the range of 0.1 to 2000 g / 10 min (measured according to the GB / T 2682-2000 method).

[0020] In another preferred embodiment, the polypropylene (PP) is a medical grade, a specialized resin for automotive interiors, or a specialized resin for food contact applications. In another preferred embodiment, the polypropylene is a meltblown grade resin, a syringe grade resin, or a protective equipment grade resin.

[0021] In another preferred embodiment, the polypropylene (PP) is a resin exclusively used for realizing electronic and electrical components. In another preferred embodiment, the polyethylene is ultra-high molecular weight polyethylene UHMWPE or cross-linked polyethylene PEX.

[0022] In another preferred embodiment, the polymer is a modified polymer or polymer product. In another preferred embodiment, the polymer is polymer fine particles, and the particle size of the fine particles is 0.05 mm to 5 mm, preferably 0.1 to 3 mm.

[0023] In another preferred embodiment, the steam is high-pressure steam or low-pressure steam. In another preferred embodiment, the temperature of the steam is selected depending on the melting point of the polymer. In another preferred embodiment, the temperature of the water vapor is 20 to 50° C. lower than the melting point of the polymer, preferably 20 to 30° C. lower than the melting point of the polymer.

[0024] In another preferred example, when the particle size of the polymer is less than 1 mm and the VOC content in the polymer is less than 2000 ppm, the time for maintaining the polymer at a temperature corresponding to saturated steam is 0.5 to 3 hours, preferably 0.5 to 2 hours.

[0025] In another preferred embodiment, when the particle size of the polymer is <1 mm and the VOC content is ≥ 2000 ppm, the time for maintaining the polymer at a temperature corresponding to saturated water vapor is 1 to 5 hours, preferably 1 to 3 hours.

[0026] In another preferred example, when the polymer diameter is ≧1 mm and the VOC content is <1000 ppm, the time for maintaining the polymer at a temperature corresponding to saturated water vapor is 1 to 5 hours, preferably 2 to 4 hours.

[0027] In another preferred embodiment, when the particle size of the polymer material is ≧1 mm and the VOC content is ≧1000 ppm, the time for maintaining the polymer at a temperature corresponding to saturated steam is 3 to 7 hours, preferably 3 to 5 hours, and most preferably 3 to 4 hours.

[0028] In another preferred embodiment, the steam is a mixture of steam and water in phase equilibrium. In another preferred embodiment, the step (a) comprises the following substeps: (a1) charging the polymeric material into a facility, preferably a vertical or horizontal facility; (a2) passing the steam through the equipment in step (a1) and directly contacting the steam with the polymer continuously for 0.5 to 6 hours in a phase equilibrium state, and simultaneously discharging the steam that has come into contact with the polymer; (a3) dehydrating and drying the polymeric material; (a4) The polymer material dehydrated and dried in step (a3) is discharged and collected.

[0029] In another preferred embodiment, the method further comprises a step of preheating the polymer material before the step (a1). In another preferred embodiment, the method further comprises the step of quenching the purified and discharged polymeric material to lower its temperature. In another preferred embodiment, the method further comprises a step of pre-dehydrating the polymer material before the step (a).

[0030] In another preferred embodiment, in the step (a1), the polymer is divided and fed into the equipment, and then steps (a2) to (a4) are carried out to realize an intermittent operation. In another preferred embodiment, the steps (a1) to (a4) are carried out continuously, where the continuous operation means that the polymer continuously enters the equipment, passes through steps (a2) to (a3), and is continuously discharged and collected in operation (a4).

[0031] In another preferred embodiment, the method further comprises the step of blowing nitrogen gas through the entire reaction system before carrying out the substep (a1) to adjust the oxygen content of the reaction system to less than 5% (v / v).

[0032] In another preferred embodiment, the equipment is a device capable of achieving steam distillation. In a second aspect of the present invention, there is provided an apparatus for highly efficient removal of volatile organic compounds (VOCs), reducing polymer odors, and removing inorganic ash from polymers, the apparatus comprising: Steam stripping equipment (2); a feed valve set (8) located upstream of the steam stripping facility and connected to the top feed port of the steam stripping tower for controlling the feeding of polymer to the steam stripping tower; A set of take-off valves (9) located downstream of said steam stripping tower for controlling the outflow of polymer from said steam stripping tower.

[0033] In another preferred embodiment, the reaction facility further comprises a preliminary dehydration tower (1) located upstream of the set of feed valves. In another preferred embodiment, the apparatus further comprises a cooler (6), the inlet of which is connected to the exhaust outlet of the steam stripping tower, and the outlet of which is connected to a condensate tank (7).

[0034] In another preferred embodiment, the apparatus further comprises a circulating water cooling system for rapidly cooling and lowering the temperature of the polymer discharged from the steam stripping tower, and preferably, the circulating water cooling system comprises: a heat exchanger (3) located downstream of the extraction valve set and connected to a circulating water tank via a transfer pump (4); A venturi feeder (5) having a first inlet connected to the take-off valve assembly and a second inlet connected to the heat exchanger.

[0035] In another preferred embodiment, the exhaust outlet of the steam stripping tower is connected to the cooler via a blower (10). In a third aspect of the present invention, there is provided a method for highly removing volatile organic compounds (VOCs), reducing polymer odor, and removing inorganic ash from polymers, the method being carried out in an apparatus as described in the second aspect above, and comprising the steps of: (i) introducing polymer through the feed valve set (8) and into the feed port at the top of the steam stripping tower (2); (ii) introducing steam into the steam stripping tower and allowing it to exchange heat with the polymer so that the operating pressure inside the steam stripping tower corresponds to the saturated vapor pressure; (iii) controlling the rotary take-off valve assembly (9) so that the polymer is discharged; Preferably, prior to steps (i) to (iii), the system is purged with nitrogen gas so that the oxygen content of the gas phase components in the steam stripping tower is less than 1%, preferably less than 0.1%, more preferably less than 100 ppm.

[0036] In another preferred embodiment, during the step (ii) above, condensed water is periodically discharged from the bottom of the steam stripping tower. In another preferred embodiment, the steps (ii) and (iii) are carried out simultaneously (i.e., during step (ii), the rotary take-off valve is controlled to be on to ensure the residence time of the material in the steam equipment).

[0037] In another preferred embodiment, the method further comprises the step of (iv) introducing the polymer into a venturi feeder (5) and mixing it with cooled condensed water to quench the polymer and transport it to a downstream dehydration step. Preferably, the method further comprises the step of discharging the exhaust gas from an exhaust outlet of the steam stripping tower.

[0038] In another preferred embodiment, the method further comprises, before the step (i), a step of placing the polymer in a pre-dehydration tower (1) to perform a pre-dehydration step. In another preferred embodiment, the exhaust gas is cooled in a cooler (6) after being discharged, and then enters a condensate tank (7). Preferably, the method further includes a step of introducing non-condensable components of the exhaust gas into an exhaust gas treatment system, mixing them with steam, and then introducing them again into the steam stripping tower (2).

[0039] In another preferred embodiment, the method is carried out in an apparatus comprising: Slightly negative pressure steam stripping tower (302); a feed valve group (308) located upstream of the slightly negative pressure steam stripping tower, connected to the top feed port of the slightly negative pressure steam stripping tower, for controlling the feeding of resin into the slightly negative pressure steam stripping tower; A take-off valve set (309) is located downstream of the slightly negative pressure steam stripping tower, for controlling the outflow of resin from the slightly negative pressure steam stripping tower.

[0040] Preferably, the apparatus further comprises a pre-dehydration tower (301) located upstream of the set of feed valves; and / or Negative pressure blower (307); and / or a cooler (306) having an inlet connected to the outlet of a negative pressure blower at the exhaust discharge of said slightly negative pressure steam stripping tower; and / or a heat exchanger (303) located downstream of the set of withdrawal valves and connected to a circulating water tank via a transfer pump (304); and / or The first inlet includes a set of take-off valves and the second inlet includes a venturi feeder (305) connected to the heat exchanger.

[0041] When using the above device, the method comprises the steps of: (i) introducing the polymer into the feed valve set (308) and allowing it to enter the top feed port of the slightly negative pressure steam stripping tower (302); (ii) introducing steam into the water at the bottom of the slightly negative pressure steam stripping tower to generate steam which exchanges heat with the polyethylene or ethylene copolymer, thereby controlling the temperature in the tower so that the temperature of the polyethylene or ethylene copolymer is maintained at 50 to 95°C, thereby removing impurity molecules in the gas phase; (iii) Activating the rotary take-off valve assembly (309) to discharge the heavy resin.

[0042] Preferably, the method further comprises the steps of: (iv) The polyethylene or ethylene copolymer is quenched and cooled by introducing the polyethylene or ethylene copolymer into a venturi feeder (305) so that it mixes with circulating cooling water.

[0043] Preferably, the method further includes, before the step (i), a step of placing the resin in a pre-dehydration tower (301) to perform a pre-dehydration step. Preferably, the method further comprises a step of controlling the vacuum level of the slightly negative pressure steam stripping tower by introducing the exhaust gas discharged from the top of the slightly negative pressure steam stripping tower into a negative pressure blower (307), and suitably, the method further comprises a step of cooling the exhaust gas discharged by the negative pressure blower (307) by introducing it into a cooler (6).

[0044] In another preferred embodiment, the method is carried out in an apparatus comprising: Wet nitrogen gas steam stripping tower (202); a feed valve set (208) located upstream of the wet nitrogen gas steam stripping tower, connected to the top feed port of the wet nitrogen gas steam stripping tower, for controlling the feeding of resin into the wet nitrogen gas steam stripping tower; A set of outlet valves (209) located downstream of the wet nitrogen gas steam stripping tower for controlling the outflow of resin from the wet nitrogen gas steam stripping tower.

[0045] The apparatus further includes a pre-dehydration tower (201) located upstream of the feed valve set. The apparatus further includes a cooler (206) having an inlet connected to the exhaust outlet of the wet nitrogen gas steam stripping tower and an outlet connected to a condensate tank (207), and preferably further includes a nitrogen gas heater (211) located upstream of the cooler for heating and sending the exhaust gas discharged from the exhaust outlet of the wet nitrogen gas steam stripping tower; The apparatus further includes a circulating water cooling system for rapidly cooling and lowering the temperature of the PE resin discharged from the wet nitrogen gas steam stripping tower, and preferably, the circulating water cooling system includes: (i) a heat exchanger (203) located downstream of the set of outlet valves and connected to a circulating water tank via a transfer pump (204); (ii) a venturi feeder (205) having a first inlet connected to the take-off valve set and a second inlet connected to said heat exchanger;

[0046] When using the above device, the method comprises the steps of: (1) introducing the resin crude product through the charging valve set (208) into the charging port at the top of the wet nitrogen gas steam stripping tower (202); (2) Wet nitrogen gas is introduced into the wet nitrogen gas steam stripping tower and heat-exchanged with the resin crude product, and the resin crude product is heated to 50 to 95°C, thereby desorbing VOCs from the resin; (3) Control the rotary take-out valve assembly (209) so that the resin crude product is discharged.

[0047] More preferably, the method further comprises the step of (4) introducing the crude resin product into a venturi feeder (205) and mixing it with cooled condensed water to quench the resin and lower its temperature, and then transporting the resin to a centrifugal dehydration step downstream of the apparatus.

[0048] More preferably, the method further comprises the step of discharging the exhaust gas from the exhaust outlet of the wet nitrogen gas steam stripping tower. After being discharged, the exhaust gas is preferably cooled in a cooler (206) and then enters a condensate tank (207).

[0049] When using the above device, the method is carried out in the following device: A buffer tank (401) for storing polymeric materials that require temporary VOC removal and odor reduction; A horizontal rotary furnace assembly is located downstream of the charging buffer tank and includes a first horizontal rotary furnace (402) and a second horizontal rotary furnace (403), which are configured in series, and each of the first horizontal rotary furnace and the second horizontal rotary furnace has a material inlet, a steam inlet valve, and an exhaust discharge valve.

[0050] Preferably, the device further comprises: a flash distillation tank (407) for storing fresh make-up water and producing clean make-up steam by flash distillation; a first heat exchanger (E-101) and a second heat exchanger (E-102) for periodically exchanging heat to lower the temperature of the discharged steam and for exchanging heat to raise the temperature of fresh make-up water; A water pump (P-101) for driving fresh make-up water into the heat exchanger inside the flash distillation tank.

[0051] Preferably, the apparatus further comprises a steam compressor (406) for pressurizing the steam in the flash distillation tank. Preferably, the apparatus further includes a granule centrifugal dehydrator (404) and a vibrating screen (405), and includes a drying facility for drying the devolatilized product.

[0052] In another preferred embodiment, the method comprises the steps of: (1) A polymer that needs to be VOC-free and / or odor-reduced is placed in a charging buffer tank (401), the first horizontal rotary kiln (402) and the second horizontal rotary kiln (403) are operated, and steam is continuously introduced into the horizontal rotary kiln components, while the material inlet is opened for charging; (2) The polymer is allowed to remain in the horizontal rotary furnace part, and the VOC is allowed to form an azeotrope with the vapor. Then, the exhaust valve is opened to discharge the azeotrope from the horizontal rotary furnace part.

[0053] Preferably, after the step (2), the method further comprises a step of introducing the discharged azeotrope into a first heat exchanger (E-101) for heat exchange to reduce its temperature to 80°C to 90°C, and then introducing the same into a second heat exchanger (E-102) for secondary heat exchange to ultimately reduce its temperature to 40°C to 55°C.

[0054] Preferably, the method further comprises the steps of: first passing the external fresh replenishment water through a second heat exchanger (E-102) for heat exchange before entering the flash distillation tank (407); passing the fresh replenishment water inside the flash distillation tank through a circulation pump and then into the first heat exchanger (E-101) for heat exchange and raising the temperature to 100-105°C; and finally, feeding the fresh replenishment water again into the flash distillation tank for flash distillation, passing the vapor phase through a steam compressor for heating and raising the temperature of the vapor to 110-120°C.

[0055] Preferably, the method further comprises the step of drying the polymer after it has been discharged from the horizontal rotary furnace. In another preferred example, steam distillation can be used to achieve de-VOC of the polymer, reduce the odor of the polymer, and lower the ash content of the polymer.

[0056] Of course, it is understood that within the scope of the present invention, the above-mentioned technical features of the present invention and the technical features specifically described below (e.g., in the Examples) can be combined with each other to form new or preferred technical solutions, which will not be described here one by one due to space limitations. [Brief explanation of the drawings]

[0057] [Figure 1] Figure 1 is a structural schematic diagram of an apparatus for removing VOCs and reducing odor levels from a polymer (preferably polypropylene) in one preferred embodiment of the present invention, where 1 - pre-extractor, 2 - steam stripping tower, 3 - heat exchanger, 4 - transfer pump, 5 - venturi feeder, 6 - cooler, 7 - condensate tank, 8 - rotary feed valve set, 9 - rotary take-off valve set, 10 - blower. [Figure 2] 2 is a structural schematic diagram of an apparatus for removing VOCs and reducing odor levels from polyethylene in one preferred embodiment of the present invention, including: 201-preliminary dehydrator, 202-moist nitrogen gas steam stripping tower, 203-heat exchanger, 204-transport pump, 205-venturi feeder, 206-cooler, 207-condensate tank, 208-rotary charge valve set, 209-rotary discharge valve set, 210-blower, 211-nitrogen gas heater; 221-underwater particle cutting system, 222-underwater particle cutting circulating water tank, 224-CWR (circulating cooling water return), 225-transport circulating water tank, 226-centrifugal dehydration process, 227-steam rising porous plate, 228-fresh nitrogen gas flow, 229-steam flow, 230-exhaust gas treatment system, 231-CWS (circulating cooling water supply). [Figure 3] 3 is a structural schematic diagram of an apparatus for removing VOCs and reducing odor levels from polyethylene in one preferred embodiment of the present invention, including: 301 - preliminary dehydrator; 302 - slightly negative pressure steam stripping tower; 303 - heat exchanger; 304 - transfer pump; 305 - venturi feeder; 306 - cooler; 307 - negative pressure blower; 308 - rotary feed valve set; 309 - rotary discharge valve set; 321 - underwater particle cutting system; 322 - underwater particle cutting circulating water tank; 324 - CWR (circulating cooling water delivery); 325 - transport circulating water tank; 326 - centrifugal dehydration process; 328 - steam flow; 329 - exhaust treatment system; 330 - nitrogen gas flow; 331 - CWS (circulating cooling water supply). [Figure 4] 4 is a structural schematic diagram of an apparatus for removing VOCs and reducing odor levels from a polymer (preferably ethylene propylene rubber) in one preferred embodiment of the present invention, where 401 is a charging buffer tank, 402 is a first horizontal rotary kiln, 403 is a second horizontal rotary kiln, 404 is a granule centrifugal dehydrator, 405 is a vibrating screen, 406 is a steam compressor, 407 is a flash distillation tank, E101 is a first heat exchanger, E102 is a second heat exchanger, and P101 is a water pump flash distillation tank. DETAILED DESCRIPTION OF THE INVENTION

[0058] Specific Embodiments After extensive research, the inventors have developed a method for highly removing VOCs, reducing odor levels, and removing inorganic ash from polymer resins, as well as an apparatus for achieving this objective. This method involves continuously exposing the polymer to steam, allowing the organic volatile components (VOCs) encapsulated in the polymer resin, including those that cause strong odors, to migrate and diffuse, forming an azeotrope with the steam, achieving a high level of removal. This method also achieves the effect of removing ash by dissolving inorganic salts (e.g., ash) encapsulated in the resin in the steam. The method also provides an apparatus for achieving this effect. The operating principle of the method and apparatus provided by this method is that, while the chain fragments of resins undergo rapid movement within a certain temperature range, the physical form of the resin's original particles is not destroyed and they do not form agglomerates. This accelerates the diffusion and migration of VOCs in the resin, while simultaneously accelerating the steam stripping process, which utilizes the high level of removal of residual VOCs in the resin through steam distillation. Based on the above findings, the inventors have completed the present invention.

[0059] How to remove VOCs and reduce odor levels in resins In order to overcome the shortcomings of existing technologies, reduce the VOC content of resin products in existing production equipment, lower odor levels, improve product quality, and reduce VOC emissions in the packaging process of production equipment, this invention proposes a process for efficiently removing polymer impurities (e.g., VOCs, polymer odors, inorganic salts, etc.). The principle is that when the resin is maintained under a certain temperature condition for a certain time, low molecular weight VOCs, odor molecules, and inorganic salts (e.g., ash) encapsulated in the polymer resin are sufficiently migrated and diffused, and then removed by steam stripping.

[0060] The method of the present invention includes a step of contacting a polymer material with water vapor at 100 to 200°C for 0.5 to 6 hours continuously, thereby causing the organic matter in the polymer to enter the gas or liquid phase, thereby reducing the VOC (high boiling point or low vapor pressure organic matter) content and odor level in the polymer.

[0061] In a preferred embodiment, the VOC in the polymer can be reduced to a minimum of 1 ppm, and the odor level can be reduced to 3.0, meeting the requirements of medical-grade or electronic-grade resins. In addition to the usual VOC removal and odor reduction, this method simultaneously reduces the inorganic ash content in the polymer, thereby achieving the effect of removing ash from the polymer. In a preferred embodiment, after the removal process, the ash content in the polymer can be reduced by more than 20% of the original ash content, reaching as low as 0.011%. Preferably, direct contact of steam / water / polymer is used to achieve better results. By continuously contacting the polymer with steam at 100-200°C for 0.5-6 hours, inorganic substances in the polymer are extracted into the aqueous phase. When the polymer is contacted with water in phase equilibrium with the steam, better ash removal effects can be achieved, reaching 50 ppm.

[0062] The method of the present invention can effectively reduce VOCs in polymers, and preferably, in the method of the present invention, the reaction system is isolated from air or oxygen during the treatment process. The isolation of air or oxygen means that the oxygen content of the reaction system is less than 5% (v / v) during the complete removal process. Specifically, before operating according to the method, the reaction system is first sprayed with an inert gas or water vapor to replace the air in the reaction system, which will produce a better effect. In a preferred embodiment, the oxygen content of the gas phase components is less than 1%, preferably less than 0.1%, and most preferably less than 100 ppm.

[0063] For better results, steam or condensed water is discharged simultaneously with the removal step, at a rate of 1 to 200 kg of steam / ton of polymer / hour, and an equal amount of steam is introduced to maintain the pressure and steam temperature in the reaction system.

[0064] To ensure a high removal effect, the steam discharge rate is preferably 1 to 200 kg steam / ton of polymer / hour, and to obtain better economy, it is preferably 1 to 100 kg steam / ton of polymer / hour, in another preferred example, it is more preferably 5 to 50 kg steam / ton of polymer / hour, and most preferably 5 to 25 kg steam / ton of polymer / hour.

[0065] In a preferred embodiment, the removal of cooling condensate is performed intermittently or continuously. The type of the polymer is not particularly limited, and may be a powder or particulate material, and in one preferred example, may be a pre-manufactured polymer product.

[0066] The polymer may be of various types, but for example, in a preferred embodiment, the polymer is polyethylene (PE), polypropylene (PP), polybutene PB-1, acrylonitrile / butadiene / styrene terpolymer (ABS), olefin block copolymer (OBC), nylon (PA), polycarbonate (PC), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), ethylene propylene rubber, polystyrene, or polyphenylene sulfide.

[0067] In one preferred embodiment of the present invention, the polymer is polypropylene (PP) and random copolymer polypropylene. In one preferred embodiment of the present invention, said polymer is a modified polymer or product of said polymer.

[0068] In one preferred embodiment of the present invention, the melt index of the polypropylene (PP) or random copolymer polypropylene (PPR) is in the range of 0.1 to 2000 g / 10 min (measured according to the GB / T 2682-2000 method).

[0069] In one preferred embodiment of the present invention, the polypropylene (PP) is a resin for medical grade, for automotive interior use, or for food contact applications, specifically, a meltblown grade resin, a resin for syringes, or a resin for protective gear.

[0070] In one preferred embodiment of the present invention, the polypropylene (PP) is a dedicated resin for realizing electronic and electrical components. In one preferred embodiment of the present invention, the polyethylene is ultra-high molecular weight polyethylene UHMWPE and cross-linked polyethylene PEX.

[0071] In the reaction process of the present invention, the steam may be high-pressure steam or low-pressure steam, i.e., the temperature of the steam can be selected based on the melting point of the polymer. Preferably, the temperature of the steam is 100°C to 200°C, which is 20 to 50°C lower than the melting point of the polymer to be simultaneously treated. To achieve better results, the temperature of the steam is preferably 100°C to 200°C, which is 20 to 30°C lower than the melting point of the polymer to be simultaneously treated.

[0072] In one embodiment of the present invention, the temperature of the saturated steam can be controlled by the pressure of the steam. The correlation between the temperature and pressure of saturated steam is well known to those skilled in the art, and an appropriate pressure can be selected by referring to a correlation table of the temperature and pressure of saturated steam. In the above method, the polymer is heated to a temperature corresponding to the saturated steam by directly contacting the material with the saturated steam, without preheating the material in the process.

[0073] The contact time and temperature can be determined depending on the type of material actually being treated. When the particle size of the polymer is less than 1 mm and the VOC content in the polymer is less than 2000 ppm, the time for maintaining the polymer at a temperature corresponding to saturated water vapor is preferably 0.5 to 3 hours, more preferably 0.5 to 2 hours; When the particle size of the polymer is less than 1 mm and the VOC content is ≧2000 ppm, the time for maintaining the polymer at a temperature corresponding to saturated steam is preferably 1-5 hours, and more preferably 1-3 hours to obtain a better effect; When the particle size of the polymer is more than 1 mm and the VOC content is less than 1000 ppm, the time for maintaining the polymer at a temperature corresponding to saturated steam is preferably 1 to 5 hours, and more preferably 2 to 4 hours to obtain a better effect; When the particle size of the polymer is more than 1 mm and the VOC content is ≧1000 ppm, the time is preferably 3 to 7 hours, more preferably 3 to 5 hours to obtain a better effect, and most preferably 3 to 4 hours.

[0074] In one preferred embodiment of the present invention, the method comprises the following substeps: (a1) charging the polymeric material into a reaction facility, preferably a vertical facility or a horizontal facility; (a2) passing the steam through the reactor in step (a1) and continuously bringing the steam into direct contact with the polymer, thereby generating heat and mass transfer and maintaining a phase equilibrium state for 0.5 to 6 hours, and simultaneously discharging the steam that has come into contact with the polymer from the reactor; (a3) dehydrating and drying the polymeric material; (a4) The polymer material dehydrated and dried in step (a3) is discharged and collected.

[0075] Here, the polymer may or may not be preheated before step (1). In step (1), the polymer may be introduced into the equipment in portions, and steps (2) to (4) may be carried out to achieve intermittent operation. Steps (1) to (4) may also be carried out continuously to achieve the above-mentioned effect. Here, the continuous operation means that the polymer is continuously introduced into the equipment, passes through steps (2) to (3), and is continuously withdrawn and collected in step (4). Preferably, the contact time between the water vapor and the polymer must be at least 0.5 hours to ensure sufficient removal of organic volatile components with high boiling points or low saturated vapor pressures in the polymer.

[0076] Since the method of the present application is preferably carried out under conditions that are isolated from air or oxygen, in one preferred embodiment, the above-mentioned operation further comprises, before operation (1), a step of blowing the entire reaction system with nitrogen gas so that the oxygen content of the reaction system is less than 5%.

[0077] In another preferred embodiment, the temperature of the reaction system is 100 to 200°C during the reaction process. There are no particular limitations on the apparatus used in the method of the present invention, and any apparatus capable of achieving steam distillation can achieve removal of volatile organic compounds (VOCs) from polymers.

[0078] Polypropylene Gas Removal Device One application of the method of the present invention is a polypropylene removal device, and in one preferred embodiment, the device used comprises: Steam stripping towers (2); a feed valve set (8) located upstream of the steam stripping tower and connected to the feed port at the top of the steam stripping tower for controlling the feeding of polymer into the steam stripping tower; A set of take-off valves (9) located downstream of said steam stripping tower for controlling the outflow of polymer from said steam stripping tower.

[0079] In another preferred embodiment, the apparatus further comprises a pre-dehydration tower (1) located upstream of the set of feed valves. In another preferred embodiment, the apparatus further comprises a cooler (6), the inlet of which is connected to the exhaust outlet of the steam stripping tower, and the outlet of which is connected to a condensate tank (7).

[0080] In another preferred embodiment, the apparatus further comprises a circulating water cooling system for rapidly cooling the polymer discharged from the steam stripping tower to lower its temperature.

[0081] In another preferred embodiment, the circulating water transport system includes: a heat exchanger (3) located downstream of the extraction valve set and connected to a circulating water tank via a transfer pump (4); The first inlet includes a set of take-off valves and the second inlet includes a venturi feeder (5) connected to the heat exchanger.

[0082] In another preferred embodiment, the exhaust outlet of the steam stripping tower is connected to the cooler via a blower (10). When the device is used as a scavenger, a method for scavenging volatile organic compounds (VOCs) and reducing odor levels in the polymer comprises the steps of: (i) introducing polymer through the feed valve set (8) and into the feed port at the top of the steam stripping tower (2); (ii) introducing steam into the steam stripping tower and allowing it to exchange heat with the polymer so that the operating pressure inside the steam stripping tower corresponds to the saturated vapor pressure; (iii) controlling the rotary take-off valve assembly (9) so that the polymer is discharged; Preferably, prior to steps (i) to (iii), the system is purged with nitrogen gas so that the oxygen content of the gas phase components in the steam stripping tower is less than 1%, preferably less than 0.1%, more preferably less than 100 ppm.

[0083] In another preferred embodiment, the method further comprises the step of (iv) introducing the polymer into a venturi feeder (5) and mixing it with cooled condensed water to quench the polymer and lower its temperature, and then transporting the polymer to a centrifugal dehydration step downstream of the apparatus. Preferably, the method further comprises the step of discharging the exhaust gas from an exhaust outlet of the steam stripping tower.

[0084] In another preferred embodiment, the method further comprises, before the step (i), a step of introducing the polymer into a pre-dehydration tower (1) to perform a pre-dehydration step. In another preferred embodiment, the exhaust gas is cooled in a cooler (6) after being discharged, and then enters a condensate tank (7). Preferably, the method further includes a step of introducing non-condensable components of the exhaust gas into an exhaust gas treatment system, mixing them with steam, and then introducing them again into the steam stripping tower (2).

[0085] In this method, polypropylene is continuously contacted with water vapor at 100-200°C for 0.5-6 hours, and the resulting polypropylene has a low VOC of 1 ppm, a low ash content of 50 ppm, and an odor level of 3.0, which meets the requirements for medical-grade or electronic-grade resins.

[0086] Polyethylene gas removal device One application of the method of the present invention is a polyethylene removal device, which in one preferred embodiment comprises: Wet nitrogen gas steam stripping tower (2); a feed valve set (8) located upstream of the wet nitrogen gas steam stripping tower, connected to the top feed port of the wet nitrogen gas steam stripping tower, for controlling the feeding of PE resin into the wet nitrogen gas steam stripping tower; A set of outlet valves (9) is located downstream of the wet nitrogen gas steam stripping tower for controlling the outflow of the PE resin from the wet nitrogen gas steam stripping tower.

[0087] In another preferred embodiment, the wet nitrogen gas steam stripping tower is a tower in which the material deposition and flow pattern within the tower is a dense-phase moving bed structure. In another preferred embodiment, the wet nitrogen gas steam stripping tower is a tower having a hot water collector installed at the bottom thereof.

[0088] In another preferred embodiment, in the wet nitrogen gas steam stripping tower, hot nitrogen gas is aerated from the bottom of the tower to produce wet nitrogen gas. In another preferred embodiment, the apparatus includes an externally installed wet nitrogen gas generator, and when the wet nitrogen gas is generated in the wet nitrogen gas steam stripping tower, it is introduced into the wet nitrogen gas steam stripping tower to contact the material.

[0089] In another preferred embodiment, the feed valve set is a rotary feed valve set. In another preferred embodiment, the take-off valve set is a rotary take-off valve set. In another preferred embodiment, the rotary feed valve set is a combination of two or more rotary feeders.

[0090] In another preferred embodiment, the rotary take-off valve set is a combination of two or more rotary take-off valves. In another preferred embodiment, the rotary extractor is in the form of a gravity flap valve or in the form of a wing valve.

[0091] In another preferred embodiment, the upstream side is upstream in the flow direction of the PE resin. In another preferred embodiment, the wet nitrogen gas steam stripping tower further comprises a steam rising porous plate located within the steam stripping tower.

[0092] In another preferred embodiment, the apparatus further comprises a pre-dehydration tower (1) located upstream of the set of feed valves. In another preferred embodiment, the pre-dehydration tower is a pre-dehydration tower of the existing structure of the original PE unit.

[0093] In another preferred embodiment, the pre-dewatering tower is a centrifugal dewatering tower. In another preferred embodiment, the apparatus further comprises a cooler (6), the inlet of which is connected to the exhaust outlet of the wet nitrogen gas steam stripping tower, and the outlet of which is connected to a condensate tank (7).

[0094] In another preferred embodiment, the apparatus further includes a circulating water cooling system for rapidly cooling the PE resin discharged from the wet nitrogen gas steam stripping tower to lower its temperature.

[0095] In another preferred embodiment, the circulating water transport system includes: a heat exchanger (3) located downstream of the extraction valve set and connected to a circulating water tank via a transfer pump (4); A venturi feeder (5) having a first inlet connected to the take-off valve assembly and a second inlet connected to the heat exchanger.

[0096] In another preferred embodiment, the exhaust outlet of the wet nitrogen gas steam stripping tower is connected to the cooler via a blower (10). In another preferred embodiment, the blower is a centrifugal blower or a roots blower.

[0097] In another preferred embodiment, the apparatus further includes a nitrogen gas heater (11) located upstream of the cooler for heating and sending the exhaust gas discharged from the exhaust outlet of the wet nitrogen gas steam stripping tower.

[0098] In a second aspect of the present invention, there is provided a method for removing VOCs and reducing odor levels of polymers, comprising the steps of: (1) Introduce resin through the charging valve set (8) into the charging port at the top of the wet nitrogen gas steam stripping tower (2); (2) Wet nitrogen gas is introduced into the wet nitrogen gas steam stripping tower and heat-exchanged with the resin, and the resin is heated to 50 to 95°C, thereby desorbing VOC molecules from the resin; (3) Control the rotary outlet valve assembly (9) so that the resin is discharged; In another preferred embodiment, the moist nitrogen gas is saturated moist nitrogen gas (ie, the water vapor content in the nitrogen gas corresponds to the saturated water vapor partial pressure at the temperature to which the resin is to be heated).

[0099] In another preferred embodiment, the humid nitrogen gas is unsaturated humid nitrogen gas. In another preferred embodiment, the wet nitrogen is simply hot nitrogen gas. In another preferred embodiment, in the step (2), the resin is heated to 70 to 95°C, preferably 80 to 90°C.

[0100] In another preferred embodiment, in the step (2), the resin is retained in a wet nitrogen gas steam stripping tower for 0.5 to 5 hours, preferably 1 to 2 hours. In another preferred embodiment, the method further comprises the step of (4) introducing the resin into a venturi feeder (5) and mixing it with cooled condensed water to rapidly cool the resin and then transporting the resin to a centrifugal dehydration step downstream of the apparatus.

[0101] In another preferred embodiment, the cooled condensed water is transported from the transport circulating water tank to the venturi feeder (5) by the transport pump (4) after being cooled in the heat exchanger (3). In another preferred embodiment, material enters the tower from the top and moves from top to bottom within the tower in a dense phase moving bed.

[0102] In another preferred embodiment, in the step (4), the resin is rapidly cooled to 60°C or less, preferably 50°C or less, more preferably 40°C or less, using a venturi feeder. In another preferred embodiment, the step (4) further comprises a step of collecting one of the treated resins in a material tank, lowering the temperature with nitrogen gas, and subjecting it to a subsequent step.

[0103] In another preferred embodiment, the step (4) further comprises a step of further lowering the temperature of the treated resin using another temperature lowering device. In another preferred embodiment, the other temperature-reducing equipment is selected from the group consisting of a rotary furnace equipment with a coil cooler or a stirring equipment with a temperature-reducing equipment.

[0104] In another preferred embodiment, the method further comprises, before the step (1), a step of introducing the resin into a pre-dehydration tower (1) to perform a pre-dehydration step. In another preferred embodiment, after the preliminary dehydration step, the water content of the resin is 1 to 10 wt %, preferably 1 to 5 wt %.

[0105] In another preferred embodiment, the resin is a mixture of resin and water from the underwater particle cutting process of a PE unit. In another preferred embodiment, after the preliminary dewatering step is completed, the removed water is returned to the underwater particle cutting step.

[0106] In another preferred embodiment, the method further comprises the step of discharging the exhaust gas from the exhaust outlet of the wet nitrogen gas steam stripping tower. In another preferred embodiment, the exhaust gas is discharged, then enters a cooler (6) to be cooled, and then enters a condensate tank (7).

[0107] In another preferred embodiment, the method further includes a step of introducing non-condensable components in the exhaust gas into an exhaust gas treatment system, mixing them with fresh nitrogen gas to be replenished, and then heating the mixture with a nitrogen gas heater (6) before introducing the mixture into the wet nitrogen gas steam stripping tower (2).

[0108] In another preferred embodiment, the non-condensable components are periodically discharged, and preferably, the amount periodically discharged is determined depending on the VOC content in the cooled and condensed nitrogen gas. In another preferred embodiment, the circulating nitrogen gas is heated with steam to 50 to 95°C, preferably 70 to 95°C, more preferably 80 to 90°C.

[0109] In another preferred example, in the steps (1) to (3), the oxygen content of the gas phase components in the steam stripping tower is less than 1%, preferably less than 0.1%, and more preferably less than 100 ppm.

[0110] Slightly negative pressure polyethylene gas removal device Another embodiment of the present invention involves the removal of polyethylene gases under slightly negative pressure conditions. To this end, the inventors have designed an apparatus for removing gas phase impurities in polyethylene or ethylene copolymers, which comprises: Slightly negative pressure steam stripping tower (302); a feed valve group (308) located upstream of the slightly negative pressure steam stripping tower, connected to the top feed port of the slightly negative pressure steam stripping tower, for controlling the feeding of resin into the slightly negative pressure steam stripping tower; A take-off valve set (309) is located downstream of the slightly negative pressure steam stripping tower, for controlling the outflow of resin from the slightly negative pressure steam stripping tower.

[0111] In another preferred embodiment, the slightly negative pressure steam stripping tower is a tower in which the material deposition and flow pattern within the tower is a dense phase moving bed structure. In another preferred embodiment, the slightly negative pressure steam stripping tower is a tower having a hot water generator installed at its bottom, the steam is introduced into a water storage tray at the bottom of the tower, and the temperature of the water storage tray can be controlled.

[0112] In another preferred embodiment, the apparatus further includes an external hot water inlet located at the bottom of the tower, the external hot water inlet being for pumping externally placed hot water at a constant temperature into the bottom of the tower.

[0113] The feed valve set may be a rotary feed valve set (a combination of two or more rotary feeders), and the unload valve set is a rotary unload valve set (a combination of two or more rotary unloaders).

[0114] In another preferred embodiment, the rotary extractor is in the form of a gravity flap valve or in the form of a wing valve. In another preferred example, the upstream refers to the upstream in the flow direction of the resin, and includes resin transported from a particle cutting system in a production device and commercially available resin purchased from outside and placed in the device.

[0115] In another preferred embodiment, the slightly negative pressure steam stripping tower further comprises a steam rising porous plate located within the tower, and / or a nitrogen gas inlet located at the bottom of the tower.

[0116] In another preferred embodiment, the apparatus further comprises a pre-dehydration tower (301) located upstream of the set of feed valves. In another preferred embodiment, the pre-dehydration tower is a pre-dehydration tower of an existing structure in the original polyethylene or ethylene copolymer production equipment, and preferably, the pre-dehydration tower is a centrifugal dehydration tower.

[0117] In another preferred embodiment, the apparatus further includes a negative pressure blower connected to the exhaust outlet at the top of the slightly negative pressure steam stripping tower for controlling the degree of vacuum within the tower.

[0118] In another preferred embodiment, the apparatus further includes a cooler (306) having an inlet connected to the outlet of the negative pressure blower of the exhaust gas discharge of the slightly negative pressure steam stripping tower. The condensed liquid from the outlet of the cooler is collected and then transported to a plant-wide wastewater treatment system or returned to the underwater particle cutting system, and the non-condensable gas from the outlet of the cooler is transported to an exhaust gas treatment system.

[0119] In another preferred embodiment, the liquid phase outlet of the cooler is connected to a wastewater treatment system, or an underwater particle cutting system, or an exhaust treatment system. In another preferred embodiment, the apparatus further includes a circulating water cooling transport system, which is for rapidly cooling and lowering the temperature of the resin discharged from the slightly negative pressure steam stripping tower.

[0120] In another preferred embodiment, the circulating water cooling transport system includes: a heat exchanger (303) located downstream of the extraction valve set and connected to a circulating water tank via a transfer pump (304); A venturi feeder (305) having a first inlet connected to the take-off valve set and a second inlet connected to the heat exchanger.

[0121] In another preferred embodiment, the circulating water cooling transport system can be replaced by the following: the material from the discharge valve set (309) is fed into a stirred buffer tank, and then the mixture of water and material is transported to the downstream process by a transport pump. A Venturi cooling transport mode is preferably used.

[0122] In another preferred embodiment, the venturi feeder (305) may be replaced by a stirred tank, and a transfer pump is located below the stirred tank to transport the quenched water and material mixture to a downstream centrifugal dewatering step.

[0123] In another preferred embodiment, the circulating water cooling transport system includes: Buffer tank; A transfer pump connected to said buffer tank.

[0124] In another preferred embodiment, the material from the withdrawal valve set (309) is transported to a stirred buffer tank, and then the water and material mixture is transported to downstream processes by a transfer pump. In another preferred embodiment, the exhaust outlet of the slightly negative pressure steam stripping tower is connected to the cooler via a negative pressure blower (307).

[0125] In another preferred embodiment, the negative pressure blower is a centrifugal blower or a roots blower. When the device is used as a scavenger, a method for scavenging volatile organic compounds (VOCs) and reducing odor levels in the polymer comprises the steps of: (i) introducing polyethylene or ethylene copolymer into the charge valve set (308) and into the top charge port of the slightly negative pressure steam stripping tower (302); (ii) introducing steam into the water at the bottom of the slightly negative pressure steam stripping tower to generate steam which exchanges heat with the polyethylene or ethylene copolymer, thereby controlling the temperature in the tower so that the temperature of the polyethylene or ethylene copolymer is maintained at 50 to 95°C, thereby removing impurity molecules in the gas phase; (iii) The rotary take-off valve assembly (309) is operated so that the resin is discharged.

[0126] In another preferred embodiment, the temperature in the tower corresponds to the boiling point temperature of water ±5° C. at the operating pressure in the tower. In another preferred embodiment, the steam is superheated steam (ie, the temperature and pressure of the steam exceed the saturated vapor pressure corresponding to the hot water temperature).

[0127] In another preferred embodiment, the hot water temperature is a corresponding saturation temperature or a corresponding non-saturation temperature under the conditions of the required vacuum in the tower. In another preferred embodiment, in the step (2), the resin is heated to 40 to 95°C. Specifically, the heating temperature is adjusted according to the softening temperature of the material, and generally corresponds to a temperature close to the softening temperature of the resin to be heated.

[0128] In another preferred embodiment, in the step (2), the resin is retained in a wet nitrogen gas steam stripping tower for 1 to 5 hours, preferably 1 to 3 hours. In another preferred embodiment, the method further comprises the step of (iv) introducing the resin into a venturi feeder (305) and mixing it with cooled condensed water to quench the resin and lower its temperature, and then transporting the resin to a centrifugal dewatering step downstream of the apparatus.

[0129] In another preferred embodiment, the polyethylene or ethylene copolymer is cooled by quenching and then introduced into a centrifugal dehydration step. In another preferred embodiment, the polyethylene or ethylene copolymer is introduced into a stirred tank containing water and quenched to lower the temperature, and the cooled resin and water mixture is transported by a transfer pump to a downstream centrifugal dewatering step.

[0130] In another preferred embodiment, the method further comprises the step of (iv) introducing the resin into a stirred tank containing water and mixing it with cooled condensed water to quench the resin and lower its temperature, and then transporting the resin by a pump to a centrifugal dehydration step downstream of the apparatus.

[0131] In another preferred embodiment, the cooled condensed water is transported from the transport circulating water tank to the venturi feeder (5) or the agitation tank by the transport pump (304) after being cooled in the heat exchanger (303).

[0132] In another preferred embodiment, material enters the tower from the top and moves from top to bottom within the tower in a dense phase moving bed. In another preferred embodiment, in the step (4), the resin is cooled to 60°C or less, preferably 50°C or less, more preferably 40°C or less in a venturi feeder or a stirred tank, or by quenching the stirred tank.

[0133] In another preferred embodiment, the step (iv) further comprises a step of collecting one of the treated resins in a material tank, lowering the temperature with nitrogen gas, and subjecting it to a subsequent step. In another preferred embodiment, the step (iv) further comprises a step of further lowering the temperature of the treated resin using another temperature lowering device.

[0134] In another preferred embodiment, the other temperature-reducing equipment is selected from the group consisting of a rotary furnace equipment with a coil cooler or a stirring equipment with a temperature-reducing equipment. In another preferred embodiment, the method further comprises, before the step (1), a step of introducing the resin into a pre-dehydration tower (301) to perform a pre-dehydration step.

[0135] In another preferred embodiment, after the preliminary dehydration step, the water content of the resin is 1 to 10 wt %, preferably 1 to 5 wt %. In another preferred embodiment, the resin is a mixture of resin and water from the underwater particle cutting process of a polyethylene or ethylene copolymer plant.

[0136] In another preferred embodiment, after the preliminary dewatering step is completed, the removed water is returned to the underwater particle cutting step. In another preferred embodiment, the method further comprises the step of controlling the vacuum level of the slightly negative pressure steam stripping tower by introducing the exhaust gas discharged from the top of the slightly negative pressure steam stripping tower into a negative pressure blower (7), and preferably, the exhaust gas discharged by the negative pressure blower (7) is cooled by being introduced into a cooler (6).

[0137] In another preferred embodiment, after the cooling and condensing step is completed, the condensed water is introduced into an underwater particle cutting system or a wastewater treatment system, and the non-condensed gas is introduced into an exhaust treatment system. In another preferred example, in the steps (1) to (3), the oxygen content of the gas phase components in the steam stripping tower is less than 1%, preferably less than 0.1%, and more preferably less than 100 ppm.

[0138] The apparatus and method provided by the present invention are suitable for polyethylene or ethylene copolymers, particularly LDPE, LLDPE, POE, and OBC, and more effective for low-melting LDPE, POE, and OBC. In another preferred embodiment, the polyethylene or ethylene copolymer is selected from the group consisting of LDPE, LLDPE, POE, and OBC, more preferably LDPE, POE, and OBC, and most preferably LDPE.

[0139] Ethylene Propylene Rubber Removal Equipment Another embodiment of the present invention is used for the removal of VOCs and odors from ethylene propylene rubber. In this regard, the inventors have designed an apparatus for removing gas phase impurities from polyethylene or ethylene copolymers, and have provided an apparatus for continuously removing volatile organic compounds (VOCs) and reducing odors in polymers, comprising: A buffer tank (401) for storing polymeric materials that require temporary VOC removal and odor reduction; a horizontal rotary kiln assembly located downstream of the charging buffer tank, comprising a first horizontal rotary kiln (402) and a second horizontal rotary kiln (403) in a series configuration, each of the first horizontal rotary kiln and the second horizontal rotary kiln having a material inlet, a steam inlet valve, and an exhaust discharge valve; and the polymer is selected from the group consisting of binary ethylene propylene rubber (EPM), ternary ethylene propylene rubber (EPDM), low density polyethylene (LDPE), polyolefin elastomer (POE) and olefin block copolymer (OBC).

[0140] In another preferred embodiment, the first horizontal rotary furnace and the second horizontal rotary furnace are connected via a pipe, and preferably, a connecting valve is installed in the pipe. In another preferred embodiment, the polymer is heated to a predetermined temperature with saturated steam and allowed to stand for a predetermined time, whereby any VOC remaining in the EPDM is completely desorbed and discharged by the steam and condensate.

[0141] In another preferred embodiment, the device further comprises: a flash distillation tank (407) for storing fresh make-up water and producing clean make-up steam by flash distillation; a first heat exchanger (E-101) and a second heat exchanger (E-102) for periodically exchanging heat to lower the temperature of the discharged steam and for exchanging heat to raise the temperature of fresh make-up water; A water pump (P-101) for driving fresh make-up water into the heat exchanger inside the flash distillation tank.

[0142] In another preferred embodiment, the water pump drives fresh make-up water into a second heat exchanger to raise its temperature, and then the water enters the flash distillation tank to release heat, thereby flash distilling the fresh make-up water.

[0143] In another preferred embodiment, the apparatus further comprises a steam compressor (406) for pressurizing the steam in the flash distillation tank. In another preferred embodiment, the apparatus further includes a granule centrifugal dehydrator (404) and a vibrating screen (405), and includes a drying facility for drying the devolatilized product.

[0144] In another preferred embodiment, the horizontal rotary furnace further includes an agitator, and the agitator is an impeller rotary agitator. In another preferred embodiment, the apparatus is installed after the polymer extrusion and particle cutting process, preferably after the ethylene propylene rubber manufacturing equipment.

[0145] Using the above apparatus, a method for continuously removing volatile organic compounds (VOCs) and reducing odors in polymers is provided, said method being carried out in the above apparatus and comprising the steps of: (1) A polymer that needs to be VOC-free and / or odor-reduced is placed in a charging buffer tank (401), the first horizontal rotary kiln (402) and the second horizontal rotary kiln (403) are operated, and steam is continuously introduced into the horizontal rotary kiln components, while the material inlet is opened for charging; (2) Allowing the polymer to remain in the horizontal rotary furnace part and forming an azeotrope with the VOC vapor, and then opening the exhaust discharge valve to discharge the azeotrope from the horizontal rotary furnace part; Here, the polymer is selected from the group consisting of ethylene propylene rubber, low density polyethylene, polyolefin elastomer, or olefin block copolymer.

[0146] In another preferred embodiment, the horizontal rotary furnace element is operated continuously or intermittently during step (1). In another preferred embodiment, in the step (1), the horizontal rotary furnace is operated under pressure, and the operating pressure is equal to the saturated steam pressure corresponding to the temperature of the polymer.

[0147] In another preferred embodiment, in the step (1) above, the charge is maintained and the rotation speed of the motor of the horizontal rotary furnace is adjusted according to the requirements of the reaction time and speed. In another preferred example, the temperature in the rotary furnace during the step (2) is 105 to 120°C, preferably 110 to 115°C, and more preferably 115 to 120°C.

[0148] In another preferred embodiment, the temperature of the steam is 100 to 120°C. In another preferred embodiment, in the step (2), the residence time is 2 to 3 hours, preferably 2.5 to 3 hours.

[0149] In another preferred embodiment, the ethylene propylene rubber is a virgin ethylene propylene rubber. In another preferred embodiment, the ethylene propylene rubber is a commercially available ethylene propylene rubber resin.

[0150] In another preferred embodiment, in the steps (1) and (2), the filling rate of the total volume of water and materials in the horizontal steam stripping tower is 20% to 80%, preferably 30% to 70%, and most preferably 50% to 70%, and / or The volume ratio of the above material to water is preferably ≦1:10 to 1:0.5, more preferably ≦1:5 to 1:0.5, and most preferably ≦1:3 to 1:1.

[0151] In another preferred example, after the step (2), the method further comprises a step of introducing the discharged azeotrope into a first heat exchanger (E-101) for heat exchange to reduce its temperature to 80°C to 90°C, and then introducing the same into a second heat exchanger (E-102) for secondary heat exchange to ultimately reduce its temperature to 40°C to 55°C.

[0152] In another preferred embodiment, the method further comprises the steps of: first passing the external fresh replenishment water through a second heat exchanger (E-102) for heat exchange, and then entering the flash distillation tank (407); passing the fresh replenishment water inside the flash distillation tank through a circulation pump, and then forcing it into the first heat exchanger (E-101) for heat exchange, thereby raising the temperature to 100-105°C; and finally, feeding the fresh replenishment water into the flash distillation tank again for flash distillation, and passing the vapor phase through a steam compressor for heating, thereby raising the temperature of the vapor to 110-120°C. In another preferred embodiment, the flash distilled liquid phase water is returned to the flash distillation tank.

[0153] In another preferred embodiment, the fresh make-up water is periodically exchanged with the exhausted steam to recover the residual heat and generate the steam. In another preferred embodiment, the flash distillation tank operates at atmospheric pressure.

[0154] In another preferred example, during the treatment process in the flash distillation tank, fresh supplementary water is flash distilled using the heat released after the steam provided to the first heat exchanger enters the atmospheric flash distillation tank to generate new steam, which is then compressed by a compressor to obtain fresh steam that is isothermal and isobaric to the steam inlet.

[0155] In another preferred example, the fresh replenishment water does not need to be on all the time, but when it is on, it is turned on so that the water level line inside the flash distillation tank reaches a standard, and then, after the reaction starts, it is turned on and off depending on the height of the level gauge of the flash distillation tank, so that the water level inside the flash distillation tank is at an appropriate level.

[0156] In another preferred example, when the flash distilled steam is at atmospheric pressure, the temperature of the steam is 95 to 105°C. In another preferred embodiment, the method further comprises compressing and heating the vapor after the flash distillation with a compressor, so that the flash distilled vapor has the same pressure and temperature as the vapor at the vapor inlet.

[0157] In another preferred embodiment, the method further includes a residual heat recovery and steam generation step: after step (1) is completed, the steam containing VOCs and odor components flowing out of the reactor enters a primary heat exchanger for primary heat exchange, and then enters a secondary heat exchanger for secondary heat exchange until the temperature drops to less than 50°C, after which the oil-containing wastewater is transported to a factory wastewater system.

[0158] In another preferred embodiment, the method further comprises the step of drying the polymer after it is discharged from the horizontal rotary furnace. In another preferred embodiment, the drying is carried out in a granule centrifuge and a vibrating screen.

[0159] In another preferred embodiment, the polymer is dried and then packaged to obtain the final product. In another preferred embodiment, the granule drying system is a granule centrifugal dryer and vibrating screen in an existing EPDM, EPM, POE, OBC production facility.

[0160] In another preferred embodiment, a preliminary dewatering step is carried out prior to the step (1), and preferably, the preliminary dewatering step comprises dewatering a mixture of water and material from an underwater particle cutting system of an ethylene propylene rubber production plant using a preliminary dewatering machine until the wet content of the material is ≦70%, preferably ≦50%, and most preferably ≦30%.

[0161] In another preferred embodiment, the preliminary dewatering equipment is a dewatering machine having a sieve mesh structure. In another preferred embodiment, the pre-dewatering equipment is a centrifugal dewatering equipment. In another preferred embodiment, in the step (1), the reaction system is isolated from air or oxygen. Preferably, the isolation from air or oxygen means that the oxygen content of the reaction system is less than 5% (v / v) throughout the entire process, preferably less than 1% (v / v), preferably less than 0.1% (v / v), more preferably less than 100 ppm.

[0162] In another preferred embodiment, the method further comprises continuously introducing steam into the reaction system and simultaneously discharging the steam and / or condensed water from the cooling system, and preferably, the discharge rate of the steam and / or condensed water from the cooling system is 1 to 200 kg steam / ton of polymer / hour, preferably 1 to 120 kg steam / ton of polymer / hour, more preferably 5 to 50 kg steam / ton of polymer / hour, and most preferably 5 to 25 kg steam / ton of polymer / hour.

[0163] In another preferred embodiment, the ethylene propylene rubber has a Mooney viscosity (125°C) of 10 to 150M. In another preferred embodiment, the melt index of the polyolefin elastomer is 0.5 to 40 g / 10 min (230° C., 2.16 kg).

[0164] Compared to existing technologies, the advantages of the present invention include: (1) After VOC removal using the method of the present invention, the VOC content of the final packaged polymer product is much lower than that of the untreated polymer product, at a minimum of 1 ppm or less (based on the VDA277 standard test), and the odor level is usually below grade 3, at a minimum of grade 2 or less (based on the VW50180 test), which is much lower than the VOC content and odor level of commercially available products of the same model. Furthermore, products with an original VOC content of less than 40 ppm can have their VOC content and odor level further reduced, so they can be used to manufacture polymer raw materials with high VOC levels (for example, raw materials for medical meltblown cloth masks).

[0165] (2) The treatment process is simple. Only one set of steam stripping tower and auxiliary equipment is added between the original two processes. The installation space is small and does not affect the operation and installation of the original equipment.

[0166] (3) Steam has a large latent heat and high heat transfer efficiency. It can control the appropriate temperature range during the treatment process and quickly desorb VOC molecules, resulting in high treatment efficiency, low steam consumption, no wastewater production, no impact on resin quality, and no phenomena such as clumping that affect equipment operation. (4) The investment and operating costs of the equipment are low, and the product quality is significantly improved.

[0167] The present invention will be further described below with reference to specific examples. It is understood that these examples are only used to illustrate the present invention and do not limit the scope of the present invention. In the following examples, experimental methods for which no specific conditions are described were generally carried out under conventional conditions or under conditions recommended by the manufacturer. Unless otherwise specified, percentages and parts are calculated by weight.

[0168] Steaming plastics to remove VOCs, reduce odor levels, and remove ash can be done intermittently or continuously, and the appropriate operation mode can be selected depending on the situation. Different operation modes do not affect the effectiveness of steaming.

[0169] Common method: Intermittent operation Plastic particles (powder) are placed into a steam stripping facility, which is then purged with nitrogen gas and the air is removed. Saturated steam at a specified temperature is then introduced, and the steam discharge rate is controlled so that the operating pressure of the steam stripping facility corresponds to the pressure of the saturated steam. Steam stripping is carried out for a specified period of time, during which condensed water is periodically discharged from the bottom of the steam stripping facility. After steam stripping is complete, the facility is emptied, and the material is thoroughly dehydrated and dried before being cooled to a specified temperature to obtain acceptable material.

[0170] Common method: continuous operation Plastic particles (powder) are placed in the material tank at the top of the steam stripping equipment. After the air is discharged, a rotary valve controls the material's speed into the steam stripping equipment, introducing saturated steam at a specified temperature. The steam's discharge rate from the steam stripping equipment is controlled so that the steam stripping equipment's operating pressure corresponds to the saturated steam pressure. Condensed water is periodically discharged from the bottom of the steam stripping equipment. The steam stripping equipment's removal valve is turned on and off to ensure the material remains in the steam stripping equipment for a certain period of time. The material from the steam stripping equipment is thoroughly dehydrated and dried and cooled to the specified temperature to obtain acceptable material.

[0171] Examples 1 to 38 The following Examples 1 to 38 were carried out using the apparatus shown in Figure 1. Among them, Examples 1, 32, 33, 34, and 35 were performed intermittently, while the other Examples were performed continuously. Whether the operation was intermittent or continuous only differs in the process operation, but does not affect the removal effect.

[0172] [Table 1] TIFF0007719768000002.tif145170

[0173] The following Examples 39 to 44 were carried out using the apparatus shown in FIG. 2 (throughput: 1 kg / h). Example 39 After the water particles were removed from the production equipment, they were further centrifuged and dehydrated. The resulting 1% water-containing high-pressure LDPE granules (LDPE, the VOC content of the production equipment's packaging: 120 ppm, odor level: 4.5) were loaded into a slightly negative pressure steam stripping tower in the experimental equipment. A valve connected to a water storage tank was installed at the bottom of the tower, and steam was used to heat the water to 60°C. A negative pressure blower was used at the top of the tower to maintain the absolute pressure inside the tower at approximately 19,930 Pa. The hot water evaporated into steam and rose further into the tower, heating the polyethylene granules. After heating for 2 hours, the material was quenched to 45°C with cold water. The material was removed, and the polyethylene resin was then centrifuged and dried using the industrial processing method, i.e., centrifuged and air-dried. VOC content (VDA 277): 28 ppm; Odor level: Class 3.5.

[0174] Example 40 After the water particles were removed from the production equipment and further centrifuged, the resulting 1% water-containing high-density polyethylene granules (HDPE, slurry method; VOC content of the production equipment's packaging: 165 ppm, odor level: 4.5) were loaded into a slightly negative pressure steam stripping tower in the experimental equipment. A valve connected to a water storage tank was attached at the bottom of the tower, and steam was used to heat the water to 75°C. A negative pressure blower at the top of the tower controlled the absolute pressure inside the tower to approximately 38,560 Pa. The hot water evaporated into steam, which then rose into the tower and heated the polyethylene granules. After heating for 2 hours, the material was quenched to 45°C with cold water. The material was removed, and the polyethylene resin was centrifuged and dried using the industrial processing method, i.e., centrifuged and air-dried. VOC content (VDA 277): 26 ppm; Odor level: Class 3.6.

[0175] Example 41 After the water particles were removed from the production equipment and further centrifuged, the resulting 1% water-containing high-density polyethylene granules (HDPE, slurry method; VOC content of the production equipment's packaging: 165 ppm, odor level: 4.8) were loaded into a slightly negative pressure steam stripping tower in the experimental equipment. A valve connected to a water storage tank was attached at the bottom of the tower, and water was heated to 75°C using steam. A negative pressure blower at the top of the tower controlled the absolute pressure inside the tower to approximately 38,560 Pa. The hot water evaporated into steam and rose further into the tower, heating the polyethylene granules. After heating for 2 hours, the material was quenched to 45°C with cold water. The material was removed, and the polyethylene resin was centrifuged and dried using the industrial processing method, i.e., centrifuged and air-dried. VOC content (VDA 277): 22 ppm; Odor level: Class 3.7.

[0176] Example 42 Commercially available POE resin (VOC content: 160 ppm, odor level: 4.6) was loaded into a slightly negative pressure steam stripping tower in an experimental device. A valve connected to a water tank was attached to the bottom of the tower, and water was heated to 70°C using steam. A negative pressure blower at the top of the tower controlled the absolute pressure inside the tower to approximately 31180 Pa. The hot water evaporated into steam and rose into the tower, heating the POE granules. After heating for 3 hours, the material was rapidly cooled to 40°C with cold water. The POE resin was removed and treated according to industrial processing methods, i.e., centrifugal dehydration and air blow drying. VOC content (VDA 277): 35 ppm; Odor level: Class 3.8.

[0177] Example 43 Commercially available OBC resin (VOC content: 250 ppm, odor level: 4.5) was loaded into a slightly negative pressure steam stripping tower in an experimental device. A valve connected to a water tank was attached to the bottom of the tower, and water was heated to 80°C using steam. A negative pressure blower at the top of the tower controlled the absolute pressure inside the tower to approximately 47,370 Pa. The hot water evaporated into steam and rose into the tower, heating the OBC granules. After heating for 3 hours, the material was rapidly cooled to 40°C with cold water. The OBC resin was removed and treated according to industrial processing methods, i.e., centrifugal dehydration and air blow drying. VOC content (VDA 277): 40 ppm; Odor level: Class 3.6.

[0178] Example 44 Commercially available LLDPE resin (VOC content: 185 ppm, odor level: 4.8) was loaded into a slightly negative pressure steam stripping tower in an experimental device. A valve connected to a water tank was attached to the bottom of the tower, and water was heated to 65°C using steam. A negative pressure blower at the top of the tower controlled the absolute pressure inside the tower to approximately 25,020 Pa. The hot water evaporated into steam, which then rose into the tower to heat the LLDPE granules. After heating for 3 hours, the material was rapidly cooled to 40°C with cold water. The LLDPE resin was removed and processed according to industrial processing methods, i.e., centrifugal dehydration and air blow drying. VOC content (VDA 277): 35 ppm; Odor level: Class 3.2.

[0179] Example 45 Steaming ethylene propylene rubber to remove VOCs and reduce odor levels can be done intermittently or continuously, and the appropriate operation mode can be selected depending on the situation. Different operation modes do not affect the effectiveness of steaming.

[0180] Common Method 1: Intermittent Operation The polymer and water are placed in a steam stripping device, which is then purged with nitrogen gas. After the air is removed, saturated steam at a predetermined temperature is introduced, and the steam discharge rate from the steam stripping device is controlled so that the operating pressure of the steam stripping device corresponds to the pressure of the saturated steam. Steam stripping is carried out for a predetermined time, during which condensed water is periodically discharged from the bottom of the steam stripping device. After steam stripping is completed, the device is emptied, and the material is thoroughly dehydrated and dried and cooled to a predetermined temperature to obtain a qualified material.

[0181] Common Method 2: Continuous Operation The polymer and water are placed in the material tank at the top of the steam stripping equipment. After the air is discharged, the rotary valve controls the rate at which the material enters the steam stripping equipment. Saturated steam at a specified temperature is introduced, and the rate at which the steam is discharged from the steam stripping equipment is controlled so that the operating pressure of the steam stripping equipment corresponds to the pressure of the saturated steam. Condensed water is periodically discharged from the bottom of the steam stripping equipment. The steam stripping equipment's removal valve is turned on and off to ensure the material remains in the steam stripping equipment for a certain period of time. The material from the steam stripping equipment is thoroughly dehydrated and dried and cooled to the specified temperature to obtain acceptable material.

[0182] Among them, Examples 45-1, 45-22, 45-23, 45-24, and 45-25 are intermittent operations, while the other Examples are continuous operations. Whether they are intermittent or continuous operations is just a difference in the process operation, and does not affect the removal effect.

[0183] [Table 2]

[0184] [Table 3]

[0185] [Table 4]

[0186] All documents related to the present invention are incorporated herein by reference as if each document were individually incorporated by reference. After reading the above content of the present invention, it should be understood that those skilled in the art can make various changes and modifications to the present invention, and that equivalents thereof are within the scope of the claims of the present invention.

Claims

1. 1. A method for removing volatile organic compounds (VOCs), reducing odors, and removing inorganic ash in a polymer, comprising: a step of removing volatile organic compounds (VOCs) and odor-causing components in the polymer by continuously contacting water vapor with the polymer; a step of dissolving and removing inorganic ash in the polymer by continuously contacting the polymer with water vapor; (a) a step of continuously contacting water vapor in a phase equilibrium state with a polymer in a reaction system for 0.5 to 6 hours; Including, The polymer is selected from the group consisting of polypropylene (PP), ethylene propylene rubber (EPDM, EPM), polyolefin elastomer (POE), polybutene PB-1, acrylonitrile / butadiene / styrene terpolymer (ABS), olefin block copolymer (OBC), nylon (PA), polycarbonate (PC), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene or polyphenylene sulfide, or a combination thereof; In the contacting process, the oxygen content of the reaction system is less than 0.1% (v / v); wherein step (a) comprises the following substeps: (a1) charging the polymeric material into a facility; (a2) passing the steam having a temperature of 100 to 200°C (excluding the steam having a temperature of 100°C) through the equipment in step (a1) and directly contacting the steam with the polymer in a phase equilibrium state for 0.5 to 6 hours, while simultaneously discharging the steam that has come into contact with the polymer; (a3) dehydrating and drying the polymeric material; (a4) The polymeric material dehydrated and dried in step (a3) is discharged and collected.

2. 2. The method according to claim 1, wherein in the step (a), the water vapor in a phase equilibrium state is continuously contacted with the polymer in the reaction system for 0.5 to 3 hours.

3. 2. The method according to claim 1, wherein the oxygen content of the reaction system is less than 100 ppm during the contacting step.

4. 2. The method according to claim 1, further comprising, before step (a), a step of replacing air in the reaction system by blowing an inert gas or water vapor into the reaction system.

5. 2. The method of claim 1, further comprising the step of continuously introducing steam into the reaction system and simultaneously discharging the steam and / or condensed water from the reaction system, wherein the rate of discharging the steam is 1 to 200 kg of steam / ton of polymer / hour.

6. 2. The method of claim 1, wherein the polymer is polypropylene (PP) or random copolymer polypropylene (PPR), and the melt index of the polypropylene (PP) or random copolymer polypropylene (PPR) is in the range of 0.1 to 2000 g / 10 min (measured according to GB / T 2682-2000 method).

7. 2. The method according to claim 1, wherein the temperature of the steam is 20 to 50° C. lower than the melting point of the polymer.

8. When the particle size of the polymer is less than 1 mm and the VOC content in the polymer is less than 2000 ppm, the time for maintaining the polymer at a temperature corresponding to saturated steam is 0.5 to 3 hours; When the particle size of the polymer is less than 1 mm and the VOC content is ≥ 2000 ppm, the polymer is maintained at a temperature corresponding to saturated water vapor for 1 to 5 hours; When the polymer diameter is ≧1 mm and the VOC content is <1000 ppm, the polymer is maintained at a temperature corresponding to saturated water vapor for 1 to 5 hours; When the particle size of the polymer material is ≧1 mm and the VOC content is ≧1000 ppm, the time for maintaining the polymer at a temperature corresponding to saturated water vapor is 3 to 7 hours.

2. The method of claim 1 .

9. 2. The method according to claim 1, characterized in that it is carried out in an apparatus comprising: Steam stripping tower (2); a feed valve set (8) located upstream of the steam stripping tower and connected to the feed port at the top of the steam stripping tower for controlling the feeding of polymer into the steam stripping tower; A set of take-off valves (9) located downstream of said steam stripping tower for controlling the outflow of polymer from said steam stripping tower.

10. 10. The method of claim 9, wherein the reaction equipment further comprises: A preliminary dewatering tower (1) located upstream of the feed valve set; and / or a cooler (6) whose inlet is connected to the exhaust outlet of the steam stripping tower and whose outlet is connected to a condensate tank (7); and / or a circulating water cooling system for rapidly cooling the polymer discharged from the steam stripping tower to lower its temperature;

11. The circulating water cooling system a heat exchanger (3) located downstream of the set of withdrawal valves and connected to a circulating water tank via a transfer pump (4); and / or a venturi feeder (5) whose first inlet is connected to the outlet valve assembly and whose second inlet is connected to the heat exchanger; 11. The method of claim 10, comprising:

12. 12. The method of claim 11, comprising the steps of: (i) introducing polymer through the feed valve set (8) and into the feed port at the top of the steam stripping tower (2); (ii) introducing steam into the steam stripping tower and heat exchanging with the polymer so that the operating pressure inside the steam stripping tower corresponds to the saturated vapor pressure; (iii) The rotary take-off valve assembly (9) is controlled so that the polymer is discharged.

13. 2. The method according to claim 1, characterized in that it is carried out in an apparatus comprising: Wet nitrogen gas steam stripping tower (202); a feed valve set (208) located upstream of the wet nitrogen gas steam stripping tower, connected to the top feed port of the wet nitrogen gas steam stripping tower, for controlling the feeding of resin into the wet nitrogen gas steam stripping tower; a set of outlet valves (209) located downstream of the wet nitrogen gas steam stripping tower for controlling the outflow of resin from the wet nitrogen gas steam stripping tower; The apparatus further includes a pre-dehydration tower (201) located upstream of the set of feed valves; The apparatus further includes a cooler (206) having an inlet connected to the exhaust outlet of the wet nitrogen gas steam stripping tower and an outlet connected to a condensate tank (207).

14. 14. The method of claim 13, comprising the steps of: (1) The resin crude product is introduced through the charging valve set (208) into the charging port at the top of the wet nitrogen gas steam stripping tower (202); (2) Wet nitrogen gas is introduced into the wet nitrogen gas steam stripping tower and heat-exchanged with the resin crude product, and the resin crude product is heated to 50-95°C to desorb VOCs from the resin; (3) Control the rotary take-off valve assembly (209) so that the resin crude product is discharged.

15. 2. The method according to claim 1, characterized in that it is carried out in an apparatus comprising: A ration buffer tank (401) for temporary storage of polymeric materials requiring VOC removal and odor reduction; A horizontal rotary kiln assembly is located downstream of the charging buffer tank and includes a first horizontal rotary kiln (402) and a second horizontal rotary kiln (403), which are configured in series, and each of the first horizontal rotary kiln and the second horizontal rotary kiln has a material inlet, a steam inlet valve, and an exhaust discharge valve.

16. 16. The method of claim 15, comprising the steps of: (1) Put the polymer that needs to be VOC-free and / or odor-reduced into the charging buffer tank (401), operate the first horizontal rotary kiln (402) and the second horizontal rotary kiln (403), and continuously introduce steam into the horizontal rotary kiln components, while simultaneously opening the material inlet; (2) The polymer is retained in the horizontal rotary furnace part, and the VOC is allowed to form an azeotrope with the vapor. Then, the exhaust valve is opened to discharge the azeotrope from the horizontal rotary furnace part.

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