CN112454726A

CN112454726A - Polymer impurity removal method based on steam distillation

Info

Publication number: CN112454726A
Application number: CN202010432661.7A
Authority: CN
Inventors: 不公告发明人
Original assignee: Shanghai Institute of Organic Chemistry of CAS
Current assignee: Shanghai Institute of Organic Chemistry of CAS
Priority date: 2019-09-09
Filing date: 2020-05-20
Publication date: 2021-03-09

Abstract

The invention provides a method for deeply removing VOC in polymer resin and products thereof and remarkably reducing the odor of the polymer resin and the products thereof by a steam distillation method and a device thereof. The method provided by the invention can also remove residual inorganic ash in the polymer resin. The method comprises the steps that saturated steam and materials are heated at a certain temperature and are continuously contacted for a certain time at 100-200 ℃, Volatile Organic Compounds (VOC) and inorganic small molecules (ash) which are adsorbed on the surface of the polymers and wrapped in the polymers are promoted to be enriched in a gas phase or a liquid phase and discharged, so that the VOC and the ash in the polymer materials are reduced, and the odor of polymer resin or the materials is reduced to a better level.

Description

Polymer impurity removal method based on steam distillation

Technical Field

The invention belongs to the field of polymer production, and particularly provides a process for efficiently removing impurity molecules, particularly VOC, odor molecules and ash in a polymer.

Background

In recent years, the requirements for light weight of automobile products, environmental protection of plastic products in the production and living fields of household appliances, plastic toys, food contact materials, medical materials and the like are increasingly increased. The polymer resin has excellent comprehensive performances of no toxicity, low density, easy processing, high impact strength, good corrosion resistance and heat resistance, high cost performance and the like, so the polymer resin is widely applied to interior and exterior trimming parts of automobiles, household appliances, toy products, food packaging materials and medical materials.

Under the influence of multiple factors such as the purity of a polymerized monomer, catalyst residue, a polymerization process, decomposition of an auxiliary agent, degradation of resin and the like, Volatile Organic Compounds (VOC) are still commonly released to different degrees in the commercially available resin, according to the report of the American international technical evaluation center, the VOC is one of the most main threats to human health in the modern society, the quality of air is directly related to the human health, and the harm of VOC pollution to the human health has attracted attention of China, production enterprises and consumers.

With the increasing awareness of environmental protection of society and the increasing requirements of laws and regulations related to environmental protection, the problems of VOC and odor in plastics are more and more emphasized by consumers, production enterprises and management departments. VOC index of raw materials and products from factories is started by most product manufacturers, wherein the total carbon volatilization of interior materials is required to be less than 80 mu g C/g in the automobile industry. The newly revised national standard GB 4806.1-2016 food contact material and product general safety requirement clearly requires that the food contact material and the product have no smell touch. In addition, because the VOC content of the existing resin is high, the produced resin needs to be replaced repeatedly after entering a packaging bin, on one hand, the difficulty of a packaging procedure is increased, and on the other hand, the phenomenon that replacement gas exceeds the standard and is discharged frequently occurs along with the coming of a new atmospheric emission law and regulation. On 7/1 of 2017, the emission standard of synthetic resin industrial pollutants, new edition, is forced to be implemented, wherein the emission limit of non-methane total hydrocarbons of general enterprises is regulated to be 100mg/m 3. For the areas which need to take protective measures because the development density is higher, the environmental bearing capacity begins to weaken, or the atmospheric environment capacity is smaller, the ecological environment is fragile, and the serious atmospheric environmental pollution problem easily occurs, the pollution of enterprises should be strictly controlledDye discharge behavior, implementing a more stringent emission limit (60 mg/m)³) Therefore, the reduction of VOC in the production and processing of plastics has become a very urgent problem.

In view of the current situation, some famous foreign enterprises and research institutions have made different degrees of research on low-VOC plastics, and have made some progress. In the processing field, measures for reducing VOC and odor of plastic products mainly comprise: (1) the screening and using effects of the auxiliary agent are better, the compatibility is stronger, and the auxiliary agent is more stable. Or an auxiliary agent system with a synergistic effect, and the stability can be realized due to the lower addition amount, so that the VOC and the odor in the resin can be effectively reduced. (2) And optimizing the processing technology. The high-temperature extrusion granulation is adopted, a vacuumizing mode is used in the extrusion process, and the manufactured particles are baked and dried at high temperature, so that residues in the polypropylene can be removed to a certain degree. (3) Adding a component with good adsorption effect on low-molecular residues. It was found that the addition of inorganic porous materials such as volcanic ash and zeolite molecular sieve in a certain amount can also eliminate VOC in polypropylene, although the effect is greatly influenced by the specific surface, pore structure, surface structure, pore size and pore size distribution of the materials.

The measures have certain effect on the release of new VOC generated in the processing process, but are not enough to solve the problem of high VOC content of the resin raw material. In addition, the addition of large amounts of adsorptive additives to the resin feedstock results in a large amount of ash in the resin. Ash refers to the residual metal and non-metal oxides of the resin after complete combustion at high temperatures. The resin with high ash content seriously affects the plastic processing technology, especially the processing mode of stretching processing for film materials, spinning materials and the like, the higher ash content not only greatly increases the production cost, but also causes great influence on the physical and chemical properties of the product, and influences the exertion of the mechanical and mechanical properties of the plastic: causing white spots and defects of the film material; the yarn breaking occurs in the spinning process, the mechanical strength is reduced, and the like. Taking polypropylene as an example, high-purity PP with lower ash content (mass fraction is generally less than 0.0080%) has good application prospect in the fields of electronic appliances, medicines, foods, textiles and the like. The national drug administration stipulates in the standard compilation of packaging materials and containers in direct contact with drugs, and the mass fractions of metal elements such as copper, cadmium, chromium, lead, tin and barium in a PP infusion bottle are measured by adopting an atomic absorption spectrophotometry and are required to be not more than 0.0003%, and the mass fraction of ash is required to be not more than 0.0050% when the PP film is used as a capacitor film. At present, the ash content of most of commercially available resins is about 0.03-0.3%, and how to reduce the ash content, improve the stability of plastics in the processing and using processes and give full play to the performance of the plastics is also an urgent problem to be solved.

In view of the foregoing, there is a lack in the art of a method for efficiently removing VOCs, ash and reducing odor levels from resins.

Disclosure of Invention

The invention aims to provide a method for removing VOC and ash in polymer materials and reducing odor grade.

In a first aspect of the present invention, a method for deeply removing Volatile Organic Compounds (VOC) from a polymer, reducing odor of the polymer, and removing inorganic ash is provided, wherein the method comprises: the polymer is continuously contacted by the water vapor to remove Volatile Organic Compounds (VOCs) and odor-forming components from the polymer.

In another preferred embodiment, the process is carried out under atmospheric or pressurized conditions.

In a second aspect of the present invention, there is provided a method for deeply removing inorganic ash from a polymer, the method further comprising: the steam is continuously brought into contact with the polymer, thereby dissolving and removing the inorganic ash from the polymer.

In another preferred embodiment, water vapor and water in phase equilibrium are simultaneously contacted with the polymer.

In another preferred embodiment, the method comprises the step (a):

(a) in the reaction system, the water vapor in a phase equilibrium state is continuously contacted with the polymer for 0.5 to 6 hours (example 38), preferably 0.5 to 3 hours.

In another preferred embodiment, the organic material is selected from the group consisting of: volatile Organic Compounds (VOCs), odor components, or combinations thereof.

In another preferred embodiment, the inorganic ash content is removed, which means that the ash content in the polymer is reduced by more than or equal to 20 percent based on the original ash content (concentration); most preferably, the concentration is less than 110 ppm.

In another preferred embodiment, the organic is deeply removed to reduce the VOC in the polymer to less than or equal to 100ppm, preferably less than or equal to 50ppm, more preferably less than or equal to 10ppm, and most preferably less than or equal to 1ppm (as measured by VDA 277).

In another preferred embodiment, the organic removal means that the polymer material has an odor rating of 3 or less, preferably 2 or less (as tested by VW 50180).

In another preferred embodiment, the temperature of the water vapor is 100-200 ℃.

In another preferred embodiment, during the contacting, the reaction system is isolated from air or oxygen; preferably, the air or oxygen exclusion refers to the oxygen content of the system in the complete removal process being less than 5% (v/v); preferably, the oxygen content of the system is less than 1% (v/v), preferably less than 0.1% (v/v), more preferably less than 100 ppm.

In another preferred example, the method further comprises: purging the system with an inert gas or steam to displace air from the system before step (a) is performed.

In another preferred example, the method further comprises: continuously introducing water vapor into the reaction system, and simultaneously discharging the vapor and/or condensed water; preferably, the steam discharge speed is 1-200Kg of water steam/ton of polymer/hour; preferably 1 to 120Kg of water vapor per ton of polymer per hour; more preferably 5 to 50Kg of steam per ton of polymer per hour, most preferably 5 to 25Kg of steam per ton of polymer per hour.

In a further preferred embodiment, the removal of steam and/or condensed water is carried out intermittently or continuously.

In another preferred embodiment, the polymer is selected from the group consisting of: polyethylene (PE), polypropylene (PP), polybutylene 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 combinations thereof.

In another preferred embodiment, the polymer is polypropylene (PP) or polypropylene random copolymer PPR; preferably, the polypropylene (PP) or polypropylene random copolymer PPR has a melt index in the range of 0.1-2000g/10min (measured in GB/T2682-2000 method).

In another preferred example, the polypropylene (PP) is a special resin for medical grade, automotive interior or food contact applications.

In another preferred embodiment, the polypropylene is melt-blown resin, injector special resin or protective article special resin.

In another preferred example, the polypropylene (PP) is a resin dedicated for realizing electronic and electric parts.

In another preferred example, the polyethylene is ultrahigh molecular weight polyethylene UHMWPE or crosslinked polyethylene PEX.

In another preferred embodiment, the polymer is a modified polymer, or a polymer article.

In another preferred embodiment, the polymer is a polymer particle, and the particle size of the particle is 0.05mm-5mm, preferably 0.1-3 mm.

In another preferred example, the water vapor is high-pressure water vapor or low-pressure water vapor.

In another preferred embodiment, the temperature of the water vapor is selected based on the melting point of the polymer.

In another preferred embodiment, the temperature of the water vapor is 20 to 50 ℃ lower than the melting point of the polymer, preferably 20 to 30 ℃ lower than the melting point of the polymer.

In another preferred embodiment, when the particle size of the polymer is less than 1mm and the VOC content in the polymer is less than 2000ppm, the time for keeping the polymer at the temperature corresponding to the saturated water vapor is 0.5-3 hours, and more preferably 0.5-2 hours.

In another preferred embodiment, when the particle size of the polymer is less than 1mm and the VOC content is greater than or equal to 2000ppm, the time for keeping the polymer at the temperature corresponding to the saturated water vapor is 1-5 hours, preferably 1-3 hours.

In another preferred embodiment, when the particle size of the polymer is larger than or equal to 1mm and the VOC content is less than 1000ppm, the time for keeping the polymer at the temperature corresponding to the saturated water vapor is 1-5 hours, preferably 2-4 hours.

In another preferred embodiment, when the particle size of the polymer material is larger than or equal to 1mm and the VOC content is larger than or equal to 1000ppm, the time for keeping the polymer at the temperature corresponding to the saturated water vapor is 3-7 hours, preferably 3-5 hours, and most preferably 3-4 hours.

In another preferred embodiment, the water vapor is a mixture of water vapor and water in a phase equilibrium state.

In another preferred embodiment, the step (a) includes the following sub-steps:

(a1) filling the polymer material in a device, preferably the device is vertical or horizontal;

(a2) passing said water vapor through the interior of said apparatus in step (a1) and continuously contacting the polymer at phase equilibrium for a period of time ranging from 0.5 to 6 hours while removing the water vapor after contacting the polymer;

(a3) dehydrating and drying the polymer material;

(a4) discharging and collecting the polymer material dehydrated and dried in the step (a 3).

In another preferred example, before the step (a1), the method further comprises the steps of: preheating the polymer mass.

In another preferred embodiment, the method further comprises the steps of: and carrying out quenching and temperature reduction on the polymer material discharged after purification.

In another preferred embodiment, before the step (a), the method further comprises the steps of: and carrying out pre-dehydration treatment on the polymer material.

In another preferred embodiment, the polymer is added to the device in batches in the step (a1) and the steps (a2) - (a4) are carried out, so as to realize batch operation.

In another preferred embodiment, the steps (a1) - (a4) are performed continuously, wherein the continuous operation means that the polymer continuously enters the apparatus, passes through the steps (a2) - (a3), and is continuously discharged and collected in the operation (a 4).

In another preferred example, the method further comprises: purging the entire system with nitrogen gas prior to said substep (a1) to bring the oxygen content of the system to less than 5% (v/v).

In another preferred embodiment, the apparatus is a device capable of achieving steam distillation.

In a second aspect of the present invention, there is provided an apparatus for deeply removing Volatile Organic Compounds (VOC) from polymers, reducing odor of the polymers, and removing inorganic ash, the apparatus comprising:

a steam stripping device (2);

a feed valve block (8) located upstream of said steam stripping means, said feed valve block being connected to a top feed inlet of said steam stripping column for controlling polymer flow into said steam stripping column;

a discharge valve block (9) downstream of said steam stripper, said discharge valve block being adapted to control the flow of polymer out of the steam stripper.

In another preferred example, the reaction equipment also comprises a predehydration tower (1) positioned at the upstream of the feeding valve group.

In another preferred example, the device also comprises a condenser (6), wherein the inlet of the condenser is connected with the tail gas outlet of the steam stripping tower, and the outlet of the condenser is connected with a condensate tank (7).

In another preferred example, the device further comprises a circulating water cooling system, wherein the circulating water cooling system is used for rapidly cooling the polymer discharged from the steam stripping tower; preferably, the circulating water cooling system comprises:

the heat exchanger (3) is positioned at the downstream of the discharge valve group and is connected with the circulating water tank through a delivery pump (4);

the venturi feeder (5), the first entry of venturi feeder links to each other with the valves of unloading, the second entry with the heat exchanger link to each other.

In another preferred example, the tail gas outlet of the steam stripping tower is connected with the condenser through a blower (10).

In a third aspect of the present invention, there is provided a method for deeply removing Volatile Organic Compounds (VOC) from polymers, reducing odor of polymers, and removing inorganic ash, wherein the method is performed using the apparatus according to the second aspect of the present invention, and the method comprises the steps of:

(i) introducing the polymer into a top feed inlet of a steam stripping tower (2) through a feed valve group (8);

(ii) introducing steam into said steam stripper to exchange heat with said polymer to cause the operating pressure within said steam stripper to correspond to the saturated vapor pressure;

(iii) the polymer is discharged under the control of a rotary discharge valve group (9);

preferably, the system of apparatuses is purged with nitrogen before carrying out said steps (i) to (iii) to ensure that the oxygen content of the gas phase components in the stripper is less than 1%, preferably less than 0.1%, more preferably less than 100 ppm.

In another preferred embodiment, during said step (ii), the condensed water is periodically discharged from the bottom of the steam stripper.

In another preferred embodiment, said steps (ii) and (iii) are carried out simultaneously (i.e. during step (ii), the rotary discharge valve is controlled to be in an open state to ensure the retention time of the material in the steaming device).

In another preferred embodiment, the method further comprises the steps of: (iv) introducing the polymer into a Venturi feeder (5) to mix the polymer with condensed water, so as to carry out quenching and cooling on the polymer and then convey the polymer to a downstream dehydration process of a device; preferably, the method further comprises the steps of: the tail gas is discharged through a tail gas outlet of the steam stripping tower.

In another preferred embodiment, before step (i), the method further comprises the steps of: the polymer is fed to a predehydration column (1) for a predehydration step.

In another preferred example, the tail gas is discharged and then enters a condenser (6) for condensation, and then enters a condensate tank (7); preferably, the method further comprises passing the non-condensable components of the tail gas to a tail gas treatment system and then mixing with steam and re-passing the mixture to the steam stripping column (2).

In another preferred embodiment, the removal of VOC of the polymer, the reduction of odor of the polymer, and the reduction of ash of the polymer can be achieved by steam distillation.

It is to be understood that within the scope of the present invention, the above-described features of the present invention and those specifically described below (e.g., in the examples) may be combined with each other to form new or preferred embodiments. Not to be reiterated herein, but to the extent of space.

Drawings

Fig. 1 is a schematic diagram of the construction of the polymer VOC removal, odor-rating reduction device of the present invention.

The system comprises a pre-dehydrator 1, a steam stripping tower 2, a heat exchanger 3, a delivery pump 4, a Venturi feeder 5, a condenser 6, a condensate tank 7, a rotary feeding valve bank 8, a rotary discharging valve bank 9 and a blower 10.

Detailed Description

The present inventors have conducted extensive and intensive studies over a long period of time to provide a method for deep removal of VOC from polymer resins, reduction of odor levels, removal of inorganic ash, and an apparatus for achieving the same. The method is characterized in that water vapor is continuously contacted with a polymer, so that organic volatile compounds (VOC) wrapped in polymer resin and organic volatile compounds causing serious odor are fully migrated and diffused and form an azeotrope with the water vapor, and thus, deep removal is realized; the method can also promote inorganic salt (such as ash) and the like wrapped in the resin to be fully dissolved in the water vapor to achieve the effect of deashing; the present case provides simultaneously and can reach the device of this effect. The working principle of the method and the device provided by the scheme is that the process of diffusing and transferring the VOC component in the resin and simultaneously stripping and removing the VOC component along with steam stripping is accelerated by utilizing the characteristics that the chain segment movement of the resin is intensified within a certain temperature range, the original particle physical form of the resin is not damaged, and no agglomeration occurs, and the process utilizes steam distillation to realize deep removal of residual VOC in the resin. Based on the above findings, the inventors have completed the present invention.

Method for removing VOC (volatile organic compounds) of resin and reducing odor grade

In order to overcome the defects of the prior art, reduce the VOC content of resin products in the prior production device, reduce the odor level, improve the product quality and reduce the VOC emission problem in the packaging process of the production device, the invention provides a process method for efficiently removing polymer impurities (such as VOC, polymer odor, inorganic salt and other impurities).

The method of the invention comprises the following steps: the water vapor is continuously contacted with the polymer material at the temperature of 100-200 ℃ for 0.5-6 hours, and the organic matters in the polymer enter a gas phase or a liquid phase, so that the VOC (organic matters with high boiling points or low vapor pressure) content and the odor grade in the polymer are reduced.

In a preferred embodiment, the VOC in the polymer can be reduced to a minimum of 1 ppm; the odor grade can reach 3.0, and the requirements of medical grade or electronic grade resin are met.

The method can simultaneously reduce the content of inorganic ash in the polymer on the basis of removing VOC and odor levels conventionally, thereby achieving the effect of deashing the polymer. In a preferred embodiment, after the removing step is carried out, the ash content in the polymer can be reduced by more than 20 percent based on the original ash content and can be as low as 0.011 percent; more preferably, direct steam/water/polymer contact can achieve superior results. Since the water vapor is continuously contacted with the polymer at 100-200 ℃ for 0.5-6 hours, inorganic substances in the polymer are extracted to the water phase, and a better deashing effect can be achieved up to 50ppm when the water vapor and the water in a phase equilibrium state are contacted with the polymer.

The method can effectively reduce VOC in the polymer, and preferably, the reaction system is isolated from air or oxygen during the treatment process of the method. The air or oxygen isolation means that the oxygen content of the system in the complete removal process is lower than 5 percent; specifically, before the operation of the method, inert gas or water vapor is used for purging the system to replace air in the system, so that a better effect can be achieved; in a preferred embodiment, the oxygen content of the gas phase component is less than 1%; more preferably, less than 0.1%; most preferably less than 100 ppm.

To obtain a better result, the removal step is carried out while keeping the steam or condensed water being discharged at a rate of 1-200Kg steam/ton polymer/hour. At the same time, the same amount of water vapor is introduced to maintain the pressure and the water vapor temperature in the system.

In order to ensure the effect of deep removal, the steam discharge speed is preferably 1-200Kg of water steam/ton of polymer/hour; for better economy, 1-100 Kg of water vapor is preferably used per ton of polymer per hour; in another preferred embodiment, the amount of steam is more preferably 5 to 50 Kg/ton/hr, and most preferably 5 to 25 Kg/ton/hr.

In a preferred embodiment, the condensation water removal can be carried out intermittently or continuously.

The polymer type is not particularly limited and may be a powder or a pellet, and in a preferred embodiment, may be an already prepared polymer product.

The polymer may be of various types, for example in a preferred embodiment the polymer is Polyethylene (PE), polypropylene (PP), polybutylene 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.

In a preferred embodiment of the invention, the polymer is polypropylene (PP) and polypropylene random copolymer PPR.

In a preferred embodiment of the present invention, the polymer may be a modified polymer or an article of the polymer.

In a preferred embodiment of the present invention, the polypropylene (PP) or polypropylene random copolymer PPR has a melt index in the range of 0.1 to 2000g/10min (measured under the GB/T2682-2000 method).

In a preferred embodiment of the invention, the polypropylene (PP) is a resin for achieving medical grade, automotive interior specific or food contact applications; in particular to melt-blown resin, special resin for an injector or special resin for a protective article.

In a preferred embodiment of the present invention, the polypropylene (PP) is a resin dedicated for realizing electronic and electrical components.

In a preferred embodiment of the invention, the polyethylenes are ultra high molecular weight polyethylene UHMWPE and cross-linked polyethylene PEX.

In the reaction process of the invention, the water vapor can be high-pressure water vapor or low-pressure water vapor; that is, the temperature of the water vapor may be selected according to the melting point of the polymer; preferably, the temperature of the steam is 100-200 ℃, and is 20-50 ℃ lower than the melting point of the polymer to be treated; in order to achieve better effect, the temperature is preferably 100-200 ℃, and is 20-30 ℃ lower than the melting point of the polymer to be treated.

In one embodiment of the invention, the temperature of the saturated water vapor can be controlled by the pressure of the water vapor; the temperature and pressure of the saturated steam are known to those skilled in the art, and the appropriate pressure may be selected by reference to a saturated steam temperature and pressure look-up table.

In the process, saturated steam can be brought into direct contact with the material, so that the polymer is heated to a temperature corresponding to that of the saturated steam, without preheating the material in the process.

The contact time and the contact temperature may be determined according to the kind of the material actually treated. Preferably:

when the particle size of the polymer is less than 1mm and the VOC content in the polymer is less than 2000ppm, the time for keeping the polymer at the temperature corresponding to saturated water vapor is preferably 0.5-3 hours, and more preferably 0.5-2 hours;

when the particle size of the polymer is less than 1mm and the VOC content is more than or equal to 2000ppm, the time for keeping the polymer at the temperature corresponding to saturated water vapor is preferably 1-5 hours, and more preferably 1-3 hours for achieving a better effect;

the particle size of the polymer is larger than 1mm, the VOC content is lower than 1000ppm, the time for keeping the polymer at the temperature corresponding to saturated water vapor is preferably 1-5 hours, and in order to achieve a better effect, the time is more preferably 2-4 hours;

the particle size of the polymer is larger than 1mm, the VOC content is more than or equal to 1000ppm, preferably 3-7 hours, in order to achieve better effect, more preferably 3-5 hours, and most preferably 3-4 hours.

In a preferred embodiment of the invention, the method may comprise the sub-steps of:

(a1) filling the polymer material into a reaction device, preferably, the device is a vertical device or a horizontal device;

(a2) passing said water vapor through the interior of said reaction apparatus in step (a1) and continuously contacting it directly with the polymer for heat and mass transfer, while maintaining the state of phase equilibrium for 0.5 to 6 hours, while withdrawing the water vapor from said reaction apparatus after contacting it with the polymer;

(a3) dehydrating and drying the polymer material;

Wherein, prior to step (1), the polymer may or may not be preheated; the polymer in the step (1) can be added into equipment in batches, and steps (2) to (4) are carried out, so that batch operation is realized; steps (1) - (4) can also be continuously carried out, so that continuous operation is realized and the effect is achieved; wherein the continuous operation means that the polymer continuously enters the device, passes through the steps (2) to (3), and is continuously discharged and collected in the operation (4); preferably, in order to ensure that the organic volatile components with high boiling point or low saturated vapor pressure in the polymer are sufficiently removed, the contact time of the water vapor and the polymer needs to be ensured to be not less than 0.5 hour.

Since the process of the present application is preferably carried out in the absence of air or oxygen, in a preferred embodiment, the operation further comprises purging the entire system with nitrogen before carrying out operation (1), ensuring that the oxygen content of the system is less than 5%.

In another preferred embodiment, the temperature of the system during the reaction process is 100-200 ℃.

The device adopted by the method of the invention is not particularly limited, and the device capable of realizing steam distillation can realize the removal of Volatile Organic Compounds (VOC) in the polymer. In a preferred embodiment, the apparatus used comprises:

a steam stripping column (2);

a feed valve block (8) located upstream of said steam stripper, said feed valve block being connected to a top feed inlet of said steam stripper for controlling polymer flow into said steam stripper;

In another preferred embodiment, the device further comprises a predehydration tower (1) located upstream of the inlet valve group.

In another preferred example, the device further comprises a circulating water cooling system, and the circulating water cooling system is used for rapidly cooling the polymer discharged from the steam stripping tower.

In another preferred embodiment, the circulating water delivery device includes:

When the device is used as a removing device, the method for removing Volatile Organic Compounds (VOC) in the polymer and reducing the odor grade comprises the following steps:

preferably, the system of apparatuses is purged with nitrogen before carrying out said steps (1) to (3) to ensure that the oxygen content of the gaseous components in the stripper is less than 1%, preferably less than 0.1%, more preferably less than 100 ppm.

In another preferred embodiment, the method further comprises the steps of: (iv) introducing the polymer into a Venturi feeder (5) to mix the polymer with condensed water, so as to carry out quenching and cooling on the polymer and then convey the polymer to a centrifugal dehydration process at the downstream of the device; preferably, the method further comprises the steps of: the tail gas is discharged through a tail gas outlet of the steam stripping tower.

In another preferred embodiment, before step (i), the method further comprises the steps of: the polymer is introduced into a predehydration tower (1) for predehydration.

The method can realize continuous contact of polypropylene and water vapor for 0.5-6 hours at the temperature of 100-200 ℃, so that the VOC of the polypropylene is as low as 1ppm, the ash content is as low as 50ppm, the odor grade can reach 3.0, and the requirements of medical grade or electronic grade resin are met.

Compared with the prior art, the invention has the advantages that:

(1) the VOC content in the final discharge packaging polymer finished product is far lower than that of an untreated polymer finished product by adopting the method for VOC removal, the VOC content can be as low as below 1ppm (tested according to VDA277 standard), the odor grade can be generally as low as 3 grade, the odor grade is as low as 2 grade (tested by VW 50180), and the VOC content and the odor grade are far lower than those of a product with the same market grade. And the VOC content and the odor grade of the product with the original VOC content of less than 40ppm can be still further reduced, so the method can be used for preparing high-grade polymer raw materials (such as medical melt-blown mask raw materials).

(2) The treatment process is simple, namely only one set of steam stripping tower and auxiliary facilities are needed to be added between the two original working procedures, the layout is small, and the operation and the layout of the original device are not influenced.

(3) The latent heat of steam is big, and heat transfer efficiency is high, and the suitable temperature interval of treatment process control, the VOC molecule is analytic fast, therefore the treatment effeciency is high, and the steam quantity is few, and no waste water produces, and does not influence the resin quality, also can not appear the phenomenon that influences the device operation such as caking.

(4) The investment and the operation cost of the device are low, and the quality of the product is improved.

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The experimental procedures, in which specific conditions are not noted in the following examples, are generally carried out under conventional conditions or conditions recommended by the manufacturers. Unless otherwise indicated, percentages and parts are by weight.

The VOC in the plastics is removed by adopting steam, the odor grade is reduced, the operation of removing ash can be intermittent operation or continuous operation, and a proper operation mode is selected according to the working condition. The different operations do not affect the effectiveness of the steam treatment.

The general method comprises the following steps: batch operation

Adding plastic particles (powder) into steaming equipment, replacing with nitrogen, introducing saturated steam at a certain temperature after discharging air, controlling the discharge speed of the steam from the steaming equipment, and maintaining the operating pressure of the steaming equipment corresponding to the pressure corresponding to the saturated steam. And steaming for a certain time, and periodically discharging condensed water from the bottom of the steaming equipment in the period. And after steaming is finished, emptying the equipment, thoroughly dehydrating and drying the material, and cooling to a certain temperature to obtain a qualified material.

The general method comprises the following steps: continuous operation

Adding plastic particles (powder) into a bin at the top of the steaming equipment, after air is discharged, controlling the speed of the material entering the steaming equipment through a rotary valve, introducing saturated steam at a certain temperature, controlling the discharge speed of the steam from the steaming equipment, and maintaining the operating pressure of the steaming equipment corresponding to the pressure corresponding to the saturated steam. The condensation water is periodically drained from the bottom of the decatizing apparatus. The opening of a discharge valve of the steaming equipment is controlled, and the retention time of the material in the steaming equipment is ensured. And (3) thoroughly dehydrating and drying the material discharged from the steaming equipment, and cooling to a certain temperature to obtain a qualified material.

The examples 1, 32, 33, 34 and 35 are batch operation, and the other examples are continuous operation, and the process operation is different regardless of batch or continuous operation, so that the removal effect is not influenced.

All documents referred to herein are incorporated by reference into this application as if each were individually incorporated by reference. Furthermore, it should be understood that various changes and modifications of the present invention can be made by those skilled in the art after reading the above teachings of the present invention, and these equivalents also fall within the scope of the present invention as defined by the appended claims.

Claims

1. A method for deeply removing Volatile Organic Compounds (VOC), reducing odor of polymers and removing inorganic ash from polymers, which comprises the following steps: the polymer is continuously contacted by the water vapor to remove Volatile Organic Compounds (VOCs) and odor-forming components from the polymer.

2. A method for deeply removing inorganic ash in a polymer is characterized by further comprising the following steps: the steam is continuously brought into contact with the polymer, thereby dissolving and removing the inorganic ash from the polymer.

3. A method according to claim 1 or 2, wherein the method comprises step (a):

(a) in the reaction system, the water vapor in a phase equilibrium state is continuously contacted with the polymer for 0.5 to 6 hours, preferably 0.5 to 3 hours.

4. The method of claim 1 or 2, wherein during said contacting, said reaction system is isolated from air or oxygen; preferably, the air or oxygen exclusion refers to the oxygen content of the system in the complete removal process being less than 5% (v/v); preferably, the oxygen content of the system is less than 1% (v/v), preferably less than 0.1% (v/v), more preferably less than 100 ppm.

5. The method of claim 1 or 2, wherein the method further comprises: purging the system with an inert gas or steam to displace air from the system before step (a) is performed.

6. The method of claim 1 or 2, wherein the method further comprises: continuously introducing water vapor into the reaction system, and simultaneously discharging the vapor and/or condensed water; preferably, the steam discharge speed is 1-200Kg of water steam/ton of polymer/hour; preferably 1 to 120Kg of water vapor per ton of polymer per hour; more preferably 5 to 50Kg of steam per ton of polymer per hour, most preferably 5 to 25Kg of steam per ton of polymer per hour.

7. The method of claim 1 or 2, wherein the polymer is selected from the group consisting of: polyethylene (PE), polypropylene (PP), polybutylene 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 combinations thereof.

8. The process of claim 1, wherein said polymer is polypropylene (PP) or polypropylene random copolymer PPR; preferably, the polypropylene (PP) or polypropylene random copolymer PPR has a melt index in the range of 0.1-2000g/10min (measured in GB/T2682-2000 method).

9. The process according to claim 1 or 2, wherein the temperature of the water vapour is 20 to 50 ℃ below the melting point of the polymer, preferably 20 to 30 ℃ below the melting point of the polymer; preferably, the water vapor is a mixture of water vapor and water in a phase equilibrium state.

10. The method of claim 1 or 2,

when the particle size of the polymer is less than 1mm and the VOC content in the polymer is less than 2000ppm, the time for keeping the polymer at the temperature corresponding to the saturated water vapor is 0.5-3 hours, and more preferably 0.5-2 hours;

when the particle size of the polymer is less than 1mm and the VOC content is more than or equal to 2000ppm, the time for keeping the polymer at the temperature corresponding to the saturated water vapor is 1-5 hours, preferably 1-3 hours;

when the particle size of the polymer is larger than or equal to 1mm and the VOC content is less than 1000ppm, the time for keeping the polymer at the temperature corresponding to the saturated water vapor is 1-5 hours, preferably 2-4 hours;

when the particle size of the polymer material is larger than or equal to 1mm and the VOC content is larger than or equal to 1000ppm, the time for keeping the polymer at the temperature corresponding to the saturated water vapor is 3-7 hours, preferably 3-5 hours, and most preferably 3-4 hours.

11. A method as claimed in claim 1 or 2, wherein step (a) comprises the sub-steps of:

(a3) dehydrating and drying the polymer material;

12. An apparatus for deeply removing Volatile Organic Compounds (VOC), reducing odor and removing inorganic ash from a polymer, said apparatus comprising:

a steam stripping device (2);

a discharge valve block (9) downstream of said steam stripper for controlling polymer flow out of the steam stripper;

optionally, the reaction apparatus further comprises:

a predehydration tower (1) located upstream of the inlet valve group; and/or

A condenser (6), wherein the inlet of the condenser is connected with the tail gas outlet of the steam stripping tower, and the outlet of the condenser is connected with a condensate tank (7); and/or

The circulating water cooling system is used for rapidly cooling the polymer discharged from the steam stripping tower; (preferably, the circulating water cooling system comprises a heat exchanger (3) positioned at the downstream of the discharge valve group, the heat exchanger is connected with the circulating water tank through a delivery pump (4), and/or

The first inlet of the Venturi feeder is connected with the discharging valve group, and the second inlet of the Venturi feeder is connected with the heat exchanger).

13. A method for deeply removing Volatile Organic Compounds (VOC) from polymers, reducing odor of polymers and removing inorganic ash, wherein the method is performed by using the apparatus of claim 12, and the method comprises the steps of:

preferably, before carrying out said steps (i) to (iii), the system of apparatuses is purged with nitrogen to ensure that the oxygen content of the gaseous components in the stripper is less than 1%, preferably less than 0.1%, more preferably less than 100 ppm;

preferably, the method further comprises the steps of: (iv) introducing the polymer into a Venturi feeder (5) to mix the polymer with condensed water, so as to carry out quenching and cooling on the polymer and then convey the polymer to a downstream dehydration process of a device; preferably, the method further comprises the steps of: discharging tail gas through a tail gas outlet of the steam stripping tower;

preferably, before step (i), the method further comprises the steps of: adding the polymer to a predehydration tower (1) for a predehydration step;

preferably, the tail gas enters a condenser (6) for condensation after being discharged, and then enters a condensate tank (7); preferably, the method further comprises passing the non-condensable components of the tail gas to a tail gas treatment system and then mixing with steam and re-passing the mixture to the steam stripping column (2).