JP2004123813A - Method of recycling plastic by removing additive and solvent recovery apparatus to be used therein - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of recovering a plastic having rationality from not only environmental but also economical aspects by recovering a solvent containing unnecessary various additive components extracted from recovered plastic members with high efficiency. <P>SOLUTION: In the method of recycling a plastic by removing additives which comprises an operation of extracting the additives with a solvent from the plastic containing the additives and a solvent recovery operation of recovering the solvent separated from the additives by the distillation of the additive-extracted solvent, the solvent recovery operation comprises evaporation of the solvent in a distiller, solvent recovery from the additive-extracted solvent by the condensation of the evaporation component, and solvent recovery by the condensation of the solvent vapor to be discharged from a vent of a screw extruder with the vent connected to the discharge outlet for the condensation component in the distiller. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a plastic recycling method for obtaining a recycled plastic material having high reuse value by extracting unnecessary additives from plastic members collected from various containers, home appliances, OA equipment, and the like. The present invention relates to a solvent recovery device to be used.
[0002]
[Prior art]
BACKGROUND ART Plastics that are easy to process, lightweight, and have excellent mechanical strength are widely used as housing materials and internal component materials for home electric appliances, OA appliances, and the like. Depending on the purpose of use, there are many cases where flame resistance, light resistance, oxidation resistance, antistatic property, high fluidity, etc. are required as a resin composition, and various additives are mixed and used for the purpose of improving resin properties. That is the current situation.
[0003]
From the perspective of environmental protection, the shift from the conventional economy of mass production and mass disposal to a recycling-oriented economy has been demanded, and the recycling of containers and packaging and the recycling of household electrical products have been enacted. Recycling is strongly demanded. However, in the case of material recycling, where resin is used again as a resin, there is a problem that the intrinsic performance of the resin is significantly impaired by the mixture of foreign substances or different kinds of resins. It is currently under consideration.
[0004]
In addition, some plastic additives are substances that are endocrine disrupting substances, are known to have a significant effect on ecosystems, or are harmful when subjected to improper treatment such as burning. Many of them are known to be produced, and it is not preferable to re-distribute them as they are on the market again as they contain them, since this increases the risk to the human body and ecosystem.
[0005]
In other words, there is a need for a plastic recycling system that can remove unnecessary additives from plastic members collected from used containers, home appliances, OA equipment, and the like, and obtain a recycled plastic material having high reuse value. I have.
[0006]
Under such circumstances, we have already proposed a method of extracting and removing additives and the like with a solvent (see Patent Documents 1 and 2).
[0007]
[Patent Document 1]
JP 2001-151930 A [Patent Document 2]
Japanese Patent Application Laid-Open No. 2002-37914
[Problems to be solved by the invention]
However, since the price of plastics is inherently inexpensive, it is economically required that recycled plastics that are recycled are also sufficiently inexpensive. However, it is necessary to efficiently collect solvents used for extraction processing such as additives. For example, there has been a problem that the cost of the solvent alone is uneconomical.
[0009]
In addition, when recovering the solvent, distillation is mainly used, but it is common practice to optimize the process based on the properties of the additive, which is the extract to be distilled residue. Variations in the formulation are wide, and it is difficult to take out as a distillation residue having a sufficiently small remaining amount of the solvent simply by putting it into an existing solvent recovery device.
[0010]
In the present invention, not only environmental aspects but also economical aspects can be obtained by efficiently recovering a solvent from a solvent containing unnecessary various additive components extracted from plastic members recovered from various containers, home appliances, OA equipment, and the like. It is an object of the present invention to provide a plastic recycling method which is rational in nature, and a solvent recovery device used for the method.
[0011]
[Means for Solving the Problems]
The plastic recycling method for removing an additive according to the present invention includes an operation of extracting the additive from the plastic containing the additive with a solvent, and recovering the solvent obtained by separating the additive by distillation from the solvent from which the additive is extracted. In a method of recycling a plastic for removing an additive, which includes a solvent recovery operation, the solvent recovery operation recovers a solvent from a solvent in which the additive is extracted by evaporation of the solvent in the still and condensation of the evaporated components, and It is characterized in that it includes solvent recovery by condensation of solvent vapor exhausted from a vent of a screw extruder with a vent connected to a concentrated component outlet.
[0012]
Further, the plastic recycling method for removing an additive according to the present invention is characterized in that the supply of the concentrated component from the concentrated component discharge port of the still to the vented screw extruder is performed by a gear pump.
[0013]
Further, the plastic recycling method for removing additives according to the present invention is characterized in that the vented screw extruder is a single-screw or twin-screw vented screw extruder.
[0014]
Further, the plastic recycling method for removing additives according to the present invention is characterized in that the still is a thin-film still.
[0015]
Further, the plastic recycling method for removing an additive according to the present invention is characterized in that a thickener is added to a solvent from which the additive has been previously extracted when the solvent is evaporated in a still.
[0016]
More preferably, the thickener is a polymer compound having a glass transition temperature of 60 ° C. or more and 150 ° C. or less, a weight average molecular weight of 1,000 or more and 50,000 or less, and being soluble in the solvent. It is characterized by.
[0017]
More preferably, the thickener is characterized by a kinematic viscosity at 100 ° C. or less 10,000 mm ² / sec or more 1,000,000 mm ² / sec.
[0018]
Further, the plastic recycling method for removing additives according to the present invention is characterized in that, among the additive components to be extracted, the weight ratio of components having a melting point higher than the evaporation temperature in the still is adjusted to less than 50%. I do.
[0019]
Further, in the method for recycling a plastic for removing an additive according to the present invention, the evaporator is a thin film evaporator, and when the evaporator evaporates the solvent in the evaporator, a powder in which the additive is extracted in advance is insoluble in the solvent. Is added.
[0020]
More preferably, the additive is a halogen-based flame retardant, and the powder insoluble in the solvent is calcium hydroxide or calcium carbonate.
[0021]
Further, the plastic recycling method for removing an additive according to the present invention is characterized in that, among the additive components to be extracted, the weight ratio of the component whose melting point is equal to or higher than the evaporation temperature in the still is less than 50%. .
[0022]
Further, the plastic recycling method for removing additives in the present invention includes connecting the nozzle tip of a vented screw extruder to a flash evaporation tank in which the pressure is reduced to 0.001 MPa or less, and recovering the solvent by condensation of vaporized solvent vapor. It is characterized by the following.
[0023]
Further, the solvent recovery device according to the present invention is a screw extruder with a vent connected to a solvent recovery part from a solvent in which an additive is extracted by evaporation of the solvent in the still and condensation of the evaporated component, and a concentrated component outlet of the still. A solvent recovery unit for condensing the solvent vapor exhausted from the vent, and a gear pump supply unit for the concentrated component from the concentrated component discharge port of the still to the vented screw extruder.
[0024]
More preferably, the still is characterized in that the still is a thin-film still.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described based on examples with reference to the drawings.
[0026]
FIG. 1 is a block diagram showing a flow of a plastic recycling method for removing an additive according to the present invention.
[0027]
In the block diagram of the plastic recycling method shown in FIG. 1, 1 is an operation of extracting an additive from a plastic containing an additive by using a solvent, and 2 is recovering a solvent obtained by separating the additive by distillation from the solvent from which the additive was extracted. 2 is a solvent recovery operation step, wherein 2 is a solvent recovery step from the solvent in which the additive is extracted by evaporating the solvent and condensing the evaporated component in at least 3 stills, and connected to the concentrated component outlet of the 4th still. And a solvent recovery step by condensation of the solvent vapor exhausted from the vent of the screw extruder with vent.
[0028]
The operation of extracting the additive from the plastic containing the additive with a solvent is not particularly limited, but a heat stabilizer, a stabilizing aid, a plasticizer, an antioxidant, a light stabilizer, a flame retardant, Polycarbonate (PC) resin containing additives soluble in any solvent such as lubricants, antistatic agents, flame retardants, smoke suppressants, powder treating agents, defoamers, processing aids, mold release agents, lubricants , Polyamide resin, saturated polyester resin, polystyrene (PS) resin, AS resin, ABS resin, acrylic resin, polyarylene sulfide resin, polyarylene ester resin, polyphenylene ether (PPE) resin, modified PPE resin, polyethylene, polypropylene, etc. Thermoplastic resins such as polyolefin resin, vinyl chloride resin, vinylidene chloride resin, polybutadiene, butadiene Nsuchiren copolymer, butadiene - acrylonitrile copolymer, polyisoprene, a plastic such as synthetic rubber acrylic rubber, urethane rubber, and silicone rubber are of interest.
[0029]
As a solvent to be used, a solvent capable of dissolving only additives without dissolving plastics may be used. Specific examples include isopropanol, butanol, pentanol, hexanol, heptanol, 1-octanol, 2-octanol and the like, and glycols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, diethylene glycol methyl ether, Diethylene glycol ethyl ether, diethylene glycol propyl ether, diethylene glycol butyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether, triethylene glycol methyl ether, triethylene glycol ethyl ether, triethylene glycol propyl Ether, Ethylene glycol butyl ether, tripropylene glycol methyl ether, tripropylene glycol ethyl ether, tripropylene glycol propyl ether, tripropylene glycol butyl ether, and the like.
[0030]
Recyclable plastics include, for example, plastic molded products used in household appliances and office automation equipment included in waste products, OA and office equipment, electrical and electronic products, vehicle parts, and other covers. , Cases, sheets and the like.
[0031]
The extraction operation can be performed by bringing the plastic and the solvent into contact with each other with or without heating, and then separating the solvent. Preferably, a method of filtering after mixing with a batch type stirrer, a method of finely pulverizing the plastic together with the solvent by mortaring and the like, a method of separating the solvent after pouring and injecting and mixing into a screw kneader, and the like. Can be done.
[0032]
In order to separate the additive from the solvent containing the additive by the extraction operation, distillation is basically performed. If the solubility of the additive in the solvent has a large temperature dependence, there is a method of recovering the solvent by solid-liquid separation of the dissolved additive using a temperature difference.However, when the recovered solvent is used again in the extraction operation The smaller the residual amount of the additive, the higher the extraction efficiency using the additive, and therefore, there is no advantage over the solvent separation by the distillation operation.
[0033]
In the distillation, the extracted solvent is introduced into the still 5 as shown in FIG. 2 to evaporate the solvent, and the evaporated component is condensed in the condenser 6 to recover the solvent. Although the extracted additive remains in the distillation residue after evaporating the solvent in the evaporator, some solvent remains without evaporation. By connecting a screw extruder 8 with a vent to the concentrated component discharge port 7 for taking out the concentrated component in such a still from the still, the solvent vapor exhausted from the vent 9 is condensed and collected in another condenser 10. The solvent can be further recovered from the distillation residue introduced into the screw extruder.
[0034]
As a result, most of the solvent used for the extraction operation can be recovered by combining the condensed recovered amount in the still and the exhaust condensed amount of the vented screw extruder.
[0035]
It is preferable to use the gear pump 11 for supplying the concentrated component from the concentrated component discharge port of the still to the vented screw extruder. Although the distillation residue is not moved only by gravity, the gravity applied to the moving passage changes depending on the liquid level of the residue, and as a result, the amount of movement tends to fluctuate, and stable operation becomes difficult.
[0036]
The use of a gear pump is preferable because the influence of the fluctuation of gravity and the vent exhaust on the screw extruder side can be reduced and the supply amount can be stabilized.
[0037]
The still is preferably a thin-film still. The thin-film still is used in the continuous process, but it is possible to efficiently evaporate volatile components by heating the material to be distilled while mechanically forming a thin film, making the still more compact and reducing the amount of residual solvent in the distillation residue. can do.
[0038]
In the transfer of the concentrated component from the concentrated component discharge port of the still to the vented screw extruder, if the concentrated component is powdered, fluidity cannot be obtained. And it becomes difficult to control the pressure in the still.
[0039]
Therefore, it is preferable to add a thickener to the solvent from which the additives have been extracted in advance. By adding a thickener, powdering of the concentrated component can be suppressed, or the viscosity can be increased to make a viscous liquid, so that the above problems can be solved.
[0040]
As such a thickener, a polymer compound having a glass transition temperature of 60 ° C. or more and 150 ° C. or less, a weight average molecular weight of 1,000 or more and 50,000 or less, and being soluble in the solvent is used. Is preferred. If the glass transition temperature of the thickener is less than 60 ° C., the properties of the distillation residue discharged from the screw extruder at room temperature will not become a solid that is easy to handle, and if it exceeds 150 ° C., concentration will proceed in the still. The glass transition temperature is preferably in the range of 60 ° C. or more and 150 ° C. or less, since it is difficult to move from the concentrated component discharge port of the still to the screw extruder with vent.
[0041]
Further, the weight average molecular weight is preferably 1,000 or more and 50,000 or less in order to ensure fluidity in a temperature range of 100 ° C. to 200 ° C. in the still.
[0042]
It must be soluble in the solvent used for extraction to contribute as a thickener.
[0043]
Further, the thickener is preferably a kinematic viscosity of less 10,000 mm ² / sec or more 1,000,000 mm ² / sec at the 100 ° C.. Such kinematic viscosity becomes difficult to vacuum at the vent sealing property is lowered in the is 10,000 mm ² / s vented screw extruder, distiller exceeds 1,000,000 mm ² / s The kinematic viscosity at 100 ° C. is not less than 10,000 mm ² / sec and 1,000,000. it is preferable that 000mm is ² / sec or less.
[0044]
In addition, it is preferable to adjust the weight ratio of the extracted additive component having a melting point equal to or higher than the evaporation temperature in the still to less than 50%. Among the additive components to be extracted, when the weight ratio of the components whose melting point is equal to or higher than the evaporation temperature in the still becomes more than 50%, granulation, powderization, Alternatively, agglomeration may occur, making it difficult to move the concentrated component discharge port of the still to the screw extruder with vent, and in the case of a thin-film still, there may be problems such as obstruction of rotation of the internal rotating blades of the still. Therefore, it is preferable to adjust to less than 50%. In order to adjust the content to less than 50%, the plastics from which the additives are to be extracted in advance should be subjected to an infrared spectroscopy, a near-infrared spectroscopy, or a type analysis of additives by heating or combustion gas analysis. It can be realized by appropriately mixing and adjusting.
[0045]
Subsequently, the additive is removed, including an operation of extracting the additive from the plastic containing the additive with a solvent, and a solvent recovery operation of recovering the solvent obtained by separating the additive by distillation from the solvent from which the additive is extracted. In the method for recycling plastic, the distillation apparatus is a thin-film distillation apparatus, and when the solvent is evaporated in the distillation apparatus, powder that is insoluble in the solvent is added to the solvent from which the additive has been extracted in advance. A method of recycling plastics for removing the agent will be described.
[0046]
When concentration is performed in the thin-film evaporator 12 as shown in FIG. 3, when the concentrate is solid even at the internal temperature of the evaporator, the solidified powder is solidified by stirring the rotating blades 13 of the thin-film evaporator. It is possible. However, when the concentrate is an additive, the concentrate is not always solid even at the temperature in the still, so that even if the solvent as a volatile component is sufficiently volatilized, the concentrate may not become powdery. Therefore, when evaporating the solvent in the distillation apparatus, by adding a powder insoluble in the solvent to the solvent from which the additive has been extracted in advance, it becomes possible to handle the concentrate in powder form. The pulverized concentrated component can be periodically taken out from the bottom of the thin-film evaporator by operating the valve 14.
[0047]
Preferably, the additive is a halogen-based flame retardant, and the powder insoluble in the solvent is calcium hydroxide or calcium carbonate. Since concentrated halogen-based flame retardants are generally environmentally hazardous substances, they are discarded by appropriate treatment such as high-temperature incineration.In this case, a base must be added to neutralize the hydrogen halide generated by decomposition. Therefore, it is preferable to use calcium hydroxide or calcium carbonate as a substitute for the base as a powder insoluble in a solvent without unduly increasing the amount of waste.
[0048]
Subsequently, the nozzle tip of the screw extruder with a vent is connected to a flash evaporation tank in which the pressure is reduced to 0.001 MPa or less, and the solvent is removed by condensation of vaporized solvent vapor. The recycling method of the waste will be described.
[0049]
As shown in FIG. 4, by connecting to the flash evaporation tank 15 evacuated to 0.001 MPa or less at the nozzle tip of the vented screw extruder, the residual solvent is further removed from the residue obtained by vaporizing and removing the residual solvent by the vented screw extruder. Solvent can be vaporized. By condensing and collecting the vaporized solvent vapor, the solvent recovery rate is further improved.
[0050]
Subsequently, a solvent recovery section from the solvent from which the additive is extracted by evaporation of the solvent in the still and condensation of the evaporated components, which is suitable for the plastic recycling method for removing the additive of the present invention, and concentration of the still The solvent recovery section by condensation of the solvent vapor exhausted from the vent of the screw extruder with vent connected to the component discharge port, and the gear pump supply section of the concentrated component to the screw extruder with vent from the concentrated component discharge port of the still. A solvent recovery apparatus having the following will be described.
[0051]
As shown in FIG. 5, a solvent recovery unit for introducing a vapor of a solvent volatilized from a distiller 5 having a heating means 17 using a heating medium such as steam into a condenser 6 having a cooling means such as cold water and condensing the vapor. Is provided first. A decompression device 18 using a vacuum pump may be provided to decompress the entire system according to the boiling point of the solvent. At this time, the condenser 6 needs to be installed in the middle of the exhaust path.
[0052]
Concentrated components are deposited at the bottom of the evaporator, and a vented screw extruder 8 is connected to a concentrated component discharge port 7 for discharging the concentrated components, and the vent port 9 is depressurized by a decompression device 19 such as a vacuum pump. Secondly, there is provided a solvent recovery section for collecting the solvent vapor exhausted from the vent port 9 by a condenser 10 provided with a cooling means such as cold water in the middle of the exhaust path to the vacuum pump.
[0053]
In order to independently evaporate the solvent from the object, it is necessary to insulate the internal pressure between the two.However, between the outlet of the concentrated component of the still and the material inlet of the screw extruder with vent, the concentrated component is evaporated. This can be realized by providing the gear pump supply unit 20.
[0054]
Preferably, the still is a thin-film still. In the case of a thin-film evaporator, the solvent recovery operation can be performed continuously, so that the transfer of the concentrated components from the evaporator to the vented screw extruder can also be continuously processed. Can be realized stably. As shown in FIG. 6, such a thin film still has a rotary falling type thin film still 22 having a rotating blade 13 rotated by a prime mover 21 to forcibly form a thin film of a target liquid. A falling-film distillation unit 24 that causes the target liquid to flow down on the surface of the heat exchanger 23 through which a large number of heat mediums pass can be given.
[0055]
【The invention's effect】
As described above, according to the present invention, various kinds of containers, home appliances, OA equipment, by recovering the solvent with high efficiency from the solvent containing unnecessary various additive components extracted from the plastic member collected from It is possible to obtain a plastic recycling method that is economically rational as well as an environmental one, and a solvent recovery device used for the method.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the procedure of the plastic recycling method of the present invention. FIG. 2 is a configuration diagram of a solvent recovery section in the plastic recycling method of the present invention. FIG. 3 is a thin film distillation used in the plastic recycling method of the present invention. FIG. 4 is a configuration diagram of a solvent recovery unit in the plastic recycling method of the present invention. FIG. 5 is a configuration diagram of a solvent recovery device of the present invention. FIG. 6 is a rotary falling film in the solvent recovery device of the present invention. FIG. 7 is a view showing a distillation apparatus. FIG. 7 is a view showing a falling film type distillation apparatus in the solvent recovery apparatus of the present invention.
1 Extraction operation step of an additive from a plastic containing an additive by a solvent 2 Solvent recovery operation step of recovering a solvent from which an additive has been separated by distillation from a solvent from which the additive has been extracted 3 Evaporation of solvent and evaporation component in a still Recovery step 4 from the solvent from which the additive was extracted by condensation of the solvent. Solvent recovery step 5 by condensing the solvent vapor exhausted from the vent of the screw extruder with vent connected to the concentrated component discharge port of the still. 7 Condensed component discharge port 8 Vent screw extruder 9 Vent port 10 Another condenser 11 Gear pump 12 Thin film still 13 Rotating blade 14 Valve 15 Flash evaporation tank 16 Further condenser 17 Heating means 18, 19 Decompression device 20 Gear pump supply unit 21 Prime mover 22 Rotating falling film thin-film still 23 Heat exchanger 24 Falling film still 25 Heated steam Mouth 26 uncondensed vapor outlet 27 condensate outlet

Claims (13)

Recycling of plastics to remove additives, including the operation of extracting additives from plastics containing additives with solvents and the solvent recovery operation of recovering the solvents from which additives were separated by distillation from the solvents from which the additives were extracted In the method, the solvent recovery operation is performed by recovering the solvent from the solvent from which the additive is extracted by evaporating the solvent in the still and condensing the evaporated component, and venting the vented screw extruder connected to the concentrated component outlet of the still. A method for recycling a plastic for removing an additive, comprising recovering a solvent by condensing a solvent vapor exhausted from a solvent. The method for recycling a plastic for removing an additive according to claim 1, wherein the supply of the concentrated component from the concentrated component discharge port of the still to the vented screw extruder is performed by a gear pump. The method according to claim 1, wherein the vented screw extruder is a single-screw or twin-screw vented screw extruder. The method according to claim 1, wherein the distiller is a thin-film distiller. The method for recycling a plastic for removing an additive according to claim 1, wherein a thickener is added to the solvent from which the additive has been extracted in advance when the solvent is evaporated in the still. The thickener is a polymer compound having a glass transition temperature of 60 ° C. or more and 150 ° C. or less, a weight average molecular weight of 1,000 or more and 50,000 or less, and being soluble in the solvent. A plastic recycling method for removing an additive according to claim 5. Thickener, characterized in that the kinematic viscosity at 100 ° C. or less 10,000 mm ² / sec or more 1,000,000 mm ² / s, plastic to remove the additive according to claim 5 Recycling method. 2. The plastic according to claim 1, wherein the weight ratio of the extracted additive component having a melting point higher than the evaporation temperature in the still is adjusted to less than 50%. Recycling method. Recycling of plastics to remove additives, including the operation of extracting additives with additives from plastics containing additives, and the operation of recovering the solvents from which additives were separated by distillation from the solvents from which additives were extracted In the method, the evaporator is a thin-film evaporator, and when the solvent is evaporated in the evaporator, a powder that is insoluble in the solvent is added to the solvent from which the additive has been extracted in advance. Do plastic recycling method. The plastics for removing an additive according to claim 9, wherein the additive is a halogen-based flame retardant, and the powder insoluble in the solvent is calcium hydroxide or calcium carbonate. Method. The removal of the additive according to claim 1, wherein the tip of the nozzle of the vented screw extruder is connected to a flash evaporation tank in which the pressure is reduced to 0.001 MPa or less, and the method includes solvent recovery by condensation of vaporized solvent vapor. Do plastic recycling method. The solvent recovery section from the solvent from which the additive was extracted by evaporation of the solvent and the condensation of the evaporated components in the still, and the solvent vapor exhausted from the vent of the screw extruder with vent connected to the concentrated component outlet of the still. A solvent recovery device, comprising: a solvent recovery unit by condensation; and a gear pump supply unit for a concentrated component from a concentrated component discharge port of a still to a screw extruder with a vent. 13. The solvent recovery device according to claim 12, wherein the still is a thin film still.

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