JP5368815B2 - Method for recovering thermoplastic aromatic polyester resin from multilayer molded body - Google Patents

Description

  The present invention relates to a method for recovering a thermoplastic aromatic polyester resin from a multilayer molded article containing a thermoplastic aromatic polyester resin layer and a polyglycolic acid layer. More specifically, the present invention relates to a method for recovering a thermoplastic aromatic polyester resin that can recover a reusable high-purity thermoplastic aromatic polyester resin from the multilayer molded body by a dry process.

  Polyethylene terephthalate (hereinafter sometimes abbreviated as “PET”) can be molded into a bottle by, for example, blow molding. This bottle (hereinafter abbreviated as “PET bottle”) is widely used as a container for various liquid beverages. PET has insufficient gas barrier properties such as oxygen gas barrier properties and carbon dioxide gas barrier properties. Therefore, it is difficult to sufficiently satisfy the required performance for improving the long-term storage stability of the liquid beverage, and the PET bottle cannot be used satisfactorily as a container for beer or other carbonated beverages.

  The above problem is not limited to PET, but also applies to other thermoplastic aromatic polyester resins such as polyethylene naphthalate. Even when a container made of a thermoplastic aromatic polyester resin is used in a technical field other than a container for liquid beverages, an improvement in gas barrier properties is demanded in order to enhance the storage stability and alteration prevention of the contents. Thermoplastic aromatic polyester resins are used in a wide range of technical fields such as packaging materials as sheets and films, but are difficult to apply to applications that require gas barrier properties.

  As a method for improving the gas barrier property of a thermoplastic aromatic polyester resin molded article, a method of combining a gas barrier resin is known. However, general-purpose gas barrier resins such as polyvinyl alcohol, ethylene-vinyl alcohol copolymer, and polyvinylidene chloride have a low gas barrier property under high humidity environment or are heated under melt molding conditions of thermoplastic aromatic polyester resin. There was a problem that it was easy to deteriorate.

  On the other hand, polyglycolic acid is a biodegradable resin material excellent in gas barrier properties, and has been developed as a gas barrier resin in the field of packaging materials such as bottles and films. Specifically, a method of combining polyglycolic acid has been proposed in order to improve gas barrier properties of bottles and films made of thermoplastic aromatic polyester resins such as PET.

  For example, International Publication No. 03/037624 (Patent Document 1), Japanese Patent No. 3997102 (Patent Document 2), and International Publication No. 2006/107099 (Patent Document 3) have a polyglycolic acid layer as a core. A multilayer blow-molded container having a layer configuration in which a thermoplastic polyester resin layer is disposed as an inner layer and an outer layer is disclosed. Patent Documents 1 to 3 show thermoplastic aromatic polyester resins such as polyethylene terephthalate and polyethylene naphthalate as thermoplastic polyester resins.

  Japanese Patent Application Laid-Open No. 10-80990 (Patent Document 4) discloses a gas barrier composite film having a layer structure in which a thermoplastic resin film is laminated on one side or both sides of a polyglycolic acid film. Patent Document 4 exemplifies thermoplastic aromatic polyesters such as polyethylene terephthalate and polyethylene naphthalate as the thermoplastic resin forming the thermoplastic resin film.

  A multilayer molded body such as a multilayer container or multilayer film in which a thermoplastic aromatic polyester resin layer and a polyglycolic acid layer are combined is excellent in gas barrier properties, heat resistance, molding processability, transparency, durability, and the like. However, since the multilayer molded body has a polyglycolic acid layer in the thermoplastic aromatic polyester resin layer, it is difficult to recycle the thermoplastic aromatic polyester resin.

  In recent years, the need to recycle plastics has been widely recognized from the viewpoints of environmental conservation and resource saving, and efforts for recycling and legislation are being promoted in various fields. Since PET bottles are mass-produced and widely used as containers for various liquid beverages, recycling is a particularly important issue in forming a recycling-oriented economic society. In addition to recycling used PET bottles, the reuse of defective products in the production process of thermoplastic aromatic polyester resin products is also an important issue from the viewpoint of saving resources and reducing production costs.

  Recovering and reusing thermoplastic aromatic polyester resin from a multilayer molded article containing a thermoplastic aromatic polyester resin layer and a polyglycolic acid layer is not only a recycling viewpoint, but also development of applications of the multilayer molded article It is also an important issue in trying to achieve this. However, unlike a single-layer molded body such as a conventional PET bottle, a thermoplastic aromatic polyester resin layer is separated from a multilayer molded body in which a polyglycolic acid layer is composited, and can be reused. It has been a very difficult task to recover the thermoplastic aromatic polyester resin.

  Conventionally, several proposals have been made on a method for recycling a thermoplastic aromatic polyester resin from a multilayer molded article containing a thermoplastic aromatic polyester resin layer and a polyglycolic acid layer.

  For example, in WO 03/097468 (Patent Document 5), after crushing a bottle having a layer structure of PET / polyglycolic acid / PET, the crushed material is heated to a temperature of, for example, 80 ° C. A recycling method is disclosed in which the sample is immersed in an aqueous sodium solution for a long time, then filtered, washed with water, and dried.

  In WO 2005/049710 pamphlet (Patent Document 6), after crushing a bottle having a layer structure of PET / polyglycolic acid / PET, hold the crushed material in a high temperature and high humidity environment for a long time, or A method is disclosed in which the polyglycolic acid layer is soaked in hot water for a long period of time so that the water content of the polyglycolic acid layer is 0.5 mass% or more. After adjusting the water content of the polyglycolic acid layer, the crushed material is immersed in an aqueous sodium hydroxide solution heated to a temperature of, for example, 85 ° C., then filtered, washed with water, and dried.

  According to the methods disclosed in Patent Documents 5 and 6, a thermoplastic aromatic polyester resin not containing polyglycolic acid can be recovered. However, in these methods, it is necessary to hydrolyze the polyglycolic acid by immersing the crushed material of the multilayer molded body in a sodium hydroxide aqueous solution heated to a high temperature for a long time. Therefore, the recycling process itself is dangerous and complicated, the processing time is long, and a waste liquid processing process is also required. If the amount of water in the polyglycolic acid layer is increased by immersing the crushed material in high-temperature water, the immersion time in the aqueous sodium hydroxide solution can be shortened, but a long time is required for the immersion process in high-temperature water. And

  According to chemical recycling using depolymerization of a thermoplastic aromatic polyester resin, a PET bottle or the like can be returned to a raw material monomer. However, when the chemical recycling method is applied to a multilayer molded article containing a thermoplastic aromatic polyester resin layer and a polyglycolic acid layer, in addition to increasing the cost of the recycling process, it is necessary to separate impurities caused by the polyglycolic acid It becomes.

International Publication No. 03/037624 Pamphlet Japanese Patent No. 3997102 International Publication No. 2006/107099 Pamphlet Japanese Patent Laid-Open No. 10-80990 International Publication No. 03/097468 Pamphlet International Publication No. 2005/049710 Pamphlet

  An object of the present invention is to provide a heat which can recover a reusable high-purity thermoplastic aromatic polyester resin by a dry process from a multilayer molded article containing a thermoplastic aromatic polyester resin layer and a polyglycolic acid layer. The object is to provide a method for recovering a plastic aromatic polyester resin.

  The present inventors have disclosed a high-purity thermoplastic aromatic polyester that can be recycled from the multilayer molded article by a dry process based on mechanical grinding and selection, not a wet process using an aqueous sodium hydroxide solution. Intensive research was conducted on how to recover the resin. As a result, the present inventors processed the multilayer molded body with a specific type of pulverizer to obtain a pulverized material having a substantially uniform size, and then the pulverized material was selected for a specific type of dry specific gravity difference. As a result of sorting using a machine, the pulverized product was separated into layers during these treatment steps, and it was found that the polyglycolic acid component (crushed piece) and the thermoplastic aromatic polyester resin component (crushed piece) could be precisely sorted. .

  The thermoplastic aromatic polyester resin component recovered by the method of the present invention is a high-purity product having a low polyglycolic acid content, and can be used as it is or by diluting with a new thermoplastic aromatic polyester resin. It can be reused as a raw material resin. On the other hand, the polyglycolic acid component recovered by the method of the present invention can be reused as it is as a polyglycolic acid resin, or depolymerized and returned to the monomer glycolide. Since polyglycolic acid is decomposed in a natural environment, the recovered polyglycolic acid component can be biodegraded by being embedded in soil or treated with activated sludge. The present invention has been completed based on these findings.

According to the present invention, in a method for recovering a thermoplastic aromatic polyester resin from a multilayer molded article containing a thermoplastic aromatic polyester resin layer and a polyglycolic acid layer,
(1) A rotor having a plurality of rotating blades attached to the peripheral portion at regular intervals is housed in a housing to which a plurality of fixed blades are attached. It contains a thermoplastic aromatic polyester resin layer and a polyglycolic acid layer using a pulverizer configured to pulverize the solid material by cutting it between the tip and pass the pulverized material through a screen of a predetermined mesh. Step 1 of pulverizing the multilayer molded body to obtain a pulverized product;
(2) A dry specific gravity difference sorter comprising a slanted net-like deck and configured to vibrate the deck while blowing wind from the bottom of the deck to sort the solid material on the deck by the specific gravity difference. Supplying the mill with the pulverized product 2; and
(3) The mechanical external force including the shearing force at the time of cutting with the pulverizer and the vibration force on the deck of the dry specific gravity difference sorter on the deck when the dry specific gravity difference sorter is operated. The pulverized product is separated into a thermoplastic aromatic polyester resin component and a polyglycolic acid component, and a relatively high specific gravity polyglycolic acid component is recovered from the lower part of the deck, and relatively Recovering the low specific gravity thermoplastic aromatic polyester resin component from the upper part of the deck; 3;
A method for recovering a thermoplastic aromatic polyester resin from a multilayer molded article is provided.

  According to the present invention, high purity reusable from a multilayer molded article containing a thermoplastic aromatic polyester resin layer and a polyglycolic acid layer by a dry process combining mechanical grinding and dry layer separation. The thermoplastic aromatic polyester resin can be recovered.

  Since the recovered thermoplastic aromatic polyester resin has a high purity, it can be reused as a raw material resin for molding as it is or by diluting with a new thermoplastic aromatic polyester resin. On the other hand, the recovered polyglycolic acid component can be depolymerized and returned to the monomer glycolide, for example.

  Polyglycolic acid is one of the representative biodegradable plastics with a low environmental impact. A multilayer molded article that makes use of characteristics such as gas barrier properties of polyglycolic acid has a small environmental load. Moreover, according to the recovery method of the present invention, each resin component can be efficiently recovered from the multilayer molded body and reused. Therefore, the present invention contributes to the technical development of an environmentally friendly multilayer molded body provided with a circulation type system.

It is a fragmentary sectional view of an example of the grinder used by the present invention. It is explanatory drawing of an example of the dry-type specific gravity difference sorter used by this invention.

1. Thermoplastic aromatic polyester resin Examples of the thermoplastic aromatic polyester resin include amorphous polyethylene terephthalate copolymer containing polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and 1,4-cyclohexanedimethanol as copolymerization components. Examples thereof include a blend (PETG), polybutylene terephthalate (PBT), poly-1,4-cyclohexylenedimethylene terephthalate / isophthalate copolymer (PCTA), and a mixture of two or more thereof. Among these, PET and PEN are preferable and PET is more preferable from the viewpoints of availability and molding processability.

  PET is not only polyethylene terephthalate homopolymer, but also copolyester in which part of PET acid component is replaced with isophthalic acid or naphthalene dicarboxylic acid; copolyester in which part of PET glycol component is replaced with special diol such as diethylene glycol Etc. are also included. In these copolyesters (CO-PET), the copolymerization ratio of the third component such as isophthalic acid is not particularly limited, but is usually 2 to 8 mol%.

  PETG is an amorphous polyethylene terephthalate copolymer containing 1,4-cyclohexanedimethanol (CHDM) as a copolymerization component. More specifically, PETG is a copolyester obtained by replacing a part of ethylene glycol, which is a glycol component constituting PET, with 1,4-cyclohexanedimethanol. The proportion of 1,4-cyclohexanedimethanol in the glycol component is usually 30 to 35 mol%. As PETG, those manufactured and sold by Eastman Chemical Company, Sky Green Company, etc. are preferably used.

  PCTA is a thermoplastic saturated copolyester obtained by polycondensation of 1,4-cyclohexanedimethanol with terephthalic acid and isophthalic acid. As PCTA, the product name Kodar THERMEX 6761 (registered trademark) of Eastman Chemical Co., USA is preferably used.

2. Polyglycolic acid Polyglycolic acid is a homopolymer or copolymer containing a repeating unit represented by the formula — [— O—CH ₂ —CO —] —. The content of the repeating unit represented by the above formula in the polyglycolic acid is usually 60% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, and the upper limit is 100% by mass. When the content ratio of the repeating unit represented by the above formula is too low, gas barrier properties and heat resistance are lowered.

  Polyglycolic acid can be synthesized by dehydration polycondensation of glycolic acid, dealcoholization polycondensation of glycolic acid alkyl ester, ring-opening polymerization of glycolide, and the like. Among these, according to the ring-opening polymerization method of glycolide, polyglycolic acid (also referred to as “polyglycolide”) having a high molecular weight (high melt viscosity) can be easily produced. In the ring-opening polymerization method, glycolide is heated to a temperature of about 120 ° C. to about 250 ° C. in the presence of a small amount of a catalyst (for example, a cationic catalyst such as tin organic carboxylate, tin halide, antimony halide, etc.). And ring-opening polymerization. The ring-opening polymerization is preferably performed by bulk polymerization or solution polymerization.

  In order to synthesize a polyglycolic acid copolymer, as comonomer, for example, ethylene oxalate, lactide, lactones (for example, β-propiolactone, β-butyrolactone, pivalolactone, γ-butyrolactone, δ-valerolactone, β Cyclic monomers such as methyl-δ-valerolactone, ε-caprolactone, trimethylene carbonate, and 1,3-dioxane; lactic acid, 3-hydroxypropanoic acid, 3-hydroxybutanoic acid, 4-hydroxybutanoic acid, 6- Hydroxycarboxylic acids such as hydroxycaproic acid or alkyl esters thereof; substantially equivalents of aliphatic diols such as ethylene glycol and 1,4-butanediol and aliphatic dicarboxylic acids such as succinic acid and adipic acid or alkyl esters thereof A mixture of moles; or these Using the above species, it may be copolymerized. Among these comonomers, the cyclic monomer is preferable. These cyclic monomers can be subjected to ring-opening copolymerization under the glycolide ring-opening polymerization conditions.

  The comonomer is usually used in a proportion of 40% by mass or less, preferably 30% by mass or less, more preferably 20% by mass or less, based on the total amount of charged monomers. When the proportion of comonomer used increases, the crystallinity of the polymer produced is impaired. When polyglycolic acid loses its crystallinity, its heat resistance, gas barrier properties, mechanical strength and the like are lowered.

3. Multilayer molded body The multilayer molded body containing the thermoplastic aromatic polyester resin layer and the polyglycolic acid layer is not particularly limited. For example, a multilayer container (for example, a multilayer bottle), a multilayer film, a multilayer sheet, a multilayer pipe, etc. Can be mentioned. Although the collection | recovery method of this invention can be applied to the multilayer molded object already used as a liquid beverage container etc., it is not limited to it. The recovery method of the present invention can be used in the molding process such as defective products at the time of molding, defective products of a multilayer preform (multilayer parison) at the time of blow molding, and cut products at the end when manufacturing a multilayer film or a multilayer sheet. It can also be applied to non-defective products and various types of regrind. Therefore, the multilayer molded body includes defective products in the molding process. When the multilayer molded body is a multilayer container, the shape thereof may be not only a bottle but also any shape.

  As the layer structure of the multilayer molded body, the following layer structure can be exemplified when a thermoplastic aromatic polyester resin is represented by PET and polyglycolic acid is abbreviated as PGA.

(1) PET / PGA
(2) PET / PGA / PET
(3) PET / PGA / PET / PGA
(4) PET / PGA / PET / PGA / PET
(5) PET / PGA / PET / PGA / PET / PGA / PET

  In these multilayer molded articles, an adhesive layer can be interposed between the respective layers as desired. In the case of a multilayer container, from the viewpoint of heat resistance and molding processability, it is preferable that an adhesive layer is not interposed between the thermoplastic aromatic polyester resin layer and the polyglycolic acid layer. The multilayer molded body may contain other resin layers, but in the case where it is difficult to remove or sort out other resin layers, in order to efficiently recover the thermoplastic aromatic polyester resin, It is preferable that other resin layers are not included.

  The multilayer molded body is preferably a multilayer blow molded container or a preform thereof containing at least one polyglycolic acid layer as an intermediate layer in a polyethylene terephthalate layer. The multilayer blow molded container or the preform thereof preferably has a layer structure of “PET / PGA / PET” and “PET / PGA / PET / PGA / PET”, but is not limited thereto.

  The multilayer bottle can be produced by, for example, a direct blow molding method of a coextruded multilayer preform (multilayer parison); a stretch blow molding method of a co-injected multilayer preform. The multilayer sheet and the multilayer film can be produced by a coextrusion method, a dry lamination method, an extrusion lamination method, or the like. In order to produce a stretched multilayer film, the stretched multilayer film can be produced by a stretching method of the multilayer film, a lamination method of the stretched films, or the like. The multilayer sheet and the multilayer film can also be produced by an inflation method. The multilayer pipe can be manufactured by a coextrusion method.

  The multilayer molded article applied to the recovery method of the present invention is typically a multilayer blow molded container or a preform thereof containing at least one polyglycolic acid layer as an intermediate layer in a polyethylene terephthalate layer.

  The mass ratio of the thermoplastic aromatic polyester resin and the polyglycolic acid in the multilayer molded body is usually in the range of 99.5: 0.5 to 55:45. This mass ratio can be appropriately determined depending on the shape of the multilayer molded body and the purpose of use. In the multilayer molded body intended to improve the gas barrier properties by the polyglycolic acid layer, this mass ratio is preferably 99: 1 to 80:20, from the viewpoint of balancing gas barrier properties, mechanical strength, heat resistance, and the like. Preferably it exists in the range of 98.5: 1.5-90: 10. However, the recovery method of the present invention can also be applied to a multilayer molded body outside the range of these mass ratios.

  When the multilayer molded body is a multilayer sheet, a multilayer film, or a multilayer pipe, the thickness of the thermoplastic aromatic polyester resin layer (plurality of the thermoplastic aromatic polyester resin layer and the polyglycolic acid is within a desired mass ratio range). The ratio of the total thickness in the case of layers) and the thickness of the polyglycolic acid layer (total thickness in the case of multiple layers) can be arbitrarily set, but the polyglycolic acid layer is thinner than the thermoplastic aromatic polyester resin layer It is preferable. The thickness ratio (A / B) between the thermoplastic aromatic polyester resin layer (A) and the polyglycolic acid resin layer (B) in the multilayer molded body is preferably 2 or more, more preferably 4 or more. If the polyglycolic acid component layer is thicker than the thermoplastic aromatic polyester resin component layer, layer separation tends to be insufficient.

  When the multilayer molded body is a multilayer container such as a multilayer blow molded bottle, the total thickness of the container body (side wall) is usually in the range of 100 μm to 5 mm, preferably 150 μm to 3 mm, more preferably 300 μm to 2 mm. The thickness (total thickness in the case of a plurality of layers) of the thermoplastic aromatic polyester resin layer in the barrel portion of the multilayer container is usually in the range of 50 μm to 4.5 mm, preferably 100 μm to 2.5 mm, more preferably 150 μm to 1 mm. Is within. The thickness of the polyglycolic acid layer in the trunk of the multilayer container (total thickness in the case of multiple layers) is usually in the range of 1 to 200 μm, preferably 3 to 100 μm.

  In a multilayer container such as a multilayer bottle, the opening end (neck portion) is preferably a single layer of a thermoplastic aromatic polyester resin. Since the bottom of the multilayer container is generally thick, it can be a thermoplastic aromatic polyester resin single layer, but a core layer made of a polyglycolic acid layer may be disposed.

  When the multilayer molded body is a preform (parison) before blow molding, the total layer thickness and each layer thickness are larger than those in the multilayer container.

  The thermoplastic aromatic polyester resin layer and the polyglycolic acid layer may each contain various additive components. Examples of the additive component include a colorant, a heat stabilizer, a light stabilizer, a moisture proofing agent, a waterproofing agent, and a lubricant.

4). Collection method In the collection method of the present invention, as step 1, a rotor having a plurality of rotary blades attached to the peripheral portion is housed in a housing having a plurality of fixed blades attached thereto, and is rotated by the rotation of the rotor. A thermoplastic aromatic polyester using a pulverizer configured to pulverize a solid material by cutting between the tip of each rotary blade and the tip of a fixed blade and pass the pulverized product through a screen of a predetermined mesh. A step of pulverizing the multilayer molded body containing the resin layer and the polyglycolic acid layer to obtain a pulverized product is included.

  FIG. 1 is a cross-sectional view showing a main part of an example of a pulverizer used in the present invention. A plurality of rotary blades 12 are attached to the peripheral portion of the rotor 11. The number of rotary blades is usually 3 or 5 or 7, but is not limited thereto. A rotor 11 is accommodated in a housing 16 (referred to as “cutter house”) composed of partition walls 14 and 15. In the housing 16, a fixed blade 13 is attached to the partition walls 14 and 15 directly or via a fixing member. The number of fixed blades is usually in the range of 2 to 4, but is not limited thereto. The crusher may be one in which a plurality of combinations of a rotor having a plurality of rotating blades and a plurality of fixed blades are arranged in parallel.

  A multilayer molded body such as a multilayer bottle is supplied to a pulverizer, and pulverized by cutting between the tip of each rotary blade rotating by the rotation of the rotor and the tip of the fixed blade. A pulverized product having a certain shape can be obtained by cutting the multilayer molded body using the pulverizer having such a structure. The pulverized product can be obtained as a pulverized product having a uniform size by passing it through a screen of a predetermined mesh arranged on the side from below or below the rotor.

  The pulverized material cut between the tip of each rotary blade and the tip of the fixed blade rotated by the rotation of the rotor and passed through a screen of a predetermined mesh has a shape similar to pellets or flakes. The pulverized product has a substantially uniform size mainly defined by the screen mesh.

  That is, the pulverized product obtained in the step 1 of the present invention was cut between the tip of each rotary blade and the tip of the fixed blade rotated by the rotation of a rotor having a plurality of rotary blades attached to the peripheral edge at regular intervals. Therefore, it is not a powder but has a shape similar to a pellet or flake having a certain size. Since the pulverized material after cutting passes through a screen of a predetermined mesh, it has a substantially uniform size corresponding to the size of the mesh. When the pulverizer is used, a pulverized product having a uniform size can be obtained in which the generation of dust powder is minimized.

  In step 1, the multilayer molded body is made into a pellet-like or flake-like pulverized product having a substantially uniform size, and the pulverized product is then subjected to a dry specific gravity difference sorter to produce a thermoplastic aromatic polyester resin component and a polyglycol. It can be sorted into acid components.

  Although the thermoplastic aromatic polyester resin layer and the polyglycolic acid layer in the pulverized product are separated by pulverization by cutting in step 1 and passing through the screen, this separation is not yet complete. It is obtained as having a certain uniform size. After that, supply of the pulverized product to the dry specific gravity difference sorter, vibration on the deck, mechanical external force such as wind power on the deck, the layer separation of the pulverized product becomes almost complete, and each component is sorted. It becomes possible.

  Examples of the pulverizer having the above-described configuration include medium-sized pulverizers Rapid 300, 400, and 500 series manufactured by Kawata Corporation. The Rapid 300 series medium pulverizer has a rotor diameter of 260 mm. The Rapid 400 series medium pulverizer has a rotor diameter of 350 mm. The medium size grinder of the Rapid 500 series has a rotor diameter of 450 mm. Three or five rotary blades are attached to each rotor at equal intervals. The number of fixed blades is in the range of 2-4.

  The mesh of the screen is preferably in the range of 4 to 20 mmφ, more preferably 4 to 12 mmφ. If the screen mesh is too small, when the pulverized product is separated, it becomes difficult to sort each component by layer separation using a dry specific gravity difference sorter. If the screen mesh is too large, the pulverized product becomes large, resulting in incomplete separation of the pulverized product and difficulty in sorting by layer separation.

  In particular, in the case of a multilayer blow molded container, the opening (neck) has a single layer structure of a thermoplastic aromatic polyester resin layer. In many cases, the bottom also has a single layer structure of a thermoplastic aromatic polyester resin layer. Since the single-layer structure portion is in contact with the polyglycolic acid layer, when it is cut into large pieces and passed through a large mesh screen, a pulverized product including this contact portion is obtained. Fragments in which the monolayer structure portion is in contact with the polyglycolic acid layer cannot be separated. Therefore, it is preferable to make the screen mesh within the above range and to perform pulverization by cutting under conditions that allow the screen to pass through the screen having the mesh, in order to recover the high-purity thermoplastic aromatic polyester resin component.

  In step 2 of the recovery method of the present invention, an inclined net-like deck is provided, and the deck is vibrated while blowing air from under the deck, so that the solid material on the deck is sorted based on the difference in specific gravity. The pulverized product is supplied to a dry specific gravity difference sorter configured as described above.

  The dry specific gravity difference sorter used in the present invention includes an inclined net-like deck, and is configured to vibrate the deck while blowing up wind from the bottom of the deck. By supplying solid material consisting of a mixture with different specific gravity onto the deck of the dry specific gravity difference sorter and tilting and vibrating the deck, the heavy specific gravity material moves upward while vibrating on the deck. The specific gravity moves to the lower part of the deck because the wind force reduces the friction with the deck. This dry specific gravity difference sorter is a kind of specific gravity difference sorter using wind power.

  FIG. 2 shows a schematic cross-sectional view of an example of the dry specific gravity difference sorter used in the present invention. The dry specific gravity difference sorter includes a net-like deck 21 (sometimes referred to as “deck net”). As shown in FIG. 2, the deck 21 is inclined. The pulverized material 26 is supplied onto the deck 21 in the sorting tank 22 from the inlet 25 provided at the upper part of the deck 21. In order to convey the pulverized product to the charging port 25, an inclined screw conveyor (not shown) is usually used.

  The angle of the deck 21 can usually be adjusted within a range of 9.0 to 13.0 degrees. In the present invention, the angle of the deck 21 can be arbitrarily set, but it is preferable to adjust within the range of 10.0 to 12.0 degrees from the viewpoint of the selection efficiency of each component due to the difference in specific gravity.

  Examples of the model of the deck include a mesh type, a saw blade type (for example, a saw blade type having a hole of 1 mmφ or 3 mmφ), a looper type (a net having a large number of vertical holes), and the like. In order to efficiently separate the components separated into layers, it is preferable to use a looper type deck (for example, a net provided with a number of vertical holes of 12 × 2 mm).

  The deck 21 is configured to vibrate by an electrical vibration device (not shown). Control of vibration is performed by adjusting the frequency (frequency) to the inverter, usually within a range of 0 to 80 Hz. In the present invention, it is preferable to operate within a range of 30 to 70 Hz.

  A blower 31 is disposed under the deck 21, and a wind 32 is sent from the blower 31 so as to hit the entire back surface of the deck 21. Wind power is adjusted by varying the frequency of the inverter to a fan (not shown), typically in the range of 0-60 Hz. In the present invention, the frequency is preferably in the range of 20 to 50 Hz.

  The finely pulverized pulverized material passing through the mesh of the deck 21 is discharged as powder 30 from the dust collection outlet 29. The fine powder floating on the deck 21 by the wind force is discharged as dust 24 from the dust collection port 23. The discharged powder and dust are collected in a dust collector (not shown).

  By tilting and vibrating the deck 21, the high specific gravity material in the mixture moves upward while vibrating on the deck 21, and is discharged from the high specific gravity material discharge port 27 as a high specific gravity material 28. On the other hand, the low specific gravity in the mixture moves to the lower part of the deck 21 because the wind force reduces friction with the deck 21 and is discharged from the low specific gravity discharge port 34 as the low specific gravity 33.

  A shielding plate (weir) is provided on the upper surface in the vicinity of the lower portion of the deck 21 to control the discharge amount of the low specific gravity (not shown). As this type of dry specific gravity difference sorter, for example, Kawata Corporation wind sorter SH-2DK can be mentioned.

  In step 3 of the recovery method of the present invention, the dry specific gravity difference sorter is operated, and the shear force at the time of cutting with the crusher and the vibration force on the deck of the dry specific gravity difference sorter are operated on the deck. The pulverized product is separated into a thermoplastic aromatic polyester resin component and a polyglycolic acid component by a mechanical external force including the above, and a relatively high specific gravity polyglycolic acid component is recovered from the lower part of the deck. And a relatively low specific gravity thermoplastic aromatic polyester resin component is recovered from the upper part of the deck.

  The pulverized product of the multilayer molded body is separated into a thermoplastic aromatic polyester resin layer and a polyglycolic acid layer by receiving mechanical external force such as shearing force at the time of cutting with a pulverizer and sieving with a screen. However, the pulverized product that has passed through the screen retains the shape of the pulverized product having a substantially uniform size. When this pulverized product is supplied onto a dry specific gravity difference sorter deck and subjected to vibration and wind, the layers are separated almost completely on the deck, and the separated thermoplastic aromatic polyester resin component and polyglycolic acid component are separated. Are sorted out.

For example, in the case of a homopolymer, the specific gravity of the polyglycolic acid resin is about 1.60 g / cm ³ . On the other hand, the specific gravity of polyethylene terephthalate is 1.38 to 1.39 g / cm ³ . Thus, there is a specific gravity difference between the polyglycolic acid and the thermoplastic aromatic polyester resin. However, since the specific gravity difference is not so large, it is necessary to devise in order to perform the selection using the dry specific gravity difference sorter. If the pulverized product has the same shape, the high specific gravity resin is usually recovered from above the deck. According to the method of the present invention, a relatively high specific gravity polyglycolic acid component is recovered from the lower portion of the deck, and a relatively low specific gravity thermoplastic aromatic polyester resin component is recovered from the upper portion of the deck. To do.

  Since the multilayer molded body is formed by integrally forming the layers, it is necessary to first separate the layers in order to perform selection. The inventors of the present invention pulverize a multilayer molded body using the above-mentioned type of pulverizer, thereby receiving a mechanical external force such as shearing force during cutting with a pulverizer and sieving with a screen. It has been found that a thermoplastic aromatic polyester resin layer and a polyglycolic acid layer are separated.

  When the multilayer molded body is pulverized into fine powder, it is difficult or inefficient to sort by a dry specific gravity difference sorter using wind power. On the other hand, if the size of the pulverized product is not substantially uniform even when the multilayer molded body is pulverized, the components of large fragments are high regardless of the specific gravity, even when trying to sort using a dry specific gravity difference sorter. It will be mixed in specific gravity.

  Therefore, in the present invention, the multilayer molded body is pulverized into a substantially uniform pulverized product using the pulverizer having the specific configuration. If observed finely, the size of each component (each component separated in layers) in the pulverized product is not necessarily uniform, but this may have a serious adverse effect on the selection by the dry specific gravity separator. Absent.

  Even if the pulverized material is separated during pulverization by the pulverizer, it is not sufficient for selecting each component. Therefore, in the present invention, using a specific dry specific gravity difference sorter, the layers are separated to an almost completely separable state by vibration on the deck and wind force to precisely sort each component.

  According to the recovery method of the present invention, 90% by mass or more, preferably 93% by mass or more, more preferably 95% by mass or more of the polyglycolic acid contained in the multilayer molded product is used as a standard by differential gravity sorting. The removed thermoplastic aromatic polyester resin component can be recovered. The upper limit of this removal rate is usually 99% by mass, and in many cases 98% by mass.

  According to the recovery method of the present invention, when the amount of polyglycolic acid contained in the thermoplastic aromatic polyester resin component is determined as the amount of glycolic acid, the amount of residual glycolic acid is usually 5,000 ppm or less, preferably 4,000 ppm or less. More preferably, a high-purity thermoplastic aromatic polyester resin component of 3,000 ppm or less can be recovered. The lower limit of the amount of residual glycolic acid is usually 300 ppm, and in many cases 500 ppm. Even when the content of polyglycolic acid in the multilayer molded body is large, according to the recovery method of the present invention, high purity thermoplastic resin with a small amount of polyglycolic acid contained in the thermoplastic aromatic polyester resin component The aromatic polyester resin component can be recovered. The amount of polyglycolic acid can be quantified by a method in which polyglycolic acid is hydrolyzed and converted to glycolic acid, and glycolic acid is measured by high performance liquid chromatography.

  Such a highly pure thermoplastic aromatic polyester resin can be reused as it is, but if diluted with a new thermoplastic aromatic polyester resin, the content of polyglycolic acid can be further reduced. This diluted product can be used as a resin material for molding.

  The thermoplastic aromatic polyester resin component recovered by the recovery method of the present invention may be further purified as necessary. In that case, a washing method using an aqueous alkali solution or an aqueous acid solution (for example, Patent Document 5). And the method described in 6) can be applied. Even when such a wet process is used in combination, since the content of polyglycolic acid to be removed from the thermoplastic aromatic polyester resin component is very small, the washing conditions can be greatly relaxed.

  On the other hand, the polyglycolic acid component can be converted to glycolide by depolymerization. The polyglycolic acid component can also be biodegraded by treatment with activated sludge.

  Hereinafter, the present invention will be described more specifically with reference to examples. The measuring method is as follows.

(1) Quantification method of residual polyglycolic acid The amount of residual polyglycolic acid contained in the polyethylene terephthalate component (crushed piece) recovered by a dry specific gravity difference sorter was quantified as the amount of glycolic acid by the following procedure. The amount of residual polyglycolic acid was determined as the average of three measurements for the same sample (n = 3).

a) A flat bottom flask containing a magnetic stirrer was charged with 20 g of a polyethylene terephthalate crushed piece and 100 ml of an aqueous NaOH solution having a concentration of 15% by mass and stoppered with a three-way cock. One of the three-way cocks was connected to a nitrogen balloon (a rubber balloon filled with nitrogen gas), and the other was connected to a vacuum pump.

b) While stirring the contents of the flat bottom flask, deaeration was performed with a vacuum pump, and substitution with nitrogen gas from a nitrogen balloon was performed three times in total every 10 minutes.
c) The contents were allowed to stand at room temperature for 12 hours without stirring under nitrogen gas replacement.
d) The contents were then heated to 90 ° C. and stirred for 4 hours.
e) After cooling the contents to room temperature, the three-way cock was removed.

f) While cooling the contents with ice, 46 g of HCl having a concentration of 35% by mass was added to stop the reaction.
g) The contents were filtered to remove the precipitate.
h) Water was added to the filtrate to dilute it 100 times (volume).
i) The diluted solution was subjected to quantitative determination of glycolic acid using high performance liquid chromatography (HPLC).

<HPLC conditions>
Apparatus: SYSTEM CONTROLLER SCL-10A VP
LIQUID CHROMATOGRAPH LC-20A
COLOMN OPEN CTO-20A
UV / VIS DETECTOR SPD-20A; λ = 210 nm
(All of these are manufactured by SHIMADZU)
Column: Inert sil ODS-3V 250 × 4.6 mm × two in series Column temperature: 40 ° C.
Mobile phase: 0.1 M ammonium dihydrogen phosphate + phosphoric acid flow rate: 0.7 ml / min
Injection volume: 20 μl
Detection limit: 0.1 ppm

[Example 1]
1. Production of Multilayer Preform As polyglycolic acid (PGA), a homopolymer (melting point = 221 ° C.) having a melt viscosity of 500 Pa · s measured at a temperature of 270 ° C. and a shear rate of 122 sec ⁻¹ was used. Polyethylene terephthalate (PET; IV value = 0.8 dl / g, melting point = 252 ° C.) was used as the thermoplastic aromatic polyester resin.

  After pre-drying these resins and sufficiently removing moisture, using a two-kind / three-layer co-injection molding machine, the injection cylinder tip temperature at the inner and outer layers side is 280 ° C., the intermediate layer injection cylinder tip temperature 255 ° C, hot runner block portion temperature to join is set to PET 280-290 ° C and PGA255 ° C, and by the sequential molding method, the open end has a PET single-layer structure, and at the trunk and bottom, the intermediate layer PGA A multi-layered bottomed preform was made with the layer embedded in the PET layer. The layer structure was a three-layer structure of PET / PGA / PET. The weight of the multilayer preform was about 25 g, and the content of polyglycolic acid was 4% by mass.

  This multilayer preform can be formed into a multilayer stretch blow molding container by, for example, cold blown method at a resin temperature of 100 ° C. and blowing compressed air in a stretch blow molding mold cavity and performing stretch blow molding. Is. In Example 1, a recovery experiment was conducted using the multilayer preform as a multilayer molded body.

2. Grinding process 1
As a pulverizer, Kawata Co., Ltd. medium size pulverizer Rapid 300-45 (cutter house = 450 × 260 mm, rotor diameter = 260 mm, motor capacity = 7.5 kW, rotary blade = 3, fixed blade = 4) was used. . A screen of mesh = 8 mmφ was used as the screen.

  The multilayer preform is supplied to the pulverizer, and the multilayer preform is pulverized by cutting between the tip of each rotary blade and the tip of the fixed blade rotated by the rotation of the rotor, and passed through the screen. Thus, a pulverized product having a uniform size was obtained. When a part of the pulverized product was taken out and observed, it was found that the PET layer (1.7 mm) and the PGA layer (0.15 mm) were separated.

3. Supply process to dry specific gravity difference sorter As a dry specific gravity difference sorter, Kawata Co., Ltd. wind sorter SH-2DK having the structure shown in FIG. 2 was used. As the net-like deck, a looper type deck (a net provided with many 12 × 2 mm vertical holes) was used. The deck angle was adjusted to 11.2 degrees. A shielding plate (weir) whose height is adjusted to 85 mm is provided on the upper surface near the lower portion of the deck. While the dry specific gravity difference sorter was in operation, the pulverized material obtained in Step 1 was fed to the middle of the deck.

4). Specific gravity difference selection process 3
The vibration of the deck was adjusted by setting the frequency (frequency) to the inverter to 55 Hz. The wind power from the blower was adjusted by setting the frequency of the inverter to the fan to 31 Hz.

  By inclining and vibrating the deck, the layer separation of the PET component (crushed piece) and the PGA component (crushed piece) is completed, and the PGA component with high specific gravity is discharged from the lower part of the deck, and from the upper part of the deck The low specific gravity PET component was discharged. The fine powder was discharged through a deck net. In this way, the PET component (pulverized pieces) was collected by a dry specific gravity difference sorter.

5. Analysis Result When the collected PET component (crushed piece) was quantitatively analyzed, the content of glycolic acid (hydrolyzate of polyglycolic acid) was 2,636 ppm. As a result of calculating the amount of polyglycolic acid contained in the collected PET component based on this measured value, it was found that 95% by mass of the total amount of polyglycolic acid contained in the multilayer preform was removed. This PET component (pulverized piece) has high purity, and can be sufficiently used as a resin material for molding, for example, by diluting with new PET.

[Example 2]
A multilayer preform was produced in the same manner as in Example 1 except that the polyglycolic acid content of the multilayer preform was 2% by mass [PET layer (1.7 mm) and PGA layer (0.08 mm)]. Using this, a recovery experiment was conducted. When the collected PET component (crushed piece) was quantitatively analyzed, the content of glycolic acid (polyglycolic acid hydrolyzate) was 994 ppm. As a result of calculating the amount of polyglycolic acid contained in the collected PET component based on this measured value, it was found that 96% by mass of the total amount of polyglycolic acid contained in the multilayer preform was removed. This PET component (pulverized piece) has high purity, and can be sufficiently used as a resin material for molding, for example, by diluting with new PET.

  The thermoplastic aromatic polyester resin obtained by the recovery method of the present invention can be reused as a raw material resin for molding. The polyglycolic acid obtained by the recovery method of the present invention can be reused or used as a raw material for producing glycolide.

DESCRIPTION OF SYMBOLS 11 Rotor 12 Rotating blade 13 Fixed blade 14 Bulkhead 15 Bulkhead 16 Housing 21 Reticulated deck 22 Sorting tank 23 Dust collection port 24 Dust 25 Input port 26 Pulverized material 27 High specific gravity material discharge port 28 High specific gravity material 29 Dust collection discharge port 30 Powder 31 Blower 32 Wind 33 Low specific gravity 34 Low specific gravity discharge port

Claims (3)

In a method for recovering a thermoplastic aromatic polyester resin from a multilayer molded article containing a thermoplastic aromatic polyester resin layer and a polyglycolic acid layer,
(1) A rotor having a plurality of rotating blades attached to the peripheral portion at regular intervals is housed in a housing to which a plurality of fixed blades are attached. It contains a thermoplastic aromatic polyester resin layer and a polyglycolic acid layer using a pulverizer configured to pulverize the solid material by cutting it between the tip and pass the pulverized material through a screen of a predetermined mesh. Step 1 of pulverizing the multilayer molded body to obtain a pulverized product;
(2) A dry specific gravity difference sorter comprising a slanted net-like deck and configured to vibrate the deck while blowing wind from the bottom of the deck to sort the solid material on the deck by the specific gravity difference. Supplying the mill with the pulverized product 2; and
(3) The mechanical external force including the shearing force at the time of cutting with the pulverizer and the vibration force on the deck of the dry specific gravity difference sorter on the deck when the dry specific gravity difference sorter is operated. The pulverized product is separated into a thermoplastic aromatic polyester resin component and a polyglycolic acid component, and a relatively high specific gravity polyglycolic acid component is recovered from the lower part of the deck, and relatively Recovering the low specific gravity thermoplastic aromatic polyester resin component from the upper part of the deck; 3;
A method for recovering a thermoplastic aromatic polyester resin from a multilayer molded article.   The recovery method according to claim 1, wherein the multilayer molded article is a multilayer blow molded container or a preform thereof containing at least one polyglycolic acid layer as an intermediate layer in a polyethylene terephthalate layer.   The recovery method according to claim 1, wherein the multilayer molded body has a polyglycolic acid layer having a thickness smaller than that of the thermoplastic aromatic polyester resin layer.

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