Method of recycling polyurethane foam

Abstract

To provide an efficient method of recycling a polyurethane foam.SOLUTION: The method of recycling a polyurethane foam comprises a crushing step in which a polyurethane foam is passed between a pair of rolls and crushed by compression between the rolls, and a hydrolysis step in which a product processed after the crushing step is hydrolysed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a method for recycling polyurethane foam. [Background technology]

[0002] Patent Document 1 discloses a method for decomposing a urea compound. In this method, the urea compound is hydrolyzed in carbon dioxide in a supercritical or subcritical state using water in a liquid or gaseous state to recover the corresponding amine. Patent Document 1 discloses that in this method, the mass ratio of the urea compound to water during hydrolysis is water / urea compound=20 / 1 to 160 / 1, and that if the amount of water is too small, the diffusion of water into the urea compound is insufficient.

[0003] Patent Document 2 discloses a method for pulverizing a thermosetting resin. This method for pulverizing a thermosetting resin includes a compression pulverization step of pulverizing the thermosetting resin by compression pulverization. This compression pulverization step is a roll compression pulverization step in which the thermosetting resin is introduced between a pair of rolls rotating while being biased in a direction toward each other, and compressed and pulverized. In the roll compression pulverization step, water may be added between the pair of rolls when the thermosetting resin is introduced, and adding water at the time of introduction reduces the average particle size of the obtained urethane fine powder.

[0004] Non-Patent Document 1 discloses an environmentally friendly decomposition method for polyurethane. Non-Patent Document 1 discloses that polyurethane is mainly used as a foam, which is a type of foam, and that polyurethane foam has a significantly lower density than other polymer materials. Non-Patent Document 1 also discloses that the hydrolysis reaction of polyurethane using CO2 (carbon dioxide) and water has an extremely low environmental impact. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2009 / 130842 [Patent Document 2] JP 2002-326224 A [Non-patent literature]

[0006] [Non-Patent Document 1] Development of an environmentally friendly decomposition method for polyurethane, Journal of the Adhesion Society of Japan, Vol. 54, No. 9, 2018, p. 343-348, Taku Motokumachi, [Retrieved May 31, 2023], Internet<https: / / www.jstage.jst.go.jp / article / adhesion / 54 / 9 / 54_9-4 / _pdf / -char / ja> Summary of the Invention [Problem to be solved by the invention]

[0007] Polyurethane is a compound of polyol and amine. Polyurethane can be recycled as a raw material for synthesizing polyurethane by hydrolyzing it into polyol and amine. However, polyurethane foam is bulky, and there is a problem that it is difficult to handle and inefficient to hydrolyze it. For example, polyurethane foam is bulky and has a low bulk density, and it is difficult to increase the density and put it into a decomposition treatment tank where hydrolysis is performed, and the efficiency of the hydrolysis treatment is low. Specifically, the decomposition treatment tank becomes large, and the amount of water used and the amount of energy used during hydrolysis increase. In addition, the concentration of polyol and amine in the treated product after hydrolysis is low, and the recovery of them becomes inefficient. Therefore, an efficient polyurethane foam recycling method is desired.

[0008] The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide an efficient method for recycling polyurethane foam. [Means for solving the problem]

[0009] In order to achieve the above object, the method for recycling polyurethane foam according to the present disclosure includes the steps of: A crushing step of passing the polyurethane foam between a pair of rolls and compressing and crushing the polyurethane foam between the pair of rolls; and a hydrolysis step of hydrolyzing the treated product after the pulverization step. Effect of the Invention

[0010] According to the present disclosure, an efficient method for recycling polyurethane foam can be provided. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a flow diagram of a polyurethane foam recycling method according to an embodiment of the present invention. [Diagram 2] FIG. 1 is an explanatory diagram of an overview of a polyurethane foam recycling method according to an embodiment of the present invention. [Diagram 3] FIG. 2 is a schematic side view of a roll portion of a roll press. [Figure 4] FIG. 2 is a front view illustrating a roll portion of a roll press. [Diagram 5] FIG. 1 is a flow diagram of a grinding process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The polyurethane foam recycling method according to the embodiment of the present disclosure will be described with reference to the drawings. First, an overview of the polyurethane foam recycling method according to the embodiment will be described.

[0013] The polyurethane foam recycling method according to this embodiment (hereinafter sometimes referred to as this recycling method) includes a crushing step in which polyurethane foam as a treated material is passed between a pair of rolls and compressed and crushed between the pair of rolls, and a hydrolysis step in which the treated material after the crushing step is hydrolyzed.

[0014] According to the present recycling method, the recycling of polyurethane foam can be made more efficient.

[0015] Specifically, bulky polyurethane foam can be made to have a high bulk density by compression pulverization between rolls, which allows it to be charged at a high density into a decomposition tank where polyurethane is hydrolyzed into polyol and amine. By allowing the polyurethane foam to be charged at a high density into the decomposition tank, the efficiency of the hydrolysis in the decomposition tank can be increased, thereby making the recycling of the polyurethane foam more efficient. The polyurethane foam recycling method according to this embodiment will be described in detail below.

[0016] As described above, the method for recycling polyurethane foam according to this embodiment (the present recycling method) includes a crushing step in which polyurethane foam as a treated material is compressed and crushed between a pair of rolls, and a hydrolysis step in which the treated material after the crushing step is hydrolyzed. In addition to the crushing step and the hydrolysis step, the present recycling method may further include a separation and cutting step in which a treatment target material (e.g., waste material) containing polyurethane foam is cut or sorted to separate the polyurethane foam to be subjected to the crushing step, a water addition step in which water is added to the treated material from the crushing step, and a separation and recovery step in which the polyol and amine obtained by hydrolysis are separated and recovered.

[0017] In this recycling method, as an example, a separation and cutting step (step S1), a crushing step (step S2), a water kneading step (step S3, an example of a water adding step), a hydrolysis step (step S4), and a separation and recovery step (step S5) are carried out in this order as shown in the flow diagram in Figure 1. In Figure 1, PFU stands for polyurethane foam.

[0018] As an example, this recycling method is realized by a plant 100 shown in Fig. 2. The plant 100 may include a separating and cutting device 1 that performs a separating and cutting process, a roll press device 2 that performs a pulverizing process, an agitator 3 that performs a water kneading process, a decomposition treatment tank 4 that performs a hydrolysis process, and a separation tank 5 that performs a separation and recovery process.

[0019] The separating and cutting process is a process in which an object to be treated containing polyurethane foam, such as a seat of a scrapped vehicle, is broken or cut by the separating and cutting device 1, and the polyurethane foam to be recycled by this recycling method is sorted and separated from other foreign matter to extract the polyurethane foam. The extracted polyurethane foam is preferably cut into a shape and size that can be processed in the crushing process. The separating and cutting device 1 may be, for example, a cutting device, a breaking device, a sorting device, a separating device, etc. for waste treatment, either alone or in combination.

[0020] The object to be treated containing polyurethane foam may be a seat of a scrapped vehicle, a bed, a sofa, a heat insulating material, etc. The object to be treated may be of any type as long as it contains polyurethane foam and can be separated.

[0021] In the separating and cutting step, the polyurethane foam may be separated into block-shaped foam pieces having a thickness of, for example, about 10 cm, a width of 20 cm, and a length of 30 cm. The foam pieces separated in the separating and cutting step are subjected to the pulverizing step described below. The foam pieces may be of any size as long as they do not cause problems in handling in the pulverizing step.

[0022] In the crushing step, the foam pieces described above are compressed and crushed as the processed material in the roll press device 2. The compression and crushing of the foam pieces in the roll press device 2 may be performed once or repeatedly two or more times. Hereinafter, the process of providing the foam pieces or treated pieces obtained by compressing and crushing the foam pieces in the roll press device 2 as the processed material to the roll press device 2 and crushing them may be referred to as a pass. For example, "two passes" or "two passes" means that the compression and crushing of the foam pieces or treated pieces in the roll press device 2 is repeated two times. The number of times the foam pieces or treated pieces are provided to the roll press device 2 may be referred to as the number of passes.

[0023] Increasing the number of passes may decrease the average particle size of the processed product after the pulverization process and increase the bulk density. In this embodiment, the processed product after the pulverization process refers to the processed pieces after the last pass.

[0024] The average particle size of the processed material (processed pieces) after the pulverization process is 500 μm or less. The average particle size of the processed material after the pulverization process is preferably 160 μm or less. This is because the bulk density is likely to be high if the average particle size of the processed material after the pulverization process is 160 μm or less. The average particle size in this embodiment is a volume average diameter based on a volume-based particle size distribution measured by a laser diffraction / scattering type particle size distribution measuring device (manufactured by Seishin Enterprise Co., Ltd., model: LMS-3000). In this embodiment, methanol is used as a solvent when measuring the average particle size. The processed material was dispersed when measuring the average particle size using a wet dispersion unit (Hydro MV) attached to the above measuring device, with the output of the built-in ultrasonic probe set to 10% and the rotation speed of the built-in stirrer set to 1750 rpm.

[0025] The bulk density of the processed material (processed pieces) after the crushing process is 0.10 g / cc (g / cm 3 ) or more, more preferably 0.16 g / cc or more. If the particle size of the treated product after the pulverization step is 0.10 g / cc or more, the treatment efficiency in the hydrolysis treatment step described below is improved.

[0026] In this embodiment, the bulk density of the treated material (treated piece) is the quiet density by the funnel filling method. The quiet density in this embodiment is obtained by gently pouring the treated material into a container with a capacity of 1000 cc using a funnel with an outlet diameter of 10 mm, allowing the treated material to overflow from the container, cutting the container opening, measuring the mass of the treated material filled in the container, and calculating based on this mass and the container capacity. In this embodiment, the bulk density of the treated material is the density when the treated material is in a dry state without containing water. Specifically, the bulk density of the treated material in this embodiment is a value measured after drying the treated material, which is the object of the measurement of bulk density, overnight (16 hours) in a shelf-type drying chamber with the internal atmosphere set at 60°C.

[0027] As shown in Figs. 3 and 4, the roll press device 2 has a cylindrical roll 21 and a cylindrical roll 22 having the same diameter as the roll 21. The roll 22 is disposed adjacent to the roll 21 with the axial direction of the central axis of the cylindrical shape of the roll 22 aligned with the axial direction of the central axis of the cylindrical shape of the roll 21. Fig. 3 shows a schematic diagram of the rolls 21 and 22 of the roll press device 2 as viewed along the axial direction of the rolls 21 and 22 (side view). Fig. 4 shows a schematic diagram of the rolls 21 and 22 of the roll press device 2 as viewed perpendicularly to a virtual plane overlapping with the central axes of the rolls 21 and 22 (front view).

[0028] The rolls 21 and 22 are driven by a driving source such as a motor and rotate around the central axis of each cylindrical shape as the rotation axis. The rotation directions of the rolls 21 and 22 are opposite to each other. When a foam piece or treated piece (raw material 28) is supplied between the rolls 21 and 22 from the side where the surface of the roll 21 and the surface of the roll 22 approach each other, the foam piece or treated piece is pulled between the rolls 21 and 22 due to friction between the surface of the roll 21 and the surface of the roll 22, and the treated piece (crushed material 29) that has been crushed by compression between the rolls 21 and 22 is discharged outside the rolls 21 and 22. Compression and crushing proceeds between the rolls 21 and 22 due to compression between the rolls 21 and 22 and friction between the rolls 21 and 22.

[0029] In this embodiment, for example, the rotation axis of the roll 21 may be movable toward or away from the rotation axis of the roll 22. The clearance C (see FIG. 4) between the rolls 21 and 22 is, for example, not less than 0 mm and not more than 2 mm.

[0030] The roll 21 may be biased toward the roll 22, and the biasing force, i.e., the load F applied between the rolls 21 and 22 (see FIG. 3), is, for example, 1 t / cm to 3 t / cm (9.8 kN / cm to 29.4 kN / cm) per unit length in the axial direction between the rolls 21 and 22. Hereinafter, the value obtained by converting the load F applied between the rolls 21 and 22 into a load per unit length (cm) in the axial direction between the rolls 21 and 22 may be referred to as the linear pressure.

[0031] When the foam pieces are pulverized in multiple passes in the roll press device 2, the linear pressure may be constant (the same) between each pass, or the linear pressure may be different for each pass. For example, the linear pressure may be low (less than 1 t / cm, e.g., 0.07 t / cm) in the first pass as a pretreatment, and the linear pressure may be high (e.g., 2 t / cm) in the second and subsequent passes.

[0032] The rotation speed of the rolls 21, 22, in terms of the peripheral speed of the rolls 21, 22, is, for example, not less than 0.050 m / s and not more than 0.500 m / s.

[0033] The diameters D1 and D2 of the rolls 21 and 22 are, for example, 150 mm or more and 600 mm or less. The axial length (width) of the rolls 21 and 22 is, for example, 150 mm or more and 600 mm or less. The diameter and axial length of the rolls 21 and 22 can be the same.

[0034] In the grinding step, water may be added (another example of a water adding step). When water is added in the grinding step, water may be added to the foam pieces that are the processed product before they are fed to the first pass. When water is added in the grinding step, water may be added to the foam pieces or processed products that are the processed product during the pass, i.e., while the foam pieces or processed products are being compressed and ground, or water may be added to the processed products in the middle of multiple passes (between passes). When water is added during a pass, it is preferable to add water before supplying the processed products to the rolls 21, 22. When water is added between passes, it is preferable to add water to the processed products after the immediately previous pass before they are fed to the next pass.

[0035] The total amount of water added to the treated material in the pulverization step, i.e., the amount of water added to the treated material by the end of the pulverization step, may be 3% to 20% (e.g., 15%) of the mass of polyurethane in the treated material. By adding water in the pulverization step, the pressure applied to the polyurethane foam in the roll press is made uniform, the pulverization efficiency is improved, and the bulk density of the treated material after the pulverization step may be increased.

[0036] It should be noted that the addition of water in the grinding step is not essential and can be omitted.

[0037] In the crushing step, a crushing process may be performed to crush the treated material (treated pieces) after the crushing step of the foam pieces. The crushing process may be performed by stirring with a stirring device such as a Henschel mixer. The crushing process may increase the bulk density of the treated material. The crushing process increases the bulk density of the treated material by, for example, 30%.

[0038] That is, the pulverization step may be performed, for example, as shown in the flow diagram of Fig. 5. In detail, the pulverization step may include a pretreatment press (step S21) performed with a line pressure lower than that of the subsequent passes, addition of water to the treated pieces after the pretreatment press (e.g., addition of 10% water relative to the mass of polyurethane, step S22), repeated passes (compression pulverization) (e.g., 5 passes, step S23), further addition of water to the treated pieces (e.g., further addition of 5% water, step S24), repeated passes (compression pulverization) (e.g., 3 passes, step S25), and disintegration by stirring, for example, in a Henschel mixer (step S26).

[0039] The water kneading step is a step of adding water to the treated material (treated pieces) after the pulverization step and mixing it. In the water kneading step, it is preferable to mix the treated material and water by kneading. In the water kneading step, it is preferable to add water so that the mass of water after mixing is 5% to 300%, preferably 30% to 200%, relative to the mass of polyurethane in the treated material. The bulk density of the treated material may increase due to the kneading of the treated material and water in the water kneading step. The treated material kneaded with water changes from a so-called cake-like state to a slurry-like state.

[0040] In the following, the kneaded product obtained by adding water to the processed product (processed pieces) after the pulverization process and mixing them may be collectively referred to as the processed product after the pulverization process. The water kneading process is not essential in this recycling method and can be omitted.

[0041] In the water kneading step, a known kneader may be used, such as a ribbon type mixer, a co-kneader, a paddle type mixer, or a roll type kneader.

[0042] The hydrolysis step is a step in which the polyurethane in the treated product after the pulverization step is hydrolyzed in the presence of water and carbon dioxide under pressure and heat. The hydrolysis in the hydrolysis step may be carried out in a decomposition treatment tank 4.

[0043] In the hydrolysis step, the treated material (treated pieces) supplied from the previous step is fed into the decomposition treatment tank 4. In addition to the treated material, water and carbon dioxide are also supplied to the decomposition treatment tank 4. The decomposition treatment tank 4 has a tank body 40 which is a reaction vessel into which the treated material is fed, and a heater 41 which heats the tank body 40. The tank body 40 may have a supply valve 45 which allows or prohibits the supply of carbon dioxide to the tank body 40, and a release valve 46 which allows or prohibits the release (exhaust, discharge) of gas (carbon dioxide) from the tank body 40.

[0044] When polyurethane foam is left as is (untreated), it has an extremely low bulk density (for example, about 0.04 g / cc), and the mass that can be put into the decomposition tank 4 is extremely small. However, in this recycling method, the bulk density of the treated material (treated pieces) is increased by compression crushing, and when the water kneading process is performed, the bulk density is further increased by this. Therefore, in this recycling method, the mass of the treated material (polyurethane) that can be put into the decomposition tank 4 is increased. This makes it possible to reduce the capacity of the decomposition tank 4 required for the hydrolysis treatment. This also makes it possible to reduce the amount of water and carbon dioxide used to be supplied to the decomposition tank 4. Furthermore, it makes it possible to reduce the energy required for adjusting the temperature and pressure of the contents of the decomposition tank 4. Therefore, in this recycling method, the hydrolysis treatment can be performed efficiently.

[0045] In the hydrolysis step, water is preferably supplied to the decomposition treatment tank 4 so that the mass of water relative to the mass of polyurethane in the treated material (treated pieces) in the decomposition treatment tank 4 is 5% to 1000%, preferably 20% to 400%, and more preferably 50% to 300%. The amount of water required in the decomposition treatment tank 4 is equal to or more than the amount of water consumed in the hydrolysis of polyurethane, and is an amount that allows the entire treated material to come into contact with water.

[0046] In the hydrolysis step, the partial pressure of carbon dioxide is set to 3 MPa or more and 20 MPa or less, preferably 4 MPa or more and 15 MPa or less, which promotes the hydrolysis of polyurethane.

[0047] In the hydrolysis step, the temperature inside the decomposition treatment tank 4 is set to 150° C. or higher, preferably 180° C. or higher. By setting the temperature inside the decomposition treatment tank 4 to 150° C. or higher, the hydrolysis of polyurethane is promoted. If the temperature inside the decomposition treatment tank 4 is 280° C. or lower, the hydrolysis reaction rate is high.

[0048] The separation and recovery process is a process of separating polyol and amine from the solution hydrolyzed in the decomposition treatment tank 4. The separation and recovery process can be carried out, for example, by supplying water and an organic solvent (e.g., chloroform) into the separation tank 5 and performing an extraction process based on the difference in solubility of polyol and amine in water and organic solvent. In this example, the amine is extracted into the aqueous phase as a water-soluble component, and the polyol is extracted into the oil phase (organic solvent side) as a water-insoluble component. After these extractions, the oil phase and the aqueous phase are separately recovered, so that the polyol and amine can be separated. The oil phase and the aqueous phase can be filtered as necessary, and then the organic solvent and water can be evaporated from the oil phase and the aqueous phase to concentrate and recover the polyol and amine. The separation and recovery process described above is an example. The adoption of other separation and recovery methods is not excluded in this recycling method.

[0049] In this recycling method, the solution containing the decomposition products hydrolyzed in the decomposition treatment tank 4 has a low water content and a high polyol and amine concentration. This makes it possible to reduce the amount of organic solvent used in the separation and recovery process, and also to reduce the energy required to remove water and organic solvents by evaporation or the like. In other words, the separation and recovery of polyol and amine can be made more efficient. EXAMPLES

[0050] The present recycling method will be described below based on examples.

[0051] In this example, polyurethane foam was prepared according to the formula shown in Table 1, and processed by compression and crushing based on this recycling method to obtain processed material (processed pieces) to be put into a decomposition treatment tank. In this example, the particle size and bulk density were measured as properties of the processed material (processed pieces) after the crushing step or the water kneading step, and the amount that can be put into was evaluated by putting it into a container (volume 150 ml) simulating a decomposition treatment tank.

[0052] [Table 1]

[0053] In Table 1, Polyether polyol (OH #56) means polyether polyol (hydroxyl value mgKOH / g). TDI80 means tolylene diisocyanate (containing about 80% of 2,4-tolylene diisocyanate). Silicone Surfactant means silicone surfactant. Bis(2-dimethylaminoethyl)ether means bis(2-dimethylaminoethyl)ether. DPG means dipropylene glycol. DABCO means triethylenediamine. Stannous octoate means stannous octoate.

[0054] The polyurethane foam was separated and cut into chunks of foam pieces with a thickness of about 5 cm, width of 10 cm, and length of 30 cm, and subjected to a crushing process. In the crushing process, the foam pieces were passed multiple times through a roll press machine (manufactured by Seishin Enterprise Co., Ltd., model: 150 type, roll diameter 150 mm, axial length 150 mm) to produce treated pieces.

[0055] In the pulverization process, treated pieces were produced by changing the number of passes. In addition, treated pieces were produced in which water was added during the pulverization process and treated pieces were not added. In addition, treated pieces were produced in which a crushing process was performed during the pulverization process and treated pieces were not added. In addition, treated pieces were produced in which a water kneading process was performed after the pulverization process and treated pieces were not added.

[0056] When the crushing step was carried out, crushing was carried out using a commercially available juicer mixer (Model MX-X701, manufactured by Panasonic Corporation) as a small mixing and crushing device similar to a Henschel type mixer.

[0057] When performing the water kneading step, the treated pieces were placed in a kitchen bowl, water was dropped onto the treated pieces, and the pieces were stirred with a spatula.

[0058] Table 2 shows the treatment in the pulverization process, the presence or absence of a water kneading process and the amount of water added (g), the particle size (μm) of the treated pieces, the bulk density (g / cc), and the amount that can be added (g) for this example. As for the treatment in the pulverization process, the presence or absence of a pretreatment press, the amount of water added (g), the number of passes (times) of compression pulverization, and the presence or absence of crushing are shown. The amount that can be added is the upper limit when the polyurethane foam is added while still containing water to a 150 ml decomposition treatment tank described below.

[0059] [Table 2]

[0060] As shown in Table 2, in each Example, the first water addition was performed after the pretreatment pressing and before the compression and pulverization. In particular, in Examples 4 to 6, the second water addition was performed during the repeated passes of the compression and pulverization. In Table 2, the repeated passes of the compression and pulverization immediately after the first water addition are marked as the first pass. When water was added during the repeated passes of the compression and pulverization, the repeated passes of the compression and pulverization immediately after the water addition are marked as the second pass. As shown in Table 2, the comparative example is an untreated polyurethane foam as it is.

[0061] The linear pressure in the pretreatment press is 0.07 t / cm, and the clearance between the rolls is 1 mm. The linear pressure during compression and crushing is 2 t / cm, and the clearance between the rolls is 0 mm. The clearance between the rolls of the roll press machine used in this embodiment is the clearance when no load is applied, and when a foam piece or a treated piece is supplied between the rolls, the clearance expands while maintaining the linear pressure. The rotation speed of the rolls is 0.078 m / s to 0.236 m / s (10 rpm to 30 rpm) in terms of the peripheral speed of the rolls.

[0062] From the properties of the treated pieces shown in Table 2, it can be seen that the particle size of the treated pieces decreases as the total number of passes of compression crushing increases, and the bulk density of the treated pieces increases as the total number of passes of compression crushing increases.

[0063] It can be seen that the amount of the treated pieces that can be put in increases with increasing bulk density. Also, it can be seen that if the water kneading step is adopted as in Example 6, the amount that can be put in increases further compared to when it is not adopted (Examples 1 to 5, especially Example 5).

[0064] Thus, the amount of the processed pieces according to this embodiment that can be put into the decomposition treatment tank can be 20 times or more larger than that of the processed pieces according to the comparative example. In particular, when the water kneading process is adopted, the amount that can be put into the decomposition treatment tank can be 100 times or more larger.

[0065] The treated pieces of Examples 5 and 6 were further subjected to a hydrolysis step in which the polyurethane in the treated pieces was hydrolyzed in the presence of water and carbon dioxide under pressure and heat, and were evaluated as in Examples 7 to 17 shown in Table 3.

[0066] First, the treated pieces of Example 5 or Example 6 and water were charged into a stainless steel autoclave with a capacity of 150 ml according to the charge amount (g) and water addition amount (g) shown in Table 3. The charge amount shown in Table 3 is the mass of polyurethane in the treated pieces (a value obtained by subtracting the mass of water in the treated pieces). The water addition amount shown in Table 3 is the mass of water present in the reaction vessel, which is the total mass of the water already contained in the treated pieces and the water newly charged into the reaction vessel. Then, according to the pressure (MPa), temperature (°C) and time (hr) shown in Table 3, carbon dioxide was injected into the autoclave until the pressure inside the autoclave reached a predetermined pressure with the autoclave discharge valve closed, and the autoclave supply valve was closed, and then the autoclave was heated to a predetermined temperature with a heater and held at that temperature for a predetermined time to cause a reaction (hydrolysis). Hereinafter, the time held for hydrolysis may be referred to as reaction time.

[0067] [Table 3]

[0068] After the above-mentioned holding (after reaction), the autoclave was cooled using ice water as a coolant, and the temperature of the reaction vessel in the autoclave was rapidly cooled (to 100°C or less within 3 minutes). The coolant was appropriately replaced, and the reaction vessel was cooled for a total of about 15 minutes to below room temperature, after which the release valve of the autoclave was opened to release carbon dioxide. Thereafter, the polyurethane hydrolyzate (hereinafter referred to as decomposition product) was taken out of the reaction vessel and transferred to a vessel used as a separation tank.

[0069] Water and chloroform were then added to the container into which the decomposition product had been transferred, and an extraction process was carried out based on the difference in solubility between the water-soluble and water-insoluble components in the decomposition product in water and organic solvents. The water-soluble and water-insoluble components (which were liquid and oily residues) were then separated and collected. The water-insoluble components were dissolved in deuterated chloroform (CDCl3) and analyzed by proton-nuclear magnetic resonance ( 1 H-NMR measurements were performed, and the compound was dissolved in N,N-dimethylformamide and subjected to gel permeation chromatography (GPC) measurements. By comparing the raw material polyether polyol as a standard, it was found that part of the water-insoluble components was polyether polyol having a structure derived from tolylene diisocyanate.

[0070] The water-insoluble components were dried under reduced pressure, and then weighed to obtain the amount (g) of the water-insoluble components recovered. The decomposition and recovery rate (%) of the water-insoluble components was calculated based on the amount (g) of the water-insoluble components recovered. Here, the decomposition and recovery rate is the value obtained by dividing the amount of the water-insoluble components recovered by the theoretical maximum recoverable amount calculated based on the formulation shown in Table 1.

[0071] As shown in Table 3, the treated pieces of Examples 5 and 6, which had increased bulk density, showed high decomposition and recovery rates of more than 74% under all of the conditions of Examples 7 to 17.

[0072] In Examples 7 to 17, when the ratio of the amount of water added to the amount of charge was 1 or less than 1, the separation and recovery rate of each was high. Therefore, in this recycling method, the water content in the solution containing the decomposition product can be reduced to increase the concentration of polyol and amine. Therefore, it is considered that this recycling method can reduce the energy required to remove water by evaporation or the like. In other words, it is considered that this recycling method can efficiently separate and recover polyol and amine.

[0073] Thus, the treated material (treated pieces) after the treatment according to this embodiment can reduce the size of the decomposition treatment tank required for the hydrolysis treatment, reduce the amount of water and carbon dioxide used for the hydrolysis treatment, and reduce the energy required for the hydrolysis treatment, compared to the case where the treated material according to the comparative example is used, and the hydrolysis treatment can be carried out efficiently. Furthermore, since the amount of water used for the hydrolysis treatment can be reduced, the amount of solvent used in the separation and recovery step after the hydrolysis treatment can be reduced, and the energy required for removing water and organic solvents can be reduced, and the separation and recovery treatment can be carried out efficiently.

[0074] In this way, an efficient method for recycling polyurethane foam can be provided.

[0075] Note that the embodiments disclosed in this specification are merely examples, and the embodiments of the present disclosure are not limited thereto, and may be modified as appropriate within the scope of the purpose of the present disclosure. [Industrial Applicability]

[0076] The present disclosure is applicable to methods for recycling polyurethane foams. [Explanation of symbols]

[0077] 1: Separating and cutting device 100:Plant 2: Roll press device 21: Roll 22: Roll 28: Raw materials 29: Crushed material 3: Mixer 4: Decomposition treatment tank 40: Tank body 41: Heater 45: Supply valve 46: Release valve 5: Separation tank C: Clearance D1: Diameter D2 :Diameter F: Load

Claims

1. a crushing step of passing a polyurethane foam as a processing material between a pair of rolls and compressing and crushing the polyurethane foam between the pair of rolls; a hydrolysis step of hydrolyzing the treated product after the pulverization step.

2. 2. The method for recycling polyurethane foam according to claim 1, wherein in the crushing step, a load applied between the pair of rolls is 1 t / cm or more and 3 t / cm or less per unit length in the axial direction of the rolls.

3. 3. The method for recycling polyurethane foam according to claim 2, wherein in the pulverizing step, the polyurethane foam is passed between the pair of rolls two or more times.

4. The hydrolysis step comprises: In the presence of carbon dioxide having a partial pressure of 3 MPa or more, 3. The method for recycling polyurethane foam according to claim 2, wherein the method is carried out at a temperature of 150° C. or higher.

5. The method further includes a water addition step of adding water to the treated material, The method for recycling a polyurethane foam according to claim 1 , wherein the water addition step is carried out before the hydrolysis step.

6. In the pulverization step, The polyurethane foam is passed between the pair of rolls one or more times, The method for recycling polyurethane foam according to claim 5, wherein the water addition step is carried out during or between the passes.

7. 6. The method for recycling polyurethane foam according to claim 5, wherein in the water addition step, water is added so that the mass of water is 5% or more and 100% or less relative to the mass of polyurethane in the treated product.

8. 5. The method for recycling a polyurethane foam according to claim 1, wherein the treated product after the pulverization step has an average particle size based on a volumetric particle size distribution of 160 μm or less.

9. 5. The method for recycling polyurethane foam according to claim 1, wherein the treated product after the pulverization step has a static density of 0.10 g / cc or more.

10. The water addition step includes a water kneading step of adding water to the treated material after the pulverization step and mixing the water, The method for recycling polyurethane foam according to claim 5 , wherein in the water kneading step, water is added so that the mass of water is 5% or more and 300% or less of the mass of polyurethane in the treated material.

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