Method for recycling polyurethane foam

Abstract

Provided is an efficient method for recycling a polyurethane foam. This method for recycling a polyurethane foam comprises: a pulverization step for passing a polyurethane foam between a pair of rolls and compressing and pulverizing the polyurethane foam between the pair of rolls; and a hydrolysis step for hydrolyzing the processed product after the pulverization step.

Description

How to recycle polyurethane foam

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

[0002] Patent Document 1 discloses a method for decomposing a urea compound. In this method, the urea compound is hydrolyzed using liquid or gaseous water in supercritical or subcritical carbon dioxide, and the corresponding amine is recovered. 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 includes a compression pulverization step in which the thermosetting resin is pulverized 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 that are rotated while being biased toward each other, and then compressed and pulverized. In the roll compression pulverization step, water may be added between the pair of rolls when the thermosetting resin is introduced. Adding water during introduction reduces the average particle size of the resulting urethane fine powder.

[0004] Non-Patent Document 1 discloses an environmentally friendly decomposition method for polyurethane. Non-Patent Document 1 also discloses that polyurethane is mainly used for urethane foam, which is a foamed material, and that urethane foam has a significantly lower density than other polymer materials. ２ It has been disclosed that the hydrolysis reaction of polyurethane using (carbon dioxide) and water has an extremely low environmental impact.

[0005] International Publication No. 2009 / 130842 Japanese Patent Application Laid-Open No. 2002-326224

[0006] Development of an environmentally friendly decomposition method for polyurethane, Journal of the Adhesion Society of Japan, Vol. 54, No. 9, 2018, pp. 343-348, Taku Honkucho, [Retrieved May 31, 2023], Internet: https: / / www.jstage.jst.go.jp / article / adhesion / 54 / 9 / 54_9-4 / _pdf / -char / ja>

[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, which makes handling difficult and inefficient during hydrolysis. For example, polyurethane foam is bulky and has a low bulk density, making it difficult to increase the density and introduce it into a decomposition treatment tank where hydrolysis is performed, resulting in low efficiency of the hydrolysis treatment. Specifically, the decomposition treatment tank becomes larger, which increases the amount of water used and the amount of energy used during hydrolysis. Furthermore, the concentrations of polyol and amine in the treated product after hydrolysis are low, making their recovery 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.

[0009] To achieve the above object, the method for recycling polyurethane foam according to the present disclosure includes a crushing step of passing 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 processed product obtained after the crushing step.

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

[0011] Fig. 1 is a flow diagram of a polyurethane foam recycling method according to an embodiment of the present invention. Fig. 2 is an explanatory diagram of an overview of a polyurethane foam recycling method according to an embodiment of the present invention. Fig. 3 is a schematic side view of a roll part of a roll press. Fig. 4 is an explanatory front view of the roll part of a roll press. Fig. 5 is a flow diagram of a pulverization process.

[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 the present 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 this 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 compressing and crushing it between rolls, which allows it to be introduced at a high density into a decomposition tank where the polyurethane is hydrolyzed into polyol and amine. By allowing the polyurethane foam to be introduced at a high density into the decomposition tank, the efficiency of the hydrolysis treatment 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 polyurethane foam recycling method according to this embodiment (the present recycling method) includes a crushing step in which a polyurethane foam is compressed and crushed between a pair of rolls as a treated material, 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 material to be treated (e.g., waste material) containing the polyurethane foam is cut or sorted to separate the polyurethane foam for use in 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 chart of Figure 1. In Figure 1, PFU stands for polyurethane foam.

[0018] This recycling method is realized, for example, 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 a processing object containing polyurethane foam, such as a seat of a scrapped vehicle, is broken or cut using 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 shapes and dimensions 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, or the like for waste treatment, either alone or in combination.

[0020] The object to be treated containing polyurethane foam may be a seat of a vehicle to be scrapped, 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 cutting and separating step, the polyurethane foam may be separated into chunks of foam pieces, each having a thickness of about 10 cm, a width of 20 cm, and a length of about 30 cm. The foam pieces separated in the cutting and separating step are subjected to the pulverizing step described below. The foam pieces may be of any size that does not cause problems in handling in the pulverizing step.

[0022] In the crushing step, the foam piece described above is compressed and crushed as a processed material in the roll press device 2. The compression and crushing of the foam piece in the roll press device 2 may be performed once or may be repeated two or more times. Hereinafter, the process of subjecting the foam piece or a processed piece obtained by compressing and crushing the foam piece in the roll press device 2 as a processed material to the roll press device 2 and crushing it may be referred to as a pass. For example, "two passes" or "two passes" refers to the compression and crushing of the foam piece or processed piece in the roll press device 2 being repeated twice. The number of times the foam piece or processed piece is subjected to the roll press device 2 may also be referred to as the number of passes.

[0023] Increasing the number of passes may decrease the average particle size of the processed material after the pulverization process and increase the bulk density. In this embodiment, the processed material 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 if the average particle size of the processed material after the pulverization process is 160 μm or less, the bulk density tends to be high. The average particle size in this embodiment is a volume average diameter based on a volume-based particle size distribution measured using a laser diffraction / scattering particle size distribution measuring device (manufactured by Seishin Enterprise Co., Ltd., model: LMS-3000). In this embodiment, methanol is used as the solvent when measuring the average particle size. The processed material was dispersed using a wet dispersion unit (Hydro MV) attached to the 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 pulverization process is 0.10 g / cc (g / cm ３ 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 pieces) refers to the quiet density measured by the funnel filling method. The quiet density in this embodiment is determined by gently pouring the treated material into a 1000 cc container using a funnel with a 10 mm outlet diameter, allowing the treated material to overflow from the container, then leveling the container opening and measuring the mass of the treated material filled in the container, and then calculating the quiet density based on this mass and the container volume. In this embodiment, the bulk density of the treated material refers to the density of the treated material when it 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, the bulk density of which is to be measured, overnight (16 hours) in a shelf-type drying chamber with the internal atmosphere set to 60°C.

[0027] As shown in Figures 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 central axis of the cylindrical roll 22 aligned along the axial direction of the central axis of the cylindrical roll 21. Figure 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). Figure 4 shows a schematic diagram of the rolls 21 and 22 of the roll press device 2 as viewed perpendicularly to an imaginary plane overlapping 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 their respective cylindrical shapes. The rolls 21 and 22 rotate in opposite directions. When a foam piece or treated piece (raw material 28) is supplied between the rolls 21 and 22 from the side where the surfaces of the rolls 21 and 22 approach each other, the foam piece or treated piece is pulled between the rolls 21 and 22 due to friction between the surfaces of the rolls 21 and 22, and is compressed and crushed between the rolls 21 and 22, and the crushed treated piece (crushed material 29) is discharged outside the rolls 21 and 22. Compression and crushing proceed 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 and away from the rotation axis of the roll 22. The clearance C (see FIG. 4) between the rolls 21 and 22 is, for example, 0 mm or more and 2 mm or less.

[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 or more and 3 t / cm or less (9.8 kN / cm or more and 29.4 kN / cm or less) 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 crushed 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 and 22 is, for example, 0.050 m / s or more and 0.500 m / s or less in terms of the peripheral speed of the rolls 21 and 22 .

[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 lengths (widths) of the rolls 21 and 22 are, for example, 150 mm or more and 600 mm or less. The diameters and axial lengths of the rolls 21 and 22 can be the same.

[0034] In the grinding step, water may be added (another example of a water addition step) (an example of a water addition step during grinding). When water is added in the grinding step, the foam pieces, which are the processed product, may be added with water before being subjected to the first pass. When water is added in the grinding step, water may be added to the processed foam pieces or processed pieces during a pass, i.e., while the processed foam pieces or processed pieces are being compressed and ground, or water may be added to the processed pieces during multiple passes (between passes). When water is added during a pass, it is preferable to add water before supplying them to the rolls 21 and 22. When water is added between passes, it is preferable to add water to the processed pieces after the previous pass before being subjected 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. Adding water in the pulverization step may make the pressure applied to the polyurethane foam in the roll press uniform, improve pulverization efficiency, and increase the bulk density of the treated material after the pulverization step.

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

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

[0038] That is, the pulverization step may be carried out, for example, as shown in the flow diagram of Fig. 5. More specifically, the pulverization step may include pretreatment pressing (step S21) performed at a lower linear pressure than in subsequent passes, adding water to the treated pieces after pretreatment pressing (e.g., adding 10% water relative to the mass of polyurethane, step S22), repeating passes (compression pulverization) (e.g., five passes, step S23), adding more water to the treated pieces (e.g., adding another 5% water, step S24), repeating passes (compression pulverization) again (e.g., three 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 them. In the water kneading step, it is preferable to mix the treated material and water by kneading them. In the water kneading step, it is preferable to add water so that the mass of water after mixing is 5% to 300%, preferably 20% to 200%, and more preferably 30% to 200%, relative to the mass of polyurethane in the treated material. Kneading the treated material and water in the water kneading step may increase the bulk density of the treated material. The treated material kneaded with water changes from a so-called cake-like state to a slurry-like state.

[0040] Hereinafter, the kneaded product obtained by adding water to the processed material (processed pieces) after the pulverization process may be collectively referred to as the processed material 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 mixer, a co-kneader, a paddle mixer, or a roll 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 introduced 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 introduced, and a heater 41 that heats the tank body 40. The tank body 40 may have a supply valve 45 that allows or prohibits the supply of carbon dioxide to the tank body 40, and a release valve 46 that 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 (e.g., approximately 0.04 g / cc), and the mass that can be introduced into the decomposition treatment 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 if a water-kneading step 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 introduced into the decomposition treatment tank 4 is increased. This makes it possible to reduce the capacity of the decomposition treatment tank 4 required for the hydrolysis treatment. This also makes it possible to reduce the amount of water and carbon dioxide used to supply to the decomposition treatment tank 4. Furthermore, it makes it possible to reduce the energy required to adjust the temperature and pressure of the contents of the decomposition treatment tank 4. Therefore, this recycling method allows for efficient hydrolysis treatment.

[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) 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 greater than the amount 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 preferably 3 MPa or more and 20 MPa or less, and more 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 should be 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 set to 280°C or lower, the hydrolysis reaction rate is high.

[0048] The separation and recovery process is a process for separating polyols and amines from the solution hydrolyzed in the decomposition treatment tank 4. This 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 the solubilities of the polyols and amines in water and the 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) as a water-insoluble component. After these extractions, the oil and aqueous phases can be separately recovered to separate the polyols and amines. The oil and aqueous phases can be filtered, if necessary, and then the organic solvent and water can be evaporated from the oil and aqueous phases to concentrate and recover the polyols and amines. Note that the separation and recovery process described above is merely an example. Other separation and recovery methods are not excluded from 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 step, and also to reduce the energy required to remove water and organic solvent by evaporation or the like. In other words, the separation and recovery of polyol and amine can be made more efficient.

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

[0051] In this example, polyurethane foam was prepared according to the formulation shown in Table 1, and processed by compression and crushing according to this recycling method to obtain processed material (processed pieces) to be introduced into a decomposition treatment tank. In this example, the processed material (processed pieces) after the crushing step or the water-kneading step were measured for their properties, such as particle size and bulk density, and were also introduced into a container (volume 150 ml) simulating a decomposition treatment tank to evaluate the amount that could be introduced.

[0052]

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

[0054] The polyurethane foam was separated into chunks of foam pieces approximately 5 cm thick, 10 cm wide, and 30 cm long, cut, and subjected to a crushing process in which the foam pieces were passed through a roll press (manufactured by Seishin Enterprise Co., Ltd., Model: 150, roll diameter 150 mm, axial length 150 mm) multiple times 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 with and without adding water during the pulverization process. In addition, treated pieces were produced with and without crushing treatment during the pulverization process. In addition, treated pieces were produced with and without a water-kneading process after the pulverization process.

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

[0057] When the water kneading step was carried out, the treated pieces were placed in a kitchen bowl, water was added dropwise to the treated pieces, and the pieces were stirred using a spatula.

[0058] Table 2 shows the treatment in the pulverization step, whether or not a water kneading step was performed and the amount of water added (%), the particle size (μm) of the treated pieces, the bulk density (g / cc), and the amount that can be added (g) for this example. The treatment in the pulverization step shows whether or not a pretreatment press was performed, the amount of water added (%), the number of passes (times) for compression pulverization, and whether or not crushing was performed. The amount that can be added is the upper limit when polyurethane foam containing water is added to a 150 ml decomposition treatment tank described below.

[0059]

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

[0061] The linear pressure in the pretreatment press was 0.07 t / cm, and the clearance between the rolls was 1 mm. The linear pressure during compression and pulverization was 2 t / cm, and the clearance between the rolls was 0 mm. The clearance between the rolls of the roll press machine used in this example was the clearance when no load was applied. When a foam piece or treated piece was supplied between the rolls, the clearance expanded while maintaining the linear pressure. The rotation speed of the rolls was 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 processed pieces shown in Table 2, it can be seen that the particle size of the processed pieces decreases as the total number of passes of compression pulverization increases, and the bulk density of the processed pieces increases as the total number of passes of compression pulverization increases.

[0063] It can be seen that the amount of the treated pieces that can be put into the pulp increases with increasing bulk density. Furthermore, it can be seen that when the water kneading step is adopted as in Example 6, the amount that can be put into the pulp 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 example that can be introduced into the decomposition treatment tank can be increased by 20 times or more compared to the processed material of the comparative example. In particular, when the water kneading process is adopted, the amount that can be introduced into the decomposition treatment tank can be increased by 100 times or more.

[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 amounts (g) and water addition amounts (g) shown in Table 3. The charge amounts shown in Table 3 are the mass of polyurethane in the treated pieces (minus 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 with the autoclave discharge valve closed until the predetermined pressure was reached, and the autoclave supply valve was closed. The autoclave was then heated to a predetermined temperature with a heater and maintained at that temperature for a predetermined time to allow reaction (hydrolysis). Hereinafter, the time maintained for hydrolysis may be referred to as the reaction time.

[0067]

[0068] After the above-mentioned holding period (after the reaction), the autoclave was cooled using ice water as a coolant, and the temperature of the reaction vessel inside 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 until the temperature reached room temperature or below, 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 removed from the reaction vessel and transferred to a container 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 treatment 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 recovered. The resulting water-insoluble components were extracted with deuterated chloroform (CDCl ３ ) dissolved in proton-nuclear magnetic resonance ( １ H-NMR measurements were performed, and the sample 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 component was a polyether polyol with a structure derived from tolylene diisocyanate.

[0070] The water-insoluble components were subjected to a reduced pressure drying treatment, and then weighed to obtain the amount (g) of the water-insoluble components recovered. Based on this, the decomposition recovery rate (%) of the water-insoluble components was calculated. Here, the decomposition recovery rate was calculated by dividing the amount of the water-insoluble components recovered by the theoretically 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 a high decomposition recovery rate of over 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 feed was 1 or less, the separation and recovery rates were high. Therefore, in this recycling method, the water content in the solution containing the decomposition product can be reduced, thereby increasing the concentrations of polyol and amine. Therefore, this recycling method is thought to be able to reduce the energy required to remove water by evaporation or the like. In other words, this recycling method is thought to be able to efficiently separate and recover polyol and amine.

[0073] Thus, the treated material (treated pieces) according to this example can reduce the size of the decomposition treatment tank required for the hydrolysis treatment, reduce the amounts of water and carbon dioxide used in the hydrolysis treatment, and reduce the energy required for the hydrolysis treatment, compared to when the treated material according to the comparative example is used, thereby enabling the hydrolysis treatment to be carried out efficiently. Furthermore, since the amount of water used in 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, allowing the separation and recovery treatment to be carried out efficiently.

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

[0075] It should be noted that the embodiments disclosed in this specification are merely examples, and the embodiments of the present disclosure are not limited to these, and can be modified as appropriate within the scope of the purpose of the present disclosure.

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

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

Claims

1. A method for recycling polyurethane foam, comprising: a crushing step of passing a polyurethane foam as a treated material 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 material after the crushing step.

2. A method for recycling polyurethane foam as described in claim 1, wherein in the crushing step, the 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. A method for recycling polyurethane foam as described in claim 2, wherein in the crushing step, the polyurethane foam is passed between the pair of rolls two or more times.

4. A method for recycling polyurethane foam as described in claim 2, wherein the hydrolysis step is carried out in the presence of carbon dioxide having a partial pressure of 3 MPa or more at a temperature of 150 degrees or more.

5. A method for recycling polyurethane foam according to any one of claims 1 to 4, further comprising a water addition step of adding water to the treated material, the water addition step being carried out before the hydrolysis step.

6. A method for recycling polyurethane foam as described in claim 5, wherein in the crushing step, the polyurethane foam is passed between the pair of rolls one or more times, and the water addition step is carried out during or between the passes.

7. A method for recycling polyurethane foam as described in 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 material.

8. A method for recycling polyurethane foam described in any one of claims 1 to 4, wherein the average particle diameter based on the volume-based particle size distribution of the treated material after the pulverization step is 160 μm or less.

9. A method for recycling polyurethane foam described in any one of claims 1 to 4, wherein the static density of the treated material after the pulverization step is 0.10 g / cc or more.

10. A method for recycling polyurethane foam as described in claim 5, wherein the water addition process includes a water kneading process in which water is added to the treated material after the crushing process and mixed, and in the water kneading process, water is added so that the mass of water is 5% or more and 300% or less relative to the mass of polyurethane in the treated material.

11. A method for recycling polyurethane foam as described in any one of claims 1 to 10, further comprising a water addition step of adding water to the treated material, the water addition step being carried out before the hydrolysis step, and in the water addition step, water is added so that the mass of water is 20% or more and 300% or less relative to the mass of polyurethane in the treated material.

12. A method for recycling polyurethane foam as described in claim 11, wherein the water addition process includes a water addition process during grinding in which water is added to the treated material during the grinding process, and a water kneading process in which water is added to the treated material after the grinding process and mixed.

13. A method for recycling polyurethane foam as described in claim 12, wherein in the hydration process during grinding, water is added to the treated material during the grinding process so that the mass of water is 3% or more and 20% or less relative to the mass of polyurethane in the treated material.

14. A method for recycling polyurethane foam according to claim 12 or 13, wherein the hydrolysis in the hydrolysis step is carried out in a decomposition treatment tank, and the treated material after the water addition step is introduced into the decomposition treatment tank.

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