Recovery method of monomer

Abstract

To provide a recovery method of monomers capable of improving a recovery rate and a recovery concentration of dicarboxylic acid derived from polyesters, when recovering the monomers from a resin composition containing polyesters and polyurethanes.SOLUTION: A method for recovering monomers is a method to recover monomers from resin compositions that include polyester and polyurethane. The method for recovering monomers includes a step of depolymerizing the polyester and polyurethane contained in the resin composition in the presence of a solvent capable of swelling the polyester and polyurethane, alcohol, and a base, a step of extracting the depolymerized products of the polyester and polyurethane with hydrophilic and hydrophobic solvents, respectively, and a step of acidifying the depolymerized product of polyester extracted with the hydrophilic solvent.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for recovering monomers from a resin composition including a polyester and a polyurethane. [Background technology]

[0002] In recent years, there has been an increased effort to significantly reduce waste generation through waste prevention, reduction, recycling and reuse. To achieve this, research and development is being carried out on methods to recover monomers from waste, including polyester.

[0003] Patent Document 1 describes a process in which commercially available products whose main component is polyester and / or waste materials whose main component is polyester generated in the process of manufacturing these products are collected, and these are used as raw materials to carry out a depolymerization reaction with ethylene glycol and a transesterification reaction with methanol, thereby separating and purifying dimethyl terephthalate and ethylene glycol. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2002-167469 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the process described in Patent Document 1, when recovering monomers from a resin composition containing a polyester and a polyurethane, the recovery rate and recovery concentration of dicarboxylic acid derived from the polyester are insufficient.

[0006] The present invention aims to provide a method for recovering monomers, which can improve the recovery rate and recovery concentration of dicarboxylic acid derived from polyester when recovering monomers from a resin composition containing polyester and polyurethane. [Means for solving the problem]

[0007] (1) A method for recovering a monomer from a resin composition containing a polyester and a polyurethane, comprising the steps of: depolymerizing a polyester and a polyurethane contained in the resin composition in the presence of a solvent capable of swelling the polyester and the polyurethane, an alcohol, and a base; extracting a depolymerized product of the polyester and a depolymerized product of the polyurethane with a hydrophilic solvent and a hydrophobic solvent, respectively; and acid-precipitating the depolymerized product of the polyester extracted with the hydrophilic solvent.

[0008] (2) The method for recovering a monomer according to (1), wherein the alcohol is methanol, the solvent capable of swelling the polyester and polyurethane is tetrahydrofuran, and the base is sodium hydroxide.

[0009] (3) The method for recovering a monomer according to (1) or (2), wherein the hydrophilic solvent is water and the hydrophobic solvent is ethyl acetate.

[0010] (4) The method for recovering a monomer according to any one of (1) to (3), wherein the temperature for depolymerizing the polyester and polyurethane is 45° C. or higher and 75° C. or lower. Effect of the Invention

[0011] According to the present invention, it is possible to provide a method for recovering a monomer, which is capable of improving the recovery rate and recovery concentration of a dicarboxylic acid derived from a polyester when recovering a monomer from a resin composition containing a polyester and a polyurethane. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram showing a method for recovering a monomer in Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described.

[0014] A method for recovering a monomer according to one embodiment of the present invention is a method for recovering a monomer from a resin composition containing a polyester and a polyurethane.

[0015] Examples of polyesters include polyethylene terephthalate and polybutylene terephthalate. Polyurethanes include, for example, polyether polyol residues. The resin composition may further include resins such as polyolefins (polypropylene, polyethylene, etc.), polyamides (polyamide 6, polyamide 66, etc.), and cotton, in addition to polyesters and polyurethanes, and may further include additives such as fillers.

[0016] The resin composition is not particularly limited, but may be, for example, shredder dust obtained by shredding scrapped cars, which contains, for example, polyester fiber and polyurethane foam.

[0017] In the method for recovering a monomer according to the present embodiment, first, the polyester and polyurethane contained in the resin composition are depolymerized in the presence of a solvent capable of swelling the polyester and polyurethane, an alcohol, and a base.

[0018] The solvent capable of swelling polyester and polyurethane is not particularly limited, but examples thereof include methyl ethyl ketone, tetrahydrofuran, and dichloromethane. Among these, tetrahydrofuran is preferred in terms of reactivity in the depolymerization reaction.

[0019] The alcohol is not particularly limited as long as it is capable of transesterifying the polyester with the alcohol, and examples of the alcohol include methanol and ethanol. Among these, methanol is preferred in terms of reactivity in the transesterification reaction.

[0020] The base is not particularly limited as long as it can depolymerize polyester and polyurethane, and examples thereof include sodium hydroxide, potassium hydroxide, and potassium t-butoxide. Among these, sodium hydroxide is preferred in terms of reactivity in the depolymerization reaction.

[0021] The depolymerization temperature is preferably 45° C. or more and 75° C. or less, and more preferably 45° C. or more and 65° C. or less. When the depolymerization temperature is 45° C. or more, the depolymerization time is shortened, and when the depolymerization temperature is 75° C. or less, side reactions such as depolymerization of polyamide and depolymerization of cotton are suppressed. The depolymerization time is not particularly limited, but is, for example, 5 hours or more and 20 hours or less.

[0022] Next, the depolymerized polyester and the depolymerized polyurethane are extracted with a hydrophilic solvent and a hydrophobic solvent, respectively.

[0023] Examples of the depolymerized polyester include dicarboxylates (such as disodium terephthalate) and dialcohols (such as ethylene glycol and butylene glycol). Examples of the depolymerized polyurethane include polyether polyols.

[0024] The hydrophilic solvent is not particularly limited as long as it can extract the depolymerized product of polyester, and examples thereof include water. The hydrophobic solvent is not particularly limited as long as it can extract the depolymerized product of polyurethane, and examples thereof include ethyl acetate, propyl acetate, butyl acetate, methyl ethyl ketone, and cyclohexane. Among these, ethyl acetate is preferred in terms of the extractability of the depolymerized product of polyurethane.

[0025] In addition, when the resin composition further contains resins and additives other than polyester and polyurethane, it is preferable to recover the filtrate by filtration after extracting the depolymerized polyester and the depolymerized polyurethane. When it is necessary to further separate the recovered filtrate, for example, the filtrate is separated by specific gravity.

[0026] Next, the depolymerized polyester extracted with the hydrophilic solvent is subjected to acid precipitation. This causes the dicarboxylic acid to precipitate. The dicarboxylic acid is recovered, for example, by filtering and drying the residue. This improves the recovery rate and concentration of the dicarboxylic acid. At this time, the dialcohol is recovered, for example, by distilling the filtrate. Meanwhile, the depolymerized polyurethane extracted with the hydrophobic solvent is recovered by distilling off the hydrophobic solvent from the filtrate.

[0027] The pH during acid precipitation is preferably 4 or less, more preferably 3 or less. When the pH during acid precipitation is 4 or less, the dicarboxylic acid is sufficiently precipitated. The acid used for acid precipitation is not particularly limited, but examples thereof include hydrochloric acid, sulfuric acid, and nitric acid. Among these, sulfuric acid is preferred in terms of the precipitation property of the dicarboxylic acid.

[0028] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and the above embodiment may be modified as appropriate within the scope of the spirit of the present invention. EXAMPLES

[0029] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0030] [Resin composition] A resin composition was obtained by mixing 4 g each of polyethylene terephthalate (PET), polyurethane (PU) containing polyether polyol (PO) residues, polypropylene (PP), polyethylene (PE), polyamide 6 (PA6), and cotton.

[0031] [Example 1] As shown in Figure 1, polyester-derived monomers were recovered from the resin composition. First, 50 mL of tetrahydrofuran, 50 mL of methanol, and 2 g of sodium hydroxide were added to the resin composition, and the mixture was stirred at 65 °C for 20 hours to depolymerize PET and PU. Next, the solvent was removed using an evaporator, and 200 mL of water was added to extract the depolymerized PET. Next, the depolymerized PU was extracted into 150 mL of ethyl acetate using a separatory funnel, and this operation was repeated three times to recover the aqueous phase, and then the oil phase was recovered by vacuum filtration. Next, the filtrate was washed with a mixed solvent (20 mL of water / 20 mL of ethyl acetate), and the filtrate was dried overnight at 80 °C to recover a mixture of PP, PE, PA6, and cotton. In addition, a mixed solvent (20 mL of water / 20 mL of ethyl acetate) was added to the filtrate, and the aqueous phase and the oil phase were recovered using a separatory funnel. Here, the aqueous phase contained disodium terephthalate (TPA·2Na) and ethylene glycol (EG), and the oil phase contained PO.

[0032] After adding 100 mL of saturated saline to the oil phase, the oil phase was washed and collected using a separatory funnel. Next, magnesium sulfate and 20 mL of ethyl acetate were added to dry the oil phase, followed by filtration under reduced pressure and washing the magnesium sulfate with 20 mL of ethyl acetate. Next, 20 mL of ethyl acetate was added to the filtrate, and the solvent was removed using an evaporator, followed by drying at 80°C overnight to collect PO.

[0033] On the other hand, a 2N aqueous sulfuric acid solution was added to the aqueous phase until the pH reached 2, and terephthalic acid (TPA) was precipitated, followed by filtration under reduced pressure. The residue was then washed with 20 mL of methanol, and dried overnight at 80°C to recover TPA. As a result, the recovery rate of TPA was 99% by mass, and the recovery concentration of TPA was 98% by mass. The filtrate was distilled using an evaporator, and ethylene glycol (EG) was recovered.

Claims

1. A method for recovering monomers from a resin composition containing a polyester and a polyurethane, comprising the steps of: depolymerizing the polyester and polyurethane contained in the resin composition in the presence of a solvent, an alcohol, and a base capable of swelling the polyester and polyurethane; extracting the depolymerized polyester and the depolymerized polyurethane with a hydrophilic solvent and a hydrophobic solvent; and a step of subjecting the depolymerized polyester extracted with the hydrophilic solvent to acid precipitation.

2. the alcohol is methanol; the solvent capable of swelling the polyester and polyurethane is tetrahydrofuran; 2. The method for recovering monomers according to claim 1, wherein the base is sodium hydroxide.

3. the hydrophilic solvent is water, 3. The method for recovering a monomer according to claim 1, wherein the hydrophobic solvent is ethyl acetate.

4. 3. The method for recovering monomers according to claim 1, wherein the temperature for depolymerizing the polyester and polyurethane is 45° C. or higher and 75° C. or lower.

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