Method for producing polyurea

Abstract

To provide a method for producing polyurea which absorbs carbon dioxide contained in a gas including carbon dioxide, and enables production of polyurea through effective utilization of the absorbed carbon dioxide without separation of it.SOLUTION: A method for producing polyurea according to the present invention comprises: a first step of contacting an amino compound having two or more amino groups in the molecule with a carbon dioxide-containing gas, thereby yielding a carbamic acid compound; and a second step of polymerizing the carbamic acid compound to yield polyurea. In the first step, it is preferable to contact a solution having the amino compound dissolved in a solvent with the carbon dioxide-containing gas.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing polyurea.

Background Art

[0002] In recent years, the greenhouse effect caused by carbon dioxide has been pointed out as one of the causes of global warming, and international measures have become an urgent task in protecting the global environment.

[0003] In particular, since most of the energy required for social activities is obtained from fossil fuels such as coal, oil, and natural gas, the amount of carbon dioxide generated from these fossil fuels is enormous, and reducing carbon dioxide from this energy source is effective in suppressing global warming.

[0004] Therefore, for example, in combustion facilities such as factories and thermal power plants, methods for removing and recovering carbon dioxide in combustion exhaust gas generated and discharged by combustion are being actively studied.

[0005] For example, in Patent Document 1, a method for removing and recovering carbon dioxide in combustion exhaust gas by bringing the combustion exhaust gas into contact with an absorption liquid using an aqueous solution of an amine compound as the absorption liquid, and a method for storing the recovered carbon dioxide without releasing it into the atmosphere are disclosed.

[0006] However, in the method described in Patent Document 1, after carbon dioxide is absorbed by the absorption liquid, it is separated and recovered from the absorption liquid by heating, and the absorption liquid is regenerated, so thermal energy is required, and from the viewpoint of energy saving, it was not always satisfactory.

[0007] Therefore, a method that can effectively utilize carbon dioxide absorbed by the absorption liquid without separating it has been desired.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] An object of the present invention is to provide a method for producing polyurea that can absorb carbon dioxide contained in a gas containing carbon dioxide and effectively utilize the absorbed carbon dioxide without separating it to produce polyurea.

Means for Solving the Problems

[0010] Such an object is achieved by the present invention described in the following (1) to (5). (1) A first step of contacting an amino compound having two or more amino groups in the molecule with a gas containing carbon dioxide to obtain a carbamic acid compound; A second step of polymerizing the carbamic acid compound to obtain polyurea, and a method for producing polyurea, characterized by comprising the steps.

[0011] (2) The method for producing polyurea according to (1) above, wherein in the first step, a solution in which the amino compound is dissolved in a solvent is contacted with the gas containing carbon dioxide.

[0012] (3) The method for producing polyurea according to (2) above, wherein in the first step, at least a part of the carbamic acid compound is precipitated from the solution.

[0013] (4) The method for producing polyurea according to any one of (1) to (3) above, wherein in the second step, the carbamic acid compound is polymerized in a pressure-resistant container.

[0014] (5) The method for producing polyurea according to any one of (1) to (4) above, wherein the gas containing carbon dioxide is exhaust gas from a factory or a thermal power plant.

Effects of the Invention

[0015] According to the present invention, it is possible to provide a method for producing polyurea that can absorb carbon dioxide contained in a gas containing carbon dioxide and effectively utilize the absorbed carbon dioxide to produce polyurea without separating it.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0017] Hereinafter, preferred embodiments of the present invention will be described in detail. [1] Method for producing polyurea The method for producing polyurea of the present invention will be described.

[0018] The method for producing polyurea of the present invention includes a first step of bringing an amino compound having two or more amino groups in the molecule into contact with a gas containing carbon dioxide to obtain a carbamic acid compound, and a second step of polymerizing the carbamic acid compound to obtain polyurea. It is characterized by having.

[0019] According to the method for producing polyurea of the present invention, in the first step, by bringing an amino compound having two or more amino groups in the molecule into contact with a gas containing carbon dioxide, carbon dioxide contained in the gas can be absorbed into the amino compound.

[0020] Specifically, when the amino compound and carbon dioxide react, a carbamic acid compound is formed.

[0021] Further, according to the method for producing polyurea of the present invention, in the second step, polyurea can be obtained by polymerizing the carbamic acid compound.

[0022] Thus, according to the method for producing polyurea of the present invention, by using a gas containing carbon dioxide as a raw material, carbon dioxide contained in the gas is absorbed, and polyurea can be produced by effectively utilizing the absorbed carbon dioxide without separating it.

[0023] Furthermore, according to the method for producing polyurea of the present invention, since the carbon dioxide absorbed by the amino compound is incorporated into the polyurea skeleton, the steps of separating the absorbed carbon dioxide and regenerating the amino compound can be omitted. This can also contribute to the reduction of thermal energy.

[0024] [1-1] First step In the first step, an amino compound having two or more amino groups in the molecule is brought into contact with a gas containing carbon dioxide to obtain a carbamic acid compound.

[0025] [1-1-1] Amino compound The amino compound is not particularly limited as long as it has two or more amino groups in the molecule. Examples include linear diamines having a linear structure, branched diamines having a branched structure, alicyclic diamines, aromatic diamines, ether-containing diamines having an ether bond in the linear chain, diamines having a nitrogen atom in the linear chain, and the like.

[0026] Examples of the linear diamine include 1,6-hexamethylenediamine, ethylenediamine, 1,3-propanediamine, and the like.

[0027] Examples of the branched diamine include 1,2-propanediamine, 2-methylpentamethylenediamine, and the like.

[0028] Examples of the alicyclic diamine include 1,3-cyclohexyldiamine, 1,3-bis(aminomethyl)cyclohexane, hexahydrometaphenylenediamine, isophoronediamine, 4,4'-methylenebis(cyclohexylamine), and the like.

[0029] Examples of the diamine having an aromatic ring include p-xylylenediamine, m-xylylenediamine, and the like.

[0030] Examples of the ether-containing diamine include polyether diamines such as the compound represented by the following formula (3).

[0031]

Chemical formula

[0032] Examples of the diamine having a nitrogen atom in the linear chain include the compound represented by the following formula (4) and the like.

[0033] [Chemical]

[0034] In addition to the diamine described above, a compound having three or more amino groups in the molecule may also be used as the amino compound.

[0035] [1-1-2] Gas containing carbon dioxide The gas containing carbon dioxide is not particularly limited as long as it is a gas component containing carbon dioxide. For example, air, exhaust gas discharged from boilers or gas turbines in factories or thermal power plants, coal gasification gas, synthesis gas, coke oven gas, petroleum gas, natural gas, and other gases contained therein can be mentioned. Among them, the gas containing carbon dioxide is preferably exhaust gas from a factory or a thermal power plant.

[0036] Thereby, carbon dioxide in the exhaust gas from a factory or a thermal power plant can be removed, and the recovered carbon dioxide can be effectively utilized as a raw material for polyurethane. In addition, it can also contribute to the reduction of carbon dioxide released from factories or thermal power plants into the atmosphere.

[0037] When exhaust gas from a factory or a thermal power plant is used as the gas containing carbon dioxide, for example, gas components other than carbon dioxide and fine particles contained in the gas may be removed by passing the exhaust gas through a filter. Thereby, the reaction in the first step can be carried out more suitably.

[0038] The concentration of carbon dioxide contained in the gas containing carbon dioxide is preferably 0.001% by volume or more and 20.0% by volume or less, more preferably 0.5% by volume or more and 15.0% by volume or less, and even more preferably 1.0% by volume or more and 10.0% by volume or less.

[0039] As a result, carbon dioxide contained in the gas and the amino compound can be brought into contact with each other more efficiently, and the reaction to obtain a carbamic acid compound from the amino compound and carbon dioxide can proceed more favorably.

[0040] As described above, in the first step, an amino compound having two or more amino groups in the molecule is brought into contact with a gas containing carbon dioxide to obtain a carbamic acid compound.

[0041] In the first step, examples of the method of bringing an amino compound having two or more amino groups in the molecule into contact with a gas containing carbon dioxide include methods such as gas-liquid contact and gas-solid contact, but the method by gas-liquid contact is preferred.

[0042] As a result, the amino compound and the gas containing carbon dioxide can be brought into contact with each other more efficiently.

[0043] Specific examples of the method by gas-liquid contact include, for example, a method of bringing an amino compound solution in which an amino compound is dissolved in a solvent into contact with a gas containing carbon dioxide, and a method of bringing a liquid-state amino compound obtained by melting it into contact with a gas containing carbon dioxide. Among them, the method of bringing an amino compound solution in which an amino compound is dissolved in a solvent into contact with a gas containing carbon dioxide is preferred.

[0044] As a result, the amino compound and the gas containing carbon dioxide can be brought into contact with each other more efficiently.

[0045] As the solvent, a liquid component that does not react with the amino compound and carbon dioxide can be used. For example, water, alcohol (such as methanol, ethanol, propanol, isopropanol, butanol, tert-butanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, etc.), tetrahydrofuran, dioxane, acetonitrile, N-methyl-2-pyrrolidone, dimethylformamide, dimethyl sulfoxide, benzene, toluene, xylene, pyridine, etc. can be mentioned. These may be used alone or in combination of two or more.

[0046] The concentration of the amino compound in the amino compound solution is preferably 10% by mass or more and 100% by mass or less, more preferably 20% by mass or more and 80% by mass or less, and even more preferably 30% by mass or more and 75% by mass or less.

[0047] Thereby, the amino compound in the amino compound solution and carbon dioxide in the gas can be brought into contact more efficiently, and the reaction to obtain a carbamic acid compound from the amino compound and carbon dioxide can proceed more preferably.

[0048] As a method of bringing an amino compound solution in which an amino compound is dissolved in a solvent into contact with a gas containing carbon dioxide, for example, a method of supplying a gas containing carbon dioxide toward the surface of the amino compound solution, a method of disposing the amino compound solution in a container, and supplying a gas containing carbon dioxide into the space in the container in which the amino compound solution is disposed can be mentioned.

[0049] In this case, the amino compound solution may be stirred, or the gas containing carbon dioxide may be circulated or recycled in the space.

[0050] Thereby, the amino compound solution and the gas containing carbon dioxide can be brought into contact more efficiently, and the reaction to obtain a carbamic acid compound from the amino compound and carbon dioxide can proceed more preferably.

[0051] In the first step, a gas containing carbon dioxide may be blown into the amino compound solution in which the amino compound is dissolved in a solvent to cause bubbling.

[0052] Thereby, the amino compound solution and the gas containing carbon dioxide can be brought into contact more efficiently, and the reaction to obtain a carbamic acid compound from the amino compound and carbon dioxide can proceed more preferably.

[0053] In the first step, the temperature at which the amino compound is brought into contact with the gas containing carbon dioxide is preferably 0°C or higher and 80°C or lower, more preferably 5°C or higher and 60°C or lower, and even more preferably 10°C or higher and 40°C or lower.

[0054] Thereby, the reaction to obtain a carbamic acid compound from the amino compound and carbon dioxide can proceed more preferably.

[0055] In the first step, the pressure (gauge pressure) at which the amino compound is brought into contact with the gas containing carbon dioxide is preferably 0.05 MPa or higher and 5.0 MPa or lower, more preferably 0.05 MPa or higher and 3.0 MPa or lower, and even more preferably 0.1 MPa or higher and 2.0 MPa or lower.

[0056] Thereby, the reaction to obtain a carbamic acid compound from the amino compound and carbon dioxide can proceed more preferably.

[0057] Depending on the combination of the amino compound and the carbamic acid compound to be produced and the solvent, in the first step, at least a part of the produced carbamic acid compound may precipitate from the solution.

[0058] Specifically, for example, as shown in the examples described later, when a solution in which 1,6-hexamethylenediamine as an amino compound is dissolved in ethanol is brought into contact with a gas containing carbon dioxide, as shown in the following formula (1), one amino group of 1,6-hexamethylenediamine reacts with carbon dioxide to form 6-aminohexylcarbamic acid as a carbamic acid compound. Since the solubility of this 6-aminohexylcarbamic acid in ethanol is extremely low, it precipitates as a solid from the solution.

[0059]

Chemical formula

[0060] Thus, in the first step, by precipitating at least a part of the carbamic acid compound from the solution, for example, the precipitated carbamic acid compound can be suitably used as a raw material with few impurities in the second step.

[0061] In the above case, when one of the two amino groups of the amino compound reacts with carbon dioxide, it becomes a monocarboxylic acid compound insoluble in the solvent and precipitates. However, in the precipitated state, it is difficult to contact the monocarboxylic acid compound with carbon dioxide. Therefore, the reaction in which the amino group remaining in the monocarboxylic acid compound reacts with carbon dioxide to form a dicarboxylic acid compound hardly proceeds.

[0062] In addition, since the reaction between the dissolved unreacted amino compound and carbon dioxide preferentially occurs, most of the obtained carbamic acid compounds become monocarboxylic acid compounds in which only one of the two amino groups of the amino compound reacts with carbon dioxide.

[0063] The precipitated carbamic acid compound may be separated by methods such as filtration and centrifugation. And a washing treatment may be performed on the separated carbamic acid compound.

[0064] Thereby, substances other than the carbamic acid compound, such as unreacted amino compounds, etc., can be removed, and the polymerization reaction in the second step can be carried out more preferably.

[0065] Also, when the generated carbamic acid compound is in a dissolved state in the solvent and does not precipitate as a solid, the generated carbamic acid compound may be separated by methods such as extraction, concentration, reprecipitation, centrifugation, filtration, column chromatography, etc.

[0066] In the above description, as a method of bringing an amino compound having two or more amino groups in the molecule into contact with a gas containing carbon dioxide, the case of bringing an amino compound solution in which the amino compound is dissolved in a solvent into contact with a gas containing carbon dioxide has been mainly described, but it is not limited thereto. For example, a solid-state amino compound may be brought into contact with a gas containing carbon dioxide.

[0067] [1-2] Second Step In the second step, the carbamic acid compound obtained in the first step is polymerized to obtain polyurea.

[0068] The polymerization reaction may be carried out in the absence of a solvent (solvent-free) or in the presence of a solvent.

[0069] Examples of the solvent include water, alcohol (e.g., methanol, ethanol, propanol, isopropanol, butanol, tert-butanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, etc.), tetrahydrofuran, dioxane, acetonitrile, N-methyl-2-pyrrolidone, dimethylformamide, dimethyl sulfoxide, benzene, toluene, xylene, pyridine, etc. These may be used alone or in combination of two or more.

[0070] The amount of the solvent used is preferably 1000 parts by mass or less, more preferably 100 parts by mass or more and 500 parts by mass or less, and even more preferably 200 parts by mass or more and 300 parts by mass or less with respect to 100 parts by mass of the carbamic acid compound as the polymerization component. Thereby, the polymerization reaction of the carbamic acid compound can proceed more suitably.

[0071] Note that at least a part of the carbamic acid compound may be in a dissolved state in the solvent, or may be in a dispersed state in the solvent (dispersion medium).

[0072] The polymerization reaction may be carried out in the absence of a catalyst (non-catalytic) or in the presence of a catalyst, but it is preferably carried out in the presence of a catalyst.

[0073] Thereby, the polymerization reaction of the carbamic acid compound can be promoted and the yield of the polyurea can be improved.

[0074] As the catalyst, for example, a basic catalyst can be used. Examples of the basic catalyst include hydroxides of alkali metals or alkaline earth metals such as sodium hydroxide, potassium hydroxide, and calcium hydroxide; carbonates such as sodium carbonate and calcium carbonate; oxides such as lime; sulfites such as sodium sulfite; phosphates such as potassium phosphate and sodium phosphate; and amines such as ammonia, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, hexamethylenetetramine, and pyridine.

[0075] The amount of the catalyst used is preferably 0.005 parts by mass or more and 20 parts by mass or less, more preferably 0.01 parts by mass or more and 15 parts by mass or less, and even more preferably 0.02 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the carbamic acid compound as the polymerization component.

[0076] This enables the polymerization reaction of the carbamic acid compound to be more suitably promoted and the yield of the polyurea to be further improved.

[0077] In the second step, it is preferable to carry out the reaction of polymerizing the carbamic acid compound in a pressure-resistant container.

[0078] Thus, for example, when heated in the second step, even if CO 2 is desorbed from the carbamic acid compound, the desorbed CO 2 will be present in the same system of the pressure-resistant container. Therefore, CO 2 and the compound from which CO 2 has been desorbed from the carbamic acid compound can react again to regenerate the carbamic acid compound, enabling the polymerization reaction to proceed more suitably and increasing the yield of the polyurea.

[0079] In the second step, the reaction time for polymerizing the carbamic acid compound is preferably 0.5 hours or more and 24 hours or less, more preferably 1 hour or more and 12 hours or less, and even more preferably 2 hours or more and 10 hours or less.

[0080] This can suppress the increase in the time required for the production of polyurea while increasing the yield of the polyurea.

[0081] In the second step, the reaction temperature for polymerizing the carbamic acid compound is preferably 0°C or more and 300°C or less, more preferably 50°C or more and 250°C or less, and even more preferably 100°C or more and 200°C or less. This enables the polymerization reaction of the carbamic acid compound to proceed more suitably.

[0082] In the second step, the reaction pressure (gauge pressure) when polymerizing the carbamic acid compound is preferably 0.1 MPa or more and 15.0 MPa or less, more preferably 1.0 MPa or more and 13.0 MPa or less, and even more preferably 5.0 MPa or more and 10.0 MPa or less. Thereby, the polymerization reaction of the carbamic acid compound can proceed more suitably.

[0083] For the polyurea obtained as described above, for example, purification may be performed if necessary.

[0084] As described above, the preferred embodiments of the present invention have been described, but the present invention is not limited thereto.

[0085] For example, the method for producing polyurea of the present invention may have steps other than the above-described steps (for example, a pretreatment step, an intermediate treatment step, a post-treatment step, etc.).

[0086] More specifically, between the first step and the second step, or after the second step, there may be an intermediate treatment step or a post-treatment step in which a chemical reaction other than the above proceeds. Examples of such steps include, for example, when the amino compound has a functional group other than an amino group, a step of converting the functional group of the carbamic acid compound obtained through the first step into another chemical structure, or when the amino compound has a functional group other than an amino group and the functional group is protected by a protecting group, a step of removing the protecting group (deprotection step) from the carbamic acid compound obtained through the first step or the polyurea obtained through the second step.

[0087] Also, for example, in the above description, the case where the carbamic acid compound precipitated from the amino compound solution is separated in the first step has been described, but the method for producing polyurea of the present invention is not limited thereto. For example, the carbamic acid compound precipitated in the first step may not be separated and may be polymerized in the second step while being precipitated (dispersed) in the solution.

[0088] Further, for example, when the carbamic acid compound generated in the first step is dissolved in a solvent, it may be polymerized in the second step while remaining in the dissolved state in the solution.

Examples

[0089] Hereinafter, the present invention will be described in detail based on specific examples, but the present invention is not limited thereto.

[0090] (Example 1) [2] Production of polyurea [2-1] First step 1,6-Hexamethylenediamine as an amino compound was dissolved in ethanol to a concentration of 50% by mass. 50 mL of this amino compound solution was placed in a reaction vessel.

[0091] A test gas was filled in a sealed container at 40 °C under atmospheric pressure, and the reaction vessel containing the amino compound solution was placed and left for 100 minutes.

[0092] As the test gas, a model combustion exhaust gas (equivalent to LNG combustion) at 40 °C having a composition of CO 2 : 3 mol%, O 2 : 16 mol%, N 2 : 81 mol% was used. The CO 2 concentration of the test gas was 30,000 ppm.

[0093] 1,6-Hexamethylenediamine in the solution reacted with carbon dioxide in the test gas to form 6-aminohexylcarbamic acid. At least a part of 6-aminohexylcarbamic acid precipitated as a solid, and the solution became cloudy.

[0094] The precipitated 6-aminohexylcarbamic acid was separated by filtration and washed with ethanol.

[0095] [2-2] Second step To the 6-aminohexyl carbamic acid obtained in the first step, N-methyl-2-pyrrolidone was added as a solvent (dispersion medium), and further, potassium phosphate was added as a catalyst and mixed to obtain a reaction mixture.

[0096] The amount of the solvent used was 150 parts by mass with respect to 100 parts by mass of 6-aminohexyl carbamic acid, and the addition amount of the catalyst was 10 parts by mass with respect to 100 parts by mass of 6-aminohexyl carbamic acid.

[0097] Note that at least a part of the 6-aminohexyl carbamic acid was in a state of being dispersed in N-methyl-2-pyrrolidone.

[0098] The reaction mixture was placed in a pressure-resistant container, heated to 200 °C under atmospheric pressure, and reacted for 7 hours. After the reaction was completed, a white solid was confirmed in the pressure-resistant container. This white solid was scraped off and washed with water.

[0099] (Example 2) As the amino compound solution, a solution obtained by dissolving 1,3-bis(aminomethyl)cyclohexane in ethanol to a concentration of 75% by mass was used, and as the test gas, a mixed gas having a composition of CO 2 : 10 mol%, N 2 : 90 mol% was used. The first step and the second step were carried out in the same manner as in Example 1 above to obtain a white solid.

[0100] In this example, in the first step, 1,3-bis(aminomethyl)cyclohexane in the solution reacted with carbon dioxide in the test gas to produce 3-(aminomethyl)cyclohexylmethyl carbamic acid.

[0101] (Example 3) As the amino compound solution, a solution obtained by dissolving isophoronediamine in ethanol to a concentration of 30% by mass was used, and as the test gas, a mixed gas of CO 2 : 3 mol%, N 2The first and second steps were carried out in the same manner as in Example 1 except that a mixed gas having a composition of 97 mol% was used, and a white solid was obtained.

[0102] In this example, in the first step, isophoronediamine in the solution reacted with carbon dioxide in the test gas to produce 5-amino-1,3,3-trimethylcyclohexylmethylcarbamic acid.

[0103] [3] Evaluation As shown below, for each of the above examples, the absorbability of CO in the first step was evaluated, and evaluations were also made on the carbamic acid compound obtained in the first step and the white solid obtained in the second step. 2

[0104] [3-1] Absorbability of CO 2 In the first step, the concentration of CO contained in the gas in the sealed container was measured using a CO analyzer (total organic carbon analyzer). 2 2 The time change of the CO concentration of the gas in the sealed container in Example 1 is shown in FIG. 1. 2

[0105] As shown in FIG. 1, CO contained in the test gas in the sealed container was removed by being adsorbed by 1,6-hexamethylenediamine in the ethanol solution, and the CO concentration of the gas in the sealed container could be reduced from 30000 ppm to nearly 0 ppm. 2 2

[0106] Also, when the sealed container was filled with air instead of the test gas and adsorbed in the same manner, the CO concentration in the container could be reduced from 400 ppm to nearly 0 ppm. 2 Similar results were obtained for Examples 2 and 3 as well.

[0107] [3-2] IR Spectrum The IR spectra of the carbamic acid compound obtained in the first step and the white solid obtained in the second step were measured using Fourier transform infrared spectroscopy (FT-IR), and it was confirmed that the polymerization reaction was proceeding.

[0108] More specifically, in Example 1, as shown in the following formula (2), it can be said that 6-aminohexylcarbamic acid polymerized to form polyurea. In Example 2, as shown in the following formula (5), it can be said that 3-aminomethylcyclohexylmethylcarbamic acid polymerized to form polyurea. In Example 3, as shown in the following formula (6), it can be said that 5-amino-1,3,3-trimethylcyclohexylmethylcarbamic acid polymerized to form polyurea. In formulas (2), (5), and (6), n is an integer of 2 or more.

[0109]

Chemical formula

[0110]

Chemical formula

[0111]

Chemical formula

[0112] Figure 2 is the IR spectrum of 6-aminohexylcarbamic acid obtained in the first step and the white solid obtained in the second step in Example 1. Figure 3 is the IR spectrum of 3-aminomethylcyclohexylmethylcarbamic acid obtained in the first step and the white solid obtained in the second step in Example 2. Figure 4 is the IR spectrum of 5-amino-1,3,3-trimethylcyclohexylmethylcarbamic acid obtained in the first step and the white solid obtained in the second step in Example 3.

[0113] [3-3] Thermogravimetric measurement Regarding the carbamic acid compound obtained in the first step and the white solid obtained in the second step, using a thermogravimetric analyzer (TG), the temperature was raised from 30 °C to 600 °C at a rate of 10 °C / min under a nitrogen atmosphere, and the weight loss was measured.

[0114] Figure 5 is a diagram showing the thermogravimetric changes of 6-aminohexyl carbamic acid obtained in the first step and the white solid obtained in the second step in Example 1. Figure 6 is a diagram showing the thermogravimetric changes of 3-aminomethylcyclohexylmethyl carbamic acid obtained in the first step and the white solid obtained in the second step in Example 2. Figure 7 is a diagram showing the thermogravimetric changes of 5-amino-1,3,3-trimethylcyclohexylmethyl carbamic acid obtained in the first step and the white solid obtained in the second step in Example 3.

[0115] As shown in Figures 5 to 7, the weight of the monomeric carbamic acid compound decreased rapidly when the temperature exceeded 100 °C, while the white solid showed a tendency of gradually decreasing weight before 100 °C.

[0116] Thus, according to the method for producing polyurea of the present invention, by using a gas containing carbon dioxide as a raw material, carbon dioxide contained in the gas can be recovered, and the recovered carbon dioxide can be effectively utilized to produce polyurea.

[0117] In particular, according to the method for producing polyurea of the present invention, carbon dioxide absorbed by the amino compound can be incorporated and fixed in the polyurea skeleton without separation.

[0118] In addition, in the second step, except that 1,8-diazabicyclo[5.4.0]-7-undecene (DBU) was used instead of potassium phosphate as the catalyst, when treated in the same manner as in Example 1, it was confirmed that polyurea was produced by efficiently absorbing carbon dioxide as in each of the above examples.

[0119] Also, in the second step, while variously changing the heating temperature in the range of 0°C or higher and 300°C or lower and variously changing the reaction time in the range of 0.5 hours or longer and 24 hours or shorter, when the treatment was carried out in the same manner as in Example 1, it was confirmed that, as in each of the above Examples, carbon dioxide was efficiently absorbed and polyurea was produced.

Claims

1. A first step of contacting an amino compound having two or more amino groups in the molecule with a gas containing carbon dioxide to obtain a carbamic acid compound; and a second step of polymerizing the carbamic acid compound to obtain polyurea.

2. 2. The method for producing polyurea according to claim 1, wherein in the first step, a solution in which the amino compound is dissolved in a solvent is contacted with the gas containing carbon dioxide.

3. The method for producing polyurea according to claim 2 , wherein in the first step, at least a part of the carbamic acid compound is precipitated from the solution.

4. The method for producing polyurea according to claim 1 or 2, wherein in the second step, the carbamic acid compound is polymerized in a pressure-resistant vessel.

5. 3. The method for producing polyurea according to claim 1, wherein the gas containing carbon dioxide is exhaust gas from a factory or a thermal power plant.

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