Polymer and method for synthesis thereof

Abstract

A polymer having a structure that includes a repeating unit (I) which is an N,N'-methylene diimine derivative represented by formula (1) or formula (2) and a repeating unit (II) which is a substituted or unsubstituted divalent hydrocarbon group. Polymers in which *1 to *3, *12, and *13 in formulas (1) and (2) each represent bonding positions and R11 in formula (2) is a monovalent aliphatic hydrocarbon group can be produced at low cost and are degradable.

Description

Polymer and method for synthesizing same

[0001] The present invention relates to polymers and methods for their synthesis.

[0002] In today's world where addressing environmental issues has become a top priority, ammonia is once again attracting attention as a next-generation raw material for a carbon-free society. Ammonia does not produce any carbon dioxide when burned (4NH ３ +30 ２ →2N ２ +6H ２ O) For this reason, it can be used as a new energy source to replace fossil fuels, and there are high expectations for its use in fuel, power generation, hydrogen storage, and more.

[0003] Ammonia can also be used as a material for polymers, including plastics. The plastics industry is moving toward a carbon-free society, and ammonia-based plastics have the potential to significantly advance this research. Nitrogen-containing polymers made from ammonia include urea resins, melamine resins, polyacrylonitrile, polyurethanes, polyamides, and polyimides. For example, Patent Document 1 discloses an aromatic polyimine obtained by dissolving an aromatic polyimine oligomer (A) synthesized from an aromatic dialdehyde and a diamine, a ketone resin (B), and an alkoxysilane (C) in a solvent, and then casting and heating the resulting composition onto a suitable substrate. Patent Document 2 also discloses a polyimine used as a curing agent for rubber compositions, in which a hydrocarbon group containing at least two carbon atoms is present between two imine groups.

[0004] As a general trend, polymers containing nitrogen atoms in the main chain generally have higher heat resistance than those composed of hydrocarbons. There are two thought to be factors that increase heat resistance. One is that they contain rigid structures such as amide bonds and imide bonds. The other is that they form network polymers with many cross-linking points due to the reactivity of amines. This rigid structure is also a factor in the mechanical strength and other properties of functional materials.

[0005] In recent years, polymer recycling has also been attracting attention due to environmental concerns. Currently, there are three methods for recycling polymer materials: thermal recycling, in which they are used as fuel for thermal power generation; material recycling, in which they are physically crushed into powder or flakes and then remolded for use; and chemical recycling, in which they are decomposed through chemical reactions and used for further applications. Compared to other processing methods, chemical recycling has the advantages of lower carbon dioxide emissions, lower refining costs, and higher purity after refining, making it the most environmentally friendly processing method.

[0006] JP 11-269380 A JP 2015-528845 A

[0007] As mentioned above, conventional nitrogen-containing polymers have the advantages of high heat resistance and mechanical strength, but they tend to be more expensive than petroleum-derived plastics. One reason for this is that conventional nitrogen-containing polymers cannot be synthesized directly from ammonia, but rather via a nitrogen-containing monomer. Ammonia is first converted into a nitrogen-containing monomer such as an amine, and then the monomer is polymerized to obtain the nitrogen-containing polymer. For this reason, there has been a demand for a nitrogen-containing polymer that can be synthesized directly from ammonia in one step.

[0008] As mentioned above, chemical recycling is an excellent polymer recycling method, but it requires research starting from molecular design and has not yet been put to practical use, with the chemical recycling rate for waste plastics in Japan remaining at 4% as of 2020. Under these circumstances, there has been a demand for nitrogen-containing polymers that are degradable and can be chemically recycled.

[0009] The present invention solves these problems by providing a polymer that can be produced at low cost and has degradability.

[0010] As a result of extensive research into achieving the above object, the inventors have found that the above object can be achieved by the following configuration.

[0011] [1] A polymer having a structure including a repeating unit (I) which is an N,N'-methylenediimine derivative represented by the formula (1) or (2) described below, and a repeating unit (II) which is a substituted or unsubstituted divalent hydrocarbon group, wherein in the formula (1) and the formula (2), *1 to *3, *12, and *13 respectively represent bonding positions, and in the formula (2), R １１ is a monovalent aliphatic hydrocarbon group. [2] The polymer according to [1], wherein the repeating unit (I) is a trivalent group represented by formula (1). [3] The polymer according to [2], wherein the repeating unit (II) is a divalent aliphatic hydrocarbon group. [4] The polymer according to [3], wherein the repeating unit (II) is a divalent linear alkylene group having 4 or more carbon atoms. [5] The structure including the repeating unit (I) and the repeating unit (II) is constituted by a repeating unit represented by (3) described below, and in formula (3), R １ is a divalent aliphatic hydrocarbon group. [6] The polymer according to any one of [2] to [4], wherein the repeating unit (I) is a divalent group represented by formula (2), and the repeating unit (II) is a divalent group containing an aromatic ring. [7] The polymer according to [1], wherein the structure containing the repeating unit (I) and the repeating unit (II) is constituted by a repeating unit (IV) represented by formula (4) below, and in formula (4), R １１ is a monovalent aliphatic hydrocarbon group, and R １２is a divalent group containing an aromatic ring. [8] A method for synthesizing a polymer according to any one of [1] to [7], comprising reacting at least one type of aldehyde with ammonia. [9] The method for synthesizing a polymer according to [8], wherein the repeating unit (I) of the polymer is a trivalent group represented by formula (1), and the at least one type of aldehyde is the repeating unit (II) of the polymer, a dialdehyde in which two aldehyde groups are bonded to a substituted or unsubstituted divalent hydrocarbon group.

[10] The method for synthesizing a polymer according to [8], wherein the repeating unit (I) of the polymer is a divalent group represented by formula (2), and the at least one type of aldehyde is the repeating unit (II) of the polymer, a dialdehyde in which two aldehyde groups are bonded to a substituted or unsubstituted divalent hydrocarbon group, and R in formula (2). １１ The method for synthesizing a polymer according to [8], wherein the polymer contains a monoaldehyde having one aldehyde group bonded to a monovalent aliphatic hydrocarbon group represented by the formula:

[0012] The present invention provides a polymer that can be produced at low cost and is degradable.

[0013] 1 is an IR spectrum of the network polyimine synthesized in Experiment 1. 2 is a diagram showing the results of TG and DTG measurements of the network polyimine synthesized in Experiment 1. 3 is a diagram showing the results of DSC measurements of the network polyimine synthesized in Experiment 1. 4 is a diagram showing the results of DSC measurements of the linear polyimine synthesized in Experiment 2. １ 1 is a diagram showing the results of H-NMR measurement; 2 is an IR spectrum of the linear polyimine synthesized in Experiment 2; 3 is a diagram showing the results of TG and DTG measurement of the linear polyimine synthesized in Experiment 2; 4 is a diagram showing the results of DSC measurement of the linear polyimine synthesized in Experiment 2; 5 is a diagram showing the decomposition reaction formula of the linear polyimine synthesized in Experiment 2; 6 is a diagram showing the results of the decomposition treatment of the linear polyimine of Experiment 2 １ 1 shows the results of H-NMR measurement. 1 shows the IR spectrum of the network polyimine synthesized in Experiment 3. １３1 is a diagram showing the results of C solid-state NMR measurement; FIG. 2 is a diagram showing the results of TG and DTG measurement of the network polyimine synthesized in Experiment 3; FIG. 3 is a diagram showing the results of DSC measurement of the network polyimine synthesized in Experiment 3; FIG. 4 is a diagram showing the results of C solid-state NMR measurement of the network polyimine synthesized in Experiment 3 after decomposition treatment; １ 1 shows the results of H-NMR measurement. 2 shows an image of a molded product of the linear polyimine synthesized in Experiment 4 and its flexibility. １ 1 shows the results of H-NMR measurement. 1 is an IR spectrum of the linear polyimine synthesized in Experiment 4. 2 is a stress-strain curve of the linear polyimine synthesized in Experiment 4. 3 is an image showing the state of a linear polyimine film from Experiment 4 immersed in 0.1 M hydrochloric acid at room temperature. 4 is a comparative image of the linear polyimine from Experiment 4 when immersed in each solvent and after immersion for 4 days.

[0014] The present invention will be described in detail below. The following description of the constituent elements may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0015] In the description of groups (atomic groups) in this specification, when a notation does not specify whether the group is substituted or unsubstituted, it encompasses both unsubstituted and substituted groups, as long as it does not impair the effects of the present invention. For example, the term "alkyl group" encompasses not only alkyl groups without a substituent (unsubstituted alkyl groups) but also alkyl groups with a substituent (substituted alkyl groups). This also applies to each compound.

[0016] [First Embodiment] The polymer of this embodiment has a structure including a repeating unit (I) which is an N,N'-methylenediimine derivative represented by the following formula (1), and a repeating unit (II) which is a substituted or unsubstituted divalent hydrocarbon group: In formula (1), *1 to *3 each represent a bonding position.

[0017] The repeating unit (I) represented by formula (1) is a trivalent group. Therefore, a structure including the repeating unit (I) and the repeating unit (II) is a network structure (three-dimensional network structure), and the polymer of this embodiment is a network polymer (network polyimine). A network polymer is a general term for a polymer in which the polymer chain has a network structure (three-dimensional network structure).

[0018] The repeating unit (I), which is a trivalent group, is a crosslinking point of the network structure. The network polymer of this embodiment has high heat resistance and mechanical strength because the repeating unit (I) contains an imine bond, which is a rigid structure. Furthermore, it is preferable that the repeating unit (I) and the repeating unit (II) are alternately bonded. This ensures solubility, processability, heat resistance, and mechanical strength.

[0019] In the network structure, when repeating units (I) and repeating units (II) are bonded alternately, repeating units (II) are bonded to the bonding positions *1 to *3 in the formula (1) of the repeating unit (I), respectively.

[0020] The repeating unit (II) is not particularly limited as long as it is a substituted or unsubstituted divalent hydrocarbon group. The hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group. The aliphatic hydrocarbon group may be a divalent group that is linear, branched, cyclic, or a combination thereof, and may have, for example, 1 to 18 or 3 to 8 carbon atoms. In one embodiment, it may have 10 to 16 carbon atoms. The aromatic hydrocarbon group may have 5 to 24 or 6 to 12 carbon atoms and may be a group derived from a monocyclic compound or a group derived from a fused ring compound. The repeating unit (II) may also be a divalent group composed of an aliphatic hydrocarbon group and an aromatic hydrocarbon group. Examples of the substituent include a hydroxyl group, an amino group, an alkoxy group (e.g., a methoxy group, an ethoxy group), a cyano group, a halogen atom (e.g., a fluorine atom, a chlorine atom, a bromine atom), and an ionic hydrophilic group (e.g., a carboxylate, a sulfonate).

[0021] A divalent aliphatic hydrocarbon group is preferred as the repeating unit (II). The polymer of this embodiment is degradable as described below. However, if the acidity of the central carbon sandwiched between the two nitrogen atoms in formula (1) increases, intramolecular cyclization may occur, resulting in the formation of an imidazoline ring. It is more advantageous in terms of the degradability of the polymer if intramolecular cyclization does not occur. By bonding an aliphatic hydrocarbon group, which is an electron-donating group, to at least bonding position *1 of the three bonding positions in formula (1), the acidity of the central carbon is reduced, further suppressing intramolecular cyclization, thereby further improving the degradability of the polymer. Furthermore, from the viewpoint of accelerating polymer synthesis, the divalent aliphatic hydrocarbon group is preferably a linear alkylene group having 4 or more carbon atoms or 4 to 8 carbon atoms.

[0022] The network structure of this embodiment may have only one type of group as the repeating unit (II), or may have multiple types of groups. However, from the viewpoint of minimizing the types of raw materials and saving the effort of raw material management, it is preferable that the repeating unit (II) constituting the network structure is of one type. In this case, the same type of repeating unit (II) is bonded to all of the bonding positions *1 to *3 of formula (1) of the repeating unit (I). That is, the network polymer of this embodiment preferably has a network structure constituted by the repeating unit (III) represented by the following formula (3). In formula (3), R １ is a divalent hydrocarbon group, and *31 to *33 each represent a bonding position. Examples of the divalent hydrocarbon group include those described for the repeating unit (II), and preferred embodiments are also the same.

[0023] In a network structure formed by repeating units (III), the bonding position *32 of one repeating unit (III) is bonded to the bonding position *31 of another repeating unit (III). Furthermore, the bonding position *33 of one repeating unit (III) is bonded to the bonding position *31 of yet another repeating unit (III). That is, the network structure formed by repeating units (III) has a structure represented by the following formula (5). In formula (5), * represents a bonding position, and R １ is the same as that explained in equation (3).

[0024] The network structure of this embodiment may be composed of only the repeating units (I) and (II), or may contain other functional groups as long as the effects of this embodiment are achieved. However, it is preferable that the main structural units of the network structure are the repeating units (I) and (II).

[0025] The molecular weight of the network polymer of this embodiment is not particularly limited, but may be, for example, a weight average molecular weight of 1,000 to 1,000,000, or 10,000 to 100,000.

[0026] <Method for Producing Network Polymer> The network polymer of this embodiment can be synthesized by reacting an aldehyde with ammonia. Therefore, unlike conventional nitrogen-containing polymers, the network polymer of this embodiment does not require the use of a nitrogen-containing monomer, significantly reducing production costs and time. In this embodiment, the aldehyde is a dialdehyde, which is a repeating unit (II) in which a substituted or unsubstituted divalent hydrocarbon group is bonded to two aldehyde groups. For example, a reaction solution is prepared by first dissolving the dialdehyde in a solvent and then adding ammonia dissolved in the solvent. The reaction solution is stirred for a predetermined time to allow the reaction to occur, thereby obtaining the product network polymer. Formula (6) illustrating the synthesis of the network polymer is shown below. In Formula (6), R represents the repeating unit (II). As such, the network polymer can be synthesized in a very simple one-batch process using ammonia. The raw material ammonia may be in a gaseous state or dissolved in the reaction solution (solvent). Furthermore, ammonium ions, ammonium salts, etc. may also be used as an ammonia source.

[0027] The reaction conditions (synthesis conditions) and the like are not particularly limited and can be adjusted as appropriate, but may be adjusted to the following ranges from the viewpoint of promoting the reaction. Examples of the solvent for the reaction solution include protic solvents such as water, methanol, ethanol, butanol, pentanol, hexanol, and 2-isopropanol. The concentration of the dialdehyde in the reaction solution may be 10 mM to 1 M (M = mol / L), or 50 mM to 0.5 M, and the ammonia concentration may be 20 mM to 2 M, or 100 mM to 1 M. The reaction temperature may be 25°C to 100°C, and the reaction time may be 1 hour to 12 hours.

[0028] After the synthesis reaction, the synthesized network polymer may be subjected to reprecipitation, filtration, washing, drying, etc. by a general-purpose method, if necessary.

[0029] <Degradability of Network Polymer> The network polymer of this embodiment is degradable. In this specification, degradable refers to the property of being decomposable into monomers or oligomers by a chemical reaction. The degradable network polymer of this embodiment is expected to be chemically recycled. The network polymer of this embodiment is decomposed, for example, by an acidic decomposition solution. When the network polymer of this embodiment is placed under acidic conditions, the reverse reaction of the above-mentioned formula (6) occurs, and the network polymer can be decomposed into the raw material aldehyde (monomer) or its oligomer and ammonia (ammonium ions in the acidic solution). Furthermore, the network polymer of this embodiment preferably exhibits decomposition under strong acid conditions (for example, pH 1 or less). This allows the network polymer to remain stable without decomposing during use in general applications.

[0030] The conditions for the decomposition treatment of the network polymer are not particularly limited and can be adjusted as appropriate, but may be adjusted within the following ranges from the viewpoint of promoting the decomposition reaction. The decomposition liquid preferably contains an inorganic acid (an aqueous solution of an inorganic acid), and examples of the inorganic acid include hydrochloric acid and sulfuric acid. These inorganic acids may be used alone or in combination. The concentration of the inorganic acid may be 0.1N to 1N, or 0.1N to 0.3N. The decomposition liquid may further contain an organic solvent such as methanol, ethanol, acetone, acetonitrile, dioxane, or N,N-dimethylformamide (DMF), and preferably contains acetonitrile from the viewpoint of promoting the decomposition reaction. These organic solvents may be used alone or in combination.

[0031] The network polymer (polyimine) of the present embodiment described above can reduce production costs and time, and has high heat resistance and mechanical strength, as well as being degradable. This makes it possible to expect applications in a variety of fields, such as adhesives, garbage bags, paints, building materials, medical devices, and solid fuels.

[0032] [Second Embodiment] In the first embodiment described above, an N,N'-methylenediimine derivative represented by formula (1) was used as the repeating unit (I). In contrast, in this embodiment (second embodiment), an N,N'-methylenediimine derivative represented by the following formula (2) is used as the repeating unit (I). That is, the polymer of this embodiment has a structure including a repeating unit (I) which is an N,N'-methylenediimine derivative represented by formula (2) and a repeating unit (II) which is a substituted or unsubstituted divalent hydrocarbon group. In formula (2), *12 and *13 each represent a bonding position, and R １１ represents a monovalent aliphatic hydrocarbon group.

[0033] Since the repeating unit (I) represented by formula (2) is a divalent group, the structure including the repeating unit (I) and the repeating unit (II) is linear, and the polymer of this embodiment is a linear polymer (linear polyimine). The polymer of this embodiment is a polyimine containing many imine bonds, which are rigid structures, and therefore has sufficiently high heat resistance and mechanical strength for a linear polymer. Furthermore, since the polymer of this embodiment is a linear polymer, it is soluble in organic solvents and has high moldability, and can be molded into, for example, a film. From the viewpoint of further improving heat resistance and mechanical strength, it is preferable that the repeating unit (I) and the repeating unit (II) are bonded alternately in the linear structure.

[0034] In formula (2), R １１ is not particularly limited as long as it is a monovalent aliphatic hydrocarbon group, and may be a monovalent group that is linear, branched, cyclic, or a combination thereof, and may have, for example, 1 to 18 carbon atoms, or 3 to 8 carbon atoms. On the other hand, when the number of carbon atoms is 10 to 16, thermoforming such as press molding becomes easier, and excellent degradability is also achieved. From the viewpoint of promoting polymer synthesis, R １１ (monovalent aliphatic hydrocarbon group) is preferably a linear alkyl group. １１ is an aliphatic hydrocarbon group which is an electron-donating group, intramolecular cyclization is suppressed, resulting in superior decomposition properties.

[0035] The substituted or unsubstituted divalent hydrocarbon group of the repeating unit (II) may be the same as that described in the first embodiment. Furthermore, in this embodiment, the repeating unit (II) is preferably a divalent group containing an aromatic ring. By including an aromatic ring, which has a rigid structure, the heat resistance and mechanical strength of the polymer are further improved. Examples of divalent groups containing an aromatic ring include the groups shown below. In the groups shown below, * indicates a bonding position.

[0036] The polymer of this embodiment may have only one type of group as the repeating unit (II), or may have multiple types of groups. However, from the viewpoint of minimizing the types of raw materials and saving the effort of raw material management, it is preferable that the repeating unit (II) constituting the linear structure is of one type. In this case, the same type of repeating unit (II) is bonded to the bonding positions *12 and *13 of formula (2) of the repeating unit (I). That is, the polymer of this embodiment preferably has a linear structure constituted by the repeating unit (IV) represented by the following formula (4). In formula (4), R １１ is a monovalent aliphatic hydrocarbon group, and R １２ is a divalent group containing an aromatic ring. １１ Examples of the (monovalent aliphatic hydrocarbon group) include the above-mentioned forms, and the preferred embodiments are also the same. １２ Examples of the divalent group containing an aromatic ring include the forms explained for the repeating unit (II), and preferred embodiments are also the same.

[0037] The linear structure of the polymer of this embodiment may be composed of only the repeating units (I) and (II), or may contain other functional groups as long as the effects of this embodiment are achieved. However, it is preferable that the main structural units of the linear structure are the repeating units (I) and (II).

[0038] The molecular weight of the polymer of this embodiment is not particularly limited, but may be, for example, a weight average molecular weight of 1,000 to 10,000,000, 1,000 to 1,000,000, or 10,000 to 100,000.

[0039] <Method for Producing Polymer> The polymer of this embodiment can be synthesized by reacting an aldehyde with ammonia (or a salt thereof). More specifically, the polymer of this embodiment can be synthesized by reacting a dialdehyde having two aldehyde groups bonded to a substituted or unsubstituted divalent hydrocarbon group, which is a repeating unit (II) constituting the polymer, and R １１The polymer can be synthesized by reacting a monoaldehyde, which is a monovalent aliphatic hydrocarbon group having one aldehyde group bonded to it, with ammonia (or a salt thereof). For example, first, a dialdehyde and a monoaldehyde are dissolved in a solvent, and then ammonia (or a salt thereof) dissolved in the solvent is added to prepare a reaction solution. The reaction solution is stirred for a predetermined time to allow the reaction to proceed, and a polymer is obtained as a product. Formula (7) explaining the synthesis of the polymer is shown below. In formula (7), R １１ is a monovalent aliphatic hydrocarbon group, and R １２ is a divalent group containing an aromatic ring. As described above, the polymer of this embodiment can be synthesized in a very simple one-batch process using ammonia (or a salt thereof), similar to the polymer of the first embodiment. Note that TEA in the following formula is an abbreviation for triethylamine.

[0040] The reaction conditions (synthesis conditions) and the like are not particularly limited and can be adjusted as appropriate, but may be adjusted within the following ranges from the viewpoint of promoting the reaction. Examples of solvents for the reaction solution include N,N-dimethylformamide (DMF), dimethyl sulfoxide, ethyl acetate, butyl acetate, and methyl ethyl ketone. The dialdehyde concentration in the reaction solution may be 10 mM to 1 M (M = mol / L) or 50 mM to 0.5 M, the monoaldehyde concentration may be 10 mM to 1 M (M = mol / L) or 50 mM to 0.5 M, and the ammonia concentration (e.g., the concentration of ammonium acetate as an ammonia source) may be 10 mM to 20 M or 200 mM to 1 M. The reaction temperature may be 25°C to 100°C, and the reaction time may be 1 hour to 12 hours.

[0041] After the synthesis reaction, the synthesized polymer may be subjected to reprecipitation, filtration, washing, drying, etc. by a general method, if necessary.

[0042] <Degradability of Polymer> The polymer of this embodiment is degradable and is expected to be chemically recycled, similar to the polymer of the first embodiment. The conditions for the decomposition treatment of the polymer are not particularly limited and can be adjusted appropriately, but may be adjusted to the same range as in the first embodiment from the viewpoint of promoting the decomposition reaction.

[0043] The polymer (linear polyimine) of this embodiment described above can reduce production costs and production time, and has high heat resistance and mechanical strength, as well as degradability. Furthermore, since the polymer of this embodiment is a linear polymer, it has high formability and can be molded into, for example, a film. This makes it possible to expect applications in a variety of applications, such as adhesives, garbage bags, paints, building materials, medical devices, and solid fuels.

[0044] The present invention will be described in more detail below with reference to examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the examples shown below.

[0045] [Experiment 1] A network polymer (network polyimine) was synthesized by the method described below: In this experiment, the repeating unit (II) of the polymer was a divalent aliphatic hydrocarbon group.

[0046] (1) Synthesis of dialdehyde Before synthesizing the network polymer, the monomer adipaldehyde was synthesized. The reaction formula and synthesis method are shown below.

[0047] Silica gel (105 g, 1.75 mol) was dispersed in methylene chloride (500 mL) and saturated aqueous sodium periodate solution (0.65 M, 105 mL, 68.2 mmol) was added dropwise to obtain a flaky suspension. To this was added a solution of cyclohexane-1,2-diol (6.08 g, 52.3 mmol) in methylene chloride (200 mL), and the mixture was stirred at room temperature for 24 hours. The reaction mixture was filtered through a glass filter and thoroughly washed with methylene chloride. The product was obtained by drying on a rotary evaporator (colorless liquid, yield: 86%). The product was identified by elution with cyclohexane-1,2-diol (6.08 g, 52.3 mmol) in methylene chloride (200 mL). １ H-NMR confirmed that adipaldehyde was produced.

[0048] (2) Synthesis of Network Polyimine The synthesized adipaldehyde (2.28 g, 20 mmol) was dissolved in ethanol (10 mL), concentrated aqueous ammonia (2 mL) was added, and the mixture was heated and stirred at 100°C for 12 hours in a pressure vessel (2.2 atm). The reaction product was filtered, washed with ethanol, and then dried overnight at 100°C, yielding a brown solid product (yield: 58%). The synthetic reaction scheme for network polyimine is shown below.

[0049] <Structural analysis of network polymer> The following structural analysis results confirmed that the reaction described by the above formula occurred and a network polyimine was synthesized in Experiment 1. Note that, since the network polymer synthesized in Experiment 1 had low solubility in organic solvents, an attempt was made to identify the structure by solid analysis.

[0050] The infrared spectroscopy (IR) spectrum of the network polymer was measured using a Fourier transform infrared spectrophotometer (FT / IR6100, manufactured by JASCO Corporation). The measurement was performed using the ATR method. An MCT detector was used, and the IR spectrum was measured from 600 to 4000 cm while being cooled with liquid nitrogen. －１ The analysis was carried out in a measurement range of 1000 m / s. The results are shown in Figure 1. In Figure 1, the vertical axis represents absorbance, and the horizontal axis represents wave numbers (unit: cm －１ ) represents

[0051] As shown in Figure 1, －１ The imine peak (C=N stretching vibration) was observed at 1630 cm －１ ) is generally consistent with the peaks of the primary amine and aldehyde, which is evidence of the formation of polyimine. As the terminals do not show peaks for primary amines or aldehydes, they are thought to exist as imines.

[0052] <Evaluation of degradability of network polymer> The network polymer (10 mg) of Experiment 1 was dissolved in a mixture of hydrochloric acid and acetonitrile (volume ratio, HCl:CH ３ A mixed solvent (decomposition solution: 1.2 mL) of 1,000 toluene, 1,000 nitrite ... １Analysis by H-NMR confirmed that the network polymer was decomposed into oligomers.

[0053] <Evaluation of Thermal Properties of Network Polymer> First, the 5% weight loss temperature T ５％ was calculated. ２ :O ２ Measurements were performed from 20 to 1000°C using a Pt pan at a ratio of 0.05 to 0.1 (Tg = 4:1). The measurement results (Tg and DTG) are shown in Figure 2A. In Figure 2A, the first vertical axis (left side) represents thermogravimetric Tg (unit: %), the second vertical axis (right side) represents thermogravimetric derivative (DTG, unit: μg / sec), and the horizontal axis represents temperature (unit: °C). The 5% weight loss temperature T ５％ The 5% weight loss temperature T was defined as the temperature at which 5% of the weight of the sample before the thermogravimetry was decomposed. ５％ The temperature was 300°C.

[0054] Next, the glass transition temperature was measured by differential scanning calorimetry (DSC) using a differential scanning calorimeter (Shimadzu Corporation, DSC 60 Plus). The measurement range was -50°C to 250°C, the heating rate was 20°C / min, and a two-cycle temperature program was performed under a nitrogen atmosphere. The heat quantity was measured during the heating process of the second cycle. The results are shown in Figure 2B. In Figure 2B, the vertical axis represents heat flow (unit: mW, denoted as DSC in the figure), and the horizontal axis represents temperature (unit: °C). As shown in Figure 2B, no glass transition temperature was observed in the DSC measurement. It is common for network polymers to lack a glass transition temperature (the glass transition temperature is higher than the thermal decomposition temperature), and this is thought to be the case for this system as well. These results confirm that the network polymer of Experiment 1 has high heat resistance.

[0055] Next, the degradability of the sample subjected to the DSC measurement was evaluated. The evaluation method was the same as that described above in <Evaluation of Degradability of Network Polymer>. When the sample after DSC measurement (i.e., the polymer after heating) was treated in a decomposition solution, it showed the same degradability as the sample before DSC measurement (i.e., the polymer before heating). From these results, it was confirmed that the network polymer of Experiment 1 was resistant to changes such as intramolecular cyclization even when heated, and the polymer had excellent degradability.

[0056] [Experiment 2] A linear polymer was synthesized by the method described below.

[0057] (1) Synthesis of dialdehyde Before synthesizing the linear polymer, the monomer 4-methylenebis(4,4'-salicylaldehyde) was synthesized. The reaction formula and synthesis method are shown below.

[0058] s-Trioxane (1.00 g, 11 mmol) was placed in a 50 mL two-neck flask and purged with nitrogen. Salicylaldehyde (8.95 g, 73 mmol), acetic acid (10 g), and sulfuric acid (0.309 g) were added, and the mixture was heated and stirred at 85°C for 22 hours. When the reaction vessel was allowed to cool, a white solid precipitated, which was filtered and then dissolved in methanol. Reprecipitation with water was carried out, and the solid was dried overnight at 105°C (milky white solid, yield: 31%). The product was identified by precipitation in deuterated chloroform. １ H-NMR confirmed that the desired monomer was produced.

[0059] (2) Synthesis of Linear Polyimine The synthesized methylenebis(4,4'-salicylaldehyde) (12.8 g, 50 mmol), butyraldehyde (3.6 g, 50 mmol), and DMF (100 ml) were mixed and dissolved. Ammonium acetate (77 g, 1 mol) and triethylamine (80 ml) were added simultaneously and stirred for 1 hour, resulting in a yellow solution. The solution was diluted with DMF (200 ml) and reprecipitated using methanol. The filtered solid was dried overnight at 100°C to obtain the product (yellow powder, yield: 75%). The reaction formula for the linear polymer synthesis is shown below. The yield of the linear polymer was 75%.

[0060] <Structural Analysis of Linear Polymer, etc.> From the structural analysis results below, it was confirmed that in Experiment 2, the reaction explained by the above formula occurred and linear polyimine was synthesized.

[0061] (1) １ Since the linear polymer synthesized in Experiment 2 was soluble in organic solvents, H-NMR measurement was performed using a Fourier transform nuclear magnetic resonance spectrometer (JNM-AL400S, manufactured by JEOL Ltd.). １ The structure was identified by H-NMR. Measurements were performed at room temperature using a frequency of 400 MHz and deuterated dimethyl sulfoxide (DMSO) as the solvent. Chemical shifts were referenced to tetramethylsilane (0 ppm). The results are shown in Figure 3. In the figure, the vertical axis represents signal intensity, and the horizontal axis represents chemical shift values ​​(unit: ppm). As shown in Figure 3, the NMR spectrum shows roughly correct integral values, confirming the selective synthesis of linear polyimine.

[0062] (2) Infrared Spectroscopic Analysis Infrared spectroscopic analysis of the polymer (linear polyimine) of Experiment 2 was carried out in the same manner as for the polymer (network polyimine) of Experiment 1. The results are shown in Figure 4. In Figure 4, the vertical axis represents absorbance and the horizontal axis represents wavenumber (cm －１ ) The IR spectrum confirmed the C═N stretching vibration derived from methanediamine.

[0063] (3) Molecular Weight Measurement The molecular weight of the polymer in Experiment 2 was measured by gel permeation column chromatography (GPC) using a liquid chromatograph (LC) system (manufactured by JASCO Corporation). The sample was dissolved in tetrahydrofuran (THF) to prepare a concentration of 10 mg / mL. The molecular weight was calculated using polystyrene (PS) as the standard. The measurement results were a number average molecular weight Mn of 3,900, a weight average molecular weight Mw of 16,000, and a polydispersity index (Mw / Mn) of 4.1.

[0064] <Evaluation of Thermal Properties of Linear Polymer> The thermal properties of the polymer (linear polymer) in Experiment 2 were evaluated using the same method as for the polymer (network polyimine) in Experiment 1 described above. TG-DTA measurements were performed using an Al pan from 20 to 500°C. The measurement results (Tg and DTG) are shown in Figure 5A. The vertical and horizontal axes are defined in the same way as in Figure 2A. The 5% weight loss temperature T ５％ The glass transition temperature was 213°C. DSC measurement was performed from -50°C to 150°C at a heating rate of 20°C / min. The results are shown in Figure 5B. The vertical and horizontal axes are defined in the same way as in Figure 2B. No glass transition temperature was confirmed in Figure 5B. These results confirmed that the polymer of Experiment 2 has high heat resistance as a linear polymer.

[0065] <Moldability> It was confirmed that a polymer sheet could be produced by dissolving the polymer of Experiment 2 in chloroform and casting it on a silicon mold. It was also confirmed that the produced sheet had the following degradability.

[0066] <Evaluation of Degradability of Linear Polymer> (1) Quantitative Evaluation of Decomposition Reaction Figure 6A shows the decomposition reaction formula of the linear polyimine synthesized in Experiment 2. It was confirmed that the polymer of Experiment 2 was decomposed into the two raw aldehydes shown in Figure 6A by immersing it in a hydrochloric acid solution. In order to confirm the quantitativeness of this reaction, １ The reaction was followed by H-NMR measurement, and the imine peak of the polymer and the aldehyde peak of the monomer were compared before and after the reaction.

[0067] First, deuterated hydrochloric acid (0.2 mL) and deuterated DMSO (1 mL) were added to the polymer (10 mg) obtained in Experiment 2, and the mixture was stirred at room temperature for 12 hours. １ H-NMR measurement was performed. Ethylene carbonate was used as an internal standard. The results are shown in Figure 6B. In Figure 6B, the vertical axis represents signal intensity, and the horizontal axis represents chemical shift value (unit: ppm). In addition, "m" in the figure means multiplet. １The H-NMR measurement results confirmed that the polymer of Experiment 2 was decomposed into methylenebis(4,4'-salicylaldehyde) (conversion rate: 95%) and butyraldehyde (conversion rate: 93%). Ammonium ions (ammonium chloride) were also produced by the decomposition of the polymer.

[0068] (2) Effect of Composition of Decomposition Liquid The polymer sheets prepared in the above-mentioned <Moldability> evaluation were used as samples, and the samples were immersed in decomposition liquids of various compositions and left at room temperature to evaluate whether the samples were decomposed or not.

[0069] Experiments were conducted using decomposition solutions containing six types of organic solvents (methanol, ethanol, acetone, acetonitrile, dioxane, and DMF). Of these solvents, only DMF dissolved the polymer from Experiment 2, while acetone, dioxane, and DMF dissolved the monomer. Concentrated hydrochloric acid and various organic solvents were mixed to adjust the HCl concentration to three levels: 1.2 M, 0.12 M, and 0.012 M. A total of 18 decomposition solutions were prepared, with six solvents and three hydrochloric acid concentrations. A polymer sheet (18 mg) was submerged in 5 mL of each solution and allowed to stand at room temperature, and the progress was observed.

[0070] In the 0.012M system, except for DMF, in which the polymer dissolves, the sheet shape remained partially intact even after three days, and the reaction did not proceed. In the 1.2M system, the polymer sheet completely dissolved within six hours, and complete or partial decomposition was confirmed. However, in many solvents, the red color deepened with further time, and side reactions occurred. From the above, it was found that decomposition and side reactions proceeded rapidly in the 1.2M system, so care must be taken during processing. In the 0.12M system, decomposition proceeded slowly, and the reaction of deepening the red color was hardly observed. In conclusion, the polymer sheet decomposed under strong acid conditions (e.g., pH 1 or less) even when using an organic solvent. Therefore, in general applications, it does not decompose during use and can remain stable. Furthermore, from the perspective of suppressing side reactions, a hydrochloric acid concentration of 0.12M was effective.

[0071] [Experiment 3] A network polymer (network polyimine) was synthesized by the method described below: In the polymer in this experiment, the repeating unit (II) was a divalent group containing an aromatic ring.

[0072] Terephthalaldehyde (6 mmol) was placed in a Young's tube and purged with nitrogen. After dissolving in ethanol (5 mL), 2 mM ammonia ethanol solution (10 mL) was added and stirred at 60°C for 12 hours, yielding a powder product. This was filtered, washed with ethanol, and dried overnight at 100°C. The yield was 98%. The synthetic reaction scheme for network polyimine is shown below.

[0073] <Structural Analysis of Network Polymer> From the structural analysis results below, it was confirmed that in Experiment 3, the reaction explained by the above formula occurred and a network polyimine was synthesized.

[0074] (1) Infrared Spectroscopic Analysis Infrared spectroscopic analysis of the polymer in Experiment 3 was carried out in the same manner as for the polymer in Experiment 1. The results are shown in Figure 7. In Figure 7, the vertical axis represents absorbance and the horizontal axis represents wavenumber (unit: cm －１ As shown in FIG. 7, the synthesized polymer has a peak at 1630 cm －１ A characteristic C═N stretching vibration peak of methanediamine was observed around this point, suggesting the formation of a polyimine.

[0075] (2) １３ C solid-state NMR measurement of the polymer synthesized in Experiment 3 was performed using a nuclear magnetic resonance spectrometer (JEOL, JNM ECA 500). １３ C solid-state NMR measurements were carried out. The measurement conditions were a frequency of 500 MHz, a MAS (Magic Angle Spinning) rotation speed of 15 kHz, and a contact time of 2 msec, and measurements were carried out using the CP-MAS (Cross Polarization Magic Angle Spinning) method and the DD-MAS (Dipolar Decoupling Magic Angle Spinning) method. The sample was in the form of a powder, and all measurements were carried out at room temperature. The results are shown in Figure 8. In Figure 8, the vertical axis represents signal intensity, and the horizontal axis represents chemical shift values ​​(unit: ppm).

[0076] The NMR spectrum confirmed an aromatic peak at 120-140 ppm and an imine peak at 160-170 ppm. The peak at 76 ppm is thought to be the central carbon peak of methanediamine. The chemical shift of this peak is highly dependent on the substituent on the directly bonded aromatic ring, and is thought to be shifted upfield by the electron-withdrawing imine being attached at the para position.

[0077] <Evaluation of Thermal Properties of Network Polymer> The thermal properties of the polymer in Experiment 3 were evaluated using the same method as for the polymer in Experiment 1. Note that the polymer obtained in Experiment 3 undergoes an intramolecular cyclization reaction when heated, so in this measurement, an imidazoline polymer that had been previously heat-treated was measured. The reaction formula for the intramolecular cyclization reaction is shown below.

[0078] TG-DTA measurements were performed under atmospheric conditions (N ２ :O ２ The temperature range of 20 to 1000°C was measured using a platinum pan at a ratio of 0.05 to 0.1 (Tg = 4:1). The measurement results (Tg and DTG) are shown in Figure 9A. The vertical and horizontal axes in Figure 9A are defined in the same way as in Figure 2A. The 5% weight loss temperature T ５％ The glass transition temperature was 381°C. DSC measurements were performed from -50°C to 300°C at a heating rate of 10°C / min. The results are shown in Figure 9B. The definitions of the vertical and horizontal axes in Figure 9B are the same as in Figure 2B. No glass transition temperature was confirmed from the results in Figure 9B. When compared with the heat resistance temperature of general thermosetting resins, the heat resistance temperature of the polymer in Experiment 3 was equivalent to that of phenolic resin (340-380°C), indicating that it had very good heat resistance.

[0079] <Evaluation of degradability of network polymer> First, 5 mL of N,N-dimethylformamide (DMF) and 1 mL of 1 M hydrochloric acid were added to 25 mg of polymer and stirred. The polymer dissolved in the acidic decomposition solution (a mixture of DMF and HCl) in about 30 minutes, forming a yellow solution. After further leaving it at 70°C for 12 hours, the solution became colorless. The solvent was evaporated by blowing nitrogen, yielding a white solid.

[0080] Next, regarding the obtained white solid, １ H-NMR measurements were performed at room temperature using a frequency of 400 MHz and deuterated dimethyl sulfoxide (DMSO) as the solvent. Chemical shifts were referenced to tetramethylsilane (0 ppm). The results are shown in Figure 10. In Figure 10, the vertical axis represents signal intensity, and the horizontal axis represents chemical shift values ​​(units: ppm).

[0081] As shown in Figure 10, the NMR spectrum showed peaks for the raw material terephthalaldehyde and ammonium ion (ammonium chloride), confirming decomposition into the raw materials. Finally, the solid was washed with water and dried overnight at 100°C to obtain a white solid. The decomposition yield was 92%. The imidazoline polymer after heat treatment was also subjected to a similar decomposition evaluation, but the imidazoline polymer showed no decomposition.

[0082] [Experiment 4] A linear polyimine was synthesized in the same manner as in the above [Experiment 2], except that dodecanal was used instead of butyl aldehyde (butanal). The synthesis was carried out in two steps as in [Experiment 2]. The reaction formula is as follows. As a result of GPC measurement, the number average molecular weight Mn of the obtained linear polyimine in terms of polystyrene was 1.58 × 10 ６ and the weight average molecular weight is 2.58×10 ６ The polydispersity index (PDI) was 1.81. The GPC measurement method was the same as in Experiment 2.

[0083] Step 1

[0084] Step 2

[0085] <Confirmation of press moldability> The moldability of the obtained linear polymer was confirmed. First, the gel-like material obtained as a result of the above synthesis was poured into a polytetrafluoroethylene mold. Then, it was degassed at 100°C for 2 hours, cured in a hot press (120°C, 10 MPa, 10 minutes), and post-cured at 130°C for 2 hours. Figure 11 shows the obtained plate-shaped molded product and an image showing its flexibility. Although it is shown in monochrome (pointillism) in the image, the molded product is uniform, orange, and transparent.

[0086] <Structural Analysis of Linear Polymer, etc.> From the structural analysis results below, it was confirmed that in Experiment 4, the reaction explained by the above formula occurred and linear polyimine was synthesized.

[0087] (1) １ H-NMR measurement: １ The structure of the linear polymer was identified by H-NMR measurement. The results are shown in Figure 12. In the figure, the vertical axis represents signal intensity, and the horizontal axis represents chemical shift value (ppm). The NMR spectrum confirmed the synthesis of a linear polyimine with the desired structure.

[0088] (2) Infrared Spectroscopic Analysis Infrared spectroscopic analysis of the linear polymer of Experiment 4 was carried out in the same manner as in Experiment 2. The results are shown in Figure 13. In the figure, the vertical axis represents absorbance and the horizontal axis represents wave number (cm －１ ) The IR spectrum confirmed the C=N stretching vibration (indicated as "C=N bond stretching oscillation" in the figure). Additionally, the aliphatic stretching vibration (indicated as "Aliphatic stretching vibration" in the figure) thought to be derived from the dodecyl group was also confirmed.

[0089] <Evaluation of Thermal Properties of Linear Polymer> The thermal properties of the linear polymer in Experiment 4 were evaluated using the same method as in Experiment 2. As a result, it was found that the Tmax value of the linear polymer, i.e., the temperature at which weight loss is maximum, is 400°C or higher. This indicates that the linear polymer in Experiment 4 has excellent thermal stability. The results are shown in Table 1 below.

[0090] Similarly, DSC measurement was performed on the linear polyimine synthesized in Experiment 4. The glass transition temperature was found to be 78.1°C. The results are shown in Table 1 below. From the above results, it is presumed that the aliphatic hydrocarbon group of a certain length (dodecyl group in this example) promotes the movement of molecular chains and contributes to the formation of a glass transition point (temperature) in a temperature range suitable for thermoforming.

[0091] <Evaluation of Mechanical Properties of Linear Polymer> The mechanical properties of the linear polymer of Experiment 2 were evaluated. (1) Tensile Test Figure 14 shows the stress-strain curve of the linear polymer of Experiment 2. The test specimen had a width of 10 mm, a length of 6 mm, and a thickness of 0.1 mm, and the tensile speed was 1 mm / min. The test temperature was room temperature. From the results of Figure 14, the tensile strength was 25.4 MPa. This value was higher than that of other polyimines. The inset image shows a broken test specimen.

[0092] (2) Dynamic Viscoelasticity Measurement The test was performed using a tensile vibration method (frequency 1 Hz). The test specimen had a gauge length of 4 mm, a width of 6.3 mm, and a thickness of 0.1 mm, a load of 1.5 N, a displacement of 0.24 mm, and a measurement temperature range of -10 to 200°C. The glass transition temperature (°C) and storage modulus obtained from the test results are shown in Table 1. It was speculated that the high glass transition temperature obtained from the above test was mainly due to the high content of π-conjugated Schiff base structures and the high rigidity resulting from the associated hydrogen bonds. Although not shown, this speculation was also supported by the height of the tan δ peak.

[0093] The following table shows the physical property values ​​of the linear polymer obtained by the above tests in Experiment 4. In the table below, Tg represents the glass transition temperature.

[0094] <Evaluation of Degradability of Linear Polymer> The following formula is the decomposition reaction formula of the linear polyimine synthesized in Experiment 4.

[0095] Figure 15 shows images of the linear polymer film from Experiment 4 immersed in 0.1 M hydrochloric acid at room temperature. The solution was colorless immediately after immersion (left image). Although it is not clear from the image, the linear polymer is actually transparent, ranging from yellow to orange, immediately after immersion. Six hours after immersion (right image), the solution turned light yellow. The linear polymer film disappeared (no longer visible) in the solution. The clumps visible in the image are stirring bars. These results confirm that an imine bond exchange reaction occurred under acidic conditions, leading to decomposition into the starting materials.

[0096] <Solubility and Chemical Resistance Test> Rectangular test pieces (1-5 mg) of the linear polymer synthesized in Experiment 4 were immersed in 2 mL of different solvents (toluene, DMF, acetone, THF, DMSO, water) at room temperature for 4 days. The solid and liquid phases were then separated. The solvent was removed from the surface of the removed test piece, and the remaining mass was measured. The mass change rate D (%) was calculated according to the following formula: D (%) = (1 - W2 / W1) x 100 (Formula) where W1 is the initial mass of the test piece before immersion, and W2 is the mass of the test piece after immersion (after soaking for 4 days in the ambient environment).

[0097] The following table shows the mass change rates of the test pieces before and after immersion in different solvents at room temperature for four days, as obtained from the above test results. Figure 16 also shows comparative images of the test pieces immersed in each solvent at the time of immersion and after four days of immersion. Column (a) shows the image at the time of immersion, and column (b) shows the image after four days of immersion. Initially (at the time of immersion), the test pieces sunk in all solvents, but after four days of immersion, the test pieces immersed in DMF floated in the solvent. All test pieces were transparent, ranging from yellow to orange.

[0098] The polymer of the present embodiment described above can reduce production costs and time and is degradable, which makes it possible to expect it to be used in a variety of applications, such as adhesives, garbage bags, paints, building materials, medical devices, and solid fuels.

Claims

1. A polymer comprising: A repeating unit (I) which is an N,N'-methylenediimine derivative represented by the following formula (1) or formula (2), and a repeating unit (II) which is a substituted or unsubstituted divalent hydrocarbon group, In the formula (1) and the formula (2), *1 to *3, *12, and *13 each represent a bonding position. In the formula (2), R １１ is a monovalent aliphatic hydrocarbon group, 【Chemical 1】 【Chemistry 2】

2. The polymer according to claim 1 , wherein the repeating unit (I) is a trivalent group represented by formula (1).

3. The polymer according to claim 2 , wherein the repeating unit (II) is a divalent aliphatic hydrocarbon group.

4. The polymer according to claim 3 , wherein the repeating unit (II) is a divalent linear alkylene group having 4 or more carbon atoms.

5. The structure including the repeating unit (I) and the repeating unit (II) is constituted by a repeating unit represented by the following formula (3): In the formula (3), R １ The polymer of claim 2 , wherein is a divalent aliphatic hydrocarbon group. 【Chemistry 3】

6. The repeating unit (I) is a divalent group represented by the formula (2), The polymer according to claim 1 , wherein the repeating unit (II) is a divalent group containing an aromatic ring.

7. The structure including the repeating unit (I) and the repeating unit (II) is constituted by a repeating unit (IV) represented by the following formula (4): In the formula (4), R １１ is a monovalent aliphatic hydrocarbon group, and R １２ The polymer according to claim 6 , wherein is a divalent group containing an aromatic ring. 【Chemistry 4】

8. A method for synthesizing the polymer of any one of claims 1 to 7, comprising: A method for synthesizing a polymer comprising reacting at least one aldehyde with ammonia.

9. The repeating unit (I) of the polymer is a trivalent group represented by formula (1), 9. The method for synthesizing a polymer according to claim 8, wherein the at least one aldehyde is the repeating unit (II) of the polymer, that is, a dialdehyde in which two aldehyde groups are bonded to a substituted or unsubstituted divalent hydrocarbon group.

10. The repeating unit (I) of the polymer is a divalent group represented by formula (2), the at least one aldehyde The repeating unit (II) of the polymer is a dialdehyde having two aldehyde groups bonded to a substituted or unsubstituted divalent hydrocarbon group, and In the formula (2), R １１ The method for synthesizing a polymer according to claim 8, wherein the polymer comprises a monoaldehyde having one aldehyde group bonded to a monovalent aliphatic hydrocarbon group represented by the formula:

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