Method for producing polyamide

Abstract

Provided is a method for producing a polyamide that has an exceptional appearance after heating. The method for producing a polyamide includes: a step for heating a composition that contains a diamine represented by formula (1), a dicarboxylic acid, and a solvent; and a step for removing the solvent during and after the composition heating step, or only after the heating step. The method also includes adding a basic compound and / or a base generator to the composition during the composition heating step and / or before the heating step. In formula (1), X is a hetero atom, and n is an integer of 0-5. The portion of the ring including X represents a cyclic structure including X.

Description

Technical Field

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

Background Art

[0002] Problems such as global warming and depletion of oil resources are becoming increasingly serious, and from the perspective of global environmental conservation, the use of biomass plastics has attracted attention. As biomass plastics, polylactic acid, polybutylene succinate, and more recently, bio-polyethylene have been developed. However, these biomass plastics have a melting point of less than 180°C and are inferior in heat resistance. As a method for enhancing the heat resistance of plastics, it is effective to use aromatic monomers or alicyclic monomers, but the types of aromatic monomers and alicyclic monomers derived from biomass are limited. Among them, in recent years, polyamides using 2,5-bis(aminomethyl)tetrahydrofuran obtained from biomass have been studied (Non-Patent Document 1).

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, regarding the properties and improvement of polyamides using 2,5-bis(aminomethyl)tetrahydrofuran as a raw material diamine, it cannot be said that they have been sufficiently studied. In particular, as a result of the studies conducted by the present inventors, it has been found that polyamides using 2,5-bis(aminomethyl)tetrahydrofuran as a raw material diamine may have inferior appearance after heating. An object of the present invention is to solve such problems, and an object thereof is to provide a method for producing a polyamide having excellent appearance after heating.

Means for Solving the Problem

[0005] As a result of investigations by the inventors in view of the above problems, it has been found that the above problems can be solved by allowing a basic compound to be present during the polycondensation reaction of a diamine such as 2,5-bis(aminomethyl)tetrahydrofuran and a dicarboxylic acid. Specifically, the above problems have been solved by the following means. <1> A step of heating a composition containing a diamine represented by formula (1), a dicarboxylic acid, and a solvent, and including a step of removing the solvent during and / or after the heating step of the composition, or after the heating step, and adding a basic compound and / or a base generator to the composition during and / or before the heating step of the composition, a method for producing a polyamide. Formula (1)

Chemical formula

Chemical formula

[0006] The present invention makes it possible to provide a method for producing a polyamide having excellent appearance after heating.

Embodiments for Carrying Out the Invention

[0007] Hereinafter, the content of the present invention will be described in detail. In this specification, "~" is used to mean including the numerical values described before and after it as the lower limit value and the upper limit value. In this specification, measured values, various physical property values, and characteristic values are those at 23°C unless otherwise specified. In this specification, "parts by mass" indicates the relative amount of components, and "mass%" indicates the absolute amount of components. In this specification, the polyamide before solid-phase polymerization may be referred to as a prepolymer and distinguished from the polyamide after solid-phase polymerization. Also, when simply referring to "polyamide", it is intended to include both the prepolymer and the polyamide after solid-phase polymerization.

[0008] The method for producing a polyamide of the present invention (hereinafter, sometimes simply referred to as "the production method of the present invention") includes a step of heating a composition containing a diamine, a dicarboxylic acid, and a solvent represented by formula (1) (hereinafter, sometimes referred to as "monomer composition"), and a step of removing the solvent during and / or after the heating step of the composition, or after the heating step. During and / or before the heating step of the monomer composition, a basic compound and / or a base generator is added to the monomer composition. Formula (1)

Chemical formula

[0009] By adopting such a configuration, a polyamide having excellent appearance after heating can be obtained. More specifically, it becomes possible to keep the degree of yellowing (ΔYI) low. Although this mechanism is not binding, it is presumed to be as follows. That is, the diamine represented by formula (1) contains a cyclic structure containing a heteroatom represented by a tetrahydrofuran ring. In such a cyclic structure containing a heteroatom, it is considered that a proton easily coordinates to the heteroatom. In the present invention, it is presumed that a basic compound traps a proton, suppresses the coordination of the proton to the cyclic structure containing a heteroatom, and at the same time suppresses the protonation of the amino group of the diamine represented by formula (1), thereby retaining the nucleophilicity of the amino group. As a result, it is presumed that amidation proceeds more easily. Furthermore, in the production method of the present invention, by more closely examining the type of basic compound, a polyamide having a high 5% mass loss temperature can be obtained. Hereinafter, the production method of the present invention will be described in detail.

[0010] The production method of the present invention includes a step of heating a composition containing a diamine represented by formula (1), a dicarboxylic acid, and a solvent (hereinafter sometimes referred to as a "monomer composition"), and a step of removing the solvent during and after the heating step of the composition, or after the heating step.

[0011] Formula (1)

Chemical formula

[0012] First, the diamine represented by formula (1) contained in the monomer composition will be described. In the above formula (1), X is a nitrogen atom, an oxygen atom or a sulfur atom, preferably an oxygen atom or a sulfur atom, and more preferably an oxygen atom. In the above formula (1), the ring portion containing X is preferably a heterocyclic ring composed of one heteroatom and 2 to 8 carbon atoms, more preferably a heterocyclic ring composed of one heteroatom and 3 to 5 carbon atoms, and even more preferably a heterocyclic ring composed of one heteroatom and 4 carbon atoms. The heterocyclic ring may be an aromatic ring or a non-aromatic ring, but a non-aromatic ring is preferred. Specific examples of the cyclic structure containing X include a furan ring, a tetrahydrofuran ring, a thiophene ring, and a tetrahydrothiophene ring. A furan ring and a tetrahydrofuran ring are preferred, and a tetrahydrofuran ring is more preferred. In the above formula (1), n is preferably 1 or 2, and more preferably 1, each independently.

[0013] The diamine represented by formula (1) is preferably the diamine represented by formula (2). Formula (2)

Chemical formula

[0014] Furthermore, the diamine represented by formula (1) is preferably 2,5-bis(aminomethyl)tetrahydrofuran. The above monomer composition may contain only one kind of the diamine represented by formula (1), or may contain two or more kinds.

[0015] Also, the above monomer composition may contain a diamine other than the diamine represented by formula (1) within a range not departing from the gist of the present invention. Examples of the diamine other than the diamine represented by formula (1) include aliphatic diamines (including alicyclic diamines) and aromatic diamines.

[0016] Specific examples of the aliphatic diamine can refer to the description in paragraph 0016 of International Publication No. 2016 / 056340, the content of which is incorporated herein. As the aromatic diamine, the description in paragraph 0052 of International Publication No. 2017 / 126409 can be referred to, and the content of which is incorporated herein. In addition, as another diamine, 2,5-bis(aminomethyl)furan is also exemplified. In the present invention, among the diamines contained in the monomer composition, the proportion of the diamine represented by the formula (1) is preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 99% by mass or more, and may be substantially 100% by mass. Substantially 100% by mass means that the diamine other than the diamine contained unintentionally such as impurities is the diamine represented by the formula (1).

[0017] Next, the dicarboxylic acid contained in the monomer composition will be described. The type of the dicarboxylic acid contained in the monomer composition is not particularly defined, and known dicarboxylic acids can be widely used. Aromatic dicarboxylic acids and / or aliphatic dicarboxylic acids are preferred, and aromatic dicarboxylic acids are more preferred.

[0018] Examples of the aliphatic dicarboxylic acid include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, 4,4'-methylenebis(2-methylcyclohexane-1-carboxylic acid), 4,4'-methylenebis(cyclohexane-1-carboxylic acid), decahydro-1,4-naphthalenedicarboxylic acid, 4,4'-oxybis(cyclohexane-1-carboxylic acid) and 4,4'-thiobis(cyclohexane-1-carboxylic acid). Succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid and dodecanedicarboxylic acid are preferred, and glutaric acid, adipic acid and sebacic acid are more preferred.

[0019] Examples of the aromatic dicarboxylic acid include isophthalic acid, terephthalic acid, orthophthalic acid, 1,2-naphthalenedicarboxylic acid, 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 1,7-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid. Isophthalic acid and terephthalic acid are more preferred, and terephthalic acid is even more preferred.

[0020] In particular, in the present invention, it is preferable that the dicarboxylic acid contained in the monomer composition contains at least one selected from phthalic acid, isophthalic acid, terephthalic acid, glutaric acid, adipic acid, and sebacic acid, and terephthalic acid is more preferred. The monomer composition may contain only one kind of dicarboxylic acid or may contain two or more kinds.

[0021] Here, regarding the molar ratio (A / C ratio) of diamine to dicarboxylic acid in the monomer composition used in the present invention, the lower limit thereof is preferably 0.8 < A / C, more preferably 1.0 ≤ A / C, and may be 1.0 < A / C. Further, the upper limit of the A / C ratio is preferably A / C < 1.2. By setting it to be less than the upper limit value, the appearance of the polyamide after heating can be further improved, and the heat resistance (5% mass loss temperature) can be further improved.

[0022] The monomer composition used in the present invention may contain raw material monomers that constitute polyamide other than the above diamine and dicarboxylic acid. Specifically, lactams such as ε-caprolactam, valerolactam, laurolactam, undecalactam, and aminocarboxylic acids such as 11-aminoundecanoic acid and 12-aminododecanoic acid can be exemplified. In the monomer composition used in the present invention, among the raw material monomers that become the constituent units of polyamide (raw material monomers such as diamine, dicarboxylic acid, lactam, aminocarboxylic acid, etc.), the total proportion of diamine and dicarboxylic acid is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, even more preferably 95% by mass or more, still even more preferably 98% by mass or more, and yet even more preferably substantially 100% by mass. Substantially 100% by mass means that all except the raw material monomers unintentionally contained such as impurities are diamine or dicarboxylic acid.

[0023] Next, the solvent contained in the monomer composition will be described. As long as it does not deviate from the gist of the present invention, a known solvent can be adopted. Examples include water, methanol, and ethanol, and water is preferred. The proportion of the solvent in the monomer composition used in the present invention is, for example, 20 to 80% by mass. It is preferable that 90% by mass or more in the solvent is water, and it may be 95% by mass or more, or may be 99% by mass or more. The monomer composition used in the present invention may contain only one kind of solvent or may contain two or more kinds of solvents. When containing two or more kinds, it is preferable that the total amount is within the above range.

[0024] In addition to the above, the monomer composition used in the present invention may contain other components such as additives commonly used in the synthesis of polyamides. Specifically, examples include reaction accelerators other than basic compounds and base generators, antioxidants, catalysts, dyes, pigments, chain limiters, lubricants, flame retardants, light stabilizers, plasticizers, nucleating agents, etc. Further, as other components, sodium acetate, calcium acetate, etc. for gelation or prevention of fish eyes are also exemplified. The total amount of the other components in the monomer composition is preferably 3 parts by mass or less, more preferably 1 part by mass or less, based on 100 parts by mass of the raw material monomers contained in the monomer composition.

[0025] Next, the step of heating the monomer composition and the step of removing the solvent during and after the heating step of the composition, or after the heating step, in the production method of the present invention will be described. In the present invention, by the step of heating the monomer composition, diamine and dicarboxylic acid usually polymerize in a molten state to form a low-molecular polyamide (prepolymer). The step of removing the solvent is carried out during and after the heating step of the composition, or after the heating step, but it is preferably carried out after the heating step. Further, when removing the solvent, it is preferable to remove the condensed water together. The removal of the solvent is carried out by discharging the solvent from the reaction system (for example, the reaction vessel) to the outside of the system. In the production method of the present invention, even when the removal of the solvent is carried out after the heating step, the condensed water may be removed from the heating step. Here, heating means applying heat, and by applying heat, usually the temperature rises, but it also includes the meaning of maintaining a high-temperature state.

[0026] In the step of obtaining the prepolymer of the monomer composition, the heating temperature is preferably such that the maximum heating temperature is 150°C or higher, more preferably 180°C or higher, and even more preferably 190°C or higher. By setting the temperature to be not lower than the lower limit value, the discoloration of the prepolymer can be more effectively suppressed while increasing the degree of polymerization. Further, the heating temperature of the monomer composition is preferably 260°C or lower, more preferably 250°C or lower, even more preferably 230°C or lower, and still more preferably 220°C or lower. By setting the temperature to be not higher than the upper limit value, the discoloration of the prepolymer can be more effectively suppressed. The heating time is preferably 0.5 hours or longer, more preferably 1 hour or longer. Also, the upper limit of the heating time is preferably 4 hours or shorter, more preferably 3 hours or shorter.

[0027] The monomer composition may be pressurized during heating in the step of obtaining the prepolymer. In this case, the pressure is preferably 0.1 MPa or higher. By setting the pressure to be not lower than the lower limit value, the formation of the prepolymer from diamine and dicarboxylic acid can proceed more effectively. Also, the pressure is preferably 5 MPa or lower.

[0028] Next, regarding the addition of a basic compound and / or a base generator (preferably a basic compound) to the monomer composition during and / or before the heating step of the monomer composition (preferably during the heating step of the monomer composition) in the production method of the present invention, an explanation will be given. In the production method of the present invention, it is presumed that by adding a basic compound, amidation proceeds more easily as described above. On the other hand, in the production method of the present invention, a base generator is a compound that generates a basic compound when stimulated by heat or the like. Therefore, even when a base generator is added, a basic compound is generated during heating or the like of the monomer composition, and it is presumed that amidation proceeds more easily as described above.

[0029] The basic compound used in the present invention and the basic compound generated from the base generator (hereinafter sometimes referred to as "basic compound etc.") is not particularly defined, but it is preferably less basic than the diamine represented by formula (1). Specifically, the value obtained by subtracting the pH of the basic compound etc. from the pH of the diamine represented by formula (1) is preferably 0.1 or more, and more preferably 0.2 or more. The upper limit of the value obtained by subtracting the pH of the basic compound etc. from the pH of the diamine represented by formula (1) is preferably 5 or less, more preferably 4 or less, further preferably 3 or less, still more preferably 2 or less, and even more preferably 1 or less. The pH here is the pH of the solution when the basic compound etc. or the diamine represented by formula (1) is dissolved in the solvent contained in the monomer composition at 23 °C to a concentration of 0.55 mmol / solvent 40 g. When two or more diamines represented by formula (1) are used, the pH of these mixtures is taken as the above pH. Further, when two or more basic compounds generated from the basic compound and / or the base generator are used, the pH of the mixture of these basic compounds is taken as the above pH. Since the basic compound etc. is less basic than the diamine represented by formula (1), it is presumed that the salt of the diamine represented by formula (1) and the dicarboxylic acid is preferentially formed, and the basic compound can effectively trap the excess protons. In particular, by setting the upper limit of the difference between the pH of the diamine represented by formula (1) and the pH of the basic compound etc. to 2 or less, ΔYI after heating becomes lower, and further, the 5% mass loss temperature tends to be higher. Also, the basic compound etc. used in the present invention preferably has a pH of 7 to 11. The pH here is the pH of the solution when the basic compound etc. is dissolved in the solvent contained in the monomer composition at 23 °C to a concentration of 0.55 mmol / solvent 40 g. By adopting such a configuration, while maintaining the nucleophilicity of the amino group, the coordination of protons to the furan ring can be more effectively suppressed.

[0030] The basic compound etc. is preferably selected from ammonia, organic amines, salts of ammonia and weak acids, and metal salts of weak acids, more preferably selected from ammonia and metal salts of weak acids, and even more preferably ammonia. Also, by using ammonia, organic amines or salts of ammonia and weak acids (more specifically, ammonia or salts of ammonia and weak acids, particularly ammonia), polyamides with even better heat resistance can be obtained. Specifically, polyamides with a higher 5% mass loss temperature can be obtained. In particular, even at the prepolymer stage, a high 5% mass loss temperature can be achieved.

[0031] The organic amine is preferably selected from trialkylamines, dialkylamines, and monoalkylamines. The carbon number of the alkyl group constituting the alkylamine is preferably 1 to 10, more preferably 1 to 5, and even more preferably 1 to 3 respectively.

[0032] Examples of the weak acid used in the salt of ammonia and weak acid include carbonic acid and acetic acid, and acetic acid is preferred. On the other hand, examples of the weak acid used in the metal salt of weak acid include carbonic acid and acetic acid, and acetic acid is preferred. Also, the metal used in the metal salt of weak acid is preferably an alkali metal or an alkaline earth metal, more preferably an alkali metal, even more preferably lithium, sodium, or potassium, and still more preferably potassium.

[0033] The total amount of the basic compound and / or the base generator is preferably 0.1 mol or more, more preferably 0.3 mol or more, may be 1 mol or more, and may be 5 mol or more, per 100 mol of the dicarboxylic acid contained in the monomer composition. By setting the amount to be not less than the lower limit value, the appearance of the resulting polyamide becomes better, and the degree of polymerization tends to be further improved. On the other hand, the upper limit of the total amount of the basic compound and / or the base generator is preferably 100 mol or less, more preferably 60 mol or less, and even more preferably 15 mol or less, per 100 mol of the dicarboxylic acid contained in the monomer composition. By setting the amount to be not more than the upper limit value, a prepolymer having a higher 5% mass loss temperature tends to be obtained. As for the basic compound and the base generator, only one kind may be used respectively, or two or more kinds may be used. When two or more kinds are used, it is preferable that the total amount is within the above range.

[0034] Here, the preferable physical properties of the above prepolymer will be described. The above prepolymer is a polymer having two or more amide bonds, and its weight average molecular weight is usually 3,000 or more, preferably 5,000 or more, and usually 20,000 or less, more preferably 15,000 or less. The number average molecular weight of the above prepolymer is usually 2,000 or more, preferably 3,000 or more, and usually 10,000 or less, more preferably 8,000 or less.

[0035] The 5% mass loss temperature of the prepolymer is, for example, preferably such that the lower limit is 260°C or higher, more preferably 340°C or higher, even more preferably 350°C or higher, still more preferably 360°C or higher, and even more preferably 380°C or higher. The 5% mass loss temperature of the prepolymer is, for example, preferably such that the upper limit is 410°C or lower, and may be 400°C or lower. Such a high mass loss temperature can be effectively obtained by using ammonia, an organic amine, or a salt of ammonia and a weak acid as the basic compound, etc. In particular, it is effective when ammonia is used as the basic compound, etc. The 5% mass loss temperature of the prepolymer is measured by the method described in the examples below.

[0036] In the method for producing the polyamide of the present invention, the above prepolymer may be used as it is as the polyamide, or may be further heated. When the prepolymer is used as it is as the polyamide, the prepolymer may be purified before use. In the method for producing the polyamide of the present invention, it is preferable to further heat under reduced pressure conditions after the step of heating the monomer composition and removing the solvent. In the present invention, by heating the prepolymer under reduced pressure conditions (preferably under vacuum conditions), additional polymerization proceeds, and a polyamide with a higher molecular weight (the polyamide after solid-phase polymerization) can be obtained.

[0037] The heating temperature of the prepolymer (the heating temperature during solid-phase polymerization) is preferably such that the maximum heating temperature is 220°C or higher, more preferably 230°C or higher, even more preferably 240°C or higher, and even more preferably 245°C or higher. By setting the lower limit value or higher, the late-stage polycondensation (solid-phase polymerization) of the prepolymer tends to proceed more effectively. Also, the heating temperature of the prepolymer is preferably 300°C or lower, more preferably 280°C or lower, even more preferably 270°C or lower, and even more preferably 260°C or lower. By setting the upper limit value or lower, denaturation and discoloration can be more effectively suppressed. The heating time of the prepolymer is preferably 0.25 hours or more, more preferably 0.5 hours or more. Also, the upper limit of the heating time is preferably 5 hours or less, more preferably 3 hours or less.

[0038] Next, the preferred physical properties of the polyamide after solid-phase polymerization obtained by the production method of the present invention will be described. The weight-average molecular weight of the polyamide after solid-phase polymerization obtained by the production method of the present invention is preferably 30,000 or more, more preferably 40,000 or more, may be 50,000 or more, or may be 60,000 or more. Also, the weight-average molecular weight is, for example, 300,000 or less, may be 200,000 or less, or may be 150,000 or less. The number-average molecular weight of the polyamide after solid-phase polymerization obtained by the production method of the present invention is preferably 5,000 or more, more preferably 8,000 or more, further preferably 10,000 or more, may be 11,000 or more, or may be 13,000 or more. Also, the number-average molecular weight is, for example, 50,000 or less, may be 30,000 or less, or may be 20,000 or less. The dispersity (Mw / Mn) of the polyamide after solid-phase polymerization obtained by the production method of the present invention may be 1.5 or more, or may be 2.0 or more. By setting it to be not less than the lower limit value, the mechanical strength of the obtained polyamide tends to be higher. Also, the dispersity (Mw / Mn) of the polyamide after solid-phase polymerization is preferably 10.0 or less, more preferably 8.0 or less, and further preferably 6.0 or less. By setting it to be not more than the upper limit value, since there are few oligomers, the heat resistance is high and the moldability also tends to be good. The weight-average molecular weight and the number-average molecular weight are measured by the methods described in the examples below.

[0039] The 5% mass loss temperature of the polyamide after solid-phase polymerization obtained by the production method of the present invention is preferably 371°C or higher, more preferably 380°C or higher, still more preferably 385°C or higher, and even more preferably 390°C or higher. By setting it to the above lower limit value (especially 390°C or higher), it can be preferably used for applications that require heat resistance. The upper limit of the 5% mass loss temperature of the polyamide after solid-phase polymerization is not particularly defined, but for example, it may be 410°C or lower, or 400°C or lower. The 5% mass loss temperature is measured by the method described in the examples below.

[0040] The yellowness index (ΔYI) of the polyamide after solid-phase polymerization obtained by the production method of the present invention is preferably 30 or less, more preferably 20 or less, still more preferably 15 or less, even more preferably 13 or less, and even more preferably 12 or less. By setting it to the above upper limit value, a molded product with more suppressed coloring can be obtained. The lower limit value of ΔYI of the polyamide after solid-phase polymerization is not particularly defined, but for example, 1 or more is practical, and 5 or more also sufficiently satisfies the required performance. ΔYI is measured by the method described in the examples below.

[0041] The polyamide after solid-phase polymerization obtained by the production method of the present invention preferably satisfies at least one of the above weight-average molecular weight, number-average molecular weight, dispersity, 5% mass loss temperature, and yellowness index (ΔYI), more preferably satisfies two or more of these, and still more preferably satisfies all of them.

[0042] Next, the uses of the polyamide obtained by the production method of the present invention will be described. The polyamide obtained by the production method of the present invention can be used as a resin composition containing polyamide, and further as a molded product formed by molding the resin composition. Details of the resin composition, the method for molding a molded article, the use of the molded article, etc. can be referred to the descriptions in paragraphs 0026 to 0040 of JP-A-2019-026686, the description in paragraph 0039 of JP-A-2018-165298, and the descriptions in paragraphs 0045 to 0048 of JP-A-2018-087319, and these contents are incorporated herein.

Example

[0043] The present invention will be described more specifically with reference to the following examples. The materials, amounts used, ratios, treatment details, treatment procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

[0044] <Synthesis Example of 2,5-Bis(aminomethyl)tetrahydrofuran> Into an autoclave reaction vessel with a capacity of 300 cc, 20.70 g (0.1641 mol) of weighed 2,5-bis(aminomethyl)furan (manufactured by Carbosynth Co., Ltd., FB187031801), 120 mL of tetrahydrofuran, and 8.00 g of an Rh catalyst-containing substance (manufactured by N.E. Chemcat Corporation, 317-160042) were placed. After thoroughly purging with nitrogen, hydrogen was filled up to 6 MPaG. After reacting at 90 °C for 1 hour, the reaction solution was taken out from the reaction vessel and pressure-filtered under an Ar atmosphere. After distilling off the solvent from the product to obtain a crude product, it was purified by distillation under reduced pressure at 1 hPa and 130 °C to obtain 2,5-bis(aminomethyl)tetrahydrofuran. The above Rh catalyst-containing substance is obtained by supporting the powder of the Rh catalyst on carbon, 55% by mass is water, 45% by mass is the Rh catalyst, 5% by mass of this Rh catalyst is Rh, and 40% by mass is carbon. Incidentally, when 2,5-bis(aminomethyl)tetrahydrofuran was dissolved in pure water to a concentration of 0.55 mmol / 40 g of pure water at 23 °C, the pH of the solution was 11.01.

[0045] Example 1 <Synthesis of Polyamide> Into an autoclave reaction vessel with a capacity of 30 cc, 0.712 g (3.08 mmol) of terephthalic acid (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., PTM6633), 0.60 g of pure water, 0.472 g (3.08 mmol) of 2,5-bis(aminomethyl)tetrahydrofuran synthesized above, and 15 μL of 7% by mass aqueous ammonia (prepared from special grade aqueous ammonia (28% by mass ammonia) manufactured by Kishida Chemical Co., Ltd.) were added. After thoroughly purging with nitrogen, the system was heated to 200 °C while stirring. After one and a half hours, the generated water and the charged water were removed from the system, and heating was continued for an additional 30 minutes. After the reaction, the prepolymer was taken out of the reaction vessel and post-polycondensation (solid-phase polymerization) was carried out in a vacuum dryer at 250 °C for 1 hour to obtain polyamide.

[0046] <5% mass loss temperature> For the prepolymer obtained in the above synthesis example and the polyamide after solid-phase polymerization, the 5% mass loss temperature was measured respectively. Specifically, the prepolymer or the polyamide after solid-phase polymerization to be measured was heated from 30 °C to 400 °C at a heating rate of 10.5 °C / min. An aluminum disk was used as a reference. Taking the initial sample mass as 100%, the temperature at which the mass became 95% was defined as the 5% mass loss temperature. The unit was shown in °C. For the measurement, TGDTA7220 manufactured by Hitachi High-Tech Science Corporation was used.

[0047] <Degree of yellowing (ΔYI)> Using hexafluoroisopropanol as a solvent, 42.5 mg of the polyamide after the above solid-phase polymerization was dissolved in 60 mL of the solvent to adjust the concentrations to be the same, and a sample solution was obtained. The yellowness index (YI) of the solvent and the sample solution was determined, and the difference in the yellowness index between the sample solution and the solvent was defined as the degree of yellowing (ΔYI). For the measurement, Spectro Color Meter SE2000 manufactured by Nippon Denshoku Industries Co., Ltd. was used.

[0048] <Measurement of weight-average molecular weight (Mw) and number-average molecular weight (Mn)> The measurement of Mw and Mn of the polyamide after solid-phase polymerization was carried out by gel permeation chromatography. Specifically, 5 mL of 1,1,1,3,3,3-hexafluoroisopropanol was added to 10 mg of the polyamide after solid-phase polymerization to be measured, and the mixture was filtered through a membrane filter (pore size 0.2 μm) to obtain a sample solution. In addition, for the measurement, GPC-104 (using an RI detector) manufactured by Shoko Scientific Co., Ltd. was used. As the column, Shodex GPC LF-404 manufactured by Showa Denko KK was used. If it is difficult to obtain the above-mentioned equipment, etc. due to obsolete model numbers, etc., other equipment having equivalent performance may be used for the gel permeation chromatography apparatus and the column. Eluent: 1,1,1,3,3,3-hexafluoroisopropanol (+10 mmol sodium trifluoroacetate) The measurement conditions are shown below. Flow rate: 0.3 mL / min Column temperature: 40 °C Standard substance: Polymethyl methacrylate Sample concentration: 0.2 mass / volume% Injection volume: 10 μL The dispersity (Mw / Mn) was calculated from the values of Mw and Mn measured above.

[0049] Example 2, Example 3, Example 4, Example 5, Comparative Example 1 In Example 1, the type and amount of the basic compound were changed as shown in Table 1, and the others were carried out in the same manner. Potassium acetate manufactured by Fujifilm Wako Pure Chemical Corporation, 166-03172 was used, and as a powder, it was put into an autoclave reaction vessel together with terephthalic acid, 2,5-bis(aminomethyl)tetrahydrofuran and pure water. The results are shown in Table 1 below.

[0050]

Table 1

Claims

1. A step of heating a composition containing a diamine represented by formula (2), a dicarboxylic acid, and a solvent, and a step of removing the solvent during and after the heating step of the composition, or after the heating step, wherein, during the heating step of the composition, a basic compound and / or a base generator is added to the composition A method for producing a polyamide. Formula (2) 【Chemical 1】 (In formula (2), n is an integer from 0 to 5.)

2. The method for producing a polyamide according to claim 1, wherein the diamine represented by formula (2) contains 2,5-bis(aminomethyl)tetrahydrofuran.

3. The method for producing a polyamide according to claim 1 or 2, wherein the molar ratio of the diamine to the dicarboxylic acid contained in the composition is 0.8 < diamine / dicarboxylic acid < 1.

2.

4. The method for producing a polyamide according to any one of claims 1 to 3, which includes adding the basic compound to the composition.

5. The method for producing a polyamide according to any one of claims 1 to 4, wherein the basic compound and the basic compound generated from the base generator each contain at least one selected from ammonia, organic amines, salts of ammonia and weak acids, and metal salts of weak acids.

6. The method for producing a polyamide according to claim 5, wherein the basic compound and the basic compound generated from the base generator each contain at least one selected from ammonia and metal salts of weak acids.

7. The method for producing a polyamide according to any one of claims 1 to 6, wherein for the basic compound and the basic compound generated from the base generator, when each is dissolved in the solvent contained in the composition to a concentration of 0.55 mmol / 40 g of the solvent at 23°C, the pH of the solution is 7 to 11.

8. The method for producing a polyamide according to any one of claims 1 to 7, wherein the total amount of the basic compound and / or the base generator is 0.1 to 100 mol with respect to 100 mol of the dicarboxylic acid contained in the composition.

9. The method for producing a polyamide according to any one of claims 1 to 8, wherein the dicarboxylic acid contains at least one selected from phthalic acid, isophthalic acid, terephthalic acid, glutaric acid, adipic acid, and sebacic acid.

10. The method for producing a polyamide according to any one of claims 1 to 9, further comprising heating under reduced pressure after the step of removing the solvent. **Claim 11** In the composition, the value obtained by subtracting the pH of the basic compound generated from the basic compound and the base generator from the pH of the diamine represented by the formula (2) is 0.1 or more and 5 or less, and the pH is the solvent contained in the composition, the basic compound, the basic compound generated from the base generator, or the diamine represented by the formula (2), and when dissolved at 23 ° C. to a concentration of 0.55 mmol / solvent 40 g, it is the pH of the solution. The method for producing a polyamide according to any one of claims 1 to 10.

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