Biodegradable polyamide resin, molded body, and laminate

Abstract

This biodegradable polyamide resin contains a structural unit (a) represented by formula (I): −NR−X−CO− (in which at least one of the following is a hetero-free hydrocarbon group or a hetero-containing hydrocarbon group: a first substituent of a divalent hetero-free hydrocarbon group or a second substituent of a divalent hetero-containing hydrocarbon group that constitutes the X; and a third substituent that can constitute the R). When subjected to a biodegradability test with a manometric respirometry, the biodegradable polyimide resin or the like demonstrates that the induction period for maintaining a biodegradation degree of 10 mass% or less is at least 5 days.

Description

Biodegradable polyamide resin, molded body and laminate

[0001] The present invention relates to a biodegradable polyamide resin, a molded article, and a laminate.

[0002] Patent Documents 1 to 3 and Non-Patent Document 1 disclose polyamide resins containing structural units derived from monomers having four carbon atoms as synthetic resin materials.

[0003] Specifically, Patent Document 1 discloses a copolymer of 2-pyrrolidone and ε-caprolactam having a branched structure with two or more branches derived from an initiator. Patent Document 2 discloses nylon 4 fibers using nylon 4 derived from 2-pyrrolidinone with a high molecular weight, specifically a weight-average molecular weight of 564,335 (paragraph

[0053] ). Patent Document 3 discloses a poly[imino(1-oxo-1,4-butanediyl)] polymer containing an [imino(1-oxo-1,4-butanediyl)] structural unit. Non-Patent Document 1 discloses a copolymer of 2-pyrrolidinone and its methyl derivative.

[0004] JP 2013-108098 A JP 2019-137934 A International Publication No. 2022 / 039199

[0005] A. DERATANI et al., “Copolymerization of 2-pyrrolidone and its methyl derivatives Thermal properties used for determination of the copolymer structure”, Chemi. zvesti. , vol. 30, No. 3, p. 292-300 (1976)

[0006] In recent years, there has been a demand for synthetic resins with excellent biodegradability.

[0007] Biodegradability has been investigated in Patent Documents 1 and 3. Patent Document 3 merely investigates whether the inherent biodegradability of polyamide 4 can be maintained. Patent Document 1 merely investigates from the perspective of the branched structure derived from the initiator. On the other hand, Patent Document 2 and Non-Patent Document 1 do not investigate biodegradability at all.

[0008] Therefore, there is still room for further study regarding the biodegradability of polyamide resins. Specifically, it has been found that, due to the excellent biodegradability of polyamide resins, decomposition occurs during storage, and the expected physical properties may not be exhibited under actual usage conditions. If it is possible to extend the period until biodegradation begins while maintaining the final biodegradation rate of polyamide resins, it is expected that the practical use of polyamide resins in various applications will be improved.

[0009] Therefore, the present invention aims to solve the above problems, and its object is to provide a polyamide resin that is biodegradable and has excellent storage stability, as well as a molded article and a laminate that contain the polyamide resin.

[0010] As a result of intensive research aimed at solving the above-mentioned problems, the present inventors have conceived the following invention and found that the above-mentioned problems can be solved. That is, the present invention is as follows: [1] A biodegradable polyamide resin containing a structural unit (a) represented by the following formula (I), which has an induction period of 5 days or more during which the degree of biodegradation is maintained at 10% by mass or less in a biodegradability test using a manometric respirometry method. Formula (I): —NR—X—CO— (In formula (I), X represents a divalent non-heterocyclic hydrocarbon group having 1 to 16 carbon atoms, which may or may not have a first substituent, or a divalent hetero-containing hydrocarbon group having 1 to 16 carbon atoms, which may or may not have a second substituent; R represents a hydrogen atom or a third substituent; and the structural unit (a) has at least one of the first substituent, the second substituent, and the third substituent, and the first substituent, the second substituent, and the third substituent are each independently a monovalent non-heterocyclic hydrocarbon group having 1 to 16 carbon atoms, which may or may not have a fourth substituent, or a monovalent hetero-containing hydrocarbon group having 1 to 16 carbon atoms, which may or may not have a fifth substituent.) [2] The biodegradable polyamide resin according to [1], wherein X in formula (I) is an alkylene group having 4 or less carbon atoms. [3] The structural unit (a) is a compound represented by the formula (I), wherein X is C ２－４ an alkylene group, provided that ２－４ [4] The biodegradable polyamide resin according to [1] or [2], which contains a structural unit (a1) in which at least one hydrogen atom bonded to an alkylene group is substituted with an alkyl group. ３－４ an alkylene group, provided that ３－４The biodegradable polyamide resin according to [1] or [2], which contains a structural unit (a2) in which at least one hydrogen atom bonded to the alkylene group is substituted with a methyl group. [5] The biodegradable polyamide resin according to any one of [1] to [4], which further contains an unbranched [imino(1-oxobutane-1,4-diyl)] structural unit as a structural unit (b) different from the structural unit (a). [6] The polyamide resin according to [5], in which the total content of the structural unit (a) and the structural unit (b) in the polyamide resin is 50 mol % or more. [7] The biodegradable polyamide resin according to any one of [1] to [6], in which the content of the structural unit (a) in the polyamide resin is more than 4 mol %. [8] The biodegradable polyamide resin according to any one of [1] to [7], in which the crystallization rate (1 / (Tm-Tc)) calculated from the melting point (Tm) and the recrystallization temperature (Tc) is 0.030 or more. [9] A molded article comprising the biodegradable polyamide resin according to any one of [1] to [8].

[10] The molded article according to [9], which is one selected from fibers and films.

[11] A laminate comprising at least one layer comprising the biodegradable polyamide resin according to any one of [1] to [8].

[0011] According to the present invention, it is possible to provide a polyamide resin that is biodegradable and has excellent storage stability; and a coating liquid, a molded article, and a laminate that contain the polyamide resin.

[0012] The following describes an example of an embodiment of the present invention (hereinafter, sometimes referred to as "this embodiment"). However, the embodiment described below is an example for embodying the technical idea of ​​the present invention, and the present invention is not limited to the following description. Furthermore, although preferred embodiments are shown in this specification, a combination of two or more of the individual preferred embodiments is also a preferred embodiment. For matters shown as numerical ranges, when there are several numerical ranges, the lower limit and upper limit can be selectively combined to form a preferred embodiment. In this specification, when a numerical range is described as "XX to YY," it means "XX or more and YY or less."

[0013] [Biodegradable Polyamide Resin] The biodegradable polyamide resin according to this embodiment is a biodegradable polyamide resin containing a structural unit (a) having a specific branched chain, and in a biodegradability test using a manometric respirometry method, the induction period during which the biodegradability is maintained at 10% by mass or less is 5 days or more. The biodegradable polyamide is preferably a polyamide resin having a biodegradability (mass%) of 50% by mass or more after 28 days in the biodegradability test described below, and more preferably a polyamide resin having a biodegradability of more than 60% by mass. This allows the polyamide resin according to this embodiment to have excellent storage stability while retaining biodegradability.

[0014] (Structural Unit (a)) The structural unit (a) is represented by the formula (I) described below. As represented by formula (I), the structural unit (a) is a structural unit capable of forming an amide bond and contains at least one branched chain. The structural unit capable of forming an amide bond may be, for example, a structural unit derived from caprolactam, or may be a structural unit that can be generated by the reaction of an amine with a carboxylic acid. The branched chain may be, for example, derived from a substituent previously introduced into the monomer, or may be introduced after the monomer is polymerized. The structural unit (a) may be one type or two or more types, as long as it is represented by formula (I).

[0015] Formula (I): —NR—X—CO— (In formula (I), X represents a divalent non-heterocyclic hydrocarbon group having 1 to 16 carbon atoms which may or may not have a first substituent, or a divalent non-heterocyclic hydrocarbon group having 1 to 16 carbon atoms which may or may not have a second substituent; R represents a hydrogen atom or a third substituent; and the structural unit (a) has at least one of the first substituent, the second substituent, and the third substituent, and the first substituent, the second substituent, and the third substituent are each independently a monovalent non-heterocyclic hydrocarbon group having 1 to 16 carbon atoms which may or may not have a fourth substituent, or a monovalent non-heterocyclic hydrocarbon group having 1 to 16 carbon atoms which may or may not have a fifth substituent.)

[0016] (X in formula (I)) X in the above formula (I) is a divalent linking group, and as described above, is a divalent non-hetero group-containing hydrocarbon group or a divalent hetero group-containing hydrocarbon group. The number of carbon atoms in the divalent non-hetero group-containing hydrocarbon group is the number of carbon atoms in the divalent non-hetero group-containing hydrocarbon group excluding the first substituent. In addition, the number of carbon atoms in the divalent non-hetero group-containing hydrocarbon group does not include the number of carbon atoms in the carbonyl group in formula (I) (i.e., 1). The number of carbon atoms in the divalent hetero group-containing hydrocarbon group is the number of carbon atoms in the divalent hetero group-containing hydrocarbon group excluding the second substituent. In addition, the number of carbon atoms in the divalent hetero group-containing hydrocarbon group does not include the number of carbon atoms in the carbonyl group in formula (I) (i.e., 1).

[0017] (X: Divalent Hetero-free Hydrocarbon Group) The divalent hetero-free hydrocarbon group that can constitute X in formula (I) does not contain bonds such as ether bonds, thioether bonds, imino bonds, amide bonds, and imide bonds (hereinafter, these are also collectively referred to as "divalent hetero-linking groups"). The divalent hetero-free hydrocarbon group may be linear or may contain a cyclic structure. As described above, the divalent hetero-free hydrocarbon group may or may not have a first substituent. In a preferred embodiment, the divalent hetero-free hydrocarbon group has a first substituent. The first substituent will be described later.

[0018] When the divalent non-heterocyclic hydrocarbon group is linear, the number of carbon atoms therein is preferably 1 to 12, more preferably 1 to 6, even more preferably 1 to 4, and even more preferably 1 to 3. Examples of linear divalent non-heterocyclic hydrocarbon groups include a methylene group, an ethylene group, a trimethylene group (n-propylene group), an n-butylene group, and an n-hexylene group. Of these, from the viewpoint of enhancing biodegradability, X in formula (I) is preferably an alkylene group having 4 or less carbon atoms, i.e., a methylene group, an ethylene group, a trimethylene group (n-propylene group), or an n-butylene group. In one embodiment, X in formula (I) is a trimethylene group.

[0019] When the divalent non-heterocyclic hydrocarbon group contains a cyclic structure, the number of carbon atoms therein is preferably 3 to 16, preferably 3 to 12, and more preferably 4 to 6. Examples of the divalent hydrocarbon group containing a cyclic structure include an arylene group, a cycloalkylene group, a hydrocarbon group containing an arylene group, and a hydrocarbon group containing a cycloalkylene group.

[0020] Any hydrogen atom of the divalent non-heterocyclic hydrocarbon group may be substituted with a substituent other than the first substituent. Examples of such a substituent include a halogen atom, an amino group, a hydroxy group, a carboxy group, and an acid anhydride group. However, from the viewpoint of suppressing unintended polymerization reactions, it is preferable that the substituent other than the first substituent is a low-reactivity substituent. From this viewpoint, it is preferable that the substituent other than the first substituent excludes, for example, an amino group, a hydroxy group, a carboxy group, and an acid anhydride group.

[0021] (First Substituent) When the divalent non-heterocyclic hydrocarbon group has a first substituent, as described above, the first substituent is a monovalent non-heterocyclic hydrocarbon group having 1 to 16 carbon atoms, which may or may not have a fourth substituent, or a monovalent non-heterocyclic hydrocarbon group having 1 to 16 carbon atoms, which may or may not have a fifth substituent. When -N-X-CO- in the above formula (I) is used as the main chain, the first substituent constitutes a branched chain (side chain). When the first substituent is a monovalent non-heterocyclic hydrocarbon group, its carbon number is the number of carbon atoms in the portion of the monovalent non-heterocyclic hydrocarbon group excluding the fourth substituent. When the first substituent is a monovalent non-heterocyclic hydrocarbon group, its carbon number is the number of carbon atoms in the portion of the monovalent non-heterocyclic hydrocarbon group excluding the fifth substituent.

[0022] (First Substituent: Monovalent Hetero-free Hydrocarbon Group) The monovalent hetero-free hydrocarbon group that can constitute the first substituent does not contain a divalent hetero linking group. The monovalent hetero-free hydrocarbon group may be linear or may contain a cyclic structure. As described above, the monovalent hetero-free hydrocarbon group may or may not have a fourth substituent. The fourth substituent will be described later.

[0023] When the monovalent non-heterocyclic hydrocarbon group is linear, the number of carbon atoms therein is preferably 1 to 12, more preferably 1 to 6, even more preferably 1 to 4, and still more preferably 1 to 3. Examples of linear monovalent non-heterocyclic hydrocarbon groups include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, and an n-hexyl group. In one embodiment, the monovalent non-heterocyclic hydrocarbon group is a methyl group.

[0024] When the monovalent non-heterocyclic hydrocarbon group contains a cyclic structure, the number of carbon atoms therein is preferably 3 to 16, more preferably 3 to 12, and even more preferably 4 to 6. Examples of the monovalent hydrocarbon group containing a cyclic structure include an aryl group, a cycloalkyl group, a hydrocarbon group containing an arylene group, and a hydrocarbon group containing a cycloalkylene group.

[0025] (Fourth Substituent) When the monovalent non-heterocyclic hydrocarbon group has a fourth substituent, the first example of the fourth substituent is the same as the first substituent. However, it is preferable that the fourth substituent does not include a substituent that the first substituent may have. The second example of the fourth substituent can include a halogen atom, an amino group, a hydroxy group, a carboxy group, and an acid anhydride group. However, from the viewpoint of suppressing unintended polymerization reactions, it is preferable that the second example of the fourth substituent is a substituent with low reactivity. From this viewpoint, it is preferable that, for example, an amino group, a hydroxy group, a carboxy group, and an acid anhydride group are excluded from the second example of the fourth substituent. Therefore, the fourth substituent is preferably one selected from the group consisting of a monovalent non-heterocyclic hydrocarbon group having 1 to 16 carbon atoms, a monovalent heterocyclic hydrocarbon group having 1 to 16 carbon atoms, a halogen atom, an amino group, a hydroxy group, a carboxy group, and an acid anhydride group, and more preferably one selected from the group consisting of a monovalent non-heterocyclic hydrocarbon group having 1 to 16 carbon atoms, a monovalent heterocyclic hydrocarbon group having 1 to 16 carbon atoms, and a halogen atom.

[0026] (First Substituent: Monovalent Heterocyclic-Containing Hydrocarbon Group) The monovalent heterocyclic-containing hydrocarbon group that can constitute the first substituent is a monovalent hydrocarbon group containing the heterolinking group described above. The heterolinking group is not limited to the examples described above. The monovalent heterocyclic-containing hydrocarbon group preferably has at least one heterolinking group selected from an ether bond, a thioether bond, an imino bond, an amide bond, and an imide bond. The heterolinking group is usually interposed between carbon-carbon bonds, but may also be interposed between carbon-oxygen bonds, carbon-nitrogen bonds, or carbon-sulfur bonds. Preferably, the heterolinking group is interposed between carbon-carbon bonds. The monovalent heterocyclic-containing hydrocarbon group may be linear or may contain a cyclic structure. The carbon number and examples when the monovalent heterocyclic-containing hydrocarbon group is linear, and the carbon number and examples when the monovalent heterocyclic-containing hydrocarbon group contains a cyclic structure are the same as those described for the monovalent non-heterocyclic hydrocarbon group. As described above, the monovalent hetero-containing hydrocarbon group may or may not have a fifth substituent. The fifth substituent is the same as the fourth substituent. However, it is preferable that the fifth substituent does not include a substituent that the first substituent may have.

[0027] (X: Divalent Heterocyclic-Containing Hydrocarbon Group) The divalent heterocyclic-containing hydrocarbon group that can constitute X in formula (I) is a divalent hydrocarbon group containing the heterolinking group described above. The heterolinking group is not limited to the examples described above. The divalent heterocyclic-containing hydrocarbon group preferably has at least one heterolinking group selected from an ether bond, a thioether bond, an imino bond, an amide bond, and an imide bond. The heterolinking group is usually interposed between carbon-carbon bonds, but may also be interposed between carbon-oxygen bonds, carbon-nitrogen bonds, or carbon-sulfur bonds. Preferably, the heterolinking group is interposed between carbon-carbon bonds. The divalent heterocyclic-containing hydrocarbon group may be linear or may contain a cyclic structure. The carbon number and examples when the divalent heterocyclic-containing hydrocarbon group is linear, and the carbon number and examples when the divalent heterocyclic-containing hydrocarbon group contains a cyclic structure are the same as those described for the divalent non-heterocyclic hydrocarbon group. As described above, the divalent hetero-containing hydrocarbon group may or may not have a second substituent. The second substituent is the same as the first substituent. When -N-X-CO- in the above formula (I) is used as the main chain, the second substituent constitutes a branched chain (side chain).

[0028] (R in formula (I)) When R in formula (I) is a third substituent, the third substituent is the same as the first substituent. The third substituent may or may not have a substituent that the first substituent can have. When -N-X-CO- in formula (I) above is used as the main chain, the third substituent constitutes a branched chain (side chain).

[0029] As described above, the structural unit (a) has at least one of the first substituent, the second substituent, and the third substituent. That is, in the above formula (I), X is a divalent non-heterocyclic hydrocarbon group of 1 to 16 carbon atoms having a first substituent, or a divalent non-heterocyclic hydrocarbon group of 1 to 16 carbon atoms having a second substituent, and R is a hydrogen atom, or X is a divalent non-heterocyclic hydrocarbon group of 1 to 16 carbon atoms having no first substituent, or a divalent non-heterocyclic hydrocarbon group of 1 to 16 carbon atoms having no second substituent, and R is a third substituent, or X is a divalent non-heterocyclic hydrocarbon group of 1 to 16 carbon atoms having a first substituent, or a divalent non-heterocyclic hydrocarbon group of 1 to 16 carbon atoms having a second substituent, and R is a third substituent. Thus, when -N-X-CO- in the above formula (I) is the main chain, the structural unit (a) has at least one branched chain. Preferably, X is a divalent non-heterocyclic hydrocarbon group having 1 to 16 carbon atoms and having a first substituent, or a divalent non-heterocyclic hydrocarbon group having 1 to 16 carbon atoms and having a second substituent, and R is a hydrogen atom. More preferably, X is a divalent non-heterocyclic hydrocarbon group having 1 to 16 carbon atoms and having a first substituent, and R is a hydrogen atom.

[0030] In one aspect of this embodiment, the structural unit (a) is a compound represented by the formula (I) wherein X is C ２－４ an alkylene group, provided that ２－４ In another aspect of this embodiment, the structural unit (a) includes a structural unit (a1) in which at least one hydrogen atom bonded to an alkylene group is substituted with an alkyl group. That is, in the structural unit (a1), the first substituent is an alkyl group. In another aspect of this embodiment, the structural unit (a) is a structural unit represented by the formula (I), wherein X is C ３－４ an alkylene group, provided that ３－４The structural unit (a2) includes a structural unit in which at least one hydrogen atom bonded to the alkylene group is substituted with a methyl group. That is, in the structural unit (a2), the first substituent is a methyl group. In a preferred aspect of this embodiment, the structural unit (a) is a structural unit derived from 3-methyl-2-pyrrolidone or 4-methyl-2-pyrrolidone. In another preferred aspect of this embodiment, the structural unit (a) is a structural unit derived from 3-methyl-2-piperidone or 4-methyl-2-piperidone. The structural unit (a) may be any of the following: C ２－４ Alkylene group, more preferably C ３－４ By employing a structural unit containing an alkylene group as a branched chain, the biodegradable polyamide resin according to this embodiment can have higher biodegradability than when a structural unit not containing a branched chain is employed.

[0031] (Structural Unit (b)) The biodegradable polyamide resin according to this embodiment may further contain an unbranched imino(1-oxo-1,4-butanediyl) structural unit as a structural unit (b) different from the structural unit (a). The structural unit (b) is, for example, a structural unit derived from 2-pyrrolidone. By including the structural unit (b) in the biodegradable polyamide resin, it is possible to provide a polyamide resin that ensures a certain degree of biodegradability.

[0032] At least one of the hydrogen atoms bonded to the hydrocarbon group constituting the structural unit (b) may be a substituent. Examples of such a substituent include a halogen atom. However, from the viewpoint of suppressing unintended polymerization reactions, such a substituent is preferably a low-reactivity substituent. From this viewpoint, it is preferable that the substituent excludes, for example, an amino group, a hydroxy group, a carboxy group, and an acid anhydride group.

[0033] From the viewpoint of further improving the mechanical properties of the biodegradable polyamide resin, in one aspect of this embodiment, the content of the structural unit (b) in the biodegradable polyamide resin is 50 mol% or more, preferably 55 mol% or more, more preferably 60 mol% or more, even more preferably 65 mol% or more, and even more preferably 70 mol% or more, and in some cases may be 78 mol% or more or 80 mol% or more. The upper limit of the content of the structural unit (b) in the polyamide resin is determined naturally depending on the content of the structural unit (a) and other structural units, but may be, for example, 99 mol% or less, 98 mol% or less, 97 mol% or less, 96 mol% or less, less than 96 mol%, 95 mol% or less, 94 mol% or less, 93 mol% or less, 92 mol% or less, or 91 mol% or less, and in some cases may be 90 mol% or less, 89 mol% or less, 88 mol% or less, or 87 mol% or less.

[0034] (Other structural units (c)) The biodegradable polyamide resin according to this embodiment may contain a structural unit (c) different from the structural unit (a) and the structural unit (b). The structural unit (c) is preferably a structural unit derived from a monomer capable of reacting with a monomer capable of constituting the structural unit (a) or the structural unit (b). The structural unit (c) may be one type or two or more types. In one aspect, the biodegradable polyamide resin does not contain the structural unit (c). In another aspect, the biodegradable polyamide resin contains the structural unit (c).

[0035] An example of the structural unit (c) is the structural unit (c-1) represented by the following formula (II): Formula (II): —NR ｃ -X ｃ -CO- (in formula (II), X ｃ is a divalent hydrocarbon group having 1 to 16 carbon atoms and no hetero group, which may or may not have a sixth substituent, or a divalent hydrocarbon group having 1 to 16 carbon atoms and no hetero group, which may or may not have a seventh substituent, R ｃ is a hydrogen atom, an acyl group, a hydroxyalkyl group, or an alkoxyalkyl group.

[0036] (X in formula (II) ｃ ) X in the above formula (II)ｃ is a divalent linking group, and as described above, is a divalent non-hetero group-containing hydrocarbon group or a divalent hetero group-containing hydrocarbon group. The number of carbon atoms in the divalent non-hetero group-containing hydrocarbon group is the number of carbon atoms in the divalent non-hetero group-containing hydrocarbon group excluding the sixth substituent. The number of carbon atoms in the divalent non-hetero group-containing hydrocarbon group does not include the number of carbon atoms in the carbonyl group in formula (II) (i.e., 1). The number of carbon atoms in the divalent hetero group-containing hydrocarbon group is the number of carbon atoms in the divalent hetero group-containing hydrocarbon group excluding the seventh substituent. The number of carbon atoms in the divalent hetero group-containing hydrocarbon group does not include the number of carbon atoms in the carbonyl group in formula (II) (i.e., 1).

[0037] X in the above formula (II) ｃ is the same as X in the above formula (I). Preferably, X ｃ The number of carbon atoms of the divalent non-hetero hydrocarbon group or divalent hetero-containing hydrocarbon group constituting X is preferably larger than the number of carbon atoms of the divalent non-hetero hydrocarbon group or divalent hetero-containing hydrocarbon group constituting X. This allows the polyamide resin to be endowed with properties different from those of the structural unit (a). The sixth substituent is the same as the first substituent described above, or is a halogen atom, an amino group, a hydroxy group, a carboxy group, or an acid anhydride group. The seventh substituent is the same as the second substituent described above, or is a halogen atom, an amino group, a hydroxy group, a carboxy group, or an acid anhydride group. However, it is preferable that monovalent non-hetero hydrocarbon groups and monovalent hetero-containing hydrocarbon groups are excluded from the sixth substituent. It is preferable that monovalent non-hetero hydrocarbon groups and monovalent hetero-containing hydrocarbon groups are excluded from the seventh substituent. That is, X ｃ is preferably a divalent non-heterocyclic hydrocarbon group having no sixth substituent or a divalent non-heterocyclic hydrocarbon group having no seventh substituent. The sixth and seventh substituents are preferably halogen atoms.

[0038] In the above formula (II), R ｃ When R is an acyl group, the number of carbon atoms therein is preferably 1 to 6, more preferably 1 to 4. In one aspect of this embodiment, R ｃ is an acetyl group. ｃThe structural unit in which is an acetyl group can be obtained, for example, by reacting the produced biodegradable polyamide resin with acetic anhydride or the like.

[0039] In the above formula (II), R ｃ When R is a hydroxyalkyl group, it preferably has 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms. ｃ is a methylol group. ｃ The structural unit in which is a methylol group can be obtained, for example, by reacting the produced biodegradable polyamide resin with formaldehyde.

[0040] In the above formula (II), R ｃ When R is an alkoxyalkyl group, the number of carbon atoms therein is preferably 2 to 6, more preferably 2 to 4. Here, the number of carbon atoms in the alkoxyalkyl group is the total number of carbon atoms in the alkoxy group and the alkyl group. In one aspect of this embodiment, R ｃ is a methoxymethyl group. In the structural unit (c-1), R ｃ The structural unit in which is a methoxymethyl group can be obtained, for example, by reacting the produced biodegradable polyamide resin with chloromethyl methyl ether.

[0041] The content of the structural unit (c) in the biodegradable polyamide resin can be appropriately set depending on the content of other structural units, as long as it does not excessively impair the intended effects of the present invention. In one aspect of this embodiment, the content (mol%) of the structural unit (c) in the biodegradable polyamide resin is greater than the content of the structural unit (a). In another aspect of this embodiment, the content (mol%) of the structural unit (c) in the biodegradable polyamide resin is greater than the total content of the structural unit (a) and the structural unit (b). In yet another aspect of this embodiment, the content (mol%) of the structural unit (c) in the biodegradable polyamide resin is less than the content of the structural unit (a) or less than the total content of the structural unit (a) and the structural unit (b). In a particular aspect of this embodiment, the biodegradable polyamide resin does not contain the structural unit (c).

[0042] [Physical properties of biodegradable polyamide resin]

[0043] (Content Ratio) In the present embodiment, when the biodegradable polyamide resin contains both the structural unit (a) and the structural unit (b), from the viewpoint of improving storage stability while maintaining biodegradability, the molar ratio of the structural unit (a) to the structural unit (b) is preferably more than 4 / less than 96 to 35 / 65, more preferably 5 / 95 to 35 / 65, even more preferably 7 / 93 to 35 / 65, still more preferably 9 / 91 to 35 / 65, and in some cases may be 10 / 90 to 35 / 65.

[0044] In the present embodiment, when the biodegradable polyamide resin contains both the structural unit (a) and the structural unit (c), from the viewpoint of improving storage stability while maintaining biodegradability, the molar ratio of the structural unit (a) to the structural unit (c) is preferably 10 / 90 to 95 / 5, more preferably 15 / 85 to 95 / 5, even more preferably 20 / 80 to 95 / 5, and still more preferably 25 / 75 to 95 / 5.

[0045] In the present embodiment, when the biodegradable polyamide resin contains the structural unit (a), the structural unit (b), and the structural unit (c), from the viewpoint of improving storage stability while maintaining biodegradability, the molar ratio of the structural unit (a):the structural unit (b):the structural unit (c) is preferably 5 / 65 / 30 to 35 / 64 / 1, more preferably 5 / 70 / 25 to 5 / 69 / 1, even more preferably 7 / 75 / 23 to 30 / 69 / 1, and still more preferably 10 / 75 / 15 to 30 / 69 / 1.

[0046] In this embodiment, when the biodegradable polyamide resin contains both the structural unit (a) and the structural unit (b), from the viewpoint of improving storage stability while maintaining biodegradability, the total content of the structural unit (a) and the structural unit (b) in the biodegradable polyamide resin is preferably 50 mol% or more, more preferably 60 mol% or more, even more preferably 70 mol% or more, and still more preferably 80 mol% or more.

[0047] In this embodiment, from the viewpoint of enhancing biodegradability, the content of the structural unit (a) in the biodegradable polyamide resin is preferably more than 4 mol%, more preferably 5 mol% or more, even more preferably 8 mol% or more, still more preferably 9 mol% or more, and particularly preferably 10 mol% or more. From the viewpoint of enhancing biodegradability and storage stability, the content may be 12 mol% or more, 15 mol% or more, or 18 mol% or more.

[0048] (Molecular Weight) From the viewpoint of excellent mechanical strength, the weight average molecular weight (Mw) of the biodegradable polyamide resin according to this embodiment is preferably 10,000 or more, more preferably 20,000 or more, even more preferably 25,000 or more, and still more preferably 30,000 or more. From the viewpoint of improving biodegradability, the weight average molecular weight (Mw) is preferably 250,000 or less, more preferably 200,000 or less, even more preferably 150,000 or less, and still more preferably 130,000 or less.

[0049] From the viewpoint of excellent mechanical strength, the number average molecular weight (Mn) of the biodegradable polyamide resin according to this embodiment is preferably 5,000 or more, more preferably 10,000 or more, even more preferably 15,000 or more, and in some cases may be 20,000 or more. From the viewpoint of improving biodegradability, the number average molecular weight (Mn) is preferably 150,000 or less, more preferably 100,000 or less, even more preferably 50,000 or less, and still more preferably 40,000 or less.

[0050] From the viewpoint of more reliably achieving the intended effects of the present invention, the molecular weight distribution (Mw / Mn) of the biodegradable polyamide resin according to this embodiment is preferably 15.0 or less, more preferably 10.0 or less, even more preferably 8.0 or less, and still more preferably 5.0 or less. The Mw / Mn of the polyamide resin is usually 1.0 or more.

[0051] The number average molecular weight and weight average molecular weight can be measured by gel permeation chromatography (GPC), more specifically, by the method described in the Examples section below.

[0052] [Practicality] (Biodegradability) In the biodegradability test described above, the biodegradable polyamide resin according to this embodiment has a biodegradability of preferably 50% by mass or more, more preferably 51% by mass or more, even more preferably 55% by mass or more, and still more preferably more than 60% by mass after 28 days. This makes it possible to provide a polyamide resin with excellent biodegradability.

[0053] (Storage Stability) Furthermore, as described above, in a biodegradability test using the manometric respirometry method, the biodegradable polyamide resin according to this embodiment has an induction period of 5 days or more during which the biodegradability is maintained at 10% by mass or less. Such an induction period is preferably 7 days or more, and more preferably 10 days or more. Specifically, the biodegradability test using the manometric respirometry method can be the biodegradation test described in the Examples section below. Such an induction period of 5 days or more can provide a polyamide resin with excellent storage stability. Therefore, according to this embodiment, a biodegradable polyamide resin that has both biodegradability and excellent storage stability can be provided. Such a biodegradable polyamide resin can be said to be highly practical in situations where storage stability is required.

[0054] [Thermal Properties] (Melting Point (Tm)) From the viewpoint of heat resistance, the melting point (Tm) of the biodegradable polyamide resin according to this embodiment is preferably 200°C or higher, more preferably 210°C or higher, even more preferably 220°C or higher, and even more preferably 225°C or higher. There is no particular upper limit to the melting point of the biodegradable polyamide resin, but from the viewpoint of moldability and the like, it is preferably 320°C or lower. That is, the melting point of the biodegradable polyamide resin is preferably 200 to 320°C.

[0055] (Crystallization Temperature (Tc)) From the viewpoint of crystallinity, the crystallization temperature (Tc) of the biodegradable polyamide resin according to this embodiment is preferably 170°C or higher, more preferably 175°C or higher, even more preferably 180°C or higher, and still more preferably 185°C or higher. There is no particular upper limit to the crystallization temperature of the biodegradable polyamide resin, but from the viewpoint of moldability and the like, it is preferably 310°C or lower. That is, the crystallization temperature of the biodegradable polyamide resin is preferably 170 to 310°C.

[0056] The melting point and crystallization temperature can be measured using a differential scanning calorimetry (DSC) analyzer. More specifically, they can be measured by the method described in the Examples section below.

[0057] (Crystallization Rate) From the viewpoint of crystallinity, the crystallization rate of the biodegradable polyamide resin according to this embodiment is preferably 0.020 or more, more preferably 0.025 or more, and may be 0.030 or more in some cases. There is no particular upper limit to the crystallization rate of the biodegradable polyamide resin, but it may be, for example, 0.070 or less or 0.060 or less. That is, the crystallization rate of the biodegradable polyamide resin is preferably 0.020 to 0.070, more preferably 0.025 to 0.070, and even more preferably 0.030 to 0.070. The crystallization rate is calculated from the melting point (Tm) and the recrystallization temperature (Tc), specifically, 1 / (Tm-Tc).

[0058] [Method for producing biodegradable polyamide resin] The biodegradable polyamide resin according to this embodiment can be produced by polymerizing a monomer capable of forming the structural unit (a) described above together with a monomer capable of forming the structural unit (b) and / or a monomer capable of forming the structural unit (c), as needed.

[0059] The polymerization method is not limited as long as a biodegradable polyamide resin exhibiting the desired effects of the present invention can be obtained. Known polymerization methods include a method in which a monomer is ring-opened and then polycondensed, a method in which the monomer is hydrolyzed with a small amount of water and then ring-opened and then polycondensed, and a method in which ring-opening polymerization is carried out by anionic polymerization. From the viewpoint of reaction rate, the method in which ring-opening polymerization is carried out by anionic polymerization is preferred.

[0060] The method for ring-opening polymerization of a monomer capable of forming the structural unit (a) by anionic polymerization is not particularly limited, and bulk polymerization, solution polymerization, suspension polymerization, or the like can be applied. From the viewpoint of ease of isolation and purification of the polymer, suspension polymerization is preferred. In this case, a method in which an aprotic solvent incompatible with the monomer capable of forming the structural unit (a) is used and the reaction solution is vigorously stirred to forcibly form a suspension and then polymerize is preferred. Examples of aprotic solvents include aliphatic hydrocarbon solvents such as hexane, octane, decane, dodecane, undecane, tridecane, decalin, 2,2,4,6,6-pentamethylheptane, cyclohexane, decene, isoparaffin, liquid paraffin, kerosene, petroleum ether, and ligroin. These solvents can be used alone or in combination of two or more. The amount of the aprotic solvent added is not particularly limited, and can be in the range of 0.1 to 30 parts by mass, 0.1 to 20 parts by mass, 0.1 to 10 parts by mass, 0.1 to 5 parts by mass, 0.5 to 5 parts by mass, or the like, per part by mass of the total weight of the monomer capable of forming the structural unit (a), the monomer capable of forming the structural unit (b), and / or the monomer capable of forming the structural unit (c).

[0061] The polymerization catalyst used when ring-opening polymerizing a monomer capable of forming the structural unit (a) by anionic polymerization is not particularly limited, and known catalysts commonly used in the ring-opening polymerization of lactams can be used. Specific examples include alkali metals such as sodium, potassium, and lithium; alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; alkali metal hydrides such as sodium hydride; metal alcoholates such as sodium ethylate and potassium t-butoxide; and basic organometallic compounds such as lithium alkyls, potassium alkyls, and sodium alkyls. These catalysts can be used alone or in combination of two or more. The amount of polymerization catalyst added is not particularly limited, but can be in the range of 0.001 to 0.1 mol, or 0.01 to 0.1 mol, per 1 mol of the monomer capable of forming the structural unit (a).

[0062] The polymerization initiator used when ring-opening polymerizing a monomer capable of forming the structural unit (a) by anionic polymerization is not particularly limited, and known initiators commonly used in the ring-opening polymerization of lactams can be used. Specific examples include gases such as carbon dioxide and sulfur dioxide; acylated lactams such as N-acetylpyrrolidone and N-acetyl ε-caprolactam; carboxylic acid halides such as acetyl chloride, stearoyl chloride, and benzene-1,3,5-tricarbonyl trichloride; carboxylic acid anhydrides such as acetic anhydride and phthalic anhydride; carboxylic acid esters such as methyl carboxylic acid ester; lactones such as γ-butyrolactone and ε-caprolactone; isocyanate compounds such as tolylene 2,4-diisocyanate; and reaction products of these polymerization initiators with a polymerization catalyst. These polymerization initiators can be used alone or in combination of two or more. The amount of the polymerization initiator used is not particularly limited, but can be in the range of 0.00001 to 0.1 mol, 0.00001 to 0.01 mol, or 0.00005 to 0.001 mol per 1 mol of the monomer capable of forming the structural unit (a).

[0063] When multiple types of monomers are used, such as a monomer capable of forming the structural unit (a), a monomer capable of forming the structural unit (b), and a monomer capable of forming the structural unit (c), it is preferable to additionally supply the monomers that tend to be in short supply during the polymerization reaction. Sequential addition is preferred as a method for additionally supplying monomers during the polymerization reaction.

[0064] The polymerization temperature when the monomer capable of forming the structural unit (a) is subjected to ring-opening polymerization by an anionic polymerization method is not particularly limited, but from the viewpoint of the reaction rate, it is preferably 20 to 80°C, more preferably 30 to 70°C, and even more preferably 40 to 60°C.

[0065] [Resin Composition] The resin composition according to this embodiment contains the biodegradable polyamide resin described above and other components exemplified below. In one aspect, the resin composition further contains, in addition to the biodegradable polyamide resin described above, other resins (for example, polyolefin resins, polyester resins (for example, polybutylene succinate, polybutylene adipate terephthalate, polyhydroxyalkanoate, etc.), polyamide resins, polyvinyl chloride resins, ABS resins, polylactic acid resins, polyvinyl acetate resins, ethylene-vinyl acetate copolymer resins, vinyl alcohol-based resins (polyvinyl alcohol, ethylene-vinyl alcohol copolymers, polyvinyl acetal, etc.), and polysaccharides (starch, cellulose, etc.) within a range that does not impair the effects of the present invention.

[0066] In one embodiment, the resin composition contains, in addition to the biodegradable polyamide resin described above, various additives (e.g., heat stabilizers, antioxidants, light stabilizers, UV absorbers, antistatic agents, colorants (e.g., color pigments), smoothing agents, plasticizers, antibacterial agents, biorepellents (e.g., marine organism repellents), fungicides, and deodorizers) within a range that does not impair the effects of the present invention. The amount of the additives may be, for example, 5% by mass or less, preferably 1% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.3% by mass or less, relative to the biodegradable polyamide resin.

[0067] In one embodiment, the resin composition may contain a solvent (e.g., an organic solvent), in which case the biodegradable polyamide resin may be dissolved in the solvent, or may be dispersed in the solvent without being dissolved.

[0068] As described above, the resin composition according to this embodiment preferably contains the biodegradable polyamide resin described above and at least one selected from other resins, additives, and solvents.

[0069] [Molded Article] The molded article according to this embodiment contains the biodegradable polyamide resin or the resin composition described above. The biodegradable polyamide resin described above has sufficient biodegradability, so that the environmental burden can be reduced. The molded article according to this embodiment can be obtained, for example, by dissolving the biodegradable polyamide resin described above in a solvent and molding it into any shape. Therefore, the molded article according to this embodiment can be formed into, for example, a fiber or a film.

[0070] The molded article according to the present embodiment can also be formed into any desired shape by melt molding the polyamide resin described above. The molding method is not particularly limited, but examples thereof include injection molding, blow molding, extrusion molding, vacuum molding, pressure molding, casting, compression molding, and foam molding as methods for forming three-dimensional objects, inflation molding, T-die molding, casting, and extrusion press molding as methods for forming films and sheets, and melt spinning as a method for forming fibers.

[0071] [Laminate] The laminate according to this embodiment includes at least one layer containing the biodegradable polyamide resin described above. Preferably, the laminate according to this embodiment includes a substrate and a layer containing the biodegradable polyamide resin described above formed on the surface of the substrate. The layer containing the biodegradable polyamide resin may be formed on multiple surfaces of the substrate.

[0072] Examples of the substrate of the laminate according to this embodiment are not particularly limited, and include, for example, paper and resin molded bodies (for example, molded bodies made from thermoplastic resins or thermosetting resins such as polyethylene (PE) resin, polypropylene (PP) resin, polymethyl methacrylate (PMMA) resin, polyethylene terephthalate (PET) resin, polycarbonate (PC) resin, polyvinyl chloride (PVC) resin, polystyrene (PS) resin, alicyclic acrylic resin, alicyclic polyolefin resin, poly-4-methylterpene-1 resin, vinylidene chloride resin, and transparent epoxy resin).

[0073] [Manufacturing Method of Molded Article and Laminate] The manufacturing method of the molded article and laminate is not particularly limited, and various conventional molding methods can be adopted. For example, a laminate can be formed by dissolving a biodegradable polyamide resin in a solvent, applying the obtained solution to a substrate using a bar coater, and, after curing as necessary, peeling the cured product from the substrate of the laminate to obtain a molded article.

[0074] [Uses] The biodegradable polyamide resin of the present embodiment has excellent storage stability while being biodegradable, and therefore can be used in a wide range of applications where molded articles and laminates are required.

[0075] Examples of applications include electrical and electronic components, automotive parts (intake system parts, cooling system parts, fuel system parts, interior parts, exterior parts, electrical parts, etc.), vehicle-related parts, general and industrial machinery parts, sporting goods, daily necessities, home and office supplies, furniture parts, industrial materials, civil engineering materials, industrial materials, fishing materials, agricultural and forestry materials, medical and sanitary products, food and beverage containers, and clothing (outerwear, innerwear, uniforms, surgical gowns, hospital gowns, white coats, work clothes, swimwear, ski wear, aprons, hats, belly warmers). , socks, gloves, mufflers, etc.), various household items (futons, futon covers, pillow covers, beds, bed covers, blankets, sheets, bath mats, towels, tablecloths, curtains, shower curtains, nets, doorknob covers, diaper covers, slippers, etc.), building materials (carpets, curtains, etc.), industrial materials (ropes, etc.), agricultural, forestry and fisheries materials (fishing nets, etc.), civil engineering materials (geotextiles, etc.).

[0076] In particular, it is useful for applications requiring biodegradability, such as agricultural films such as agricultural mulch films, greenhouse films, and seedling cups, seedling or seedling raising pots, disposable food containers (e.g., knives, forks, spoons, straws, cups, trays, bottles, take-out food packs, etc.), packaging containers, food packaging films, packaging materials, shopping bags or plastic bags, surgical sutures, and resin molded articles such as geotextiles.

[0077] The present invention will be specifically explained below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0078] The polyamide resins obtained in the examples and comparative examples described below were measured and evaluated according to the methods described below.

[0079] [1. Content (mol %) of structural unit (a), structural unit (b), and structural unit (c)] The polyamide resins obtained in the examples and comparative examples described below were analyzed using a nuclear magnetic resonance spectrometer "LAMBDA 500" manufactured by JEOL Ltd. １ H-NMR was measured. 1,1,1,3,3,3-hexafluoro-2-propanol-d2 (hereinafter referred to as "HFIP-d2") was used as the deuterated solvent. Measurements were performed at room temperature. The contents (mol%) of the structural units (a), (b), and (c) constituting the polyamide resin were determined using the integral values ​​of the peaks (1) to (3) below. Here, calculations were performed so that the sum of the mol% of the structural units (a), (b), and (c) was 100 mol%. Specifically, the mol% of the structural unit (a) was calculated based on the integral value of the peak (1) below, the mol% of the structural unit (b) was calculated based on the integral value of the peak (2) below, and the mol% of the structural unit (c) was calculated based on the integral value of the peak (3) below. The results are shown in Table 1. (1) 0.9 ppm to 1.0 ppm (protons of the side chain methyl group of the substituent lactam), (2) 1.7 ppm to 1.9 ppm (protons of methylene in the main chain of polyamide 4), (3) 1.3 ppm to 1.4 ppm (protons of methylene in the main chain of polyamide 6)

[0080] [2. Measurement of Weight-Average Molecular Weight (Mw) and Number-Average Molecular Weight (Mn)] The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the polyamide resins obtained in the Examples and Comparative Examples described below were measured using a size-exclusion high-performance liquid chromatography system "HLC-8320GPC" manufactured by Tosoh Corporation. The measurement results are shown in Table 1. The measurement conditions were as follows: Column: Two HFIP-based columns "GMHHR-H(S)" manufactured by Tosoh Corporation connected in series Standard sample: PMMA Solvent and mobile phase: 20 mM sodium trifluoroacetate-HFIP solution Flow rate: 0.35 mL / min Temperature: 40°C Sample solution concentration: 0.1 wt% (filtered through a filter with an opening diameter of 0.45 μm) Injection volume: 10 μL Detector: RI

[0081] [3. Practicality] The polyamide resins obtained in the Examples and Comparative Examples were subjected to a biodegradability test using the manometric respirometry method as described below to measure the induction period and the degree of biodegradation, and the practicality of the polyamide resins was evaluated from the viewpoints of storage stability and biodegradability.

[0082] (Biodegradability test) 5 mg of a polyamide resin powder sample and activated sludge (obtained from a sewage treatment plant) were added to a culture medium with a total volume of 200 ml, and the MLSS concentration (suspension concentration) was adjusted to 30 ppm by mass. Using an Oxitop (a pressure sensor-type BOD meter manufactured by WTW), the culture was cultured at 22°C for 28 days. The amount of oxygen consumed by biodegradation during this culture period was measured, and the biodegradability (mass%) was calculated based on a comparison with the theoretical oxygen demand calculated from the polymer composition. The induction period was also determined based on the definition described below.

[0083] (Evaluation of biodegradability) The degree of biodegradability (mass%) after 28 days was evaluated according to the following criteria: A: Biodegradability greater than 60 mass% B: Biodegradability equal to or greater than 50 mass% C: Biodegradability less than 50 mass%

[0084] (Evaluation of storage stability) The induction period was defined as the period during which the biodegradability remained at 10% by mass or less, and was evaluated according to the following criteria: A: induction period of 10 days or more B: induction period of 5 days or more but less than 10 days C: induction period of less than 5 days

[0085] (Overall evaluation of practicality) The induction period and biodegradability were evaluated according to the following criteria: A: Biodegradability was evaluated as A, and storage stability was evaluated as A. B: Either biodegradability or storage stability was evaluated as B. C: Either biodegradability or storage stability was evaluated as C.

[0086] Example 1 A reactor equipped with a reflux condenser, a stirrer, a thermometer, a nitrogen inlet, and a post-addition liquid inlet was prepared, and the interior of the system was completely purged with nitrogen. This reactor was charged with 1.2 parts by mass of tetramethylammonium chloride, 31.3 parts by mass of a mixture of 2-pyrrolidone (hereinafter also referred to as "2PY") and 4-methyl-2-pyrrolidone (hereinafter also referred to as "4MPY") (2PY / 4MPY = 5 / 5 (molar ratio)), and 57.9 parts by mass of liquid paraffin, and the mixture was stirred. As a result, the mixture in the reactor became a suspension. To the suspended mixture, 14.4 parts by mass of a THF solution (1 M) of potassium tert-butoxide was added. Thereafter, the pressure inside the system was reduced to 1 kPa, the internal temperature was raised to 50°C, and stirring was continued for 1 hour.

[0087] Thereafter, the internal temperature was cooled to 30°C, and 0.4 parts by mass of N-acetyl-ε-caprolactam (hereinafter also referred to as "AcCL") was added, and polymerization was initiated while the temperature was maintained at 30°C. 24 hours after the start of the polymerization reaction, 3.9 parts by mass of 2-pyrrolidone (2PY) was added. The polymerization reaction was then continued for another 24 hours while maintaining the temperature at 30°C. The polymerization reaction was terminated by adding 0.4 parts by mass of methanol to the reaction solution. The internal temperature was then cooled to room temperature, and stirring was continued for 10 minutes. Thereafter, 9.5 parts by mass of acetic acid was added to the reaction solution, and stirring was continued for another 15 minutes.

[0088] The white solid was filtered off from the resulting reaction solution, and the product was recovered as a powder. The product was then purified as follows: First, the product was stirred and washed in a beaker containing 150 mL of THF. The product was then filtered and recovered three times. This meant that the product was washed three times in total. Furthermore, the same washing procedure using methanol was repeated four times. The resulting white solid was dried in a dryer at 40°C and 1.3 Pa for 20 hours.

[0089] In this way, the polyamide resin according to Example 1 was obtained. The obtained polyamide resin was subjected to the above-mentioned measurements and evaluations.

[0090] Example 2 The same reactor as used in Example 1 was prepared, and the inside of the system was completely purged with nitrogen. To this reactor, 104.2 parts by mass of a mixture of 2-pyrrolidone (2PY) and 4-methyl-2-pyrrolidone (4MPY) (2PY / 4MPY=5 / 5 (molar ratio)) and 81.6 parts by mass of a THF solution (1 M) of potassium tert-butoxide were added. Thereafter, the pressure inside the system was reduced to 1 kPa, and the internal temperature was raised to 50°C, and stirring was continued for 1 hour.

[0091] Thereafter, the internal temperature was cooled to 30° C., 3.5 parts by mass of AcCl was added, and polymerization was initiated while the temperature was kept at 30° C. Then, the polymerization reaction was carried out for a total of 96 hours.

[0092] The polymerization reaction was terminated by adding 5.8 parts by mass of methanol to the reaction solution. The internal temperature was then cooled to room temperature, and stirring was continued for 10 minutes. Thereafter, 13.5 parts by mass of acetic acid was added to the reaction solution, and stirring was continued for another 15 minutes.

[0093] The white solid was filtered off from the resulting reaction solution and recovered as a product, which was then purified in the same manner as in Example 1.

[0094] In this way, a polyamide resin according to Example 2 was obtained. The obtained polyamide resin was subjected to the above-mentioned measurements and evaluations.

[0095] Example 3 The same reactor as used in Example 1 was prepared, and the inside of the system was completely purged with nitrogen. 3.9 parts by mass of tetramethylammonium chloride, 104.2 parts by mass of a mixture of 2-pyrrolidone (2PY) and 4-methyl-2-pyrrolidone (4MPY) (2PY / 4MPY=5 / 5 (molar ratio)), and 192.8 parts by mass of liquid paraffin were charged into the reactor and stirred. As a result, the mixture in the reactor became a suspension.

[0096] To the mixture in a suspended state, 48.0 parts by mass of a tetrahydrofuran (hereinafter also referred to as "THF") solution (1 M) of potassium tert-butoxide was added. Thereafter, the pressure inside the system was reduced to 1 kPa, and the internal temperature (liquid temperature of the mixture) was raised to 50°C, and stirring was continued for 1 hour.

[0097] Thereafter, the internal temperature was cooled to 30°C, 1.4 parts by mass of AcCl was added, and polymerization was initiated while the temperature was kept at 30°C.

[0098] During the polymerization reaction, a total of 26.9 parts by mass of 2-pyrrolidone (2PY) was successively fed after the start of polymerization so that the molar ratio of 2PY / 4MPY in the system was constant. In this manner, the polymerization reaction was carried out for a total of 4 hours at 30°C.

[0099] The polymerization reaction was terminated by adding 3.4 parts by mass of methanol to the reaction solution. The internal temperature was then cooled to room temperature, and stirring was continued for 10 minutes. Thereafter, 7.4 parts by mass of acetic acid was added to the reaction solution, and stirring was continued for an additional 15 minutes.

[0100] The white solid was filtered off from the resulting reaction mixture and recovered as a product, which was then purified in the same manner as in Example 1.

[0101] In this way, a polyamide resin according to Example 3 was obtained. The obtained polyamide resin was subjected to the above-mentioned measurements and evaluations.

[0102] Example 4 A polymerization reaction was carried out in the same manner as in Example 3, except for the following changes (1) to (9). (1) The amount of tetramethylammonium chloride used was changed from 3.9 parts by mass to 1.2 parts by mass. (2) 104.2 parts by mass of a mixture of 2PY and 4MPY (2PY / 4MPY = 5 / 5 (molar ratio)) was changed to 32.1 parts by mass of a mixture of 2PY and 3-methyl-2-pyrrolidone (hereinafter also referred to as "3MPY") (2PY / 3MPY = 7 / 3 (molar ratio)). (3) The amount of liquid paraffin used was changed from 192.8 parts by mass to 59.4 parts by mass. (4) The amount of potassium tert-butoxide THF solution (1 M) used was changed from 48.0 parts by mass to 15.2 parts by mass. (5) The amount of AcCL used was changed from 1.4 parts by mass to 0.4 parts by mass. (6) The total amount of 2PY used after the start of polymerization to be sequentially fed was changed from 26.9 parts by mass to 11.5 parts by mass. (7) The polymerization reaction time was changed from 4 hours to 5 hours. (8) The amount of methanol used to terminate the polymerization reaction was changed from 3.4 parts by mass to 1.1 parts by mass. (9) The amount of acetic acid used was changed from 7.4 parts by mass to 2.4 parts by mass.

[0103] Example 5 A polymerization reaction was carried out in the same manner as in Example 4, except for the following changes (1) and (2): (1) 32.1 parts by mass of a mixture of 2PY and 3MPY (2PY / 3MPY=7 / 3 (molar ratio)) was replaced with 19.9 parts by mass of a mixture of 2PY and 4MPY (2PY / 4MPY=5 / 5 (molar ratio)); (2) A polymerization reaction was carried out for 5 hours without sequentially feeding a total of 11.5 parts by mass of 2-pyrrolidone (2PY) during the polymerization reaction, i.e., the additional supply amount of 2PY was 0 parts by mass.

[0104] Example 6 A polymerization reaction was carried out in the same manner as in Example 4, except for the following change (1): (1) 32.1 parts by mass of a mixture of 2PY and 3MPY (2PY / 3MPY = 7 / 3 (molar ratio)) was changed to 32.1 parts by mass of a mixture of 2PY and 4MPY (2PY / 4MPY = 7 / 3 (molar ratio)).

[0105] The white solid was filtered off from the resulting reaction mixture and recovered as a product, which was then purified in the same manner as in Example 3.

[0106] In this way, a polyamide resin according to Example 6 was obtained. The obtained polyamide resin was subjected to the above-mentioned measurements and evaluations.

[0107] Example 7 A reactor identical to that used in Example 1 was prepared, and the inside of the system was completely purged with nitrogen. 28.5 parts by mass of a mixture of 2PY and 4MPY (2PY / 4MPY=7 / 3 (molar ratio)), 15.1 parts by mass of a THF solution (1 M) of potassium tert-butoxide, and 4.0 parts by mass of ε-caprolactam (hereinafter also referred to as "εCL") were added to this reactor. Thereafter, the pressure inside the system was reduced to 1 kPa, and the internal temperature was raised to 50°C, and stirring was continued for 1 hour.

[0108] Then, 0.4 parts by mass of AcCl was added to initiate polymerization, and the polymerization reaction was carried out for a total of 5 hours. The polymerization reaction was terminated by adding 1.2 parts by mass of methanol to the reaction solution. The internal temperature was then cooled to room temperature, and stirring was continued for 10 minutes. Thereafter, 2.6 parts by mass of acetic acid was added to the reaction solution, and stirring was continued for an additional 15 minutes.

[0109] The white solid was filtered off from the resulting reaction solution and recovered as a product, which was then purified in the same manner as in Example 1.

[0110] In this way, a polyamide resin according to Example 7 was obtained. The obtained polyamide resin was subjected to the above-mentioned measurements and evaluations.

[0111] Example 8 A polymerization reaction was carried out in the same manner as in Example 1, except for the following changes (1) and (2): (1) 31.3 parts by mass of a mixture of 2PY and 4MPY (2PY / 4MPY = 5 / 5 (molar ratio)) was replaced with 33.7 parts by mass of a mixture of 2PY and 4-methyl-2-piperidone (hereinafter also referred to as "4MPI") (2PY / 4MPI = 5 / 5 (molar ratio)); (2) 57.9 parts by mass of liquid paraffin was changed to 62.5 parts by mass; and (3) the polymerization temperature was changed from 30°C to 40°C.

[0112] Comparative Example 1 A reactor identical to that used in Example 1 was prepared, and the inside of the system was completely purged with nitrogen. 33.5 parts by mass of 2PY and 16.7 parts by mass of a THF solution (1 M) of potassium tert-butoxide were added to this reactor. Thereafter, the pressure inside the system was reduced to 1 kPa, and the internal temperature was raised to 50°C, and stirring was continued for 1 hour.

[0113] The internal temperature was then cooled to 30°C, 0.5 parts by mass of AcCl was added to initiate polymerization, and the polymerization reaction was carried out for a total of 24 hours. The polymerization reaction was terminated by adding 1.2 parts by mass of methanol to the reaction solution. The internal temperature was then cooled to room temperature, and stirring was continued for 10 minutes. Thereafter, 2.6 parts by mass of acetic acid was added to the reaction solution, and stirring was continued for an additional 15 minutes.

[0114] The white solid was filtered off from the resulting reaction solution and recovered as a product, which was then purified in the same manner as in Example 1.

[0115] In this way, a polyamide resin according to Comparative Example 1 was obtained. The obtained polyamide resin was subjected to the above-described measurements and evaluations.

[0116] Comparative Example 2 A reactor identical to that used in Example 1 was prepared, and the inside of the system was completely purged with nitrogen. 20.5 parts by mass of 2PY, 11.7 parts by mass of εCL, and 14.7 parts by mass of a THF solution (1 M) of potassium tert-butoxide were added to this reactor. Thereafter, the pressure inside the system was reduced to 1 kPa, and the internal temperature was raised to 50°C, and stirring was continued for 1 hour.

[0117] Then, 0.4 parts by mass of AcCl was added to initiate polymerization, and the polymerization reaction was carried out for a total of 5 hours. The polymerization reaction was terminated by adding 1.2 parts by mass of methanol to the reaction solution. The internal temperature was then cooled to room temperature, and stirring was continued for 10 minutes. Thereafter, 2.3 parts by mass of acetic acid was added to the reaction solution, and stirring was continued for an additional 15 minutes.

[0118] The white solid was filtered off from the resulting reaction solution and recovered as a product, which was then purified in the same manner as in Example 1.

[0119] In this way, a polyamide resin according to Comparative Example 2 was obtained. The obtained polyamide resin was subjected to the above-mentioned measurements and evaluations.

[0120] Comparative Example 3 A reactor identical to that used in Example 1 was prepared, and the inside of the system was completely purged with nitrogen. 33.0 parts by mass of a mixture of 2PY and 4MPY (2PY / 4MPY=9 / 1 (molar ratio)) and 16.2 parts by mass of a THF solution (1 M) of potassium tert-butoxide were added to this reactor. Thereafter, the pressure inside the system was reduced to 1 kPa, and the internal temperature was raised to 50°C, and stirring was continued for 1 hour.

[0121] The internal temperature was then cooled to 30°C, 0.5 parts by mass of AcCl was added to initiate polymerization, and the polymerization reaction was carried out for a total of 24 hours. The polymerization reaction was terminated by adding 1.3 parts by mass of methanol to the reaction solution. The internal temperature was then cooled to room temperature, and stirring was continued for 10 minutes. Thereafter, 2.5 parts by mass of acetic acid was added to the reaction solution, and stirring was continued for an additional 15 minutes.

[0122] The white solid was filtered off from the resulting reaction solution and recovered as a product, which was then purified in the same manner as in Example 1.

[0123] In this way, a polyamide resin according to Comparative Example 3 was obtained. The obtained polyamide resin was subjected to the above-mentioned measurements and evaluations.

[0124] The measurement results and evaluation results for Examples 1 to 7 and Comparative Examples 1 to 3 are shown in Tables 1 and 2.

[0125] Comparative Example 4 A reactor identical to that used in Example 1 was prepared, and the inside of the system was completely purged with nitrogen. To this reactor, 32.7 parts by mass of a mixture of 2PY and 4MPI (2PY / 4MPI=6 / 4 (molar ratio)), 60.5 parts by mass of liquid paraffin, and 16.2 parts by mass of a THF solution (1 M) of potassium tert-butoxide were added. Thereafter, the pressure inside the system was reduced to 1 kPa, and the internal temperature was raised to 50°C, and stirring was continued for 1 hour.

[0126] The internal temperature was then cooled to 40°C, 0.5 parts by mass of AcCl was added to initiate polymerization, and the polymerization reaction was carried out for a total of 24 hours. The polymerization reaction was terminated by adding 1.3 parts by mass of methanol to the reaction solution. The internal temperature was then cooled to room temperature, and stirring was continued for 10 minutes. Thereafter, 2.5 parts by mass of acetic acid was added to the reaction solution, and stirring was continued for an additional 15 minutes.

[0127] The white solid was filtered off from the resulting reaction solution and recovered as a product, which was then purified in the same manner as in Example 1.

[0128] In this way, a polyamide resin according to Comparative Example 4 was obtained. The obtained polyamide resin was subjected to the above-mentioned measurements and evaluations.

[0129]

[0130]

[0131] From Tables 1 and 2, it can be seen that the biodegradable polyamide resins according to the Examples had sufficient biodegradability compared to the polyamide resin according to Comparative Example 2, and also had superior storage stability compared to the polyamide resins according to Comparative Examples 1, 3, and 4. This shows that, from the viewpoint of superior practicality, it is preferable for biodegradable polyamide resins to contain structural units derived from monomers having specific branched chains.

[0132] The polyamide resin of the present invention is useful in a variety of applications requiring biodegradability, more preferably in a variety of applications requiring storage stability before use, and is useful for, for example, molded articles and laminates.

Claims

1. A biodegradable polyamide resin comprising a structural unit (a) represented by the following formula (I), which has an induction period of 5 days or more during which the biodegradability is maintained at 10% by mass or less in a biodegradability test using a manometric respirometry method. Formula (I): -NR-X-CO- (In formula (I), X is a divalent non-heterocyclic hydrocarbon group having 1 to 16 carbon atoms which may or may not have a first substituent, or a divalent non-heterocyclic hydrocarbon group having 1 to 16 carbon atoms which may or may not have a second substituent, R is a hydrogen atom or a third substituent, provided that the structural unit (a) has at least one of the first substituent, the second substituent, and the third substituent, and the first substituent, the second substituent, and the third substituent are each independently a monovalent non-heterocyclic hydrocarbon group having 1 to 16 carbon atoms which may or may not have a fourth substituent, or a monovalent non-heterocyclic hydrocarbon group having 1 to 16 carbon atoms which may or may not have a fifth substituent.) 2. The biodegradable polyamide resin according to claim 1, wherein X in formula (I) is an alkylene group having 4 or less carbon atoms.

3. The structural unit (a) is represented by the formula (I), wherein X is C ２－４ An alkylene group, provided that ２－４ The biodegradable polyamide resin according to claim 1, comprising a structural unit (a1) in which at least one hydrogen atom bonded to an alkylene group is substituted with an alkyl group.

4. The structural unit (a) is represented by the formula (I), wherein X is C ３－４ An alkylene group, provided that ３－４ The biodegradable polyamide resin according to claim 1, comprising a structural unit (a2) in which at least one hydrogen atom bonded to an alkylene group is substituted with a methyl group.

5. The biodegradable polyamide resin according to claim 1, further comprising an unbranched imino(1-oxobutane-1,4-diyl) structural unit as a structural unit (b) different from the structural unit (a).

6. The polyamide resin according to claim 5, wherein the total content of the structural units (a) and (b) in the polyamide resin is 50 mol % or more.

7. The biodegradable polyamide resin according to claim 1, wherein the content of the structural unit (a) in the polyamide resin is more than 4 mol %.

8. The biodegradable polyamide resin according to claim 1, having a crystallization rate (1 / (Tm-Tc)) calculated from the melting point (Tm) and recrystallization temperature (Tc) of 0.030 or more.

9. A molded article comprising the biodegradable polyamide resin according to any one of claims 1 to 8.

10. The molded article according to claim 9, which is one selected from fibers and films.

11. A laminate comprising at least one layer containing the biodegradable polyamide resin according to any one of claims 1 to 8.

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