Polyamide resin, coating liquid, molded body, and laminate

Abstract

This 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 measured with a differential scanning calorimeter (DSC), the polyamide resin exhibits a recrystallization peak having a half-value width (°C) of 10 or less when the temperature falls.

Description

Polyamide resin, coating liquid, molded body and laminate

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

[0002] Known synthetic resins include aliphatic polyesters (such as polycaprolactone, polybutylene succinate, polyethylene succinate, polyglycolic acid, and polylactic acid), polyvinyl alcohol-based resins, and polyamino acids. Among these, aliphatic polyesters are known as practical resins because they can be melt-molded.

[0003] 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.

[0004] Patent Document 2 discloses that nylon 4 derived from 2-pyrrolidinone having a high molecular weight, specifically a weight-average molecular weight of 564,335, was used to produce nylon 4 fibers (paragraph

[0053] ).

[0005] Patent Document 3 discloses a poly[imino(1-oxo-1,4-butanediyl)] polymer containing an [imino(1-oxo-1,4-butanediyl)] structural unit. According to Patent Document 3, such a polymer can be stably melt-molded (paragraph

[0032] ).

[0006] In Non-Patent Document 1, a copolymer of 2-pyrrolidinone and its methyl derivative was prepared, and the thermal properties of the obtained copolymer, specifically the glass transition temperature, melting point, and thermal decomposition temperature, were studied.

[0007] JP 2013-108098 A JP 2019-137934 A International Publication No. 2022 / 039199

[0008] 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)

[0009] As resin materials with excellent melt moldability, the polymer disclosed in Patent Document 3 and the copolymer disclosed in Non-Patent Document 1 are possible candidates.

[0010] However, the inventors' research has revealed that although these resin materials have excellent melt moldability, they may not necessarily have excellent solubility in solvents. If a resin material with excellent solubility at relatively low temperatures could be provided, it would be possible to, for example, shorten the preparation time of the coating liquid, reduce the amount of solvent required for preparation, and reduce the thermal energy required for heating during preparation, thereby reducing the burden on the manufacturing process. Note that resin materials with excellent solubility can be used for other purposes as well, not limited to coating liquids.

[0011] Therefore, the present invention aims to solve the above problems, and an object of the present invention is to provide a polyamide resin having excellent solubility in solvents; and a coating liquid, a molded body, and a laminate containing the polyamide resin.

[0012] 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 polyamide resin containing a structural unit (a) represented by the following formula (I), wherein the half-width (°C) of a recrystallization peak during cooling measured using a differential scanning calorimeter (DSC) is 10 or less: 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 hetero-containing 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 hetero-containing hydrocarbon group having 1 to 16 carbon atoms which may or may not have a fifth substituent.) [2] The structural unit (a) is a compound represented by the formula (I), ２－４ an alkylene group, provided that ２－４ [3] The polyamide resin according to [1], 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 an alkylene group, provided that ３The polyamide resin according to [1], which contains a structural unit (a2) in which at least one hydrogen atom bonded to the alkylene group is substituted with a methyl group. [4] The polyamide resin according to any one of [1] to [3], which further contains an unbranched imino(1-oxo-1,4-butanediyl)] structural unit as a structural unit (b) different from the structural unit (a). [5] The polyamide resin according to [4], in which the content of the structural unit (b) in the polyamide resin is 50 mol % or more. [6] The polyamide resin according to [4] or [5], in which the molar ratio of the structural unit (a) to the structural unit (b) is 10 / 90 to 25 / 75. [7] The polyamide resin according to any one of [1] to [6], in which the crystallization rate (1 / (Tm-Tc)) calculated from the melting point (Tm) and the recrystallization temperature (Tc) is 0.030 or more. [8] A coating liquid comprising the polyamide resin according to any one of [1] to [7] and a solvent. [9] A molded article comprising the polyamide resin according to any one of [1] to [7].

[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 polyamide resin according to any one of [1] to [7].

[0013] According to the present invention, it is possible to provide a polyamide resin having excellent solubility in a solvent, and a coating liquid, a molded article, and a laminate containing the polyamide resin.

[0014] 1 is a graph showing the relationship between heat flow (W / g) and temperature (°C) obtained by measurement using a differential scanning calorimeter (DSC) for the polyamide resin according to Example 1. 2 is a graph showing the relationship between heat flow (W / g) and temperature (°C) obtained by measurement using a differential scanning calorimeter (DSC) for the polyamide resin according to Comparative Example 1.

[0015] 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."

[0016] [Polyamide Resin] The polyamide resin according to the present embodiment is a polyamide resin containing a structural unit (a) having a specific branched chain, and the half width (°C) of the recrystallization peak during cooling measured using a differential scanning calorimeter (DSC) is equal to or less than a specific threshold value, thereby providing the polyamide resin with excellent solubility in solvents.

[0017] (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 at least one of the structural units contains a 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).

[0018] 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.)

[0019] (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).

[0020] (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.

[0021] 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 still 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.

[0022] 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.

[0023] 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.

[0024] (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.

[0025] (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.

[0026] 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.

[0027] 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.

[0028] (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.

[0029] (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.

[0030] (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).

[0031] (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).

[0032] 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.

[0033] 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 an alkylene group, provided that ３The 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. The structural unit (a) may be a C ２－４ Alkylene group, C ３ By employing a structural unit that includes a hydrocarbon group with a small number of carbon atoms, such as an alkylene group, as a branched chain, the polyamide resin according to this embodiment tends to have higher solubility in solvents.

[0034] (Half width of recrystallization peak) The polyamide resin according to this embodiment has a half width (°C) of the recrystallization peak during cooling measured using a differential scanning calorimeter (DSC) of 10 or less. By confirming that the half width of the recrystallization peak during cooling of the polyamide resin obtained by polymerization is 10 or less, it is possible to provide a polyamide resin having excellent solubility in solvents.

[0035] First, data showing the relationship between heat flow (W / g) and temperature (° C.) obtained by measurement using DSC will be described.

[0036] FIG. 1 is a graph showing the relationship between heat flow (W / g) and temperature (° C.) obtained by measuring the polyamide resin according to Example 1 described later using DSC.

[0037] As shown in the graph of FIG. 1, when a polyamide resin is measured using DSC, a peak is usually observed during cooling (hereinafter, this peak is referred to as a "recrystallization peak").

[0038] Then, the statistical half-width of the recrystallization peak can be determined. When, for example, a differential scanning calorimeter "Q1000" manufactured by TA Instruments Co., Ltd. is used as the differential scanning calorimeter, it is possible to output the value of the half-width.

[0039] Even when a differential scanning calorimeter that cannot output the half-width value is used, data showing the relationship between heat flow (W / g) and temperature (°C) can usually be obtained, so the half-width can be calculated. To calculate the half-width, a baseline is set on the graph, two points on the recrystallization peak are determined where the distance from the heat flow value of the baseline to the maximum heat flow value of the recrystallization peak (the heat flow value corresponding to 212°C in the example shown in Figure 1) is half the distance, and the absolute value (°C) of the temperature difference between these two points is calculated. As the baseline, for example, a straight line connecting two points at the base of the recrystallization peak where the difference in heat flow values ​​is sufficiently close to zero (the heat flow value corresponding to around 180°C and the heat flow value corresponding to around 250°C in the example shown in Figure 1) can be used.

[0040] The sharper the recrystallization peak, the smaller the half-width value, and the broader the recrystallization peak, the larger the half-width value. The polyamide resin according to this embodiment has a half-width (°C) of the recrystallization peak during cooling measured using DSC of 10 or less, as described above. That is, when the polyamide resin according to this embodiment is measured using DSC, the recrystallization peak is sharp. On the other hand, as illustrated in the comparative examples in the Examples section described later, polyamide resins that do not exhibit the effects of the present invention have half-width values ​​greater than 10. For reference, FIG. 2 shows a graph illustrating the relationship between heat flow (W / g) and temperature (°C) obtained by measuring the polyamide resin according to Comparative Example 1 described later using DSC.

[0041] In the polyamide resin according to the present embodiment, the half-width (°C) is, to be precise, 10.0 or less, preferably 9.8 or less, more preferably 9.6 or less, and may be 9.4 or less, 9.2 or less, 9.0 or less, 8.0 or less, or 7.0 or less, depending on the case. The lower limit of the half-width is a finite value as long as a recrystallization peak is observed, but may be 1.0 or more or 1.5 or more.

[0042] Although it is unclear why a polyamide resin having excellent solubility in a solvent can be provided when the half-width (°C) of the recrystallization peak is 10 or less, it is believed that by adjusting the amount of monomer charged and controlling the polymerization appropriately, the target polyamide resin can be produced as intended, and this leads to the observation of a sufficiently small half-width of the recrystallization peak. Therefore, when a polyamide resin that cannot be said to have excellent solubility in a solvent is obtained, it is possible to provide a polyamide resin having excellent solubility in a solvent as in this embodiment by adjusting the amount of monomer charged and controlling the polymerization.

[0043] The content of the structural unit (a) in the polyamide resin can be appropriately set according to the content of other structural units.From the viewpoint of improving solubility in solvents, the content of the structural unit (a) in the polyamide resin is preferably 3 mol% or more, more preferably 4 mol% or more, even more preferably 5 mol% or more, and even more preferably 10 mol% or more.When the polyamide resin does not contain the structural unit (b) described later, the content of the structural unit (a) may be further increased.The content (mol%) of various structural units in the polyamide resin can be determined by the method described in the Examples section below.

[0044] (Structural Unit (b)) The polyamide resin according to this embodiment may further contain a non-branched 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 polyamide resin, it is possible to provide a polyamide resin with excellent melt-moldability, as described in Patent Document 3.

[0045] 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.

[0046] From the viewpoint of further improving the mechanical properties of the polyamide resin, in one aspect of this embodiment, the content of the structural unit (b) in the 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 naturally determined 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, or 97 mol% or less.

[0047] (Other structural units (c)) The 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 of one type or two or more types.

[0048] 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.

[0049] (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).

[0050] 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.

[0051] 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 ｃis an acetyl group. ｃ The structural unit in which is an acetyl group can be obtained, for example, by reacting the produced polyamide resin with acetic anhydride or the like.

[0052] 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 polyamide resin with formaldehyde.

[0053] 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 polyamide resin with chloromethyl methyl ether.

[0054] The content of the structural unit (c) in the polyamide resin can be appropriately set depending on the content of other structural units. In one aspect of this embodiment, the content (mol%) of the structural unit (c) in the 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 polyamide resin is greater than the total content of the structural unit (a) and the structural unit (b).

[0055] [Physical properties of polyamide resin]

[0056] (Content Ratio) In the present embodiment, when the polyamide resin contains both the structural unit (a) and the structural unit (b), from the viewpoint of increasing solubility in a solvent, the molar ratio of the structural unit (a) to the structural unit (b) is preferably 3 / 97 to 25 / 75, more preferably 4 / 96 to 25 / 75, even more preferably 5 / 95 to 25 / 75, and still more preferably 10 / 90 to 25 / 75.

[0057] In the present embodiment, when the polyamide resin contains both the structural unit (a) and the structural unit (c), from the viewpoint of increasing solubility in a solvent, the molar ratio of the structural unit (a) to the structural unit (c) is preferably 3 / 97 to 25 / 75, more preferably 4 / 96 to 25 / 75, even more preferably 5 / 95 to 25 / 75, and still more preferably 10 / 90 to 25 / 75.

[0058] In the present embodiment, when the polyamide resin contains the structural unit (a), the structural unit (b), and the structural unit (c), from the viewpoint of increasing solubility in a solvent, the molar ratio of the structural unit (a):the structural unit (b):the structural unit (c) is preferably 1 / / 1 / 98 to 98 / 1 / 1, more preferably 2 / 4 / 94 to 15 / 30 / 55, even more preferably 3 / 6 / 91 to 10 / 30 / 60, and still more preferably 3 / 10 / 87 to 10 / 30 / 60.

[0059] (Molecular Weight) From the viewpoint of excellent mechanical strength, the weight average molecular weight (Mw) of the 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 solubility in solvents, 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.

[0060] From the viewpoint of excellent mechanical strength, the number average molecular weight (Mn) of the polyamide resin according to the present 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 solubility in solvents, 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.

[0061] From the viewpoint of enhancing solubility in a solvent, the molecular weight distribution (Mw / Mn) of the 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.

[0062] 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.

[0063] [Thermal Properties] (Melting Point (Tm)) From the viewpoint of heat resistance, the melting point (Tm) of the 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 still more preferably 230°C or higher. There is no particular upper limit to the melting point of the 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 polyamide resin is preferably 200 to 320°C.

[0064] (Crystallization Temperature (Tc)) From the viewpoint of crystallinity, the crystallization temperature (Tc) of the polyamide resin according to this embodiment is preferably 180°C or higher, more preferably 185°C or higher, even more preferably 190°C or higher, and still more preferably 195°C or higher. There is no particular upper limit to the crystallization temperature of the 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 polyamide resin is preferably 180 to 310°C.

[0065] 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.

[0066] (Crystallization Rate) From the viewpoint of crystallinity, the crystallization rate of the polyamide resin according to this embodiment is preferably 0.025 or more, more preferably 0.030 or more, and may be 0.035 or more in some cases. There is no particular upper limit to the crystallization rate of the polyamide resin, but it may be, for example, 0.070 or less or 0.060 or less. That is, the crystallization rate of the polyamide resin is preferably 0.025 to 0.070, 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).

[0067] [Solubility] (Solubility during Stirring) The polyamide resin according to this embodiment exhibits excellent solubility in a solvent under stirring conditions (solubility during stirring), preferably in a solvent at a relatively low temperature such as room temperature. Specifically, when stirred in the presence of a sufficient amount of solvent, it tends to dissolve within 3 hours. This eliminates the need to heat the solvent, and allows the heating temperature to be kept to a minimum. A solvent that is soluble in polyamide resins, such as 1,1,1,3,3,3-hexafluoro-2-propanol (hereinafter also referred to as "HFIP"), is typically selected as the solvent. Solubility during stirring can be evaluated, for example, by the method described in the Examples section below. (Volume Swelling Ratio) When immersed in a solvent under non-stirring conditions (static conditions), the polyamide resin tends to first swell and then dissolve in the solvent. Dissolution in the solvent can be confirmed, for example, by visually observing a colored polyamide resin becoming transparent. The polyamide resin according to this embodiment takes a short time to reach a dissolved state in a solvent under non-stirring conditions (static conditions). Specifically, when immersed in a sufficient amount of solvent, it tends to dissolve within 120 minutes, preferably within 90 minutes, more preferably within 60 minutes, and even more preferably within 30 minutes. Therefore, it is possible to eliminate the need to heat the solvent or minimize the heating temperature. The volume swelling ratio can be evaluated, for example, by the method described in the Examples section below, by multiplying the volume ratio before and after immersion in the solvent.

[0068] [Mechanical Properties] (Tensile Modulus) The tensile modulus of the polyamide resin according to this embodiment is preferably 700 MPa or more, more preferably 800 MPa or more, even more preferably 900 MPa or more, and even more preferably 1000 MPa or more. Therefore, the polyamide resin according to this embodiment has the effect of having sufficiently high mechanical strength while having excellent solubility in the above-mentioned solvents. (Tensile Strength) The tensile strength of the polyamide resin according to this embodiment is preferably 15 MPa or more, more preferably 18 MPa or more, even more preferably 21 MPa or more, and even more preferably 25 MPa or more. Therefore, the polyamide resin according to this embodiment has the effect of having sufficiently high mechanical strength while having excellent solubility in the above-mentioned solvents.

[0069] The tensile modulus and tensile strength can be measured using a tensile tester, more specifically, by the method described in the Examples section below.

[0070] [Method for Producing Polyamide Resin] The polyamide resin according to the present 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 necessary.

[0071] The polymerization method is not limited as long as the half-width (° C.) of the recrystallization peak of the resulting polyamide resin satisfies the condition of 10° C. or less. 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.

[0072] 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).

[0073] 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).

[0074] 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).

[0075] 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.

[0076] 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.

[0077] [Resin Composition] The resin composition according to this embodiment contains the polyamide resin described above and other components exemplified below. In one aspect, the resin composition further contains, in addition to the 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.

[0078] In one embodiment, the resin composition contains, in addition to the 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, biological repellents (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 polyamide resin.

[0079] In one embodiment, the resin composition may contain a solvent (e.g., an organic solvent), in which case the polyamide resin may be dissolved in the solvent, or may be dispersed in the solvent without being dissolved.

[0080] As described above, the resin composition according to the present embodiment preferably contains the polyamide resin described above and at least one selected from other resins, additives, and solvents.

[0081] [Coating Liquid] The coating liquid according to this embodiment contains the polyamide resin described above and a solvent. Since the polyamide resin described above has excellent solubility in solvents, the solvent used in the coating liquid is not limited as long as it can dissolve the polyamide resin. Examples of solvents include fluoroalcohols such as HFIP, dimethyl sulfoxide, and water / alcohol mixed solvents. Since the coating liquid according to this embodiment contains a polyamide resin with excellent solubility, it can be prepared with reduced burden on the manufacturing process. Furthermore, the coating liquid according to this embodiment usually becomes a cured product upon drying. Therefore, the coating liquid according to this embodiment can be molded into, for example, a film.

[0082] The coating fluid according to this embodiment may further contain various additives (e.g., inorganic particles (talc, silica, mica (layered silicate), clay, etc.), fillers, processing stabilizers, weathering stabilizers, colorants, UV absorbers, antioxidants, antistatic agents, flame retardants, plasticizers, other thermoplastic resins, lubricants, fragrances, antifoaming agents, deodorizers, extenders, release agents, mold release agents, reinforcing agents, mildew inhibitors, preservatives, radical generators, crystallization rate retarders, and combinations thereof) within the range that does not impair the effects of the present invention. The content of other additives is not particularly limited, and an appropriate amount can be selected by one skilled in the art.

[0083] [Molded Article] The molded article according to this embodiment contains the polyamide resin or the resin composition described above. Since the polyamide resin has excellent solubility in solvents, the molded article according to this embodiment can be produced with reduced burden in the manufacturing process. The molded article according to this embodiment can be obtained by dissolving the polyamide resin 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.

[0084] 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.

[0085] [Laminate] The laminate according to this embodiment includes at least one layer containing the polyamide resin described above. Preferably, the laminate according to this embodiment includes a substrate and a layer containing the polyamide resin described above formed on the surface of the substrate. The layer containing the polyamide resin may be formed on multiple surfaces of the substrate.

[0086] 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).

[0087] [Method for producing molded body and laminate] There is no particular limitation on the method for producing the molded body and laminate, and various conventional molding methods can be adopted. For example, a laminate can be formed by dissolving a 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 body.

[0088] [Uses] The polyamide resin of the present embodiment can be molded into any shape (for example, fiber or film) due to its excellent solubility and melt moldability, and can therefore be used in a wide range of applications required for molded articles and laminates. Examples of applications include electrical and electronic parts, 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, household goods, 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, etc.). , 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.).

[0089] 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.

[0090] The polyamide resins obtained in the examples and comparative examples described below were measured and evaluated according to the methods described below.

[0091] [1. Calculation of the molar ratio (a) / (b)] The molar ratio (a) / (b) of the polyamide resins obtained in the examples and comparative examples described below was calculated using a nuclear magnetic resonance spectrometer "LAMBDA 500" manufactured by JEOL Ltd. １H-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 molar ratio (a) / (b) of the structural unit (a) constituting the polyamide resin to the structural unit (b) was calculated using the integral values ​​of the peaks (1) to (3) below. Here, the mol% of the structural unit (a) and the mol% of the structural unit (b) were calculated so that the sum of the mol% of the structural unit (a) and the mol% of the structural unit (b) was 100 mol%, and then the molar ratio (a) / (b) was calculated. Specifically, the integral value of the peak (3) below was set to 100 mol%, and the mol% of the structural unit (a) was calculated based on the integral value of the peak (1) below, and the mol% of the structural unit (b) was calculated based on the integral value of the peak (2) 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). When the polyamide resin contains the structural unit (c), the mole percentages of the structural unit (a) and the structural unit (b) were calculated so that the sum of the mole percentages of the structural unit (a), the mole percentages of the structural unit (b), and the mole percentages of the structural unit (c) was 100 mole%, and then the molar ratio (a) / (b) was calculated.

[0092] [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

[0093] [3. Evaluation of Thermal Properties] [3-1. Measurement of Melting Point (Tm) and Crystallization Temperature (Tc)] Using a differential scanning calorimeter "Q1000" manufactured by TA Instruments, Inc., the thermal properties of the polyamide resins obtained in the following examples and comparative examples were measured under the conditions of a heating / cooling rate of 10°C / min and a temperature range of 0°C to 270°C. 1 to 3 mg of finely powdered polyamide resin was prepared as the measurement sample. The melting point (Tm) was measured using the value obtained during the second heating. The crystallization temperature (Tc) was measured using the peak-top temperature of the recrystallization peak during cooling. The crystallization rate was calculated from the melting point (Tm) and the recrystallization temperature (Tc). Specifically, the crystallization rate was calculated based on (1 / (Tm - Tc)). These results are shown in Table 1.

[0094] [3-2. Calculation of half-width] The half-width (°C) of the recrystallization peak during cooling was determined from the data showing the relationship between heat flow (W / g) and temperature (°C) obtained by the measurement using DSC in 3-1 above. Specifically, the half-width value can be output by using a differential scanning calorimeter "Q1000," and this output value was used.

[0095] [4. Evaluation of Solubility] [4-1. Solubility during Stirring] HFIP at room temperature as a solvent was placed in a separable flask equipped with an anchor-shaped stirring blade and a reflux tube, and stirring was initiated at a speed of 100 rpm. The polyamide resins obtained in the examples and comparative examples described below were weighed out to a concentration of 2% by mass, and then added little by little to the solvent using a powder funnel, followed by stirring at room temperature for 3 hours. After 3 hours had passed, the state of dissolution of the polyamide in the solvent was visually observed. The observation results are shown in Table 2.

[0096] [4-2. Measurement of Volume Swelling Ratio] The polyamide resins obtained in the Examples and Comparative Examples described below were filled into a graduated cylinder while tapping the side of the cylinder. After filling was complete, the volumetric filling amount V1 (mL) was read from the graduated cylinder's scale. The volumetric filling amount of the polyamide resin was adjusted to 1.0 mL as much as possible so that it would be consistent across all evaluations. Next, the same volume as V1 (i.e., 1.0 mL) of HFIP as a solvent was poured into the graduated cylinder while tapping the side of the cylinder. This allowed the polyamide resin to be impregnated with HFIP. The measurement start time (i.e., 0 minutes) was the time when the polyamide resin settled after standing. The time required for settling was within 1 minute in all measurements. Thereafter, the volume V2 of the polyamide resin after 1 minute, 30 minutes, 60 minutes, and 120 minutes was read from the graduated cylinder's scale. V2 / V1 was then calculated, and this was defined as the volumetric swelling ratio (times). The volumetric swelling ratio at time 0 minutes was defined as 1.0 (times). The results are shown in Table 2. In Table 2, "dissolved" in the volume swelling ratio column indicates that the polyamide resin was completely dissolved in the solvent at the time of evaluation, and the volume could no longer be read from the graduations on the measuring cylinder.

[0097] [4-3. Overall evaluation] Based on the results of 4-1 and 4-2 above, the solubility of each polyamide resin was overall evaluated according to the following criteria A to E. A: When the polyamide resin was dissolved after 3 hours of stirring and within 30 minutes of impregnation and standing B: When the polyamide resin was dissolved after 3 hours of stirring and within 60 minutes of impregnation and standing C: When the polyamide resin was dissolved after 3 hours of stirring and within 120 minutes of impregnation and standing D: When the polyamide resin was dissolved after 3 hours of stirring but did not dissolve even after 120 minutes of impregnation and standing E: When the polyamide resin was not dissolved after 3 hours of stirring

[0098] [5. Evaluation of Mechanical Strength: Measurement of Tensile Modulus and Tensile Strength] (1) Preparation of Films Using the polyamide resins obtained in the Examples and Comparative Examples described below, films with a thickness of 10 μm were prepared as follows. First, a 10% by mass solution of 2,2,2-trifluoroethanol was prepared using the polyamide resin. This gave a coating solution.

[0099] Next, the obtained coating liquid was coated at room temperature on the surface of a substrate (PET film) having a thickness of 100 μm using a bar coater. This resulted in a laminate consisting of the substrate and the coating liquid. Subsequently, this laminate was dried in a hot air dryer at 40°C. As a result, the coating liquid became a film-like cured product (molded product), and as a result, a laminate consisting of the substrate and the molded product was obtained. Thereafter, the film-like molded product was peeled off from the substrate of the obtained laminate. This resulted in a film having a thickness of 10 μm.

[0100] (2) Preparation of Test Pieces The 10 μm thick film prepared in (1) above was cut into a 10 mm wide dumbbell shape. This prepared test pieces for mechanical strength evaluation. Each test piece was conditioned for one week in a storage environment of 23°C and 50% RH.

[0101] (3) Measurements The test pieces obtained in (2) above were measured for tensile modulus and elongation at break using an autograph (AG-5000B manufactured by Shimadzu Corporation) (measurement conditions: load cell 1 kN, tensile speed 10 mm / min, chuck distance 70 mm). The tensile strength was calculated from the elongation at break. The same measurement was carried out five times, and the average value was used. The results are shown in Table 3.

[0102] Example 1 A reactor equipped with a reflux condenser, a stirrer, a thermometer, a nitrogen inlet, and a feed port for a post-addition liquid was prepared, and the interior 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 (hereinafter also referred to as "2PY") and 4-methyl-2-pyrrolidone (hereinafter also referred to as "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.

[0103] 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.

[0104] Thereafter, the internal temperature was cooled to 30°C, and 1.4 parts by mass of N-acetyl-ε-caprolactam (hereinafter also referred to as "AcCL") was added, and polymerization was initiated while the temperature was kept at 30°C.

[0105] 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.

[0106] 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.

[0107] A white solid was filtered from the resulting reaction solution and recovered as a product. 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.

[0108] 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.

[0109] Example 2 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, 74.2 parts by mass of a mixture of 2PY and 4MPY (2PY / 4MPY=5 / 5 (molar ratio)), 48.0 parts by mass of a THF solution (1 M) of potassium tert-butoxide, 31.1 parts by mass of ε-caprolactam (hereinafter also referred to as "εCL"), and 192.8 parts by mass of liquid paraffin were added. Thereafter, the pressure inside the system was reduced to 1 kPa, and the internal temperature was raised to 80°C, and stirring was continued for 1 hour.

[0110] The mixture was then heated to an internal temperature of 130°C, 1.4 parts by mass of AcCl was added, polymerization was initiated, and the polymerization reaction was carried out for a total of 2 hours. 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.

[0111] 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.

[0112] 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.

[0113] Example 3 A polymerization reaction was carried out in the same manner as in Example 1, 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) The mixture of 2PY and 4MPY (2PY / 4MPY = 5 / 5 (molar ratio)) was changed from 104.2 parts by mass to 32.1 parts by mass of the mixture of 2PY and 4MPY (2PY / 4MPY = 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.

[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 Example 3 was obtained. The obtained polyamide resin was subjected to the above-mentioned measurements and evaluations.

[0116] Example 4 A polymerization reaction was carried out in the same manner as in Example 3, except for the following change (1): (1) 32.1 parts by mass of a mixture of 2PY and 4MPY (2PY / 4MPY = 7 / 3 (molar ratio)) was replaced with 32.1 parts by mass of a mixture of 2-pyrrolidone (2PY) and 3-methyl-2-pyrrolidone (hereinafter also referred to as "3MPY") (2PY / 3MPY = 7 / 3 (molar ratio)).

[0117] 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.

[0118] In this way, a polyamide resin according to Example 4 was obtained. The obtained polyamide resin was subjected to the above-mentioned measurements and evaluations.

[0119] Example 5 A reactor identical to that used in Example 1 was prepared, and the interior of the system was completely purged with nitrogen. 1.2 parts by mass of tetramethylammonium chloride, 31.3 parts by mass of a mixture of 2-pyrrolidone (2PY) and 4-methyl-2-pyrrolidone (4MPY) (2PY / 4MPY = 5 / 5 (molar ratio)), and 57.9 parts by mass of liquid paraffin were charged into the reactor and stirred. As a result, the mixture in the reactor became a suspension. 14.4 parts by mass of a THF solution (1 M) of potassium tert-butoxide was added to the suspension. 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.

[0120] Thereafter, the internal temperature was cooled to 30°C, and 0.4 parts by mass of AcCl was added to initiate polymerization while maintaining the temperature 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.

[0121] 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.

[0122] In this way, a polyamide resin according to Example 5 was obtained. The obtained polyamide resin was subjected to the above-mentioned measurements and evaluations.

[0123] 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. 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 to the reactor. The pressure inside the system was then reduced to 1 kPa, and the internal temperature was raised to 50°C, followed by stirring for 1 hour.

[0124] Thereafter, the internal temperature was cooled to 30° C., and 3.5 parts by mass of N-acetyl-ε-caprolactam (hereinafter also referred to as “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.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] Comparative Example 2 A polymerization reaction was carried out in the same manner as in Example 3, except for the following changes (1) and (2): (1) 32.1 parts by mass of a mixture of 2PY and 4MPY (2PY / 4MPY = 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.

[0129] 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.

[0130] 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.

[0131] The measurement results and evaluation results for Examples 1 to 5 and Comparative Examples 1 and 2 are shown in Tables 1 to 3.

[0132]

[0133]

[0134]

[0135] From Tables 1 and 2, it can be seen that the polyamide resins according to Examples 1 to 5, which contain structural units derived from monomers having branched chains and have a half-width (°C) of the recrystallization peak during cooling measured using DSC of 10 or less, have excellent solubility in solvents even at relatively low temperatures such as room temperature.

[0136] Furthermore, Table 3 shows that the polyamide resins of Examples 1 to 5, like the polyamide resins of Comparative Examples 1 and 2, had a tensile modulus of 700 MPa or more and a tensile strength of 15 MPa, and therefore had excellent solubility in solvents without compromising mechanical strength.

[0137] The polyamide resin of the present invention is useful in various applications requiring excellent solubility, such as coating solutions, molded articles, and laminates.

Claims

1. A polyamide resin comprising a structural unit (a) represented by the following formula (I), in which the half-width (°C) of a recrystallization peak upon cooling measured using a differential scanning calorimeter (DSC) is 10 or less: 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 structural unit (a) is represented by the formula (I), wherein X is C ２－４ An alkylene group, provided that ２－４ The 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.

3. The structural unit (a) is represented by the formula (I), wherein X is C ３ An alkylene group, provided that ３ The 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.

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

5. The polyamide resin according to claim 4, wherein the content of the structural unit (b) in the polyamide resin is 50 mol % or more.

6. The polyamide resin according to claim 4, wherein the molar ratio of the structural unit (a) to the structural unit (b) is from 10 / 90 to 25 / 75.

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

8. A coating liquid comprising the polyamide resin according to any one of claims 1 to 7 and a solvent.

9. A molded article comprising the polyamide resin according to any one of claims 1 to 7.

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 polyamide resin according to any one of claims 1 to 7.

Images