Polyamide resin

Abstract

Disclosed is a polyamide resin which has a constituent unit (A) that is derived from a diamine and a constituent unit (B) that is derived from a dicarboxylic acid, wherein: the constituent unit (A) contains at least one constituent unit (A1) which is selected from the group consisting of a constituent unit that is derived from meta-xylylenediamine and a constituent unit that is derived from para-xylylenediamine, and a constituent unit (A2) that is derived from ortho-xylylenediamine; and the content of the constituent unit (A2) is 0.006 to 0.15 part by mass with respect to 100 parts by mass of the constituent unit (A1).

Description

Polyamide resin

[0001] The present invention relates to a polyamide resin.

[0002] Polyamide resins using xylylenediamine as the primary diamine component are useful as various molding materials due to their excellent mechanical properties, such as strength and modulus of elasticity. Furthermore, these polyamide resins are also useful as packaging materials due to their excellent barrier properties against gases such as oxygen and carbon dioxide. When polyamide resins are used as molding materials, it is known that the crystallization rate is increased by adding a nucleating agent to the polyamide resin in order to improve the molding processability of the polyamide resin and the transparency and physical properties of the resulting molded product. For example, Patent Document 1 discloses monoterpene diphenols in which two phenol molecules are added to one monoterpene molecule, and polyamide nucleating agents that are metal salts of monoterpene diphenols, as well as polyamide compositions containing the same.

[0003] Japanese Patent Application Publication No. 11-158370

[0004] As described above, adding a nucleating agent increases the crystallization rate, but a separate step of mixing the nucleating agent into the polyamide resin before molding is required, which creates problems such as limitations on the equipment and methods involved in mixing and molding. Furthermore, because the nucleating agent is dispersed in the polyamide resin, there is a risk that the mechanical properties and transparency of molded articles made from compositions containing the polyamide resin may be reduced. Therefore, there has been a demand for improving the crystallization rate of polyamide resins without using a nucleating agent. The present invention has been made in light of these circumstances, and the object of the present invention is to provide a polyamide resin that has a high crystallization rate and rapid crystallization without using a nucleating agent.

[0005] The present inventors discovered that the above-mentioned problems can be solved by including a specific ratio of xylylenediamine isomers in a polyamide resin having structural units derived from xylylenediamine, and thus completed the invention.

[0006] That is, the present invention relates to the following items [1] to

[11] . [1] A polyamide resin having a diamine-derived structural unit (A) and a dicarboxylic acid-derived structural unit (B), wherein the structural unit (A) contains at least one structural unit (A1) selected from the group consisting of meta-xylylenediamine-derived structural units and para-xylylenediamine-derived structural units, and an ortho-xylylenediamine-derived structural unit (A2), and the content of the structural unit (A2) is 0.006 to 0.15 parts by mass per 100 parts by mass of the structural unit (A1). [2] The polyamide resin according to item [1] above, wherein the dicarboxylic acid contains at least one selected from the group consisting of aliphatic dicarboxylic acids having 4 to 20 carbon atoms, terephthalic acid, and isophthalic acid. [3] The polyamide resin according to [2] above, wherein the total content of the structural units (A1) and (A2) in the structural units (A) is 70 mol% or more, and the content of structural units derived from an aliphatic dicarboxylic acid having 4 to 20 carbon atoms in the structural units (B) is 50 mol% or more. [4] The polyamide resin according to any one of [1] to [3] above, wherein the dicarboxylic acid contains at least one selected from the group consisting of adipic acid, sebacic acid, and dodecanedioic acid. [5] The polyamide resin according to any one of [1] to [4] above, wherein the structural unit (A1) is a structural unit derived from metaxylylenediamine. [6] A method for producing a polyamide resin, comprising a step of introducing a diamine (a) and a dicarboxylic acid (b) into a reaction system and carrying out a polycondensation reaction, wherein the diamine (a) contains at least one diamine (a1) selected from the group consisting of metaxylylenediamine and paraxylylenediamine, and orthoxylylenediamine (a2), and the amount of orthoxylylenediamine (a2) introduced is 0.006 to 0.15 parts by mass per 100 parts by mass of the diamine (a1). [7] A method for producing a polyamide resin according to [6] above, wherein the dicarboxylic acid (b) contains at least one selected from the group consisting of an aliphatic dicarboxylic acid having 4 to 20 carbon atoms, terephthalic acid, and isophthalic acid.[8] A method for producing a polyamide resin according to [7] above, wherein the total amount of diamine (a1) and orthoxylylenediamine (a2) incorporated in diamine (a) is 70 mol % or more, and the content of aliphatic dicarboxylic acid having 4 to 20 carbon atoms in dicarboxylic acid (b) is 50 mol % or more. [9] A method for producing a polyamide resin according to any one of [6] to [8] above, wherein dicarboxylic acid (b) contains at least one selected from the group consisting of adipic acid, sebacic acid, and dodecanedioic acid.

[10] A method for producing a polyamide resin according to any one of [6] to [9] above, wherein diamine (a1) is metaxylylenediamine.

[11] A method for producing a polyamide resin according to any one of [6] to

[10] above, further comprising a step of solid-state polymerization.

[0007] According to the present invention, a polyamide resin having a high crystallization rate and rapid crystallization can be provided without using a crystal nucleating agent. As the crystallization rate of the polyamide resin increases, its moldability improves and molded articles maintaining high transparency can be produced. Therefore, the polyamide resin of the present invention and the polyamide resin obtained by the production method of the present invention can be suitably used as materials for packaging films, hollow containers, various molded articles, fibers, etc.

[0008] [Polyamide Resin] The polyamide resin of the present invention has a diamine-derived structural unit (A) and a dicarboxylic acid-derived structural unit (B), wherein the structural unit (A) contains at least one structural unit (A1) selected from the group consisting of meta-xylylenediamine-derived structural units and para-xylylenediamine-derived structural units, and an ortho-xylylenediamine-derived structural unit (A2), and the content of the structural unit (A2) is 0.006 to 0.15 parts by mass per 100 parts by mass of the structural unit (A1).

[0009] The polyamide resin of the present invention has a diamine-derived structural unit (A) and a dicarboxylic acid-derived structural unit (B). In the polyamide resin of the present invention, the structural unit (A) and the structural unit (B) form an amide structure. The structural unit (A) contains at least one structural unit (A1) selected from the group consisting of meta-xylylenediamine-derived structural units and para-xylylenediamine-derived structural units, and an orthoxylylenediamine-derived structural unit (A2), and the content of the structural unit (A2) is 0.006 to 0.15 parts by mass per 100 parts by mass of the structural unit (A1).

[0010] The polyamide resin of the present invention is also preferably a polyamide resin (biomass thermoplastic resin) produced using recycled resin or biomass raw materials. By using a biomass thermoplastic resin, the environmental impact can be reduced. For example, in a xylylenediamine-based polyamide resin, bioadipic acid can be used as the biomass raw material. Mass balance certified (ISCC PLUS) adipic acid can also be used. Mass balance certification means that the amount of renewable raw materials or bio-based raw materials used at each factory or production facility and the amount of products produced or shipped are quantified and guaranteed together with the quality.

[0011] <Structural Unit (A)> The structural unit (A) is a structural unit derived from a diamine, and contains at least one structural unit (A1) selected from the group consisting of structural units derived from meta-xylylenediamine and structural units derived from para-xylylenediamine, and a structural unit (A2) derived from ortho-xylylenediamine, and the content of the structural unit (A2) is 0.006 to 0.15 parts by mass per 100 parts by mass of the structural unit (A1).

[0012] The structural unit (A1) is at least one structural unit selected from the group consisting of metaxylylenediamine-derived structural units and paraxylylenediamine-derived structural units, and from the viewpoints of gas barrier properties and crystallization rate, a metaxylylenediamine-derived structural unit is preferred. By containing the structural unit (A1), the polyamide resin of the present invention will have excellent crystallization rate, melt moldability, mechanical properties, and gas barrier properties.

[0013] The content of the structural unit (A1) in the structural unit (A) is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, still more preferably 95 mol% or more, and even more preferably 99 mol% or more, and the structural unit (A) may be composed only of the structural unit (A1) and the structural unit (A2). When the content of the structural unit (A1) is 70 mol% or more, the polyamide resin of the present invention will have excellent crystallization rate, melt moldability, mechanical properties, and gas barrier properties.

[0014] The structural unit (A) further contains a structural unit (A2) derived from orthoxylylenediamine, and the content of the structural unit (A2) is 0.006 to 0.15 parts by mass per 100 parts by mass of the structural unit (A1). From the viewpoints of improving the crystallization rate and improving the mechanical properties, and of polymerization efficiency, the content of the structural unit (A2) derived from orthoxylylenediamine, relative to 100 parts by mass of the structural unit (A1), is 0.006 to 0.15 parts by mass, preferably 0.010 to 0.14 parts by mass, more preferably 0.020 to 0.13 parts by mass, even more preferably 0.030 to 0.12 parts by mass, still more preferably 0.040 to 0.10 parts by mass, still more preferably 0.050 to 0.10 parts by mass, still more preferably 0.050 to 0.090 parts by mass, still more preferably 0.050 to 0.080 parts by mass, and still more preferably 0.050 to 0.070 parts by mass. Furthermore, from the viewpoint of improving the crystallization rate using a particularly small amount of orthoxylylenediamine-derived structural unit (A2), the content of the structural unit (A2) derived from orthoxylylenediamine, relative to 100 parts by mass of the structural unit (A1), is 0.006 to 0.080 parts by mass, preferably 0.006 to 0.070 parts by mass, more preferably 0.010 to 0.070 parts by mass, even more preferably 0.010 to 0.060 parts by mass, still more preferably 0.010 to 0.050 parts by mass, still more preferably 0.010 to 0.040 parts by mass, still more preferably 0.010 to 0.030 parts by mass, and even more preferably 0.010 to 0.020 parts by mass. The total content of the structural unit (A1) and the structural unit (A2) in the structural unit (A) is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and even more preferably 99 mol% or more. There is no upper limit, but it is preferably 100 mol% or less. The structural unit (A) may consist only of the structural unit (A1) and the structural unit (A2). When the total content of the structural unit (A1) and the structural unit (A2) is 70 mol% or more, the polyamide resin of the present invention will have excellent crystallization rate, melt moldability, mechanical properties, and gas barrier properties.

[0015] The structural unit (A) may contain a structural unit other than the structural unit (A1) and the structural unit (A2). That is, it may contain a structural unit derived from a diamine other than meta-xylylenediamine, para-xylylenediamine, or orthoxylylenediamine. Examples of diamines other than meta-xylylenediamine, para-xylylenediamine, and orthoxylylenediamine (diamines from which structural units other than the structural unit (A1) and the structural unit (A2) are derived) include aliphatic diamines such as tetramethylenediamine, pentamethylenediamine, 2-methylpentanediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, dodecamethylenediamine, 2,2,4-trimethylhexamethylenediamine, and 2,4,4-trimethylhexamethylenediamine; Examples of diamines that can be used include, but are not limited to, alicyclic diamines such as 1,4-bis(aminomethyl)cyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, bis(4-aminocyclohexyl)methane, 2,2-bis(4-aminocyclohexyl)propane, bis(aminomethyl)decalin, and bis(aminomethyl)tricyclodecane; and diamines having an aromatic ring such as bis(4-aminophenyl)ether, paraphenylenediamine, and bis(aminomethyl)naphthalene. These diamines can be used alone or in combination of two or more.

[0016] <Structural Unit (B)> The structural unit (B) is a structural unit derived from a dicarboxylic acid. From the viewpoints of crystallization rate, moldability, gas barrier properties, and mechanical properties, the dicarboxylic acid (the dicarboxylic acid from which the structural unit (B) is derived) preferably contains at least one selected from the group consisting of an aliphatic dicarboxylic acid having 4 to 20 carbon atoms, terephthalic acid, and isophthalic acid, more preferably contains an aliphatic dicarboxylic acid having 4 to 20 carbon atoms, and even more preferably contains an aliphatic dicarboxylic acid having 4 to 12 carbon atoms. Furthermore, from the viewpoints of crystallization rate, moldability, gas barrier properties, and mechanical properties, the dicarboxylic acid (the dicarboxylic acid from which the structural unit (B) is derived) is more preferably at least one selected from the group consisting of an aliphatic dicarboxylic acid having 4 to 20 carbon atoms, terephthalic acid, and isophthalic acid, more preferably is an aliphatic dicarboxylic acid having 4 to 20 carbon atoms, and even more preferably is an aliphatic dicarboxylic acid having 4 to 12 carbon atoms. Examples of aliphatic dicarboxylic acids having 4 to 20 carbon atoms include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, 1,11-undecanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,16-hexadecanedicarboxylic acid, and 1,18-octadecanedicarboxylic acid. Among these, from the viewpoint of crystallinity and high elasticity, at least one selected from the group consisting of adipic acid, sebacic acid, and dodecanedioic acid is preferred, at least one selected from the group consisting of adipic acid and sebacic acid is more preferred, and adipic acid is even more preferred. These dicarboxylic acids may be used alone or in combination of two or more.

[0017] Other dicarboxylic acids that can be used as the dicarboxylic acid include aliphatic dicarboxylic acids having 3 or less carbon atoms, such as oxalic acid and malonic acid; and aromatic dicarboxylic acids other than terephthalic acid and isophthalic acid, such as 2,6-naphthalenedicarboxylic acid.

[0018] The content of the aliphatic dicarboxylic acid having 4 to 20 carbon atoms in the dicarboxylic acid is preferably 50 mol% or more, more preferably 70 to 100 mol%, and even more preferably 85 to 100 mol%. When the content of the aliphatic dicarboxylic acid having 4 to 20 carbon atoms in the dicarboxylic acid is within the above range, the resulting polyamide resin will have excellent crystallization rate, moldability, gas barrier properties, and mechanical properties. The content of the aliphatic dicarboxylic acid having 4 to 20 carbon atoms in the dicarboxylic acid is the same as the content of the structural units derived from the aliphatic dicarboxylic acid having 4 to 20 carbon atoms in the structural unit (B). From the same viewpoint as above, the content of the structural units derived from the aliphatic dicarboxylic acid having 4 to 20 carbon atoms in the structural unit (B) is preferably 50 mol% or more, more preferably 70 to 100 mol%, and even more preferably 85 to 100 mol%.

[0019] The polyamide resin of the present invention, having the above-described structure, becomes a polyamide resin having a high crystallization rate while maintaining high transparency. Since the moldability improves with the increase in the crystallization rate of the polyamide resin, the crystallization process time during molding can be shortened. That is, the molding cycle is accelerated, and the productivity of molded products can be improved. Furthermore, problems such as a decrease in the mechanical properties and transparency of molded products, which are caused by adding a crystal nucleating agent to improve the moldability of the polyamide resin, can be avoided.

[0020] <Properties of Polyamide Resin, etc.> The polyamide resin of the present invention has a high crystallization rate and exhibits rapid crystallization. This improves the moldability of the polyamide resin, thereby shortening the crystallization process time during molding. This shortens the molding cycle, thereby improving the productivity of molded articles. Furthermore, problems such as a decrease in the mechanical properties and transparency of molded articles, which are caused by the addition of a crystal nucleating agent to improve the moldability of polyamide resins, can be avoided. The crystallization rate of a polyamide resin can be evaluated by measuring its half-crystallization time. Here, the half-crystallization time refers to the time it takes for a crystalline material to progress halfway through crystallization when transitioning from a molten state to a crystalline state. The shorter the half-crystallization time, the higher the crystallization rate and the faster the crystallization of the material. The half-crystallization time of the polyamide resin of the present invention at 120°C is preferably 3,000 seconds or less, more preferably 2,950 seconds or less, even more preferably 2,900 seconds or less, even more preferably 2,800 seconds or less, and even more preferably 2,700 seconds or less. Specifically, the crystallization half time can be measured by the method described in the Examples.

[0021] The polyamide resin may contain additives such as delustering agents, heat stabilizers, weathering agents, ultraviolet absorbers, plasticizers, flame retardants, antistatic agents, coloring inhibitors, and antigelling agents depending on the application and purpose, as long as the effects of the present invention are not impaired.

[0022] The polyamide resin of the present invention can be molded into various shapes by conventionally known molding methods. Examples of molding methods include injection molding, blow molding, extrusion molding, compression molding, vacuum molding, press molding, direct blow molding, rotational molding, sandwich molding, and two-color molding. The polyamide resin of the present invention has an improved crystallization rate, which shortens the crystallization process time during molding. In other words, the molding cycle is faster, resulting in improved productivity. Furthermore, the polyamide resin of the present invention, which has a high crystallization rate, is suitable as a material for packaging films, hollow containers, various molded products, fibers, etc., and since it does not impair the transparency of the molded products, it is particularly suitable for packaging films, hollow containers, etc., which require high transparency.

[0023] [Method for producing polyamide resin] The polyamide resin of the present invention may be produced by any method, but is preferably obtained by the following production method. The following method for producing a polyamide resin is also included in the present invention. The method for producing a polyamide resin of the present invention is a method for producing a polyamide resin comprising the steps of introducing a diamine (a) and a dicarboxylic acid (b) into a reaction system and carrying out a polycondensation reaction, wherein the diamine (a) contains at least one diamine (a1) selected from the group consisting of meta-xylylenediamine and para-xylylenediamine, and orthoxylylenediamine (a2), and the amount of orthoxylylenediamine (a2) introduced is 0.006 to 0.15 parts by mass per 100 parts by mass of the diamine (a1).

[0024] The polyamide resin production method of the present invention also preferably produces polyamide resin (biomass thermoplastic resin) using recycled resin or biomass raw materials. By producing biomass thermoplastic resin using recycled resin or biomass raw materials, environmental impact can be reduced. For example, in the production of xylylenediamine-based polyamide resin, bioadipic acid can be used as the biomass raw material. Mass balance certified (ISCC PLUS) adipic acid can also be used. Mass balance certification means that the amount of renewable raw materials or biomaterials used at each factory or production facility and the amount of products produced or shipped are quantified and guaranteed along with their quality.

[0025] The method for producing a polyamide resin of the present invention includes a step of introducing a diamine (a) and a dicarboxylic acid (b) into a reaction system and carrying out a polycondensation reaction. The diamine (a) contains at least one diamine (a1) selected from the group consisting of meta-xylylenediamine and para-xylylenediamine, and orthoxylylenediamine (a2), and the amount of orthoxylylenediamine (a2) introduced is 0.006 to 0.15 parts by mass per 100 parts by mass of the diamine (a1).

[0026] <Diamine (a)> The diamine (a) in the present production method contains at least one diamine (a1) selected from the group consisting of meta-xylylenediamine and para-xylylenediamine, and orthoxylylenediamine (a2), and the amount of orthoxylylenediamine (a2) incorporated is 0.006 to 0.15 parts by mass per 100 parts by mass of the diamine (a1).

[0027] The diamine (a1) is at least one diamine selected from the group consisting of metaxylylenediamine and paraxylylenediamine, and is preferably metaxylylenediamine from the viewpoints of gas barrier properties and crystallization rate. By including the diamine (a1), the polyamide resin obtained by this production method has excellent crystallization rate, melt moldability, mechanical properties, and gas barrier properties.

[0028] The amount of diamine (a1) incorporated in diamine (a) is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, still more preferably 95 mol% or more, and still more preferably 99 mol% or more, and diamine (a) may consist of only diamine (a1) and diamine (a2). When the amount of diamine (a1) incorporated is 70 mol% or more, the polyamide resin obtained by this production method has excellent crystallization rate, melt moldability, mechanical properties, and gas barrier properties.

[0029] The diamine (a) further contains orthoxylylenediamine (a2), and the amount of orthoxylylenediamine (a2) introduced is 0.006 to 0.15 parts by mass per 100 parts by mass of the diamine (a1). The amount of orthoxylylenediamine (a2) introduced is, from the viewpoints of improving the crystallization rate and improving the mechanical properties, and of polymerization efficiency, 0.006 to 0.15 parts by mass, preferably 0.010 to 0.14 parts by mass, more preferably 0.020 to 0.13 parts by mass, even more preferably 0.030 to 0.12 parts by mass, still more preferably 0.040 to 0.10 parts by mass, still more preferably 0.05 to 0.10 parts by mass, still more preferably 0.050 to 0.090 parts by mass, still more preferably 0.050 to 0.080 parts by mass, and still more preferably 0.050 to 0.070 parts by mass, relative to 100 parts by mass of diamine (a1). Furthermore, from the viewpoint of improving the crystallization rate with a particularly small amount of orthoxylylenediamine (a2), the amount of orthoxylylenediamine (a2) introduced is 0.006 to 0.080 parts by mass, preferably 0.006 to 0.070 parts by mass, more preferably 0.010 to 0.070 parts by mass, even more preferably 0.010 to 0.060 parts by mass, still more preferably 0.010 to 0.050 parts by mass, still more preferably 0.010 to 0.040 parts by mass, still more preferably 0.010 to 0.030 parts by mass, and still more preferably 0.010 to 0.020 parts by mass, relative to 100 parts by mass of diamine (a1). The total amount of diamine (a1) and orthoxylylenediamine (a2) incorporated in diamine (a) is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, still more preferably 95 mol% or more, and even more preferably 99 mol% or more. There is no upper limit, but it is preferably 100 mol% or less. Diamine (a) may consist only of diamine (a1) and orthoxylylenediamine (a2). When the total amount of diamine (a1) and orthoxylylenediamine (a2) incorporated is 70 mol% or more, the polyamide resin obtained by this production method will have excellent crystallization rate, melt moldability, mechanical properties, and gas barrier properties.

[0030] The diamine (a) may contain a diamine other than the diamine (a1) and orthoxylylenediamine (a2). That is, a diamine other than meta-xylylenediamine, para-xylylenediamine, or orthoxylylenediamine may be contained. Examples of diamines other than meta-xylylenediamine, para-xylylenediamine, or orthoxylylenediamine include aliphatic diamines such as tetramethylenediamine, pentamethylenediamine, 2-methylpentanediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, dodecamethylenediamine, 2,2,4-trimethylhexamethylenediamine, and 2,4,4-trimethylhexamethylenediamine; and 1,3-bis(aminomethyl)cyclohexane. Examples of diamines include, but are not limited to, alicyclic diamines such as 1,4-bis(aminomethyl)cyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, bis(4-aminocyclohexyl)methane, 2,2-bis(4-aminocyclohexyl)propane, bis(aminomethyl)decalin, and bis(aminomethyl)tricyclodecane; and diamines having an aromatic ring such as bis(4-aminophenyl)ether, paraphenylenediamine, and bis(aminomethyl)naphthalene. These diamines can be used alone or in combination of two or more.

[0031] <Dicarboxylic Acid (b)> From the viewpoints of crystallization rate, moldability, gas barrier properties, and mechanical properties, the dicarboxylic acid (b) preferably contains at least one selected from the group consisting of an aliphatic dicarboxylic acid having 4 to 20 carbon atoms, terephthalic acid, and isophthalic acid, more preferably contains an aliphatic dicarboxylic acid having 4 to 20 carbon atoms, and even more preferably contains an aliphatic dicarboxylic acid having 4 to 12 carbon atoms. Furthermore, from the viewpoints of crystallization rate, moldability, gas barrier properties, and mechanical properties, the dicarboxylic acid (b) is preferably at least one selected from the group consisting of an aliphatic dicarboxylic acid having 4 to 20 carbon atoms, terephthalic acid, and isophthalic acid, more preferably an aliphatic dicarboxylic acid having 4 to 20 carbon atoms, and even more preferably an aliphatic dicarboxylic acid having 4 to 12 carbon atoms. Examples of aliphatic dicarboxylic acids having 4 to 20 carbon atoms include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, 1,11-undecanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,16-hexadecanedicarboxylic acid, and 1,18-octadecanedicarboxylic acid. Among these, from the viewpoint of crystallinity and high elasticity, at least one selected from the group consisting of adipic acid, sebacic acid, and dodecanedioic acid is preferred, at least one selected from the group consisting of adipic acid and sebacic acid is more preferred, and adipic acid is even more preferred. These dicarboxylic acids may be used alone or in combination of two or more.

[0032] Other dicarboxylic acids that can be used as the dicarboxylic acid (b) include aliphatic dicarboxylic acids having 3 or less carbon atoms, such as oxalic acid and malonic acid; and aromatic dicarboxylic acids other than terephthalic acid and isophthalic acid, such as 2,6-naphthalenedicarboxylic acid.

[0033] The content (introduced amount) of the aliphatic dicarboxylic acid having 4 to 20 carbon atoms in the dicarboxylic acid (b) is preferably 50 mol % or more, more preferably 70 to 100 mol %, and even more preferably 85 to 100 mol %. When the content (introduced amount) of the aliphatic dicarboxylic acid having 4 to 20 carbon atoms in the dicarboxylic acid is within the above range, the resulting polyamide resin will have excellent crystallization rate, moldability, gas barrier properties, and mechanical properties.

[0034] <Polycondensation Reaction> The polycondensation reaction of diamine (a) and dicarboxylic acid (b) is not particularly limited, and any method, such as a pressurized method or a normal pressure dropping method, can be used. One example is melt polycondensation (melt polymerization). Specifically, a salt of diamine and dicarboxylic acid is heated in the presence of water under normal or increased pressure, and polycondensed in the molten state while removing the added water and water produced by polycondensation. Another example is a method in which the diamine is directly added to the molten dicarboxylic acid and polycondensed under normal or increased pressure. In this case, to maintain the reaction system in a homogeneous liquid state, the diamine is continuously added to the dicarboxylic acid, and during this time, the reaction system is heated so that the reaction temperature does not fall below the melting points of the resulting oligoamide and polyamide, while the polycondensation proceeds. Among the above methods, the melt polymerization method in which the diamine is dropped into molten dicarboxylic acid under normal or increased pressure and polymerized in the molten state while removing the condensed water is preferred because it narrows the molecular weight distribution of the resulting polyamide resin.

[0035] There are no particular limitations on the method for introducing orthoxylylenediamine (a2) into the reaction system. Examples include a method of directly introducing orthoxylylenediamine (a2) into the polycondensation reaction system, and a method of introducing a mixture of orthoxylylenediamine (a2) and another diamine (including (a1)) or orthoxylylenediamine (a2) and a dicarboxylic acid into the reaction system. Examples of a method for adjusting the amount of orthoxylylenediamine (a2) introduced to the above-mentioned range include a method of adding orthoxylylenediamine (a2) or a method of adding diamine (a1). Specifically, in the present invention, for example, a mixture of isomers can be used as the raw materials for each component contained in diamine (a) (hereinafter also referred to as raw material diamine (a)). That is, for example, a crude product containing orthoxylylenediamine, which is generated during the production of metaxylylenediamine and / or paraxylylenediamine, can be used as the raw material for diamine (a1) (hereinafter also referred to as raw material diamine (a1)). In such a case, when preparing the diamine (a), the amount of orthoxylylenediamine (a2) introduced can be appropriately adjusted to the above-mentioned amount by adding high-purity orthoxylylenediamine (a2) or diamine (a1) to the crude product.

[0036] In the method for producing a polyamide resin of the present invention, it is preferable to include a step of measuring the amount of orthoxylylenediamine (a2) contained in the raw material diamine (a) or raw material diamine (a1) before introducing diamine (a) and dicarboxylic acid (b) into the reaction system. It is also preferable to include a step of measuring the amount of orthoxylylenediamine (a2) contained in the raw material diamine (a) or raw material diamine (a1) and adjusting the amount of orthoxylylenediamine (a2) introduced to 0.006 to 0.15 parts by mass per 100 parts by mass of diamine (a1). Examples of methods for adjusting the amount introduced include adding orthoxylylenediamine (a2) and adding diamine (a1). The amount of orthoxylylenediamine (a2) can be measured by, for example, performing GC measurement of diamine (a) or diamine (a1) (such as starting diamine (a) or starting diamine (a1)), creating a calibration curve, and determining the content of orthoxylylenediamine (a2) from the ratio of the peak value derived from diamine (a1) to the peak value derived from orthoxylylenediamine (a2).

[0037] Furthermore, in the production of the diamine (a1) (metaxylylenediamine, paraxylylenediamine, or a mixture thereof) used in the present invention, if it is possible to use a specific catalyst and production conditions to carry out a reaction in parallel to produce a predetermined amount of orthoxylylenediamine (a2), such a method can be used. In this case, the content of orthoxylylenediamine (a2) in diamine (a1) can be determined by gas chromatography (GC) analysis or the like. For example, a method can be used in which GC measurement of diamine (a1) containing orthoxylylenediamine (a2) is performed, a calibration curve is created, and the content of orthoxylylenediamine (a2) is determined from the ratio of the peak value derived from diamine (a1) to the peak value derived from orthoxylylenediamine (a2).

[0038] The molar ratio of diamine to dicarboxylic acid (diamine / dicarboxylic acid) is preferably 0.9 to 1.1, more preferably 0.93 to 1.07, even more preferably 0.95 to 1.05, and still more preferably 0.97 to 1.02. When the molar ratio is within the above range, the polymer is likely to be polymerized.

[0039] In order to promote the amidation reaction, a phosphorus atom-containing compound may be added to the polycondensation reaction system. Examples of the phosphorus atom-containing compound include phosphinic acid compounds such as dimethylphosphinic acid and phenylmethylphosphinic acid; diphosphite compounds such as hypophosphorous acid, sodium hypophosphite, potassium hypophosphite, lithium hypophosphite, magnesium hypophosphite, calcium hypophosphite and ethyl hypophosphite; phosphonic acid, sodium phosphonate, potassium phosphonate, lithium phosphonate, potassium phosphonate, magnesium phosphonate, calcium phosphonate, phenylphosphonic acid, ethylphosphonic acid, sodium phenylphosphonate, potassium phenylphosphonate, lithium phenylphosphonate, diethyl phenylphosphonate and sodium ethylphosphonate. Examples of suitable phosphorus-containing compounds include phosphonous acid compounds such as sodium phosphonite, lithium phosphonite, potassium phosphonite, magnesium phosphonite, calcium phosphonite, phenylphosphonous acid, sodium phenylphosphonite, potassium phenylphosphonite, lithium phenylphosphonite, and ethyl phenylphosphonite; and phosphorous acid compounds such as phosphorous acid, sodium hydrogen phosphite, sodium phosphite, lithium phosphite, potassium phosphite, magnesium phosphite, calcium phosphite, triethyl phosphite, triphenyl phosphite, and pyrophosphorous acid. Among these, metal hypophosphites such as sodium hypophosphite, potassium hypophosphite, and lithium hypophosphite are particularly preferred from the viewpoint of promoting the amidation reaction, with sodium hypophosphite being particularly preferred. However, the phosphorus atom-containing compound that can be used in the present invention is not limited to these compounds.

[0040] From the viewpoint of promoting the amidation reaction, the amount of the phosphorus atom-containing compound added to the polycondensation reaction system is preferably 0.1 to 1,000 ppm, more preferably 1 to 600 ppm, and even more preferably 5 to 400 ppm, calculated as the phosphorus atom concentration in the polyamide resin.

[0041] From the viewpoint of controlling the polycondensation reaction rate, an alkali metal compound may be further present in the polycondensation reaction system. As the alkali metal compound, an alkali metal hydroxide or an alkali metal acetate is usually used. Examples include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, lithium acetate, sodium acetate, potassium acetate, rubidium acetate, and cesium acetate, with at least one selected from sodium hydroxide and sodium acetate being preferred. These compounds may be used alone or in combination of two or more. The alkali metal compound may be added separately to the polycondensation reaction system, or may be derived from a dicarboxylic acid, which is a raw material for the polyamide resin.

[0042] The amount of alkali metal compound used is preferably 0.05 to 1,000 ppm, more preferably 0.25 to 600 ppm, and even more preferably 0.5 to 400 ppm, calculated as the alkali metal atom concentration in the polyamide resin. This amount is the total amount of the alkali metal compound added to the polycondensation system and the alkali metal compound derived from the dicarboxylic acid that is the raw material for the polyamide resin. The amount of alkali metal compound used is such that the value obtained by dividing the number of moles of the alkali metal compound by the number of moles of the phosphorus atom-containing compound is preferably 0.5 to 1.0, more preferably 0.55 to 0.95, and even more preferably 0.6 to 0.9. Within the above range, the amidation reaction proceeds at an appropriate rate.

[0043] When a sodium compound is used as the alkali metal compound, the ratio of the phosphorus atom concentration to the sodium atom concentration (Na / P) in the polyamide resin is preferably 0.4 to 0.9, more preferably 0.4 to 0.8, and even more preferably 0.4 to 0.7. Within the above ranges, the amidation reaction proceeds at an appropriate rate, making it easy to control the molecular weight of the polyamide resin. The phosphorus atom concentration and sodium atom concentration in the polyamide resin can be measured by known methods such as ICP atomic emission spectroscopy, ICP mass spectroscopy, and X-ray photoelectron spectroscopy.

[0044] The temperature of the polycondensation reaction is preferably 150 to 300°C, more preferably 160 to 280°C, and even more preferably 170 to 270°C. If the polymerization temperature is within the above range, the polymerization reaction proceeds quickly. Furthermore, since thermal decomposition of the monomer, oligomer during polymerization, polymer, etc. is unlikely to occur, the properties of the obtained polyamide resin are good.

[0045] The polycondensation reaction time is preferably 1 to 5 hours from the start of dropwise addition of the diamine. By setting the polycondensation reaction time within the above range, the molecular weight of the polyamide resin can be sufficiently increased and coloration of the resulting polyamide resin can be suppressed.

[0046] The polyamide resin obtained as described above is removed from the polymerization vessel, preferably pelletized, and then dried and crystallized as necessary before use. Furthermore, in order to increase the degree of polymerization of the polyamide resin, the production method of the present invention preferably further comprises a step of solid-state polymerization. Solid-state polymerization can be carried out by known methods, such as heating in a nitrogen atmosphere at a temperature of 100°C or higher but below the melting point of the polyamide for 1 to 24 hours. Suitable heating devices used in drying or solid-state polymerization include continuous heating and drying devices, rotary drum-type heating devices such as tumble dryers, conical dryers, and rotary dryers, and conical heating devices equipped with internal rotors such as Nauta mixers. However, the present invention is not limited to these, and known devices can also be used.

[0047] The polyamide resin obtained by the production method of the present invention has a high crystallization rate while maintaining high transparency. The improved crystallization rate of the polyamide resin improves moldability, allowing for a shortened crystallization process time during molding. This shortens the molding cycle, improving the productivity of molded products. Furthermore, problems such as a decrease in mechanical properties and transparency that result from the addition of a crystal nucleating agent to improve the moldability of the polyamide resin can be avoided.

[0048] The present invention will be specifically described below with reference to examples. However, the present invention is not limited to these examples. In these examples, various measurements were carried out by the following methods.

[0049] <Crystallization Half Time (Evaluation of Crystallization Rate)> The crystallization half time of the polyamide resin pellets obtained after solid-state polymerization in the Examples and Comparative Examples was measured. The crystallization half time was measured under the following conditions using a depolarized light intensity measuring device (manufactured by Kotaki Seisakusho Co., Ltd., Model: MK701). The polyamide resin pellets were sliced ​​to approximately 1.5 mm to obtain test pieces. The test pieces were then placed in the device and melted at 280°C for 90 seconds, after which they were immersed in an oil bath at 120°C to measure the crystallization half time at 120°C. The crystallization half times for the polyamide resins obtained in the Examples and Comparative Examples are shown in Table 1. The shorter the crystallization half time, the higher the crystallization rate and the faster the crystallization, which is preferable.

[0050] <Crystallization Half Time Reduction Efficiency (Evaluation of Crystallization Rate Improvement Effect)> The reduction rate of the crystallization half time relative to the content of structural units derived from orthoxylylenediamine (amount of orthoxylylenediamine introduced) was defined as the crystallization half time reduction efficiency and calculated using the following formula. The larger the value of the crystallization half time reduction efficiency, the higher the crystallization rate relative to the amount of orthoxylylenediamine, which is preferable. (Crystallization Half Time Reduction Efficiency) = [(Crystallization Half Time (Seconds) of Polyamide Resin of Comparative Example 1) - (Crystallization Half Time (Seconds) of Polyamide Resin of Each Example)] / (Amount of orthoxylylenediamine introduced of Each Example) where the amount of orthoxylylenediamine introduced is the amount (parts by mass) introduced relative to 100 parts by mass of meta-xylylenediamine (the amount of orthoxylylenediamine (a2) introduced is the amount (parts by mass) introduced relative to 100 parts by mass of diamine (a1)).

[0051] <Production of Polyamide Resin> Example 1 (Preparation of orthoxylylenediamine-Containing metaxylylenediamine) Approximately 10 kg of metaxylylenediamine containing orthoxylylenediamine (orthoxylylenediamine-containing metaxylylenediamine) was prepared, the orthoxylylenediamine content of which was adjusted to 0.081 parts by mass per 100 parts by mass of metaxylylenediamine. (Polycondensation Reaction) A reaction vessel equipped with a stirrer, a partial condenser, a total condenser, a thermometer, a dropping funnel, a nitrogen inlet tube, and a strand die was charged with 10 kg (68.43 mol) of adipic acid (manufactured by BASF). After thorough nitrogen substitution, the system was further heated to 194°C and melted while stirring under a small amount of nitrogen flow. Next, 9.265 kg (68.03 mol) of the orthoxylylenediamine-containing metaxylylenediamine was added dropwise to molten adipic acid under stirring, and the resulting condensed water was discharged from the system while the internal temperature was continuously raised to 240°C over 2 hours. After the completion of the dropwise addition of the orthoxylylenediamine-containing metaxylylenediamine, the internal temperature was increased, and when it reached 250°C, the pressure inside the reaction vessel was reduced. The internal temperature was then further increased to 255°C, and the melt polycondensation reaction was continued for 20 minutes. The system was then pressurized with nitrogen, and the resulting polymer was removed from the strand die and pelletized to obtain a polyamide resin after the polycondensation reaction but before solid-state polymerization. (Solid-State Polymerization) 300 g of the polyamide resin after the polycondensation reaction but before solid-state polymerization was placed in a 2-L eggplant-shaped flask, thoroughly purged with nitrogen, and then heated in an oil bath at 190°C for 4 hours while reducing the pressure to carry out solid-state polymerization, thereby obtaining polyamide resin (1).

[0052] Example 2 Polyamide resin (2) was obtained in the same manner as in Example 1, except that approximately 10 kg of orthoxylylenediamine-containing metaxylylenediamine, which was prepared so that the orthoxylylenediamine content was 0.060 parts by mass per 100 parts by mass of metaxylylenediamine, was prepared and used in the polycondensation reaction.

[0053] Example 3 Polyamide resin (3) was obtained in the same manner as in Example 1, except that approximately 10 kg of orthoxylylenediamine-containing metaxylylenediamine, which was prepared so that the orthoxylylenediamine content was 0.038 parts by mass per 100 parts by mass of metaxylylenediamine, was prepared and used in the polycondensation reaction.

[0054] Example 4 Polyamide resin (4) was obtained in the same manner as in Example 1, except that approximately 10 kg of orthoxylylenediamine-containing metaxylylenediamine, which was prepared so that the orthoxylylenediamine content was 0.013 parts by mass per 100 parts by mass of metaxylylenediamine, was prepared and used in the polycondensation reaction.

[0055] Example 5 Polyamide resin (5) was obtained in the same manner as in Example 1, except that approximately 10 kg of orthoxylylenediamine-containing metaxylylenediamine, which was prepared so that the orthoxylylenediamine content was 0.008 parts by mass per 100 parts by mass of metaxylylenediamine, was prepared and used in the polycondensation reaction.

[0056] Comparative Example 1 Polyamide resin (6) was obtained in the same manner as in Example 1, except that approximately 10 kg of orthoxylylenediamine-containing metaxylylenediamine, which was prepared so that the orthoxylylenediamine content was 0.005 parts by mass per 100 parts by mass of metaxylylenediamine, was prepared and used in the polycondensation reaction.

[0057]

[0058] As shown in Table 1, the polyamide resins of the examples, which are polyamide resins of the examples, have a crystallization rate that is higher than that of the polyamide resins obtained by the methods of the comparative examples, by controlling the amount of constitutional units derived from orthoxylylenediamine within a specific range. Therefore, the polyamide resins of the present invention have a high crystallization rate and are fast in crystallization, which improves moldability and allows the production of molded articles that maintain high transparency, making them suitable for use as materials for packaging films, hollow containers, various molded articles, fibers, etc.

Claims

1. A polyamide resin having a structural unit (A) derived from a diamine and a structural unit (B) derived from a dicarboxylic acid, in which the structural unit (A) contains at least one structural unit (A1) selected from the group consisting of structural units derived from meta-xylylenediamine and structural units derived from para-xylylenediamine, and a structural unit (A2) derived from ortho-xylylenediamine, and the content of the structural unit (A2) is 0.006 to 0.15 parts by mass per 100 parts by mass of the structural unit (A1).

2. The polyamide resin according to claim 1, wherein the dicarboxylic acid comprises at least one selected from the group consisting of an aliphatic dicarboxylic acid having 4 to 20 carbon atoms, terephthalic acid, and isophthalic acid.

3. The polyamide resin according to claim 2, wherein the total content of the structural units (A1) and (A2) in the structural unit (A) is 70 mol % or more, and the content of structural units derived from an aliphatic dicarboxylic acid having 4 to 20 carbon atoms in the structural unit (B) is 50 mol % or more.

4. The polyamide resin according to any one of claims 1 to 3, wherein the dicarboxylic acid comprises at least one selected from the group consisting of adipic acid, sebacic acid and dodecanedioic acid.

5. The polyamide resin according to any one of claims 1 to 4, wherein the structural unit (A1) is a structural unit derived from metaxylylenediamine.

6. A method for producing a polyamide resin, comprising the steps of introducing a diamine (a) and a dicarboxylic acid (b) into a reaction system and carrying out a polycondensation reaction, wherein the diamine (a) contains at least one diamine (a1) selected from the group consisting of metaxylylenediamine and paraxylylenediamine, and orthoxylylenediamine (a2), and the amount of orthoxylylenediamine (a2) introduced is 0.006 to 0.15 parts by mass per 100 parts by mass of the diamine (a1).

7. The method for producing a polyamide resin according to claim 6, wherein the dicarboxylic acid (b) contains at least one member selected from the group consisting of an aliphatic dicarboxylic acid having 4 to 20 carbon atoms, terephthalic acid, and isophthalic acid.

8. The method for producing a polyamide resin according to claim 7, wherein the total amount of diamine (a1) and orthoxylylenediamine (a2) introduced in diamine (a) is 70 mol % or more, and the amount of aliphatic dicarboxylic acid having 4 to 20 carbon atoms introduced in dicarboxylic acid (b) is 50 mol % or more.

9. The method for producing a polyamide resin according to any one of claims 6 to 8, wherein the dicarboxylic acid (b) contains at least one selected from the group consisting of adipic acid, sebacic acid and dodecanedioic acid.

10. The method for producing a polyamide resin according to any one of claims 6 to 9, wherein the diamine (a1) is metaxylylenediamine.

11. The method for producing a polyamide resin according to any one of claims 6 to 10, further comprising a step of carrying out solid-state polymerization.

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