Method for producing polyamide microparticles

Abstract

The present invention provides polyamide microparticles that exhibit a small average deviation in the coefficient of dynamic friction when the microparticles are rubbed together, a small average deviation in the coefficient of dynamic friction over time, and are also marine biodegradable. [Solution] Polyamide fine particles according to one aspect of the present invention have a ratio r of voids on the particle surface and a BET specific surface area A, which is the specific surface area of ​​the particle surface measured by the BET method. BET The ratio (r / A) BET The polymer or copolymer is characterized by having a ratio of 6.0 to 100.0 and being mainly composed of repeating structural units represented by the following chemical formula (1). TIFF2026065078000026.tif18170 (In chemical formula (1), x is an integer between 2 and 3.)

Description

[Technical Field]

[0001] This invention relates to polyamide fine particles and a method for producing the same. [Background technology]

[0002] Polyamide microparticles possess excellent toughness and heat resistance, making them suitable for use in aircraft, automobiles, cosmetics, and other applications. In particular, in cosmetics, polyamide microparticles are used in powder foundations and other products due to their superior lubricity.

[0003] However, in recent years, concerns have been raised about the impact of microplastics in the ocean on ecosystems, and there is a growing movement to restrict the use of microplastics. Under these circumstances, marine biodegradable plastics, which are broken down into naturally occurring substances by the action of microorganisms, are attracting attention. Marine biodegradability is also required for polyamide microparticles, and development to obtain such polyamide microparticles is progressing rapidly.

[0004] For example, Patent Document 1 discloses polyamide 4 fine particles with a smooth surface and a sphericity of 95, which are marine biodegradable.

[0005] Patent Document 2 discloses polyamide 4 fine particles that are marine biodegradable, have a moderate sphericity, and are porous.

[0006] Patent Document 3 discloses polyamide 4 fine particles that are marine biodegradable, have moderate sphericity, and low surface smoothness.

[0007] Patent Document 4 discloses polyamide 4 fine particles that are marine biodegradable and have moderate sphericity and a large variation in sphericity. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2020-100846 [Patent Document 2] Japanese Patent Publication No. 2016-186068 [Patent Document 3] International Publication No. 2017 / 195705 [Patent Document 4] International Publication No. 2019 / 069799 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] However, Patent Document 1 does not provide specific examples of polyamide 4 fine particles with a smooth surface and a sphericity of 96 or higher, nor does it mention the average deviation of the coefficient of dynamic friction when the fine particles are rubbed together, nor the average deviation of the coefficient of dynamic friction after rubbing over time (hereinafter sometimes abbreviated as the coefficient of dynamic friction after time has elapsed).

[0010] In Patent Document 2, polyamide 4 nanoparticles are produced by bringing 2-pyrrolidone, a monomer of polyamide 4, into contact with a compressible fluid to form microparticles. However, the resulting polyamide 4 nanoparticles were of moderate sphericity, hollow, and porous. As a result, the average deviation of the dynamic friction coefficient when the nanoparticles were rubbed together, and the average deviation of the dynamic friction coefficient after time had elapsed, were both large, and these average deviations of the dynamic friction coefficients were insufficient from the viewpoint of the slipperiness of the polyamide 4 nanoparticles.

[0011] In Patent Document 3, polyamide 4 fine particles are produced by dissolving polyamide 4 in hot water and reprecipitation it. However, the resulting polyamide 4 fine particles did not have high sphericity, exhibited large variations in sphericity, and had low surface smoothness. As a result, the average deviation of the dynamic friction coefficient when the fine particles were rubbed together and the average deviation of the dynamic friction coefficient after time had elapsed were large, and these average deviations of the dynamic friction coefficients were all insufficient from the viewpoint of the slipperiness of the polyamide 4 fine particles.

[0012] In Patent Document 4, polyamide 4 fine particles are produced by suspension polymerization of 2-pyrrolidone using a lithium salt in an aprotic solvent. However, the resulting polyamide 4 fine particles had moderate sphericity, large variations in sphericity, and rough surfaces. As a result, the average deviation of the coefficient of dynamic friction when the fine particles were rubbed together, and the average deviation of the coefficient of dynamic friction over time, were both insufficient from the viewpoint of the slipperiness of the polyamide 4 fine particles.

[0013] Therefore, in view of the problems of the prior art, the present invention aims to provide polyamide fine particles that have a small average deviation of the coefficient of dynamic friction when the fine particles are rubbed together, a small average deviation of the coefficient of dynamic friction after time has elapsed, and are also marine biodegradable. [Means for solving the problem]

[0014] In view of the above problems, the present inventors conducted extensive research and found that fine particles having a specific polyamide structure in which the ratio of the proportion of voids on the particle surface to the specific surface area of ​​the particle surface is within a predetermined range, or fine particles having a specific polyamide structure with a sphericity of 96 or higher, exhibit excellent average deviation of the coefficient of dynamic friction when the fine particles are rubbed together, excellent average deviation of the coefficient of dynamic friction over time, and are also marine biodegradable, thus completing the present invention.

[0015] In other words, in order to solve the above-mentioned problems and achieve the objective, the polyamide fine particles according to the present invention have a ratio r of voids on the particle surface and a BET specific surface area A, which is the specific surface area of ​​the particle surface measured by the BET method. BET The ratio (r / A) BET The polymer or copolymer is characterized by having a ratio of 6.0 to 100.0 and being mainly composed of repeating structural units represented by the following chemical formula (1).

[0016] [ka] (In chemical formula (1), x is an integer between 2 and 3.)

[0017] Furthermore, the polyamide fine particles according to the present invention have the BET specific surface area A in the above invention. BET 0.8m 2 / g or more 5.0m 2 It is characterized by being less than or equal to / g.

[0018] Furthermore, the polyamide fine particles according to the present invention are characterized in that they have a sphericity of 90 or higher.

[0019] Furthermore, the polyamide fine particles according to the present invention are characterized in that the amount of impurities contained is 0.50% by weight or less.

[0020] Furthermore, the polyamide fine particles according to the present invention are characterized in that, in the above invention, the volume-average particle diameter is 0.1 μm or more and 100 μm or less.

[0021] Furthermore, the polyamide fine particles according to the present invention are characterized in that the standard deviation of sphericity is 2.00 or less.

[0022] Furthermore, the polyamide fine particles according to the present invention are characterized in that x in the chemical formula (1) is 3.

[0023] Furthermore, the polyamide fine particles according to the present invention are characterized in that, in the above invention, the time-dependent stability index, which is an index indicating the stability against deterioration of the feel of polyamide fine particles that are continuously rubbed over time, is calculated by the following formula and is 0.60 or higher. Stability over time index = 1 / (Standard deviation of sphericity × (1 + amount of impurities)) (In the above formula, the standard deviation of sphericity is the standard deviation of the sphericity of the polyamide fine particles. The amount of impurities contained is the amount of impurities contained in the polyamide fine particles.)

[0024] Furthermore, the present invention relates to a method for producing polyamide fine particles, comprising as raw materials a resin (A) which is a polymer or copolymer mainly composed of repeating structural units represented by the following chemical formula (1), and a resin (B) which is an emulsion-forming resin capable of forming an emulsion with the resin (A) in a molten state, the method comprising: an emulsion-forming step of melting and mixing the resin (A) and the resin (B) at a melting temperature above their respective melting points to form an emulsion in which particulate resin (A) is dispersed in the resin (B); an immobilization step of cooling the molten mixture in which the emulsion of the resin (A) and the resin (B) has been formed to a temperature below the crystallization temperature of the resin (A) to immobilize the emulsion; and a recovery step of washing and removing the resin (B) with a washing solution which is a non-solvent of the resin (A) to recover polyamide fine particles made of the resin (A), wherein the melt viscosity ratio of the resin (A) and the resin (B) at 270°C is 4.3 or more and 125.0 or less.

[0025] [ka] (In chemical formula (1), x is an integer between 2 and 3.)

[0026] Furthermore, the method for producing polyamide fine particles according to the present invention is characterized in that the immobilization step includes a holding step of maintaining the temperature of the molten mixture in a temperature range above the crystallization temperature of the resin (A) and below the melting point of the resin (A), and a cooling step of cooling the temperature of the molten mixture after being maintained in the temperature range to a temperature range below the crystallization temperature of the resin (A).

[0027] Furthermore, the method for producing polyamide fine particles according to the present invention is characterized in that, in the holding step, the temperature of the molten mixture is maintained in the temperature range for 30 minutes or more and 10 hours or less.

[0028] Furthermore, the method for producing polyamide fine particles according to the present invention is characterized in that the immobilization step includes a holding step of holding the temperature of the molten mixture in a temperature range of 1 second to 10 minutes, where the temperature is above the crystallization temperature of the resin (A) and below the melting point of the resin (A), and a cooling step of cooling the temperature of the molten mixture after holding it in the temperature range to a temperature range below the crystallization temperature of the resin (A).

[0029] Furthermore, the method for producing polyamide fine particles according to the present invention is characterized in that, in the above invention, the emulsion formation step includes a heating step of raising the temperature of the resin (A) and the resin (B) from room temperature to the melting temperature.

[0030] Furthermore, the method for producing polyamide fine particles according to the present invention is characterized in that, in the above invention, the melt viscosity of the resin (B) at 270°C is 0.40 Pa·s or more and 5.00 Pa·s or less.

[0031] Furthermore, the method for producing polyamide fine particles according to the present invention is characterized in that, in the above invention, the resin (B) is polyethylene glycol.

[0032] Furthermore, the method for producing polyamide fine particles according to the present invention is characterized in that, in the emulsion formation step, the resin (A) and the resin (B) are melted and mixed at a melting temperature of the melting point of resin (A) + 5°C or more and 280°C or less.

[0033] Furthermore, the polyamide fine particles according to the present invention are characterized by having a sphericity of 96 or higher and comprising a polymer or copolymer mainly composed of repeating structural units represented by the following chemical formula (1).

[0034] [ka] (In chemical formula (1), x is an integer between 2 and 3.)

[0035] Furthermore, the polyamide fine particles according to the present invention are characterized in that the amount of impurities contained is 0.50% by weight or less.

[0036] Furthermore, the polyamide fine particles according to the present invention have a BET specific surface area A, which is the specific surface area of ​​the particle surface measured by the BET method in the above invention. BET 5.0m 2 It is characterized by being less than or equal to / g.

[0037] Furthermore, the polyamide fine particles according to the present invention are characterized in that, in the above invention, the volume-average particle diameter is 0.1 μm or more and 100.0 μm or less.

[0038] Furthermore, the polyamide fine particles according to the present invention are characterized in that the standard deviation of sphericity is 2.00 or less.

[0039] Furthermore, the polyamide fine particles according to the present invention are characterized in that x in the chemical formula (1) is 3.

[0040] Furthermore, the polyamide fine particles according to the present invention are characterized in that, in the above invention, the time-dependent stability index, which is an index indicating the stability against deterioration of the feel of polyamide fine particles that are continuously rubbed over time, is calculated by the following formula and is 0.60 or higher. Stability over time index = 1 / (Standard deviation of sphericity × (1 + amount of impurities)) (In the above formula, the standard deviation of sphericity is the standard deviation of the sphericity of the polyamide fine particles. The amount of impurities contained is the amount of impurities contained in the polyamide fine particles.) [Effects of the Invention]

[0041] The present invention provides polyamide fine particles that exhibit a small average deviation in the coefficient of dynamic friction when the fine particles are rubbed together, a small average deviation in the coefficient of dynamic friction over time, and are also marine biodegradable. [Brief explanation of the drawing]

[0042] [Figure 1] Figure 1 is a photograph of the polyamide fine particles of Example 1 observed at 2,000x magnification using a scanning electron microscope. [Figure 2] Figure 2 is a photograph of the polyamide fine particles of Example 1 observed at 10,000x magnification using a scanning electron microscope. [Figure 3] Figure 3 is a photograph of the polyamide microparticles of Example 21 observed at 2,000x magnification using a scanning electron microscope. [Figure 4] Figure 4 is a photograph of the polyamide fine particles of Example 21 observed at 10,000x magnification using a scanning electron microscope. [Modes for carrying out the invention]

[0043] The following describes in detail preferred embodiments of polyamide fine particles and methods for producing the same according to the present invention. The present invention is based on the inventions exemplified in Embodiments 1 and 2 below, but is not limited to Embodiments 1 and 2, and can be implemented with various modifications depending on the purpose and application.

[0044] <Embodiment 1> (Polyamide microparticles) The polyamide fine particles according to Embodiment 1 of the present invention are characterized by having a sphericity of 96 or higher and being composed of a polymer or copolymer mainly composed of repeating structural units represented by the following chemical formula (1), and are surface-smooth and highly spherical polyamide fine particles.

[0045] [ka] (In chemical formula (1), x is an integer between 2 and 3.)

[0046] First, the structure and form of the polyamide fine particles according to Embodiment 1 of the present invention (hereinafter sometimes referred to as polyamide fine particles (P1)) will be described. The polyamide fine particles (P1) are fine particles made of a polymer or copolymer having the structural unit represented by the above chemical formula (1) as the main repeating structural unit. In the above chemical formula (1), x is 2 or 3. If x is neither 2 nor 3, the polyamide fine particles (P1) will not have sufficient marine biodegradability. It is preferable that x be 3 from the viewpoint of excellent handling properties of the polyamide fine particles (P1). Furthermore, the polyamide fine particles (P1) may include crosslinked structures or branched structures to the extent that they do not impair the effects of the invention according to Embodiment 1.

[0047] The sphericity of polyamide microparticles (P1) is 96 or higher. Polyamide microparticles with a sphericity of less than 96 exhibit a large average deviation in the coefficient of dynamic friction, resulting in a less pleasant tactile feel. Furthermore, continuous rubbing of polyamide microparticles with a sphericity of less than 96 causes aggregation and twisting among the microparticles, increasing the average deviation in the coefficient of dynamic friction over time, and consequently worsening the feel when the polyamide microparticles are used. Therefore, when using polyamide microparticles in cosmetics or paints, a smooth feel cannot be achieved. From these perspectives, the sphericity of polyamide microparticles (P1) is 96 or higher, preferably 97 or higher, more preferably 98 or higher, and even more preferably 100, as described above. The upper limit for the sphericity of polyamide microparticles (P1) is 100.

[0048] The standard deviation of the sphericity of the polyamide fine particles (P1) is preferably 2.00 or less. When the standard deviation of the sphericity is 2.00 or less, when the polyamide fine particles (P1) are continuously rubbed, deterioration of the feel due to aggregation or twisting is unlikely to occur, and the average deviation of the coefficient of kinetic friction after the passage of time becomes small. Thereby, when using the polyamide fine particles (P1) for applications such as cosmetics and paints, it is preferable that a smooth feeling can be given. The standard deviation of the sphericity of the polyamide fine particles (P1) is more preferably 1.75 or less, still more preferably 1.50 or less, even more preferably 1.30 or less, and particularly preferably 1.10 or less. In addition, in the polyamide fine particles (P1), the lower limit value of the standard deviation of the sphericity is theoretically 0.

[0049] In addition, the sphericity of the polyamide fine particles (P1) and the standard deviation of the sphericity are determined from a photograph of the polyamide fine particles (P1) taken at a magnification of 2,000 times or more and 5,000 times or less by, for example, a scanning electron microscope. Specifically, 50 polyamide fine particles (P1) are randomly observed, and are determined according to the following mathematical formulas (1) and (2) from the minor diameter and major diameter of the observed polyamide fine particles (P1). In addition, the value of the sphericity is expressed as an integer by rounding. For example, when the calculated value of the sphericity is 99.5 or more, the sphericity of the polyamide fine particles (P1) is expressed as 100.

[0050] [Number] (T: sphericity (average value), a i : major diameter of each fine particle, b i : minor diameter of each fine particle, n: number of measurements)

[0051] [Number] (s: standard deviation of sphericity, T i : sphericity of each fine particle, T: sphericity (average value), n: number of measurements)

[0052] In the above formulas (1) and (2), the number of measurements n is the number of measurements for sphericity, minor axis, and major axis of the target microparticles. For example, in Embodiment 1 of the present invention, the number of measurements n for polyamide microparticles (P1) is, for example, n = 50.

[0053] The volume-average particle diameter of the polyamide fine particles (P1) is preferably within the range of 0.1 μm to 100.0 μm. A volume-average particle diameter of 100.0 μm or less is preferable because it provides a superior feel when the polyamide fine particles (P1) are touched and reduces the average deviation of the dynamic friction coefficient immediately after the start of measurement. The dynamic friction coefficient immediately after the start of measurement refers to the dynamic friction coefficient of the target fine particles (polyamide fine particles (P1) in Embodiment 1) immediately after the start of measurement, that is, the dynamic friction coefficient at the stage when the fine particles begin to rub against each other. The upper limit of the volume-average particle diameter of the polyamide fine particles (P1) is more preferably 50.0 μm or less, even more preferably 30.0 μm or less, particularly preferably 15.0 μm or less, even more preferably 13.0 μm or less, and especially preferably 10.0 μm or less. Furthermore, a volume-average particle diameter of 0.1 μm or more is preferable because it reduces the likelihood of aggregation between the polyamide particles (P1), suppresses the deterioration of feel due to aggregation, and reduces the average deviation of the dynamic friction coefficient immediately after the start of measurement and after time has passed. The lower limit of the volume-average particle diameter of the polyamide particles (P1) is more preferably 0.3 μm or more, even more preferably 0.5 μm or more, and particularly preferably 1.0 μm or more.

[0054] The particle size distribution index (P1) of the polyamide fine particles (P1) is preferably 3.0 or less. A P1 size distribution index of 3.0 or less results in excellent fluidity and good slipperiness in applications using the polyamide fine particles (P1), such as paints and cosmetics. The P1 size distribution index of the polyamide fine particles (P1) is more preferably 2.0 or less, even more preferably 1.5 or less, particularly preferably 1.3 or less, and especially preferably 1.2 or less. Theoretically, the lower limit of the P1 size distribution index is 1.0.

[0055] The volume-average particle diameter and number-average particle diameter of polyamide microparticles (P1) refer to the volume-average particle diameter and number-average particle diameter measured by a laser diffraction / scattering particle size analyzer, respectively. Furthermore, the particle size distribution index of polyamide microparticles (P1) is calculated using the volume-average particle diameter and number-average particle diameter values ​​obtained as described above, according to the following formula (3).

[0056]

number

[0057] BET specific surface area A of polyamide microparticles (P1) BET It is 5.0m 2 It is preferable that the value is less than or equal to / g. The surface smoothness of the polyamide fine particles (P1) is determined by the BET specific surface area A due to gas adsorption. BET It can be expressed as follows: The less the polyamide nanoparticles (P1) have a hollow structure and the smoother the surface of the polyamide nanoparticles (P1), the higher the BET specific surface area A. BET The value of BET specific surface area A will decrease. BET The smaller the value of A, the less deterioration in tactile feel occurs due to aggregation or twisting of the polyamide microparticles (P1) when the polyamide microparticles (P1) are rubbed, and the smaller the average deviation of the kinetic friction coefficient over time. Therefore, the BET specific surface area A BET The smaller the size, the better. From the perspective of the feel when the polyamide microparticles (P1) are rubbed, the BET specific surface area A of the polyamide microparticles (P1) BET The upper limit is 5.0m 2 It is preferable that the amount be less than or equal to 4.0m 2 It is more preferable that it be less than or equal to / g, and 3.0m 2 It is even more preferable that it be less than or equal to / g, and 2.0m 2 It is even more preferable that it be less than or equal to / g, and 1.0m 2 It is particularly preferable that the amount be less than or equal to / g.

[0058] Note that the BET specific surface area A BETThis is the specific surface area of ​​the particle surface measured by the BET method, and can be measured, for example, in accordance with the Japanese Industrial Standard (JIS standard) JIS R1626 (1996) "Method for measuring specific surface area by gas adsorption BET method".

[0059] The weight-average molecular weight of the polyamide fine particles (P1) is preferably 2,000 or more and 2,000,000 or less. A weight-average molecular weight of 2,000 or more is preferable because it reduces the likelihood of deterioration of the tactile feel due to aggregation or twisting of the polyamide fine particles (P1) when they are continuously rubbed, and reduces the average deviation of the dynamic friction coefficient over time. The lower limit of the weight-average molecular weight of the polyamide fine particles (P1) is more preferably 3,000 or more, even more preferably 4,000 or more, and especially preferably 5,000 or more. A weight-average molecular weight of 2,000,000 or less is preferable because it reduces the average deviation of the dynamic friction coefficient immediately after the start of measurement, resulting in a superior feel when the polyamide fine particles (P1) are rubbed together. The upper limit of the weight-average molecular weight of the polyamide fine particles (P1) is more preferably 1,000,000 or less, even more preferably 500,000 or less, particularly preferably 100,000 or less, especially preferably 50,000 or less, and even more preferably less than 30,000.

[0060] The weight-average molecular weight can be calculated, for example, using gel permeation chromatography (hereinafter sometimes abbreviated as GPC). Specifically, a solvent in which the compound dissolves, such as hexafluoroisopropanol, is used as the mobile phase, polymethyl methacrylate (PMMA) is used as the standard substance, and the column is matched to the solvent. For example, when using hexafluoroisopropanol, at least one of Shimadzu GLC's "Shodex GPC HFIP-806M" and "Shodex GPC HFIP-LG" can be used, and the weight-average molecular weight can be measured using a differential refractometer as the detector.

[0061] The amount of impurities contained in the polyamide fine particles (P1) is preferably 0.50% by weight or less, based on 100.00% by weight of the total weight of the polyamide fine particles (P1). In this invention, impurities refer to components other than resin (A) described later that are contained in the polyamide fine particles (P1), such as resin (B) described later, or catalysts and initiators used in the production of resin (A) described later. If the amount of impurities is 0.50% by weight or less, when the polyamide fine particles (P1) are rubbed continuously, deterioration of the texture due to aggregation and twisting of the polyamide fine particles (P1) is less likely to occur, and the average deviation of the dynamic friction coefficient after time has elapsed is small. For this reason, it is preferable to use polyamide fine particles (P1) in cosmetics and paints as it can provide a smooth feel. The amount of impurities is more preferably 0.30% by weight or less, and especially preferably 0.10% by weight or less. Furthermore, the lower limit of the amount of impurities is theoretically 0.00% by weight.

[0062] The amount of impurities can be determined by measuring the content of each organic and inorganic substance other than the resin (A) described below in the polyamide fine particles (P1), and then calculating the total amount of these impurities. The content of organic substances can be determined by analyzing them using methods such as NMR, FT-IR, GC-MS, and liquid chromatography, either individually or in combination. The content of inorganic substances can be measured, for example, by the ash content when the polyamide fine particles are ashed at 550°C.

[0063] The polyamide microparticles (P1) preferably have a time-dependent stability index of 0.60 or higher, calculated by the following formula (4). The time-dependent stability index is an index that indicates the stability against deterioration of feel due to aggregation and twisting of microparticles (polyamide microparticles (P1) in Embodiment 1) when rubbed continuously over time. The larger the value of the time-dependent stability index, the better the microparticles can maintain their excellent feel even when rubbed for a long time. For example, when polyamide microparticles (P1) are used in cosmetic applications, the excellent feel of the polyamide microparticles (P1) can be maintained for a long time. In particular, a time-dependent stability index of 0.60 or higher is preferable because when the polyamide microparticles (P1) are rubbed continuously, deterioration of the feel due to aggregation and twisting of the polyamide microparticles (P1) is less likely to occur, and the average deviation of the dynamic friction coefficient after time has passed is small. The lower limit of the time-dependent stability index of the polyamide microparticles (P1) is more preferably 0.70 or higher, and even more preferably 0.80 or higher.

[0064]

number

[0065] In the above formula (4), s is the standard deviation of the sphericity of the polyamide microparticles (P1). This standard deviation of sphericity can be calculated using the above formula (2). The amount of impurities contained is the amount of impurities contained in the polyamide microparticles (P1).

[0066] Furthermore, the polyamide microparticles (P1) are marine biodegradable. Marine biodegradability refers to the property of being decomposed by microorganisms in the sea. In this invention, as an indicator of marine biodegradability, according to JIS K6955 (2006), a decomposition of 10% or more two months after the test is considered to be marine biodegradable. From the viewpoint of exhibiting good marine biodegradability of polyamide microparticles (P1), the lower limit of marine biodegradability of polyamide microparticles (P1) is preferably 15% or more, more preferably 20% or more, and even more preferably 30% or more. Also, if the marine biodegradability is too high, the period during which the polyamide microparticles (P1) can be used as a product (product life of polyamide microparticles (P1)) will be shortened. For this reason, the upper limit of marine biodegradability of polyamide microparticles (P1) is preferably 90% or less, more preferably 80% or less, and even more preferably 70% or less.

[0067] (Method for producing polyamide microparticles) Next, a method for producing polyamide fine particles according to Embodiment 1 of the present invention will be described in detail. The polyamide fine particles (P1) described above can be produced by the production method according to this Embodiment 1 of the invention.

[0068] More specifically, the method for producing polyamide fine particles according to Embodiment 1 of the present invention (hereinafter sometimes abbreviated as the method for Embodiment 1) is a method for producing polyamide fine particles (P1) using as raw materials a resin (A) which is a polymer or copolymer mainly composed of repeating structural units represented by the chemical formula (1) described above, and a resin (B) which is an emulsion-forming resin capable of forming an emulsion with resin (A) in a molten state. The method for producing polyamide fine particles (P1) according to Embodiment 1 includes an emulsion formation step, an immobilization step, and a recovery step. The emulsion formation step is a step of melting and mixing resin (A) and resin (B) at a melting temperature that is above their respective melting points to form an emulsion in which particulate resin (A) is dispersed in resin (B). The immobilization step is a step of cooling the molten mixture in which the emulsion of resin (A) and resin (B) has been formed to a temperature below the crystallization temperature of resin (A) to immobilize the emulsion. The recovery step involves washing away the resin (B) in the immobilized molten mixture with a washing solution that is a non-solvent of resin (A), thereby recovering polyamide fine particles made of resin (A). In addition, in the manufacturing method of this embodiment 1, the melt viscosity ratio of resin (A) and resin (B) at 270°C is 4.3 or more and 125.0 or less.

[0069] [Resin (A)] Resin (A) is a polymer resin used in the manufacturing method of Embodiment 1 as a raw material for polyamide fine particles (P1), and more specifically, is a polymer or copolymer having the structural unit represented by chemical formula (1) as the main repeating structural unit.

[0070] [ka] (In chemical formula (1), x is an integer between 2 and 3.)

[0071] In the above structural unit of resin (A), x is either 2 or 3. If x is neither 2 nor 3, the polyamide fine particles (P1) made of resin (A) will not have sufficient marine biodegradability. From the viewpoint of excellent handling properties of polyamide fine particles (P1), it is preferable that x is 3. Furthermore, resin (A) may include crosslinked structures or branched structures to the extent that it does not impair the effects of the invention according to this embodiment 1.

[0072] Furthermore, in Embodiment 1, the melt viscosity of resin (A) at 270°C is not particularly limited, but is preferably 0.02 Pa·s or more and 1.00 Pa·s or less. Resin (A) preferably has a certain viscosity in order to disperse in particulate form in resin (B), which will be described later, and form an emulsion with resin (B). The lower limit of the melt viscosity of such resin (A) at 270°C is preferably 0.02 Pa·s or more, more preferably 0.03 Pa·s or more, and even more preferably 0.04 Pa·s or more. Also, from the viewpoint of maintaining a spherical shape without the emulsion diameter becoming too large when forming an emulsion between resin (A) and resin (B), the upper limit of the melt viscosity of resin (A) at 270°C is preferably 1.00 Pa·s or less, more preferably 0.80 Pa·s or less, even more preferably 0.50 Pa·s or less, and especially preferably 0.30 Pa·s or less.

[0073] The melt viscosity of resin (A) can be measured using a rheometer. Specifically, the complex viscosity of resin (A) measured 5 minutes after the start of measurement under the conditions of a temperature of 270°C and a frequency of 1 Hz can be determined as the melt viscosity of resin (A).

[0074] The resin (A) used in the manufacturing method of Embodiment 1 can be manufactured using known polymerization methods. Specifically, the production of resin (A) can be carried out by polycondensation reactions of amino acids such as 4-aminobutyric acid and 3-aminopropionic acid, or ring-opening polymerization of lactams such as 2-pyrrolidone and 2-azetidinone. Examples of this ring-opening polymerization include ring-opening polymerization by hydrolysis using water and anionic ring-opening polymerization. Examples of this anionic ring-opening polymerization include anionic ring-opening polymerization using alkali metals such as sodium and potassium, hydroxides, hydrides, and salts of alkali metals such as sodium hydroxide, potassium hydroxide, sodium hydroxide, potassium hydroxide, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium-t-butoxide, potassium-t-butoxide, sodium pyrrolidone, and potassium pyrrolidone, as well as organometallic compounds such as butyllithium and butylmagnesium as initiators. Resin (A) can be manufactured by the polycondensation reactions and ring-opening polymerization described above. When anionic ring-opening polymerization is used in the production of resin (A), it is preferable to add a polymerization accelerator to improve the yield. Known polymerization accelerators can be used, such as N-acyl-caprolactam, N-acyl-pyrrolidone, and N-acyl-azetidinone. Polymerization may be carried out in a solvent or in bulk without a solvent. When a solvent is used, there are no particular restrictions on the solvent as long as polymerization proceeds; solution polymerization may be carried out in a good solvent for resin (A), or suspension polymerization may be carried out in a non-solvent environment for resin (A).

[0075] Furthermore, there are no particular restrictions on the copolymerization components of resin (A), as long as they do not impair the effects of the present invention. Examples include amino acids such as 3-aminopropionic acid, 2-aminopropionic acid, alanine, glycine, and valine, and lactones such as β-propion lactone, γ-butyrolactone, δ-valerolactone, and ε-caprolactone. These are preferred as copolymerization components of resin (A) from the viewpoint of not impairing the marine biodegradability of polyamide microparticles (P1) and providing added value such as moisturizing properties when polyamide microparticles (P1) are used in cosmetics.

[0076] [Resin (B)] Resin (B) is a polymer resin used together with resin (A) as a raw material for polyamide fine particles (P1) in the manufacturing method of Embodiment 1. More specifically, it is an emulsion-forming resin that can form a polymer / polymer emulsion with resin (A) in a molten state. A polymer / polymer emulsion is an emulsion in which two types of resins that are immiscible with each other in a molten state are used, and the other resin is dispersed in a spherical shape within one of the two resins. In the manufacturing method of Embodiment 1, the polymer / polymer emulsion is an emulsion in which particulate (spherical) resin (A) is dispersed in resin (B). Such a polymer / polymer emulsion can be formed by the interfacial tension and melt viscosity of these two types of resins satisfying a specific balance.

[0077] The resin (B) in the manufacturing method of Embodiment 1 is not particularly limited as long as it is an emulsion-forming resin that forms a polymer / polymer emulsion with the resin (A) in a molten state. Specific examples of such emulsion-forming resins include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polypentamethylene glycol, polyhexamethylene glycol, and alkyl ethers obtained by encapsulating one or both of these hydroxyl groups with methyl, ethyl, propyl, isopropyl, butyl, hexyl, octyl, decyl, dodecyl, hexadecyl, or octadecyl groups, or alkylphenyl ethers obtained by encapsulating with octylphenyl groups. In particular, when washing away resin (B) in the recovery process described later after forming a polymer / polymer emulsion with resin (A), water can be used as the washing solvent, which is advantageous from an economic and, above all, environmental standpoint. Therefore, it is preferable that resin (B) is one or more selected from the group consisting of polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and their alkyl ether derivatives. Furthermore, polyethylene glycol is most preferred as resin (B) from the viewpoint that it can form a good polymer / polymer emulsion with resin (A) in a molten state, and the resulting polyamide fine particles (P1) have high sphericity and a small standard deviation of sphericity. In addition, as long as the effects of the present invention are not impaired, two or more of the above-mentioned emulsion-forming resins may be used simultaneously as resin (B).

[0078] Furthermore, in the manufacturing method of Embodiment 1, the melt viscosity of resin (B) at 270°C is preferably 0.40 Pa·s or more and 5.00 Pa·s or less. Resin (B) needs to have an appropriate viscosity in order to form a polymer / polymer emulsion with resin (A) in the molten state. From this viewpoint, the melt viscosity of resin (B) is preferably 0.40 Pa·s or more and 5.00 Pa·s or less. From the viewpoint of preventing the particle size of polyamide fine particles (P1) from becoming too coarse, providing a good tactile feel when touching polyamide fine particles (P1), and reducing the average deviation of the dynamic friction coefficient immediately after the start of measurement, the lower limit of the melt viscosity of resin (B) at 270°C is preferably 0.40 Pa·s or more, more preferably 0.60 Pa·s or more, and even more preferably 0.80 Pa·s or more. Furthermore, from the viewpoint of preventing the particle size of the polyamide fine particles (P1) from becoming too small, suppressing deterioration of the tactile feel when touching the polyamide fine particles (P1) due to aggregation, etc., and reducing the average deviation of the coefficient of dynamic friction over time, the upper limit of the melt viscosity of the resin (B) at 270°C is preferably 5.00 Pa·s or less, more preferably 4.00 Pa·s or less, even more preferably 3.00 Pa·s or less, and especially preferably 2.00 Pa·s or less.

[0079] Furthermore, in the manufacturing method of Embodiment 1, the melt viscosity ratio of resin (A) and resin (B) at 270°C is 4.3 or more and 125.0 or less. In this manufacturing method, the formation of a polymer / polymer emulsion between resin (A) and resin (B) in a molten state enables the formation of polyamide fine particles (P1) that have excellent surface smoothness, high sphericity, and little variation in sphericity. Therefore, the formation of a polymer / polymer emulsion between resin (A) and resin (B) is essential for producing marine biodegradable polyamide fine particles (P1) that have a small average deviation of the dynamic friction coefficient when the fine particles are rubbed together, and also a small average deviation of the dynamic friction coefficient after time has elapsed. Although the principle has not been fully elucidated, only when resin (A) and resin (B) satisfying the above condition of a melt viscosity ratio of 4.3 to 125.0 are melt-mixed, the balance between the interfacial tension and melt viscosity of resin (A) and resin (B) is maintained within a suitable range, and as a result, the properties of polyamide fine particles (P1) are obtained.

[0080] If the melt viscosity ratio of resin (A) and resin (B) at 270°C is less than 4.3, the emulsion diameter of resin (A) in resin (B) becomes too large in the molten state of resin (A) and resin (B), and as a result, a polymer / polymer emulsion cannot be formed between resin (A) and resin (B). From the viewpoint of improving the smoothness and reduced foreign body sensation when touching the polyamide fine particles (P1) and reducing the average deviation of the dynamic friction coefficient immediately after the start of measurement, the melt viscosity ratio is preferably 10.0 or higher, more preferably 15.0 or higher, and even more preferably 20.0 or higher.

[0081] On the other hand, if the melt viscosity ratio of resin (A) and resin (B) at 270°C exceeds 125.0, the emulsion diameter of resin (A) formed in resin (B) becomes excessively small, and the stability of the emulsion between resin (A) and resin (B) is lost, making it impossible to obtain polyamide fine particles (P1). From the viewpoint of improving the tactile feel when the polyamide fine particles (P1) are continuously rubbed and reducing the average deviation of the coefficient of dynamic friction over time, the melt viscosity ratio is preferably 100.0 or less, more preferably 75.0 or less, even more preferably 50.0 or less, and particularly preferably 40.0 or less.

[0082] The melt viscosity of resin (B) can be measured using a rheometer. Specifically, the complex viscosity of resin (B) measured 5 minutes after the start of measurement under the conditions of a temperature of 270°C and a frequency of 1 Hz can be determined as the melt viscosity of resin (B). Furthermore, using the determined melt viscosities of resin (A) and resin (B), the melt viscosity ratio of resin (A) and resin (B) at 270°C can be calculated from the following formula (5).

[0083]

number

[0084] [Emulsion formation process] The manufacturing method of Embodiment 1 includes an emulsion formation step, as described above. This emulsion formation step involves melting and mixing the resin (A) and resin (B) described above at a temperature above their respective melting points (melting temperature) to form a polymer / polymer emulsion of these resins (A) and (B). Hereinafter, the emulsion formation step in the manufacturing method of Embodiment 1 will be referred to as the emulsion formation step (ST1).

[0085] The melting temperature in the emulsion formation step (ST1) is the temperature at which resin (A) and resin (B) are melted and mixed. There are no particular restrictions as long as it is above the respective melting points of resin (A) and resin (B), and it can be selected according to the type of resin (A). From the viewpoint of producing polyamide fine particles (P1) with higher sphericity and a smaller standard deviation of sphericity, the melting temperature is preferably 5°C or higher than the melting point of resin (A). On the other hand, the upper limit of the melting temperature is preferably 280°C or lower, as this can suppress the decomposition of resin (A) in the melted and mixed state with resin (B), and a stable polymer / polymer emulsion can be formed between resin (A) and resin (B), resulting in higher sphericity of the resulting polyamide fine particles (P1). From the viewpoint of further improving sphericity, the upper limit of the melting temperature is more preferably 270°C or lower. The melting and mixing time between resin (A) and resin (B) in the emulsion formation step (ST1) may be about 1 minute to 10 hours.

[0086] The melting points of resin (A) and resin (B) used in the emulsion formation process (ST1) can be measured using differential scanning calorimeter (DSC). For example, resin (A) can be heated in a nitrogen atmosphere from 30°C to an endothermic peak indicating the melting point of polyamide at a rate of 20°C / min, held for 1 minute, then cooled to 30°C at a rate of 20°C / min, and the peak of the endothermic peak when the cooled resin (A) is further heated at 20°C / min can be measured as the melting point of resin (A). The melting point of resin (B) can be measured in the same manner as the melting point of resin (A).

[0087] Furthermore, the emulsion formation step (ST1) preferably includes a heating step in which the raw materials, resin (A) and resin (B), are heated from room temperature to the melting temperature. Although the detailed principle is not known, heating these raw materials, resin (A) and resin (B), from room temperature makes it possible to form a more uniform and shape-stable polymer / polymer emulsion of resin (A) and resin (B). Therefore, from the viewpoint of having high sphericity of the resulting polyamide fine particles (P1) and a small standard deviation of said sphericity, it is preferable that the emulsion formation step (ST1) includes the heating step.

[0088] In the emulsion formation step (ST1), the melt mixing ratio of resin (A) and resin (B) can be exemplified as 25:75 to 75:25, depending on the mass ratio ((A):(B)) of resin (A):(B). If the melt mixing ratio of resin (A) and resin (B) is within the above range, the interfacial tension and melt viscosity of the melted resin (A) and resin (B) can be balanced within a suitable range, and a polymer / polymer emulsion of resin (A) and resin (B) can be formed. For this reason, it is preferable that the melt mixing ratio of resin (A) and resin (B) in the emulsion formation step (ST1) is within the above range. From the viewpoint of increasing the sphericity of the resulting polyamide fine particles (P1), the melt mixing ratio is more preferably 30:70 to 75:25, even more preferably 40:60 to 75:25, and particularly preferably 50:50 to 75:25.

[0089] Furthermore, in the emulsion formation step (ST1), fine particles can be produced without stirring the molten mixture of resin (A) and resin (B). However, stirring of the molten mixture may be performed in order to uniformly control the volume-average particle size and particle size distribution of the resulting polyamide fine particles (P1). Known devices such as stirring blades, melt kneaders, and homogenizers can be used as stirring devices. For example, examples of stirring blades include propellers, paddles, flats, turbines, cones, anchors, screws, and helical types. The stirring speed depends on the type of resin (B) and the melt viscosity, but it is preferable to be in the range of 0 to 2,000 rpm from the viewpoint of uniformly transferring heat even in large devices while preventing liquid from adhering to the walls and changing the mixing ratio. The lower limit of the stirring speed is more preferably 10 rpm or more, even more preferably 30 rpm or more, and particularly preferably 50 rpm or more. The upper limit of the stirring speed is more preferably 1,600 rpm or less, even more preferably 1,200 rpm or less, and particularly preferably 800 rpm or less.

[0090] In the manufacturing method of Embodiment 1, additives may be added and melt-mixed in the emulsion formation step (ST1) to the extent that they do not impair the effects of the present invention. Examples of such additives include surfactants, dispersants, antioxidants, heat stabilizers, weathering agents, lubricants, pigments, dyes, plasticizers, antistatic agents, and flame retardants. Two or more of these may be used.

[0091] The amount of the above additive can be selected as appropriate, but it is preferable that it is between 0.00% by weight and 15.00% by weight relative to 100.00% by weight of the total of resin (A) and resin (B). From the viewpoint of fully exhibiting the effect of the additive, the lower limit of the amount of the above additive is more preferably 0.01% by weight or more, even more preferably 0.05% by weight or more, and especially preferably 0.10% by weight or more, relative to 100.00% by weight of the total of resin (A) and resin (B). Furthermore, from the viewpoint of reducing the amount of impurities contained in the obtained polyamide fine particles (P1), the upper limit of the amount of the above additive is more preferably 10.00% by weight or less, even more preferably 5.00% by weight or less, especially preferably 3.00% by weight or less, and particularly preferably 1.00% by weight or less, relative to 100.00% by weight of the total of resin (A) and resin (B).

[0092] [Immobilization process] The manufacturing method of Embodiment 1 includes an immobilization step, as described above. This immobilization step involves cooling the molten mixture, in which a polymer / polymer emulsion of resin (A) and resin (B) has been formed by the emulsion formation step (ST1), to a temperature below the crystallization temperature of resin (A), thereby immobilizing the polymer / polymer emulsion (i.e., making it non-flowing). Hereinafter, the immobilization step in the manufacturing method of Embodiment 1 will be referred to as the immobilization step (ST2).

[0093] As for the cooling method of the molten mixture of resin (A) and resin (B) in the immobilization process (ST2), there are no limitations as long as the effects of the invention according to Embodiment 1 are not impaired. Examples include discharging the molten mixture into a cleaning solution described later and rapidly cooling it in the cleaning solution, adding the cleaning solution described later to the mixing apparatus after mixing the molten mixture and rapidly cooling the molten mixture, air-cooling the molten mixture in the mixing apparatus and then discharging or transferring it into the cleaning solution described later, or discharging the molten mixture into the atmosphere to cool it and then transferring it to the cleaning solution described later. The cooling rate of the molten mixture is also not particularly limited as long as the effects of the invention according to Embodiment 1 are not impaired, and it may be rapidly cooled or naturally cooled.

[0094] Furthermore, the immobilization step (ST2) preferably includes a holding step of maintaining the temperature of the molten mixture of resin (A) and resin (B) within a predetermined temperature range, and a cooling step of cooling the molten mixture after the holding step. This holding step maintains the temperature of the molten mixture within a predetermined temperature range. 混合物 This is a step of holding the mixture in a temperature range above the crystallization temperature of resin (A) and below the melting point of resin (A) for 1 second to 10 minutes. This cooling step is performed to cool the temperature of the molten mixture after holding it in the above temperature range. 混合物 This is a step of cooling the resin (A) to a temperature below its crystallization temperature. Hereinafter, the holding step and the cooling step in the manufacturing method of Embodiment 1 will be referred to as the holding step (ST2-1) and the cooling step (ST2-2), respectively.

[0095] In the immobilization step (ST2), the holding step (ST2-1) and cooling step (ST2-2) described above are performed sequentially, thereby efficiently immobilizing the particulate resin (A) in the polymer / polymer emulsion of resin (A) and resin (B) into spherical shapes with high sphericity and smooth surfaces. In the holding step (ST2-1), the temperature of the molten mixture of resin (A) and resin (B) is t 混合物 During the period in which the above temperature range is maintained for 1 second to 10 minutes, the temperature of the molten mixture t 混合物 The temperature may be kept constant, increased, or decreased. In the cooling step (ST2-2), the temperature of the molten mixture after being held in the above temperature range by the holding step (ST2-1) is... 混合物 The cooling rate and cooling time are set so that the temperature can be reduced to below the crystallization temperature of resin (A).

[0096] Furthermore, in the holding process (ST2-1), the temperature of the molten mixture t 混合物The holding time for maintaining the above temperature range is preferably 1 second to 10 minutes. This is because when the upper limit of the holding time is 10 minutes or less, it is easier to sufficiently reduce the proportion of concave voids on the particle surface of the resin (A) fixed in particulate form, and polyamide fine particles (P1) with high sphericity and a smooth surface can be efficiently produced. The upper limit of the holding time is more preferably 5 minutes or less, even more preferably 3 minutes or less, and especially preferably 1 minute or less. The lower limit of the holding time is the temperature t of the molten mixture. 混合物 Due to operational considerations of the device used to maintain the temperature within the above temperature range, the duration is 1 second or longer.

[0097] [Recovery Process] The manufacturing method of Embodiment 1 includes a recovery step, as described above. This recovery step involves washing the molten mixture of resin (A) and resin (B), which form a polymer / polymer emulsion immobilized by the immobilization step (ST2), with a washing solution that is a non-solvent of resin (A), thereby washing away resin (B) from the molten mixture and recovering polyamide fine particles (P1) made of resin (A). Hereinafter, the recovery step in the manufacturing method of Embodiment 1 will be referred to as the recovery step (ST3).

[0098] The cleaning solution used in the recovery process (ST3) is not particularly limited as long as it is a non-solvent of resin (A) and a solvent that can dissolve and remove resin (B), as described above. Examples of such cleaning solutions include alcohols such as methanol, ethanol, and isopropanol, water-soluble ketones such as acetone, and water. From the standpoint of economic considerations and environmental considerations during production, water is most preferably used as the cleaning solution.

[0099] The cleaning method in the recovery step (ST3) is not particularly limited as long as it can remove the resin (B) from the immobilized molten mixture, and any method that can dissolve or remove the resin (B) from the molten mixture by bringing it into contact with the cleaning solution is acceptable. For example, as this cleaning method, a cleaning method such as slurry cleaning can usually be used while applying shear force or stirring force to the molten mixture. In addition, the molten mixture may be heated as appropriate in the recovery step (ST3). The concentration of polyamide fine particles contained in the cleaning solution when cleaning the molten mixture is not particularly limited, but can be exemplified as 0.01% by weight or more and 50.00% by weight or less. From the viewpoint of increasing the recovery efficiency of resin particles in the cleaning operation, the lower limit of the concentration of polyamide fine particles is more preferably 0.05% by weight or more, even more preferably 0.10% by weight or more, especially preferably 0.50% by weight or more, and particularly preferably 1.00% by weight or more. Furthermore, from the viewpoint of efficiently washing and removing the resin (B) from the molten mixture in a single wash, the upper limit of the concentration of the polyamide fine particles is more preferably 40.00% by weight or less, and even more preferably 30.00% by weight or less.

[0100] There are no particular restrictions on the method for recovering polyamide fine particles (P1) in the recovery process (ST3), and methods such as reduced pressure, pressure filtration, decantation, centrifugation, and spray drying can be appropriately selected. Furthermore, the recovered polyamide fine particles (P1) may be dried as needed. This drying process is preferably carried out below the melting point of the polyamide fine particles (P1), and may be performed under reduced pressure. There are no particular restrictions on the drying method for the recovered polyamide fine particles (P1), and methods such as air drying, hot air drying, heat drying, reduced pressure drying, and freeze-drying can be appropriately selected.

[0101] As described above, Embodiment 1 of the present invention comprises polyamide fine particles (P1) having a sphericity of 96 or higher and composed of a polymer or copolymer mainly consisting of repeating structural units represented by the above-mentioned chemical formula (1). Therefore, the polyamide fine particles (P1) are marine biodegradable and have excellent sphericity and surface smoothness, resulting in polyamide fine particles with small average deviations of the coefficient of dynamic friction when the fine particles are first rubbed together and small average deviations of the coefficient of dynamic friction after the fine particles have been rubbed together over time. In other words, the polyamide fine particles (P1) are marine biodegradable and have excellent lubricity when rubbed together.

[0102] Furthermore, by setting the standard deviation of the sphericity of the polyamide fine particles (P1) to 2.00 or less, variations in the sphericity of the polyamide fine particles (P1) can be suppressed, thereby promoting a reduction in the average deviation of each of the dynamic friction coefficients mentioned above. This contributes to improving the lubricity when the polyamide fine particles (P1) are rubbed together.

[0103] Furthermore, by limiting the amount of impurities in the polyamide fine particles (P1) to 0.50% by weight or less, or by setting the time-dependent stability index of the polyamide fine particles (P1) to 0.60 or higher, it is possible to promote a decrease in the average deviation of the dynamic friction coefficient after the polyamide fine particles (P1) have been rubbed together over time. This contributes to further improvement in the slipperiness of the polyamide fine particles (P1) after being rubbed together over time, and as a result, the excellent slipperiness and good tactile feel of the polyamide fine particles (P1) can be maintained for a longer period of time. Moreover, by satisfying both the amount of impurities in the polyamide fine particles (P1) to 0.50% by weight or less and the time-dependent stability index to 0.60 or higher, the decrease in the average deviation of the dynamic friction coefficient can be further promoted, thereby further improving the slipperiness of the polyamide fine particles (P1). As a result, the excellent slipperiness and good tactile feel of the polyamide fine particles (P1) can be maintained for an even longer period of time.

[0104] Furthermore, according to the method for producing polyamide fine particles according to Embodiment 1 of the present invention, polyamide fine particles (P1) having the excellent properties described above can be produced. In particular, polyamide fine particles (P1) can be efficiently produced by controlling the temperatures of resin (A) and resin (B) when forming the polymer / polymer emulsion, and the temperature of the molten mixture when immobilizing the molten mixture of these resins (A) and resin (B).

[0105] <Embodiment 2> (Polyamide microparticles) The polyamide fine particles according to Embodiment 2 of the present invention have a ratio r of voids on the particle surface and a BET specific surface area A BET The ratio (r / A) BET The polyamide fine particles are characterized by having a coefficient of 6.0 or higher and 100.0 or lower, and being composed of a polymer or copolymer mainly composed of repeating structural units represented by the following chemical formula (1), and having a porous surface and being perfectly spherical. For this reason, the polyamide fine particles according to Embodiment 2 of the present invention are marine biodegradable, have a small average deviation of the coefficient of dynamic friction immediately after the start of measurement and a small average deviation of the coefficient of dynamic friction after time has passed, and in addition have excellent lipophilicity.

[0106] [ka] (In chemical formula (1), x is an integer between 2 and 3.)

[0107] The structure and form of the polyamide fine particles according to Embodiment 2 of the present invention (hereinafter sometimes referred to as polyamide fine particles (P2)) will be described below. Polyamide fine particles (P2) are fine particles made of a polymer or copolymer having the structural unit represented by the above chemical formula (1) as the main repeating structural unit. Note that the chemical formula (1) in Embodiment 2 of the present invention is the same as the chemical formula (1) in Embodiment 1 described above. That is, if x in chemical formula (1) is neither 2 nor 3, the polyamide fine particles (P2) will not have sufficient marine biodegradability, and from the viewpoint of excellent handling properties of polyamide fine particles (P2), it is preferable that x is 3. Furthermore, polyamide fine particles (P2) may include crosslinked structures or branched structures to the extent that they do not impair the effects of the invention according to Embodiment 2.

[0108] The ratio of voids (r) on the particle surface of polyamide microparticles (P2) and the BET specific surface area (A) BET The ratio (r / A) BET The specific surface area (BET) is between 6.0 and 100.0. The above voids are concave voids on the porous surface of polyamide microparticles (P2). The ratio r of these voids is, for example, the ratio of the voids on the particle surface to the surface area of ​​the particle surface in a scanning electron microscope image of the polyamide microparticles (P2) taken from any direction. BET This is the specific surface area of ​​the fine particles (polyamide fine particles (P2) in Embodiment 2) measured by the BET method. BET If the ratio (r / A) is less than 6.0, the affinity of polyamide microparticles (P2) to oil decreases, for example, the dispersion stability of polyamide microparticles (P2) in linseed oil decreases. Therefore, when polyamide microparticles (P2) are incorporated into products such as paints and cosmetics, the dispersibility of the polyamide microparticles (P2) decreases, leading to a decrease in performance due to aggregation and sedimentation of the polyamide microparticles (P2), thus impairing the feel of the product. In addition, polyamide microparticles (P2) have a ratio (r / A). BET The larger the BET specific surface area A, the larger the BET specific surface area A. BETCompared to other fine particles with similar values, it also tends to have improved marine biodegradability. From the viewpoint of lipophilicity and marine biodegradability of polyamide fine particles (P2), the ratio (r / A BET The ratio (r / A) is 6.0 or higher, preferably 8.0 or higher, more preferably 10.0 or higher, and even more preferably 12.0 or higher. BET If the ratio (r / A) exceeds 100.0, it is basically difficult to manufacture polyamide fine particles (P2). Therefore, the ratio (r / A) BET The upper limit of ) is 100.0 or less.

[0109] BET specific surface area A of polyamide microparticles (P2) BET It is 0.8m 2 / g or more 5.0m 2 It is preferable that the value is less than or equal to / g. The surface smoothness of the polyamide fine particles (P2) is determined by the BET specific surface area A due to gas adsorption. BET It can be expressed as follows: The less the polyamide microparticles (P2) have a hollow structure and the smoother the surface of the polyamide microparticles (P2), the higher the BET specific surface area A. BET The value of BET specific surface area A will decrease. BET The smaller the value of A, the less deterioration in tactile feel occurs due to aggregation and twisting of polyamide microparticles (P2) when the polyamide microparticles (P2) are rubbed, and the smaller the average deviation of the kinetic friction coefficient over time. Therefore, the BET specific surface area A BET The smaller the size, the better. From the perspective of the feel when rubbing polyamide fine particles (P2) continuously, BET specific surface area A BET The upper limit is 5.0m 2 It is preferable that the amount be less than or equal to 4.0m 2 It is more preferable that it be less than or equal to / g, and 3.0m 2 It is even more preferable that it be less than or equal to / g, and 2.0m 2 It is even more preferable that it be less than or equal to / g, and 1.0m 2 It is particularly preferable that the BET specific surface area A is less than or equal to 1g. BET 0.8m 2 If the amount is above / g, the marine biodegradability of polyamide microparticles (P2) tends to improve. Therefore, BET specific surface area ABET The lower limit is 0.8m 2 Preferably 0.9 m 2 More preferably / g or more. Note that the specific surface area A of polyamide fine particles (P2) BET BET This can be measured in the same manner as the polyamide fine particles (P1) of Embodiment 1 described above.

[0110] The void ratio r of polyamide microparticles (P2) is, for example, the ratio of voids to the particle surface in a scanning electron microscope image of the particle taken from any direction, and is preferably 5.0% or more and 80.0% or less. When the void ratio r is 5.0% or more, the biodegradability of polyamide microparticles (P2) in the ocean is slightly improved. From the viewpoint of marine biodegradability, the lower limit of the void ratio r is preferably 5.0% or more, more preferably 10.0% or more, even more preferably 20.0% or more, and especially preferably 30.0% or more. Furthermore, if the void ratio r becomes too high, the particle shape of the polyamide microparticles (P2) cannot be maintained, and the particle properties of the polyamide microparticles (P2) tend to be significantly impaired. Therefore, in order to express the particle properties of polyamide microparticles (P2), the upper limit of the void ratio r is preferably 80.0% or less, more preferably 75.0% or less, and even more preferably 70.0% or less.

[0111] The void ratio r can be determined by observing the surface irregularities of 50 randomly selected microparticles from photographs of microparticles taken at magnifications of 2,000x to 5,000x using a scanning electron microscope, calculating the ratio of the area of ​​recesses (i.e., the area of ​​voids) to the surface area of ​​a single particle, and then taking the average value of these ratios.

[0112] The sphericity of the polyamide fine particles (P2) is preferably 90 or higher. When the sphericity of the polyamide fine particles (P2) is 90 or higher, the average deviation of the dynamic friction coefficient of the polyamide fine particles (P2) tends to be smaller, improving the feel when touching the polyamide fine particles (P2). In addition, when the polyamide fine particles (P2) are rubbed continuously, they are less likely to aggregate or twist with each other, which tends to reduce the average deviation of the dynamic friction coefficient over time, improving the feel when the polyamide fine particles (P2) are used continuously. For this reason, when using polyamide fine particles (P2) in cosmetics or paints, a smooth feel can be provided. From these viewpoints, the lower limit of the sphericity of the polyamide fine particles (P2) is preferably 90 or higher, more preferably 92 or higher, even more preferably 96 or higher, especially preferably 97 or higher, even more preferably 98 or higher, and particularly preferably 100. Furthermore, the theoretical upper limit for the sphericity of polyamide microparticles (P2) is 100.

[0113] The standard deviation of the sphericity of polyamide fine particles (P2) is preferably 2.00 or less. When the standard deviation of sphericity is 2.00 or less, deterioration of the tactile feel due to aggregation and twisting is less likely to occur when the polyamide fine particles (P2) are rubbed continuously, and the average deviation of the coefficient of dynamic friction over time is small. This is preferable because it can provide a smooth feel when polyamide fine particles (P2) are used in cosmetics and paints. The standard deviation of the sphericity of polyamide fine particles (P2) is more preferably 1.75 or less, even more preferably 1.50 or less, especially preferably 1.30 or less, and particularly preferably 1.10 or less. Furthermore, theoretically, the lower limit of the standard deviation of sphericity for polyamide fine particles (P2) is 0.

[0114] The sphericity of the polyamide microparticles (P2) and the standard deviation of said sphericity are calculated based on formulas (1) and (2), respectively, in the same manner as for the polyamide microparticles (P1) in Embodiment 1 described above.

[0115] The volume-average particle diameter of the polyamide fine particles (P2) is preferably within the range of 0.1 μm to 100.0 μm. A volume-average particle diameter of 100.0 μm or less is preferable because it provides a superior feel when touching the polyamide fine particles (P2) and reduces the average deviation of the dynamic friction coefficient immediately after the start of measurement. The upper limit of the volume-average particle diameter of the polyamide fine particles (P2) is more preferably 50.0 μm or less, even more preferably 30.0 μm or less, particularly preferably 15.0 μm or less, even more preferably 13.0 μm or less, and especially preferably 10.0 μm or less. Furthermore, a volume-average particle diameter of 0.1 μm or more is preferable because it reduces the likelihood of aggregation between the polyamide fine particles (P2), suppresses the deterioration of feel due to aggregation, and reduces the average deviation of the dynamic friction coefficient immediately after the start of measurement and after time has passed. The lower limit of the volume-average particle diameter of the polyamide fine particles (P2) is more preferably 0.3 μm or larger, even more preferably 0.5 μm or larger, and particularly preferably 1.0 μm or larger.

[0116] The particle size distribution index (P2) of polyamide fine particles is preferably 3.0 or less. A P2-3.0 P2

[0117] The volume-average particle diameter and number-average particle diameter of the polyamide microparticles (P2) are measured using a laser diffraction / scattering particle size analyzer, similar to the polyamide microparticles (P1) in Embodiment 1 described above. Furthermore, the particle size distribution index of the polyamide microparticles (P2) is calculated based on formula (3), similar to the polyamide microparticles (P1) in Embodiment 1 described above.

[0118] The weight-average molecular weight of the polyamide fine particles (P2) is preferably 2,000 or more and 2,000,000 or less. A weight-average molecular weight of 2,000 or more is preferable because it reduces the likelihood of deterioration of the tactile feel due to aggregation or twisting of the polyamide fine particles (P2) when they are continuously rubbed, and reduces the average deviation of the dynamic friction coefficient over time. The lower limit of the weight-average molecular weight of the polyamide fine particles (P2) is more preferably 3,000 or more, even more preferably 4,000 or more, and especially preferably 5,000 or more. A weight-average molecular weight of 2,000,000 or less is preferable because it reduces the average deviation of the dynamic friction coefficient immediately after the start of measurement, resulting in a superior feel when the polyamide fine particles (P2) are rubbed together. The upper limit of the weight-average molecular weight of the polyamide fine particles (P2) is more preferably 1,000,000 or less, even more preferably 500,000 or less, particularly preferably 100,000 or less, especially preferably 50,000 or less, and even more preferably less than 30,000. The weight-average molecular weight of the polyamide fine particles (P2) can be measured in the same manner as the polyamide fine particles (P1) of Embodiment 1 described above.

[0119] The amount of impurities contained in the polyamide fine particles (P2) is preferably 0.50% by weight or less, based on 100.00% by weight of the total weight of the polyamide fine particles (P2). The impurities contained in the polyamide fine particles (P2) are components other than the resin (A) contained in the polyamide fine particles (P2), and examples include those similar to those of the polyamide fine particles (P1) in Embodiment 1 described above. If the amount of impurities contained in the polyamide fine particles (P2) is 0.50% by weight or less, when the polyamide fine particles (P2) are rubbed continuously, deterioration of the tactile feel due to aggregation and twisting of the polyamide fine particles (P2) is less likely to occur, and the average deviation of the dynamic friction coefficient after time has elapsed is small. For this reason, it is preferable to use polyamide fine particles (P2) in cosmetics and paints as it can provide a smooth feel. The amount of impurities contained in the polyamide fine particles (P2) is more preferably 0.30% by weight or less, and especially preferably 0.10% by weight or less. Furthermore, the lower limit of the amount of impurities contained in the polyamide fine particles (P2) is theoretically 0.00% by weight. The amount of impurities contained in the polyamide fine particles (P2) can be determined in the same way as the polyamide fine particles (P1) in Embodiment 1 described above.

[0120] The time-dependent stability index of the polyamide microparticles (P2) is defined in the same way as in Embodiment 1 described above, and is preferably 0.60 or higher. The higher the time-dependent stability index of the polyamide microparticles (P2), the better the feel can be maintained even when the polyamide microparticles (P2) are rubbed for a long time. For example, when the polyamide microparticles (P2) are used in cosmetic applications, the excellent feel of the polyamide microparticles (P2) can be maintained for a long time. In particular, when the time-dependent stability index is 0.60 or higher, deterioration of the feel due to aggregation and twisting of the polyamide microparticles (P2) is less likely to occur when the polyamide microparticles (P2) are rubbed for a long time, and the average deviation of the dynamic friction coefficient after time has passed is small, which is preferable. The lower limit of the time-dependent stability index of the polyamide microparticles (P2) is more preferably 0.70 or higher, and even more preferably 0.80 or higher. The time-dependent stability index of the polyamide microparticles (P2) is calculated by formula (4) described above, in the same way as the polyamide microparticles (P1) in Embodiment 1 described above. In this case, in the above-mentioned formula (4), s is the standard deviation of the sphericity of the polyamide microparticles (P2), and the amount of impurities contained is the amount of impurities contained in the polyamide microparticles (P2).

[0121] Furthermore, the polyamide microparticles (P2) have marine biodegradability as defined in the same way as the polyamide microparticles (P1) of Embodiment 1 described above. From the viewpoint of exhibiting good marine biodegradability of polyamide microparticles (P2), the lower limit of marine biodegradability of polyamide microparticles (P2) is preferably 15% or more, more preferably 20% or more, and even more preferably 30% or more. Also, if the marine biodegradability is too high, the period during which the polyamide microparticles (P2) can be used as a product (product life of polyamide microparticles (P2)) will be shortened. For this reason, the upper limit of marine biodegradability of polyamide microparticles (P2) is preferably 90% or less, and more preferably 80% or less.

[0122] (Method for producing polyamide microparticles) Next, a method for producing polyamide fine particles according to Embodiment 2 of the present invention will be described in detail. The polyamide fine particles (P2) described above can be produced by the production method according to this Embodiment 2 of the invention.

[0123] More specifically, the method for producing polyamide fine particles according to Embodiment 2 of the present invention (hereinafter sometimes abbreviated as the Method for Embodiment 2) is a method for producing polyamide fine particles (P2) using as raw materials a resin (A) which is a polymer or copolymer mainly composed of repeating structural units represented by the above-mentioned chemical formula (1), and a resin (B) which is an emulsion-forming resin capable of forming an emulsion with resin (A) in a molten state. The Method for Embodiment 2 includes an emulsion formation step, an immobilization step, and a recovery step. The emulsion formation step is a step of melting and mixing resin (A) and resin (B) at a temperature above their respective melting points (melting temperature) to form an emulsion (polymer / polymer emulsion) in which particulate resin (A) is dispersed in resin (B). The immobilization step is a step of cooling the molten mixture of resin (A) and resin (B) in which the emulsion has been formed to a temperature below the crystallization temperature of resin (A) to immobilize the emulsion. The recovery step involves washing away the resin (B) in the immobilized molten mixture with a washing solution that is a non-solvent of resin (A), thereby recovering polyamide fine particles (P2) made of resin (A). In addition, in the manufacturing method of this embodiment 2, the melt viscosity ratio of resin (A) and resin (B) at 270°C is 4.3 or more and 125.0 or less.

[0124] [Resin (A) and Resin (B)] In the manufacturing method of Embodiment 2, the resins (A) and (B) that are raw materials for the polyamide fine particles (P2) are the same as the resins (A) and (B) in the manufacturing method of Embodiment 1 described above.

[0125] For example, the resin (A) of Embodiment 2 is a polymer or copolymer mainly composed of repeating structural units represented by the chemical formula (1) described above, and may include crosslinked structures or branched structures to the extent that it does not impair the effects of the invention according to Embodiment 2. Furthermore, the resin (A) of Embodiment 2 is the same as that of Embodiment 1 described above in terms of its melt viscosity at 270°C, the method for deriving the melt viscosity, the polymerization method, and the copolymer components.

[0126] The resin (B) of Embodiment 2 is an emulsion-forming resin that can form a polymer / polymer emulsion with the resin (A) in a molten state, similar to Embodiment 1 described above. Specific examples of this resin (B) include those similar to those of Embodiment 1 described above. In particular, the most preferred specific example of resin (B) is polyethylene glycol, similar to that of Embodiment 1 described above. Furthermore, the melt viscosity of this resin (B) at 270°C and the method for deriving it are also the same as those of Embodiment 1 described above, for example, it is preferable that the melt viscosity is 0.40 Pa·s or more and 5.00 Pa·s or less.

[0127] Furthermore, in the manufacturing method of Embodiment 2, the melt viscosity ratio of resin (A) and resin (B) at 270°C is 4.3 or more and 125.0 or less. In this manufacturing method, the formation of a polymer / polymer emulsion by resin (A) and resin (B) in a molten state enables the formation of polyamide fine particles (P2) that have a porous surface, yet possess moderately high sphericity and low variation in sphericity. Therefore, it is essential for producing marine biodegradable polyamide fine particles (P2) that have a small average deviation of the dynamic friction coefficient when the fine particles are rubbed together, and also a small average deviation of the dynamic friction coefficient after time has elapsed. Although the principle has not been fully elucidated, only when resin (A) and resin (B) satisfying the above condition of a melt viscosity ratio of 4.3 or more and 125.0 or less are melt-mixed, the balance between the interfacial tension and melt viscosity of resin (A) and resin (B) is maintained within a suitable range, and as a result, the properties of polyamide fine particles (P2) are obtained.

[0128] If the melt viscosity ratio of resin (A) and resin (B) at 270°C is less than 4.3, the emulsion diameter of resin (A) in resin (B) becomes too large in the molten state of resin (A) and resin (B), and as a result, a polymer / polymer emulsion cannot be formed between resin (A) and resin (B). From the viewpoint of improving the smoothness and reduced foreign body sensation when touching the polyamide fine particles (P2) and reducing the average deviation of the dynamic friction coefficient immediately after the start of measurement, the melt viscosity ratio is preferably 10.0 or higher, more preferably 15.0 or higher, and even more preferably 20.0 or higher.

[0129] On the other hand, if the melt viscosity ratio of resin (A) and resin (B) at 270°C exceeds 125.0, the emulsion diameter of resin (A) formed in resin (B) becomes excessively small, and the stability of the emulsion between resin (A) and resin (B) is lost, making it impossible to obtain polyamide fine particles (P2). From the viewpoint of improving the tactile feel when the polyamide fine particles (P2) are continuously rubbed and reducing the average deviation of the coefficient of dynamic friction over time, the melt viscosity ratio is preferably 100.0 or less, more preferably 75.0 or less, even more preferably 50.0 or less, and particularly preferably 40.0 or less. The melt viscosity ratio in Embodiment 2 can be calculated based on the same formula (5) as in Embodiment 1 described above.

[0130] [Emulsion formation process] The manufacturing method of Embodiment 2 includes an emulsion formation step, as described above. Hereinafter, the emulsion formation step in the manufacturing method of Embodiment 2 will be referred to as the emulsion formation step (ST11). This emulsion formation step (ST11) is a step in which resin (A) and resin (B) are melted and mixed at a melting temperature above their respective melting points to form a polymer / polymer emulsion of resin (A) and resin (B), similar to the emulsion formation step (ST1) in Embodiment 1 described above.

[0131] For example, the melting temperature in the emulsion formation step (ST11) is the temperature at which resin (A) and resin (B) are melted and mixed, and can be selected according to the type of resin (A), similar to the emulsion formation step (ST1) of Embodiment 1 described above. From the viewpoint of producing polyamide fine particles (P2) with a porous surface, higher sphericity, and a smaller standard deviation of sphericity, the melting temperature is preferably 5°C or higher than the melting point of resin (A). On the other hand, the upper limit of the melting temperature is preferably 280°C or lower, as this can suppress the decomposition of resin (A) in the melted and mixed state with resin (B), and can form a stable polymer / polymer emulsion between resin (A) and resin (B), thereby increasing the sphericity of the resulting polyamide fine particles (P2). From the viewpoint of further increasing the sphericity, the upper limit of the melting temperature is more preferably 270°C or lower.

[0132] Furthermore, the emulsion formation step (ST11) preferably includes a heating step, similar to the emulsion formation step (ST1) of Embodiment 1 described above, in order to ensure that the resulting polyamide fine particles (P2) have high sphericity and a small standard deviation of that sphericity, in order to achieve this. This step is performed by heating the raw materials, resin (A) and resin (B), from room temperature to the melting temperature.

[0133] Furthermore, in the emulsion formation step (ST11), fine particles can be produced without stirring the molten mixture of resin (A) and resin (B). However, stirring of the molten mixture may be performed in order to uniformly control the volume-average particle size and particle size distribution of the resulting polyamide fine particles (P2). The stirring device and stirring speed at this time are the same as those used in the emulsion formation step (ST1) of Embodiment 1 described above.

[0134] In the emulsion formation step (ST11), the melting and mixing time between resin (A) and resin (B), and the method for deriving the melting points of resin (A) and resin (B) are the same as in the emulsion formation step (ST1) of Embodiment 1 described above. Also, in the emulsion formation step (ST1), the melting and mixing ratio between resin (A) and resin (B), and the addition of additives when melting and mixing resin (A) and resin (B) are the same as in the emulsion formation step (ST1) of Embodiment 1 described above.

[0135] [Immobilization process] The manufacturing method of Embodiment 2 includes an immobilization step, as described above. This immobilization step involves cooling the molten mixture in which a polymer / polymer emulsion of resin (A) and resin (B) has been formed by the emulsion formation step (ST11) to a temperature below the crystallization temperature of resin (A), thereby immobilizing the polymer / polymer emulsion. Hereinafter, the immobilization step in the manufacturing method of Embodiment 2 will be referred to as the immobilization step (ST12).

[0136] The immobilization step (ST12) preferably includes the holding step and cooling step described below. This holding step involves the temperature t of the molten mixture of resin (A) and resin (B) described above. 混合物 This is a step of maintaining the mixture in a temperature range above the crystallization temperature of resin (A) and below the melting point of resin (A). This cooling step is performed to reduce the temperature of the molten mixture after it has been maintained in the above temperature range. 混合物 This is a step of cooling the resin (A) to a temperature below its crystallization temperature. Hereinafter, the holding step and the cooling step in the manufacturing method of Embodiment 2 will be referred to as the holding step (ST12-1) and the cooling step (ST12-2), respectively.

[0137] In the immobilization step (ST12), the holding step (ST12-1) and cooling step (ST12-2) described above are performed sequentially, thereby efficiently immobilizing the particulate resin (A) in the polymer / polymer emulsion of resin (A) and resin (B) into spherical objects with a porous surface and perfectly spherical shape.

[0138] In the immobilization process (ST12), during the holding process (ST12-1), the temperature t of the molten mixture of resin (A) and resin (B) is controlled. 混合物 It is preferable to maintain the above temperature range for 30 minutes to 10 hours. 混合物 During the holding period, in the holding process (ST12-1), the temperature of the molten mixture t 混合物 The temperature can be kept constant, increased, or decreased.

[0139] In the holding process (ST12-1), the temperature of the molten mixture in the above temperature range t 混合物 If the holding time is 30 minutes or more, the crystallization of the resin (A) proceeds while maintaining the shape of the emulsion formed in the emulsion formation step (ST11) described above, and this makes it possible to produce spherical polyamide fine particles (P2) that appear to have a porous surface and form a thread-like shape. For this reason, the above temperature t 混合物 A lower limit of 30 minutes or more is preferred for the holding time. From the viewpoint of increasing the proportion r of voids on the surface of polyamide fine particles (P2), the above temperature t 混合物 The lower limit of the holding time is more preferably 45 minutes or more, and even more preferably 60 minutes or more. Also, the temperature of the molten mixture in the above temperature range is t 混合物 If the holding time is 10 hours or less, the progression of decomposition of the crystallized resin (A) can be suppressed, thereby improving the sphericity of the polyamide fine particles (P2) and reducing the standard deviation of said sphericity. Therefore, the above temperature t 混合物 The upper limit of the holding time is preferably 10 hours or less, more preferably 8 hours or less, even more preferably 5 hours or less, especially preferably 3 hours or less, and particularly preferably 2 hours or less.

[0140] Note that the temperature t of the molten mixture in the above temperature range 混合物If the holding time is more than 10 hours or less than 30 minutes, the surface-smooth and highly spherical polyamide microparticles (P1) in Embodiment 1 described above and the surface-porous and spherical polyamide microparticles (P2) in Embodiment 2 will mix together, and as a result, the respective properties of these polyamide microparticles (P1) and polyamide microparticles (P2) will be inhibited. For this reason, the above temperature t 混合物 It is undesirable for the retention time to exceed 10 hours or be less than 30 minutes.

[0141] Furthermore, in the immobilization process (ST12), during the cooling process (ST12-2), the temperature of the molten mixture after being held in the above temperature range by the holding process (ST12-1) is... 混合物 The cooling rate and cooling time are set so that the temperature can be reduced to below the crystallization temperature of resin (A).

[0142] As for the method of cooling the molten mixture of resin (A) and resin (B) in the immobilization step (ST12), any method may be used as long as it does not impair the effects of the invention according to Embodiment 2. For example, a specific example of the cooling method is the same as that of the immobilization step (ST2) in Embodiment 1 described above.

[0143] [Recovery Process] The manufacturing method of Embodiment 2 includes a recovery step, as described above. This recovery step involves washing the molten mixture of resin (A) and resin (B), which form a polymer / polymer emulsion immobilized by the immobilization step (ST12), with a washing solution that is a non-solvent of resin (A), thereby washing and removing resin (B) from the molten mixture and recovering polyamide fine particles (P2) made of resin (A). Hereinafter, the recovery step in the manufacturing method of Embodiment 2 will be referred to as the recovery step (ST13).

[0144] The washing solution, washing method, and method for recovering polyamide fine particles (P2) in the recovery step (ST13) are the same as those in the recovery step (ST3) of Embodiment 1 described above.

[0145] As described above, in Embodiment 2 of the present invention, the ratio r of voids on the particle surface and the BET specific surface area A BET The ratio (r / A) BET The polyamide fine particles (P2) have a BET specific surface area of ​​6.0 or more and 100.0 or less, and consist of a polymer or copolymer mainly composed of the repeating structural unit represented by the above chemical formula (1). Therefore, the polyamide fine particles (P2) have a BET specific surface area of ​​A BET Compared to other fine particles of comparable quality, polyamide fine particles have superior marine biodegradability, excellent lipophilicity, and exhibit small average deviations in the coefficient of dynamic friction both when the particles are first rubbed together and after continuous rubbing over time. In other words, polyamide fine particles (P2) are fine particles that have excellent marine biodegradability and lipophilicity, as well as excellent lubricity when rubbed together.

[0146] Furthermore, by setting the standard deviation of the sphericity of the polyamide fine particles (P2) to 2.00 or less, variations in the sphericity of the polyamide fine particles (P2) can be suppressed, thereby promoting a reduction in the average deviation of each of the dynamic friction coefficients mentioned above. This contributes to improving the lubricity when the polyamide fine particles (P2) are rubbed together.

[0147] Furthermore, the BET specific surface area A of polyamide microparticles (P2) BET 0.8m 2 / g or more 5.0m 2 By setting the coefficient to less than / g, it is possible to promote a reduction in the average deviation of each of the above dynamic friction coefficients, thereby contributing to an improvement in the slipperiness when polyamide fine particles (P2) are rubbed together, and further improving marine biodegradability.

[0148] Furthermore, according to the method for producing polyamide fine particles in Embodiment 2 of the present invention, polyamide fine particles (P2) having the excellent properties described above can be produced. In particular, by controlling the temperature of the molten mixture (polymer / polymer emulsion) when immobilizing the molten mixture of resin (A) and resin (B) which are raw materials, it is possible to differentiate between the polyamide fine particles (P1) of Embodiment 1 and the polyamide fine particles (P2) of Embodiment 2, and efficiently produce the desired polyamide fine particles (P2).

[0149] <Application> The polyamide microparticles (P1) according to Embodiment 1 and the polyamide microparticles (P2) according to Embodiment 2 of the present invention are marine biodegradable, have excellent sphericity, and exhibit small average deviations in the coefficient of dynamic friction immediately after measurement and after time has elapsed. The average deviation of the coefficient of dynamic friction immediately after measurement is a numerical value that represents the feel of the polyamide microparticles immediately after touching them. The smaller the average deviation of the coefficient of dynamic friction immediately after measurement, the less foreign matter or roughness there is when rubbing the polyamide microparticles with your fingers, and the better the feel when touched. For this reason, polyamide microparticles (P1) and polyamide microparticles (P2) with small average deviations in the coefficient of dynamic friction immediately after measurement can be suitably used, for example, in cosmetic applications. The average deviation of the coefficient of dynamic friction after time has elapsed is a numerical value that represents whether or not there is deterioration in the feel due to aggregation or twisting when the polyamide microparticles are rubbed continuously. The smaller the average deviation of the coefficient of dynamic friction after time has elapsed, the less likely it is that deterioration in the feel due to aggregation or twisting of the polyamide microparticles will occur. Therefore, when polyamide microparticles (P1) and polyamide microparticles (P2) are used as appropriate in applications such as cosmetics and paints, the smoothness of the product can be maintained for a long period of time, and an excellent feel can be provided.

[0150] Furthermore, the polyamide microparticles (P1) according to Embodiment 1 and the polyamide microparticles (P2) according to Embodiment 2 of the present invention exhibit high sphericity and small average deviations in the coefficient of dynamic friction immediately after measurement and after time has elapsed. Therefore, when incorporated into cosmetics, they not only provide a smooth feel when used, but also fill in skin irregularities and scatter light in various directions, resulting in a soft-focus effect that makes wrinkles and other imperfections less noticeable. Moreover, since polyamide microparticles (P2) also have excellent lipophilicity, they blend well with oils when incorporated into cosmetics, further improving the feel.

[0151] Cosmetic applications include foundations such as liquid and powder foundations, concealers, sunscreens, makeup bases, lipsticks and lipstick bases, body powders and solid face powders, solid powder eyeshadows, wrinkle creams, and skincare lotions, as well as other external skin and hair preparations primarily for cosmetic purposes, and the dosage form is not limited. The dosage form may be any of the following: liquid preparations such as aqueous solutions, emulsions, and suspensions; semi-solid preparations such as gels and creams; or solid preparations such as powders, granules, and solids. Other examples of dosage forms include emulsion preparations such as creams and emulsions, oil-gel preparations such as lipsticks, powder preparations such as foundations, and aerosol preparations such as hair styling products.

[0152] Furthermore, the polyamide microparticles (P1) and (P2) described above can be used in applications other than cosmetics, such as paints for buildings, automobiles, metal products, and electrical appliances, as well as toners for laser printers and copiers, etc., taking advantage of their spherical properties. There are no limitations on their applications.

[0153] Polyamide fine particles (P1) and polyamide fine particles (P1) are produced by the respective manufacturing methods of Embodiments 1 and 2 described above. In particular, the present invention makes it possible to easily produce marine biodegradable polyamide fine particles that have a small average deviation of the coefficient of dynamic friction when the fine particles are rubbed together, and also have a small average deviation of the coefficient of dynamic friction over time, which has been difficult to achieve until now. [Examples]

[0154] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. The materials, evaluation items, and evaluation methods used in the examples and comparative examples are as follows.

[0155] [Sphericity, standard deviation of sphericity] The sphericity and standard deviation of polyamide microparticles were determined by observing 50 randomly selected polyamide microparticles from photographs of polyamide microparticles taken under the following conditions using a scanning electron microscope, and calculating their short and long axes according to the following formulas (1) and (2). The sphericity values ​​were rounded to the nearest integer; for example, a value of 99.5 or higher was represented as 100. <Condition> • Equipment: Hitachi High-Technologies Corporation TM1000 miniscope • Magnification: 2,000-5,000x

[0156]

number

[0157]

number

[0158] In the examples and comparative examples, when deriving the sphericity and standard deviation of polyamide fine particles, the number of measurements in equations (1) and (2) was set to n=50.

[0159] [BET specific surface area] BET specific surface area A of polyamide microparticles BET The specific surface area was calculated by measuring the krypton gas adsorption isotherm at liquid nitrogen temperature under the following conditions, in accordance with the Japanese Industrial Standard (JIS standard) JIS R1626 (1996) "Method for measuring specific surface area by gas adsorption BET method". <Condition> • Equipment: BELSORP-max manufactured by Nippon Bell Co., Ltd. • Gas: Krypton gas Sample amount: approximately 0.2g • Pretreatment: Degass under reduced pressure at 80°C for approximately 5 hours.

[0160] [Percentage of voids r, ratio (r / A) BET )] The void ratio r on the surface of polyamide nanoparticles was calculated based on 50 randomly selected polyamide nanoparticles from images of polyamide nanoparticles taken with a scanning electron microscope under the following conditions. In this process, the surface of each polyamide nanoparticle was binarized using image analysis software, and the ratio of the recess area to the surface area of ​​each polyamide nanoparticle was calculated. The target void ratio r was then determined from the average value of these ratios. <Condition> • Equipment: Hitachi High-Technologies Corporation TM1000 miniscope • Magnification: 2,000-5,000x Image analysis software: Winroof

[0161] Furthermore, the void ratio r calculated as described above is used for the BET specific surface area A. BET By dividing by the value of , the void ratio r and the BET specific surface area A are obtained. BET The ratio (r / A) BET ) was calculated.

[0162] [Volume-average particle diameter, particle size distribution index] The volume-average particle diameter and number-average particle diameter of the polyamide microparticles were determined under the following conditions. The particle size distribution index was calculated using the volume-average and number-average particle diameters obtained above, according to formula (3) below. <Condition> • Equipment: Nikkiso Co., Ltd. Laser diffraction / scattering particle size distribution analyzer (Microtrac MT3300EXII) ·Dispersion medium: water ·Flow rate: 50% • Number of washes: 3 • Ultrasonic output: 40W • Ultrasound duration: 180 seconds • Number of degassing cycles: 3

[0163]

number

[0164] [Melting point, crystallization temperature] The melting point and crystallization temperature of resin (A), a raw material for polyamide fine particles, were measured under the following conditions. The peak of the exothermic peak appearing in step (c) of the following temperature program was defined as the crystallization temperature, and the endothermic peak in step (e) of the following temperature program was defined as the melting point. <Condition> • Equipment: Differential scanning calorimeter (DSCQ20) manufactured by TA Instruments Corporation • Sample amount: 10 mg • Atmosphere: Under nitrogen flow • Temperature program: Step (a) Increase the temperature from 30°C until the endothermic peak indicating the melting point of the polyamide is reached. Step (b) Hold for 1 minute Step (c) Cool down to 30°C Step (d) Hold for 1 minute Step (e) Increase the temperature from 30°C until the endothermic peak indicating the melting point of the polyamide is reached. ·Temperature increase / decrease rate: 20℃ / min

[0165] [Melting viscosity, melting viscosity ratio] The melt viscosity of resin (A) and resin (B), which are raw materials for polyamide fine particles, was determined by measuring the melt viscosity 5 minutes after the start of measurement under the following conditions. The melt viscosity ratio of resin (B) to resin (A) was calculated using the following formula (5) based on the determined melt viscosities. <Condition> • Equipment: Physica MCR501 manufactured by Anton Paar • Measuring jig: Parallel plate (PP25, φ25mm) ·Measurement position: 1.0mm • Frequency: 1Hz ·Temperature condition: 270℃

[0166]

number

[0167] [Amount of impurities contained] The amount of impurities contained in polyamide microparticles was determined by measuring organic and inorganic substances other than the resin (A) contained in the polyamide microparticles under the following conditions, and calculating the total amount as the amount of impurities. If the amount of impurities was significantly less than 0.1% by weight and could not be detected, it was noted as "undetectable."

[0168] Of the impurities contained in polyamide microparticles, the amount of organic matter is: 1 The results were obtained by 1H-NMR under the following conditions. <Condition> ·Equipment: JEOL 500MHz nuclear magnetic resonance device • Nuclide: 1 H • Sample concentration: Approximately 1% by weight • Solvent: D2SO4 • Total number of times: 256

[0169] The amount of inorganic impurities in the polyamide microparticles was determined by calcining approximately 5 g of polyamide microparticles in an electric furnace under the following conditions, and then recovering the ash after cooling the calcined polyamide microparticles. <Condition> • Equipment: Thomas Scientific Instruments TMF-5 ·Ashing temperature: 550℃ • Ashing time: 6 hours

[0170] [Weight average molecular weight] The weight-average molecular weight of polyamide microparticles was determined by dissolving 0.5 g of polyamide microparticles in 4 mL of HFIP (with 0.005 N-sodium trifluoroacetate added), filtering the solution through a 0.45 μm filter, and measuring the molecular weight under the following conditions. <Condition> • Equipment: Gel permeation chromatography (Waters) • Detector: Differential refractometer Waters 410 (manufactured by Waters Corporation) • Columns: Shodex GPC HFIP-806M (2 pieces) + HFIP-LG (manufactured by Shimadzu GLC Co., Ltd.) ·Flow rate: 0.5mL / min • Sample injection volume: 0.1 mL ·Temperature: 30℃ • Molecular weight calibration: Polymethyl methacrylate (PMMA)

[0171] [Time-dependent stability index] The time-dependent stability index of polyamide microparticles was calculated using the standard deviation of sphericity and the amount of impurities present, as described above, by formula (4) below. If the amount of impurities was undetectable, the amount of impurities in formula (4) was set to 0.0, and the time-dependent stability index of polyamide microparticles was calculated accordingly.

[0172]

number

[0173] [Marine biodegradable] The marine biodegradability of polyamide microparticles was evaluated according to the Japanese Industrial Standard (JIS) JIS K6955 (2006) by mixing 100 mg of polyamide microparticles into 100 g of soil and measuring BOD. If the polyamide microparticles showed a degradation of 10% or more two months after the start of the test, they were considered to be marine biodegradable.

[0174] [Coefficient of dynamic friction during fine particle friction] As an indicator of the tactile feel of polyamide microparticles, the polyamide microparticles were spread smoothly onto a sample stage, and the coefficient of dynamic friction was measured under the following conditions by moving the sample stage. The average deviation of 10 measurements was then calculated. <Condition> • Equipment: KES-SE-STP friction tester manufactured by Kato Tech Co., Ltd. Sample amount: 0.01g • Sample surface area: 2cm x 10cm • Sample stage movement speed: 1 mm / min

[0175] The immediate feel of polyamide microparticles upon contact can be represented by the average deviation of the dynamic friction coefficient immediately after the start of measurement (hereinafter referred to as the average deviation of the dynamic friction coefficient immediately after). The smaller the average deviation of the dynamic friction coefficient immediately after, the smoother and better the feel of the polyamide microparticles when rubbed between fingers, with less foreign matter sensation and roughness.

[0176] Furthermore, the presence or absence of deterioration in tactile feel due to aggregation or twisting of polyamide microparticles when the polyamide microparticles are continuously rubbed can be expressed by the average deviation of the dynamic friction coefficient 5 minutes after the start of the above measurement (hereinafter referred to as the average deviation of the dynamic friction coefficient after 5 minutes). The smaller the average deviation of the dynamic friction coefficient after 5 minutes, the less deterioration in tactile feel due to aggregation or twisting of polyamide microparticles occurs, and the smoother and better the feel when used in applications such as cosmetics and paints.

[0177] [Dispersion stability in linseed oil] As an indicator of the lipophilicity of polyamide microparticles, the dispersion stability in linseed oil was evaluated. In this evaluation, after dispersing polyamide microparticles in linseed oil, the permeability of the linseed oil immediately after dispersion and the permeability of the linseed oil after standing for one day were measured under the following conditions, and the difference was calculated using the following formula (6). <Condition> ·Equipment: TURBISCAN Lab manufactured by Sanyo Trading Co., Ltd. • Sample amount: 2g • Flaxseed oil quantity: 18g • Sample bottle capacity: 20mL • Measurement position: 3 mm above the bottom of the sample bottle

[0178]

number

[0179] The smaller the difference in permeability of polyamide microparticles, the better their lipophilicity. When the difference in permeability is 20 or less, they can be said to have sufficiently high lipophilicity. High lipophilicity allows polyamide microparticles to maintain a stable dispersion state in the oil when incorporated into the oil, enabling them to exhibit their properties without impairment.

[0180] <Reference example 1> In Reference Example 1, resin (A)-1 was synthesized as an example of resin (A), which is a raw material for polyamide nanoparticles. Specifically, in an oil bath at 50°C, purified 2-pyrrolidone (127.7 g (1500 mmol)) and potassium t-butoxide (3.37 g (30 mmol)) were added to a 500 mL flask and uniformly dissolved. 1-acetyl-2-caprolactam (3.46 g (30 mmol)) was added as an initiator, the system was purged with nitrogen, and polymerization was carried out for 4 hours to obtain a mass. The obtained mass was pulverized, washed with ethanol, and vacuum-dried at 80°C for 24 hours to obtain resin (A)-1, a 2-pyrrolidone polymer with a melting point of 263°C, a crystallization temperature of 232°C, and a melt viscosity of 0.04 Pa·s.

[0181] <Reference example 2> In Reference Example 2, resin (A)-2 was synthesized as an example of resin (A), which is a raw material for polyamide nanoparticles. Specifically, in an oil bath at 50°C, purified 2-pyrrolidone (127.7 g (1500 mmol)) and potassium t-butoxide (3.37 g (30 mmol)) were added to a 500 mL flask and uniformly dissolved. 1-acetyl-2-caprolactam (3.46 g (30 mmol)) was added as an initiator, the system was purged with nitrogen, and polymerization was carried out for 24 hours to obtain a mass. The obtained mass was pulverized, washed with ethanol, and vacuum dried at 80°C for 24 hours to obtain resin (A)-2, a 2-pyrrolidone polymer with a melting point of 264°C, a crystallization temperature of 232°C, and a melt viscosity of 0.10 Pa·s.

[0182] <Reference example 3> In Reference Example 3, resin (A)-3 was synthesized as an example of resin (A), which is a raw material for polyamide nanoparticles. Specifically, in an oil bath at 50°C, purified 2-pyrrolidone (127.7 g (1500 mmol)) and potassium t-butoxide (3.37 g (30 mmol)) were added to a 500 mL flask and uniformly dissolved. 1-acetyl-2-caprolactam (2.30 g (20 mmol)) was added as an initiator, the system was purged with nitrogen, and polymerization was carried out for 72 hours to obtain a mass. The obtained mass was pulverized, washed with ethanol, and vacuum-dried at 80°C for 24 hours to obtain resin (A)-3, a 2-pyrrolidone polymer with a melting point of 265°C, a crystallization temperature of 233°C, and a melt viscosity of 0.20 Pa·s.

[0183] <Reference example 4> In Reference Example 4, resin (A)-4 was synthesized as an example of resin (A), which is a raw material for polyamide nanoparticles. Specifically, in an oil bath at 50°C, purified 2-pyrrolidone (102.1 g (1200 mmol)), ε-caprolactone (34.2 g (300 mmol)), and potassium t-butoxide (3.37 g (30 mmol)) were added to a 500 mL flask and uniformly dissolved. 1-acetyl-2-caprolactam (3.46 g (30 mmol)) was added as an initiator, the system was purged with nitrogen, and polymerization was carried out for 4 hours to obtain a mass. The obtained mass was pulverized, washed with ethanol, and vacuum-dried at 80°C for 24 hours to obtain resin (A)-4, a 2-pyrrolidone / caprolactone copolymer with a melting point of 193°C, a crystallization temperature of 170°C, and a melt viscosity of 0.03 Pa·s.

[0184] <Reference example 5> In Reference Example 5, resin (A)-5 was synthesized as an example of resin (A), which is a raw material for polyamide nanoparticles. Specifically, in an oil bath at 50°C, purified 2-azetidinone (85.3 g (1500 mmol)), ε-caprolactone (34.2 g (300 mmol)), and potassium t-butoxide (3.37 g (30 mmol)) were added to a 500 mL flask and uniformly dissolved. 1-acetyl-2-caprolactam (3.46 g (30 mmol)) was added as an initiator, the system was purged with nitrogen, and polymerization was carried out for 10 hours to obtain a mass. The obtained mass was pulverized, washed with ethanol, and vacuum-dried at 80°C for 24 hours to obtain resin (A)-5, a 2-azetidinone / caprolactone copolymer with a melting point of 272°C, a crystallization temperature of 240°C, and a melt viscosity of 0.06 Pa·s.

[0185] <Other items used> Other materials used are as follows: (monomer) • 2-Pyrrolidone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), molecular weight 85.1 • ε-Caprolactone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), molecular weight 114.1 · 2-Azetidinone (manufactured by FUJIFILM Wako Pure Chemical Corporation), molecular weight 71.1 · 4-Aminobutyric acid (special grade manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), 103.1 (Catalyst) · Potassium t-butoxide (manufactured by Tokyo Chemical Industry Co., Ltd.), molecular weight 112.2 (Initiator) · 1-Acetyl-2-caprolactam (manufactured by Tokyo Chemical Industry Co., Ltd.), molecular weight 115.2 · 1-Acetyl-2-pyrrolidone (manufactured by Tokyo Chemical Industry Co., Ltd.), molecular weight 127.1 · 1,3,5-Benzene tricarbonyl trichloride (manufactured by Tokyo Chemical Industry Co., Ltd.), molecular weight 265.5 · Palmitoyl chloride (manufactured by Tokyo Chemical Industry Co., Ltd.), molecular weight 274.9 (Additive) · Irganox1098 (registered trademark) (manufactured by BASF) · Lithium chloride (manufactured by Kanto Chemical Co., Inc.), molecular weight 42.4 · TAICROS (manufactured by Evonik Degussa Japan Co., Ltd.)

[0186] Also, as resin (B) which is one raw material of the polyamide fine particles, resin (B)-1 and resin (B)-2 shown below were used.

[0187] (Resin (B)-1) Resin (B)-1 is polyethylene glycol manufactured by FUJIFILM Wako Pure Chemical Corporation. This Resin (B)-1 was used by mixing a first molecular weight fraction (melt viscosity 0.15 Pa·s) having a weight average molecular weight of 6,000, a second molecular weight fraction (melt viscosity 0.78 Pa·s) having a weight average molecular weight of 20,000, and a third molecular weight fraction (melt viscosity 6.57 Pa·s) having a weight average molecular weight of 35,000 so as to obtain a desired melt viscosity.

[0188] (Resin (B)-2) Resin (B)-2 is polyvinyl alcohol manufactured by Nippon Synthetic Chemical Industry Co., Ltd. The melting point of this Resin (B)-2 is 190°C, the saponification degree is 99.1%, and the melt viscosity is 0.52 Pa·s.

[0189] <Example 1> In Example 1, resin (A)-1 of Reference Example 1 above was used as resin (A), and resin (B)-1 above was used as resin (B) to produce polyamide fine particles. Resin (B)-1 is polyethylene glycol with a melt viscosity of 0.87 Pa·s. The melt viscosity ratio of these resin (A)-1 and resin (B)-1 at 270°C is 21.7.

[0190] Specifically, resin (A)-1 (36 g) and resin (B)-1 (36 g) were added to a pressure-resistant container made of SUS316 having a 100 mL reaction tank (hereinafter sometimes referred to as an autoclave). After replacing the inside of the system with nitrogen, resin (A)-1 and resin (B)-1 were heated to 270°C in a nitrogen flow state, and melted and mixed for 30 minutes while stirring at 500 rpm using a stirring blade to form a polymer / polymer emulsion. After the melt mixing of resin (A)-1 and resin (B)-1, while continuing the nitrogen flow, the melt mixture of resin (A)-1 and resin (B)-1 in the tank was cooled to room temperature. At this time, the time during which the temperature t 混合物 of the melt mixture was maintained in the temperature range above the crystallization temperature of resin (A)-1 and below the melting point of resin (A)-1 was 1 minute. Water (800 g) was added to the obtained melt mixture, heated to 80°C, and stirred for 1 hour. The obtained slurry was filtered, water (800 g) was added to the filtrate, heated to 80°C, and stirred and washed for 1 hour. Then, the slurry passed through a 200 μm sieve to remove aggregates was filtered again, and the isolated filtrate was dried at 80°C for 12 hours to obtain a powder (25.4 g). At this time, there were no aggregates larger than 200 μm. The results of the scanning electron micrograph of the obtained powder are shown in FIGS. 1 and 2. In Example 1, as shown in FIGS. 1 and 2, it was confirmed that polyamide fine particles were obtained.

[0191] When the polyamide fine particles of Example 1 were evaluated for marine biodegradability, it was found that the polyamide fine particles were 30% decomposed one month after the start of the test. Therefore, the polyamide fine particles of Example 1 had marine biodegradability. Other properties and effects (evaluation results) of the polyamide fine particles of Example 1 are shown in Table 1 below.

[0192] <Example 2> In Example 2, polyamide fine particles were prepared and evaluated using the same method as in Example 1, except that the mixing mass ratio of resin (A)-1 and resin (B)-1 during melt mixing was changed to 25:75. The properties and effects of the polyamide fine particles in Example 2 are shown in Table 1.

[0193] <Example 3> In Example 3, polyamide fine particles were prepared and evaluated using the same method as in Example 1, except that the mixing mass ratio of resin (A)-1 and resin (B)-1 during melt mixing was changed to 65:35. The properties and effects of the polyamide fine particles in Example 3 are shown in Table 1.

[0194] <Example 4> In Example 4, polyamide fine particles were prepared and evaluated using the same method as in Example 1, except that the mixing mass ratio of resin (A)-1 and resin (B)-1 during melt mixing was changed to 75:25. The properties and effects of the polyamide fine particles in Example 4 are shown in Table 1.

[0195] <Example 5> In Example 5, polyamide fine particles were prepared and evaluated in the same manner as in Example 1, except that the resin (B)-1 used was changed to polyethylene glycol (melt viscosity 4.80 Pa·s, melt viscosity ratio with resin (A)-1 120), which had a different melt viscosity than in Example 1. The properties and effects of the polyamide fine particles in Example 5 are shown in Table 1.

[0196] <Example 6> In Example 6, polyamide fine particles were prepared and evaluated using the same method as in Example 1, except that the resin (B)-1 used was changed to polyethylene glycol (melt viscosity 3.00 Pa·s, melt viscosity ratio with resin (A)-1 75.0), which has a different melt viscosity than that used in Example 1. The properties and effects of the polyamide fine particles in Example 6 are shown in Table 1.

[0197] <Example 7> In Example 7, polyamide fine particles were produced and evaluated in the same manner as in Example 1, except that the resin (B)-1 used was changed to polyethylene glycol having a melt viscosity different from that in Example 1 (melt viscosity: 2.00 Pa·s, melt viscosity ratio to resin (A)-1: 50.0). The properties and effects of the polyamide fine particles of Example 7 are shown in Table 1.

[0198] <Example 8> In Example 8, polyamide fine particles were produced and evaluated in the same manner as in Example 1, except that the resin (B)-1 used was changed to polyethylene glycol having a melt viscosity different from that in Example 1 (melt viscosity: 0.40 Pa·s, melt viscosity ratio to resin (A)-1: 10.0). The properties and effects of the polyamide fine particles of Example 8 are shown in Table 1.

[0199] <Example 9> In Example 9, polyamide fine particles were produced and evaluated in the same manner as in Example 1, except that the resin (B)-1 used was changed to polyethylene glycol having a melt viscosity different from that in Example 1 (melt viscosity: 0.33 Pa·s, melt viscosity ratio to resin (A)-1: 8.3). The properties and effects of the polyamide fine particles of Example 9 are shown in Table 2 described later.

[0200] <Example 10> In Example 10, polyamide fine particles were produced and evaluated in the same manner as in Example 1, except that the resin used as resin (A) was changed to resin (A)-2 of Reference Example 2. The properties and effects of the polyamide fine particles of Example 10 are shown in Table 2.

[0201] <Example 11> In Example 11, polyamide fine particles were produced and evaluated in the same manner as in Example 1, except that the resin used as resin (A) was changed to resin (A)-3 of Reference Example 3. The properties and effects of the polyamide fine particles of Example 11 are shown in Table 2.

[0202] <Example 12> In Example 12, polyamide microparticles were prepared and evaluated in the same manner as in Example 1, except that the resin used as resin (A) was changed to resin (A)-4 from Reference Example 4, and the temperature during the melt-mixing of resin (A)-4 and resin (B)-1 was changed to 200°C. In the evaluation of the marine biodegradability of the polyamide microparticles in Example 12, 35% of the polyamide microparticles had decomposed one month after the start of the test. Therefore, the polyamide microparticles of Example 12 were marine biodegradable. Other properties and effects of the polyamide microparticles of Example 12 are shown in Table 2.

[0203] <Example 13> In Example 13, polyamide fine particles were prepared and evaluated in the same manner as in Example 1, except that the washing (stirring and washing of the filtered product with the above-mentioned water) was omitted, the slurry liquid obtained after melting and mixing was filtered, and the isolated filtered product was dried at 80°C for 12 hours. The properties and effects of the polyamide fine particles of Example 13 are shown in Table 2.

[0204] <Example 14> In Example 14, polyamide microparticles were prepared and evaluated in the same manner as in Example 1, except that 0.36 g of Irganox 1098 was added as an additive during the melt-mixing process. In the evaluation of the marine biodegradability of the polyamide microparticles in Example 14, 28% of the polyamide microparticles had decomposed one month after the start of the test. Therefore, the polyamide microparticles of Example 14 were marine biodegradable. Other properties and effects of the polyamide microparticles of Example 14 are shown in Table 2.

[0205] <Example 15> In Example 15, polyamide microparticles were prepared and evaluated in the same manner as in Example 1, except that 0.36 g of lithium chloride was added as an additive during the melt-mixing process. In the evaluation of the marine biodegradability of the polyamide microparticles in Example 15, 30% of the polyamide microparticles had decomposed after one month from the start of the test. Therefore, the polyamide microparticles of Example 15 were marine biodegradable. Other properties and effects of the polyamide microparticles of Example 15 are shown in Table 2.

[0206] <Example 16> In Example 16, polyamide microparticles were prepared and evaluated in the same manner as in Example 1, except that 0.29 g of TAICROS was added as an additive during the melt-mixing process. In the evaluation of the marine biodegradability of the polyamide microparticles in Example 16, 20% of the polyamide microparticles had decomposed one month after the start of the test. Therefore, the polyamide microparticles of Example 16 were marine biodegradable. Other properties and effects of the polyamide microparticles of Example 16 are shown in Table 2.

[0207] <Example 17> In Example 17, polyamide fine particles were prepared and evaluated in the same manner as in Example 1, except that the resin used as resin (A) was changed to resin (A)-5 from Reference Example 5, and the temperature during the melt mixing of resin (A)-5 and resin (B)-1 was changed to 280°C. The properties and effects of the polyamide fine particles of Example 17 are shown in Table 2.

[0208] <Example 18> In Example 18, polyamide microparticles were prepared and evaluated in the same manner as in Example 1, except that the amount of water used as the washing solution was changed from a total of 1600 g to a total of 400 g. The properties and effects of the polyamide microparticles in Example 18 are shown in Table 2.

[0209] <Example 19> In Example 19, polyamide microparticles were prepared and evaluated in the same manner as in Example 1, except that the amount of water used as the washing solution was changed from a total of 1600g to a total of 800g. The properties and effects of the polyamide microparticles in Example 19 are shown in Table 2.

[0210] <Example 20> In Example 20, polyamide microparticles were prepared and evaluated in the same manner as in Example 1, except that the amount of water used as the washing solution was changed from a total of 1600g to a total of 1200g. The properties and effects of the polyamide microparticles in Example 20 are shown in Table 2.

[0211] <Example 21> In Example 21, polyamide fine particles were prepared using resin (A)-1 from Reference Example 1 as resin (A) and resin (B)-1 as resin (B). Resin (B)-1 is polyethylene glycol with a melt viscosity of 0.87 Pa·s. The melt viscosity ratio of resin (A)-1 and resin (B)-1 at 270°C is 21.7.

[0212] In detail, resin (A)-1 (36g) and resin (B)-1 (36g) were added to a SUS316 autoclave with a 100mL reaction vessel. After purging the system with nitrogen, resin (A)-1 and resin (B)-1 were heated from room temperature to 270°C under nitrogen flow conditions, and melt-mixed for 30 minutes while stirring at 500 rpm using a stirring blade to form a polymer / polymer emulsion. After the melt-mixing of resin (A)-1 and resin (B)-1, the temperature of the molten mixture of resin (A)-1 and resin (B)-1 was maintained while continuing the nitrogen flow. 混合物 The mixture was kept warm at 237°C, which is 5°C above the melting point of resin (A)-1. At this time, the temperature t 混合物 The mixture was held in a temperature range above the crystallization temperature of resin (A)-1 and below the melting point of resin (A)-1 for 60 minutes. The molten mixture was then dispensed into a container with water (800g), cooled to room temperature, and then reheated to 80°C and stirred for 1 hour. The resulting slurry was filtered, water (800g) was added to the filtered product, and the mixture was heated to 80°C and stirred for 1 hour. The slurry was then passed through a 200μm sieve to remove aggregates, filtered again, and the isolated filtered product was dried at 80°C for 12 hours to obtain powder (25.4g). No aggregates larger than 200μm were present. Scanning electron microscope images of the obtained powder are shown in Figures 3 and 4. In Example 21, it was confirmed that polyamide fine particles were obtained, as shown in Figures 3 and 4.

[0213] The polyamide microparticles obtained in Example 21 as described above were evaluated for marine biodegradability and other properties. The characteristics and effects of the polyamide microparticles in Example 21 are shown in Table 3 below.

[0214] <Example 22> In Example 22, polyamide fine particles were prepared and evaluated in the same manner as in Example 21, except that the resin used as resin (A) was changed to resin (A)-3 from Reference Example 3, and the mixing mass ratio of resin (A)-3 to resin (B)-1 during melt mixing was changed to 70:30. The properties and effects of the polyamide fine particles of Example 22 are shown in Table 3.

[0215] <Example 23> In Example 23, the resin (B)-1 used was changed to polyethylene glycol (melt viscosity 3.00 Pa·s, melt viscosity ratio with resin (A)-1 75.0), which has a different melt viscosity than in Example 21. The mixing mass ratio of resin (A)-1 to resin (B)-1 during melt mixing was changed to 30:70. The temperature during melt mixing of resin (A)-1 and resin (B)-1 was changed to 280°C. 混合物 Polyamide nanoparticles were prepared and evaluated in the same manner as in Example 21, except that the holding time in the temperature range above the crystallization temperature of resin (A)-1 and below the melting point of resin (A)-1 was changed to 90 minutes. The properties and effects of the polyamide nanoparticles of Example 23 are shown in Table 3.

[0216] <Example 24> In Example 24, the temperature of the molten mixture t 混合物 Polyamide nanoparticles were prepared and evaluated in the same manner as in Example 22, except that the holding time in the temperature range above the crystallization temperature of resin (A)-3 and below the melting point of resin (A)-3 was changed to 90 minutes. The properties and effects of the polyamide nanoparticles of Example 24 are shown in Table 3.

[0217] <Example 25> In Example 25, polyamide fine particles were prepared and evaluated in the same manner as in Example 21, except that the resin used as resin (A) was changed to resin (A)-2 from Reference Example 2, and the mixing mass ratio of resin (A)-2 and resin (B)-1 during melt mixing was changed to 65:35. The properties and effects of the polyamide fine particles of Example 25 are shown in Table 3.

[0218] <Example 26> In Example 26, except that the time for maintaining the temperature t of the above molten mixture 混合物 in the temperature range exceeding the crystallization temperature of Resin (A)-1 and less than the melting point of Resin (A)-1 was changed to 150 minutes, polyamide fine particles were produced and evaluated in the same manner as in Example 21. The properties and effects of the polyamide fine particles of Example 26 are shown in Table 3.

[0219] <Example 27> In Example 27, except that the time for maintaining the temperature t of the above molten mixture 混合物 in the temperature range exceeding the crystallization temperature of Resin (A)-3 and less than the melting point of Resin (A)-3 was changed to 30 minutes, polyamide fine particles were produced and evaluated in the same manner as in Example 22. The properties and effects of the polyamide fine particles of Example 27 are shown in Table 3.

[0220] <Example 28> In Example 28, except that the time for maintaining the temperature t of the above molten mixture 混合物 in the temperature range exceeding the crystallization temperature of Resin (A)-1 and less than the melting point of Resin (A)-1 was changed to 30 minutes, polyamide fine particles were produced and evaluated in the same manner as in Example 21. The properties and effects of the polyamide fine particles of Example 28 are shown in Table 3.

[0221] <Example 29> In Example 29, except that the time for maintaining the temperature t of the above molten mixture 混合物 in the temperature range exceeding the crystallization temperature of Resin (A)-1 and less than the melting point of Resin (A)-1 was changed to 30 minutes, polyamide fine particles were produced and evaluated in the same manner as in Example 23. The properties and effects of the polyamide fine particles of Example 29 are shown in Table 3.

[0222] <Example 30> In Example 30, except that the time for maintaining the temperature t of the above molten mixture 混合物 in the temperature range exceeding the crystallization temperature of Resin (A)-3 and less than the melting point of Resin (A)-3 was changed to 180 minutes, polyamide fine particles were produced and evaluated in the same manner as in Example 22. The properties and effects of the polyamide fine particles of Example 30 are shown in Table 3.

[0223] <Example 31> In Example 31, the temperature of the molten mixture t 混合物 Polyamide nanoparticles were prepared and evaluated in the same manner as in Example 23, except that the holding time in the temperature range above the crystallization temperature of resin (A)-1 and below the melting point of resin (A)-1 was changed to 45 minutes. The properties and effects of the polyamide nanoparticles of Example 31 are shown in Table 3.

[0224] <Example 32> In Example 32, the temperature t of the molten mixture was 混合物 Polyamide nanoparticles were prepared and evaluated in the same manner as in Example 22, except that the holding time in the temperature range above the crystallization temperature of resin (A)-3 and below the melting point of resin (A)-3 was changed to 300 minutes. The properties and effects of the polyamide nanoparticles of Example 32 are shown in Table 3.

[0225] <Example 33> In Example 33, the mixing mass ratio of resin (A)-3 and resin (B)-1 during melt mixing was changed to 75:25, and the temperature of the molten mixture was changed to t 混合物 Polyamide nanoparticles were prepared and evaluated in the same manner as in Example 22, except that the holding time in the temperature range above the crystallization temperature of resin (A)-3 and below the melting point of resin (A)-3 was changed to 55 minutes. The properties and effects of the polyamide nanoparticles of Example 33 are shown in Table 4 below.

[0226] <Example 34> In Example 34, the resin (B)-1 used was changed to polyethylene glycol (melt viscosity 4.80 Pa·s, melt viscosity ratio with resin (A)-1 120) which has a different melt viscosity than in Example 21, the mixing mass ratio of resin (A)-1 and resin (B)-1 during melt mixing was changed to 30:70, and the temperature during melt mixing of resin (A)-1 and resin (B)-1 was changed to 280°C, and the temperature of the above molten mixture t 混合物 Polyamide nanoparticles were prepared and evaluated in the same manner as in Example 21, except that the holding time in the temperature range above the crystallization temperature of resin (A)-1 and below the melting point of resin (A)-1 was changed to 110 minutes. The properties and effects of the polyamide nanoparticles of Example 34 are shown in Table 4.

[0227] <Example 35> In Example 35, polyamide fine particles were prepared and evaluated in the same manner as in Example 21, except that the resin (B)-1 used was changed to polyethylene glycol (melt viscosity 3.00 Pa·s, melt viscosity ratio with resin (A)-1 75.0), which has a different melt viscosity than that used in Example 21. The properties and effects of the polyamide fine particles of Example 35 are shown in Table 4.

[0228] <Example 36> In Example 36, polyamide fine particles were prepared and evaluated in the same manner as in Example 21, except that the resin (B)-1 used was changed to polyethylene glycol (melt viscosity 0.40 Pa·s, melt viscosity ratio with resin (A)-1 10.0), which has a different melt viscosity than that used in Example 21. The properties and effects of the polyamide fine particles of Example 36 are shown in Table 4.

[0229] <Example 37> In Example 37, polyamide nanoparticles were prepared and evaluated in the same manner as in Example 21, except that the resin used as resin (A) was changed to resin (A)-2 from Reference Example 2. The properties and effects of the polyamide nanoparticles in Example 37 are shown in Table 4.

[0230] <Example 38> In Example 38, polyamide fine particles were prepared and evaluated in the same manner as in Example 21, except that the mixing mass ratio of resin (A)-1 and resin (B)-1 during melt mixing was changed to 70:30. The properties and effects of the polyamide fine particles in Example 38 are shown in Table 4.

[0231] <Example 39> In Example 39, polyamide fine particles were prepared and evaluated in the same manner as in Example 21, except that the mixing mass ratio of resin (A)-1 and resin (B)-1 during melt mixing was changed to 30:70. The properties and effects of the polyamide fine particles in Example 39 are shown in Table 4.

[0232] <Example 40> In Example 40, polyamide fine particles were prepared and evaluated using the same method as in Example 21, except that the temperature during the melt mixing of resin (A)-1 and resin (B)-1 was changed to 264°C. The properties and effects of the polyamide fine particles in Example 40 are shown in Table 4.

[0233] <Example 41> In Example 41, polyamide microparticles were prepared and evaluated in the same manner as in Example 21, except that the amount of water used as the washing solution was changed from a total of 1,600 g to a total of 400 g. The properties and effects of the polyamide microparticles in Example 41 are shown in Table 4.

[0234] <Example 42> In Example 42, polyamide microparticles were prepared and evaluated in the same manner as in Example 21, except that the amount of water used as the washing solution was changed from a total of 1,600 g to a total of 1,200 g. The properties and effects of the polyamide microparticles in Example 42 are shown in Table 4.

[0235] <Comparative Example 1> In Comparative Example 1, polyamide nanoparticles were prepared using resin (B)-1, which is polyethylene glycol with a weight-average molecular weight of 20,000, as resin (B), and a different resin from resin (A). Specifically, 4-aminobutyric acid (4g), resin (B)-1 (6g), and water (10g) as a solvent were added to a 100mL autoclave, sealed, and then subjected to nitrogen at 10 kg / cm³. 2 The system was replaced up to this point. The pressure in the system was reduced to 0.1 kg / cm² while releasing nitrogen. 2 After adjustment, the temperature was raised to 240°C. At this time, the pressure in the system was 10 kg / cm². 2 After reaching that point, the pressure is reduced to 10 kg / cm². 2 The pressure of the water vapor was controlled by slightly releasing it to maintain the desired temperature. After the temperature reached 240°C, 0.2 kg / cm³ was released. 2 Polymerization was initiated by releasing pressure at a rate of min. At this point, the internal solution was uniformly transparent. The pressure in the system was reduced to 0 kg / cm² while the temperature was raised to 255°C. 2 The pressure is reduced to 0 kg / cm². 2As soon as this was achieved, heating was maintained while flowing nitrogen for 1 hour to complete the polymerization. After polymerization, the internal solution was suspended. Nitrogen was again supplied at 10 kg / cm³. 2 After filling to the required level, the mixture was allowed to cool to room temperature. Water was added to the resulting solid and heated to 80°C to dissolve the dissolved material. The resulting slurry was filtered, and water (40g) was added to the filtered product and washed at 80°C. Subsequently, the slurry was passed through a 200μm sieve to remove aggregates, and the resulting product was filtered again to isolate it. The filtered product was dried at 80°C for 12 hours to obtain polyamide fine particles.

[0236] The polyamide fine particles of Comparative Example 1, obtained as described above, were evaluated in the same manner as in Example 1. The properties and effects of the polyamide fine particles of Comparative Example 1 are shown in Table 5 below.

[0237] <Comparative Example 2> In Comparative Example 2, pure water and resin (A)-1 from Reference Example 1 were added to a 1 L autoclave so that the concentration of resin (A)-1 relative to the pure water was 1% by weight. The autoclave was then heated to an internal temperature of 150°C to dissolve resin (A)-1 in the hot water. After heating, the temperature of the hot water was maintained for 30 minutes, and then the hot water was cooled to room temperature to obtain a suspension solution in which fine particles of resin (A)-1 were dispersed in pure water. Furthermore, this suspension solution was filtered through filter paper, and the material retained on the filter paper was vacuum-dried at 80°C for 8 hours to obtain the polyamide fine particles of Comparative Example 2. The polyamide fine particles of Comparative Example 2 obtained in this way were evaluated in the same manner as in Example 1. The properties and effects of the polyamide fine particles of Comparative Example 2 are shown in Table 5.

[0238] <Comparative Example 3> In Comparative Example 3, purified 2-pyrrolidone (21.3 g (0.25 mol)) and potassium t-butoxide (0.346 g (3 mmol)) were added to a flask equipped with a vacuum device, and the mixture was heated under reduced pressure at 50°C to react with potassium t-butoxide (hereinafter referred to as "catalyst"). As a result, a mixture of 2-pyrrolidone and the potassium salt of 2-pyrrolidone, which is a basic polymerization catalyst, was obtained.

[0239] The mixture obtained above (5.98 g) was packed into the reaction vessel of an autoclave containing a raw material addition pot and a 100 mL reaction vessel, and 1-acetyl-2-pyrrolidone (0.18 g) was packed into the addition pot. Subsequently, carbon dioxide was filled into the reaction vessel until the internal pressure reached 6 MPa, and the internal temperature was set to 40°C to melt the mixture. Then, 1-acetyl-2-pyrrolidone was supplied from the addition pot. After that, the pressure was further increased to 30 MPa, and the polymerization reaction of 2-pyrrolidone was carried out in the reaction vessel for 120 minutes. After the reaction was completed, the pressure was released, the vessel was refilled (to 30 MPa), and the pressure was released again. The fine particles were then removed, washed with water, and dried to obtain the polyamide fine particles of Comparative Example 3. The polyamide fine particles of Comparative Example 3 obtained in this way were evaluated in the same manner as in Example 1. The properties and effects of the polyamide fine particles of Comparative Example 3 are shown in Table 5.

[0240] <Comparative Example 4> In Comparative Example 4, 2.55 g (500 mmol) of 2-pyrrolidone 4, a 2-pyrrolidone solution containing 24.3% sodium 2-pyrrolidone (7.93 g (18 mmol as sodium 2-pyrrolidone)), and 50 g of anhydrous hexane were added to a 500 mL flask and stirred. Then, 0.27 g (1.0 mmol) of 1,3,5-benzenetricarbonyl trichloride and palmitoyl chloride (1.64 g (6.0 mmol)) were added, and the mixture was stirred at 50°C for 8 hours and left overnight at room temperature. The reaction mixture was filtered, washed with methanol and tetrahydrofuran, air-dried under a nitrogen stream, and then dried under reduced pressure at 60°C to obtain the polyamide fine particles of Comparative Example 4. The polyamide fine particles of Comparative Example 4 obtained in this way were evaluated in the same manner as in Example 1. The properties and effects of the polyamide fine particles of Comparative Example 4 are shown in Table 5.

[0241] <Comparative Example 5> In Comparative Example 5, polyamide nanoparticles were prepared in the same manner as in Example 1, except that the resin (B)-1 in Example 1 was changed to polypropylene glycol with a different melt viscosity (melt viscosity 5.50 Pa·s, melt viscosity ratio with polyamide 4 (PA4) 137.5). However, in Comparative Example 5, the emulsion diameter became too fine, making it impossible to stably maintain the polymer / polymer emulsion, and thus polyamide nanoparticles could not be obtained.

[0242] <Comparative Example 6> In Comparative Example 6, polyamide fine particles were prepared in the same manner as in Example 1, except that resin (B)-1 in Example 1 was replaced with polypropylene glycol (melt viscosity 0.15 Pa·s, melt viscosity ratio with PA4 3.8) which had a different melt viscosity. However, in Comparative Example 6, resin (A)-1 and the above polypropylene glycol could not maintain balance, and a polymer / polymer emulsion could not be formed, so polyamide fine particles could not be obtained.

[0243] <Comparative Example 7> In Comparative Example 7, polyamide fine particles were prepared in the same manner as in Example 1, except that the mixing mass ratio of resin (A)-1 and resin (B)-1 during melt mixing was changed to 90:10. However, in Comparative Example 7, resin (A)-1 and resin (B)-1 could not maintain balance, and a polymer / polymer emulsion could not be formed, so polyamide fine particles were not obtained.

[0244] <Comparative Example 8> In Comparative Example 8, polyamide fine particles were prepared in the same manner as in Example 1, except that the mixing mass ratio of resin (A)-1 and resin (B)-1 during melt mixing was changed to 10:90. However, in Comparative Example 8, phase inversion occurred, and polyamide fine particles were not obtained.

[0245] <Comparative Example 9> In Comparative Example 9, polyamide fine particles were prepared in the same manner as in Example 1, except that the resin used as resin (B) was changed to resin (B)-2, which is polyvinyl alcohol (melt viscosity 0.52 Pa·s, melt viscosity ratio with resin (A)-1 13.0). However, the interfacial tension and melt viscosity of resin (A)-1 and resin (B)-2 were not balanced, and polyamide fine particles could not be obtained.

[0246] <Comparative Example 10> In Comparative Example 10, polyamide fine particles were prepared in the same manner as in Example 21, except that the resin used as resin (B) was changed to resin (B)-2, which is polyvinyl alcohol (melt viscosity 0.52 Pa·s, melt viscosity ratio with resin (A)-1 13.0). However, the interfacial tension and melt viscosity of resin (A)-1 and resin (B)-2 were not balanced, and polyamide fine particles could not be obtained.

[0247] <Comparative Example 11> In Comparative Example 11, polyamide fine particles were prepared in the same manner as in Example 21, except that resin (A)-1 and resin (B)-1 were placed in an autoclave heated to 200°C. However, the interfacial tension and melt viscosity of resin (A)-1 and resin (B)-1 were not balanced, and polyamide fine particles could not be obtained.

[0248] <Comparative Example 12> In Comparative Example 12, the temperature t of the molten mixture was 混合物 Polyamide nanoparticles were prepared and evaluated in the same manner as in Example 22, except that the holding time in the temperature range above the crystallization temperature of resin (A)-3 and below the melting point of resin (A)-3 was changed to 20 minutes. The properties and effects of the polyamide nanoparticles of Comparative Example 12 are shown in Table 5.

[0249] <Comparative Example 13> In Comparative Example 13, the temperature t of the molten mixture was 混合物Polyamide nanoparticles were prepared and evaluated in the same manner as in Example 21, except that the holding time in the temperature range above the crystallization temperature of resin (A)-1 and below the melting point of resin (A)-1 was changed to 20 minutes. The properties and effects of the polyamide nanoparticles of Comparative Example 13 are shown in Table 5.

[0250] <Comparative Example 14> In Comparative Example 14, the temperature t of the molten mixture was 混合物 Polyamide nanoparticles were prepared and evaluated in the same manner as in Example 23, except that the holding time in the temperature range above the crystallization temperature of resin (A)-1 and below the melting point of resin (A)-1 was changed to 20 minutes. The properties and effects of the polyamide nanoparticles of Comparative Example 14 are shown in Table 5.

[0251] <Comparative Example 15> In Comparative Example 15, polyamide fine particles were prepared and evaluated using the same method as in Example 21, except that the temperature during the melt mixing of resin (A)-1 and resin (B)-1 was changed to 290°C. The properties and effects of the polyamide fine particles of Comparative Example 15 are shown in Table 5.

[0252] [Table 1]

[0253] [Table 2]

[0254] [Table 3]

[0255] [Table 4]

[0256] [Table 5] [Industrial applicability]

[0257] As described above, the polyamide fine particles according to the present invention and the method for producing the same are suitable for realizing polyamide fine particles that have a small average deviation of the coefficient of dynamic friction when the fine particles are rubbed together, a small average deviation of the coefficient of dynamic friction over time, and are also marine biodegradable.

Claims

1. The ratio r of voids on the particle surface and the BET specific surface area A, which is the specific surface area of ​​the particle surface measured by the BET method. BET The ratio (r / A) BET ) is between 6.0 and 100.0, A polymer or copolymer consisting mainly of repeating structural units represented by the following chemical formula (1), Polyamide fine particles characterized by the following features. 【Chemistry 1】 (In chemical formula (1), x is an integer between 2 and 3.)

2. The BET specific surface area A BET 0.8m 2 / g or more 5.0m 2 It is less than or equal to / g. Polyamide fine particles according to feature 1.

3. The sphericity is 90 or higher. Polyamide fine particles according to claim 1 or 2.

4. The amount of impurities contained is 0.50% by weight or less. Polyamide fine particles according to any one of features 1 to 3.

5. The volume-average particle diameter is 0.1 μm or more and 100 μm or less. Polyamide fine particles according to any one of features 1 to 4.

6. The standard deviation of sphericity is 2.00 or less. Polyamide fine particles according to any one of features 1 to 5.

7. In the above chemical formula (1), x is 3. Polyamide fine particles according to any one of features 1 to 6.

8. The time-dependent stability index, which indicates the stability of polyamide microparticles against deterioration of tactile properties when rubbed over time, is calculated using the following formula and is 0.60 or higher. Polyamide fine particles according to any one of features 1 to 7. Stability over time index = 1 / (Standard deviation of sphericity × (1 + amount of impurities)) (In the above formula, the standard deviation of sphericity is the standard deviation of the sphericity of the polyamide fine particles. The amount of impurities contained is the amount of impurities contained in the polyamide fine particles.)

9. A method for producing polyamide fine particles using as raw materials a resin (A) which is a polymer or copolymer mainly composed of repeating structural units represented by the following chemical formula (1), and a resin (B) which is an emulsion-forming resin capable of forming an emulsion with the resin (A) in a molten state, The emulsion forming step involves melting and mixing the resin (A) and the resin (B) at a melting temperature that is above their respective melting points to form an emulsion in which particulate resin (A) is dispersed in resin (B), A solidification step is to cool the molten mixture in which the emulsion of resin (A) and resin (B) is formed to a temperature below the crystallization temperature of resin (A) and to solidify the emulsion. A recovery step is to wash away the resin (B) with a washing solution that is a non-solvent of the resin (A) and recover polyamide fine particles made of the resin (A), Includes, The melt viscosity ratio of resin (A) and resin (B) at 270°C is 4.3 or more and 125.0 or less. A method for producing polyamide fine particles characterized by the above. 【Chemistry 2】 (In chemical formula (1), x is an integer between 2 and 3.)

10. The aforementioned immobilization step is, A holding step of maintaining the temperature of the molten mixture in a temperature range above the crystallization temperature of the resin (A) and below the melting point of the resin (A), A cooling step in which the temperature of the molten mixture after being maintained in the aforementioned temperature range is cooled to a temperature below the crystallization temperature of the resin (A), A method for producing polyamide fine particles according to claim 9, characterized by including the following:

11. In the holding step, the temperature of the molten mixture is maintained within the temperature range for 30 minutes or more and 10 hours or less. A method for producing polyamide fine particles according to feature 10.

12. The aforementioned immobilization step is, A holding step of maintaining the temperature of the molten mixture in a temperature range of 1 second to 10 minutes above the crystallization temperature of the resin (A) and below the melting point of the resin (A), A cooling step in which the temperature of the molten mixture after being maintained in the aforementioned temperature range is cooled to a temperature below the crystallization temperature of the resin (A), A method for producing polyamide fine particles according to claim 9, characterized by including the following:

13. The emulsion formation step includes a heating step of raising the temperature of resin (A) and resin (B) from room temperature to the melting temperature. A method for producing polyamide fine particles according to any one of the features 9 to 12.

14. The melt viscosity of the resin (B) at 270°C is 0.40 Pa·s or more and 5.00 Pa·s or less. A method for producing polyamide fine particles according to any one of the features 9 to 13.

15. The resin (B) is polyethylene glycol. A method for producing polyamide fine particles according to any one of features 9 to 14.

16. In the emulsion formation step, the resin (A) and the resin (B) are melted and mixed at a melting temperature of the melting point of the resin (A) + 5°C or higher and 280°C or lower. A method for producing polyamide fine particles according to any one of features 9 to 15.

17. A polymer or copolymer having a sphericity of 96 or higher, a standard deviation of the sphericity of 2.00 or less, and whose main component is a repeating structural unit represented by the following chemical formula (1), Polyamide fine particles characterized by the following features. 【Transformation 3】 (In chemical formula (1), x is an integer between 2 and 3.)

18. The amount of impurities contained is 0.50% by weight or less. Polyamide fine particles according to feature 17.

19. BET specific surface area A is the specific surface area of ​​the particle surface measured by the BET method. BET 5.0m 2 It is less than or equal to / g. Polyamide fine particles according to feature 17 or 18.

20. The volume-average particle diameter is 0.1 μm or more and 100.0 μm or less. Polyamide fine particles according to any one of features 17 to 19.

21. In the above chemical formula (1), x is 3. Polyamide fine particles according to any one of claims 17 to 20.

22. The time-dependent stability index, which indicates the stability of polyamide microparticles against deterioration of tactile properties when rubbed over time, is calculated using the following formula and is 0.60 or higher. Polyamide fine particles according to any one of features 17 to 21. Stability over time index = 1 / (Standard deviation of sphericity × (1 + amount of impurities)) (In the above formula, the standard deviation of sphericity is the standard deviation of the sphericity of the polyamide fine particles. The amount of impurities contained is the amount of impurities contained in the polyamide fine particles.)

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