JP4940878B2 - Method for producing porous polyamide powder - Google Patents

Description

  The present invention relates to a method for producing porous polyamide powder.

  Since the porous polyamide powder has high lipophilicity, it has been studied to use it as a cosmetic raw material such as a cleansing mask and a chromatographic filler. In addition, use as a carrier or adsorbent for various catalysts in the food industry, the medical field, and the like has also been studied. Furthermore, it has been studied to use a colorant on porous polyamide powder and use it as an electrophotographic toner, or as an electronic material for a display device.

As a method for producing porous polyamide powder, Patent Document 1 discloses that a polyamide-containing mixed solution is prepared by mixing a polyamide solution, a non-solvent of the polyamide and water, and then the polyamide-containing mixed solution is allowed to stand. , A method comprising depositing polyamide porous particles in the polyamide-containing mixed solution is disclosed. In the example of Patent Document 1, the preparation of the polyamide-containing mixed solution is performed by adding a mixed solvent of a polyamide non-solvent and water to the polyamide solution. In this example, there are described production examples of a plurality of porous polyamide powders having different conditions such as the composition of the polyamide-containing mixed liquid and the liquid temperature. Porous polyamide powders having different particle sizes depending on those conditions are described. Has been obtained.
JP 2002-80629 A

As disclosed in Patent Document 1 above, porous polyamide powder is obtained by precipitating polyamide porous particles in a polyamide-containing mixed solution prepared by mixing a polyamide solution, a non-solvent of the polyamide and water. When producing the product, it is possible to control the particle size of the obtained porous polyamide powder by appropriately setting the composition and temperature of the polyamide-containing mixed solution. However, in industrial mass production facilities, it is complicated to set the composition of the polyamide-containing mixed solution and the liquid temperature (particularly, the composition of the polyamide-containing mixed solution) in accordance with the target particle size. .
Accordingly, an object of the present invention is to provide a method for producing a porous polyamide powder that can easily control the particle size even in industrial mass production facilities.

  The present inventor examined a method for producing porous polyamide powders having different particle sizes without changing the composition of the polyamide-containing mixed solution. In the preparation of the polyamide-containing mixed solution, the mixed solvent of polyamide non-solvent and water was used. In addition, the polyamide solution is added in portions while stirring the mixed solvent, so that only the ratio of the amount of the polyamide solution added first and the amount of the polyamide solution added thereafter is changed. It has been found that the particle size of the porous polyamide powder obtained can be controlled without changing the composition of the polyamide-containing mixed solution.

  Therefore, the present invention prepares a polyamide-containing mixed solution by mixing a polyamide solution, a non-solvent of the polyamide and water, and then allowing the polyamide-containing mixed solution to stand in the polyamide-containing mixed solution. A method for producing a porous polyamide powder, comprising precipitating polyamide porous particles, followed by drying, wherein the preparation of the polyamide-containing mixed solution is carried out in a mixed solvent of polyamide non-solvent and water. A method for producing a porous polyamide powder, which is performed by adding a polyamide solution in portions while stirring.

Preferred embodiments of the method for producing the porous polyamide powder of the present invention are as follows.
(1) The amount of the polyamide solution added first in divided addition is in the range of 0.01 to 3.5 parts by mass as the amount of polyamide contained in the polyamide solution with respect to 100 parts by mass of the mixed solvent of polyamide non-solvent and water. Amount.
(2) The amount of polyamide solution initially added in divided addition is 1 to 85% by mass as the amount of polyamide contained in the polyamide solution with respect to the amount of polyamide contained in the total polyamide solution added to the mixed solvent of polyamide non-solvent and water. It is the quantity which becomes the range of
(3) The time until the start of the addition of the next polyamide solution after the addition of the first polyamide solution in the divided addition is in the range of 3 to 360 seconds.
(4) The polyamide is polyamide 6.
(5) The solvent of the polyamide solution is an aromatic alcohol, formic acid or a mixture thereof.
(6) The water content with respect to the total amount of the mixed solvent of the polyamide non-solvent and water is in the range of 2 to 90% by mass.
(7) The polyamide non-solvent is an aliphatic alcohol, an aliphatic ketone, or a mixture thereof.

  By using the method for producing a porous polyamide powder of the present invention, the particle size of the obtained porous polyamide powder can be controlled without changing the composition of the final polyamide-containing mixed solution.

  The method for producing a porous polyamide powder of the present invention comprises preparing a polyamide-containing mixed solution by mixing a conventionally known polyamide solution, a non-solvent of the polyamide and water, and then allowing the polyamide-containing mixed solution to stand. The method comprises the steps of precipitating polyamide porous particles in the polyamide-containing mixed solution and then drying, the main feature of which is to prepare the polyamide-containing mixed solution as described above, The solution of polyamide is divided and added to a mixed solvent of water and water while stirring the mixed solvent.

  Examples of the polyamide used as a raw material in the method for producing the porous polyamide powder of the present invention include polyamide 6, polyamide 66, polyamide 11, polyamide 12, polyamide 610, polyamide 66 / T (T represents a terephthalic acid component), and mixtures thereof. Can be mentioned. In particular, polyamide 6 is preferable.

  The polyamide solution used in the present invention generally has a polyamide concentration in the range of 0.1 to 30% by mass, preferably in the range of 0.2 to 25% by mass, particularly preferably in the range of 5 to 25% by mass.

  The solvent of the polyamide solution is preferably one that is at least partially compatible with water. Examples of the solvent for the polyamide solution include aromatic alcohol, formic acid or a mixture thereof. Examples of aromatic alcohols include phenol, o-cresol, m-cresol, p-cresol and chlorophenol.

  The polyamide solution may contain a freezing point depressant as long as the polyamide particles are not precipitated. As the freezing point depressant, water, aliphatic alcohol, aliphatic ketone, or a mixture thereof can be used. The content of the freezing point depressant in the polyamide solution is generally in the range of 0.1 to 30% by mass, preferably in the range of 5 to 25% by mass.

  In the mixed solvent of the polyamide non-solvent and water used in the present invention, the water content relative to the total amount is generally in the range of 2 to 90% by mass, preferably in the range of 5 to 85% by mass.

  The polyamide non-solvent is preferably one that does not dissolve 0.01% by mass or more of polyamide at a liquid temperature of 25 ° C. The polyamide non-solvent is preferably one in which the solvent of the polyamide solution and water are at least partially compatible (one that dissolves in a small amount), particularly preferably one in which water is compatible. Examples of polyamide non-solvents can include aliphatic alcohols, aliphatic ketones, or mixtures thereof. Examples of the aliphatic alcohol include aliphatic alcohols having 1 to 4 carbon atoms such as methanol, ethanol and isopropanol. Examples of the aliphatic ketone include aliphatic ketones having 1 to 5 carbon atoms such as acetone and methyl ethyl ketone.

  In the production method of the present invention, a polyamide solution, a polyamide non-solvent, and water are mixed. First, a polyamide non-solvent and water are mixed to prepare a mixed solvent, and then the mixed solvent is stirred into the mixed solvent. The polyamide-containing mixed solution is prepared by adding the polyamide solution in portions. The number of times the polyamide solution is added in portions is usually 2 to 5 times, preferably 2 or 3 times, particularly preferably 2 times. In the divided addition of the polyamide solution, it is preferable that the polyamide solution added first and the polyamide solution added thereafter have the same composition.

  The porous polyamide powder produced from the polyamide-containing mixture prepared by split addition of the polyamide solution was manufactured from the polyamide-containing mixture prepared by adding at once the amount of polyamide solution to be finally added by split addition. Compared to porous polyamide powder, the particle size tends to be smaller. The degree of the particle size reduction of the porous polyamide powder can be controlled by changing the ratio of the amount of the polyamide solution added first in the divided addition and the amount of the polyamide solution added thereafter. That is, the particle size of the porous polyamide powder produced from the polyamide-containing mixed solution prepared by adding the polyamide solution dividedly is determined by the amount of the polyamide solution added first in the divided addition and the amount of the polyamide solution added thereafter. Can be controlled by changing the ratio of.

  In the divided addition of the polyamide solution to the mixed solvent of the polyamide non-solvent and water, the amount of the polyamide solution added first is 0 as the amount of polyamide contained in the polyamide solution with respect to 100 parts by mass of the mixed solvent of the polyamide non-solvent and water. The amount is preferably in the range of 0.01 to 3.5 parts by mass, more preferably in the range of 0.05 to 3.0 parts by mass, and in the range of 0.1 to 1.0. Is particularly preferred. In addition, the amount of the polyamide solution added first in divided addition is 1 to 85 mass as the amount of polyamide contained in the polyamide solution with respect to the amount of polyamide contained in the total polyamide solution added to the mixed solvent of polyamide non-solvent and water. %, Preferably in an amount in the range of 5 to 70% by mass, particularly preferably in an amount in the range of 10 to 30% by mass.

  The divided addition of the polyamide solution is preferably completed before the polyamide porous particles are precipitated, that is, before the polyamide solution starts to become cloudy due to the precipitation of the polyamide porous particles. The time from the end of the addition of the first polyamide solution to the start of the addition of the next polyamide solution is generally in the range of 3 to 360 seconds, preferably in the range of 5 to 80 seconds.

  In the production method of the present invention, after the addition of the polyamide solution to the mixed solvent of the polyamide non-solvent and water is completed and a uniform polyamide-containing mixed solution is formed, stirring is stopped and the polyamide-containing mixture is stopped. By allowing the solution to stand, polyamide porous particles are precipitated in the polyamide-containing mixed solution. The liquid temperature of the polyamide-containing mixed liquid for depositing the polyamide porous particles is generally in the range of 3 to 80 ° C, preferably in the range of 3 to 30 ° C. The lower the temperature of the polyamide-containing mixed liquid, the smaller the particle size of the obtained polyamide porous particles tends to be smaller.

  As a method of preparing a polyamide-containing mixed liquid having a target liquid temperature, a method of adding a polyamide solution adjusted to a target liquid temperature to a mixed solvent adjusted to a target liquid temperature, or a target liquid temperature A method of adding a polyamide solution adjusted to a higher liquid temperature to a mixed solvent adjusted to a liquid temperature lower than the target liquid temperature can be used. The latter method is preferred when the concentration of the polyamide solution is 15% by mass or higher. By increasing the temperature of the polyamide solution, the viscosity of the polyamide solution is reduced and the fluidity is improved, so that the addition time of the polyamide solution to the mixed solvent is shortened. By shortening the addition time, the time from the start of addition of the polyamide solution to the preparation of a uniform polyamide-containing mixed solution is shortened, and the particle diameter of the polyamide porous particles precipitated in the polyamide-containing mixed solution is likely to be uniform. Become. In this way, when a polyamide solution having a high concentration is reduced in its solution viscosity and divided addition is performed, a porous polyamide powder having a narrow particle size distribution can be advantageously produced in a productive and economical manner. The liquid temperature of the polyamide solution is preferably higher in the range of 5 to 60 ° C. than the liquid temperature of the mixed solvent, and particularly preferably higher in the range of 10 to 40 ° C. Specifically, the temperature of the polyamide solution is preferably in the range of 35 to 80 ° C, and particularly preferably in the range of 40 to 70 ° C.

  In the production method of the present invention, the polyamide porous particles precipitated in the polyamide-containing mixed solution can be separated from the mixed solution by a usual method such as centrifugation, decantation, or filtration. For example, after adding a low specific gravity solvent such as methanol to the mixed liquid in which the polyamide porous particles are precipitated to increase the difference in specific gravity between the mixed liquid and the polyamide porous particles, a method such as centrifugation or decantation is used. The polyamide porous particles may be separated. The precipitated polyamide porous particles may be further washed several times with methanol, acetone or the like and separated by a method such as centrifugation or decantation. The polyamide porous particles separated from the mixed solution can be dried by a usual drying method such as hot air drying, vacuum drying, stirring drying and the like. Alternatively, the polyamide porous particles may be dried by spray drying the mixed liquid in which the polyamide porous particles are deposited.

  The porous polyamide powder obtained by the production method of the present invention is an aggregate of porous particles in which each particle has a large number of pores on its surface. It is preferable that 70% or more of the polyamide porous particles constituting the porous polyamide powder have a single spherulite structure. Here, the spherulite structure means a structure peculiar to a crystalline polymer in which polymer fibrils are three-dimensionally or radially grown from one or more nuclei near the center of the particle.

  The porous polyamide powder obtained by the production method of the present invention generally has a number average particle size in the range of 3 to 30 μm, particularly in the range of 5 to 20 μm. The particle size distribution index (PDI) (= Dv / Dn) defined as the ratio of the volume average particle diameter (Dv) to the number average particle diameter (Dn) of the porous polyamide powder is generally 1.0 to 2.5. Is preferably in the range of 1.0 to 1.5. The particle size distribution index is one of the indexes representing the uniformity of the particle size distribution of the porous polyamide powder. The particle size distribution index is closer to 1.0 and the spread of the particle size distribution is smaller (the particle size is uniform). Means that.

  The porous polyamide powder obtained by the production method of the present invention can be used as a cosmetic raw material such as a cleansing mask and a chromatographic filler. It can also be used in the food industry and the medical field as a carrier or adsorbent for various catalysts. Furthermore, a colorant can be carried on porous polyamide powder and used as an electrophotographic toner, or used as an electronic material for a display device or the like.

  In this example, the evaluation of the porosity of the polyamide powder, the evaluation of the particle structure, and the measurement of the number average particle diameter and the volume average particle diameter were performed as follows.

(Evaluation of the porosity of polyamide powder)
The evaluation of the porosity of the polyamide powder is performed by observing the surface of the particles constituting the polyamide powder using a scanning electron microscope.

(Evaluation of particle structure)
Evaluation of the particle structure of the polyamide powder is performed by observing the cross section of the particles constituting the polyamide powder using a transmission electron microscope.

(Measurement of number average particle diameter and volume average particle diameter)
About 50000 particles in the polyamide powder, the particle size is measured using a Coulter counter, the number average particle size (Dn) is calculated by the following equation (1), and the volume average particle size is calculated by the following equation (2). (Dv) is calculated.

  Here, Xi is the particle size of each particle, and n is the number of particles measured (50000).

[Example 1]
Methanol 900g and water 225g were charged into a 2L separable flask equipped with three stirring blades and a paddle blade. A mixed solvent of water and water was prepared. While stirring this mixed solvent of methanol and water, polyamide 6 (number average molecular weight: 13000) was dissolved in a solvent containing 90:10 (mass ratio) of phenol and methanol in the mixed solvent. 4.5 g of the prepared polyamide solution having a concentration of 10% by mass (0.04 parts by mass as the amount of polyamide based on 100 parts by mass of the mixed solvent) was added (first stage). Next, 30 seconds after the addition of the first stage polyamide solution was completed, the addition of 145.5 g of a polyamide solution having the same composition as the polyamide solution charged in the first stage was started (second stage), and the polyamide-containing mixture A liquid was prepared. The polyamide-containing mixture immediately after the addition of the second-stage polyamide solution was transparent.
After 60 seconds from the addition of the second-stage polyamide solution, stirring was stopped. 65 seconds after the stirring was stopped, polyamide 6 particles were precipitated in the polyamide-containing mixed solution, and the mixed solution began to become cloudy. Thereafter, the polyamide-containing mixed liquid was allowed to stand for 1 hour while maintaining the liquid temperature at 25 ° C. After standing, the polyamide 6 particles were taken out from the polyamide-containing mixed solution by suction filtration, repeatedly with methanol, washed and dried.

  When the obtained polyamide 6 powder was observed with a scanning electron microscope, it was confirmed that the particles constituting the obtained polyamide 6 powder were porous particles. Furthermore, when a cross section of a plurality of porous particles was observed with a transmission electron microscope, it was confirmed that all the porous particles had a spherulite structure in which fibrils were grown radially from the central nucleus. The obtained porous polyamide 6 powder had a number average particle size of 18.0 μm, a volume average particle size of 21.0 μm, and a particle size distribution index of 1.17.

[Example 2]
The same procedure as in Example 1 except that the addition amount of the first-stage polyamide solution was 15 g (0.13 parts by mass as the amount of polyamide with respect to 100 parts by mass of the mixed solvent) and the addition amount of the second-stage polyamide solution was 135 g. Polyamide 6 powder was produced.
When the obtained polyamide 6 powder was observed with a scanning electron microscope, it was confirmed that the particles constituting the obtained polyamide 6 powder were porous particles. Furthermore, when a cross section of a plurality of porous particles was observed with a transmission electron microscope, it was confirmed that all the porous particles had a spherulite structure in which fibrils were grown radially from the central nucleus. The obtained polyamide 6 powder had a number average particle size of 13.3 μm, a volume average particle size of 14.6 μm, and a particle size distribution index of 1.10.

[Example 3]
The same procedure as in Example 1 except that the addition amount of the first-stage polyamide solution was 30 g (0.27 parts by mass as the amount of polyamide with respect to 100 parts by mass of the mixed solvent) and the addition amount of the second-stage polyamide solution was 120 g. Polyamide 6 powder was produced.
When the obtained polyamide 6 powder was observed with a scanning electron microscope, it was confirmed that the particles constituting the obtained polyamide 6 powder were porous particles. Furthermore, when a cross section of a plurality of porous particles was observed with a transmission electron microscope, it was confirmed that all the porous particles had a spherulite structure in which fibrils were grown radially from the central nucleus. The obtained polyamide 6 powder had a number average particle size of 12.4 μm, a volume average particle size of 13.4 μm, and a particle size distribution index of 1.10.

[Example 4]
The same procedure as in Example 1 was conducted except that the addition amount of the first-stage polyamide solution was 60 g (0.53 parts by mass as the amount of polyamide with respect to 100 parts by mass of the mixed solvent) and the addition amount of the second-stage polyamide solution was 90 g. Polyamide 6 powder was produced.
When the obtained polyamide 6 powder was observed with a scanning electron microscope, it was confirmed that the particles constituting the obtained polyamide 6 powder were porous particles. Furthermore, when a cross section of a plurality of porous particles was observed with a transmission electron microscope, it was confirmed that all the porous particles had a spherulite structure in which fibrils were grown radially from the central nucleus. The obtained polyamide 6 powder had a number average particle size of 11.9 μm, a volume average particle size of 13.0 μm and a particle size distribution index of 1.09.

[Example 5]
The same procedure as in Example 1 was conducted, except that the addition amount of the first-stage polyamide solution was 90 g (0.80 parts by mass as the amount of polyamide with respect to 100 parts by mass of the mixed solvent) and the addition amount of the second-stage polyamide solution was 60 g. Polyamide 6 powder was produced.
When the obtained polyamide 6 powder was observed with a scanning electron microscope, it was confirmed that the particles constituting the obtained polyamide 6 powder were porous particles. Furthermore, when a cross section of a plurality of porous particles was observed with a transmission electron microscope, it was confirmed that all the porous particles had a spherulite structure in which fibrils were grown radially from the central nucleus. The obtained polyamide 6 powder had a number average particle size of 11.8 μm, a volume average particle size of 13.3 μm, and a particle size distribution index of 1.13.

[Example 6]
The same procedure as in Example 1 except that the addition amount of the first-stage polyamide solution was 120 g (1.07 parts by mass as the amount of polyamide with respect to 100 parts by mass of the mixed solvent) and the addition amount of the second-stage polyamide solution was 30 g. Polyamide 6 powder was produced.
When the obtained polyamide 6 powder was observed with a scanning electron microscope, it was confirmed that the particles constituting the obtained polyamide 6 powder were porous particles. Furthermore, when a cross section of a plurality of porous particles was observed with a transmission electron microscope, it was confirmed that all the porous particles had a spherulite structure in which fibrils were grown radially from the central nucleus. The obtained polyamide 6 powder had a number average particle size of 17.8 μm, a volume average particle size of 23.0 μm, and a particle size distribution index of 1.29.

[Reference Example 1]
Instead of adding the polyamide solution in two portions, a polyamide 6 powder was produced in the same manner as in Example 1 except that 150 g of the polyamide solution was added at a time to prepare a polyamide-containing mixed solution.
When the obtained polyamide 6 powder was observed with a scanning electron microscope, it was confirmed that the particles constituting the obtained polyamide 6 powder were porous particles. Furthermore, when a cross section of a plurality of porous particles was observed with a transmission electron microscope, it was confirmed that all the porous particles had a spherulite structure in which fibrils were grown radially from the central nucleus. The obtained polyamide 6 powder had a number average particle size of 19.5 μm, a volume average particle size of 23.1 μm, and a particle size distribution index of 1.18.

  Table 1 below shows the amount of polyamide solution added in Examples 1 to 6 and Reference Example 1, the temperature of the polyamide-containing mixture, the number average particle size and the particle size distribution index of the obtained porous polyamide powder. Shown together. As shown in Table 1 below, by changing the addition amount of the polyamide solution added to the mixed solvent of methanol and water between the first step and the second step, the final addition amount of the polyamide solution is not changed. It turns out that it becomes possible to control the number average particle diameter of the obtained porous polyamide powder.

Table 1
────────────────────────────────────────
Amount of polyamide solution added Polyamide Porous polyamide powder
───────────── Containing liquid mixture ─────────────
First stage Second stage liquid temperature Number average particle size Particle size distribution index
(G) (g) (° C.) (μm) (−)
────────────────────────────────────────
Example 1 4.5 145.5 25 18.0 1.17
Example 2 15 135 25 13.3 1.10
Example 3 30 120 25 12.4 1.10.
Example 4 60 90 25 11.9 1.09
Example 5 90 60 25 11.8 1.13
Example 6 120 30 25 17.8 1.29
────────────────────────────────────────
Reference Example 1 150-25 19.5 1.18
────────────────────────────────────────

[Example 7]
A polyamide 6 powder was produced in the same manner as in Example 3, except that the temperature of the mixed solvent of methanol and water and the temperature of the polyamide solution and the temperature of the polyamide-containing mixed solution at the time of standing were changed to 15 ° C.
When the obtained polyamide 6 powder was observed with a scanning electron microscope, it was confirmed that the particles constituting the obtained polyamide 6 powder were porous particles. Furthermore, when a cross section of a plurality of porous particles was observed with a transmission electron microscope, it was confirmed that all the porous particles had a spherulite structure in which fibrils were grown radially from the central nucleus. The obtained polyamide 6 powder had a number average particle size of 6.8 μm, a volume average particle size of 7.7 μm, and a particle size distribution index of 1.17.

[Reference Example 2]
Instead of adding the polyamide solution in two portions, a polyamide 6 powder was produced in the same manner as in Example 7, except that a polyamide-containing mixed solution was prepared by adding 150 g of the polyamide solution at a time.
When the obtained polyamide 6 powder was observed with a scanning electron microscope, it was confirmed that the particles constituting the obtained polyamide 6 powder were porous particles. Furthermore, when a cross section of a plurality of porous particles was observed with a transmission electron microscope, it was confirmed that all the porous particles had a spherulite structure in which fibrils were grown radially from the central nucleus. The obtained polyamide 6 powder had a number average particle size of 17.1 μm, a volume average particle size of 22.9 μm, and a particle size distribution index of 1.34.

[Example 8]
A polyamide 6 powder was produced in the same manner as in Example 3 except that the liquid temperature of the mixed solvent of methanol and water and the liquid temperature of the polyamide solution, and the liquid temperature when the polyamide-containing mixed liquid was allowed to stand were changed to 5 ° C.
When the obtained polyamide 6 powder was observed with a scanning electron microscope, it was confirmed that the particles constituting the obtained polyamide 6 powder were porous particles. Furthermore, when a cross section of a plurality of porous particles was observed with a transmission electron microscope, it was confirmed that all the porous particles had a spherulite structure in which fibrils were grown radially from the central nucleus. The obtained polyamide 6 powder had a number average particle size of 5.2 μm, a volume average particle size of 7.1 μm, and a particle size distribution index of 1.37.

[Reference Example 3]
Instead of adding the polyamide solution in two portions, a polyamide 6 powder was produced in the same manner as in Example 8, except that a polyamide-containing mixed solution was prepared by adding 150 g of the polyamide solution at a time.
When the obtained polyamide 6 powder was observed with a scanning electron microscope, it was confirmed that the particles constituting the obtained polyamide 6 powder were porous particles. Furthermore, when a cross section of a plurality of porous particles was observed with a transmission electron microscope, it was confirmed that all the porous particles had a spherulite structure in which fibrils were grown radially from the central nucleus. The obtained polyamide 6 powder had a number average particle size of 11.7 μm, a volume average particle size of 14.1 μm, and a particle size distribution index of 1.21.

  Example 3, Example 7, Example 8, and the amount of polyamide solution added in Reference Examples 1 to 3, the liquid temperature of the polyamide-containing mixture, the number average particle size and particle size distribution of the resulting porous polyamide powder The indices are summarized in Table 2 below. As shown in Table 2 below, it can be seen that when the polyamide solution is added in portions, the number average particle size of the porous polyamide powder varies greatly depending on the temperature of the polyamide-containing solution.

Table 2
────────────────────────────────────────
Amount of polyamide solution added Polyamide Porous polyamide powder
───────────── Containing liquid mixture ─────────────
First stage Second stage liquid temperature Number average particle size Particle size distribution index
(G) (g) (° C.) (μm) (−)
────────────────────────────────────────
Example 3 30 120 25 12.4 1.10.
Example 7 30 120 15 6.8 1.17
Example 8 30 120 5 5.2 1.37
────────────────────────────────────────
Reference Example 1 150-25 19.5 1.18
Reference Example 2 150-15 17.1 1.34
Reference Example 3 150-5 11.7 1.21
────────────────────────────────────────

[Example 9]
Example 3 except that the mixed solvent of methanol and water was a mixed solvent of 750 g of isopropanol and 450 g of water, and the solvent of the polyamide solution was a mixed solution containing phenol and isopropanol in a ratio of 90:10 (mass ratio). Similarly, polyamide 6 powder was produced.
When the obtained polyamide 6 powder was observed with a scanning electron microscope, it was confirmed that the particles constituting the obtained polyamide 6 powder were porous particles. Furthermore, when a cross section of a plurality of porous particles was observed with a transmission electron microscope, it was confirmed that all the porous particles had a spherulite structure in which fibrils were grown radially from the central nucleus. The obtained polyamide 6 powder had a number average particle size of 12.9 μm, a volume average particle size of 14.1 μm and a particle size distribution index of 1.09.

[Reference Example 4]
Instead of adding the polyamide solution in two portions, a polyamide 6 powder was produced in the same manner as in Example 9, except that 150 g of the polyamide solution was added at a time to prepare a polyamide-containing mixed solution.
When the obtained polyamide 6 powder was observed with a scanning electron microscope, it was confirmed that the particles constituting the obtained polyamide 6 powder were porous particles. Furthermore, when a cross section of a plurality of porous particles was observed with a transmission electron microscope, it was confirmed that all the porous particles had a spherulite structure in which fibrils were grown radially from the central nucleus. The obtained polyamide 6 powder had a number average particle size of 20.0 μm, a volume average particle size of 23.6 μm, and a particle size distribution index of 1.18.

  The amount of polyamide solution added in Example 9 and Reference Example 4, the temperature of the polyamide-containing mixed solution, the number average particle size and particle size distribution index of the obtained porous polyamide powder are summarized in Table 3 below. As shown in Table 3 below, it can be seen that even when isopropanol is used as the polyamide non-solvent, the number average particle size of the obtained porous polyamide powder can be controlled by dividing the polyamide solution.

Table 3
────────────────────────────────────────
Amount of polyamide solution added Polyamide Porous polyamide powder
───────────── Containing liquid mixture ─────────────
First stage Second stage liquid temperature Number average particle size Particle size distribution index
(G) (g) (° C.) (μm) (−)
────────────────────────────────────────
Example 9 30 120 25 12.9 1.09
────────────────────────────────────────
Reference Example 4 150-25 20.0 1.18
────────────────────────────────────────

[Example 10]
A polyamide 6 powder was produced in the same manner as in Example 3 except that the polyamide concentration of the polyamide solution was 20% by mass.
When the obtained polyamide 6 powder was observed with a scanning electron microscope, it was confirmed that the particles constituting the obtained polyamide 6 powder were porous particles. Furthermore, when a cross section of a plurality of porous particles was observed with a transmission electron microscope, it was confirmed that all the porous particles had a spherulite structure in which fibrils were grown radially from the central nucleus. The obtained polyamide 6 powder had a number average particle size of 7.4 μm, a volume average particle size of 11.0 μm, and a particle size distribution index of 1.49.

[Reference Example 5]
Instead of adding the polyamide solution in two portions, a polyamide 6 powder was produced in the same manner as in Example 10, except that a polyamide-containing mixed solution was prepared by adding 150 g of the polyamide solution at a time.
When the obtained polyamide 6 powder was observed with a scanning electron microscope, it was confirmed that the particles constituting the obtained polyamide 6 powder were porous particles. Furthermore, when a cross section of a plurality of porous particles was observed with a transmission electron microscope, it was confirmed that all the porous particles had a spherulite structure in which fibrils were grown radially from the central nucleus. The obtained polyamide 6 powder had a number average particle size of 16.9 μm, a volume average particle size of 19.3 μm and a particle size distribution index of 1.14.

  Table 4 below collectively shows the amount of polyamide solution added in Example 10 and Reference Example 5, the temperature of the polyamide-containing mixed solution, the number average particle size and the particle size distribution index of the obtained porous polyamide powder. As shown in Table 4 below, it can be seen that even when the concentration of the polyamide solution is 20% by mass, the number average particle size of the obtained porous polyamide powder can be controlled by the divided addition of the polyamide solution.

Table 4
────────────────────────────────────────
Amount of polyamide solution added Polyamide Porous polyamide powder
───────────── Containing liquid mixture ─────────────
First stage Second stage liquid temperature Number average particle size Particle size distribution index
(G) (g) (° C.) (μm) (−)
────────────────────────────────────────
Example 10 30 120 25 7.4 1.49
────────────────────────────────────────
Reference Example 5 150-25 16.9 1.14
────────────────────────────────────────

[Example 11]
Methanol 90 kg and water 22.5 kg were put into a 200 L flask equipped with three stirring blade paddle blades and stirred at a rotational speed of 150 rpm while adjusting the liquid temperature to 25 ° C. A mixed solvent with water was prepared. While continuing stirring of the mixed solvent of methanol and water, a polyamide solution (solvent: phenol / methanol = 90/10 (mass ratio) with a concentration of polyamide 6 (number average molecular weight: 130000) of 10% by mass was added to the mixed solvent. ), Liquid temperature: 25 ° C.) 3.0 kg was added (first stage). Next, 30 seconds after the addition of the first stage polyamide solution was completed, the addition of 12.0 kg of a polyamide solution having the same composition as the polyamide solution charged in the first stage was started to prepare a polyamide-containing mixed solution (2 Stage). The polyamide-containing mixture immediately after the addition of the second-stage polyamide solution was transparent.
After 60 seconds from the addition of the second-stage polyamide solution, stirring was stopped. 62 seconds after the stirring was stopped, polyamide 6 particles were precipitated in the polyamide-containing mixed solution, and the mixed solution began to become cloudy. Thereafter, the polyamide-containing mixed liquid was allowed to stand for 1 hour while maintaining the liquid temperature at 25 ° C. After standing, the polyamide 6 particles were taken out from the polyamide-containing mixed solution by centrifugation, repeatedly washed with methanol, washed and dried.

  When the obtained polyamide 6 powder was observed with a scanning electron microscope, it was confirmed that the particles constituting the obtained polyamide 6 powder were porous particles. Furthermore, when a cross section of a plurality of porous particles was observed with a transmission electron microscope, it was confirmed that all the porous particles had a spherulite structure in which fibrils were grown radially from the central nucleus. The obtained porous polyamide 6 powder had a number average particle size of 9.3 μm, a volume average particle size of 11.4 μm, and a particle size distribution index of 1.22.

[Reference Example 6]
Instead of adding the polyamide solution in two portions, polyamide 6 powder was produced in the same manner as in Example 11 except that 15.0 kg of the polyamide solution was added at a time to prepare a polyamide-containing mixed solution.
When the obtained polyamide 6 powder was observed with a scanning electron microscope, it was confirmed that the particles constituting the obtained polyamide 6 powder were porous particles. Furthermore, when a cross section of a plurality of porous particles was observed with a transmission electron microscope, it was confirmed that all the porous particles had a spherulite structure in which fibrils were grown radially from the central nucleus. The obtained polyamide 6 powder had a number average particle size of 18.0 μm, a volume average particle size of 21.0 μm, and a particle size distribution index of 1.17.

  The amount of polyamide solution added in Example 11 and Reference Example 6, the temperature of the polyamide-containing mixed solution, the number average particle size and particle size distribution index of the obtained porous polyamide powder are summarized in Table 5 below. As shown in Table 5 below, it can be seen that even when the amount of the polyamide solution added is large, the number average particle size of the resulting porous polyamide powder can be controlled by dividing the polyamide solution.

Table 5
────────────────────────────────────────
Amount of polyamide solution added Polyamide Porous polyamide powder
───────────── Containing liquid mixture ─────────────
First stage Second stage liquid temperature Number average particle size Particle size distribution index
(Kg) (kg) (° C) (μm) (-)
────────────────────────────────────────
Example 11 3.0 12.0 25 9.3 1.22
────────────────────────────────────────
Reference Example 6 15.0-25 18.0 1.17
────────────────────────────────────────

[Example 12]
Into a 10 L flask equipped with 3 inclined paddles and 4 parallel baffle plates, 3.75 kg of isopropanol and 2.25 kg of water were added, and the liquid temperature was adjusted to 22 ° C., and the mixture was stirred at a stirring speed of 200 rpm. Thus, a mixed solvent of methanol and isopropanol was prepared. Concentration 20% by mass prepared by dissolving polyamide 6 (number average molecular weight 13000) in a solvent containing phenol and isopropanol in a ratio of 90:10 (mass ratio) while continuing to stir the mixed solvent. 0.15 kg of the polyamide solution was added by heating to a liquid temperature of 60 ° C. (first stage). The mixed solution after the addition of the first-stage polyamide solution was transparent. Then, with further stirring, after 30 seconds from the completion of the addition of the first stage polyamide solution, addition of 0.60 kg of a polyamide solution having the same composition as the polyamide solution charged in the first stage and a liquid temperature of 60 ° C. Starting (second stage), a polyamide-containing mixture was prepared. The polyamide-containing mixture immediately after the addition of the second-stage polyamide solution was transparent.
After 15 seconds had elapsed since the addition of the second-stage polyamide solution (55 seconds after the start of the first-stage charging), stirring was stopped. One second after the stirring was stopped, polyamide 6 particles were precipitated in the polyamide-containing mixed solution, and the mixed solution began to become cloudy. The liquid temperature of the polyamide-containing mixed liquid was 25 ° C. The solution was allowed to stand for 1 hour while maintaining the liquid temperature at 25 ° C. After standing, the polyamide 6 particles were taken out from the polyamide-containing mixed solution by centrifugation, repeatedly washed with hot isopropaneol, washed and dried.

  When the obtained polyamide 6 powder was observed with a scanning electron microscope, it was confirmed that the particles constituting the obtained polyamide 6 powder were porous particles. Furthermore, when a cross section of a plurality of porous particles was observed with a transmission electron microscope, it was confirmed that all the porous particles had a spherulite structure in which fibrils were grown radially from the central nucleus. The obtained porous polyamide 6 powder had a number average particle size of 10.9 μm, a volume average particle size of 12.1 μm, and a particle size distribution index of 1.11.

[Reference Example 7]
Instead of adding the polyamide solution in two portions, a polyamide 6 powder was produced in the same manner as in Example 12 except that a polyamide-containing mixed solution was prepared by adding 0.75 kg of the polyamide solution at a time.
When the obtained polyamide 6 powder was observed with a scanning electron microscope, it was confirmed that the particles constituting the obtained polyamide 6 powder were porous particles. Furthermore, when a cross section of a plurality of porous particles was observed with a transmission electron microscope, it was confirmed that all the porous particles had a spherulite structure in which fibrils were grown radially from the central nucleus. The obtained polyamide 6 powder had a number average particle size of 17.3 μm, a volume average particle size of 20.2 μm, and a particle size distribution index of 1.17.

  The amount of polyamide solution added in Example 12 and Reference Example 7, the temperature of the polyamide-containing mixed solution, the number average particle size and particle size distribution index of the obtained porous polyamide powder are summarized in Table 6 below. As shown in Table 6 below, by heating and adding a high-concentration polyamide solution in a divided manner, the number average particle size of the resulting porous polyamide powder is maintained while maintaining the particle size distribution index (that is, the spread of the particle size distribution). It can be seen that it is possible to control.

Table 6
────────────────────────────────────────
Amount of polyamide solution added Polyamide Porous polyamide powder
───────────── Containing liquid mixture ─────────────
First stage Second stage liquid temperature Number average particle size Particle size distribution index
(Kg) (kg) (° C) (μm) (-)
────────────────────────────────────────
Example 12 0.15 0.60 25 10.9 1.11.
────────────────────────────────────────
Reference Example 7 0.75-25 17.3 1.17
────────────────────────────────────────

Claims (8)

  A polyamide-containing mixed solution is prepared by mixing a polyamide solution, a non-solvent of the polyamide and water, and then the polyamide-containing mixed solution is allowed to stand to precipitate polyamide porous particles in the polyamide-containing mixed solution. A method for producing a porous polyamide powder comprising: drying the polyamide-containing mixed solution, and stirring the mixed solvent in a mixed solvent of a polyamide non-solvent and water while stirring the mixed solvent. A method for producing a porous polyamide powder, which is carried out by adding a solution dividedly.   The amount of the polyamide solution to be added first in divided addition is an amount in the range of 0.01 to 3.5 parts by mass as the amount of polyamide contained in the polyamide solution with respect to 100 parts by mass of the mixed solvent of polyamide non-solvent and water. The manufacturing method of the porous polyamide powder of Claim 1.   The amount of the polyamide solution initially added in the divided addition is in the range of 1 to 85% by mass as the amount of polyamide contained in the polyamide solution with respect to the amount of polyamide contained in the total polyamide solution added to the mixed solvent of polyamide non-solvent and water. The method for producing a porous polyamide powder according to claim 1, wherein   The method for producing a porous polyamide powder according to claim 1, wherein the time from the end of addition of the first polyamide solution in the divided addition to the start of addition of the next polyamide solution is in the range of 3 to 360 seconds.   The method for producing a porous polyamide powder according to claim 1, wherein the polyamide is polyamide 6.   The method for producing a porous polyamide powder according to claim 1, wherein the solvent of the polyamide solution is an aromatic alcohol, formic acid or a mixture thereof.   The method for producing a porous polyamide powder according to claim 1, wherein the water content in the mixed solvent of the polyamide non-solvent and water is in the range of 2 to 90% by mass.   The method for producing a porous polyamide powder according to claim 1, wherein the polyamide non-solvent is an aliphatic alcohol, an aliphatic ketone, or a mixture thereof.