JPS58219235A - Production of nylon powder - Google Patents

Abstract

PURPOSE:Nylon is dissolved in a specific solvent, combined with a poor solvent for reprecipitation, then the solvents are evaporated off to permit easy production of a nylon powder used as raw material for powder coating or adsorbent in no need of specific conditions and facilities. CONSTITUTION:Nylon such as nylon 6, 66, 610, 612, 6/66, 6/66/610, 6/66/612, is dissolved in a solvent of 2,2,2-trifluoroethanol (abbreviated to TFE) or in its high-concentration solution in water, preferably of less than 5wt% water content, and the resultant solution, preferably of 1-10wt% nylon concentration, is combined under stirring with a poor solvent such as water or a TFE low concentration solution, preferably of lower than 10wt%. Then, TFE is evaporated off from the mother liquor to give a nylon powder. The amoun of the poor solvent added to the solution is optimally 1-3 times the weight of the solvent in the nylon solution.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing nylon powder, particularly a method for producing nylon powder by a reprecipitation method.

Nylon powder has great industrial value as a raw material for powder coatings, adsorbents, cosmetic bases, sintered molded products, etc.
Various manufacturing methods have been proposed.

A typical manufacturing method involves dissolving nylon in an appropriate solvent.

This is a so-called reprecipitation method in which nylon powder is precipitated by utilizing the solubility difference due to temperature or by adding a poor solvent that mixes uniformly with the solvent.

Regarding the former, is ethylene glycol etc. a solvent for nylon? Polyhydric alcohol (U.S. Pat. No. 2,639,278), ε-cagflectam aqueous solution (% Kosho 43-1
8616), dimethylacetamide (Special Publication No. 1973)
-24812), hydrous lower alcohol (Special Publication No. 5
3-46218), but all of these require considerable high temperatures (e.g., 130°C or higher), and some require high pressures (e.g., 10 Kf/- or higher > 1). There are drawbacks.

Regarding the latter, acids such as inorganic acids and organic acids (Japanese Patent Publication No. 38-13520) have been proposed as solvents for nylon, and high temperatures are not necessarily necessary and room temperature is sufficient, but special paulownia There are disadvantages such as the need for equipment and the fact that the degree of polymerization is significantly reduced due to depolymerization of the nylon.

As a result of intensive studies to improve the above-mentioned drawbacks of the reprecipitation method, the present inventors dissolved nylon in a specific solvent, added a poor solvent for reprecipitation, and removed the solvent by distillation. It has been found that nylon powder with a particle size of 1 μm to several hundred μm can be easily obtained by this method.

That is, in the present invention, nylon is dissolved in a solvent consisting of 2.2.2-trifluoroethanol (hereinafter abbreviated as TFE) or a concentrated aqueous solution of TFE, and a poor solvent consisting of water or a dilute aqueous solution of TFB is stirred into the nylon solution. In this method, TFE is directly removed from the mother liquor by distillation. Here, the mother liquor means a solution, suspension, slurry, etc. in which at least a part of the poor solvent has been added to the nylon solution, or in which at least a part of the solvent has already been removed. It does not matter whether it is completely dissolved, partially dissolved and the rest precipitated, or completely precipitated.

The present invention will be explained in more detail below.

Examples of nylon used in the present invention include nylon 6, 66, 610, 612, 6/66, 6/
66/61G.

6/66/612, etc. All of these are dissolved in TFE or a concentrated aqueous solution of TFE.

The concentration of nylon in a nylon solution consisting of nylon and TFE or a concentrated aqueous solution of TFE can vary widely, but if the concentration is too high, nylon may precipitate in lumps, films, or fibers when a poor solvent is added. 0.1 to 15 wt., preferably 1.0 wt.
~10 wt is practical.

In the present invention, TFE or a concentrated aqueous solution of TFE is used as a solvent for nylon. TFE is a fluorine-containing alcohol that is completely compatible with water, methanol, acetone, etc., and has strong properties, and is hardly corrosive to various metals. Nylon 6, 66, 610, 612.

6/66, 6/66/610, 6/66/612, etc. are of course soluble in TFE alone, but when water is added to 20 wt%
It also dissolves in a concentrated aqueous solution of TFE contained below. However, if the water content is high, it will take a long time to dissolve the nylon or require high temperature and pressure, so the water content is preferably 10 wt% or less, particularly preferably 5 wt% or less. is practical. In the case of TlI'E alone or a concentrated aqueous solution of TFB with a water content of 5 wt% or less, nylon can be dissolved in a short time under normal pressure at a temperature near the boiling point of TF'E (approximately 74°C). can. Also, of course, if the amount of water is less than 5wt,
% or more, the nylon can be dissolved at a temperature above the boiling point of TFE and at a relatively low pressure, for example, about 4/- or less. Note that when dissolving nylon that has a solubility at room temperature or higher, it is of course necessary to heat it, but even when dissolving nylon that has a solubility at or below room temperature, it is possible to shorten the dissolution time by using, for example, TFE. boiling point
It is preferable to heat and melt at a temperature around □ (approximately 74° C.).

In the present invention, water or a dilute aqueous solution of Vi tile is used as a poor solvent for reprecipitation. In the case of a dilute aqueous solution of TFE, a large amount may be added even if the TFE concentration is, for example, about 30 wt %, but from a practical standpoint, the TFE concentration is preferably 10 wt % or less. Note that it is preferably more practical to use a dilute aqueous solution of TFB than water. because.

This is because when a dilute aqueous solution of TFB is used as a poor solvent, it is possible to simplify the purification by distillation of water-containing TFB separated from the mother liquor by distillation as described below.

The amount of poor solvent added can be changed depending on the type and concentration of nylon in the nylon solution, but if the amount added is small, T in the mother liquor will increase.
As FE is distilled and separated, nylon precipitates in a form other than powder (lump, film, or fiber).Even if it precipitates in powder form, the fluidity of the mother liquor may deteriorate, so the weight of the poor solvent A practical amount is 0.5 to 5 times, preferably 1 to 3 times, the weight of the solvent in the nylon solution.

Note that it is necessary to stir the nylon solution when adding the poor solvent; otherwise, nylon will not precipitate in the form of a powder, but will precipitate in the form of lumps, films, or fibers.

Of course, stirring must be continued during the distillative separation of TFB3 from the mother liquor.

In the present invention, in order to completely remove TFB from the nylon powder, i9 TFE is directly removed from the mother liquor by distillation. Nylon powder is removed by normal V-filtering, water washing, etc.
i In the method of removing TFE, a low concentration TFE aqueous solution (
In contrast, with the method of the present invention, in which TFE is directly removed from the mother liquor by distillation, it is possible to omit the water washing step. In the present invention, the distillation separation of TFE from the mother liquor is preferably started before the addition of the poor solvent is completed.

Compared to starting the distillative separation of TFE from the mother liquor after the addition of the poor solvent is completed, this method has the advantage of saving time and making it possible to downsize the apparatus. Such an advantage is particularly noticeable when the distillative separation of TFB from the mother liquor is started at the same time as the addition of the antisolvent to the nylon solution is started.

Note that it is also possible to concentrate a portion of TFB from the nylon solution by distilling off the nylon solution before starting addition of the poor solvent, then start adding the poor solvent, and continue distilling and separating TFB thereafter.

In the present invention, the distillation separation of TFB from the mother liquor is completed by
At the point when TFE is no longer detected in the distillate,
TFE can be detected by gas chromatography or the like. Note that nylon has completely precipitated by the time TFE is distilled and separated.

After that, it is impossible to add a poor solvent to the edge.
That is, the poor solvent should be added at the latest until the distillation of TFE from the mother liquor is completed. However, for the purpose of improving fluidity, etc., TFB was added to the mother liquor after the distillation separation of TFB was completed.
There is no problem with further adding water that does not contain FE. When separating TFE from the mother liquor by distillation, by selecting the distillation equipment and distillation conditions appropriately, the water content can be adjusted to a level that can be used as a solvent. Low (e.g. 5wt% or less) TF
After collecting the concentrated aqueous solution, the TFE concentration is relatively low (for example, TOwt), which cannot be used as a solvent as it is.
% or less) Obtain a TFFI aqueous solution, and then perform simple distillation to recover a concentrated aqueous TFE solution (e.g., concentration 5 wt% or less) that can be used as a solvent and a dilute aqueous TFE solution (e.g., concentration 10 wt% or less) that can be used as a poor solvent. It is also possible to do this.

Note that during the distillation separation of TFE from the mother liquor, in order to enable stirring of the mother liquor, the total weight of TFE and water in the mother liquor is calculated by adding the nylon (dissolved and undissolved) in the mother liquor. It is practical to maintain the weight at least 6 times, preferably at least 9 times, the total weight of

Furthermore, it is practically preferable to carry out the distillation separation of TFE from the mother liquor under normal pressure and at a temperature near the boiling point of the mother liquor. Since the temperature has reached approximately 100°C, it is presumed that the diffusion or extraction of TFE from inside the nylon powder is almost complete when the distillation separation of TFB from the mother liquor is completed.

When the distillation separation of TFE from the mother liquor is completed, an aqueous slurry of nylon powder is obtained. If the water slurry is further subjected to ordinary filtration and drying, dry nylon powder with a particle size of 1 μm to several hundred μm can be obtained. The thick ones are only those with particle diameters of 1 to several microns that are clustered together. Therefore, in addition to normal grinding,
By performing a classification operation, dry nylon powders of various particle sizes of 1 μm or more can be easily obtained. Further, the degree of polymerization of such dry nylon powder is not much different than the degree of polymerization of nylon before being dissolved in a solvent consisting of a concentrated aqueous solution of TFB or TFH.

Furthermore, as already mentioned, TFE has almost no corrosivity to various metals, so the material of the equipment for carrying out the method of the present invention does not need to be special, and ordinary carbon steel or stainless steel can be used. Steel is sufficient. Next, the present invention will be specifically explained with reference to Examples.

Example 1 11.1 t nylon 66 and moisture content 0.1 wt %
The following TFEtoor was charged into a flask with an internal volume of 500 cc equipped with a stirrer, a dropping funnel, a thermocouple (with a glass protective tube), and a complete set of distillation equipment for TFE distillation, and heated with a mantle heater while stirring. A transparent nylon solution was obtained by maintaining the temperature at 74° C. for 2 hours while adjusting the heater voltage to prevent TFB from distilling out. Water as an anti-solvent was added to this solution under stirring using a dropping funnel at a rate of 5.2 r/min, while also controlling the distillation of TFE by adjusting the heater voltage while maintaining the temperature of the mother liquor at approximately When the temperature was maintained at 74° C., nylon began to precipitate when approximately 40 liters of water had been added. After this point, water addition was continued while adjusting the heater voltage so that the water-containing TFE was distilled out at a rate of about 3.1 F/min. The composition of the distillate was analyzed by gas chromatography (the filler was 20% P B G 20 M
/ Chromosorb W), and when TFE was no longer detected in the distillate, the addition of water and the heating of the heater were stopped, but at this point the temperature of the mother liquor was about 1
It was 00℃. The total amount of water added (including about 4Of until the start of nylon precipitation) was 225f, and the total amount of distillate was 141f. The mother liquor was air-cooled for about 3 hours while stirring, and then filtered through a 60-mesh wire mesh.7. The P solution is ms, A
Filtered through P paper, and nylon 6 with high moisture content was left on the P paper.
A cake of 6 powders was obtained. As a result of observing this cake under a microscope, the particle size of the nylon powder was 1 to 250μ,
Among the large particles, particles with a particle size of 1 to 10μ were aggregated.

Furthermore, when the P solution filtered through N[1SAF paper was analyzed by gas chromatography, TFE was not detected.

Example 2 TFB containing 8.72 nylon 66 and 5 wt% water
A concentrated aqueous solution of 100 F was charged into the same flask as in Example 1, and heated at 74° C. for 3 hours. A dilute aqueous TFE solution containing 10 wt of Tli'B as a poor solvent was added to the obtained nylon solution at a rate of 3.5 f/min, while suppressing the distillation of TFE and maintaining the temperature of the mother liquor at about 74 mm. It was kept at ℃. When about 44 f of the above dilute aqueous TFg solution was added, nylon began to precipitate, and the Tsukuda liquid became slightly cloudy. When approximately 62% of the solution was added, the mother liquor became even more cloudy, but the precipitation of nylon had not yet been completed. At this point, distillation was started at a rate of 11.897 minutes for the famous water TFFli, and the addition was stopped when the amount of 'II' FE dilute aqueous solution added (including 5Of until the start of distillation) reached 300 fK. After that, distillation of water-containing TFg '1
2. The distillation was continued at a rate of 100°C, and the distillation was stopped when TFE was no longer detected in the distillate. The temperature of the mother liquor at the time of discontinuation of distillation was about 100°C, and the temperature of the distillate up to that point was 152F. By cooling the mother liquor in the air and filtering it in the same manner as in Example 1, a cake of nylon 66 powder with a high moisture content is obtained, and the particle size of the powder is 1 to 250μ.
Met.

Example 3 'I containing 8.7f nylon 66 and 1 wt water
'FD concentrated aqueous solution was charged into the same flask as in Example 1, and heated at 74°C for 2 hours. At the same time as starting to add a dilute aqueous TFE solution containing 5vrt% of TFE as a poor solvent to the obtained nylon solution at a rate of 2.791 minutes,
Distillation of the water-containing TFE f started at a rate of 1.597 minutes. The addition was stopped when the amount of TFE dilute aqueous solution added reached 20of, but the distillation of water-containing TFE was 1.79.
It continued at a speed of 7 minutes. Distillation was stopped when TFE was no longer detected in the distillate, but the total amount of distillate was 17
It was 1 f. The mother liquor at 100°C was prepared in the same manner as in Example 1.
By air cooling and filtration, a cake of nylon 66 powder with high water content is obtained, and the particle size of the powder is 1 to 250.
It was μ.

Examples 4 to 18 When experiments similar to those in Example 3 were conducted under the conditions shown in Table 1, cakes of high moisture content nylon powder were obtained in all cases.
The particle size of the powder was 1-250μ.

Explanation of symbols in Table 1 N A S 6/6S copolymer nylon/ (weight ratio TO/30) N B: 6/66/610 copolymer nylon (weight ratio 75/15/1G) N C: 6/66 /6
12 copolymerized nylon (weight ratio 75/15/1G) SA: TFE concentrated aqueous solution with water content of 0.1 wt or less SB:
TFE concentrated aqueous solution with 1 wt water content SC: Moisture S wt%
TFE concentrated aqueous solution NSA: TFE 1 wt
% of TFK dilute aqueous solution NSB! TFE 5wt
% TFE dilute aqueous solution NSC: TFE 10 wt
96 TFE dilute aqueous solution Example 19 TF containing 0.6F nylon 6 and water in s wt %
A concentrated aqueous solution of E at 300 F was charged into the same flask as in Example 1, and heated at 74°C for 1 hour. Water was added as a poor solvent to the obtained nylon solution while suppressing the distillation of TFE\2.
The water was added at a rate of 9 f/min, and the addition of water was stopped when the amount of water added reached 1502 ml. Then, x the water-containing TFE,
Distillation was started at a rate of avA-, and distillation was stopped when TFE was no longer detected in the distillate, but the total amount of distillate was 2982. The mother liquor at 0100°C was air-cooled for about 15 hours. After that, a cake of nylon 6 powder with a high moisture content was obtained by filtration in the same manner as in Example 1, and the particle size of the powder was 1 to 250 μm.

Example 20 Nylon 1f was dissolved in 100 CC of 98% sulfuric acid,
Nylon 66 of 43.4 F with a relative viscosity (hereinafter abbreviated as sulfuric acid relative viscosity) measured at 25°C using an Ostwald viscometer of 2.74 and a concentrated aqueous TFE solution containing 1 wt% of water. 500 F into a flask with an internal volume of 2 tons equipped with a stirrer, a dropping funnel, a thermocouple (with a glass protection tube), and a distillation tank for TFE distillation.
The mixture was heated with a mantle heater while stirring. Heat to 74°C while adjusting the heater and -1 voltage to prevent TFE from distilling out.
A clear nylon solution was obtained after holding for 2 hours. Water as a poor solvent was added to this solution at a rate of s, zr/min, and at the same time, water-containing TFE began to be distilled out at a rate of 2.7 F/min. The addition of water was stopped when the amount of water added reached 1500 f, but the distillation of water-containing TFE was a
, a continued at a speed of V1 min. Distillation was stopped when TFE was no longer detected in the distillate, and the total amount of distillate was 769 f. After air cooling the mother liquor at 100°C,
After filtering through an 80-mesh wire mesh and drying the filtrate in a small spray dryer, dry nylon powder with a particle size of ~200 μm was obtained, and its relative viscosity in sulfuric acid was 2.70. The dry nylon powder thus obtained was further pulverized using a pneumatic pulverizer, and the particle size distribution was measured using a laser integrated particle size analyzer, and the results shown in Table 2 were obtained.

Table 2 Example 21 Water was distilled from 769v of the distillate of Example 20 to 2
．． TFE concentrated aqueous soluble fi 489 f and TF containing 3
276 vol of a dilute aqueous TFE solution containing 6.4 g of E was obtained. The former TFE concentrated aqueous solution 489F and 42.5
Nylon 6 having a relative viscosity of 2.45 was charged into the same flask as in Example 20, and heated at 74° C. for 2 hours to obtain a transparent nylon solution. 'Add the above T to this solution.
At the same time as addition of 276% dilute aqueous FE solution was started at a rate of 7.8 v/min, distillation of water-containing TFE was started at a rate of 3.5 y1 min. After adding 276f of the TFE dilute aqueous solution, add 700v of water to 7. Addition was made at a rate of sr/min. Distillation was stopped when FE was no longer detected in the distillate, and the total amount of distillate was 772 f. 10
When the mother liquor at 0° C. was air-cooled, filtered, and dried in the same manner as in Example 20, dry nylon 6 powder with a particle size of 1 to 200 μm was obtained, and its sulfuric acid relative viscosity was 2.40.

Example 22 Water was extracted from the distillate 772f of Example 21 by distillation.
516v of TFB concentrated aqueous solution containing 6wt% was obtained. Example 2: Nylon 610 having a relative viscosity of 2.78 and the above TFE concentrated aqueous solution 5161
Add 1032 f of water to the same flask as 0 and heat at 74°C for 2 hours to obtain a transparent nylon solution.
At the same time as starting the addition at a rate of 97 minutes, add 3
．． Distillation was started at a rate of 2 t/min. After the addition of water was completed, the distillation rate was changed to 4.1 t/min, and the distillation was stopped when TFE was no longer detected in the distillate, but the total amount of distillate was It was 749f. When the mother liquor at 100° C. was air-cooled, filtered and dried in the same manner as in Example 20, dry nylon 610 powder with a particle size of 1 to 200 μm was obtained, and its acid relative viscosity was 2.74.

Patent applicant: Asahi Kasei Industries, Ltd. 271

Claims (1)

[Claims] 1. Nylon is dissolved in a solvent consisting of 2.2.2-) refluoroethanol or 2.2.2-) IJ fluoroethanol concentrated aqueous solution, and water or 2.
, 2.2-) A method for producing nylon powder, characterized in that a poor solvent consisting of a dilute aqueous solution of fluoroethanol is added under stirring, and 2.2.2-IJ fluoroethanol is directly removed from the mother liquor by distillation. 2 Production method according to claim 1, in which the distillation is started at the latest before the addition of the poor solvent is finished; Production method table according to claim 2, in which the distillation is started at the same time as the addition of the poor solvent is started. Nylon is nylon 6.66.610, 612.6
/66°6/66/610, 6/66/612, manufacturing method 5 according to claim 1, wherein the nylon concentration in the nylon solution is 0.1. ~15w
The manufacturing method 6 according to claim 1, which is
The manufacturing method 7 according to claim 5, wherein the nylon concentration in the nylon solution is 1 to 10 wt %; The manufacturing method according to claim 1, wherein the solvent is 2.2.2-trifluoroethanol. Method & Manufacturing method 9 according to claim 1, in which the solvent is a concentrated aqueous solution of 2,2.2-,iJ fluoroethanol containing 5 wt% or less of water; Claim 1, in which the poor solvent is water The production method according to claim 1, wherein the poor solvent is a dilute aqueous solution of 2,2.2-) refluoroethanol containing 10 wt% or less of 2.2.2-) refluoroethanol. Method 11: The weight of the poor solvent added is 0.5 to 5 times the weight of the solvent in the nylon solution.Production method 12 according to claim 1: The weight of the poor solvent added is 0.5 to 5 times the weight of the solvent in the nylon solution. 13. The manufacturing method according to claim 1, in which the distillation is carried out under normal pressure and at a temperature near the boiling point of the mother liquor. 2.2.2-) Production method 15 according to claim 1, wherein the total weight of refluoroethanol and water is maintained at 6 times or more the weight of nylon in the mother liquor. 2.2.2-) The total weight of IJ fluoroethanol and water in the mother liquor is maintained at 9 times or more the weight of nylon in the liquid.
Production method 16 described in item 4, water content separated by distillation from the mother liquor 2.2.2
- further distillation of trifluoroethanol to 5 wt water
2,2.2-) Concentrated aqueous solution of 2,2.2-) refluoroethanol containing % or less and 2.2.2-) Dilute aqueous solution of 2,2,2-trifluoroethanol containing 4 io wt % or less of refluoroethanol. death. Manufacturing method 17 according to claim 1, using each as a solvent and a poor solvent, Nylo Y6, 66.610.612, 6/66.
At least one nylon selected from the group consisting of 6/66/610, 6/66/612, and 5 wt water.
When the concentration of nylon is 1 = 10 in a solvent consisting of a concentrated aqueous solution of 2,2.2-) refluoroethanol containing 1% or less
2,2.2 containing 10 wt% or less of refluoroethanol.
-) A poor solvent consisting of a dilute aqueous solution of refluoroethanol is added so that the weight of the poor solvent is 1 to 3 times the weight of the solvent, and at the same time as the addition of the poor solvent is started, 2.2
．． 2-) Begin removing the refluoroethanol by distillation, and repeat the distillation until the total weight of 2.2.2-) refluoroethanol and water in the mother liquor is 9 times the weight of the nylon in the mother liquor.
2.2.2-2-1-Refluoroethanol is maintained under normal pressure and at a temperature near the boiling point of the mother liquor until the entire amount of 1-refluoroethanol is substantially removed.
Manufacturing method described in section