JPS58219236A - Production of nylon powder - Google Patents

Abstract

PURPOSE:After nylon is dissolved in a specific solvent, a poor solvent is added thereto for reprecipitation to permit easy production of a nylon powder used as 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 2,2,2-trifluoroethanol (abbreviated to TFE) or a solvent mainly consisting of the same, preferably a solvent containing less than 5wt% water, so that the concentration of the nylon becomes preferably 1-10%. The resultant solution is combined with a poor solvent which does not dissolve nylon at room temperature and is compatible with the TFE solution such as water, methanol or acetone, preferably under stirring in an amount of 1-3 times the weight of the solvent to effect precipitation of the nylon, thus producing a nylon powder. When nylon 11 or nylon 12 is employed, TFE containing phenol as a dissolution aid is recommended.

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 is used in powder coatings, adsorbents, and cosmetic bases.

It has great industrial value as a raw material for sintered molded products, etc., and various methods for producing it have been proposed.

A typical manufacturing method is the so-called reprecipitation method, in which nylon is dissolved in a suitable solvent and 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, polyhydric alcohols such as ethylene glycol (U.S. Pat. No. 2,639,278), ε-caprolactam aqueous solution (Japanese Patent Publication No. 43-1) are used as solvents for nylon.
8616), dimethylacetamide (Special Publication No. 1973)
-24812), hydrous lower alcohol (Special Publication No. 5
3-46218), but all of these require considerably high temperatures (e.g., 130°C or higher), and some require high pressures (e.g., 10 kg/clIL2 or higher).
There are disadvantages such as some requiring

Regarding the latter, acids such as inorganic acids and organic acids (Japanese Patent Publication No. 38-13520, etc.) are used as solvents for nylon.
□It has been proposed that high temperatures are not necessarily necessary and room temperature is sufficient, but there are drawbacks such as the need for equipment made of special materials and the depolymerization of nylon, which significantly reduces the degree of polymerization in °C. .

The inventors of the present invention have made extensive studies to improve the above-mentioned drawbacks of the reprecipitation method, and have found that by dissolving nylon in a specific solvent and adding a poor solvent for reprecipitation, the particle size ranges from lμ to several hundred. It has been found that μ nylon powder can be easily obtained.

That is, the present invention dissolves nylon in a solvent mainly composed of 2.2.2-) refluoroethanol (hereinafter abbreviated as TFg) or TFE, and the nylon is not dissolved at room temperature and is substantially compatible with TFE. It is an object of the present invention to provide a method for producing nylon powder, which comprises adding a completely miscible poor solvent to the nylon solution under stirring to precipitate nylon.

The present invention will be explained in more detail below.

The nylon used in the present invention includes, for example, nylon
6, 66, 610, 612, 6/66, 6/6
6/610゜6/66/612 Cicada can be mentioned, and both of these can be dissolved in TFE or a solvent mainly composed of TFE. Nylon 11 and 12 are difficult to dissolve in TFE, but phenol, metacresol, etc.
Since it dissolves in 'rFE containing 1 to 10 wt% of these solubilizers, the method of the present invention can also be applied to nylon 11 and 12 if TFE containing 1 to 10 wt% of these solubilizers is used. .

The concentration of nylon in a nylon solution consisting of nylon and TFE or a TFE-based solvent can vary considerably, but if the concentration is high, the nylon will form lumps when a poor solvent is added.
Since nylon powder cannot be obtained due to precipitation in the form of a film or fibers, a practical amount is 0.1 to 15 wt%, preferably 1 to 10 wt%.

In the present invention, TFE or a solvent containing TFE as a main component is used as a solvent for nylon. TFE is a fluorine-containing alcohol that is completely compatible with water, methanol, acetone, etc., and has almost no corrosivity to various metals. Nylon 6.66°610, 612, 6/66,
6/66/6]0.6/66/612 etc., T
It is possible to use not only FE alone, but also TFE containing a poor solvent such as water, methanol, acetre, etc.; Therefore, the content of these poor solvents is 20 wt% or less, preferably 10 wt% or less.
A practical content is 5 wt% or less, particularly preferably 5 wt% or less. If the poor solvent content is 5 wt% or less, nylon can be dissolved in a short time under normal pressure at a temperature near the boiling point of TFE (about 74°C). It should be noted that, of course, when the amount is less than 5 wt%, even when it is more than 5 wt%, TFE
relatively low pressure at a temperature above the boiling point of, e.g. 4 kij
/an'' or less. In the case of nylon 11'P12, etc., it is difficult to dissolve in TFE alone (so it contains 1 to 10 wt% of a solubilizing agent such as phenol or metacresol). It is preferable to use TFE that has a
TFE or a solvent containing TFE as a main component is appropriately selected.

1. C. Of course, when dissolving nylon with a solubility higher than that at room temperature, it is necessary to heat it, but even when dissolving nylon with a solubility lower than that at room temperature, in order to shorten the dissolution time, for example, the boiling point of TFE is used. It is preferable to heat and melt at a temperature around 4°C.

The poor solvent for reprecipitation used in the present invention may be any solvent as long as it does not dissolve nylon at room temperature and has substantially complete compatibility with TFE. In the case of most nylons, water, methanol, acetone, etc. can be suitably used, but in the case of special nylons, such as water-soluble nylons and alcohol-soluble nylons, it is necessary to select a poor solvent. Caution is required. In addition, TFE is contained in the poor solvent.
may be contained, for example, about 3 Q wt%,
If the TFE content is high, nylon will not precipitate unless a large amount of poor solvent is added, so from a practical standpoint, the TFE content in the poor solvent is preferably 10 wt% or more. In addition,
n-hexane, which has almost no compatibility with TFE, and TF
Even if benzene or the like which is only compatible with E is added to the nylon solution, nylon powder cannot be obtained.

The temperature of the nylon solution when adding the poor solvent for reprecipitation to the nylon solution may be any degree Celsius, and may be, for example, a temperature near the boiling point of TFE (about 74 degrees Celsius) or room temperature. However, depending on the type and concentration of nylon, if the temperature is lowered to around room temperature after heating and dissolving nylon, nylon may precipitate in an agar-like form even before adding a poor solvent. The temperature of the nylon solution when adding the solvent needs to be selected appropriately.

The amount of poor solvent added can also be changed depending on the type and concentration of nylon in the nylon solution, but if the amount added is small, the precipitation of nylon in the nylon solution may be incomplete, or even if nylon is completely precipitated. The weight of the poor solvent added is 0.5 to 5 times, preferably 1 to 3 times, the weight of the TFE or TFE-based solvent in the nylon solution, since the fluidity of the produced nylon powder may deteriorate. is practical.

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

(9) When the slurry of nylon powder obtained by adding a poor solvent to the nylon solution by the method of the present invention is subjected to ordinary r-filtration, washing, drying, etc., dry nylon with a particle size of 1 μm to several hundred μm is produced. Powder is obtained, but if the particle size is large, the particle size is 1μ to several μ
It's just a bunch of stuff. Therefore, dry nylon powders of various particle sizes of 1 μm or more can be easily obtained by further carrying out conventional pulverization and classification operations. Further, the degree of polymerization of these dry nylon powders is almost the same as the degree of polymerization of nylon before being dissolved in TFE or a solvent containing TFE as a main component.

Furthermore, as mentioned above, TFE has almost no corrosivity to various metals, so unless a corrosive substance is used as a poor solvent or dissolution aid, the apparatus for carrying out the method of the present invention cannot be used. The material does not need to be special; ordinary carbon steel or stainless steel is sufficient.

In addition, by filtering and washing the slurry of nylon powder obtained by precipitating nylon from a nylon solution, TFE
A solution containing 5K TFE is obtained, and by performing a normal distillation operation, it is possible to recover TFE or a TFE-based solvent that can be used to dissolve nylon. Focusing on the point of recovering and reusing TFE by distillation, water, which has a boiling point about 26°C higher than TFE, is used as a poor solvent, and TFI containing a small amount of water is recovered by simple distillation, and then nylon is added to it. It is practical to dissolve it.

Next, the present invention will be specifically explained with reference to Examples.

Example 1 Nylon 66 of 2.11 and TFElooy- with a water content of 0.1 wt% or less were mixed in a 50-liter container equipped with a stirrer, a reflux condenser, a 9-dropping funnel, and a thermocouple (with a glass retaining tube).
The mixture was charged into a 0 Cc flask, heated with a mantle heater while stirring, and kept at 74°C for 1 hour to obtain a transparent nylon solution. Keeping the temperature of this solution at 74 °C, add 2 mL of water as antisolvent using a dropping funnel while stirring.
A slurry of nylon powder was obtained by adding 00 t at a rate of about 5 i. This slurry was filtered through a 60-mesh wire mesh, and then the r solution was filtered through N115AP paper, and further washed with water 11 to obtain a cake of nylon powder with a high moisture content as a residue on the f paper. As a result of observation under a microscope, the particle size of the nylon powder was 1 to 250 microns, and the larger particles had agglomerated particles with a particle size of 1 to 10 microns.

Example 2~lO When Example 1 was repeated by changing the amount of nylon 66 charged, the dissolution time of nylon, the temperature of the nylon solution at the time of water addition, and the amount of water added as shown in Table 1, high water content was obtained in all cases. A cake of nylon 66 powder was obtained, and the particle size of the powder was 1 to 2.
It was 50μ.

Table 1 (12) Examples 11 to 17 Example 1 was repeated by changing the amount of nylon 6 charged, the dissolution time of nylon, the temperature of the nylon solution at the time of water addition, and the amount of water added as shown in Table 2. In both cases, a cake of nylon 6 powder with high moisture content was obtained, and the particle size of the powder was ~250.
It was μ.

Table 2 Examples 18-22 Nylon charge constant (8,7F), moisture content 0.1wt
% of TFE or less (loo P ), nylon dissolution time constant (2 hours), water addition amount constant (300
When Example 1 was repeated under the conditions of 9), changing the type of nylon as shown in Table 3, a cake of nylon powder with a high moisture content was obtained in each case (13), and the particle size of the powder was 1 to 1. It was 250μ.

Examples 23 to 25 T with different metacresol content as shown in Table 4
Example 1 was repeated under the same conditions as Example 1, except that F E 1009- and 2.19-nylon 11 were charged into a flask and heated and melted at 74°C for 2 hours. A cake of nylon (14) l1 powder with moisture content is formed, and the particle size of the powder is 1-250μ.
Met.

Table 4 Example 26 TFE 100% containing 5 wt% phenol
and 11.19 nylon 12 into a flask, 7
Example 1 except that it was heated and dissolved at 4°C for 3 hours.
When Example 1 was repeated under the same conditions as above, a cake of nylon 12 powder with a high moisture content was obtained in each case, and the particle size was 1.
It was ~300μ.

Examples 27 to 31 Same as Example 1 except that the poor solvent added to the nylon solution was changed as shown in Table 5, and the temperature of the nylon solution (15) at the time of addition of the poor solvent was maintained at 25°C. When Example 1 was repeated under the same conditions, a cake of nylon 66 powder with a high moisture content was obtained in each case, and the particle size of the powder was 1-2.
It was 50μ.

Examples 32-35 Solvent 100? as shown in Table 6 And 5.3? nylon 6
Example 1 was repeated under the same conditions as Example 1, except that 6 and 6 were placed in a flask and heated and dissolved at 74°C for 3 hours. In each case, a cake of nylon 66 powder with a high water content was obtained. The particle size of the powder was 1 to 250μ.

(16) Example 36\38 Solvent 150V and 7.9 f nylon 66 as shown in Table 7 were charged into a pressure-resistant autoclave with an internal volume of 500eC, and after nitrogen purging, the autoclave was kept at 110°C for 3 () minutes. The pressure was below 4 kl/cm' in all cases. then 7
After cooling to 0°C, 150V of water was injected at a rate of about 49-7 minutes, cooled to room temperature, taken out, and the same filtration and washing as in Example 1 were repeated, resulting in a high water content. A cake of nylon 66 powder was obtained, and the particle size of the powder was 1 to 2.
It was 50μ.

(17) Table 7 Nylon 19 was dissolved in io cc of 98% sulfuric acid, and the relative viscosity (hereinafter abbreviated as sulfuric acid relative viscosity) measured at 25°C using an Ostold viscometer was 2.7.
40.0p nylon 66 and TFE460f with a moisture content of 1wt% were placed in a flask with an internal volume of 2 mm equipped with a stirrer, a reflux condenser, a dropping funnel, and a thermocouple (with a glass eel preservation tube). A transparent nylon solution was obtained by heating with a mantle heater while stirring and maintaining at 74° C. for 3 hours. The temperature of this solution was maintained at 74° C., and water 1380 F as a poor solvent was added at a rate of about 10 p/min while stirring (18) to obtain a slurry of nylon powder. This slurry is 8
The liquid was passed through a wire mesh with 0 mesh, and then the liquid was passed through NuSAP paper for 1 hour, and then washed with water for 5 minutes to obtain a cake of nylon powder with a high water content as a residue on the paper, and the particle size of the powder was 1.
It was ~200μ. This cake was collected in a glass wide-mouthed bottle, and water was added to obtain 800 y of slurry. This slurry was then dried in a small spray dryer.
A dry nylon powder with a particle size of 1 to 200 μm was obtained, and its sulfuric acid relative viscosity was 271.

Example 40 Example 39 is repeated using nylon 61G, which has a sulfuric acid relative viscosity of 278, in place of nylon 66, and the particle size l
A ~200μ dry nylon 610 powder was obtained with a sulfuric acid relative viscosity of 2.76.

Example 41 Nylon 6 with a sulfuric acid relative viscosity of 245
Repeating Example 39 using instead of
A dry nylon 6 powder of 00 μm was obtained, and its sulfuric acid relative viscosity was 2.41.

(19) The particle size of the powder obtained by further crushing this dry powder in a mortar was 1 to 140μ.

Patent applicant: Asahi Kasei Industries, Ltd. (20)

Claims (1)

[Claims] 1 Nylon 2.2.2-) Refluoroethanol or)'! , 2,2.2-) Dissolve nylon in a solvent containing trifluoroethanol as a main component, and add a poor solvent that does not dissolve nylon at room temperature and has substantially complete compatibility with 21212-trifluoroethanol to the core nylon solution. Method 2 for producing nylon powder, characterized in that the nylon is added under stirring to precipitate nylon.
6, 610, 612. 6/66, 6/66/610.6/66/612 The manufacturing method 3 according to claim 1, wherein the nylon concentration in the nylon solution is 0.1 to 0.1. 15wt
% Manufacturing method according to claim 1 4 Manufacturing method according to claim 3 where the nylon concentration in the nylon solution is 1 = 10 wt% Solvent power 2.2.2
- Claim 1 which is trifluoroethanol
Manufacturing method described in Section 6 The solvent is a poor solvent such as water, methanol, acetone, etc.
2,2.2-) refluoroethanol containing 1% or less, the manufacturing method 7 according to claim 1, wherein the nylon is nylon 11 or 12, and the solvent is a dissolution aid such as phenol or metacresol. 1 to 10
A manufacturing method according to claim 1, which is sulfur 2,2,2-trifluoroethanol containing wt%, and a patent in which the poor solvent is at least one selected from the group consisting of water, methanol, and acetone. Manufacturing method 9 according to claim 1, manufacturing method 10 according to claim 8, in which the poor solvent is water, 2.2.2-) refluoroethanol, and the poor solvent is water. Manufacturing method 11 according to claim 1 or 4, wherein the solvent contains water at 5 wt% or less 2, 2.2-
) refluoroethanol and the poor solvent is water, the manufacturing method 12 according to claim 1 or 4. The added weight of the poor solvent is 0.5 to 5% of the weight of the solvent in the nylon solution.
Manufacturing method 13 according to claim 1, in which the weight of the poor solvent is 1 to 3 times the weight of the solvent in the nylon solution 14 Manufacturing method according to claim 12, in which the weight of the poor solvent is 1 to 3 times the weight of the solvent in the nylon solution 66, 610, 612,
6/66, 6/66/6] 0, 6/66/612
The concentration of nylon is 1 to 1 in a solvent consisting of a small amount (2,2.2-) of 2,2.2-
0 wt%, and 1 to 1% of the weight of the solvent.
The manufacturing method according to claim 1, wherein 3 times the weight of water is added to the nylon solution.