JPH0873602A - Production of polyamide powder - Google Patents

Abstract

PURPOSE: To produce the subject powder useful for powder coating material, adsorbent, cosmetic base, etc., on an industrial scale at a low cost without causing the agglomeration and stringing of the polyamide by carrying out alkali catalyst polymerization of an alicyclic lactam in a specific polymerization medium. CONSTITUTION: This powder is produced by the alkali catalyst polymerization of (A) a 6-12C alicyclic lactam in (B) a polymerization medium consisting of a polymer solution dissolving the component A and unable to dissolve the produced polyamide using (C) an alkali catalyst such as an alkali metal, its hydroxide or borohydride. The component B is preferably a 1-20wt.% solution of PS produced by dissolving a PS having an average molecular weight of 100,000-300,000 in ethylbenzene, chlorobenzene or chlorotoluene. The amount of the component C is 0.01-10mol, especially 0.1-5mol based on 100mol of the component A.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing polyamide powder. More specifically, the present invention relates to a method for producing polyamide powder which is used in various fields such as powder coating, adsorbents, cosmetic bases, medical fields, biochemistry, and other information materials and adhesives.

[0002]

2. Description of the Related Art Conventional methods for producing polyamide powder include a method of mechanically pulverizing pelletized massive polyamide, a method of utilizing a difference in solubility depending on temperature with an appropriate solvent, or a method of using a poor solvent in a poor solvent. A so-called reprecipitation method in which a precipitate is precipitated by injecting is typical, but the powder produced by the method used for producing these ordinary plastic powders is not spherical and has an uneven shape. It has a defect that spherical fine particles cannot be obtained due to its regular shape or porous shape. Further, as a method for producing a polyamide powder, there are known a method of polymerizing a monomer in a molten state in a state of being dispersed in a non-solvent, and a method of spraying and cooling polyamide in a molten state to form a fine powder.

For example, in JP-B-45-29832, a cyclic lactam is heated and melted in paraffin, and an alkali metal salt of an aliphatic monocarboxylic acid or a salt with an alkaline earth metal is added as a dispersant. A method for producing a polyamide powder in which a molten monomer is dispersed and alkali-catalyzed polymerization is proposed. Further, Japanese Patent Application Laid-Open No. 5-70598 discloses that a 0.5% meta-cresol solution at 25 ° C. has a relative viscosity of 1.05 or more and 1.40 or less and does not polycondense itself by heating.
Is sprayed in a molten state and cooled to obtain a particle size of 2
A method for producing powder of 0 μm or less is shown.

[0004]

However, these conventional techniques are not industrially sufficiently satisfactory. For example, in JP-B-45-29832, a raw material lactam obtained by adding a salt of an aliphatic monocarboxylic acid having 11 or more carbon atoms with an alkali metal or an alkaline earth metal as a dispersant and heating and melting the medium in a medium. Although a method of dispersing and carrying out an alkali-catalyzed polymerization has been proposed, it is not necessarily an advantageous method for industrial implementation. In addition, JP-A-5-
The method of spraying and cooling molten polyamide shown in the specification of Japanese Patent No. 70598 has a drawback that it is necessary to use a raw material polyamide having a sufficiently low melt viscosity to obtain spherical particles and an ordinary polyamide cannot be used. In addition, large-scale equipment is required to prevent the polyamide from coagulating and forming into filaments, which is not industrially satisfactory. An object of the present invention is to provide a method for producing polyamide powder by an industrially advantageous method.

[0005]

In view of the above circumstances, the inventors of the present invention have conducted extensive research into a method for producing a polyamide powder by polymerizing an alicyclic lactam, and as a result, the raw material lactam was dissolved. It was found that polyamide powder can be produced by alkali-catalyzed polymerization using a polymer solution that is insoluble in the produced polyamide as a polymerization medium, and completed the present invention. That is, the present invention is characterized in that, when an alicyclic lactam having 6 to 12 carbon atoms is subjected to alkali-catalyzed polymerization, the lactam is dissolved and a polymer solution insoluble in the produced polyamide is used as a polymerization medium. It is a method for producing a polyamide powder.

The method of the present invention will be described in detail. Under stirring in an inert gas atmosphere, the starting lactam is dissolved in the polymer solution which is insoluble in the produced polyamide,
Polymerization starts when the alicyclic lactam having 6 to 12 carbon atoms and the alkali catalyst are dissolved and the temperature is raised to the usual polymerization temperature adopted in the alkali catalyst polymerization, specifically 120 to 180 ° C. and the cocatalyst is added. As a result, the solution is gradually suspended and finely divided polyamide is precipitated in a dispersed state. After carrying out the polymerization for a predetermined time, the polymer particles are separated from the polymer suspension by a known mechanical separation method. As the separation method, for example, a method such as suction filtration, pressure filtration, continuous filtration, centrifugal sedimentation or the like is used. Subsequently, a polyamide powder is obtained by drying by a known method such as vacuum drying and ventilation drying.

As the lactam used in the present invention, alicyclic lactam having 6 to 12 carbon atoms can be used alone or in combination. The concentration of the raw material lactam charged in the polymerization medium is usually preferably 20% by weight or less, more preferably 15% by weight or less. The smaller the charge concentration of the raw material lactam in the polymerization medium, the more uniform the polyamide having a smaller particle size is formed. Therefore, the particle size of the polyamide can be controlled by adjusting the lactam charge concentration.

The solvent used in the polymer solution used as the polymerization medium in the present invention is one that dissolves the polymer, one that dissolves the starting lactam, one that does not dissolve the formed polyamide, and a lactam. Those which are stable to the polymerization reaction are used, and for the purpose of the present invention, one or more solvents selected from the group consisting of ethylbenzene, chlorobenzene and chlorotoluene are preferably used. A solvent for dissolving the polymer,
Further, a solvent insoluble to both the raw material lactam and the produced polyamide can be used by adding it to the polymer solution. Examples of the solvent insoluble in both the raw material lactam and the produced polyamide include aliphatic hydrocarbons such as normal octane, normal paraffin, and isoparaffin, and cycloaliphatic hydrocarbon water such as decahydronaphthalene.

Examples of the polymer used in the polymer solution used as the polymerization medium in the present invention include polyethylene, polypropylene, poly (ethylene-propylene),
Although hydrocarbon-based polymers such as polystyrene, poly (styrene-vinyltoluene), hydrogenated poly (styrene-butadiene) and the like can be mentioned, for the purpose of producing uniform-shaped polyamide powder particles of the present invention, Polystyrene having an average molecular weight of 100,000 to 300,000 is preferably used.

The concentration of the polymer in the polymer solution used as the polymerization medium is usually in the range of 1 to 20% by weight, preferably 5 to 15% by weight. If the concentration of the polymer is less than 1% by weight, polyamide particles having a uniform shape cannot be obtained or the polyamide precipitated during the polymerization aggregates into a lump, and if it exceeds 20% by weight, the viscosity during the polymerization increases. Therefore, it becomes difficult to stir the solution and it becomes difficult to separate the produced polymer from the polymerization medium.

Many substances have already been found as catalysts and cocatalysts for the alkali-catalyzed polymerization of lactams, and these catalysts and cocatalysts are effective and can be used in the method of the present invention. The cocatalyst is not particularly limited, and a substance known per se can be used. For example, as a catalyst, alkali metals such as lithium, sodium and potassium, or their hydroxides, borohydrides and oxides, and further, butyllithium, diphenylmagnesium, diisobutylaluminum, sodium amide, organometallic compounds such as Grineer's reagent, etc. Can be used. Further, as a co-catalyst, N-acetyl-ε-caprolactam, N-acetyl-α
Known compounds such as N-acylated lactams such as -pyrrolidone, organic isocyanates, acid chlorides, acid anhydrides, esters, urea derivatives, carbodiimides and phosphorus compounds such as phosphorus trichloride can be used.

The amounts of the alkali polymerization catalyst and the cocatalyst used vary depending on the type of the starting lactam and the type of the catalyst and the cocatalyst. It is about molar.

[0013]

The present invention will be described in detail below with reference to examples, but the method of the present invention is not limited to the examples.

Example 1 200 equipped with nitrogen introducing tube, reflux tube and calcium chloride tube
In a ml two-necked flask under a nitrogen stream, an average molecular weight of 280
6.68 g of 000 polystyrene, 6.00 g of ε-caprolactam and 0.16 g of NaH were added and dissolved in 60 g of ethylbenzene. After the temperature was raised to 120 ° C., 72 μl of N-acetyl-ε-caprolactam was added dropwise, and 1 as it was.
After reacting at 20 ° C. for 3 hours, it was cooled to room temperature. Then, after repeating washing with ethylbenzene, centrifugation, and decantation, it was filtered using a 0.2 μm membrane filter, dried at room temperature for 12 hours, and then dried under reduced pressure at 60 ° C. for 2 days to obtain nylon 6 polyamide powder. 2.5 g was obtained. The shape of this powder was observed with a scanning electron microscope, and it was found to be spherical with good uniformity. The particle diameter was measured by a laser diffraction method to find that the average particle diameter was 6.0 μm and the minimum particle diameter was 0.1.
The maximum particle size was 15.0 μm.

Example 2 Polymerization of ε-caprolactam was carried out in the same manner as in Example 1 except that ethylbenzene as a solvent was changed to chlorobenzene to obtain 2.1 g of polyamide powder of nylon 6. The shape of this powder was observed with a scanning electron microscope, and it was found to be spherical with good uniformity. The particle size was measured by a laser diffraction method to find that the average particle size was 4.7 μm and the minimum particle size was 0.1 μm.
m, and the maximum particle size was 9.3 μm.

Example 3 Polymerization of ε-caprolactam was carried out in the same manner as in Example 1 except that ethylbenzene as a solvent was changed to chlorotoluene to obtain 2.3 g of nylon 6 polyamide powder. The shape of this powder was observed with a scanning electron microscope, and it was found to be spherical with good uniformity. The particle diameter was measured by a laser diffraction method to find that the average particle diameter was 5.3 μm and the minimum particle diameter was 0.1 μm.
m, and the maximum particle size was 10.1 μm.

Example 4 200 equipped with a nitrogen introducing tube, a reflux tube and a calcium chloride tube
In a ml two-necked flask under a nitrogen stream, an average molecular weight of 280
6.68 g of 000 polystyrene, 6.00 g of ω-laurolactam and 0.23 g of NaH were added and dissolved in 60 g of chlorobenzene. After the temperature was raised to 120 ° C., 72 μl of N-acetyl-ε-caprolactam was added dropwise, and 1 as it was.
After reacting at 20 ° C. for 3 hours, it was cooled to room temperature. Then, after repeating washing with chlorobenzene, centrifugation, and decantation, it was filtered using a 0.2 μm membrane filter, dried at room temperature for 12 hours, and then dried under reduced pressure at 60 ° C. for 2 days to obtain nylon 12 polyamide. Powder 1.3g
I got The shape of this powder was observed with a scanning electron microscope, and it was found to be a spherical shape with good uniformity. When the particle size was measured by a laser diffraction method, the average particle size was 7.2 μm and the minimum particle size was 0.
The particle size was 1 μm and the maximum particle size was 14.3 μm.

Comparative Example 1 200 equipped with a nitrogen introducing tube, a reflux tube and a calcium chloride tube
Under a nitrogen stream, 6.00 g of ε-caprolactam and 0.16 g of NaH were placed in a ml two-necked flask and dissolved in 60 g of ethylbenzene. After the temperature was raised to 120 ° C., 72 μl of N-acetyl-ε-caprolactam was added dropwise, and the reaction was continued at 120 ° C. for 3 hours and then cooled to room temperature. Then, after repeating washing with ethylbenzene, centrifugation, and decantation, the mixture was filtered using a 0.2 μm membrane filter, dried at room temperature for 12 hours, and then at 60 ° C. for 2 hours.
After drying under reduced pressure for a day, 2.3 g of polyamide of nylon 6 was obtained. When observed by a scanning electron microscope, this polyamide was an atypical aggregate.

[0019]

INDUSTRIAL APPLICABILITY The polyamide powder obtained by the method of the present invention can be used for various applications such as powder coatings, adsorbents, cosmetic bases, medical fields, biochemistry, and other information materials and adhesives. it can.

Claims (3)

[Claims] 1. An alkali-catalyzed polymerization of an alicyclic lactam having 6 to 12 carbon atoms, which is characterized in that the lactam is dissolved and a polymer solution insoluble to the polyamide produced is used as a polymerization medium. Method for producing polyamide powder. 2. The polymer solution has an average molecular weight of 1,000.
The method for producing a polyamide powder according to claim 1, wherein a 1 to 20% by weight solution of polystyrene of 0 to 300,000 is used. 3. The method for producing a polyamide powder according to claim 1, wherein at least one solvent selected from the group consisting of ethylbenzene, chlorobenzene and chlorotoluene is used as a solvent for the polymer solution.