JPH0456050B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing fine powder of nylon resin at low cost by a melting method. (Prior art) Nylon powder is manufactured by cryo-mechanical pulverization or melting, but since it is difficult to obtain spherical particles by mechanical pulverization, nylon powder is generally melted except for those for special purposes. Manufactured by law. Therefore, the conventional dissolution method uses nylon pellets.
Since the particles had been dissolved in a solvent that had a boiling point of 190° to 250° and was not compatible with water, the resulting particles had to be washed with other organic solvents. Furthermore, this method requires a classification operation because the particle size range obtained is wide. For these reasons, it has been practically impossible to reduce manufacturing costs using conventional melting methods. (Objective of the Invention) The object of the present invention is to produce nylon resin spherical particles in high yield through simpler operations, and to wash the produced particles with water or eliminate the need for washing with water. An object of the present invention is to provide a manufacturing method that can significantly reduce cleaning costs. Furthermore, it is an object of the present invention to provide a manufacturing method in which the distribution range of the produced powder can be narrowed, the particle size distribution range can be adjusted, and particles can be obtained without the need for classification. (Solution Means and Features of the Present Invention) As a result of research on various water-soluble low-boiling solvents that can achieve these objectives, the present inventor found that morpholine (including ethylmorpholine and methylmorpholine, hereinafter the same) is effective. I discovered something. It has also been confirmed that poorly soluble resins such as nylon 6, 66 and 666 can be easily dissolved using a mixed solvent of morpholine and propylene glycol. These solvents can not only be easily removed by washing with water, but also have the advantage that the washing step can be omitted if the product particles are used, for example, as a colored paint and the solvent is morpholine alone. Furthermore, the amount of nylon resin dissolved in the solvent is
It is possible to obtain up to 50 kg per 100 kg, and the particle size and particle size distribution can be changed depending on the amount dissolved. Therefore, the classification work becomes easier or can be made unnecessary. (Structure of the Invention) The present invention provides non-oxidizing nylon resin pellets in an amount not exceeding 50 parts by weight to 100 parts by volume of morpholine alone or a mixed solvent of less than 30 parts by volume of propylene glycol based on morpholine. A step of thermally dissolving the solvent while stirring at a temperature at which the solvent does not boil in an atmosphere, a step of slowing down the stirring to gradually cool it, and precipitating nylon fine particles with a particle size of 5 to 80 μm during this gradual cooling process, The method consists of a step of separating the solvent, and either filtration or vacuum recovery is selected as the solvent separation means. In the present invention, the maximum amount of nylon resin dissolved is 50 parts by weight per 100 parts by volume of the solvent. Further, the amount of propylene glycol that acts as a boiling point elevating agent is preferably less than 30 parts by weight in consideration of later solvent recovery and the like. Furthermore, although the rotational speed of the stirring blade in the particle precipitation step is not absolute, it slightly affects the particle shape and particle size, so if it is desired to produce more fine particles, that is, in the case of a low concentration solution, a lower speed is better. (Example 1) 5 kg of morpholine 100 and nylon 12 were put into a dissolution tank with a volume of 150, and nitrogen gas was sealed at 1 kg/cm ² .
The mixture was heated to 130° C. and the stirring speed was set to 300 rpm. After about 1 hour, it was completely dissolved, so I changed the stirring speed.
Heating was stopped at 100 rpm and cooled slowly. It was confirmed that the liquid became cloudy at about 100°C and nylon fine particles were precipitated. Thereafter, when the liquid temperature reached approximately 70°C, the liquid was introduced into a filter press to separate the solvent and precipitated particles.
The filtered particles were washed with warm water at about 70°C and dehydrated and dried. (Example 2) When 40 kg of nylon 12 was used under the same conditions as in Example 1, the dissolution time was about 1 hour and 30 minutes. In this case, filter separation was impossible or inefficient due to the viscosity of the solution, so the solvent was recovered at about 10 mmHg or less. The particles taken out from the dissolution tank were treated in the same manner as in Example 1. The particle size and particle size distribution of each of the above examples were as shown in the table below. 【table】

Claims (1)

[Claims] 1 In a container equipped with a stirring and heating device,
Add 1 to 50 parts by weight of nylon resin pellets to morpholine.
After dissolving morpholine alone or a mixed solvent containing less than 30 parts by volume of propylene glycol in 100 parts by volume of a mixed solvent in a non-oxidizing atmosphere, stirring is slowed down and the mixture is slowly cooled. A method for producing fine nylon resin powder, which comprises precipitating fine nylon particles in a cooling process, and then recovering the solvent under reduced pressure or separating the solvent and the fine particles by filtration.