JPS59120263A - Manufacture of fine particles - Google Patents

Abstract

PURPOSE:To obtain a large amount of fine particles having a desired particle size in a short time, by supplying a material melted with heat to a two-fluid nozzle and atomizing it into fine particles while specifying the caliber of a liquid ejection part, the positional relationship of a nozzle opening for each fluid and the flow amout ratio of each fluid. CONSTITUTION:In a two-fluid nozzle, the caliber a (mm.) of a liquid ejection part is defined by a>S1/50 in relation with the feed amount S1 (g/min) of a liquid, and the distance b (mm.) of each top end of air and liquid supply pipes is defined by 2.0>b>0.01. Thereafter, a material, e.g. resin, under a condition melted with heat is supplied to the two-fluid nozzle and atomized into fine particles while controlling an air supply speed S2 (l/min) at 0.03<S1/S2<0.35. Air, inert gas or steam is used as an atomizing gas at a temp. higher by about 50 deg.C than the melting point of the material, and its pressure is held above about 2kg/cm<2>. Hence, the large amount of fine particles having a particle size below about 10mu is obtained. Said fine particles may be used as a toner for powder coating, electrophotography, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for producing fine particles, and more particularly to a method and apparatus for producing particles that are more precise and less imitable than conventional ones. Fine resin powder? Conventionally known production methods include precipitation and pulverization. The precipitation method is a method in which a substance is dissolved in a solvent, kept cool, and then the dissolving power is lowered by adding a poor solvent, lowering the heat, or removing a solvent to precipitate the substance into particles, and then the particles are taken out. Although this method may be effective for materials for which good solvent and precipitation conditions exist, it is not necessarily suitable as a method for producing general resin fine powders. Another major problem in practical application is that it takes time and effort to separate the solvent used from the processing solution.Other problems with this method include mixing other components into the material. The most commonly used method for producing fine powder is the pulverization method. In this method the material is ground by mechanical means. Various types of devices for this purpose are known depending on the purpose, and pulverization devices using pressurized air and the like are also known, particularly for the purpose of obtaining fine particles. However, a major drawback of this method is that it requires a very high energy level. Also, can materials be denatured due to the crushing force during crushing? In order to prevent this effect, materials are sometimes cooled (frozen), but this is not always effective and does not have a positive impact on costs.

In the octopus method, only one irregularly shaped particle is given.0 As a method to solve the drawbacks of such conventional fine particle manufacturing methods, a method of manufacturing particles by a spraying method has been proposed, but it is not known in the past. This method is an inconvenient method for producing relatively coarse particles of several tens to several hundred microns, and is especially difficult to produce fine particles.
・There was no wisdom regarding the illegality.

An object of the present invention is to provide a novel method for producing microparticles that overcomes the drawbacks of the conventional methods for producing microparticles. Another object of the present invention is to demonstrate a spray atomization method that makes it possible to produce fine particles in -J City.

Another object of the present invention is to show a method for obtaining fine particles having a uniform shape. In order to achieve the above-mentioned objects, the method of the raw wood invention is to supply a material in a heated molten state to two fluids)) and liquid supply speed S'z
(t 7 minutes) and sacrificial body supply rate 82 (11 minutes) A method for producing fine powder characterized by carrying out atomization under conversion conditions that satisfy the following conditions: 2' □ a) Sz150 (醋) 2, o>b>o, o't (throat) 0.03<31/S2<0.35 However, a: Liquid supply port diameter (-) b: Liquid supply pipe Distance between the tip and the tip of the gas supply pipe (conventional two-fluid nozzle)! The method of producing fine particles using I is well known and does not require costly processes such as repeated cooling, and can produce particles close to spherical. Therefore, it has been put into practical use for atomization in winter, etc. ing.

However, when we continued to discuss the conditions for atomization using the conventionally known two-fluid nozzle, we found that the conventional atomization conditions were insufficient and the above-mentioned conditions were necessary to achieve the purpose of the present invention. It is recognized that this is the case.

In order to achieve the object of the present invention, we first investigated the conditions for obtaining fine particles in relation to the method, and found that all conventional nozzles have an S, /S2 of 0.4 to 20.
However, in order to achieve the object of the present invention, it has become clear that it is required to be 0.035 or less, more preferably 0.3 or less. This means providing sufficient gas space for adult leaves. To achieve this, the flow rate can be increased by increasing the diameter of the gas nozzle compared to the conventional nozzle, or by increasing the flow rate by reducing the pressure of the atomizing gas. Either method may be used, but it is desirable that the spray pressure be 2 kg/cn1 or more.

In this way, when the conditions for achieving stable atomization when the atomizing gas flow rate is extremely large compared to the conventional one are horizontally divided, the present inventors found that the relationship between the opening vibration of the fluid nozzle and the gas nozzle is 1. I discovered that it is essential. That is, it has been found that it is necessary that the distance between the tip of the gas supply tube and the tip of the housing supply tube in the drawings satisfies the above relationship.

In atomization under the above conditions, a much larger amount of gas is supplied than in the conventional method when a liquid is supplied. In this case, the water is 0. (If the pressure is less than 1, the liquid will flow backwards rather than atomize due to the large amount of gas. Conventionally, in such cases, a method was used to pressurize the liquid and supply it, but the present invention For the purpose of atomization, i is not 1. If 1 jc b is greater than 2 y++π, li & granulation cannot be achieved to a certain extent.

Further, when we next discussed the method for obtaining uniform particles, which is another object of the present invention, it was found that it is necessary to obtain particles with a particle size of 1/50.

Conventionally, a means the diameter of the liquid discharge part, which is determined according to the amount of liquid supplied, but generally a means S, 15 to S.
It was about L/20. In the present invention, the condition mentioned herein means that the aperture of the liquid discharge y:+s is sufficiently large with respect to the amount of liquid supplied. According to the inventors' thoughts, since the liquid is supplied through the tube wall and is atomized for 1 minute, the diameter is large for the weight loss, or the liquid film on the tube wall is thin. It is thought that uniform particles are formed.

Polyolein, wax polyamide, polyolein, polyester, polystyrene, etc. are used as the material for carrying out the present invention.The most preferred material is I-lyolefin, which has a clear melting point like wax and has an extremely low viscosity above the melting point. Also, it is a phase material that has the property of rapidly solidifying below its melting point. Mixtures of individual thermoplastic vocal fats that are mixable with each other may also be used.

Additionally, additives for each building may be mixed as necessary. The additives may include, for example, stabilizers against light and ultraviolet rays, colorants such as pigment dyes, and fillers such as gold octoxide galesthene.

Air, inert gas, or water vapor is used as the gas for the erecting pot. The gas is heated to a temperature approximately 0° C. higher than the melting point of the material.

The fine particles produced by the method of the present invention can be used in a variety of applications. One suitable application is the use of so-called powder coatings, which contain a coloring material.

Another suitable application is electrophotography, electrostatography,
This is a toner used in magnetic recording methods or electrostatic printing methods.

Conventionally, the intended toner is prepared by mixing a thermoplastic resin and a coloring material such as a dye or a pigment, melting and kneading the mixture at high temperature, cooling the mixture to room temperature, and pulverizing it into fine particles. However, the shape and particle size of the toner manufactured by this method are not constant, and it is essentially difficult to obtain uniformity between toners and within the toner, which makes it difficult to put the toner into practical use. Inadequacies in performance can be found in various ways (and producing toner using this manufacturing method requires a great deal of expense), especially in the process of obtaining fine particle toner. This required a lot of energy, which resulted in high equipment costs and running costs.

Moreover, such a manufacturing method greatly limits the type of Hamura to be used. In other words, in order to obtain uniform fine particles, it was necessary to select a material with a uniform crosstalk or a thick core with good crosstalk properties.

Furthermore, in order to obtain a fine powder toner, particular attention was paid to the fine pulverization characteristics of the material, which poses a major problem in terms of productivity. In other words, in order to be made into a toner, the binder must first be brittle, and this does not necessarily match the characteristics of the binder required from the performance of the toner. It could not be used for

A method for producing fine particles according to the present invention for the above #J problem? 'i gives a fundamental solution.

In other words, a large amount of fine particles of a desired particle size can be obtained in an extremely short period of time.

When used as a toner, preferred materials include compounds having C42 to C5o carbonized ice chains known as so-called waxes, derivatives thereof, low-molecular polyolefins, polyamides, etc., which are melt-kneaded with a colorant and used. . Other additives and fillers may be added as necessary, and a magnetic material may be added to impart magnetic properties.

Further, additives such as fine particulate silica may be mixed and used in order to improve flow properties and handling properties.

Furthermore, the surfaces of the particles produced by the method of the present invention may be coated with a resin to form so-called microcapsules.

As an alternative method, a conventionally known encapsulation technique can be used.

For example, U.S. Patent No. 3,338,991, U.S. Pat. No. 3,326, U.S. Pat.
Methods such as those described in Japanese Patent No. 848 and Japanese Patent No. 3,502,582 can be used.

Example 1 The following materials were mixed.

Low molecular weight polyethylene 50 parts Paraffin wax 50 parts Carbon black 10 parts or more After melting and mixing the mixture to make a homogeneous mixture, 150 parts
'C of the drawing a = 1.5, b = 0.1
Using a two-fluid nozzle of S, = 60 g-/min S, = 38
The tinning gas which was atomized under the conditions of 0 t/min was air and the gas temperature was 120°C. The tinned particles were collected in the gas. The resulting particles have a perfect spherical shape and are similar to a cylindrical shape. The dispersion of the powder was uniform and the powder had extremely good fluidity.

The average particle size was 9.5μ.Next, the fine particles were mixed with 1 part of ultra-coarse aqueous silica powder per 100 parts of the powder, and further 0.2 parts of 24HM was added to the iron powder. The mixture was mixed to form a developer, then supplied to a developer having a magnetic sleeve, and brought into contact with a photoconductor having positive electrostatic warts for development, resulting in an extremely clear image. Next, this image was transferred onto plain paper using corona discharge, and then passed through two pressure rollers with a linear pressure of 5 kg, whereupon it was completely fixed.

Example 2 The following materials were mixed.

Paraffin: 60 parts Carnauba wax: 40 parts Magnetite: 50 parts The above mixture was melt-mixed to form a homogeneous mixture, which was then atomized and collected under the same conditions as in Example 1. The average particle size was 9.0μ.

Next, the particles were dispersed in the styrene dimethylamine ethyl methacrylate copolymer solution having a particle number of 10% obtained in the next step, and sprayed using a spray drying device to coat the surface with a resin.

Finely powdered silica was added to the resulting fine powder to form a dust image agent, and then an extremely clear image was obtained when a positive image was developed. Also, in the same way as Example 1, Transfer Comparative Example 1 The same nozzle and the same nozzle were used in Example 1 except that the nozzle a = 0.5 mm and Sl = 90y-/min S, = -200t/min. It became a reality. The average particle size was 25 μm and the particle size distribution was wide.

As in Example 1, the image quality of 191 used as a toner was poor and the transfer efficiency was poor.

Comparative Example 2 When a nozzle with b = 0.005 mm was used in Example 1, the liquid did not come out of the nozzle and could not be converted.

Example 3 Using the material of Example 1, a=5. 2υ1 of Ob=0.2
1. Using body nozzle S, = 3077 minutes 52 = 500t
The average particle size that exceeded the atomization rate per minute was 8μ, and the average particle size was slightly smaller than b.
It was.

[Brief explanation of the drawing]

The drawing is a perspective view of a 2v1 body nozzle used in the present invention. Procedural amendment ■(・(Form 9 1 Indication of the case + 14 Japan 1997) Petition No. 231 No. 2 No. 2 Appearance of the invention, leap to the case (k Applicants: 4, 1 person) Address: Tokyo, MO 3305 Shizusu Building, 2-116-2 Marunouchi, 113-ku, Tokyo, 11-1 of the amendment order 8. Contents of the amendment The following matters in the specification of the present application will be amended as shown in the attached sheet.Note 1, Invention 419-

Claims (1)

[Claims] A material in a heated molten state is supplied to a two-fluid nozzle, and the liquid supply rate is S1. jS'/min) and part feeding speed 52 (1/min)
A method for producing fine powder, characterized in that the atomization is carried out under atomization conditions that satisfy the condition of 5 per cent or less for atomization. a) 81150 (master) 2.0) b>0.01 (throat) 0.03<81/82<, 0.35 However, a: Liquid supply port diameter (deaf) b: Liquid supply pipe tip and gas supply pipe Distance to tip