JPS59232124A - Production of fine spherical particles of thermoplastic resin - Google Patents

Abstract

PURPOSE:To produce exactly sphrerical, particles of a thermoplastic resin in a manner of industrial advantage, by pre-mixing a thermoplastic resin with a nonsolvent for this resin at a specified temperature, agitating the mixture at a high speed to form a suspension and cooling it. CONSTITUTION:A vessel equipped with a heater and an agitator is charged with a thermoplastic resin (A) having a m.p. or softening point <=300 deg.C and a melt viscosity <=10,000P (e.g., PE) and a nonsolvent (B) for component A, having a b.p. higher than the m.p. or softening point of component A by at least 50 deg.C (e.g., silicone oil) and these components are pre-mixed at a temperature higher than the fluidized point of component A by at least 10 deg.C at a power requirement of 0.5-5kW per m<3> of the mixture of components A and B. The formed mixture is transferred to a high-speed mixer and agitated at the same temperature as that in the pre-mixng and an agitator speed of 2,000-15,000rpm to suspend molten component A in component B, and the suspension is cooled.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing thermoplastic resin spherical fine particles. Specifically, the present invention relates to an industrially advantageous method for producing fine, spherical thermoplastic resin particles.

As a method for producing fine particles of thermoplastic resin, a method of precipitating a thermoplastic resin by cooling a heated solution of thermoplastic resin, or a method of mixing a solution of thermoplastic resin and a non-solvent of thermoplastic resin However, these methods require time to dissolve the thermoplastic resin in a solvent, and the processing amount is determined by the solubility of the resin. This method was not completely satisfactory, as the amount of treatment per solvent used could not be increased.

As a result of intensive research into the production of thermoplastic resin fine particles, the present inventors found that when stirring a mixture of a thermoplastic resin and a non-solvent of the resin at a temperature equal to or higher than the pour point of the resin, A suspension of spherical molten resin in a non-solvent is formed, and by cooling this suspension, true spherical resin particles can be obtained. '12g).

When using this method, true spherical thermoplastic resin fine particles with a particle size of about 10θμ can be produced in a short time, but the stirring speed has a large effect on the particle size of the thermoplastic resin fine particles obtained. In order to obtain fine particles with a small diameter, high speed and strong stirring is required.For example, in order to produce fine particles with a particle size of Sθμ or less, ? o o Kw/m” or more power is required.

For this reason, this method requires high power costs, and large-scale high-speed stirring equipment for large-scale production is special and extremely expensive, so improvements are still needed for large-scale production. .

As a result of further research, the present inventors found that by stirring and mixing a thermoplastic resin and a non-solvent for the thermoplastic resin at a temperature higher than the pour point of the thermoplastic resin, a crude product of the molten thermoplastic resin was obtained. It has been shown that when using a two-step method of creating a mixture in which particles are almost uniformly suspended and stirring this mixture using a high-speed stirrer, fine particles of thermoplastic resin with uniform particle size can be formed with a small amount of power. Heading The invention has been completed.

That is, the purpose of the present invention is to industrially advantageously produce thermoplastic resin fine particles, and this purpose is to
A thermoplastic resin and a non-solvent for the thermoplastic resin are premixed at a temperature equal to or higher than the pour point of the thermoplastic resin, and further, at that temperature, the mixture is introduced into a high-speed stirrer at a rotation speed of 000 revolutions per minute or more. This is achieved by forming a suspension in which the melt of the thermoplastic resin is suspended in the non-solvent and then cooling it.

The present invention will be explained in detail below.

Thermoplastic resins used in the present invention include polyolefins such as polyethylene and polypropylene, polystyrene, polyvinyl chloride, polyacrylate, and polymethacrylate, and polyesters such as vinyl resins, polyethylene terephthalate, and polybutylene terephthalate. Nylon 6, Nylon 6 Otsu, Nylon T, /bb
Examples include polyamides such as , nylon//, nylon/λ, and polycarbonates.

31 In the present invention, the pour point, that is, the melting point for crystalline resins and the softening point for amorphous resins, is 3θθC
Below, it is preferable to use one having a melt viscosity of about 23θC or less, and a melt viscosity of 100 poise or less, preferably soo.

It is preferable to select one having a diameter of less than 2000 voids, more preferably 2000 voids or less.

The non-solvent for the thermoplastic resin has a boiling point higher than the pour point of the target thermoplastic resin, preferably s higher than the above pour point.
has a boiling point as high as oc or higher, does not dissolve the target thermoplastic resin even at temperatures higher than the pour point, and
It is preferable to select a material whose viscosity at a temperature higher than the above pour point is 1/2 centipoise or more, preferably 10 to 500 centipoise.

A non-solvent having a boiling point lower than the pour point of the target thermoplastic resin may not be usable, but it is not a good idea as it requires pressurization to raise the temperature.

Nonsolvents for thermoplastic resins may be selected from those that satisfy the above conditions depending on the type of thermoplastic resin, but typical examples include silicone oil, liquid paraffin, and lubricating oil. mineral oil, decane, such as
Examples include hydrocarbons such as undecane, dodecane, tetradecane, and hexadecane.

In the present invention, first, a thermoplastic resin and a nonsolvent are premixed at a temperature equal to or higher than the pour point of the thermoplastic resin.

The mixing ratio of the thermoplastic resin and the non-solvent may be such that the molten resin can be dispersed as a dispersed phase, and usually the thermoplastic resin is mixed with the non-solvent at a ratio of θ, θ/~/weight times, preferably O
It is preferable to select from the range of 0θ to O,S times the weight. Although a small amount of thermoplastic resin is a serious disadvantage in practice, it is not a good idea because the amount to be treated is small relative to the amount of non-solvent.

As a device for pre-mixing thermoplastic resin and non-solvent,
There are no particular restrictions on the equipment as long as it is capable of heating and stirring sufficiently; containers with jacket-type or coil-type heaters, and various types of stirrers, such as fan turbine type, disk turbine type, and Faudler type. Examples include devices that are combined with a stirrer such as a propeller type, anchor type, etc.

The temperature for forming a mixture in which the molten resin is dispersed is
It is preferable to select a temperature higher than the pour point of the thermoplastic resin used by about /θC or more, preferably about 20 to 70'Q higher. If the temperature is extremely low, the melting fraction of the resin will be sufficient and power will be increased.

On the other hand, if it is too high, there is a risk of deterioration of the resin.

Stirring in this premixing may be performed to such an extent that the molten resin is almost uniformly dispersed in the nonsolvent, and there are no particular restrictions on the shape or particle size of the dispersed molten resin. For stirring for this purpose, the total amount of thermoplastic resin and non-solvent/m"Aso, s-left Kw, preferably O15~,?
It is best to use a power of around KW. If the stirring power is too low, it will not be possible to mix sufficiently, making it difficult to supply a uniformly dispersed mixture to the next high-speed stirrer, interfering with stable operation, or causing the particle size of the resin particles in the product to be uneven. It will cause many inconveniences. On the other hand, increasing the stirring power is not inconvenient in terms of operation or product quality, but no special effect can be expected from increasing the stirring power, and losses due to increased power costs will be large, so it is not a good idea.

The thus premixed mixture is then introduced into a high speed stirrer to form a suspension. Examples of high-speed stirrers include those with stirring blades that rotate at high speed, those with bladed stirring blades that rotate at high speed, and those with a disc with a bottle that rotates at high speed. It is advantageous to have both functions. Specific examples of such high-speed stirrers include Tokushu Kika Kogyo's trademark, Pipeline Homomixer or Homomitsukline Mill,
Another example is Komatsu Zenoah's trademark, Disinch Grater, etc.

The temperature during high-speed stirring is within the range of the temperature during mixing described above.

The rotation speed of the stirring blades etc. in high-speed stirring is 5oo per minute.
o rotations or more, preferably about 3000 to /kOθO rotations. The number of rotations has a great influence on the particle size of the product resin fine particles; the higher the number of rotations, the smaller the particle size; conversely, the lower the number of rotations, the larger the particle size.

In addition to the rotation speed mentioned above, the particle size of the product resin fine particles depends on the type and amount of thermoplastic resin and non-solvent, temperature, type of equipment,
Since it changes depending on other conditions, it is necessary to select the rotation speed including these conditions so as to obtain the desired particle size.

The suspension extracted from the high-speed stirrer is then cooled, and part or most of the suspension may be circulated to the preceding premixing device.

The suspension formed by the high-speed stirrer is cooled to solidify the molten resin into fine resin particles.

Although there are no particular restrictions on the means of cooling, rapid cooling is preferable because it reduces the chances of fusion of the molten resins and shortens the time, and the above suspension is prepared separately. A method of lowering the temperature by mixing with a non-solvent at a lower temperature is suitable.

After cooling, the resin particles are separated from the suspension by means such as filtration or centrifugation, and the resin particles are shredded or washed and dried to form a product.

When using the method of the present invention, compared to the method of making a suspension from a mixture of a thermoplastic resin and a non-solvent in one step,
This method is industrially advantageous because it is possible to obtain a suspension with a power of about /SO and to produce fine resin particles with a more uniform particle size.

The resin particles produced by the method of the present invention have a smooth surface, a true spherical shape, a narrow particle size distribution, and good fluidity, so they are suitable for cosmetic bases, paints, powder molding, rotary molding, etc.

Hereinafter, the present invention will be specifically explained with reference to examples, but the present invention is not limited to the following examples as long as it goes beyond the gist thereof.

Example / Stirring tank with 301 jacket (inner diameter 2 gog cm) having fan turbine type stirrer with blade diameter / ta cln
) Ron 6 beg/k! ! The temperature was raised to 2A; Or, and the mixture was stirred for 75 minutes at a stirrer rotation speed of ttSθ rotations per minute for premixing.

While maintaining the temperature of the stirring tank and continuing stirring, the mixture is extracted from the bottom of the stirring tank in 3 tons per minute using a high-speed stirrer with a rotation speed of 10θOθ per minute (stirring blade diameter 3m, manufactured by Tokushu Kika Kogyo ■, trademark, Pipeline Homo Mixer). was introduced to form a suspension.

Room temperature silicone oil 2θ was sequentially poured into the suspension. The temperature at the end of the injection was /3°C, and the nylon solidified while remaining dispersed.

This dispersion was separated using a centrifuge, and the resulting cake-like nylon was dispersed in methylene chloride, washed, and centrifuged again to dry it.

When the obtained nylon was observed under a microscope, it was found to be perfectly spherical fine particles with a smooth surface, and the particle size was λ to gμ.

In addition, the power for pre-mixing is 0.0.7 Kw (bald Kw
/m8), the high-speed stirring is Oo Kw, and the total amount of power used is 0. It was θ evening Kwh.

Comparative Example/A stirring tank with a 301 jacket and a fan turbine type stirrer with a blade diameter of 211 Crn (inner diameter: tg, gCrn).

o, 5kyt preparation, 2! The mixture was heated to OC and stirred for 1S minutes at a stirrer speed of 700 revolutions per minute to form a suspension.

Thereafter, the same operation as in Example 1 was carried out, and the obtained nylon had a perfect spherical shape with a smooth surface, and the particle size was S ~
It was 10μ.

ti, power B 11. OKw (3g OKw/m”
), and the amount of electricity used was OKwh.

Example 11 having a fan turbine type stirrer with a blade diameter of 4 tcrn
- Stirring tank with 301 jacket (inner diameter, 2S, Crn)
A high-speed stirrer with a stirring blade diameter of 3 cm (manufactured by Tokushu Kika Kogyo ■,
Using a device connected to a Pipeline Homomixer (Trademark, Pipeline Homo Mixer), silicone oil with a viscosity of Sθ centipoise at 2kOC and polycarbonate/kF with a molecular weight of 5ooo were placed in a stirring tank. The mixture was heated to 2jrOC and stirred for 75 minutes at a stirrer rotation speed of 1 ISO rotation per minute for premixing.

While maintaining the temperature of the stirring tank and continuing stirring, the mixture was drawn out from the bottom of the stirring tank at a rate of at/min and introduced into a high-speed stirrer with a rotational speed of 10,000 revolutions per minute to form a suspension.

The suspension was sequentially poured into silicone oil xot at room temperature. The temperature at the end of the pouring was /307: and the polycarbonate solidified while remaining dispersed.

This dispersion was separated using a centrifuge, and the resulting cake-like polycarbonate was dispersed in n-hexane, washed, centrifuged again, and dried.

When the obtained polycarbonate was observed under a microscope, it was found to be fine particles with smooth surfaces and spherical shapes on both sides, and the particle size was ~Sμ.

In addition, the power for pre-mixing is 0.03 Kw (Ha1 IKW
/m8), the high-speed stirring was O.Kw, and the total amount of power used was O.OS Kw.

Sender: Mitsubishi Chemical Industries, Ltd. Representative: Patent Attorney Hase - 1 other person

Claims (2)

[Claims] (1) A thermoplastic resin and a non-solvent for the thermoplastic resin are premixed at a temperature higher than the pour point of the thermoplastic resin, and at that temperature, the mixture is heated in a high-speed stirrer at 5 ooo rotations per minute or higher. A method for producing spherical fine particles of a thermoplastic resin, which comprises introducing a thermoplastic resin into the non-solvent to form a suspension in which the melt of the thermoplastic resin is suspended, and then cooling. (2) The total amount of the thermoplastic resin and the non-solvent in the premix is 1
2. The method according to claim 1, wherein the mixture is stirred and mixed with a power of O, S to j Kw for ms.