JPS59204621A - Production of truly spherical fine synthetic resin particle - Google Patents

Abstract

PURPOSE:To obtain the titled fine particles having a uniform particle diameter and improved fluidity, by feeding a thermoplastic melt to the inner wall surface of a hollow rotating body having a downward opening, dispersing the melt from an edge as droplets by the centrifugal force while jetting a heating gas thereon, and cooling and solidifying the droplets. CONSTITUTION:A thermoplastic resin containing no solvent is melted in a melting vessel 21 under heating, fed through a double-pipe type transfer pipe 22 and an injection inlet 4 to the inner wall surface in a hollow rotating body 1 of a granulating structure 25 consisting of the hollow rotating body 1 having a downward extending opening and an outer cylinder 2, and dispersed from the edge of the rotating body 1 as droplets by the centrifugal force. In the process, the edge of the rotating body 1 is kept at a higher temperature than the melting point of the melt by feeding a heating gas fed from a gas inlet pipe 24 through a gas inlet 3 to the outer wall surface of the rotating body 1, and the heating gas is jetted from a slit 5 across the flying surface of the droplets at 10-1,000m/ sec linear velocity. The droplets are then cooled and solidified by a cooling gas 26 in a granulating can 23 to afford the aimed fine particles.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing spherical fine particles of thermoplastic resin, particularly polyolefin.

Particulate thermoplastic resins have traditionally been used in the fields of rotary molding and powder coating. In particular, relatively medium to low molecular weight polyolefins with a molecular weight of 30,000 or less are used in a wide range of applications such as pigment dispersants and processability improvers during plastic processing, various mold release agents, and wax product additives. Its particle size is several 1
The size is from 00 microns to too many microns and the shape is irregular.

However, in recent years, powders have come to be required to be spherical and have a uniform particle size distribution from the viewpoint of good fluidity and ease of uniform dispersion into plastic or wax-like materials. Furthermore, different particle sizes are required depending on the application.

By the way, it is known that there are two types of conventional techniques for powderizing thermoplastic resins.

The first type is mechanical comminution. For example, a method is known in which a suitable force-coating agent is added and the pulverization is carried out as it is at θ~gOC, or mechanically pulverized with something like a ball mill while the solvent is evaporated at low temperature.
b3o).

In this method, the particle size distribution is wide, the shape is irregular, has an acute fracture surface, and is far from spherical.

The second type is a dissolution/precipitation method, which includes heating and dissolving using a specific solvent and then cooling and precipitating, or adding a poor solvent to precipitate.

Various proposals have been made for this method depending on the solvent separation method (Japanese Patent Publication No. 1986/1996/Buru 5S).
7.Special public Sho 31-170g, Special public Sho 1Ib-Goo 9q
/) After filtration, centrifugation or evaporation of the solvent, agglomeration of the polymer particles is inevitable in the drying process of the particle cake, requiring re-grinding. Furthermore, the shape of the particles is not spherical.

The eighth type involves dispersing the molten polymer in a solvent under high shear agitation with the aid of various dispersants and then cooling. The dispersant is a surfactant, and the solvent is water. For example, a block copolymer of ethylene oxide and propylene oxide is used as the surfactant (Japanese Patent Publication No. 39-X
3qs). Although spherical particles can be obtained relatively easily in this method, it has drawbacks such as the need for a special shear stirring device, and the fact that the dispersant remains on the product particles, causing an undesirable effect and impairing commercial value.

The tth method is a method of spraying a thermoplastic resin melt into the atmosphere, and a method using a Japanese Patent Publication No. 1983-11IO'1VC2 fluid nozzle has been proposed.

Although this method is an excellent method for obtaining perfectly spherical particles with simple equipment, as described in the specification, high pressure (10 o-so θ psig) is required to inject the melt, and the particle size It has drawbacks such as wide distribution and easy formation of fibrous substances.

The present inventors have made extensive studies to overcome these drawbacks and obtain substantially spherical particles with a sharp particle size distribution in any desired diameter. The present invention has been achieved by discovering that a method of

That is, the object of the present invention is to provide truly spherical thermoplastic resin, especially polyolefin particles, having a particle size of 1,000 μm, and the object is to provide a thermoplastic resin melt, which is substantially free of solvent, in a downward direction. The molten material is supplied to the inner wall surface of a hollow rotating body having a widened opening, and the melt is dispersed as droplets by centrifugal force from the edge of the rotating body, and at this time, the edge is supplied to the outer wall surface of the rotating body. 14 of the melt by heating gas
(1! Both the point and the point are heated and maintained at a high temperature, and the heated gas is cut from the edge to the flying surface of the droplet at a linear velocity of 10 to 10o.
This can be easily achieved by ejecting the liquid at a rate of 100 m/sec and cooling and solidifying the dispersed fine droplets by contacting them with cold gas.

The thermoplastic resins used in the present invention include polyolefin resins such as polyethylene and polypropylene, ζ polycarbonate resins, fluororesins, polyester resins, styrene resins, acrylic resins, polyamide resins, polyacetal resins, vinyl acetate resins, vinyl chloride resins, etc. viscosity/
d7! /1 or less is preferably used.

Particularly favorable results are obtained when the present invention is applied to polyolefin resins. Polyolefin resins include polyethylene, polypropylene, and polybutylene, and the polymers include not only homopolymers but also copolymers with other α-olefins.

In the case of polyethylene/Intrinsic viscosity of 30C tetralin solution θ, o lI to 8 θ/g, density o, qθ to O0 rizag/CC, in the case of polypropylene/3! ; c Intrinsic viscosity of tetralin solution O1θ/~0. ! ;dl/? , density θ, g
Those having A to 0.9/f/cc are preferably used. The method of the present invention utilizes substantially solvent-free polymers. When using a solvent-containing polymer, that is, a polymer in the form of a solution dissolved in a solvent, the product powder becomes porous particles, which increases the blood loss hardness,
This is undesirable because it results in poor transparency and sometimes results in a decrease in bulk density.

In the present invention, a hollow rotating body having an opening that expands downward is used as a means for dispersing and granulating the polymer, but the downward expansion does not necessarily need to cover the entire inner wall surface.

The rotating body can take various shapes such as a conical shape, a cup shape, and a hemispherical tube. The size of the rotating body is determined by the polymer
Although it varies depending on M and the target particle size, the diameter of the lower edge is usually between 30 rMn and θθ. The larger the amount to be processed or the smaller the particle size, the larger the diameter needs to be, but if it is too large, high-speed rotation becomes difficult. 5orran
~30θmm is preferably used.

The preferred condition is that the rotation speed of the disk is IOθ to SO, OθO revolutions/minute. The particle size can be controlled by the rotation speed. When rotating at high speed, the diameter of the resin particles becomes smaller, but the dimensional accuracy of the rotating part is required, and it is difficult to manufacture the rotating part at speeds exceeding go, ooθ rotations/minute. Usually, the rotational speed is controlled by a combination of an electric motor and a speed increaser, or a compressed air drive motor to obtain the desired particle size.

The molten polyolefin is introduced into the inner wall surface of the rotating body,
Centrifugal force forms a thin film on the inner wall, which forms droplets along the edges and disperses into the cooling gas stream. The cooling gas stream removes the heat of crystallization of the molten polyolefin that has been cooled in advance and becomes droplets, thereby solidifying the droplets. In the case of polyolefins, is the heat of crystallization normal for polyolefins? Since the Kcal is as high as 5 to 6 Q, it is necessary to supply a sufficient cold air flow to match the amount of polyolefin to be treated. However, the cold air flow often cools the rotating body, especially the edges and the surrounding space. For this reason, irregularly shaped particles and fibers are generated, making it difficult to obtain truly spherical particles. This tendency becomes more pronounced as the scale of the facility increases, and conventional methods such as strengthening heat retention in the surrounding area are completely insufficient. The reason for this is presumed to be that the high-speed rotation of the rotating disk draws in a cold air flow.

The inventors of the present invention solved the above problem by (1) heating the molten resin to a sufficiently high temperature, and (2) directing the heated gas to the outside of the rotating plate @ 11 (on the side opposite to the surface on which the liquid film of the resin is formed). 24 people,
We have found that it is important to spray the edges.

For example, in the case of molten polyolefin, at least a
It is necessary to heat the heated gas to a temperature higher than oc, preferably soC, and the temperature of the heated gas is at least higher than the melting point, preferably at least lθC higher than the melting point, and the area to be blown is melted. The space several millimeters outside the edge and periphery of the rotating body, where the resin liquid film leaves as droplets, is the flight surface of the droplets. Since the droplets fly in a direction perpendicular to the rotational axis due to centrifugal force, the heated gas is blown against the edge of the rotating body and at the same time, it is blown parallel to the rotational axis so as to cut the flying surface of the droplets at right angles. For example, a fixed outer cylinder is installed on the outside of a rotating body that rotates at high speed, a polyolefin melt is introduced into the inner surface of the rotating body, heated gas is introduced into the gap between the outer surface of the rotating body and the outer cylinder, and the edge of the rotating body is heated. This can be easily accomplished by blowing out the heated gas from a slid formed by the end and the fixed outer cylinder. The width of the slit must be wide enough to prevent the edge of the rotating body from coming into contact with the fixed outer cylinder during high-speed rotation, but if it is too wide, the amount of heated gas may be excessive in order to obtain the heated gas jetting speed. , the temperature of the granulation can increases. However, if the resin droplets are not sufficiently cooled, the particles may coalesce and form lumps. Therefore, it is more efficient to make the slit width as narrow as the rotating body manufacturing precision allows. Usually 0.2~. ym preferably 0.
! ;-& fins.

As described above, heat retention at the edge of the rotating body is achieved,
This can prevent the resin from forming into fibers, but in addition, the heated gas becomes a high-speed jet stream due to the slits at the edge of the rotating body, resulting in molten resin droplets (or liquid film in some cases) separating from the edge of the rotating body. (sometimes a liquid column) is further atomized and sprayed in the direction of the gas exit.

As the heating gas, inert gas such as N2, Hθ, Ar, water vapor, CO2, air, etc. can be used, but N2 is preferably used from the viewpoint of prevention of dust explosion and economical efficiency.

The gas ejection speed is /θ~ioo at the slit portion.

m7 seconds. The larger the ejection speed, the smaller the particle size.

Therefore, the particle size can be controlled by both the rotational speed of the rotating body and the gas ejection speed.

Since the molten resin is granulated by cooling and solidifying, it is not a good idea to flow more heating gas than necessary. Therefore, if the desired grain size is θ to 7000μ, it is desirable to control the grain size by the rotational speed of the rotating body. At this time, the heating gas may have a minimum flow rate necessary to maintain the edge of the rotating body at a high temperature, which is usually /~som/hour. Gas linear velocity at slit part is 70m
It is 7 seconds or less. When the desired particle size is /~lθθμ, the linear velocity of the heated gas is increased to 10 m/sec to 10θθm/sec and the linear velocity is controlled within this range to control the particle diameter. In this case, the amount of heating gas is usually 10-/30θg/hour. l
In order to obtain ultrafine particles of ~70μ, it is necessary to maximize the rotational speed of the rotating body and further increase the scrap line speed. It is possible to control the resin particle size in this way, but the conditions are: the desired particle size, the manufacturing accuracy of the structure consisting of the rotating body and the fixed external wire, the precision of the high-speed rotating motor, and the high-speed rotation. Suitable conditions can be selected as appropriate from the standpoint of equipment and economy, such as eccentricity, vibration, and cost of hot gas.

Figure / shows an example in which the rotating body is conical, and Figure 2 is an example in which the rotating body is cup-shaped.
As long as the gist of the present invention is followed, the present invention is not limited to FIGS. 7 to λ. In either case, the structure is such that the molten resin is introduced into the inner wall surface of the rotating body, and the heated gas is introduced into the outer wall surface to heat the weave ends and the vicinity thereof.

In the figure, / and l/ are rotating bodies, c, /, and 2 are outer cylinders, 3 and /3 are heating gas inlets, g and /4' are molten resin injection ports, and S and l on the left are slits. .

Note that it is necessary to heat the rotating body in advance before introducing the molten resin, and the above heating gas introduction method and the above rotating body structure are also useful for that purpose.

The thus obtained thermoplastic resin particles have a true spherical shape, a narrow particle size distribution, and a smooth particle surface. I can do it.

As for the width of the particle size distribution, Rosin Ramler (Rosi
n, -Ramm1er) in which the value of n in the equation is 2 or more can be obtained.

Next, examples will be shown.

In the actual JOI PLI, the intrinsic viscosity, density, foot point, particle size distribution, and bulk density were each measured by the following methods.

Deadness limit: Determined using a 7-point method using an Utbelohde viscometer.

Polyethylene/3θC tetralin solution polypropylene 733C dense f: According to JIS K b7bO.

Melting point: PerkinElmer differential scanning calorimeter DSC-
/B type was used to determine the peak of the endothermic thermogram.

Particle size: average particle size of goμ or more, if above, use a standard sieve (, T
IS-zggθl) was measured using a rotary tube sieve shaker.

Light transmission if the average particle size is less than gθμ Use a type particle size distribution analyzer (the dispersion medium is n-hexane).

The average particle size is determined by cumulative weight! It is expressed as a particle size of Oq6, and the particle size distribution is the Rosin-Rammler distribution function R = / 00
The n value of e=” is plotted using Rosin-Ramm1er plot (10
g (calculate n from the slope of 2-12-1o = nlogz+b').

Bulk density: JIS-6? Ko/by.

Comparative Example 1 According to 71:l- in Figure J, the intrinsic viscosity was 0. / 3'dl/
S'.

Approximately 100 kfi of polyethylene having a density of 0.9 &f/cc and a melting point of 7.2 IC was charged into a melting pot having a volume of 11001 cm, and the resin was heated and melted by passing a heating medium of 2 kOC through the jacket of the melting pot. This was passed through a double pipe type transfer pipe 22, and the resin temperature was controlled to be /90 CVC, and the diameter was /m.

It was led to the top of 13 granulation cans with a height of 5 m. The top of the inside of the granulation can consists of a conical rotating body with a diameter of 5 orran and a cone angle of 60 degrees, preheated with /30'l:N and gas 21I, and a fixed outer cylinder. A granulation structure 2S (shown in the figure) with a clearance of /1lli from the cylinder is attached, and is rotated at 100θ rotations per minute. The molten polyethylene was introduced into the rotating plate at a flow rate of 10 kg/hour. Heating N used during preheating.

Gas was subsequently supplied at a linear velocity of 2 m/sec at the slit section.

In addition, N2 gas cooled to about 3 SC, 26
was introduced at a rate of 9 Nd/min.

The particles generated in the granulation can were extracted from the bottom of the can, collected by a bag filter 27, and extracted from the bottom as a product.

The product particles had a particle size distribution of /gO microns.

This is expressed as the ratio of the particle size at a cumulative fraction of 2S% and the particle size at a cumulative fraction of 7S%, which is 1I (21Oμ/lSθμ=waste), which is an extremely sharp distribution.

The bulk density was 0.3 Of/ca, the shape was completely spherical, and the particles were transparent.

Comparative Example - In Comparative Example 1, the rotation speed of the rotating body was /0.000rp
The experiment was carried out under the same conditions except that m was changed. The results are shown in Table-/.

Example 1 In Comparative Example 1, the linear velocity of the heating gas at the slit portion was /t
The experiment was carried out under the same conditions except that m/t3ec was used.

The results are shown in Table-/. As is clear from the comparison with the results of Comparative Example 2, it can be seen that the higher the linear velocity of the heating gas at the slit section, the smaller the average particle diameter.

Examples A to D The same operation as in Comparative Example 1 was carried out under the conditions of raw polyolefin, resin temperature, extrusion tube, rotating body diameter, clearance, heating gas temperature, and linear speed shown in Table 1 to obtain a transparent material. True spherical fine particles were obtained. The results are shown in Table 5.

Example S Same as Comparative Example 1 under the conditions shown in Table 1 using modified polyethylene grafted with maleic anhydride lθo o ppm, having a limiting viscosity of WO, / 7 dl/t, a density of 0, 6, and a melting point of 1 OC. Table 1 shows the particle size, particle size distribution, and bulk density of transparent true spherical fine particles obtained.

Example 6.7 Intrinsic viscosity 0. /kodl/? , density θ, ? 0, melting point/A
;O'l:), the same operation as in Comparative Example/ was carried out under the conditions shown in Table/, to obtain transparent true spherical fine particles. Displays particle size, particle size distribution, and bulk density.

[Brief explanation of drawings]

Figures/-2 are a vertical cross-sectional view (a) and a front view (b) as seen from below, showing an example of the shape of the rotating body used in the present invention. In the figures, l and // are the rotating body, and 3 and /3 are heating gas inlets, q and /lI are injection ports for molten resin, and S and /S are slits. FIG. 3 is an example of a flow for producing thermoplastic resin fine particles according to the present invention, in which 21 is a melting pot, 22 is a transfer pipe,
23 is a granulation can, 2D is a nitrogen gas introduction pipe, 2S is a granulation structure, 26 is a cooling nitrogen gas introduction pipe, and Koku is a bag filter. Applicant: Mitsubishi Chemical Industries, Ltd. Agent: Patent attorney: Yo Hase and 7 others Figure 1 Figure 2 Procedural amendments (in broad daylight) Showa SG 1999 Sword 12th Japan Patent Office Commissioner Kazuo Wakasugi 1 Indication of the case Showa 1986 Special Permit No. 0≠Hiroshi 1 2 Name of the invention Process for manufacturing true spherical synthetic resin fine particles 3 Person making the amendment Applicant (JRIO) Mitsubishi Chemical Industries, Ltd. 4 Agent Address: 2-5 Marunouchi, Chiyoda-ku, Tokyo 100 Japan No. 2 Mitsubishi Chemical Industries, Ltd. (6806) For BuT Physician Hase - (Others 1)
Name) 5 Subject of amendment Contents of amendment in column 6 of “Detailed Description of the Invention” of the specification (1) 13-A OKca on page 1, line 1 of the specification
1 J is corrected as [3-A Ocal J. (2) On page 12 of the same page, Hiroyuki, correct the phrase "of heatable gas" to read "of heated gas." (3) “Ubbelohde viscometer” on page 13/co line
Correct the statement to read "Ubbelohde viscometer." (4) Delete “wo” in front of () in the 1st≠page line. that's all

Claims (2)

[Claims] (1) A thermoplastic resin melt containing substantially no solvent is supplied to the inner wall surface of a hollow rotating body having a downwardly expanding opening, and the melt is applied to droplets from the edge of the rotating body by centrifugal force. At this time, the edge is heated and maintained at a temperature higher than the melting point of the melt by heating gas supplied to the outer wall surface of the rotating body, and the heating gas is applied from the edge to the flying surface of the droplets. Cut it and eject it at a linear velocity of lO~/θ00tn/sec,
A method for producing thermoplastic resin spherical particles, which comprises bringing dispersed fine droplets into contact with cold gas to cool and solidify them. (2) A fixed outer cylinder is provided on the outside of the rotating body, and heated gas is introduced into the gap between the outer surface of the rotating body and the outer cylinder to maintain the temperature of the edge of the rotating body. The manufacturing method according to claim 1, in which the heated gas is ejected from a slit formed with a fixed outer cylinder.