JPH0292508A - Preparation of spherical mini-pellet and its apparatus - Google Patents

Abstract

PURPOSE:To attempt to prepare a spherical mini-pellet by feeding a thermoplastic resin pellet with a specified diameter under an inclined condition and heating and shrinking it in a temp. range higher than the softening point of the thermoplastic resin while it is vibrated. CONSTITUTION:It is essential that the diameter of a thermoplastic resin pellet is in the range of 0.3-5mm. It is pref. that the ratio of length/diameter of the raw material pellet is in the range of 1.1-1.5 to obtain a sphere close to a true sphere. A hot plate 3 is equipped with a heater 6 as a heat source in its central layer and is inclined at 5-15 deg. from the horizontal position. A vibrating plate 4 equipped with a vibrating source 5 through springs 7 is furnished. The raw material pellet is controlled in the temp. range 5-15 deg.C higher than the softening temp. of the resin pellet and it is fed on the hot plate 3 vibrated by means of the vibrating source 5. The pellet moves on the hot plate from its higher position to its lower position and during moving, it is softened and shrunk by heating and rotated by vibration. It becomes thereby round as the corners disappear.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method and apparatus for producing spherical mini-pellets used in powder compacts such as porous sintered bodies.

(Prior art) True spheres of thermoplastic resins such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyamide, and polyester, which are conventionally used in fields such as cosmetics and paints, have very small particle sizes and are usually Those with a diameter of μ or subscale are used. These true spheres are
Generally, it is produced by a crystallization method or the like in a solution that uses a large amount of solvent.

However, with such a method, it is not only difficult to produce a true sphere having a diameter of 0.31 mm or more, but also undesirable from the viewpoint of solvent safety management and economics.

On the other hand, generally commercially available thermoplastic resin pellets are manufactured by cutting strands extruded from an extruder (strand cut), underwater cutting, etc., but they have a particle size of 51 m or more. Generally, the shape is cylindrical or close to cylindrical.

However, in recent years, true spherical particles such as mini pellets (0.3 to 5! IIQ rank 1), which are smaller than regular pellets, are expected to be applied in fields such as porous sintered products, processed powder products, and granular binders. It's coming.

(Problems to be Solved by the Invention) The present invention was made to meet the above needs, and an object of the present invention is to provide a method and apparatus for obtaining spherical mini-pellets easily and inexpensively. It is something.

(Means for Solving the Problems) The present invention provides thermoplastic resin pellets having a diameter in the range of 0.3 to 5IIIm, which are supplied in an inclined state, and are vibrated so that the pellets do not fuse together or form lumps. However, a method for producing spherical mini-pellets characterized by heating and shrinking at a temperature range of 5 to 15 degrees Celsius higher than the softening point of the thermoplastic resin, and a hot plate tilted from the horizontal;
The apparatus for producing spherical mini-pellets is characterized by having at least a vibration source that vibrates the hot plate and a heating source that heats the hot plate.

Examples of the thermoplastic resin of the present invention include homopolymers such as the above-mentioned high, medium and low density polyethylene, polypropylene, polybutene-1, etc., ethylene, propylene, butene-1, hexene-1,4-methyl-pentene-1, etc. General-purpose thermoplastic resins such as polyolefin resins such as α-olefin interpolymers, polystyrene resins, and polyvinyl chloride resins; or ultra-high molecular weight polyethylenes, polyamide resins, polyester resins, fluorine resins, and ABS resins. , polycarbonate resin, polyphenylene ether resin,
Examples include engineering plastics such as polyphenylene sulfide resins, polysulfone resins, and polyether/ether ketone resins, modified products and mixtures thereof, and those blended with organic and inorganic fillers and additives.

It is important that the diameter of the thermoplastic resin pellet is in the range of 0.3 to 5 ms. The diameter of the pellet is 0.3m
If it is less than 111, there is a high probability that the pellets will fuse together, which is not preferable. On the other hand, if it exceeds 5 m111, the physical properties of the final product such as a porous sintered body will deteriorate, which is not preferable.

In particular, as raw material pellets, it is desirable that the ratio of length (L)/diameter (D) be in the range of 1.1 to 1.5 in that a sphere close to a pearl can be obtained.

In the method of the present invention, the above-mentioned raw material pellets are fed in an inclined state, and a comb-shaped guide is provided as necessary to prevent the pellets from fusing together or forming lumps, and the thermoplastic resin is prevented from vibrating. It is important to carry out the heat shrinkage in a temperature range 5 to 15°C higher than the softening point of .

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail below with reference to the drawings, including the apparatus and molding method thereof.

FIG. 1 shows a schematic diagram of an example of an apparatus according to the present invention, which includes at least a hot plate inclined from the horizontal, a vibration source for vibrating the hot plate, and a heating source for heating the hot plate. This is a device for manufacturing spherical mini-pellets, which is characterized by:

That is, the hot plate 3 includes a plate-shaped heater 6 in the center layer as a heating source. Further, the hot plate 3 is inclined by 5 to 15 degrees, preferably 7 to 13 degrees from the horizontal, and has a diaphragm 4 below which a vibration source 5, usually a vibrator, is attached via a spring 7. The above-mentioned inclination can be adjusted by expanding and contracting the length of the support leg 8 attached to the hot plate 3 through the inclination adjustment hole 9.

Furthermore, the periphery of at least the heated portion of the hot plate 3 is covered with a heat insulating box 2 and a box lid 1 for keeping that portion warm.

In order to form spherical pellets using this device, raw material pellets (raw material pellets are made by passing commercially available pellets through an extruder and cutting them into strands to have the above diameter and L/D specially The inclination angle is first adjusted to a temperature range of 5 to 15 degrees Celsius higher than the softening point of the thermoplastic resin pellets, and the size is smaller than commercially available pellets. 5 onto a vibrated hot plate 3.

The pellets move from a high position to a low position on the hot plate 3, and as they do so, they are heated and softened, and the stretched pellets are heated and contracted, causing them to roll as they are vibrated. The corners are removed and it becomes rounded.

If the difference between the above-mentioned molding temperature and the softening point of the thermoplastic resin is less than 5° C., problems such as poor sphericity of the pellets or a significantly longer molding time, resulting in an increase in the size of the apparatus, arise. On the other hand, if the temperature exceeds 15℃, the pellets will fuse together.
Phenomena such as clumping occur.

Further, the amplitude of the vibration is approximately 5 to 10 mm.

The time during which the pellets are in contact with the portion of the hot plate 3 kept at a predetermined temperature varies depending on the particle size, temperature, etc. of the pellets to be supplied, but is usually adjusted within the range of 5 to 300 seconds. The contact time is controlled by the length and inclination of the hot plate 3.

(Example) Examples are shown below.

[Forming equipment] Hot plate: Width 400mm x length 700Il1m
Example 1 Commercially available polypropylene resin [! degree 0.90g/cm3 melt flow rate (VFR) = 0.5g/10m1n,
, Softening point -150℃ Product name: Nisseki Polypro EIIO
G, manufactured by Nippon Petrochemicals Ltd.] was passed through an extruder to form cylindrical pellets (diameter (D) = 1.3 mIIIX length (L) -
1.5 mm) was granulated.

As a result of molding this pellet under the molding conditions below, the diameter was approximately 1
．． 011 spheres were obtained.

[Forming conditions] Hot plate setting temperature: 155°C Hot plate inclination angle = 10 degrees Hot plate amplitude: 8 mm Pellet feeding rate: 3 g/ff1in Heating contact time
: 7 seconds Example 2 Commercially available polyethylene resin [density - 0,956 g/cm3
Melt index (MI) -1, Og/sin, softening point -124°C Product name: Nisseki Stafrene E710, manufactured by Nippon Petrochemicals) is passed through an extruder into cylindrical pellets (diameter (0) / 1.Imm x length (L)・1.30111)
was granulated.

As a result of molding the pellet under the molding conditions below, the pellet had a diameter of approximately 0.
A sphere of 8++ m was obtained.

[Molding conditions] Hot plate setting temperature = 129°C Hot plate inclination angle 710 degrees Hot plate amplitude: 8 mm + pellet feeding speed: 3.5 Kg/■in.

Heating contact time = 6 seconds Example 3 Commercially available polyethylene resin [density - 0,921 g/c 3
Melt index (M1): 5.0 g/win, Softening point: 94°C Product name: Nisseki Rexron J40, manufactured by Nippon Petrochemicals) was passed through an extruder into cylindrical pellets (diameter (D) = 3 mm x length). (L)-3,5o+m) was granulated.

As a result of molding the pellets under the molding conditions below, the pellets had a diameter of approximately 2.
A spherical pellet of 8 mm was obtained.

[Molding conditions] Hot plate setting temperature = 100°C Hot plate inclination angle = 15 degrees Hot plate amplitude: 6mlml Pellet speed: 4.5Kg/ll1n Heating contact time
= 5 seconds (effect of the present invention).

As described above, according to the method of the present invention, porous sintered products,
Spherical mini-pellets, which are expected to be applied in the fields of processed powder products, granular binders, etc., can be obtained easily and inexpensively. In addition, the device is a simple device that is equipped with a vibration source as shown in the example and transmits the vibration of the diaphragm through a spring. It is easy to transform into a pearl, and it can be transformed with a small amount of space.

[Brief explanation of drawings]

FIG. 1 is a side view of the main parts of the spherical mini-pellet manufacturing apparatus of the present invention. In FIG. 1, arrows indicate the direction of movement of the resin pellets. 1: Box lid 2: Heat insulation box 3: Hot plate 4: Vibration plate 5: Vibration source 6: Plate heater 7: Spring
8: Support leg 9: Inclination adjustment hole Patent applicant Nippon Petrochemical Co., Ltd.

Claims (1)

[Claims] 1) Thermoplastic resin pellets having a diameter in the range of 0.3 to 5 mm are supplied in an inclined state, and the thermoplastic resin is A method for producing spherical mini-pellets, characterized by heat shrinking at a temperature range of 5 to 15°C higher than the softening point of the resin. 2) The thermoplastic resin pellet has a length (L)/diameter (
The method for producing spherical minipellets according to claim 1, characterized in that the ratio of D) is in the range of 1.1 to 1.5. 3) An apparatus for producing spherical mini-pellets, comprising at least a hot plate tilted from the horizontal, a vibration source for vibrating the hot plate, and a heating source for heating the hot plate.