JPH10309533A - Powder classifying method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the deposition on an edge by the release effect of a lubricant, to prolong the time interval between the regular cleanings of the edge and to realize a large industrial profit at the time of classifying a powder by dividing the passage into plural passages by incorporating the lubricant into the powder. SOLUTION: The fine powder dispersed in a gas and having a relatively feeble inertia force flows into a passage 3 sharply turned along a Coanda-effect block 2 from a raw material feed nozzle 1, the small powder having a small inertia force flows into a passage 4, and the coarse powder having a large inertia force flows into the gently curved passage 5. The powder having an inertia force is slightly shifted from the passage 5 and partly collided with the F edge 6 and M edge 7. The powder having a strong adhering or aggregating property or the one easy to melt by the heat of the collision energy is likely to adhere to the edges 6 and 7 little by little in collision. However, since the powder contains a lubricant, the adhesion to the edge is reduced by the release effect.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for classifying powders comprising a powder composed of at least one kind of thermoplastic resin or a powder containing at least one kind of thermoplastic resin into a desired distribution. It is. For example, it is used in a method for producing an electrophotographic toner in which a fine powder or a coarse powder is removed from a raw material powder having a wide particle size distribution and only a desired particle size distribution is extracted and used.

[0002]

2. Description of the Related Art An elbow jet manufactured by Nippon Steel Mining Co., Ltd. is known as an apparatus for classifying a powder having a distribution in particle diameter or a powder having a distribution in weight. In this apparatus, powder is blown out from a nozzle together with gas, and is sucked into a plurality of flow paths. At that time, the particle diameter or weight of the powder sucked into each flow path is divided by the kinetic inertia force of the powder. The point at which the particle size or weight is divided is controlled by moving the position of a member that divides the flow path, which is called an edge, to obtain a desired distribution. When producing electrophotographic toner with this apparatus, the flow path is generally divided into three directions, coarse powder and fine powder flow in the flow paths on both sides, and coarse powder and fine powder are removed in the center flow path. A toner powder having a sharp particle size distribution flows. The powder having a sharp particle size distribution flowing through the central flow path is subjected to desired post-processing, and then used as a product.

[0003]

When a powder such as toner is classified by the above-mentioned classifier elbow jet, a phenomenon occurs in which the powder adheres and accumulates on the edge dividing the flow path, thereby narrowing the flow path. There are cases. For this reason, a change in the wind speed or turbulent flow of the gas flowing to each flow path occurs, and the accuracy of classification decreases. In such a case, it is necessary to temporarily suspend the production and clean the powder adhering to the edge, and the production is troublesome. In the case of toner particles, there is a difference in the degree of adhesion and accumulation due to the difference in composition and the thermal characteristics of the binder resin that is the main component of the toner particles.In the case of a recent low-softening point toner, this phenomenon may appear remarkably. is there. This phenomenon is considered to occur because the energy at which the powder collides with the edge becomes heat and the powder softens instantaneously. A similar phenomenon is assumed even when the powder that does not soften has strong adhesiveness and cohesiveness.

[0004]

Means for Solving the Problems The inventors of the present invention have solved the present problem and have studied for stable production. As a result, it has been found that at least one kind of powder or at least one kind of thermoplastic resin is used.
In a method for classifying powder by flowing a gas in which a powder containing a type of thermoplastic resin is dispersed along a flow path and classifying the powder by dividing the flow path into a plurality of flow paths, a lubricant is used in the powder. To solve this problem. It is considered that the adhesion to the edge is reduced by the releasing effect of the lubricant. According to the present invention, the interval of the periodic cleaning of the edge is extended, and a great industrial advantage is realized.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In the classification method used in the present invention, a powder is dispersed in a gas and flows through a channel. As a method of dispersing the powder in the gas, a pipe and a nozzle are provided at a bottom portion of the hopper for the powder deposited on the hopper or the like, and the compressed gas is blown out from the nozzle and flown to disperse the powder. Is deposited, and then fed into a gas flow path to be dispersed and flowed.

[0006] In the classification zone, the flow path is divided into a plurality of parts, and due to a difference in inertial force due to a difference in particle size and a difference in weight of the powder,
The powder is divided into a plurality of flow paths and flows. The behavior in the classification zone will be described with an example of an elbow jet manufactured by Nippon Steel Mining Co., Ltd. The gas in which the powder is dispersed is supplied from the raw material supply nozzle 1 and the fine powder flow path 3, the fine powder flow path 4, the coarse powder flow path 5 and flow into the respective flow paths. A fine powder having a relatively small inertia flows into the fine powder flow path 3 which is sharply bent along the Coanda block 2, and then a fine powder having a small inertia force flows into the fine powder flow path 4.
The coarse powder having a large inertia force flows into the coarse powder flow path 5 that bends gently. Although an example in which the flow path is divided into three directions is described, the number of divided paths may be two directions or four or more directions.

[0007] The powder dispersed in the gas flows into the respective flow paths along with the flow of the gas.
The gas flows while slightly shifting from the gas flow in the direction of the coarse powder flow path 5. Therefore, some of the powder collides with the fine powder channel 3 of the F edge 6 and the M edge 7. If the powder has strong adhesiveness or cohesiveness, or is easily melted or softened by the heat of the collision energy, there is a risk that the powder will gradually adhere to the edge during the collision. The powder used in the present invention contains a lubricant. Due to the releasing effect of the lubricant, the adhesion to the edge is reduced.

As the lubricant used in the present invention, hydrocarbon-based, fatty acid-based, fatty acid amide-based, ester-based, alcohol-based, metal soap, and mixed-based lubricants (for classification of these lubricants, Handbook of Supplementary Plastics and Rubber Additives) (See Chemical Industry). These may be used alone or as a mixture. Among them, a lubricant having a melting point of 50 ° C. or more and 100 ° C. or less is particularly preferable.

The amount of the lubricant used in the present invention varies depending on the composition, particle size and addition method of the powder, and is not particularly limited as long as it has an appropriate releasing effect, but is preferably in the range of 1 to 20% by weight. More preferably, it is in the range of 3 to 10% by weight. In order for the lubricant to be added to the powder and exhibit the effect, the lubricant must be dispersed or dissolved in at least the thermoplastic resin contained in the powder. In this case, other additives in addition to the lubricant may be simultaneously dispersed or dissolved in the thermoplastic resin. There is no particular limitation on the addition method as long as the conditions are satisfied. For example, in the case of an electrophotographic toner which is a kneaded and pulverized product of various additives and a binder resin, the toner may be added at the stage of polymerization of the binder resin, or the binder resin and the lubricant may be dissolved and mixed in the solvent, and then the solvent may be distilled off. You may leave. Further, it may be added at the toner kneading stage.

[0010] The crushed powder used in the present invention is effective for those having strong adhesion and cohesion, and those which are easily melted or softened by the energy of collision or the like. Taking the electrophotographic toner as an example of the powder used in the present invention, a thermoplastic resin is used as a binder resin as a main component of the toner. Since the toner is melted and fixed to the paper by heat, the lower the glass transition point or the softening point of the flow tester of the binder resin, the lower the temperature. However, when the glass transition point and the flow tester softening point are low, as described above, the melting and softening tend to occur due to the energy of collision and the like, and the performance desired for the toner and the ease of classifying and manufacturing are contradictory. . That is, the present invention is particularly effective for a toner having a low glass transition point or a softening point of a flow tester of a binder resin.

As the binder resin, various known resins suitable for toner can be used. For example, styrene resin, vinyl chloride resin, rosin-modified maleic resin, phenol resin, epoxy resin, saturated polyester resin, unsaturated polyester resin, low molecular weight polyethylene, low molecular weight polypropylene, ionomer resin, polyurethane resin, silicone resin, ketone resin , An ethylene-ethyl acrylate copolymer, a xylene resin, a polyvinyl butyral resin, and the like. Preferred examples of the resin used in the present invention include a styrene resin, a saturated or unsaturated polyester resin, and an epoxy resin. . Particularly preferred are styrene resins and polyester resins.

As the styrene resin, polystyrene,
Polychlorostyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-
Vinyl chloride copolymer, styrene-vinyl acetate copolymer,
Styrene-maleic acid copolymer, styrene-acrylate copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-
Butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-phenyl acrylate copolymer, etc.), styrene-methacrylate copolymer (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate) Copolymer, styrene-butyl methacrylate copolymer, styrene-octyl methacrylate copolymer, styrene-phenyl methacrylate copolymer), styrene-α-methyl methyl acrylate copolymer, and styrene-acrylonitrile-acryl And acid ester copolymers.

The polyester resin includes a crosslinkable polyester resin and a non-crosslinkable polyester resin. The crosslinkable polyester resin is obtained by polycondensation of a divalent carboxylic acid monomer, a divalent alcohol monomer, and a trivalent or higher polyvalent carboxylic acid monomer or polyhydric alcohol monomer. 2
As the monovalent alcohol monomer, ethylene glycol,
Diethylene glycol, triethylene glycol, 1,
Diols such as 2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, and 1,4-butenediol, bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylene-modified bisphenol A And other dihydric alcohol monomers. The divalent carboxylic acid monomer is mainly composed of isophthalic acid, terephthalic acid, adipic acid, sebacic acid, diphenic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, and anhydrides or lower alkyl esters of these acids. Is mentioned. Examples of the trivalent or higher polycarboxylic acid include trimellitic acid, cyclohexanetricarboxylic acid, naphthalenetricarboxylic acid, butanetricarboxylic acid, hexanetricarboxylic acid, octanetetracarboxylic acid, anhydrides of these acids, and others. Examples of the trihydric or higher polyhydric alcohol monomer include trimethylolethane, trimethylolpropane, glycerin, and pentaerythritol.

The non-crosslinkable polyester resin is obtained by polycondensation containing a divalent carboxylic acid monomer and a divalent alcohol monomer as main components. Examples of the dihydric alcohol monomer and the divalent carboxylic acid monomer include those similar to the crosslinkable polyester resin. In addition, two or more kinds of binder resins can be used in combination without being limited to one kind.

As the binder resin used for full color which requires gloss and transparency, a non-crosslinkable and narrow molecular weight distribution resin is preferable among styrene resins and polyester resins. Is more preferred. Those having a weight average molecular weight of 5 times or less of the number average molecular weight are preferable, and those having a weight average molecular weight of 3 times or less are more preferable.

In this case, the polyhydric carboxylic acid monomer or polyhydric alcohol having a valency of 3 or more is used within a range that does not substantially lose the properties of the non-crosslinkable resin, that is, a range that gives the linear polymer a highly branched structure. About 2 mol% or less of a monomer or the like may be added. Also, it is not limited to using one by one,
Two or more binder resins may be used in combination.

The softening point of the binder resin, which is a thermoplastic resin used in the present invention, is preferably 160 ° C. or less, more preferably 135 ° C. or less, as measured by a flow tester method. If the temperature exceeds 160 ° C,
It is not preferable because sufficient low-temperature fixability cannot be obtained and the fixing strength tends to deteriorate. As a binder resin used for full color where glossiness and transparency are required, 1
Those having a temperature of 20 ° C. or lower are preferable, and those having a temperature of 110 ° C. or lower are more preferable. The lower the softening point is, the better the fixing property is, and it is preferable. However, as the softening point is lowered, the glass transition point described later is also lowered.

The glass transition temperature of the binder resin is preferably such that the transition start (inflection point) as measured by a differential thermal analyzer is 50 ° C. or more and 75 ° C. or less. When the glass transition temperature is lower than 50 ° C., thermal stability during long-term storage is poor, causing aggregation and solidification of the toner, which is problematic in use.
When the temperature is 75 ° C. or higher, there is a margin in fusing the toner and pulverizing the fine powder, but the softening point increases as the glass transition point increases, so that the fixing property tends to deteriorate. The average particle size of the toner is preferably 5 to 20 μm.

Generally, a method using a Coulter counter is widely used for the particle diameter of the toner. The average particle size of the toner used in the present invention is as follows. A 100 μm aperture is used for the Coulter Counter TA-II, the toner particles are dispersed in isotons, and the toner particle size distribution is measured using channels 3 to 16. Measured and determined by volume average.

The softening point of the binder resin, which is a thermoplastic resin, was measured using a flow tester method. In a flow tester (CFT500 manufactured by Shimadzu Corporation), the diameter is 1 mm.
Using a nozzle having a length of 10 mm, the heating body is set at 80 ° C., and 1 g of the binder resin is charged. After lightly pressing the plunger and preheating for 300 seconds, a pressure of 30 kg / square cm is applied, and the temperature is raised at a rate of 6 ° C./min. The binder resin is softened by the temperature rise, the binder resin is extruded from the nozzle, and the plunger descends. The softening point is the temperature at the midpoint of the plunger's descent distance from the start to the end of the descent.

The glass transition point of the binder resin which is a thermoplastic resin is determined by a differential thermal analyzer (DT-30 manufactured by Shimadzu Corporation).
About 20 mg of a binder resin into a sample cell, and set it in a measuring section.
After heating to 00 ° C. and cooling to room temperature, the temperature was raised again at 10 ° C./min. A tangent was drawn from each of the smooth curves before and after the inflection temperature portion of the DTA curve, and the intersection of the tangents was drawn. Glass transition point. The present invention can be used for the production of two-component developer toner, magnetic one-component toner, non-magnetic one-component toner, black toner, monocolor toner, and full-color toner.

[0022]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. Example 1 100 parts by weight of a branched polyester resin (constituent monomers: polyoxypropylene bisphenol A, polyoxyethylene bisphenol A, terephthalic acid, trimellitic acid Flow tester softening point 112 ° C. Glass transition point 67 ° C.) Pigment Pigment Blue 15 5 5 parts by weight of a charge control agent (LR147 manufactured by Nippon Carlit Co., Ltd.) 5 parts by weight of a lubricant (M2222SL manufactured by NOF Corporation) (melting point: 76.0 ° C.), kneading with a twin-screw kneader, and crushing And pulverization to obtain a toner powder raw material having a broad molecular weight distribution.

The toner powder raw material was classified using an Elbow Jet EJ-05-3S manufactured by Nippon Steel Mining Co., Ltd. at a treatment amount of about 8 kg / Hr. About 16 kg of processing can be performed without any problem during the time, and the average particle size is 9.1 μm and 4 to 16 μm.
It was possible to procure a powder having a sharp particle size distribution having a distribution of at least volume%.

Example 2 A toner powder raw material was procured by the same composition and in the same manner as in Example 1, except that the lubricant was changed to Kawa Wax L manufactured by Kawaken Fine Chemical Co., Ltd. Using this powder, classification was carried out in the same manner as in Example 1. Although there was slight adhesion to the edge, the treatment of about 8 kg could be carried out without any problem in about 1 hour. 9.1 μm 4-16 μm
A powder having a sharp particle size distribution having a distribution of 99% by volume or more was obtained.

Example 3 100 parts by weight of a linear polyester resin (constituent monomers: polyoxypropylene bisphenol A, polyoxyethylene bisphenol A, terephthalic acid Flow tester Softening point 105 ° C. Glass transition point 60 ° C.) Pigment Blue 155 3 parts by weight of a charge control agent (LR147 manufactured by Nippon Carlit Co., Ltd.) 5 parts by weight of a lubricant (HNP-9 manufactured by Nippon Seiro Co., Ltd.) (melting point: 85.5 ° C.) Powder materials were procured. Using this powder, classification was carried out in the same manner as in Example 1. Although there was slight adhesion to the edge, the treatment of about 8 kg could be carried out without any problem in about 1 hour. A powder having a sharp particle size distribution of 9.1 μm and a distribution of 99% by volume or more in 4 to 16 μm could be obtained.

Example 4 Styrene-butyl acrylate copolymer resin 100 parts by weight (flow tester softening point 130 ° C., glass transition point 60 ° C.) Polypropylene 3 parts by weight Charge control agent (quaternary ammonium salt) 2 parts by weight Lubricant (Nippon Oil & Fat) 5 parts by weight (M2222SL, manufactured by Co., Ltd.) (melting point: 76.0 ° C.), kneaded with a biaxial kneader, crushed and pulverized to obtain a toner powder raw material having a broad molecular weight distribution. Using this powder, classification was carried out in the same apparatus as in Example 1 at a treatment amount of about 7 kg / Hr. The classification was completed in about 1 hour and 30 minutes, but adhesion to the edge was hardly observed, and the average particle diameter was 11%. A powder having a sharp particle size distribution of 0.7 μm could be obtained.

Example 5 Styrene-butyl acrylate copolymer resin 100 parts by weight (flow tester softening point 130 ° C. Glass transition point 60 ° C.) Polypropylene 3 parts by weight Charge control agent (quaternary ammonium salt) 2 parts by weight Lubricant (Kawaken 5 parts by weight, manufactured by Fine Chemical Co., Ltd. (melting point: 85.5 ° C.), kneaded with a twin-screw kneader, crushed and pulverized to obtain a toner powder raw material having a broad molecular weight distribution. Obtained. Using this powder, classification was carried out in the same apparatus as in Example 1 at a treatment amount of about 7 kg / Hr. The classification was completed in about 1 hour and 30 minutes, but adhesion to the edge was hardly observed, and the average particle diameter was 11%. A powder having a sharp particle size distribution of 0.8 μm could be obtained.

Example 6 100 parts by weight of a crosslinkable polyester resin (constituent monomers: ethylene glycol, polyoxypropylene-modified bisphenol A, terephthalic acid, trimellitic acid) Flow tester softening point 148 ° C. Glass transition point 71 ° C. Charge control agent (chromium) 1 part by weight of carbon-containing azo dye) 6 parts by weight of carbon black 2 parts by weight of low molecular weight polypropylene 5 parts by weight of lubricant (Kawawa wax L manufactured by Kawaken Fine Chemicals Co., Ltd.) (melting point: 85.5 ° C.) The mixture was kneaded with a kneader, crushed and pulverized to obtain a toner powder raw material having a broad molecular weight distribution. Using this powder, classification was carried out in the same apparatus as in Example 1 at a processing rate of about 7 kg / Hr. The classification was completed in about 1 hour.
Almost no adhesion to the edge was observed, and the average particle size was 8.5μ.
As a result, a powder having a sharp particle size distribution having a distribution of 99% by volume or more in 4 to 16 μm in m could be obtained.

Comparative Example 1 A toner powder raw material was obtained by the same composition and in the same manner as in Example 1 except that the lubricant was omitted.
When the same classification was performed, about 2 mm of protrusion-like adhesion grew at the tip of the edge in 20 minutes, and it was necessary to temporarily stop the operation and perform cleaning.

Comparative Example 2 A toner powder raw material was obtained by using the same composition and the same method as in Example 2 except that the lubricant was omitted.
When the same classification was performed, protrusion-like adhesion of about 2 mm or more grew on the edge tip in 15 minutes, and it was necessary to temporarily stop the operation and perform cleaning.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a powder classification method that can be used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Raw material supply nozzle 2 Coanda block 3 Fine powder flow path 4 Fine powder flow path 5 Coarse powder flow path 6 F edge 7 M edge

Claims (8)

[Claims] 1. A method in which a powder of at least one kind of thermoplastic resin or a gas in which a powder containing at least one kind of thermoplastic resin is dispersed flows along a flow path, and the flow path is divided into a plurality of flow paths. A method for classifying powders, comprising: a method for classifying powders by using a lubricant. 2. The powder classification method according to claim 1, wherein the gas flow has a curvature where the flow path is divided into a plurality. 3. The powder classification method according to claim 1, wherein the melting point of the lubricant is 50 ° C. or more and 100 ° C. or less. 4. The powder classification method according to claim 1, wherein a glass transition point of the thermoplastic resin is 50 ° C. or more and 75 ° C. or less. 5. The powder classification method according to claim 1, wherein the softening point of the thermoplastic resin is 160 ° C. or less. 6. The powder classification method according to claim 1, wherein the thermoplastic resin is a polyester resin and / or a styrene resin. 7. The method according to claim 1, wherein the powder is a dry electrophotographic toner. 8. The method according to claim 7, wherein the powder is a color toner.