JPS62237466A - Preparation of toner for developing electrostatic charge image - Google Patents

Abstract

PURPOSE:To obtain the titled toner causing no offsetting to a pressing roll, and causing also no contamination of carrier, developing sleeve, and photosensitive body by granulating the toner by the suspension granulation method to a desired particle size, then cooling quickly the obtd. toner particles. CONSTITUTION:Toner particles are formed by granulating a kneaded material contg. a binder resin having 1-100 poise melt viscosity at 120 deg.C and a colorant in the molten state in a liquid medium. Formed toner particles are cooled quickly at -0.1 deg.C/sec cooling velocity. When such toner is used in a copying machine, sticking of toner particles by melting to a developing sleeve or drum of a photosensitive body are avoided, and offsetting to a fixing roll is caused hardly, moreover, the toner becomes invulnerable to blocking.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a toner for developing electrostatic images used in electrostatic photography or magnetic recording.

[Conventional technology]

Conventionally, electrophotographic development methods such as the powder cloud method, fapunshi method, cascade development method, and magnetic brush development method have been known, but the toners used in these methods are natural or synthetic resins containing dyes and pigments. For example, in the magnetic brush development method, which is currently in widespread use, a two-component developer consisting of a mixture of iron powder called a carrier and toner is used. In the case of such a two-component developer, in order to maintain good development, maintenance and adjustment to prevent carrier contamination, toner concentration fluctuations, etc. are necessary and complicated. A developing method using a one-component developer containing powder is beginning to be developed and put into practical use.

If you want to keep the developed toner image.

An operation called "fixing" is performed. Such a fixing method involves melting the toner in a heat chamber.
A method in which the toner is melted with a heated roller and simultaneously pressed onto the support surface, a method in which the toner is melted and adhered using a solvent, and the solvent is then removed, a resin solution called a fixer, etc. Methods such as coating and fixing on top are known, but from the point of view of energy saving and non-pollution, energy-saving fixed fixing methods such as rigid rollers or pressure fixing methods using rigid rollers and auxiliary heating are being used. be. The pressure fixing method is such that there is no risk of burning the copy sheet.

There are many advantages such as copying without waiting time when the copying machine is turned on, high-speed fixing, and simple structure of the fixing device. However, with current toner, the pressure roller A good fixed image cannot be obtained unless a high pressure of about 30 kg/cm is applied to the recording medium, and by applying such a high pressure, problems such as curling, glossiness, and wrinkles of the recording medium occur. A mechanically strong fixing device is required, resulting in an increase in size and cost.For this reason, it is desired to develop a toner that can be fixed with the lowest possible pressure. To solve this problem, toners have been proposed in which a soft material for low-pressure fixing is coated with a hard shell resin.

Producing such a pressure fixing type toner by the above-mentioned pulverization method has several disadvantages. For example, in pressure fixing toners, resins with good pressure fixing properties are used as binding resins, but these resins are soft and therefore extremely difficult to crush and cause lumber 4 to adhere to production equipment. A problem arises in that production is interrupted due to the phenomenon of sticking.

Therefore, in order to make these materials into fine particles, it is necessary to use so-called freeze pulverization, which involves cooling the raw materials to make them brittle and lowering the temperature atmosphere, resulting in a very high cost.

To solve these problems, Japanese Patent Application Laid-Open No. 59-12706
As disclosed in No. 3, a method has been proposed in which a material containing a binder resin compound and a pigment is melt-kneaded and then atomized in a liquid medium in a molten state, that is, "suspension granulation". Although the method is suitable for producing low energy constant fixation toners (eg, toners that fix with negligible pressure), there are still improvements to be made.

For example, when granulation is performed using a suspension granulator, the molten particle size of the particles remains constant as long as water, the dispersion medium, is kept at a constant temperature and stirring is continued at a constant circumferential speed. Toner particles are obtained by "suspension granulation" due to the equilibrium force between the force of the agitator's dispersion force that tries to tear the particles into small pieces and the force that causes the particles to collide with each other and coagulate. The particle size of is determined.

However, after particles with the desired particle size are obtained, the heat retention of the water, which is the dispersion medium, is stopped and the temperature of the dispersion medium is lowered, even if stirring is continued.

As the melt viscosity of particles increases over time, the force required to tear off toner that has collided, aggregated, and fused together increases in proportion to the increase in viscosity, but the stirring force does not change, resulting in a change in particle size distribution. It is difficult to obtain a toner that simultaneously satisfies the physical properties necessary for a toner, such as developing properties and fixing properties, and that it shifts to a larger extent, and in most cases, two or more types are used. In reality, a mixture of these substances is used.

When granulation is performed using the suspension granulation method described above using a binder resin and a color pigment, which are a mixture of two or more substances, the granulated particles themselves are still molten immediately after granulation. The two or more substances constituting the binder are in a uniformly mixed state with each other. However, when the temperature of the granulated particles gradually begins to decrease after granulation, the substance with the higher melting point of the two or more binders begins to precipitate first, and the substance with the lower melting point solidifies later, so the granulated particles has a non-uniform sea-island phase separation structure in which high melting point substances are dispersed in islands in a sea of low melting point substances. Particularly when a crystalline substance is used, this sea-island phase separation phenomenon is remarkable, and large islands are likely to be formed.

A core material with such a sea-island phase separation structure differs from the case where two or more types of binder resins are uniformly mixed, and mainly has the characteristics of a low melting point material, that is, the same characteristics as a core material made only of a low melting point material and a coloring agent. has. For this reason, the mechanical strength is weaker than when using a core material in which two or more types of binder resin are uniformly mixed, and when such toner is used in a copying machine, it may cause damage to the developing sleeve or photoreceptor drum. It has disadvantages such as easy fusion, easy offset to the fixing roller, and easy toner blocking.

An object of the present invention is to provide a toner having a sharp particle size distribution.

[Problem that the invention seeks to solve]

An object of the present invention is to provide a toner that does not cause offset to a pressure roller and does not cause contamination of a carrier, a developing sleeve, and a photoreceptor.

A further object of the present invention is to provide a toner that is stable and does not change even when used many times, is stable even when stored for a long period of time, and does not block in a storage container.

[Means and actions for solving the problem] A kneaded material of a binder resin and a colorant having a melt viscosity of 1-100 poise at 120° C. is granulated in a liquid medium in a molten state to form toner particles. The present inventors have found that the above problems can be solved by forming toner particles and rapidly cooling the formed toner particles at a cooling rate of -0.1'O/sec or more, and have arrived at the present invention. In other words, after the desired particle size is obtained after granulation using the suspension granulation method, rapid cooling is performed to increase the viscosity to the extent that the particles do not fuse together even if they collide. (that is, in a solid state), it becomes possible to suppress agglomeration due to fusion after granulation.Also, by using a mixture of two or more binder resin substances and a colorant, "suspension granulation method" is used. By rapidly cooling the material after granulation, it is possible to suppress the occurrence of a sea-island phase separation phenomenon in which high melting point substances are dispersed in the form of islands in a sea of low melting point substances.

Furthermore, when a crystalline substance is used as a binder material, the sea-island phase separation phenomenon may occur even if it is rapidly cooled. While the islands of the sea-island phase separation structure are large, the islands of the rapidly cooled toner are dispersed in the form of ultrafine particles, so it is thought that the toner properties are close to those of a homogeneous mixture.

The melt viscosity at 120° C. of the core material used in the present invention is 1-1° after the mixture of the binder resin and colorant is melted and mixed at a shear rate of 10 sec-1.

poise, preferably 2 to 50 poise.

More preferably, 3 to 20 poise is good.

If it is less than 1 poise, the viscosity during melt-kneading is too low and shear is difficult to be applied, making it impossible to obtain a product with good dispersibility of colorants such as magnetic substances and pigments.

If the viscosity exceeds 100 pots, the viscosity is too high, so the suspension granulation method produces a sharp particle size distribution.

In other words, it is difficult to obtain monodispersed particles. In the suspension granulation method, the quenching rate after granulation must be -0.1''C/sec or higher.

-〇, Below 1°C/SeC, the sea-island phase separation phenomenon tends to occur, and the slower the cooling rate, the more pronounced the phenomenon becomes.

Further, the slower the cooling rate, the more likely the core material particles after granulation will be reagglomerated and the particle size distribution will shift to a larger one, which is not preferable.

Furthermore, the apparent viscosity of the molten mixture of toner consisting of the core material binder resin, colorant, and magnetic substance measured at a shear rate of 10 sec-1 at 120°C is the shear rate o,
Fixability is determined by an apparent viscosity of 115 or less measured at 5 seconds.

Desirable due to manufacturing method.

The fact that the faster the shedding speed is, the lower the apparent viscosity is is generally referred to as thixotropy.Thickotropic properties promote toner deformation due to shear between pressure rollers during fixing, and reduce fixing performance. Improve.

Also, after melting and kneading this core material, it is poured into an aqueous medium,
In the method of granulation by applying a strong shearing force using a homomixer or the like in the presence of an emulsifier, etc., the apparent viscosity of the core material is On the other hand, after shearing, that is, when the molten mixture is in a low velocity state, the apparent viscosity increases, causing coalescence of particles and the coloring agent inside the particles. Reduces agglomeration and distortion of pigments such as magnetic substances.

Although various types of viscosity meters are used for measuring viscosity, a rotating double cylinder (rotor) type viscometer was used in the present invention.

In the case of a rotor type viscometer, the sliding speed is determined by the following formula.

(sec-1) Rc: Cup radius (cm) Rb: Rotor radius (cm) h: Rotor height cm) ω: Rotor rotational angular velocity N: Rotational speed (r p m) Also, the shear stress is S=M/2πRb2h , M: viscous torque, η=S/D, η: viscosity. Therefore, the shear rate viscosity can be determined by measuring the torque from the shape of the rotor of the viscometer.

As the binder resin of the present invention, the following can be used alone or in combination.

A11ied Chem's AC polyethylene, Sanyo Chemical's Sunwax, HoechstAG (7) Hoechst wax, Mikata Petrochemical's Hiwax, BASF's A wax, NUC's DQOJ, Mikata Bo IJ 'y Mical (7) E LVAX .

There are various grades such as Showa Yuka's 5hodex.

- For example, A11i as a polyethylene wax
AC#1702, AC#617 manufactured by ed Chem
, ACtt6, ACtt7, AC#8.

AC#9, AC#615゜Sanyo Chemical Sunwax 1
71F, 151P, 131F, 161F.

165P, Hoechst wax manufactured by Hoechst AG, PE130, PE190, PE520° High wax manufactured by Mikata Petrochemical 110P, 210F, 220P, 3
10F, 320F, 200F.

410F, 405F, 400P, BASF manufactured by BASF
There are wax, AM wax, etc.

Also, as oxidized polyethylene wax, AC629,
AC655, AC380, AC690, AC392, Sunwax E300.

HiWAX4202E, 4053E, Hoechs t
PAD521, PAD522, Showa Yuka 5ho
1ex6050,6200,5050゜50B0.52
20, F6050V, Mikata Petrochemical Hi-Zex 1
200J, 2100J.

2200J, 5100J, Furukawa Chemical Stacren E60
1, Es5o, Es7o, Mikata Polychemical Miraso 7U e 023) (, A CeaON.

FL60. FL67 is exemplified. Examples of low melting point substances for adjusting the melt viscosity at 120'O of a melt-kneaded material consisting of a binder resin and a colorant include the following.

(1) Cn H2n + 2 (n = 18~50
), and one example of a compound having some unsaturated bonds therein is C: 2B n -0ctacosaneC32n
-DotriacontaneC,36n -He
xatriacontane, and also includes squalene C30H50 and squalane [2,6,10,15,19,23 hexamethyltetracosane (C30H82)].

(2) Fatty acids having a hydrocarbon chain as described above, such as those shown in the following table.

(3) Alcohols and esters thereof can also be used (1), for example, as shown in the following table.

L'roalcohol' (4) Chlorides of the above substances, such as chlorinated paraffin, can also be used.

(5) Amides and bisamides having hydrocarbon chains of CI2 to C50 can also be used, such as those shown in the following table.

, 3F-N N'-melenebisamide These are commercially available singly or in mixtures. Generally, they are known as paraffin wax, microcrystalline wax, montan wax, ceremin wax, osikelite, carnauba wax, rice wax, shellack wax, Zasol wax, metal soap, amide wax, and lubricant.

Manufacturers and product names include paraffin wax (Nippon Oil), paraffin wax (Nippon Oil), micro wax (Nippon Oil), microcrystalline wax (Nippon Oil), and Hoechst wax (Hoechst).
AG), Diamond Wax (Shin Nippon Rika), Suntite (Seiko Chemical), Panacet (Nippon Oil & Fats), etc.

Typical grades of paraffin wax include those shown in the first table.

Table 4 Paraffin wax and microwax (Table 5) Paraffin wax (Nichigen Yusei υ Others, such as Hoechst wax OF (partially saponified ester wax of montanic acid, Hoechst AG) Hoechst wax E (montanic acid partially saponified ester wax, Hoechst AG) Acid ester wax.

Hoechst AG) hoechst wax GL3 (partially saponified synthetic wax, HEX)AG), etc.

These can be used alone or in a mixture.

The binder resin of the toner of the present invention generally contains various dyes and pigments as colorants. As such dyes and pigments, 1
For example, carbon black, nigrosine dye, lamp black, Sudan black SM, first yellow G,
Benzidine Yellow, Pigment Yellow, India First Orange, Irgadine Red, Valanitroaniline Red, Toluidine Fist Red, Carmine FB
, Permanent Bordeaux FRR.

Pigment Orange R, Resole Red 2G,
Lake Red C, Rhodamine FB.

Roguemi 7B Lake, Methyl Violet B Lake,
Phthalocyanine Blue, Pigment Blue, Brilliant Green B, Phthalocyanine Green, Oil Yellow GG, Zapon First Niro CGG, Kayaset Y963, Kayaset YG, Sumiplast J20-0G, Zapon First Orange RR, Oil Scarlet, Sumi Plast Orange G, Orazole War Brown B, Pomegranate First Scarlet CG, Eizen Spiron Fist Red BEH, Oil Pink OP, etc. can be applied.

In order to use the toner as a magnetic toner, it may contain magnetic powder. Such magnetic powder uses materials that become magnetized when placed in a magnetic field, such as iron, cobalt,
These include powders of ferromagnetic metals such as nickel, or alloys and compounds such as magnetite, hematite, and ferrite. The content of this magnetic powder is 15 to 70% based on the weight of the toner.
Good weight percentage.

Next, one aspect of the present invention will be explained in detail.

After melt-kneading a mixture consisting of a binder resin and a colorant, the mixture is dispersed with stirring into a dispersion medium to which a dispersant has been added;
Continue stirring until the desired particle size is achieved. At this time, the preferred temperature range of the dispersion liquid is 70 to 120°C. When water is used as the dispersion medium, a temperature of 100°C or higher can be obtained by applying pressure.

At temperatures below 70°C, the viscosity of the molten mixture increases, making it difficult to granulate it by stirring. Even at a temperature of 120°C or higher, no improvement in granulation properties or advantages as a toner was observed.
In addition, there is a risk that the melt-kneaded product itself may change in quality, and furthermore, energy consumption during granulation becomes excessive, which is unfavorable in terms of production efficiency.

Thereafter, the dispersion is heated to -0.1°C or above, preferably -0.
Quenched material particles are obtained at a cooling rate of 2 to −20° C./sec. Methods for rapid cooling at a cooling rate of -0.1"C or higher include spraying the dispersion medium and core material particles into cold air, or removing only the core material particles and placing them in cold water. .

A method in which both the dispersion medium and the core material particles are introduced into water is preferred because of the simplicity of the production process.

The preferred temperature range of the dispersion after cooling is -10 to 50°C.
It is. If the temperature is 50° C. or higher, the core particles are not sufficiently solidified, which is not preferable for the properties of the obtained toner. -1
There is no improvement in toner properties by lowering the temperature to below 0°C, and on the contrary, energy consumption for cooling becomes excessive.
Unfavorable in terms of production efficiency.

If the method is to put it in water, it is then filtered.

After drying, the core material particles are taken out in powder form. A shell material can be provided around the core material particles taken out as a powder by a known method, for example, by a spray drying method.

In-liquid drying method, phase separation method from organic solution system, and 1ns
In order to provide the toner of the present invention with insulation properties and appropriate triboelectric properties, a multilayer shell structure may be provided.

Example Next, the present invention will be explained with reference to Examples.

Carnauba wax 40 parts by weight Polyethylene wax 201 parts (average molecular weight 700) Paraffin wax 40ffiffiff
l (viscosity 13 cps at 100°C) Magnetic material 80
Part by weight: 0.5 parts by weight of Duomin T (hydrophobic amine manufactured by Lion Armour) (Silica manufactured by Nippon Aerosil Co., Ltd.) 60
g in water at 97°C, stirred with an Ajihomo mixer (manufactured by Tokushu Kika Kogyo), and measured with a Coulter counter. When the volume average particle diameter reached 10.5 gm, stirring was stopped at 97°C. An aqueous dispersion of toner particles was put into a 6041 container containing 30 kg of ice and rapidly cooled. The particle size distribution of the toner particles after quenching was measured using a Coulter counter, and it was found that the volume average particle size was 12 l, indicating that no aggregation occurred during cooling.

At this time, it took 70 seconds for the aqueous dispersion at 97° C. to reach 40″C, and the quenching rate was 0.71″0/see.

The kneaded product has a viscosity of 8 poise at a shear rate of 10 sec-t at 120°C, and a shear rate of 0.55 ec-t.
The viscosity at the time of 1 was 60 poise.

After filtration, water washing, and drying, a developer was prepared by mixing 0.4 wt % of Nibsil E (silica manufactured by Nippon Silica) per Ikg of toner. When I put toner in the developing section of a PC-30 (Canon pressure fixing copying machine) and ran it for 5000 copies, the initial image density was 1.50.The image density after the 5000th copy was 1.52. There was no change in density, and when the top of the developing sleeve and drum after 5,000 sheets were observed, no fused toner was found. Also, the offset property of the toner with respect to the fixing roller was observed, and there was no offset to the roller.

The cooling rate after granulation of the core material particles of Example 1 was 0.014°C.
Suspension granulation was carried out in the same manner as in Example 1 except that the temperature was changed to /s 6 C.

The particle size distribution after cooling was measured with a Coulter counter and showed a volume average particle size of 13.5IL, indicating that aggregation occurred during the cooling process. As in Example 1, this toner was put into the developing device of PC-30 and subjected to durability for 5,000 sheets. The initial image density was 1.48, and the 5,000th sheet was 1.49, with no change in image density. However, from around the 4000th sheet, 6 to 8 dot-like stains were observed on the image, which appeared to be the result of toner being fused onto the drum. After the drum had been used for 5,000 sheets, the drum was taken out and its surface was observed, and 10 to 20 pieces of toner were found to be fused to the edges of the drum.

lOg of the toner of Example 1 and the toner of Comparative Example 1, respectively.
A comparison of the toners after placing the toner in a 50cc bead force and leaving it in a dryer at 50°C for one month revealed that the toner of Example 1 flowed out just by tilting the bee force, but the toner of Comparative Example 1 had no bee force. It didn't flow unless I hit it and gave it some vibration.

Bo'J ethylene wax 40 parts by weight (average molecular weight 1500) Paraffin wax 60 parts by weight ff1 (10 parts by weight)
Viscosity at 0°C 13 cps) Phthalocyanine Blue 5 ffi fa
0.5 parts by weight of Duomin T (hydrophobic amine manufactured by Lion Armor) The above mixture was melt-kneaded at 120°C for 2 hours in an attritor, and 7 kg of Erosyl 20 was added to the molten state at 120°C.
9 in which 30g of 0 (silica manufactured by Nippon Aerosil Co., Ltd.) was dispersed.
5℃ water 20! Disperse granulation in L using an Ajihomo mixer (Tokushu Kika Kogyo type), stop stirring when the particle size reaches 11.5 gm, and pour the above toner into a 60M container containing 30Kg of ice. A 95°C aqueous dispersion containing particles dispersed therein was charged. 8 by the time the aqueous dispersion at 95°C reaches 45°C.
The quenching rate was 0.63°C/sec. When the particle size distribution after cooling was determined by ΔI11, it was found that no agglomeration occurred during the cooling process at 11.9 l. Shear rate of the kneaded product at 120°C: 10 sec-1
The viscosity at 1 kg was 5 poise, and the viscosity at 0.5 sec was 40 poise. It was used as an externally added developer. The initial image density was 1.30 when toner was put into the color developing section of the PC-30 and the durability was used for 2000 sheets.
After running 2000 sheets, the image density was 1.28 and there was no change in image density.

When the drum ball on the developing sleeve was observed after 2,000 sheets had been used, no toner fusion was observed.

Further, no offset of toner to the fixing roller was observed.

The cooling rate of the core material after suspension granulation in Example 2 was 0.02°C.
Pelletization was carried out in the same manner as in Example 2 except that the particle size was changed to /sec. When the particle size distribution after granulation was measured, it was found that aggregation occurred at a volume average particle diameter of 14.2 ILm. .

As in Example 2, the image density was 1.25 at the initial stage and 1.20 after 2000, and there was no change in the image density during the durability. In addition, no fused toner was observed on the drum surface after 2,000 sheets of printing, but there was a 0.5 m fused substance at the end of the developing sleeve along the circumferential direction of the sleeve.
A toner fused area with a width of m was observed.

Claims (1)

[Claims] (1) Melt viscosity at 120°C is 1 to 100 pois
A kneaded material containing a binder resin and a coloring agent is molten and granulated in a liquid medium to form toner particles, and the formed toner particles are cooled at a cooling rate of -0.1° C./sec or more. A method for producing a toner for developing an electrostatic image, characterized by rapid cooling.