JPH03166554A - Electrophotographic toner binder - Google Patents

Abstract

PURPOSE:To obtain a sufficiently lower limit of a fixing temperature and the lower limit of hot offset temperature by using a styrene-butadiene resin specified in each of glass transition point, melt viscosity, and molecular weight distribution. CONSTITUTION:The toner binder comprises the styrene-butadiene resin or the styrene-butadiene resin and as a releasing agent, a polypropylene resin containing an isotactic type in an amount of >=75 % and having a melt viscosity of <=1000 cps at 160 deg.C, and the binder has a glass transition point of 45-65 deg.C, and a 10<4> poise apparent viscosity temperature of 100-130 deg.C measured by a flow tester, and an Mw/Mn of 2-5, thus permitting the obtained electrophotographic toner binder to be not only superior in fixability but also in hot offset resistance and usability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a toner binder for electrophotography, and particularly to a toner binder for electrophotography that has excellent fixing properties and is suitable for a heat-fixing type copying machine or printer.

[Prior Art] Conventionally, as an image forming method in electrophotography, a photoreceptor drum is generally used as an image carrier, and after forming an electric latent image on the photoreceptor by various means, a toner is used to form an image. There is a method of developing the toner image, transferring it to a transfer agent such as paper as necessary, and fixing the toner image by heating or pressure. Copies are obtained by this method. Currently, a so-called hot roll fixing method, in which heat and pressure are applied simultaneously, is widely used as a method for fixing toner images. This is a method of fixing the toner image onto the image receiving sheet by bringing the image receiving sheet carrying the toner image into contact with a heated roller. In recent years, with improvements in the efficiency and energy saving of copying operations, it has become desirable to fix images at lower temperatures. On the other hand, when the roll temperature increases, the toner fuses to the roll (hot offset).
appears.

It is desirable that this hot offset temperature be high. In order to satisfy these two characteristics, styrene-acrylic or styrene-butadiene resins obtained by emulsion polymerization or suspension polymerization using an inorganic dispersant have traditionally been used in electrophotographic toner binders. It has been proposed (for example, Japanese Patent Publication No. 12147/1983).

[Problems to be Solved by the Invention] However, the electrophotographic toner binder made of styrene-butadiene resin used in these methods has problems such as insufficient fixing minimum temperature and hot offset temperature.

[Means for Solving the Problems] The present inventors have arrived at the present invention as a result of extensive research into toner binders for electrophotography that have a sufficient minimum fixing temperature and hot offset temperature. That is, the present invention uses a styrene-butadiene resin or a styrene-butadiene resin with an isotactic content of 75% as a mold release agent.
% or more, the melt viscosity at 180°C is 1000 cps or less, and the glass transition point is 4.
5℃ or higher and 65℃ or lower, and the temperature at which the apparent viscosity measured by a flow tester is 104 poise is 100℃ or higher, 1
The toner binder for electrophotography is characterized in that the temperature is 30° C. or lower and Mw/Mn is 2 or more and 5 or less.

Examples of the styrene-butadiene resin include resins made from styrene monomers, butadiene monomers, and other monomers if necessary.

Styrene monomers include styrene, alkylstyrene (e.g. α-methylstyrene, p-methylstyrene)
etc. Among these, styrene is preferred.

Examples of the butadiene monomer include 1,3-butadiene.

Other monomers include (meth)acrylic acid ester monomers [alkyl (meth)acrylates (alkyl groups having 1 to 18 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meta)
Acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, and stearyl (
(meth)acrylate), hydroxyl group-containing (meth)acrylate (hydroxylethyl (meth)acrylate, etc.), amino group-containing (meth)acrylate (dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, etc.)], vinyl ester (vinyl acetate, etc.), vinyl ether, (vinylethyl ether, etc.), aliphatic hydrocarbon vinyl (α-olefin, isoprene, etc.), nitrile group-containing vinyl compounds [(meth)acrylonitrile, etc.], N-vinyl compounds (N- vinylpyrrolidone, etc.), unsaturated carboxylic acids or their anhydrides [
(meth)acrylic acid, maleic anhydride, itaconic anhydride, etc.] and mixtures of two or more of these. Further, a small amount of a crosslinkable monomer (divinylbenzene, ethylene glycol diacrylate, etc.) having two or more polymerizable functional groups in the molecule can also be used.

The content of the styrenic monomer is usually 70% or more and 95% or less, preferably 80% or more, based on the weight of the total monomers.
It is 92% or less. The butadiene content is usually 3% or more and 20% or less, preferably 8% based on the weight of all monomers.
Above, it is 15% or less. If it is less than 3%, a sufficient minimum fixing temperature may not be obtained when used as a toner binder for electrophotography. If it exceeds 20%, the toner may block when stored for a long period of time when used as an electrophotographic toner, and may not be able to be supplied to the developing machine of a copying machine.

The content of other monomers is usually 1% based on the weight of total monomers.
It is 5% or less, preferably 10% or less. The content of crosslinkable monomers is usually 3% or less, based on the weight of total monomers.

The styrene-butadiene resin can be obtained by known radical polymerization of a styrene monomer, a butadiene monomer, and, if necessary, other monomers, such as suspension polymerization or solution polymerization.

As a suspension polymerization method, for example, after completely dissolving a water-soluble organic dispersant in water, the above monomers, a water-soluble organic dispersant,
Examples include a method of adding a polymerization initiator and, if necessary, a surfactant, a water-soluble inorganic compound, a chain transfer agent, etc., and polymerizing.

Water-soluble organic dispersants include starch, gelatin, acrylamide, partially saponified polyvinyl alcohol, partially saponified polymethyl methacrylate, polyacrylic acid and its salts, cellulose, ether cellulose (methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, etc.), polyalkylene oxide, polyvinylpyrrolidone,
Examples include polyvinylimidazole and sulfonated polystyrene. Among these, partially saponified polyvinyl alcohol is preferred.

In addition to the organic dispersant, an inorganic dispersant can also be used if necessary. Examples of the inorganic dispersant include calcium phosphate.

Examples of polymerization initiators include radical polymerization initiators that have a decomposition temperature of 50 to 155°C to obtain a half-life of 10 hours and are soluble in styrene, such as azo initiators (azobisisobutyronitrile, azobisisovalero (nitrile, etc.), peroxide-based initiators [penzoyl peroxide, t-butyl peroxy isopyl carbonate, lauroyl peroxide, di-t-butyl peroxide, t-butyl cumyl peroxide, dicumyl peroxide, t-butyl peroxide, -butylperoxybenzoate, 1,1-bis(t-butylperoxy) 3,3,5-trimethylcyclohexane, and the like, or a mixture of two or more thereof can be mentioned.

Examples of the surfactant include higher fatty acid salts such as sodium oleate, higher alcohol sulfate ester salts such as sodium lauryl sulfate and ammonium lauryl sulfate, alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, and naphthalene sulfonates. . Among these, preferred are alkylbenzene sulfonates.

Examples of water-soluble inorganic compounds include salting-out agents such as sodium chloride and calcium chloride, radical polymerization inhibitors such as nitrates, and weakly alkaline inorganic salts such as calcium hydrogen carbonate to remove residual polymerization initiator liquid. be able to.

As a chain transfer agent, the chain transfer constant for styrene at 110°C is 5X10-3 to IX10-''
Known chain transfer agents such as 2,4-diphenyl-1-pentene can be used.

The amount of the above component used is usually 0.1 to 100 parts of the water-soluble organic dispersant per 1000 parts of water, based on the weight.
Preferably it is 1 to 50 parts. This organic dispersant is 0.1
Even if the amount is less than 1, the stability of the droplets can be maintained by using an inorganic dispersant. In addition, the monomer is water 100
The amount of surfactant is 0.1 part or less, and the polymerization initiator is 0.0 parts per 100 parts of monomer. Ol~20
parts, preferably 0.05 to 10 parts.

Polymerization is carried out by sealing the above raw materials under an inert gas atmosphere, stirring conditions (usually 50 to 300 rpm), and temperature (usually
40~140℃, preferably 60~100℃), 3~
Do it for 50 hours. After the polymerization is completed, the styrene-butadiene resin according to the present invention can be obtained by cooling and washing the obtained particles with water.

Examples of the solution polymerization method include a method in which a polymerization initiator is dissolved in the following monomer, and the solution is polymerized while being dropped into an organic solvent.

The types and amounts of monomers and polymerization initiators can be handled in the same manner as in the case of suspension polymerization.

Examples of organic solvents that dissolve monomers include toluene and xylene. The amount is monomer 10
It can be used in an amount of 1,000 to 2,000 parts by weight relative to 0 parts by weight.

For polymerization, the above-mentioned organic solvent is usually placed in a colben, and the temperature is generally maintained at 70 to 120° C. and the stirring speed is maintained at 50 to 300 rpm. Next, in a dropping funnel, polymerization is carried out while dropping the monomer in which the polymerization initiator has been dissolved.The glass transition point is 45°C.
The temperature is above 65°C. If the glass transition temperature is less than 45°C, agglomeration and blocking are likely to occur when stored for a long period of time, and if the glass transition temperature exceeds 65°C, the lower limit temperature for fixing is insufficient. ℃ or lower, preferably 105℃ or higher and 120℃ or lower. If it is less than 100℃, a sufficient hot offset temperature cannot be obtained, and if it is less than 130℃
If it exceeds this temperature, a sufficient minimum fixing temperature cannot be obtained. The temperature at which the apparent viscosity is 10' poise is determined using a flow tester at a load of 10 kg/cm", orifice of 1 mm,
, The viscosity was measured at a heating rate of 6°C/min, and the apparent viscosity was 10'
This is the read value of the temperature that becomes a poise. As the flow tester, CFT-500 model manufactured by Shimadzu Corporation can be used.

The sum/Mn of the styrene-butadiene resin according to the present invention is 2 or more and 5 or less. When Mw/Mn exceeds 5, sufficient lower limit fixing temperature and hot offset temperature cannot be obtained when used as toner.

The electrophotographic toner binder of the present invention may contain a polypropylene resin having an isotactic content of 75% or more and a melt viscosity of 1000 cps or less at 160° C. as a mold release agent.

If the isotactic content is less than 75%, the fluidity of the toner decreases when used as a toner binder for electrophotography, and the toner may not be supplied to the developing machine.

The isotactic content of the polypropylene resin used in the present invention is 998 cm −1 as measured by an infrared spectrophotometer.
It is determined by the following formula from the absorbance at (D993) and the absorbance at 974 cm -1 (D974).

Isotactic content (%) ”D993 / D974
It is 0 cps or less. Melt viscosity at 180°C is 10
If the temperature exceeds 0.00 cps, a sufficient hot offset temperature may not be obtained when used in an electrophotographic toner. The melt viscosity of the polypropylene resin at 160° C. is measured using a Pruckfield rotational viscometer. Conditions other than the measurement temperature are based on JIS-K1557-1970.

An oil bath with a temperature regulator is used to adjust the temperature of the measurement sample. The content of polypropylene resin is usually 30 parts by weight per 1000 parts by weight of styrene-butadiene resin.
It is 0 parts by weight or less, preferably 100 parts by weight or less.

The method for producing the above polypropylene resin is not particularly limited, but for example, 1) the isotactic content is 75
2) By underpolymerizing propylene (propylene polymer) 3) Thermal reduction of high molecular weight polypropylene resin or maleic of propylene polymer Acid derivatives (maleic anhydride, dimethyl maleate, diethyl maleate, di-2-ethylhexyl maleate, etc.) adducts, heat-reduced products of high molecular weight polypropylene resins or oxides of propylene polymers, 4) Heat-reduced molecular weight polypropylene resins or grafted modified propylene polymers with styrene monomers can also be used. Among these, 1) one based on heat reduction of a high molecular weight polypropylene resin is preferred from the viewpoint of easy production.

The styrene-butadiene resin can be added to the polypropylene resin during toner production, mixed in advance with the styrene-butadiene resin, or added during polymerization of the styrene-butadiene monomer. . The electrophotographic toner binder of the present invention can be mixed with a colorant and various additives, if necessary, to form an electrophotographic toner.

Coloring agents include carbon, iron black, and benzidine yellow.
Examples include quinacridine, rhodamine B, and phthalocyanine. Powder of ferromagnetic metal such as iron, cobalt, nickel, magnetite, hematite ferrite, etc. may be used as magnetic powder together with the coloring agent.

Furthermore, various additives include charge control agents (nigrosine,
quaternary ammonium salts, etc.).

As a part of the electrophotographic toner, the binder for electrophotographic toner of the present invention is usually 45 to 95% by weight, preferably 7% by weight.
0 to 90% by weight, a coloring agent usually in an amount of 3 to 50% by weight, and various other additives in an amount of IO weight% or less. The production of the toner binder for electrophotography is not particularly limited; l) After dry blending the components of the toner, melt-kneading, coarsely pulverizing, and finally pulverizing using a jet pulverizer. It is also possible to further classify the powder to obtain a fine powder with a particle size of usually 2 to 20μ, or 2) to make the styrene-butadiene resin into a powder with a particle size of 20μ or less, and to fuse the components of other toners to the surface of the powder. .

The electrophotographic toner is mixed with carrier particles such as iron powder, glass beads, nickel powder, ferrite, etc., if necessary, and used as a developer for an electrical latent image. Furthermore, a hydrophobic colloidal silicate fine powder can also be used to improve the fluidity of the powder.

The above-mentioned electrophotographic toner is transferred to a transfer agent (paper, polyester film, etc.) by being heated in a heat-fixing heat roll section of a copying machine, such as a heat-fixing copying machine or a printer.
is fixed and used as recording material.

[Example] The present invention will be further explained with reference to Examples below, but the present invention is not limited thereto.

In the examples, all parts represent parts by weight.

Example 1 A mixture of 900 parts of styrene and 100 parts of butadiene, 50 parts of penzoyl peroxide and 50 parts of 2,4-diphenyl-1-pentene are mixed in a pressurized autoclave with 50 parts of phosphoric acid and 0.0 parts of an alkylbenzene sulfonate. Dispersed in 2700 parts of an aqueous solution containing 5 parts,
Polymerization was carried out at 0-95°C for 2 hours. The pearl-like resin obtained by polymerization was filtered, treated with dilute nitric acid, and washed with ion exchange water. As a result, a styrene-butadiene resin having a glass transition temperature of 55° C., a temperature at which the apparent viscosity becomes 10' poise was 110° C., and a sum/Mn of 3 was obtained.

This is used as the electrophotographic toner binder of the present invention.

Example 2 920 parts of styrene, 80 parts of butadiene and polypropylene resin (isotactic content 85%, 160°C
melt viscosity at 100 cps) with 50 parts of penzoyl peroxide and 5 parts of calcium bicarbonate.
Polymerization was carried out in the same manner as in Example 1. The pearl-like resin obtained by polymerization was filtered and then washed with ion-exchanged water. This results in a glass transition temperature of 60°C and an apparent viscosity of 104
A composition consisting of a styrene-butadiene resin and a polypropylene resin having a poise temperature of 125° C. and a Mw/Mn of 4 was obtained. This is used as the electrophotographic toner binder of the present invention.

Example 3 50 parts of azobisisovaleronitrile was dissolved in 850 parts of styrene and 150 parts of butadiene, and the solution was placed in a dropping funnel. 120 autoclave containing 2000 parts of xylene
℃ and stirring speed of 200 rpm, the monomer and polymerization initiator in the dropping funnel were added dropwise over 2 hours. Polymerization was continued for an additional hour, then taken out and topped with xylene. As a result, the glass transition temperature is 50°C,
A composite consisting of a styrene-butadiene resin and a polypropylene resin was obtained, the temperature at which the apparent viscosity was 104 poise was 110° C., and the ratio Aw/Mn was 4. This is used as the electrophotographic toner binder of the present invention.

Comparative Example 1 900 parts of styrene, 100 parts of butadiene and 10 parts of penzoyl peroxide were dispersed in 2700 parts of an aqueous solution containing 50 parts of calcium phosphate and 0.5 part of alkylbenzene sulfonate in a pressurized autoclave.
Polymerization was carried out at 85°C for 6 hours. The pearl-like resin obtained by polymerization was filtered, treated with dilute nitric acid, and washed with ion-exchanged water. As a result, the temperature at which the glass transition temperature is 60°C and the apparent viscosity is 104 poise is 135°C and Mw/M
A styrene-butadiene resin in which n is 4 was obtained.

Comparative Example 2 Using this as a toner binder for comparative electrophotography A mixture of 700 parts of styrene and 300 parts of butadiene and 50 parts of penzoyl peroxide were placed in a pressurized autoclave in an aqueous solution containing 50 parts of calcium phosphate and 0.5 parts of an alkylbenzene sulfonate. It was dispersed in 2,700 parts and polymerized at 80 to 95°C for 2 hours. The pearl-like resin obtained by polymerization was filtered, treated with dilute nitric acid, and washed with ion-exchanged water. As a result, a styrene-butadiene resin having a glass transition temperature of 35°C, a temperature at which the apparent viscosity becomes 10' poise was 105°C, and an Aw/Mn of 7 was obtained. This was used as a comparative electrophotographic toner binder.

Reference Example 1 Using the electrophotographic toner binder of Example 1, an electrophotographic toner was produced by the following method. Furthermore, an electrophotographic developer was produced.

Toner preparation method Toner binder for electrophotography 87 parts Polypropylene resin 4 parts (Viscol 660P manufactured by Sanyo Chemical Co., Ltd.) (Isotactic content 86%) (Melt viscosity at 160°C 70 cps) Carbon black 8 parts (Mitsubishi Chemical Co., Ltd.) MA-100) Charge control agent manufactured by Kogyo Co., Ltd.
1 part (Spiron Black TRH manufactured by Hodogaya Chemical Industry Co., Ltd.) The above mixture was powder-blended and then kneaded for 10 minutes at 140°C and 30 rpm in a Labo Plastomill, and the mixed material was mixed in a jet mill PJMIOO (Japan Pneumatic Co., Ltd.). The powder was pulverized using Fine powder of 2 μm or less was cut from the finely ground material using a powder air classifier MSD (manufactured by Nippon Pneumatic Co., Ltd.). Aerosil R972 (
A toner for electrophotography was obtained by uniformly mixing 3 parts of Nippon Aerosil).

Method for Preparing Developer 25 parts of the above toner were mixed with iooo parts of carrier iron powder for electrophotography (F-100 manufactured by Nippon Tetsuko Co., Ltd.) to obtain a developer.

Reference Examples 2 and 3, Comparative Reference Examples 1 and 2 Using the electrophotographic compositions of Examples 2 and 3 and Comparative Examples 1 and 2, Reference Examples 2 and 3 and Comparative Examples were prepared in the same manner as in Reference Example 1, respectively. Developers of Reference Examples 1 and 2 were obtained. Table 1 shows the evaluation results for each developer.

Table 1 Developer Evaluation Results Lower Limit of Fixation Using a commercially available heat fixing type copying machine, the evaluation was carried out at a heat roll temperature that gave a residual rate of 40% after peeling off cellophane tape.

E Less than 120°C 0120°C or more and less than 140°C P 140°C or more Hot offset resistance A commercially available heat fixing type copying machine was used, and evaluation was made based on the temperature of the heat roll at which hot offset occurs.

E 200°C or more 0 180°C or more less than 200°C P L less than 80°C The electrophotographic toner containing the electrophotographic toner binder of the present invention not only has a low minimum fixing temperature but also has excellent hot offset resistance. It could be confirmed.

[Effect of the invention]

Claims (1)

[Claims] 1. It is made of styrene-butadiene resin, has a glass transition temperature of 45°C or more and 65°C or less, and has an apparent viscosity of 10^4 poise measured by a flow tester at a temperature of 100°C.
The toner binder for electrophotography is characterized by having a temperature of 130° C. or lower and a weight average molecular weight (Mw)/number average molecular weight (Mn) of 2 or more and 5 or less. 2. Consisting of a styrene-butadiene resin and a polypropylene resin with an isotactic content as a mold release agent of 75% or more and a melt viscosity of 1000 cps or less at 160°C, and a glass transition temperature of 45°C or higher and 65°C or lower. Yes, the temperature at which the apparent viscosity measured by a flow tester is 10^4 poise is 100°C or more and 130°C or less, and the weight average molecular weight (Mw)/number average molecular weight (Mn) is 2 or more and 5 or less. Toner binder for electrophotography.