JPH0812481B2 - Toner binder for electrophotography - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrophotographic toner binder, and more particularly to an electrophotographic toner binder suitable for a heat fixing type copying machine or printer having excellent fixing properties.

[Prior Art] Conventionally, as an image forming method in an electrophotographic method, a photoconductor drum is generally used as an image carrier, an electric latent image is formed on the photoconductor by various means, and then developed with toner. However, there is a method of transferring the toner image to a transfer agent such as paper and fixing the toner image by heating or pressure as required, and a copy is obtained by this method. As a fixing method of a toner image, a so-called thermal roll fixing method in which heat and pressure are applied at the same time is widely adopted at present. this is,
This is a method of fixing the toner image on the image receiving sheet by bringing the image receiving sheet carrying the toner image into contact with a heated roller. In recent years, as the copying work becomes more efficient and energy is saved, fixing at a lower temperature has come to be attempted. On the other hand, when the roll temperature rises, a phenomenon (hot offset) in which the toner is fused to the roll appears. This hot offset temperature is desired to be high. In order to satisfy these two characteristics, a styrene-acrylic resin or a styrene-butadiene resin obtained by emulsion polymerization or suspension polymerization using an inorganic dispersant has conventionally been used as a toner binder for electrophotography. It has been proposed (for example, Japanese Patent Publication No. 57-12147).

[Problems to be Solved by the Invention] However, the electrophotographic toner binder made of a styrene-butadiene resin used in these methods has a problem that a sufficient fixing lower limit temperature and hot offset temperature cannot be obtained.

[Means for Solving the Problems] The present inventors have arrived at the present invention as a result of earnestly examining an electrophotographic toner binder having a fixing lower limit temperature and a hot offset temperature. That is, the present invention has a styrene-butadiene resin or a styrene-butadiene resin and an isotactic content of 75 as a release agent.
% Polypropylene resin with a melt viscosity of 1000 cps or less at 160 ℃, glass transition point of 45 ℃ or more, 65
℃ or less, the apparent viscosity by flow tester is 10 ⁴
Poise temperature is 100 ℃ or more, 130 ℃ or less, Mw / Mn is 2
The toner binder for electrophotography is characterized in that it is 5 or more and less than 5.

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

Examples of the styrene-based monomer include styrene and alkyl styrene (eg, α-methyl styrene, p-methyl styrene). Of these, styrene is preferred.

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

Other monomers include (meth) acrylic acid ester-based 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, (vinyl ethyl Ether, etc.) Aliphatic hydrocarbon vinyl (α-olefin, isoprene, etc.), vinyl compound containing nitrile group [(meth) acrylonitrile, etc.], N-vinyl compound (N-vinylpyrrolidone, etc.), unsaturated carboxylic acid or its anhydride [(Meth) acrylic acid, maleic anhydride, itaconic anhydride, etc.] and mixtures of two or more of these. Further, a small amount of a crosslinkable monomer having two or more polymerizable functional groups in the molecule (divinylbenzene, ethylene glycol diacrylate, etc.) can be used.

The content of styrene-based monomer is usually 70% or more, 95% or less, preferably 80% or more, 92% based on the weight of all monomers.
It is the following. The butadiene content is usually 3% or more and 20% or less, preferably 8% or more, 15% or more based on the weight of all monomers.
% Or less. If it is less than 3%, a sufficient lower limit fixing temperature may not be obtained when used as a toner binder for electrophotography. If it exceeds 20%, when it is used as an electrophotographic toner,
If stored for a long time, the toner will block,
In some cases, it cannot be supplied to the developing machine of the copying machine.

Content of other monomers is usually based on the weight of all monomers
It is 15% or less, preferably 10% or less. The content of the crosslinkable monomer is usually 3% or less based on the weight of all the monomers.

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

As a method of suspension polymerization, for example, after completely dissolving a water-soluble organic dispersant in water, the above-mentioned monomer, water-soluble organic dispersant, polymerization initiator, other surfactants if necessary, water-soluble inorganic compounds, A method in which a chain transfer agent or the like is added and polymerization is performed can be mentioned.

Water-soluble organic dispersants include starch, gelatin, acrylamide, partially saponified polyvinyl alcohol, partially saponified polymethylmethacrylate, polyacrylic acid and its salts, cellulose, ether cellulose (methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, etc.), polyalkylene. Examples thereof include oxide, polyvinylpyrrolidone, polyvinylimidazole, sulfonated polystyrene and the like. Of these, partially saponified polyvinyl alcohol is preferable.

If necessary, an inorganic dispersant can be used together with the organic dispersant. Examples of this inorganic dispersant include calcium phosphate.

As a polymerization initiator, a radical polymerization initiator having a decomposition temperature of 50 to 155 ° C. for obtaining a 10-hour half-life and soluble in styrene, for example, an azo-based initiator (azobisisobutyronitrile, azobisisovalero). Nitrile etc.), peroxide-based initiator [benzoyl peroxide, t-butyl peroxyisopropyl carbonate, lauroyl peroxide, di-t-butyl peroxide, t-butyl cumyl peroxide, dicumyl peroxide, t-butyl Peroxybenzoate, 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, etc.] or a mixture of two or more thereof.

Examples of the surfactant include higher fatty acid salts such as sodium oleate, higher alcohol sulfate salts such as sodium lauryl sulfate and ammonium lauryl sulfate, alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, and naphthalenesulfonate. . Of these, alkylbenzene sulfonate is preferable.

Examples of the water-soluble inorganic compound include salting-out agents such as sodium chloride and calcium chloride, radical polymerization inhibitors such as nitrates, and weak alkaline inorganic salts such as calcium hydrogencarbonate for removing the residue of the polymerization initiator.

As the chain transfer agent, a known chain transfer agent having a chain transfer constant for styrene at 110 ° C. of 5 × _{10 −3} to 1 × _{10 −2} , for example, 2,4-diphenyl 1-pentene can be used.

The amount of the above components used is usually 0.1 to 100 parts, preferably 1 to 50 parts, based on 1000 parts by weight of the water-soluble organic dispersant. Even when the organic dispersant is less than 0.1, the stability of the droplets can be maintained by using the inorganic dispersant. Also, the monomer content is 50-70 for 1000 parts of water.
0 part, 0.1 part or less of a surfactant, a polymerization initiator is a monomer 100
The amount is 0.01 to 20 parts, preferably 0.05 to 10 parts.

Polymerization is performed by sealing the above raw materials under an inert gas atmosphere, stirring conditions (usually 50 to 300 rpm), temperature (usually 40 to 140 rpm).
C., preferably 60 to 100.degree. C.) for 3 to 50 hours. After completion of the polymerization, the particles obtained by cooling are washed with water to obtain the styrene-butadiene resin according to the present invention.

Examples of the solution polymerization method include a method in which a polymerization initiator is dissolved in the following monomer and the polymerization is carried out while dropping it in an organic solvent.

The type and amount of the monomer and the polymerization initiator can be handled in the same manner as in the suspension polymerization.

Examples of the organic solvent that dissolves the monomer include toluene and xylene. The amount is 10
1000 to 2000 parts by weight can be used with respect to 0 parts by weight.

For the polymerization, the above organic solvent is usually put in Kolben, and the temperature is usually kept at 70 to 120 ° C. and the stirring speed is kept at 50 to 300 rpm. Next, polymerization can be performed while dropping the monomer in which the polymerization initiator is dissolved in a dropping funnel. Polymerization is usually 3-50
Do on time. The glass transition point of the electrophotographic toner binder according to the present invention is 45 ° C. or higher and 65 ° C. or lower. If the glass transition temperature is lower than 45 ° C, aggregation blocking tends to occur when stored for a long period of time, and if the glass transition temperature exceeds 65 ° C, the lower limit fixing temperature is insufficient.

The temperature at which the apparent viscosity of the electrophotographic toner binder according to the present invention by the flow tester becomes ₁₀₄ poise is 100 ° C.
The temperature is 130 ° C or lower, preferably 105 ° C or higher and 120 ° C or lower. If it is less than 100 ° C, a sufficient hot offset temperature cannot be obtained, and if it exceeds 130 ° C, a sufficient lower limit fixing temperature cannot be obtained. The temperature at which the apparent viscosity is 10 ⁴ poise is 10 kg / cm ² with a flow tester, 1 mm x 1 mm orifice,
It is the value obtained by measuring the viscosity at a temperature rising rate of 6 ° C./min and reading the temperature at which the apparent viscosity becomes 10 ⁴ poise. A Shimadzu CFT-500 type can be used as the flow tester.

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

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

Isotactic content of the polypropylene resin used in the present invention is determined by the following formula from the absorbance of 998 ^-1 in an infrared spectrophotometer (D ₉₉₃₎ and absorbance at 974cm ^-1 (D _974).

Isotactic content (%) = D ₉₉₃ / D ₉₇₄ × 100 The melting temperature of the polypropylene resin used in the present invention at 160 ° C. is 1000 cps or less, preferably 500 cos. If the melt viscosity at 160 ° C. exceeds 1000 cps, a sufficient hot offset temperature may not be obtained when used as an electrophotographic toner. Polypropylene resin 16
The melt viscosity at 0 ° C. is measured using a Brookfield type rotational viscometer. Conditions other than measurement temperature are JIS-K1557
-1970 An oil bath with a temperature regulator is used to adjust the temperature of the measurement sample. The content of the polypropylene resin is usually 300 parts by weight or less, preferably 100 parts by weight or less, relative to 1000 parts by weight of the styrene-butadiene resin.

The production method of the polypropylene resin is not particularly limited, but for example, 1) the isotactic content is 75
% Or more by thermal degradation of high molecular weight polypropylene resin 2) by low polymerization of propylene (propylene polymer) 3) Thermal degradation of high molecular weight polypropylene resin or maleic propylene polymer Acid derivatives (maleic anhydride, maleic acid dimethyl ester, maleic acid diethyl ester, maleic acid di-2-
Ethylhexyl ester etc.) adduct, thermal degradation product of high molecular weight polypropylene resin or oxide of propylene polymer, 4) Thermal degradation product of high molecular weight polypropylene resin or grafting of propylene polymer with styrene monomer Modified products can also be used. Of these, the one obtained by thermal degradation of the high molecular polypropylene resin of 1) is preferable from the viewpoint of easy production.

The styrene-butadiene-based resin may be added to the polypropylene-based resin at the time of toner production, premixed with the styrene-butadiene-based resin, or added at the time of styrene-butadiene-based monomer polymerization. The electrophotographic toner binder of the present invention may contain a colorant, if necessary.
Further, various additives and the like can be blended to obtain an electrophotographic toner.

Examples of the colorant include carbon, iron black, benzidine yellow, quinacdrine, rhodamine B and phthalocyanine. As a magnetic powder, a powder of a ferromagnetic metal such as iron, cobalt, nickel or magnetite, hematite, ferrite or the like may be used together with the colorant.

Further, as various additives, a charge adjusting agent (nigrosine, quaternary ammonium salt, etc.) and the like can be mentioned.

As a component of the electrophotographic toner, the binder for electrophotographic toner of the present invention is usually 45 to 95% by weight, preferably 70 to
90% by weight, usually 3 to 50% by weight of colorant, and 10% by weight or less of various other additives are used. The production of the electrophotographic toner binder is not particularly limited, but 1)
After dry blending the components of the toner, melt-kneading and coarsely pulverizing, finally finely pulverizing with a jet pulverizer, further classifying to obtain fine powder having a particle size of 2 to 20 μ,
2) It is also possible to make the styrene-butadiene-based resin into a powder having a particle size of 20 μm or less and to fuse other toner components to the surface thereof.

The photographic toner is mixed with carrier particles such as iron powder, glass beads, nickel powder, and ferrite, if necessary, and used as a developer for an electric diving image. In addition, hydrophobic colloidal silica fine powder can be used for improving the fluidity of the powder.

The toner for electrophotography is fixed on a transfer agent (paper, polyester film, etc.) by being heated by a heat fixing heat roll section of a copying machine such as a heat fixing type copying machine or a printer, and used as a recording material.

[Examples] Hereinafter, the present invention will be further described with reference to Examples, but the present invention is not limited thereto. In the examples, all parts are parts by weight.

Example 1 Mixture of 900 parts styrene and 100 parts butadiene with 50 parts benzoyl peroxide and 2,4-diphenyl 1-
50 parts of pentene was dispersed in 2700 parts of an aqueous solution containing 50 parts of calcium phosphate and 0.5 part of alkylbenzene sulfonate in a pressure autoclave, and polymerization was carried out at 80 to 95 ° C for 2 hours. After filtering the pearl resin obtained by polymerization,
It was treated with dilute nitric acid and washed with deionized water. As a result, a styrene-butadiene-based resin having a glass transition temperature of 55 ° C., an apparent viscosity of 10 ⁴ poises of 110 ° C. and an Mw / Mn of 3 was obtained. This is used as the electrophotographic toner binder of the present invention.

Example 2 A mixture of 920 parts of styrene, 80 parts of butadiene and 10 parts of a polypropylene resin (isotactic content 85%, melt viscosity at 160 ° C. 100 cps), 50 parts of benzoyl peroxide and 5 parts of calcium hydrogen carbonate were used. Polymerized in the same manner as 1. The pearl-like resin obtained by the polymerization was filtered and then washed with ion-exchanged water. This gives a glass transition temperature of 60 ° C and an apparent viscosity of 10 ⁴ poise at 125 ° C.
A composition comprising a styrene-butadiene-based resin and a polypropylene-based resin having an 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 placed in a dropping funnel. Autoclave containing 200 parts of xylene at 120 ℃, stirring speed 20
The rate was maintained at 0 rpm, and the monomer and the polymerization initiator in the dropping funnel were added dropwise thereto over 2 hours. Polymerization was further performed for 1 hour, and the product was taken out and topped with xylene. As a result, a composition comprising a styrene-butadiene resin and a polypropylene resin having a glass transition temperature of 50 ° C., an apparent viscosity of 10 ⁴ poise and a temperature of 110 ° C. and an Mw / Mn of 4 was obtained. 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 benzoyl 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 pressure autoclave and polymerized at 60 to 85 ° C. for 6 hours. I did. The pearl-like resin obtained by the polymerization was filtered, treated with dilute nitric acid, and washed with deionized water. As a result, a styrene-butadiene-based resin having a glass transition temperature of 60 ° C., an apparent viscosity of 10 ⁴ poises of 135 ° C. and an Mw / Mn of 4 was obtained. This is used as a comparative electrophotographic toner binder.

Comparative Example 2 A mixture of 700 parts of styrene and 300 parts of butadiene and 50 parts of benzoyl 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 pressure autoclave and polymerized at 80 to 95 ° C for 2 hours. Was done. The pearl-like resin obtained by the polymerization was filtered, treated with dilute nitric acid, and washed with deionized water. As a result, a styrene-butadiene resin having a glass transition temperature of 35 ° C., an apparent viscosity of 10 ⁴ poises of 105 ° C. and an Mw / Mn of 7 was obtained. This is used as a comparative electrophotographic toner binder.

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

Toner preparation method Toner binder for electrophotography 87 parts Polypropylene resin 4 parts (Viscole 660P manufactured by Sanyo Kasei Co., Ltd.) (isotactic content 86%) (melt viscosity at 160 ° C 70 cps) Carbon black 8 parts (Mitsubishi Chemical Industries MA-100 Co., Ltd. Charge control agent 1 part (Hodogaya Chemical Co., Ltd. spiron black TRH) The above compound was powder blended and then kneaded with a Labo Plastomill at 140 ° C. and 30 rpm for 10 minutes. Jet mill kneaded material
Pulverized with PJM100 (manufactured by Nippon Pneumatic). Fine powder of 2 μm or less was cut from the finely pulverized material using a powder air classifier MSD (manufactured by Nippon Pneumatic). 1000 parts of the obtained powder was uniformly mixed with 3 parts of Aerosil R972 (Japan Aerosil) to obtain an electrophotographic toner.

Method for preparing developer A developer was obtained by mixing 25 parts of the above toner with 1000 parts of iron powder for electrophotography (F-100 manufactured by Nippon Iron Powder Co., Ltd.).

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,
In the same manner as in Reference Example 1, the developers of Reference Examples 2 and 3 and Comparative Reference Examples 1 and 2 were obtained. Table 1 shows the evaluation results of each developer.

Lower limit of fixing Using a commercially available heat fixing type copying machine, evaluation was carried out at the temperature of a heat roll having a residual rate of 40% due to cellophane tape peeling.

E Less than 120 ° C. G 120 ° C. or more but less than 140 ° C. P 140 ° C. or more Hot offset resistance A commercially available thermal fixing type copying machine was used and evaluated by the temperature of the heat roll at which hot offset occurs.

E 200 ° C. or higher G 180 ° C. or higher but lower than 200 ° C. P lower than 180 ° C. The electrophotographic toner containing the electrophotographic toner binder of the present invention has not only a low lower limit fixing temperature but also excellent hot offset resistance. Was confirmed.

In the present invention, the measurement of Mw / Mn is a patent application (1) filed by the applicant on November 14, 1989.
It was carried out by the method described in Production Example 1 of the title "Release agent for electrophotographic toner" of the invention.

[Advantages of the Invention] When the electrophotographic toner binder of the present invention is used as an electrophotographic toner containing the same, it is excellent not only in fixability but also in hot offset resistance, and its utility is extremely high.

Claims (2)

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