JPH07287419A - Production of binder resin for electrophotographic toner - Google Patents

Abstract

PURPOSE:To produce a binder resin for a toner excellent in fixability, anti- offsetting property and blocking resistance by bringing a low mol. wt. component into soln. polymn. in a soln. of a high mol. wt. component. CONSTITUTION:When a binder resin for an electrophotographic toner having two or more peaks in gel permeation chromatogram is produced, a low mol. wt. component is brought into soln. polymn. in a soln of a high mol. wt. component. Since this soln. polymn method is adopted, a solvent acts as a chain transfer agent and mol. wt. is easily regulated to the lower mol. wt. side as compared with a seed polymn. method. Since the low and high mol. wt. components form a uniform network at the time of polymn., a more uniform polymer is easily obtd. as compared with a method by which low and high mol. wt. components are separately polymerized and the resultant polymers are blended by a known method. The objective resin having a peak of <=10,000 on the lower mol. wt. side is easily obtd. and a toner contg. the resin as a binder has satisfactory fixability, anti-offsetting property and blocking resistance.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a binder resin for an electrophotographic toner. More specifically, the present invention relates to a method for producing a binder resin having two or more peaks in a gel permeation chromatogram (hereinafter abbreviated as GPC).

[0002]

2. Description of the Related Art A toner for developing an electrostatic image obtained by pulverizing and classifying a binder resin in which a colorant or the like is dispersed is quickly fixed, and the toner is transferred to the surface of a fixing roller. It is necessary that the so-called offset phenomenon, in which the passing transfer material is soiled by the toner on the roller, does not occur. Therefore, it is necessary that the toner melts rapidly at a low temperature during fixing, and that the molten toner exhibits cohesiveness during melting.

Further, the toner is required to exhibit good fluidity without generating fine powder due to mechanical impact due to agitation in the developing device, and without causing aggregation of the toner itself. Should not block during storage or transportation. Such a toner has remarkably deteriorated fluidity and chargeability,
It can no longer function as a developer. It is extremely difficult to design a toner that satisfies all of these performances, and in particular, fixing performance and offset resistance / blocking resistance are contradictory performances, so it is extremely difficult to achieve both performances at the same time. . Therefore, the binder resin, which is the main component of the toner, is required to have delicate hardness and heat melting characteristics.

[0004]

Therefore, many proposals have heretofore been made regarding the molecular weight and the molecular weight distribution of polymers used as binder resins. Among them, a toner using a non-crosslinked vinyl resin having two or more peaks in GPC as disclosed in JP-A-56-16144 as a binder resin has a good balance between fixability, offset resistance and blocking resistance. It is valid. In the production method, a method of dissolving each resin of a low molecular weight component and a high molecular weight component in a common solvent and then evaporating the solvent or a so-called seed polymerization method is proposed, but the former is uniform mixing and evaporation. In phase separation in the process, the latter is problematic in polymerizing low molecular weight components. Particularly in the latter case, it is extremely difficult to polymerize a binder resin having a peak at 10,000 or less in GPC, which makes it difficult to design a binder resin having excellent fixability.

[0005]

Means for Solving the Problems The present inventors have solved the above-mentioned problems by providing a binder resin for an electrophotographic toner having excellent fixability (low temperature fixability, fix strength, etc.), offset resistance and blocking resistance. As a result of extensive studies to provide a production method, it was found that a binder resin having excellent properties can be obtained by solution polymerization of a low molecular weight component in a state where a high molecular weight component is dissolved.

That is, the gist of the present invention is 2 in GPC.
A method for producing a binder resin for an electrophotographic toner having three or more peaks, characterized in that solution polymerization of a low molecular weight component is carried out in a solution in which a high molecular weight component is dissolved. Hereinafter, the present invention will be described in detail.

In the present invention, since the solution polymerization method is used for the polymerization of the low molecular weight component, the solvent acts as a chain transfer agent, and the molecular weight can be easily designed to a lower molecular weight side than the seed polymerization method. Furthermore, since a low molecular weight component and a high molecular weight component form a uniform network during polymerization, a uniform polymer can be obtained more easily than a method in which they are separately polymerized and then blended by a known method. When dissolving the high molecular weight component, the concentration is preferably 5 to 30% by weight, and the concentration is 3
If it is higher than 0% by weight, the high-molecular-weight component swells to make uniform polymerization difficult. On the contrary, if it is lower than 5% by weight, there is no problem in the reaction but a large amount of solvent is consumed, resulting in poor efficiency. The weight average molecular weight of the high molecular weight component is 20.
20,000 to 2,000,000 is preferable, 200,
If it is lower than 000, hot offset tends to occur,
On the contrary, if it is higher than 2,000,000, the solubility in a solvent is lowered, which is not preferable.

On the other hand, the monomer concentration in the solution polymerization of the low molecular weight component is preferably 5 to 80% by weight based on the solvent.
When the monomer concentration is lower than 5% by weight, there is no problem in the reaction but it is not preferable in terms of efficiency. On the contrary, when it is higher than 80% by weight, the heat generation during the polymerization becomes large, and the chain transfer efficiency to the solvent is lowered, resulting in a low molecular weight. There arises a problem that it is difficult to design the molecular weight on the side. The reaction temperature and the reaction time may be appropriately selected depending on the kind and amount of the polymerization initiator, the boiling point of the solvent, and the like, and it is not particularly limited, but the reaction temperature is 30 to 150.
Generally, the reaction time is 3 to 15 hours at 0 ° C. The weight average molecular weight of the obtained low molecular weight component is 1,000 to 1.
It is preferably in the range of 10,000, 10,000
If it is higher, the fixability of the toner is poor, and if it is lower than 1,000, the blocking resistance is deteriorated, which is not preferable.

The method for polymerizing the high molecular weight component to be dissolved and the solvent for dissolving the high molecular weight component are not particularly limited,
Examples of the solvent include ketones such as acetone, ethers such as propylene glycol monomethyl ether, and aromatics such as toluene. For example, suspension polymerization method,
The weight average molecular weight is 20 by a known method such as an emulsion polymerization method.
After polymerizing about 20,000 to 2,000,000 styrene-based resin, the resin is dissolved in a solvent such as acetone or toluene, and styrene or a monomer such as styrene and an acrylic acid ester or a methacrylic acid ester mixture is added, Using a polymerization initiator such as benzoyl peroxide or azoisobisbutyronitrile, a weight average molecular weight of 1,000 to 1
It suffices to solution polymerize 50,000 styrene-based oligomers.

Although the styrene resin has been described above, the present invention can be carried out with other resins. Other resins include vinyl resins including the above styrene resins, phenol resins, natural resin-modified phenol resins, natural resin-modified maleic acid resins, acrylic resins, methacrylic resins, polyvinyl acetate resins, silicone resins, polyester resins, polyurethanes. Resin, polyamide resin, furan resin,
Epoxy resin, xylene resin, polyvinyl butyral resin, terpene resin, coumarone indene resin, petroleum resin and the like can be used.

Particularly, the present invention has a GPC of 10,000.
The present invention solves various problems that occur when a binder resin having one or more peaks is produced below, and is particularly effective when producing the binder resin. Among the above resins, vinyl resin is desirable. The vinyl-based resin is a resin having a structural unit corresponding to a vinyl-based monomer, and as the vinyl-based monomer, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, 2,
4-dimethylstyrene, pn-butylstyrene, p-
tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, p-methoxy styrene, p-phenyl styrene,
3,4-dichlorostyrene, p-chlorostyrene, α-
Styrenes such as methylstyrene; methyl acrylate,
Ethyl acrylate, propyl acrylate, butyl acrylate, octyl acrylate, cyclohexyl acrylate, stearyl acrylate, benzyl acrylate, furfuryl acrylate, hydroxyethyl acrylate, hydroxybutyl acrylate, dimethylaminomethyl acrylate, acrylic acid Dimethylaminoethyl, acrylic acid i
Acrylic acid esters such as so-butyl, lauryl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, tetrahydrofurfuryl acrylate; methyl methacrylate , Ethyl methacrylate, propyl methacrylate, octyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, stearyl methacrylate, benzyl methacrylate,
Furfuryl methacrylate, dimethylaminomethyl methacrylate, dimethylaminoethyl methacrylate, hydroxyethyl methacrylate, hydroxybutyl methacrylate, iso-butyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, phenyl methacrylate, lauryl methacrylate, Methacrylic acid esters such as tetrahydrofurfuryl methacrylate; ethylenically unsaturated monoolefins such as ethylene, propylene, butylene, iso-butylene; vinyl halides such as vinyl chloride, vinyl bromide, vinyl fluoride; vinyl acetate, Vinyl esters such as vinyl propionate; vinyl methyl ether, vinyl ethyl ether, vinyl is
Vinyl ethers such as o-butyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and methyl iso-propenyl ketone; dimethyl fumarate, dibutyl fumarate, dioctyl fumarate, dioctyl maleate, dimethyl maleate, diethyl maleate, Diesters of unsaturated dibasic acids such as dibutyl maleate; monomethyl maleate, monoethyl maleate, monobutyl maleate, monooctyl maleate,
Monoesters of unsaturated dibasic acids such as monomethyl fumarate, monoethyl fumarate, monobutyl fumarate, monooctyl fumarate; acrylic acid, methacrylic acid, cinnamic acid, fumaric acid, maleic acid, maleic anhydride, itaconic acid, etc. Unsaturated carboxylic acids; acrylamide, methacrylamide, N-substituted acrylamide, N-substituted methacrylamide, acrylamidopropanesulfonic acid, N-vinylpyrrole, N-vinylcarbazole, N-vinylindole, N-vinylpyrrolidene, acrylonitrile,
Examples thereof include N-vinyls such as methacrylonitrile.

The vinyl resin may be a homopolymer or a copolymer, and corresponds to one or more kinds of monomers selected from the group consisting of styrene monomers, acrylic acid ester monomers and methacrylic acid ester monomers. A vinyl resin having a structural unit is more desirable. The binder resin for electrophotographic toner obtained by the present invention,
It can be made into a toner together with a colorant and the like by a usual method and used as a developer. The developer obtained by the present invention exhibits extremely good fixability, offset resistance and blocking resistance. As the colorant used for the toner, all known ones can be used, and examples thereof include carbon black, nigrosine, benzidine yellow, quinacridone,
Rhodamine B and phthalocyanine blue are available.

The toner can be used in both a dry one-component developer and a two-component developer, and as a one-component magnetic substance,
Ferromagnetic alloys such as ferrite, magnetite, etc., such as iron, cobalt, nickel, etc., or alloys containing no compound or ferromagnetic element but exhibiting ferromagnetism by appropriate heat treatment, eg, manganese. -Copper-
Examples include alloys of a type called Heusler alloys containing aluminum or manganese such as manganese-copper-tin and copper, or chromium dioxide. The magnetic body is
It is uniformly dispersed in the binder resin in the form of fine powder having an average particle size of 0.3 to 30 μm. The content of the magnetic particles is preferably 20 to 70 parts by weight per 100 parts by weight of the binder,
Particularly, 40 to 70 parts by weight is desirable.

The charge control of the toner may be performed by the binder resin and the colorant itself, but a charge control agent may be used in combination if necessary. A quaternary ammonium salt, a basic / electron-donating organic substance can be used as the positive charge control agent, and a metal chelate, an alloy dye, an acidic or electron-withdrawing organic substance, etc. can be used as the negative charge control agent. The addition amount of the charge control agent can be determined in consideration of the chargeability of the binder resin, the manufacturing method including the addition amount / dispersion method of the colorant, and the chargeability of other additives. 0.1 to 10 parts by weight is suitable. In addition, inorganic particles such as metal oxides or inorganic substances surface-treated with the organic substance may be used. These charge control agents may be mixed and added to the binder resin, or may be used in the form of being attached to the surface of the toner particles.

Furthermore, a solid electrolyte, a polymer electrolyte,
The electrical properties of the toner can be controlled by adding a charge transfer complex, a conductor such as a metal oxide such as tin oxide, a semiconductor, a ferroelectric substance, a magnetic substance, or the like. In addition, auxiliary agents such as various plasticizers and release agents may be added to the toner for the purpose of adjusting thermal characteristics and physical characteristics. The appropriate amount of addition is 0.1 to 10 parts by weight.

Further, for the toner particles, TiO ₂ ,
By adding fine powder such as Al ₂ O ₃ or SiO ₂ and coating the surface of the toner particles with these, the fluidity and aggregation resistance of the toner can be improved. The addition amount is preferably 0.1 to 10 parts by weight. Various conventionally used toner manufacturing methods can be applied to the toner manufacturing method. For example, the following examples can be given as general manufacturing methods. First, an additive such as a charge control agent is added to a binder resin and a colorant, and the mixture is uniformly dispersed by a ball mill, a V-type mixer, an S-type mixer, a Henschel mixer, or the like. Next, the dispersion is melt-kneaded with a double-arm kneader, a pressure kneader or the like. The mixture is crushed by a crusher such as a hammer mill, a jet mill or a ball mill, and the obtained powder is classified by an air classifier or the like.

The obtained toner can be mixed with a carrier to form a developer for electrophotography, if necessary, and can be used for copying by a conventional electrophotographic method. As the carrier, it is preferable to use 10 to 100 parts of a magnetic substance such as a known iron powder-based or ferrite-based carrier or a material coated on the surface thereof with respect to 1 part of the toner.

[0018]

EXAMPLES Specific examples of the present invention will be described below, but the present invention is not limited to these examples. (Example 1) A styrene-n-butyl acrylate copolymer having a weight average molecular weight of 1,500,000 obtained by polymerization by an emulsion polymerization method was dissolved in 10-fold amount (weight ratio) of acetone.
3% by weight of benzoyl peroxide, 25% by weight of styrene monomer and 10% by weight of acrylic acid based on acetone
-Butyl monomer was added and polymerized at 80 ° C for 5 hours to obtain a binder resin A.

Example 2 Styrene-acrylic acid n having a weight average molecular weight of 500,000 obtained by polymerization by suspension polymerization
-The butyl copolymer was dissolved in 10 times (weight ratio) of acetone, and then 5% by weight of benzoyl peroxide, 25% by weight of styrene monomer and 10% by weight of n-butyl acrylate monomer were added to the acetone. In addition, polymerization was carried out at 80 ° C. for 5 hours to obtain a binder resin B.

Example 3 A styrene-n-butyl acrylate copolymer having a weight average molecular weight of 1,500,000 obtained by polymerization by an emulsion polymerization method was dissolved in 10 times (weight ratio) of propylene glycol monomethyl ether. Then, 5% by weight of azoisobisbutyronitrile, 25% by weight of styrene monomer and 10% by weight of n-butyl acrylate monomer were added to propylene glycol monomethyl ether, and the mixture was polymerized at 90 ° C. for 5 hours to obtain binder resin C. Got

(Example 4) Styrene-acrylic acid n having a weight average molecular weight of 500,000 obtained by polymerization by suspension polymerization
After dissolving the butyl copolymer in 10 times (weight ratio) of propylene glycol monomethyl ether, 7% by weight of azoisobisvaleronitrile, 25% by weight of styrene monomer and 10% by weight of propylene glycol monomethyl ether were dissolved. The n-butyl acrylate monomer of was added and polymerized at 80 ° C. for 5 hours to obtain a binder resin D.

(Comparative Example 1) An emulsion of a styrene-n-butyl acrylate copolymer having a weight average molecular weight of 1,500,000 was prepared by polymerizing by an emulsion polymerization method, followed by styrene monomer / n-butyl acrylate monomer / peroxide. A benzoyl (weight ratio = 2.5 / 1 / 0.3) mixed solution was added in an amount of 3.8 times (weight ratio) of the copolymer, and then the mixture was mixed at 80 ° C. for 5 hours.
Binder resin E was obtained by time seed polymerization.

Comparative Example 2 A styrene-n-butyl acrylate copolymer emulsion having a weight average molecular weight of 500,000 was prepared by polymerizing by an emulsion polymerization method, and then styrene monomer / n-butyl acrylate monomer / n- Dodecyl mercaptan / benzoyl peroxide (weight ratio = 2.5 / 1 /
A 0.5 / 0.5) mixed solution was added in an amount 3.8 times (weight ratio) of the copolymer, and then seed polymerization was carried out at 80 ° C. for 5 hours to obtain a binder resin F.

Comparative Example 3 A styrene-n-butyl acrylate copolymer emulsion having a weight average molecular weight of 500,000 was prepared by polymerizing by emulsion polymerization, and then styrene monomer / n-butyl acrylate monomer / azobis. After adding a mixed solution of isobutyronitrile (weight ratio = 2.5 / 1 / 0.5) in an amount of 3.8 times the weight of the copolymer (weight ratio), 9
Seed polymerization was performed at 0 ° C. for 10 hours to obtain a binder resin G.

(Comparative Example 4) A styrene-n-butyl acrylate copolymer emulsion having a weight average molecular weight of 500,000 was prepared by polymerizing by emulsion polymerization, and then styrene monomer / n-butyl acrylate monomer / n- Dodecyl mercaptan / benzoyl peroxide (weight ratio = 2.5 / 1 /
A 1 / 0.7) mixed solution was added in an amount 3.8 times (weight ratio) of the copolymer, and then seed polymerization was performed at 90 ° C. for 10 hours to obtain a binder resin H.

The binder resins A to H obtained were subjected to GPC measurement, and the values shown in Table 1 were obtained. In the present invention, a usual known method is used to measure the molecular weight distribution of the polymer. For example, an appropriate method for normal GPC may be used as follows.

[0027]

[Table 1] 1. Measurement conditions Temperature: 40 ° C. Solvent: Tetrahydrofuran Flow rate: 0.5 ml / min Sample concentration: 0.1 wt% Sample injection amount: 100 μl

2. Column As a column used for appropriately measuring the molecular weight region of 10 ^{3 to} 2 × 10 ^6, a combination of a plurality of commercially available polystyrene gel columns is used. In the measurement of the present invention, GMHXL (30 cm ×, manufactured by Tosoh Corporation)
2) were used. 3. Calibration curve Standard polystyrene is used to prepare the calibration curve. The standard polystyrene is, for example, Pressure.
chemical Co. Manufactured by Tosoh Co., Ltd. and having a molecular weight of, for example, 6 × 10 ² , 2.8 × 10 ³ , 6.2.
^{× 10 3, 1.03 × 10 4} , 1.67 × 10 4, 4.
39 × 10 ⁴ , 1.02 × 10 ⁵ , 1.86 × 10 ⁵ ,
4.22 x 10 ⁵ , 7.75 x 10 ⁵ , 1.26 x 10
^It is suitable to use ⁶ and use at least about 10 standard polystyrenes. 4. Detector A RI (refractive index) detector is used as the detector.

[0029]

[Table 2]

Further, using binder resins A to H, 3 parts by weight of polypropylene wax (“Viscor 550P” manufactured by Sanyo Chemical Co., Ltd.) and 100 parts by weight of resin, carbon black (“# 30 manufactured by Mitsubishi Kasei Co., Ltd.”) were used. 6 parts by weight, Nigrosine dye ("Bontron N" manufactured by Orient Chemical Co., Ltd.
-04 ") 2 parts by weight were dispersed and mixed, and then melt-kneaded using a twin-screw extruder. After cooling, it was coarsely pulverized by a hammer mill and then finely pulverized by a supersonic jet mill pulverizer. The obtained powder is classified with an air classifier, and the average particle size is 1
Toners I to P of 0.3 μm were obtained.

Each of the above toners and an average particle size of 50 to 80 μm
The above ferrite carrier was mixed to obtain a developer having a toner concentration of 4.0%, and a fixing test (fixing lower limit temperature and fixing strength) was conducted according to the following method. The results are shown in Table 2. Lower limit temperature of fixing: A developing unfixed sample is passed through while changing the roll temperature of a fixing machine having a roll rotation speed of 400 mm / sec. The lowest temperature at which the fixed toner did not peel off was defined as the minimum fixing temperature. Fixing strength: A fixing device having a roll rotation speed of 400 mm / sec and a roll temperature of 150 ° C. is used to pass a sheet of undeveloped sample for fixing. The formed fixed image is subjected to a friction fastness test, and the image densities of the fixed image before and after the peeling of the toner are measured with a reflection densitometer, and the following formula [Formula I] is used.
The fixing ratio was calculated by using the above as an index of fixing strength.

[0032]

[Equation 1]

[0033]

[Table 3]

Compared with the toners M to P of the comparative examples, the toners I to L obtained according to the present invention were excellent in terms of the lower limit fixing temperature and the fixing strength, and showed good fixing properties.

[0035]

According to the present invention, a resin having a peak on the low molecular weight side of 10,000 or less can be easily obtained, and a toner using the resin as a binder has an extremely good fixing property, offset resistance and blocking resistance. Shows sex.

Claims (4)

[Claims] 1. A method for producing a binder resin for an electrophotographic toner having two or more peaks in a gel permeation chromatogram, wherein solution polymerization of a low molecular weight component is carried out in a solution in which a high molecular weight component is dissolved. And manufacturing method. 2. The production method according to claim 1, which is a method for producing a binder resin for an electrophotographic toner having one or more peaks at 10,000 or less in a gel permeation chromatogram. 3. The method according to claim 1, wherein the binder resin for electrophotographic toner is a vinyl resin. 4. The method according to claim 3, wherein the vinyl resin has a structural unit corresponding to one or more kinds of monomers selected from the group consisting of styrene monomers, acrylic acid ester monomers and methacrylic acid ester monomers. The manufacturing method described.