JP4822065B2 - Resin composition for electrophotographic toner - Google Patents

Description

  The present invention is resistant to hot offset, excellent in low-temperature fixability, stably charged even after continuous printing, and excellent in durability (development durability) for obtaining good images. The present invention relates to a resin composition for an electrophotographic toner that can suitably obtain an electrophotographic toner for a system.

  The powder toner used in the electrophotographic method has electrical properties such as tribocharging and electrical resistance related to development and transfer performance, thermal properties related to fixing performance and heat resistance (storage stability), and fluidity. In addition, in the properties of the powder such as hardness, an appropriate level according to the use conditions is required.

  Conventionally, as a resin material used for powder toner, polystyrene, styrene-acrylic copolymer, polyester, epoxy resin, butyral resin and the like can be mentioned, and the detailed design of the resin varies depending on its application. Proposals have been made.

  In particular, the heat roller fixing resin is required to improve the fixing performance to the transfer paper and the anti-offset performance. The toner fixing performance is achieved by overheating and fusing with a fixing roller or the like and fixing to a transfer paper. The anti-offset performance is that the toner melted by the heating roller does not cause cold offset and loses its viscosity. The hot offset does not occur at the time. Therefore, high-molecular weight thermoplastic resins and partially crosslinked thermoplastic resins have been mainly used as resins that have been used for electrophotographic toners. For this reason, it is necessary to set a high temperature for fixing and fixing the electrophotographic toner (fixing temperature), and the current social demand for energy saving is not fully satisfied.

  In such a situation, in order to obtain an electrophotographic toner having a low fixing temperature, for example, an electrophotographic toner comprising colored particles containing a rosin ester having an acid value of 2 or less and an external additive is disclosed (for example, Patent Document 1). However, even with the electrophotographic toner described in Patent Document 1, it is necessary to set the fixing temperature to about 135 ° C., and there is a demand for a resin composition for electrophotographic toner that can be used at a lower fixing temperature.

JP 2003-322997 A

  The problem of the present invention is that it has excellent low-temperature fixability, hot offset resistance and low-temperature fixability, and is stably charged even during continuous printing, and has excellent durability (development durability) that provides a good image. An object of the present invention is to provide a resin composition for an electrophotographic toner that can suitably obtain an electrophotographic toner for a roll fixing system.

  As a result of intensive studies, the inventors of the present invention contain a polyester resin (R) having a softening point of 80 to 120 ° C. and a polyester resin (S) having a softening point of 160 ° C. or higher. Further, rosin is used as the polyester resin (R). A fixing temperature of 95 to 115 is obtained by using a polyester resin obtained by using a polyester resin obtained as an essential component and a polyester resin obtained by using a polyvalent epoxy compound as an essential component as the polyester resin (S). The fixing temperature can be as low as about 20 to 40 ° C. compared to the toner of Patent Document 1, and the temperature at which the hot offset phenomenon starts (offset start temperature) is also high as 195 to 210 ° C., which is excellent in offset resistance and durability. Even after 10 hours of continuous printing, an electrophotographic toner having no developmental unevenness such as streaks and excellent development durability can be obtained. Heading and the like, which resulted in the completion of the present invention.

  That is, the present invention polycondenses rosin (a), polyhydric alcohol (b1), one or more polybasic acids (c1) selected from the group consisting of polybasic acids, anhydrides thereof and lower alkyl esters thereof. A polyester resin (R) having a softening point of 80 to 120 ° C., a polyhydric epoxy compound (d), a polyhydric alcohol (b2), a polybasic acid, anhydrides thereof, and lower alkyl esters thereof. An electrophotographic toner resin composition comprising: a polyester resin (S) having a softening point of 160 ° C. or higher obtained by polycondensation with at least one selected polybasic acid (c2). Is.

  According to the present invention, it is possible to provide a resin composition capable of obtaining an electrophotographic toner having both low temperature fixability, hot offset property, and development durability.

  The polyester resin (R) used in the present invention is one or more polybasic acids (c1) selected from the group consisting of rosin (a), polyhydric alcohol (b1), polybasic acid, anhydrides thereof, and lower alkyl esters thereof. ) And a softening point of 80 to 120 ° C. When the softening point is lower than 80 ° C., the glass transition point (Tg) of the polyester resin is lowered, which is not preferable because the hot offset resistance is not sufficient. When the softening point is higher than 120 ° C., the low-temperature fixability is deteriorated. As the polyester resin (R) used in the present invention, a polyester resin (R1) having a softening point of 90 to 110 ° C. is preferable because a resin composition capable of producing an electrophotographic toner having excellent low-temperature fixability can be obtained. 90-110 degreeC polyester resin (R2) is more preferable.

  The rosin (a) used in the present invention is a general term for low-volatile resin acids obtained from trees, and the main component is derived from natural products including abietic acid, which is a kind of tricyclic diterpenes, and isomers thereof. It is a substance. Specific components include, for example, neoabietic acid, dehydroabietic acid, pimaric acid, isopimaric acid, and pulpstriic acid in addition to abietic acid, and rosin (A) used in the present invention is a mixture thereof. There are three types of rosins: gum rosin obtained from raw pine resin, wood rosin obtained from pine root, and tall oil rosin obtained from pulp. In the present invention, rosin (disproportionated rosin) obtained by dehydrogenating the rosin to increase the ratio of dehydroabietic acid in the rosin can also be used as the rosin (a). Rosin belongs to a monocarboxylic acid as a chemical structure, and a carboxyl group is a typical reactive group. As the rosin (A) used in the present invention, one or more rosins selected from the group consisting of gum rosin, wood rosin, tall oil rosin and these disproportionated rosins are preferable. In addition, rosin (a) can be used alone or in combination of two or more at any ratio.

  Among the polyester resins (R) used in the present invention, the rosin (a) is added in an amount of 0.000 to 100 parts by weight in total of the rosin (a), a polyhydric alcohol (b1) described later, and a polybasic acid (c1). A polyester resin obtained by using 1 to 40 parts by weight is preferable because a toner having excellent low-temperature fixability is obtained, and a polyester resin obtained by using 0.5 to 25 parts by weight is more preferable.

  Examples of the polyhydric alcohol (b1) used in the present invention include divalent alcohols and trivalent or higher alcohols.

  Examples of the divalent alcohols include ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, and triethylene. Aliphatic diols such as glycol and neopentyl glycol;

Bisphenol A derivatives such as bisphenol A and bisphenol polyalkylene oxide adducts; and alicyclic diols such as cyclohexanedimethanol.

  In the present invention, aliphatic monoepoxy compounds such as Cardura E10 “monoglycidyl ester of branched fatty acid manufactured by Shell Chemical Co.” can also be used as diols.

  Examples of the trivalent or higher alcohols include glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol, 2-methylpropanetriol, and the like.

  Among the polyhydric alcohols (b1) used in the present invention, a polyhydric alcohol containing a dihydric alcohol is preferable because a resin composition for an electrophotographic toner capable of producing a toner excellent in offset resistance and low-temperature fixability can be obtained. . Among the divalent alcohols, one or more alcohols selected from the group consisting of ethylene glycol, propylene glycol and neopentyl glycol are preferable.

  A polyhydric alcohol (b1) may be used independently and may use 2 or more types together. Moreover, you may use monoalcohols, such as a stearyl alcohol, as needed within the range which does not impair the effect of this invention.

  As the polybasic acid (c1) used in the present invention, acid anhydrides of these polybasic acids and their lower alkyl esters can also be used as polybasic acids. Examples of the polybasic acid (c1) include saturated polybasic acids and unsaturated polybasic acids.

  Examples of the saturated polybasic acid, saturated polybasic acid and lower alkyl ester of saturated polybasic acid include, for example, adipic acid, sebacic acid, orthophthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, succinic anhydride, Dibasic acids such as alkyl succinic acid having 8 to 18 carbon atoms, alkyl succinic anhydride, alkenyl succinic acid, alkenyl succinic anhydride; trimellitic acid, trimellitic anhydride, cyanuric acid, pyromellitic acid, pyromellitic anhydride And polybasic acids. Examples of the alkyl mentioned here include alkyl esters having 8 to 18 carbon atoms.

  Examples of the unsaturated polybasic acid include maleic acid, maleic anhydride, and fumaric acid.

  The polybasic acid (c1) may be used alone or in combination of two or more. Moreover, you may use monobasic acids, such as benzoic acid and p-tert- butylbenzoic acid, as needed.

  Among the polybasic acids (c1) used in the present invention, a toner excellent in offset resistance and low-temperature fixability can be obtained, so that one kind selected from the group consisting of divalent basic acids, their anhydrides and their lower alkyl esters Polybasic acids containing the above compounds are preferred, and isophthalic acid and terephthalic acid are more preferred among one or more compounds selected from the group consisting of the divalent basic acids, their anhydrides and their lower alkyl esters.

  Furthermore, as the above-mentioned polybasic acid (c1), those in which part or all of the carboxy group is alkenyl ester or allyl ester can also be used.

  The polyester resin (R) used in the present invention is composed of rosin (a), polyhydric alcohol (b1), polybasic acid, anhydride thereof, and one or more polybasic acids selected from the group consisting of these lower alkyl esters ( It is a polyester resin obtained by polycondensation with c1) and having a softening point of 80 to 120 ° C. Such a polyester resin can be variously prepared, for example, so that the rosin (a), the polyhydric alcohol (b1), and the polybasic acid (c1) can be obtained in a polyester resin having a softening point of 80 to 120 ° C. It can be produced by selecting and polycondensing these.

  Specific examples of the production of the polyester resin (R) include, for example, the presence of an esterification catalyst (dibutyltin oxide, tetrabutyl titanate, paratoluenesulfonic acid, etc.) or a transesterification catalyst (lead compound, tin compound, Any production method such as transesterification using lower alkyl esters such as dicarboxylic acid methyl ester, atmospheric pressure dehydration reaction, reduced pressure and vacuum dehydration reaction, solution polycondensation method, solid phase polycondensation reaction in the presence of zinc compound You may carry out in. The polyesterification reaction at this time can be traced by measuring the acid value, hydroxyl value, viscosity or softening point (ring and ball method).

  As an apparatus used at this time, for example, a recirculation-type production apparatus such as a reaction vessel equipped with a nitrogen inlet, a thermometer, a stirring device, a rectifying tower, etc. can be suitably used, and a deaeration port is provided. Extruders, continuous reactors, kneaders and the like can also be used. In the dehydration condensation, the esterification reaction can be promoted by reducing the pressure of the reaction system as necessary. Furthermore, a known and commonly used catalyst can be added to accelerate the esterification reaction.

  The polyester resin (R) used in the present invention is a component that imparts low-temperature fixability to an electrophotographic toner. Therefore, the polyester resin (R) is desirably a polyester resin having a low molecular weight and a low viscosity while maintaining the glass transition point (Tg).

  The polyester resin (S) used in the present invention is one or more polybasic compounds selected from the group consisting of polyvalent epoxy compounds (d), polyhydric alcohols (b2), polybasic acids, anhydrides thereof, and lower alkyl esters thereof. It must be obtained by polycondensation with acid (c2) and have a softening point of 160 ° C. or higher. When the softening point is lower than 160 ° C., it is not preferable because it is difficult to obtain an electrophotographic toner excellent in hot resistance. As the polyester resin (S) used in the present invention, a polyester resin (S1) having a softening point of 170 to 210 ° C. is preferable because a resin composition capable of producing an electrophotographic toner having excellent offset resistance can be obtained. Is more preferably 170 to 210 ° C. polyester resin (S2).

  In the present invention, the softening point was measured with a ring and ball automatic softening point measuring machine (ASP-MG) manufactured by Meitec.

  The polyvalent epoxy compound (d) is a compound having two or more epoxy groups in one molecule, and examples thereof include a divalent to tetravalent epoxy compound and a pentavalent or higher valent epoxy compound.

  Examples of the divalent to tetravalent epoxy compounds include bisphenol type epoxy resins such as bisphenol A type epoxy resins, novolac type epoxy resins, ethylene glycol diglycidyl ether, glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, Examples include trimethylolethane triglycidyl ether, pentaerythritol tetraglycidyl ether, hydroquinone diglycidyl ether, and the like.

  Examples of the pentavalent or higher epoxy compound include a cresol novolac type epoxy resin, a phenol novolac type epoxy resin, a polymer or copolymer of a vinyl compound having an epoxy group, an epoxidized resorcinol-acetone condensate, and a partially epoxidized polybutadiene. Etc.

  Among the polyvalent epoxy compounds (d) used in the present invention, a divalent epoxy compound is preferable because a resin composition for an electrophotographic toner capable of producing an electrophotographic toner having good hot offset resistance is obtained. Among epoxy compounds, a bisphenol type epoxy resin is preferable because of good plasticizer resistance, and a bisphenol A type epoxy resin is more preferable.

  Further, since the reactivity is good and the polyester resin (S) can be easily obtained, a cresol novolac type epoxy resin and a phenol novolac type epoxy resin are more desirable.

  Two or more of the divalent to tetravalent epoxy compounds and the pentavalent or higher epoxy compounds may be used in combination.

  Among the polyester resins (S) used in the present invention, the polyvalent epoxy compound (d) is a total of 100 weights of the polyvalent epoxy compound (d), the polyhydric alcohol (b2) described later, and the polybasic acid (c2). The polyester resin obtained by using 0.1 to 30 parts by weight with respect to parts is preferable because a toner having excellent anti-offset property is obtained, and the polyester resin obtained by using 0.5 to 20 parts by weight is more preferable.

  Examples of one or more polybasic acids (c2) selected from the group consisting of the polyhydric alcohol (b2) and a polybasic acid, anhydrides thereof, and lower alkyl esters thereof include, for example, the polyhydric alcohol (b1), A polybasic acid (c1) etc. are mentioned. At this time, the polyhydric alcohol (b2) and the polyhydric alcohol (b1), the polybasic acid (c2) and the polybasic acid (c2) may be the same or different. Good.

  Among the polyhydric alcohols (b2) used in the present invention, a polyhydric alcohol containing a dihydric alcohol is preferable because a resin composition for an electrophotographic toner capable of producing a toner excellent in offset resistance and low-temperature fixability can be obtained. . Among the divalent alcohols, one or more alcohols selected from the group consisting of ethylene glycol, propylene glycol and neopentyl glycol are preferable.

  Among the polybasic acids (c2) used in the present invention, a toner excellent in offset resistance and low-temperature fixability can be obtained, so that one kind selected from the group consisting of divalent basic acids, their anhydrides and their lower alkyl esters Polybasic acids containing the above compounds are preferred, and isophthalic acid and terephthalic acid are more preferred among one or more compounds selected from the group consisting of the divalent basic acids, their anhydrides and their lower alkyl esters.

  The polyester resin (S) used in the present invention contains at least one polyvalent epoxy compound (d), polyhydric alcohol (b2), polybasic acid, anhydride thereof, and a lower alkyl ester thereof. A polyester resin obtained by polycondensation with a basic acid (c2) and having a softening point of 160 ° C. As such a polyester resin, for example, a polyester resin can be obtained in which the polyhydric epoxy compound (d), the polyhydric alcohol (b2), and the polybasic acid (c2) have a softening point of 160 ° C. or higher. It can be produced by variously selecting and polycondensing these.

  As a specific example at the time of manufacturing the said polyester resin (S), the specific example shown at the time of manufacture of the said polyester resin (R) can be mentioned, for example.

  The polyester resin (S) used in the present invention is a component that imparts hot offset resistance to the electrophotographic toner. Therefore, it is desirable that the polyester resin (S) is a partially crosslinked high molecular weight and high viscosity polyester resin.

  As the content ratio [(R) / (S)] of the polyester resin (R1) and the polyester resin (S1) in the resin composition for an electrophotographic toner of the present invention, electrophotography excellent in low-temperature fixability and offset resistance. Since the resin composition which can manufacture a toner is obtained, 0.1-9 are preferable by weight ratio, and 0.4-2.5 are more preferable.

  As the resin composition for an electrophotographic toner of the present invention, a resin composition further containing a release agent is preferable. By including a release agent, it is possible to prevent the toner from being offset to a fixing roll of a copying machine or a printer and to fix the toner at a low temperature. Examples of the release agent include wax.

  As the wax, for example, polypropylene wax, polyethylene wax, polyamide wax, Fischer-Tropsch wax, synthetic ester wax, various natural waxes and the like can be used as appropriate, and among them carnauba wax, montan ester wax, rice wax, and the like. And / or scale insect wax is preferably used.

  Examples of a method for preparing an electrophotographic toner using the resin composition for an electrophotographic toner of the present invention include a preparation method including the following steps. First, after preparing a mixture by premixing the resin composition for an electrophotographic toner of the present invention, a colorant and, if necessary, a charge control agent, a wax, a flow regulator and the like with a Henschel mixer or the like, this mixture is mixed with 3 The mixture is melt kneaded with an apparatus such as a roll, a pressure kneader, or a twin screw extruder to obtain a kneaded product. Next, the kneaded product is cooled, coarsely pulverized, and toner particles having a predetermined particle diameter are obtained by a method such as a mechanical pulverization method using a turbo mill or an air pulverization method using a jet mill. Further, the toner particles are generally classified by an air classifier or the like as necessary. Usually, the volume average particle diameter is adjusted to 5 to 15 μm. In addition, the toner particles thus prepared are generally mixed with fine particles such as silica powder, titanium oxide and alumina as external additives in order to improve the fluidity of the powder and the charging characteristics. is there.

  Examples of the colorant include various carbon blacks produced by a thermal black method, an acetylene black method, a channel black method, a furnace black method, a lamp black method and the like in the case of a black toner. . In the case of color toner, phthalocyanine bull, aniline bull, calco oil bull, ultramarine bull, methylene bull chloride, malachite green oxate, chrome yellow, quinoline yellow, dupont oil red, rose bengal Pigments, nigrosine-type or rhodamine-type dyes, and the like, which can be used alone or in combination of two or more.

  As the charge control agent, various substances from low molecular weight compounds to high molecular weight compounds can be used. Typical examples include a nigrosine dye, a quaternary ammonium salt compound, and a monomer having an amino group. There are polymer compounds obtained by polymerization, organometallic complexes, chelate compounds, and the like.

  The flow modifier is added to improve the fluidity of the toner. For example, vinylidene fluoride fine powder, polytetrafluoroethylene fine powder, wet or dry silica fine powder, and the like can be used. .

  When the electrophotographic toner obtained using the resin composition for an electrophotographic toner of the present invention is used as a two-component developer, printing can be performed at a remarkably low fixing temperature as compared with a conventional electrophotographic toner, Moreover, the thermal stability of the electrophotographic toner is good, and further, an excellent electrophotographic toner having no offset phenomenon can be obtained without causing a decrease in elasticity of the binder resin itself.

  Next, the present invention will be specifically described with reference to Examples and Comparative Examples. In the examples, “parts” means parts by weight unless otherwise specified.

Synthesis Example 1 [Synthesis of polyester resin (R)]
202 g of gum rosin (acid value 167 mgKOH / g), 268 g of ethylene glycol, 141 g of propylene glycol, 946 g of terephthalic acid and 1.0 g of tetrabutyl titanate are placed in a glass 2-liter four-necked flask and gradually heated in a nitrogen stream. The mixture was reacted at 240 ° C. for 5 hours, then the temperature was lowered to 235 ° C., and reacted at 40 mmHg under reduced pressure for 3 hours to obtain a polyester resin (R1). The obtained polyester resin (R1) was a solid at room temperature, an acid value of 11 mgKOH / g, and a softening point of 102 ° C.

Synthesis example 2 (same as above)
Hartol X [Hallima Kasei Co., Ltd. tall oil rosin, acid value 165 mg KOH / g] 200 g, neopentyl glycol 546 g, propylene glycol 70 g, terephthalic acid 946 g and dibutyltin oxide 1.0 g in a 2-liter glass four-necked flask The mixture was gradually heated in a nitrogen stream and reacted at 245 ° C. for 4 hours, then the temperature was lowered to 235 ° C. and reacted under reduced pressure of 40 mmHg for 3 hours to obtain a polyester resin (R2). The obtained polyester resin (R2) was a solid at room temperature, an acid value of 12 mgKOH / g, and a softening point of 95 ° C.

Synthesis Example 3 [Synthesis of polyester resin (S)]
262 g of ethylene glycol, 293 g of neopentyl glycol, 795 g of terephthalic acid, 340 g of isophthalic acid, 37 g of epiclone 850 (bisphenol A type epoxy resin manufactured by Dainippon Ink & Chemicals, Inc.) and 0.86 g of dibutyltin oxide were added to 2 liters of glass. Put in a four-necked flask, gradually raise the temperature in a nitrogen stream, react at 245 ° C. for 6 hours, then lower the temperature to 235 ° C., react for 4 hours under reduced pressure of 40 mmHg, polyester resin (S1) Got. The obtained polyester resin (S1) was a solid at room temperature, an acid value of 10 mgKOH / g, and a softening point of 185 ° C.

Synthesis example 4 (same as above)
1026 g of polyoxypropylene (2,2) -2,2-bis (4-hydroxyphenyl) propane, 448 g of terephthalic acid, 13 g of epiclone N-695 [cresol novolac type epoxy resin manufactured by Dainippon Ink and Chemicals, Inc.] Put 0.9 g of tetraisopropyl titanate into a 2-liter glass four-necked flask, gradually raise the temperature in a nitrogen stream, react at 240 ° C. for 5 hours, then lower the temperature to 230 ° C., and reduce the pressure to 50 mmHg. Under the reaction for 3 hours, a polyester resin (S2) was obtained. The obtained polyester resin (S2) was a solid at room temperature, an acid value of 13 mgKOH / g, and a softening point of 170 ° C.

Synthesis Example 5 (Synthesis of polyester resin for comparison)
268 g of ethylene glycol, 141 g of propylene glycol, 996 g of terephthalic acid and 1.0 g of tetrabutyl titanate are placed in a glass 2-liter four-necked flask, gradually heated in a nitrogen stream, and allowed to react at 240 ° C. for 5 hours. Then, the temperature was lowered to 235 ° C. and reacted for 3 hours under a reduced pressure of 40 mmHg to obtain a comparative polyester resin 1 ′. The obtained polyester resin 1 ′ for comparison was a solid at normal temperature, an acid value of 12 mgKOH / g, and a softening point of 101 ° C.

Synthesis example 6 (same as above)
193 g of ethylene glycol, 233 g of propylene glycol, 697 g of terephthalic acid, 232 g of trimellitic anhydride and 1.0 g of dibutyltin oxide are placed in a glass 2-liter four-necked flask and gradually heated in a nitrogen stream to 245 ° C. Then, the temperature was lowered to 230 ° C. and reacted for 2 hours under a reduced pressure of 70 mmHg to obtain a polyester resin 2 ′ for comparison. The obtained polyester resin 2 ′ for comparison was a solid at normal temperature, an acid value of 13 mgKOH / g, and a softening point of 175 ° C.

Example 1
46 parts of polyester resin (R1), 46 parts of polyester resin (S1), 5 parts of carbon black MA-11 (manufactured by Mitsubishi Chemical), 1 part of Bontron S34 (charge control agent made by Orient Chemical) and Biscol 550P (polypropylene wax made by Sanyo Chemical) 2 parts were mixed with a Henschel mixer and then kneaded with a biaxial kneader to obtain a kneaded product. The kneaded material thus obtained was pulverized and classified. 3 parts of silica R972 (manufactured by Nippon Aerosil Co., Ltd.) was mixed with a Henschel mixer and sieved to obtain a resin composition A for electrophotographic toner. 5 parts of the obtained resin composition A and 95 parts of a carrier (silicone resin-coated ferrite carrier) were mixed and stirred to prepare an electrophotographic toner 1. For toner 1, the fixing start temperature, offset resistance, and development durability were evaluated according to the following evaluation methods. The evaluation results are shown in Table 3.

<Evaluation of fixing start temperature>
The set temperature of the heat roll was changed from 80 ° C. to 210 ° C. in steps of 5 ° C., and solid printing was performed. When solidity is applied to the solid print part, the image density before and after the test is measured with a Macbeth densitometer (RD-918), and the ratio of the density value after peeling to the value before the test is displayed in%. The temperature at which the ratio becomes 80% or more was determined as the fixing start temperature. The lower this temperature, the better the low-temperature fixability of the electrophotographic toner. The fastness test was conducted using a Gakushin type friction fastness tester (load: 200 g, rubbing operation: 5 strokes).

<Evaluation method of offset start temperature>
When the set temperature of the heat roll was changed from 80 ° C. to 210 ° C. in increments of 5 ° C., the solid print portion was offset again on the same paper and displayed at the lowest temperature that could be visually confirmed. The higher this temperature, the better the offset resistance.

The fixing start temperature and offset resistance were evaluated under the following heat roller fixing machine conditions.
Roll material: Upper; Polytetrafluoroethylene, Lower; Silicone Upper roll load: 7Kg / 350mm
Nip width: 4mm
Paper threading speed: 280 cm / sec

<Development durability evaluation method>
The exclusive toner was removed from the cartridge of a commercially available printer, and the obtained electrophotographic toner 1 was filled in the washed cartridge, and continuous printing was performed for 10 hours. A state where the toner layer on the developing sleeve was uniform and no defect was generated was judged as ◯, and a case where a non-uniform portion such as a streak occurred was judged as x.

Examples 2-4 and Comparative Examples 1-2
Except for the formulations shown in Tables 1 and 2, electrophotographic toners 2 to 4 and comparative electrophotographic toners 1 'to 4' were prepared in the same manner as in Example 1. In the same manner as in Example 1, the fixing start temperature, offset resistance, and development durability were evaluated. The evaluation results are shown in Table 2 in Table 3.

Footnotes in Tables 1 and 2 MA-11: Carbon black MA-11
S34: Bontron S34
550P: Biscol 550P
R972: Silica R972

Claims (15)

Softening obtained by polycondensation of rosin (a), polyhydric alcohol (b1), polybasic acid, its anhydride, and one or more polybasic acid (c1) selected from the group consisting of these lower alkyl esters One or more selected from the group consisting of a polyester resin (R) having a point of 80 to 120 ° C., a polyvalent epoxy compound (d), a polyhydric alcohol (b2), a polybasic acid, an anhydride thereof, and a lower alkyl ester thereof. A resin composition for an electrophotographic toner, comprising a polyester resin (S) having a softening point of 160 ° C. or higher obtained by polycondensation with a polybasic acid (c2). The resin composition for an electrophotographic toner according to claim 1, wherein the rosin (a) is at least one rosin selected from the group consisting of gum rosin, wood rosin, tall oil rosin and disproportionated rosin. The polyester resin (R) is obtained using 0.1 to 40 parts by weight of rosin (a) with respect to 100 parts by weight in total of rosin (a), polyhydric alcohol (b1) and polybasic acid (c1). 2. The resin composition for an electrophotographic toner according to claim 1, wherein the resin composition is a polyester resin. The resin composition for an electrophotographic toner according to claim 1, wherein the polyhydric alcohol (b1) is a polyhydric alcohol containing a dihydric alcohol. The resin composition for an electrophotographic toner according to claim 4, wherein the divalent alcohol is one or more alcohols selected from the group consisting of ethylene glycol, propylene glycol, and neopentyl glycol. 2. The electrophotographic toner according to claim 1, wherein the polybasic acid (c1) is a polybasic acid containing one or more compounds selected from the group consisting of divalent basic acids, anhydrides thereof, and lower alkyl esters thereof. Resin composition. The resin composition for an electrophotographic toner according to claim 6, wherein the one or more compounds selected from the group consisting of the divalent basic acid, its anhydride, and lower alkyl esters thereof are terephthalic acid and / or isophthalic acid. The resin composition for an electrophotographic toner according to claim 1, wherein the polyvalent epoxy compound (d) is a bisphenol type epoxy compound. The polyester resin (S) contains the polyvalent epoxy compound (d) in an amount of 0.1 to 100 parts by weight in total of the polyvalent epoxy compound (d), the polyhydric alcohol (b2), and the polybasic acid (c2). The resin composition for electrophotographic toner according to claim 1, which is a polyester resin obtained by using 30 parts by weight. The resin composition for an electrophotographic toner according to claim 1, wherein the polyhydric alcohol (b2) is a polyhydric alcohol containing a dihydric alcohol. The resin composition for an electrophotographic toner according to claim 10, wherein the divalent alcohol is one or more alcohols selected from the group consisting of ethylene glycol, propylene glycol, and neopentyl glycol. 2. The electrophotographic toner according to claim 1, wherein the polybasic acid (c2) is a polybasic acid containing one or more compounds selected from the group consisting of divalent basic acids, anhydrides thereof, and lower alkyl esters thereof. Resin composition. 13. The resin composition for an electrophotographic toner according to claim 12, wherein the one or more compounds selected from the group consisting of the divalent basic acid, its anhydride, and lower alkyl esters thereof are terephthalic acid and / or isophthalic acid. The polyester resin (R) is a polyester resin (R1) having a softening point of 90 to 110 ° C., the polyester resin (S) is a polyester resin (S1) having a softening point of 170 to 210 ° C., and the polyester resin (R1) and the polyester The resin composition for an electrophotographic toner according to any one of claims 1 to 13, wherein a content ratio [(R1) / (S1)] to the resin (S1) is 0.1 to 9 by weight ratio. The resin composition for an electrophotographic toner according to claim 1, further comprising a release agent.