TONER AND METHOD FOR PRODUCING TONER

Abstract

The toner has a toner particle that contains a binder resin, wherein the binder resin contains a styrene-acrylic resin that has a structure derived from a crosslinking agent, the binder resin includes tetrahydrofuran-insoluble matter in an amount of from 5 mass % to 60 mass % of the binder resin, and the crosslinking agent contains a polymeric compound provided by an addition reaction at least between a particular multifunctional (meth)acrylate compound and a particular polyvalent mercapto compound.

Claims

1. A toner comprising a toner particle that contains a binder resin, wherein the binder resin contains a styrene-acrylic resin that has a structure derived from a crosslinking agent, the binder resin includes tetrahydrofuran-insoluble matter in an amount of from 5 mass % to 60 mass % of the binder resin, and the crosslinking agent contains a polymeric compound provided by an addition reaction at least between a compound represented by formula (1) and a compound represented by formula (2): ##STR00004## in formula (1), R.sup.1 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; L.sup.1 represents an m-valent linear or branched aliphatic hydrocarbon group optionally having a hydroxy group, or an ether bond-containing m-valent linear or branched aliphatic hydrocarbon group optionally having a hydroxy group; and m is an integer from 3 to 6. in formula (2), L.sup.2 represents an alkylene group; L.sup.3 represents an n-valent linear or branched aliphatic hydrocarbon group optionally having a hydroxy group, or an ether bond-containing n-valent linear or branched aliphatic hydrocarbon group optionally having a hydroxy group; and n is an integer from 3 to 6.

2. The toner according to claim 1, wherein the crosslinking agent has a weight-average molecular weight (Mw) of from 4,000 to 50,000.

3. The toner according to claim 1, wherein the crosslinking agent includes a total of at least 10 acryloyl groups and methacryloyl groups per molecule.

4. The toner according to claim 1, wherein the polymeric compound is a dendritic acrylate or a dendritic methacrylate.

5. The toner according to claim 1, wherein the crosslinking agent further comprises a compound represented by formula (3): ##STR00005## in formula (3), R.sup.2 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; L.sup.4 represents a p-valent linear or branched aliphatic hydrocarbon group optionally having a hydroxy group, or an ether bond-containing p-valent linear or branched aliphatic hydrocarbon group optionally having a hydroxy group; and p is an integer from 2 to 6.

6. A method for producing the toner according to claim 1, the method comprising: a step of obtaining the binder resin by polymerizing a polymerizable monomer composition comprising the crosslinking agent and a polymerizable monomer that produces the binder resin.

7. A method for producing the toner according to claim 1, the method comprising: a step of dispersing and granulating, in an aqueous medium, a polymerizable monomer composition comprising the crosslinking agent and a polymerizable monomer that produces the binder resin to form particles of the polymerizable monomer composition; and a step of obtaining toner particles by copolymerizing the polymerizable monomer and crosslinking agent contained in the particles of the polymerizable monomer composition.

Description

EXAMPLES

[0116] The present invention is more specifically described in the following using examples. The present invention is not limited by the examples that follow. The number of parts in the examples and comparative examples is on a mass basis in all instances unless specifically indicated otherwise.

[0117] Production of Crosslinking Agent 1

[0118] 230 g of propylene glycol monomethyl ether, 20 g of pentaerythritol tetra(mercaptoacetate), 220 g of a mixture of dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate (M-402, Toagosei Co., Ltd.), 0.1 g of hydroquinone, and 0.01 g of benzyldimethylamine were added to a 1-L four-neck flask, and a reaction was run for 12 hours at 60 C. to give crosslinking agent 1.

[0119] Analysis of crosslinking agent 1 gave the following: number of acryloyl groups per 1 molecule=100, mixture of unreacted dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate=30 mass %.

[0120] Production of Crosslinking Agents 2 to 8

[0121] Crosslinking agents 2 to 8 were obtained using the same production method as for crosslinking agent 1, but changing the starting materials and number of parts of addition as shown in Table 1.

[0122] The multifunctional (meth)acrylate compound used for crosslinking agent 3 is a mixture of dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate (M-400, Toagosei Co., Ltd.).

[0123] The multifunctional (meth)acrylate compound used for crosslinking agent 4 is a mixture of pentaerythritol tetraacrylate and pentaerythritol triacrylate (M-305, Toagosei Co., Ltd.).

[0124] The crosslinking agent 8 was purified by dialysis using a semipermeable membrane having a molecular weight cut off of 3,500.

[0125] Crosslinking agents 1 to 8 had dendritic structures.

TABLE-US-00001 TABLE 1 mercapto compound (for adjustment of number of amount of number of (meth)acryloyl compound with (meth)acryloyl groups per 1 formula (3) compound with formula (1) compound with formula (2) groups) Mw molecule (mass %) crosslinking dipentaerythritol 220 g pentaerythritol 20 g 12000 100 30 agent 1 hexaacrylate/ tetra(mercaptoacetate) dipentaerythritol pentaacrylate crosslinking pentaerythritol 180 g trimethylolpropane 25 g 4500 20 10 agent 2 tetraacrylate tri(mercaptoacetate) crosslinking dipentaerythritol 250 g pentaerythritol 40 g sec-butyl 2 g 45000 120 20 agent 3 hexaacrylate/ tetra(mercaptoacetate) mercaptan dipentaerythritol pentaacrylate crosslinking pentaerythritol 160 g trimethylolpropane 25 g 3500 15 10 agent 4 tetraacrylate tri(mercaptoacetate) pentaerythritol triacrylate crosslinking dipentaerythritol 250 g dipentaerythritol 30 g sec-butyl 5 g 55000 140 40 agent 5 hexaacrylate hexa(mercaptoacetate) mercaptan crosslinking pentaerythritol 180 g trimethylolpropane 25 g sec-butyl 0.3 g 4600 12 10 agent 6 tetraacrylate tri(mercaptoacetate) mercaptan crosslinking pentaerythritol 180 g trimethylolpropane 25 g sec-butyl 0.5 g 4700 9 10 agent 7 tetraacrylate tri(mercaptoacetate) mercaptan crosslinking pentaerythritol 180 g trimethylolpropane 25 g 4600 18 purified agent 8 tetraacrylate tri(mercaptoacetate) (detection limit)

[0126] Crosslinking Agents 9 to 11

[0127] The commercial crosslinking agents given in Table 2 were used for crosslinking agents 9 to 11.

TABLE-US-00002 TABLE 2 crosslinking 1,6-hexanediol Tokyo Chemical agent 9 diacrylate Industry Co., Ltd. crosslinking pentaerythritol Shin-Nakamura agent 10 tetraacrylate Chemical Co., Ltd. crosslinking dipentaerythritol Shin-Nakamura agent 11 hexaacrylate Chemical Co., Ltd.

[0128] Toner 1 Production

[0129] An aqueous medium was prepared by adding 9.0 parts of tricalcium phosphate to 1300.0 parts of deionized water heated to a temperature of 60 C. and stirring at a stirring rate of 15,000 rpm using a T. K. Homomixer (Tokushu Kika Kogyo Co., Ltd.).

[0130] In addition, a mixture was prepared by mixing the following binder resin starting materials while stirring at a stirring rate of 100 rpm using a propeller-type stirrer.

TABLE-US-00003 styrene 75.0 parts n-butyl acrylate 25.0 parts crosslinking agent 1 1.5 parts The following were then added to the resulting solution. cyan colorant 6.5 parts (C. I. Pigment Blue 15:3) negative charge control agent 0.5 parts (Bontron E-84, Orient Chemical Industries Co., Ltd.) hydrocarbon wax (Tm = 78 C.) 10.0 parts

[0131] The mixture was then heated to a temperature of 65 C. and a polymerizable monomer composition was subsequently prepared by dissolving and dispersing with stirring at a stirring rate of 10,000 rpm using a T. K. Homomixer (Tokushu Kika Kogyo Co., Ltd.).

[0132] The polymerizable monomer composition was then introduced into the aforementioned aqueous medium;

TABLE-US-00004 Perbutyl PV 10.0 parts (10-hour half-life temperature = 54.6 C. (NOF Corporation))
was added as polymerization initiator; and granulation was performed by stirring at a temperature of 70 C. for 20 minutes at a stirring rate of 15,000 rpm using a T. K. Homomixer.

[0133] The stirrer was changed over to a propeller-type stirrer and, while stirring at a stirring rate of 200 rpm, a polymerization reaction was run on the styrene and n-butyl acrylate, which were the polymerizable monomers in the polymerizable monomer composition, for 5 hours at a temperature of 85 C. to produce a toner particle-containing slurry. The slurry was cooled when the polymerization reaction was finished. Hydrochloric acid was added to the cooled slurry to bring the pH to 1.4 and the calcium phosphate salt was dissolved by stirring for 1 hour. The slurry was then washed with 10-fold water and filtered and dried, and the particle diameter was subsequently adjusted by classification to obtain a toner particle.

[0134] 1.5 parts of hydrophobic silica fine particles (primary particle diameter: 7 nm, BET specific surface area: 130 m.sup.2/g), which had been treated with dimethyl silicone oil at 20 mass % with reference to the silica fine particles, was mixed as external additive with 100.0 parts of the aforementioned toner particle for 15 minutes at a stirring rate of 3,000 rpm using a Mitsui Henschel mixer (Mitsui Miike Chemical Engineering Machinery Co., Ltd.) to obtain a toner. The properties of the obtained toner 1 are given in Table 3.

[0135] Production of Toners 2 to 15

[0136] Toners 2 to 15 were obtained by the same production method as for toner 1, but changing the starting materials, number of parts of addition, and production conditions as shown in Table 3. The properties of the obtained toners are shown in Table 3.

[0137] Toner 16 Production

[0138] An aqueous medium was prepared by adding 9.0 parts of tricalcium phosphate to 1300.0 parts of deionized water heated to a temperature of 60 C. and stirring at a stirring rate of 15,000 rpm using a T. K. Homomixer (Tokushu Kika Kogyo Co., Ltd.).

[0139] In addition, a mixture was prepared by mixing the following binder resin starting materials while stirring at a stirring rate of 100 rpm using a propeller-type stirrer.

TABLE-US-00005 styrene 52.5 parts n-butyl acrylate 17.5 parts styrene-type starburst 30.0 parts dendrimer described in Japanese Patent Application Laid-open No. H07-219272 The following were then added to the resulting solution. cyan colorant (C. I. 6.5 parts Pigment Blue 15:3) negative charge control agent 0.5 parts (Bontron E-84, Orient Chemical Industries Co., Ltd.) hydrocarbon wax (Tm = 78 C.) 10.0 parts

[0140] The mixture was then heated to a temperature of 65 C. and a polymerizable monomer composition was subsequently prepared by dissolving and dispersing with stirring at a stirring rate of 10,000 rpm using a T. K. Homomixer (Tokushu Kika Kogyo Co., Ltd.).

[0141] The polymerizable monomer composition was then introduced into the aforementioned aqueous medium;

TABLE-US-00006 Perbutyl PV 7.0 parts (10-hour half-life temperature = 54.6 C. (NOF Corporation))
was added as polymerization initiator; and granulation was performed by stirring at a temperature of 70 C. for 20 minutes at a stirring rate of 15,000 rpm using a T. K. Homomixer.

[0142] The stirrer was changed over to a propeller-type stirrer and, while stirring at a stirring rate of 200 rpm, a polymerization reaction was run on the styrene and n-butyl acrylate, which were the polymerizable monomers in the polymerizable monomer composition, for 5 hours at a temperature of 85 C. to produce a toner particle-containing slurry. The slurry was cooled when the polymerization reaction was finished. Hydrochloric acid was added to the cooled slurry to bring the pH to 1.4 and the calcium phosphate salt was dissolved by stirring for 1 hour. The slurry was then washed with 10-fold water and filtered and dried, and the particle diameter was then adjusted by classification to obtain a toner particle.

[0143] 1.5 parts of hydrophobic silica fine particles (primary particle diameter: 7 nm, BET specific surface area: 130 m.sup.2/g), which had been treated with dimethylsilicone oil at 20 mass % with reference to the silica fine particles, was mixed as external additive with 100.0 parts of the aforementioned toner particle for 15 minutes at a stirring rate of 3,000 rpm using a Mitsui Henschel mixer (Mitsui Miike Chemical Engineering Machinery Co., Ltd.) to obtain a toner 16.

TABLE-US-00007 TABLE 3 amount of THF- insoluble mass matter crosslinking agent parts (mass %) toner 1 crosslinking agent 1 1.5 40 toner 2 crosslinking agent 1 0.8 8 toner 3 crosslinking agent 1 2.0 60 toner 4 crosslinking agent 2 0.7 40 toner 5 crosslinking agent 3 1.7 40 toner 6 crosslinking agent 4 0.5 40 toner 7 crosslinking agent 5 1.8 40 toner 8 crosslinking agent 6 1.0 40 toner 9 crosslinking agent 7 1.2 40 toner 10 crosslinking agent 8 1.0 40 toner 11 crosslinking agent 9 0.5 40 toner 12 crosslinking agent 10 0.4 40 toner 13 crosslinking agent 11 0.4 40 toner 14 crosslinking agent 2 1.0 65 toner 15 crosslinking agent 2 0.2 3 toner 16 starburst dendrimer 30.0

[0144] Image Evaluations

[0145] The image evaluations were performed using a partially modified commercial color laser printer [HP LaserJet Enterprise Color m553dn]. A modification has been made to enable the printer to operate even with only one color process cartridge. Another modification enabled the temperature at the fixing unit to be freely varied.

[0146] The toner in the black toner process cartridge installed in this color laser printer was removed; the interior was cleaned with an air blower; the particular toner (350 g) was introduced into the process cartridge; the toner-refilled process cartridge was installed in the color laser printer; and the following image evaluations were performed. The specific items in the image evaluation are as follows.

[0147] Gloss

[0148] A solid image (toner laid-on level: 0.6 mg/cm.sup.2) was printed at a fixation temperature of 170 C., and the gloss value was measured using a PG-3D (Nippon Denshoku Industries Co., Ltd.). Letter-size plain paper (XEROX 4200 paper, Xerox Corporation, 75 g/m.sup.2) was used as the transfer material.

Evaluation Criteria

[0149] A: the gloss value is equal to or greater than 30
B: the gloss value is less than 30 and equal to or greater than 20
C: the gloss value is less than 20 and equal to or greater than 15
D: the gloss value is less than 15

[0150] Offset Property

[0151] A halftone (toner laid-on level: 0.3 mg/cm.sup.2) image was fixed on the transfer material at different fixation temperatures (190 C. to 220 C.), and the evaluation was performed based on the temperature at which offset was not produced. The fixation temperature is the value measured for the fixing roller surface using a noncontact thermometer. Plain paper (XEROX 4200 paper, letter size, 75 g/m.sup.2, Xerox Corporation) was used for the transfer material.

A: offset does not occur at 210 C.
B: offset is produced at 210 C.
C: offset is produced at 200 C.
D: offset is produced at 190 C.

[0152] Streaking (Developing Performance)

[0153] Operating in a high-temperature, high-humidity environment (temperature 32 C./humidity 80% RH), a 50000-print print-out test was performed using a horizontal line image having a print percentage of 1%. After the completion of this test, a halftone (toner laid-on level: 0.3 mg/cm.sup.2) image was printed out on letter-size XEROX 4200 paper (75 g/m.sup.2, Xerox Corporation), and the presence/absence of vertical streaks in the halftone image in the paper discharge direction was scored and the durability was evaluated as follows.

Evaluation Criteria

[0154] A: no production
B: vertical streaks in the paper discharge direction are produced at from 1 to 3 locations in the halftone image
C: vertical streaks in the paper discharge direction are produced at from 4 to 6 locations in the halftone image
D: vertical streaks in the paper discharge direction are produced at 7 or more locations in the halftone image, or a vertical streak with a width of 0.5 mm or more is produced

Examples 1 to 10

[0155] The evaluations given above were performed in Examples 1 to 10 using each of toners 1 to 10 for the toner. The results of the evaluations are given in Table 4.

Comparative Examples 1 to 6

[0156] The evaluations given above were performed in Comparative Examples 1 to 6 using each of toners 11 to 16 for the toner. The results of the evaluations are given in Table 4.

TABLE-US-00008 TABLE 4 streaking (developing offset gloss performance) Example 1 toner 1 A A (40) A Example 2 toner 2 A A (40) A Example 3 toner 3 A A (35) A Example 4 toner 4 A A (30) A Example 5 toner 5 A A (35) A Example 6 toner 6 A B (25) B Example 7 toner 7 B B (20) A Example 8 toner 8 A A (30) A Example 9 toner 9 A B (20) A Example 10 toner 10 A A (30) C Comparative Example 1 toner 11 C D (5) A Comparative Example 2 toner 12 C D (10) A Comparative Example 3 toner 13 C D (10) A Comparative Example 4 toner 14 C D (10) A Comparative Example 5 toner 15 D A (30) D Comparative Example 6 toner 16 B B (25) D

[0157] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

[0158] This application claims the benefit of Japanese Patent Application No. 2018-204456, filed Oct. 30, 2018, which is hereby incorporated by reference herein in its entirety.