JP2002162781A - Toner binder for electrophotography - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner binder which has good low temperature fixability and a high hot offsetting temperature and is excellent in image property when converted into a toner. SOLUTION: The toner binder for electrophotography contains a high molecular weight styrene acryl-based resin (HP) and a low molecular weight styrene acryl-based resin (LP) and the (HP) contains a vinyl monomer unit (a) having a hydrolyzable organosillicon group and/or its crosslinked substance as a structural unit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a toner binder for electrophotography.

[0002]

2. Description of the Related Art In an electrophotographic process using dry toner powder, when fixing a toner transferred onto paper or the like,
It is desirable that the minimum fixing temperature (hereinafter abbreviated as MFT) is low (low-temperature fixability), and that the temperature at which hot offset occurs on the surface of the heat roll, film or belt (hereinafter abbreviated as HOT) is high (resistance to heat). Hot offset). In order to obtain a clear image, a toner having a high triboelectric charge is preferable (charging characteristics).

Conventionally, polystyrene resins, styrene-acrylic copolymers, polyester resins, epoxy resins, and the like have been generally used as binder components of the dry toner. Among them, polystyrene resins are preferred in terms of performance such as grindability and chargeability and cost. Based resins and styrene-acrylic resins are widely used. In order to satisfy the low-temperature fixing property and the hot offset resistance, many methods have been proposed for improving the resin by widening the molecular weight distribution of the resin. As a method of expanding the molecular weight distribution, a method of using a vinyl-based crosslinking agent for vinyl-based resins (JP-A-61-215558, JP-A-63-44665, and JP-A-63-22)
No. 3014, JP-A-4-202307),
In the molecular weight distribution, a toner binder having two peaks in a high molecular weight portion and a low molecular weight portion (JP-B-63-321)
No. 80, JP-B-63-32382) or toner binders obtained by crosslinking a carboxyl group-containing vinyl resin with a glycidyl compound (JP-A-6-11890, JP-A-6-222612). .

[0004]

However, as described above,
In a conventional toner binder having a crosslinked structure, a phenomenon in which a crosslinked portion is severely cut by kneading during kneading into a toner and the melt elasticity of the toner is reduced is observed. Therefore, in order to maintain hot offset resistance, it is necessary to use a large amount of a cross-linking component or a high molecular weight component, and the melt viscosity of the resin is significantly higher than that of a resin having no cross-linking structure. Had become. For this reason, the crosslinked toner binder tends to deteriorate the low-temperature fixability of the toner as compared with the non-crosslinked toner binder. In addition, in the conventional method of crosslinking by utilizing the reaction of the functional group in the polymer, when the amount of the functional group is increased and the degree of crosslinking of the binder is increased to improve the hot offset resistance, the amount of the polar group increases. As a result, the charging characteristics of the toner binder become insufficient. As described above, in the conventional technology, in recent years, demands for high image quality of copiers, facsimiles, and printers, and trends for more hot offset resistance and lower-temperature fixing properties due to faster and smaller hardware are increasing. It is hard to say that we can handle it enough.

[0005]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve these problems, and as a result, the styrene-acrylic resin contains an organosilicon compound, and the organosilicon compound is mixed with water. By forming a crosslinked structure by a decomposition reaction, a technique was developed in which the crosslinked portion was hardly cut by kneading in the toner forming process, and the melt elasticity of the toner was hardly reduced. That is, the present invention provides a high molecular weight styrene-acrylic resin (HP) and a low molecular weight styrene-acrylic resin (LP).
Wherein (HP) contains a vinyl monomer unit (a) having a hydrolyzable organic silicon group and / or a crosslinked product thereof as a constituent unit.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. In the present invention, high molecular weight styrene-acrylic resin (HP)
Is a compound containing a vinyl monomer unit (a) having a hydrolyzable organic silicon group and / or a crosslinked product thereof as a constituent unit. Examples of the hydrolyzable organic silicon group in (a) include a group represented by the following general formula (1).

[0007]

Embedded image

Wherein R ¹ is an alkyl or aryl group having 1 to 12 carbon atoms, R ² is a halogen group, an acyloxy group, an amide group, an aminoxy group, an alkenyloxy group, an amino group, an oxime group, an alkoxy group or Thioalkoxy group,
b is an integer of 0 to 2. ]

R ¹ is preferably an alkyl group having 1 to 12 carbon atoms, and more preferably an alkyl group having 1 to 3 carbon atoms. R ² is preferably an acyloxy group, an alkenyloxy group, an alkoxy group or a thioalkoxy group,
More preferably, it is an alkoxy group. b is preferably 0 or 1. Specific examples of (a) include vinylsilanes [vinylmethyldimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, etc.], (meth) acryloxyalkylsilanes [γ- Methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-acryloxypropyltriethoxysilane, etc.] Can be Of these, (meth) acryloxyalkylsilanes are preferred, and γ-
(Meth) acryloxypropyltrimethoxysilane is particularly preferred. The crosslinked product (a) refers to a product obtained by subjecting a hydrolyzable organic silicon group to a crosslinking reaction with water. The crosslinking reaction is carried out by heating if necessary. The content of the vinyl monomer unit (a) having a hydrolyzable organic silicon group and / or a crosslinked product thereof in (HP) is usually 0.01 to 20% by weight, preferably 1 to 15% by weight. is there.

The styrene monomer used for the styrene-acrylic resin of (HP) includes styrene, α-methylstyrene, p-methoxystyrene, p-hydroxystyrene, p-acetoxystyrene and the like. As the acrylic monomer, alkyl groups having 1 to 18 carbon atoms, such as butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, and stearyl (meth) acrylate And alkyl (meth) acrylate. The ratio between the styrene monomer and the acrylic monomer is 95/5 to 5/95 by weight, preferably 90/10 to 20/80, and particularly preferably 85/95.
/ 15 to 40/60. In order to increase the elasticity of the binder, divinyl compounds such as divinylbenzene, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and divinyltoluene are used in a single unit. It is preferably used in an amount of 0.1 mol% or less based on the body. More preferably, 0.00005 to 0.1.
001 mol%. Further, other vinyl monomers other than these styrene monomers and acrylic monomers may be copolymerized. Other vinyl monomers include vinyl esters such as vinyl acetate; vinyl ethers such as vinyl ethyl ether; aliphatic hydrocarbon vinyl such as α-olefin, isoprene, butadiene; and (meth) acrylonitrile. .

The weight average molecular weight of (HP) is preferably 5
10,000 to 2,000,000, more preferably 70,000 to 180
10,000, particularly preferably 100,000 to 1.5 million. When the weight average molecular weight is 50,000 or more, the HOT of the toner does not decrease. When the weight average molecular weight is 2,000,000 or less, the MFT of the toner does not increase. The weight average molecular weight can be determined, for example, by gel permeation chromatography (G
PC method). The glass transition point of (HP) is preferably from 40 to 80 ° C, more preferably from 50 to 80 ° C.
75 ° C. The glass transition point is, for example, ASTM (D34
It is measured by the method 18-2).

As the polymerization method for producing (HP), any method such as solution polymerization, bulk polymerization, and suspension polymerization can be selected. The polymerization initiator is not particularly limited. For example, azo initiators such as azobisisobutyronitrile and azobisisovaleronitrile; benzoyl peroxide, di-t-butyl peroxide, lauroyl peroxide, dicumyl Peroxide initiator such as peroxide; 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane, 1,1-bis (t-butylperoxy) 3,3,5- Trimethylcyclohexane,
A polyfunctional polymerization initiator having two or more peroxide groups in one molecule, such as di-t-butylperoxyhexahydroterephthalate; diallylperoxydicarbonate;
Examples thereof include polyfunctional polymerization initiators having one or more peroxide groups and one or more polymerizable unsaturated groups in one molecule, such as t-butyl peroxyallyl carbonate. Of these, preferred are monofunctional polymerization initiators.

The solvent used when (HP) is obtained by solution polymerization is not particularly limited, but aromatic solvents such as toluene, xylene and ethylbenzene, ester solvents such as ethyl acetate and butyl acetate, dimethylformamide,
Dimethyl sulfoxide, methyl ethyl ketone and the like can be mentioned. Preferably, dimethylformamide, xylene,
It is toluene.

When (HP) is obtained by suspension polymerization, it can be polymerized in water using an inorganic salt dispersant such as calcium carbonate and calcium phosphate, and an organic dispersant such as polyvinyl alcohol and methylated cellulose. The polymerization temperature is preferably from 50 to 190C, more preferably from 60 to 170C. The polymerization is preferably performed in the presence of an inert gas such as nitrogen.

Low molecular weight styrene-acrylic resin (L
As the styrene-based monomer and acrylic-based monomer used in P), the same ones as those described in the above (HP) can be used. The weight average molecular weight of (LP) is preferably 3,000 to
It is less than 50,000, more preferably 3,500 to 40,000, particularly preferably 4000 to 30,000. When the weight average molecular weight is 3,000 or more, the heat-resistant storage stability of the toner becomes good. When the weight average molecular weight is less than 50,000, the MFT of the toner does not increase. The glass transition point of (LP) is preferably from 40 to 80 ° C, more preferably from 50 to 75 ° C.

As the polymerization method for producing (LP), any method such as solution polymerization, bulk polymerization, suspension polymerization and the like can be selected. Of these, solution polymerization is preferred. (L
When P) is polymerized by solution polymerization, it can be polymerized by the solution polymerization method described above. The polymerization initiator for polymerizing (LP) is not particularly limited, and examples thereof include the polymerization initiators described above. Preferred among these are monofunctional initiators.

The toner binder of the present invention comprises (HP) and (LP), and the weight ratio of (HP) to (LP) is preferably 70/30 to 5/95, more preferably 60/40 to 10/95. / 90, particularly preferably 50/50
２０20/80.

The weight average molecular weight of the toner binder of the present invention composed of (HP) and (LP) is preferably 3
It is 10,000 to 1,000,000, more preferably 50,000 to 900,000, and particularly preferably 100,000 to 800,000. Further, the glass transition point is preferably 30C to 150C, more preferably 35C to 90C, and particularly preferably 4C to 90C.
0 ° C to 80 ° C.

The method of crosslinking the toner binder of the present invention includes, for example, (HP) and (L) before crosslinking.
P), water is added to the system, and the mixture is heated (H
A method in which at least a part of P) is subjected to a hydrolysis reaction and crosslinked. In the above reaction, the reaction of (a) in (HP) is preferably performed at least up to a reaction rate of 70%. If the reaction is performed without using a kneader, the hot offset property of the obtained toner binder is improved, More preferred.

An example of a method for producing an electrophotographic toner which is used for the toner binder of the present invention is as follows. The toner binder is usually 45 to 95% by weight based on the weight of the toner, and a known coloring agent (carbon black, iron black, Benzidine yellow, quinacdrine, rhodamine B, phthalocyanine, etc.)
Is usually used in a proportion of 5 to 10% by weight and magnetic powder (compounds of iron, cobalt, nickel, hematite, ferrite, etc.) is usually used in a proportion of 0 to 50% by weight, and various additives [charge adjusting agent (metal complex, nigrosine, nigrosine) are used. ), Lubricants (such as polytetrafluoroethylene, low molecular weight polyolefins, fatty acids, or metal salts or amides thereof) and the like]. The amount of these additives is usually 0 to 10% by weight based on the weight of the toner. The electrophotographic toner is dry-blended with the above components, melt-kneaded, coarsely pulverized, and finally finely pulverized using a jet pulverizer or the like to obtain fine particles having a particle size of 5 to 20 μm. The electrophotographic toner is used as a developer for an electric latent image by being mixed with carrier particles such as iron powder, glass beads, nickel powder, and ferrite as needed. Further, hydrophobic colloidal silica fine powder can be used to improve the fluidity of the powder.

The electrophotographic toner is used after being fixed on a support (paper, polyester film, etc.). Examples of the fixing method include a method using a contact heating type fixing device (heat roll) and a method in which a film or a belt is interposed between a heating member and paper (for example, JP-A-4-70688 and JP-A-4-12558). No. Preferred is a contact heating type fixing device.

[0022]

The present invention will be further described with reference to the following examples, but the present invention is not limited to these examples. Hereinafter, “parts” indicates “parts by weight”. The methods for measuring the properties of the resins obtained in Synthesis Examples, Examples and Comparative Examples are described below.

Molecular weight measurement apparatus: HLC-802A manufactured by Tosoh Corporation Conditions: column TSK gel GMHXL manufactured by Tosoh Corporation Measurement temperature: 40 ° C. Sample solution: 0.25 wt% tetrahydrofuran solution Solution injection amount: 100 μl Detector: Refraction Rate detector The molecular weight calibration curve was created using standard polystyrene.

Glass transition point (Tg) measurement device: RDC220 manufactured by Seiko Instruments Inc. Condition: ASTM (D3418-2) method

Preparation of Resin (HP) Production Example 1 200 parts of xylene was placed in an autoclave reaction vessel equipped with a thermometer, a stirrer, and a nitrogen inlet tube.
719.2 parts of styrene and n-butyl acrylate 27
A mixed monomer of 1.6 parts and 9.2 parts of γ-methacryloxypropyltrimethoxysilane, and di-t-
A mixture of 1.5 parts of butyl peroxide and 100 parts of xylene was added dropwise over 3 hours. After dropping, the mixture was aged at 170 ° C. for 1 hour to complete the polymerization. Thereafter, the solvent was removed under reduced pressure to obtain a resin (HP1). GPC of (HP1)
Has a weight average molecular weight of 104,000 and a glass transition point of 6
It was 0 ° C.

Production Example 2 A resin was produced in the same manner as in Production Example 1 except that the mixed monomer was 713 parts of styrene, 271.6 parts of n-butyl acrylate, and 15.4 parts of γ-methacryloxypropyltrimethoxysilane. (HP2) was obtained. The weight average molecular weight of (HP2) determined by GPC was 105,000, and the glass transition point was 61 ° C.

Production Example 3 728.4 parts of styrene mixed with n-acrylic acid
A resin (HP3) was obtained in the same manner as in Production Example 1 except that the mixed monomer was 271.6 parts of butyl. G of (HP3)
The weight average molecular weight by PC was 105,000, and the glass transition point was 59 ° C.

Preparation of Resin (LP) Production Example 4 452 parts of xylene was placed in the same apparatus as in Production Example 1, and after replacing with nitrogen, a mixed monomer of 845 parts of styrene and 155 parts of n-butyl acrylate was added at 170 ° C., and an initiator. As di-t-
A mixture of 6.4 parts of butyl peroxide and 125 parts of xylene was added dropwise over 3 hours. After dropping, the mixture was aged at 170 ° C. for 1 hour to complete the polymerization. Thereafter, the solvent was removed under reduced pressure to obtain a resin (LP1). GP of (LP1)
The weight average molecular weight by C is 14,000 and the glass transition point is 6
It was 0 ° C.

Preparation of Toner Binder (TB) Production Examples 5 to 6 100 parts of xylene was charged into a cooling pipe and a kolben equipped with a stirrer, and the amount of (HP) shown in Table 1 was added and dissolved.
After adding (LP) and purging with nitrogen, the mixture was stirred at 150 ° C. for 2 hours while stirring to dissolve uniformly. Thereafter, water (40% of the charged amount of (HP)) was added, and the mixture was stirred for 3 hours to cause a crosslinking reaction. After that, the solvent was removed under reduced pressure at 170 ° C., and the resin (TB1) 〜
(TB2) was obtained. Table 1 also shows the weight average molecular weight and Tg of (TB).

[0030]

[Table 1]

Comparative Example 1 A comparative toner binder (TB3) was obtained by using the components shown in Table 2 in the same manner as in Example 1. Table 2 also shows the weight average molecular weight and Tg of (TB3).

[0032]

[Table 2]

Use Examples and Comparative Use Examples The evaluation of the toner binder was performed in two ways: a two-component development system and a one-component development system. Evaluation of Two-Component Development System # In each of 88 parts of the toner binder of the present invention in Production Examples 5 to 6 and the toner binder of Comparative Example 1, 7 parts of carbon black (MA100 manufactured by Mitsubishi Chemical Corporation) and 7 parts of low molecular weight polypropylene (Sanyo Chemical Industries, Ltd.) Viscol 550P) 3 parts and charge control agent (Hodogaya Chemical Industries Spiron Black TRH) 2
After uniform mixing, the mixture is kneaded with a twin-screw extruder at an internal temperature of 150 ° C., and the cooled product is finely pulverized with a jet mill and classified with a dispersion separator, and toners a to c having an average particle diameter of 12 μm are formed.
I got

Test Example 1 To 3 parts of each of the toners a to c, 97 parts of a ferrite carrier (F-100 manufactured by Powdertech) were mixed uniformly, and the toner was applied to paper using a commercial copying machine (AR-5030 manufactured by Sharp). The image is transferred, and the toner on the transferred paper is converted into a fixing unit of a commercial copying machine (BD-7720, manufactured by Toshiba Corporation).
The fixing test was performed at a speed of 35 sheets / minute on four papers. The image quality was determined based on the image density after fixing. The test results are as shown in Table 3.

Test Example 2 Each of the toners a to c was placed in a polyethylene bottle,
After being kept in a constant temperature water bath at 50 ° C. for 8 hours, the mixture was transferred to a 42-mesh sieve and shaken for 10 seconds using a powder tester manufactured by Hosokawa Micron Corporation, and the weight% of the toner remaining on the sieve
Was measured and a heat resistance storage test was performed. The smaller the number, the better the heat-resistant storage stability. If it is less than 35%, it can be used without any problem. Table 3 shows the results.

[0036]

[Table 3]

* 1 A black solid portion having an image density of 1.2 was rubbed by a Gakushin-type fastness tester (friction portion = paper) with five reciprocations, and the image density of the solid portion after rubbing was 70% or more. Heat roll temperature at which the remaining copy was obtained. * 2 Heat roll temperature when toner is hot offset * 3 ◎: Image density (ID)> 1.4, ○: (ID) 1.0 to 1.
4, △: (ID) <1.0

In the evaluation by the two-component developing system, the toners a and b using the binder of the present invention all showed a low-temperature fixability without impairing the heat-resistant storage stability and image quality as compared with the toner c using the comparative binder. Excellent balance of hot offset resistance.

Evaluation of one-component developing system 48.8 parts of magnetic powder (EPT-1000, manufactured by Toda Kogyo KK) was added to 48.8 parts of the toner binder of the present invention in Production Examples 5 to 6 and 48.8 parts of the toner binder of Comparative Example 1, respectively. Low molecular weight polypropylene (Hymer TP-3 manufactured by Sanyo Chemical Industries, Ltd.)
2) 2 parts, and charge adjuster (T by Hodogaya Chemical Co., Ltd.)
-77) After uniformly mixing 0.4 parts, kneading is performed with a twin-screw extruder at an internal temperature of 130 ° C., and the cooled product is finely pulverized with a jet mill, classified with a dispersion separator, and classified into toners A to C having an average particle diameter of 8 μm. I got

Test Example 3 Toners A to C were transferred to a toner image on paper by using a commercially available laser beam printer (manufactured by Canon Inc., LBP-210), and the transferred toner on paper was used in the same manner as in Test Example 1 described above. , A fixing test and evaluation of image quality were performed. The test results are as shown in Table 4.

Test Example 4 Toners A to C were tested for heat resistance and storage stability in the same manner as in Test Example 2. If it is less than 35%, it can be used without any problem. Table 4 shows the results.

[0042]

[Table 4]

* 1 A black solid portion having an image density of 1.2 was rubbed with a Gakushin-type fastness tester (friction portion = paper) in two reciprocations, and the image density of the solid portion after rubbing was 70% or more. Heat roll temperature at which the remaining copy was obtained. * 2 Heat roll temperature when toner is hot offset * 3 ◎: Image density (ID)> 1.4, ○: (ID) 1.0 to 1.
4, △: (ID) <1.0

In the evaluation by the one-component developing system, the toners A and B using the binder of the present invention all showed a low-temperature fixability without impairing the heat resistance storage stability and the image quality as compared with the toner C using the comparative binder. Excellent balance of hot offset resistance.

[0045]

As described above, the toner binder of the present invention maintains heat-resistant storage stability and low-temperature fixability by introducing a small amount of a reactive functional group and increases the molecular weight, and is excellent in image properties and hot offset resistance. Toner is obtained.

Claims (5)

[Claims] 1. A high molecular weight styrene-acrylic resin (H
P) and a low molecular weight styrene-acrylic resin (LP), wherein (HP) contains a vinyl monomer unit (a) having a hydrolyzable organosilicon group and / or a crosslinked body thereof as a constituent unit. Characteristic toner binder for electrophotography. 2. The electrophotographic toner binder according to claim 1, wherein the content of (a) and / or a crosslinked product thereof in (HP) is 0.01 to 20% by mass. 3. The electrophotographic toner binder according to claim 1, wherein (a) has at least one alkoxy group. 4. The toner binder for electrophotography according to claim 1, wherein (a) has one silicon atom. 5. The electrophotographic toner binder according to claim 1, wherein (HP) is obtained by subjecting a part of (a) to a crosslinking reaction with water.