JPH02308175A - Resin for electrophotographic toner and its manufacturing method - Google Patents

Abstract

PURPOSE:To improve blocking resistance by mixing specified polyester resin (A) with specified polyester resin (B) in a specified ratio, allowing this resin mixture to react with an isocyanato compd. and using the resulting urethane modified polyester resin. CONSTITUTION:Polyester resin (A) having 1,000-15,000 number average mol. wt. and 10-100 hydroxyl value is mixed with polyester resin (B) having 1,000-5,000 number average mol. wt. and <10 acid and hydroxyl values in total in 20:80-60:40 weight ratio, this resin mixture is allowed to react with 0.3-0.99 mol equiv. isocyanato compd. basing on 1 mol equiv. hydroxyl group in the polyester resin A and the resulting urethane modified polyester resin having 40-75 deg.C glass transition point is used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a resin for electrophotographic toners, a method for producing the same, and a toner composition containing the resin, and more particularly relates to a resin for toners with high moisture resistance stability.

[Background technology]

In electrophotography, an electrical latent image is formed on a photoreceptor by various means using a photoconductive substance, and then this latent image is developed using a toner, and if necessary, an electrical latent image is formed on an image support such as paper. After the image is transferred to a computer, the image is fixed using a heating roll or the like to obtain an image. Various toner resins have been studied for use here, but polyester resin, when melted, disperses toner additives such as carbon black and wets the transfer paper well, and has excellent fixing properties. It is currently used as a toner for heating roll fixing because it has the advantage of being superior to other toners.

With regard to electronic photography, from the standpoint of information transmission, it is required to provide clear images in a stable state at all times.

However, in toners using conventional polyester resins, hydrophilic groups such as carboxyl groups and hydroxyl groups derived from the monomers that make up the polymer exist at the polymer ends, so changes in the environment, especially humidity changes, can affect the fluidity of the toner. Storage stability and charging characteristics changed significantly, making it impossible to provide clear images at all times.

As a means of solving this problem, a method has been proposed in which, for example, adding hydrophobic silica fine powder to the toner composition to improve these characteristic changes, but the method of adding hydrophobic fine powder does not Although the characteristics of the photoreceptor have been improved to some extent, the basic problem has not been solved yet, such as the surface of the photoreceptor of the copying machine being damaged by the hydrophobic silica fine powder.

[Disclosure of the invention]

An object of the present invention is to provide a resin for electrophotographic toners that exhibits good pulverizability during toner preparation, is resistant to environmental changes, particularly humidity changes, and has excellent blocking resistance.

Another object of the present invention is to provide an electrophotographic toner composition that has good fixing properties, excellent moisture resistance, and can produce good images without fogging.

According to the invention, the number average molecular weight is between 1,000 and 15,0
Polyester resin (A
) and a polyester resin (B) with a number average molecular weight of 1,000 to s, ooo and a total of acid value and hydroxyl value of less than 10
0.3 to 0.99 molar equivalent of isocyanate compound (C) per 1 molar equivalent of hydroxyl group of the polyester resin (A) is reacted with a resin mixture having a ratio of 20 F 80 to 60: 40 by weight. There is provided a resin for electrophotographic toner comprising a urethane-modified polyester resin (D) having a glass transition point of 40 to 75°C.

Furthermore, according to another aspect of the present invention, there is provided an electrophotographic toner composition containing the above-mentioned urethane-modified polyester resin (D) and various commonly used compounding agents.

According to still another aspect of the present invention, the above polyester resin (A
) and a polyester resin (B) are kneaded with an isocyanate and reacted together.

[Best mode for carrying out the invention]

The polyester resin (A) referred to in the present invention is obtained by polycondensation of a polyhydric carboxylic acid and a polyhydric alcohol. The polyhydric carboxylic acids mentioned here include, for example, aliphatic dibasic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, hexahydrophthalic anhydride, and phthalic anhydride, phthalic acid, and terephthalic anhydride. Examples include aromatic dibasic acids such as isophthalic acid, and lower alkyl esters thereof.

In addition, examples of the polyhydric alcohol mentioned here include ethylene glycol, 2-propylene glycol, 1.3
-Propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, ■.

Examples include diols such as 6-henan diol, neopentyl glycol, diethylene glycol, dipropylene glycol, hydrogenated bisphenol A1 bisphenol A propylene oxide adduct, and triols such as glycerin, trimethylolpropane, and trimethylolethane. can. Among these, bisphenol A propylene oxide adduct is preferred.

As the polycondensation method, commonly known high temperature polycondensation, solution polycondensation, etc. are used.

The molecular weight of the polyester resin (A) is 1000 to 15000 in number average molecular weight, and 100 to 15000 in number average molecular weight.
If it is less than 0, the resulting urethane-modified polyester resin (D
) The molecular weight of the urethane-modified resin (D) decreases during melt-kneading during toner production, causing fogging and deterioration of offset resistance. do.

Furthermore, if the hydroxyl value is less than 10, the offset resistance of the toner obtained will be reduced, while if it is greater than 100, the heat resistance of the obtained urethane-modified resin will be reduced.

The polyester resin (B) is obtained by the same method as the polyester resin (A), and has a number average molecular weight of 1000 to 5.
The polyhydric carboxylic acid and polyhydric alcohol used are polyester resins having a total acid value and hydroxyl value of less than 10, preferably less than 8.
) can also be exemplified here. A particularly preferred polyester resin (B) is a condensate of a bisphenol A propylene oxide compound, trimethylolpropane, and dimethyl terephthalate.

The molecular weight of the polyester resin (B) is 10 in number average molecular weight.
00-5000, preferably 2000-4000.

If the number average molecular weight of the polyester resin (B) is less than 1,000, the offset resistance of the toner obtained using the urethane modified resin (D) will decrease. On the other hand, if it exceeds 5,000, the fixability and crushability of the toner deteriorate.

In addition, when the sum of the acid value and hydroxyl value of the polyester resin (B) is 10 or more, the terminal carboxyl groups and hydroxyl groups have strong hydrophilicity, so changes in the environment, especially temperature changes may affect the toner's fluidity and storage stability. Furthermore, the charging characteristics change significantly, fogging occurs, and clear images cannot be obtained at all times.

Further, when the hydroxyl value is 10 or more, transesterification reaction tends to occur (as a result, the molecular weight distribution becomes narrower, and the fixing properties and anti-offset properties of the toner deteriorate).

The preferred ranges of acid value and hydroxyl value are each 4 or less.

The ratio of polyester resin (A) to polyester resin (B) is 20:80 to 60:240 by weight. If the weight ratio of the polyester resin (A) is less than 20, the offset resistance will be reduced and the fixing temperature range will be narrowed, while if it is more than 60, the crushability will be poor.

Examples of the isocyanate compound (C) of the present invention include hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, and tetramethylxylylene diisocyanate.

The commonly used range of isocyanate compound (C) is:
0.3 per molar equivalent of hydroxyl group in polyester resin (A)
If the amount of the isocyanate compound is less than 0.3 molar equivalent, the amount is preferably from 0.5 to 0.99 molar equivalent, and 0.5 to 0.95 molar equivalent is particularly preferred, the offset resistance of the toner decreases. On the other hand, if the amount exceeds 0.99 molar equivalent, the viscosity increases significantly during the reaction.
In some cases, the viscosity of the urethane-modified polyester resin (D) increases too much, resulting in a viscosity that makes stirring difficult, so-called ultra-high viscosity, which is not preferred in practice.

The urethane-modified polyester resin (D) can be obtained, for example, by the following method. That is, in the coexistence of polyester resins (A) and (B), without a solvent or in the presence of a solvent, the isocyanate compound (C) is added all at once, in portions, or continuously at a temperature of 60 to 190°C, and the mixture is heated at this temperature for several minutes. Obtained by reacting for ~ several hours.

In a preferred embodiment, the polyester resin (A) is produced using a single-screw extruder or a twin-screw extruder equipped with a built-in screw.
There is a method in which a mixture of (B) and isocyanate compound (C) is continuously kneaded and the reaction is carried out.

In particular, by using a twin-screw extruder, the mixing and dispersing effects of the resin component and the isocyanate compound are improved, and the average residence time of the reaction product in the reaction zone of the extruder is lengthened. As such a twin-screw extruder, a twin-screw co-rotating intermeshing extruder is particularly preferred.

Further, it is desirable that the accuracy of the raw material feeder that supplies the mixture of polyester resins (A) and (B) at a predetermined mixing ratio to the extruder and the metering pump for injecting the liquid isocyanate compound be as high as possible. The amount of resin supplied is determined in consideration of the average residence time. As for the specifications of the extruder, it is necessary to increase the average residence time of the contents in the extruder in order to sufficiently react the polyester resin (A) and the isocyanate compound (C) in the mixture. For this purpose, the L/D (ratio of screw length [L] to screw diameter [D]) of the extruder is usually 10 or more, preferably 2.
0 or more and 60 or less. More specifically, the screw of the extruder is made of polyester resins (A) and (B).
The feed zone is divided into a feed zone, a volatile component removal zone, and a reaction zone when viewed from the supply port, and the length of each zone is L/D. It is preferable to design the screw so that the number of zones is 20 to 40. As for the operating conditions, it is preferable that the temperature setting is performed independently in each zone. Typically, the feed zone is 30°C to 100°C, the volatile component removal zone is 100 to 250°C, and the reaction zone is 1
It is desirable to accurately control the temperature within the range of 20°C to 220°C.

The continuous component removal zone can be omitted when volatile components or solvents are not present in the raw resin or are extremely small, and the feed zone and reaction zone can be lengthened accordingly.

The cylinder of the extruder can be heated by either an electric heater or a heating medium.
Although a heating medium type that can provide uniform heating is preferable to a single electric heater type that tends to cause localized heating, either type can be used in the present invention.

Further, the rotational speed of the screw is related to the supply amount of raw resin and welding, but it is preferably adjusted so that the average residence time of the contents in the reaction zone is 15 to 25 minutes.

The glass transition temperature of the urethane-modified polyester resin (D) is in the range of 40 to 75°C, preferably 50 to 60'C. If the glass transition temperature is less than 40° C., the blocking resistance of the toner deteriorates. On the other hand, if the temperature exceeds 75°C, the fixing properties of the toner deteriorate.

In the electrophotographic toner composition of the present invention, a suitable colorant, a charge control agent, and further additives are blended with the resin (D) as necessary.

Suitable colorants include, for example, carbon blank, aniline blue, alcoyl blue, chrome yellow, Uno1 tramarine blue, quinoline yellow methylene blue, phthalocyanine blue, malachite green, rose bengal, magnetite, and the like.

In addition, as the charge control agent, all conventionally known charge control agents can be blended. Examples include nigrosine, triphenylmethane dyes, chromium complexes of 3,5-di-t-butylsalicylic acid, etc. .

As additives, all conventionally known additives such as colloidal silica, zinc stearate, low molecular weight polypropylene, stearamide, methylene bisstearamide, etc. can be used.

The above resin and other compounds are premixed using a Henschel mixer, etc., then melt-kneaded using a kneader or the like at a temperature of IOθ to 180°C, and the resulting mass is crushed and classified to have a particle size of 5 to 15μ.
- It can be used as particles for electrophotographic toners.

〔Example〕

Next, the present invention will be specifically explained with reference to Examples.

Note that hereinafter "parts" represent parts by weight unless otherwise specified.

Production example A-T-A-V This example is a production example of polyester resin (A).

A 5140 flask was equipped with a reflux condenser, a water separator, a nitrogen gas inlet tube, a thermometer, and a stirring device, and the polybasic acids and polyhydric alcohols shown in Table 1 were charged into the flask. Dehydration polycondensation is carried out at ~240°C.

The reaction was stopped at an acid value of <1, and polyester resins A-1 to 2 were obtained.

Production example B-1-B-■ This example is a production example of polyester resin (B).

5I! , 40 flasks were equipped with a reflux condenser, a water or alcohol separation device, a nitrogen gas inlet tube, a thermometer, and a stirring device, and the polybasic acids or lower alkyl esters of polybasic acids and polybasic acids shown in Table 2 were prepared. Charge alcohol and conduct dehydration polycondensation or dealcoholization polycondensation at 220 to 240 °C while introducing nitrogen into the flask. When the acid value or hydroxyl value reaches a predetermined value, the reaction is stopped and polyester resin B-1 ~B-■ was obtained.

Production Examples 1-15 This example is a production example of urethane-modified polyester resin (D).

Polyester resins (A) and (B) obtained above
were ground to a particle size of 0.5 to 1 mm, weighed to the mixing ratio shown in Table 3, and premixed using a Henschel mixer. This is then extruded using twin screws a (-Japan Steel Works type TEX-30
, L/D was 30, the feed zone was 6, the devolatilization component removal zone was 2, and the reaction zone was 22) for urethane modification. As extrusion conditions, the extruder cylinder temperature was set so that the resin temperature was 170'C. For urethane modification, premixed resin is mixed using a quantitative feeder.
The resin was continuously fed into an extruder at a rate of 4 kg/Hr, melted and kneaded, the volatile matter in the resin was removed in vacuum through a vent hole installed in the extruder, and then the predetermined amount shown in Table 3 was added through an injection nozzle. Isocyanate compound (C) (tolylene diisocyanate) was continuously supplied using a metering pump, and the reaction was carried out such that the average convection time after the injection nozzle was 20 minutes. Obtained urethane-modified polyester resin (D)
was cooled and coarsely crushed.

Examples 1 to 15 6 parts by weight of carbon black MA-100 (manufactured by Mitsubishi Kasei ■) to 100 parts by weight of the urethane-modified polyester resin (D) obtained in Production 'g11 to 15, and Spiron black TRH as a charge control agent. (manufactured by Fukadogaya Chemical)
2 parts by weight, polypropylene wax Viscole 55
After dispersing and mixing 2 parts by weight of 0P (manufactured by Sanyo Chemical Industries, Ltd.) and 3 parts by weight of the bisamide wax Armowax IEBS (manufactured by Lion Armor Company) in a Henschel mixer, the mixture was placed in a twin-screw kneader PCM30 (manufactured by Ikegai Iron Works, Ltd.). The mixture was melt-kneaded at 160° C. to obtain a bulk toner composition.

This composition was coarsely pulverized with a hammer mill, then finely pulverized with a jet pulverizer (model ID52 manufactured by Nippon Pneumatic Co., Ltd.), and then air-classified to obtain an average particle size of 10μ (3% by weight of 5μ or less, 20μ). 2% by weight) of toner particles were obtained. The properties of the obtained toner particles are shown in Table 4.

Add 4 parts by weight of this toner to ferrite carrier F-150 (
The mixture was mixed with 100 parts by weight of Nippon Tetsu Powder ■ to prepare a two-component developer.

Commercially available magnetic brush type copy Il (Toshiba ■ReoDry 8
411), room temperature 25°C, relative humidity 50% and 80%
A copying test was conducted by changing the temperature of the heat roller in an environment of 50%. The evaluation results of the fixing temperature range and PVC plasticizer migration resistance are shown in Table 4.

Furthermore, Table 4 also shows the results of evaluating changes in image density and occurrence of fog when up to 50,000 copies were made.

Notes in the table are as follows.

1) Bisphenol A-(2,2)-propylene oxide adduct (manufactured by Nii Toatsu Kagaku ■) 2) JIS K5400 method 3) Monodisperse standard polystyrene as the standard, 't
Gel permeation chromatography (using tetrahydrofuran as the ldl liquid and a refractometer as the detector)
4) Weight average molecular weight determined by the same method as in 4) above 5) Pyridine-acetic anhydride method 6) Glass transition temperature determined by differential scanning calorimetry (DSC) 7) Tolylene diisocyanate 8 ) The degree of aggregation of the powder is visually measured after the manufactured toner is left in an environment of a temperature of 50° C. and a relative humidity of 50% and 80% for 24 hours as follows.

◎; Not agglomerated at all O; Slightly agglomerated, but can be loosened by shaking the container Δ; Some aggregates are not loosened even if the container is shaken well ×; Completely agglomerated 9) Finely pulverized; The crushability is determined as follows from the yield of particles having a particle size of 5 to 20 μm obtained by classification.

A; Yield of 90% or more B; Yield of 80 to less than 90% C; Yield of 70 to less than 80% D; Yield of less than 70% 10) The molten toner adheres to the heat fixing roll and is fixed to the copy paper again. The lowest heat fixing roll surface temperature at which the so-called offset phenomenon begins to occur 11) Apply 125 g of toner on a 2 cm x 2 cm solid black image using a Gakushin friction fastness tester (manufactured by Daiei Kagaku Seiki Seisakusho). The minimum heat fixing roll surface temperature required for the weight residual rate of one layer of toner to exceed 80% after rubbing with a sand eraser 50 times under a load of /c-12) A commercially available PVC sheet ( Containing 50% by weight of dioctyl phthalate, manufactured by Mitsui Toatsu Chemical Co., Ltd.) were layered and heated to 50°C for 24 hours at 20g/a.
After applying a load of a and leaving it to stand, the PVC sheet was peeled off at room temperature. At this time, the state of transfer of the toner to the PVC sheet is visually determined as follows.

◎: No migration of dye and toner is observed O: Only dye has migrated △: Part of toner has migrated ×: Most of toner has migrated 13) After 50,000 sheets of copying The degree of blackness of solid black areas in the image is determined visually.

14) In the image after 50,000 copies, visually determine the degree of staining of the white background due to toner adhering to the white background.

◎; No stain O; Slight stain Δ; Considerable stain ×; Severe stain As can be seen from the results in Table 4, the toner obtained by the present invention has excellent pulverizability during preparation and is easy to store. It is highly resistant to environmental changes, especially humidity changes, and has excellent blocking resistance, thus making it possible to obtain good images with good fixing properties and no fogging.

Claims (3)

[Claims] (1) Polyester resin (A) with a number average molecular weight of 1,000 to 15,000 and a hydroxyl value of 10 to 100 and a polyester resin (A) with a number average molecular weight of 1,000 to 5,000 and a total of acid value and hydroxyl value of less than 10 For a resin mixture in which the ratio of polyester resin (B) is 20:80 to 60:40 by weight,
0.0% per mole of hydroxyl group of the polyester resin (A).
An electrophotographic toner resin comprising a urethane-modified polyester resin (D) having a glass transition temperature of 40 to 75°C, obtained by reacting 3 to 0.99 molar equivalents of an isocyanate compound (C). (2) The above polyester resin (A) and (
Glass transition temperature by continuously kneading 0.3 to 0.99 molar equivalent of isocyanate compound (C) per mole of hydroxyl group of polyester resin (A) to the resin mixture with B). A method for producing a urethane-modified polyester resin (D) having a temperature of 40 to 75°C. (3) An electrophotographic toner composition containing the resin according to claim 1.