JPH02250062A - Electrophotographic toner composition - Google Patents

Abstract

PURPOSE:To enhance low temperature fixability and offset resistance and to enlarge an allowable fixing temperature range by using as a main component a urethane-modified polyester resin having both maximum and minimum loss tangent values of 0.7 - 2.5 measured in the frequency range of 10<-2> - 10Hz at 150 deg.C. CONSTITUTION:The urethane-modified polyester resin to be used as the main component has both maximum and minimum loss tangent values of 0.7 - 2.5, preferably, 1.0 - 2.1 measured in the frequency range of 10<-2> - 10Hz at 150 deg.C, and it is preferred to have a glass transition point of 45 - 75 deg.C. If the minimum value is <0.7, the low temperature fixability of a toner is deteriorated, and the allowable fixing temperature range is narrowed, and if the maximum value is >2.5, the offset resistance of the toner is deteriorated and the range is also narrowed, thus permitting low temperature fixability and offset resistance to be enhanced and an allowable fixing temperature range to be enlarged.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a toner composition for electrophotography, and more particularly to a toner composition for electrophotography that is excellent in both low-temperature fixing properties and anti-offset properties.

(Prior Art) 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 toner, and if necessary, it is printed on paper, etc. After the image is transferred onto an image support, it 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,
It is currently used as a toner resin for heating roll fixing because it has the advantages of dispersing toner colorants such as carbon black, wetting transfer paper well, and having excellent fixing properties. There is.

[Problem to be Solved by the Invention 1] In electrophotography, from the standpoint of information transmission, it is required to always provide clear images in a stable state. In recent years, copying speeds have tended to increase as the amount of information to be processed increases. As the copying speed increases, the surface temperature of the heat-fixing roll decreases significantly as the number of copies increases due to the amount of heat taken away by the copying paper. Even if the surface temperature of the heat fixing roll fluctuates like this,
It is necessary to provide a toner that has a wide allowable fixing temperature range and can always be stably fixed without causing offset phenomenon or fixing failure.

In conventional toners using polyester resin, in order to improve anti-offset properties, methods have been used to introduce additives such as low molecular weight polyolefins, or to partially include a gel component in the resin. However, in such a method, the lower limit (low-temperature fixability) and/or upper limit (low-temperature fixability) of the toner's allowable fixing temperature is affected by temperature fluctuations on the surface of the heat-fixing roll.
At present, the offset resistance is exceeded, and the fundamental solution to the problem has not been reached.

An object of the present invention is to provide an electrophotographic toner composition that has excellent low-temperature fixing properties and anti-offset properties, and has a wide allowable fixing temperature range.

[Means for Solving the Problems] As a result of intensive studies to achieve the above object, the inventors of the present invention have developed a loss tangent (loss tangent) within a specific range as a toner resin.
The inventors have discovered that by using a urethane-modified polyester resin having a tan δ), it is possible to obtain an excellent toner that was not possible with conventional techniques, and have completed the present invention.

According to the invention, from 10-” to 10Hz at 150°C
Measured in the frequency range of Provided is an electrophotographic toner composition containing as a main component a urethane-modified polyester resin in which both the maximum value and minimum value of loss tangent (tan δ) are within the range of 0.7 to 2.5.

The urethane-modified polyester resin used in the present invention is a resin obtained by reacting an isocyanate compound (C) with a mixture of a polyester resin (A) and a polyester resin (B) defined below.

The above polyester resin (A) is obtained by polycondensation of a polyhydric carboxylic acid or a lower alkyl ester of a polyhydric carboxylic acid and a polyhydric alcohol, and has an OH value of 20 to 20.
60 mgKOR/g.

The above-mentioned polyhydric carboxylic acids and their lower alkyl esters include malonic acid, cohelic acid, glutaric acid, adipic acid,
Aliphatic dibasic acids such as azelaic acid, sebacic acid, hexahydrophthalic anhydride, and phthalic anhydride, phthalic acid,
Examples include aromatic dibasic acids such as terephthalic acid and isophthalic acid, and their methyl esters and ethyl esters.

In addition, examples of the polyhydric alcohols include ethylene glycol, 1.2-propylene glycol, 1.3-propylene glycol, 1.3-butylene glycol, and 1.4-propylene glycol.
Examples include diols such as butylene glycol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, hydrogenated bisphenol A1 bisphenol A propylene oxide adduct, and triols such as glycerin, trimethylolpropane, and trimethylolethane. can do. Among these, bisphenol A propylene oxide adduct is preferred.

As a method for carrying out the above polycondensation, generally known high temperature polycondensation, solution polycondensation, etc. can be used.

The molecular weight of the polyester resin (A) is preferably -
, the number average molecular weight is 2000 to 5000. When using a polyester resin (A) with a number average molecular weight of less than 2000, the heat resistance of the resulting urethane-modified polyester resin is poor, and the molecular weight of the urethane-modified polyester resin decreases during melt-kneading during toner production, resulting in poor fogging. This is undesirable because it causes generation and deterioration of offset resistance. Furthermore, when a polyester resin (A) having a number average molecular weight of more than 5,000 is used, the resin strength of the resulting urethane-modified polyester resin decreases, which is not preferable.

The above polyester resin (B) is obtained by the same method as the above polyester resin (A), and has an OH value of l.
It is a polyester resin of OmgKOH/g or less, and its number average molecular weight is preferably 2,000 to 4,000.

If the number average molecular weight of the polyester resin (B) is less than 2,000, the offset resistance of the toner obtained using the produced urethane-modified polyester resin is undesirably lowered. In addition, when the number average molecular weight of the polyester resin (B) exceeds 4,000, the low-temperature fixability and pulverizability of the toner obtained using the produced urethane-modified polyester resin deteriorate, which is undesirable. Polyester resin (B
) The polyhydric carboxylic acid or its lower alkyl ester and polyhydric alcohol used in the synthesis of the polyester resin (A) include those exemplified in the case of the synthesis of the polyester resin (A).

The mixing ratio of polyester resin (A) and polyester resin (B) is preferably 10:90 to 80:20.

Examples of the isocyanate compound (C) include hexamethylene diisocyanate, isophorone diisocyanate, 2.4-)lylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, and tetramethylxylylene diisocyanate.

The amount of the isocyanate compound (C) added is not particularly limited, but it is usually the amount of the isocyanate compound (based on the total OH groups of the polyester resin (A) and the polyester resin (B)).
Equivalent ratio of NCO group in C) NCO10H is 0.3 to 1.9
This amount falls within the range of 9.

The urethane-modified polyester resin can be obtained, for example, by the following method. That is, polyester resin (A
) and polyester resin (B) in the absence of a solvent or in the presence of a solvent.
It is obtained by charging the mixture all at once or in portions at ~180°C and reacting at that temperature for several minutes to several hours.

As an alternative method, the isocyanate compound (C) may be continuously added to a mixture of the polyester resin (A) and the polyester resin (B) using a kneading means having a built-in screw and kneaded to cause the reaction. As the kneading means, an extruder is preferable, and a twin-screw extruder is particularly preferable.

The ratio of the length (L) to the diameter (D) of the screw (L/
D) is preferably 20-60. The kneading conditions are usually 120 to 200°C and a residence time of 5 to 30 minutes.

In the present invention, the urethane-modified polyester resin obtained as described above has a loss tangent (tan) within a specific range.
δ) is essential. Defining the resin used in electrophotographic toner compositions by the loss tangent (tan δ) has not been considered in the past.The value of the loss tangent (tan δ) of the toner resin depends on the temperature conditions at the time of measurement, Although it differs depending on the frequency domain conditions, if it is measured under specific temperature and frequency domain conditions, it will be a specific value.
Measurements were made in the frequency range of −2 to 10 Hz.

The urethane-modified polyester resin used in the present invention is 15
Both the maximum and minimum values of loss tangent (tan δ) measured in the frequency range of 10-2 to 10 Hz at 0°C are 0.
．． It is essential that it is within the range of 7 to 2.5, preferably within the range of 1.0 to 2.1. The minimum value is 0.
If it is less than 7, the low-temperature fixability of the toner using the resin deteriorates, and the allowable fixing temperature range becomes narrow. On the other hand, if the maximum value exceeds 2.5, the offset resistance of the toner using the resin deteriorates, and the allowable fixing temperature range becomes narrow.

Moreover, it is preferable that the glass transition temperature of the urethane-modified polyester resin is 45 to 75°C.

The electrophotographic toner composition of the present invention is a mixture of a urethane-modified polyester resin, a suitable colorant, a charge control agent, and, if necessary, additives.

Suitable colorants include carbon black, aniline blue, alcohol blue, chrome yellow, ultramarine blue, quinoline yellow methylene blue, phthalocyanine blue, malachite green, rose bengal,
Examples include magnetite.

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

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

After premixing the above resin and other ingredients using a Henschel mixer, etc., use a kneader or the like to mix the mixture at a temperature of 100 to 18°C.
The agglomerates obtained by melt-kneading at 0° C. are pulverized and classified to form particles having a particle size of 5 to 15 μm, which can be used as electrophotographic toners.

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

Hereinafter, "parts" refer to parts by weight unless otherwise specified.

Production example I~■ This example is a production example of polyester resin (A).

A 5j240 flask was equipped with a reflux condenser, a water separator, a nitrogen gas inlet tube, a thermometer, and a stirring device, and the types and amounts of polybasic acids and polyhydric alcohols shown in Table 1 were charged, and nitrogen was introduced into the flask. Dehydration polycondensation was carried out at 220 to 240° C. while the mixture was being introduced. When the acid value became less than 1, the reaction was stopped to obtain polyester resins (A)-2 to (2).

Manufacturing example i%V This example is a production example of polyester resin (B).

A 5℃, 40 flask was equipped with a reflux condenser, a water or alcohol separation device, a nitrogen gas inlet tube, a thermometer, and a stirring device, and polybasic acids or lower polybasic acids of the types and amounts shown in Table 2 were prepared. An alkyl ester and a polyhydric alcohol were charged, and dehydration polycondensation or dealcoholization polycondensation was performed at 220 to 240°C while introducing nitrogen into the flask. When the acid value or hydroxyl value reached a predetermined value, the reaction was stopped to obtain polyester resin (B) ixv.

Production examples-2 to 10 This example is an example of manufacturing a urethane-modified polyester resin.

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. A twin screw extruder (Nippon Steel Co., Ltd.)
30), urethane modification was carried out in the following manner. As extrusion conditions, the extruder cylinder temperature was set so that the resin temperature was 150° C., and the screw rotation speed was adjusted so that the average residence time of the resin was 20 minutes. For urethane modification, premixed resin is continuously fed to the extruder at a predetermined flow rate using a metered feeder, melted and kneaded, and volatile components in the resin are removed in vacuum from the first vent hole installed in the extruder. Next, a predetermined amount of the isocyanate compound (tolylene diisocyanate) shown in Table 3 was added from the second ventro.
C) was continuously supplied using a metering pump to carry out the reaction. The obtained urethane-modified polyester resin was cooled and coarsely crushed.

Examples Carbon black MA was added to 100 parts by weight of the urethane-modified polyester resin obtained in Production Examples 2 to 10.
-100 (manufactured by Mitsubishi Kasei Corporation), and 6 parts by weight of Subiron Black TRH (Hodogaya Chemical Co., Ltd.) as a charge control agent.
After dispersing and mixing 2 parts by weight of (manufactured by Ikegai Iron Works Co., Ltd.) using a Henschel mixer, 1 part
The mixture was melt-kneaded at 6.0° C. to obtain a bulk toner composition.

This composition was roughly pulverized with a hammer mill, then finely pulverized with a jet pulverizer (model ID5Z, manufactured by Nippon Pneumatic Co., Ltd.), and then air-classified to obtain an average particle size of 10 μm (3% by weight of 5 μm or less, 2% of 20 μm or more). % by weight) was obtained.

Add 4 parts by weight of this toner to ferrite carrier F-150.
(manufactured by Nippon Tetsuko Co., Ltd.) was mixed with 100 parts by weight to prepare a two-component developer.

A copying test was conducted using a commercially available magnetic brush copying machine (ReoDry 8411, manufactured by Toshiba Corporation) at a room temperature of 25° C. while changing the heat roller temperature. Table 3 shows the evaluation results of the allowable fixing temperature.

As can be seen from the results in Table 3, it can be seen that the toner obtained according to the present invention has excellent low-temperature fixing properties and offset resistance.

Notes in the table are as follows.

1) Bisphenol A-(2,2)-propylene oxide adduct (manufactured by Mitsui Toatsu Chemical Co., Ltd.) 2) Monodisperse standard polystyrene was used as the standard, tetrahydrofuran was used as the eluent, and a refractometer was used as the detector. gel permeation chromatography (GPC)
) Number average molecular weight determined by 3) Weight average molecular weight determined by the same method as 2) above 4)
JIS K5400 method 5) Pyridine-acetic anhydride method 6) Glass transition temperature determined by differential scanning calorimetry (DSC) 7) Loss tangent determined by dynamic viscoelasticity measurement at 150°C
tan δ) minimum value to maximum value 8) The lowest heat fixing roll surface temperature at which the so-called offset phenomenon, in which molten toner adheres to the heat fixing roll and is fixed onto the copy paper again, begins to occur.9) Offset occurrence temperature and lower limit fixing temperature. Differences [Effects of the Invention] The composition of the present invention has excellent low-temperature fixing properties and anti-offset properties, and has a wide allowable fixing temperature range, so it has excellent practical performance as a toner composition for electrophotography. There is.

Claims (1)

[Claims] 1. Both the maximum and minimum values of loss tangent (tan δ) measured in the frequency range of 10^-^2 to 10 Hz at 150°C are within the range of 0.7 to 2.5. An electrophotographic toner composition containing a urethane-modified polyester resin as a main component. 2. Using a kneading means with a built-in screw, add to the mixture of polyester resin (A) and polyester resin (B),
NC of isocyanate compound (C) with respect to total OH groups of polyester resin (A) and polyester resin (B)
The isocyanate compound (C) is continuously added and kneaded in an amount such that the equivalent ratio NCO/OH of O groups is within the range of 0.3 to 1.99.
^-^ Loss tangent measured in the frequency range of 2 to 10 Hz (
Both the maximum and minimum values of tan δ) are 0.7 to 2.5
A method for producing a urethane-modified polyester resin within the scope of.