JPH09160294A - Polyester resin for full color toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure superior fixability, image stability, blocking resistance and coloring ability and to prevent image distortion even in running use over a long period of time. SOLUTION: This resin consists of dicarboxylic acids including arom. dicarboxylic acid by >=50mol% of the total amt. of all acids, diols including arom. diol by 40-120mol% of the total amt. of all acids and aliphatic diol by 10-105mol% of the total amt. of all acids and polycarboxylic acid having >=3 COOH groups and/or polyol having >=3 OH groups by 1-30mol% of the total amt. of all acids and has a mol.wt. distribution by gel permeation chromatography in which the ratio of Mw to Mn is 3-20 and the main peak exists in a mol.wt. region of >=15,000, 1,000-3,000P melt viscosity at 130 deg.C and <=0.5wt.% gel fraction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester resin useful as a binder resin for a dry full color toner used for developing an electrostatic charge image or a magnetic latent image in electrophotography, electrostatic recording, electrostatic printing and the like. More specifically, the present invention relates to a polyester resin for a full-color toner, which is excellent in fixing property, image stability, blocking resistance, and color developability and does not cause image distortion even during long-term running use.

[0002]

2. Description of the Related Art In a method for obtaining a permanent visible image from an electrostatic charge image, an electrostatic charge image formed on a photoconductive photosensitive member or an electrostatic recording material is developed with a toner charged in advance by friction. Is fixed. In the case of a magnetic latent image,
The latent image on the magnetic drum is developed with toner containing a magnetic material and then fixed. For fixing, the toner image obtained by development is directly fused on the photoconductive photoreceptor or the electrostatic recording body, or the toner image is transferred onto paper or film and then fused onto the transfer sheet. Done by.
The fusion of the toner image is performed by contact with solvent vapor, pressurization and heating, and the heating method includes a non-contact heating method using an electric oven and a pressure heating method using a pressure roller.
On the other hand, in order to obtain a color image, it is necessary to adhere toners of 3 to 4 colors to the transfer paper in the above-mentioned developing process, and then to develop and fix the toners of respective colors while being melt-mixed in the fixing process. .

Therefore, a binder resin for a full-color toner is required to have a good mixing property in the fixing step, a good color developability and a sharp melt property, and a polyester resin is usually used. However, when a binder resin having a good sharp melt property is used, there is a problem that an offset phenomenon occurs in the fixing process. In order to prevent this offset phenomenon, it is conceivable to crosslink the binder resin, but in general, the crosslinkable resin is not suitable as a binder resin for a full-color toner because its sharp melt property is deteriorated. Therefore, the offset phenomenon is usually prevented by applying silicone oil or the like to the surface of the fixing roller. However, if silicone oil or the like is applied to the surface of the fixing roller, the oil may adhere to the copy, which may hinder handling.
When copying to a film such as an HP sheet, the phenomenon is remarkable. In addition, in recent years, due to the increase in speed of copying machines and printers, long-term running use, etc., there is a problem of fixing property at low temperature, and image distortion due to temperature rise of heat roller during long-term running use. It is emerging. In particular, it has been pointed out that the occurrence of image distortion becomes remarkable when printing is performed on a film such as an OHP sheet immediately after printing on a large number of sheets of paper.

[0004]

A method of lowering the molecular weight and the softening temperature of the resin has been used to impart a sharp melt property to the binder resin, but such a binder resin impairs the resin strength. Therefore, there is a problem that the filming property of the toner is lowered, the charging of the toner is not stable, and the stability of the image density is poor. In order to improve the image density stability of such a toner, methods such as changing the composition of the binder resin and adding a trace amount of a crosslinking agent have been carried out. However, even with such a binder resin, it was not possible to simultaneously solve the color developability, the fixability at low temperature, and the image distortion. The present invention has been made to solve the above-mentioned drawbacks, and its object is to provide excellent fixing properties, image stability, blocking resistance, and color development, even during long-term running use. An object of the present invention is to provide a polyester resin for full-color toner that does not cause image distortion.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies in view of the problems of the conventional binder resin as described above, and as a result, have found that a specific polyester resin can achieve the object. This has led to the invention. That is, the polyester resin for full-color toner of the present invention comprises a dicarboxylic acid component containing 50 mol% or more of an aromatic dicarboxylic acid (a) with respect to the total acid component, and 40 to 120 mol% of aromatic with respect to the total acid component. Group diol (b), a diol component containing 10 to 105 mol% of the aliphatic diol component (c) with respect to the total acid component, and 1 to 3 with respect to the total acid component
0 mol% of trivalent or higher polycarboxylic acid and / or 3
A polyester resin composed of a polyhydric alcohol (e) having a valency or more and a weight average molecular weight (Mw) in a molecular weight distribution in gel permeation chromatography.
/ Number average molecular weight (Mn) is 3 to 20, and molecular weight is 1500
It has a main peak in the region of 0 or less, a melt viscosity at 130 ° C. of 1000 to 3000 poise, and a gel fraction of 0.5.
It is characterized by being less than or equal to wt%.

The aromatic dicarboxylic acid (a) constituting the polyester resin of the present invention is selected from aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid and their lower alkyl esters. Examples of the lower alkyl ester of terephthalic acid and isophthalic acid include dimethyl terephthalic acid, dimethyl isophthalic acid, diethyl terephthalic acid, diethyl isophthalic acid, dibutyl terephthalic acid and dibutyl isophthalic acid. Acids, isophthalic acid or their lower alkyl esters are preferred. The above aromatic dicarboxylic acids or lower alkyl esters thereof can be used alone or in combination of two or more. These aromatic dicarboxylic acids raise the glass transition temperature of the polyester resin, contribute to the improvement of the blocking resistance of the toner, and have the effect of improving the moisture resistance of the toner due to the hydrophobic property thereof. Therefore, the amount of the aromatic dicarboxylic acid needs to be 50 mol% or more, preferably 60 mol% or more, based on all the acid components. Among them,
The terephthalic acid type is effective in increasing the glass transition temperature of the binder resin, and the isophthalic acid type is effective in increasing the reactivity, so that it is preferable to use the use balance after changing the use balance depending on the purpose.

In the present invention, if necessary, in combination with the above-mentioned aromatic dicarboxylic acid, for example, phthalic acid, sebacic acid, isodecyl succinic acid, fumaric acid, adipic acid and their monomethyl, monoethyl, dimethyl and diethyl. Esters and the like, as well as other dicarboxylic acids such as their acid anhydrides can also be used. Since these dicarboxylic acids greatly affect the fixing property and blocking resistance of the toner, it is necessary to consider these properties before use.
It is preferably used in the range of 30 mol% or less based on all acid components.

Further, the aromatic diol (b) constituting the polyester resin of the present invention has a glass transition temperature of the polyester resin to improve the blocking resistance of the toner and to control the reactivity of the resin. It is an ingredient. Examples of the aromatic diol (b) include polyoxypropylene- (2.0) -2,2-bis (4-hydroxyphenyl) propane and polyoxypropylene-.
(2.3) -2,2-bis (4-hydroxyphenyl)
Propane, polyoxypropylene- (2.8) -2,2
-Bis (4-hydroxyphenyl) propane, polyoxypropylene- (3.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene- (2.
0) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene- (2.3) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene- (2.8) -2 , 2-bis (4-hydroxyphenyl) propane, polyoxyethylene- (3.0)-
2,2-bis (4-hydroxyphenyl) propane and the like can be mentioned, and these can be used alone or in combination of two or more kinds. Among them, polyoxypropylene (n) -2,2-bis (4-hydroxyphenyl) propane (2.1 ≦ n ≦ 2.5), polyoxyethylene-
(N) -2,2-bis (4-hydroxyphenyl) propane (2.0 ≦ n ≦ 3.0) is preferable.

Since these aromatic diols (b) are prone to thermal decomposition at high temperatures, when used in combination with a dicarboxylic acid which requires high reactivity, the aromatic diol (b) is contained in an amount of 40 to 40 relative to the total acid component.
It is necessary to use it in the range of 120 mol%, and preferably in the range of 45 to 100 mol%. This is because when the aromatic diol (b) is less than 40 mol%, the glass transition temperature of the polyester resin is lowered and the blocking resistance of the toner is lowered. Also,
This is because if the aromatic diol (b) exceeds 120 mol%, the reactivity is remarkably reduced and the reaction does not proceed to the desired degree of polymerization.

The aliphatic diol (c) constituting the polyester resin of the present invention improves the polycondensation reaction rate of the resin, and is, for example, ethylene glycol, neopentyl glycol, propylene glycol, butanediol, polyethylene glycol, etc. These may be used alone or in combination of two or more. Among them, ethylene glycol, neopentyl glycol, and butanediol are preferable from the viewpoint of fixing property as a toner. Aliphatic diol (c) is 10 with respect to the total acid component.
Used in the range of ~ 105 mol%, preferably 15 ~ 1
It is in the range of 00 mol%. When the aliphatic diol (c) is less than 10 mol%, the reactivity is remarkably lowered and the reaction does not proceed to a desired degree of polymerization, and when it exceeds 105 mol%, the glass transition temperature and the resin strength of the polyester resin are lowered. This is because the blocking resistance of the toner is deteriorated.

The trivalent or higher polyvalent carboxylic acid or the trivalent or higher polyhydric alcohol (e) constituting the polyester resin of the present invention improves the balance between the molecular weight, the molecular weight distribution and the melt viscosity of the polyester resin, In addition to suppressing image distortion, the resin strength of the polyester resin is increased to improve the image stability of the toner. Examples of the trivalent or higher polycarboxylic acid include trimellitic acid, pyromellitic acid, 1,2,4-cyclohexanetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1 , 2,
Examples thereof include 5-hexanetricarboxylic acid, 1,2,7,8-octanetetracarboxylic acid and acid anhydrides thereof. Moreover, as the polyhydric alcohol having 3 or more valences, sorbitol, 1,2,3,6-hexanetetralol,
1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,
4-butanetriol, 1,2,5-pentatriol, glycerol, 2-methylpropanetriol, 2
-Methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene and the like can be mentioned. Among them,
Trimellitic acid and its acid anhydride, pentaerythritol, and trimethylolpropane are preferable. These trivalent or higher polyvalent carboxylic acids or trivalent or higher polyhydric alcohols (e) can be used alone or in combination of two or more.

In the present invention, a trivalent or higher polyvalent carboxylic acid and / or a trivalent or higher polyhydric alcohol (e)
Is used in the range of 1 to 30 mol% with respect to the total acid component, and preferably in the range of 2 to 28 mol%. this is,
This is because when the trivalent or higher polyvalent carboxylic acid and / or the trivalent or higher polyhydric alcohol (e) is less than 1 mol%, the resin strength of the polyester resin is lowered and the image stability of the toner is impaired. This is because when the content exceeds 100%, the melt viscosity of the polyester resin becomes high, and the fixability and color developability of the toner deteriorate.

Although the polyester resin of the present invention contains such a cross-linking unit as a constitutional unit, it does not form a highly cross-linked structure and suppresses gelation of the polyester resin as much as possible. The structure is such that a part of the structure is lightly crosslinked or a branched structure is formed. For this reason, the polyester resin may be a binder resin that does not contain a gel component or has an extremely low gel fraction in the range of 0.5% by weight or less.
It is preferable in that the resin strength can be imparted without deteriorating the sharp melt property, and a good balance between the fixing property of the toner and the color developing property and the image stability can be achieved. When the gel fraction of the polyester resin exceeds 0.5% by weight, the color developability of the toner deteriorates, and the range is preferably 0.3% by weight or less.

The polyester resin for toner of the present invention having the above constitution has a weight average molecular weight (M) in the molecular weight distribution by gel permeation chromatography.
w) / number average molecular weight (Mn) of 3 to 20, molecular weight of 150
It must have a main peak in the region of 00 or less and a melt viscosity at 130 ° C. of 1000 to 3000 poise. This is the weight average molecular weight (M
When w) / number average molecular weight (Mn) is less than 3, image distortion occurs, and when it exceeds 20, the fixability of the toner is deteriorated, and the range of 4 to 18 is preferable. Also,
This is because if the main peak in the molecular weight distribution of the polyester resin is in the region where the molecular weight exceeds 15,000, the fixability of the toner will be poor, and it is preferably in the region of 14,000 or less. Further, when the melt viscosity of the polyester resin at 130 ° C. is less than 1000 poise, image distortion occurs,
This is because if it exceeds 3000 poise, the fixing property of the toner is deteriorated, and it is preferably in the range of 1100 to 2900 poise.

In the polyester resin of the present invention, the softening temperature is 100 to 120 ° C. and the acid value is 3 to 20 mg.
KOH / g and the glass transition temperature are preferably in the range of 50 to 70 ° C. This is because if the softening temperature of the polyester resin is less than 100 ° C., the blocking resistance of the toner tends to decrease, and if it exceeds 120 ° C., the fixing property of the toner tends to deteriorate, and preferably 102.
The range is to 118 ° C. Further, if the acid value of the polyester resin is less than 3 mgKOH / g, the rise of charging of the toner tends to decrease, and if it exceeds 20 mgKOH / g, the moisture resistance of the toner tends to decrease.
It is preferably in the range of 4 to 18 mgKOH / g. Further, when the glass transition temperature of the polyester resin is less than 50 ° C., the blocking resistance of the toner tends to decrease, and when it exceeds 70 ° C., the toner fixability tends to decrease, which is preferable. Is in the range of 52 to 68 ° C.

The production of the polyester resin for full-color toner of the present invention is not particularly limited, and it can be produced by a commonly used method. For example, the above polymerization components (a) to (e) are charged into a reaction kettle,
An esterification reaction or a transesterification reaction is performed by heating the mixture. At this time, an esterification catalyst or a transesterification catalyst used in a normal esterification reaction or transesterification reaction such as sulfuric acid, titanium butoxide, dibutyltin oxide, magnesium acetate, and manganese acetate can be used, if necessary. . Next, water or alcohol generated by the reaction is removed according to a conventional method. After that, a polymerization reaction is subsequently carried out. At this time, the polymerization is carried out under a vacuum of 150 mmHg or less while distilling and removing the diol component. In the polymerization, generally known polymerization catalysts such as titanium butoxide, dibutyltin oxide, tin acetate, zinc acetate, tin disulfide, antimony trioxide, germanium dioxide and the like can be used. The polymerization temperature and the amount of the catalyst are not particularly limited, and may be arbitrarily set as needed.

[0017]

The present invention will be described below in detail with reference to examples. In addition, the physical property of the polyester resin in an Example and a comparative example was measured by the following measuring methods. Weight average molecular weight /
The number average molecular weight (Mw / Mn) and the molecular weight of the main peak were determined by gel permeation chromatography (HCL-82 manufactured by Tosoh Corporation) using tetrahydrofuran as a solvent.
00). The melt viscosity was 130 ° C. using a flow tester (CFT-500 manufactured by Shimadzu Corporation).
The temperature was measured using a 0.5 mmφ × 15 mm nozzle under a load of 10 kgf. Softening temperature (℃)
Is a flow tester (CFT-500 manufactured by Shimadzu Corporation)
At 1.0 mmφ × 10 mm, a load of 30 kgf and a heating rate of 3 ° C./minute were used to measure the temperature at a constant rate, and the temperature when half the amount of 1.0 g of the sample was discharged was softened. Temperature. The glass transition temperature (° C) was measured by using a differential scanning calorimeter (manufactured by Shimadzu Corporation) at the tangent line of the endothermic curve near the glass transition temperature when measured at a temperature rising rate of 5 ° C / min, and the contact point with the baseline. The glass transition temperature was used. The acid value was measured by a titration method using a KOH solution. In the composition analysis, the resin was hydrolyzed with hydrazine and quantified by liquid chromatography.

Further, the performance evaluation of the toners in Examples and Comparative Examples was carried out according to the following method. Fixability Using a full-color copying machine with a variable temperature and a heat roller coated with silicone oil, the minimum fixing temperature on paper when printed at a printing speed of 7 sheets / minute was measured and evaluated according to the following criteria. . ◯: Fixing possible at 130 ° C. Δ: Fixing is possible at 140 ° C. X: Fixing is impossible at 140 ° C.

Blocking resistance 5 g of toner is put in a glass sample bottle and the temperature is 50 ° C.
For 24 hours. Thereafter, the sample was cooled to room temperature, the state of aggregation was visually observed, and evaluated according to the following criteria. ◯: Toner is dispersed when the sample bottle is turned upside down. Δ: Disperse when the sample bottle is turned upside down and tapped 2-3 times. ×: No dispersion occurs even if the sample bottle is turned upside down and hit twice or three times.

Image Stability A full-color copying machine having a heat roller coated with silicone oil and having a variable temperature was used to perform a printing test of 10,000 sheets at a printing speed of 7 sheets / min. The change was evaluated according to the following criteria. ◯: There is almost no change in image density. Δ: A slight decrease in image density was observed, but it was at a practical level. X: A decrease in image density is seen.

Image distortion Using a full-color copying machine having a heat roller coated with silicone oil and having a variable temperature, a printing test was performed on 10,000 sheets of paper at a printing speed of 7 sheets / minute, and then on an OHP sheet. Printing was performed, and the generation state of distortion of the obtained printed image was evaluated according to the following criteria. A: Almost no image distortion occurs. Δ: Although some image distortion was observed, it was at a practical level. X: The occurrence of image distortion is observed.

Coloring property An OHP sheet was printed at a printing speed of 7 sheets / min using a temperature-variable full-color copying machine having a heat roller coated with silicone oil. And the image projected by the projector was evaluated according to the following criteria. ◯: High light transmittance and almost no shadow on the image. Δ: The image was slightly shaded, but was at a practical level. X: Light transmittance is low, and a shadow is seen in the image.

Examples 1 to 13 The monomer mixture was charged into a reaction vessel equipped with a distillation column according to the charging composition shown in Table 1. Further, 500 ppm of antimony trioxide was added to all the acid components, the temperature in the reaction system was kept at 260 ° C., the stirring rotation speed was 120 rpm, and water was distilled from the reaction system about 8 times after the esterification reaction started.
After an hour, the reaction was terminated when no more water was distilled. Next, the temperature in the reaction system is maintained at 220 ° C., the pressure is reduced over about 40 minutes until the degree of vacuum in the reaction container reaches 1.0 mmHg, the diol component is distilled from the reaction system, and the condensation reaction is performed. When the desired softening temperature was reached, the pressure inside the reaction vessel was returned to normal pressure, and the polyester resin was taken out of the reaction vessel. Table 1 shows the composition analysis results of the obtained polyester resin, and Table 2 shows the measurement results of physical properties. Further, using the toner containing the obtained polyester resin as a binder resin, fixing property, blocking resistance, image stability and image distortion were evaluated, and the results are shown in Table 2.

[0024]

[Table 1]

[0025]

[Table 2]

Comparative Examples 1 to 7 Polyester resins were obtained in the same manner as in the examples except that the composition of the polymerization charge was as shown in Table 3. The composition analysis results of the obtained polyester resin are shown in Table 3, and the physical property measurement results are shown in Table 4. Further, using the toner obtained by using the obtained polyester resin as a binder resin, fixing property, blocking resistance, image stability and image distortion were evaluated, and the results are shown in Table 4.

[0027]

[Table 3]

[0028]

[Table 4]

The abbreviations in the table represent the following compounds, respectively. TPA: terephthalic acid IPA: isophthalic acid TMA: trimellitic acid EG: ethylene glycol diol A: polyoxypropylene- (2.3) -2,
2-bis (4-hydroxyphenyl) propane diol B: polyoxyethylene- (2) -2,2-bis (4-hydroxyphenyl) propane

[0030]

The polyester resin for full-color toner of the present invention is excellent in fixing property as a toner, image stability, blocking resistance and color development property, and does not cause image distortion even during long-term running use.

Claims (1)

[Claims] 1. A dicarboxylic acid component containing 50 mol% or more of an aromatic dicarboxylic acid (a) based on the total acid component, and 40 to 120 mol% of an aromatic diol (b) based on the total acid component. A diol component containing 10 to 105 mol% of the aliphatic diol (c) with respect to the acid component, and 1 to 30 mol% of a trivalent or higher polyvalent carboxylic acid with respect to the total acid component, and / or
Alternatively, a polyester resin composed of a polyhydric alcohol (e) having a valence of 3 or more and having a weight average molecular weight (Mw) / number average molecular weight (Mn) of 3 to 20 in a molecular weight distribution in gel permeation chromatography, Has a main peak in the molecular weight range of 15,000 or less, 130 ° C
A polyester resin for a full-color toner, which has a melt viscosity of 1000 to 3000 poises and a gel fraction of 0.5% by weight or less.