JP3009162B2 - Polyester resin for toner - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a polyester resin useful as a dry toner used for developing an electrostatic image in electrophotography, electrostatic recording, electrostatic printing, and the like. More specifically, it is excellent in blocking resistance, melt fluidity and fixability, especially for full color where high melt fluidity is required, for high speed copying machines and high speed printers where low temperature fixability is required, and for powder coatings And a polyester resin useful as a resin.

[Conventional technology]

In a method of obtaining a permanent visible image from an electrostatic image, an electrostatic image formed on a photoconductive photoreceptor or an electrostatic recording medium is developed by a toner previously charged by friction, and then fixed. Fixing is performed by directly fusing the toner image obtained by development on the photoconductive photoreceptor or electrostatic recording material, or by transferring the toner image on paper or film and then fusing it on a transfer sheet. Done. The fusion of the toner image is performed by contact with a solvent vapor, pressurization and heating. As the heating method, there are a non-contact heating method using an electric oven or a flash method and a pressure heating method using a heating roller, and the latter is mainly used recently in which a high-speed fixing process is required.

Further, in order to obtain a color image, in the above-described developing step, toners of three to four colors must be adhered to transfer paper, and then, in a fixing step, various toners must be colored and fixed while being melted and mixed. As described above, there is a strong demand for a binder for a full-color toner which has a good mixing property in the fixing step, in other words, a resin having a good melt fluidity. When a binder having good melt fluidity is used, there is a problem that an offset phenomenon occurs in a fixing process. However, if the binder is cross-linked or polymerized to prevent the offset phenomenon, the melt fluidity is reduced, and the binder is not suitable for full-color copying. Therefore, a method of applying silicone to the surface of a fixing roller of a copying machine to prevent offset has been used.

In recent years, there has been a strong demand for high-speed and energy-saving fixing units, and in copiers and printers other than full-color copiers, there are many cases in which a method of applying silicone to a fixing roller is adopted as an offset prevention measure.

Hitherto, as a resin for a toner, a low molecular weight polyester resin comprising a divalent unsaturated carboxylic acid and an aromatic diol component has been proposed. However, since the aromatic diol component has poor reactivity with the unsaturated carboxylic acid, a reaction at a high temperature is required in order to obtain the desired physical properties, and therefore, the aromatic diol is decomposed and produces a bad smell. . Problems such as deterioration of image quality occur.

Further, aromatic diols are generally expensive, and toners using a large amount thereof are not industrially preferable at present when copying machines are popularized.

Furthermore, since unsaturated carboxylic acid is used as the divalent carboxylic acid, there is a concern that a pollution problem may occur due to hydroquinone used as a radical reaction inhibitor.

Under the circumstances described above, as a low-molecular weight toner binder resin having full color and fixability, a resin having good melt fluidity and thermal stability and good polymerization reactivity is strongly desired.

[Problems to be solved by the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a resin binder for toner having a low softening temperature and excellent in melt fluidity, fixability and blocking resistance. This resin is particularly useful for full color, which requires high melt fluidity, and for high-speed copying machines or high-speed printers, which require low-temperature fixability, or for powder coatings.

[Means and actions for solving the problem]

The present invention relates to (a) at least one kind of dicarboxylic acid component selected from terephthalic acid component and isophthalic acid component, and (b) 20 to 80 mol% of the following formula [I] based on all carboxylic acid components. Diol components: [Wherein, R is an alkyl group having 2 or 3 carbon atoms,
x and y are integers and 2 ≦ x + y ≦ 6. ), And (c) 20-10 based on the total carboxylic acid component
0 consists mole% of an aliphatic diol component, in gel permeation chromatography (GPC), the weight-average molecular weight M _W is 3000 to 20,000, a number average molecular weight M _n of 1,000 to
00, a glass transition temperature T _g of 40 to 70 ° C., and a softening temperature of 70
A polyester resin for toner, which is characterized by a temperature of up to 130 ° C.

In the present invention, the terephthalic acid component is a component introduced from terephthalic acid and its lower alkyl ester, and the isophthalic acid component is a component introduced from isophthalic acid and its lower alkyl ester. Here, as the lower alkyl ester, those having 1 to 4 carbon atoms in the alkyl group are preferably used. Terephthalic components allowed improved glass transition temperature T _g, and contribute to the improvement of blocking resistance, also isophthalic acid component is effective on the reactivity and control of the softening temperature of the polymerization.

Specific examples of the diol component represented by the formula [I] used in the present invention include polyoxypropylene- (n)
-Polyoxyethylene- (n ')-2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene
(N) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene- (n) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene
(N) -2,2-bis (4-hydroxyphenyl) propane and the like, and particularly, polyoxypropylene- (n) -2,2-bis (4-hydroxyphenyl) in which 2.1 ≦ n ≦ 2.5 is satisfied. Propane is preferred. Such a diol component has an advantage that the glass transition temperature _Tg is improved and the reaction is easily controlled. However, since this diol component is liable to undergo thermal decomposition at high temperatures, it is difficult to use the diol component together with an aromatic dicarboxylic acid requiring a high reaction temperature. 80 mol%. Its preferred amount is 29-70 mol%.

Specific examples of the aliphatic diol used in the present invention include ethylene glycol, diethylene glycol, 1,
Examples thereof include 2-butanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, and propylene glycol. These aliphatic diols are
It has the effect of increasing the rate of the condensation polymerization reaction. Among these, ethylene glycol, neopentyl glycol, and butanediol are preferred from the viewpoint of fixability. The amount of the aliphatic diol used is 20 to 100 mol%, preferably 30 mol%.
That is all.

As long as the properties of the polyester are not impaired, the above (a) terephthalic acid and isophthalic acid, (b) a diol represented by the formula (I), and (c) a fat are generally used in an amount of 10 mol% or less based on the weight of the polyester. A monomer other than each component of the group diol can be co-condensed.

The polyester resin for a toner of the present invention has a weight average molecular weight _Mw of 3,000 to 20,000 and a number average molecular weight _Mn of 1,000 to 1,000.
0, glass transition temperature T _g 40-70 ° C, softening temperature 70-130 ° C
It is important that

When the weight average molecular weight _Mw is less than 3,000, the melt fluidity and the fixability of the resin are improved, but the glass transition temperature _Tg is remarkably reduced and the blocking resistance becomes poor.
On the other hand, when the weight average molecular weight _Mw exceeds 20,000, the melt fluidity and the fixability of the resin decrease. Therefore, the weight average molecular weight _Mw must be 3000-20000, especially 3000
~ 15000 is preferred.

The number average molecular weight _Mn is 10 from the correspondence with the weight average molecular weight _Mw.
It should be from 00 to 10,000, particularly preferably from 2000 to 7500.

When the glass transition temperature T _g is in the range of 40 to 70 ° C. good blocking resistance is obtained. In general, the addition of inorganic powder such as silica to the toner, blocking resistance is improved, particularly in the case a low T _g of the binder, the effect is remarkable. When T _g is in the range of 40 to 70 ° C., the blocking resistance is good even without adding an inorganic powder. However, T _g is 40 ° C
If it is less than 1, the fixing property is good, but the blocking property is extremely poor, and the blocking property is not good even if an inorganic powder is added. If T _g exceeds 70 ° C., the fixability becomes poor. Preferred glass transition temperature The T _g is 50-65 ° C..

While softening temperature becomes good melt flowability and fixing property is less than 70 ° C., lowering of the glass transition temperature T _g is remarkable, anti-blocking performance is lowered. On the other hand, the softening temperature is 130 ° C
If the ratio exceeds the above range, the melt fluidity and the fixing property are deteriorated, so that it is not suitable as a full-color toner or a toner for a high-speed machine.

The polyester resin of the present invention is a general polyester synthesis method, that is, after a dicarboxylic acid component and a diol component are subjected to an esterification reaction or a transesterification reaction, polycondensation is performed while distilling a low-boiling diol component out of the system. Synthesized by the method. For the polycondensation, known polymerization catalysts, for example, titanium tetrabutoxide, dibutyltin oxide, tin acetate, zinc acetate, tin disulfide, antimony trioxide, germanium dioxide and the like can be used.

The polyester resin of the present invention can be used as a dry toner as it is or by blending with another toner resin. Even when blended with another toner resin, the fixability of the toner is improved without impairing the blocking resistance. The polyester resin of the present invention can be used not only as a binder for general toner but also as a powder coating.

In the present invention, the "softening temperature" is measured using a flow tester CFT-500 manufactured by Shimadzu Corporation under the conditions of a 1 mmφ × 10 mm nozzle, a load of 30 kgf, and a constant heating rate of 3 ° C./min. The temperature at which 1/2 of 1 g of the sample has flowed out.

The glass transition temperature T _g refers to the temperature at the intersection of the base line of the chart and the tangent to the endothermic curve near T _g when measured at a heating rate of 5 ° C./min using a differential scanning calorimeter.

Weight average molecular weight _Mw and number average molecular weight _Mn are manufactured by Tosoh Corporation
Refers to _Mw and _Mn as measured by GPC HCL-8200.

〔Example〕

Examples of the present invention will be described below, but the present invention is not limited to these embodiments.

Example 1 Terephthalic acid, isophthalic acid, ethylene glycol,
Neopentyl glycol, polyoxypropylene (2.
3) -2,2-Bis (4-hydroxyphenyl) propane was charged into a reaction vessel according to the composition shown in Table 1-1, and further, antimony trioxide as a polymerization catalyst was charged at 400 ppm based on the dicarboxylic acid component. Next, at an internal temperature of 230 ° C, the stirring
The esterification reaction was carried out for 5 hours under normal pressure while maintaining at 00 rpm. Next, the internal temperature was kept at 240 ° C. and the stirring rotation speed was 200 rpm, and the pressure was gradually reduced over 40 minutes until the degree of vacuum reached 1.0 mmHg, and ethylene glycol was distilled under the reduced pressure. The end point of the polycondensation was determined when the softening temperature was traced and the desired softening temperature was reached. About 10 hours after the start of the reduced pressure, a desired softening temperature was obtained. Therefore, the reaction system was returned to normal pressure, and the polymerization was terminated to obtain a pale yellow solid. Table 1-2 shows the results of resin composition analysis and characteristic value measurement.

In view of the weight average molecular weight _Mw and the softening temperature in Table 1-2, Resins A to H have good melt fluidity, and good mixing and smoothness. In this case, the image sharpness is good, and when used for general toner, good fixability is exhibited. further,
Resin A~H glass transition temperature T _g of the in Table 1-2 it can be seen that even over blocking resistance.

Example 2 Dimethyl terephthalate, dimethyl isophthalate, ethylene glycol, polyoxypropylene (2,4) -2,2-
Bis (4-hydroxyphenyl) propane was charged into a reaction vessel in accordance with the composition shown in Table 2-1, and titanium tetrabutoxide as a polymerization catalyst was further added based on a dicarboxylic acid component.
500 ppm was added. Next, at an internal temperature of 200 ° C, the stirring speed is 200 rp.
m, the pressure was gradually reduced over 40 minutes until the degree of vacuum reached 1.0 mmHg, and ethylene glycol was distilled off under this reduced pressure. The end point of the polycondensation was determined when the softening temperature was followed and the desired softening temperature was reached. About 9 hours after the start of depressurization, the desired softening temperature was obtained, so the reaction system was returned to normal pressure,
The polymerization was terminated.

The obtained resin was a yellow-red solid. Table 2-2 shows the results of resin composition analysis and characteristic value measurement.

Next, using an extruder, the resin I and the resin X for general toner were melt-kneaded at a ratio shown in Table 2-3 to obtain resins K and L. Softening temperature and the T _g of the obtained resin are shown in Table 2-3.

From Table 2-3, the resin obtained by blending a low molecular weight polyester is compared with the toner resin X, while retaining the T _g, the softening temperature is decreased. This means that, compared to resin X, resins I and J do not lose blocking resistance,
It indicates that the low-temperature fixability is improved.

The melt kneading was carried out at 150 ° C. and 50 rpm using a conical type bidirectional twin screw extruder manufactured by Härke Buchler Instrumental.

Comparative Example 1 Terephthalic acid, isophthalic acid, ethylene glycol,
Polyoxypropylene (2,3) -2,2-bis (4-hydroxyphenyl) propane is charged into a reaction vessel according to the composition shown in Table 3-1. Further, a polymerization catalyst and antimony trioxide are charged at 500 ppm based on a dicarboxylic acid component. did. Polycondensation was carried out in the same manner as in Example 1 except for the other production methods and production conditions. As a result, pale yellow solids M, N, and O were obtained. Table 3-2 shows the results of resin composition analysis and characteristic value measurement.

Since Table 3-2 Resin M uses a diol A large amount, although the melt flowability and fixing property is good, T _g is lowered, blocking resistance is poor. Moreover, the use of the bad diol A reactive in a large amount, were subjected to condensation for 18 hours, the molecular weight The T _g was not increased. When the polymerization temperature was raised to 270 ° C., a large amount of distillate of diol A was observed.

Although resin N is a good melt flowability and fixing property, T _g
And the blocking resistance is poor.

Resin O has a molecular weight M _w of there 40000, T _g but is has high blocking resistance good softening temperature is high, not suitable for toner is required high melt flowability and high fixing property. Also, the grindability was poor.

〔The invention's effect〕

The polyester resin of the present invention has a low softening temperature, excellent melt fluidity, excellent fixability and blocking resistance,
It is useful as a resin binder for toner. Further, an image generated from this toner is excellent in sharpness.

Continued on the front page (72) Inventor Ryo Funato 4-1-160 Sunadabashi, Higashi-ku, Nagoya City, Aichi Prefecture Mitsubishi Rayon Co., Ltd. Product Development Research Center (72) Inventor Koichi Ito 4-1-160 Sunadabashi, Higashi-ku, Nagoya City, Aichi Prefecture (56) References JP-A-61-176949 (JP, A) JP-A-63-109447 (JP, A) JP-A-55-40407 (JP, A) JP-A-63 JP-A-163469 (JP, A) JP-A-59-128558 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 9/08

Claims (2)

(57) [Claims] (1) at least one dicarboxylic acid component selected from (a) a terephthalic acid component and an isophthalic acid component, and (b) 20 to 80 mol% of the following formula (I) based on the total carboxylic acid component. The diol component represented: [Wherein, R is an alkyl group having 2 or 3 carbon atoms,
x and y are integers and 2 ≦ x + y ≦ 6. ), And (c) 20-10 based on the total carboxylic acid component
It is composed of 0 mol% of an aliphatic diol component, and has a weight average molecular weight _Mw of 3,000 to 20,000 and a number average molecular weight M measured by gel permeation chromatography (GPC).
_n is 1000-10000, glass transition temperature T _g is 40-70 ° C.,
A polyester resin for toner having a softening temperature of 70 to 130 ° C. 2. The polyester resin for a toner according to claim 1, wherein (c) the aliphatic diol component is at least one selected from ethylene glycol, neopentyl glycol and butanediol.