JP3050235B2 - 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, a polyester resin having excellent blocking resistance, melt fluidity and fixability, and particularly useful for full color applications requiring high melt fluidity, and high-speed copiers and high-speed printers requiring low-temperature fixability. About.

[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 and fixed by a toner previously charged by friction. Fixing is performed by directly fusing the toner image obtained by development on the photoconductive photoreceptor or the electrostatic recording medium, or by fusing the toner image onto a transfer sheet after transferring the toner image onto paper or film. This is done by: The fusion of the toner image is performed by contact with 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. On the other hand, 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, apply silicone to the fixing roller surface of the copier,
A technique for preventing offset is used.

In recent years, where high speed and energy saving in the fixing unit are strongly demanded, even in copying machines and printers other than full-color copying machines,
In many cases, a method of applying silicone to a fixing roller is employed.

Hitherto, as a resin for a toner, a low-molecular-weight polyester comprising a divalent carboxylic acid and an aromatic diol that provides a rigid polymer has been proposed in order to impart blocking resistance in addition to good melt fluidity. However, the aromatic diol component has poor reactivity, and therefore, in order to obtain desired physical properties, a reaction at a high temperature is necessary, so that the aromatic diol is decomposed, giving off a bad smell or deteriorating the image quality. And the like. In addition, aromatic diols have poor reactivity, so their molecular weight is limited, and a large amount of excessively pulverized products are generated in the toner production process.

Furthermore, examples of using an unsaturated dicarboxylic acid to increase the reactivity with an aromatic diol are introduced, but the effect is small, and in addition, a pollution problem is caused by hydroquinone used as a radical reaction inhibitor. There is a concern that this will occur.

[Problems to be solved by the invention]

From the above situation, as a low-molecular weight toner binder resin of full color and fixability, melt fluidity,
There is a strong demand for a resin having good thermal stability and polymerization reactivity and excellent pulverization characteristics.

The present inventors have co-condensed an aromatic diol to increase the thermal stability of the toner, and to avoid the deterioration of the pulverization productivity and the decrease in the reactivity during the toner production as described in the prior art as described above. As a result of investigation, it has been found that these problems can be solved by making the polymer structure branched using a trivalent or higher acid or alcohol.

That is, by providing a branched structure, the polymer becomes a rigid polymer, and the generation of over-pulverized products during production is suppressed. In addition, since the reactivity is also improved, a polymer having good melt fluidity and excellent thermal stability is obtained even at a low polymerization temperature at which no decomposition product is generated.

[Means and actions for solving the problem]

The present invention relates to (a) at least one selected from trivalent or higher acid components and trivalent or higher alcohols, and (b) at least one selected from terephthalic acid and isophthalic acid and lower alkyl esters thereof. Seed, (c) a diol component represented by the following formula [I] (Wherein R is an ethylene group or a propylene group, x
And y are integers and 2 ≦ x + y ≦ 6. ) And (d) an aliphatic diol, wherein the component (c) is at most 80 mol% with respect to the total acid component, and has a weight average molecular weight M _w
3,000 to 20,000, a number average molecular weight _Mn of 1,000 to 10,000, a glass transition temperature T _g of 40 to 70 ° C, and a softening temperature of 80 to 130 ° C,
15% by weight of finely pulverized material with a particle size of 5μm or less during pulverization
A polyester resin characterized by the following is provided.

Specific examples of the (a) trivalent or higher valent acid component and alcohol used in the present invention include trimellitic acid (1,2,4-benzenetricarboxylic acid), 1,2,4-cyclohexanetricarboxylic acid, 2,5, 7-naphthalenetricarboxylic acid, 1,2,4-
Butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,2,4,5-benzenetetracarboxylic acid, 1,2,7,8-octanetetracarboxylic acid and their acid anhydrides and lower alkyl esters And 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,
Examples thereof include 4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene, and pentaerythritol. These acid components and alcohols are used alone or as a mixture. From the viewpoint of cost and production stability, the amount of use thereof is preferably 0.2 to 20 mol% based on the total acid components.

In the present invention, as the dicarboxylic acid component (b),
Terephthalic acid and its lower alkyl esters, and isophthalic acid and its lower alkyl esters are used. As the lower alkyl group, an alkyl group having 1 to 4 carbon atoms is used. While these aromatic dicarboxylic acid components are generally useful for producing rigid polymers,
In particular terephthalic components allowed improved T _g, and contribute to the improvement of blocking resistance, also isophthalic component has an effect in the regulation of reactivity and the softening temperature of the polymerization.

Specific examples of the diol component (c) 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, etc., and in particular, polyoxypropylene- (n) -2,2-bis (4-hydroxy Phenyl) 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 a high temperature, it is difficult to use the diol component together with an aromatic dicarboxylic acid which requires a high reaction temperature. % Or less. Its preferred amount is 10 to 70 mol%.

Specific examples of the aliphatic diol (d) used in the present invention include ethylene glycol, diethylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4
-Butanediol, neopentyl glycol, propylene glycol and the like. These aliphatic diols have an 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 mol% or more, preferably 30 mol% to 100 mol%.

As long as the properties of the polyester are not impaired, generally, in the range of 10 mol% or less based on the polyester, the (a) trivalent or higher acid component and / or trivalent or higher alcohol,
Monomers other than the components of (b) terephthalic acid, isophthalic acid and their lower alkyl esters, (c) the diol represented by the formula [I], and (d) the aliphatic 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, the glass transition temperature T _g is 40 to 70 ° C., a softening temperature of 80 to 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 between 3000 and 20000, which is
~ 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..

The melt flowability and fixing property and a softening temperature is less than 80 ° C. but becomes good, a decrease in 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.

In the present invention, the term “over-pulverized product having a particle size of 5 μm or less” refers to a particle having a particle size of 5 μm, which is generated when the resin is pulverized and is difficult to use as a toner.
m or less, and the amount of generation is preferably 15% by weight or less, more preferably 10% by weight or less of the resin pulverized matter in consideration of the toner production yield.

The polyester resin of the present invention is a general polyester synthesis method, that is, a method of subjecting a dicarboxylic acid component and a diol component to an esterification reaction or a transesterification reaction, and then performing a polycondensation while distilling a low boiling point diol component out of the system. Synthesized by 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 a 1 mmφ × 10 mm nozzle using a flow tester CFT-500 manufactured by Shimadzu Corporation.
It is the temperature at which 1/2 of 1 g of the sample has flowed out when measured at a constant temperature increase rate of 3 ° C./min with a load of 30 kgf.

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 M _w and M _n as measured by GPC HCL-8200.

In the present invention, the pulverizability is evaluated by a supersonic jet pulverizer LABOJET (model LJ) of Nippon Pneumatic Industries, Ltd.
This was performed using Set the classification point to 25μm and 90 minutes in 30 minutes
When the resin of g was charged, a resin having a volume average particle size of 8 to 11 μm and a ratio of an over-pulverized product having a particle size of 5 μm or less of 15% by weight or less was determined to have good pulverizability. In addition,
The initial particle size of the resin charged into LABOJET was set to 3 mm or less using a chopper mill.

〔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, trimellitic acid, ethylene glycol, pentaerythritol and polyoxypropylene- (2,3) -2,2-bis (4-hydroxyphenyl) propane were charged into a reaction vessel according to the composition shown in Table 1. Then, 400 ppm of antimony trioxide as a polymerization catalyst was added based on the dicarboxylic acid component.

Next, the internal temperature was set to the temperature shown in Table 1 and the stirring rotation speed was set to 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 off under this reduced pressure. The end point of the polycondensation was determined when the softening temperature was traced and the desired softening temperature was reached. After the polycondensation time in Table 1, the resins R _{1 to} R ₆
I got

Table 1 than the resin R ₁ to R ₆ is the polycondensation temperature is low, even if short polycondensation reaction time, the melt fluidity is high good T _g is less over-pulverized product production amount, is excellent in grinding property I knew it was there.

Example 2 Example 1 was repeated except that the charge composition was changed as shown in Table 2.
To obtain a resin R ₇ to R ₁₀ by the same procedure as. The physical properties of the resin R ₇ to R ₁₀ are shown in Table 2. Table 2 from the resin R ₇ to R ₁₀ are the polycondensation reaction temperature is low, even if the polycondensation reaction time is short, good The T _g melt fluidity is high, over-pulverized product ratio is small, the grinding characteristics It turned out to be excellent.

Except that the Comparative Example 1 prepared composition was changed as shown in Table 3 was conducted in the same manner as in Example 1 to obtain resin R ₁₁ to R _14.

Table 3 shows the physical property values of R _{11 to} R ₁₅ .

The resin R ₁₁ is engaged 15 hours condensation at a polymerization temperature 260 ° C., the molecular weight does not increase sufficiently, a large amount of generated decomposition distillate to give a brown burnt resin.

The resin R ₁₂ is had good melt fluidity and heat resistance, the over-ground product has a large amount of generated.

The resin R ₁₃ has good melt flowability low softening temperature, over-pulverized material a large amount of generated, it was found that the toner production yield is poor.

Resin R _14, the molecular weight M _w of there 33000, T _g is high, the softening temperature is high, not suitable for toner is required high melt flowability and high fixing property. In addition, the grindability was large and the particle size was poor.

The resin R ₁₅ is a good melt flowability because of its low softening temperature, T _g blocking resistance becomes poor low.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masayuki Taku 4-1, 1-1 Ushikawadori, Toyohashi-shi, Aichi Prefecture Inside the Mitsubishi Rayon Co., Ltd. Toyohashi Office (72) Inventor Masahiro Ito 4-1-1 Sunadabashi, Higashi-ku, Nagoya-shi, Aichi Prefecture No. 60 Mitsubishi Rayon Co., Ltd. Product Development Laboratory (72) Inventor Koichi Ito 4-1-1 Sunadabashi, Higashi-ku, Nagoya City, Aichi Prefecture Mitsubishi Rayon Co., Ltd. Product Development Laboratory (56) References JP-A-61-284772 (JP) JP-A-1-105957 (JP, A) JP-A-1-259370 (JP, A) JP-A-2-82 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB (Name) G03G 9/087

Claims (1)

(57) [Claims] (1) at least one selected from (a) a trivalent or higher acid component and a trivalent or higher alcohol; and (b) at least one selected from terephthalic acid and isophthalic acid and lower alkyl esters thereof. One kind, (c) a diol component represented by the following formula [I] (Wherein R is an ethylene group or a propylene group, x
And y are integers and 2 ≦ x + y ≦ 6. ) And (d) an aliphatic diol, wherein the component (c) is at most 80 mol% with respect to the total acid component, and has a weight average molecular weight M _w
3,000 to 20,000, a number average molecular weight _Mn of 1,000 to 10,000, a glass transition temperature T _g of 40 to 70 ° C, and a softening temperature of 80 to 130 ° C,
15% by weight of finely pulverized material with a particle size of 5μm or less during pulverization
A polyester resin for a toner, comprising: