JP2988704B2 - Dry toner - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a dry toner used for developing an electrostatic image or a magnetic latent image in electrophotography, electrostatic recording, electrostatic printing, and the like. More specifically, the present invention relates to a dry toner containing a polyester resin having excellent low-temperature fixing properties and high-temperature offset properties.

[Conventional technology]

In order to obtain a permanent visible image from the electrostatic image, a method is employed in which an electrostatic image formed on a photoconductive photoreceptor or an electrostatic recording medium is developed with a toner previously charged by friction and then fixed. . In the case of a magnetic latent image, a method is used in which the latent image on the magnetic drum is developed with toner containing a magnetic material and then fixed. Fixing involves directly fusing the toner image obtained by development on the photoconductive photoreceptor or electrostatic recording medium, or transferring the toner image onto paper or film and then fusing it on a transfer sheet. Done by Fusion of toner images is performed by contact with solvent vapor, pressurization and heating. There are two types of heating methods: non-contact heating using an electric oven and pressure heating using a pressure roller. Recently, the latter is mainly used.

The toner used in the dry development method includes a one-component toner and a two-component toner. The two-component toner is first melt-kneaded with a resin, a colorant, a charge control agent, and other necessary additives to sufficiently uniformly disperse the mixture, then coarsely and finely pulverized, and classified into a predetermined particle size range. Manufactured. The one-component toner is similarly manufactured by adding magnetic iron powder in addition to the components of the two-component toner.

Since the resin is the main component in the compounding of the toner, it controls most of the performance required for the toner. Therefore, the resin for the toner is required to have good dispersibility of the colorant in the melt kneading step in the toner production stage, good pulverizability in the pulverization step, etc., and also in the toner use stage, fixability, offset property, Various performances such as good blocking properties and good electrical properties are required. Epoxy resins, polyester resins, polystyrene resins, methacrylic resins, and the like are known as resins used in the production of toners. Polymers have been used. However, polyester resins have attracted attention because they can be fixed at lower temperatures and have excellent PVC plasticizer resistance of the fixed toner images.

The polyester resin directly esterifies the dihydric carboxylic acid or its lower alkyl ester and diol,
Although it is produced by a condensation reaction by transesterification, the polyester resin for toner has a weak cross-linking structure by co-condensing a trivalent or more carboxylic acid or alcohol in addition to the above in order to impart offset resistance in the fixing step. It has been proposed that

However, the method of imparting a weak crosslinked structure using a trivalent or higher polyvalent carboxylic acid or polyhydric alcohol has a limited molecular weight distribution, has excellent fixing properties inherent to polyester, and has a low molecular weight. The property that a polymer is easily obtained is not fully utilized. As a method for imparting a high fixing property and a high offset property, a method of using a large amount of a polycarboxylic acid or a polyhydric alcohol to broaden the molecular weight distribution has been proposed, but this method is difficult to produce industrially. Even if it can be manufactured, it is difficult to stably obtain certain physical properties, and the manufacturing cost increases.

Further, as another method of expanding the molecular weight distribution, a method of blending a cross-linked polymer and a low-molecular polymer has been proposed, but uniform mixing is extremely difficult. This leads to deterioration of charging characteristics.

Polyester is excellent in high-temperature offset resistance because its SP value is different from that of Teflon applied to the fixing roller compared to styrene resin. Therefore, even with the above-mentioned proposed method, it is possible to have a fixing area equal to or higher than that of the styrene resin. However, in view of the inherent properties of polyester, it is possible to further expand the fixing area, and there is a strong demand for a binder resin having such a wide fixing area.

[Problems to be solved by the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a dry toner having good fixability and excellent hot offset property.

More specifically, by providing crystallinity to a conventional crosslinked polyester resin, a dry toner containing a crystalline crosslinked polyester resin having very good low-temperature fixability and excellent high-temperature offset property is provided. It is in.

[Means and actions for solving the problem]

The dry toner of the present invention comprises a unit derived from terephthalic acid and / or a lower alkyl ester thereof and a carbon number of 2
And a unit derived from a linear alkylene glycol and a unit derived from a trivalent or higher polyhydric carboxylic acid and / or a polyhydric alcohol, and the total amount of these units is 60 mol% based on the total monomer amount. A polyester resin having the above, having Tc +, a softening temperature Ti of 110 ° C or less, a glass transition temperature Tg of 40 ° C to 75 ° C, and containing a crystalline crosslinked polyester resin having a crosslinked structure. It is characterized by the following.

The polyester resin of the present invention contains, as one component, a unit derived from terephthalic acid and / or a lower alkyl ester thereof. Specific examples of the lower alkyl ester of terephthalic acid include dimethyl terephthalate, diethyl terephthalate, dibutyl terephthalate, and the like, and dimethyl terephthalate is preferred in terms of cost and crystallinity.

The polyester resin of the present invention further contains a unit derived from a linear alkylene diol having 2 to 4 carbon atoms. Specific examples of the linear alkylene diol having 2 to 4 carbon atoms include ethylene glycol, propylene glycol, and 1,4-butanediol. Among them, ethylene glycol has an effect of increasing Tc +, and has an effect of decreasing propylene glycol Tc +.

The polyester resin of the present invention further contains a unit derived from a trivalent or higher polycarboxylic acid and / or a polyhydric alcohol. Specific examples of trivalent or higher polycarboxylic acids include trimellitic acid, pyromellitic acid, 1,2,4-cyclohexanetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, and 1,2,4-naphthalenetricarboxylic acid. , 1,2,5-hexanetricarboxylic acid, 1,2,7,8-octanetetracarboxylic acid and anhydrides thereof. Specific examples of the trihydric or higher polyhydric alcohol include sorbitol, 1,2,
3,6-hexanetetralol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, sucrose, 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. These are used alone or as a mixture.
Such a polyfunctional monomer has the effect of increasing the Tg of the resin and can impart elasticity to the polymer even in a temperature range higher than the melting point of the crystalline polymer. Since the crosslinked structure has the effect of increasing the offset resistance together with the crystal portion, the degree of crosslinking may be freely set according to the fixing temperature and copying speed of the copying machine used.

The amount of the trivalent or higher polyhydric carboxylic acid and / or polyhydric alcohol unit is preferably 0.5 to 20 mol% based on the total monomer amount. If the amount is less than 0.5 mol%, it is difficult to obtain the desired high-temperature offset resistance.

The total amount of terephthalic acid and / or its alkyl ester unit, linear alkylene glycol unit and trivalent or higher polycarboxylic acid and / or polyhydric alcohol unit must be not less than 60 mol% based on all monomer units. No. If the total amount thereof is less than 60 mol%, the resulting polyester has low crystallinity, and when it is used as a toner, the desired high-temperature offset property and anti-blocking property cannot be obtained. Their total amount is preferably at least 70-95 mol%. The amounts of terephthalic acid and / or its alkyl ester unit and linear alkylene glycol unit are not particularly limited, but the former is preferably 50 to 100% based on the total acid component, and the latter is preferably The content is preferably 50 to 60 mol% based on the alcohol component.

In producing the polyester resin of the present invention, monomers other than the above monomers can be used according to the required performance. That is, generally, a monomer commonly used as a raw material of polyester may be used as long as the effects of the present invention are maintained. For example, as dicarboxylic acids, isophthalic acid, phthalic acid,
Sebacic acid, isodecyl succinic acid, maleic acid, fumaric acid, adipic acid, and monomethyl, monoethyl, dimethyl, diethyl esters thereof, and the like, and isophthalic acid and dimethyl esters thereof are particularly preferable in terms of blocking resistance and cost. . These dicarboxylic acids and lower esters thereof affect the fixability and blocking resistance of the toner. When an aromatic isophthalic acid is used, the blocking resistance is improved, but the fixability is lowered. Conversely, when an aliphatic sebacic acid or adipic acid is used, the fixing property is improved, but the Tg is lowered, which leads to a decrease in blocking resistance. In the case of aliphatic acids, this tendency is stronger for longer-chain monomers.

The diols used in combination include aliphatic and aromatic diols, and specific examples of the aliphatic diol include neopentyl glycol, polyethylene glycol, cyclohexane dimethanol, hydrogenated bisphenol A and the like. In view of this, neopentyl glycol is preferred. Specific examples of the aromatic diol include polyoxyethylene- (2.0) -2,2-bis (4-hydroxyphenyl) propane and polyoxypropylene- (2.
0) -2,2-bis (4-hydroxyphenyl) propane,
Polyoxypropylene (2.2) -polyoxyethylene-
(2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (6) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2.2) -2,2-bis ( 4-hydroxyphenyl) propane, polyoxypropylene- (2.4) -2,2-bis (4-
(Hydroxyphenyl) propane, polyoxypropylene (3.3) -2,2-bis (4-hydroxyphenyl) propane and the like, which are used alone or as a mixture. Since the aromatic diol has an effect of increasing Tg, the blocking resistance is improved. Among the diol components, aromatic diols and alicyclic diols such as cyclohexane dimethanol and hydrogenated bisphenol A are already known to be able to control the reactivity and to improve the wear resistance.

An important feature of the polyester of the present invention is that the softening temperature Ti is 11
0 ° C. or less. When Ti exceeds 110 ° C., the polymer is the same as a conventional crosslinkable polymer, and the low-temperature fixability is not improved, and the object of the present invention is not achieved.
Therefore, Ti needs to be 110 ° C. or less, preferably 8
0 to 105 ° C.

Addition of an inorganic powder such as silica to the toner is effective in improving the anti-blocking property, and the effect is particularly remarkable when the glass transition temperature Tg of the resin binder is low. However, a resin having a Tg of 40 ° C. or higher has good blocking resistance even without adding an inorganic powder. When the Tg exceeds 75 ° C., the blocking resistance becomes good, but the low-temperature fixability deteriorates. Therefore, Tg needs to be 40-75 ° C., preferably 50
~ 70 ° C.

The polyester resin for a crystalline crosslinked toner of the present invention is prepared as follows. The esterification reaction or transesterification reaction is performed by charging the monomer into a reaction vessel and heating and raising the temperature. At this time, an esterification catalyst or a transesterification catalyst such as sulfuric acid, titanium butoxide, dibutyltin oxide, magnesium acetate, and manganese acetate, which is used in a usual esterification reaction or transesterification reaction, can be used as necessary. Next, water or alcohol generated by the reaction is removed according to a conventional method.

Subsequently, a polymerization reaction is carried out. At this time, the polymerization is carried out while distilling and removing the diol component under a vacuum of 150 mmHg or less. In the polymerization, generally known polymerization catalysts, for example, titanium butoxide, dibutyltin oxide, tin acetate,
Zinc acetate, tin sulfide, antimony oxide, germanium oxide, 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.

In the present invention, Tc + and Tg are determined as follows. That is, using a differential scanning calorimeter, the heating rate was 5 ° C.
The temperature at the intersection of the tangent to the endothermic curve near the Tg and the chart, the baseline measured at / min, was Tg, and the peak of the exothermic curve was Tc +. Tc + refers to the temperature at which the polymer crystallizes at elevated temperatures.

The crosslinked structure as referred to in the present invention refers to a structure of a resin having a point at which the torque of a reaction system sharply increases when polymerized at a temperature equal to or higher than the melting point of the resin, that is, a so-called gel point.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to Examples,
Embodiments of the present invention are not limited to these.

In Examples, the composition of the resin was determined by hydrolyzing the resin with hydrazine and performing liquid chromatography.

Example 1 According to the composition shown in Table 1-1, 100 mol parts of terephthalic acid, 97 mol parts of ethylene glycol, 3 mol parts of pentaerythritol, and 20 mol parts of hydrogenated bisphenol A were charged into a reaction vessel having a distillation column. Further, 0.03 parts by weight of dibutyltin oxide was added to the reaction vessel with respect to all the acid components, and the internal temperature was lowered to 26%.
After the esterification reaction was carried out at 0 ° C. and stirring speed of 200 rpm under normal pressure for 5 hours, the pressure in the reaction system was reduced to 1.0 mmHg over 30 minutes, and the internal temperature was maintained at 260 ° C. while distilling ethylene glycol. The condensation reaction was performed for 2 hours to obtain a pale yellow transparent resin R-1. The obtained resin R-1 has a Tc + of 152 ° C.
Softening temperature Ti was 92 ° C and Tg was 64.2 ° C. Table 1-2 shows the composition analysis result and physical properties of the resin R-1.

5% by weight of carbon black (Mitsubishi Kasei # 50), 2% by weight of PP wax (Sanyo Chemical Biscol 550-P), 1% by weight of Bontron S-34 (Orient Chemical Industries) based on 92% by weight of resin (R-1) % Was premixed with a Hexchel mixer, and then melt-kneaded at 175 ° C. and 80 rpm using a Haake biaxially conical extruder. The melt-kneaded product was cooled to room temperature, coarsely ground by a hammer mill, and then ground to 22 μm or less using a jet mill. Then, using a pneumatic classifier of Nippon Pneumatic Co., Ltd., the particle size was adjusted to 5 to 22 μm to obtain toner T-1. Table 1-3 shows the fixing test results and the blocking resistance test results of Toner T-1.

The fixing area here is defined as the temperature at which the density decay rate when the tape peeling test is performed is 10% or less after the toner is evenly sprinkled on the paper and passed through a temperature variable fixing roller. It refers to the temperature range until high-temperature offset occurs. The speed of the fixing roller was set to 150 mm / sec, and cellotape No. 405 (Nichiban) was used as the tape.

For the evaluation of blocking resistance, 5 g of the toner was placed in a 50-ml glass sample bottle, left in a high-temperature bath at 50 ° C. for 50 hours, and then observed for the degree of aggregation. The degree of aggregation was evaluated based on criteria set as follows.

 The sample bottle left at 50 ° C. for 50 hours is cooled to room temperature, and A: The toner drops just by inverting the sample bottle.

B: The toner drops when the sample bottle is turned upside down and shaken lightly.

C: Invert the sample bottle and tap lightly to drop toner.

D: When the sample bottle is turned upside down and strong vibration is applied, toner drops.

E: Even if the sample bottle is turned upside down and strong vibration is applied, the toner does not fall.

 The cohesion degrees A, B, and C were determined to be usable.

Table 1-3 shows that the toner T-1 has a wide fixing area and good blocking resistance.

Examples 2 to 4 The same operations as in Example 1 were carried out except that the monomer charging composition was as shown in Table 2-1 to obtain resins R-2 to R-4. Table 2-2 shows the composition analysis results and the resin physical properties of the resins R-2 to R-4.

In the melt-kneading process, the same operation as in Example 1 is performed except that the melt-kneading temperature is set at a temperature higher by 15 ° C. than the Tc + of the resin, and the toners T-2 to T- corresponding to the resins R-2 to R-4 are used.
4 was obtained. Table 2-3 shows the results of the fixing test and the blocking resistance test of T-2 to T-4.

Table 2-3 shows that the toners T-2 to T-4 have a wide fixing area and good blocking resistance.

Comparative Examples 1 to 3 The same operation as in Example 1 was performed except that the monomer charging composition was as shown in Table 3-1 to obtain resins R-5 to R-7. Table 3-2 shows the analysis results and the resin physical properties of the resins R-5 to R-7.

Except that the melt kneading is performed at a temperature 15 ° C. higher than each Tc + in Table 3-2, the same operation as in Example 1 is performed, and R-5, R-6, R−
Thus, toners T-5, T-6, and T-7 corresponding to No. 7 were obtained. However,
R-5 was melt-kneaded at 150 ° C. Table 3-3 shows the results of the fixing test and the blocking resistance test of T-5 to T-7.

As can be seen from Table 3-3, since T-5 does not have Tc +, the high-temperature offset is good, but the fixability decreases. When the molecular weight was reduced to improve the fixability, high-temperature offset disappeared. Further, since T-6 has a high Ti content, 230 ° C. or more was required to exceed a fixing rate of 90%. T-
Sample No. 7 had a low Tg, and thus had a low blocking resistance. Therefore, it is considered that the resins R-5 to R-7 are not suitable as toner resins.

〔The invention's effect〕

The dry toner prepared from the crystalline cross-linked polyester resin of the present invention has excellent low-temperature fixing properties and high-temperature offset properties.

Continued on the front page (72) Inventor Masayuki Taku 4-1, Ushikawa-dori, Toyohashi-shi, Aichi Prefecture 2 Inside the Toyohashi Works of Mitsubishi Rayon Co., Ltd. (72) Inventor Masahiro Ito 4-1-160 Sunadabashi, Higashi-ku, Nagoya City, Aichi Prefecture Mitsubishi (72) Inventor Koichi Ito 4-160 Sunadabashi, Higashi-ku, Nagoya City, Aichi Prefecture Mitsubishi Rayon Co., Ltd. Product Development Research Laboratory (56) References JP-A-56-21136 (JP, A) JP-A-1-307767 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 9/08-9/097

Claims (1)

(57) [Claims] (1) a unit derived from terephthalic acid and / or a lower alkyl ester thereof, a unit derived from a linear alkylene glycol having 2 to 4 carbon atoms, and a trivalent or higher polycarboxylic acid and / or polyhydric alcohol; A polyester resin having a total amount of 60 mol% or more based on the total amount of monomers, having a Tc +, a softening temperature Ti of 110 ° C. or less, and a glass transition temperature A dry toner having a Tg of 40 ° C. to 75 ° C. and containing a crystalline crosslinked polyester resin having a crosslinked structure.