JP2988703B2 - 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 particularly, the present invention relates to a dry toner containing a polyester resin having excellent low-temperature fixability, offset resistance and blocking resistance.

[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 manufactured by first melting and kneading a colorant, a charge control agent and other necessary additives to sufficiently disperse them uniformly, and then performing coarse pulverization and fine pulverization and classifying them into a predetermined particle size range. Is done. 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.
Copolymers with (meth) acrylates 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 crosslinked structure by co-condensing a trivalent or less 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-based 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 which has good fixability, excellent high-temperature offset property, and good blocking resistance.

More specifically, an object of the present invention is to provide a dry toner containing a crystalline polyester resin having elasticity and good high-temperature offset property by imparting a partial crystal structure to the polyester resin.

[Means for solving the problem and operation]

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
A polyester resin containing at least 50 mol% of units derived from linear alkylene glycols based on the total monomer units used, having a crystallization point Tc− of 200 ° C. or lower,
It is characterized by containing a crystalline polyester resin having a softening temperature Ti of 110 ° C. or less, an acid value of 30 mg KOH / g or less, and a glass transition temperature Tg of 40 to 75 ° C.

Specific examples of the lower alkyl ester of terephthalic acid used in the present invention include dimethyl terephthalate and diethyl terephthalate, and dimethyl terephthalate is preferred in view of cost and usability.

The linear alkylene diol having 2 to 6 carbon atoms used in the present invention refers to ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-heptanediol and 1,6-hexanediol. Of these, ethylene glycol, 1,4-butanediol and 1,6-hexanediol are preferred because they contribute to crystallinity and are effective in controlling crystallization.

The total amount of terephthalic acid and / or its lower alkyl ester units and linear alkylene glycol units must be at least 50% based on all monomer units. If the total amount is less than 50 mol%, the crystallinity of the resulting polyester is low, and when the toner is used, the elasticity is low and the desired high-temperature offset property cannot be obtained. Their total amount is preferably at least 60 mol%. The total amount of terephthalic acid and / or a lower alkyl ester unit thereof and a linear alkylene glycol unit is important, but the respective amounts of both are not particularly limited.

The most important point in the present invention is that the polyester resin is 200 ° C.
Has the following crystallization point Tc-, softening temperature Ti is 110 ° C or less, acid value is 30 mgKOH / g or less, and glass transition temperature Tg
Is 40 to 75 ° C.

Melt kneading needs to be performed at a temperature of Tc- or more to make the polyester resin have a crystal part. If Tc− is higher than 200 ° C., melt kneading must necessarily be performed at or near 200 ° C. When the temperature exceeds 200 ° C., in the case of polyester, a decomposition reaction or rearrangement occurs, and physical properties change. Therefore, Tc− needs to be 200 ° C. or lower, and preferable Tc− is 190 ° C. or lower.

If the softening temperature Ti of the polyester resin is higher than 110 ° C,
Although it is very advantageous for the high-temperature offset, the fixing property is not different from the fixing area of the conventional polyester, and is far from the intention of the present invention. Therefore, Ti is 110
C. or lower, preferably 105 ° C. or lower.

If the acid value of the polyester resin is greater than 30 mgKOH / g, it tends to absorb moisture, and when such a resin is used as a toner, the humidity dependence of the charge amount of the toner is undesirably high.

The addition of an inorganic powder such as silica to the toner is effective for improving the blocking resistance, 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, the Tg must be between 40 and 75 ° C, preferably between 50 and 70 ° C.

In the present invention, monomers other than the above terephthalic acid, its lower alkyl ester and linear alkylene glycol can be used in combination with the above monomers in the range of the composition described in the claims depending on the required required performance. . Generally, known monomers can be used as raw materials for polyester. For example, isophthalic acid, phthalic acid,
Examples include dicarboxylic acids such as sebacic acid, isodecyl succinic acid, maleic acid, fumaric acid, and adipic acid, and lower esters such as monomethyl acid, monoethyl, dimethyl, and diethyl ester. Particularly, isophthalic acid and its dimethyl ester are resistant to blocking. It is preferable in terms of performance and cost. These divalent carboxylic acids and lower esters thereof affect the fixability and blocking resistance of the toner. When an aromatic dicarboxylic acid such as isophthalic acid is used, the blocking resistance is improved, but the fixability is lowered. Conversely, aliphatic sebacic acid and adipic acid are
Although the fixing property is improved, the Tg is lowered, which leads to a decrease in the low blocking property. In the case of aliphatic acids, this tendency is stronger for longer-chain monomers.

Aliphatic and aromatic diols are used as the diol other than the linear alkylene glycol having 2 to 6 carbon atoms. Examples of the aliphatic diol include neopentyl glycol, polyethylene glycol, cyclohexane dimethanol, hydrogenated bisphenol A, and the like. Neopentyl glycol is preferred from the viewpoint of fixability. Examples of the aromatic diol include polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2.0) -2,2-bis (4-hydroxyphenyl) propane, and 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, poly Oxypropylene (3.3) -2,2-bis (4-hydroxyphenyl) propane and the like. Since the aromatic diol has an effect of increasing Tg, the blocking resistance is improved. These diols are used alone or in combination of two or more.

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.

The crystalline polyester resin of the present invention is preferably a linear polyester resin having no crosslinked structure, but may be a crosslinked polyester resin having a crosslinked structure. When the polymer has a crosslinked structure, a polyfunctional monomer can be used in combination. Examples of polyfunctional monomers include trimellitic acid, pyromellitic acid, 1,2,4-
Cyclohexanetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,
Polycarboxylic acids such as 2,5-hexanetricarboxylic acid and 1,2,7,8-octanetetracarboxylic acid and anhydrides thereof, and sorbitol, 1,2,3,6-hexanetetralol, 4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, sucrose, 1,2,4-butanetriol, 1,2,5-pentatriol, glycerol, 2-methylpropanetriol,
And polyhydric alcohols such as -methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene. These polyfunctional monomers are used alone or in combination of two or more. Such polyfunctional monomers are
In addition to the effect of increasing Tg, the resulting crosslinked structure has the effect of increasing the offset resistance together with the crystal part.

The polyester resin for a crystalline 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, the crystallization point Tc− and the glass transition temperature
Tg is determined as follows. That is, using a differential scanning calorimeter, the temperature at the intersection of the tangent of the endothermic curve near the Tg and the chart when measured at a heating rate of 5 ° C./min is Tg, and −5 ° C./250° C./min. The peak of the exothermic curve measured in minutes was defined as Tc−. The softening temperature Ti referred to in the present invention is:
The temperature at which the resin starts to flow when measured using a flow tester (T-500, manufactured by Shimadzu Corporation) at a nozzle of 1.0 mmφ × 10 mm, a load of 30 kgf and a heating rate of 3 ° C./min.

〔Example〕

Hereinafter, the polyester resin of the present invention will be specifically described with reference to examples.

In the composition analysis in the examples, the polyester resin was hydrolyzed with hydrazine and quantified using liquid chromatography.

Example-1 According to the composition of Table 1-1, 100 mol parts of terephthalic acid, 100 mol parts of ethylene glycol, and 20 mol parts of polyoxypropylene (2.3) -2,2-bis (4-hydroxyphenyl) propane were distilled. Into a reaction vessel having Further, dibutyltin oxide was added to the reaction vessel in an amount of 0.03% by weight based on all acid components, the internal temperature was set to 260 ° C, and the number of rotations of the stirring was set to 200 rpm.
After performing the esterification reaction under normal pressure for 5 hours, the pressure in the reaction system was reduced to 1.0 mmHg over 30 minutes, the internal temperature was maintained at 260 ° C, and the condensation reaction was performed for 2 hours while distilling ethylene glycol, A pale yellow transparent resin R-1 was obtained. The obtained resin R-1 had a Tc− of 152 ° C., a Ti of 90 ° C., and an acid value of 6.0 mgKOH /
g and Tg was 62.9 ° C. Table 1-2 shows the composition analysis result of the obtained 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 Henschel mixer, and then melt-kneaded at 165 ° C. and 130 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 test results of the fixing property and the blocking resistance of the 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. Cellotape No. 405 (Nichiban) was used for the tape.

For the evaluation of the 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 Resins R-2 to R-4 were obtained in the same manner as in Example 1, except that the monomer charge composition was changed as shown in Table 2-1. 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 to 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.
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 5 Resins R-5 to R-9 were obtained in the same manner as in Example 1, except that the monomer charging composition was changed as shown in Table 3-1. Table 3-1 shows the results of the composition analysis and the resin physical properties of the resins R-5 to R-9.

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 was performed to obtain R-5, R-6, and R-5.
As a result, toners T-5, T-6, T-7, T-8 and T-9 corresponding to -7 were obtained. However, R-5 was melt-kneaded at a temperature of 150 ° C. T
Table 3-3 shows the results of the fixing test and the blocking resistance test of -5 to T-9.

As can be seen from Table 3-3, T-5 did not have Tc-, so that the resin could not have elasticity, a high-temperature offset occurred at a low temperature, and the fixing area was zero.

Further, since T-6 has a high Tc-, it was necessary to perform melt kneading at a temperature around 250 ° C. Therefore, during melt-kneading, a large amount of decomposed products were generated, and a bad smell was also generated.

For T-7, slight Tc- was observed at around 80 ° C, but the blocking resistance was reduced due to the low Tg.

Since T-8 has a high Ti of 220 ° C., it is predictable that the high-temperature offset is good, but the fixability was poor and the fixing rate could not be cleared to 90% unless the temperature was raised to 220 ° C. At a temperature of 200 ° C. or less, a cold offset occurred.

T-9 has good thermal properties of toner, but has an acid value of 35 mg.
Since it is as high as KOH / g, it can be seen that the electrical properties, particularly the humidity dependency of charging, are high. Therefore, it is considered that the resins R-5 to R-9 are not suitable as toner resins.

〔The invention's effect〕

The dry toner prepared from the crystalline polyester resin of the present invention has both good fixing properties, high-temperature offset properties and blocking resistance.

──────────────────────────────────────────────────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 Research Laboratory (72) Inventor Koichi Ito 4-1-1 Sunadabashi, Higashi-ku, Nagoya City, Aichi Prefecture Mitsubishi Rayon Co., Ltd. Product Development Research Laboratory (56) References JP-A-55-40407 (JP) , A) JP-A-62-289850 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 9/08-9/097

Claims (2)

(57) [Claims] 1. A polyester resin containing at least 50 mol% of units derived from terephthalic acid and / or a lower alkyl ester thereof and units derived from a linear alkylene glycol having 2 to 6 carbon atoms, based on all monomer units used. The crystallization point Tc− is 200 ° C. or less, and the softening temperature Ti is 1
A dry toner comprising a crystalline polyester resin having a temperature of 10 ° C. or less, an acid value of 30 mg KOH / g or less, and a glass transition temperature Tg of 40 to 75 ° C. 2. The dry toner according to claim 1, wherein the crystalline polyester resin is a polyester resin having no crosslinked structure.