JPH04120555A - Polyester resin for crystalline crosslinked type toner - Google Patents

Abstract

PURPOSE:To improve fixability and high-temp. offset property by using the polyester resin which has a crystallization point Tc+, is specified in softening temp. Ti to <=110 deg.C and is specified to glass transition temp. Tg to 40 to 75 deg.C and has a crosslinked structure. CONSTITUTION:Crystallinity is imparted to the crosslinked polyester resin, by which the good low-temp. fixability and the excellent high-temp. offset property are imparted to the resin. Namely, this resin contains the unit derived from terephthalic acid and/or lower alkyl ester thereof and the unit derived form 2 to 4C straight chain alkylene glycol and the unit derived from trivalent or higher valency carboxylic acid and/or polyhydric alcohol and the total of these units is >=60mol% of the total monomer amt. The resin has Tc+, <=110 deg.C softening temp. Ti and 40 to 75 deg.C glass transition temp. Tg and is provided with the crosslinked structure. The low-temp. fixability and high-temp. offset property are improved in this way.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is useful as a dry toner used for developing electrostatic images or magnetic latent images in electrophotography, electrostatic recording, electrostatic printing, etc. Regarding polyester resin. More specifically, the present invention relates to a polyester resin having excellent low-temperature fixing properties and high-temperature offset properties.

[Conventional technology]

In order to obtain a more permanent image than an electrostatic charge image, the electrostatic charge image formed on the photoconductive photoreceptor or electrostatic recording medium must be prepared in advance.
A method is adopted in which the toner is developed using frictionally charged toner and then fixed. In the case of a magnetic latent image, a method is used in which the latent image on a magnetic drum is developed with toner containing a magnetic material and then fixed. Fixing involves directly fusing the toner image obtained by development onto a photoconductive photoreceptor or electrostatic recording medium, or by transferring the toner image onto paper or film and then fusing it onto a transfer sheet. carried out by Fusing of toner images is performed by contact with solvent vapor, pressure, and heating.Heating methods include non-contact heating using an electric oven and pressure heating using a pressure roller, but there is a need for faster fixing processes. Recently, the latter has been mainly used.

Toners used in the dry development method include one-component toners and two-component toners. Two-component toner consists of resin,
The colorant, charge control agent, and other necessary additives are melt-kneaded and sufficiently uniformly dispersed, then coarsely pulverized, finely pulverized, and classified into a predetermined particle size range. (2) Component toner is produced in the same manner as in the two-component toner by adding magnetic iron powder in addition to each of the components.

Since the resin is the main component in the toner formulation, it controls most of the performance required of the toner. In the toner production stage, resins for toners are required to have good colorant dispersibility in the melt-kneading process and good pulverization properties in the pulverization process, and also to have good fixing properties and offset properties in the toner use stage. It is required to have a variety of performances such as good resistance, blocking properties, and electrical properties. Epoxy resins, polyester resins, polystyrene resins, methacrylic resins, etc. are known as resins used in toner production.
Copolymers of styrene and (meth)acrylic acid ester have been mainly used as resins for pressure bonding and heat fixing systems.

However, polyester resin H is attracting attention because it can be fixed at a lower temperature and the fixed toner image has excellent resistance to vinyl chloride plasticizers.

Polyester resins are produced by direct esterification of divalent carboxylic acids or their lower alkyl esters and diols, or by condensation reaction through transesterification, but in polyester resins for toners, a method for imparting offset resistance during the fixing process is used. In addition to the above, it has been proposed to co-condense trivalent or higher carboxylic acids or alcohols to provide a weak crosslinked structure.

However, in the method of creating a weak crosslinking structure using trivalent or higher polycarboxylic acids or polyhydric alcohols, there is a limit to the spread of the molecular weight distribution. The property of easily obtaining polymers is not fully utilized. As a method of imparting high fixing properties and high offset properties, a method has been proposed that uses large amounts of polyhydric carboxylic acids or polyhydric alcohols that broaden the molecular weight distribution, but this method is difficult to manufacture industrially. Even if it could be manufactured, it would be difficult to stably obtain certain physical properties, and the manufacturing cost would also increase.

In addition, as another method to widen the molecular weight distribution, a method of blending crosslinked high molecular weight polymers and low molecular weight polymers has been proposed, but it is very difficult to mix uniformly, so when made into a toner, it causes poor scattering and This leads to deterioration of charging characteristics.

Compared to styrene-based resins, polyester has an SP value that is far superior to that of Teflon, which is used to coat the fixing roller, and is therefore superior in terms of high-temperature offset resistance. Therefore, even with the above-mentioned proposed method, it is possible to have a fixing area that is equal to or larger than a styrene resin disk. However, given the inherent properties of polyester, it is possible to further expand the fixing area, and the emergence of a binder resin with such a wide fixing area is eagerly awaited.

[Problem to be solved by the invention]

An object of the present invention is to provide a polyester resin for toner that has good fixing properties and excellent high-temperature offset properties.

More specifically, by imparting crystallinity to conventional cross-linked polyester resin, it has very good low-temperature fixing properties.
Furthermore, it is an object of the present invention to provide a polyester resin for a crystalline crosslinked toner that has excellent high-temperature offset properties.

[Means and effects for solving the problems] The crystalline crosslinked polyester resin for toner of the present invention is composed of a unit derived from terephthalic acid and/or its lower alkyl ester and a linear alkylene glycol having 2 to 4 carbon atoms. A polyester resin containing a unit derived from a polyhydric carboxylic acid having a valence of 3 or more and a unit derived from a polyhydric alcohol, and the total amount of these units is 60 mol% or more based on the total monomer amount, Tc+, softening temperature T
1 is 110°C or less, and the glass transition temperature Tg is 40°C
The polyester resin of the present invention, which is characterized by having a temperature of 75° C. and a crosslinked structure, contains a unit derived from terephthalic acid and/or a lower alkyl ester thereof as a component. Specific examples of lower alkyl esters of terephthalic acid include dibutyl terephthalate, dimethinobeterephthalate, and diethinobeterephthalate, but dimethyl terephthalate is preferred from the viewpoint of cost and imparting crystallinity.

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

The polyester resin of the present invention further includes a unit derived from a trivalent or higher polyhydric carboxylic 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. ,
Examples include 1.25-hexanetricarboxylic acid, 1.2.7.8 octanetetracarboxylic acid, and acid anhydrides thereof. Specific examples of trihydric or higher polyhydric alcohols include:
Sorbitol, 1,2.3.6-hexanetetralol, 1,4-sorbitan, pentaerythritonovezipentaerythritonobetripentaerythritonope sucrose,
1.2.4-butanetriol, 1.2.5-pentatriol, chrycerol, 2-methylpropanetriol 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1. 3
．． Examples include 5-trihydroxymethylbenzene,
These may be used alone or as a mixture. Such a polyfunctional monomer has the effect of increasing the Tg of the resin, and can also impart elasticity to the polymer even in a temperature range above the melting point of the crystalline polymer. In this way, the crosslinked structure has the effect of increasing offset resistance together with the crystalline portion, so the degree of crosslinking can be freely set according to the fixing temperature and copying speed of the copying machine used.

The amount of trivalent or higher polyhydric carboxylic acid and/or polyhydric alcohol units is preferably 0.5 to 20 mol % based on the total amount of monomers used. 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 units, direct decomposition type alkylene glycol units, and trivalent or higher polyhydric carboxylic acid and/or polyhydric alcohol units is 60 mol% or more based on the total 51 mer units. There must be. If the total amount thereof is less than 60 mol %, the crystallinity of the polyester produced is low, and when it is made into a toner, the desired high temperature offset properties and anti-blocking properties cannot be obtained. Their total amount is preferably 70-95
It is mol% or more. Note that the respective amounts of terephthalic acid and/or its alkyl ester units and direct-quenching alkylene glycol units are not particularly limited, but the former is preferably 50 to 100% of the total acid component, and the latter is 50% to 100% of the total acid component. It is preferably 50 to 60 mol% based on the alcohol component.

When producing the polyester resin of the present invention, monomers other than the above-mentioned monomers can be used in combination depending on the required performance. That is, in general, monomers commonly used as raw materials for polyester may be used as long as the effects of the present invention are maintained. For example, dicarboxylic acids include isophthalic acid, phthalic acid, sebacic acid, isodecyl succinic acid, maleic acid, fumaric acid, adipic acid, and monomethinobemonoethinobedimethinobediethyl esters thereof, particularly isophthalic acid. And these dimethyl esters are preferred in terms of blocking resistance and cost. These dicarboxylic acids and their lower esters affect the fixing properties and blocking resistance of the toner. When aromatic isophthalic acid is used, blocking resistance is improved, but fixing performance is reduced. On the other hand, when aliphatic sebacic acid or adipic acid is used, fixing properties are improved, but the Tg is lowered, leading to a decrease in blocking resistance. In the case of aliphatic acids, this tendency is stronger for longer chain monomers).

Diols used in combination include aliphatic and aromatic diols. Specific examples of aliphatic diols include neopentyl glycol, polyethylene glycol, cyclohexanedimethanol, hydrogenated hisphenol A, etc. Neopentyl glycol is preferred from the viewpoint of properties.

Specific examples of aromatic diols include polyoxyethylene-(2,0)-2,2-bis(4-hydroxyphenyl)propane, 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)furopane, polyoxypropylene (2,2)-2,2-bis(4-hydroxyphenyl)furopane, polyoxypropylene-(2,4)2.2
-bis(4-hydroxyphenyl)propane, polyoxinepropylene(3,3)-2,2bis(4-hydroxyphenyl)propane, etc., which may be used alone or as a mixture. Since aromatic diols have the effect of increasing Tg, blocking resistance is improved. Among the diol components, aromatic diols and cyclohexane dimetatools, hydrogenated bisphenol A and alicyclic diols, etc. can adjust the reactivity and
It is also already known that wear resistance is improved.

The important feature of the polyester of the present invention is that the softening temperature T1 is 1
The temperature should be 10°C or less. When Ti exceeds 110° C., the polymer is no different from a conventional crosslinked polymer, and no improvement is seen in low-temperature fixing properties, so that the object of the present invention cannot be achieved. Therefore, T1 needs to be 110°C or less, preferably 80 to 105°C.

Adding an inorganic powder such as silica to the toner is effective in improving blocking resistance, and this effect is particularly significant when the glass transition temperature Tg of the resin binder is low. However, resins with a Tg of 40° C. or higher have good bubbling resistance even without the addition of inorganic powder. When Tg exceeds 75° C., blocking resistance becomes good, but low-temperature fixability deteriorates.

Therefore, Tg needs to be 40 to 75°C, preferably 50 to 70°C.

The polyester resin for crystalline crosslinked toner of the present invention is prepared as follows. An esterification reaction or transesterification reaction is carried out by charging the monomers into a reaction vessel and heating and raising the temperature. At this time, sulfuric acid, titanium butoxide, dibutyltin oxide, magnesium acetate,
Esterification or transesterification catalysts used in conventional esterification or transesterification reactions, such as manganese acetate, can be used. Next, water or alcohol produced in the reaction is removed according to a conventional method.

Subsequently, a polymerization reaction is carried out, but at this time 150 mmH
Polymerization is carried out while distilling and removing the diol component under a vacuum of less than 100 g. In the polymerization, commonly known polymerization catalysts such as titanium butoxide, dibutyltin oxide, tin acetate, zinc acetate, tin disulfide, antimony trioxide, germanium dioxide, etc. can be used. The polymerization temperature and the amount of catalyst are not particularly limited, and may be arbitrarily set as necessary.

In the present invention, Tc-+- and Tg are determined as follows. In other words, the chart, baseline, and T when measured using a differential scanning calorimeter at a heating rate of 5°C/min.
Let Tg be the temperature at the intersection of the tangents of the endothermic curve near g,
Moreover, the peak of the exothermic curve was defined as Tc+. Tc+ refers to the temperature at which the polymer crystallizes under elevated temperature.

The term "crosslinked structure" as used in the present invention refers to a structure possessed by a resin that exceeds the so-called gelation point, which is the point at which the torque of the reaction system rapidly increases when polymerized at a temperature higher than the melting point of the resin.

〔Example〕

The present invention will be specifically described below with reference to Examples, but the embodiments of the present invention are not limited thereto.)

In the examples, the composition of the resin was determined by hydrolyzing the resin with hydrazine and quantifying it by 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, Pentaerys IJ)-
3 mol parts of hydrogenated bisphenol A and 20 mol parts of hydrogenated bisphenol A were charged into a reaction vessel equipped with a distillation column. Furthermore, 0.03 parts by weight of dibutyltin oxide based on the total acid components was added to the reaction vessel, and the internal temperature was maintained at 260°C and the stirring rotation speed was 200 rpm.
After carrying out the esterification reaction under normal pressure for 5 hours, the pressure inside the reaction system was reduced to 1.0 mmHg over 30 minutes, and the internal temperature was reduced to 260 mmHg.
The condensation reaction was carried out for 2 hours while maintaining the temperature at 0.degree. C. to distill off ethylene glycol, to obtain a pale yellow clear husk resin R-1. The obtained resin R-1 had a Tc- of 152°C, a softening temperature T1 of 92°C, and a Tg of 64.2°C. The compositional analysis results and physical property values of Resin R-1 are shown in Table 1-2.

Table 1-1 Monomer charge composition (mol parts) Resin R Table 1-2 Composition and characteristics of 1 Resin (R-1) 92% by weight, carbon black (Mitsubishi Kasei #50) 5% by weight, PP wax (
2% by weight of Sanyo Kasei Viscol 550-P) and 1% by weight of Bontron 5-34 (Orient Chemical Industry) were premixed using a Hexiel mixer, and then heated at 175°C using a Hague biaxial conical type extruder with different directions. , 8
Melt kneading was performed at 0 rpm. The melt-kneaded product was cooled to room temperature, coarsely pulverized with a hammer mill, and then pulverized to 22 mm or less using a jet mill. Thereafter, using a wind classifier manufactured by Nippon Pneumatic Co., Ltd., the particle size was adjusted to 5 to 22 to obtain toner T-1. Table 1-3 shows the fixing test results and blocking resistance test results of Toner T-1.

Table 1-3 Characteristics of Toner T-1 The fixing area in Section 22 refers to the density attenuation when toner is uniformly sprinkled onto paper, passed through a temperature-variable fixing roller, and then subjected to a tape peel test. This refers to the temperature range from the temperature at which the rate drops to 10% or less until a high temperature offset occurs. The speed of the fixing roller was set at 150 mm/sec, and Cellotape No. 405 (Ciban) was used as the tape.

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

A sample bottle that had been left at 50°C for 50 hours was cooled to room temperature. A: The toner falls out just by turning the sample bottle upside down.

B: Turn the sample bottle upside down and shake it lightly to remove the toner.

C: Turn the sample bottle upside down and tap it lightly to remove the toner.

D: If you turn the sample bottle upside down and give it strong vibration, the toner will fall off.

E: The toner does not fall even if the sample bottle is turned upside down and subjected to strong vibrations.

Note that the aggregation degrees A, B, and C were determined to be usable.

From Table 1-3, it can be seen that toner T-1 has a wide fixing area and good blocking resistance.

Examples 2 to 4 Resins R-2 to R-4 were obtained by carrying out the same operation as in Example 1, except that the monomer charging composition was changed as shown in Table 2-1.

The compositional analysis results and resin physical property values of Resins R-2 to R-4 are shown in Table 2-2.

Table 2-1 Monomer charge composition (mol parts) Diol A: Polyoxypropylene (2,3) 2.2-
Bis(4-hydroxyphenyl)propanediol B: Polyoxyethylene (2,3)-22-bis(4-hydroxyphenyl)propane Table 2-2 Composition and characteristics of resin Diol A: Polyoxypropylene (2,3) )-2,
2-bis(4-hydroxyphenyl)propane diol B Nipolyoxyethylene(2,3)-22-
In the bis(4-hydroxyphenyl)propane melt-kneading step, the same operation as in Example 1 was carried out except that the melt-kneading temperature was 15° C. higher than the Tc+ of the resin, and it corresponded to resins R, -2 to R-4. Toner T-2～
T-4 was obtained. The results of the fixing test and blocking resistance test for T-2 to T-4 are shown in Table 2-3.

Table 2-3 Characteristics of Toner From Table 2-3, it can be seen that toners T-2 to T-4 have a wide fixing area and good blocking resistance.

Comparative Examples 1 to 3 Resins R-5 to R-7 were obtained by carrying out the same operation as in Example 1, except that the monomer charge composition was changed as shown in Table 3-1.

Table 3 shows the analysis results and resin physical properties of resins R-5 to R-7.
-2.

Table 3-1 Monomer charge composition (mol parts) Diol A; polyoxypropylene (2,3) 2.2-
Bis(4-hydroxyphenyl)propanediol B: Polyoxyethylene (2,3)-22-bis(4-hydroxyphenyl)propane Table 3-2 Resin composition and properties Diol A: Polyoxypropylene (2,3) -2,2
-Bis(4-hydroxyphenyl)propanediol B: polyoxyethylene (2,3)-2゜2-
Bis(4-hydroxyphenyl)propane Table 3-3 R-5
, R-6, R-7 toner T-5T-6, T-
I got a 7. However, R-5 was melt-kneaded at 150°C.

The results of the fixing test and blocking resistance test for T-5 to T-7 are shown in Table 3-3.

As shown in Table 3-3, since T-5 does not have Tc+, high-temperature offset is good, but fixability is degraded. When the molecular weight was lowered to improve fixing properties, high-temperature offset disappeared.

Furthermore, since T-6 had a high T1, it required a temperature of 230° C. or higher to achieve a fixing rate of over 90%. Since T-7 has a low Tg,
Blocking resistance decreased. Therefore, resins R-5 to R
-7 is considered not suitable as a resin for toner.

〔Effect of the invention〕

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

Claims (1)

[Claims] 1. Units derived from terephthalic acid and/or its lower alkyl esters, units derived from linear alkylene glycols having 2 to 4 carbon atoms, and units derived from trivalent or higher polyhydric carboxylic acids and/or polyhydric alcohols. and the total amount of these units is 60 mol% or more based on the total monomer amount, the polyester resin comprising Tc
+, a softening temperature Ti of 110° C. or less, a glass transition temperature Tg of 40° C. to 75° C., and a crosslinked structure.