JPH04202345A - Binder for toner - Google Patents

Abstract

PURPOSE:To provide a developing agent toner binder for developing electrostatic images formed by an electrophotographing method, electrostatic photographing method, electrostatic recording method, etc., by adding an oxazoline group- containing polymer to a polymer containing free carboxyl groups. CONSTITUTION:The objective binder comprises (A) 100 pts.wt. of a polymer containing free carboxyl groups in an acid equivalent of 0.01-5m equivalent/g and (B) 1-200 pts.wt., preferably 10-200 pts.wt., of an oxazoline group-containing polymer. The polymer A is preferably a styrenic polymer having a glass transition temperature of 30-80 deg.C, and the polymer B is also preferably a styrenic polymer having a glass transition temperature of 30-110 deg.C and a number-average mol.wt. of 3000-100000.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to electrophotography, electrostatic photography, and electrostatic recording [Prior art and problems] Conventional electrophotographic methods include US Pat. No. 2,297,691; No. 2,357,809, etc., an electrical latent is created by uniformly charging a photoconductive insulating layer, then exposing the layer to light, and dissipating the charge on the exposed portions. An image is formed, and the latent image is made visible by attaching colored, electrically charged fine powder called toner (development process), and the resulting visible image is transferred to a transfer material such as transfer paper. (transfer process), heating,
It consists of permanently fixing (fixing step) using pressure or other suitable fixing methods. As described above, the toner must have the functions required not only in the development process but also in each of the transfer and fixing processes.

Generally, toner is subjected to mechanical frictional force due to shearing force and impact force during mechanical operation in a developing device, and deteriorates during copying of tens to tens of thousands of sheets. To prevent such toner deterioration, it is best to use strong resins with large molecular weights that can withstand mechanical friction forces, but these resins generally have a high softening point and are suitable for non-contact fixing methods such as oven fixing and infrared fixing. With radiant fixing, the thermal efficiency is poor, so fixing is not sufficient.Also, since the contact fixing method has good thermal efficiency, even in the widely used heat roller constant fixing method, it is necessary to use the heat roller to achieve sufficient fixing. It is necessary to raise the temperature, which not only causes problems such as deterioration of the fixing device, curling of paper, and increased energy consumption. In this case, the production efficiency is significantly reduced.For this reason, adhesive resins having a very high degree of polymerization and even a high softening point cannot be used.

On the other hand, the heat roller constant fixing method has extremely good thermal efficiency because the heating roller surface and the toner image surface of the sheet to be fixed are in pressure contact. When the surfaces come into contact, the toner adheres to the surface of the heating roller and is transferred to the subsequent transfer paper, which tends to cause the so-called offset phenomenon.To prevent this phenomenon, the surface of the heating roller is coated with a releasable material such as fluorine-based resin. In addition to this, we also apply a release agent such as silicone oil to the back of the heating roller.

However, the method of applying silicone oil etc. is 1.
The fixing device becomes larger, which not only increases cost but also makes it more complicated, which can easily cause trouble (which is not desirable).

Also, Japanese Patent Publication No. 55-6895, Japanese Patent Publication No. 56-98202
As described in the above publication, there is a method of improving the offset phenomenon by widening the molecular weight distribution width of the adhesive resin, but generally the degree of polymerization of the resin increases and the fixing temperature used must also be set high.

As a further improved method, the offset phenomenon is improved by making the resin asymmetrical and crosslinking, as described in Japanese Patent Publication No. 57-493, Japanese Patent Application Publication No. 50-448.36, and Japanese Patent Application Publication No. 57-37353. There is a way to do this, but the fixation point has not been improved.

Generally, the minimum fusing temperature is between the low temperature offset and the high temperature offset, so the usable temperature range is between the minimum fusing temperature and the high temperature offset.The minimum fusing temperature should be lowered as much as possible, and the temperature at which high temperature offset occurs should be raised as much as possible. This makes it possible to lower the usable fixing temperature and widen the usable temperature range, resulting in energy savings, high-speed fixing, and prevention of paper curl. In addition, since double-sided copying can be performed without trouble, there are many advantages such as making the copying machine more intelligent, controlling the temperature of the fixing device more accurately, and relaxing the tolerance range.

Therefore, resins and toners with good fixing properties and offset resistance are always desired.

When using styrene-based adhesive resin to meet such requirements, Japanese Patent Application Laid-open Nos. 49-65232 and 1977-
As described in No. 28840 and JP-A No. 50-81342, methods of adding paraffin wax, low molecular weight polyolefin, etc. as anti-offset agents are known; It has also been confirmed that the agent deteriorates quickly.

Polyester resin inherently has good fixing properties, and can be sufficiently fixed even in a non-contact fixing method, as described in U.S. Pat. It was difficult to use.

As described in JP-A-50-44836, JP-A-57-37353, and JP-A-57-109875, polyester resins with improved offset resistance using polyhydric carboxylic acids have sufficient resistance for use. Those that do not have offset properties, or those that do have offset properties, often sacrifice the low-temperature fixing properties that polyester resins inherently have, which poses a problem. On the other hand, toners using polyester resins may have poor fluidity compared to styrene-based toners, and may become agglomerated, resulting in poor toner transportability within the developing device, reduced developability, and uneven image formation. A visible image with poor image quality, such as background smudge, was sometimes formed.

In order to improve the fluidity of toner, a large amount of fluidity improver such as hydrophobic silica fine powder is added, and as a result, the surface of the electrostatic image support is cleaned using a urethane rubber blade or the like. If the blade is used, toner particles may become trapped between the blade and the electrostatic image support, resulting in poor cleaning and smearing of the visible image.
In addition, when using an image forming apparatus that has a recycling system in which toner that has been developed but has not been transferred is returned to the developing device for reuse, fine particles of hydrophobic silica are embedded in the surface of the toner particles. The fluidity of the liquid was reduced and a visible image of poor quality could be formed.

In addition, in order to solve these problems,
Although it has been disclosed that a cross-linking agent based on oxazoline, which is a low-molecular-weight compound as shown in No. 8, can be used to solve the problem, it is still not sufficient.

[Problems to be Solved by the Invention] As described above, conventional toner binders have some drawbacks, and it is necessary to consider not only the balance of fixing offset but also the balance with charging characteristics as mentioned above. There is a need to.

An object of the present invention is to provide a binder for toner that overcomes the above-mentioned drawbacks.

Another object of the present invention is to provide a toner binder that is stable even under toner fusing conditions in high speed copying machines.

Yet another object of the present invention is to provide a toner binder that can be fused at relatively high speeds with relatively little thermal energy.

Still another object of the present invention is to apply to a heat roll,
To provide a toner binder that does not fuse to a heat roll or stain paper or lubricator.

Yet another object of the present invention is to provide a toner binder that is impact resistant.

Yet another object of the present invention is to provide a triboelectrically stable toner binder.

Still another object of the present invention is to provide a toner binder that does not easily contaminate equipment.

Still another object of the present invention is to provide a toner binder that is less likely to form lumps.

[Means for solving the problems] That is, the present invention provides (A) free carboxyl groups in an amount of 0.01 to 5 milliequivalents/g.
(B) 1 to 20 parts by weight of a polymer containing an oxazoline group to 100 parts by weight of the polymer containing an acid equivalent of
This relates to a toner binder characterized in that it contains 0 parts by weight.

The polymer (A) containing free carboxyl groups used in the present invention is a polymer having free carboxyl groups at an acid equivalent ratio of 0.01 to 5 meq/g. Such polymers (A) include free carboxyl group-containing polymerizable monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, and fumaric acid alone or in mixtures thereof, and these monomers. A copolymer obtained by polymerizing and a copolymerizable unsaturated monomer according to a conventionally known method;
Polymers containing free carboxyl groups by hydrolyzing homopolymers or copolymers obtained by polymerizing unsaturated monomers that generate carboxyl groups by hydrolysis; Known polymerization initiators contained; polymers containing free carboxyl groups introduced using chain transfer agents, polymerization terminators, etc. can be mentioned.

When the amount of free carboxyl groups contained in the polymer (A) is less than 0.01 meq/g, an offset phenomenon is observed. Moreover, if it exceeds 5 milliequivalents/g, environmental characteristics will be affected.

Examples of unsaturated monomers copolymerizable with the free carboxyl group-containing polymerizable monomers include methyl esters, ethyl esters, propyl esters, butyl esters of unsaturated basic acids such as acrylic acid and methacrylic acid; Esters such as 2-ethylhexyl ester, hydroxyethyl ester, and hydroxypropyl ester; acrylamide, methacrylamide, their N-substituted acrylamides and methacrylamide; methyl alcohol and ethyl of unsaturated dibasic acids such as maleic acid and itaconic acid; Mono- and diesters with lower alkyl alcohols such as alcohol and propyl alcohol; one or more unsaturated monomers such as acrylonitrile, methacrylonitrile, vinyl acetate, vinyl chloride, vinylidene chloride, styrene, ethylene, butadiene, etc. can be used.

Other examples of the polymer (A) include condensation of polycarboxylic acids such as phthalic anhydride, maleic anhydride, terephthalic acid, trimellitic acid, and pyromellitic acid with polyhydric alcohols such as ethylene glycol and propylene glycol. Examples include polyester polycarboxylic acids obtained by a polymerization reaction; alkyd polycarboxylic acids obtained by a polycondensation reaction of a polyhydric alcohol such as glycerin with a polycarboxylic acid or a fatty acid.

From the viewpoint of thermal properties of the developer, the polymer (A) is preferably a styrene resin having a glass transition temperature of 30 to 80°C. If the glass transition temperature is less than 30° C., the storage stability of the toner will be poor, and if it is higher than 80° C., the fixing temperature will become high, which is not practical.

The oxazoline group-containing polymer (B) used in the present invention has the general formula (I) (wherein R, R2, R, R4 are each independently hydrogen, halogen, alkyl, aralkyl, phenyl or substituted phenyl (R5 is an acyclic organic group having an addition-polymerizable unsaturated bond.) and optionally at least one other monomer (b) are polymerized. It is preferable that the polymer be obtained by

Addition-polymerizable oxazoline (a
) is represented by the above-mentioned -Funazo (I), and specific examples include 2-vinyl-2-oxacillin, 2-vinyl-4-methyl-2-oxacillin, 2-vinyl-5-
Methyl-2-oxazoline, 2-impropenyl-2-
Oxazoline, 2-isopropenyl-4-methyl-2-
Oxazoline, 2-isopropenyl-5-ethyl-2-
Examples include oxazoline, and one or a mixture of two or more of these can be used. Among them,
2-impropenyl-2-oxazoline is industrially easily available (preferably).

The other monomer (b) used in the present invention is not limited as long as it is a monomer copolymerizable with the addition-polymerizable oxazoline (a), such as methyl (meth)acrylate, butyl (meth)acrylate, ( meth)acrylic acid-
(meth)acrylic ester acids such as 2-ethylhexyl; unsaturated nitriles such as (meth)acrylonitrile; unsaturated amides such as (meth)acrylamide and N-methylol (meth)acrylamide; vinyl acetate, vinyl propionate, etc. vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; a-olefins such as ethylene and propylene; halogen-containing a1 β-unsaturated motumers such as vinyl chloride, vinylidene chloride, and vinyl fluoride; styrene, α- a of methylstyrene, etc.

Examples include β-unsaturated aromatic motumar granules, and one or a mixture of two or more of these can be used.

Among these, particularly from the viewpoint of thermal properties, the polymer (B) is preferably a styrene resin having a glass transition temperature of 30-110'C. If the glass transition temperature is less than 30°C, the storage stability of the toner will be poor, and if it is higher than 110°C, the fixing temperature will be high (both of which are not practical).

In order to obtain a polymer using the addition-polymerizable oxazoline (a) and, if necessary, at least one other monomer (b), polymerization may be performed by a conventionally known polymerization method.

For example, in the emulsion polymerization method, various methods can be employed, such as a method in which a polymerization catalyst, water, a surfactant, and a monomer are mixed all at once and polymerized, a monomer dropping method, a multistage polymerization method, and a pre-emulsion method. Conventionally known polymerization catalysts can be used, such as hydrogen peroxide, potassium persulfate, 2,
Common radical polymerization initiators such as 2'-azobis(2-amidinopropane) dibasic acid salts can be used. Also,
Examples of the surfactant include conventionally known anionic, nonionic, cationic, amphoteric surfactants and reactive surfactants. The polymerization temperature is usually O~1
00°C, preferably 50-80°C, polymerization time usually 1-80°C
It is 10 hours.

In addition, examples of solvents that can be used when employing the solution polymerization method include toluene, hexane, methyl ethyl ketone, ethyl cellosolve, edyl acetate, and isopropyl alcohol, and one or more of these solvents can be used.
A mixture of the two can be used. Examples of the polymerization initiator include common radical polymerization initiators such as azobisisobutyronitrile and benzoyl peroxide. The reaction temperature is room temperature to 200°C, preferably 40 to 200°C.
The temperature range is 120°C.

The polymer (B) is 1 part by weight per 100 parts by weight of the polymer (A).
It is preferable to blend 200 parts by weight, more preferably 10 to 200 parts by weight.
It is more preferable to mix 200 parts by weight. If it is less than 1 part by weight, heat offset will occur, and if it exceeds 200 parts by weight, the composition will have a high flow initiation temperature and will be impractical.

The polymer (B) has a number average molecular weight of 3,000 to 1
It is preferably 00,000, and more preferably from 10,000 to ]00,000. The number average molecular weight of the polymer (B) is 3.0
If it is less than 00, it contains oligomers and storage stability becomes difficult.

In addition, if the number average molecular weight of the polymer (B) exceeds 100,000, it will be difficult to diffuse into the polymer chains to be kneaded and the reaction will occur. The melt viscosity of the toner increases, which adversely affects kneading and fixing properties during manufacturing.

In the present invention, the addition polymerizable oxazoline (a) in which the polymer (B) has one oxazoline group and at least one radically polymerizable unsaturated group in one molecule is 0.1 to 1
It is preferable that it is obtained by polymerizing 0% by weight and 99.9 to 90% by weight of other monomer (b).

In the present invention, if the amount of addition polymerizable oxazoline (a) used is less than 0.1% by weight, problems such as heat offset and deterioration of charging characteristics due to residual acid groups will occur. If it exceeds 10% by weight, problems will occur in charging characteristics such as environmental characteristics.

The most common method for obtaining the electrophotographic developing composition of the present invention is to mix the above-mentioned polymer (A) and polymer (B) by about 0.5 to 50%
millimeter particle size and carbon black, and if necessary, styrene resin, styrene-acrylic resin, styrene-butadiene resin, epoxy resin, maleated rosin, petroleum resin, coloring agent, and a small amount of electrical charge. After adding the conditioning agent and mixing with Henschel mixer etc., kneader
Examples of methods include melt-kneading at a temperature of 100 to 150[deg.] C. and crushing and classifying the resulting mass to obtain particles with a particle size of 5 to 20 [mu]m.

The effect of the present invention is that the resins undergo heat treatment while maintaining an appropriate shearing force during melt mixing, so that the reaction between the acid groups in the polymer (A) and the oxazoline groups in the polymer (B) is prevented. It is mild and provides good kneading properties. Furthermore, the dispersibility of colorants such as (B) and charge control agents is improved, and charging stability is also improved.

[Example] Next, the present invention will be specifically explained with reference to Examples.

Note that hereinafter "parts" represent parts by weight unless otherwise specified.

Production Example I A flask equipped with a stirrer, an inert gas introduction tube, a reflux condenser, and a thermometer was charged with 400 parts of deionized water in which 0.2 part of polyvinyl alcohol was dissolved. There, 160 parts of styrene and 40 parts of n-butyl acrylate were prepared in advance.
A mixture of 16 parts of benzoyl peroxide dissolved in a polymerizable monomer consisting of 5 parts and 1.6 parts of methacrylic acid was charged and stirred at high speed to form a uniform suspension.

Next, while blowing nitrogen gas, the mixture was heated to 80'C, stirred continuously at this temperature for 5 hours to carry out a polymerization reaction, and then cooled to obtain a polymer suspension. This polymer suspension was filtered, washed, and then dried to obtain a styrene resin (1) having carboxyl groups.゛The acid value of the stichine resin (1) is
It was 0.2 milliequivalent/g.

Production Example 2 AIBNB was dissolved in a polymerizable monomer consisting of 200 parts of toluene, 170 parts of styrene, 30 parts of 2EHA, and 1 part of acrylic acid in the same flask as in Production Example 1, and then heated to 70°C while blowing nitrogen gas. And at this temperature 10
The mixture was stirred continuously for a period of time to carry out a polymerization reaction, and then cooled to obtain a polymerization solution. 7,000 parts of methanol was added to this polymerization solution for reprecipitation, followed by drying to obtain a styrene resin (2) having carboxyl groups.

The acid value of the styrene resin (2) is 0.12 milliequivalent/
It was g.

Production Example 3 100 parts of toluene and 100 parts of methyl isobutyl ketone were charged into a flask equipped with a dropping funnel, a stirrer, an inert gas introduction tube, a reflux condenser, and a thermometer, and heated to 80° C. while blowing nitrogen gas. A mixture prepared in advance by dissolving 2 parts of benzoyl peroxide in a polymerizable monomer consisting of 97 parts of styrene and 3 parts of 2-isopropenyl-2-oxazoline was added dropwise from the dropping funnel over a period of 2 hours. The mixture was stirred for an additional 5 hours to carry out a polymerization reaction, and then cooled to obtain a polymer solution. 7,000 parts of methanol was added to this polymer solution, reprecipitation was performed, and then dried to obtain a styrenic resin (3) having an oxazoline group as a reactive group.

The number average molecular weight of the styrene resin (3) is Mn=30.
It was 000.

Production Example 4 A flask equipped with a stirrer, an inert gas introduction tube, a reflux condenser, and a thermometer was charged with 400 parts of deionized water in which 0.2 part of polyvinyl alcohol was dissolved. 196 parts of styrene and 2-impropenyl-2 prepared in advance therein.
- A mixture of 8 parts of benzoyl peroxide dissolved in a polymerizable monomer consisting of 4 parts of oxacillin was charged and stirred at high speed to form a uniform suspension. Next, the mixture was heated to 80° C. while blowing nitrogen gas, and stirred at this temperature for 5 hours to carry out a polymerization reaction, and then cooled to obtain a polymer suspension. This polymer suspension was filtered, washed, and dried to obtain a styrenic resin (4) having an oxazoline group as a reactive group.

The molecular weight of the resin (4) was determined by GPC measurement to be Mn=20.
It was 000.

Comparative Production Example 1 Comparative resin (1) was obtained by carrying out the same operation as in Production Example 1 except that 1.6 parts of methacrylic acid was not used.

Comparative Production Example 2 The same operation as Production Example 3 was carried out except that 2-isopropenyl-2-oxacillin was not used, and comparative resin (2
) was obtained.

Example 1 Styrenic resin obtained in Production Example 1 [50 parts, Production Example 3
38 parts of the styrenic resin (3) obtained in
Orient Chemical ■ Bontron N-01) 1 part, screw:
]-Jl, 2 parts of 550p and 9 parts of carbon black (MA600 manufactured by Mitsubishi Kasei ■) are premixed,
Then, the mixture was melt-mixed in a two-shaft mixer adjusted to 140"C for a residence time of about 1 minute. After cooling the resulting mixture,
It was ground with a hemmer mill and further finely ground with a jet mill equipped with a classifier. The obtained toner had an average particle diameter of 7.
It was 12 μm. 95 parts of iron powder was added to 5 parts of this toner and stirred using a ball mill to obtain developer (1).

The amount of charge of the developer (1) was +10LLc/g.

Next, the developer (1) was transferred to an electrostatic copying machine (5F manufactured by Sharp ■).
A copying test was conducted with the fixing roll temperature changed from 120°C to 230°C. 140
Good fixation and clear images can be obtained from 230°C.
However, no offset phenomenon was observed at all.

A similar test was conducted with the speed of the fixing roll reduced to 10 mm/sec, but no offset phenomenon was observed. Furthermore, continuous copying was performed using an actual machine, and stable images were obtained even after 100,000 copies. Further, there was no occurrence of copy paper getting caught up or staining on the back side.

Example 2 In Example 1, the styrenic resin (1) obtained in Production Example 1 and the styrenic resin (3) obtained in Production Example 3 were replaced with the styrenic resin (3) obtained in Production Example 2, respectively. 2)
The same operation as in Example 1 was carried out except that the styrene resin (4) obtained in Production Example 4 was used to prepare developer (2).
I got it.

The amount of charge of the developer (2) was +11 μc/g. Next, the same test as in Example 1 was conducted using the developer (2). As a result, good fixing was achieved even at 140'C, and clear images were obtained, and no offset phenomenon was observed even at 230'C.

Further, even when the speed of the fixing roll was reduced to 10mm 1 sec, no offset phenomenon was observed. Furthermore, continuous copying was performed using an actual machine, and even after 100,000 copies, stable images were obtained, and no copy paper was caught in or the back surface was stained.

Comparative Example 1 In Example 1, the comparative polymer (1) obtained in Comparative Production Example 1 was used instead of the styrene resin (1), and the comparative polymer (1) obtained in Comparative Production Example 2 was used instead of the styrene resin (3). A comparative developer (1) was obtained by performing the same operation as above except that the comparative polymer (2) was used.

When a test was conducted in exactly the same manner as in Example 1, the temperature was 160°C.
Offset occurred, and the temperature range where fixing and non-offset are compatible has become shorter.

Claims (1)

[Claims] 1. 1 to 200 parts by weight of (B) a polymer containing oxazoline groups to 100 parts by weight of (A) a polymer containing free carboxyl groups at an acid equivalent of 0.01 to 5 meq/g. A toner binder containing parts by weight. 2. The toner binder according to claim 1, wherein the polymer (A) is a styrene resin having a glass transition temperature of 30 to 80°C. 3. The toner binder according to claim 1, wherein the polymer (B) is a styrene resin having a glass transition temperature of 30 to 110°C. 4. The toner binder according to claim 3, wherein the polymer (B) has a number average molecular weight of 3,000 to 100,000. 5. 0.1 to 10% by weight of an addition-polymerizable oxazoline (a) in which the polymer (B) has one oxazoline group and at least one radically polymerizable unsaturated group in one molecule, other monomers ( b)99. 4. The toner binder according to claim 3, which is obtained by polymerizing 9 to 90% by weight.