GB2101757A - Toner - Google Patents

Abstract

A toner exhibiting excellent effects such as off-set resistance, developing characteristics, etc. can be obtained by incorporating a polymer for binder obtained by crosslinking a polymer having carboxyl groups with a value of weight average molecular weight/number average molecular weight (Mw/Mn) of more than 4.0 in a toner.

Description

SPECIFICATION Toner This invention relates to a toner for developing electrostatic images in electrophotography, electrostatic recording, electrostatic printing, etc., and particularly, to a toner suitable for hot roller fixing and a method for production thereof.

In the prior art, there have been known a number of electrophotographic methods as disclosed in U.S.P. 2,297,691, U.S.P.

3,666,363 and U.S.P. 4,071,361. Generally speaking, electrostatic latent images are formed by various means on a photosensitive material by utilization of a photoconductive material, then said latent images are developed by use of a toner and transferred, if necessary, to a receiving material such as paper, followed by fixing with heat, pressure or solvent vapor to give a copy.

For the step of fixing a toner image to a sheet such as paper which is the final step in the procedure as described above, there have been developed various methods and devices.

The most general method at present is the pressure heating system with a hot roller.

According to the pressure heating system, fixing is effected by permitting a toner image surface on a sheet to be fixed while contacting under pressurization with the surface of a hot roller of which surface is formed of a material having a releasing characteristic relative to the toner. This method, since the hot roller is contacted under pressurization with the toner image on a sheet to be fixed, this method is very good in thermal efficiency in fusion adhesion of the toner image onto the sheet to be fixed.However, according to the above method, as the surface of a roller is contacted under pressurization with a toner image under molten state, a part of the image may be adhered and transferred onto the roller surface, which is in turn retransferred onto the subsequent sheet to be fixed, thereby causing so called off-set phenomenon to result in contamination of the sheet to be fixed. It has been deemed as one of the essential conditions in the hot roller fixing system to avoid adhesion of a toner onto the heat fixing roller surface.

As generally practiced in the prior art, for the purpose of avoiding adhesion of a toner onto the fixing roller surface, for example, the roller surface is formed of a material excellent in releasing characteristic relative to the toner such as silicone rubber or a fluorine type resin, and further the roller surface is coated with a thin film of a liquid with good releasing characteristic for prevention of off-set and fatigue on the roller surface. However, while it is very effective in prevention of off-set of the toner, this method gives an unpleasant odor to user by evaporation of the liquid for prevention of off-set by heating and a device for supplying the liquid for prevention of off-set is required, whereby there remains the problem of rendering the fixing device more complicated, or others.For this reason, an approach to prevent off-set by way of supplying a liquid for prevention of off-set is not preferred, but rather under the present situation development of a toner with a wide range of fixing temperatures having high off-set resistance is desired and needed.

As described in U.S.P. 3,941,898, such an off-set phenomemon is prone to occur where a low molecular weight resin is employed.

Therefore, as described in said Patent, there is presented a method to prevent an off-set phenomenon by use of a crosslinked resin.

According to the investigations made by the present inventors, it has been found that a toner prepared only by use of a crosslinked resin is not necessarily good. In particular, when the crosslinking degree is made higher, pigments become poorly dispersed in a binder resin to be exposed on the toner surface, thereby lowering developing characteristics of the toner and further increasing the fixing temperature.

In case of a magnetic toner, there are problems such as increase of fixing temperature to worsen off-set resistance, etc.

As a matter of course, a toner is required to be excellent in anti-blocking characteristic, developing characteristics, transfer characteristic and cleaning characteristic as well as fixing characteristics, but the toner of prior art has one or more defects as mentioned below. That is, most of toners which readily melt by heating at a relatively low temperature are liable to be caked or agglomerated during storage or in a copying machine. Most of toners will become bad in frictional electrical characteristics and free flowing characteristics by humidity changes of environment.Also, in most of toners, through collision between the toner particles and carrier particles by repeated development after continuous use as well as mutual dererioration of toner, carrier particles and the photosensitive plate by contact of the photosensitive plate with them, the image obtained will be changed in density or the background density is increased, to lower the quality of copies. Further, in most of toners, when the density of the copied image is attempted to be increased by increase of the quantity of toner adhered to the photosensitive plate having a latent image, there may be caused so called fogging phenomemon.

Thus, it has been earnestly desired to have a toner excellent in various toner characteristics and suitable for the hot roller fixing method.

The present invention is aimed at enabling the production of a toner having good physical and chemical characteristics and which avoids the defects of the toners of prior art as described above.

The invention is also aimed at enabling the production of a toner for hot roller fixing having good fixing characteristics as well as good off-set resistance.

The invention is also aimed at enabling the production of a toner for hot roller fixing which is good in charging characteristic, exhibiting constantly stable charging characteristic during usage, and capable of providing a clear image without fogging.

The invention is also aimed at enabling the production of a toner for hot roller fixing which is excellent in free flowing property, without giving rise to agglomeration and also excellent impact strength.

The invention is also aimed at enabling the producion of a toner for hot roller fixing which gives little adhered material onto a toner holding member or the surface of a photosensitive material.

The invention is also aimed at enabling the production of a toner capable of hot roller fixing which can exhibit good and uniform magnetic characteristic when employed as a magnetic developer.

In one aspect, the specific feature of the present invention resides in a toner comprising a polymer for binder obtained by crosslinking a polymer having carboxyl groups with a value of weight average molecular weight/number average molecular weight (Mw/Mn) of more than 4.0 and a method for production thereof.

As the crosslinking agent, there may be employed any compound which is not specifically limited, so long as it can act as a crosslinking agent on carboxyl groups, but a decomposable metal compound is primarily used. As other crosslinking agents, there may also be used amines selected from polyoxyethylene alkylamines and alkyl propylenediamines, etc.

Further, in another aspect of the present invention, the specific feature resides in a method, which comprises mixing a decomposable metal compound with a polymer having no carboxyl group, adding the resultant mixture containing the above decomposable metal compound to a polymer having carboxyl groups, and melt kneading the blend thereby to allow the polymer having carboxyl groups to react with the decomposable metal compound in the production step.

The toner for hot roller fixing according to the present invention is excellent in physical and chemical characteristics, and by use of the present toner, good hot roller fixing may be effected without generation of off-set even when no liquid for prevention of off-set is coated on the surface of a fixing roller. Therefore, the fixing device can be made simplified and light weight, and further stable and very excellent developing characteristics possessed by the toner enable marked improvement in stability and reliability of the copying machine.

That is, in the toner according to the present invention, a binder resin is brought to a state crosslinked by the reaction with, for example, an amine or a decomposable metal compound, whereby the mechanical properties at normal temperature can be improved tn be excellent in impact strength as well as toughness and further charging characteristics can be improved, resulting in improvement in the developing characteritics as a toner. Further, by fixing of the toner by a hot roller fixer, off-set resistance at higher temperatures can markedly be improved. Whereas, the present toner exhibits a fixing temperature which is substantially as low as the toner prepared from the corresponding unreacted polymer.

Such a fixing characteristic as mentioned above is particularly excellent when the toner has a melt index in the range of from 0.01 to 10 9/10 min. (particularly preferably 0.1 to 6 g/10 min.) (test conditions: temperature = 125"C, load = 10 kg, filling quantity = 5-8 g). Measurement of melt index was herein conducted according to the manual cutting method by means of the device as described in JIS K 7210, which is the flow test method of thermoplastic materials accord- ing to the Japanese Industrial Standard.

According to the method for production of the toner of the present invention, the crosslinking reaction between a polymer having carboxyl groups and an amine or a decomposable metal compound proceeds gradualiy and therefore the crosslinking reaction during the production step can easily be controlled to give readily a toner having a desired melt viscosity.

Further, according to one of the production methods of the present invention, toner materials such as dye or pigment and charging controlling agent are dispersed into the polymer at the stage when the reaction between the polymer having carboxyl groups and an amine or a decomposable metal compound has scarcely proceeded, thus affording more uniform dispersion than dispersion of dye or pigment into a crosslinked polymer with high crosslinking degree, and thereafter the polymer for binder is crosslinked to a desired extent by the gradual reaction between the polymer having carboxyl groups and an amine or a decomposable metal compound. Accordingly, in the toner produced based on the method of the present invention, the toner components such as dye or pigment, magnetic powders and charging controlling agents are dispersed uniformly in a toner, resulting in stabilization of electrical characteristics and charging characteristics such as specific resistance as well as marked improvement in developing characteristics of toner.

In the present invention, there is employed a polymer having carboxyl groups with a value of weight average molecular weight/ number average molecular weight (Mw/Mn) of more than 4.0 (particularly preferably more than 10) and preferably a weight average molecular weight (Mw) of 100,000 or more.

By use of such a polymer, a polymer having desired melt viscosity can be prepared easily by a moderate reaction with an amine or a decomposable metal compound as crosslinking agent and therefore a toner having desired fixing characteristics can be produced stably.

Further, a polymer having carboxyl groups may preferably have a melt index value of 0.01 to 10 g/min., particularly preferably 0.1 to. 5 g/min. under the conditions of 125"C, 2 kg of load.

As described in detail below, when a polymer with Mw/Mn < 4, Mw < 100,000 is employed, in order to obtain a toner having desired fixing characteristics by the reaction with an amine or a decomposable metal compound as crosslinking agent, it is necessary to set the quantity of a crosslinking agent and the reaction conditions so that the aforesaid reaction may occur more abundantly, as compared with the case when employing a polymer with Mw/Mn of more than 4.0. Under such conditions, it is very difficult to terminate the reaction timely so as to obtain a toner exhibiting off-set resistance, and therefore it is not possible to produce a toner having desired fixing characteristics with good reproducibility and stability.

On the other hand, when a polymer with Mw/Mn > 4, Mw > 100,000 is employed, the polymer may be lightly reacted with an amine or a decomposable metal compound to effect crosslinking in order to impart off-set resistance to the resultant toner. Hence, the reaction can be carried out under moderate conditions, whereby the reaction can be controlled easily to enable stable production of a toner excellent in fixing characteristics. Further, when a polymer with Mw/Mn > 4, Mw > 100,000 is lightly crosslinked, the molecular weight distribution is much more broadened to enable imparting off-set resistance to the toner while suppressing the minimum fixing temperature at a low level.

As the electrophotographic characteristics to be possessed by a toner, other than the fixing characteristics and mechanical characteristics as described above, there are frictional charging characteristics. For improvement in charging characteristics, it is generally practiced to add a charging controlling agent to the toner.

Therefore, unless an additive such as a charging controlling agent is uniformly dispersed in a toner, frictional charging characteristics of the toner may remarkably be inhibited, whereby clear images can difficultly be obtained.

Therefore, in preparation of a toner, in order to effect uniform dispersion of additives such as charging controlling agents or colorants in a polymer, it is generally practiced to melt kneading starting materials at a temperature around a softening point at which a polymer exhibits a high melt viscosity state.

When melt kneading is performed at high melt viscosity region, the additives such as charging controlling agent or colorant can be dispersed uniformly through the shearing force by internal frictions of the polymer to give a toner having desired coloration or charging characteristics.

However, when a polymer with Mw/Mn > 4, Mw > 100,000 is melt kneaded at a high melt viscosity region, the internal frictions of the polymer are so great that the shearing force becomes too strong, whereby cleavage of molecular chains may occur to invite lowering of melt viscosity and affect deleteriously off-set resistance.For example, when the aforesaid polymer having about 5 g/10 min. of melt index is melt kneaded on a roll mill at a temperature (about 1 20 C) slightly lower than the softening point (agent 1 35 C) of the polymer as measured by the ball and ring method, the melt index is excessively increased to a value approximately twice as much as the original value, with the result that the temperature range where off-set phenomenon occurs becomes very narrower than the case when the aforesaid polymer is melt kneaded at a temperature (1 80 C) considerably higher than the softening point of the polymer.

The present inventors have found that the problems of off-set resistance and dispersibility of additives can be solved by applying a slight degree of crosslinking to the polymer upon melt kneading, thereby cancelling lowering of viscosity through cleavage of molecular chains.

According to the method as described above, melt kneading can be carried out at a high viscosity region near the softening point of the polymer, and therefore additives can be dispersed very uniformly to give toners which are stabilized in charging characteristics and further broad in non-off-set temperature range.

The polymer with a value of Mw/Mn greater than 4.0 and preferably with a Mw greater than 100.000 can be synthesized by use of conventional polymerization techniques such as solution polymerization, suspension polymerization, emulsion polymerization, mass polymerization, etc. As the method for controlling Mw/Mn, there may be mentioned the method in which several kinds of resins with different molecular weights are mixed under dissolved or molten state; the method in which preparation is performed by changing the reaction temperature in the course of the polymerization reaction; the method in which preparation is performed by incorporating initiators or chain transfer agents; and the method in which crosslinking is applied to some extent during formation of a polymer from a monomer to increase Mw/Mn and Mw.Among these preparation methods, the method in which Mw/Mn is controlled by suppressing the degree of crosslinking within a low range is the most suitable method for the present invention, and it can be accomplished by, for example, adding a minute amount (preferably 0.01 to 10% by weight) of a polyfunctional monomer to the polymerization reaction system.

On the other hand, as a process for synthesis of the above polymer, the solution polymerization technique is suitable. In the emulsion polymerization technique or the suspension polymerization technique, monomers are emulsified or dispersed by using additives such as surfactants of dispersion stabilizers in the continuous phase of water before polymerization, and the resultant polymer is recovered by addition of salts. Thus, the resultant polymer contains hydrophilic additives as mentioned above. When such hydrophilic additives are present in a toner, the toner will absorb moisture under humid conditions to give deleterious effects to electrical properties of the toner such as reduction in specific resistance. Further, since the polymer to be used in the present invention has hydrophilic carboxyl groups, it is difficult to obtain a stable reaction.Also in case of mass polymerization technique, such a problem as gel effect may be caused at high polymerization degree, and the polymerization reaction can very difficultly be controlled when obtaining a polymer with a great value of Mw/Mn.

On the other hand, according to the solution polymerization technique, polymerization is generally carried out in a hydrophobic organic solvent and therefore no hydrophilic additive is required to be used. Further, due to the presence of a solvent, the polymerization reaction can be controlled with relative ease. However, in solution polymerization, when the crosslinking degree is made greater, there is the problem of formation of insoluble gels in a solvent to made control of the polymerization reaction or recovery of the polymer difficult.Accordingly, by synthesizing a polymer by solution polymerization having a crosslinking degree within the range ensuing no such problem as mentioned above, and further reacting the polymer having slight degree of crosslinking prepared by solution polymerization with, for example, an amine or a decomposable metal compound during the production step of a toner thereby to increase the crosslinking degree to the extent where a melt viscosity adapted for the fixing characteristics of the toner is obtained, there can be used the polymer having excellent characteristics as described above prepared from the solution polymerization technique more simply for a toner for heat roller fixing.

In the present invention, the value of Mw/Mn is calculated from the value measured by gel permeation chromatography. The measurement was performed under the conditions of a temperature of 25"C, by flowing tetrahydrofuran as solvent at a flow rate of 1 ml/min. and injecting 0.5 ml of a sample solution in tetrahydrofuran with a sample concentration of 8 mg/ml. As the column, for the purpose of measuring accurately the molecular weight region of 103 to 2 X 1 OF, It is preferred to combine plural number of commercially available polystyrene gel columns.

For example, there may preferably be employed a combination of ll-Styrage! 500, 103, 1 04, 105 produced by Waters Co. or a combination of Shodex A-802, 803. 804. 805 produced by Showa Denko Co. In measuring the molecular weight of a sample, the molecular weight distribution was calculated from the relation between the logarithmic values of the calibration curve prepared from several kinds of mono-dispersed polystyrene standard samples and the count numbers.As the standard polystyrene samples for preparation of the calibration curve, there may suitably be employed those with molecular weight of 6 102, 2.1 X 103, 4 X 103, 1.75 X 104, 5.1 X 104, 1.1 X 105, 3.9 X 105, 8.6 X ,C)5, 2 X 106, 4.48 x 106 produced by Pressure Chemical Co. or Toyo Soda Manufacturing Co., Ltd., and at least about 10 kinds of standard polystyrene samples should be used.

As the detector, there is employed RI (refraction index) detector.

As monomers containing carboxyl groups constituting the polymers having carboxyl groups, there may be included, for example, acrylic acid and a- or alkyl derivatives thereof such as acrylic acid, methacrylic acid, a-ethylacrylic acid, crotonic acid, and the like, unsaturated dicarboxylic acids and mono-ester derivatives thereof such as fumaric acid, maleic acid, citraconic acid and the like. Such monomers, either as a single species or as a mixture, can be copolymerized with other monomers to prepare desired polymers having carboxyl groups.

As monomers copolymerizable with monomers having carboxyl groups as mentioned above, there may be included, for example, styrene, methyl styrene, p-chlorostyrene, vinyl naphthalene, substituted derivatives of mono-carboxylic acids having a double bond such as methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylte, octyl methacrylate, acrylonitirle, methacrylonitrile, acrylamide, etc., diester derivatives of dicarboxylic acids having a double bond such as dibutyl maleate, dimethyl maleate, etc.; vinyl chloride and vinyl esters such as vinyl acetate, vinyl benzoate, etc.; ethylenic olefins such as ethylene, propylene, butylene, etc.; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone. etc.; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, etc.; aromatic divinyl compounds such as divinyl benzene, divinyl naphthalene, etc.; carboxylates having two double bonds such as ethyleneglycol diacrylate, ethyleneglycol dimethacrylate, 1 3-butanediol dimethacrylate, etc.; divinyl compounds such as divinylaniline, divinylether, divinylsulfide, divinylsulfone, etc.; and divinyl compounds having 3 or more vinyl groups, either as a single species or a mixture.

The proportion of a monomer containing carboxyl group to be contained in a polymer having carboxyl groups may be 0.1 to 30% by weight to give a better result, preferably 0.5 to 20% by weight to give a particularly preferable result.

As decomposable metal compounds to be used in the present invention, there may be employed the following compounds containing metallic ions, including metallic ions with valences of mono-valence or more. Suitable mono-valent metallic ions may include Na+, Li+, Cs+, Ag+, Hg+, Cu+, etc., suitable divalent metallic ions Be2+, Mg2+, Ca2+, Hg2+, Sr2+, Pb2+, Fe2+, Co2+, Ni2+, Zn2+, etc.; and suitable tri-valent metallic ions Al3+, Sc3+, Fe3+, Co3+, Ni3+, Cur3+, Y3+, etc.

Among the above metallic ion compounds, more readily decomposable compounds will give favorable results. This may perhaps due to the fact that a compound susceptible of decomposition can more readily be bonded to the carboxyl group in a polymer. Such a decomposable metal compound may preferably have a decomposition temperature in the range of from 1 Q0 C to 600on, particularly preferably from 1 60 C to 400"C. The decomposition temperature of a metal compound can be determined by a thermal analysis such as thermobalance.

In the present invention, a metal compound having a decomposition temperature as mentioned above is allowed to react at a temperature lower than the decomposition temperature. If it is reacted at a temperature of the decomposition temperature or higher, a metal compound is decomposed rapidly and undergoes a vigorous reaction with a carboxyl containing polymer, whereby the reaction can difficultly be controlled and the degree of crosslinking is increased so much that the increase of the fixing temperature may undesirably be liable to be invited. Whereas, when a metal compound is reacted with a polymer at a temperature lower than the decomposition temperature, a part of the metal compound is gradually decomposed, whereby the reaction can proceed moderately to make easier control of the reaction, thus enabling stable production of a toner having desired fixing performance.

Among decomposable metal compounds, organometallic type compounds are excellent in compatibility with or dispersibility in a polymer and therefore crosslinking with metallic ions can proceed more uniformly in a polymer to give more excellent results. Further, among the decomposable organometallic compounds as mentioned above, particularly those containing organic compounds enriched in vaporizing or sublimating tendency as ligands or counter-ions are useful.Among the organic compounds capable of forming coordination or counter-ion with a metallic ion, those having such properties as mentioned above may be exempified by salicylic acid or derivatives thereof such as salicyclic acid, salicylamide, salicylamine, salicylaldehyde, salicylosalicyclic acid, di-t-butylsalicyclic acid, and the like; ss-diketones such as acetylacetone, propionacetone and the like; low molecular carboxylic acid salts such as acetates, propionates and the like.

In the present invention, the temperature at which a polymer is allowed to react with a decomposable metal compound is lower than the decomposition temperature of the metal compound (preferably lower by 50"C or more) and therefore most of the decomposable metal compounds do not undergo reaction with the aforesaid polymer. Hence, it is required to use an excessive amount of a decomposable metal compound to be contained in the toner according to the present invention, which amount depends on the compound employed but is desired to be generally 0.01 to 20 parts by weight based on 100 parts by weight of the polymer, preferably 0.1 to 10 parts by weight to give a particularly excellent result.

As an amine to be used for crosslinking a polymer having carobxyl groups in the present invention, there may be employed a polyoxyethylene alkylamine having the following formula:

wherein a and b represent integers of 2 to 4, which may either identical or different, x and y integers of 1 to 50, which may either ientical or different, and R an alkyl group (inclusive also of branched alkyl and cycloalkyl) having about 8 to 30 carbon atoms.

Among the polyoxyethylene alkylamines having the above formula, a solid substance which is waxy under the conditions of normal pressure and normal temperature is excellent.

Although a low molcular weight liquid alkoxylated amine can crosslink a polymer having carboxyl groups similarly as a solid alkoxylated amine, there may be caused the problem of bleeding of unreacted liquid alkoxylated amine from the toner. For this reason, a solid alkoxylated amine is preferred.

As another amine capable of crosslinking a polymer having carboxyl groups, there may also be employed an alkyl propylenediamine having the following formula:

wherein R is an alkyl (also inclusive of branched alkyl and cycloalkyl) having about 8 to 30 carbon atoms.

Among the diamines having the above formula, a solid substance which is waxy under the conditions of normal pressure and normal temperature is excellent. Although a low molecular weight liquid diamine can crosslink a polymer having carboxyl groups similarly as a solid diamine, there may be caused the problem of bleeding of unreacted liquid diamine from the toner. For this reason, a solid diamine is preferred.

In the present invention, the reaction between a polymer and an amine requires an excessive amount of a reactive amine, since not all of the amine employed undergo the reaction. Such an amount, which may also differ depending on the amine employed, is desired to be generally in the range of 0.01 to 20 parts by weight based on 100 parts by weight of the polymer, preferably 0. 1 to 10 parts by weight to give an excellent result.

In the present invention, the reaction, in which a polymer having carboxyl groups is reacted with a crosslinking agent to form a polymer for binder, may be performed according to the method wherein the metal compound or the amine as described above is reacted with a polymer having carboxyl groups when it is softened and kneaded or the method wherein the metal compound or the amine is added to a solution of the polymer in hot xylene to perform the reaction.

In view of the post-treatment after the reaction, the method according to melt kneading is the most suitable for the present invention A polymer reaction product may previously be prepared by the reaction to form a binder, followed by preparation of a toner together with other toner materials, or alternatively, the above reaction per se may be conducted during heating kneading of toner materials in the course of toner preparation, followed by pulverization to provide a toner.

Further, since the temperature at which a polymer is reacted with a decompossable metal compound is lower than the decomposition temperature of the decomposable metal compound, most of the decomposable metal compound will not react with the aforesaid polymer. Therefore, unless a decomposable metal compound is dispersed uniformly throughout a polymer having carboxyl groups, the reaction between the metal compound and the polymer may proceed ununiformly in a toner binder resin, whereby crosslinking is effected only ununiformly to make it difficult to obtain a toner having desired fixing characteristics.

Accordingly, preparation of a toner having desired fixing characteristics is made easier by mixing thoroughly previously a decomposable metal compound with a non-reactive polymer to be dispersed therein, adding a predetermined amount of fine powders of the dispersion to a reactive polymer and then melt kneading the mixture thereby to allow a decomposable metal compound to react with the polymer uniformly.

When the problem of fixing performance is taken into consideration, while depending on the molecular weight or molecular weight distribution of the polymer for pre-dispersion, too much content of the toner mixed in said polymer may deleteriously affect the mixing characteristics. Thus, it is preferred to disperse 1 to 50 parts by weight of a decomposable metal compound based on 100 parts by weight of a polymer for pre-dispersion (particularly preferably 5 to 30 parts by weight).

Further, it is suitable to add 1 to 50 parts by weight of the above dispersion (more preferably, 1 to 30 parts by weight) to 100 parts by weight of a reactive polymer so that 0.01 to 20 parts by weight of a decomposable metal compound (particularly preferably 0.1 to 10 parts by weight) may be contained based on 100 parts by weight of the reactive polymer.

As a polymer for the aforesaid pre-dispersion, there may be employed polymers containing no carboxyl group. As such polymers, there may be employed, for example, homopolymers of styrene or substituted styrene such as polystyrene, poly-p-chlorostyrene, polyvinyltoluene and the like, copolymers of styrene such as:: styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer, styrene-methacylic acid ester copolymer, styrene-methyl-a-chloromethacrylate co polymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, and the like, polyethylene, polypropylene, polyvinyl chloride, phenolic resins, natural resin modified phenolic resins, acrylic ester resins, methacrylic ester resins, polyvinyl acetate, silicone resins, polyurethanes, fu ran resins, epoxy resins, xylene resins, poly vinyl butyral, terpene resins, coumarone indene resins, petroleum resins, and the like.

As the method for pre-dispersion, there may be employed the method wherein a decompo sable metal compound may be melt kneaded with a non-reactive polymer by means of a roll mill, a kneader or an extruder, followed by pulversization of the resulting mass; the method wherein a non-reactive polymer and a decomposable metal compound are mixed in a solution, followed by drying and pulverization; or the method wherein a mixed solution is subjected to spray drying to obtained fine powders.

Further, in the present invention, as the method for preparation of a toner by reacting a polymer having carboxyl groups with a decomposable metal compound in a pre-dispersion, there may be mentioned the method wherein a polymer having carboxyl groups is reacted with a starting material of toner containing the pre-dispersion during melt kneading by means of a roll mill, a kneader or an extruder, followed by pulversization to give a toner.

On the other hand, in the toner of the present invention, if the gel content in the polymer after the reaction with an amine, a metal compound, etc. exceeds 50%, crosslinking degree is too much, whereby the temperature at which the polymer can be softened is increased markedly to make undersirably the fixing temperature of the toner prepared higher. Therefore, the gel content in the crosslinked polymer is desired to be not more than 50%, particularly 35% or less to give a particularly good result, exhibiting substantially the same fixing temperature as uncrosslinked polymer. The gel content in the present invention is the ratio of the polymer portion made insoluble by crosslinking in a solvent, and may be used as a kind of index representing the crosslinking degree of a highly crosslinked polymer. The gel content is defined as the value measured in the following manner.That is, a certain weight (W, g) of a polymer after the reaction with an amine or a metal compound is weighed, and the soluble portions of the polymer are removed with a solvent by means of a Soxhlet's extractor with the use of a glass filter of G-3, and further the remaining sample not extracted is dried and weighed (W2 g). The gel content is calculated as W2/W, X 100(%). As such a solvent, a non-polar solvent is preferable and extraction is performed herin by use of benzene for 50 hours.

Further, among the polymers for binder crosslinked by the reaction with an amine, a metal compound, etc., those having glass transition temperatures of 50"C or higher are excellent, because they do not cause such problems as agglomeration of a toner within a developing vessel or adhesion onto the surface of a photosensitive material. Particularly, those having glass transition temperatures of 50"C to 80"C are preferred. In order that a crosslinked polymer may have such a glass transition point of 50"C or higher, a polymer having carboxyl groups before crosslinking may preferably have a glass transition point of 40"C or higher. The glass transition temperature of a polymer can be measured by a differential scanning calorimeter.

In the present invention, the principal resin component is a polymer for binder crosslinked according to the method as described above.

It may also contain other polymers or resins mixed therein, if desired, so long as the fixing characteristics are not impaired thereby. Examples of available other resins may include: homopolymers of styrene or substituted styrene such as polystyrene, poly-p-chlorostyrene, polyvinyltoluene and the like, copolymers of styrene such as: styrene-p-ch lorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-methyl- < x-chloromethacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, and the like, polyethylene, polypropylene, polyvinyl chloride, phenolic resins, natural resin modified phenoloc resins, acrylic ester resins, methacrylic ester resins, polyvinyl acetate, silicone resins, polyurethanes, furan resins, epoxy resins, xylene resins, polyvinyl butyral, terpene resins, coumarone-indene resins, petroleum resins, and the like.

In particular, by addition of an ethylenic olefine homopolymer or an ethylenic olefin copolymer having a melt viscosity of 106 cps.

at 140"C into a toner in an amount of 0.1 to 10% by weight (more preferably 0.2 to 5% by weight), there can be improved dispersibility or compatibility of pigments or magnetic fine particles for a toner, and bad influences on the surface of photosensitive material or cleaning members can also be reduced.

As the olefin homopolymer and olefin copolymer, there may be mentioned polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copoymer, ethylene-ethyl acrylate copolymer, and the like.

In the case of polymers, the polymers preferably contain 50 mole%--100 mole% of an olefin monomer, more preferably 60 mole%100 mole%.

The melt viscosity is measured by Brookfield method. According to the present invention, the measurement is conducted by attaching a small amount sample adapter to the Btype visometer.

In the toner according to the present invention, there may be employed any suitable pigment or dye as colorant. For example, there are well known dyes and pigments such as carbon black, iron black, phthalocyanine blue, ultramarine, guinacridone, benzidine yellow and others.

Further, when the toner of the present invention is made into a magnetic toner, there may be also incorporated strongly magnetic elements and alloys or compounds containing these such as alloys or compounds of iron, cobalt, nickel or manganese as exemplified by magnetite, y-hematite, ferrite, etc. or other magnetic powders of conventional magnetic materials such as strongly magnetic alloys, also for the purpose of giving the function of a colorant at the same time. There may also be added carbon black, nigrosin, metal complex salts, colloidal silica powders, fluorine type resin powders, metal salts of higher fatty acids, etc. for the purpose of charging control or prevention of agglomeration.

The toner of the present invention can be applied for various developing methods. For example, there may be mentioned the magnetic brush developing method, the cascade developing method, the method using conductive magnetic toner as disclosed in U.S.

Patent 3,909,258, the method using high resistance magnetic toner as disclosed in Japanese Laid-Open Patent Application No.

31136/78, the method as disclosed in Japanese Laid-Open Patent Application No.

42141/79, No. 18656/80 and others, the fur brush method, the powder-cloud method, the impression method, et".

The toner image formed on a sheet to be fixed such as paper by use of the toner according to the present invention can be fixed with a hot roller without generation of off-set phenomenon of toner even when a fixing roller is used without supplying a liquid for prevention of off-set to its surface. As a fixing roller, there may be used a roller having a smooth surface formed of a fluorine type resin such as Teflon (produced by Du Pont), Fluon (produced by ICI) and Kel-F (produced by 3M), or silicone rubber, silicone resin, etc., or in some cases a roller having a metallic surface.

In the following, there are shown Preparation examples of vinyl type polymers.

I. In a separable flask, there were charged 40 parts by weight of toluene, and further 75 parts by weight of styrene, 20 parts by weight of butyl methacrylate, 5 parts by weight of maleic acid and 0.5 part by weight of divinylbenzene were added thereto. After the gas phase was replaced with nitrogen gas, while maintaining the reaction system at 80'C, a solution of 0.3 part by weight of benzoyl peroxide dissolved in 10 parts by weight of toluene was added dropwise over 30 minutes by use of a dropping funnel replaced with nitrogen gas, followed further by stirring at 80"C for 10 hours.Subsequently, 5 parts by weight of a toluene solution containing 0.3 part by weight of benzoyl peroxide were added dropwise to the reaction mixture, which was further elevated to 90"C and maintained thereat for 5 hours to complete polymerization. After cooling, the polymer was precipitated in a large volume of methanol. The precipitate was filtered off, dried at 60"C and recovered. The polymer had a Mw,'Mn of 24, Mw being 216,000.

II. Preparation example I was repeated except that 80 parts by weight of styrene, 1 8 parts by weight of butyl acrylate, 2 parts by weight of acrylic acid and 0.3 part by weight of divinylbenzene were employed as monomers. Mw/Mn was found to be 1 9 and Mw 188,000.

III. Preparation example I was repeated except that 60 parts by weight of styrene, 10 parts by weight of methyl methacrylate, 20 parts by weight of butyl acrylate, 10 parts by weight of methacrylic acid, and 0.7 part by weight of divinylbvenzene were employed as monomers. Mw/Mn was found to be 40 and Mw 324,000.

IV. Preparation example I was repeated except that 70 parts by weight of styrene, 10 parts by weight of butyl methacrylate, 20 parts by weight of monobutyl maleate, and 0.5 part by weight of divinylbenzene were employed as monomers. Mw/Mn was found to be 1 3 and Mw 123,000.

As the next step, the reactions between the foregoing polymers and decomposable metal compounds were carried out as follows: V. One hundred (100) parts by weight of the polymer synthesized in Preparation example I and 0.8 part by weight of iron (III) acetylacetonate (decomposition temperature: 340"C) were kneaded at 150"C for 30 minutes by means of a roll mill. The gel content of the crosslinked polymer was determined by extraction with toluene as the solvent. The gel content was found to be 24%.

VI. One hundred (100) parts by weight of the polymer synthesized in Preparation example II were added to 100 parts by weight of xylene and dissolved therein, while elevating the temperature up to 120"C. To the polymer solution, there was added one part by weight of cobalt (III) acetylacetonate (decomposition temperature: 310on) to carry out the reaction at 120"C for 5 hours. After the reaction, xylene was removed to obtain the polymer.

The crosslinked polymer was found to have a gel content of less than 1%.

VII. The reaction was carried out similarly as Preparation example V except that 100 parts by weight of the polymer synthesized in Preparation example Ill was used as polymer and 2 parts by weight of chromium (III) salicylate as metal compound. The gel content was found to be 32%.

VIII. The reaction was carried out on a roll mill similarly as Preparation example V except that 100 parts by weight of the polymer synthesized in Preparation example IV was used as polymer and 5 parts by weight of zinc complex salt of di-t-butylsalicyclic acid as metal compound. The gel content was found to be 19%.

The present invention is further illustrated by the following Examples.

Example 1 One hundred (100) parts by weight of the crosslinked polymer synthesized in Preparation example V and 60 parts by weight of magnetite were kneaded by means of a roll mill and, after cooling, pulverized by means of an air-jet type pulverizer Further, particles of 5 to 20j were selected by classification to provide a toner. The melt index of the toner was measured under the conditions of 125"C, 10 kg to be 0.87 g/10 min.

A developer was prepared by adding externally 0.5 part by weight of hydrophobic colloidal silica to 100 parts by weight of the toner.

The above developer was applied to a commercially available copying machine NP400RE (produced by Canon, Inc.). The fixing temperature of the above toner was 150"C and no off-set phenomenon was observed within the fixing temperature of 150'C to 210"C.

Further, durability test was conducted by copying continuously 50,000 sheets of papers by setting the temperature of the fixing roller at 170"C, whereby the image reflection density was maintained substantially constantly at around 1.0 from the initial stage to after copying 50,000 sheets. After copying of 50,000 sheets, there was observed no off-set phenomenon on the fixing roller, without occurrence of any trouble such as adhesion onto the surface of the photosensitive material drum or others and agglomeration within a developing vessel.

Comparative Example 1 A developer was prepared similarly as in Example 1, except that 100 parts by weight of the polymer synthesized in Example 1 was mixed as such, without reaction with a metal compound, with 60 parts by weight of magnetite.

The fixing temperature was approximately 150 C, being the same as the toner of Example 1, but off-set phenomenon became more intense until clear trace of image was recognized on the surface of the fixing roller at 180"C.

Similarly as in Example 1, continuous copying durability was tested, whereby traces of off-set product retransferred began to appear on the image after copying about 500 sheets, and copying was discontinued after copying of 1000 sheets.

Comparative Example 2 To 100 parts by weight of a styrene-butyl methacrylate-monobutyl maleate copolymer (monomer ratio = 75:20:5, Mw/Mn = 2.8, Mw = 32,000) synthesized according to the solution polymerization method was added 1 5 parts by weight of iron acetylacetonate, and the mixture was melt kneaded at 150 C.

However, reproducibility of this reaction was very bad and no polymer endowed with a constant degree of crosslinking can be prepared stably. Further, even when the reaction was successfully carried out, the resulant toner has a melt index of 0.36/10 min., but the minimum fixing temperature was found to be increased to a great extent to 180"C.

Example 2 One hundred parts by weight of the polymer synthesized in Preparation example VI, 60 parts by weight of magnetite were formed into a toner and further to a developer, similarly as in Example 1.

When evaluated similarly as in Example 1, fixing can be effected at 150 C, and no offset formed at 150"C to 200"C or higher.

Durability was also excellent.

Example 3 A toner was prepared and evaluated similarly as in Preparation example I, except that 100 parts by weight of the polymer synthesized in Example VII, 50 parts by weight of ferrite and 5 parts by weight of carbon black were employed.

The fixing temperature was 160"C, without formation of off-set at 160"C to 200"C, and durability was also good.

Example 4 A toner was prepared and further subjected to evaluation similarly as in Example 1, except that 100 parts by weight of the polymer of Preparation example VIII was employed. Very excellent results were obtained.

Example 5 One hundred (100) parts by weight of the polymer synthesized in Preparation example I and 0.5 part by weight of aluminum (III) acetylacetonate (decomposition temperature: 193"C) were allowed to react on a roll mill to crosslink the polymer. Further, 100 parts by weight of the reaction product were kneaded by means of a roll mill with 60 parts by weight of magnetite and 2 parts by weight of a polyethylene wax (melt viscosity: about 1 20 centipoise at 140"C). The kneaded product was cooled and pulverized, followed by classification, to obtain a toner. The toner was found to have a melt index of 1.15 g/10 min. under the conditions of 125"C, 10 kg.

This toner was formed into a developer and evaluated similarly as in Example 1. The fixing temperature was 150 C without formation of off-set from the fixing temperature to 200"C or higher. There was no change recognized in the durability test by copying of 50,000 sheets.

Example 6 One hundred (100) parts by weight of the polymer synthesized in Preparation example I was allowed to react with 2 parts by weight of chromium salt of di-t-butylsalicyclic acid on a roll mill to prepare a toner, which was then subjected to evaluation. Very excellent results were obtained.

Example 7 In Preparation example VI, the reaction was carired out by replacing the metal compound with 5 parts by weight of lithium acetylacetonate. Eighty parts by weight (80) of the reaction product, 20 parts by weight of a styrene-butyl methacrylate copolymer (produced by Sanyo Chemicals, trade name SSM- 73) and 60 parts by weight of magnetite were kneaded by means of a roll mill. The cooled kneaded product was pulverized into a toner, which was then evaluated. Good results were obtained.

Example 8 One hundred parts parts (100) by weight of the polymer synthesized in Preparation example Ill and 2 parts by weight of magnesium acetylacetonate were allowed to react on a roll mill, and further keaded with 60 parts by weight of magnetite and 5 parts by weight of a polypropylene wax (melt viscosity: 400 centripoise at 140"C). The resulting toner showed excellent characteristics.

Example 9 One hundred parts parts (100) by weight of the polymer synthesized in Preparation example 1 and 2 parts by weight of cobalt (il) acetylacetonate (gradually decomposed at 100"C or higher) were allowed to react on a roll mill. One hundred parts by weight of the reaction product, 8 parts parts by weight of carbon black and 4 parts by weight of a metal complex dye were melt kneaded on a roll mill.

After pulverization, the particles with sizes of about 5 to 20y were selected to make a toner. A developer was prepared by mixing 10 parts by weight of this toner and 90 parts by weight of carrier iron powders (trade name: EFV 250/400, produced by Nippon Iron Powder Co. Ltd.). The developer was applied to a commercially available copying machine (trade name: NP-5000, produced by Canon K.K.). Fixing was possible at 150on with no off-set recognized at all in the temperature range up to 210"C, and durability was also very excellent.

Comparative Example 3 One hundred (100) parts by weight of the polymer obtained in Preparation example I and 4 parts by weight of the metal complex dye as used in Example 9 were thoroughly melt kneaded on a roll mill, and further kneaded with 8 parts by weight of carbon black. Then, similarly as in Example 9. a toner was prepared and evaluated. But, although the fixing temperature was 1 50'C, off-set occurred intensively on the roller at 1 80 C or higher. Thus, this toner cannot practically be used.

The above example may be considered to indicate that no stable crosslinking of the polymer will proceed with a metal compound accoridng to a simple reaction method.

Example 10 In a separable flask, there were charged 90 parts by weight of xylene, and further 75 parts by weight of styrene, 20 parts by weight of butyl acrylate, 5 parts by weight of monobutyl maleate and 0.5 part by weight of divinylbenzene were added thereto. After the gas phase was replaced with nitrogen gas, while maintaining the reaction system at 80on, a solution of 1.2 part by weight of benzoyl peroxide dissolved in 10 parts by weight of xylene was added, followed by stirring for 10 hours. Then, the reaction mixture was elevated to 95"C and maintained thereat for 3 hours to complete the polymerization. After cooling, the polymer was precipitated in a large volume of methanol. The precipitate was filtered off, dried sufficiently at 50"C and recovered.The resultant polymer had a Mw/Mn of 27, Mw being 233,000.

On hundred (100) parts by weight of the above polymer, 0.6 part by weight of iron (III) acetylacetonate (decomposition temperature: 310"C) and 60 parts by weight of magnetite were melt kneaded on a roll mill at 1 50 C for 30 minutes and, after cooling, pulverized by means of an air-jet type pulverizer. Further, particles of 5 to 20y were selected by wind force classification to provide a toner.The melt index of the toner was measured under the conditions of 125 C, 10 kg to be 0.84 g/10 min. A developer was prepared by adding externally 0.5 part by weight of hydrophobic colloidal silica to 100 parts by weight of-the toner and evaluated by applying to a commercially available copying machine NP-400RE (produced by Canon I < . K.). The minimum fixing temperature of the above toner was 1 50 C and no off-set phenomenon was observed within the fixing temperature of 1 50 C to 210'C.

Further, durability test was conducted by copying continuously 50,000 sheets of papers by setting the temperature of the fixing roller at 1 70 C, whereby the image reflection density was maintained substantially constantly at around 1.0 from the initial state to after copying 50,000 sheets. After copying of 50,000 sheets, there was obserbed no off-set phenomenon to the fixing temperature, with out occurrence of any trouble such as adhesion onto the surface of the phtosensitive matieral drum or others and agglomeration within a developing vessel.

Comparative Example 4 A toner was prepared similarly as in Exam ple 10, except that no iron (III) acetylacetonate was added, and a developer was prepared therefrom.

The toner had a melt index (125"C, 10 kg) of subtantially the same value as the co polymer for the toner material of 15.96 g/10 min.

The minimum fixing temperature was ap proximately 150 C, being the same as the toner of Example 10, but off-set phenomenon became more intense until clear trace of image was recognized on the surface of the fixing roller at 180 C.

Similarly as in Example 10, continuous copying durability was tested, whereby traces of off-set product retransferred began to ap pear on the image after copying about 500 sheets, and copying was discontinued after copying of 1000 sheets, because such a phenomenon became more intense.

Comparative Example 5 To 100 parts by weight of a styrene-butyl acrylate-monobutyl maleate copolymer (monomer ratio = 75:20:5, Mw/Mn = 2.8, Mw = 35,000) synthesized according to the solution polymerization method were aded 60 parts by weight of magnetite and 1 5 parts by weight of iron (III) acetylacetonate, and the mixture was melt kneaded at 150 C. Particles with sizes of 5 to 20y were selected by pulverization and classification to provide a toner. The toner had a melt index of 0.36 g/10 min.However, the minimum fixing temperature was found to be increased to a great extent to 180 C. Further, for preparation of the toner, it is necessary to terminate the reaction between a carboxyl containing polymer and iron acetylacetonate after it has been progressed until the reaction produce exhibits off-set resistance. It is extremely difficult to terminate timely the reaction so that such a characteristic may be exhibited, and it has not been possible to produce stably a toner due to lack of reproducibility.

On the other hand, as shown in Example 10, when Mw/Mn of the unreacted carboxyl containing polymer is more than 4 (preferably more than 10), and Mw preferably more than 100,000, the carboxyl containing polymer may be crosslinked by the reaction to a light extent with a decomposable metal compound in order to impart off-set resistance to the toner, whereby the reaction can easily be controlled to enable stable production of a toner excellent in fixing characteristics. Further, when a polymer with Mw/Mn > 4, preferably with Mw > 1 00,000, is lightly crosslinked by the reaction with a decomposable metal compound, the molecular weight becomes much more widely be distributed, whereby imparting off-set resistance to the toner while the minimum fixing temperature is suppressed at a low ievel.

Example 11 A toner was prepared from 100 parts by weight of a styrene-butyl methacrylate-acrylic acid copolymer (monomer ratio: 65:33:2, Mw = 1 74,000, Mw/Mn = 23), 3 parts by weight of chromium salt of di-t-butylsalicyclic acid, 60 parts by weight of magnetite and 2 parts by weight of a polyethylene wax (melt viscosity: 120 centipoise at 140'0) and subjected to evaluation similarly as in Example 10.

There was obtained a toner with excellent off-set resistance and stable developing characteristics.

Example 12 A toner prepared according to the substantially same method as in Example 10 from 100 parts by weight of a styrene-butyl acry late-methacrylic acid copolymer (monomer ratio: 75:15:10, Mw= 176,000, Mw/Mn = 18), 2 parts by weight of aluminum acetyl-acetonate and 60 parts by weight of magnetite was found to have good fixing characteristics and good durability.

Example 13 One hundred parts by weight of a styrenebutyl methacrylate-monobutyl maleate copolymer (monomer ratio: 70:15:15, Mw = 136,000, Mw/Mn = 12), 5 parts by weight of zinc salt of di-t-butyl-salicyclic acid, 8 parts by weight of carbon black and 4 parts by weight of a metal complex dye (trade name: Zapon Fast Black, C. I. Acid Black 63, produced by BASF) were thoroughly melt kneaded in a small scale pressure kneader.

After cooling, the mass was pulverized and particles with sizes of about 5 to 20ssb were selected to provide a toner. A developer was prepared by mixing 10 parts by weight of the toner and 90 parts by weight of carrier iron powders (trade name: EFV 250/400, produced by Nippon Iron Powder Co., Ltd.). This developer was applied to a commercially available copying machine (trade name: NP-5000, produced by Canon K. K.). As the result, fixing could be effected at 150 C and there was no off-set observed up to a temperature range of 200 C or higher. Durability was found to be also excellent.

Example 14 In a separable flask, there were charged 70 parts by weight of xylene, and further 75 parts by weight of styrene, 1 5 parts by weight of butyl acrylate, 10 parts by weight of monobutyl maleate and 0.5 part by weight of divinylbenzene were added thereto. After the gas phase was replaced with nitrogen gas, the temperature was maintained at 85"C and a solution of 1 part by weight of benzoyl perox ide dissolved in 10 parts by weight of xylene was added dropwise over 30 minutes with a dropping funnel replaced with nitrogen, fol lowed by stirring at 85"C for 10 hours. Then, the reaction mixture was elevated to 95"C and maintained thereat for 3 hours to complete polymerization. After cooling, the polymer was precipitated in a large volume of methanol.

The precipitate was filtered off, dried sufficiently at 50"C and recovered. The resultant polymer has a Mw/Mn of 24, Mw being 276,000.

Then, 100 parts by weight of a styrene butyl methacrylate (trade name: X-230, produced by lonac Co.) and 25 parts by weight of cobalt (III) acetylacetonate (decomposition temperature: 310"C) were thoroughly melt kneaded on a roll mill, cooled and pulverized.

Ond hundred parts by weight of the poly mer synthesized by the solution polymerization method as described above, 20 parts by weight of the above pre-blend and 60 parts by weight of magnetite were melt kneaded on a roll mill at 105"C, followed by pulverizing, and thereafter particles with sizes of about 5 to 20y were selected to provide a toner. The melt index of the toner was measured under the conditions of 1 25 C, 10 kg to be 1.25 g/10 min.

A developer was prepared by adding externally 0.4 part by weight of hydrophobic colloidal silica to 100 parts by weight of the above toner.

This developer was applied to a commercially available copying machine NP-400 RE (produced by Canon K. I < .). The minimum fixing temperature of the above toner was 1 50 C and no off-set phenomenon was observd within the fixing temperature of 1 50 C to 210"C.

Further, durability test was conducted by copying continuously 50,000 sheets of papers by setting the temperature of the fixing roller at 1 70 C, whereby the image reflection density was maintained substantially constantly at around 1.0 from the initial stage to after copying 50,000 sheets. After copying of 50,000 sheets, there was observed no off-set phenomenon to the fixing temperature, without occurrence of any adhesion to the surface of the photosensitive body drum or agglomeration within a developer.

Comparative Example 6 One hundred (100) parts by weight of the carboxyl containing polymer as prepared in Example 14, 1 6 parts by weight of a styrenebutyl mechacrylate copolymer used as predispersion in Example 1 4 and 60 parts by weight of magnetite were melt kneaded on a roll mill and a developer was prepared therefrom similarly as in Example 1.

The toner has a melt index of 1 8 g 10 min. and the minimum fixing temperature was approximately 145"C. But at said temperature, there was recognized slightly off-set phenomenon, which was further intensified with the elevation of the fixing temperature until the traces of image became clearly recogni zable on the surface of a fixing roller at 170"C.

Further, continuous durability test was commenced similarly as in Example 14, but the traces of off-set toner retransferred onto the paper appeared on the image after about 5GO sheets of copying, whereupon the durability test was discontinued.

Example 15 A reactive polymer was synthesized in substantially the same manner as in Example 14, except that the monomers employed were 70 parts by weight of styrene, 25 parts by weight of butyl methacrylate, 5 parts by weight of acrylic acid and 0.8 part by weight of divinylbenzene. Mw/Mn of the polymer was 34.5, Mw being 327,000.

Then, to 100 parts by weight of a styrene polymer (trade name: D-125, produced by Hercules Inc.) were added 10 parts by weight of iron (Ill) acetylacetonate (decomposition temperature: 340"C) and melt kneaded on a roll mill. Similarly as in Example 14, 100 parts by weight of the reactive polymer, 10 parts by weight of the pulverized product of the pre-blend and 60 parts by weight of magnetite were kneaded to prepare a developer, which was subjected to evaluation.

The toner had a melt index of 0.76 g/10 min. and the minimum temperature was 160"C without any off-set from this temperature up to 200"C or higher, and its durability was also good.

Example 16 A styrene-butyl acrylate-maleic acid copolymer (monomer ratio: 80:17:3, Mw/Mn = 12.4, Mw = 128,000) was synthesized in substantially the same manner as in Example 14.

Then, 100 parts by weight of the styrene polymer as used in Example 1 5 and 40 parts by weight of chromium complex of di-t-butylsalicyclic acid were dissolved in 100 parts by weight of toluene and dried to prepare a preblend.

Further, 100 parts of the reactive polymer, 25 parts by weight of the above pre-blend, 60 parts by weight of magnetite and 3 parts by weight of a polyethylene wax (melt viscosity: about 1 20 centipoise at 140"C) were made similarly as in Example 14 into a developer, which was then evaluated. It exhibited very excellent fixing characteristics.

Example 17 In Example 14, a pre-blend was prepared by use of 20 parts by weight of aluminum acetylacetonate (decompostion temperature: 193"C) in place of cobalt (III) acetylacetonate.

Then, 100 parts by weight of the reactive polymer of Example 14, 5 parts by weight of the pulverized product of the above pre-blend, 60 parts by weight of mangetite and 5 parts by weight of polypropylene wax (melt viscosity: about 400 centipoise) were formed similarly as described in Example 1 4 into a toner.

There was obtained a toner having very good fixing and developing characteristics.

Example 18 One hundred parts by weight of the styrene polymer of Example 1 5 was melt kneaded with 30 parts by weight of zinc complex of dit-butylsalicyclic acid.

Then, 100 parts by weight of the reactive polymer of Example 15, 20 parts by weight of the pulverized product of the above pre-blend, 8 parts by weight of carbon black and 4 parts by weight of a metal complex dye (trade name: Zapon Fast Black, C.l Acid Black 63, produced by BASF) were thoroughly kneaded in a small scale pressure kneader. After cooling, the mass was pulverized and particles with sizes of about 5 to 20jet were selected to provide a toner. A developer was prepared by mixing 10 parts by weight of the toner and 90 parts by weight of carrier iron powders (trade name: EFV 250/400, produced by Nippon Iron Powder Co., Ltd.). This developer was applied to a commercially available copying machine (trade name: NP-5000, produced by Canon K. K.).

As the result, fixing could be effected at 150"C and there was no off-set observed up to a temperature range of 200"C or higher.

Durability was found to be also very excellent.

Example 19 In a separable flask, there were charged 90 parts by weight of xylene, and further 75 parts by weight of styrene, 20 parts by weight of butyl methacrylate, 5 parts by weight of maleic acid and 0.5 part by weight of divinylbenzene were added thereto. After the gas phase was replaced with nitrogen gas, the temperature was maintained at 80"C and a solution of 0.8 part by weight of benzoyl peroxide dissolved in 10 parts by weight of xylene was added dropwise over 30 minutes with a dropping funnel replaced with nitrogen, followed by stirring at 80"C for 10 hours.

Then, 5 parts by weight of a toluene solution containing 0.3 part by weight of benzoyl peroxide was added dropwise and further the reaction mixture was elevated to 90"C and maintained thereat for 5 hours to complete polymerization. After cooling, the polymer was precipitated in a large volume of methanol.

The precipitate was filtered off, dried sufficiently at 60"C and recovered. The resultant polymer had a Mw/Mn of 26, Mw being 243,000.

One hundred parts by weight of the above polymer, 0.3 part by weight of Nissan Nymeen (commercial condensation product between a primary aliphatic amine and ethylene oxide sold by Nippon Oil 8 Fats Co., Ltd., x + y = 2), 60 parts by weight of magnetite and 4 parts by weight of a metal complex dye (trade name: Zapon Fast Black B,C.I. Acid Black 63, produced by BASF) were formulated similarly as in Example 1 to prepare a toner.

The toner had a melt index under the conditions of 125"C, 10 kg of 1.36 kg/10 min. When this toner was evaluated as a developer similarly as in Example 1, similar results as in Example 1 were obtained.

Comparative Example 7 A developer was prepared by producing a toner in a way similarly to in Example 19, except that there was added no Nissan Nymeen S-202.

The toner had a melt index of 16.86 g/10 min. (125"C, 10 kg), being substantially the same value as that of the copolymer for the toner material.

The minimum fixing temperature was approximately 150"C, being the same as the toner of Example 19, but off-set phenomenon became more intense until clear trace of image was recognized on the surface of the fixing roller at 180"C.

Similarly as in Example 19, continuous copying durability was tested, whereby traces of off-set product retransferred began to appear on the image after copying about 500 sheets, and copying was discontinued after copying of 1000 sheets because such a phenomenon was further intensified.

Example 20 Ond hundred (100) parts by weight of a styrene-butyl acrylate-acrylic acid copolymer (monomer ratio: 80:18:2, Mw/Mn = 19, Mw = 188,000), 0.5 part by weight of Nissan Nymeen T2-260 (polyoxyethylene tallow alkylamine, x + y = 60, commercially sold by Nippon Oil 8 Fats Co., Ltd), 60 parts by weight of magnetite, 4 parts by weight of the metal complex dye of Example 1 9 and 2 parts by weight of a polyethylene wax (melt viscosity: 1 20 centipoise at 140"C) were made into a toner and evaluated similarly as in Example 1. There was obtained a toner excellent in off-set resistance and stable in developing characteristic.

Example 21 A toner prepared in substantially the same manner as in Example 1 9 from 100 parts by weight of a styrene-butyl acrylate-methacrylic acid copolymer (monomer ratio: 75:15:10, Mw/Mn = 28, Mw = 310,000), 0.2 part by weight of polyoxyethylene-octadecyl amine (x + y = 10), 60 parts by weight of magnetite, and 4 parts by weight of the metal complex dye of Example 1 9 was found to have good fixing characteristics and stable durability.

Example 22 One hundred (100) parts by weight of a styrene-butyl methacrylate-monobutyl maleate copolymer (monomer ratio: 70:15:15, Mw/Mn = 8, Mw = 11 5,000), 1 part by weight of Nissan Nymeen S-220 (ethylene oxide derivative of octadecyl-amine, x + y = 20, commercially sold by Nippon Oil 8 Fats Co., Ltd.), 8 parts by weight of carbon black, and 4 parts by weight of the metal complex dye of Example 1 9 were melt kneaded in a small scale pressure kneader.

After cooling the mass was pulverized and particles with sizes of about 5 to 20M were selected to provide a toner. A developer was prepared by mixing 10 parts by weight of the toner and 90 parts by weight of carrier iron powders (trade name: EFV 250/400, produced by Nippon Iron Powder Co., Ltd.). This developer was applied to a commercially available copying machine (trade name: NP-5000, produced by Canon K. K.).

As the result, fixing could be effected at 150"C and there was no off-set obserbed up to a temperature range of 200"C or higher.

Duraibility was found to be also very excellent.

Example 23 Similarly as in Example 1, one hundred (100) parts by weight of the polymer prepared in Example 19, 0.3 part by weight of Nissan Amine DTH (hardened tallow alkylpropylenediamine, commercially sold by Nippon Oil 8 Fats Co. Ltd.), 60 parts by weight of magnetitie, 4 parts by weight of a metal complex dye (trade name: Zapon Fast Black B,C.I Acid Black 63, produced by BASF) were made into a toner.

The toner had a melt index under the conditions of 125"C, 10 kg of 1.24 g/10 min. When this toner was evaluated as a developed similarly as in Example 1, similar results as in Example 1 were obtained.

Comparative Example 8 A developer was prepared similarly as in Example 23, except that there was added no amine DTH.

The toner had a melt index of 16.86 g/10 min. (125"C, 10 kg), being substantially the same value as that of the copolymer for the toner material.

The minimum fixing temperature was approximately 150to, being the same as the toner of Example 23, but as a temperature was elevated, off-set phenomenon became more intense until clear trace of image was recognized on the surface of the fixing roller at 180"C.

Similarly as in Example 23, continuous copying durability was tested, whereby traces of off-set product retransferred began to appear on the image after copying about 500 sheets, and copying was discontinued after copying of 1000 sheets because it was further intensified.

Example 24 One hundred (100) parts by weight of a styrene-butyl acrylate-acrylic acid copolymer (monomer ratio: 80:1 8:2, Mw/Mn = 19, Mw = 1 88,000), 0.5 part by weight of Nissan Amine DTH, 60 parts by weight of magnetite, 4 parts by weight of the metal complex dye of Example 23 and 2 parts by weight of a polyethylene wax (melt viscosity: 1 20 centipoise at 140"C) were made into a toner and evaluated similarly as in Example 23. There was obtained a toner extremely excellent in off-set resistance and stable in developing characteristic.

Example 25 A toner prepared in substantially the same manner as in Example 23 from 100 parts by weight of a styrene-butyl acrylate-methacrylic acid copolymer (monomer ratio: 75:15:10, Mw/Mn = 28, Mw = 310,000), 0.2 part by weight of Nissan Amine DT (tallow alkylpropylenediamine produced by Nippon Oil 8 Fats Co., Ltd.), 60 parts by weight of magnetite, and 4 parts by weight of the metal complex dye of Example 23 was found to have good fixing characteristics and stable durability.

Example 26 One hundred (100) parts by weight of a styrene-butyl methacrylate-monobutyl maleate copolymer (monomer ratio: 70:15:15, Mw/Mn = 8, Mw = 115,000), 1 part by weight of Nissan Amine DT, 8 parts by weight of carbon black, and 4 parts by weight of the metal complex dye of Example 23 were melt kneaded in a small scale pressure kneader.

After cooling, the mass was pulverized and particles with sizes of about 5 to 20y were selected to provide a toner. A developer was prepared by mixing 10 parts by weight of the toner and 90 parts by weight of carrier iron powders (trade name: EFV 250/450, produced by Nippon Iron Powder Co., Ltd.). This developer was applied to a commercially available copying machine (trade name: NP-5000, produced by Canon K. K.). As the result, fixing could be effected at 150"C and there was no off-set observed up to a temperature range of 200"C or higher. Durability was found to be also very excellent.

In the above Examples, vinyl type polymers containing carboxyl groups are shown by way of Examples, but other polymers having carboxyl groups may also be applicable.

Claims (21)

1. A toner which comprises a binder material obtained by reacting a polymer having carboxyl groups with a value of weight average molecular weight/number average molecular weight (Mw/Mn) of more than 4.0 with a cross-linking agent.

2. A toner according to claim 1 wherein the crosslinking agent is a decompsable metal compound.

3. A toner according to claim 2 wherein the metal compound has a decomposition temperature of 100"C to 600"C.

.

4. A toner according to claim 1 wherein the crosslinking agent is an amine selected from polyoxyethylene akylamines and alkyl propylenediamines.

5. A toner according to any preceding claim wherein the polymer having carboxyl groups is a vinyl type polymer.

6. A toner according to any preceding claim wherein the polymer having carboxyl groups is an already crosslinked polymer.

7. A toner according to any preceding claim wherein the polymer having carboxyl groups is prepared by solution polymerisation.

8. A toner according to any preceding claim wherein the gel content of the binder material is 50% or less.

9. A toner according to any preceding claim wherein the binder material has a glass transition temperature of 50"C or higher.

1 0. A method of producing a toner which comprises the step of reacting a polymer having carboxyl groups with a value of weight average molecular weight/number average molecular weight (Mw/Mn) of more than 4.0 with a crosslinking agent.

11. A method according to claim 10 wherein the crosslinking agent is a decomposable metal compound.

12. A method according to claim 11 wherein the reaction is carried out at a temperature lower than the decomposition temperature of the decomposable metal compound.

1 3. A method according to claim 10 wherein the crosslinking agent is an amine selected from polyoxyethylene alkylamines and alkyl propylenediamines.

14. A method for producing a toner which comprises the step of reacting a crosslinking agent with a mixture containing a polymer having carboxyl groups with a value of weight average molecular weight/number average molecular weight (Mw/Mn) of more than 4.0 and a toner material.

15. A method according to claim 14 wherein the crosslinking agent is a decomposable metal compound.

16. A method according to claim 14 wherein the crosslinking agent is an amine selected from polyoxyethylene alkylamines and alkyl propylenediamines.

1 7. A method according to any of claims 14 to 1 6 wherein the toner material comprises a colorant.

1 8. A method according to any of claims 14 to 1 7 wherein the toner material comprises a magnetic powder.

1 9. A method for production of toner which comprises mixing a decomposable metal compound with a polymer having no carboxyl group, adding the resultant mixture containing the above decomposable metal compound to a polymer having carboxyl groups, and melt kneading the blend thereby to allow the polymer having carboxyl groups to react with the decomposable metal compound in the production step.

20. A toner substantially as described herein with reference to any one of the Examples (excluding Comparative Examples).

21. A method of making a toner substantially as described herein with reference to any one of the Examples (excluding Comparative Examples).