DK150720B - POSITIVELY RECHARGEABLE TONER POWDER FOR THE PREPARATION OF ELECTROSTATIC IMAGES AND PROCEDURE FOR THE PREPARATION OF SUCH TONER POWDER - Google Patents

Description

150720 \

The invention relates to a positively rechargeable toner powder consisting essentially of finely divided colored toner particles containing an insulating thermoplastic resin, coloring agents and a polarity control agent. The invention further relates to a process for making such a toner powder.

By electrophotography, latent electrostatic images are formed on a suitable surface. To make these images visible, powder softeners of the so-called two-component type are widely used. These are developers containing fine, black or differently colored toner particles and relatively large carrier particles. Upon contact with or friction against the carrier particles, the toner particles receive an electrostatic charge and as a result, they adhere to the carrier particles. Generally, the composition of toner and carrier particles is chosen such that the toner particles get a charge of a polarity as opposed to the polarity of the latent electrostatic image to be developed. When the toner powder is brought into contact with this image, the toner particles are released from the carrier particles by virtue of the electrostatic charge of the image and deposited on the latent image, and as a result, it becomes visible. In direct electrophotography, the powder image is usually fixed by heat on the surface on which it has been deposited. For indirect electrophotography, the powder image is transferred to a receiving surface and then fixed. The heating is usually carried out by means of radiant heat in a so-called jet melting apparatus or by contacting the powder image with a heated surface such as a roller and / or belt, thereby producing a combination of heat and pressure fixation. Two-component powder developers can contain, as carrier particles, powdery materials of widely varying composition. For example, they can consist of metal such as iron or nickel, metal oxide, such as chromium oxide or alumina, glass, sand or quartz. Metal carrier particles, especially iron particles, are frequently used in practice. In particular, iron particles are frequently used in powder developers for use in the so-called magnetic brush development, in which the method is developed by means of magnetic transport means for the electrostatic image to be developed.

The toner particles in the two-component powder developers consist essentially of an insulating, thermoplastic resin, or a mixture of such resins, and one or more coloring agents. Conventional natural and synthetic polymers are used as thermoplastic resins. Examples of widely used thermoplastic resins are polystyrene, copolymers of styrene with an acrylate and / or methacrylate, polyamides, modified phenol formaldehyde resins, polyester resins and epoxy resins. Carbon, black is commonly added as a coloring agent in black toner powders, and in pharyngeal toner powders, e.g. used in multi-color electrophotographic production processes, organic dyes are added to the thermoplastic resin.

Generally, the aforementioned resins themselves cannot be positively charged sufficiently. Most of them are negatively charged by contact with iron particles. Thus, the addition of a polarity control means, i.e. a means which makes the tri-electric charge sufficiently positive if one wants a positively rechargeable two-component powder developer suitable for magnetic brush development. Among the polarity regulators that have been found effective, mention may be made of amino compounds, quaternary ammonium compounds and organic dyes, in particular basic dyes and their salts such as the hydrochlorides. Examples of conventional polarity regulators are benzyl-dimethyl-hexadecyl-ammonium chloride and decyl-trimethyl-ammonium chloride, nigrosine base, nigrosine hydrochloride, safranin T and crystal violet. In particular, nigrosine base and nigrosine hydrochloride are often used as a polarity regulator.

The basic requirements that a toner powder in general and a positively rechargeable toner powder in particular must meet are pronounced polarity, good charging properties such as sufficient recharge, uniform charge distribution, charge stability and low moisture and temperature sensitivity, good melt properties that are also properly reproducible, thermal stability and good durability during long-term use. In addition, for a toner powder for use in an electro-copier with a contact melting apparatus, the melting range should be suitably as wide as possible. For use in a photocopier with a jet melting apparatus, the melting range should preferably be as small as possible.

While a number of the hitherto proposed negatively rechargeable toner powders fulfill the above-mentioned properties to a reasonable degree, this is to a much lesser extent the positively rechargeable toner powders. This applies in particular to their charge stability, the reproducibility of their melting properties, their thermal stability and especially their uniform charge and permanence. In order to achieve uniform charge with good permanence for the toner particles, the polarity control means must be distributed completely homogeneously throughout the resin. As is well known, toner powders are commonly produced by the so-called kneading method, the extrusion method or the hot melt method. In these processes, the resin is homogeneously blended in the molten state with the coloring agents, the polarity regulator and, if desired, other components. After cooling, the solid mass thus obtained is ground to particles of the desired degree of fineness, and all of these particles must have the exact same composition in order to obtain a toner powder with which good image quality can be obtained. However, the positively-acting polarity control agents, which are preferably used, often do not dissolve or only poorly in the thermoplastic resins or resin mixtures to be used for the toner powders, so that the desired homogeneity cannot be achieved. This is especially true of the highly preferred substances nigrosine base and nitrosine hydrochloride.

In the few cases where positive-acting polarity control agents are found, which for the intended purpose are sufficiently dissolved in the thermoplastic resin, such as e.g. In the case of polyamides, the resin itself has several not very favorable properties, and as a result, toner powders made on this basis do not very well fulfill the above-mentioned basic properties, such as e.g. the moisture and temperature sensitivity of the charge.

The object of the present invention is to provide a positively rechargeable toner powder which generally satisfies the above-mentioned basic requirements and, in particular, to a large extent satisfies the claims which it has proved difficult to realize, in particular for positively rechargeable toner powders, for uniform charging. , charge stability and permanence, reproducibility of the melting properties, thermal stability and sensitivity to humidity. A further object is to provide a method by which the toner powder according to the invention can be made "tailor-made" in a simple and economical way.

The positively rechargeable toner powder of the invention is characterized in that the thermoplastic resin comprises at least 50 wt. S of an epoxy resin having an epoxy equivalent weight of at least 10,000 and obtained by modifying its epoxy groups for at least 5%. in the case of a monofunctional carboxylic acid and / or monofunctional phenol, which, apart from the carboxyl or hydroxy group, does not carry any substituents which are reactive to the epoxy groups of the resin powder and for a maximum of 95%. they by intermolecular reaction or by cross-linking using a polyfunctional epoxy hardener.

By epoxy resins is meant in the present context condensation products of a polyphenol, in particular a bisphenol, with a halohydrin, in particular epichlorohydrin.

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The modified epoxy resin to be used in the toner powder of the invention may e.g. is obtained by modifying one of the commercially available epoxy resins or a mixture of such resins which, as is well known, has an epoxy equivalent weight (hereinafter referred to as EEV) significantly below that of the present invention. the present case required a minimum value of 10,000. The choice of resin (s) to be used as the starting product for this purpose is mainly determined by the requirement that the toner powder must be stable at temperatures up to 50 ° C and that it must have a melting point between 65 and 150 ° C. The first requirement is that, until the melting step, temperatures up to 50 ° C can occur at each stage, such as storage, residence and processing, in the copier. The second requirement is specifically related to the maximum permissible temperature of the copy paper during melting, as otherwise discoloration or even burning may occur. In copiers using a less combustible base material than paper, e.g. glass or metal, of course, higher melting point resins can also be used for the toner powder.

As examples of epoxy resins which are quite useful as a starting product for the preparation of the modified epoxy resin to be used in the toner powder of the invention, mention may be made of Epikoti 10000 (mp 90-100 ° C, EEV 850-940, both data of the supplier). indications], Epikote ^ .006 (115-125 ° C, EEV 1550-1900), EpikotJ 1007 (120-130 ° C, EEV 1700-2050), and Epikote ^ L009 (140-155 ° C, EEV 23QQ-3400 However, as will be explained below, it is also possible, in certain circumstances, to use epoxy resins with lower or higher melting points than the above as the starting product.

The toner powder of the invention may contain epoxy resin wherein between 5 and 100% of the epoxy groups are modified with a monofunctional carboxylic acid and / or phenol. The required EEV of 10,000 or higher can be achieved by modifying approx. 80-100% of the epoxy groups in the starting epoxy resin selected with a monofunctional carboxylic acid and / or phenol. However, it can also be obtained by modifying at least approx. 80% of the epoxy resin epoxy groups partly with a monofunctional carboxylic acid and / or phenol and partly by intermolecular reaction. Of course, it must be ensured during the modification process that the necessary conditions for implementing both types of modifications are present. Usually, these conditions are met if the temperature and duration of the modification process are properly selected. The intermolecular reaction between the epoxy resin groups of the epoxy resin generally proceeds satisfactorily at temperatures between 150 and 250 ° C and residence times of 120 to 5 minutes. At said temperatures, the modification by the monofunctional carboxylic acid and / or phenol proceeds considerably faster than the intermolecular reaction.

The desired minimum value for EEV can also be obtained by combining the modification by a monofunctional carboxylic acid and / or phenol with a modification carried out by cross-linking using one of the known polyfunctional epoxy curing agents. Examples of suitable curing agents for this purpose include succinic anhydride, maleic anhydride, succinic acid and bisphenol A. Since such crosslinking reactions usually proceed very quickly at 110 to 150 ° C, the said combination leads to the desired result within a few minutes when the modification takes place. place at temperatures between about, 100 and 150 ° C.

In all cases, however, at least 5% of the epoxy groups in the epoxy resin selected as the starting product for the preparation of the toner powder of the invention must be modified with a monofunctional carboxylic acid and / or phenol, since otherwise the toner powder does not meet the above-mentioned requirements with respect to melting point and reproducibility of the melt properties. What percentage of epoxy grouping is modified with a monofunctional carboxylic acid and / or phenol, and which by intermolecular reaction and curing, respectively, depends on the purpose of the toner powder of the invention.

If the toner powder is intended to produce a developer for use in apparatus equipped with a jet melting apparatus, it is advisable to modify as large a percentage as possible, usually at least 50%, and preferably at least 75%, of the epoxy groups in the resin selected as the starting product. a carboxylic acid and / or phenol. The fact is that for use in a jet melting apparatus, the toner powder must have as small a melting range as possible with as low an initial melting point as possible. By modifying as large a percentage as possible of the epoxy groups with a monofunctional carboxylic acid and / or phenol and as small a percentage as possible by intermolecular reaction or by epoxy curing, the melting zone, which is mostly very small itself, changes and the initial melting point of the starting product for carrying out the modification, the epoxy resin selected only to a practically insignificant degree. A further advantage of a modification almost exclusively with a monofunctional carboxylic acid and / or phenol is that the modification can be carried out very quickly and at relatively low temperatures in a highly reproducible manner.

If the toner powder is intended to produce a developer for use in contact melters, which is especially preferred over beam melters in copiers to achieve high printing speeds, the best results will be obtained, depending on the modification of the epoxy groups in the monopile or monosilicon selected as the starting product. and / or phenol is closer to the required minimum value of 5%, while the remaining modification percentage required to achieve the minimum epoxy equivalent weight of 10,000 is obtained by intermolecular reaction between the epoxy resin epoxy groups or by epoxy curing. The resin thus obtained, and thus the toner powder obtained therefrom, has a large melting range, which is a desirable property for toner powders for developers designed for use in appliances provided with a contact melting apparatus. Generally, the melting range of the modified epoxy resin is increased as the percentage of the modification with a monofunctional carboxylic acid and / or phenol is closer to the minimum value of 5%. However, the melting point of the modified resin is then shifted to a higher level, so that in some cases it may be desirable to modify more than 5% of the epoxy groups with a monofunctional carboxylic acid and / or phenol, otherwise the melting point of the obtained resin will be too high. high to proper and economical melting. However, within certain limits, this disadvantage can be countered by starting from an epoxy resin having a relatively low melting point, such as Epicote Q04, 1002 or 1001.

Suitable embodiments of the toner powder of the invention are set forth in claims 2-5.

Except for the carboxyl and hydroxyl group, respectively, the monofunctional carboxylic acids and / or phenols to be used to modify the epoxy resin used as a starting product must not contain any additional substituent which can react with the epoxy groups in the epoxy resin under the conditions prevailing during the co-purging process. Particularly suitable are aliphatic and aromatic carboxylic acids and phenols as well as those substituted by one or more alkyl, aralkyl, cycloalkyl, aryl, alkylaryl, alkoxy or non-volatile or substantially not, under the conditions prevailing during the modification process.

Examples of such carboxylic acids include benzoic acid, 2,4-dimethylbenzoic acid, 4- (α, α-dimethylbenzyl) -benzoic acid, 4-phenylbenzoic acid and 4-ethoxybenzoic acid. Also mentioned are the saturated aliphatic carboxylic acids: heptanoic, nonanoic, dodecanoic and isododecanoic, hexadecanoic and octadecanoic.

Examples of the above phenolic compounds include 4-n-butylphenol, 4-n-pentylphenol, 2,3,4,6-tetramethylphenol, 2,3,5,6-tetramethylphenol, 4- (α, α -dimethylbenzyl) phenol, 4-cyclohexylphenol, 3-methoxyphenol, 4-methoxyphenol and 4-ethoxyphenol.

Of the above compounds, it is most preferred to use octadecanoic acid, substituted or unsubstituted benzoic acid and 4- (α, α-dimethylbenzyl) phenol.

The modification of the epoxy resin selected as the starting product to form the modified epoxy resin for use in the toner powder of the invention is preferably done during the preparation of the toner powder itself. Surprisingly, it has been found that the modification process in this way can be carried out well and satisfactorily regulated so that a "tailor-made" toner powder of excellent quality can be obtained in this way. In addition, in this case, no special catalyst or other additive is required to perform the modification with the monofunctional carboxylic acid and / or the phenol satisfactorily, which is a further advantage.

Admittedly, it is possible to perform the modification of the epoxy resin selected as a starting product in a separate process. However, this process is associated with a number of difficulties and, consequently, it is less appropriate. Eg. a special operation and in most cases a catalyst is required to properly regulate the modification with the monofunctional carboxylic acid and / or phenol. In most cases, this catalyst must be completely removed again with the solvents used. This is not only troublesome, but often it is not sufficiently successful and, as a result, the toner powder thus produced is generally rapidly destroyed.

The method of the invention is set forth in claim 6, and a suitable embodiment thereof is set forth in claim 7.

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The toner powder according to the invention can be prepared by one of the commonly known methods for making toner powders, such as e.g. kneading, extrusion or hot melt method. In the first two methods, the resin, the polarity control agent, the coloring agents and, if desired, other constituents are generally mixed at ca. 90 to 130 ° C, while in the latter method, this mixture is usually carried out at ca. 200 ° C. After cooling, the mass obtained is ground to particles of the desired degree of fineness, usually between 2 and 50 μιη.

Of the three manufacturing methods mentioned above, the hot melt method has been found to be the most suitable for making toner powder according to the invention. The toner powder produced by this process is found to be even more satisfactory and to be more reproducible, especially with respect to its essential properties such as charge properties, stability and melting properties than when the other two methods are used. In addition, most polarity regulators and dyes dissolve sufficiently in the resin at temperatures around 200 ° C so that the homogeneous composition of the toner powder required for the charging properties can be achieved without the need for special measures.

However, the toner powder of the invention of satisfactory quality can also be obtained by the kneading and extrusion process, provided certain precautions are observed. The thing is that at the temperatures at which these two processes are generally carried out, 90 to 130 ° C, the most common polarity control agents and dyes are not dissolved in the resin sufficiently to obtain the desired homogeneous mixture. This is particularly true with regard to the preferred polarity control agents of the nigrosine type.

In such cases, a substance capable of speeding up the dissolution of the polarity control agent as described in the previously published Dutch application No. 7415325 may be used "."

Generally, the amounts to be used range from a few percent to a few tens of percent.

In particular, it is convenient to use the diphenyl phthalate or N-cyclohexyl-p-toluene sulfonamide mentioned in the aforementioned patent application.

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Furthermore, since the modification of the epoxy groups in the starting epoxy resin selected by intermolecular reaction proceeds relatively slowly at said temperatures, it is advisable if the necessary modification of the epoxy groups is conveniently carried out only partially with the monofunctional carboxylic acid and / or phenolic with crosslinking using a polyvalent epoxy hardener.

Although the use of the compounds described in the aforementioned Dutch patent application as solution accelerators is in fact superfluous if the toner powder according to the invention is produced by the hot melt process, its use can nevertheless also be advantageous in this case for a number of reasons. Eg. For example, the addition thereof to the reaction mixture causes a diminished melting point of the recently obtained toner powder, and thus allows, as a starting product for preparing the toner powder of the invention, to use epoxy resins whose melting point is higher than 150 ° C. It is also possible to make this addition to bring the toner powder's melting point back to the desired value, should this have become too high as a result of the majority of the epoxy groups in the epoxy resin being modified by intermolecular reaction or crosslinking with a polyvalent epoxy hardener.

In addition to the modified epoxy resin or the mixture of modified epoxy resins, the finely divided toner particles in the toner powder of the invention may contain other ingredients. In particular, the modified epoxy resin may be admixed with a phenoxy resin such as e.g. Rutapoj ^ b7-17, a product of Messrs. Bakelite. However, the ratio of modified epoxy resin to phenoxy resin should be at least 1: 1, preferably at least 1.5-1.75: 1.

The addition of phenoxy ocean peaks, a generic term for amorphous poly (hydroxy-ethers) derived from diphenols and epichlorohydrin and having a high molecular weight, expands the melting range of the toner particles. This gives e.g. the possibility of preparing a toner powder which is based on an epoxy resin which is exclusively or predominantly modified with a monofunctional carboxylic acid and / or phenol and which is also suitable for use in an apparatus provided with a contact melting apparatus.

For the preparation of a two component type powder developer, the toner powder according to the invention, either immediately after its manufacture or at a later stage, is mixed with the desired carrier particles. If the developer is intended for magnetic brush development, a carrier of magnetic iron particles which may be provided with a surface layer is inverted. The desired particle size for the carrier is known to those skilled in the art. Generally, its dimensions range from 50 to 150 μπι. Depending on the particle size of the two components, the two-component developer generally contains from 1 to 8% by weight of toner particles.

The inducers thus obtained can be used satisfactorily to induce latent electrostatic images with a negative charge, such as e.g. obtained on electrophotographic elements based on zinc oxide.

The invention is further illustrated by the following examples.

Example 1 In a container equipped with a stirrer and oil bath heating, 468 g of the Epikot® epoxy resin 466 g (EEV = 1700, supplied by Shell) is gradually added at 200 ° C to a mixture of 36 g of nigrosine base (Color Index, 3rd ed. No. 50415: 1), 60 g of N-cyclohexyl-p-toluenesulfonamide and 30 g of benzoic acid. After mixing, the ingredients were completely dissolved in each other. Then, 36 g of carbon was added and the whole was stirred for 2 hours at 200 ° C to give a satisfactory dispersion of the carbon. The hot melt was then cooled and the mass ground and screened in a manner known per se to a toner powder having a particle size between 8 and 27 μπι. The EEV value of the benzoic acid modified resin in the toner powder, which was determined by analogy with the method of analysis 2.3.2.7.2. used by Synthetic Materials Institute T.N.O., Delft, exceeded 40,000. The content of unreacted benzoic acid in the toner powder was less than 0.1%. Accordingly, the resin had been modified for 90% with benzoic acid. The toner powder had a glass transition temperature (Tg) of 56 ° C. This Tg was determined from the D.S.C. thermogram recorded by a Du Pont 990 thermal analyzer. Even after prolonged heating to 200 ° C, a temperature well above the temperature usually used in melting appliances, Tg remained constant at 56 ° C, indicating that the toner was thermally stable.

4 parts by weight of the toner powder thus prepared were thoroughly mixed with 96 parts by weight of iron powder having a particle size between about. 55 and 130 μπι. The toner powder in the developer thus obtained had a pronounced positive polarity. The triboelectric charge was 12 150720 to +13 μθ per day. g toner powder. By means of this developer, combined with a zinc oxide photoconductor as described in the description of Dutch patent application 7217484, first-class copies on plain paper were obtained in an automatic working photocopier, the developer allowing wide tolerances with respect to the setting of the apparatus functions and with taking into account the concentration of the toner. The toner powder also showed a very good permanence during prolonged use in the copier. In an endurance test at which the concentration of the toner in the developer was kept constant by the addition of extra toner powder to compensate for the toner powder used in the copying process, good quality copies were still obtained after making 40,000 prints. In a jet melting apparatus as described in the description of Dutch patent application No. 7205491, the toner powder can be fixed fast and well on paper at a fixation temperature of approx. 150 ° C. The toner powder could also be fixed in a contact melting apparatus. The contact melting apparatus used was provided with a roller coated with silicone rubber, the upper layer of which had previously been aged by a prolonged copying process. Smelting areas were found that were narrower, but more similar to practice than using new silicone rubber. The effective contact time of the copy with the heated roller amounted to 1.3 seconds. The toner powder had a reasonable melting range, namely from 87 to 109 ° C (range width 22 ° C). In this case, the lower limit was the temperature at which the melting of the toner powder was just sufficient, and the upper limit was the temperature at which the transfer of the melted toner powder to the silicone rubber set.

Example 2

The preparation of Example 1 was repeated in batches of 630 g, 6.3 kg and 125 kg respectively. The measurement and copy results for the toner powder so obtained were practically the same as described in Example 1, one of which can be concluded that the reproducibility of the manufacture is good.

Example 3 In a powder mixer, a ground mixture of nigrosine base, N-cyclohexyl-p-toluenesulfonamide and benzoic acid at room temperature was mixed with Epikote® 006 and carbon in the ratios of Example 1.

This mixture was then extruded in one operation in a double-screw laboratory extrusion model, Davo M.S.2.1, at a temperature of 150 ° C in the kneading zones. The residence time was approx. 5 minutes. The cooled melt was worked up into toner powder and tested in the manner described in Example 1 to obtain practically the same results. These results, obtained after a preparation whereby the residence time and temperature conditions were distinctly different from those used in Example 1, illustrate that there is a wide margin with respect to the applicable manufacturing conditions.

Example 4

Following the procedure described in Example 1, a hot melt was prepared from 36 g of nigrosine base, 60 g of N-cyclohexyl-p-toluenesulfonamide, 416.8 g of Epikoti® .006 and 36 g of carbon, but now with 51.2 g. of the modifying compound 4- (α, α-dimethylbenzyl) phenol (= β-cumylphenol, supplied by Fluka). After cooling, grinding and sieving, a toner powder with a particle size of between 7 and 28 μπι was obtained. The EEV value of the modified epoxy resin was greater than 40,000. The modification rate was 100%. The Tg of the toner powder was 50 ° C and remained constant after prolonged heating to 200 ° C.

In a developer prepared as in Example 1, the toner powder could be provided with a pronounced positive charge of 13 uC / g. The toner powder hardly dusted during use, suggesting a largely uniform charge distribution. Excellent image quality was achieved. The toner powder was uniquely permanent and could be fixed in a jet melting apparatus at a setting temperature of 145 ° C. The contact melting range was 81 to 107 ° C (width 26 ° C).

Using the above composition, a toner powder was also prepared in an A.M.K. kneading mixer at an equilibrium temperature of approx. 110 ° C and a total residence time of 2 hours. The EEV value of the thus obtained modified resin was 15,000. Its Tg was 54 ° C and remained almost unchanged after heating for some time to 200 ° C. The copy and melt results were practically the same as for the toner powder produced by the hot melt method.

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Example 5

Following the procedure of Example 1, a hot melt was prepared from 36 g of nigrosine base, 30 g of N-cyclohexyl-p-toluenesulfonamide, 406.6 g of Epikote ™ 100e and 36 g of carbon, but now with 61.4 g of the modifying compound octadecanoic acid (equivalent weight = 285). After cooling, grinding and sieving, a toner powder with a particle size of between 8 and 32 µm was obtained. Its Tg was 43 ° C and remained constant, even after heating for some time up to 200 ° C. The EEV value of the modified resin was 40,000. The modification rate was 90%. In a developer prepared as in Example 1, the toner powder could be provided with a pronounced positive charge of 14 µC / <. It dusted very little. Very good image quality was achieved. The toner powder was suitably pernanent, could be fixed in a jet melting apparatus at 135 ° C, and had a contact melting range of 75 to 98 ° C (width 23 ° C).

Example 6 In a reaction vessel as described in Example 1, 528 g of EpikotJ ™ 004 (EEV = 900), 36 g of nigrosine base and 66 g of benzoic acid were mixed for 1 hour at 200 ° C. The components are thus completely dissolved in each other. Then, 36 g of carbon was added and stirring was continued for another hour at 200 ° C. The cooled melt was ground and sieved to a toner powder having a particle size of between 8 and 24 µm. The EEV value was 40,000. Before and after heating to 200 ° C, the toner powder had a constant Tg value of 63 ° C. The charge of the toner powder in a 4% developer was 11 µC / g. Good image quality was achieved. The toner powder could be fixed to paper at a temperature of 155 ° C in the jet melting apparatus. The contact melting range was 87 to 103 ° C (width 16 ° C).

Example 7

Example 1 was repeated, but now with 36 g of nigrosine hydrochloria (Color Index, 3rd edition # 50415) instead of the nigrosine base. The EEV value and the constant Tg value for the toner powder were 40,000 and 66 ° C, respectively. Satisfactory copying and melting results were obtained.

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Example 8

Example 1 was repeated, but now with 31.9 g of 2-hydroxybenzoic acid instead of benzoic acid and with 436.1 g of Epikot® L006. The degree of modification was 90¾. The EEV value and the constant Tg value were 40,000 and 57 ° C, respectively. Satisfactory copying and melting results were obtained.

Example 9

Example 1 was repeated, but now with 41.1 g of 3,4-dimethoxybenzoic acid instead of benzoic acid and with 426.9 g of Epikote 1006. The degree of modification was 90S. The EEV value and the constant Tg value were 40,000 and 57 ° C, respectively. Good copy and melt results were obtained.

Example 10 (Comparative Example)

The preparation of Example 1 was repeated but now omitting the modifying compound benzoic acid. The cooled melt could only be milled with difficulty, and the toner powder obtained could not be fixed in the jet melting apparatus below the burning limit of the paper.

Example 11

Following the method of Example 1, a hot melt was prepared from 30 g of nigrosine base, 75 g of N-cyclohexyl-p-toluenesulfonamide, 12.5 g of 4- (α, α-dimethylbenzyl) phenol, 352.5 g Epicote ^ .006 and 30 g of carbon. The EEV value was 21,000. The remainder of the unreacted modifier compound was <0.1%. The Tg value was 54 ° C and did not change after heating for 30 minutes to 200 ° C.

The degree of modification induced by the phenol amounted to 30%. In a developer prepared in the manner described in Example 1, from the cooled melt, toner powder having a particle size of between 7 and 31 µm obtained a pronounced positive charge of 13 µC / g. The toner powder provided excellent copies in a copier, allowing wide tolerances in setting the device's functions and the concentration of the toner. In a jet melting apparatus, the toner powder could be fixed at a temperature of 155 ° C.

In the contact melting apparatus described above, the melting range was 88 to 121 ° C (width 33 ° C).

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Example 12

Analogous to the procedure of Example 1, a hot melt was prepared from 36 g of nigrosine, 60 g of N-cyclohexyl-p-toluene sulfonamide, 51.6 g of benzoic acid, and 372 g of Epicot® .004. After mixing for 1 hour, the EEV value of the resin increased from 900 to 40,000 (90% modification). Then 36 g of carbon and 96 g of Rutapox® OT-1 were added and stirring was continued for 1 hour at 220 ° C (Rutapox 07-17 is a bi-phenol-A-epichlorohydrin-phenoxy resin having an average molecular weight of 25 to 30,000 , supplied by Bakelite). The Tg value of the mixture was 47 ° C and remained constant after heating to 200 ° C. The toner powder produced from this mixture had a particle size distribution between 9 and 28 µm. The achievable charge was 12 µC / g. Excellent copies were obtained. The toner powder could be fixed in a jet melting furnace at 145 ° C and had a wide contact melting range, namely 79 to 114 ° C (width 35 ° C).

A comparable toner powder which did not contain Rii · tapox 07-17, but only modified EpikotJ% 004 as a resin, had a contact melting range of 80 to 96 ° C (width 16 ° C).

Example 13 In a powder mixer, a ground mixture of 36 g of nigrosine base, 60 g of N-cyclohexyl-p-toluenesulfonamide, 9.7 g of benzoic acid and 9.3 g of succinic acid was mixed with 36 g of carbon and 449 g of Epicote .006. This mixture was then extruded at 160 ° C. The residence time in the extrusion device was approx. 5 minutes. The mixture had a constant Tg value of 61 ° C. The EEV value was greater than 40,000. The modification rate with benzoic acid was 30%. The toner, after being mixed with iron to give a 4%, gives a good image quality and has a wide contact melting range of 89 to 129 ° C (width 40 ° C).

Example 14 In the same manner as in Example 1, 36 g of nigrosine base, 60 g of N-cyclohexyl-p-toluenesulfonamide, 468 g of Epikote® Oe and 36 g of carbon were mixed for 2 hours at 200 ° C. Then a mixture of 6 g of nigrosine base, 10 g of N-cyclohexyl-p-toluenesulfonamide, 5.0 g of benzoic acid 79 g of Epikote% 006 and 6 g of carbon was added and stirred for an additional 30 minutes at 200 ° C. . After cooling, grinding and sieving, a two-grain powder was obtained which, after examination in the manner described in Example 1

Claims (3)

150720 gave a good copy quality with wide tolerances in terms of toner / iron ratio and in setting the apparatus. The constant Tg value was 68 ° C and the EEV value was 40,000. The amount of benzoic acid modified epoxy resin in the toner was 15%. The toner could be fixed well at a setting temperature of 170 ° C in the jet melting apparatus. In the arrangement described above, the cash melting range was 99 to 148 ° C (width 49 ° C). Example 15 Substantially in the same manner as described in Example 1, a hot melt was prepared by heating a mixture of 341.6 g Epicotyl 100l (mp 60-70 ° C; Durrance; EEV 450-500) with continuous stirring. 124.4 g of 4- (α, α-dimethylbenzyl) phenol 48.0 g of nigrosine base GB 48.0 g Printex ^ G for 1 hour to 200 ° C. The EEV value of the EpikotJ1OO1 used was found to be increased to 16,300. Then little by little /? 5 \ 240. RutapoxvsO7-17 while maintaining the temperature at 200 ° C and with continued stirring. After approx. another 1 hour the mixture turned out to be completely homogeneous. Then the mixture was cooled and ground and sieved to a toner powder with a particle size between 8 and 25 μπι. The contact melting range of this toner powder ranged from 83 to 140 ° C, making it particularly suitable for use in a developer for use in a copier equipped with a contact melting apparatus. 1. Positive rechargeable toner powder consisting essentially of finely divided colored toner particles containing an insulating thermoplastic resin, coloring agents and a polarity regulator, characterized in that the thermoplastic resin comprises at least 50% by weight of an epoxy resin which has an epoxy equivalent weight of at least 10,000 and is obtained by modifying its epoxy groups for at least 5% with a monofunctional carboxylic acid and / or a monofunctional phenol bearing no substituent except the carboxyl or hydroxyl group.