EP0681225A1 - Electrostatic toner comprising phenacyl compounds - Google Patents

Abstract

Electrostatic toner contains a polymeric binder and, as charge stabiliser, a phenylacyl cpd. of formula (I): Het (+) - L - CD - Phe-R An (-) (I); Het (+) = a positively charged gp. derived from an heterocycle of the pyrazole, imidazole, pyridine, (iso)quinoline series; L = 1-8C alkylene; Phe = phenylene, opt. with an annelated benzene ring; R = H, OH, 1-4C alkoxy, NH2, 1-4C mono- or dialkylamino or an opt. substd. 1-6C alkyl, phenyl, phenoxy, mono- or diphenylamino or N-(1-4C alkyl)-N-phenyl-amino gp.; and An (-) = the equiv. of an anion. Also claimed is the use of (I) as charge stabiliser in electrostatic toners.

Description

in der
der Ring A benzoanelliert sein kann und

Het^⊕

den positiv geladenen Rest eines Heterocyclus, der aus der Pyrazol-, Imidazol-, Pyridin-, Chinolin- oder Isochinolinreihe stammt,

L

C₁-C₈-Alkylen,

R

Wasserstoff, gegebenenfalls substituiertes C₁-C₆-Alkyl, gegebenenfalls substituiertes Phenyl, Hydroxy, C₁-C₄-Alkoxy, gegebenenfalls substituiertes Phenoxy, Amino, C₁-C₄-Mono- oder Dialkylamino, gegebenenfalls substituiertes Mono- oder Diphenylamino oder gegebenenfalls substituiertes N-(C₁-C₄-Alkyl)-N-phenylamino und

An^⊖

das Äquivalent eines Anions bedeuten,

sowie die Verwendung der obengenannten Verbindungen als Ladungsstabilisatoren in elektrostatischen Tonern.The present invention relates to new electrostatic toners containing a polymeric binder and a charge of a compound of formula I as a charge stabilizer

in the
the ring A can be fused to benzo and

Het ^⊕

the positively charged residue of a heterocycle which comes from the pyrazole, imidazole, pyridine, quinoline or isoquinoline series,

L

C₁-C₈ alkylene,

R

Hydrogen, optionally substituted C₁-C₆-alkyl, optionally substituted phenyl, hydroxy, C₁-C₄-alkoxy, optionally substituted phenoxy, amino, C₁-C₄-mono- or dialkylamino, optionally substituted mono- or diphenylamino or optionally substituted N- (C₁ -C₄-alkyl) -N-phenylamino and

On ^⊖

mean the equivalent of an anion,

and the use of the above compounds as charge stabilizers in electrostatic toners.

Latent electrostatic image recordings are developed by inductively depositing the toner on the electrostatic image. The charge stabilizers stabilize the electrostatic charge on the toner. This makes the picture more vivid and sharper.

• Fähigkeit zur Entwicklung des latenten elektrostatischen Bildes zu einem farbstarken sichtbaren Bild.
• Leichte Verteilbarkeit in der Tonerzubereitung, um ein störungsfreies, konturenscharfes, gleichförmiges Bild zu erzeugen.
• Unempfindlichkeit gegen Feuchtigkeit.
• Hohe Thermostabilität.

The charge stabilizers used must meet a wide range of requirements:

• Ability to develop the latent electrostatic image into a highly visible color image.
• Easily distributable in the toner preparation in order to produce a trouble-free, contour-sharp, uniform image.
• Insensitivity to moisture.
• High thermal stability.

From WO-A-93/02397, WO-A-93/02400, WO-A-93/02053 and WO-A-93/02054 electrostatic toners are known which, as charge stabilizers, contain pyridinium salts containing ester groups, such as N- (ethoxycarbonylmethyl ) have pyridinium tetraphenylborate or N- (2-benzoyloxyethyl) pyridinium tetraphenylborate.

However, it has been shown that the charge stabilizers of the prior art frequently have deficiencies in their requirement profile.

It was therefore an object of the present invention to provide a new electrostatic toner which has charge stabilizers which have advantageous performance properties.

We have found that this object is achieved by the electrostatic toners described in the introduction, containing phenacyl derivatives of the formula I as charge stabilizers.

All of the alkyl and alkylene groups occurring in the abovementioned formula I can be either straight-chain or branched.

When substituted alkyl groups appear in the above formula I, e.g. Hydroxy, C₁-C₄-alkoxy, carboxyl or C₁-C₄-alkoxycarbonyl come into consideration. The alkyl groups then generally have 1 or 2 substituents.

When substituted phenyl groups occur in the above formula I, e.g. C₁-C₄ alkyl, C₁-C₄ alkoxy, halogen or hydroxy come into consideration. The phenyl groups then generally have 1 to 3 substituents.

Suitable heterocycles Het, which are the basis of the rest Het ^⊕ , come from the pyrazole, imidazole, pyridine, quinoline or isoquinoline series.

worin

X¹, X², X³ und X⁴

unabhängig voneinander jeweils für Wasserstoff oder C₁-C₆-Alkyl und

X⁵

für Wasserstoff, Carboxyl, Carbamoyl oder C₁-C₄-Alkoxycarbonyl stehen.

For example, you have the following structures:

wherein

X¹, X², X³ and X⁴

independently of one another each for hydrogen or C₁-C₆-alkyl and

X⁵

represent hydrogen, carboxyl, carbamoyl or C₁-C₄ alkoxycarbonyl.

R, X¹, X², X³ and X⁴ are e.g. Methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl, hexyl or 2-methylpentyl.

R radicals are also, for example, carboxymethyl, 2-carboxyethyl, 2- or 3-carboxypropyl, 2- or 4-carboxybutyl, 2-hydroxyethyl, 2- or 3-hydroxypropyl, 2- or 4-hydroxybutyl, 2-methoxyethyl, 2-ethoxyethyl , 2-propoxyethyl, 2-isopropoxyethyl, 2-butoxyethyl, 2- or 3-methoxypropyl, 2- or 3-ethoxypropyl, 2- or 3-propoxypropyl, 2- or 3-butoxypropyl, 2- or 4-methoxybutyl, 2- or 4-ethoxybutyl, 2- or 4-propoxybutyl, 2- or 4-butoxybutyl, methoxycarbonylmethyl, ethoxycarbonylmethyl, 2-methoxycarbonylethyl, 2-ethoxycarbonylethyl, 2- or 3-methoxycarbonylpropyl, 2- or 3-ethoxycarbonylpropyl, 2- or 4- Methoxycarbonylbutyl, 2- or 4-ethoxycarbonylbutyl, 2-, 3- or 4-methylphenyl, 2,4-dimethylphenyl, 2-, 3- or 4-methoxyphenyl, 2,4-dimethoxyphenyl, 2-, 3- or 4-hydroxyphenyl , 2,4-dihydroxyphenyl, 2-, 3- or 4-chlorophenyl, 2,4-dichlorophenyl, methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, phenoxy, 2-, 3- or 4-methylphenoxy , 2,4-dimethylphenoxy, 2-, 3- or 4- Methoxyphenoxy, 2,4-dimethoxyphenoxy, 2-, 3- or 4-hydroxyphenoxy, 2,4-dihydroxyphenoxy, 2-, 3- or 4-chlorophenoxy, 2,4-dichlorophenoxy, mono- or dimethylamino, mono- or Diethylamino, mono- or dipropylamino, mono- or diisopropylamino, mono- or dibutylamino, mono- or diphenylamino, mono- or bis (4-chlorophenyl) amino or N-methyl-N-phenylamino.

Residues X⁵ are still e.g. Methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, isopropoxycarbonyl or butoxycarbonyl.

Residues L are e.g. CH₂, (CH₂) ₂, (CH₂) ₃, (CH₂) ₄, (CH₂) ₅, (CH₂) ₆, (CH₂) ₇, (CH₂) ₈, CH (CH₃) CH₂ or CH (CH₃) CH (CH₃ ).

Suitable anions on which the equivalent of an anion (An ⁽ ) is based are, for example, inorganic or organic anions, such as halide, for example fluoride, chloride, bromide or iodide, sulfate, hydrogen sulfate, methanesulfonate, trifluoromethanesulfonate, 2-hydroxyethanesulfonate, tetraphenylborate, tetrafluoroboroboron Toluene sulfonate, nitrate, perchlorate, 1-hydroxyethane-1,1-diphosphonate, phosphate, hydrogen phosphate, dihydrogen phosphate, formate, acetate, oxalate, citrate or tartrate.

Tetrafluoroborate is an anion.

Electrostatic toners containing a compound of the formula I in which Het ^{H is} derived from a heterocycle from the pyridine series, in particular from a pyridine of the formula IIc, are preferred.

Also preferred are electrostatic toners containing a compound of formula I in which L is C₁-C₆-alkylene, especially C₁- or C₂-alkylene.

Also preferred are electrostatic toners containing a compound of formula I in which ring A is not benzo-fused and R is hydrogen, C₁-C₄-alkyl, C₁-C₄-alkoxy or phenyl.

bedeutet, in der Z für Wasserstoff, Methyl, Carboxyl oder C₁-C₄-Alkoxycarbonyl steht, wobei Wasserstoff besonders hervorzuheben ist.Electrostatic toners containing a compound of the formula I in which Het ^{⊕ is} a radical of the formula IIf are particularly important

means in which Z represents hydrogen, methyl, carboxyl or C₁-C₄-alkoxycarbonyl, hydrogen being particularly emphasized.

The phenacyl compounds of the formula I are generally compounds which are known or can be obtained by methods known per se.

in der Hal Halogen, vorzugsweise Chlor oder Brom, bedeutet und L, R und der Ring A jeweils die obengenannte Bedeutung besitzen, mit einem Heterocyclus der Formel IV



        Het   (IV),



wobei Het die obengenannte Bedeutung besitzt, umsetzen. Man erhält auf diese Weise eine Verbindung der Formel I, in der An^⊖ Halogenid bedeutet.For example, a ketone of formula III

in the Hal is halogen, preferably chlorine or bromine, and L, R and the ring A each have the abovementioned meaning, with a heterocycle of the formula IV



Het (IV),



where Het has the meaning given above. This gives a compound of the formula I in which An ^is halide.

The reaction of components III and IV is advantageously carried out in an inert solvent such as toluene, xylene, petroleum ether, ligroin, cyclohexane, acetone, tetrahydrofuran, dioxane, methanol, ethanol, isopropanol, ethyl or ethyl acetate or acetonitrile. It is usually carried out at a temperature of 40 to 130 ° C, preferably 60 to 100 ° C, and under atmospheric pressure.

By salting these compounds with salts of the formula V



M ^⊕ An ^⊖ (V),



where M ^{⊕ is} the equivalent of a metal ion, in particular an alkali metal ion, and An ^⊖ (with the exception of halide) has the abovementioned meaning, in an aqueous medium it is possible, for example, to obtain those compounds of the formula I in which An ^{⊖ is different} from halide . Further details can also be found in the examples.

The proportion of the compounds of the formula I in the electrostatic toner is generally 0.01 to 10% by weight, based on the weight of the toner.

The polymeric binders contained in the new electrostatic toners are known per se. They are generally thermoplastic and have a softening point of 40 to 200 ° C, preferably 50 to 130 ° C and in particular 65 to 115 ° C. Examples for polymeric binders are polystyrene, copolymers of styrene with an acrylate or methacrylate, copolymers of styrene with butadiene and / or acrylonitrile, polyacrylates, polymethacrylates, copolymers of an acrylate or methacrylate with vinyl chloride or vinyl acetate, polyvinyl chloride, copolymers of vinyl chloride with vinylidene chloride, copolymers of vinyl chloride with vinyl acetate, polyester resins, epoxy resins, polyamides or polyurethanes.

In addition to the above-mentioned compounds of the formula I and the polymeric binders, the toners according to the invention can contain colorants, magnetically attractable material, waxes and flow agents in known amounts.

The colorants can be organic dyes or pigments such as nigrosine, aniline blue, 2,9-dimethylquinacridone, C.I. Disperse Red 15 (C.I. 6010), C.I. Solvent Red 19 (C.I. 26 050), C.I. Pigment Blue 15 (C.I. 74 160), C.I. Pigment Blue 22 (C.I. 69 810) or C.I. Solvent Yellow 16 (C.I. 12 700) or inorganic pigments such as carbon black, red lead, yellow lead oxide or chrome yellow. Generally, the amount of the colorant present in the toner does not exceed 15% by weight based on the weight of the toner.

The magnetically attractable material can be, for example, iron, nickel, chromium oxide, iron oxide or a ferrite of the formula MeFe₂O₄, in which Me is a divalent metal, e.g. Iron, cobalt, zinc, nickel or manganese.

The toners according to the invention are produced by customary processes, e.g. by mixing the constituents in a kneader and then pulverizing or by melting the polymeric binder or a mixture of the polymeric binders, then finely dividing one or more compounds of the formula I and the other additives, if used, into the molten resin using the for Mixing and kneading machines known for this purpose, then cooling the melt to a solid mass and finally grinding the solid mass into particles of the desired particle size (generally 0.1 to 50 μm). It is also possible to dissolve the polymeric binder and the charge stabilizer in a common solvent and to add the other additives to the solution. The solution can be used as a liquid toner.

However, the liquid can also be spray-dried in a manner known per se, the solvents evaporated or the liquid freeze-dried and the solid residue ground into particles of the desired particle size.

It is also possible not to dissolve the compounds of the formula I used as charge stabilizers, but rather to disperse them finely in the solution of the polymeric binder. The toner preparation thus obtained can then be used in a xerographic imaging system, for example according to US-A-4,265,990.

The compounds of formula I mentioned above are advantageous charge stabilizers. They generally satisfy the application profile initially mentioned and are particularly distinguished by the fact that, when added to a toner preparation, they give it a favorable electrostatic charging profile, i.e. the toners can be quickly and highly charged. The charge stabilizers to be used according to the invention furthermore ensure that the charge is kept constant at a high level.

The following examples are intended to explain the invention in more detail.

A) Preparation of the phenacyl compounds Example H1 Preparation of 4-methylphenacylpyridinium bromide

64 g (0.3 mol) of 4-methylphenacyl bromide were placed in 80 ml of acetone and heated to 60 ° C. Then 24 g (0.3 mol) of pyridine were slowly added dropwise. The reaction mixture was stirred at 60 ° C. for 1 hour and cooled to room temperature. The precipitated solid was filtered and washed with acetone. After drying, 82.5 g (corresponding to a yield of 94%) of the title compound were obtained in the form of a yellow powder. The purity of the product was over 99%.

Example H2 Preparation of 4-methylphenacylpyridinium tetrafluoroborate

30 g (0.1 mol) of 4-methylphenacylpyridinium bromide were placed in 120 ml of water and heated to 60 ° C. Then 11 g (0.1 mol) of sodium tetrafluoroborate were added and the mixture was slowly cooled to room temperature. The mixture was stirred at room temperature for 1 hour and the precipitated product was filtered off and washed with water. After drying, 22.2 g (corresponding to a yield of 74%) of the title compound were obtained in the form of a yellow solid. The purity of the product was over 99%.

Example H3 Preparation of 4-methylphenacylpyridinium tetraphenylborate

The title compound was prepared analogously to Example 2 from 4-methylphenacylpyridinium bromide and sodium tetraphenylborate in a yield of 100%.

Example H4 Preparation of 4-methoxyphenacylpyridinium bromide

The title compound was prepared analogously to Example 1 from 4-methoxyphenacyl bromide and pyridine in a yield of 97%.

Example H5 Preparation of 4-methoxyphenacylpyridinium tetrafluoroborate

The title compound was prepared analogously to Example 2 from 4-methoxyphenacylpyridinium bromide and sodium tetrafluoroborate in a yield of 85%.

Example H6 Preparation of 4-methoxyphenacylpyridinium tetraphenylborate

The title compound was prepared analogously to Example 2 from 4-methoxyphenacylpyridinium bromide and sodium tetraphenylborate in a yield of 100%.

Example H7 Production of 3-methoxyphenacylpyridinium chloride

The title compound was prepared analogously to Example 1 from 3-methoxyphenacyl chloride and pyridine in a yield of 93%.

Example H8 Production of naphthacylpyridinium bromide

The title compound was prepared analogously to Example 1 from ω-bromo-2-acetonaphthone and pyridine in a yield of 96%.

Example H9 Production of 4-tert-butylphenacylpyridinium chloride

The title compound was prepared analogously to Example 1 from 4-tert-butylphenacyl chloride and pyridine in a yield of 94%.

Example H10 Production of 4-isopropylphenacylpyridinium chloride

The title compound was prepared analogously to Example 1 from 4-isopropylphenacyl chloride and pyridine in a yield of 93%.

Example H11 Preparation of 4-phenylphenacylpyridinium bromide

The title compound was prepared analogously to Example 1 from 4-phenylphenacyl bromide and pyridine in a yield of 95%.

B) application

The application examples were carried out with colorant-free toner models consisting of resin and the charge stabilizers according to the invention.

I. Production of the toners Example A1

0.2 g of the compound from Example H1 was introduced into a solution of 10 g of a non-crosslinked styrene / butyl acrylate resin in 100 ml of p-xylene at room temperature and then freeze-dried and ground. Toner particles with an average particle size of 50 μm were produced by screening.

Example A2

10 g of a non-crosslinked styrene / butyl acrylate resin and 0.2 g of the compound from Example H1 were mixed intensively in a mixer, kneaded at 120 ° C., extruded and ground. Toner particles with an average particle size of 50 μm were produced by screening.

Example A3

0.2 g of the compound from Example H2 were introduced into a solution of 10 g of a linear polyester resin in 100 ml of p-xylene at room temperature and then freeze-dried and ground. Toner particles with an average particle size of 50 μm were produced by screening.

Example A4

10 g of a linear, non-crosslinked polyester resin and 0.2 g of the compound from Example H2 were mixed intensively in a mixer, kneaded at 120 ° C., extruded and ground. Toner particles with an average particle size of 50 μm were produced by screening.

Example A5

10 g of a linear, non-crosslinked polyester resin and 0.2 g of the compound from Example H3 were mixed intensively in a mixer, kneaded at 120 ° C., extruded and ground. Toner particles with an average particle size of 50 μm were produced by screening.

Example A6

0.2 g of the compound from Example H5 was introduced into a solution of 10 g of a linear polyester resin in 100 ml of p-xylene at room temperature and then freeze-dried and ground. Toner particles with an average particle size of 50 μm were produced by screening.

Example A7

10 g of a linear, non-crosslinked polyester resin and 0.2 g of the compound from Example H5 were mixed intensively in a mixer, kneaded at 120 ° C., extruded and ground. Toner particles with an average particle size of 50 μm were produced by screening.

Example A8

10 g of a linear, non-crosslinked polyester resin and 0.2 g of the compound from Example H6 were mixed intensively in a mixer, kneaded at 120 ° C., extruded and ground. There were produced by screening toner particles with an average particle size of 50 μm.

Example A9

0.2 g of the compound from Example H7 was introduced into a solution of 10 g of a non-crosslinked styrene / butyl acrylate resin in 100 ml of p-xylene at room temperature and then freeze-dried and ground. Toner particles with an average particle size of 50 μm were produced by screening.

Example A10

0.2 g of the compound from Example H8 were introduced into a solution of 10 g of an uncrosslinked styrene / butyl acrylate resin in 100 ml of p-xylene at room temperature and then freeze-dried and ground. Toner particles with an average particle size of 50 μm were produced by screening.

Example A11

0.2 g of the compound from Example H9 was introduced into a solution of 10 g of a non-crosslinked styrene / butyl acrylate resin in 100 ml of p-xylene at room temperature and then freeze-dried and ground. Toner particles with an average particle size of 50 μm were produced by screening.

Example A12

0.2 g of the compound from Example H10 was introduced into a solution of 10 g of a non-crosslinked styrene / butyl acrylate resin in 100 ml of p-xylene at room temperature and then freeze-dried and ground. Toner particles with an average particle size of 50 μm were produced by screening.

Example A13

0.2 g of the compound from Example H11 were introduced into a solution of 10 g of a non-crosslinked styrene / butyl acrylate resin in 100 ml of p-xylene at room temperature and then freeze-dried and ground. Toner particles with an average particle size of 50 μm were produced by screening.

II. Development of the developer and testing

To produce a developer, 99% by weight of a steel carrier, which had an average particle size of 100 μm, was precisely weighed in with 1% by weight of the toner and activated on a roller stand for a period specified below. The electrostatic charge of the developer was then determined. About 5 g of the activated developer were filled into a hard-blow-off cell, which was electrically connected to an electrometer, in a commercial q / m meter (company Epping GmbH, Neufahrn). The mesh size of the sieves used in the measuring cell was 63 µm.

This ensured that the toner was blown out as completely as possible, but the carrier remained in the measuring cell. The toner was almost completely removed from the carrier particles by a strong air flow (approx. 4,000 cm³ / min) and simultaneous suction, the latter remaining in the measuring cell. The charge on the carrier was registered on the electrometer. It corresponded to the amount of charging of the toner particles, but with the opposite sign. The amount of q with the opposite sign was therefore used to calculate the q / m value. The mass of blown-off toner was determined by weighing the measuring cell back and the electrostatic charge q / m was calculated therefrom.

The charge determined on the toners is summarized in the following table. table Example No. Connection from example Preparation of the toner * Charging after activation of 10 min 30 min 60 min 120min [µC / g] A1 H1 G 6.8 5.5 5.1 4.2 A2 H1 K 4.2 2.9 2.6 2.8 A3 H2 G 20.6 22.7 24.7 24.0 A4 H2 K 7.5 7.1 7.6 7.6 A5 H3 K 11.6 13.6 12.9 12.1 A6 H5 G 24.5 24.3 25.7 24.7 A7 H5 K 10.5 11.2 10.5 11.5 A8 H6 K 13.7 13.7 13.6 13.6 A9 H7 G 9.3 7.0 6.6 6.2 A10 H8 G 6.7 5.1 4.4 3.8 A11 H9 G 1.8 1.7 1.5 1.4 A12 H10 G 1.9 2.2 1.8 1.8 A13 H11 G 6.7 4.6 3.1 2.2 * The toner was prepared either by freeze-drying according to Example A1 (marked "G" in the table) or by kneading at a temperature above the softening point of the resin according to Example A2 (marked "K" in the table).

Claims (6)

Electrostatic toners containing a polymeric binder and a charge of a compound of formula I as a charge stabilizer

in the
the ring A can be fused to benzo and Het ^⊕ the positively charged residue of a heterocycle which comes from the pyrazole, imidazole, pyridine, quinoline or isoquinoline series, L C₁-C₈ alkylene, R is hydrogen, optionally substituted C₁-C₆-alkyl, optionally substituted phenyl, hydroxy, C₁-C₄-alkoxy, optionally substituted phenoxy, amino, C₁-C₄-mono- or dialkylamino, optionally substituted mono- or diphenylamino or optionally substituted N- ( C₁-C₄-alkyl) -N-phenylamino and An ^{⊖ is} the equivalent of an anion. Electrostatic toner according to claim 1, containing a compound of formula I, in which Het ^{⊕ is} derived from a heterocycle from the pyridine series. Electrostatic toners according to claim 1, containing a compound of formula I in which L is C₁-C₆ alkylene. Electrostatic toners according to claim 1, containing a compound of formula I in which ring A is not benzo-fused and R is hydrogen, C₁-C₄-alkyl, C₁-C₄-alkoxy or phenyl. Electrostatic toner according to claim 1, containing 0.01 to 10 wt .-%, based on the weight of the toner, of a compound of formula I. Use of the compounds of formula I according to claim 1 as charge stabilizers in electrostatic toners.