WO2008098929A1

WO2008098929A1 - Method for preparing polyester-polyolefin hybrid particles

Info

Publication number: WO2008098929A1
Application number: PCT/EP2008/051673
Authority: WO
Inventors: Yvonne Wilhelmina Smak; Gerardus Cornelis Overbeek
Original assignee: Dsm Ip Assets B.V.
Priority date: 2007-02-12
Filing date: 2008-02-12
Publication date: 2008-08-21

Abstract

The present invention relates to a method for preparing polyester-polyolefin hybrid aggregates comprising - providing an aqueous dispersion comprising polyester-polyolefin hybrid particles, said particles comprising a polyester and a polymerized olefinically unsaturated compound, which polymerized compound may be ungrafted or grafted to the polyester; - aggregating the hybrid particles; - preferably isolating the aggregates from the dispersion; and - preferably drying the aggregates.

Description

METHOD FOR PREPARING POLYESTER-POLYOLEFIN HYBRID PARTICLES

The invention relates to a method for preparing aggregates, comprising a polyester-polyolefin hybrid. The invention further relates to aggregates comprising a polyester-polyolefin hybrid and to a toner or developer, in particular for use in electroreprography comprising such aggregates.

Electroreprography is any process in which an image is reproduced by means of electricity and incident radiation, usually electromagnetic radiation, more usually visible light. Electroreprography comprises the technology of electrophotography which encompasses photocopying and laser printing technologies. In both these technologies a latent, electrostatic image is produced, in charge, by exposure of a photoconductive drum to light. The exposure can either be from light reflected from an illuminated image (photocopying) or from a laser which scans the drum, usually under instruction from a computer (laser printing). Once a latent image has been produced in charge it must be developed to form a visible image on the drum which can then be transferred onto a suitable substrate so a hard copy of the image is obtained (e.g. by printing onto paper).

Suitable developers, which may be liquid or dry compositions, comprise particles of a toner which are electrostatically attracted to the latent image. Liquid developers comprise a toner dispersed in an insulating liquid. Dry developers may comprise single component systems comprising a toner, or two component systems which comprise a mixture of a toner and a carrier. A toner may comprise particles of a polymeric component, a coloring agent and optionally other internal and/or external additives such as charge control agents and/or surface additives to improve the flowability of the toner particles. The polymeric component of the toner is electrically insulating to enable the toner to be electrostatically charged during the electroreprographic process. The polymer also acts to fix the toner to the printed substrate, usually by fusion of the polymer onto the substrate by heating. The coloring agent, which is usually a pigment, imparts the required color to the toner. WO 98/50828 describes a method for making particulate compositions for use in electroreprography, wherein a dispersion is made of polymer particles, such as particles made by polymerizing olefinically unsaturated monomers in an emulsion, thereby forming a polymer latex. Thereafter association of the latex is induced by adjusting the pH. This method typically requires the use of a surfactant, which may be detrimental to the product properties of the particles, unless they are removed, which adds to the complexity and manufacturing time of the particles.

It is an object of the present invention to provide a novel method for making aggregated particles comprising a polymer, in particular such aggregated particles for use in a toner or developer. In an embodiment, it is an object of the invention to provide a simple method, more in particular a method not requiring a surfactant.

It is further an object of the invention to provide novel aggregated particles comprising a polymer, in particular such aggregated particles suitable for use in a toner or a developer. It is further an object to provide a novel toner or developer for electroreprography.

One or more objects that may be solved in accordance with the invention will be apparent from the remainder of the description and/or the claims.

It is now found that one or more of the problems identified herein are solved by preparing aggregates based on a specific polymeric hybrid from a polyester and a polyolefinically unsaturated compound.

Accordingly, the present invention relates to a method for preparing polyester-polyolefin hybrid aggregates comprising - providing an aqueous dispersion comprising polyester-polyolefin hybrid particles, said hybrid particles comprising a polyester and a polymerized olefinically unsaturated compound, which polymerized compound may be ungrafted or grafted to the polyester;

- aggregating the hybrid particles, optionally in the presence of at least one additive, such as at least one additive selected from the group of colorants (including pigments and dyes); magnetic additives; charge-control agents; waxes; and flow control agents, thereby forming the aggregates;

- optionally isolating the aggregates from the dispersion; and

- optionally drying the aggregates.

In particular the dispersion may be provided by preparing an aqueous dispersion comprising a polyester and a polymerizable, olefinically unsaturated compound and polymerizing the olefinically unsaturated compound in the dispersion.

In an embodiment the method comprises

- providing the dispersion by adding the olefinically unsaturated compound to solid or molten polyester; thereafter

- dispersing the combined olefinically unsaturated compound and polyester; thereafter - starting the polymerization, usually by adding an initiator; and - adding additional olefinically unsaturated compound (which may be the same or different from the earlier added olefinically unsaturated compound), and optionally adding additional initiator (which may be the same or different from the earlier added initiator), during the polymerization In an embodiment, the method comprises

- combining the polyester, preferably a polyester essentially free of acid groups, with a surfactant; thereafter

- dispersing the polyester in the presence of the surfactant; thereafter

- adding olefinically unsaturated compound to the dispersion; and thereafter - polymerizing the olefinically unsaturated compound.

In an embodiment, the method comprises

- combining the polyester, preferably a polyester essentially free of acid groups, with a surfactant;

- adding olefinically unsaturated compound to the polyester combined with the surfactant; thereafter

- dispersing the polyester in the presence of the surfactant and the olefinically unsaturated compound; and thereafter

- polymerizing the olefinically unsaturated compound.

The invention further relates to polyester-polyolefin hybrid aggregates, such as obtainable by a method of the invention, comprising a polyester - in particular an acidic polyester as described herein - and a polymerized olefinically unsaturated compound as described herein. It should be noted that the phrase "olefinically unsaturated" in a "polymerized olefinically unsaturated compound" in general relates to such unsaturations in the compound before polymerizing the compound. These unsaturations are generally fully or partially used to form the polymer. Accordingly, the polymerized compound may be free of such unsaturations, although in principle one ore more olefinically unsaturated groups may be present in the polymerized compound.

Aggregates according to the invention may in particular be characterized by being based on primary polyester-polyolefin hybrid particles, wherein the primary hybrid particles are based on a polyester having a number average molecular weight of 1.5 to 80 kg/mol, in particular of 2.5 to 80 kg/mol, more in particular of 3.5 to 80 kg/mol and a polymerized olefinically unsaturated compound having a number average molecular weight of at least 5 kg/mol, in particular 20 to 10 000 kg/mol. -A-

In particular, the average glass transition temperature (as defined below) of the part of the hybrid formed by the polymerized olefinically unsaturated compound may be in the range of 0-110 ⁰C.

The invention further relates to a toner or developer for electroreprography, comprising aggregates according to the invention.

The invention further relates to polyester-polyolefinic (primary) hybrid particles (such as obtainable by a polymerization method) as described herein.

The invention further relates to the use of such (primary) hybrid particles for preparing a toner or developer developer for electroreprography. The invention further relates to a toner or developer for electroreprography, comprising polyester-polyolefinic (primary) hybrid particles as described herein.

The term "hybrid" is used herein for a combination of at least two different classes of polymers, namely a polyester and a polymerized olefinically unsaturated compound other than a polyester. The polymerized olefinically unsaturated compound may be referred to as the "polyolefin". The hybrid may be a composition of at least two classes of polymers wherein polymers of the different classes are essentially not covalently bound, or the hybrid may be a copolymer comprising one or more polyester segments to which one or more segments of the polymerized olefinically unsaturated compounds are essentially covalently bound. In an embodiment, the hybrid is a graft copolymer, wherein the polyester usually provides the backbone and the polymerized olefinically unsaturated compounds provide the grafts.

Usually, during polymerization (primary) hybrid particles are formed, which may thereafter be allowed to form aggregates. The diameter of the primary hybrid particles as used herein is the value that can be determined as described in ISO 13321 , using a 1 mM solution of NaCI in water.

The primary hybrid particles, generally are nanoparticles and may in particular have a (volume) average diameter of at least 50 nm, preferably of at least 70 nm. Usually, the (weight) average diameter is up to 200 nm, preferably up to 130 nm.

The term "aggregates" is used herein for particles that are formed of a cluster of smaller particles, in particular a cluster of primary hybrid particles, that are physically or chemically bound together. Floes are examples of aggregates. Floes are aggregates wherein the smaller particles are relatively loosely bound, in particular at least predominantly by relatively weak forces, such as by Van der Waals forces, hydrogen bonds or other dipole-dipole attractions, ion-dipole attractions, entanglement of polymer chains and the like, rather than at least predominantly by essentially covalent or electrostatic bonds.

A preferred diameter for the aggregates depends on the intended use. The diameter for the aggregates given herein is a linear dimension corresponding to the diameter of a sphere approximately of same volume as the aggregate of interest which may be substantially irregular in shape. The diameter may in particular be determined using a Coulter counter, as in WO 98/50828.

In particular for aggregates for use as toner or developer particles, the following applies. Usually at least 50 vol.%, in particular, at least 80 vol.%, preferably at least 90 vol.%, in particular at least 95 vol.% of the aggregates have a diameter from 2 μm to about 20 μm. Preferably said upper limit is 15 μm, in particular 10 μm. For high resolution printing, said upper limit preferably is 5 μm. For practical reasons said lower limit may be at least 3 μm. A low spread in diameter range (Ae. having a large volume fraction of the particles, within a particular range) is in particular advantageous for a high printing accuracy. For a particularly high printing accuracy, preferably at least 90 vol.% of the particles have a diameter falling within a range of 4 μm or less, for instance at least 90 vol.% of the particles having a diameter within the range of 2-6 μm, or 3-7 μm. The term "aqueous" is used herein for water and for liquids comprising water as the major solvent, i.e. more than 50 wt.% based on total liquids (excluding liquid olefinically unsaturated compound, which is generally not dissolved in water) up to 100 wt.%. In particular, the term aqueous is used in case the water content is at least 80 wt.%, at least 90wt. %, at least 95 wt.%, or at least 99 wt.%. The balance of solvent may be formed by one or more solvents that are fully dissolvable in or miscible with water at a molecular level, such as lower alcohols, in particular methanol, ethanol or propanol. A high water content is in particular preferred for avoiding an odor that may be considered as unpleasant by the end-user or avoiding a fire hazard. As used herein, the term "polymer" denotes a structure that essentially comprises a multiple repetition of units derived, actually or conceptually, from molecules of low relative molecular mass. Such polymers may include crosslinked networks, branched polymers and linear polymers. Oligomers are considered a species of polymers, i.e. polymers having a relatively low number of repetitions of units derived, actually or conceptually, from molecules of low relative molecular mass. As used herein, the term "prepolymer" denotes a polymer comprising one or more polymerizable functionalities, for instance vinyl groups.

Generally, polymers may have a number average molecular weight (Mn) of 200 Da or more, 400 Da or more, 800 Da, 1000 Da or more, 2000 Da, or more, 4000 Da or more, 8000 Da or more, 10 000 Da, or more, 100 000 Da or more or 1 000 000 Da or more. Polymers having a relatively low mass, e.g. of 8000 Da or less, in particular 4000 Da or less, more in particular 1000 Da or less may be referred to as oligomers.

The number or weight average molecular weight as used herein can be determined as described in DIN 55672. The values used herein are based on tetrahydrofuran as a solvent and polystyrene as standards.

The term "or" as used herein means "and/or" unless specified other wise.

The term "a" or "an" as used herein means "at least one" unless specified other wise.

When referring to a moiety (e.g. a compound, an additive etc.) in singular, the plural is meant to be included. Thus, when referring to a specific moiety, e.g. "compound", this means "at least one" of that moiety, e.g. "at least one compound", unless specified otherwise. The invention allows the preparation of aggregated hybrid particles in a relatively simple way, amongst others because the method may be carried out without using surfactants to facilitate dispersing the olefinically unsaturated compound or polyester, although in principle it is possible to use a surfactant.

Further, the aggregates according to the invention have satisfactory properties, or even one or more improved properties, in particular with respect to geometry; physical properties, such as melt flow rheology; mechanical properties; or size distribution, especially for use in a toner or a developer or the like.

Compared to (the manufacture of) 100 % polyolefinic aggregates suitable for use in a toner or developer or the like, such as acrylic aggregates, the invention allows the provision of a relatively cheap product, whilst maintaining such satisfactory properties, or even one or more improved properties. In particular, the invention may provide one or more of the following advantages over fully polyolefinic aggregates:

- improved fusion behavior of the aggregated primary hybrid particles; - improved high speed printing; - improved, especially more easily obtained, glossy appearance;

- comparable durability at a relatively low molecular weight of the polymerized olefinically unsaturated compound, or improved durability (of a printed image) at the same molecular weight. As used herein, the term "durability" in particular relates to scratch resistance, water resistance or resistance against ink from highlighter pens.

Further, the polyester and the olefinically unsaturated compound used in the method, respectively the polyester and the polymerized polyolefinic compound in the hybrid show satisfactory compatibility, in particular improved compatibility, compared to a process, wherein both polymers are blended. The term "compatibility" is used herein in particular to indicate that two or more moieties are sufficiently miscible without causing an unacceptable level of phase-separation, under process conditions or in the final product, in particular during use e.g. in a toner during printing.

It is in particular advantageous to carry out the polymerization of the olefinically unsaturated compound in the presence of the polyester over blending the polyester and the polyolefin with respect to obtaining a good visco-elastic behavior in a toner or developer application.

The polyester usually is a polyester comprising acidic groups, in particular carboxylic acid groups or sulfonic acid groups, although in principle, a neutral polyester may be used, especially if the dispersion is made using a suitable surfactant, such as an alkyl-ethercarboxylate, for dispersing the polyester. Unless specified otherwise, the term "acidic group" is meant to include both the free acid form, the ionised form and the corresponding salt.

Carboxylic acids groups are preferred for easy aggregation, in particular by using a pH change in order to form aggregates.

Preferably, the polyester has an acid value of at least 8 mg KOH/g polyester, in particular at least 15 mg KOH/g polyester, more in particular at least 20 mg KOH/g polyester, for facilitating the preparation of the dispersion, also in the absence of a suitable amount of a surfactant. In particular in case the forming of the aggregates involves an alteration of the pH (see below), the acid value of the polyester is usually up to 120 mg KOH/g polyester, preferably 80 mg KOH/g polyester or less, in particular 50 mg KOH/g polyester or less, 45 mg KOH/g polyester or less, or 38 mg KOH/g polyester or less, in order to facilitate the forming of aggregates. The acid value is determinable as described in ASTM D1639. The hydroxy value of the polyester, as determined according to ASTM E-1899-02, is usually from 0-300 mg KOH/g polyester. In particular, the hydroxy value may be up to 50 mg KOH/g, more in particular up to 25 mg KOH/g. Preferably, the hydroxy value is 15 mg KOH/g or less. With respect to an acid value respectively hydroxy value in a specific range, it is observed that the acid value respectively hydroxy value of the total polyester is meant. It is not necessary that essentially all individual polyester molecules have a value in such range, although this is possible. It is for instance also possible to provide a polyester with a acid value or hydroxy value in a desired range by combining suitable amounts of polyester molecules which are essentially free of acid groups or have an acid value or hydroxy value below a specified range with polyester molecules having an acid value or hydroxy value within or above a specified range.

The polyester usually has a number average molecular weight (Mn) of at least 1.5 kg/mol, in particular of at least 2.0 kg/mol, preferably of at least 3.5 kg/mol, in particular of at least 5 kg/mol, more in particular of at least 7.5 kg/mol, at least 10 kg/mol, or at least 13 kg/mol. A relatively high Mn is in particular preferred in view of favourable mechanical properties. A relatively high Mn may further be advantageous for avoiding or at least reducing undesirable sticking together of agglomerates, especially during storage of isolated agglomerates or in a final product, such as a toner, prior to final use.

The polyester usually has an Mn of up to 80 kg/mol, in particular of up to 60 kg/mol, more in particular of up to 45 kg/mol. A relatively low Mn is in particular desired for good adherence to a substrate, in particular when heated, such as in electroreprography. The polyester can be prepared using conventional polymerization procedures known to be effective for polyester synthesis.

Thus, it is well known that polyesters, which contain carbonyloxy (i.e. -C(=O)-O-) linking groups may be prepared by a condensation polymerization process in which an acid component (including ester-forming derivatives thereof) is reacted with a hydroxyl component. The acid component may be selected from one or more polybasic carboxylic acids such as di- or tri-carboxylic acids or ester-forming derivatives thereof such as acid halides, anhydrides or esters. The hydroxyl component may be one or more polyhydric alcohols or phenols (polyols) such as diols, triols, etc. (It is to be understood, however, that the polyester may contain, if desired, a proportion of carbonylamino linking groups -C(=O)-NH- (Ae. amide linking groups) by including an appropriate amino functional reactant as part of the "hydroxyl component"; such amide linkages are in fact useful in that they are more hydrolysis resistant). The reaction to form a polyester may be conducted in one or more stages (as is well known). It would also be possible to introduce in-chain unsaturation into the polyester by e.g. employing as part of the acid component an olefinically unsaturated dicarboxylic acid or anhydride.

There are many examples of polybasic carboxylic acids (or their ester forming derivatives) which can be used in polyester synthesis for the provision of the acid component. Suitable are in particular C4 to C20 aliphatic dicarboxylic acids, and alicyclic and aromatic dicarboxylic acids (of C5-C12 ring carbons (or higher functionality acids) or their ester-forming derivatives (such as anhydrides, acid chlorides, or lower alkyl esters). Specifically, suitable acids include adipic acid, fumaric acid, maleic acid, succinic acid, itaconic acid, sebacic acid, nonanedioic acid, decanedioic acid, 1 ,4-cyclohexanedicarboxylicacid, 1 ,3-cyclohexanedicarboxylic acid, 1 ,2-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid and tetrahydrophthalic acid. Anhydrides include succinic, trimeliitic, maleic, phthalic and hexahydrophthalic anhydrides.

Similarly there are many examples of polyols which may be used in polyester synthesis for the provision of the hydroxyl component. The polyol(s) preferably have from 2 to 6 (2 to 4) hydroxyl groups per molecule. Suitable polyols with two hydroxy groups per molecule include diols such as1 ,2-ethanediol, 1 ,3-propanediol, 1 ,4-butanediol, 1 ,6-hexanediol, 2,2-dimethyl-1 ,3-propanediol (neopentyl glycol), the 1 ,2-, 1 ,3- and 1 ,4-cyclohexanediols and the corresponding cyclohexane dimethanols, diethylene glycol, dipropylene glycol, and diols such as alkoxylated bisphenol A products, e.g. ethoxylated or propoxylated bisphenol A. Suitable polyols with three hydroxy groups per molecule include triols such as trimethylolpropane(1 ,1 ,1-tris (hydroxymethyl)ethane).

Suitable polyols with four or more hydroxy groups per molecule include pentaerythritol (2,2-bis(hydroxymethyl)-1 ,3-propanediol) and sorbitol (1 , 2,3,4, 5,6-hexahydroxyhexane).

The polyester preferably comprises carboxylic acid groups or sulfonic acid groups for providing or contributing to the dispersibility of the polyester in the aqueous liquid (when ionised). Such groups may be chain pendant or terminal in the polyester. In case the polyester comprises sulfonic acid groups, preferably at least 2 wt. % or at least 3 wt. % of the monomers of which the polyester is composed comprises a sulfonic acid group. In case the polyester comprises sulfonic acid groups, preferably up to 20 wt. %, or up to 15 wt. % of the monomers of which the polyester is composed comprises a sulfonic acid group. Chain-pendant sulfonic acid groups may be introduced into the polyester polymer molecules by using at least one monomer having two or more functional groups which will readily undergo an ester condensation reaction (carboxyl groups, hydroxyl groups or esterifiable derivatives thereof) and one or more (free) sulfonic acid groups or sulfonate anion groups (neutralisation of the sulfonic acid groups already having been effected in the monomer). Often, the (free) sulfonic acid or sulfonate anion containing monomer is a dicarboxylic acid monomer having at least one sulfonic acid salt group substituent (thereby avoiding any need to effect neutralization subsequent to polyester formation). Alternatively or in combination, alkyl carboxylic acid ester groups may be used as ester-forming groups. Such a monomer may therefore be part of the acid component used in the polyester synthesis.

The sulfonate anion groups usually have a counter ion selected from H+, alkali metal cation or alkaline earth metal cation (the latter being divalent and so being associated with two sulfonate anion groups instead of one), ammonium, organic amine cations such as those derived from trialkylamines (e.g. triethylamine, tributylamine), morpholine and alkanoldiamines and quaternary ammonium cations. In order to minimise odor in the resulting product, H+, alkali metal cation or alkaline earth metal cations are preferred counter ions. It is particularly preferred that the cation is selected from NH₄ ⁺, Na+, Li+ and K+. Examples of compounds for providing sulfonic acid groups are sulfonic acid substituted aromatic dicarboxylic acid such as those of formula:

wherein M is the counter-ion for the sulfonate group, in particular, ammonium, sodium, lithium, or potassium and each R' independently is H or an alkyl of 1 to 5 carbon atoms (such as methyl or ethyl). Preferred examples of sulfonic acid salt substituted aromatic dicarboxylic acids are the alkali metal salts of 5-sulfo-1 ,3-benzene dicarboxylic acid.

Particularly preferred is the sodium salt (M=Na) where R'=H, this material being commonly known as sodio-5-sulfoisophthalic acid (SSIPA).

Other useful sulfonic acid containing monomers are sulfonic acid substituted aromatic dicarboxylic acid-dihydroxyalkylesters, in particular (the alkali metal salts) which have the formula:

where M is the counter-ion for the sulfonate group, in particular, ammonium, sodium, lithium, or potassium, and R" is an alkylene radical, in particular an alkylene having up to five carbons, such as ethylene, propylene, butylene or pentylene.

Preferred examples of sulfonic acid salt substituted aromatic dicarboxylic acid dihydroxyalkylesters are the alkali metal salts of 5-sulfo-1 ,3- benzenedicarboxylic acid -1 ,3-dihydroxyethylester.

Carboxylic acid groups may be incorporated into the polyester by various means. For example, if the hydroxyl component of the reactants is stoichiometrically in excess of the acid component, a hydroxyl-terminated polyester can be formed, which may be subsequently converted to a carboxyl terminated polyester by reacting the hydroxyl groups with an appropriate reagent (such as an acid anhydride or a dicarboxylic acid). Alternatively terminal carboxyl functionality may be directly introduced by employing an appropriate stoichiometric excess of the acid component reactants. Yet further, chain-pendant carboxyl groups may be introduced by using reagents such as dimethylol propionic acid (DMPA) since if appropriate reaction condition are employed (e.g. polymerization temperature below 150 ⁰C) the hindered carboxyl group thereof does not take part to any significant extent in the ester-forming reactions during the polyester synthesis and the DMPA effectively behaves as a simple diol. Chain-pendant and/or terminal carboxyl groups could also be introduced by employing a tri- or higher functionality carboxylic acid or anhydride in the polyester synthesis such as trimellitic acid or anhydride. Combinations of each procedures could be used of course. It is thus seen that terminal or side-chain carboxyl groups or both can be introduced as desired. These can be fully or partially neutralized with an appropriate base to yield carboxylate anion groups. The counter ions used may be as for the sulfonate anions described above (H+ usually being less preferred as it usually has a relatively low acid strength) with NH₄ ⁺ or alkali metal ions such as Na+, Li+ and K+ being particularly preferred, for considerations of avoiding an odor that may not be appreciated by end-users.

The polyester may optionally incorporate hydrophilic non-ionic segments within the polyester backbone (i.e. in-chain incorporation), and/or as chain- pendant and/or terminal groups. Such groups may act to contribute to the dispersion stability or even water solubility of the polyester. For example, such polyethylene oxide chains may be introduced into the polyester during its synthesis by using as part of the hydroxyl component, ethylene oxide-containing mono, di or higher functional hydroxy compounds such as polyalkylene glycols, in particular polyethlene glycols, polypropylene glycols, polybutylene glycols and alkyl ethers of polyalkylene glycols, including combinations of any of these.

The ester may be fully saturated or comprise one or more unsaturated carbon-carbon double bonds. Unsaturated esters are in particular useful to provide a hybrid comprising a graft polymer, with the polyester as the backbone and segments comprising polymerized olefinically unsaturated compound as grafts. A graft polymer may for instance be advantageous for improved compatibility of the polyester and polymerized olefinically unsaturated compound. However, a hybrid that is essentially free of grafted polyester is in particular also suitable for preparing aggregates for use in electroreprography, such as in a toner. Examples of suitable unsaturated polyesters are in particular unsaturated polyesters wherein one or more compounds selected from the group of fumaric acid and maleic anhydride have been incorporated.

The olefinically unsaturated compound may in particular be selected from the group of acrylate esters; methacrylate esters; esters of other olefinically unsaturated carboxylic acids; unsaturated carboxylic acids - including salts thereof - such as acrylic acid and methacrylic acid; styrenes; dienes, such as 1 ,3-butadiene and isoprene; vinyl esters, such as vinyl acetate; vinyl alkanoates; prepolymers formed from any of these monomers; including mixtures comprising any of these compounds and prepolymers based on any of these compounds. In a preferred embodiment at least one olefinically unsaturated compounds represented by Formula I is used

wherein each of R¹, R², R³ and R⁴ independently represent a hydrogen or a hydrocarbon. Within the context of the present invention the term "hydrocarbon" is meant to include substituted and unsubstituted hydrocarbons, hydrocarbons with one or more heteroatoms (such as S, N, O, P) and hydrocarbons without heteroatoms, unless specifically mentioned otherwise. The heteroatom may in particular be an oxygen atom. More in particular the hydrocarbon comprising one or more heteromatoms may be an ether or an hydroxylated hydrocarbon.

The hydrocarbon may comprise 1-100 carbons, 1-40 carbons, 1- 30 carbons, 1-20 carbons or 1-12 carbons. Preferably the hydrocarbon is a linear or branched, substituted or unsubstituted alkyl or a substituted or unsubstituted cycloalkyl, which cycloalkyl usually comprises 5-12 carbons. The substituted alkyl and cycloalkyl may be in particular selected from hydroxyalkyls and hydroxycycloalkyls respectively.

R¹ preferably is a substituted or unsubstituted alkyl, in particular a substituted or unsubstituted C1-C12 alkyl, more in particular a substituted or unsubstituted C1-C8 alkyl; a substituted or unsubstituted cycloalky, in particular a substituted or unsubstituted C5-C12 cycloalkyl; or an alkylene oxide moiety. The alkoxyl may in particular be selected from the group of ethyleneoxide moieties, propylene oxide moiety, butylene oxide moiety and combinations thereof, wherein the number of alkylene oxide units preferably is 1-50, in particular 1-25, more in particular 1-10.

R² is preferably a hydrogen or a methyl. R³ is preferably hydrogen.

R⁴ is preferably hydrogen.

Specific examples of preferred olefinically unsaturated compounds include methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, and (usually C5 to C 12) isobornyl methacrylate, cyclohexyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, isobornyl acrylate and cyclohexylacrylate, styrene, substituted styrenes, such as α-methyl styrene and t-butyl styrene, acrylonitrile and methacrylonitrile.

Particularly preferred is a compound selected from the group of hydroxyethylmethacrylate, hydroxyethylacrylate, hydroxypropylmethacrylate, ethoxylated methacrylate, ethoxylated acrylate, propoxylated methacrylate, propoxylated acrylate, butoxylated methacrylate, butoxylated acrylate, caprolactone acrylate (such as TONE-M® 100, available from DOW, USA), acrylamide, methacrylamide, methoxy-polyethyleneglycol-acrylate and methoxy-polyethyleneglycol- methacrylate. The olefinically unsaturated compound may comprise more than one functional groups (polymerizable groups). This may be one or more further vinyl unsaturations or it may be a functionality which may be advantageously impart crosslinkability (crosslinking monomers for short).

Examples of polyfunctional vinyl monomers include divinylbenzene, ethylene glycol diacrylate, ethylene glycol dimethacrylate, trimethylol propane triacrylate ("TMPTA"), trimethylol propane trimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, allyl acrylate, allyl maleate, allyl methacrylate, diallyl maleate, polyethylene glycol diacrylate, and polyethylene glycol dimethacrylate.

The polymerization is preferably carried out to provide a polymerized olefinically unsaturated compound with an Mn (of the polymer, or - in case of a graft hybrid - of the grafts formed by olefinically unsaturated compound) of at least 5 kg/mol, at least 20 kg/mol or at least 50 kg/mol. The upper limit is usually not particularly critical. For practical reasons Mn may be up to 10 000 kg/mol up to 6 000 kg/mol or up to 3 000 kg/mol. The weight average molecular weight (Mw) usually is at least 20 kg/mol or more, in particular at least 80 kg/mol or at least 100 kg/mol. The upper limit is usually not particularly critical. For practical reasons Mn may be up to 20 000 kg/mol or up to 10 000 kg/mol. For a particularly good elastic behavior, preferably at least 2 wt. %, in particular 2-50 wt. %, of the polymerized olefenically unsaturated compound has a molecular weight of at least 100 kg/mol. In particular aggregates for or aggregates in a toner may suitably be used without having been crosslinked, although it is in principle possible to use crosslinked aggregates in a toner.

In particular in case aggregates are prepared that are intended to be used in electroreprography, it is preferred to use an olefinically unsaturated compound that comprises an aryl group. In particular styrene or a substituted styrene may be used. A hybrid based on such compound is in particular advantageous in a toner or developer in that electrocharging is facilitated.

If used, such aromatic compound - in particular styrene or substituted styrene - is preferably used in combination with a compound according to Formula I, the weight to weight percentage of the aromatic olefinically unsaturated compound, more in particular styrene or substituted styrene as a total of the olefinically unsaturated compounds is preferably at least 5 %, in particular at least 10 %, more in particular at least 30 %, even more in particular at least 40 %. If present, the concentration is usually up to 95 %, preferably up to 90 wt. %, in particular up to 80 wt. %, more in particular up to 70 wt. %. The balance is preferably formed by an alkyl(meth)acrylate according to formula I, and optionally up to 20 wt. % of one or more other vinyl momomers.

In a preferred method of the invention, in particular an embodiment relating to the preparation of (hybrid particles for) a toner, the concentration - based on the total sum of olefinically unsaturated compounds (other than unsaturated polyester, which may be present) - of

- one or more compounds selected from the group of styrene and substituted styrenes is 5-70 wt. %;

- the concentration of one or more compounds selected from the group of alkyl(meth)acrylates according to formula I - wherein the alkyl is preferably a C1 to

C8 unsubstituted alkyl or hydroxyalkyl - is 30-95 wt. %; and the concentration of one or more other olefinically unsaturated compounds which are optionally present, is 0-20 wt. %, in particular 1-20 wt. %, more in particular 2-20 wt. %. In particular, in case the polyester comprises acid groups the polyester may be dispersed in aqueous liquid without needing a surfactant. Dispersing the polyester may in particular be achieved by neutralizing at least part of the acid groups of the polyester, such as by adding a base, in particular a base selected from the group of amines, KOH, NaOH, LiOH, NH₄OH and ammonia (including combinations thereof), or another neutralizing agent.

The dispersing may be carried out after neutralizing at least part of the groups (e.g. by neutralizing molten or solid polyester) with a neutralizing agent. At least a part of the neutralizing agent - such as a base- may be dissolved in the aqueous liquid, after which the polyester (which may be unneutralized or at least partially neutralized) is dispersed. For facilitating the dispersing, preferably at least 50 %, in particular at least 75 %, more in particular at least 90 % or at least 99 % of the acidic groups is neutralized (ionized).

In an embodiment, aqueous liquid is added to the polyester and mixed. After sufficient aqueous liquid has been added, the dispersion of polyester in aqueous liquid will be formed by phase inversion.

The olefinically unsaturated compound may be mixed with the dispersion after the polyester has been dispersed. For facilitating the dispersing of the polyester it may be advantageous to add at least part of the olefinically unsaturated compound to the aqueous liquid before or together with the polyester.

The weight to weight ratio of the polyester to the polyolefinically unsaturated compound is usually in the range of 10:90 to 90:10. In an embodiment, the ratio is at least 15:85. In an embodiment, the ratio is up to 80:20.

Although the dispersion may be formed in the absence of a surfactant, a surfactant may be used to facilitate the dispersing, in particular in case the polyester is neutral or has a low acid value (such as below 8). A surfactant may be used in addition to a neutralization agent or as an alternative.

A conventional surfactant may be used, in particular an anionic or non-ionic surfactant, although in principle a cationic or amphoteric surfactant may be used. Examples thereof include alkylsulfonic acid salts, dialkylsulfosuccinate salts, alkyl sulfate salts, fatty acid salts (in particular sodium, potassium or ammonium salts of any of these), C12-C24 fatty alcohols, ethoxylated fatty acids, fatty amides and alkyl- ethercarboxylate surfactants. Aryl-containing analogues of the alkyl-based surfactants are also useful. If present, the surfactant concentration usually is at least 0.2 wt. %, based on the total weight of the polyester. The surfactants may in particular be used in a concentration of at least 0.5 wt. %, more in particular of at least 1 wt. %, based on the weight of the polyester. If present, the concentration is usually up to 5 wt. %, in particular up to 3 wt. %, based on the weight of the polyester. The polymerization may be carried out in the presence of one or more polymerization aids, such as a polymerization initiator. The initiator may in particular be a free-radical initiator. Examples of suitable initiators include peroxide initiators, azo- initiators and persulfate initiators. Suitably, a redox couple initiator may be used, such as a combination of a peroxide and iso-ascorbic acid or the like. The amount may, e.g., be chosen in the range of 0.05-3 wt.% based on the total of olefinically unsaturated compounds.

Polymerization conditions may be based on conditions known in the art for the olefinically unsaturated compound that is used, in particular conditions known for radical polymerization in an emulsion. Usually, the temperature will be between 0 and 100 ⁰C. For practical reasons, the reaction is preferably started at about ambient temperature (20 ⁰C). During polymerization the temperature may be 30 ⁰C or more, or 50 ⁰C or more. Preferably, the polymerization temperature is up to 98 ⁰C, up to 95 ⁰C.

The polymerization can be carried out in batch or in a semi- continuous process (in a feed process).

In a preferred embodiment one or more polyolefinically unsaturated compounds are added to the dispersion during polymerization. From a processing point of view, such embodiment may be advantageous with respect to avoiding the risk of excessive coagulation leading to excessively large hybrid particles; avoiding excessive heat development, also in the absence of a cooling system; or improved viscosity control.

Adding a polyolefinically unsaturated compounds to the dispersion during polymerization further allows, e.g., fine tuning of the product properties, for instance in case it is desired to prepare sequentially polymers with different phase compositions.

Since fusion of the agglomerated particles after the coagulation step is generally done at increased temperature, often well above the boiling point of water at high pressure, it would be advantageous if there would be a method to do this at either a lower temperature or during a shorter period of time. In addition to this there is sometimes the need for intimately mixed multiphase material, where one of the polymer phases could be produced after an initial coagulation step.

Therefore, in one embodiment additional monomer is fed into the system which is polymerized after the initial coagulation step.

The monomer can be added after the initial coagulation step followed by polymerization or the monomer can be added before or during the coagulation step followed by polymerization. Without being bound to this explanation it is believed that the monomer will plasticize the polymer particles, thus facilitating the fusing of the particles during the coagulation process. If required, additional materials may be introduced into the system with this monomer feed. The polymerization in a method of the invention allows the preparation of a hybrid, wherein the polymerized olefinically unsaturated compound (either bound to the polyester or free polymers) has an average glass transition temperature (Tg) of at least 0 ⁰C. The average (theoretical) Tg [in K] can be calculated by the following formula:

Tg^avΘ = 1000/(Z₁ M₁)

Herein i is the number of different monomers from which the polymerized olefinically unsaturated compound is composed, each n, represents the weight fraction of monomer "i" and each f, is 1000/(the glass transition temperature of a homopolymer consisting of monomer "i", in K).

It is possible to use this formula to predict the Tg^avΘfor the polyolefinic part of the hybrid that is to be made, for a specific combination of monomers of which the polyolefinic part will be composed, in a method of the invention. It is also possible to determine Tg^avΘ in a product according to the invention. The weight fractions of the monomers of which the polyolefinic part is composed can routinely be determined, e.g. by pyrolysis GC in the protocol described herein below.

The Tg of the homopolymers can be found in a polymer handbook, such as in Brandrup, J. and Immergut, E. H., Polymer Handbook, or may be routinely determined by differential scanning calorimetry (DSC) as described in L. H. Sperling in "Introduction to Physical Science, (1986) page 239-242".

The average Tg preferably is at least 20 ⁰C, in particular at least 40 ⁰C, in view of favorable block resistance.

The average Tg of the polymerized olefinically unsaturated compound is usually up to 1 10 ⁰C. Tg is preferably up to 100 ⁰C, in particular up to 80 ⁰C. A relatively low Tg is advantageous with respect to facilitating fusing the aggregated hybrid particles in the dispersion. For a favorable melt-flow behavior, an average Tg of up to 70 ⁰C is particularly preferred.

The skilled person will know how to provide a hybrid with a specific Tg, based on common general knowledge and the information disclosed herein.

Preferably, aggregates are formed after polymerization. Aggregation may in particular be achieved by reducing repulsive forces (such as due to the presence of ionic groups of the same sign at the polymer, in particular anionic groups of the polyester) between the hybrid particles, thereby allowing the hybrid particles to aggregate. Usually, aggregation may be carried out under ambient conditions (e.g. about 15-30 ⁰C), although in principle it is possible to carry out aggregation at a lower or higher temperature, with the proviso that the water or aqueous liquid remains liquid. In particular, repulsive forces may be reduced lowering the number of ionized groups. This may suitably be achieved by altering the pH. For a hybrid comprising anionic groups, such as the deprotonated acid groups of the polyester, this may be accomplished by reducing the pH to a value where a substantial amount of the anionic groups become protonated, for instance to a pH below the pK_a of the anionic groups (Ae. the pK_a applicable under the conditions in the dispersion), to a pH at least 1 pH-unit below the pK_a or a pH at least 2 pH-units below the pK_a. Usually a pH (the apparent pH, i.e. the pH measured with a calibrated pH electrode in the dispersion) in the range of 1-3 is suitable.

Any suitable acid may be used to reduce the pH, in particular any sufficiently strong acid. Examples thereof include aqueous solutions of HCI, sulfuric acid and nitric acid, formic acid, acetic acid and other acids having about the same or a lower pKa. A suitable concentration can empirically be determined, and can for instance be 1 wt. % or more, or 2 wt. % or more.

The primary hybrid particles can be allowed to aggregate until a desired average aggregate size is reached. Thereafter further aggregation can be stopped, in particular by changing the dissociation degree, such that the repulsive forces between ionic groups of the same sign are so high that further association of particles is avoided. For an hybrid comprising acidic groups this is in particular accomplished by raising the pH, e.g. to a value above the pK_a of the acidic groups, in particular to a pH of at least 1 pH-unit above the pK_a, more in particular to a pH of at least 2 pH-units above the pK_a. Usually a pH (the apparent pH, i.e. the pH measured with a calibrated pH electrode in the dispersion, under processing conditions) in the range of 7-9 is suitable.

It is also possible to stop growth by adding a surfactant (in an effective amount to accomplish sufficient repulsion), in particular a non-ionic surfactant or an anionic surfactant with a low pK_a, such as a pK_a of up to 3, in particular of 1-3. Examples thereof are phosphate based surfactants and sulfate based surfactants.

In an embodiment, the aggregate size is monitored during growing, e.g. by LASER scattering. In such an embodiment a set-point value can be set, which - when reached - allows the device for monitoring the growth to send a signal to a system that accomplished the stopping of the aggregate growth -in particular a dosing unit for altering the pH or a dosing unit for adding a surfactant to the reaction system wherein the aggregates are grown - such that further growing of the aggregates is essentially stopped.

The aggregates may be subjected to one or more of the following steps: washing, isolating and drying. If desired, the aggregates may be subjected to a crosslinking step and/or hybrid particles of the aggregate may be subjected to a fusing treatment. Fusing generally involves a treatment above the glass temperature, in particular at a temperature of at least 20 ⁰C above the average glass transition temperature, more in particular at a temperature of at least 30 ⁰C above the average glass transition temperature. In particular, the temperature may be up to 60 ⁰C above the average glass transition temperature. If desired, the fusing may be carried out in a pressurized container, for instance to avoid excessive evaporation of water or aqueous liquid, or boiling thereof. Fusing is carried out to increase the bonding of the hybrid particles forming an aggregate. It is usually carried out in the dispersion, before isolation and/or drying.

Isolation may be done in any suitable way, in particular by centrifugation or filtration.

Drying may for instance be accomplished by freeze-drying or spray drying. The aggregates may be used as such in a further application. It is also possible to provide a combination (such as a blend) of different kinds of aggregates (formed in different processes). It is also possible to add additional primary polyester-polyolefinic hybrid particles (which may be of the same type or a different type) during aggregation. In a convenient embodiment a blend is made by combining different kinds of primary polyester-polyolefinic hybrid particles in a dispersion and thereafter form aggregates.

Hybrid particles or aggregates may for instance differ in that the polyester and/or the polymerized polyolefinic compounds have a different number average molecular weight and/or weight average molecular weight. Hybrid particles or aggregates may for instance differ in chemical composition, for instance they may be composed of different monomers (qualitatively or quantitatively) or the sequence wherein the monomers are arranged in the polyester and/or polyolefinic part may be different (e.g. randomly, alternating or in blocks of different lengths). Hybrid particles or aggregates may for instance differ in average Tg or in average diameter. By combining different hybrids (as primary particles or as aggregates) one or more properties of the product may be fine-tuned, such as a mechanical property or a physico-chemical property.

Depending upon the application, the aggregate may comprise one or more additives. However, usually the polyester-polyolefenic hybrid component is the major component, the concentration usually being at least 50 wt. %, in particular at least 60 wt. % more in particular at least, 70 wt. %, at least 80 wt. %, at least 90 wt. % or at least 94 wt. %, based on total dry-weight. The concentration of the polyester- polyolefenic hybrid may be 100 % or less, in particular 99.8 or less, 99 wt. % or less, or 98 wt. % or less. Usually, one or more additives are added to the dispersion, before, during or after polymerization. One or more additives may be added to the dispersion before, during or after aggregation. It is also possible to add one or more additives or to the isolated aggregates. Adding the additive before or during aggregation is usually advantageous with respect to the efficiency of incorporating the additive into the aggregate.

For instance, in particular for a toner or developer composition one or more additives may be added, as described in WO 99/50714 or WO 98/50828. The contents of these publications in particular with respect to the additives mentioned therein and suitable ways to include such additives in the aggregates are incorporated herein by reference. More in particular one or more additives selected from the group of colorants; magnetic additives; charge-control agents; waxes; flow control agents; additives to improve charge, fusing and/or transfer properties of a toner, additives to aid cleaning of the device wherein the toner is to be used; may be included.

The term colorant as used herein encompasses both dyes (which are substantially soluble in the medium to which they are added) and pigments (which are substantially insoluble in the medium to which they are added). A colorant comprises any material which is imparts color to a medium by any mechanism, for example by attenuation, absorption, reflection and/or scattering of radiation in the region of the electromagnetic spectrum visible to the human eye. Color as used herein encompasses black, white and greys as well as hues such as red green and blue. For example color can arise by chemical processes (e. g. absorption, re-radiation, phosphorescence and/or fluorescence), physical processes (e. g. scattering of radiation by particles similar in size to the wavelength of the incident radiation) and/or by any other processes. The terms colorant and color as used herein unless the context indicates differently also includes materials which have their effect in the region of the electromagnetic spectrum which is non-visible to the human eye (such as infra red or ultra-violet radiation) and which might have application in the electroreprographic area such as for optionally invisible markers in security applications (e. g. currency and security marking). The colorant may where appropriate (e. g. within the pigmentary particles of step 'a)') comprise a dye (soluble in the medium to which it is added) and/or a pigment (insoluble in the medium to which it is added). For toner applications dyes or pigments may be used, each having different advantages. Some of the advantages of using dyes over pigments to provide color in toners comprise any of the following: less quantities of dye are required; there is less likely to be a negative influence on tribocharging efficiency; more brilliant colors can be obtained leading to better color mixing and a wide color gamut; a typical absorbance/reflectance spectra of a dye comprises sharp narrow peaks; the images produced are less grainy; the melting point and/or viscosity of toners may be lower; dyes may be chemically modified to alter toner properties; and dyes may be easily purified. Some of the advantages of using pigments over dyes to provide color in toners comprise any of the following: little bleeding or blooming problems in the image; improved light and solvent fastness; higher thermal stability; high extinction coefficients especially for particles below 100 nm in diameter; and greater chemical inertness. One of the advantages of the process of the present invention is that toner particles (aggregates) can be readily produced which comprise both dye (s) and pigment (s) with the advantages of both colorants. Alternatively as a greater variety of different colorants can be used in the present process the specific colorant (s) chosen can be selected to optimize more exactly the properties of a toner for a specific use. Preferably the toner comprises a suitable colorant, such as pigment.

If the toner is black (for producing black and white images) a preferred colorant comprises carbon black.

Colored toners (e. g. for use in color copies and color laser printers) may comprise a trichromatic set of toners, each toner in the trichromatic toner set preferably comprising a toner polymer and respectively a cyan colorant, a magenta colorant and a yellow colorant. Conventional colorants for color toners are described, for example, in US 5,102,764; US 5,032,483 and EP 0,159,166. Other suitable colorants for use in toner compositions may be selected from one or more of the following and any suitable mixtures thereof: ferrite, magnetite, metallized phthalocyanines (e. g. copper or nickel phthalocyanines, also known as Pc, which are blue), quinacridone,perylene, benzidine, nigrosine, aniline, quinoline, anthraquinone, azo disperse dye (e. g. azo pyridones, also known as AP, which are yellow), benzodifuranones (also known as BDF, e. g. those which are red),metallized lake pigments;, water insoluble or soluble basic dyes (especially the water solubletriphenylmethane dyestuff); xanthenes; monoazo and/or diazo pigments; diarylides; benzimidazolones; isolindolines; isoindolinones; and any mixtures thereof. The toner composition may in particular comprise up to 20% colorant, in particular up to 10 % colorant, more in particular up to 8 % colorant, by weight of the composition. Usually, the concentration is at least 0.1%, in particular at least 0.5%, more in particular at least 1 % by weight of the toner composition.

The colorant may comprise a magnetic additive (e. g. ferrite and/or magnetite) optionally mixed with a colored pigment, in which case the colorant is preferably present from 5% to 70% and more preferably from 10% to 50% by weight of the toner composition. Mixtures of carbon black and magnetite are available commercially and those containing from about 1% to 15% are preferred, especially those containing from 2% to 6% carbon black based on the weight of carbon black and magnetite.

Toners comprising a magnetic additive may be useful to print items for use in methods such as magnetic ink character recognition (MICR). MICR is used to machine process large volumes of printed data. Chemically produced toners of the present invention which also magnetic are particularly useful in MICR as the controlled particle size leads to sharper printed images and less tendency for the machine to detect incorrectly or fail to read the original image. Thus MICR toners of the present invention reduce the error rate in high volume applications. For certain applications security may also be an issue. The magnetic properties of an item printed using a magnetic toner are not readily detectable to the user. Thus a person who attempts to make an illicit copy will use a conventional (non-magnetic) toner and the magnetic properties of original will not be readily reproduced by conventional copying methods. Therefore MICR can also be used to distinguish between originals and illicit copies.

Colored toners are of use in color electroreprography for producing color images on sheet or film material, especially paper and transparencies (e. g. those made from plastics materials such as polyester and acetate for example for use as overhead transparencies). Particularly useful color toners are those which exhibit bright and intense colors and produce images with good fastness properties, these are especially useful for laser printing on paper.

It can been seen that it is desirable for toner compositions to comprise particles which can possess readily an electrostatic charge (tribocharge) so they can be attracted to the latent image on the drum to develop the latent image. Toners which readily tribocharge may also have the further advantage of facilitating rapid and more complete removal of any residual toner from the image drum (e. g. by electrostatic repulsion). This may improve image quality (by reducing ghost images from previous copies) and may reduce the cycle time between copies and thus increase the speed of copying. It has been found that the addition of certain charge control agents

(hereinafter known as CCAs) to toner compositions helps the production and stability of tribocharge within the toner. Use of CCAs may also lead to improved image quality when the latent image is transferred to the paper.

CCAs may be colored or substantially colorless. Colored CCAs have utility as the colorant in the toner for example as dyes or pigments depending on the substrate in which they are used. Colorless CCAs have particular utility in non-black colored toners (such as for colors which have weak shades) where adding colorless CCAs would not substantially alter the color of the toner to which they are added.

A CCA may be capable of stabilizing a positive electrostatic charge (positive charging) and/or negative electrostatic charge (negative charging). Preferred positive charging CCAs comprise amine derivatives, more preferably alkoxylated amines and/or quaternary ammonium compounds, such ascetyl pyridinium chloride or bromide.

Preferred negative charging CCAs comprise metal complexes or salts, preferably comprising an aryl moiety, for example a bis azo aryl moiety, more preferably a 2: 1 metal complex or salt of a hydroxynaphthoic acid and/or napthenic acid. Complexes of Zn or Cr may also be effective colorless negative charging CCAs (e.g. di tert-butyl salicylate complexes). CCAs may also comprise suitable electron donating dyes (e. g. nigrosine). The substituents on a CCA may be selected to improve the compatibility of the CCA with the toner resins with which they are formulated. Thus, the size and length of the substituents may be selected to optimize the physical entanglement or interlocation with the resin or they may contain reactive entities capable of chemically reacting with the resin. The amount of CCA in the toner is preferably at least about 0.1%, more preferably at least about 0.5% and most preferably at least about 1 % by weight of the toner. The amount of CCA in the toner is desirably up to about 12%, preferably up to about 10% more preferably up to about 5% and especially up to about 3% by weight of the toner. Preferably a toner comprises a suitable agent to control particle flow such as one or more of the following: alumina, silica, benzoguanine-formaldehyde resin, hydroxyapatite, flurorescein, acrylic polymer beads, titania including any suitable mixtures thereof.

The invention will now be illustrated by the following preferred preparation scenarios and the following examples.

Preparation scenarios i) Dispersion of the polyester

A. The aqueous liquid contains at least part of the neutralizing agent(s). The polyester is added to the aqueous liquid. If not all neutralizing agent is used, the remainder is added in a later stage.

B. The neutralizing agent is/are (partially or totally) added to the polyester. The neutralized polyester is added to the aqueous liquid. If a part of the neutralizing agent is added to the polyester, the remainder can either be in the aqueous liquid or added in a later stage.

C. Scenario A, wherein olefinically unsaturated compound is added to the polyester prior to dispersing it into aqueous liquid.

D. Scenario B and C combined.

E. Scenario A wherein olefinically unsaturated compound is added to the aqueous liquid, prior to dispersing the polyester into the aqueous liquid.

F. Scenario B and E combined.

G. The polyester is a polyester free of acid groups, or a polyester comprising acid groups which are not neutralized, neither is the aqueous liquid. The polyester is dispersed into aqueous liquid, which may be essentially free of neutralizing agent, using a surfactant. The surfactant can be in the aqueous liquid, added to the polyester prior to dispersing it into the aqueous liquid or a combination of the above. H. Any combination of the above described scenarios. H) Formation of the polymer based on the polyolefinic unsaturated compound

The polyolefinic unsaturated compound can be reacted in the following ways: I. Polymerizing polyolefinic unsaturated compound already present in the dispersion. J. As in I but more polyolefinic unsaturated compound is added. This can be before, during or after polymerizing the monomers that are already present. K. Adding polyolefinic unsaturated compound to the dispersion and polymerizing said compound. Those skilled in the art will recognize that the polyolefinic unsaturated compound can be one type of polyolefinic unsaturated compound or a mixture of two or more different polyolefinic unsaturated compounds.

Also, the polyolefinic unsaturated compound added can have the same or a different composition compared to polyolefinic unsaturated compound already present. Sequential and/or gradient compositions can be used in the process.

Examples

Preparation of an aqueous polyester solution based on sufonate stabilization (A)

The polyester may be made as follows: To a glass reactor fitted with a distillation column and condenser, the following ingredients are charged with stirring under nitrogen: Neopentyl glycol 1545 g

Trimethylol propane 888 g

MethoxyPEG 750 450 g (PEG nonometyl ether: Mn=750) lsophtalic acid 105O g

Sodio-5-sulphoisophtalic acid 600 g

Fascat 4100 (Sn based catalyst) 3 g

The content of the reactor is heated to 210⁰C until the desired acid value is achieved. Next, the following ingredients are added: lsophtalic acid 926 g

Adipic acid 381 g

The reaction mixture is held at 210⁰C for one hour. Vacuum is applied (200 mbar) and after 1.5 hrs a distillate is recovered. The molten polyester is cast. 200 Gram polyester is ground and added to 600 g of water at 70⁰C with agitation until complete dispersion of the polyester

Preparation of aqueous polyester solution based on carboxylate stabilization (B)

Trimethylol propane 888 g

MethoxyPEG 750 450 g (PEG nonometyl ether: Mn=750) lsophtalic acid 1976 g

Adipic acid 381 g

Fascat 4100 (Sn based catalyst) 3 g

The content of the reactor is heated to 210⁰C until the desired I acid value is achieved. The reaction temperature is reduced to 160⁰C and Trimellitic anhydride (430 g) is added to the reaction mixture.

The reaction is continued until an acid value of 28mg KOH/g is achieved. The molten polyester is cast.

200 Gram polyester is ground and added to 573 g water, containing 7 g of a 25% (w/w) ammonia solution at 70°C with agitation. Agitation is continued until complete dissolution is obtained. The solution has a solids content of 25% w/w and a pH of 8-9.

Preparation of polyester-acrylic hybrid 1 based on polyester A The hybrid may be made as follows

A polyester-acrylic hybrid with 50% polyester and 50% acrylic polymer (w/w) is prepared as follows. The acrylic composition is styrene/ethyl acrylate/hydroxyethylmethacrylate (S/EA/HEMA)= 90/5/5 (w/w/w).

To a reaction flask fitted with a stirrer and condensor, 400 g of the polyester dispersion A described above is added. 70 Grams of water are added as well. The content of the reactor is heated to 80-85⁰C under a nitrogen atmosphere. An acrylic monomer feed is prepared by mixing 90 g of styrene, 5 g of ethylacrylate, 5 g of 2-hydroxyethylmethacrylate, 0.8 g laurylmercaptan and 0.1 g sodium bicarbonate. An initiator feed is prepared by dissolving 0.3 g ammonium persulfate in 90 g of water. 10% of the above described monomer feed is added to the reactor content. After 5 minutes, 30% of the initiator feed is added and held for 5 minutes at reaction temperature. The remainder of the monomer feed is added in one hour to the reactor at reaction temperature. The initiator feed is added in one hour as well.

After this, 3.7 g of an aqueous l-ascorbic acid solution (20% w/w) and 1 g of t-butylhydroperoxyde (70% w/w) is added to the reactor at reaction temperature. The reaction mixture is held at this temperature for another hour. The dispersion is cooled to room temperature.

Preparation of polyester-acrylic hybrid 2 based on polyester B A polyester-acrylic hybrid with 50% polyester and 50% acrylic polymer (w/w) is prepared as follows. The acrylic composition is S/EA/HEMA= 90/5/5

(w/w/w).

To a reaction flask fitted with a stirrer and condensor, 400 g of the polyester dispersion B described above is added. 70 Grams of water are added as well. The content of the reactor is heated to 80-85⁰C under a nitrogen atmosphere. An acrylic monomer feed is prepared by mixing 90 g of styrene, 5 g of ethylacrylate, 5 g of

2-hydroxyethylmethacrylate, 0.8 g laurylmercaptan and 0.1 g sodium bicarbonate. An initiator feed is prepared by dissolving 0.3 g ammonium persulfate in 90 g of water. 10% of the above described monomerfeed is added to the reactor content. After 5 minutes, 30% of the initiator feed is added and held for 5 minutes at reaction temperature. The remainder of the monomer feed is added in one hour to the reactor at reaction temperature. The initiator feed is added in one hour as well.

After this, 3.7 g of an aqueous l-ascorbic acid solution (20% w/w) and

1 g of t-butylhydroperoxyde (70% w/w) is added to the reactor at reaction temperature. The reaction mixture is held at this temperature for another hour. The dispersion is cooled to room temperature.

Aggregation of hybrids 1 and 2 30.5 g of the hybrid dispersion 1 or of the hybrid dispersion 2 are mixed with a pigment dispersion (1.81 g, 26 % solids)

Aqueous HCI (2 wt. %) is added to the mixture, whilst mixing under high shear (10,000 rpm), until the pH is about 1.

The mixture is heated at 46 ⁰C and hybrid particles are allowed to aggregate until the desired size is reached (about 2 hours). A 10 % aqueous solution of surfactant (sodium dodecylbenzenesulphonate (4.6g)) is added to the this mixture to prevent further growth.

Next, the mixture is heated at 80 ⁰C for 105 min to cause fusing of the hybrid particles in the aggregates. Next, the mixture from step is cooled to 25 ⁰C, then filtered to collect the aggregates. The aggregates are washed by forming a slurry in water which are then collected by filtration. The slurrying process is repeated with dilute ammonia (3 times) then dilute HCI (once) and finally water. The washed aggregates are dried under reduced pressure at 30 ⁰C.

Protocol for determination of polvolefinic composition by PY-GC

This method describes the determination of the composition of polyolefinic copolymers using pyrolysis coupled to gas chromatography. During pyrolysis, a polymer is quickly heated up to an elevated temperature in an inert atmosphere at which it degrades in typical residue compounds.

Subsequently, these residues are separated using gas chromatography (GC) and detected using FID. After calibration using a polymer with a known chemical composition the ratio of monomers in the sample can be calculated.

Reagents and materials: Water, acetone or other solvent for dilution of the samples.

Equipment:

- Pyrola caroussel with 14 probes

- Gas chromatograph equipped with:

- Carrier gas H2, He or N2 - CIS; cooled injection system

- Column CP SiI 5 CB, 25 m x 0.32 mm i.d., df 1.2 μm (CP nr. 7760) or similar types

- Flame Ionization Detector (FID):

Required flame gasses: H2 and air Optional: He or N2 as make-up gas - Suggested operating conditions: a) pyrolysis at 550 ⁰C for 2 sec; chamber temperature 175 ⁰C b) CIS; cold injection system:

Temperature 150 ⁰C Injection mode split Split flow 20 ml/min c) GC-oven

Column head pressure: 50 kPa

Oven temperature 1 : 80 ⁰C lso time 1 : 2 min

Rate 1 : 5 °C/min

Oven temperature 2: 110 ⁰C lso time 2: 2 min

Rate 2: 15 °C/min

Oven temperature 3: 320 ⁰C lso time 3: 1 min d) FID detector (on CE instruments GC 8000 Top)

FID detector temperature: 325 ^c ¹C

H2 flow FID detector: 50 kPa

Air flow FID detector 100 kPa

- graduated cylinder 25 ml

- syringe: 5 μl with a teflon tipped plunger

Claims

1. Method for preparing polyester-polyolefin hybrid aggregates comprising

- providing an aqueous dispersion comprising polyester-polyolefin hybrid particles, said particles comprising a polyester and a polymerized olefinically unsaturated compound, which polymerized compound may be ungrafted or grafted to the polyester;

- aggregating the hybrid particles;

- preferably isolating the aggregates from the dispersion; and - preferably drying the aggregates.

2. Method according to claim 1 , wherein the dispersion is provided by

- preparing an aqueous dispersion comprising a polyester and a polymerizable, olefinically unsaturated compound; and

- polymerizing the olefinically unsaturated compound in the dispersion;

3. Method according to claim 1 or 2, wherein the polyester has a number average molecular weight of at least 1.5 kg/mol, preferably of 3.5-80 kg/mol, in particular of 5-60 kg/mol, more in particular of 13-45 kg/mol.

4. Method according to any of the preceding claims, wherein the polyester is an acidic polyester having an acid value of 8-120 mg KOH/g, preferably of 20-80 mg KOH/g.

5. Method according to any of the preceding claims, wherein the polyester is selected from the group of polyesters based on

(a) at least one acid or anhydride selected from the group of C4 to C20 aliphatic dicarboxylic acids, alicyclic and aromatic dicarboxylic acids and their ester-forming derivatives, in particular from adipic acid, fumaric acid, maleic acid, succinic acid, itaconic acid, sebacic acid, nonanedioic acid, decanedioic acid, 1 ,4-cyclohexanedicarboxylicacid, 1 ,3-cyclohexane- dicarboxylic acid, 1 ,2-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, tetrahydrophthalic acid, trimelletic acid succinic anhydride, trimellitic anhydride, maleic anhydride, phthalic anhydride, hexahydrophthalic anhydride;

(b) at least one polyol(s) having from 2 to 6 hydroxyl groups per molecule, in particular 1 ,2-ethanediol, 1 ,3-propanediol, 1 ,4-butanediol, 1 ,6-hexanediol, 2,2-dimethyl-1 ,3-propanediol (neopentyl glycol), the 1 ,2-, 1 ,3- and 1 ,4- cyclohexanediols and the corresponding cyclohexane dimethanols, diethylene glycol, dipropylene glycol, and diols such as alkoxylated bisphenol A products, e.g. ethoxylated or propoxylated bisphenol A, trimethylolpropane(1 ,1 ,1-tris (hydroxymethyl)ethane), and dimethylol propionic acid; and optionally (c) a sulfonic acid substituted aliphatic or aromatic dicarboxylic acid, in particular such carboxylic acid as defined under (a).

6. Method according to any of the preceding claims, wherein the olefinically unsaturated compound is selected from the group of acrylate esters; methacrylate esters; esters of other olefinically unsaturated carboxylic acids; unsaturated carboxylic acids - including salts thereof -, such as acrylic acid and methacrylic acid; styrenes; dienes, such as 1 ,3-butadiene and isoprene; vinyl esters, such as vinyl acetate; vinyl alkanoates; caprolactone acrylate, acrylamide, methacrylamide, methoxy-polyethyleneglycol-acrylate, methoxy- polyethyleneglycol-methacrylate, prepolymers formed from any of these monomers, including mixtures comprising any of these compounds and prepolymers based on any of these compounds, and wherein the olefinically unsaturated compound preferably is selected from the group of styrene, substituted styrene and compounds represented by Formula I

Formula I wherein each or R¹, R², R³ and R⁴ independently represent hydrogen or a hydrocarbon (which hydrocarbon optionally comprises one or more heteroatoms) including mixtures comprising any of these compounds and prepolymers based on any of these compounds.

7. Method according to any of the preceding claims, wherein the weight to weight ratio of the polyester to the polyolefinically unsaturated compound is in the range of 10:90 to 90:10, in particular in the range of 15:85 to 80:20.

8. Method according to claim 7, wherein as polyolefinically unsaturated compounds

(a) at least one ester of an olefinically unsaturated carboxylic acid, in particular an ester of (meth)acrylic acid; (b) at least one compound selected from the group of styrene and substituted styrenes; and optionally

(c) at least one other polyolefinically unsaturated monomer is used; wherein preferably component (a) is present in a concentration of 30-95 wt. %, component (b) is present in a concentration of 5-70 wt. %, and component (c) in a concentration of 0-20 wt. %, in particular of 1-20 wt. %, all based on total olefinically unsaturated compounds (other than unsaturated polyester, if present).

9. Method according to any of the preceding claims wherein the formation of the aggregates involves a change in pH of the dispersion.

10. Method according to any of the preceding claims, comprising

- dispersing the combined olefinically unsaturated compound and polyester; thereafter

- starting the polymerization, usually by adding an initiator; and

- adding further olefinically unsaturated compound (which may be the same or different from the earlier added olefinically unsaturated compound), and optionally adding further initiator (which may be the same or different from the earlier added initiator), during the polymerization.

11. Method according to any of the preceding claims, comprising

- dispersing the polyester in the presence of the surfactant; thereafter - adding olefinically unsaturated compound to the dispersion; and thereafter

- polymerizing the olefinically unsaturated compound.

12. Method according to any of the preceding claims, comprising

- combining the polyester, preferably a polyester essentially free of acid groups, with a surfactant; thereafter - adding olefinically unsaturated compound to the polyester combined with the surfactant; thereafter

- polymerizing the olefinically unsaturated compound.

13. Polyester-polyolefin hybrid aggregates, obtainable by a method according to any of the preceding claims.

14. Aggregates according to claim 13, wherein the average glass transition temperature of the polymerized olefinically unsaturated compound is in the range of 0-1 10 ⁰C, in particular in the range of 20-100 ⁰C, more in particular in the range of 40-80 ⁰C.

15. Aggregates according to any of the claims 13 or 14, wherein at least 50 vol.%, in particular, at least 80 vol.%, preferably at least 90 vol.%, in particular at least 95 vol.% of the particles have a diameter in the range of 2 μm to 20 μm.

16. Aggregates according to any of the claims 13-15, comprising at least one additive selected from the group of colorants (including pigments and dyes); magnetic additives; charge-control agents; waxes; and flow control agents.

17. Toner or developer for electroreprography, comprising aggregates according to any of the claims 13 to 16 or polyester-polyolefinic hybrid particles as defined in any of the claims 1-12.

18. Use of particles according to any of the claims 13 to 16 or polyester- polyolefinic hybrid particles as defined in any of the claims 1-12 in electroreprography.

19. Hybrid particles obtainable by preparing an aqueous dispersion comprising a polyester and a polymerizable, olefinically unsaturated compound as defined in any of the claims 1-12, and polymerizing the olefinically unsaturated compound in the dispersion.

20. Use of hybrid particles according to claim 19 to prepare a toner or developer.