WO1996020437A1

WO1996020437A1 - Composition, compound and use

Info

Publication number: WO1996020437A1
Application number: PCT/GB1995/002853
Authority: WO
Inventors: James Stanley Campbell; Peter Gregory
Original assignee: Zeneca Limited
Priority date: 1994-12-28
Filing date: 1995-12-07
Publication date: 1996-07-04
Also published as: GB9426293D0; GB9525024D0; JPH10511940A; EP0800667A1

Abstract

A toner resin composition comprising a toner resin and a metal complex or salt of 2-alkyl or aralkyl (thio) ethers of benzoic or nicotinic acid and the use of such compounds as charge control agent in electrophotography.

Description

COMPOSITION. COMPOUND AND USE

The present invention relates to a composition comprising a toner resin and 2-mercapto-benzoic, nicotinic acid, 2-mercapto-nicotinic acid and derivatives thereof including their salts and metal complexes and the use of such compounds as negative charge control agents (hereinafter CCA's). Some of the compounds are novel. JP 5011507 discloses the zinc complex of 2-thiobenzoic acid as a negative charging CCA It has now been found that certain derivatives of 2-mercapto- benzoic acid, nicotinic acid and 2-mercapto-nicotinic acid exhibit higher tribo-electric charge characteristics in electroreprographic image processes.

According to the invention there is provided a toner resin composition comprising a toner resin and a compound of formula 1 which is an aromatic thiol or thioether of a carboxylic acid (hereinafter "ATA")

including salts and metal complexes thereof; wherein

Y is =CH- or =N-;

R is halogen, hydroxy, nitro, carboxy, nitrile, optionally substituted

or two adjacent groups R together with the carbon atoms to which they are attached form a 5- or 6-membered fused ring;

R¹ is hydrogen, optionally substituted C^^-alkyl or aralkyl;

Z is hydroxy or a group of formula 1a

R² and R³ is each, independently, hydrogen, optionally substituted

cycloalkyi, aralkyl or the groups R² and R³ together with the nitrogen atom to which they are attached form a 6-membered ring; n is 0 to 3; p is 0 to 2; and X is O or S when Y is =N- or S when Y is =CH-; with the exception of the 2:1 zinc complex of 2-mercaptobenzoic acid.

\ΛΛτen two adjacent groups R together with the carbon atoms to which they are attached form a fused ring, the ring is preferably 6-membered and is especially carbocyclic such as a phenyl ring. The fused ring itself may be substituted by one or more groups R.

V ien R, R\ R² or R³ is substituted alkyl, the substituent is preferably hydroxy, halogen or nitrile. The substituent may also be a divalent group or atom such as

O O O

II II II

-O-, -C-, -C-O- , ^or -C— NH- .

It is preferred that R is alkyl. VNΛien R, R¹, R² or R³ is alkyl, it may be linear or branched and is preferably C^^-alkyl, more preferably C^-alkyl and especially C^-alkyl. Examples of such groups include methyl, ethyl, i-propyl, n-butyl, t-butyl, i-hexyl, 2-ethylhexyl, nonyl, dodecyl and octadecyl.

R² or R³ is aralkyl it is preferably benzyl or 2-phenylethyl. λΛien R² and R³ together with the nitrogen atom to which they are attached form a ring, the ring is preferably piperdinyl, morpholinyl, piperazinyl and N-alkylpiperazihyl where the alkyl group preferably contains up to a 6-carbon atoms.

Preferably, R² and R³ are not both hydrogen.

\ΛΛιen R is the group -CΓTVZ or -CH₂NR²R³ it is preferably para to the group -XR¹ when Y is =N- and preferably ortho- and/or para- to the group -XR¹ when Y is =CH-. VNΛien R is halogen, it is preferably fluorine, bromine and especially chlorine.

In a particularly preferred embodiment n is zero. The groups R to R³ are selected primarily to improve the compatibility of the ATA with the toner resin with which they are formulated. Thus, the size and length of the groups R to R³ may be selected to improve the physical entanglement or interlocation with the resin or they may contain reactive entities capable of chemically reacting with the resin.

Preferably, R, R¹, R² and/or R³ is or contains a saturated aliphatic chain and it is particularly preferred that the total number of carbon atoms is greater than four and preferably greater than 10. Preferably, the total number of aliphatic carbon atoms in R, R¹, R² and/or R³ is less than 30, more preferably less than 24 and especially less than 18.

It is preferred that Y is =N- and it is especially preferred that Y is =N- and X is S.

In a particularly preferred embodiment, the ATA is present as a salt or metal complex. The salt may be that of a primary, secondary or teriary amine or a quaternary ammonium compound (hereinafter QAC). Preferred amines or QAC's are those containing C₁.₂₄-alkyl chains, particularly where the alkyl chain contains more than 6 and especially more than 10 carbon atoms since these amines or QAC's are less volatile and are more resistant to the high temperature employed in the fabrication of toner resin compositions. Examples of amines and QAC cations are dodecylamine, octadecylamine, didecylamine, didoceylamine, tetradecylamine, dodecylamine, hexadecylamine, C_12.18-mixed alkylamines and their N-C^-alkyl or N.N-di-C^-alkyl derivatives or N-benzyl derivatives, arid particularly their methyl or ethyl derivatives, and N,N-diethyl-N-dodecyl-N-benzylammonium; N,N iimethyl-N-octadecyl-N- (dimethylbenzyl)ammonium; N,N-dimethyl-N,N-didecyl ammonium; N,N-dimethyl-N,N- didodecylammonium; N,N,N-trimethyl-N-tetradecylammonium; Nr-benzyl-N.N-dimethyl- N-C_12.18-alkyl) ammonium; NI-(dichlorober-zyl)-N, r-dirrιethyl-Nr-dode(^lamιτiOnium; N-hexadecylpyridinium; N-hexadecyl-N,N,Nr-trimethylammonium, dodecylpyridinium; N-ben--yl- I-dodecyl-N, N-bis(hydroxyethyl)ammonium; N-dodecyl-N-benzyl-N, N- dimethylammonium; N-berι-^l-N,NI-dinrιethyl-NI-(C₁₂.₁₈-alkyl)ammonium; N-dodecyl-N,N- dirri«thyl-N-(1-naphthylmethyl)ammonium and

benzylammonium cations. An especially preferred embodiment is the salt or complex of the ATA with a mono-, di- or trivalent metal.

Particulariy preferred metals are those of groups 1a, 2a, 3a, 1b, 2b, 6b, 7b and 8 of the Periodic Table according to Mendeleef as, for example, published in the inside rear cover of the Handbook of Chemistry and Physics published by The Chemical Rubber Co, Ohio, USA The especially preferred metals include Mg, Ca, Ba, Cr, Mn, Fe, Co, Ni, Cu, Zn and Al. Metal salts or complexes derived from Mg(ll), Ca(ll), Ba(ll), Zn(ll) and Al(lll) have the specific advantage that they are substantially colourless and such compounds may be used as CCA's for making coloured images whereas compounds derived from Cr(lll) and Fe(lll) tend to be strongly coloured and hence such CCA's are mainly of use for forming black images.

The salt or complex of the ATA can include more than one cation. Thus, it may comprise more than one metal or a combination of a metal together with an amine or QAC such that the salt or complex is a neutral molecule. It is preferred, however, that the salt or complex of the ATA is that of a metal. The toner resin is a thermoplastic resin suitable for use in the preparation of toner compositions. A preferred toner resin is a styrene or substituted styrene polymer or copolymer such as polystyrene or styrene-butadiene copolymer.

It is especially preferred that the toner resin is a styrene-acrylic copolymer such as a styrene-butyl methacrylate copolymer. Other suitable toner resins are polyesters, especially alkoxylated bis-phenol based polyester resins such as those described in US 5,143,809, polyvinyl acetate, polyalkenes, poly(vinyl chloride), polyurethanes, polyamides, silicones, epoxy resins and phenolic resins. Further examples of these and other resins are given in the book "Bectrophotography" by RMShafert (Focal Press), UK 2,090,008, US 4,206,064 and US 4,407,924. The toner resin composition may contain more than one ATA The ATA is preferably present in the composition from 0.1 to 12%, more preferably from 0.5 to 10% and especially from 1 to 3% by weight of the total composition.

Useful compositions are those containing the 2:1 zinc complexes of nicotinic acid, 2-rvbυtylmercaptonicotinic acid, 2-mercaptonicotinic acid, the 3:1 iron complexes of 2-n-butylmercapto-benzoic and nicotinic acids and the 2:1 calcium salt of 2-n-butylmercaptobenzoic acid.

The toner resin composition may also contain a dyestuff or pigment as colourant. Thus, according to a further aspect of the invention there is provided a toner resin composition as hereinbefore defined which further comprises a colourant. The colourant is preferably a pigment such as carbon black, magnetite, metallised phthalocyanine, quinacridone, perylene, benzidine, nigrosine, aniline, quinoline, anthraquinone, azo disperse dye, benzodifuranone, metallised lake or pigment toner or water insoluble salt of a basic dye, including mixtures thereof. The colourant may also be a water soluble basic dye, especially a triphenylmethane dyestuff. The toner composition may contain up to 20% colourant and especially from 3 to 10% relative to the total weight of the toner resin composition.

\ΛΛιen the colourant comprises magnetites or a mixture of magnetites and coloured pigment the colourant is preferably present from 5 to 70% and more preferably from 10 to 50% by weight of the toner resin 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. The toner resin composition may be prepared by any method known to the art which typically involves mixing the toner resin with the ATA and optionally the colourant by kneading in a ball mill above the melting point of the resin. Generally, this involves mixing the molten composition for several hours at temperatures from 120 to 200°C, in order to uniformly distribute the ATA and colourant (if present) throughout the toner resin. The toner resin is then cooled, crushed and micronised until the mean diameter of the particles is preferably below 20μ and, for high resolution electro- reprography, more preferably from 1 to 10μ. T e powdered colour toner or toner-resin so obtained may be used directly or may be diluted with an inert solid diluent such as fine silica by mixing for example in a suitable blending machine.

The ATA can be made by any method known to the art.

When R is the group -CH^NR^ the ATA is preferably made under conventional Mannich reaction conditions whereby a compound of formula 2

wherein X and Y are as hereinbefore defined is dissolved in aqueous alkali and the requisite amount of formaldehyde and amine of formula HN^R³ added and heated together. The amount of formaldehyde is preferably between 1.0 and 1.10 molar based on the molar concentration of the compound of formula 2. Preferably the molar amount of amine of fomriula HN^R³ is the same as the amount of formaldehyde.

The reaction is very facile and is preferably carried out at temperatures below 100°C and especially below 80°C. Preferred temperatures are above 20°C and preferably above 30°C and especially above 50°C. Suitable amines of formula HNR²R³ are N nethylethylamine;

N,N-diethylamine, N,N-dibutylamine; N,N-dihexylamine; N-methyl-2-ethylhexylamine; N-nrrethyl-2-ethylbutylamine; N,N-diethanolamine and N-methylethanolamine.

When R is the group -Ch^N R³ and R¹ is other than H in the ATA the group R is preferably introduced after the group -C^NR²^³ by heating the hydroxy or thiol precursor with R¹-Hal under alkaline, especially aqueous alkaline conditions. Hal represents chlorine and especially bromine.

When R is other than the group -CH_jNR²!^³, the group R¹ is similarly preferably inserted in the ATA by reacting the hydroxy or thiol precursor with R¹-Hal.

When R is the group -CHZ, the ATA is preferably prepared by reacting a compound of formula 3

wherein X, Y, R and p are as hereinbefore defined with formuladehyde to form a hydroxymethyl derivative and heating this preferably under aqueous alkaline conditions to produce the bis analogue as represented by the ATA of formula 1 wherein Z is a group of formula 1a as hereinbefore defined.

The amount of formaldehyde is preferably 1 mole for each mole of compound of formula 3. The ATA wherein R is -CH_jZ and R¹ is C^^-alkyl or aralkyl can be conveniently prepared from the compound containing the group -XH by reacting with a

or aralkyl halide under aqueous alkaline conditions.

The amine salts of the ATA are also prepared by methods known to the art and are conveniently prepared by adding the amine to a solution of the ATA in a suitable solvent which is preferably not a solvent for the amine salt.

The metal complexes and salts and the QAC salts are conveniently prepared by adding an inorganic salt of the appropriate metal or a QAC halide to an aqueous solution of an alkali metal salt of the ATA

The preferred metals are Mg(ll), Ba(ll), Fe(lll), Al(lll) and Zn(ll). These may all be conveniently added to the ATA as their chloride salts.

As noted hereinbefore, most of the ATA are new. According to a further aspect of the invention there is provided an ATA including salts and complexes thereof with the exception of 2-mercaptonicotinic acid, 2-hydroxynicotinic acid, 2-mercaptobenzoic acid together with its 2:1 complex with zinc and 2-S-n-butylbenzoic acid.

As noted hereinbefore the ATA's including the salts and complexes thereof are useful as CCA's.

According to a still further aspect of the invention there is provided the use of the ATA including the salts and complexes thereof as a CCA with the exception of the 2:1 zinc salt or complex of 2-mercapto-benzoic acid. The invention is further illustrated by the following examples wherein all references are to parts by weight unless indicated to the contrary.

Example 1 Preparation of 2:1 zinc salt of 2-mercaptonicotinic acid

2-mercaptonicotinic acid (15.5 parts; 0.1M ex Aldrich) was stirred in water (150 ml) and a solution of sodium hydroxide (4 parts 0.1M) in water (40ml) slowly added whereupon the mercaptan dissolved to give a pale green solution.

Zinc chloride (6.82 parts; 0.05M ex Fisons) dissolved in water (15ml) was added over 30 min to the mercaptan solution with stiπing at 55-60°C. After stirring for a further 30 min, the reactants were cooled and stirred ovemight at 20-25°C. The zinc salt separated as a pale yellow solid which was filtered, washed acid-free with water and dried.

Yield = 17.02g (91% theory) mp >300°C. This is CCA 1. Bemental analysis:

Found 38.4% C, 2.3% H, 7.6% N, 15.4% S, 16.5% Zn C^H_βN S^Zn requires : 38.6% C, 2.2% H, 7.5% N, 17.2% S, 17.5% Zn

Example 2 Preparation of the 2:1 zinc salt of 2-hydroxvnicotinic acid

Example 1 was repeated except that the 2-mercaptonicotinic acid was replaced by 2-hydroxynicotinic acid (13.9 parts, 0.1M ex Aldrich). The zinc salt was obtained as a white solid.

Yield = 17.27 parts mp>300°C. This is CCA 2. Elemental analysis:

Found 38.0% C, 3.22% H, 7.4% N, 16.7% Zn, C₁₂H₈N₂0₆Zn2H₂0 requires 38.2% C, 3.2% H, 7.4% N, 17.3% Zn Example 3

Preparation of 2-ιvbutvlmercaptobenzoic acid

Thiosalicylic acid (43.12 parts; 0.28M ex Aldrich) was added over 5-10 minutes at 20-25°C to a stirred solution of sodium hydroxide (22.4 parts, 0.56M) in 220 ml 70% aqueous ethanol. n-Butylbromide (57.54 parts, 0.42M ex Fluka) was added dropwise over 10 minutes with vigorous stirring and the reaction continued at reflux for a further 3 hours. The reactants were then cooled to 20-25°C, poured into iced water (500ml) and acidified with hydrochloric acid to a pH between 2 and 3. The pale buff precipitate was filtered, washed acid-free with water and dried at 50°C. Yield = 58.0 parts (98.6% theory) mp 87-93°C.

The product was purified by dissolving in hot dichloromethane, cooling and precipitating with n-hexane mp 97-99°C. This is CCA 3. Elemental analysis

Found 62.8% C, 6.66% H, 15.2% S C_UH_MC^S requires 62.5% C, 6.3% H, 15.3% S

Example 4

Preparation of the 2:1 zinc salt of 2-n-butylmercaptobenzoic acid

2-n-butylmercaptobenzoic acid (10.5 parts, 0.05M ex Example 3) was dissolved in water (100ml) and sodium hydroxide (2 parts, 0.05M). After heating to 55-

60°C a solution of zinc chloride (3.4 parts, 0.025M ex Fisons) in water (5mls) was added with stirring whereupon the zinc salt immediately formed as a white precipitate.

After cooling to 20-25°C the solid was filtered, washed with water and dried. Yield = 7.2 parts (30% theory) mp >300°C. This is CCA 4. Elemental analysis:

Theory 54.6% C, 5.4% H, 13.25% S

requires 52.1% C, 5.6% H, 13.1% S Examples 5 to 10 and Comparative Example A Evaluation as CCA's

A styrene/acrylic resin (300 parts, AJmacryl -3-1500 ex Image Polymers Europe) and the CCA (7.5 parts) was melt kneaded at 160-180°C for 60 minutes. The resulting toner resin was then cooled, crushed and finally ground by ball-milling until an average particle size between 5 and 25μ was obtained.

The milled toner resin (0.4 parts) was then mixed with an uncoated iron powder caπier (19.6 parts, RAV-270 ex Powder Tech Corporation, Valparaiso, Indiana, USA) in an aluminium tin for 30 min on a roller mill.

The resulting CCA composition was then evaluated using a Toshiba TB 200 blow-off apparatus and the Tribo-charge measured after 30 minutes. The results are given in Table 1 below.

Table 1

Example CCA Tribo-charge (μCg^'1)

5 1 (Ex.1) -41.20

6 2 (EΞx.2) -25.43

7 3 (Ex.3) -29.60

8 4 (Ex.4) -35.72

9 5 -41.23

10 6 -26.54

Comp. A A -32.76

Footnote to Table 1:

CCA 5 is 2-mercapto-nicotinic acid CCA 6 is 2-hydroxy-nicotinic acid

Comp A is the 2:1 Zn salt of 2-mercapto-benzoic acid

These results show that the 2-mercapto-nicotinic acid derivatives are superior to 2-hydroxy-nicotinic acid derivatives as CCA which are in turn superior to 2- mercapto-benzoic acid derivatives. Also, the thio-ether of 2-mercapto-benzoic acid is a superior CCA compared with 2-mercapto-benzoic acid itself.

Example 11 Preparation of the 2:1 zinc salt of nicotinic acid

Nicotinic acid (24.6 parts; 0.2M ex Aldrich) was dissolved in water (150ml) containing sodium hydroxide (8 parts; 0.2M). The solution was heated to 55 to 60°C and a solution of zinc chloride (13.63 parts) dissolved in water (15ml) was added dropwise over 20 minutes with stirring at 55 to 60°C. After stiπing for a further 30 minutes, the reaction mix was cooled and the product filtered, washed with water and dried at 60°C.

Yield = 28.4 parts, mp > 300°C. Elemental analysis

Theory :- 46.5% C, 2.6% H, 9.0% N, 21.1 % Zn Found :- 46.1 % C, 2.7% H, 9.0% N, 20.9% Zn

The product was found to contain 0.5% (w/w) water by Karl Fischer titration.

The tribo-electric charge was -32.0 2 μ Cgm ¹ after 30 minutes as determined using the method descreibed in Examples 5 to 10.

Example 12

Preparation of 2-n-butyl mercapto nicotinic acid

Sodium hydroxide (11.2 parts; 0.28M) was dissolved in 70% aqueous methylated spirits (100mls) at about 60°C . 2-mercapto nicotinic acid (21.7 parts; 0.14M ex Aldrich) was added slowly with stiπing whereupon the acid immediately dissolved.. Bromobutane (28.77 parts, 0.21 M ex Adrich) was added slowly and the reactants stirred at reflux for 5 hours. After cooling, the reaction mix was poured into distilled water (1 litre) and acidified to about pH 2.8 with concentrated hydrochloric acid. The product, which had separated as a white solid was filtered off, washed with water and dried. Yield 29.71 parts, mp 100-110°C. The solid was then recrystallisation from methanol and dried at 50°C (mp = 121-3°C). Elemental analysis

Theory :- 56.9% C, 6.2% H, 6.6% N, 15.2% S Found :- 57.1 % C, 5.9% H, 6.6% N, 15.3% S

Example 13

Preparation of the 3:1 iron salt of 2-rHbutyl(mercaptonicotinic add

The nicotinic add as prepared in Example 12 (12.5 parts, 0.06M) was added to water (180 mis) containing sodium hydroxide (2.4 parts, 0.06M) with stirring at

55 to 60°C. After 15 minutes, almost all the nicotinic add had dissolved. The solution was screened and ferric chloride hexahydrate (5.4 parts, 0.02M) dissolved in water

(10ml) was added with stirring at 55 to 60°C. The iron salt immediately formed as a sticky solid. The reaction mix was cooled and the sticky solid isolated, washed with water and finally dried and ground. Yield = 11.1 parts.

The tribo-electric charge after 30 minutes was -36.8 μCgm¹ as determined by the method described in Examples 5 to 10.

[Example 14

Preparation of the 2:1 caldum salt of 2-n-bϋtvlmercaptobenzoic add

The benzoic add prepared as described in Example 3 (18.36 parts,

0.087M) was dissolved in water (150ml) containing sodium hydroxide (3.48 parts,

0.087M) by stiπing at 20 to 25°C. A little solid removed and hence a little 2N sodium hydroxide solution was added to dissolve the remained solid. The solution was heated

55 to 60°C and caldum chloride dihydrate (6.39 parts, 0.043M ex Fisons) was added and the reactants stirred at 55 to 60°C for a further 30 minutes,

After cooling, the product was isolated as a white solid by filtration and was washed with water and dried at about 60°C. Yield = 14.4 parts, mp 115-135°C. Bemental analysis Theory :- 57.6% C, 5.7% H, 14.0% S, Ca 8.8% Found :- 55.3% C, 6.1 % H, 10.4% S, Ca 8.1 %

This solid was found to contain 3.8% (w w) water by Karl Fischer titration.

Example 15

Preparation of the 3:1 iron complex of 2-n-butylmercaptobenzoic add

This was prepared by the same method as that described in Example 14 except using ferric chloride hexahydrate (7.84 parts, 0.029M ex Fisons) in place of the caldum chloride. The ferric salt was obtained as an orange-brown solid (19.52 parts) mp = 135-155°C. Bemental analysis

Theory :- 58.0% C, 5.7% H, 14.1% S, 8.2% Fe Found :- 56.2% C, 6.4% H, 13.3% S, 7.6% Fe

The sample was found to contain 0.5% (w/w) water as detmined by Karl Fischer titration. This is equivalent to 95.4% strength.

The tribo-electric charge after 30 minutes was -29.65 μCgm¹ as determined by the method described in Examples 5 to 10.

Claims

Ct-AJMS

1. A toner resin composition comprising a toner resin and a compound of formula 1

induding salts and metal complexes thereof; wherein

Y is =CH- or =N-;

R is halogen, hydroxy, nitro, carboxy, nitrile, optionally substituted C^_g-alkyl, -CHZ, -CH_jN^R³ or two adjacent groups R together with the carbon atoms to which they are attached form a 5- or 6- membered fused ring; R¹ is hydrogen, optionally substituted C^^-alkyl or aralkyl,

Z is hydroxy or a group of formula 1a

R² and R³ is each, independently, hydrogen, optionally substituted C^_β-alkyl, cydoalkyi or the groups R² and R³ together with the nitrogen atom to which they are attached form a 6-membered ring, n is 0 to 3; p is 0 to 2; and

X is 0 or S when Y is =N- or S when Y is =CH-; with the exception of the 2:1 zinc complex of 2-mercaptobenzoic add.

A composition as daimed in daim 1 wherein n is zero. 3. A composition as daimed in either daim 1 or daim 2 wherein Y is =N-.

4. A composition as claimed in any one of daims 1 to 3 wherein Y is =N- and X is S.

5. A composition as daimed in any one of daims 1 to 4 wherein the ATA is a salt or complex of a metal of groups 1a,2a,3a,1b,2b,6b,7b and 8 of the Periodic Table.

6. A composition as daimed in daim 5 wherein the metal is zinc, iron or caldum.

7. A composition as daimed in daim 1 wherein the compound of formula 1 is selected from 2-mercaptonicotinic add, 2-hydroxynicotinic add, 2-n-butylmercapto benzoic add, 2-n-butylmercaptonicotinic add or their metal salts.

8. A composition as daimed in any one of daims 1 to 7 which further comprises a colourant.

9. A compound of formula 1

induding salts and metal complexes thereof; wherein

R² and R³ is each, independently, hydrogen, optionally substituted C^_β-alkyl, cyclo alkyl or the groups R² and R³ together with the nitrogen atom to which they are attached form a 6-membered ring, n is 0 to 3; p is 0 to 2; and X is 0 or 5 when Y is =N- or S when Y is =CH-; with the exception of 2-mercapto nicotinic add, 2-hydroxynicotinic add, 2-S-n-butylbenzoic add and 2-mercaptobenzoic add together with its 2:1 complex with zinc.

10. A compound as daimed in daim 9 which is the 2:1 zinc salt of 2-mercaptonicotinic add, 2-hydroxynicotinic add or 2-n-butylmercapto benzoic add.

11. A compound as daimed in daim 9 which is the 3: 1 iron salt of 2-n- butylmercapto-benzoic or nicotinic add.

12. The use of a compound of formula 1 as a charge control agent.

induding salt and metal complexes thereof; wherein

R² and R³ is each, independently, hydrogen, optionally substituted C ₁₈-alkyl, cydo alkyl or the groups R² and R³ together with the nitrogen atom to which they are attached form a 6-membered ring, n is 0 to 3; p is 0 to 2; and

X is 0 or 5 when Y is =N- or S when Y is =CH-; with the exception of the 2:1 zinc complex of 2-mercaptobenzoic add.