CA1080731A - Production of azomethine pigment - Google Patents

Abstract

Abstract of the Disclosure Process for the production of a compound of formula in pigmentary form having a mean particle size not exceeding 2.0 microns, comprising a) first reacting together 2-hydroxy-1-napthaldehyde and 2-aminophenol under aqueous alkaline non-oxidising conditions, and either neutralising the reaction product or isolating the reaction product and re-dispersing it in aqueous medium and adding to the neutralized or re-dispersed reaction production whilst applying mechanical stirring to the mixture, an aqueous solution of a coppering agent, b) separating the solid product, washing it free from inor-ganic salts and optionally drying it, and c) subjecting the dried pigmentary product to a kneading, salt-milling or aqueous milling procedure.
The pigment produced is suitable for use in the pigmentation of higher molecular weight hydrophobic organic or other organic materials.

Description

~0~3~73~

The-present inventiorl relates to a process for the ~oduction of an azomethin~ pigment.
In British Patent Specification No. 1,254,336, there is described a compound having the formula-.

O,,.Cu ~O

in pigmentary form having a mean particle size notexceeding 2.0 microns. This specificatlon also discloses processes for producing compound I, directly in pigmentary form comprising either first reacting together 2-h~droxy-1-naphthaldehyde and 2-aminophenol under aqueous alkaline non-oxidising conditions9isolating and re-dispersing this ligand and adding thereto, whilst applying mechanical stirring to the mixture, an aqueous solution of a water-soluble coppering aaent; alter~atively~ the metallisati~n step can be effected directlv after formation of the lig~nd to which has been added an excess of ammonium sulphate.

.. .
We have now ~ound that by modifying this direct aqueous process by incorporating an additional step, compound I is produced in a pigmentary form and having lmproYed properties compared with the product of the un-modifi ed process.
Accordin~ly, the presen~ invention provides a process ~or the production of a compound of formula:-,, . . ,:, ... : . .... . . : , : .
.. . . . . . ~ ..

73~

~ N _ Cll ~

in pigmentary form having a mean particle sizenot exceeding 2.0 mic.rons, comprising a) first reacting together 2-hydroxy-1-napthaldehyde and 2-aminophenol under aqueous alkaline non-oxidising conditions~and e~ther neutralising the reaction product or isolating the-reaction ~roduct and re-dispersing it in aqueous medium and adding to the neutralized or re-dispersed reaction production whilst applying mechanical stirring to the mixture, an aqueous solution of a coppering ageni, b) separating the solid product, washing it ~xee ~rom inorganic salts and optionally drying it, and c) subjecting the dried pigmentary product to a kneading, -- salt-milling or aqueous milling procedure.
In step (a), oxidation of the reactants ma~ be ~re~ented by excluding air from the reactor by the use of an inert gas atmosphere~ ~or instance a nitrogen atmosphere, however oxidation is prefera~ly prevented by the presence of a reducing agent such as sodium bisulphite, sodium dithionite, sodium sulphite or glucose in the reaction mixture. If a reducing agcnt îs used, however, it may be necessary to isolate the azomethine formed in the reaction and re suspend it prior to coppering to a~oid the reducing agent interfering in the subsequent coppering reaction. The azomethine may be isolated for instance ,.

, 84~

by the addition to the reaction m:ixture Or an acid which may itself act as the reducing agent, for example sulphurous acid. Alternatively, a reducing agent may be added with the acid.
Coppering in step (a) may be carried out at any temperature from ambient to 100C., preferably at a temperature within the range of from 80 to 100C, using an aqueous solution of` any water-soluble coppering agent.
Pre~erred coppering atents are copper acetate, cuprammonium sulphate and sodium cuprotartrate. In order to effect complete coppering, some mechanical stirring action must be exerted on the suspension, for instance by vigorous agitation or by the use of a high-speed mixer or other device.
Additions of a dispersing agent may be made, i~ desired, to expedite the coppering reaction.
I~ step (c) of the process of the invention is e~fected by means of a salt~grinding technique, the product from step b) must have been dried and the salt may be any metallic salt capable of removal on completion of the grindin~D
Examples of suitable salts are water-soluble salts remo~able ~rom ~he ground materlal by washing with water, for instance alkali metal or alkaline earth metal salts of inorganic acids or of C1-C4 alkanoic acids~ Specific examples of preferred metal salts are calcium chloride, sodium chloride, sodium acetate and mixtures thereof. These salts may be used alone ~r in conjunction with an organic solvent such as dimethyl-aniline, diethylaniline or xylene.

_ _ .. , ,_ , ",,, ., . .. , , . ~ . : .
, .

7~3~

If an aqueous i~llling t~cl~nique is used in step (c), the product from s~ep(b)l~i~ normally be wet and a preferred arrangement is bead-milling e.g. in a Sussmeyer Mill ~n the presence of solid spheres such as metal, ceramic or glass balls.
The preparations according to the invention can be manufactured particularly advantageously in a eontinuously-working or batch-wise-working kneader. The material is pre-ferably worked in the presence of a substance which assists grinding3 preferably an inorganic salt, for example, sodium chloride, potassium chloride, sodium sulphate or barium chloride. These salts can be removed by eluting with water in a simple mamler. Depending on the softening point of the copolymer used, the pr~cess can be carried out in the melt, however, it is usually advisable to add an organic solvent, preferably an organic solvent which is miscible with water, for example ethylene glycol, glycerine, glycol monoethyl ether, methyl e~hyl ketone, diacetone-alcohol or dimethylsulphoxide.
Instead of pure pigments, ready for use pigments preparations can also be used, i.e. preparations which contain in addition to the pigment for example 20 to 80%, preferably between 40 and 60%, of a carrier.
Suitable granulating assistants are preferably synthetic, semi-synthetic and natural resins. The _ S _ __ .. . . .. .... ,, .. . ....................... ~

v 7 ~

synthetic or semi-synthetic resins can be polymerisation, polycondensation or polyaddition products In principle it is possible to use all resins and binders commonly in use in the paint and printing ink industry and described, for exampl~, in the paint and varrlish raw materials tables of Karsten, 4tho and 5th. edition, Hannover, 1967 and 1972 respectively, and/or in Wagner and Sarx's book on paint resins, 5th, edition, Munich 1971. High molecular weight compounds with plastic character~ as described for example in the "Kunststoff_Taschenbuch"3 Carl Hanser Verlag, Munich ~18th. edition 1971), can also be used as granulating assistants. It is pre~erred to use those resins which do not react further chemically on contact with air or with themselves and possibly crosslink.
Preferred classes of resin are:
(a) colophonium and its derivatives in all forms, for example hydrogenated, dimerised or polymerised, esterified with mono-hydric or polyhydric alcohols, with resin ~ormers, as for example acrylic acid and butanedio~ or maleic acid and pentaerythritol, modified colophonium resin, calcium or zinc salts of colophonium, abietic acid and esters thereof; the soluble phenolic resins modified wi~h colophonium and resins based on acrylic compounds, as well as other natural resins9 as for example linseed oil varnish, shellack and other copals, and water_soluble salts of rosinamine;

....... ~.. . , . ~

. .
- , - . : :, .. . ~ . ' . .

.

3 ~

(b~ maleic resins, oil_free alkyd resins, styrenated alkyd res:ins, vinyl toluene modified alkyd resins, alkyd resins with synthetic fatty acids, linseed oil alkyd resinsg ricinenic alkyd resins, castor oil alkyd resins,soya oil alkyd resins, coconut oil alkyd resins, tall oil and fish oil alkyd resins and acrylated alkyd resins, (c~ terpene resins and terpenephenol resins;
(d) polyvinyl resins, e.g.: polyvinyl acetate, polyvinyl chloride and polyvinylidene chloride , polyvinyl acetals, polyvinyl ethers, copolymers and graft copolymers with different vinyl monomers, polyacrylic acid resins, as for example acrylic and methacrylic esters and their copol~mers;
(e) styrene polymers and copolymers;
(f) polyolefins, polyethylene, polypropylene, polybutylene, polyisobutylene, polyisoprene, substituted polyolefins, halogenated polyole~ins and their copolymers, as for ex~mple e~hylene and vinyl acetate copolymers and other synthetic resins based on unsaturated hydrocarbons, e.g. low molecular polystyrenes, and especially the polyolefins of average poly-li2 marisation with a molecular weight of 300-5000 ~Rr~n~
~ ,~
~e~, (g) polyamide and polyester resins5 as for example linear or branched polyester resins based on phthalic acid, adipic acid or sebacic acid;
(h) coumarone, indene, coumarone_indene and ketone resins;

~; .
..

73:~

(i) cellulose derivatives, e.g. cellulose ethers, as for example ethyl cellulose and benzyl cellulose in ordinary commercial form, and also cellulose esters, as for example cellulose acetate, cellulose acetobutyrate and nitrocellulose, which can also be undernitrated.
The pigment produced in accordance with the present invention may give shades ranging from greenish yellow to ~eddish yellow depending on the methods of preparation and pigmentation employed. The pigment produced is suitable for use in the pigmentation of high molecular weight hydrophobic organic or other organic materials. The pigment is distinguished by-its high colour strength, high resistance to solvents, outstandingly good fastness to overprinting and especially by its resistance to weathering when incorporated into surface coatings. The pigment Or this invention is suitable, for example, for use in the pigmentation o~ high molecular ~eight hydrophobic organic material, for instance of paints, .lacquers, printing inks, rubber, synthetic polymeric materials, paper and textile materials. In general, the pigment of the present invention exhibits good fastness properties especially to light, heat, cross-lacquering and migration, and resistance to organic solvents, such as trichloroethylene, toluene and methyl ethyl l~etone.
Comp~red with pigments of formula I produced without ~tep (c) of the process of the invention, the pigment produced according to the invention is cleaner, more trans- . ..

-- 8 _ '~` ' ' , .

'73~L

parent and exhibits higher gloss in automotive paint systcms.
The prcsent in~ention also provides a compositlon comprising an organic material and a pigment of formula I
produced according to the proces.s o~ the invent~on, as her~inbefore defined; as well as a method of colouring or~anic ma-terial comprising incorporating therein the pigmcntary product of '~he process of the present invention.
~ he high molecular weight hydrophobic organic material or other org~nic material to be coloured may bc any polymeric or other organic material capable of being pigmented oY~
o~herwise coloured. The material may be, for instance, a natural or synthetic polymer or copolymer, a coating oomposition for application to the sur~ace o~ an article, or a printing liquid medium. Howe~er, prererred materials are natural or synthetic pol~;mers o~ co-polymers, in the ~orm offilms or bulk material; paints) lacquers and other surface coating compositions, or tinting compositions for use ~n preparing such coating compositions; and printing iA~
Examples o~ polyn-ers o~ co-pol)~ers which may be pigmented i~cl~de ~inyl chloride polymers and co-polymers; polyethylene, polyacrylonitrile, polypropylene and other polyole~ines;
polystyrene and pol)styrene co-poly~ers; and natural and ~ynthetic rubbersO
~ le pre~ent invention is further illustrated by the following Examples. Parts and percentage shown therein are expressed by weight. In Examples 1 to 7 the resulting _ 9 _ .

' :,, '7~

p:l gment was found to have a mean pa:rticle siz~ not exc~ding 2 . O microns .

- 10_ .
. .
.~ ` ' ' ` ' '' ' ' ' " ' . . .
- . . :.

' , 73~

Examp~e 1 a) 17.2 Parts of 2-hydroxy~1-naphthaldehyde and 10.9 parts of 2-aminophenol were added to 150 par*s of water, with stirri~g~ A solution of 4.2 parts of sodium hydroxide in 50 parts of water was added followed by 15.6 parts of sodium bisulphite. The resulting suspension was heated to 90~C. and stirred. The product was ~iltered of~ and washed with water. The washed product was slurried in 250 parts of water with high-speed shear agitation. A solution of cuprammonium sulphate, prepared by dissolving 27~5 parts of copper sulphate crystals in 100 parts of water and adding concentrated a~nonium hydroxide solution until the initial precipitate had re-dissolved, was added. The resulting mixture was heated to 95co and stirred. The product ~as filtered off~
washed with water and dried. These were thus obtained 33 parts of green powder, having a copper content of 19.75~o.

(b) 25 parts of the product from part (a) were gro~nd w~ 6~ parts Or a~ydrous calcium chloride, tO parts of anl~drous sodium acetate and 205 parts of diethylaniline for 6 hours. The salt/pigment mixiure was dischar~cd, ad~ed to aq~eo~s acetic acid and stirred for 1 hour at 60C~
Th~ ~igment was isolated by filtration, washed free fronl acid and sal1; and dried at 60C. The pigment so obtained was cleaner and greener~ Inore transparent and had l~ er gloss in aut~motive paint systems than the product fro~
part (a).

.:

' ,' ' : , .:
.
- ' ' : . ,: : : , :~ , 8~7~ :
I

~xamplc ?

Simila~ results ~ere obtained when the anhydrous calciwn chloride used in ~.~ample 1 ~as replaced by anhydrous sodium suiphate.
Exam~le ~

Similar results were obtained when Example 1 was repeated but using 3.75 parts of diethylaniline and milling for 4 hours.
~a ~

, 20 parts of the product ~rom ~xample l(a) was ground for 16 hours in 200 parts of water using a Sussmeyer Mill and 1 mm. diameter glass beads as t~le grinding elei~ents.
The gl~ss beads were then removed by sieving and the pigment was isolated by filtration and drying at 50C.
e pi~me~t s~ obtained was stronger, cleaner~
~lightly redder, more transparent and had a higher gloss in an a~tomoti~re paint system than the product of Example t(a).

_.. ~. . , .... . . .. _ . , _ _ _ ... . ' ' '' :

.. . . . .
. ~
- - , . .

Example 5 The following constituents are placed into a laboratory kneader (nominal volume ~50 ml):
25 g of pigment according to Example la, 100 g of finely ground NaCl and 30 g of diacetone alcohol.
The mixture is kneaded for 5 hours with cooling. The kneaded material is subsequently taken up in 4 litres of water so that the NaCl and solvent become dissolved. The suspension is filtered on a suction filter; the residue is washed with as much water as required until free from salt and solvent, and the filter cake obtained is dried in a vacuum chamber at 80.
The resulting pigment produces in lacquers dyein~s having a high degree of transparency and a very good lustre.

~ .
If the procedure is carried out as in Example 5 with the exception that there is added to the kneaded ~ .~
L~ material 2.78 g of Staybelite Resin (HERCULES), then there is obtained a pigment containing 10% of resin~ which pigment is characterised by the property of being more easily incorpo~ated and by better dispersibility.

_ 13 -~.

:'.~ " '' ' ' ", . '. ' . ," ., : '' ', " , , . , . ' . ' ' ' . ' '' ' . ' " "" ' ' . ' ., ' ' '' : '' ' ' .. ' " ' ' ' ' , ~. .:

Example 7 ~ pigment preparation which can be incorporated into lacquers with little effort by simple stirring, e.g.
with a dissolver, and which produces lacquer dyeings 7 especially also in metallised lacquers 9 having outstanding transparency and an excellent lustre is obtained by processing a composition in a kneading apparatus as follows:
80 parts of pigment according to Example la, 120 parts of cellulose acetatebutyrate B (~531-1; Eastman), 400 parts of finely ground NaCl, and 120 parts of diacetone alcohol.
are kneaded for 4 hours at 70C. The kneaded material is di~n~ratedby the addition of 150 parts of water, and then granulated in the kneader for one hour with cooling. The granulate is suspended in ~4000 parts of water, and to obtain maximum fineness of granulation the suspension is passed through a colloid mill. ~iltration is subsequently performed; the residue is washed with as much wa~er as required u~til free from salt and solvent, and the resulting filter cake is dried at 80 in a vacuum chamber. There is obtained a yellow preparation having a -s~ ~ J- - 14 _ ~e ~
, - - . . . . . . .
; ' . .'~ ,. ~ . , ~ ': . , , ~ . , . ~ . . , .:
:. ~ . . : . .. . .

: , ~,,- : , 7 3~

pigment content of 40% and being of the aforementioned excellent quality, which preparation can be used, e.g., for the dyeing of lacquers.

- 15 _ :

."~__,.. _.__.. _.. . . ...... ... _.___._.. _.___.. _.. ___.. _.. _._.___.. _.~.___.. _._.. ,______.. ___.~__._.. _.~.. __~._._._.__.. ~__._-.. --'.. ''''--.'-'-~
---'''.. ~.~.t r~ ~~

,: . . : ... : , ~ : ; -: . ' ' '. ~' '. ' . ' ' .'' ' ',, ' : ' ~',, ' ' , '. . -. : ' ': , : ' ' ~ ' ,: :: :. , :. :

, .: , '. ,: : : : '- . - . . :
, ,, :. . . - . . . . .
: ' , ' ', . : .
,,: : , ':
- , . : , ' ' ' '. ' . : , . : , : . , , . .:
:, .: : . : : .: .

Claims (7)

What we claim is:

1. A process for the production of a compound of formula (I) in pigmentary form having a mean particle size not exceeding 2.0 microns, comprising a) first reacting together 2-hydroxy-1-naphthaldehyde and 2-aminophenol under aqueous alkaline non-oxidising con-ditions, and either neutralising the reaction product or isolating the reaction product and re-dispersing it in aqueous medium and adding to the neutralized or re-dispersed reaction production whilst applying mechanical stirring to the mixture, an aqueous solution of a coppering agent, b) separating the solid product, washing it free from inorganic salts and optionally drying it, and c) subjecting the dried pigmentary product to a kneading, salt-milling or aqueous milling procedure.

2. A process as claimed in claim 1 wherein the coppering agent is hydrated cupric sulphate.

3. A process as claimed in claim 1 wherein oxida-tion is prevented by the use of an atmosphere of an inert gas to exclude air.

4. A process as claimed in claim 1 wherein oxidation is prevented by the use of a reducing agent.

5. A process as claimed in claim 1 wherein the azomethine compound is isolated by the addition to the reaction mixture of an acid.

6. A process as claimed in claim 5 wherein the acid has reducing properties.

7. A process as claimed in claim 5 or 6 wherein a reducing agent is added together with the acid.