DISPERSIONS OF SOLIDS IN ORGANIC LIQUIDS

Abstract: A pigment dispersion which comprises from 5 to 90% by weight of at least one pigment and/or extender, from 0.01 to 50% by weight of a pigment dispersant which contains in its molecule at least one polar segment and at least one polymeric, non-polar, solvent compatible segment having a molecular weight in the range of from 500 to 10,000, preferably 500 to 3,000 and is derived from repeating monomer units of an unsaturated hydrocarbon; and an organic liquid dispersing medium which comprises at least a major proportion of a hydrocarbon or chlorinated hydrocarbon.

Description: DISPERSIONS OF SOLIDS IN ORGANIC LIQUIDS The present invention relates to pigment dispersions which comprise particular pigment dispersants which promote the dispersion in liquid organic media of solids, in particular, inorganic and organic pigments or dyestuffs, and to paints, enamels, printing inks and other surface coatings, and to articles made of plastics or rubbers, and other compositions which contain the dispersions of the invention. Accordingly the present invention provides a pigment dispersion which comprises from 5 to 90% by weight of at least one pigment and/or extender, from 0.01 to 50% by weight of a pigment dispersant which contains in its molecule at least one polar segment and at least one polymeric, non-polar, solvent compatible segment having a molecular weight in the range of from 500 to 10,000, preferably 500 to 3,000, and is derived from repeating monomer units of an unsaturated hydrocarbon; and an organic liquid dispersing medium which comprises at least a major proportion of a hydrocarbon or chlorinated hydrocarbon. The molecular structure of the dispersants used in the present invention is distinguished by comprising at least one segment (A) which is polymeric, non-polar and essentially hydrocarbyl in composition, the segment (A) being covalently linked to segment (B) which is polar. In simple outline, the structure of the dispersing agents may be represented by the diagrams: A-B (A) n -B A-B-A A-B-(A) n (A) n -B-(A) n etc. In relation to segment A, by non-polar polymeric and essentially hydrocarbyl, we mean that each segment comprises repeating units corresponding to one or more parent unsaturated hydrocarbon monomers such as ethylene (ethene), propylene, 1,3- butadiene or isobutylene (2-methyl-l-propene), which repeat to the extent that the average degree of polymerisation of the hydrocarbyl segment lies within the range from 10 to about 350, and preferably within the range 10 to 200, most preferably 10 to 70. With respect to the polar segment B, this may, on the one hand, consist of a group exhibiting a relatively low formula weight, not exceeding say about 400, such as carboxyl, ester, amide etc. It will be understood that such a group may be simple or may be relatively complex in structure, comprising either only one or several radicals. Indeed, in forming the dispersing agents of the invention, a preferred class of groups to be present in segment B are the half esters and substituted half esters of 1,2-dicarboxylic acids, or the amides and N - substituted amides of 1,2-dicarboxylic acids. On the other hand, segment B may be represented by a polymeric sequence of repeating polar groups or units which may be linked to segment A through one of the same type of polar groups or through a different polar group. Such repeating groups or units comprise ether groups, amides, esters, urethanes etc. while the polar unit through which segment A may be linked to the polymeric polar segment may be one of the same aforesaid types or may be different, such as a carboxyl, sulphonyl, hydrazo or ureido groups. A preferred polymeric sequence contains a plurality of urethane groups linked to segment A through a urethane, ester, amide or urea group. The degree of polymerisation of the polar segment (B) corresponds to the range from 2 to about 50, preferably from 2 to about 5. While not wishing to be limited by theory, it is believed that the polar group or groups become adsorbed onto the surface of the pigment, while the polymeric non-polar group extends into the organic liquid and sterically prevents agglomeration of the pigment particles. Compounds having a combination of polar sections and non-polar sections in the molecule are known as surfactants, but such surfactants have hydrophobic sections of relatively low molecular weight (typically up to 250) and as such, do not function as effectively as materials of the present invention. One preferred class (A) of dispersants is represented by formula I: wherein either C or D is a hydrophobic straight or branched polymeric chain, the other being hydrogen; preferred are polyethylene, butadiene or polyisobutylene; M is hydrogen or a metal ion or an ammonium or substituted ammonium ion; suitable ions are Na + , K + , NHj, HN + (Me) 3 and HN + (Et) 3 ; X is 0 or NR where R is hydrogen, alkyl (such as methyl, ethyl) cycloalkyl (such as cyclohexyl), aryl (such as phenyl) or aralkyl (such as benzyl); Q is hydrogen or TZ where T is alkylene, arylene, poly(alkylene oxide), poly(alkylene imine), polyurethane, polyurea, polyester or polyamide; and Z is hydrogen, hydroxyl, N(R) 2 or the group: The compounds represented by formula I are most conveniently prepared by a two-stage reaction procedure, the first of which is the maleinisation of unsaturated compounds having one carbon - carbon double bond located near to the end of the molecule to give the compounds of formula II. Preferred unsaturated compounds are polyisobutylene and long chain - olefins such as those produced by the oligomerisation of ethylene. Maleinisation may be carried out by heating the compound with maleic anhydride at temperatures of up to 220°. Such reactions are well known. The reaction of the compounds of formula II with alcohols or amines gives the compounds of formula I. The reaction of one mole of the compound of formula II with one mole of a mon functional alcohol or amine produces a product of the AB type. The reaction of 2 moles of the compound of formula II with one mole of a difunctional alcohol or amine produces a material of the ABA type. Suitable alcohols include methanol, ethanol, propanol; diols such as ethylene glycol; and polyalkylene oxides such as polyethylene glycol. Alternatively di-hydroxy-ter inated low molecular weight polyesters and polyurethanes may be used. The polyesters may be prepared by the reaction of a diacid (such as terephthalic acid or adipic acid), a diacid chloride (such as isophthaloyl chloride) or a diester (such as dimethyl phthalate or dimethyl adipate), with a stoichiometric excess of a diol (such as hexamethylene diol, butanediol or hydroquinone). The polyurethanes may be prepared by reaction of a di-isocyanate (such as toluene di-isocyanate, particularly the commercially available mixture of 2,4- and 2,6-toluene di-isocyanates, 4,4-di(isocyanato phenyl) methane or hexamethylene di-isocyanate with an excess of a diol as previously described. These preparations of polyurethanes and polyesters are well known and any suitable preparative procedures can be used. Hydroxy-terminated polyurethanes are particularly preferred as giving very effective dispersants for organic pigments when reacted with a compund of formula II. The anhydrides of formula II may be reacted with amines to give half amides. Suitable amines include n-butylamine, hexadecylamine, ammonia, diamines (such as 1, 2-diaminoethane) and amino alcohols (such as ethanolamine). Long-chain amines (such as hexadecyl amine) and amino alcohols (such as ethanol amine) are particularly preferred as giving very effective dispersants for inorganic pigments. Other amines which may be used are diamino-terminated polyamides and polyureas. The polyamides may be prepared by well-known procedures such as by the reaction of a dicarboxylic acid, diacid chloride or diester (as previously described) with an excess of a diamine (such as ethylene diamine, hexamethylene diamine or p-phenylene diamine). The polyureas may be made by reaction of a di-isocyanate (as previously described) with an excess of a diamine (as previously described) or by any other well-known procedure. A further class (B) of dispersants for use in the present invention is represented by formula III. A convenient method of synthesising this type of compound is by the cyclisation of the half amides represented by formula I in which X = NH. On heating, these compounds lose water and cyclise to form the amide III. A further class (C) of dispersants for use in the present invention is represented by formula IV which may be formed from the imides of formula III (Z = N(R)-) by quaternisation by standard techniques. These include reaction with methyl iodide or dimethyl sulphate. In formula IV, E may be sulphate, bisulphate, monoalkyl or monoaryl sulphate, chloride, bromide or iodide or other such inorganic or organic ion, and x is 1, 2 or 3. The reaction of polyisobutylene with maleic anhydride to give polyisobutenyl succinic anhydride (PIBSA) and subsequent reaction with a polyamine (eg tetraethylene pentamine) gives a complex mixture of products containing such compounds as V. Such additives are known as additives for lubricating oils) e.g. U.S. 3,252,908, 3,762,873, 3,632,510, Ger Offen DE 3,246,123 and 2,232,028). Such additives are used as corrosion inhibitors, oxidation inhibitors, emulsifying agents and suspending agents. In their latter role, they are able to disperse and suspend small particles of metal, carbon and other foreign matter in the oil and prevent sludge formation. In fulfilling this role, they are sometimes referred to as dispersants, but this application is quite different from the present invention. In the oil application, they suspend small amounts of solid, whereas in the present invention, the materials are able to disperse high levels (up to 90% parts by weight of total) of pigment, and in doing so must wet out the original pigment surface and any new surface produced during the milling stage, to prevent flocculation of the dispersed pigment and to reduce the viscosity of the dispersion so that it is fluid even at high pigment loadings. Another class (D) of materials claimed in the present invention is illustrated by structure VI. VI MO - C - J - C - X - polybutadiene in which X is 0 or NH; J is a divalent linking group; and M is as above defined. These compounds may be prepared from a hydroxy-terminated polybutadiene (itself made by reaction of a polybutadienyl lithium with an alkylene oxide, such as propylene oxide or ethylene oxide) with a cyclic carboxylic anhydride. Phthalic anhydride, maleic anhydride and particularly succinic anhydride are preferred. As can be seen in the examples quoted later, a dispersant which gives good dispersing efficiency for one pigment may not be as efficient for another pigment. It is an advantage of the present invention that a wide range of different dispersant types can be made and a particular product chosen for use with a particular pigment. In general, it is found that the half-esters and half-amides are effective for inorganic pigments, whereas for organic pigments, a more complex polar group such as a polyurethane group is required. The pigment dispersants used in the present invention are included in the dispersions in an amount of from 0.01 to 50% by weight based on the weight of the dispersion, preferably 0.1 to 20% by weight. These levels are lower than those normally used in such dispersions in the prior art. It is highly desirable to use the lowest level of dispersing agent necessary to achieve good dispersion both on economic grounds and to minimise any undesirable side-effects which the dispersing agent may have on the properties of the final paint, ink or the like. The pigment dispersions of the present invention contain from 5 to 90% by weight of at least one pigment based on the weight of dispersion, preferably 15 to 60% in the case of organic pigments and 40 to 90% in the case of inorganic pigments. It is highly desirable to achieve the highest possible level of solid material in the dispersion, whilst maintaining fluidity, both on economic grounds and in order to give the paint or ink manufacturer greater flexibility in product formulation. The levels of solid material in the dispersions of the present invention are in general higher than those found in the prior art. Organic liquids which are suitable as dispersing media for the pigments include aliphatic and aromatic hydrocarbons and mixtures thereof and chlorinated hydrocarbons. Preferred solvents are xylene, toluene, chlorobenzene, carbon tetrachloride, chloroform, white spirit and perchlor ethylene. The organic liquid may contain a minor proportion of a polar solvent, such as an ester, ketone or alcohol, A mixture such as xylene/butanol is suitable for use in the invention. In general, the solvent selected depends upon the final use for the dispersion and on the solubility of the other components such as resin binders used in the final paint or ink. The dispersing agent should be soluble, partially soluble or dispersible in the organic liquid. A wide range of pigments may be used in the dispersions of the present invention. Suitable materials are listed in "Encyclopedia of Chemical Technology", Third Edition, Vol 17, P. 788-870 (Wiley). Examples of typical inorganic pigments are titanium dioxide, zinc oxide, iron oxides, carbon black, the chromates, molybdates and sulphate/chromates of lead, barium and calcium, cadmium sulphide, chromium oxide, cobalt blue, lithopone, mercury-cadmium oranges and reds, ultramarine, zirconium oxide, zinc chromate and molybdate, zinc sulphide, Prussian blue and vermillion. Extenders and fillers such as calcium carbonate, talc, mica, kaolin, and barytes may also be included in the composition. Examples of typical organic pigments are those based on the azo and diazo compounds, phthalocyanines, especially copper phthalocyanines, quinacridones, dioxazines, thioindigos, indanthrones, isoindanthrones, anthraquinones, triphendioxazines, lakes and toners. The dispersing agents of the invention may be used alone, or in the case of organic pigments, may be used advantageously in conjunction with auxiliary dispersing agents based on modified pigments, such as Solsperse 22000 and Solsperse 25000, which are commercially available. The dispersions may also contain other additives such as resins, rheology-modifying agents, wetting agents, anti-settling agents, other dispersants, and preservatives, etc. The pigment dispersions of the present invention may be used in a variety of end applications, including paints, inks and other resinous coatings containing resins such as alkyd, acrylics, melamine/formaldehyde or chlorinated rubbers as the binders therefor. The dispersions may be made by conventional techniques which are well known in the art and described in "Surface Coatings - Vol 2" p 439-444 Oil and Colour Chemists Assn, Australia (Chapman § Hall). The methods which may be used include ball-milling, sand-milling, high-speed dispersing, cavitation mixing, etc. The pigment and any other solids, the organic liquid and the dispersing agent may be mixed together all at once or separately in any order. Mixing and/or grinding is continued until a stable dispersion is obtained with the mean particle size of the solid reduced to the required size, usually below 10 microns and preferably below 5 microns. The solid or aqueous slurry of the solid may be treated with a solution of the dispersing agent in a solvent or with an aqueous emulsion of such a solution. The solvent and water may subsequently be removed to give a dry pigment which can then be easily redispersed at a later stage. The present invention includes within its scope a pigment which is coated with a pigment dispersant which contains in its molecule at least one polar segment and at least one polymeric, non-polar, solvent compatible segment having a molecular weight in the range of from 500 to 10,000, preferably 500 to 3,000, and is derived from repeating monomer units of an unsaturated hydrocarbon. The coated pigments may be used in a variety of end applications. These include paints, inks, and other coatings containing resins such as alkyds, acrylics, melamine/formaldehyde or chlorinated rubbers as binders for such coatings. They may also be incorporated directly as pigments in the manufacture of plastic materials. For this end use they are incorporated into the plastic during manufacture and for processing. The coated pigments are preferably in particulate form. The invention is further illustrated by the following examples. (In the examples, toluene di-isocyanate refers to the commercially available 80:20 mixture of the 2:4- and 2:6- isomers.) Example l. Polyiaobutenyl Succinic Anhydride. Ά A mixture of Napvis D3 (polyisobutylene, average molecular weight 650, BP Chemicals, 130 g) and maleic anhydride (25.5 g 30% molar excess) was heated for 15 hours with stirring under nitrogen while the temperature was gradually increased from 180° to 215°. The dark-brown liquid was cooled, diluted with hexane and filtered to remove some brown charred material to give a 60% w/w solution of polyisobutenyl succinic anhydride (PIBSA) in hexane. Titration of a sample against methanoliσ sodium hydroxide using phenol phthalein as indicator gave an acid vale equivalent to 0.131 equivalents of anhydride per 100 g of polymer. A second sample was diluted with hexane and extracted with several portions of 1% aqueous sodium chloride solution. The combined aqueous extracts were titrated against aqueous sodium hydroxide solution using phenol phthalein as indicator. This showed that 0.030 equivalents of free maleic anhydride per 100 g polymer were present. Bound anhydride was, by difference 0.101 equivalents per 100 g of polymer, or 76% of the theoretical amount. The hexane was removed under reduced pressure to give Dispersing Agent 1 as a viscous brown liquid. B. Similarly maleinised were Hyvis 07 and Hyvis 10 (polyisobutylenes of average molecular weight 450 and 1000 respectively, BP Chemicals) . These gave Intermediates 1 and 2 respectively. Example 2. PIBSA Methyl Half-Ester. 5 To a 50% w/w solution (50 g) of Dispersing Agent 1 in xylene was added methanol (5 g) and one drop of triethylamine as catalyst. The mixture was heated under reflux under nitrogen for 3 hours using an oil bath at a maximum temperature of 10 100°. Disappearance of the anhydride absorption band in the infra-red spectrum indicated complete reaction. The product was a brown solution (Dispersing Agent 2) , an approximately 50% w/w solution of the half ester in xylene. 15 Example 3. PIBSA Methyl Half-Ester Triethylammonium Salt One equivalent of triethylamine per equivalent.of acid was added to Dispersing Agent 2 to give Dispersing Agent 3. 20 Example 4. Half-Amide from PIBSA and Ethanolamine. To a 50% solution of Dispersing Agent 1 in xylene was added slowly and with stirring one mole equivalent of ethanolamine per mole of total anhydride. The total mixture became warm 25 and external cooling was used to maintain the temperature below 50° to avoid cyclisation to the imide. The product (Dispersing Agent 4) was a brown liquid, an approximately 50% w/w solution of the half-amide in xylene. 30 Example 5. Half-Amide from PIBSA and 3-(N/N-Dimethylamino)Propylamine. Using 3-(N,N-Dimethylamino)Propylamine in place of ethanolamine. Dispersing Agent 5 was prepared as an 35 approximately 50% w/w solution of the half-amide in xylene. Example 6. Imide from PIBSA and 3-(N,N-Dimethyl mino)Propylamine. 40 Dispersing Agent 5 was heated to reflux temperature under nitrogen and the water produced was removed from the distillate using a Dean-Stark trap. Heating was continued - 15 - until no more water was produced. This took about two hours. Completion of the reaction was confirmed by the disappearance of the absorption in the infra-red spectrum at about 1650 cm 1 and 1560 cm" 1 and their replacement by an absorption band at about 1710 cm" 1 , the product was a brown solution (Dispersing Agent 6) , an approximately 50% w/w solution of the imide in xylene. Example 7. Quaternary Salt. Dispersing Agent 6 (30 g) was heated to 40° under nitrogen. Dimethyl sulphate (2.2 g) was added with stirring. The temperature of the mixture rose to 64°. When the exotherm had finished, the mixture was heated at 90° for 1 hour and then cooled to give Dispersing Agent 7 an approximately 50% w/w solution of the quaternary salt in xylene. Example 8. In a similar manner to that described in Example 4, an approximately 50% w/w solution of the half-amide in xylene (Dispersing Agent 8) was produced from Intermediate 1 and ethanolamine. Example 9. Similarly reaction of Intermediate 2 and ethanolamine gave an approximately 50% w/w solution of the half-amide in xylene (Dispersing Agent 9) . Example 10. Half-Ester from PIBSA and Polyethylene Glycol. A mixture of Dispersing Agent 1 (10 g), polyethylene glycol monomethyl ether (4.8 g, average molecular weight 350, Aldrich Chemical Company Limited) and 1,4-diazabicyclo [2.2.2] octane (DABCO 0.1 g) was heated with stirring under nitrogen at 165-170° for 6 hours to give a half-ester as a viscous brown liquid. Dispersing Agent 10. Example 11. Carbory-terminated Polybutadiene. Hydroxy-functional polybutadiene (100 g, average molecular weight 1500 by g.p.c. analysis) prepared by end-capping living polybutadienyl lithium with propylene oxide, was heated a five molar excess of succinic anhydride, xylene (10 g) , triethylamine (0.2 g) as catalyst and N,N'-diphenyl-p-phenylendiamine (0.1 g) as antioxidant, under nitrogen for 6 hours at 150°. The mixture was cooled, filtered and the solvent removed under reduced pressure from the filtrate to give Dispersing Agent 11. Example 12. Di-half-amide from PIBSA and 1,2-Diaminoethane. In a similar manner to that of Example 4, an approximately 50% w/w solution (Dispersing Agent 12) of the diamide in xylene was prepared from 2 moles of Dispersing Agent 1 per mole of 1,2-diaminoethane. Example 13. Polyisobutylene-Polyurethane-Polyisobutylene Triblock Polymer. A. Dlhydroxy-terminated Polyurethane Oligomer. A mixture of Ethylene glycol (6.2 g) and dibutyl tin dilaurate (0.1 g) in dry acetone (15 g) was warmed until a clear solution was obtained. Toluene di-isocyanate (8.7 g) was added slowly with stirring, the heat of the reaction causing the acetone to reflux. A sample taken 15 minutes after the end of the isocyanate addition showed no absorption due to isocyanate in the infra-red spectrum. The acetone was removed under reduced pressure to give a dihydroxy-terminated polyurethane oligomer (Intermediate 3) as a viscous colourless liquid which had a tendency to solidify on standing. B. A mixture of Intermediate 3 (1.7 g) , Dispersing Agent 1 (8.4 g) and DABCO (0.1 g) was heated under nitrogen for four hours at 175° with stirring. Completion of reaction was indicated by the disappearance of the anhydride absorption in the infra-red spectrum. When cool, the product was a very viscous brown liquid. Dispersing Agent 13. Example 14. Polyisobutylene-Polyamide-Polyisobutylene Triblock Polymer. A. Pi mino- erminated Polyamide Oligomer. To a solution of hexamethylene diamine (11.6 g) and triethylamine (10.1 g) in chloroform (150 g) was added slowly, and with stirring and cooling, a solution of isophthaloyl chloride (10.2 g) in chloroform (50 g) . The white slurry was filtered, the residue washed with chloroform (100 ml) and dried under reduced pressure to give a diamino-terminated polyamide oligomer (Intermediate 4) as a white powder (22 g) . B. A mixture of Intermediate 4 (1.8 g) , Dispersing Agent 1 (7.7 g) and triethylamine (1.0 g) was heated at 90° under nitrogen for 6 hours". Xylene (10 g) was added and the solution filtered. The solvent was removed from the filtrate under reduced pressure to give a viscous brown oil (Dispersing Agent 14) . Example 15. Polyisobutylene-Polyester-Polyisobutylene Triblock Polymer. A. Dihydroxy-terminated Polyester Oligomer. 1,6-Hexanediol (11.8 g) was heated to 70° under nitrogen on an oil bath and isophthaloyl chloride (15.2 g) was added in small portions over about 30 minutes. Hydrogen chloride was evolved as the reaction proceeded. When the addition was complete, the temperature was raised to 135° and held for 30 minutes to give a dihydroxy-terminated polyester oligomer (Intermediate 5) as a viscous colourless liquid which solidified on cooling. B. A mixture of Intermediate 5 (4.3 g) , Dispersing Agent 1 (7.7 g) and DABCO (0.1 g) was heated at 175° with stirring under nitrogen for four hours during which time the mixture became homogeneous. The product. Dispersing Agent 15 was a very viscous brown liquid when cool. Example 16. Polyisobutylene-Polyurea-Polyisobutylene Triblock Polymer. A. Diamino-terminated Polyurea Oligomer. To a solution of 1,6-Hexanediamine (11.6 g) in dry methyl ethyl ketone (150 ml) was added slowly, with stirring an cooling, toluene di-isocyanate (13.05 g) . The white solid formed was isolated by filtration and dried under reduced pressure to give a diamino-terminated polyurea oligomer (Intermediate 6, 24 g) as a cream-coloured solid. B. A mixture of Intermediate 6 (5.1 g) , Dispersing Agent 1 (7.9 g) and xylene (5 g) was heated for four hours at 90°. Completion of reaction was indicated by the loss o anhydride absorption in the infra-red spectrum. A further portion of xylene (5 g) was added, the mixture filtered and the xylene removed under reduced pressure t give Dispersing Agent 16 as a viscous brown liquid. Example 17. Polybutadiene-Polyurethane-Polybutadiene Triblock Polymer. A solution of toluene di-isocyanate (3.48 g) and dibutyltin dilaurate (0.1 g) in dry acetone (8 ml) was warmed to reflux temperature under nitrogen. A solution of 1,6-hexanediol (1.18 g) in dry acetone (10 ml) was added over 30 minutes an then a hydroxy-terminated polybutadiene (30 g, average molecular weight 1500) was added over about 30 minutes with stirring. The mixture was heated under reflux for a further 30 minutes and then cooled to give a very pale yellow solution (Dispersing Agent 17 72% w/w in acetone) of the triblock polymer. _ _ _, - - 87/05924 Example 18. Dispersant Containing Polyethylene As The Hydrophobe. A. A mixture of Gulftene 30+ (84 g, an alpha olefin fraction containing about 78% of olefins of carbon number 30 and above, produced by polymerisation of ethylene. Gulf Oil Chemicals Company) , maleic anhydride (20 g) and phenothiazine (0.2 g) as polymerisation inhibitor was heated to 185-220° under nitrogen with stirring for 12 hours to give a brown liquid which cooled to a pale brown wax Intermediate 7. Analysis indicated the presence of 0.138 moles of total anhydride per 100 g product (70% of theory) with 0.002 moles of free anhydride per 100 g product. B. A mixture of Intermediate 7 (10 g) and xylene (10 g) was warmed to give a clear brown solution which formed a thick slurry on cooling. Ethanolamine (0.83 ml) was added slowly with stirring and cooling to give Dispersing Agent 18, an opaque waxy approximately 50% w/w slurry in xylene containing the half-amide of polyethylene succinic anhydride and ethanolamine. Example 19. Silane-functional Dispersing Agent. In a similar manner to that described in Example 4, Dispersing Agent 1 was reacted with 3-aminopropyltrimethoxy silane (silane A-1100, Union Carbide) to give Dispersing Agent 19 as an approximately 50% w/w solution of the silane-functional half-amide in xylene. The following materials do not form part of the invention but are included for comparison purposes. Comparative Material 1. Stearic acid. Comparative Material 2. Triethylammonium salt of stearic acid. Comparative Material 3. Stearyl amide. Comparative Material 4. Half-amide from succinic anhydride and hexadecylamine. A mixture of succinic anhydride (1.25 g) , hexadecylamine (3.0 g) and methyl ethyl ketone (10 ml) was warmed until reaction was complete. The solvent was removed under reduced pressure to leave the product as a white solid. Comparative Material 5. Half-amide from hexadecyl succinic anhydride and ethanolamine. A. A mixture of 1-hexadecene (50 g) and maleic anhydride (30.7 g) was treated as in Example 1 to give hexadecenyl succinic anhydride. B. The product was treated with ethanolamine as in Example 4 to give the half-amide (Comparative Material 5) . Comparative Material 6. Lithene PM25MA (a maleinised polybutadiene prepared from 100 parts by weight of polybutadiene of average molecular weight 1300 and 25 parts by weight of maleic anhydride, Revertex Limited) . Comparative Material 7. Methyl half-ester of Lithene PM25MA. A mixture of Lithene PM25MA (100 g) and methanol (6.5 g) was heated to 100° for 2.5 hours under nitrogen under reflux. ~ Comparative Material 8. Triethylammonium salt of methyl half-ester of Lithene PM25MA. One equivalent of triethyl amine per equivalent of acid was added to Comparative Material 7 to give Comparative Material 8. Comparative Material 9. Half-amide from Lithene PM25MA and 3-(N,N-dimethylamino)propylamine. By a similar method to that of Example 4, Comparative Material 9 was produced by adding one mole of 3-(N,N-dimethylamino)propylamine per mole of anhydride to Lithene PM25MA. Examples 20-29 and Comparative Examples 1-4. Pigment dispersions were made up as follows using titanium dioxide RHD-2 (Tioxide UK Limited) as the pigment. They were dispersed by stirring and the dispersion assessed qualitatively for fluidity on a scale where: 0 = powder, 3 = thick cream, 4 » fluid, and 5 = very fluid dispersion Example Pigment Dispersant Organic Pluidity Liquid 20 RHD-2 Dispersing Agent 1 Xylene 5 16 g 0.2 g 3.8 g 21 RHD-2 Dispersing Agent 2 Xylene 5 16 g 0.4 g 3.6 g 22 RHD-2 Dispersing Agent 3 Xylene 5 16 g 0.4 g 3.6 g 23 RHD-2 Dispersing Agent 4 Xylene 5 16 g 0.4 g 3.6 g 24 RHD-2 Dispersing Agent 5 Xylene 5 16 g 0.4 g 3.6 g 25 RHD-2 Dispersing Agent 8 Xylene 5 16 g 0.4 g 3.6 g 26 RHD-2 Dispersing Agent 9 Xylene 5 16 g 0.4 g 3.6 g / 27 RHD-2 Dispersing Agent 10 Xylene 5 16 g 0.2 g 3.8 g 28 RHD-2 Dispersing Agent 11 Xylene 16 g 0.2 g 3.8 g 29 RHD-2 Dispersing Agent 12 Xylene 16 g 0.4 g 3.6 g Comparative Comparative Example Material 1 RHD-2 Comp/Material 1 Xylene 16 g 0.2 g 3.8 g 2 RHD-2 Comp/Material 2 Xylene 16 g 0.2 g 3.8 g 3 RHD-2 Comp/Material 6 Xylene 16 g 0.2 g 3.8 g RHD-2 Comp/Material 8 Xylene 16 g 0.2 g 3.8 g The poor performance of Comparative Materials 1 and 2 shows the need for the dispersing agent to contain a long polymeri hydrophobic chain. The poor performance of Comparative Materials 6 and 8 in which the hydrophilic groups are distributed at random down the hydrophobic polymer backbone, shows the need for the hydrophilic groups to be concentrated either at the end of the hydrophobic section or between hydrophobic blocks. Examples 30-37 and Comparative Examples 5-9. Similarly, dispersions were made up using titanium dioxide RCR-2 (Tioxide UK Limited) as the pigment. Example Pigment Dispersant Organic Fluidit Liquid 30 RCR-2 Dispersing Agent 1 Xylene 16 g 0.2 g 3.8 g 31 RCR-2 Dispersing Agent 3 Xylene 16 g 0.4 g 3.6 g 32 RCR-2 Dispersing Agent 4 Xylene 5 16 g 0.4 g 3.6 g 33 RCR-2 Dispersing Agent 5 Xylene 5 16 g 0.4 g 3.6 g 34 RCR-2 Dispersing Agent 8 Xylene 5 16 g 0.4 g 3.6 g 35 RCR-2 Dispersing Agent 9 Xylene 5 16 g 0.4 g 3.6 g 36 RCR-2 Dispersing Agent 10 Xylene 5 16 g 0.2 g 3.8 g 37 RCR-2 Dispersing Agent 12 Xylene 5 16 g 0.4 g 3.6 g Comparative Comparative Example Material 5 RCR-2 Comp/Material 1 Xylene 4 . 16 g 0.2 g 3.8 g 6 RCR-2 Comp/Material 2 Xylene 4 16 g 0.2 g 3.8 g 7 RCR-2 Comp/Material 3 Xylene 0 16 g 0.2 g 3.8 g 8 RCR-2 Comp/Material 4 Xylene 0 16 g 0.2 g 3.8 g 9 RCR-2 Comp/Material 5 Xylene 3 16 g 0.2 g 3.8 g Exaunples 38-44 and Comparative Examples 10-12. Dispersions were made up using red iron oxide (Bayferrox 1120-Z, Bayer) . Example Pigment Dispersant Organic Fluidity Liquid 38 1120-Z Dispersing Agent 4 Xylene 14 g 1.6 g 4.4 g 39 1120-Z Dispersing Agent 5 Xylene 14 g 1.6 g 4.4 g 40 1120-Z Dispersing Agent 7 Xylene 5 14 g 1.6 g 4.4 g 41 1120-Z Dispersing Agent 9 Xylene 14 g 1.6 g 4.4 g 42 1120-Z Dispersing Agent 2 Xylene 14 g 1.6 g 4.4 g 43 1120-Z Dispersing Agent 16 Xylene 14 g 0.8 g 5.2 g 44 1120-Z Dispersing Agent 17 Xylene 14 g 1.1 g 4.9 g Comparative Comparative Example Material 10 1120-Z Comp/Material 1 Xylene 14 g 0.8 g 5.2 g 11 1120-Z Comp/Material 2 Xylene 2-3 14 g 0.8 g 5.2 g 12 1120-Z Comp/Material 9 Xylene 14 g 0.8 g 5.2 g Examples 45-51 and Comparative Examples 13-14. Dispersions were made up using China Clay (Spes white) Example Pigment Dispersant Organic Fluidit Liquid 45 Spes white Dispersing Agent 3 Xylene 5 11 g 1.3 g 7.7 g 46 Spes white Dispersing Agent 4 Xylene 5 11 g 1.3 g 7.7 g 47 Spes white Dispersing Agent 5 Xylene 5 11 g 1.3 g 7.7 g 48 Spes white Dispersing Agent 8 Xylene 5 11 g 1.3 g 7.7 g 49 Spes white Dispersing Agent 9 Xylene 5 11 g 1.3 g 7.7 g 50 Spes white Dispersing Agent 12 Xylene 5 11 g 1.3 g 7.7 g 51 Spes white Dispersing Agent 18 Xylene 11 g 1.3 g 7.7 g Comparative Comparative Example Material 13 Spes white Comp/Material 1 Xylene 11 g 0.65 g 8.35 g 14 Spes white Comp/Material 2 Xylene 3-4 11 g 0.65 g 8.35 g Examples 52-61 and Comparative Exampl ,es 15-16. Dispersions were made up using Barytes (E-Weiss) as the pigment. Example Pigment Dispersant Organic Fluidity Liquid 52 Barytes Dispersing Agent 1 Xylene 5 17 g 0.2 g 2.8 g 53 Barytes Dispersing Agent 3 Xylene 5 17 g 0.4 g 2.6 g 54 Barytes Dispersing Agent 4 Xylene 5 17 g 0.4 g 2.6 g 55 Barytes Dispersing Agent 5 Xylene 5 17 g 0.4 g 2.6 g 56 Barytes Dispersing Agent 8 Xylene 5 17 g 0.4 g 2.6 g 57 Barytes Dispersing Agent 9 Xylene 5 17 g 0.4 g 2.6 g 58 Barytes Dispersing Agent 12 Xylene 5 17 g 0.4 g 2.6 g 59 Barytes Dispersing Agent 16 Xylene 5 17 g 0.2 g 2.8 g 60 Barytes Dispersing Agent 17 Xylene 5 17 g 0.28 g 2.72 g 61 Barytes Dispersing Agent 18 Xylene 5 17 g 0.4 g 2.6 g Comparative Comparative Example Material 15 Barytes Comp/Material 1 Xylene 17 g 0.2 g 2.8 g 16 Barytes Comp/Material 2 Xylene 2-3 17 g 0.2 g 2.8 g Examples 62-66 and Comparative Examples 17-20. Dispersions were made up using Dinitraniline Orange (Pigment Orange 5) . Example Pigment Dispersant Organic Fluidity Liquid 62 Din/Orange Dispersing Agent 5 Min. Spirits 5 10 g 2 g 13 g 63 Din/Orange Dispersing Agent 6 Min. Spirits 5 10 g 2 g 13 g 64 Din/Orange Dispersing Agent 7 Min. Spirits 5 10 g 2 g 13 g 6 5 Din/Orange Dispersing Agent 10 Min. Spirits 5 10 g 1 g 14 g 6 6 Din/Orange Dispersing agent 15 Min. Spirits 5 10 g 1 g 14 g Comparative Comparative Example Material 1 7 Din/Orange Comp/Material 3 Min. Spirits 3 10 g 1 g 14 g 1 8 Din/Orange Comp/Material 4 Min. Spirits 3 10 g 1 g 14 g 19 Din/Orange Comp/Material 5 Min. Spirits 3 10 g 1 g 14 g 20 Din/Orange Comp/Material 7 Min. Spirits 3 10 g l g 14 g /05 Examples 67-70 , Dispersions were made up using Toluidine Red (Pigment Red 3) Example Pigment Dispersant Organic Fluidity Liquid 67 Tol/Red Dispersing Agent 7 Min. Spirits 4-5 7 g 1.4 g 4.9 g 68 Tol/Red Dispersing Agent 14 Min. Spirits 5 7 g 0.7 g 5.6 g 69 Tol/Red Dispersing Agent 16 Min. Spirits 7 g 0.7 g 5.6 g 70 Tol/Red Dispesing Agent 17 Min. Spirits 7 g 0.95 g 5.3 g Exaunples 71-75. Dispersions were made by ball-milling the ingredients for 6 hours. The resulting dispersions were fluid and the pigment deflocculated. Example Pigment Dispersant Organic Fluidity Liquid Phthalocyanine 71 Green 20 g Dispersing Agent Xylene 3-4 (Pigment Green 13 2 g 48 g 7) Phthalocyanine 72 Blue 20 g Dispersing Agent Min. Spirits 3. 4 (Pigment Blue 13 2 g 48 g 15:3) Dinitraniline 73 Orange 15 g Dispersing Agent Min. Spirits (Pigment 4 3 g 19.5 g Orange 5) Hansa Yellow 74 IOG 15 g Dispersing Agent Min. Spirits (Pigment 13 1.5 g 21 g Yellow 3) Toluidine Red 7 5 20 g Dispersing Agent Min. Spirits - 5 (Pigment 13 0.98 g 15.4 g Red 3) Fluidity Point Testing. One method of assessing the efficiency of dispersing agents is to measure the amount of dispersing agent required to produce a fluid dispersion of pigment. The dispersing agents were diluted with xylene to give a 25% w/v solution (i.e. 100 ml of solution contained 25 g of non-volatile material as measured by placing the sample irra vacuum oven at 120° for 1 hour) . The dispersant solution wa added dropwise from a burette to a mixture of the pigment an xylene. The mixture was stirred with a spatula and addition of dispersant solution continued until a fluid dispersion, which would flow from a spatula in an almost continuous stream, was obtained. The volume of dispersant solution added was recorded. Pigment Xylene Tioxide RHD-2 16 g 2.8 ml Tioxide CR-2 12 g 2.1 ml Red Iron Oxide 7 g 2.5 ml China Clay 11 g 6.0 ml Barytes 17 g 2.5 ml In the table below, the volumes of 25% w/v solutions of the dispersing agents are given in ml. Dispersant Pigment Dispersion RHD-2 RCR-2 Iron China Barytes oxide Clay Dispersing Agent 1 0.92 0.69 >1.0 >1.5 0.30 Dispersing Agent 2 0.76 Dispersing Agent 3 0.76 0.69 >1.5 1.36 0.33 Dispersing Agent 4 0.90 0.82 0.32 0.74 0.16 Dispersing Agent 5 0.81 0.75 0.24 0.76 0.18 Dispersing Agent 7 0.39 Dispersing Agent 8 0.84 0.76 >1.0 0.72 0.15 Dispersing Agent 9 0.97 0.95 0.33 1.00 0.16 Dispersing Agent 10 0.81 0.76 Dispersing Agent 11 1.13 Dispersing Agent 12 1.04 0.79 0.28 0.82 0.21 Dispersing Agent 19 0.74 0.80 Comparative Material 6 0.78 Comparative Material 8 0.89 Examples 76-78 and Comparative Examples 21-25. In this example it is demonstrated that making a concentrated pigment dispersion by means of the dispersing agents of the present invention gives equivalent paint properties to paints made by the conventional technique of dispersing the pigment in the presence of resin binder. The following materials were ball-milled together for 6 hours. comparative Examples 21 22 23 Phthalocyanine Blue 10 g Toluidine Red 10 g Hansa Yellow IOG 10 g Lecithin 0.1 g 0.1 g Mineral Spirits 22 g 22 g 22 g Synolac 50W 8 g 8 g 8 g (*Long oil alkyd resin, 75% in white spirit, Cray Valley Products.) These pigments dispersions were made up into air-drying paints and compared with paints made using pigment dispersions of the present invention in the following manner. A stock solution of alkyd resin and drying agents was made up: Synolac 50W 179 g Mineral Spirits 17 g 24% Lead Naphthenate 2.9 g 6% Cobalt Naphthenate 1.1 g Paints were made from this solution. Example Comparative Example 76 77 78 24 25 26 Stock Alkyd Solution 14 g 14 g 14 g 14 g 14 g 14 g Mineral Spirit 1.7 g 3.4 g 2.7 g 2 g 2 g 2 g Synolac 50W 0.8 g 0.8 g 0.8 g - Pigment Dispersion: Example No: 72 3.5 g - 75 1.8 g - 74 - - 2.5 g - Comparative Example No: 21 - - - 4 g 22 - - - - 4 g - 23 - - - - - 4 g Films of wet thickness 0.002" were laid from each paint and allowed to dry overnight. Visual comparisons were made between the two red paints, two blue paints and two yellow paints. In each case, the equivalent colour, glass and transparency was observed. Examples 79 and 80. The following ingredients were ball-milled together for 6 hours. Example 79 Example 80 Toluidine Red pigment 20 g 20 g Dispersing agent 13 1.6 g 2 g Solsperse 25000 0.4 g - (auxiliary dispersing agent) Xylene 28 g - Carbon tetrachloride - 45 a The resulting dispersions were fluid with the pigment well dispersed. Example 81. In this example, a pigment is treated with a dispersing agent of the invention to give a modified pigment which can be easily dispersed without additional dispersing agents. Toluidine Red pigment (25 g) was added to a solution of Dispersing Agent 13 (2.5 g) in cyσohexane (600 ml). The mixture was heated to reflux temperature for 30 minutes with stirring and then cooled. After filtration, the modified pigment was dried under vacuum to give a red powder. A mixture of this powder (20 g) and mineral spirits (24 ml) was ball-milled to give a fluid well-dispersed pigment dispersion. Attempts to disperse an unmodified pigment in this way only gave a very thick paste.

Claims: CLAIMS 1. A pigment dispersion which comprises from 5 to 90% bγ weight of at least one pigment and/or extender, from 0.01 to 50% by weight of a pigment dispersant which contains in its molecule at least one polar segment and at least one polymeric, non-polar, solvent compatible segment having a molecular weight in the range of from 500 to 10,000, preferably 500 to 3,000 and is derived from repeating monomer units of an unsaturated hydrocarbon; and an organic liquid dispersing medium which comprises at least a major proportion of a hydrocarbon or chlorinated hydrocarbon. 2. A pigment dispersion as claimed in claim 1 in which the polymeric non-polar segment of the pigment dispersant is derived from polybutadiene, polyisobutylene or polyethylene. 3. A pigment dispersion as claimed in claim 1 or claim 2 in which the polar segment of the pigment dispersant comprises an anhydride, mono- or di-carboxylic acid or a salt thereof, a half-ester or half-amide of a dibasic acid or a salt thereof, an amide, an amine, a quaternary amine salt, or a polymeric chain comprising a polyurethane, polyester or polyurea, or a combination of two or more of these groups. 4. A pigment dispersion as claimed in claim 1 wherein the pigment dispersant comprises one of the following: A) A compound of the formula wherein either C or D is a hydrophobic, straight or branched polymeric chain, the other being hydrogen; M is hydrogen, a metal ion, an ammonium or substituted ammonium ion; X is 0 or NR, where R is hydrogen, alkyl, cycloalkyl, aryl or arylalkyl; Q is hydrogen or TZ where T is alkylene, arylene, poly(alkylene oxide), poly(alkylene imine), polyurethane, polyurea, polyester or polyamide; and Z is hydrogen, hydroxyl, N(R) 2 (where R is as above defined) or the group. where C, D, M and X are as above defined; (B) A compound of the formula where C, D, Q, and Z are as above defined; (C) A compound of the formula where C, D, T, and R are as above defined and E is sulphate, bisulphate, mono-alkyl sulphate, monoaryl sulphate, chloride, bromide, iodide, phosphate or other inorganic or organic anion, and x is 1, 2 or 3; (D) A compound of the formula 0 0 i D VI MO - C - J - C - X - polybutadiene in which X is 0 or NH; J is a divalent linking group; and M is as above defined. 5. A pigment dispersion as claimed in claim 4 wherein in the formula of the dispersants (A), (B) and (C) one of the groups C and D in the formulae as given is polybutadiene, polyisobutylene or polyethylene. 6. A pigment dispersion as claimed in claim 4 wherein in the formula of the dispersant (A) the group T is a polyurethane prepared by the reaction of an aliphatic diol, preferably ethylene glycol and a di-isocyanate, preferably toluene di-isocyanate. 7. A pigment dispersion as claimed in claim 4 wherein in the formula of the dispersant (D) the -CH 2 -CH 2 -, -CH-CH-, or phenylene. 8. A pigment dispersion as claimed in any one of the preceding claims which comprises from 0.1 to 10% by weight of the pigment dispersant. 9. A pigment dispersion as claimed in any one of the preceding claims wherein the organic liquid dispersing medium is an diphatic hydrocarbon or a mixture thereof. 10. A paint, ink or coating composition which includes therein a pigment dispersion as claimed in any one of the preceding claims. 11. A pigment which is coated with a pigment dispersant which contains in its molecule at least one polar segment and at least one polymeric, non-polar, solvent compatible segment having a molecular weight in the range of from 500 to 10,000 presferably 500 to 3,000, and is derived from repeating monomer units of an unsaturated hydrocarbon. 12. A coated pigment as claimed in claim 11 which is in particulate form. 13. A coated pigment as claimed in claim 11 or claim 12 wherein the pigment dispersant is as defined in any one of claims 2 to 7. 14. A paint, ink or coating composition which includes therein a coated pigment as claimed in any one of claims 11 to 13. * 15. A plastics material which includes therein a coated pigment as claimed in any one of claims 11 to 13.

Inventors: ANSELL PETER JOHN, BIGNOLD ALAN JOHN, LUXTON ALAN RICHARD, ANSELL, PETER, JOHN, BIGNOLD, ALAN, JOHN, LUXTON, ALAN, RICHARD
Applicants: REVERTEX LTD, REVERTEX LIMITED
Application year: 1987
Main classification: C09D17
IPC codes: C09B67, C09C3, C09D7, C09D17