NZ249574A

NZ249574A - Surfactant consisting of a polymer having pendant chemisorptive groups and (crosslinked by) a polyether chain; polymer compositions comprising a plasticiser and a dispersed solid having the surfactant adsorbed onto the surface thereof

Info

Publication number: NZ249574A
Application number: NZ249574A
Authority: NZ
Inventors: Derrick Clifford Dobson
Original assignee: Ici Plc
Priority date: 1992-03-16
Filing date: 1993-03-12
Publication date: 1996-12-20
Also published as: AU672598B2; KR100250545B1; JPH07504846A; AU3646393A; WO1993018851A3; EP0631522A1; KR950700785A; CA2131895A1; GB9205701D0; WO1993018851A2

Description

<div class="application article clearfix" id="description"> New Zealand Paient Spedficaiion for Paient Number £49574 New Zealand No. International No. 24 9 5 74 249574 PCT/GB93/00524 NO DRAWINGS TO BE ENTERED AFTER ACCEPTANCE AND PUBUCATION Priority dates: /jb -3, • International filing date: /'a. .3 Classification: fcoiFnjsiJL*. CogQ,g//oo> Publication date: _ _ .not» 2 d OEC «96 Journal No.: f*t- ( / NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION Title of invention: Surfactant. Name, address and nationality of applicant(s) as in international application form: IMPERIAL CHEMICAL INDUSTRIES PIC, of Imperial Chemical House, Millbank, London SW1P 3JF, England. Gt WO 93/18851 PCT/GB93/00524 10 15 20 25 30 24 9 5 74 - 1 - SURFACTANT This invention relates to a surfactant, a method of making it, a dispersion containing the surfactant and a dispersed solid, a polymer composition that comprises the surfactant and a piasticiser, a method for making the dispersion, a dispersible solid comprising the surfactant, and a product coated with material comprising the discontinuous phase of the dispersion. According to a first aspect of the invention, a surfactant is characterised by a plurality of addition—copoIymer chains, on each chain an average of at least 0.5 adsorptive or chemisorptive groups and at least one monovalent polyether residue; and between the chains at least one divaler.*- polyether residue. The terms "adsorptive" and "chemisorptive" herein indicate that the chains of the surfactant are capable of adsorption or chemisorption to the surface of a phase other than that which is or comprises the surfactant. The balance of the relative proportions of the chains and the residue is such that the surfactant has sufficient solubility as such or as a sa It in a liquid to exert sur f ace activity, either in that liquid or on the surface of a solid to which it is appIjed by way of such a solution. Whereas it is be I ieved that the surfactant is mainly a two-dimensional molecule, it may be at least partly three-dimensional, provided that it has sufficient solubility. A particular embodiment of the surfactant of the present invention is characterised by the following features: (a) a plurality n of addition-copoIymer chains; (b) on at least n-2 chains, at least one, especially 3-10, optionally saIified carboxyIic acid group and at least two carboxylie ester groups; (c) at least one, especial ly 2-6 of the carboxy I ic ester groups in each chain having as its alcohol residue a monovalent polyether res i due; and r: NZ. °LT'rr j 7 - AUG 1996 WO 93/18851 249 5 74 PCT/ GB93/00524 10 15 1 0 % 30 - 2 - (d) at least one other of the carboxy I i c ester groups in each chain having as its alcohol residue a divalent polyether residue, a further end of which is the alcohol residue of the carboxy I ic ester group of another of said addition—copoiymer chains; and (e) opt i onally a carboxy tic ester group having as its alcohol residue a monovalent hybrocarbyI residue, e.g. Ci-20 hydrocarbyl. The addition—copoIymer chains may consist of (i) carboxyI-carrying units present as acid or ester in features (b) - (d) and ( i i ) other un i ts. The carboxyI-carrying units may be for example (meth)acryIic units, but are preferably 1,2—dicarboxyIic units such as ma Ieic units. The number of such carboxyl groups per 100 addition—copoIymerised monomer residues in their overall relative proportions is preferably in the range of 25 to 60, especially 45 to 55. The acid value of the addition-copoIymer chains, assuming hydrolysis of any anhydride units is suitably in the range of 150-350, especially 250-310, mg KOH/g. The free carboxyl ic acid groups in each chain are optional ly salified with for example a plurality of monovalent cations such as alkali metal, e.g. sodium, or ammonium ions. The other units may for example comprise ethylene, vinyl esters, vinyl ethers op acrylic esters, but ore most conveniently styrene. The average molecular weight of each of the addition-copoIymer chains is suitably in the range of 1000 to 5000, especially 1500 to 300. The monovalent polyether residue is suitably derived from an ether-terminated polyalkylene glycol. Such potyalkylene glycol (apart from its terminating hydrocarbyIoxy group) has an oxygen-to-carbon ratio preferably in the range of 0.25 to 0.33. 24 9 5 74 WO 93/18851 PCT/G B93/00524 - 3 - Its average molecular weight is preferably in the range of 250 to 5000, especial ly 300 to 400 including the terminating hydrocarbyIoxy group. That group is preferably Ct-A (lower) alkyl or phenyl. The divalent polyether residue is conveniently the same in oxygen—to—carbon ratio as the monovalent residue. Its average molecular weight is preferably in the range of 150 to 1000, especially 150 to 300. The invention provides in its second aspect a method of 10 making the the above particular embodiment of the surfactant of the present invention which is characterised inter alia by: (i) a plurality of copolymer chains; and (ii) on at least n-2 chains, at least one carboxyl ic acid group, 15 the method being characterised by: (a) reacting an addition-copoIymer comprising carboxyI-carrying monomer units in esterifying conditions with a monovalent polyether alcohol corresponding to the monovalent polyether group, to an extent leaving at least one esterifiable group on at least n—2 of the addition-copoIymer chains; and (b) reacting the product of step <a) in esterifying conditions with a divalent polyether alcohol. The term "esterifying" includes transesterifying and the term ^5 "esterifiabIe" includes transesterifiabIe. In this method the addition-copoIymer of carboxy I —carrying and other ethyI enic monomers may be a commercially available addition-copoIymer, such as SMA 3000A (Atochem UK Limited). Alternatively, the addition—copoIymer 30 may be prepared by the prior process step of copo I ymer i s i ng ethylenic monomers corresponding "to the carboxy I —carry i ng and other monomers of the addition—copoIymer chains. Conventional using e.g. peroxide catalysts may be used. WO 93/18851 249 5 7 PCT/G B93/00524 - 4 - The copoIymerisation reaction is preferably controlled to give an average molecular weight of each of the add i t i on-copoIymer chains in the relevant above ranges. In the method of the second aspect of the invention, both reaction steps may be carried out concurrently, but preferably step (a) is substantially completed before adding the divalent polyether alcohol. In one variant of the latter sequential embodiment, in step (a), some of the carboxylic groups are left for esterification in step (b). In an alternative, a great proportion or all of the carboxyl groups are reacted in step (a), and the divalent polyether alcohol reacts by transesterification in step (b). The carboxyI-carrying monomer unit is preferably a 1,2-di carboxy I ic unit such as ma I e i c anhydride; in such case, esterification in step (a) (e.g. with or with a derivative of an ether—terminated polyalkylene glycol), and preferably also in step (b) is carried out by ring—opening. The necessary control of the reaction is preferably effected by control of the proportions of the reactants. As a result of the ring—opening and esterification only to the extent of leaving at least one esterifiable group on at least n-2 of the addition-copoIymer chains, free carboxyl groups are made available. These may be neutralised by alkali, e.g. sodium hydroxide or ammonia (e.g. at 20 to 100, typically 60*C in the case of alkali) to i ncrease solubility in water. The relative proportions of the addition-copoIymer, the monovalent polyether alcohol and the divalent polyether a I cohoI shouId be such as to (a) cross-1 ink at least 50 mole percent of the addition—copoIymer chains, but <b) suitably not give more than 10 of such chains per surfactant molecule, because of the resulting high viscosity. 249 5 74 WO 93/18851 PCT/GB93/00524 - 5 - The proportions are preferabIy in the following ranges defined by mole equivalent fractions of ester i f iable carboxyl and alcoholic hydroxyl: carboxyl 0.64 — 0.69 hydroxy I i n monovaIent polyether alcohol 0.27 - 0.35 hydroxyl in divalent polyether alcohol 0.01 - 0.07. 1Q Whether carried out concurrently or in any sequential embodiment of step (a) and step <b), both reaction steps are carried out at temperatures typically in the range of 140* -180 * C, A solvent, for example a hydrocarbon boiling in that 15 range may be present, but it is usually preferred to carry it out in the me It. One embodiment of the particular surfactant of the present invention is characterised by a carboxylic ester group having as its alcohol residue e.g. Ci-20 hybrocarbyl. Such an ester group may be incorporated in the surfactant molecule by esterification or by use of a corresponding monomer in the production of the initial add i t i on-copoIymer. The invention in a third aspect provides a dispersion in a liquid characterised by conta ining a dispersi on—stab i I i si ng quantity of the surfactant. Where the dispersion is characterised by containing a dispersion—stabi Iising quantity of the particular surfactant of the present invention, the dispersion may also contain a 3Q minor proportion of a material characterised by the following features: (a> a plurality n of addition—copolymer chains; (b) on at least n—2 chains, at least one, especially 3—10, optionally salified carboxylic acid groups and at least two carboxyl ic ester groups; WO 93/18851 24 9 5 7 4 PCT/ G B93/00524 » 10 15 ^0 - 6 - Cc) at least one, especially 2-6 of the carboxyl ic ester groups in each chain having as its alcohol residue a monovalent polyether residue; and Cd) optionally a carboxylic ester group having as its alcohol residue a monovalent hybrocarbyl residue, e.g. C1-20 hydrocarbyI, i .e. an uncrossl inked form of the surfactant of the present invention, which may e.g. be present in the product of the present method for the particular embodiment of the surfactant of the present invention. The material of the discontinuous phase of the dispersion is preferably an inorganic solid, especially a crystal I i ne oxide or combination of oxides, particularly having at least on its surface, a combination of a volati le oxide and an involatile oxide. Thus the material of the discontinuous phase of the dispersion is preferably an inorganic crystalline carbonate, basic carbonate or hydroxide. It preferably has a crystal Iographic face simi lar to the 001 face of calcite. The invoI ati le oxide component of such material of the discontinuous phase of the dispersion is preferably at least as strong a base as magnesium oxide. Other oxides include those of aluminium, copper, zinc, vanadium, chromium, manganese, iron, cobalt and nickel and compounds which include mixtures thereof, such as clays, spinel precursors and ma Iach i tes . The dispersion is especially suitable for solid particles of high aspect ratio, for example 5:1 to 50:1. For optimal stability against flocculat ion and for low viscosity, where the material of the discontinuous phase of the dispersion is«a crystalline solid, the distance between the carboxyl groups of the surfactant is chosen to match the crystal Iographic lattice parameters of the dispersed material . wo 93/18851 r*» - 7 - Thus, for example for the caicite lattice, the carboxyl groups in the addition-copoIymer chains, are suitably separated by 4 ethylene oxide residues. It is believed that the surfactant is then substantially completely adsorbed on 5 the dispersed phase, thereby leading to an acceptable charge density at the surface, tending to act against flocculation and for low viscosity. If the number of carboxyl groups per unit length of the surfactant molecule chains were too great, the surfactant would not be uniformly and completely adsorbed. '0 It is be I i eved that, depending on the nature of the dispersed phase, the adsorption may actually be ehemisorptive i n nature. However the nature of the interaction between the chains and the sol id is not in any way relevant to or Iimiting on any '5 aspect of the present invention. The liquid forming the continuous phase of the dispersion typical ly is or comprises water, but may be or comprise a highly polar organic liquid. The dispersion may comprise other ingredients, such as pigments, texturising agents, perfumes and disinfectants, and other surfactants and poIymers. A preferred dispersion has a high sol ids content of 20—80% w/w, especially 25—75% w/w. Even at such a high solids content, the dispersion may typical ly have a relatively low viscosity, and its rheoiogical properties may be adjusted with considerable freedom by means of additives. In particular the dispersion of the present invention may have any rheology between mobi le and thixotropic using additives. 30 The dispersion is suitable for coating solid substrate surfaces with the dispersed solid. For example, a dispersion comprising fine particles is especially suitable as a printing ink of low viscosity with good stabi I ity aga inst flocculation, e.g. for wa I I papers, or 35 for applying surface fire-proofing or making abrasive papers. wo 93/18851 249 5 74 PCT/G B93/00524 - 8 - If desired, the dispersion may be caused or allowed to settle and the precipitate .'may be collected and dried. The dried material may. optionally after milling, be redispersed. The material may be redispersed in an organic medium, especially a plasticised polymer. The invention accordingly provides in its fourth aspect a composition, characterised in that it comprises a polymer containing a plasticiser and a solid dispersed material having a surfactant of the present invention adsorbed on its surface. The polymer is especially polyvinyl chloride or a copolymer of vinyl chloride, and the plasticiser is especially a dialkyl phthalate, e.g. dioctyl phthalate. The invention in a fifth aspect provides a method for making a dispersion according to the third aspect, characterised by incorporating with the sol id a quantity of a surfactant of the present invention to adsorb onto the surface of the sol id to an extent which is sufficient to stabi I i se a dispersion of the solid in the liquid. Typically this is a quantity such as to adsorb onto at least half of the relevant adsorptive sites on the surface. Incorporation of the surfactant of the present invention to adsorb onto the surface of the sol id may be carried out for exampIe — by simple mixing of the surfactant of the present invention with the sol id which has been pre—comm i nuted by wet— or dry-grind i ng ; by size reduction of the sol id in the presence of the sur factant; by (co)precipi tation of the solid in the presence of the sur factant; or by digestion in the presence of the surfactant of a sol id previously tco)precipitated in the absence of the surfactant and/or in the presence of another surfactant. wo 93/18851 - 9 - 249 5 74 PCT/G B93/00524 10 15 30 In each such method, incorporation of the surfactant of the present invention may include intensive mixing with the sol id, for example homogen i sat i on under high shear to break down secondary aggregates of the sol id and/or to effect further comminution. If the surfactant of the present invention is in the form of a salt, and the nature of the interaction between the surfactant and the solid is chemisorptive, it may be desirable to include pH adjustment in the incorporation method to neutralise a Ikaii or ammonia liberated by chemisorption of carboxyl ic acid groups to the sol id surface. The invention in its sixth aspect provides a redispersibIe solid comprising fine particles having a surfactant of the present invention adsorbed or chemisorbed on i ts surface. The surfactant wi I I be adsorbed in a quantity which is sufficient to stabilise a dispersion of the solid in a liquid, preferably sufficient to adsorb or chemisorb onto at least half of the relevant adsorptive or chemisorpt1ve sites on the sur face. The redispersibIe solid is are most conveniently made by drying the dispersion of the third aspect of the invention, but may be made by dry—mixing or melt—mixing of the sol id with the surfactant. The invention in a seventh aspect provides a method of coating a substrate with the discontinuous phase of a dispersion of the third aspect of the invention, which comprises applying the dispersion to the substrate. Any convenient method may be used, for example intaglio printing, padding, brushing, spraying, doctoring and reverse-roll coat i ng. The process may include pre I iminary adjustment of the rheology of the dispersion using additives. The liquid forming the continuous phase of the dispersion typically is removed during the coating process e.g. by evaporation. WO 93/18851 - 10 - 249574 PCT/GB93/00524 10 15 30 The dispersion is especially suitable for roller-coating paper at a shear rate of less than I sec-' . The invention accordingly provides in its eighth aspect a product coated with material comprising the discontinuous phase of the dispersion of the third aspect of the invention. Examples of such products include in particular printed papers, e.g. waI I papers, fire-proofed papers and abrasive papers. The present invention is i ! I ustrated by the f o I lowing ExampIe. EXAMPLE (a) Preparation of the surfactant The following reactants were used: styrene ma Ieic anhydride add i i i on-copoIymer (SMA) (molar ratio 3:1) of mo I ecu I ar we i ght 1900 , commerc i a I I y ava i I ab I e as SMA 3000A (Atochem UK Limited); methoxy polyethylene glycol (MeOPEG), molecular weight 350; and polyethylene glycol (PEG), molecular weight 250. The latter two reactants were dried before use by heating under vacuum. Under a nitrogen blanket and continuing nitrogen flow, SMA (1421.4g, 0.748 mole) and MeOPEG (995g, 2.843 mole) were melted together and held at I60-I65*C for 1.5 h., to effect ring-opening and esterification of the ma Ieic anhydride units in step (a) of the present method. The mixture was cooled to beiow I25*C. PEG (49.53g, 0.2447 mole) was added and stirred in for 5 to 10 min. The whole mixture was heated to I75*C and held there for 30 to 60 min., to effect further esterification of (ring-opened) ma Ieic anhydride units and cross-I inking between the chains of the SMA add i t i on —copo I ymer in step (b) of the present method. The mixture remained liquid and of stable viscosity. The product was cooled to I20'C and poured out. 24 9 5 74 WO 93/18S51 PCT/GB93/00524 - 1 I - PP A sample was dissolved over several hours in di lute sodium hydroxide at 60*C to give a solution of sa I i f i ed surfactant of final pH of 7.5 to 8.5. This surfactant is referred to as "B" below. 5 The same procedure was used with with adjusted £ auantities of the same reactants to give the surfactant referred to as "A" below. The two surfactants are summarised and compared thus: Mole ratio Esterifiable Groups 10 rat i o % SMA MeOPEG PEG CO2 H OH in OH in MeOPEG PEG Surfactant A I 3.8 0.473 0.661 0.271 0.068 Surfactant B 1 3.8 0.331 0.675 0.277 0.048 1 5 C b) Preparation of dispersion of solids in water The following aqueous slurries 1 and II were made up using 1 OOg solids in aqueous solutions of surfactants made according to (a) above: I "UItracarb", 30% w/w sol ids content (RTM, commercial ly available from Microfine Ltd, a naturally occurring crystal I i ne mineral composed of approximateLy equal amounts of huntite and hydromngnesite with a lamellar crystal habit with an aspect ratio in the range of 5:1 to 20: 1 which consequently forms aqueous slurries of high viscosity) with Surfactant A, 1.5% w/w on Ultracarb. 30 I I "Calopake F", 46.8% w/w sol ids content (commercial ly available from Rhone—PouIenc. a precipitated calcium carbonate of particle size 2.1 p Stokes equivalent d i ameter) with Surfactant B, 1.5% w/w on Calopake F. 35 WO 93/18851 PCT/GB93700574 - 12 - 1 0 Addition was made stirring at first at 250 rpm, increasing to 500 rpm, as the viscosity rose; the product was stirred for a further 10 min. The dispersion was then stored at room temperature for up to 6 days. The viscosity was measured at intervals using a Brookfield viscometer at two rpm levels. Control samples with respect to slurry 1 of dispersions at the same tota! sol ids content, using no surfactant and using each of the following known surfactants were also prepared and tested by the same procedures: SMA 3000A styrene ma Ieic anhydride addition—copoIymer sodium salt surfactant, Atochem UK Limited; Polysalt 5 poIycarboxyIic acid sodium salt, BASF; Coptal WA-OSN sodium dioctyl suIphosuccinate, hexylene glycol and ethylene glycol, ICI PATCO; Comparison samples with respect to slurry I at similar total solids content, using no surfactant and using various quantities of each of the following were also prepared and tested: Dispex N40 water—so IubIe polyacrylate, 0.65% w/w on water. Coptal WA—0SN 0.8% w/w on water. Results are set out in Tables 1 and 2 below TABLE 1: Brookfield viscosities cP of Ultracarb slurries Days Storage Sur factant SMA 300CA PoIysaIt S CoptaI WA-OSN rpm 5 5 100 1 25000 1 1840 1209 I 1920 1218 12720 1210 12800 1230 5 13850 1 3602 14520 13600 - 1 00 1663 1 78 1 1 740 1720 - 5 2520 2374 2420 2522 - 1 00 460 540 486 478 — WO 93/18851 - 13 - 249 5 74 PCT / G B93/00524 Ail slurries 30% w/w solids content. 1 0 TABLE 2: Brookfield viscosities cP of Ultracarb slurries Days Storage Surfactant solids rpm content D i spex N40 53.5 CoptaI WA-OSN I 5 too thick to measure 100 too thick to measure 5 too thick to measure 100 too thick to measure 1 5 30 5 100 68 14 t 72 14 t 74 159 76 100 (c) Preparation of pigmented polymer Precipitated calcium carbonate of particle size 4.5 p was aqueous slurried at a solids content of 14.9% w/w and heated with agitation to 85*C. Sufficient of an 18% w/w solution of surfactant B to give 2.6% w/w surfactant on the calcium carbonate dispersed phase, was heated to 75—80*C and added to the slurry with stirring. Stirring was continued at 85*C for 30 min. The product sol id was col Iected on a fi Iter, dried at 105*C for 24 h, and milled using a pin disc mill. A control sample was made by applying 1.6% w/w of stearic acid to the precipitated calcium -carbonate by slurrying in ammonium stearate solution, then filtering, drying and mi I I ing in the same way. AlI the samples of treated calcium carbonate were tested as fillers in PVC/dioctyI phthalate and PVC plastisol formulations, as follows. A PVC masterbatch was prepared from: 35 WO 93/18851 pct/CLsLJL 7 4 - 14 - Corvic P706 emulsion PVC (IC!) Vinnol C8/62V paste extender copolymer containing 8X vinyl acetate (Wacker) Tribasic lead sulphate Polycarb S (uncoated ground calcium carbonate, 30% < 2m. ECC Diisononyl phthalate 406G 280g 28g 208g 1 120g using a Hobart mixer. The formulations were prepared by mixing and then triple roller-m i 1 I i ng the foilowing: PVC masterbatch 304g Calcium oxide 4.8g Calcium carbonate treated as above 75g Estibond 262 polyamino adhesion promoter, AKZO 5g The rheological properties of these formulations were measured using a Carri-Med rheometer in controlled stress mode. The measuring system was a 4cm parallel plet^ with a 200 M 9aP• A I inked flow/creep shear stress programme was used with the following parameters: (a) 0—2000 Pa shear stress sweep over 40 sec. fo(lowed i mined i at e I y by (b) creep curve at 40 Pa for 2 min. Each sample was run 3 times with satisfactory reproduci b i I ity. Daniel gauge measurements were carried out to assess s I ump . </div>

Claims

<div class="application article clearfix printTableText" id="claims"> wo 93/18851 - 15 - 7 4 PCT/GB93/00524 ^ The PVC/dioctyl phthalate formulation using surfactant B was found to have good flow properties in paste creep tests. This gave a constant strain of 0.037 sec-1 after 20 sec., compared with 0.10 sec-' after 20 sec. for the control 5 formulation using stearic acid. ^ The PVC piastisol formulation using surfactant B gave a Daniel gauge measurement of 1mm compared with 9mm for the control formulation using stearic acid. In the paste creep tests, it gave a value of about 0.5 jq sec-' after tO sec., compared with about 1 sec-l after 10 sec. for the control formulation using stearic acid. Its apparent viscosity at a shear stress of 2000 Pa was 5.30 Pa.s, compared with 4.76 Pa.s for the control formulation using stearic acid. 30 35 WO 93/18851 PCT/GB93/00524 - 16 - 249 5 74, CLAIMS

1. A surfactant characterised by a plurality of addition-copoIymer chains, on each chain an average of at least 0.5 adsorptive or chemisorptive groups and at least one monovalent polyether residue; and between the chains at least one divalent polyether residue.

2. A surfactant according to claim I, characterised by the following features: (a) a plurality n of addition—copoIymer chains; (b) on at least n—2 chains, at least one optional ly saIified carboxyIic acid group and at least two carboxylic ester groups; (c) at least one of the carboxyl ic ester groups in each chain having as its alcohol residue a monovalent polyether residue; and (d) at least one other of the carboxy I i c ester groups in each chain having as its alcohol residue a divalent polyether residue, a further end of which is th«s alcohol residue of the carboxylic ester group of another of said addition—copoIymer chains; and (e) optionally a carboxylie ester group having "as i ts alcohol residue a monovalent hybrocarbyI residue.

3. A surfactant according to claim 2. characterised by (a) on at least n—2 chains, 3—10 optionally salified carboxylic acid groups and at least two carboxylic ester groups: (b) each of 2-6 of the carboxyl ic ester groups in each chain having as its alcohol residue a monovalent polyether residue; and (c) optionally a carboxylic ester group having as its alcohol residue a Ci-20 hydrocarbyI group. Bi ,| | Mlt>( N.Z. P<. I 7 - AUG 1996 WO 93/18851 PCT/G B93/00524 - 17 - 249574

4. A method of making the surfactant according to claim 2, characterised by: (a) reacting an addition-copoIymer comprising carboxyI—carrying monomer units in esterifying conditions with a monovalent polyether alcohol corresponding to the monovalent polyether group, to an extent leaving at least one esterifisble group on at least n—2 of the addition—copoIymer chains; and (b) reacting the product of step (a) in esterifying conditions with a divalent polyether alcohol.

5. A dispersion of a sol id in a I i qu i d character i sed by containing a dispersion—stabi 1ising quantity of the surfactant according to claim 1.

6. A dispersion according to claim 5, characterised in that the material of the discontinuous phase of the dispersion is an inorganic crystalline carbonate, basic carbonate or hydroxide present as solid particles of aspect ratio in the range 5:1 to 50:1, the dispersion comprises a surfactant according to claim 2, and the distance between the carboxyl groups of the surfactant is chosen to match the crystal Iograph i c lattice parameters of the dispersed material .

7. A composition. characterised in that it comprises a polymer containing a plasticiser and a solid dispersed material having a surfactant according to claim 1 adsorbed on i ts sur f ace.

8. A method for making a dispersion according claim 5, characterised by incorporating with the sol id a quantity of a surfactant of the present invention to adsorb onto at least half of the relevant adsorptive sites on the surfac* WO 93/18851 PCT/GB93/00S24 "18" 249 5 74

9. A dispersible solid comprising fine particles having a surfactant according to claim 1 adsorbed or chemisorbed onto at least half of the relevant adsorptive sites on the surface. 5

10. A product coated with material comprising the discontinuous phase of the dispersion according to either claim 5 or claim 6.

11. A surfactant as defined in claim 1 substantially as herein described with reference i o to any example thereof.

12. A method of making a surfactant as defined in claim 4 substantially as herein described with reference to any example thereof. is

13. A dispersion of a solid in a liquid as defined in claim 5 substantially as herein described with reference to any example thereof.

14. A composition as defined in claim 7 substantially as herein described with reference to any example thereof. 20

15. A method for making a dispersion as defined in claim 8 substantially as herein described with reference to any example thereof.

16. A dispersible solid as defined in claim 9 substantially as herein described with reference to any example thereof.

17. A product coated with material as defined in claim 10 substantially as herein described with reference to any example thereof. 30 35 7 - A!i3 £96 </div>