SURFACTANT

Abstract: A surfactant characterised by a plurality of addition-copolymer chains, on each chain an average of at least 0.5 chemisorptive groups and at least one monovalent polyether residue; and between the chains at least one divalent polyether residue, a method of making it, a dispersion containing the surfactant and a dispersed solid, a polymer composition that comprises the surfactant and a plasticiser, 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.

Description: SURFACTANT T is invention relates to a surfactant, a method of making it, a dispersion containing the surfactant and a dispersed sol id, a polymer composition that comprises the surfactant and a plasticiser, a method for making the dispersion, a dispersible sol id 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 plural ity of add i i on-copo I y er chains, on each chain an average of at least 0.5 adsorptive or chemi sorpt i ve groups and at least one monovalent polyether residue; and between the chains at least one divalent polyether residue. The terms "adsorptive" and "chemisorpt i ve" herein indicate that the chains of the surfactant are capable of adsorption or che i sorpt i on 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 solubi l ity as such or as a salt in a l iquid to exert surface activity, either in that I i qu i d or on the surface of a sol id to which it is appl ied by way of such a solution. Whereas it is bel ieved that the surfactant is mainly a two-dimensional molecule, it may be at least partly three-dimensional , provided that it has sufficient solubi l ity. A particular embodiment of the surfactant of the present invention is characterised by the fol lowing features: (a) a plural ity n of add i t i on—copo I ymer chains; (b) on at least n-2 chains, at least one, especial ly 3-10, optional ly sal ified carboxyl ic acid groups and at least two carboxyi ic ester groups; (c) at least one, especial ly 2—6 of the carbox i ic ester groups in each chain having as its alcohol residue a monovalent polyether residue; and Cd) at least one other of the carboxyi ic 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 carboxyi ic ester group of another of said addi t ion—copo I ymer chains; and (e) optional ly a carbox i ic ester group having as its alcohol residue a monovalent hybrocarby I residue, e.g. Cι-20 hydrocarby I . The add i ion—copo I ymer chains may consist of (i) carboxy I —carry i ng uni s present as acid or ester in features (b) - (d) and (ϊϊ) other units. The carboxy I -carryi ng units may be for example Cmeth)acr I i c units, but are preferably 1 ,2—d ϊcarboxy I i c units such as ma I eic units. The number of such carboxyi groups per 100 addit ion—copo I ymer ised monomer residues in their overal l relative proportions is preferably in the range of 25 to 60, especial ly 45 to 55. The acid value of the addi t i on—copo I ymer chains, assuming hydrolysis of any anhydride units is suitably in the range of 150-350, especial ly 250-310, mg KOH/g. The free carboxyi ic acid groups in each chain are optional ly sal ified with for example a plural ity of monovalent cations such as aI a I i metal , e.g. sodium, or ammonium ions. The other units may for example comprise ethylene, vinyl esters, vinyl ethers or aery I ic esters, but are most convenientl styrene. The average molecular weight of each of the add ϊ ion—copo 1 ymer chains is suitably in the range of 1000 to 5000, especial ly 1500 to 300. The monovalent polyether residue is suitably derived from an ether-terminated polyalkylene g I yco I . Such polyalkylene g I co I (apart from its terminating hydrocarby I oxy group) has an oxygen—to—carbon ratio preferably in the range of 0.25 to 0.33. Its average molecular weight is preferably in the range of 250 to 5000, especial ly 300 to 400 including the terminating hydrocarby I oxy group. That group is preferably Cι- ( lower) alkyl or phenyl . The divalent polyether residue is conveniently the same in oxygen— o—carbon ratio as the monovalent residue. Its average molecular weight is preferably in the range of 150 to 1000, especial ly 150 to 300. The invention provides in its second aspect a method of Q making the the above particular embodiment of the surfactant of the present invention which is characterised inter al ia by: (i) a plural ity of copolymer chains; and (i i) on at least n-2 chains, at least one carboxyi ic acid group , 5 the method being characterised by: (a) reacting an add i t i on-copo I ymer comprising carboxy I -carry i ng monomer units in esterifying conditions with a monovalent polyether alcohol corresponding to the monovalent polyether group, to an 0 extent leaving at least one esterifiable group on at least π—2 of the add i t i on—copo I ymer chains; and (b) reacting the product of step (a) in esterifying conditions with a divalent polyether alcohol . The term "esterifying" includes transester i fy i ng and the term 5 "esterifiable" includes transester i f i ab I e . In this method the add i t i on-copo I ymer of carboxy I —carry i ng and other ethylenic monomers may be a commercial l avai I ab I e add i t i on-copo I ymer , such as SMA 3000A (Atochem UK Limited). Alternati el , the add i t i on-copo I ymer Q may be prepared by the prior process step of copolymer ising ethylenic monomers correspon ing to the carboxy I—carry i ng and other monomers of the add i i on—copo I ymer chains. Conventional procedures using e.g. peroxide catalysts may be used. The copo I ymer i at i on reaction is preferably control led to give an average molecular weight of each of the add i t ϊon-copo I ymer 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 substantial ly completed before adding the divalent polyether alcohol . In one variant of the latter sequential embodiment, in step (a), some of the carboxyi ic groups are left for ester i f icat i on in step (b). In an alternative, a great proportion or al I of the carboxyi groups are reacted in step (a), and the divalent polyether alcohol reacts by transester i f i cat i on in step (b). The carboxy I —carryi ng monomer unit is preferably a 1,2— dicarboxyl ic unit sucn as ma I e i c anhydride; in such case, ester i f ϊcat ion in step (a) (e.g. with or with a derivative of an ether—terminated polyalkylene g I yco I ) , and preferably also in step Cb) is carried out by r i ng—open i ng . 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 ester if i cat ion only to the extent of leaving at least one esterifiable group on at least n—2 of the add i t i on-copo I ymer chains, free τrarboxy I groups are made avai lable. These may be neutral i sed by a I ka I i , e.g. sodium hydroxide or ammonia (e.g. at 20 to 100, typical ly όO * C in the case of alkal i) to increase solubi l ity in water . The relative proportions of the add i t i on—copoI ymer , the monovalent polyether alcohol and the divalent polyether alcohol should be such as to (a) cross—I ink at least 50 mole percent of the add i t i on—copo I ymer chains, but (b) sui ably not give more than 10 of such chains per surfactant molecule, because of the resulting high v iscosϊty. The proportions are preferably in the fo I lowing ranges defined by mole equivalent fractions of esterifiable carboxyi and alcohol ic hydroxyl : carboxyi 0.64 - 0.ό9 hydrox l in monovalent polyether alcohol 0.27 - 0.35 hydroxyl in di alent polyether alcohol 0.01 - 0.07. Whether carried out concurrently or in any sequential embodiment of step (a) and step (b), both reaction steps are carried out at temperatures typical ly in the range of 140* - I80 * C. A solvent, for example a hydrocarbon boi I i ng in that range may be present, but it is usual ly preferred to carry it out in the me I t . One embodiment of the particular surfactant of the present invention is characterised by a carboxyi ic ester group having as its alcohol residue e.g. C1-20 hybrocarb I . Such an ester group may be incorporated in the surfactant molecule by ester i f i cat i on or by use of a corresponding monomer in the production of the initial add i t i on-copo I ymer . The invention in a third aspect provides a dispersion in a l iquid characterised by containing a dispersion—stabi l ising quantity of the surfactant. Where the dispersion is characterised by containing a dispersion-stabi l ising quantity of the particular surfactant of the present invention, the dispersion may also contain a minor proportion of a material characterised by the fol lowing features : (a) a plural i y n of add i t i on—copo I ymer chains; (b) on at least n—2 chains, at least one, especial ly 3—10, op ional ly sal i f i ed carbox i ic acid groups and at least two carbox i ic ester groups; (c) at least one, especial ly 2-6 of the carboxyi ic ester groups in each chain having as its alcohol residue a monovalent polyether residue; and (d) optional ly a carboxyi ic ester group having as its alcohol residue a monovalent hybrocarbyl residue, e.g. Cι-20 hydrocarbyl , i.e. an uncrossI i nked 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 sol id, especial ly a crystal line oxide or combination of oxides, particularly having at least on its surface, a combination of a volati le oxide and an involati le oxide. Thus the material of the discontinuous phase of the dispersion is preferably an inorganic crystal l ine carbonate, basic carbonate or hydroxide. It preferably has a crystal lographic face simi I ar to the 001 face of calcite. The involati 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 1 ach i tes . The dispersion is especial ly sui able for sol id particles of high aspect ratio, for example 5: 1 to 50:1. For optimal stab i I i y against f I occu I at i on and for low viscosity, where the material of the iscontinuous phase of the dispersion is a crystal I i ne sol id, the distance between the carboxyi groups of the surfactant is chosen to match the crystal lographic lattice parameters of the dispersed material . Thus, for example for the calcite lattice, the carboxyi " groups in the add i t i on-copo I mer chains, are suitably separated by 4 ethylene oxide residues. It is be I ieved that * the surfactant is then substantial ly completely adsorbed on - 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 carboxyi groups per uni length of the surfactant molecule chains were too great, the surfactant would not be uniformly and completely adsorbed. 10 It is be I ieved that, depending on the nature of the dispersed phase, the adsorption may actual ly be chemi sorpt i ve i n nature . However the nature of the interaction between the chains and the sol id is not in any way relevant to or I imiting on any 15 aspect of the present invention. The l iquid forming the continuous phase of the dispersion typical ly is or comprises water, but may be or comprise a highly polar organic l iquid. The dispersion may comprise other ingredients, such as pigments, texturising 20 agents, perfumes and disinfectants, and other surfactants and po I ymers. A preferred dispersion has a high sol ids content of 20-80% w/w, especial ly 25-75% w/w. _ Even at such a high sol ids content, the dispersion may 25 typical ly have a relatively low viscosity, and its rheological properties may be adjusted with considerable freedom by means of additives. In particular the dispersion of the present invention may have any rheology between mob i le and thixotropic using additives. «30 The dispersion is suitable for coating sol id substrate surfaces with the dispersed sol id. ; For example, a dispersion comprising fine particles is especial ly suitable as a printing ink of low viscosity with good stabi l ity against flocculation, e.g. for wa I Ipapers, or .35 for applying surface f i re—proof i ng or making abrasive papers. If desired, the dispersion may be caused or al lowed to set le and the precipitate may be col lected and dried. The dried material may, optional ly after mi I I i ng , be redispersed. The material may be redispersed in an organic medium, especial ly a plasticϊsed polymer. The invention accordingly provides in its fourth aspect a composition, characterised in that it comprises a pol mer containing a plasticiser and a sol id dispersed material having a surfactant of the present invention adsorbed on its surface. The pol mer is especial ly pofyviπyl chloride or a copol mer of vinyl chloride, and the plasticiser is especial ly a dialkyl phthafate, e.g. d i octy I phthalate. The invention in a fi th 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 stab i I ise a dispersion of the sol id in the I iquid. Typical ly 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 examp I e — by simple mixing of the surfactant of the present invention with the sol id which has been pre—co mi nuted by wet— or dry— grindi ng ; by size reduction of the sol id in the presence of the surfactant; by (co)preci p i tat i on of the sol id in the presence of the surfactant; or by digestion in the presence of the surfactant of a sol id previously (co)precip i tated in the absence of the surfactant and/or in the presence of another surfactant. 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 sol id is chem i sorpt i ve , it may be desirable to include pH adjustment in the incorporation method to neutral ise alkal i or ammonia I iberated by chemi sorpt i on of carboxyi ic acid groups to the sol id surface. The invention in its sixth aspect provides a red i spers i b I e sol id comprising fine particles having a surfactant of the present invention adsorbed or chemisorbed on i ts surface . The surfactant wi l l be adsorbed in a quantity which is sufficient to stabi l ise a dispersion of the sol id in a l iquid, preferably sufficient to adsorb or chemisorb onto at least half of the relevant adsorptive or chemi sorpt i ve sites on the surface . The red i spers i b I e sol id 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 i ntag I io printing, padding, brushing, spraying, doctoring and reverse- rol l coat i ng . The process may include pre I iminary adjustment of the rheology of the dispersion using additives. The I i qu i d forming the continuous phase of the dispersion typical ly is removed during the coating process e.g. by evaporation. The dispersion is especial ly suitable for ro! lei—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. wa I Ipapers, f i re—proofed papers and abrasive papers. The present invention is i 1 I ustrated by the fol lowing Examp Ie. EXAMPLE Ca) Preparation of the surfactant The fol lowing reactants were used: styrene ma I e ic anhydride add i t i on-copo I mer (SMA) Cmolar ratio 3: 1) of molecular weight 1900, commercial ly avai la le as SMA 3000A (Atoche 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 nitroge-n flow, SMA (1421.4g, 0.748 mole) and MeOPEG (995g, 2.843 mole) were melted together and held at lό0-lό5 * C for 1.5 h. , to effect ring—opening and ester i f i cat i on of the maI e i c anhydride un.its in step (a) of the present method. The mixture was cooled to beiow 125 * 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 όO min. , to effect further ester i f i cat i on of (ring-opened) ma I e i c anhydride units and cross-I ink i ng between the chains of the SMA addi ti on-copo I ymer in step (b) of the present method. The mixture remained l iquid and of stable viscosity. The product was cooled to 120 * C and poured out. A sample was dissolved over several hours in di lute sodium hydroxide at όO * C to give a solution of sal 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 quantities 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 ratio % SMA MeOPEG PEG CO2H OH i n OH i n MeOPEG PEG Surfactant A 1 3.8 0.473 0.661 0.271 0.068 Surfactant B 1 3.8 0.331 0.675 0.277 0.048 15 (b) Preparation of dispersion of sol ids in water The fol lowing aqueous slurries I and II were made up using 10Og sol ids in aqueous solutions of surfactants made according to (a) above: 20 I "Ultracarb", 30% w/w sol ids content (RTM, commercial ly avai lable from Microfine Ltd, a natural ly occurring crystal l ine mineral composed of approx imateLy equal amounts of huntite and hydromagnes i te with a lamel lar 25 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. J 30 II "Calopake F" , 46.8% w/w sol ids content (commercial ly avai lable from Rhone-Pou I enc , a precipitated calcium * carbonate of particle size 2.1 μ Stokes equivalent d i ameter ) with Surfactant B, 1.5% w/w on Calopake F. 35 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 Brookf ield viscometer at two rpm levels. Control samples with respect to slurry I of dispersions at the same total sol ids content, using no surfactant and using each of the fol lowing known surfactants were also prepared and tested by the same procedures: SMA 3000A styrene ma I e i c anhydride add i t i on-copo I ymer sodium salt surfactant, Atochem UK Limited; Polysalt S po I carboxy I i c acid sodium salt, BASF; Coptal WA-0SN sodium dioctyl su I phosucci nate , hexylene glycol and ethylene glycol , ICI PATC0; Compa ison samples with respect to slurry I at simi lar total sol ids content, using no surfactant and using various quantities of each of the fol lowing were also prepared and tested: Dispex N40 water-soluble po I yacry 1 ate, 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 5 6 Al I slurries 30% w/w sol ids content. TABLE 2: Brookfield viscosities cP of Ultracarb slurries Days Storage Surfactant sol ids rpm 1 2 5 6 content Dispex N40 53.5 5 too thick to measure 100 too thick to measure Copta I WA-OSN 5 too thick to measure 100 too thick to measure I 5 68 72 74 76 100 141 141 159 100 (c) Preparation of piqmented polymer Precipitated calcium carbonate of particle size 4.5 μ was aqueous slurried at a sol ids 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 I ected on a f i Iter, dried at 105 * C for 24 h, and mi l led using a pin disc mi l l . A control sample was made by applying 1.6% w/w of stearic acid to the precipitated calcium -carbonate by slurry ing in ammonium stearate solution, then fi ltering, drying and mi I I ing in the same way. Al I the samples of treated calcium carbonate were tested as fi l l ers i n PVC/d i octy I phtha I ate and PVC . p I ast i so I formulations, as fol lows. A PVC masterbatch was prepared from: Corvic P706 emulsion PVC (ICI) 406G Vi nno I C8/62V paste extender copolymer containing 8% vinyl acetate (Wacker) 280g Tribasic lead sulphate 28g Polycarb S (uncoated ground calcium carbonate, 80% < 2μ, ECC 208g Di isononyl phthalate 1 I20g using a Hobart mixer. The formulations were prepared by mixing and then triple rol lei—mi 1 I ing the fol lowing: PVC masterbatch _304g Calcium oxide 4.8g Calcium carbonate treated as above 75g Estiboπd 262 pol amino adhesion promoter, AKZO 5g The rheological properties of these formulations were measured using a Carri-Med rheometer in control led stress mode. The measuring system was a 4cm para I lei plate with a 200 μ gap . A l inked flow/creep shear stress programme was used with the fol lowing parameters: (a) 0—2000 Pa shear stress sweep over 40 sec. fol lowed immediately by (b) creep curve at 40 Pa for 2 min. Each sample was run 3 times with satisfactory reproducibi I i y . Daniel gauge measurements were carried out to assess Iu p . 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- i after 20 * sec , compared with 0.10 sec- 1 after 20 sec. for the control 5 formulation using stearic acid. The PVC plastisol 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 10 sec- t after 10 sec , compared with about 1 sec-' 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. 15 20 25 30 35

Claims: CLA I MS 1. A surfactant characterised by a plural ity of add i t ion—copo I mer chains, on each chain an average of at least 0.5 adsorptive or chemi sorpt ive groups and at least one monovalent polyether residue; and between the chains at least one divalent polyether residue. 2. A surfactant according to claim 1, characterised by the '0 fol lowing features: Ca) a plural ity n of add i t i on-copo I mer chains; (b) on at least n-2 chains, at least one optional ly sal i f i d carboxyi ic acid groups and at least two carboxyi ic ester groups; 15 (c) at least one of the carboxyi ic ester groups in each chain having as its alcohol residue a monovalent polyether residue; and (d) at least one other of the carboxyi ic ester groups in each chain having as i s alcohol residue a divalent 0 polyether residue, a further end of which is the alcohol residue of the carboxyi ic ester group of another of said addϊ t ion—copo I ymer chains; and (e) optional ly a carboxyi ic ester group having " as its alcohol residue a monovalent hybrocarby I residue, e.g. 5 Cι-20 hydrocarbyl . 3. A surfactant according to claim 2, characterised by (a) on at least n-2 chains, 3-10 optional ly sa I i f i ed carboxyi ic acid groups and at least two carboxyi ic ester 0 groups; (b) each of 2-6 of the carboxyi ic ester groups in each chain having as its alcohol residue a monovalent polyether resi due; and (c) optional ly a carboxyi ic ester group having as its 5 alcohol residue a Cι-20 hydrocarbyl group. 4. A method of making the surfactant according to claim 2, characterised by: (a) reacting an add i t i on-copo I ymer comprising carboxy I -carry i ng 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 add i t i on-copo I mer chains; and (b) reacting the product of step (c) in esterifying 10 conditions with a divalent polyether alcohol . 5. A dispersion of a sol id in a I iquid characterised by containing a dispersion-stabi l ising quantity of the surfactant according to claim I. 15 6. A dispersion according to claim 4, characterised in that the material of the discontinuous phase of the dispersion is an inorganic crystal I ine carbonate, basic carbonate or hydroxide present as sol id particles of aspect ratio in the 20 range 5: 1 to 50: 1 , the dispersion comprises a surfactant according to claim 2, and the distance between the carboxyi groups of the surfactant is chosen to match the crystal lographic lattice parameters of the dispersed material . 7. A composition, characterised in that it comprises a polymer containing a plasticiser and a sol id dispersed material having a surfactant according to claim 1 adsorbed on i ts surface . - - ' 30 8. A method for making a dispersion according claim 5, characterised by incorporating with the sol id a quantity of a 1 surfactant of the present invention to adsorb onto at least half of the relevant adsorptive sites on the surface. 35 9. A dispersible sol id 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. 10. A product coated with material comprising the discontinuous phase of the dispersion according to claim 4.

Inventors: DOBSON DERRICK CLIFFORD, DOBSON, DERRICK, CLIFFORD
Applicants: ICI PLC, IMPERIAL CHEMICAL INDUSTRIES PLC
Application year: 1993
Main classification: B01F17
IPC codes: B01F17, B01J13, C08G81, C08J3, C08L25, C08L27, C08L71