WO1994026832A2 - Compositions de revetement dans lesquelles se produit une separation, et copolymere utilise pour cette separation - Google Patents

Compositions de revetement dans lesquelles se produit une separation, et copolymere utilise pour cette separation Download PDF

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Publication number
WO1994026832A2
WO1994026832A2 PCT/GB1994/000983 GB9400983W WO9426832A2 WO 1994026832 A2 WO1994026832 A2 WO 1994026832A2 GB 9400983 W GB9400983 W GB 9400983W WO 9426832 A2 WO9426832 A2 WO 9426832A2
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Prior art keywords
component
film
coating composition
former
polymer
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PCT/GB1994/000983
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English (en)
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WO1994026832A3 (fr
Inventor
Robert Mcintyre
Nigel Philip Briggs
John Ring
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Courtaulds Coatings (Holdings) Limited
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Priority to AU66836/94A priority Critical patent/AU6683694A/en
Publication of WO1994026832A2 publication Critical patent/WO1994026832A2/fr
Publication of WO1994026832A3 publication Critical patent/WO1994026832A3/fr

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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D167/00—Coating compositions based on polyesters obtained by reactions forming a carboxylic ester link in the main chain; Coating compositions based on derivatives of such polymers
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D163/00—Coating compositions based on epoxy resins; Coating compositions based on derivatives of epoxy resins
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D201/00—Coating compositions based on unspecified macromolecular compounds
    • C09D201/02—Coating compositions based on unspecified macromolecular compounds characterised by the presence of specified groups, e.g. terminal or pendant functional groups

Definitions

  • the present invention relates to segregating
  • coating compositions having a relatively high or high solids content, more especially those having a solids content of at least 75% and up to 100% by weight
  • Coating compositions generally comprise a solid film-forming resin, usually with one or more pigments; fillers and other additives may also be included.
  • the resins or binders can be thermoplastic but are more usually cross-linkable, in which case the final composition incorporates two co-reactive film-forming resins or incorporates a curing agent for the film-forming resin.
  • the solid film-forming resin usually with one or more pigments; fillers and other additives may also be included.
  • the resins or binders can be thermoplastic but are more usually cross-linkable, in which case the final composition incorporates two co-reactive film-forming resins or incorporates a curing agent for the film-forming resin.
  • solvent-based coating compositions the solid
  • ingredients are mixed with one or more solvents.
  • compositions having a solids content of at least 80% by volume are generally known as "high solids" systems;
  • compositions generally correspond to an approximate solids content of at least 85% by weight, although if very heavy pigments are present the weight % solids figure will be higher.
  • weight % solids figure will be higher.
  • such compositions conform to the E.C. recommended maximum solvent level of 250g/litre.
  • high solids systems is also used in the art to include 100% solids coating systems, where the composition is applied in powder or liquid form.
  • solvent-based coating compositions the solvent, pigment and other additives are mixed with the binder or resin (typically, for example, an epoxy resin), and then ground; usually the minimum particle size is 2 ⁇ m. Finally, solvent is added to achieve the reguired volume of solids for a suitable application viscosity.
  • the material is supplied together with a curing agent, which is generally in a solvent, usually as a two pack paint system, and the two components are mixed together prior to application. Application may be, for example, by spray, brush or roller.
  • Powder coating compositions are generally prepared by intimately mixing the ingredients, for example in an extruder at a temperature above the softening point of the film-forming resin but below the curing temperature of the composition (the process of extrusion), and comminuting the mixture to the desired particle size in suitable grinding equipment (the process of micronising).
  • the powder is then applied to the substrate by various means, for example by the use of fluid beds, for example in the case of a "coil” substrate consisting of a metal strip wound on a coil, or most commonly by electrostatic spray gun, and is cured on the substrate by the application of heat (the process of stoving); the powder particles melt and flow, and a film is formed.
  • melt extrusion Another application technique for 100% solids systems is melt extrusion, in which a film-forming composition is applied in melt or plastified form to a substrate through an extrusion coating die, and the substrate is preferably stoved to cure the composition.
  • Other melt application techniques are also possible.
  • solvent-based systems are in the architectural field, for example for window frames or architectural cladding
  • melt extrusion techniques for coatings on packagings, for example on metal cans, should also be mentioned; stain resistance is important here too.
  • Such properties can be achieved by applying two coats separately, but preferred is the use of a single coating composition that segregates to provide an enrichment of one polymer, having suitable top-coat properties, near the air interface, and of the polymer having suitable base-coat properties near the substrate; a bilayer system, in which there is a continuous top layer over a base layer, with an enriched content of the more
  • weatherable polymer in the layer at the air interface and the polymer with the better mechanical properties in the base layer would, of course, be especially preferred. Ideal would be a complete stratification such that the top layer is composed almost completely of the desired polymer, and with low or zero content of that polymer in the base layer, but avoiding any delamination problems which might be expected with one coat on top of another. Although with existing polyester-acrylic powder coating systems partial segregation of one component can often be obtained, formation of a true bilayer coating from a mixed polymer system has in practice been very difficult to achieve. Segregation is also known for solvent-based systems with normal and high solids
  • the present invention provides a coating composition, comprising two or more film-forming materials and having a relatively high or high solids content, more especially of at least 75% by weight, and up to 100% by weight, wherein the film-forming materials comprise
  • non-polar denotes a non-ionic species, not readily polarisable; non-polar groups have no permanent charge and a charge is not readily induced.
  • an end group is a fluorinated, chlorinated, hydrocarbon and/or silicon-containing end group and the component A film-former may contain the same or different end groups.
  • a hydrocarbon end group preferably has at least 4 carbon atoms, and preferably these are arranged in a straight chain.
  • Alkyl groups such as, for example, n-butyl or lauryl (dodecyl), should especially be mentioned.
  • the present invention also provides a coating composition comprising two or more film-forming materials and having a relatively high or a high solids content, more especially of at least 75% by weight and up to 100% by weight, in which the film-forming materials comprise (A) a fluorinated, chlorinated and/or silicon-containing film-forming component having one or more fluorinated, chlorinated, silicon-containing and/or
  • hydrocarbon end groups a hydrocarbon end group preferably comprising at least 4 carbon atoms arranged in a straight chain
  • end group is used herein to denote a carbon- and/or silicon-containing group, not only at an end of the main polymer chain, but also a pendant group or a group at the end of a pendant chain.
  • An end group may be straight-chained or branched and may include functional groups, but it is preferred that the term as used herein in relation to pendant groups is taken to exclude any functional link to the main chain.
  • end group may denote the end portion of the main polymer chain that does not contain the repeat units of the polymer, or a pendant (side) group or chain, or a group at the end of a pendant chain excluding any
  • stratification that is, the formation of a bilayer coating, as distinct from a coating in which segregation occurs but leads only to enrichment of the top-coat polymer at the air interface
  • stratification is improved when there are certain differences in surface energy and viscosity between the two segregating systems .
  • the present invention provides a coating composition comprising two or more film-forming materials and having a relatively high or a high solids content, more especially of at least 75% by weight, and up to 100% by weight, wherein the film-forming materials comprise
  • component is no more than 4 Ln Pa.s, preferably no more than 3 Ln Pa.s,
  • viscosity in high solids systems of the present invention contrasts to the situation in prior art segregating systems, which utilise lower solids contents, and where the convection currents set up by the evaporating solvent create turbulence and assist in the enrichment of the lower surface energy component at the surface; viscosity differentials are therefore not the major driving force. With increased solids content, however, this effect will diminish, and the system will be too viscous to create effective convection currents.
  • a 70% by volume (generally a 75% by weight) solids system will have a zero shear viscosity at room temperature in the range of from 1 to 5 Poise
  • an 80% by volume solids system will have a viscosity in the range of from 3 to 10 Poise
  • a higher solids system will have a correspondingly higher viscosity, for example at least 5 Poise at 90% solids and above.
  • Most 100% solids systems will also, of course, have a viscosity of at least 5 Poise at room temperature.
  • the present invention also provides a coating composition comprising two or more film-forming materials and having a solids content of at least 75% by weight, and up to 100% by weight, wherein the film-forming materials comprise
  • a film-forming component comprising a polyester, an epoxy resin, an acrylic resin, a polyurethane or a hybrid of two or more of these polymers, or one of more reactive diluents therefor,
  • the relative surface energies and zero shear viscosities of the components being such that, when the composition is applied to a substrate and a film is formed, enrichment of the fluorinated, chlorinated and/or silicon-containing polymer at the air interface is obtained.
  • Component A polymers having one or more non-polar end groups as specified above, preferably one or more end groups containing fluorine, chlorine, silicon and/or comprising a hydrocarbon group preferably having at least 4 carbon atoms arranged in a straight chain, should especially be considered in selecting the powder and solvent-based compositions with the specified surface energies and viscosities. Random copolymers with pendant groups should especially be mentioned.
  • Figures 1 to 4 show plots of the change of zero shear viscosity with temperature of various examples of fluorinated and non-fluorinated polymers
  • Figures 8(a), 8(b) and 9 to 11 show scanning
  • each film- forming component is polymeric.
  • component A the "top coat” component
  • component B forming the “base coat”
  • component B comprises a polyester (and, as will be understood, the term “polyester” includes alkyd resins), an epoxy resin, an acrylic polymer or a polyurethane or a hybrid of two or more of these polymers, or one or more reactive diluents therefor
  • component A may comprise, for example, an acrylic polymer, a polyolefin, a polyester, an epoxy resin, a polyvinyl ether or a polyurethane or a hybrid of two or more of these polymers, or one or more reactive diluents therefor.
  • the component A film-former contains at least 2%, especially at least 4%, e.g. at least 5%, especially at least 10%, more advantageously at least 15%, of repeat units free of polar groups and having a non-polar pendant group.
  • component A film-formers have up to 70 mol % or more of repeat units having non-polar end (pendant) groups; polymers with up to 50 mol % or up to 40 mol % of such units should also especially be mentioned.
  • containing F, Cl, Si and/or a hydrocarbon group having at least 4 straight chain carbon atoms, to polar end groups is at least 0.5:1, and the ratio is preferably more than 1:1, especially at least 2:1.
  • no more than 25%, especially no more than 15%, of repeat units within the component A film-former have a polar
  • At least 60%, e.g., at least 80%, and even all or substantially all end groups are fluorine-, chlorine- and/or silicon-containing and/or hydrocarbon-containing end groups.
  • suitable (non-polar) end groups there should be mentioned
  • R F (CH 2 ) 2 - pendant groups (each linked to the main chain by a COO group) where R F denotes the fluorinated alkyl groups in the commercially-available Zonyl
  • long chain hydrocarbon or fluorocarbon groups e.g. decyl, dodecyl, perfluorodecyl or perfluorododecyl, at the end of the main chain or as pendant groups on the main chain.
  • the component A film-former has a number of pendant end groups, for example a plurality of
  • compositions of the present invention have given good segregation, and, as demonstrated by work in house, segregation of suitable acrylic polymers over polyester or epoxy coatings enhances weathering performance.
  • top-coat component of relatively low viscosity and/or to utilise a base-coat component of relatively high viscosity (consistent of course with capability of film-formation); preferably the top-coat component should have a zero shear viscosity below that of the base-coat component or at most up to 4 Ln Pa.s higher than that of the base-coat component, during the critical period for segregation.
  • top-coat resins various fluoroacrylic resins
  • base-coat resin a polyester
  • the critical period for this purpose is related to the stoving temperature for the powder coating composition and this is itself dependent on the particular polymers present in the composition, more
  • stoving temperature of about 200°C may be used, but for other systems a temperature in the range of 150-260°C may, for example, be selected, and stoving at lower temperatures, e.g. 120°C, should also be considered, and in general the surface energy and
  • viscosity differences in the sixty or even up to one hundred degrees C up to the stoving temperature are important, especially in the temperature range between sixty and twenty degrees C below the stoving temperature.
  • the surface energy and viscosity differentials should be maintained throughout these temperature ranges, some variation from the specified differentials may not be important.
  • the gellation time of component A is usually at least as long as that of B.
  • gellation in powder coating compositions occurs at 50 to 70% cure, and preferably the specified relative surface energies and viscosities should apply up to 80% cure.
  • Systems in which the viscosity differential applies between the softening point of the base-coat resin and up to 50% cure should especially be mentioned.
  • the selection of the preferred component A and component B components may be made having regard to the surface energy and viscosity differences at a single temperature or over a limited temperature range, defined either in relation to the temperature of stoving, e.g. at twenty degrees C below the stoving temperature, or defined in absolute terms, e.g. at 140°C, 150°C, 160°C or 170°C, or at a temperature in the range of from 120 to 150°C, which is an important temperature range in relation to segregation for most, if not all, powder coating systems; more especially the differentials are maintained at all temperatures in that range.
  • unpigmented polyester resin used with a conventional curing agent, and component A had a surface energy > 45 dynes/cm at 120°C, > 43 dynes/cm at 130°C, > 41 dynes/cm at 140°C, > 39 dynes/cm at 160°C, > 37 dynes/cm at 180°C,
  • component B is an unpigmented polyester resin
  • the surface energy of component A is ⁇ 19 dynes/cm at 120°C, ⁇ 16 dynes/cm at 140°C, ⁇ 14 dynes/cm at 180°C, ⁇ 13 dynes/cm at 160°C, ⁇ 11 dynes/cm at 200°C; and/or the zero shear viscosity is ⁇ 9.5
  • the present invention also provides a coating composition, especially a powder coating composition, comprising
  • the surface energy of component A is at least 5 dynes/cm less than that of component B at 120°C, at least 4 dynes/cm less than that of component B at
  • the zero shear viscosity of component A is no more than 3.5 Ln Pa.s more than that of component B at 120°C, no more than 3.2 Ln Pa.s more than that of component B at 140°C, no more than 3.0 Ln Pa.s more than that of component B at 160°C, no more than 2.8 Ln Pa.s more than that of component B at 180°C, and no more than 2.6 Ln Pa.s more than that of component B at 200°C.
  • the surface energy and viscosity of component B will vary, and the surface energy and viscosity of component A should be varied correspondingly.
  • the surface energy of component A may be, respectively, ten or five dynes/cm higher than where the component B polymer is a polyester, and where the base coat is an acrylic-polyester hybrid or an aerylic-epoxy hybrid, the surface energy of component A should, in general, desirably be at least five dynes/cm less than the corresponding figure when the base coat is a polyester.
  • the viscosity and/or surface energy differences are especially important in the early stages of film formation; for example, for a 75% solids system, the differences should apply at 75% solids, and preferably up to 90% solids. More
  • the differences should apply at the solids content of the individual components when applied and up to the solids content achieved in the final coating (substantially 99%).
  • differentials are preferably maintained from the time of application to gellation.
  • viscosity and/or surface energy differentials should preferably be
  • the differentials may be judged, for example, at a temperature in the range 90 to 180°C, e.g., at 140°C or 150°C, or over the limited temperature range 120 to 150°C.
  • the differentials may be judged, for example, at an individual temperature in the range of -5 to 85°C, (for a system applied by hot twin feed, for example, at a temperature in the range of 30 to 85°C), or at a particular temperature in the range of from two to fifty-five degrees C
  • a temperature of 70°C is a suitable reference point.
  • the differentials may be judged at the solids content of the components to be applied, and for this system, especially, a single reference point is most convenient, and assessment is suitably of the component (to be added to the system) at room temperature, i.e., 20°C.
  • the present invention also provides a coating composition, comprising two or more polymeric film-forming materials and having a relatively high or high solids content, more especially of at least 75% by
  • film-forming component having one or more end groups containing fluorine, chlorine, silicon and/or a
  • melt application system at all temperatures between the softening and gellation; in the case of a controlled
  • the surface energy of component A is no more than, preferably at least 2 dynes/cm
  • the zero shear viscosity of component A is no more than 4 Ln Pa.s, for example no more than 3 Ln Pa.s, preferably no more than 2 Ln Pa.s, more than that of component B, preferably at least 2 Ln Pa.s less than that of component B.
  • viscosity differentials as specified may be important to assist the formation of bilayer films, the use of
  • compositions in which condition (ii) applies should especially be mentioned.
  • thermosetting component As has been mentioned, in a thermosetting component, as will be readily appreciated, the polymer should reach its maximum potential mobility before appreciable
  • each of the components softens before the curing of either, and remains mobile before any appreciable curing of either. It is important too that the times for each component to reach maximum mobility are not too dissimilar. These times may differ by a factor" of 10, but advantageously by a factor of 5 or less, and preferably by a factor of 2 or less. For example, if the base-coat reaches its maximum mobility after time t, the top-coat should preferably reach its maximum mobility at a time in the range of from 0.5 to 2t. As will be understood, the curing times also should be comparable; for example one may be up to 20% more than the other. Segregation, however, is often complete early, before cross-linking begins.
  • the surface energy of component A is at least 3, preferably at least 4, especially at least 6, advantageously at least 7, more especially at least 10 or at least 15, dynes/cm less than that of component B.
  • the zero shear viscosity of component A is no more than 3, preferably no more than 2, Ln Pa.s more than that of component B, and especially the
  • viscosity is no more than, for example at least 1
  • Ln Pa.s advantageously at least 2, more especially at least 3, Ln Pa.s, less than, that of component B.
  • Top-coat components having a zero shear viscosity up to 3 Ln Pa.s for example in the range of from -1 to 3, e.g. 0.5 to 3, Ln Pa.s at the point of application, and base-coat components having a zero shear viscosity of at least -1.6 Ln Pa.s, e.g. for solvent-containing systems up to -0.35 Ln Pa.s, at the point of application should especially be mentioned.
  • the use of a base-coat component having a zero shear viscosity of at least Ln 0.65 Pa.s at the point of application may ensure a suitable differential viscosity and hence good segregation.
  • the surface energy of the end groups of component A may also be considered.
  • Our results suggest that segregation may be assisted by the presence of low surface energy end groups; low surface energy groups are generally of low polarity.
  • the Zonyl monomer for example, contains the long fluorinated chain end (pendant) group, predominantly consisting of - (CH 2 ) 2 (CF 2 ) 5 CF 3 groups having a relatively low surface energy.
  • the surface energy of the end groups may be calculated by the group contribution method (see D.W. Van Krevelen, Properties of Polymers, Their Estimation and Correlation with Chemical Structure, Elsevier, 1976, 2nd edition)). Such calculations show that fluorinated, chlorinated and silicon-containing end groups have a lower surface energy than hydrocarbon end groups of corresponding length (and that all such groups have a lower surface energy than polar end groups) and that increasing the length of the fluorinated, chlorinated or silicon-containing groups decreases their surface
  • the group contribution method may also be used to calculate the surface energy of the polymer backbone and of the polymer itself, and differences between the surface energy of the end group and the surface energy of the polymer may be calculated.
  • the present invention also provides a coating composition, comprising two or more film-forming materials and having a relatively high or high solids content, more especially of at least 75% by weight and up to 100% by weight, wherein the film-forming materials comprise (A) a fluorinated, chlorinated and/or silicon-containing film-forming component, the component (A) polymer having one or more end groups having a surface energy less, preferably at least 2 dynes/cm less, than that of the polymer backbone, and
  • the surface energy of the end groups is at least 2 dynes/cm, for example at least 4 dynes/cm, preferably at least 5 dynes/cm, especially at least 10 dynes/cm, less than the surface energy of the polymer backbone units, the backbone unit being considered as the repeating unit minus the end group.
  • the backbone unit being considered as the repeating unit minus the end group.
  • polymers in which the surface energy of the component A polymer end group is at least 2 dynes/cm, preferably at least 5 dynes/cm, especially at least 10 dynes/cm, less than the surface energy of the polymer itself.
  • the end groups are preferably the non-polar end groups mentioned above, preferably fluorinated,
  • Such pendant groups bring about a reduction in surface energy and viscosity of the component.
  • the surface energy and/or zero shear viscosity differentials mentioned above should also apply.
  • the average surface energy of all the end groups containing fluorine, chlorine and/or silicon or comprising a hydrocarbon group containing at least 4 carbon atoms arranged in a straight chain is less than the surface energy of the polymer backbone and the polymer as a whole, advantageously less by the amounts mentioned above.
  • the average surface energy of all end groups is no more than that of n-butyl, i.e. 34.3 dynes/cm; advantageously each end group has a surface energy no more than 34.3 dynes/cm.
  • the specified end groups whether specified as being non-polar end groups, or as end groups containing fluorine, chlorine, silicon and/or hydrocarbon groups preferably having a C 4 or longer chain, or specified as having a surface energy or on an average surface energy less than the polymer itself, constitute at least 2 weight %, advantageously at least 4 weight %,
  • a copolymer may advantageously contain at least 2 mol %, for example at least 2.5 mol %, advantageously at least 5 mol %, preferably at least 10 mol %, especially at least 25 mol %, e.g. at least 50 mol %, more especially at least 75 mol %, of the monomer containing the specified end groups.
  • the F, Cl, Si or hydrogen content of the total of the various end groups specified is, respectively, at least 4, 8, 4 or 7% by weight of the polymer.
  • the fluorine content of all pendant groups together is more than the fluorine content of the backbone
  • the chlorine content of all pendant groups together is more than that of the backbone
  • the silicon content of all pendant groups together is more than that of the backbone
  • the overall ratio of F:C, Cl:C, Si:C and/or H:C in all the variously specified end groups is greater than the corresponding ratio in the rest of the molecule.
  • end groups have, on average, an F:C ratio of at least 1.5:1 by weight, especially at least 2:1 by weight, or a Cl:C ratio of at least 1.5:1 by weight, especially at least 2:1 by weight, or a Si:C ratio of at least 0.5:1 by weight, especially at least 1:1 by weight, or a H:C ratio of at least 2:1 by weight, especially at least 2.25:1 by weight.
  • the fluorine content is advantageously at least 5%, preferably at least 25%, e.g. at least 50%, by weight;
  • the chlorine content is advantageously at least 10%, preferably at least 20%, e.g. at least 50%, by weight; and/or the silicon content is advantageously at least 5%, preferably at least 10%, e.g. at least 25%, by weight; or (where there is no F, Cl or Si in the end group)
  • the hydrogen content is advantageously at least 8%, preferably at least 12%, e.g. at least 15%, by weight.
  • the fluorine content of the component A film-former is no more than 60 weight %, preferably no more than 50 weight %, especially no more than 40 weight %. F contents ⁇ 30%, ⁇ 25% and ⁇ 20% should especially be mentioned.
  • the presence of fluorine (or silicon) in pendant groups as specified herein represents a very efficient utilisation of the fluorine (or silicon).
  • the film-former contains at least 5 weight %, advantageously at least 7.5 weight %, especially at least 10 weight % or at least 15 weight %, of fluorine.
  • the silicon content of the component A film-former is advantageously no more than 35 weight %, preferably no more than 25 weight %, especially no more than 15 weight %. Silicon contents ⁇ 36%, ⁇ 18% and ⁇ 9% should especially be mentioned.
  • the film-former contains at least 5 weight %, advantageously at least 10 weight %, especially at least 20 weight %, of silicon.
  • the chlorine content of the component A film-former is advantageously no more than 20 weight %, preferably no more than 10 weight %, especially no more than 5 weight %. Chlorine contents ⁇ 18%, ⁇ 16% and ⁇ 8% should especially be mentioned.
  • the film-former contains at least 5 weight %, advantageously at least 10 weight %, especially at least 20 weight %, of chlorine.
  • the filmformer of component A is fluorinated and/or contains silicon.
  • a fluorinated or chlorinated polymer may be fully or partially fluorinated or chlorinated
  • the component may alternatively contain both chlorine and fluorine atoms, being fully or partially halogenated.
  • Suitable fluorinated and/or chlorinated monomers for component A are, for example, fluorinated acrylic
  • Suitable siliconised polymers are, for example,
  • silicon-modified polyesters silicon-modified acrylic polymers and silicon-modified epoxy resins.
  • the polymer may, if desired, be a copolymer based on one or more of the above. Random or statistical
  • a copolymer has a content of at least 2 %, more especially at least 10 %, by weight fluorine, chlorine and/or silicon.
  • the composition may, if desired, include more than one such component A polymer. These may, for example, be mutually compatible or incompatible but co-extruded and partially reacted.
  • Suitable end groups for component (A) are, for example,
  • Pendant end groups comprising a perfluorohydrocarbon group or a long chain hydrocarbon radical or a perfluoroether or perfluoropolyether or siloxane chain should especially be mentioned.
  • component A has R F (CH 2 ) 2 pendant end groups where R F denotes perfluorinated alkyl of at least 4, preferably at least 6, e.g. on average at least 8, carbon atoms, derived for example from an aerylate-type monomer, e.g. from a methacrylate, advantageously in an amount of 3 mol%.
  • Such groups may be present at one or, preferably, both ends of the main chain and/or, more especially, at ends of any chain branches.
  • Preferred end groups are those having group contribution parameters comparable to that of the base-coat component; long pendant groups are preferred, for example those having at least 4 Si atoms or at least 4 F- substituted carbon atoms.
  • a suitable acrylic monomer is, for example, trifluoroethyl methacrylate (TFEMA); in the resulting polymer the chain has the structure
  • R F represents (C 4 -C 20 ) perfluorinated alkyl.
  • Fluorad FX-189 Fluorad FX-189
  • CH 2 C(CH 3 )-COO-CH 2 CH 2 O-CH 2 CF 2 -(OCF 2 CF 2 ) n -OCF 2 CF 3 ,
  • n 3 or 4
  • CF 3 O-(CF 2 CF(CF 3 )O) m -(CF 2 O) n -CF 2 CH 2 -O-COC(CH 3 ) CH 2 , having a molecular weight 719 or 538 (and known by the trade name Galden Methacrylate) and the ethoxylated analogue thereof (known by the trade name Galden TX
  • Suitable functional monomers which may be included in a copolymer include glycidyl methacrylate and 2-hydroxyethyl methacrylate and the functional polyfluoropolyethers available from Ausimont, for example
  • Suitable copolymers may be, for example, based on Zonyl, TFEMA or the above silicone monomer, or on one of the above Hoechst, 3M or Ausimont monomers with, for example, one or more of methyl methacrylate, butyl methacrylate, butyl aerylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, methacrylic acid, acrylic acid or aldehyde-containing monomers (e.g.
  • acrolein for example copolymers of Zonyl monomer and methyl methacrylate, Zonyl monomer and one of the above Ausimont monomers, or a copolymer of TFEMA and MMA, BA or BMA, or copolymers of different fluorinated/silicone monomers (and optional other monomer), e.g. Zonyl plus TFEMA or Zonyl plus a Hoechst monomer, or Zonyl, the above silicone monomer and MMA.
  • Such structures are typically random polymers, which are preferred.
  • Non-crystalline, or amorphous, structures (not block copolymers) are especially to be mentioned.
  • Component A film-formers having at least 11 continuous atoms (excluding F or Cl or any F- or Cl-substituted carbon atom or any silicon atom) separating
  • the present invention further provides a coating composition comprising two or more polymeric film-forming materials and having a relatively high or high solids content, more especially of at least 75% by weight and up to 100% by weight, wherein the film-forming materials comprise
  • the component A polymer may also be a polymer of a suitable top-coat monomer having a moiety providing compatibility with component B; for example it may contain units B' mentioned below.
  • Zonyl or TFEMA may be copolymerised with polyethylene glycol methacrylate; a copolymer may, for example, contain
  • R' H or methyl, in addition to polyZonyl or PTFEMA units.
  • the polymer contains moieties which either through specific interactions, such as hydrogen bonding, or through entanglement interacts with the base-coat polymer .
  • component (B) in powder or solvent-based systems will be a polyester, epoxy, polyester-epoxy hybrid, polyurethane or acrylic polymeric film-forming component, or a hybrid system: in powder systems, usually a polyester, acrylic, epoxy, polyester-epoxy hybrid or polyester-acrylic hybrid, and in solvent-based systems usually an epoxy resin, or, alternatively, in such a system an alkyd resin may be used; in melt application systems a polyester is most common, in impingement mixing systems, a polyurethane is most common, and in hot twin feed systems, epoxy resins are usually used.
  • component B polymers have molecular weights Mn at leat 300, for example, at least 2,000 and suitably up to 15,000, for example up to 7,000, preferably in the range 2000 to 7,000, for example 5000.
  • solvent-based systems examples include the epoxy resins Epikote 828, Epikote 1001 and Epikote 1004
  • component B is generally non-fluorinated, non-chlorinated and non-silicon-containing.
  • the use of such polymers for component (B) is not excluded, provided the components (A) and (B) form a segregating system.
  • such systems may be achieved when component (B) has no fluorinated, chlorinated or silicon-containing or hydrocarbon end groups and/or when (B) is a different chemistry from (A).
  • component (A) may be a fluorinated acrylic component and component (B) a fluorinated polyester component.
  • the chemistries may, however, be the same, if component (A) has fluorinated, chlorinated, hydrocarbon and/or silicon-containing end groups, and component (B) does not.
  • composition may, if desired, include more than one such component B polymer; these will remain as one layer provided they are mutually compatible.
  • two mutually incompatible polymers for example a polyester and an acrylic polymer, may be used; if co-extruded and partially reacted with one another, these would not then stratify.
  • Such polymers are incompatible with component A polymers, and in the absence of an interface-modifying agent, the component A and component B polymers cannot be blended or mixed to form a single (stable) phase.
  • Such systems have such different surface tensions that gross defects are caused when one resin "contaminates" the other.
  • the present invention provides a coating composition, having a relatively high or high solids content, more especially of at least 75% by weight and up to 100% by weight, and comprising two film-forming components of different UV durability and surface energies, and an interface-modifying agent having a surface energy between the surface energies of the other two components, and comprising, for example, one or more moieties providing compatibility with component A and one or more moieties providing compatibility with component B.
  • bilayer coatings that is, coatings having a "top" or
  • “surface” layer that is, at the air interface
  • at least 95% of which is composed of component A is composed of component A.
  • the top layer is at least 4.7 ⁇ m ⁇ 0.5 ⁇ m up to 40 ⁇ m ⁇ 4 ⁇ m uniformity as determined by transmission electron spectroscopy (TEM) and optical microscopy.
  • TEM transmission electron spectroscopy
  • PTFEMA poly-trifluoroethyl methacrylate
  • TEM micrograph sections were also taken to confirm the structure (i.e. the thickness and uniformity of the top coat) of the bilayer system.
  • fluoropolymer and polyester which resulted in an upper layer, several microns thick, composed almost entirely (>98%) of the fluoropolymer.
  • such layer is at least 4.5 ⁇ m, more especially at least 5 ⁇ m, and advantageously 10 to 15 ⁇ m thick.
  • the top 10 ⁇ m preferably the top 20 ⁇ m, at least 50% is composed of component A.
  • interface-modifying agent (component C) gave a constant thickness of top coat at different points along the coating. Without the interface-modifying agent the thickness can vary in some cases depending on the structure of the top-coat polymer.
  • An interface-modifying agent (component C) preferably has a surface energy of at least 15 dynes/cm and preferably up to 60 dynes/cm, advantageously at least 18 dynes/cm, and advantageously up to 50 dynes/cm,
  • the surface energy of the interface-modifying agent should remain intermediate between those of components A and B during the gellation period. As described above, however, the surface energy difference requirement may conveniently be applied at only a single solids content or a single temperature or over a limited temperature range.
  • Surface energy may be determined, for example, by Dunuoy ring or Wilhelmy plate (see Physical Chemistry of surfaces 4th Edition by Arthur W. Adamson and published by John Wiley & Sons). The group contribution method mentioned above may also be used to calculate surface energy, but it does not enable the surface energy to be calculated as a function of temperature. If, however, the interface modifying agent has a surface energy intermediate between the surface energies of A and B at room temperature, our findings suggest that it generally remains intermediate at the higher temperature used for stoving of powder systems.
  • component A may have a surface energy in the range of from 6 to 35, for example 15 to 20, dynes/cm (at 130°C), component B may have a surface energy in the range of from 30 to 80, for example 30 to 60, dynes/cm
  • component C for example 30 to 40 dynes/cm at ambient temperature or 10 to 20 dynes/cm at 130°C.
  • interface-modifying agent should generally be mobile between the softening point of the polymers and
  • the viscosity of the interface-modifying agent should preferably be less than that of components A and B; a zero shear viscosity of, for example, up to 130 poise, advantageously 0.1 to 130 poise or -2.3 to 4.8 Ln Pa.s should be mentioned.
  • the interface-modifying agent may comprise one or more moieties generally compatible with component B and one or more moieties generally compatible with component A or less compatible with component B than with A;
  • it may comprise one or more moieties generally compatible with component A and one or more moieties less compatible with component A than with component B.
  • suitable interface-modifying agents include those compatible with components A and B prior to, and during, cross-linking, (that is, when mixed they give a generally clear, non-hazy, appearance), but the invention is not limited to the use of such agents.
  • Compatibility of different species may be defined, for example, as the co-existence of the species as, for example, in the common situation where a compatibiliser (such as a block copolymer) is added to a mixture of two incompatible polymers: a 'compatible' blend is formed; this is usually a dispersion of one of the polymers in the other, with the compatibiliser stabilising the system.
  • the species may be, but are not necessarily, miscible (i.e. mixing at a molecular level).
  • Compatibility may be tested, for example, by optical or thermal methods.
  • a common method of determining whether two polymers are compatible at a molecular level is Differential Scanning Calorimetry, DSC; generally, if the materials are compatible, only one glass or melting transition would be observed. Microscopy, more
  • Compatibility may come about, for example, by van der Waals forces, by covalent bonding or polar interaction.
  • the interface-modifying agent may, for example, be oligomeric or polymeric.
  • an interface-modifying agent with moieties of, or chemically related to, a film-former in each of the components A and B generally medium- to long-chain moieties are present and/or the agent is an oligomer or polymer or contains one or more oligomeric or polymeric sections.
  • the agent may comprise one or more sections A' chemically related to a component A film-former, for example to the particular film-former used in the composition, and one or more sections B' chemically related to a component B film-former, for example to the particular film-former used in the composition.
  • a block copolymer of component A and component B monomers should also be mentioned.
  • the interface-modifying agent acts as an organic pin, becoming positioned during curing between the segregating layers, the or each A' section preferably positioning itself in the layer of component A and the or each B' section preferably positioning itself in the layer of component B.
  • An A' moiety may be, for example, a halogenated moiety (being fluorinated and/or chlorinated) and/or a silicon-containing moiety, irrespective of whether component A is itself halogenated or siliconised, and in the case of a halogenated component A and a halogenated moiety A' the identity of the halogen (s) in A and A' may be the same or different; a halogenated moiety A' may be partially or fully halogenated.
  • An A' moiety may also be a hydrocarbon chain, though this is less preferable, and two or more different A' moieties may be present in the interface-modifying agent.
  • a B' moiety may also be derived from a compound suitable for preparing component B or may be a modified form of this; it may be convenient to use the same compound(s) in preparing polymer B and the interface-modifying agent.
  • B' may denote a polyester, polyether, polyacrylic or polyglycidyl ether chain; two or more different B' moieties may be present in the interface-modifying agent, and ester and ether groups may both be present.
  • a polymeric interface-modifying agent may be thermosetting or thermoplastic.
  • non-polymeric substances having the specified surface energy and that may react with component A and/or component B.
  • an interface modifying agent can improve uniformity in the segregation at different points along the coating surface and may prevent potential delamination problems.
  • interface-modifying agent may be copolymerised with a suitable base-coat monomer or, preferably, with a suitable top-coat monomer and used, respectively, as a base-coat or top-coat polymer.
  • the interface-modifying agent may, for example, comprise one or more sections comprising a fluorinated, chlorinated, hydrocarbon and/or siliconised
  • aliphatic moiety usually saturated or, if desired, containing unsaturation, for example (CF 2 ) n units where n represents a number from 1 to 40, e.g. at least 4 or 5, and
  • polyester or polyether moieties for example 1 to 10, e.g. at least 4, oligomeric units.
  • suitable A' units are as follows: -(CF 2 -CH 2 ) m - -(CH 2 -CH 2 ) m - - (CF 2 -CF 2 ) m - - (CF 2 CF 2 -O-CH 2 -CH 2 ) m - -(CF 2 -CF(CF 3 )) m - -Si(CH 3 ) 2 O-
  • n is, for example, from 1 to 20.
  • polyester units B' are as follows: where n is, for example, from 1 to 20, preferably 3 to 7
  • Suitable polyether units B' are as follows:
  • n is, for example, from 1 to 20, preferably 3 to 7
  • terephthalic acids having fluorinated end groups.
  • the molar proportions of the A' and B' moieties may be, for example, 9:1 to 1:9, advantageously 5:1 to 1:5, more especially 2:1 to 1:2, for example substantially 1:1.
  • the interface-modifying agent has, for example, a molecular weight of at least 100, preferably at least 400, more especially at least 500, and for example up to 5000, preferably up to 2000, more
  • the interface-modifying agent may have symmetrical or asymmetrical structure; for example, it may have the structure A'B'A', B'A'B' or A'B'.
  • the component may also be a block copolymer of A' and B' units (or a random copolymer may be possible) or a graft copolymer of A' and B' units; although a completely random structure should generally be avoided, a block copolymer of variable block length may be advantageous to minimise the risk of formation of micelles.
  • additional functional grouping(s) for example an acid, epoxy or hydroxy grouping, may be present, for example on the A and/or B moieties and/or at the end(s) of the chain.
  • the interface-modifying agent co-reacts with component A and/or B during curing; advantageously the interface-modifying agent has functional groups capable of reaction with both components A and B.
  • the interface-modifying agent may be, for example, a haloalkyl- and/or alkyl-terminated polyester or polyether (alkyl suitably having at least 10, e.g. 10 to 20, carbon atoms), optionally carrying one or more functional groups, for example hydroxy, epoxy or carboxy groups.
  • halo denotes fluorine and/or chlorine
  • haloalkyl denotes a partially or fully halogenated group.
  • polyester or polyether chain may have the specified termination. When both ends are terminated the terminal groups may be the same or different, but are usually the same. A functional group present may be at one or both ends of the chain and/or functional groups may be present on the polyester or polyether chain.
  • the polyester or polyether chain may have one or two fluoroalkanol terminals.
  • suitable interface-modifying agents are as follows:
  • n 2 to 100
  • n 2 to 100
  • Block copolymers of A'B' and A'B'A' structure and graft copolymers for example polyesters containing
  • the present invention also provides an interface- modifying agent which comprises
  • each moiety A' being an aliphatic hydrocarbon radical having a carbon chain of at least 2, e.g. at least 4 or 5, members, or a halogenated (fluorinated and/or chlorinated) or silicon-containing chain having at least 2, e.g. at least 4 or 5, chain members, and
  • polyester and/or polyether chain comprising at least 2, e.g. at least 4, ester and/or ether groups.
  • an aliphatic hydrocarbon radical or halogenated or silicon-containing chain (A') comprises repeating units, and where more than one such radical or chain is present in the molecule these may be the same or different, advantageously being the same or differing only in chain length.
  • a polyester/polyether chain (B') preferably also comprises repeating units, and where more than one such chain is present in the molecule these may be the same or different, advantageously being the same or differing only in chain length.
  • An end atom or group of an interface-modifying agent may be, for example, a hydrogen atom, a halogen atom (F or Cl) or a hydroxy or carboxy group.
  • the interface-modifying agents may be prepared by conventional methods, for example by condensing a suitable derivative of an acid of the general formula
  • the formation of the polyester component by reaction of the acid derivative with the alcohol HOB 2 OH may be carried out first and the polyester subsequently reacted with the alcohol A ' OH.
  • a graft copolymer may be prepared, for example, using thiomalic acid (HO 2 CCH 2 CH(SH)CO 2 H) as a chain-transfer agent in a free radical polymerisation;
  • initiator e.g. 2,2'-azobisisobutyronitrile
  • thiomalic acid would give a polymer terminated at one end with a thiomalic acid group; the other end group would be from the initiator or a proton from the chain-transfer agent.
  • Adjustment of the degree of polymerisation may be made by altering the concentration of thiomalic acid.
  • the resultant thiomalic acid derivative may be further reacted to form the acid chloride or methyl ester which may then be copolymerised into a polyester chain using a suitable diol or diacid derivative to give the graft copolymer.
  • alkyl or perfluoroalkyl side-chains may be introduced onto a polyester backbone.
  • a precursor monomeric diacid is synthesised by reacting dimethyl malonate, treated with sodium hydride and a brominated, or other similarly terminated, (perfluoro)-alkyl, for example, as follows:
  • this monomer may be used directly to form a polyester or it may be reacted further to form the acid or acid chloride prior to forming the polyester in the usual way.
  • a Zonyl polymer in which there are 11 carbon/oxygen atoms in the chain between the F-substituted carbon atoms in a homopolymer as follows
  • the carbon or silicon-containing units or end groups may also if desired contain additional carbon or silicon-containing branches, and preferably the coating composition also has the surface energy and viscosity
  • end groups are present on at least 2.5%, preferably at least 5 or 6%, e.g. at least 9 or 10%, for example on at least 15%, of the monomer units.
  • Monomer units having such end groups are preferably at least 10 weight %, advantageously at least 20 weight %, for example at least 35, or at least 50, weight %, of all the monomer units.
  • Component A polymers may be prepared by methods known in the art.
  • free-radical methods may, for example, be used, for example solution, suspension, dispersion and emulsion polymerisation methods.
  • emulsion polymerisation particular attention should be paid to the molecular weight of the product and the use of chain transfer agents.
  • the use of chain transfer agents in the preparation of the component A polymer may be especially advantageous to provide a low molecular weight polymer and hence lower viscosity product.
  • adjustment of molecular weight may also be made by adjustment of the amount of initiator and/or stabiliser used.
  • a suitable stabiliser is, for example, a poly(vinyl alcohol), molecular weight 25 ⁇ 10 3 , degree of hydrolysis 88%.
  • a poly(vinyl alcohol) molecular weight 25 ⁇ 10 3 , degree of hydrolysis 88%.
  • Such materials are commercially available, for example, from Hoechst AG and Rhone Poulenc.
  • the use of polyvinyl pyrrolidone stabilisers should also be
  • thermosetting resin-containing component generally requires a curing agent for the thermosetting resin
  • thermosetting resins may be used.
  • the same or different curing agents may be present for each polymer. Curing agents are well known, and are described, for example, in chapter 7 of the textbook "The Chemistry and Physics of Coatings", edited by R. Marrion and published by The Royal Society of Chemistry in its paperback series 1994.
  • the film-forming binder system may comprise a carboxy-functional polyester film-forming resin used with an epoxy-functional curing agent such as, for example, an epoxy resin, for example a condensed glycidyl ether of bisphenol A, or a low molecular weight tri-functional epoxy compound such as, for example, triglycidyl isocyanurate, or with a beta-hydroxyalkylamide; or a hydroxy-functional polyester used with an isocyanate-functional curing agent; or an epoxy resin used with an amine-functional curing agent such as for example, dicyandiamide or with a thiol curing agent, for example the reaction product of pentaerythritol and mercaptopropanoic acid available from Grace Brothers or Hampshire Chemicals ("Penta/Mpa"); or a functional acrylic resin, for example a carboxy-, hydroxy- or epoxy-functional resin, used with an appropriate curing agent.
  • an epoxy-functional curing agent such as, for example, an epoxy resin
  • thermosetting top-coat polymer With a thermosetting top-coat polymer, the
  • Each component A and B may be, for example, at least 1%, advantageously at least 2%, preferably from 5 to 95%, by weight of the total of components A and B.
  • component A is from 5 to 20%, and component B from 95 to 80%, but the use of 5 to 20% of component B with 95 to 80% of component A to provide good adhesion for a fluorinated coating composition should also be mentioned.
  • the segregating layer is at least 0.1 ⁇ m, more usually at least 0.2 ⁇ m, preferably at least 10 ⁇ m, and up to 50 ⁇ m, advantageously up to 20 ⁇ m.
  • compositions of the invention also include one or more solvents, for example two or three solvents, for the film-forming components and optional interface-modifying agent.
  • compositions of the invention have no more than 340 g/litre of solvent, more especially no more than 250 g/litre of solvent (these are North American and European recommended levels, respectively).
  • compositions having a solids content of at least 80% by volume or 85% by weight should especially be mentioned, more especially whichever has the lower solvent level (i.e., a lower volatile organic content).
  • a composition of the invention has a solids content of at least 90% by volume (or 95% by weight), and may, for example, be at least 95% by volume.
  • Compositions having a somewhat lower solids content for example down to 70% or 65% or down to 60% or down to 50%, by weight, should also be mentioned.
  • the composition may also include one or more interface-modifying agents which may be present, for example, in an amount of at least 0.1% and usually up to 3% by weight, advantageously up to 1%, preferably 0.5 to 2%, by weight, of the major component B or A.
  • a compound having the structure mentioned above for an interface modifying agent and having one or more fluorinated end groups may segregate as a top coat from a system consisting only of that component and a component B polymer; desirably, however, the top coat polymer should be of a higher molecular weight, for example by including one or more functional groups in an interface-modifying agent polymer so that that polymer can be cross-linked.
  • thermosetting resin is generally co-extruded with its curing agent or co-reactive other thermosetting resin; in solvent systems of the present invention where ambient cure is advantageous, the curing agent is generally separate, but mixed in immediately prior to application to the substrate. In hot twin feed systems or other dual impingement systems, the curing agent is also separate and mixed prior to application or metered in at the same times as the other components.
  • each of components A and B mixtures of film-forming binders may be used; in each component of powder systems these will generally be co-extruded.
  • a carboxy-functional polyester may be used with a carboxy-functional ( non-fluorinated and non-chlorinated) acrylic resin, and with a curing agent such as, for example, a beta-hydroxyalkylamide which serves to cure both polymers.
  • each of components A and B may comprise the polymeric binder system and where appropriate and desired one or more further ingredients selected, for example, from colouring agents, flow-promoting agents, degassing agents, catalysts, anti-oxidants, stabilising agents (for example a UV absorber or a stabiliser against UV degradation) , fillers and plasticisers.
  • components A and B are advantageously prepared separately, and are not co-extruded (although co-extrusion may be appropriate in some
  • the segregating component A preferably being distributed as discrete particles, although it may also be coated on the surface of the film-forming particles of component B; component B may alternatively be coated on to component A particles.
  • the components may be co-extruded to a limited extent, and then micronised.
  • One or more other additives may also be present as separate components.
  • an interface-modifying agent is advantageously melt-mixed, for example co-extruded, with either or each of components A and B.
  • components A and C or B and C may be melt-mixed together, and the co-extrudate and remaining component ground to suitable particle size.
  • the interface-modifying agent may be present as a separate component, and dry blended with components A and B, in which case it may be a longer chain molecule.
  • Particle size may be of importance in allowing control of the thickness of each layer.
  • the particle size of component A may be smaller than the particle size for component B.
  • the particles comprising component B may be, for example, of conventional size, for example at least 90% by volume between 20 ⁇ m and 100 ⁇ m and no more than 70% by volume ⁇ 50 ⁇ m, with a mean particle size at least 35 ⁇ m, and generally no more than 60 ⁇ m, often in the range of from 35 to 55 ⁇ m, usually 35 to 50 ⁇ m.
  • the particles comprising component A may be, for example, also of conventional size, or for example of reduced particle size, for example at least 90% by volume ⁇ 50 ⁇ m and more than 10% by volume >20 ⁇ m, with a mean particle size in the range of from 15 to 35 ⁇ m, more especially 20 to 30 ⁇ m, for example substantially 25 ⁇ m, or substantially smaller sizes, e.g. a mean size of 5 ⁇ m, may be used.
  • the mean particle size of component A may vary, for example, from 5 to 35 ⁇ m; the mean particle size of component B may also vary, for example, from 5 to 35 ⁇ m.
  • the ratio of the mean particle sizes of component A to component B is advantageously in the range of from 1:6 to 3:1, with the maximum mean particle size in any composition being advantageously 35 ⁇ m. It is believed that reduction of the particle size of the top-coat component A may lead to improved
  • Comminution may be carried out, for example, in conventional comminution devices or by jet milling in a fluid energy mill, and the powders are then mixed.
  • a preferred method for mixing particles is dry mixing of the powders in a high-shear mixer.
  • a simple example is a modification of the type of food mixer known as a liquidiser, as described for example in WO 90/06345; another example of a suitable high-shear mixer is
  • mixers of this type are sold by Freund Industrial Co. Ltd..
  • comminuting and mixing may be carried out simultaneously by feeding a mixture of components to a comminuting apparatus such as, for example, a fluid energy mill, or by feeding such a mixture in aqueous dispersion to a bead mill or ball mill.
  • a comminuting apparatus such as, for example, a fluid energy mill, or by feeding such a mixture in aqueous dispersion to a bead mill or ball mill.
  • the powders are mixed by an electrostatic mixing technique; a suitable apparatus for electrostatic mixing of powders is
  • the mixture may then be applied as a powder coating composition in the form of a dry mixture of powders;
  • the mixed powders before applying to the substrate the mixed powders may be thermofused and then reground, or agglomerated to form composite particles, for example as described in WO 90/06345.
  • the mixed powders may be thermofused and then reground, or agglomerated to form composite particles, for example as described in WO 90/06345.
  • the particles may be fused or bonded, for example as described in WO 91/18951, and in such circumstances the particle size of B may be reduced to be within the range specified above for reduced-size
  • the powder coating composition After application to the substrate the powder coating composition is cured by heating (“stoving"), usually for a period of from 5 to 30 minutes and usually at a temperature in the range of from 150 to 220°C, although in coil-coating processes shorter stoving times are generally used, for example 1 to 5 minutes at 200-220°C. It may be advantageous to introduce a stepped temperature increase into the stoving schedule, for example 5 minutes at 130°C followed by 10 minutes at 200°C.
  • the bilayer coating will generally be a thermoplastic film-forming material over a thermosetting film-forming material or a thermosetting material over another thermosetting material;
  • the components will generally be pre-mixed.
  • the composition is then applied as a film by extrusion of the melt through an extrusion coating die onto a suitable substrate, there being relative movement between the
  • the coating composition is supplied to the extrusion coating die in melt (or plastified) form.
  • the melting or plastification may be carried out in any suitable melt mixing apparatus, which may be a static or dynamic mixer, for example a Banbury mixer or a Z-blade mixer.
  • the melt-mixed composition may be supplied to the extrusion coating die by a suitable pump.
  • a conventional extruder may be used as a melt mixer. Stoving at a temperature in the range of 200 to 220°C is preferably carried out after application to the substrate; stoving times are typically about 30 sec to 1 minute. These techniques are well-known in the art.
  • compositions of the invention is as described in AU-A-10071/92 for coil applications.
  • the paint system would generally be supplied as a two- or even three-pack system.
  • the component B polymer in solution containing pigments and fillers may be together with the component A polymer such that the component A polymer exists as discrete meso phases within the component B polymer until applied.
  • the second pack would contain the curing agent(s); where required, the interface-modifying agent (e.g. an ABA block copolymer) may, for example, also be placed in the first pack. Examples are the use of an epoxy resin and a glycidyl-functional fluoropolymer, e.g.
  • a Zonyl copolymer and optionally an interface-modifying agent in the first pack and an amine curing agent in the second pack, and a hydroxy-functional Fluonate polymer available from Dainippon Inks & Chemicals
  • a suitable interface-modifying agent and an epoxy resin in the first pack and a curing agent for the epoxy and a curing agent for the Fluonate in the second pack can be considered.
  • Suitable solvents for solvent-based systems are, for example, methyl isoamyl ketone and trimethylbenzenes and blends thereof. Often in a two-pack system the solvents in the two packs will be similar, or the same solvents will be used but in different ratios.
  • Suitable application temperatures are, for example in the range of from -5 to 30°C, although higher application temperatures are also possible, for example using hot twin feed technology, and indeed may be advantageous for application of the preferred more viscous
  • compositions The preparation and application of high solids controlled temperature application compositions (hot twin feed, dual impingement, etc.) is known, and is described, for example, in commercial literature from Shell,
  • hot twin feed and “dual impingement” are used herein, however, to denote the method of application whereby different materials in a coating composition are heated and fed separately, coming into contact only shortly before application to the substrate.
  • the terms are not restricted to the supply of two separate materials, but encompass the supply of more than two materials in this way, and are more properly called “hot plural feed” and “plural impingement”.
  • Powder and solvent-based coating compositions of the present invention find application in the architectural and domestic appliance fields, and in the coating of aircraft, and for solvent-based systems and hot twin feed systems especially in the coating of ships, bridges, oil installations and structural steel. Other possible uses of compositions that should particularly be
  • polyester systems are regarded as potentially superior on a cost performance basis, with respect to weatherability, to both polyester and acrylic individually. Moreover, blending of components after the extrusion stage offers additional attractions of ease and formulating
  • additives e.g. a colouring pigment
  • An anti-corrosion pigment may be in the base layer (component B) and a colouring pigment in only the surface layer (component A).
  • a pigmented polyester component having fluorinated end groups may, for example, be used as component A, together with a non-pigmented non-fluorinated polyester as component B.
  • a non-pigmented top-coat component A having F- and/or Si-containing end/pendant groups may be used with a pigmented base-coat component B, and a UV absorber may be included in component A.
  • pigmented polyester particles coated with a fluorinated acrylic polymer may be used as component A, with an unpigmented polyester as component B, provided that, in this case, the fluorinated polymer has a
  • pigmented polyester will form the surface layer.
  • a small quantity (for example 2%) of fluorinated polymer may be added to a pigmented polyester for example.
  • component A during the melt extrusion stage in powder preparation, and after comminution the temperature may be raised above the Tg of the fluorinated polymer, for example for 1 to 2 hours, to allow the fluorinated polymer to surface.
  • MMA methyl methacrylate
  • HEMA 2-hydroxyethyl methacrylate
  • GMA glycidyl methacrylate
  • FRAD Fluorad FX-189 monomer, available from 3M company
  • PFPE perfluoropolyether monomer
  • PMMA polymethyl methacrylate
  • PBMA polybutyl methacrylate
  • PBA polybutyl acrylate
  • PA polyacrylic acid
  • PHEMA poly-hydroxyethyl methacrylate
  • PGMA polyglycidyl methacrylate
  • PTFEMA poly (trifluoroethyl methacrylate)
  • PPFPE polyperfluoropolyether
  • the Zonyl monomer used was the medium distribution Zonyl TM monomer product available from du Pont.
  • the silicone monomer used was the monomer SLM 455127 available from Wacker Chemie of structure
  • the Fluorad monomer used was the monomer Fluorad FX- 189 available from 3M company of formula
  • the perfluoropolyether monomer used was Galden TX Methacrylate available from Ausimont, Italy, of molecular weight 858, equivalent weight 848 and being the
  • a three-necked flask was fitted with a condenser and a thermometer.
  • the flask was charged with isopropanol solvent, the appropriate amount of Zonyl and half the initiator, 2,2'-azobisisobutyronitrile ("AIBN") (approx. 1g) available from Wako.
  • AIBN 2,2'-azobisisobutyronitrile
  • the mixture was blanketed with nitrogen and heated to the solvent reflux temperature while being stirred magnetically. After being refluxed for one hour, the other monomer(s), if any, and the remaining initiator (approx. 1g) dissolved in solvent, were added over 1% hours via a peristaltic pump; the total monomer and total solvent in the system were each approximately 200g.
  • This method tended to produce copolymers having two Tgs and which in subsequent experiments produced coatings that were revealed by scanning electron microscopy pictures of the cross-sections as having low molecular weight inclusions in the top layer, believed to be low molecular weight polymethyl methacrylate.
  • the polymer produced had a fluorine
  • Trifluoroethyl methacrylate polymer "DA 190"
  • PPFEMA acid-functional poly(tri- fluoroethyl methacrylate)
  • Monomer(s), solvent (isopropanol, 200ml) and initiator (lauryl peroxide, 0.7g) were charged to a reactor and purged with nitrogen while being heated to reflux (80-85°C) with the stirrer set at 150 rpm.
  • Refluxing was continued for 5 or 6 hours before cooling to below 30°C and removing solvent.
  • Fluorad FX-189 (20g) was polymerised with methyl methacrylate (20g) in isopropanol using 0.35% by weight of lauryl peroxide initiator and refluxing at 60-80°C.
  • the 50/50 PFRAD/PMMA polymer was obtained in a yield of 68.75%.
  • Galden TX Methacrylate an ethoxylated fluoropolyether monomer of molecular weight 858, (20g) was polymerised with Zonyl monomer using 0.35% by weight lauryl peroxide initiator and refluxing in isopropanol at 60-80°C.
  • a 20/80 PPFPE/PZ polymer was obtained in a similar manner in a yield of 70% and melted also at ⁇ 150°C.
  • the monomers were mixed and added at a feed rate of 5.5g per minute to 250g xylene containing 10g t-butyl-peroxybenzoate initiator (Trigonox C available from Akzo) at reflux (140°C). Refluxing was continued for 2 hours before adding a further l.25g of Triganox C as a digestion shot and refluxing for another 1 hour. The solvent was then stripped off under vacuum before drying at
  • thermoset polymer system 496.3g - 3.75g AA 99.25:0.75 6381 5982
  • the polymer produced was then double extruded with the appropriate amount of cross-linker to yield a thermoset polymer system which could be ground, sieved and sprayed in the usual manner.
  • the PZ/PMMA/PHEMA polymer was used with a caprolactam-blocked polyisocyanate cross-linker of equivalent weight 394 mol/g (IPDI - Adduct B1065 available from Htils).
  • the PZ/PMMA/PGMA polymer was used with the cross-linker dodecanedioic acid DDA of equivalent weight 115 mol/g.
  • the PZ/PA polymer was used with the cross-linker PRIMID XL-552 of equivalent weight 84 mol/g ( ava i lable from Rohm & Haas Co.).
  • a 2 litre water-jacketed reaction vessel was fitted with a solid carbon dioxide condenser, nitrogen inlet and overhead stirrer.
  • the stabiliser was predissolved in double-distilled water.
  • the stabiliser solution was added to the reaction vessel and heated to the required reaction temperature (80°C) with stirring, under nitrogen.
  • the initiator was dissolved in the monomer or monomer mixture and added to the stabiliser solution.
  • the temperature was monitored throughout the reaction. Reaction was allowed to proceed for one hour after the exotherm, and after this time the mixture was cooled to about 30°C. Throughout the cooling period stirring was maintained. Once cool, stirring was stopped and the polymer beads allowed to settle. The liquid was decanted off. The beads were filtered and washed with water, then methanol, and dried in a fan oven at 40°C.
  • the stabiliser and water (600g) were charged to the reaction vessel and purged with nitrogen while heating to 60°C; thereafter a nitrogen blanket was maintained.
  • the initiator was dissolved in the first monomer and then mixed with further monomer and/or chain transfer agent if required and added to the reactor at a steady rate with a stirrer speed of 500 rpm; a temperature of 60°C was maintained. Stirring at 500 rpm was continued for 15 minutes before reducing the stirrer speed to 150 rpm and stirring for a further 6 hours. The mixture was then cooled to below 60°C before washing thoroughly and drying the polymer beads obtained.
  • CTI Chain transfer agent
  • Fluorobase C A100 chlorotrifluoroethylene-containing polymer available from Ausimont (Milan)
  • Teflon TF 9205 polytetrafluoroethylene: PTFE
  • Kynar 500 polyvinylidenedifluoride: PVDF
  • Kynar 500 (PVDF) 61 Kynar 500 (PVDF) 61 .
  • NPB 21 (see below) 11 BASE-COAT POLYMERS USED OR INVESTIGATED IN THE EXAMPLES Polyester polymers used or investigated were as follows:
  • RP 0434, RP 0436, RP 0479 and RP 0555 acid-functional polyester polymers prepared from different blends of terephthalic and isophthalic acids, and neopentyl glycol and trimellitic anhydride, all of International Paint Ltd., England.
  • RP 0434 and RP 0479 were used with triglycidylisocyanurate (TGIC) cross-linking agent available from Ciba-Geigy AG; RP 0555 was used with PRIMID XL-552 cross-linking agent (bis(N,N-di-(2-hydroxyethyl))adipamide, a 4-functional hydroxamine) available from Rohm & Haas Co.
  • TGIC triglycidylisocyanurate
  • RP 0555 was used with PRIMID XL-552 cross-linking agent (bis(N,N-di-(2-hydroxyethyl))adipamide, a 4-functional hydroxamine) available from Rohm & Haas Co.
  • Epoxy resins used or investigated were as follows:
  • RE 0114 available from Dow Chemicals, sold as
  • Epikote 828 a liquid epoxy resin available from
  • Epikote 828 was used with Versamide 125 (a curing agent available from Cray Valley Products, England) or with
  • a resin kettle was fitted with a five-necked lid to which was fitted a nitrogen inlet, an outlet to a water bubbler and overhead stirrer. The remaining necks were blanked off.
  • the vessel was purged with nitrogen and charged with reactants terephthaloyl chloride (ex
  • the mixture was heated in an oil bath to approximately 80°C and the reagents were stirred constantly. The mixture was held at this temperature until the vigorous evolution of HCl ceased (about 2 hours). The temperature was raised to approximately 150°C for a further 2 hours with the nitrogen flow maintained. After this time the nitrogen flow was reduced to a trickle and the outlet to the water bubbler was replaced with a connection to a vacuum and evacuated for a further 2 hours with the temperature maintained at approximately 150°C.
  • the reaction mixture was left to cool to room temperature overnight.
  • the product was dispersed in an excess of dichloromethane with gentle heating to yield an opaque solution.
  • the solution was added dropwise to an excess of rapidly stirred methanol to give a dense white precipitate.
  • the precipitate was recovered by filtration and dried under vacuum at 40°C to constant weight.
  • the degree of polymerisation (dp) was calculated from the C-13 NMR spectrum of the samples dissolved in a CDCI3/DMSO (approximately 2:1 vol ratio) mixture at approximately 5%.
  • the concentration of terephthalate units was determined from the aromatic CH carbon integral and the concentration of neopentyl glycol units was determined from the aliphatic CH 2 carbon integral.
  • the concentration of the monofunctional end group was
  • reaction vessel being initially charged with 101.5 g of terephthaloyl chloride, 49.5 g of neopentyl glycol and 23.1 g of 1H,1H,2H,2H-perfluorodecanol. 95.35 g of product were isolated.
  • the dp was calculated to be approximately 11 and the ratio of perfluoro end groups to NPG hydroxyl end groups was 1:3.1. No acid end groups were detected.
  • Viscosity data was obtained using a Bohlin VOR
  • ICI Cone and Plate viscosity was measured and equated with zero shear viscosity for polymers having Newtonian shear behaviour.
  • the Figure shows that increasing the proportion of polymethyl methacrylate in the polymethyl methacrylate/ polyZonyl copolymer increases viscosity. In comparison with the 50/50 PMMA/PZ copolymer, the viscosity of the 50/50 PBMA/PZ copolymer is higher.
  • Figure 3 shows the zero shear viscosity plots of three Zonyl-containing homo- or co-polymers and two epoxy resins.
  • the epoxy resins have, in general, lower viscosities than the polyester resins shown in Figures 1 and 2; thus although the 50/50 PMMA/PZ top-coat polymer shown in Figure 3 gives good segregation with standard polyesters, for use with an epoxy resin a much lower viscosity polymer is preferred, for example the 35/65 PZ/PBA polymer shown in the Figure.
  • liquid epoxy resin Eurepox RV-A available from Schering AG is often used in solvent-containing
  • compositions which may be applied, for example at room temperature, and the graph of Figure 3 therefore includes viscosity figures at and below room temperature, as well as at temperatures appropriate for other application technologies.
  • the viscosity of the component may decrease, and when solvent is present (and usually more solvent is used with the base-coat polymer than with the top-coat polymer) the viscosity of the component may decrease by approximately up to 3 or 4 Ln Pa.s, depending on the amount of solvent.
  • the polyZonyl/ polybutyl acrylate polymer component will still have an appropriate zero shear viscosity relative to Eurepox.
  • Figure 4 shows the zero shear viscosity plots of various Zonyl/butyl acrylate/glycidyl methacrylate polymers, together with a representative epoxy resin, Eurepox RV-A. All the fluorine-containing polymers shown have lower zero shear viscosities than the Eurepox resin, and give good segregation with that epoxy resin.
  • the surface energy plot of various Zonyl/methyl methacrylate polymers are shown in Figure 5. It can be seen that the surface energy of the different Zonyl polymers increases with increased replacement of the Zonyl by polymethyl methacrylate.
  • the 10/90 Zonyl/PMMA surface energy plot may represent the approximate limit for surface energy for a segregating system with standard polyesters.
  • polyester-fluorinated acrylic powder coating systems were prepared and electrostatically sprayed on to aluminium foil or panels and stoved vertically.
  • Solvent-based compositions were applied using a drawn-down bar onto steel and aluminium substrates.
  • XPS X-ray photoelectron spectroscopy
  • Attenuated Total Reflectance (FTIR-ATR) and PhotoAcoustic Spectroscopy (FTIR-PAS) were used to determine the composition profile, as a function of depth, of the films over the range of 50 ⁇ to 20 ⁇ m.
  • FTIR-ATR Attenuated Total Reflectance
  • FTIR-PAS PhotoAcoustic Spectroscopy
  • XPS is the most surface-sensitive technique, probing to a depth of 50 ⁇
  • the FTIR results which were used to determine the composition over the sampling depth of 0.5-20 ⁇ m, provided more information on the thickness of the acrylic layer to determine whether stratification had occurred.
  • the depths calculated using FTIR are determined using the properties for pure polyester or epoxy and pure acrylic. The extent of segregation observed was
  • the two polymeric film-forming components used in each experiment were each prepared by micronising using a conventional coffee grinder and sieving through a 106 ⁇ m mesh to give a powder of conventional particle size.
  • Fluorobase C (A 100) was dry blended with a polyester component (96% RP 0555 plus 4% PRIMID cross-linker), in the proportions 5 : 95 and 10 : 90 by weight.
  • Teflon TF 9205 PTFE
  • TGIC curing agent TGIC curing agent
  • the fluorinated acrylic polymer DA 190 (PTFEMA) was dry blended with a polyester component (RP 0555 plus 4.4% TGIC cross-linker) in the weight ratio 5 : 95. After application to an aluminium substrate and stoving as described above, a bilayer film was formed, with the top 2-3 ⁇ m of the cured film being composed of 45% of
  • fluorinated acrylic polymer and the top 0.5 ⁇ m of 90 % fluorinated acrylic, for a 60-70 ⁇ m thick film.
  • a fluorinated acrylic component containing a Zonyl polymer (prepared by the method 1 solution polymerisation method) was dry blended with a polyester component (RP 0555 plus cross-linker and conventional additives) in a ratio 20:80 by weight.
  • Component 1 consisted of
  • Component 2 was as follows
  • PTFE PTFE
  • PVDF Kynar 500
  • Fluorobase C is a ter- or tetra-polymer
  • CTFE chlorotetrafluoroethylene
  • Fluorobase C A100 tested by us, contained no acid groups but nevertheless included a high proportion of polar end groups.
  • PTFE and PVDF contain no pendant groups and probably polar groups at the chain ends. End groups in all three polymers have a surface energy higher than that of the backbone/of the polymer itself. Comparison of the zero shear viscosities of the different polymers used in Examples 1 and 2 and in
  • Comparative Examples 1-3 also shows that the viscosities of Fluorobase C, Teflon and Kynar 500, which did not give adequate segregation, were substantially higher than (>>4 Ln Pa.s in most instances) that of the polyester
  • the Zonyl product used contained a mixture of fluorinated chain lengths.
  • the components were dry blended in a ratio of 20:80 by weight.
  • Example 6 Example 6 and with the copolymer having the higher polyZonyl content (Example 7) was in each case better than that obtained with PTFEMA (Example 1).
  • the 50:50 copolymer (corresponding to a molar ratio MMA:Zooyl of 5:1 to the nearest whole number) has a surface energy calculated by group contribution theory of approximately 40, which is higher than that of 100% PTFEMA
  • Example 8 10% polyZonyl (unpigmented) prepared by
  • Example 11 15% acrylic component as in Example 10
  • Example 12 reproduced Example 2, but utilised the 50:50 PMMA/PZ copolymer prepared by the solution polymerisation method 2.
  • Example 11 gave better results because the presence of pigment in Component 2 increased the surface energy and viscosity of the component.
  • Example 13 the bilayer coating containing polyZonyl prepared by suspension polymerisation was as uniform as those containing polyZonyl prepared by solution polymerisation. However, bilayer coatings containing polyZonyl prepared by suspension
  • All systems having a content of at least 20 % of component 1 formed a bilayer system with the exception of the 50/50 polybutyl methacrylate/polyZonyl polymer
  • Example 22 prepared by suspension polymerisation (Example 22). This segregated, doubling its concentration at the surface, but did not stratify fully.
  • the average surface energy of the pendant groups in the polymer can be calculated (approximately) considering the perfluorodecyl component of the Zonyl product (compare the average fluoroalkyl chain length for the monomer given above) as follows:
  • the average surface energy of the end groups is therefore less than that of the polymer backbone and consequently less than that of the polymer as a whole.
  • the zero shear viscosity of the polymer is about 4 Ln Pa.s higher than that of the polyester used.
  • top coat polymer was a 50/50 PZ/PMMA polymer prepared by suspension polymerisation, procedure 2, and the base-coat component had the following composition Wt %
  • degassing agent (benzoin) 0.3
  • Ln 1.4
  • viscosity polymer (85% and >99% fluorinated polymer at the surface in Examples 23 and 24 respectively), but with the higher viscosity polymers some segregation occurred but stratification was incomplete.
  • thermosetting top-coat systems detailed below, and based on the polymers prepared by solution polymerisation, method 4, were tested for segregation with the polyester base-coat component of Examples 23 and 24 using a weight ratio 20:80.
  • cross-linker IPDI-Adduct B1065 equivalent weight 394 mol/g available from Hüls 1.07 g of the degasser benzoin
  • the 50/50 PFRAD/PMMA polymer described above was tested for segregation with the white polyester base-coat component of Example 23 using a ratio of 20:80 by weight top-coat component to base-coat component.
  • PPFPE/PZ top-coat polymers gave good segregation with, in the case of the 20/80 polymer, over 90% fluorinated polymer at the surface according to IR data.
  • Example 30 The 20:80 PS/PZ silicone polymer described above was cryogenically ground at the temperature of liquid nitrogen to give a powder which was sieved through a 106 ⁇ m mesh as usual to give a powder of conventional particle size. This top-coat component was then mixed in a ratio of 20:80 with the polyester base-coat component of Example 23 and applied to a substrate as usual. IR data showed there to be >82% of top-coat polymer in the top 2 ⁇ m of the resultant film: good segregation had been achieved.
  • the EPON curing agent was available from Shell US.
  • the ratio of PMMA/PZ to epoxy in the top 2 microns was given by the ratio of IR bands at 1730 and 1501 cm -1 respectively, and was found to be 2.5:1, corresponding to an acrylic content of 50% in the top 2 microns.
  • Example 31 was repeated using as component 1 the polyZonyl component of Example 18 prepared by suspension polymerisation, procedure 1, run c.
  • the film gave a ratio of 2.5:1 acrylic: epoxy in the top 2 microns, corresponding to 50% acrylic in the top 2 microns.
  • thermomechanically fusing the powder particles was examined.
  • Components 1 and 2 were mixed in a coffee grinder, then melted together at 80°C under a pressure of 125kg/cm 2 for 30 sec and subsequently reground to conventional particle size and passed through the usual 106 ⁇ m sieve.
  • the component 1 used was the 100% Zonyl polymer prepared by suspension polymerisation, procedure 2, (experiment d);
  • component 2 was the polyester component of Examples 23 and 24. Dry-blending a 20:80 mixture gave a 28 ⁇ m film with a top layer of thickness 0.2 to 3.0 ⁇ m; thermofusion of the same blend gave a 30 ⁇ m film with a top layer of thickness 3 to 5 ⁇ m. There appeared to be a greater amount of fluoropolymer present in total in the thermofused film; that is, less of the fluoropolymer was lost in spraying in the case of the thermofused composition.
  • thermofusion was shown to give a thicker and more even top layer, and whereas the dry-blended sample gave an incomplete top layer in a number of places, seven out of eight of the representative areas of panel inspected with the thermofused sample showed
  • DA 190 An acid-functional fluorinated acrylic polymer
  • PTFEMA essentially PTFEMA
  • Example 34 was repeated with different compositions to investigate
  • Example 37 the pigment, the other additives and the acrylic component were melted together at 120°C before dry blending; in Example 36 the additional ingredients were incorporated in the respective component by coextrusion at 110°C.
  • Table 37 The results are summarised in the following Table.
  • the surface tension plots show how the surface tensions of the individual components and interface-modifying agents varied with temperature.
  • the polyester had a value of 38 dynes/cm at 150°C, falling to 23 dynes/cm at 200°C, while the fluorinated acrylic had a value of approximately 14 dynes/cm at 150°C, falling to 4 dynes/cm at 200°C.
  • the two interface-modifying agents NPB10 and NPB21 were found to have surface tensions of 28 and 16 dynes/cm at 150°C, falling to 23 and 11 dynes/cm at 200°C respectively.
  • the lower surface tension of the fluorinated acrylic component in comparison with the polyester component may provide the driving force for segregation.
  • NPB10 and NPB21 had surface tensions intermediate between the polyester and acrylic.
  • NPB21 had a much lower surface tension (slightly higher than the acrylic) than NPB10, which had a surface tension similar to the polyester. This might explain why the film of Example 36 (RP0434/TGIC/NPB21 coextruded + 5% dry blended acrylic) had a better surface appearance than the other 5%
  • NPB21 Since NPB21 has a much lower surface tension than the polyester but still higher than the acrylic it might have formed a thin layer between the polyester and acrylic. This should help to compatibilise the polyester and allow the acrylic to "wet out” more readily.
  • fluorinated acrylic could be determined as >95% increased such that essentially all of the fluorinated acrylic could be accounted for in the stratified layer at the surface.
  • Component 1 consisted of the fluorinated acrylic polymer DA 190 (PTFEMA) in 17.8g methyl ethyl ketone and 17g xylene prepared as follows:
  • Component 2 consisted of 200g Epikote 828 liquid epoxy resin (100% solids).
  • the system was formed by mixing the two liquids (components 1 and 2) and 135g of curing agent Versamide 125. This gave a total content of solids of 91.4%
  • the coated aluminium panels were cut down to 1cm 2 for XPS analysis. Phase separation was followed by monitoring the level of fluorine present at the surface.
  • the PGMA/PBA/PZ polymers prepared by solution polymerisation method 5 as described above were mixed in a weight ratio of 10:90 fluorine polymer to epoxy resin with a solution of Epikote 828 in xylene containing the thiol curing agent Penta/Mpa and Dabco catalyst, both available from Hampshire Chemicals, in a weight ratio epoxy: curing agent of 3.5:1.
  • the solids contents of the mixed compositions and the results achieved on application to a substrate and after curing at room temperature are shown below.
  • Table 2 gives zero shear viscosity data, and Figures 3-4 show the zero shear viscosity plots, of various top-coat polymers included in these solvent-based compositions.
  • Data for the base-coat polymer, Epikote 828, is given in Table 2, together with data for another representative epoxy resin for solvent-based systems,
  • compositions used in the Examples had a zero shear viscosity of at least 10 Poise at room temperature. All had a solids content of at least 80 % by volume, at least 85 % by weight, and contained less than 250 g/litre of solvent.
  • Illustrative scanning electron microscopy pictures of substrates coated with 20:80 mixtures of a fluorinated acrylic polymer (100% polyZonyl prepared by suspension polymerisation) with a polyester (RP 0555) are shown in Figures 8(a) and 8(b). In 8(a) the acrylic component contained 2% purple pigment and the polyester was unpigmented; in 8(b) the acrylic component was unpigmented and the polyester contained TiO 2 pigment.
  • Figure 8 is diagnostic for fluorine, and as can be seen all fluorine appears in the top layer. This is confirmed also by measurement of the width of the "top" layer in relation to the width of the entire coating on both pictures.
  • Figure 9 shows a scanning electron microscopy picture of a substrate coated with a thermomechanically fused mixture of 20% by weight of a 50/50 (by weight) Zonyl/methyl methacrylate polymer prepared by solution polymerisation with 80 % by weight of a fully formulated polyester component containing a white pigment. As can be seen, a bilayer system was produced.
  • Figure 10 shows a corresponding bilayer produced with a dry-blended mixture of 30 % by weight of a low molecular weight 50/50 Zonyl/methyl methacrylate polymer prepared by suspension polymerisation procedure 2 run c in the presence of a chain transfer agent with 70 % by weight of the same white polyester, and should be contrasted with Figure 11, where a corresponding polymer of high molecular weight and high viscosity failed to give stratification.

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Abstract

Les compositions de revêtement de l'invention, dans lesquelles se produit une séparation, contiennent au moins 75 % et jusqu'à 100 % en poids de solides, et se composent d'un composant de revêtement supérieur formant un film contenant du fluor, du chlore et/ou du silicium et un composant de couche de base approprié. Des systèmes bicouches ont été obtenus lorsque se présente une différence valable de la viscosité de cisaillement zéro et de l'énergie superficielle entre les deux composants. De préférence, la viscosité de cisaillement zéro, au niveau de la fluidité maximum du composant de couche supérieure, n'excède pas 3 Ln Pa.s de celle du composant de couche de base. Les composants de couche supérieure peuvent être thermoplastiques ou thermodurcissables, et ont de préférence un ou plusieurs groupes terminaux pendants, à teneur élevée en hydrocarbure et contenant du fluor, du chlore, du silicium et/ou C4. Des polymères dérivés des séries Zonyl de monomères ont été notamment utilisés et ont, par exemple, produit une excellente séparation dans des systèmes contenant du solvant présentant des teneurs très élevées en solides (> 90 % en volume) et dans des systèmes contenant 100 % de solides (compositions de revêtement en poudre).
PCT/GB1994/000983 1993-05-07 1994-05-06 Compositions de revetement dans lesquelles se produit une separation, et copolymere utilise pour cette separation WO1994026832A2 (fr)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6586522B1 (en) 2000-06-12 2003-07-01 3M Innovative Properties Company Water- and oil-repellent composition
WO2007085416A1 (fr) * 2006-01-27 2007-08-02 Dsm Ip Assets B.V. Résine aminoplaste pour des applications décoratives
US8044140B2 (en) 2009-06-12 2011-10-25 Toyota Motor Engineering & Manufacturing North America, Inc Methods and compositions for pigmented self-stratifying coatings
WO2016089199A1 (fr) * 2014-12-02 2016-06-09 Becker Industrial Coatings (M) Sdn. Bhd. Compositions de stratification rapide

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2192399A (en) * 1986-07-09 1988-01-13 Nippon Paint Co Ltd Coating composition
WO1990015846A1 (fr) * 1989-06-22 1990-12-27 Fina Research S.A. COMPOSITIONS PULVERULENTS THERMODURCISSABLES POUR COUCHES DE FOND ADAPTEES AUX COUCHES DE FINITION EN POLYFLUORURE DE VINYLIDENE (PVdF)

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2192399A (en) * 1986-07-09 1988-01-13 Nippon Paint Co Ltd Coating composition
WO1990015846A1 (fr) * 1989-06-22 1990-12-27 Fina Research S.A. COMPOSITIONS PULVERULENTS THERMODURCISSABLES POUR COUCHES DE FOND ADAPTEES AUX COUCHES DE FINITION EN POLYFLUORURE DE VINYLIDENE (PVdF)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6586522B1 (en) 2000-06-12 2003-07-01 3M Innovative Properties Company Water- and oil-repellent composition
US6960642B2 (en) 2000-06-12 2005-11-01 3M Innovative Properties Company Water- and oil-repellent compositions
WO2007085416A1 (fr) * 2006-01-27 2007-08-02 Dsm Ip Assets B.V. Résine aminoplaste pour des applications décoratives
EA014273B1 (ru) * 2006-01-27 2010-10-29 ДСМ АйПи АССЕТС Б.В. Аминопласт для декоративных применений, слоистый материал и композиция меламина
US8044140B2 (en) 2009-06-12 2011-10-25 Toyota Motor Engineering & Manufacturing North America, Inc Methods and compositions for pigmented self-stratifying coatings
WO2016089199A1 (fr) * 2014-12-02 2016-06-09 Becker Industrial Coatings (M) Sdn. Bhd. Compositions de stratification rapide

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