WO2023233133A1 - Matériaux de revêtement en poudre - Google Patents

Matériaux de revêtement en poudre Download PDF

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Publication number
WO2023233133A1
WO2023233133A1 PCT/GB2023/051399 GB2023051399W WO2023233133A1 WO 2023233133 A1 WO2023233133 A1 WO 2023233133A1 GB 2023051399 W GB2023051399 W GB 2023051399W WO 2023233133 A1 WO2023233133 A1 WO 2023233133A1
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polymer
powder coating
monomer
coating composition
vinyl
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PCT/GB2023/051399
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English (en)
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Steve RANNARD
Pierre Chambon
Stephen Wright
Sarah LOMAS
David Ring
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The University Of Liverpool
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Publication of WO2023233133A1 publication Critical patent/WO2023233133A1/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
    • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
    • C09D5/03—Powdery paints

Definitions

  • Powder coatings are materials which can be applied, in the form of powders, to items to be coated and which can be cured to form coatings.
  • the materials contain curable functional groups, which react during curing.
  • the reactions which occur during curing typically entail the cross-linking of polymer chains together, and/or or the reaction of smaller molecules, oligomers or polymers to form larger entities, which are hardened, toughened or solidified materials.
  • Several strategies are known for forming covalent linkages which result in cross-linked structures.
  • Methods can include, for example, one or more of: using hardeners or curing agents, using activating chemistry to affect reactivity, using initiators, and/or applying heat or irradiation.
  • the most commonly-used curable functional group in powder coating materials is the epoxide group.
  • the epoxide is ring-opened and a covalent bond is formed to another moiety, thereby resulting in a cured, cross-linked structure which is effective as a hard coating.
  • Polymers which contain curable epoxide groups are commonly referred to as epoxy resins.
  • Conventional epoxy resins often have a low molecular weight, in order to achieve sufficient epoxy groups to effect a good level of curing and hence effective powder coatings with good physical properties.
  • epoxy equivalent weight of an epoxy resin is the weight of epoxy resin per epoxy group. The higher the epoxy equivalent weight, the fewer epoxy groups are present per unit weight of resin. In certain contexts, it is desirable to have a low epoxy equivalent weight, and this is easier to achieve with smaller molecules. In the context of polymers, as the molecular weight of the material increases, it is typically more difficult to maintain the same ratio of epoxy groups to weight of the material.
  • a polymer manufacture method may result in a set number of epoxy groups per polymer molecule, so for example a polymer chain with two terminal epoxy groups with a nominal molecular weight of 1000 g/mol may be compared to the same system where the nominal molecular weight is 2000 g/mol: both may be chain extended polymers made by the same process, but the epoxy equivalent weight for the former is 500 whereas the epoxy equivalent weight for the latter is 1000.
  • a higher molecular weight polymer may conventionally have a lower concentration of epoxy groups, which impacts on the curing reaction.
  • syntheses are typically more complex, and the materials may be mixtures containing a range of components with a distribution of molecular weights.
  • step-growth polymers making “ultra high molecular weight” polymers is normally done by reacting monomers A2 + B2 to yield an intermediate AABBAA, and then using a second step to distil out the AA monomer to yield a long chain -AABB-.
  • These polymers are typically used for thermoplastic applications such as fibres and films. Performance is achieved via entanglement of the long chains.
  • molecular weight is achieved by the stoichiometric balance of AA and BB monomers. In principle this is straightforward (if extremely sensitive), but in practice it is extremely difficult: the sensitivity to monomer ratio means any weighing errors result in off-spec product.
  • Monomer purity compounds the problem, as monomers normally have some (small) fraction of mono and non-functional component. These lead to dead chain ends that cannot further react.
  • the statistical nature of the reaction means that the final reaction mixture will contain a range of molecular weights from monomers, dimers, trimers up through higher species. Some of these can be cyclic species where a polymer A------ --B has looped back on itself to react and close a loop.
  • Higher molecular weight materials are more useful in some contexts than lower molecular weight materials. Higher molecular weight materials are on the “flatter” part of the T g (glass transition temperature) versus molecular weight curve, so less susceptible to depression of T g on inclusion of low molecular weight material (plasticisation).
  • Such plasticisation can impact performance parameters, such as dirt pickup when used in external coatings.
  • Lower molecular weight materials with reactive end-groups are more biologically available, and the reactive functionality can lead to issues such as skin sensitisation; high molecular weight materials are less biologically available.
  • moving to higher molecular weight polymers results in an increase in T g , especially with known oligomeric resins. This has a negative impact on flow and levelling during curing of the coating. It would be desirable to have methodology which allows the epoxy equivalent weight to be controlled and tailored, regardless of the molecular weight of the epoxy resin.
  • the present invention provides a powder coating composition
  • a powder coating composition comprising a polymer which is a branched vinyl polymer prepared by transfer- dominated branching radical telomerisation (TBRT) of multivinyl monomer(s) and optionally monovinyl monomer(s) in the presence of chain transfer agent(s), and wherein said polymer comprises curable functional group(s).
  • a powder coating composition is a composition, in the form of a powder, which is suitable to applied to an item to be coated, and which can be cured to form a hard coating on said item.
  • the curing is effected by reaction of the above-mentioned curable functional group(s).
  • a powder coating is typically a thin layer, for example up to 4mm thick after coating on a substrate. It has a surface that is exposed to the environment and can act to protect the substrate or improve its aesthetics.
  • powder coating compositions may comprise, and indeed typically comprise, in addition to a curable resin, one or more additional component(s) selected from other reactive ingredient(s), pigment(s), filler(s), and/or additive(s).
  • the powder coating composition of the present invention may comprise, in addition to the polymer, one or more additional component(s) selected from other reactive ingredient(s), pigment(s), filler(s), and/or additive(s).
  • the powder coating composition of the present invention may comprise, in addition to the polymer, other reactive ingredient(s).
  • the present invention uses TBRT technology which allows control over the location of the curable functional groups (e.g. epoxy groups). It also provides more possibilities to alter equivalent weights of curable groups (e.g. epoxy equivalent weight) without impacting on the T g or viscosity of the polymer, which would not be possible using conventional routes, e.g. the route whereby an acid functional polyester is converted to an epoxide.
  • This inter alia solves the industrial challenge of being able to yield functional polymers (e.g. epoxy-functional polymers) that are suitable for exterior exposure and are of high reactivity, whilst having a T g & viscosity suitable for powder coating applications.
  • Branched vinyl polymers produced by TBRT which may be termed “branched vinyl TBRT polymers”, are a recognised group of polymers, as described in S. R. Cassin, P. Chambon and S. P. Rannard, Polym. Chem., 2020, 11, 7637-7649 and patent publications WO 2018/197885, WO 2018/197884 and WO 2020/089649.
  • branched vinyl TBRT polymers Following research into some properties and possible uses of said branched vinyl TBRT polymers, we have found that they are particularly well-suited for use in powder coating compositions when curable functional group(s) are present on the polymers.
  • the polymerisation of vinyl monomers using free radical chain- growth chemistry is well known.
  • a vinyl monomer has only one polymerisable vinyl group (i.e. is a monovinyl monomer)
  • polymerisation of said monomer typically results in a linear polymer.
  • a vinyl monomer has more than one polymerisable vinyl group (i.e. is a multivinyl monomer), e.g. has two polymerisable vinyl groups (i.e. is a divinyl monomer)
  • polymerisation of said monomer typically results in a branched polymer, because each of, or some of, the multivinyl monomers can become part of more than one vinyl polymer chain.
  • said branched polymer may be highly cross-linked and gelled.
  • TBRT is a method for controlling branching during the free radical polymerisation of multivinyl monomers. It entails controlling the extent of propagation relative to the extent of chain transfer, and results in a hyperbranched polymer containing a large number of interconnected linear vinyl polymer chains, wherein the average length of each linear vinyl polymer chain is short. Limited propagation relative to chain transfer can be achieved by using suitable polymerisation conditions, and in particular by using a relatively large amount of chain transfer agent.
  • TBRT is a type of telomerisation.
  • Telomerisation is a method of polymerisation of a polymerisable monomer (a “taxogen”) having an unsaturated group, resulting in a chain of taxogen residues (“taxomons”) with fragments of a further molecule (a “telogen”) attached terminally to the chain of taxomons.
  • a telomer of formula Y(A)nZ in which A is a taxomon, a residue of a taxogen, and Y and Z are fragments of a telogen, YZ.
  • the taxogen is a multivinyl monomer (often a divinyl monomer) and the telogen is a chain transfer agent (often a thiol RSH in which, according to the above terminology, Y is RS and Z is H).
  • a thiol RSH in which, according to the above terminology, Y is RS and Z is H.
  • the polymers according to this invention there is access to a different viscosity-temperature curve enabling polymers to be formulated within the T g constraint, but with better (e.g. lower) melt viscosities.
  • a further advantage is that the present invention allows the use of lower curing temperatures, whilst achieving equivalent or similar appearances and degrees of cure, when compared to conventional powder coatings baked at higher temperatures.
  • powder coating polymers have typically been manufactured by step- growth polymerisation methods, and it is conceptually very different to consider manufacturing them by chain growth methods, such as by free radical polymerisation.
  • free radical polymerisation methodology such as TBRT methodology
  • TBRT methodology can be unpredictable.
  • the behaviour of TBRT materials can vary and, in part due to the complex and extensive branching, it might have been expected that side reactions would occur and that numerous outcomes might arise.
  • Our investigations in this field have revealed a range of interesting and often unexpected properties.
  • the controlled free radical polymerisation methodology of the present invention is not only effective but also opens up new possibilities.
  • the high molecular weight and branched architecture enabled by the present invention provides options that were not previously available, for example in terms of viscosity characteristics, T g behaviour, and consequent properties and applications.
  • high molecular weight leads to issues of epoxy equivalent weights (EEW)
  • the present invention provides the possibility of high molecular weight (if desired) and controlled low EEW (if desired) at the same time, and this offers beneficial options for formulation and property control.
  • a further advantage of the present invention is the expansion of structural space in the powder coatings polymer area.
  • the present invention provides and uses new and diverse chemistries that are not normally available to powder coatings. Polymers produced by TBRT of multivinyl monomers exhibit interesting and unusual properties.
  • TBRT vinyl polymers are formed by chain-growth polymerisation, yet may exhibit characteristics of step-growth polymers. Retrosynthetic analysis of some TBRT vinyl polymers can cause them to be viewed as comprising a mixture of polyfunctional step- growth monomer residues. Although they are vinyl polymers, many of them do not resemble vinyl polymers because their chemistry may be dominated by functional groups present in the parts of the multivinyl monomer which link the vinyl groups, and/or by functional groups in the chain transfer agent. TBRT methodology enables new architectures containing step-growth motifs which would be difficult or impossible to achieve using step-growth polymerisation. The methodology may also be understood when defined using different terminology to achieve the same or similar outcomes. Therefore, from second, third and fourth aspects, the present invention can be defined as follows.
  • the present invention provides a powder coating composition
  • a powder coating composition comprising a polymer which is a branched polymer prepared by free radical vinyl polymerisation comprising residues of multivinyl monomer(s), residues of chain transfer agent(s), and optionally residues of monovinyl monomer(s), and wherein said polymer comprises curable functional group(s).
  • the present invention provides a powder coating composition comprising a polymer which is a branched polymer comprising vinyl polymer chains wherein the vinyl polymer chains comprise residues of vinyl groups of multivinyl monomers and optionally monovinyl monomers, wherein the longest chains in the polymer are not the vinyl polymer chains but rather extend through the linkages between double bonds of the multivinyl monomers, and wherein said polymer comprises curable functional group(s).
  • the present invention provides a powder coating composition comprising a polymer which is a step-growth polymer comprising a mixture of polyfunctional step growth monomer residues formed by vinyl polymerisation, and wherein said polymer comprises curable functional group(s).
  • the powder coating composition may comprise, in addition to the polymer, one or more additional component(s) selected from other reactive ingredient(s), pigment(s), filler(s), and/or additive(s).
  • the powder coating composition of the present invention may comprise, in addition to the polymer, other reactive ingredient(s).
  • the coatings may be exterior coatings, i.e. used outdoors, and therefore may be UV resistant and/or weather resistant.
  • the present invention provides the use of the polymer defined in each of the first four aspects to form a powder coating.
  • the extent of propagation may be controlled relative to the extent of chain transfer to prevent gelation of the polymer.
  • the curable functional group(s) may be incorporated via the multivinyl monomer(s), via co-polymerised monovinyl monomer(s), or via chain transfer agent(s).
  • the curable functional group(s) may be incorporated by post-functionalisation, i.e. by reaction(s) after polymerisation, to add the curable functional group.
  • an alcohol or acid may be present on the polymer; such groups (and others) may act as curable functional groups in their own right; but alternatively they can be functionalised using other reagents to add on different curable functional groups.
  • One example presented below concerns the preparation of a polymer which carries hydroxy groups and then the subsequent reaction of those hydroxy groups with cinnamoyl chloride to incorporate unsaturated functionality which is UV-curable.
  • the present invention allows the incorporation of more than one type of curable functional group in the same polymer. As shown in the figures, it is possible, for example, to have hydroxyl groups and epoxy groups in the same polymer, or acid groups and alcohol groups in the same polymer.
  • the present invention allows the incorporation of curable functional groups with backbone chemistry that would not conventionally be compatible.
  • backbone chemistry For example, conventionally, when forming polyurethanes in the backbone, and/or polyesters in the backbone, there are limitations regarding other functional groups which may also be present.
  • the present invention allows the mixing of functionalities in ways that were not previously possible.
  • the polymer may have a T g of greater than or equal to 45 degrees C.
  • the polymer may have a T g of greater than or equal to 46 degrees C, greater than or equal to 47 degrees C, greater than or equal to 48 degrees C, greater than or equal to 49 degrees C, greater than or equal to 50 degrees C, greater than or equal to 51 degrees C, greater than or equal to 52 degrees C, greater than or equal to 53 degrees C, greater than or equal to 54 degrees C, greater than or equal to 55 degrees C, greater than or equal to 56 degrees C, greater than or equal to 57 degrees C, greater than or equal to 58 degrees C, greater than or equal to 59 degrees C, or greater than or equal to 60 degrees C.
  • the T g is the glass transition temperature, and is the temperature at which a polymer transitions from an amorphous, glassy state to a rubbery or viscous state. This transition is generally reversible and can be determined by thermal or thermomechanical techniques such as differential scanning calorimetry (DSC) or dynamic mechanical analysis (DMA). T g values which are equal to or higher than this temperature are advantageous, to enable the polymers to function as storage-stable, solid, powder coating formulation ingredients.
  • the polymer may be defined by its curable functional group equivalent weight, i.e. the mass of polymer, in g, per mol of curable functional group. Where the curable functional group is an epoxide, the curable functional group equivalent weight is the epoxy equivalent weight (EEW).
  • the curable functional group equivalent weight may optionally be within the range of 100 to 10,000 g/ mol, or 100 to 5,000 g/ mol, or 100 to 3,000 g/ mol, or 100 to 2,000 g/ mol, or 100 to 1,500 g/ mol, or 100 to 1,000 g/ mol, or 100 to 900 g/ mol, or 100 to 850 g/ mol, or 250 to 5,000 g/ mol, or 250 to 3,000 g/ mol, or 250 to 2,000 g/ mol, or 250 to 1,500 g/ mol, or 250 to 1,000 g/ mol, or 250 to 900 g/ mol, or 250 to 850 g/ mol, or 500 to 10,000 g/ mol, or 500 to 5,000 g/ mol, or 500 to 3,000 g/ mol, or 500 to 2,000 g/ mol, or 500 to 1,500 g/ mol, or 500 to 1,000 g/ mol, or 500 to 900 g/ mol, or 500 to
  • the curable functional group equivalent weight (e.g. the epoxy equivalent rate) may optionally be up to 1,500 g/ mol, or optionally up to 1,000 g/ mol, or optionally up to 900 g/ mol, or optionally up to 850 g/ mol.
  • the polymer may be analysed by triple detection size exclusion chromatography (SEC).
  • the polymer may optionally have a weight average molecular weight (Mw) of 1,000 to 100,000, or 1,000 to 50,000, or 1,000 to 10,000, or 1,000 to 5,000, or 1,000 to 3,000, or 2,000 to 100,000, or 2,000 to 50,000, or 2,000 to 10,000, or 2,000 to 5,000, or 2,000 to 3,000, or 3,000 to 100,000, or 3,000 to 50,000, or 3,000 to 10,000, or 3,000 to 5,000, or 5,000 to 100,000, or 5,000 to 50,000, or 5,000 to 10,000, or 10,000 to 100,000, or 50,000 to 100, 000 g/mol.
  • the multivinyl monomer residue(s) may be divinyl monomer residue(s) and the polymer may comprise on average between 0.9 and 1.1 chain transfer agent residues per divinyl monomer residue.
  • the multivinyl monomer may have more than two vinyl groups, i.e. within the scope of the invention are polymers which may be made from not only divinyl monomers but also, for example, trivinyl and/or tetravinyl monomers. In such scenarios, the polymer may comprise on average between 0.9 and 3.3 chain transfer agent residues per multivinyl monomer residue.
  • the polymer may comprise a multiplicity of vinyl polymer chain segments having an average length of between 1 and 3 multivinyl monomer residues.
  • the polymer may be one or more of soluble, pumpable or non-gelled. This enhances the processing of the polymer within the powder coating formulation and the performance during flow and levelling and during curing.
  • the ability to flow when above T g enables melt mixing during the extrusion process, and homogeneity and levelling during the curing process.
  • One of the major advantages of the present invention is that extremely branched polymers can be achieved via radical polymerisation that would be impossible, or challenging, or extremely dangerous, to make using step-growth polymerisation. It is advantageous to be able to control the polymerisation to avoid gelled polymers. Conventional step-growth polymerisation methods have been known to result in gelled branched polymers within industrial-scale reactors, which have taken weeks to recover; this can clearly be very costly and time-consuming. Curable functional group(s) The polymers comprise curable functional groups.
  • curable functional groups are present in the polymers, in amounts which can be controlled and tailored by controlling the amount of feedstocks (monovinyl monomer, multivinyl monomer or chain transfer agent). For example, where an epoxide-carrying monovinyl monomer is used, the number of epoxide groups incorporated will correspond to the number of residues of said monomer in the polymer.
  • Suitable curable functional groups are known in the art; they are sufficiently inert during storage and during preparation of the powder coating formulations, but reactive during curing conditions under reasonable timescales. They comprise the following groups: epoxy; carboxylic acid; amine; hydroxy; isocyanate; and unsaturated groups, amongst others. They also comprise variants of the same, as known in the art, which variants also exhibit suitable cross-linking chemistries: these variants can control reactivity – e.g. activated functional groups (including activated alcohols) and blocked hardeners (e.g. blocked isocyanates).
  • the curable functional group may be an epoxide.
  • a monovinyl monomer may comprise, in addition to a polymerisable double bond, an epoxide group.
  • a suitable monovinyl monomer is glycidyl methacrylate.
  • the curable functional group may be an acid.
  • a monovinyl monomer may comprise, in addition to a polymerisable double bond, an acid group.
  • a suitable monovinyl monomer is methacrylic acid.
  • the curable functional group may be a hydroxyl group.
  • a monovinyl monomer may comprise, in addition to a polymerisable double bond, a hydroxyl group.
  • a suitable monovinyl monomer is hydroxyethylmethacrylate.
  • a divinyl monomer and/or a chain transfer agent may comprise one or more hydroxyl group.
  • the curable functional group may be one or more unsaturated bond, for example a double bond. Unsaturated functional groups can include dienes and dienophiles, such that the curing reaction may be a Diels Alder reaction.
  • the curable functional group may be one which is known in the art to be effective in powder coatings. Thermosetting powder coatings are powders which can be applied to items to be coated and which can be cured to form coatings. During curing, the curable functional groups react. Curing can be effected by heat or irradiation (e.g.
  • branched polymers may be considered to be scaffolds to which the curable functional groups are attached, and may comprise any suitable chemistry.
  • Suitable types of branched vinyl polymers include branched polyesters, which may be made from the polymerisation of monomers which comprise vinyl groups as well as ester-containing or ester-forming functionality.
  • Suitable monomers include methacrylates, acrylates and vinyl esters.
  • Suitable divinyl and multivinyl monomers include dimethacrylates, diacrylates, divinyl esters, multimethacrylates, multiacrylates, and multivinyl esters.
  • Said branched polyesters may be aliphatic polyesters, or may be aromatic polyesters if aromatic groups are also present in the monomer(s), or may be mixed aromatic/ aliphatic polyesters. Said branched polyesters may also contain other functional groups, for example by inclusion of certain chemical moieties within the monomers used in the feedstock. Therefore, further suitable types of branched vinyl polymers include branched poly(urethane-ester)s. These may be made from the polymerisation of monomers which comprise: (i) vinyl groups; (ii) ester-containing or ester-forming functionality; and (iii) urethane-containing or urethane-forming functionality. Suitable monomers include urethane dimethacrylate.
  • Types of polymer which have been found to be particularly effective in accordance with the present invention include epoxy-functional branched polyesters and epoxy- functional branched poly(urethane-ester)s.
  • Suitable types of polymer include those containing functionality selected from the following: carbonates; carbonate esters; amides; amide esters; urethanes; urethane esters; urethane amides; urethane carbonates; ureas.
  • the branched polymer may be prepared by the free radical polymerisation of a multivinyl monomer, and optionally a monovinyl monomer, in the presence of a chain transfer agent, using a source of radicals.
  • a curable functional group is present on the polymer and may be incorporated by being present on the multivinyl monomer, the monovinyl monomer and/or the chain transfer agent; or by post-functionalisation.
  • the extent of propagation may be controlled relative to the extent of chain transfer to prevent gelation of the polymer.
  • multivinyl monomer denotes monomers which have more than one free radical polymerisable vinyl group.
  • One particular class of such monomers are those which have two such vinyl groups, i.e. divinyl monomers. Therefore, the branched polymer may be prepared by the free radical polymerisation of a divinyl monomer, and optionally a monovinyl monomer, in the presence of a chain transfer agent, using a source of radicals.
  • a curable functional group is present on the polymer and may be incorporated by being present on the divinyl monomer, the monovinyl monomer and/or the chain transfer agent; or by post-functionalisation.
  • the extent of propagation may be controlled relative to the extent of chain transfer to prevent gelation of the polymer.
  • cross-linking and insolubility are avoided not by using a combination of a predominant amount of monovinyl monomer and a lesser amount of divinyl monomer, but instead by controlling the way in which a divinyl monomer, or other multivinyl monomer, reacts.
  • the branched polymer may be prepared by the free radical polymerisation of a divinyl monomer, and optionally a monovinyl monomer, in the presence of a chain transfer agent, using a source of radicals, wherein propagation is controlled relative to chain transfer to achieve a polymer having a multiplicity of vinyl polymer chain segments wherein the average number of divinyl monomer residues per vinyl polymer chain is between 1 and 3.
  • a curable functional group is present on the polymer and may be incorporated by being present on the divinyl monomer, the monovinyl monomer and/or the chain transfer agent.
  • the branched polymer may be prepared by the free radical polymerisation of a multivinyl monomer, and optionally a monovinyl monomer, in the presence of a chain transfer agent, using a source of radicals, wherein propagation is controlled relative to chain transfer to achieve a polymer having a multiplicity of vinyl polymer chain segments wherein the average number of multivinyl monomer residues per vinyl polymer chain is between 1 and 3.
  • a curable functional group is present on the polymer and may be incorporated by being present on the multivinyl monomer, the monovinyl monomer and/or the chain transfer agent.
  • the branched polymer may be prepared by the free radical polymerisation of a trivinyl monomer, and optionally a monovinyl monomer, in the presence of a chain transfer agent, using a source of radicals, wherein propagation is controlled relative to chain transfer to achieve a polymer having a multiplicity of vinyl polymer chain segments wherein the average number of trivinyl monomer residues per vinyl polymer chain is between 1 and 2.
  • a curable functional group is present on the polymer and may be incorporated by being present on the trivinyl monomer, the monovinyl monomer and/or the chain transfer agent.
  • the branched polymer may be prepared by the free radical polymerisation of a tetravinyl monomer, and optionally a monovinyl monomer, in the presence of a chain transfer agent, using a source of radicals, wherein propagation is controlled relative to chain transfer to achieve a polymer having a multiplicity of vinyl polymer chain segments wherein the average number of tetravinyl monomer residues per vinyl polymer chain is between 1 and 1.7.
  • a curable functional group is present on the polymer and may be incorporated by being present on the tetravinyl monomer, the monovinyl monomer and/or the chain transfer agent.
  • Multivinyl monomer may be incorporated, regardless of whether or not a monovinyl monomer is incorporated.
  • a monovinyl monomer may be any combination of two or more of a divinyl monomer, a trivinyl monomer, a tetravinyl monomer, or other multivinyl monomer, are incorporated, and that optionally a monovinyl monomer may also be incorporated.
  • the polymer contains more than one of each type of monomer and/or more than one type of chain transfer agent.
  • the polymer contains divinyl residues and monovinyl residues and chain transfer agent residues
  • the divinyl residues may be all the same or different
  • the monovinyl residues may be all the same or different
  • the chain transfer agent residues may be all the same or different.
  • the polymer is prepared by free radical polymerisation and any suitable source of radicals can be used.
  • this could be an initiator such as AIBN.
  • a thermal or photochemical or other process can be used to provide free radicals.
  • a large amount of initiator is not required; only a small amount of a source of radicals is required in order to initiate the reaction.
  • the skilled person is able to control the chain transfer reaction relative to the propagation reaction by known techniques.
  • the chain transfer agent caps the vinyl polymer chains and thereby limits their length. It also controls the chain end chemistry.
  • Various chain transfer agents are suitable and of low cost, and impart versatility to the method and resultant product.
  • the primary chains may be kept very short so that gel formation is avoided, whilst at the same time a high level of branching is achieved.
  • An important advantage of the present invention is that the polymer may be prepared by industrial free radical polymerisation. This is completely scalable, very straightforward and extremely cost effective. In contrast, some prior art polymers are more complex and/or more costly and/or require the use of initiator systems or more complex purification procedures.
  • the only reagents to prepare the branched polymer are one or more multivinyl monomer (for example a divinyl monomer), a chain transfer agent, a source of radicals, and optionally a solvent.
  • the present invention relates to polymers which can be prepared by the homopolymerisation of multivinyl monomers.
  • Monovinyl monomers are not required to prepare the polymer.
  • the curable functional group may be present on a monovinyl monomer, but may alternatively be present on multivinyl monomer or chain transfer agent. Nevertheless, monovinyl monomers may be incorporated, i.e. optionally a copolymerisation may be carried out to produce the polymer.
  • Monovinyl monomers are convenient means of introducing curable functional groups.
  • the polymer may incorporate not only a divinyl monomer but also an amount, optionally a lesser amount, of monovinyl monomer.
  • the molar amount of divinyl monomer relative to monovinyl monomer may be greater than 50%, greater than 75%, greater than 90% or greater than 95%, for example.
  • the ratio of divinyl monomer residues to monovinyl monomer residues may be greater than or equal to 1:1, or greater than or equal to 3:1, greater than or equal to 10:1 or greater than or equal to 20:1. Alternatively, in some scenarios, more monovinyl monomer may be used.
  • the polymer may incorporate not only one or more divinyl monomer but also monovinyl monomer, wherein for example 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 95% or more, of the vinyl monomers used are divinyl monomers.
  • the polymer may incorporate not only one or more divinyl monomer but also monovinyl monomer, wherein for example 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 95% or more, of the vinyl monomers residues in the product are divinyl monomer residues.
  • the polymer may incorporate not only one or more multivinyl monomer but also monovinyl monomer, wherein for example 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 95% or more, of the vinyl monomers used are multivinyl monomers.
  • the polymer may incorporate not only one or more multivinyl monomer but also monovinyl monomer, wherein for example 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 95% or more, of the vinyl monomers residues in the product are multivinyl monomer residues.
  • the polymer may comprise on average between 0.25 and 5 monovinyl monomer residues per multivinyl monomer (e.g.
  • divinyl) residue for example 0.25 to 4, or 0.25 to 3, or 0.25 to 2, or 0.25 to 1, or 0.25 to 0.5, or 0.5 to 5, or 0.5 to 4, or 0.5 to 3, or 0.5 to 2, or 0.1 to 1, or 1 to 5, or 1 to 4, or 1 to 3, or 1 to 2, or 2 to 5, or 2 to 4, or 2 to 3, or 3 to 5, or 3 to 4, or 4 to 5.
  • Divinyl Monomer One type of multivinyl monomer residue which may be present in the polymer is a divinyl monomer. The divinyl monomer contains two double bonds each of which is suitable for free radical polymerisation.
  • It may contain one or more other group which for example may be selected from, but not limited to: aliphatic chains; esters; amides; esters; urethanes; silicones; amines; aromatic groups; oligomers or polymers; or a combination of one or more of these; and/or which may optionally be substituted.
  • group which for example may be selected from, but not limited to: aliphatic chains; esters; amides; esters; urethanes; silicones; amines; aromatic groups; oligomers or polymers; or a combination of one or more of these; and/or which may optionally be substituted.
  • PEG groups or PDMS groups between the double bonds, or a benzene ring (e.g. as in the monomer divinyl benzene) or other aromatic groups.
  • Each vinyl group in the divinyl monomer may for example be an acrylate, methacrylate, acrylamide, methacrylamide, vinyl ester, vinyl aliphatic, or
  • the vinyl polymer chains in the final product are generally quite short and the chemistry of the longest chains in the polymer may be governed by the other chemical species in the monomer.
  • ester linkages e.g. dimethacrylates, such as EGDMA
  • amide linkages e.g. bisacrylamides
  • the polymers may be polyesters, polyamides or other polymers.
  • the monomer residues may comprise other linkages or moieties, (e.g. urethane units), thereby resulting in other types of polymer (e.g. polyurethanes).
  • the monomer residues may contain more than one type of moiety, thereby resulting in hybrid polymers.
  • monomers which contain, in addition to two vinyl groups, ester linkages and urethane linkages e.g. dimethacrylates containing urethane linkages, such as urethane dimethacrylate (UDMA)
  • UDMA urethane dimethacrylate
  • the divinyl monomer may be stimuli-responsive, e.g. may be pH, thermally, or biologically responsive.
  • the response may be degradation.
  • the linkage between the two double bonds may for example be acid- or base-cleavable, for example may contain an acetal group.
  • This allows the preparation of a commercial product which is a stimuli-responsive branched polymer.
  • a further step of cleaving divinyl monomer may be carried to remove bridges in the polymer, to produce product in which the linkages between vinyl polymer chains have been removed or reduced.
  • the polymer may be prepared using a mixture of divinyl monomers. Thus two or more different divinyl monomers may be copolymerised.
  • Multivinyl monomers other than divinyl monomers may be used, for example, trivinyl monomers, tetravinyl monomers and/or monomers with more vinyl groups. Trivinyl monomers, in particular, are useful, as they can be sourced or prepared without significant difficulty, and allow further options for producing different types of branched polymers. The discussion, disclosures and teachings herein in relation to divinyl monomers also apply where appropriate, mutatis mutandis, to other multivinyl monomers.
  • Chain transfer agent Any suitable chain transfer agent may be used. These include thiols, including optionally substituted aliphatic thiols, such as dodecane thiol (DDT).
  • Another suitable chain transfer agent is alpha-methylstyrene dimer. Another is 2-isopropoxyethanol. Other compounds having functionality which is known to allow the transfer of radical chains may be used. These can be bespoke to bring about desired functionality to the polymers.
  • the chain-end chemistry can be tailored by the choice of CTA. Thus, hydrophobic/ hydrophilic behaviour and other properties can be influenced.
  • Alkyl thiols can have quite different properties to alcohol-containing groups, acid-containing groups, or amine-containing groups, for example.
  • a mixture of CTAs may be used. Thus, two or more different CTAs may be incorporated into the product.
  • Relative amounts of chain transfer agent and divinyl monomer The relative amounts of chain transfer agent and divinyl monomer can be modified easily and optimised by routine procedures to obtain non-gelled polymers without undue burden to the skilled person.
  • the analysis of the products can be carried out by routine procedures, for example the relative amounts of chain transfer agent and divinyl monomer can be determined by NMR analysis.
  • At least 1 equivalent, or between 1 and 10 equivalents, or between 1.2 and 10 equivalents, or between 1.3 and 10 equivalents, or between 1.3 and 5 equivalents, or between 1 and 5 equivalents, or between 1 and 3 equivalents, or between 1 and 2 equivalents, or between 1.2 and 3 equivalents, or between 1.2 and 2 equivalents, of chain transfer agent may be used relative to divinyl monomer.
  • the presence of a large amount of chain transfer agent means that on average the primary vinyl polymer chains react, and are capped by, chain transfer agent, whilst they are short. This procedure amounts to telomerisation, i.e. the formation of short chains with small numbers of repeat units.
  • n+1 chain transfer agent moieties per n divinyl monomer moieties may be present per divinyl monomer moiety, optionally between 0.7 and 1.5, optionally between 0.75 and 1.3, or between 0.8 and 1.2, or between 0.9 and 1.1, or between 1 and 1.05, or approximately 1.
  • Relative amounts of chain transfer agent and trivinyl monomer Where the multivinyl monomer used is a trivinyl monomer, the following may optionally apply.
  • the reagents used optionally at least 2 equivalents, or between 2 and 20 equivalents, or between 2.4 and 20 equivalents, or between 2.6 and 20 equivalents, or between 2.6 and 10 equivalents, or between 2 and 10 equivalents, or between 2 and 6 equivalents, or between 2 and 4 equivalents, or between 2.4 and 6 equivalents, or between 2.4 and 4 equivalents, of chain transfer agent may be used relative to trivinyl monomer.
  • Relative amounts of chain transfer agent and tetravinyl monomer Where the multivinyl monomer used is a tetravinyl monomer, the following may optionally apply.
  • the reagents used optionally at least 3 equivalents, or between 3 and 30 equivalents, or between 3.6 and 30 equivalents, or between 3.9 and 30 equivalents, or between 3.9 and 15 equivalents, or between 3 and 15 equivalents, or between 3 and 9 equivalents, or between 3 and 6 equivalents, or between 3.6 and 9 equivalents, or between 3.6 and 6 equivalents, of chain transfer agent may be used relative to tetravinyl monomer.
  • chain transfer agent optionally at least 1 equivalent, or between 1 and 30 equivalents, or between 1.2 and 30 equivalents, or between 1.3 and 30 equivalents, or between 1.3 and 15 equivalents, or between 1 and 15 equivalents, or between 1 and 9 equivalents, or between 1 and 6 equivalents, or between 1.2 and 9 equivalents, or between 1.2 and 6 equivalents, of chain transfer agent may be used relative to multivinyl monomer.
  • chain transfer agent moieties are present per multivinyl monomer moiety, optionally between 0.7 and 4.5, optionally between 0.75 and 3.9, or between 0.8 and 3.6, or between 0.9 and 3.3, or between 1 and 3.15, or between approximately 1 and approximately 3.
  • the polymer may comprise on average between 0.9(x-1) and 1.1(x-1) chain transfer agent residues per multivinyl monomer residue, where “x” is the number of polymerisable vinyl groups on the multivinyl monomer.
  • x is the number of polymerisable vinyl groups on the multivinyl monomer.
  • the multivinyl monomer is a divinyl monomer
  • a typical polymeric molecule prepared as described herein will contain many vinyl polymer chains (each of which is on average quite short) linked together by the moiety which in the multivinyl monomer is between the double bonds. This is achieved by adjusting the conditions, including the amount of chain transfer agent, so that the rate of chain transfer competes with the rate of vinyl polymerisation to the desired extent.
  • the resulting chain length in this context is the kinetic chain length.
  • Extent of vinyl polymerisation when using divinyl monomers The number of propagation steps (i.e. how many divinyl monomers are added) before each chain transfer (i.e. termination of the growing vinyl polymer chain) needs to be high enough to generate a branched polymer but low enough to prevent gelation. It appears that an average vinyl polymer chain length of between 1 and 3, between 1 and 2.5, between 1 and 2.2, between 1 and 2, between 1.3 and 2, between 1.5 and 2, between 1.7 and 2, between 1.8 and 2, between 1.9 and 2, or between 1.95 and 2, or of approximately 2, divinyl monomer residues, is suitable.
  • a small number of vinyl polymer chains may contain significantly more divinyl monomer residues, for example as many as 10, 15, 18, 20 or more.
  • 90 % of the vinyl polymer chains contain fewer than 10 DVM residues, or 90% have a length of 7 or fewer, or 90% have a length of 5 or fewer, or 95% have a length of 15 or fewer, or 95% have a length of 10 or fewer, or 95% have a length of 7 or fewer, or 75% have a length of 10 or fewer, or 75% have a length of 7 or fewer, or 75% have a length of 5 or fewer, or 75% have a length of 4 or fewer, or 75% have a length of 3 or fewer.
  • the average vinyl polymer chain length, or kinetic chain length, in a scenario which assumes that there is no intramolecular reaction can be calculated as follows. If, as discussed above there are n+1 chain transfer agent moieties per n divinyl monomer moieties, and one chain transfer agent per vinyl polymer chain, then, because there are 2n double bonds per n divinyl monomers, the number of double bond residues per chain will on average be 2n/(n+1) which will tend towards 2 as the molecular weight increases.
  • the process makes a range of products which, depending on the conditions, can include low molecular weight products (the smallest being the product containing just one DVM, i.e.
  • the vinyl chain length is 1) up to high molecular weight products.
  • the product mixture is purified, and how it is purified, will of course affect the composition of the product and accordingly the length of vinyl polymer chains present.
  • the average vinyl polymer chain length in the resultant purified product may be higher.
  • the product may contain a large amount of divinyl monomer residues wherein one of the double bond residues is capped with a chain transfer agent (as opposed to being part of a chain), i.e. has a nominal chain length of 1.
  • the other double bond residues of those divinyl monomer residues may be part of a longer chain. This may be the most common form of the vinyl residue in the product.
  • the most common vinyl “chain” is that which contains only one divinyl monomer residue.
  • the two most common vinyl chains are (i) the vinyl “chain” which contains only one divinyl monomer residue and (ii) a vinyl chain which contains an integer selected from between 2 and 8, e.g. between 2 and 7, e.g. between 2 and 6, e.g. between 3 and 8, e.g. between 3 and 7, e.g. between 3 and 6, e.g. between 3 and 5, e.g.4 or 5, e.g.5, divinyl monomer residues.
  • the most common vinyl “chain” is that which contains only one divinyl monomer residue, and the second most common vinyl chain contains an integer selected from between 2 and 8, e.g.
  • the distribution of chain lengths may be bimodal, e.g. the maxima may be at chain length 1 and at a second chain length which may optionally be between 3 and 8, e.g. between 3 and 7, e.g. between 3 and 6, e.g. between 3 and 5, e.g.4 or 5, e.g.5, divinyl monomer residues.
  • the distribution of chain lengths may be bimodal, e.g. the maxima may be at chain length 1 and at a second chain length which may optionally be between 3 and 8, e.g. between 3 and 7, e.g. between 3 and 6, e.g. between 3 and 5, e.g.4 or 5, e.g.5.
  • Extent of vinyl polymerisation when using trivinyl monomers The number of propagation steps (i.e.
  • 90 % of the vinyl polymer chains contain fewer than 8 TVM residues, or 90% have a length of 5 or fewer, or 90% have a length of 4 or fewer, or 95% have a length of 10 or fewer, or 95% have a length of 8 or fewer, or 95% have a length of 5 or fewer, or 75% have a length of 8 or fewer, or 75% have a length of 6 or fewer, or 75% have a length of 4 or fewer, or 75% have a length of 3 or fewer, or 75% have a length of 2 or fewer.
  • the average vinyl polymer chain length, or kinetic chain length, in a scenario which assumes that there is no intramolecular reaction can be calculated as follows. If, as discussed above there are 2n+1 chain transfer agent moieties per n trivinyl monomer moieties, and one chain transfer agent per vinyl polymer chain, then, because there are 3n double bonds per n trivinyl monomers, the number of double bond residues per chain will on average be 3n/(2n+1) which will tend towards 1.5 as the molecular weight increases.
  • the process makes a range of products which, depending on the conditions, can include low molecular weight products (the smallest being the product containing just one TVM, i.e.
  • the vinyl chain length is 1) up to high molecular weight products.
  • the product mixture is purified, and how it is purified, will of course affect the composition of the product and accordingly the length of vinyl polymer chains present.
  • the average vinyl polymer chain length in the resultant purified product may be higher.
  • the product may contain a large amount of trivinyl monomer residues wherein two of the double bond residues are capped with a chain transfer agent (as opposed to being part of a chain), i.e. have a nominal chain length of 1.
  • the other double bond residues of those trivinyl monomer residues may be part of a longer chain. This may be the most common form of the vinyl residue in the product.
  • the most common vinyl “chain” is that which contains only one trivinyl monomer residue.
  • the two most common vinyl chains are (i) the vinyl “chain” which contains only one trivinyl monomer residue and (ii) a vinyl chain which contains an integer selected from between 2 and 7, e.g. between 2 and 6, e.g. between 2 and 5, e.g. between 3 and 7, e.g. between 3 and 6, e.g. between 3 and 5, e.g.3 or 4, e.g.3 or e.g. 4, trivinyl monomer residues.
  • the most common vinyl “chain” is that which contains only one trivinyl monomer residue, and the second most common vinyl chain contains an integer selected from between 2 and 7, e.g.
  • the distribution of chain lengths may be bimodal, e.g. the maxima may be at chain length 1 and at a second chain length which may optionally be between 3 and 7, e.g. between 3 and 6, e.g. between 3 and 5, e.g.3 or 4, e.g.3 or e.g.4.
  • Extent of vinyl polymerisation when using tetravinyl monomers The number of propagation steps (i.e.
  • Optionally 90 % of the vinyl polymer chains contain fewer than 6 tetravinyl monomer residues, or 90% have a length of 4 or fewer, or 90% have a length of 3 or fewer, or 90% have a length of 2 or fewer, or 95% have a length of 8 or fewer, or 95% have a length of 6 or fewer, or 95% have a length of 4 or fewer, or 95% have a length of 3 or fewer, or 75% have a length of 5 or fewer, or 75% have a length of 4 or fewer, or 75% have a length of 3 or fewer, or 75% have a length of 2 or fewer.
  • the average vinyl polymer chain length, or kinetic chain length, in a scenario which assumes that there is no intramolecular reaction can be calculated as follows. If, as discussed above there are 3n+1 chain transfer agent moieties per n tetravinyl monomer moieties, and one chain transfer agent per vinyl polymer chain, then, because there are 4n double bonds per n tetravinyl monomers, the number of double bond residues per chain will on average be 4n/(3n+1) which will tend towards 1.33 as the molecular weight increases.
  • the process makes a range of products which, depending on the conditions, can include low molecular weight products (the smallest being the product containing just one tetravinyl monomer residue i.e. wherein the vinyl chain length is 1) up to high molecular weight products.
  • low molecular weight products the smallest being the product containing just one tetravinyl monomer residue i.e. wherein the vinyl chain length is 1
  • high molecular weight products the average vinyl polymer chain length in the resultant purified product may be higher.
  • the product may contain a large amount of tetravinyl monomer residues wherein three of the double bond residues are capped with a chain transfer agent (as opposed to being part of a chain), i.e. have a nominal chain length of 1.
  • the other double bond residues of those tetravinyl monomer residues may be part of a longer chain.
  • This may be the most common form of the vinyl residue in the product.
  • the most common vinyl “chain” is that which contains only one tetravinyl monomer residue.
  • the two most common vinyl chains are (i) the vinyl “chain” which contains only one tetravinyl monomer residue and (ii) a vinyl chain which contains an integer selected from between 2 and 6, e.g.
  • the most common vinyl “chain” is that which contains only one tetravinyl monomer residue
  • the second most common vinyl chain contains an integer selected from between 2 and 6, e.g. between 2 and 5, e.g. between 2 and 4, e.g. between 3 and 6, e.g. between 3 and 5, e.g.3 or 4, e.g.3 or e.g. 4, tetravinyl monomer residues.
  • the distribution of chain lengths may be bimodal, e.g. the maxima may be at chain length 1 and at a second chain length which may optionally be between 3 and 6, e.g. between 3 and 5, e.g.3 or 4, e.g.3 or e.g.4.
  • Extent of vinyl polymerisation when using multivinyl monomers in general Numerical relationships and theoretical assessments have been presented above for each of divinyl monomers, trivinyl monomers and tetravinyl monomers.
  • the average number of multivinyl monomer residues per vinyl polymer chain may be as follows, where the product contains n multivinyl monomer residues: Average number of multivinyl as n tends to infinity, the monomer residues per vinyl average number of MVM r
  • the average vinyl chain length is required to decrease.
  • the following may optionally apply across the various types of multivinyl monomers discussed herein.
  • the average vinyl polymer chain length may contain the following number of multivinyl monomer residues: between 1 and 3, between 1 and 2.5, between 1 and 2.2, between 1 and 2, between 1.1 and 2, between 1.2 and 2, between 1.3 and 2, between 1.33 and 2, between 1.5 and 2, between 1.8 and 2, between 1.9 and 2, between 1.95 and 2, between 1.2 and 1.5, between 1.3 and 1.5, between 1.4 and 1.5, between 1.45 and 1.5, between 1.1 and 1.4, between 1.2 and 1.4, between 1.2 and 1.33, or between 1.3 and 1.33. Whilst the average may optionally be between 1 and 3, a small number of vinyl polymer chains may contain significantly more multivinyl monomer residues, for example as many as 3, 5, 8, 10, 15, 18, 20 or more.
  • Optionally 90 % of the vinyl polymer chains contain fewer than 10 multivinyl monomer residues, or 90% have a length of 7 or fewer, or 90% have a length of 5 or fewer, or 90% have a length of 4 or fewer, or 90% have a length of 3 or fewer, or 90% have a length of 2 or fewer, or 95% have a length of 15 or fewer, or 95% have a length of 10 or fewer, or 95% have a length of 7 or fewer, or 95% have a length of 5 or fewer, or 95% have a length of 4 or fewer, or 95% have a length of 3 or fewer, or 75% have a length of 10 or fewer, or 75% have a length of 7 or fewer, or 75% have a length of 5 or fewer, or 75% have a length of 4 or fewer, or 75% have a length of 3 or fewer, or 75% have a length of 10 or fewer, or 75% have a length of 7 or fewer,
  • the product may contain a large amount of multivinyl monomer residues wherein all but one of the double bond residues in the multivinyl monomer residue is capped with a chain transfer agent (as opposed to being part of a chain), i.e. has a nominal chain length of 1.
  • the remaining double bond residue of the multivinyl monomer residues may be part of a longer chain. This may be the most common form of the vinyl residue in the product.
  • the most common vinyl “chain” is that which contains only one multivinyl monomer residue.
  • the two most common vinyl chains are (i) the vinyl “chain” which contains only one multivinyl monomer residue and (ii) a vinyl chain which contains an integer selected from between 2 and 8, e.g.
  • the most common vinyl “chain” is that which contains only one multivinyl monomer residue, and the second most common vinyl chain contains an integer selected from between 2 and 8, e.g. between 2 and 7, e.g. between 2 and 6, e.g. between 2 and 5, e.g. between 3 and 8, e.g. between 3 and 7, e.g. between 3 and 6, e.g. between 3 and 5, e.g.3, e.g.4 or e.g. 5 multivinyl monomer residues.
  • the most common vinyl “chain” is that which contains only one multivinyl monomer residue
  • the second most common vinyl chain contains an integer selected from between 2 and 8, e.g. between 2 and 7, e.g. between 2 and 6, e.g. between 2 and 5, e.g. between 3 and 8, e.g. between 3 and 7, e.g. between 3 and 6, e.g.
  • the distribution of chain lengths may be bimodal, e.g. the maxima may be at chain length 1 and at a second chain length which may optionally be between 3 and 8, e.g. between 3 and 7, e.g. between 3 and 6, e.g. between 3 and 5, e.g.3, 4 or 5.
  • Source of radicals The source of radicals may be an initiator such as azoisobutyronitrile (AIBN).
  • AIBN azoisobutyronitrile
  • the amount used relative to divinyl monomer may be 0.001 to 1, 0.01 to 0.1, 0.01 to 0.05, 0.02 to 0.04 or approximately 0.03 equivalents.
  • a solvent such as for example toluene may be used.
  • the amount of CTA in the product can decrease. Without wishing to be bound by theory, this may be because at greater dilution intramolecular reaction is more likely, meaning that, effectively, reaction of the molecule with itself takes the place of reaction of the molecule with a CTA molecule. Accordingly, this can alter the numerical relationships discussed above, because these assume a theoretical situation in which there is no intramolecular reaction. This provides a further way of controlling the chemistry and tailoring the type of product and its properties.
  • branched polymers may comprise divinyl monomer residues and chain transfer residues, wherein the molar ratio of chain transfer residues to divinyl monomer residues is between 0.5 and 2.
  • the ratio is optionally between 0.7 and 1.5, optionally between 0.75 and 1.3, optionally between 0.8 and 1.2, optionally between 0.9 and 1.1, optionally between 1 and 1.05, optionally approximately 1.
  • Some of the vinyl polymer chains may contain as many as 18, or 15, divinyl monomer residues. Only a small proportion are this long, however: the average, for high molecular weight materials, may be around 2.
  • Optionally 90 % of the vinyl polymer chains contain fewer than 10 DVM residues, or 90% have a length of 7 or fewer, or 90% have a length of 5 or fewer, or 95% have a length of 15 or fewer, or 95% have a length of 10 or fewer, or 95% have a length of 7 or fewer, or 75% have a length of 10 or fewer, or 75% have a length of 7 or fewer, or 75% have a length of 5 or fewer, or 75% have a length of 4 or fewer, or 75% have a length of 3 or fewer).
  • the branched polymer product may comprise divinyl monomer residues and chain transfer residues, wherein 90 % of the vinyl polymer chains contain fewer than 10 DVM residues, or 90% have a length of 7 or fewer, or 90% have a length of 5 or fewer, or 95% have a length of 15 or fewer, or 95% have a length of 10 or fewer, or 95% have a length of 7 or fewer, or 75% have a length of 10 or fewer, or 75% have a length of 7 or fewer, or 75% have a length of 7 or fewer, or 75% have a length of 5 or fewer, or 75% have a length of 4 or fewer, or 75% have a length of 3 or fewer).
  • each vinyl residue may be directly linked to 0, 1 or 2 other vinyl residues as closest neighbours.
  • the branched polymer comprises divinyl monomer residues and chain transfer residues, wherein each vinyl residue is directly vinyl polymerised to on average 0.5 to 1.5 other divinyl monomer residue.
  • this may be 0.8 to 1.2, 0.8 to 1.1, 0.9 to 1, or approximately 1, on average.
  • the polymers are characterised by having a large amount of chain transfer agent incorporation, and also by having short distinct vinyl polymer chains.
  • a vinyl polymer chain will normally comprise a long saturated backbone, during the preparation of the present polymers - even though they are built up using vinyl polymerisation - most of the double bonds only react with one other double bond, or react with no other double bonds, rather than react with two other double bonds.
  • the branched polymer may comprise divinyl monomer residues and chain transfer residues, in which there is a multiplicity of vinyl polymer chain segments having an average length of between 1 and 3 divinyl monomer residues.
  • the average length may be between 1 and 2.5, between 1 and 2.2, between 1 and 2, between 1.3 and 2, between 1.5 and 2, between 1.7 and 2, between 1.8 and 2, between 1.9 and 2, between 1.95 and 2, or approximately 2.
  • the skilled person will understand how the number of double bond residues affects the carbon chain length of the resultant vinyl polymer segment.
  • a polymer chain segment comprises 2 double bond residues
  • this equates to a saturated carbon chain segment of 4 carbon atoms.
  • the incorporation of monovinyl monomers as well as divinyl monomers may affect the average vinyl chain length but does not affect the average number of divinyl monomer residues per chain. It can be a way of increasing the vinyl chains without increasing branching.
  • the branched polymer may comprise divinyl monomer residues and chain transfer residues wherein the divinyl monomer residues comprise less than 20mol% double bond functionality. In other words, in such polymer products, at least 80% of the double bonds of the divinyl monomers have reacted to form saturated carbon-carbon chains.
  • the residues may comprise less than 10mol%, or less than 5mol%, or less than 2mol%, or less than 1mol%, or substantially no, double bond functionality.
  • Another way of defining the polymer is in terms of its Mark Houwink alpha value. Optionally, this may be below 0.5.
  • the above description of polymer products relates in particular to those containing divinyl monomer residues.
  • polymer products containing other multivinyl monomer residues may include for example trivinyl monomer residues and/or tetravinyl monomer residues. Definitions and disclosures herein apply mutatis mutandis.
  • the molar ratio, on average, of chain transfer residues to multivinyl monomer residues may optionally be: - for multivinyl monomers generally: between 0.5 and 6, between 0.7 and 4.5, between 0.75 and 3.9, between 0.8 and 3.6, between 0.9 and 3.3, between 1 and 3.15, or between approximately 1 and approximately 3; - for trivinyl monomers: between 1 and 4, between 1.4 and 3, between 1.5 and 2.6, between 1.6 and 2.4, between 1.8 and 2.2, between 2 and 2.1, or approximately 2; - for tetravinyl monomers: between 1.5 and 6, between 2.1 and 4.5, between 2.25 and 3.9, between 2.4 and 3.6, between 2.7 and 3.3, between 3 and 3.15, or approximately 3.
  • - for multivinyl monomers generally: 90 % of the vinyl polymer chains contain fewer than 10 multivinyl monomer residues, or 90% have a length of 7 or fewer, or 90% have a length of 5 or fewer, or 90% have a length of 4 or fewer, or 90% have a length of 3 or fewer, or 90% have a length of 2 or fewer, or 95% have a length of 15 or fewer, or 95% have a length of 10 or fewer, or 95% have a length of 7 or fewer, or 95% have a length of 5 or fewer, or 95% have a length of 4 or fewer, or 95% have a length of 3 or fewer, or 75% have a length of 10 or fewer, or 75% have a length of 7 or fewer, or 75% have a length of 5 or fewer, or 75% have a length of 4 or fewer, or 75% have a length of 3 or fewer, or 75% have a length of 10 or fewer, or 75% have
  • the branched polymer product comprises a multiplicity of vinyl polymer chain segments having an average length of: - for multivinyl monomers generally: between 1 and 3, between 1 and 2.5, between 1 and 2.2, between 1 and 2, between 1.1 and 2, between 1.2 and 2, between 1.3 and 2, between 1.33 and 2, between 1.5 and 2, between 1.8 and 2, between 1.9 and 2, between 1.95 and 2, between 1.2 and 1.5, between 1.3 and 1.5, between 1.4 and 1.5, between 1.45 and 1.5, between 1.1 and 1.4, between 1.2 and 1.4, between 1.2 and 1.33, or between 1.3 and 1.33 multivinyl monomer residues; - for trivinyl monomers: between 1 and 2, between 1 and 1.8, between 1 and 1.7, between 1 and 1.5, between 1.1 and 1.5, between 1.2 and 1.5, between 1.25 and 1.5, between 1.3 and 1.5, between 1.4 and 1.5, or between 1.45 and 1.5, or of approximately 1.5, trivinyl monomer residues; - for tetravinyl monomers: between 1 and 1.1
  • a branched polymer product comprises multivinyl monomer residues and chain transfer residues wherein the multivinyl monomer residues comprise less than 20mol% double bond functionality.
  • the residues may comprise less than 10mol%, or less than 5mol%, or less than 2mol%, or less than 1mol%, or substantially no, double bond functionality.
  • Figures 1 to 12 show fragments of branched polymers in accordance with the present invention, each of which is prepared by the co-polymerisation of one or more divinyl monomer and a monovinyl monomer using one or more chain transfer agent, wherein said monovinyl monomer carries a curable functional group;
  • Figure 13 shows the build up of viscosity over time during the curing process in respect of a formulation of the present invention and other formulations;
  • Figures 14 to 16 show an example in accordance with the present invention where the curable functional group is an unsaturated group and curing is effected by UV;
  • Figure 17 shows the retention of gloss over time in respect of four systems, used as powder coating materials on aluminium, two of which use conventional systems and two of which use an epoxy polymer in accordance with the present invention;
  • Figure 18 shows the gloss retention, in an accelerated weathering test, of powder coatings produced from Primid formulations, and of powder coatings
  • the example structures shown in figures 1 to 12 are the result of using: - as chain transfer agent: o dodecane thiol (DDT) (figures 1 to 5, 7, 8 and 10 to 12), o dodecane thiol in combination with thiolglycerol (TG) (figure 6), o cyclohexanethiol (CHT) (figure 9) - as divinyl monomer (DVM): o ethylene glycol dimethacrylate (EGDMA) (exclusively in figures 1, 4 and 9; and in combination with other divinyl monomers in figures 3, 8, 11 and 12), o a di- aromatic ring - containing dimethacrylate (exclusively in figure 2; and in combination with other divinyl monomer in figure 3), o urethane dimethacrylate (UDMA) (exclusively in figures 5 to 7, and in combination with other divinyl monomer in figure 8), o glycerol-1,3-dimethacrylate (exclusively in figure
  • branched polymer carrying curable functional groups used in powder coating formulations
  • An example of a branched polymer carrying curable functional groups in accordance with the present invention is an epoxy polymer (“Polymer 1”) prepared by the transfer- dominated branching radical telomerisation of a divinyl monomer in the presence of an epoxy-carrying monovinyl monomer and in the presence of a chain transfer agent.
  • the divinyl monomer is urethane dimethacrylate (UDMA)
  • the monovinyl monomer is glycidyl methacrylate (GlyMA or GMA)
  • the chain transfer agent is dodecane thiol, in a ratio of 1:1:1.
  • FIG. 7 An example fragment of this epoxy polymer is illustrated in figure 5.
  • a related example (figure 7) uses methacrylic acid (MA) instead of glycidyl methacrylate.
  • Copolymerisation of UDMA with GMA (to make epoxy polymer (Polymer 1)) or MA (to make corresponding carboxyl polymer) Diurethane dimethacrylate (1 g, 2.13 mmol), 1-dodecanethiol (0.43 g, 2.13 mmol), AIBN (0.0157 g, 0.096 mmol), glycidyl methacrylate (0.32 g, 2.13mmol) or methacrylic acid (0.18 g, 2.13mmol) and ethyl acetate (17.28 mL, if using glycidyl methacrylate; or 16.09 mL, if using methacrylic acid) were added to a 50 mL round-bottomed flask and purged with nitrogen for 15 minutes.
  • Urethane acrylate resin A range of other monomers was used including commercially available multivinyl (e.g. divinyl) monomers and novel multivinyl (e.g. divinyl) monomers, some of which are shown in Figure 19.
  • IPDI isophorone diisocyanate
  • HEMA 2-hydroxyethyl methacrylate
  • IPDI dibutyltin dilaurate
  • DBTDL dibutyltin dilaurate
  • the reaction was followed by isocyanate value titration and the contents of the flask were held at 70 °C until completion.
  • the 100 ppm of methylether hydroquinone (MEHQ) was added to the reaction vessel followed by a continuous feed of HEMA (0.76 moles, 98.6 g) and the contents of the flask were raised to 80°C.
  • HEMA methylether hydroquinone
  • Urethane acrylate resin (B) Urethane acrylate resin (B) was prepared by reaction of cyclohexane dimethanol (CHDM), IPDI and HEMA. CHDM (1.37 moles, 198.1 g) was charged to a suitable reaction vessel containing butyl acetate (250 g) and the contents were heated to 70 °C, with stirring. To this, IPDI (2.06 moles, 458.0 g) was added along with 100 ppm of DBTDL. The reaction was followed by isocyanate value titration and the contents of the flask were held at 70 °C until completion.
  • CHDM cyclohexane dimethanol
  • IPDI IPDI
  • HEMA cyclohexane dimethanol
  • Isosorbide (1.37 moles, 200.0 g) was charged to a suitable reaction vessel containing butyl acetate (250 g) and the contents were heated to 70 °C, with stirring. To this, IPDI (2.05 moles, 456.4 g) was added along with 100 ppm of DBTDL. The reaction was followed by isocyanate value titration and the contents of the flask were held at 70 C until completion. 100 ppm of MEHQ was added to the reaction vessel followed by a continuous feed of HEMA (0.72 moles, 93.5 g) and the contents of the flask were raised to 80 °C.
  • Powder Coating formulations – series 1a Several powder coating formulations (formulations 1 to 6, Tables 1 and 2) were investigated. In all of these, an acid-functional polyester (Albester 5751, available from Synthomer Specialty Resins S.r.l., Italy) was used as a reactive component. In formulations 1 and 4, which are formulations in accordance with the present invention, Polymer 1 (an epoxy polymer in accordance with the present invention) was used as the other reactive component.
  • the other reactive component was hydroxyalkyl amide (HAA) (Primid XL552, available from EMS Griltech, EMS-Chemie, Switzerland) or triglycidyl isocyanurate (TGIC) (Araldite PT810, available from Huntsman Advanced Materials, Huntsman Corporation, US).
  • HAA hydroxyalkyl amide
  • TGIC triglycidyl isocyanurate
  • a curing reaction occurred by reaction between an acid functional polyester (Albester 5751) and a hardener, one of which is a branched polymer carrying a curable functional group in accordance with the present invention.
  • formulations 1, 3, 4 and 6 the reaction was between epoxy functionality (on the hardener) and acid functionality (on Albester 5751), and in formulations 2 and 5, the reaction was between hydroxy functionality (on the hardener) and acid functionality (on Albester 5751).
  • formulations 1 to 3 Table 1
  • the reactive ingredients were used at 60 % w/w. This is typical for pigmented systems. Pigments and fillers were at 40 % w/w. If moving to “stronger” pigments (than TiO 2 ) to produce colours (e.g.
  • Barium sulfate was selected as the filler, because the applications (using TGIC or HAA) were typically for outdoor use, where barium sulfate is the filler of choice.
  • calcium carbonate could be used; calcium carbonate is less suited to outdoor weather resistance.
  • Other ingredients used in this example were a flow agent, a degasser and a post- milling dry flow additive. The flow agent modifies the surface tension of the melt during curing. It provides some resistance to oil contamination of the substrate and improves flow. Flow agents are typically low molecular weight acrylates.
  • the degasser assists in removing entrapped air from the melt: it has a dual action via plasticisation of the film and a chemical mechanism for oxygen absorption.
  • Preparation of powder coating formulations The powder coating formulation ingredients (Tables 1 and 2) were dry-mixed in a (Mixaco CM6) blender and fed into a (Xtrutech) twin-screw extruder set at 100 ⁇ C, 250 rpm and 75 % torque. The extrudate was rolled flat against a chiller roller and broken into chip form (ca.1 cm mesh).
  • the resulting chip was ground in a (Retsch ZM200) impact mill to produce a powder coating composition with particle size (Malvern MasterSizer 2000) of Dv(90) ⁇ 100 microns, Dv(50) ⁇ 35 microns. Milled material was dry-blended with 0.1 % alumina dry-flow additive and sieved (104 microns, mesh 150).
  • Powder coatings were electrostatically applied to both aluminium Q-panels and Gardobond pre-treated steel panels at 106 microns thickness using a Gema Optiflex manual spray gun. Panels were stoved in an electric box oven for fifteen minutes at 200 ⁇ C to produce hard, cured coatings. Powder coating curing was additionally studied by isothermal rheometry to compare the build up of viscosity over time during the curing process. The results are shown in Figure 13. It can be seen that the slowest viscosity build is the HAA system (formulation 2), then the TGIC system (formulation 3) and the fastest is formulation 1 according to the invention. Two commercial polyesterepoxy 70:30 hybrid systems were tested for an additional comparison.
  • Formulation 1 according to the invention is considered to have a faster curing reaction and achieve higher viscosity plateau than the reference systems.
  • Properties of powder coatings Appearance of the coatings according to the invention were comparable in visual appearance to the reference coatings based on HAA and TGIC. Transparency of the clearcoat sample (formulation 4) was good, and comparable to the reference clearcoat coatings based on HAA and TGIC. Yellowing of the white coatings (due to the curing process) was assessed using a Datacolor SF600 spectrophotometer with reference to a RAL9010 standard panel as reference.
  • Formulation Formulation 4 Formulation 1 Formulation 2 Formulation 3 Clear Coat White Delamination of the white system according to the invention is comparable to the (commercially acceptable) HAA white system. It is worth noting further advantages of the present invention compared to some conventional systems, such as for example the acid (polyester) + HAA hardener system. This employs condensation esterification as the cross-linking reaction, which liberates water on curing. This water typically escapes from the film as steam. If coatings are applied too thickly the gas cannot escape, resulting in foam formation and surface defects (bubbles).
  • formulations 7 and 8 (series 1b) and 9 and 10 (series 1c). These differed from formulations 1 and 4 (in series 1a; Tables 1 and 2) in that the epoxy polymer used was not Polymer 1 but was Polymer 2 or Polymer 3.
  • Polymers 2 and 3 contain the same components as Polymer 1 (i.e. they use UDMA as divinyl monomer, DDT as chain transfer agent and GlyMA as monovinyl monomer), and the same amount of CTA relative to divinyl monomer (1:1), and differ only in the relative amount of monovinyl monomer incorporated, thereby affecting the number of epoxy groups incorporated.
  • Figure 17 shows the retention of gloss over time in respect of four systems, used as powder coating materials on aluminium: two use conventional polyester/ primid systems [Albester 6140 (HAA) and Albester 6181 (HAA)] and two use an epoxy polymer in accordance with the present invention (Polymer 3) with polyesters Albester 6140 and Albester 6181. All four perform well, i.e. retain gloss well, to the required standard. The test is an accelerated weathering test in the presence of UV irradiation at elevated temperature. In contrast, conventional polyester epoxy hybrid technology does not perform as well as systems in accordance with the present invention.
  • Figure 18 shows that, although coatings produced from Primid formulations (Albester 5250, Albester 5501 and Albester 5563) retain gloss well in an accelerated weathering test, coatings produced from formulations using a bisphenol A based epoxy resin (Albester 2662 and Albester 2230) do not. It can be seen that, even with as little as 30 wt% of conventional epoxy binder (Albester 2662), gloss retention is very poor in comparison to samples which are designed for outdoor exposure. This highlights one of the problems of conventional bisphenol A based systems, which is addressed by the present invention.
  • Formulations 11 to 16, 17 to 22 and 23 to 28 use branched epoxy polymers in which the divinyl monomers copolymerized with GlyMA are Urethane acrylate resin A, Urethane acrylate resin B and Urethane acrylate resin C respectively.
  • Formulations 11 to 13, 17 to 19 and 23 to 25 are white coatings; formulations 14 to 16, 20 to 22 and 26 to 28 are clearcoats.
  • Monomer ratios are specified in the tables.
  • the first number denotes the number of equivalents of chain transfer agent (CTA), which is DDT in the case of Urethane acrylate resin A and 4-tert-butylenzyl mercaptan in the cases of Urethane acrylate resin B and Urethane acrylate resin C.
  • CTA chain transfer agent
  • the second number denotes the number of equivalents of the novel divinyl monomer (Urethane acrylate resin A or Urethane acrylate resin B or Urethane acrylate resin C).
  • the third number denotes the number of equivalents of epoxy-functional monovinyl monomer (GlyMA).
  • the reactor was sealed with a rubber septum and the reaction medium was purged with nitrogen for 15 minutes at room temperature before stirring for 24 hours at 70 oC.
  • the reaction was left to cool to room temperature before taking a small sample for 1 H NMR analysis (in CDCl 3 ) in order to evaluate the vinyl conversion.
  • the remaining crude material was precipitated into 1 L of petroleum ether.
  • the product was collected by sedimentation and discarding the supernatant, then washed with additional petroleum ether and finally dried in a vacuum oven for 24 hours at 40 oC.
  • the product was then analysed by 1 H NMR and SEC.
  • the reactor was sealed with a rubber septum and the reaction medium was purged with nitrogen for 15 minutes at room temperature before stirring for 24 hours at 70 oC.
  • the reaction was left to cool to room temperature before taking a small sample for 1 H NMR analysis (in CDCl 3 ) in order to evaluate the vinyl conversion.
  • the remaining crude material was precipitated into 30 mL of petroleum ether.
  • the product was collected by sedimentation and discarding the supernatant, then washed with additional petroleum ether and finally dried in a vacuum oven for 24 hours at 40 oC.
  • the product was then analysed by 1 H NMR and SEC.
  • the reactor was sealed with a rubber septum and the reaction medium was purged with nitrogen for 15 minutes at room temperature before stirring for 24 hours at 70 oC.
  • the reaction was left to cool to room temperature before taking a small sample for 1 H NMR analysis (in CDCl 3 ) in order to evaluate the vinyl conversion.
  • the remaining crude material was precipitated into 30 mL of petroleum ether.
  • the product was collected by sedimentation and discarding the supernatant, then washed with additional petroleum ether and finally dried in a vacuum oven for 24 hours at 40 oC.
  • the product was then analysed by H NMR and SEC.
  • formulations 30 and 33 use TGIC, and can be compared with formulations 3 and 6; again they differ from conventional coatings in that the novel curable branched polymers of present invention replace the polyester component of the commercial coating, not the small molecule hardener component.
  • S i – i i f i l l 4 invention ( Figure 4) Acid polymer 88.58% 86.63% 82.48% according to the Powder Coating formulations – series 4 – using hydroxy-functional branched polymers
  • Formulations 35 to 40 use branched polymers which are hydroxy functional.
  • Figure 14 shows a hydroxy-functionalized branched polymer containing residues of ethyleneglycol dimethacrylate (EGDMA) as divinyl monomer, hydroxyethyl methacrylate (HEMA) as hydroxy-carrying monovinyl monomer and dodecanethiol (DDT) as chain transfer agent (CTA).
  • EGDMA ethyleneglycol dimethacrylate
  • HEMA hydroxyethyl methacrylate
  • DDT dodecanethiol
  • cinnamoyl chloride also shown in Figure 14
  • cinnamyl- carrying branched polymer shown in Figure 15
  • the cinnamyl-carrying branched polymer may then be UV-cured, reaction occurring via the double bonds.
  • Evidence of the incorporation of cinnamyl groups was provided by 1 H NMR.
  • Figure 16 shows a 1 H NMR overlay of the branched polymer before (upper) and after (upper) reaction with cinnamoyl chloride.
  • the reaction was left to cool to room temperature before taking a small sample for 1 H NMR analysis (in CDCl 3 ) in order to evaluate the vinyl conversion.
  • the crude reaction material was then split in half to allow direct comparison of the final polymers. (1) One half of the crude material was precipitated into 500 mL of petroleum ether where it was collected by settling the solids and discarding the supernatant. The polymer was washed with additional petroleum ether and then dried in a vacuum oven for 24 hours at 40 oC.

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Abstract

Une composition de revêtement en poudre comprend un polymère qui est un polymère vinylique ramifié préparé par télomérisation radicalaire à ramification dominée par transfert (TBRT) de monomère(s) multivinylique(s) et éventuellement de monomère(s) monovinylique(s) en présence d'agent(s) de transfert de chaîne, et ledit polymère comprenant un ou plusieurs groupes fonctionnels durcissables. Ledit groupe fonctionnel durcissable peut par exemple comprendre un groupe époxy.
PCT/GB2023/051399 2022-05-31 2023-05-26 Matériaux de revêtement en poudre WO2023233133A1 (fr)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1630186A1 (fr) * 2003-05-29 2006-03-01 Kaneka Corporation Composition de durcissement
WO2018197884A1 (fr) 2017-04-26 2018-11-01 The University Of Liverpool Polymères
WO2018197885A1 (fr) 2017-04-26 2018-11-01 The University Of Liverpool Polymères ramifiés
WO2020089649A1 (fr) 2018-10-31 2020-05-07 The University Of Liverpool Polymères ramifiés

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1630186A1 (fr) * 2003-05-29 2006-03-01 Kaneka Corporation Composition de durcissement
WO2018197884A1 (fr) 2017-04-26 2018-11-01 The University Of Liverpool Polymères
WO2018197885A1 (fr) 2017-04-26 2018-11-01 The University Of Liverpool Polymères ramifiés
WO2020089649A1 (fr) 2018-10-31 2020-05-07 The University Of Liverpool Polymères ramifiés

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
S. R. CASSINP. CHAMBONS. P. RANNARD, POLYM. CHEM, vol. 11, 2020, pages 7637 - 7649

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