BACKGROUND OF THE INVENTION

[0001] The present disclosure relates to a composition.

[0002] The present invention concerns compositions which, in particular but not exclusively, have improved thixotropic properties. More particularly, but not exclusively, this invention concerns a composition which can be cured to form a thermoset composition.

[0003] Fire retardant materials are well-known to those skilled in the art. Such materials include aluminium hydroxide (often known as aluminium trihydroxide or “ATH”), magnesium hydroxide, ammonium polyphosphate (“APP”), zinc hydroxystannate (“ZHS”) and triethylphosphate (“TEP”). Such materials are incorporated into, and distributed in, a carrier (typically a polymer carrier, such as PVC, polyester or ethylene vinyl acetate polymer) to provide fire retardant properties to the carrier. If the fire retardant materials are not distributed evenly in the carrier, the flame resistance performance of the carrier will be deleteriously affected. If the fire retardant material is not suitably dispersed (for example,“clumps” are formed), then one or more of the properties of the resultant material may be adversely affected (such as uniformity of the resultant material). In this connection, it is known to coat particles of ATH with a polybutadiene to facilitate dispersion of the ATH particles in an ethylene vinyl acetate polymer. Fumed silica is often added to uncured polyesters as a thickening agent and use of such fumed silica is undesirable because fumed silica may present health and safety complications.

[0004] The present invention seeks to mitigate the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved a material having the ability to alter the thixotropic properties of a material that includes particulate material, such as a fire resistant polymer composition and/or an improved unsaturated polyester composition. SUMMARY OF THE INVENTION

[0005] The present invention provides a composition comprising a functionalised unsaturated polymer, an unsaturated polyester and particles of material

[0006] It has been found that blending particles of material, such as particles of fire retardant material, with a functionalised unsaturated polymer can provide an increased viscosity, and/or enhanced thixotropic properties, for example, of an unsaturated polyester into which the particles and functionalised unsaturated polymer are dispersed. Such an increase may be desirable (for example, it may make handling more easy) and may remove or reduce the need to add thickeners (such as firmed silica) to the unsaturated polyester. The composition of the first aspect of the present invention is substantially free of silica except those at low amounts, for example, less than 1.0wt%, optionally no more than 0.8wt%, optionally no more than 0.6wt%, optionally no more than 0.4wt% and optionally no more than 0.2wt%, based on the weight of the unsaturated polyester. The composition may be a substantially silica-free composition.

[0007] The composition may comprise particles of a fire retardant material such as ATH. The particles of material, optionally fire retardant material, may be coated with the functionalised unsaturated polymer. The coating may comprise or consist of the functionalised unsaturated polymer. The composition may therefore comprise coated particles admixed with the unsaturated polyester. Such a composition may be formed, for example, by coating particles, such as fire retardant material with the functionalised unsaturated polymer, and then admixing the coated particles with the unsaturated polyester. Examples of such a composition have been found to be particularly effective.

[0008] The particles of fire retardant material may comprise an inorganic material or a mixture of inorganic materials. The particles of fire retardant material may comprise one or more metal salts. The particles of fire retardant material may comprise one or more of a hydrate, an oxide, a hydroxide, a stannate, a carbonate, a sulphate, a phosphate, a pyrophosphate, or a polyphosphate, optionally as one or more metal salt. Examples of fire retardant materials include one or more of antimony trioxide, zinc stannate, magnesium hydroxide, magnesium sulphate, aluminium hydroxide and in particular aluminium trihydroxide (ATH), zinc sulphate, zinc hydroxystannate, ammonium polyphosphate and triethyl phosphate, or mixtures thereof. The particles of fire retardant material may comprise one or more of magnesium hydroxide and aluminium hydroxide.

[0009] For the avoidance of doubt, the particles of fire retardant material may comprise more than one component. For example, the particles of fire retardant material may comprise a first component (such as ATH) and a second component (such as magnesium hydroxide).

[0010] The size of the particles, for example, particles of fire retardant material, may be determined using D50 measurements (D50 indicating the size of the particle [nominally a diameter] that 50% of a sample’s mass is smaller than). D50 is often considered to represent average particle size. D50 may be no more than lOOmicrons, optionally no more than 80microns, optionally no more than 60microns, optionally no more than 40microns, optionally no more than 20microns, optionally no more than lOmicrons and optionally no more than 5.0microns. D50 may be at least 0.5microns and at least LOmicrons.

[0011] For the avoidance of doubt, the unsaturated polyester comprises at least one C=C bond.

[0012] The unsaturated polyester is optionally a polyester capable of forming a thermoset material when subject to suitable curing conditions. Therefore, the composition may comprise one or more curing promoters. The composition may comprise a reactive monomer, such as styrene or methyl methacrylate. The composition may comprise up to 50wt% reactive monomer, optionally up to 40wt%, optionally up to 30wt%, optionally up to 20wt%, optionally up to 15wt% and optionally up to 10wt%based on the weight of the unsaturated polyester. The composition may comprise from 2wt%, optionally from 5wt% and optionally from 10wt%, based on the weight of the unsaturated polyester. The composition may comprise from 2wt% to 20wt% and optionally from 5wt% to 15wt%, based on the weight of the unsaturated polyester. The reactive monomer may act as a solvent. [0013] The nature of the unsaturated polyester is not particularly limited. For example, the unsaturated polyester may be a phthalic polyester, in which case the unsaturated polyester may comprise one or both of isophthalic and orthophthalic groups. Additionally, the unsaturated polyester may comprise dicyclopentadiene, methyl methacrylate or neo-pentyl glycol groups.

[0014] The unsaturated polyester may be thixotropic i.e. it shows thixotropic properties i.e. it shear-thins, becoming less viscous at higher shear speeds. The unsaturated polyester may have a viscosity of no more than lOPa.s, optionally no more than 5.0Pa.s, optionally no more than 3.0Pa.s, optionally no more than 2.0Pa.s and optionally no more than l.OPa.s. Such viscosities are typically measured at 25 °C, using a Brookfield viscometer, spindle no. 2 at 20rpm.

[0015] The unsaturated polyester may comprise functional groups such as epoxy groups e.g. bisphenol A epoxy groups.

[0016] The composition may comprise more than one such unsaturated polyester.

[0017] For the avoidance of doubt, the functionalised unsaturated polymer comprises at least one C=C bond.

[0018] The functionalised unsaturated polymer may be liquid in the absence of a solvent at a low temperature, optionally no more than 90°C, optionally no more than 80°C, optionally no more than 50°C, optionally no more than 25°C, and optionally at no more than 20°C. A suitable polymer which demonstrates this characteristic is liquid polybutadiene (LPBD) or liquid polyisoprene (LPI). Such polymers may be used to coat the particles at or close to ambient temperature (such as 20°C or 25°C), without the need to melt the polymer component in order to make it flow as a liquid. Such liquid polymers have been found to be effective at forming a particulate composition in accordance with the present invention. Such particulates are sometimes known as a Dry Liquid Compound or Concentrate (DLC) or a Powder Liquid Compound or Concentrate (PLC).

[0019] The viscosity of the functionalised unsaturated polymer may be at least 0.5Pa.s, and optionally at least 1.5Pa.s, measured at 25 °C, typically using a C60/1 cone on a rheometer, optionally on a Haake Rheostress viscometer.. The viscosity of the functionalised unsaturated polymer may be no more than 500Pa.s, optionally no more than 400Pa.s, optionally no more than 300Pa.s, optionally no more than 200Pa.s, optionally no more than lOOPa.s, optionally no more than 50Pa.s, optionally no more than 25Pa.s and optionally no more than lOPa.s. The viscosity of the functionalised unsaturated polymer may be from 0.5Pa.s to lOPa.s and optionally from l.OPa.s to 8Pa.s.

[0020] The composition of the present invention has the further advantage that a fine, dusty fire retardant material may be rendered non-dusty by being blended with the functionalised unsaturated polymer.

[0021] The functionalised unsaturated polymer may be obtained by, but not limited to, living anionic polymerisation, for example through the action of sec-butyl lithium or n- butyl lithium on a diene monomer. Optionally other polymerisation techniques may be employed, for example, free radical, controlled radical and cationic initiation.

[0022] Furthermore, the functionalised unsaturated polymer may be essentially a linear polymer, or a mixture of one or more linear polymers and one or more branched or hyperbranched polymers, a branched or hyperbranched polymer or a star polymer. A branched or hyperbranched polymer may be provided with branch points located along the polymer chain. Branched and hyperbranched polymers may have a lower viscosity than a corresponding linear polymer of the same molecular weight. Those skilled in the state of the art will realise that such branching may be introduced into the polymer chain through the use of suitable multi-functional monomers, optionally in the presence of a suitable chain transfer agent, or the branch points may be introduced through the use of so-called coupling agents such as multi-halogenated carbon or silicon either during the polymerisation, or as part of the termination step of said polymerisation, as may be the case in the manufacture of so-called star-branched polymers. Additionally, or alternatively the branching may be introduced through the use of a suitable monomer unit, such as an ethylinically unsaturated compound possessing a terminal halogen group. Alternatively, the functionalised unsaturated polymer may be a hyperbranched polymer (methods for the production of a hyperbranched polymer can be found in WO2015145175, which is incorporated herein by reference, particularly in relation to the methods for the synthesis of such hyperbranched polymers), or it may be a mixture of branched polymers, or a mixture of a branched polymer and a linear polymer etc. [0023] Examples of functionalised unsaturated polymers include synthetic or natural diene polymers and copolymers comprising 1,4-polymerisation products and optionally 1,2-polymerisation products, and optionally polymer having vinylic side groups, which may, or may not be cyclic in nature.

[0024] The number average molecular weight (Mn) of the functionalised unsaturated polymer may be no more than 100,000 Da, optionally no more than 90,000Da, optionally no more than 80,000Da, optionally no more than 70,000Da, optionally no more than 60,000Da, optionally no more than 50,000Da, optionally no more than 40,000Da, optionally no more than 30,000Da, optionally no more than 20,000Da, optionally no more than 10,000Da, optionally no more than 8,000 and optionally no more than 6,000Da.

[0025] The number average molecular weight (Mn) of the functionalised unsaturated polymer may be at least 500Da, optionally at least lOOODa and optionally at least 1500Da. Where a higher temperature blending process may be tolerated, then a higher molecular weight may be used.

[0026] The number average molecular weight (Mn) of the functionalised unsaturated polymer may be from 500 to 10,000Da and optionally from 1,000 to 8,000Da.

[0027] The composition may comprise more than one functionalised unsaturated polymer. Suitable dienes for use in the preparation of a functionalised unsaturated polymer for use in the compositions of this invention are suitably-functionalised butadiene, isoprene and, or chloroprene. Suitable monomers used to make such polymers may include more than one carbon-carbon double bond, but once one of the bonds has undergone an addition reaction other carbon-carbon double bonds will not i.e. the monomer is monofunctional. Examples of such monofunctional monomers optionally comprise two or more conjugated C=C groups, such as 1, 3 -butadiene , isoprene, 2, 3- dimethyl- 1 , 3 -butadiene , 2-chloro-l, 3 -butadiene, 1,3- pentadiene, and 1, 3-hexadiene, 2 , 4-hexadiene , 1, 3-octadiene, 2-methyl-l, 3-pentadiene, 2 , 3-dimethyl-l, 3-pentadiene , 3,4- dimethyl-1 , 3-hexadiene, 2, 3-diethyl-l, 3-butadiene , 4,5- diethyl-1, 3-octadiene, 3- butyl-1, 3-octadiene, 3, 7-dimethyl-l, 3, 6-octatriene, 2-methyl-6-methylene-l, 7- octadiene, 7- Methyl-3 -methylene-1, 6-octadiene, 1 , 3, 7-octatriene , 2-ethyl-l, 3- butadiene, 2-amyl-l, 3 -butadiene, a: 3, 7-dimethyl-l, 3, 7- octatriene, b: 3, 7-dimethyl-l, 3, 6-octatriene, 3,7,11 - trimethyl-1, 3, 6, 10-dodecatetraene , 7, ll-dimethyl-3- methylene- 1, 6, 10-dodecatriene , 2, 6-Dimethyl-2,4,6- octatriene, 2-phenyl-l, 3-butadiene and 2- methyl-3 -isopropyl- 1, 3 -butadiene and 1, 3 -cyclohexadiene.

[0028] The functionalised unsaturated polymer may be terminated by a hydrogen, and optionally may contain hydroxyl, carboxyl, amine or the like functional group as the at least one end group on the molecule.

[0029] The functionalised unsaturated polymer may be a copolymer of a diene with at least one mono-ethylenically unsaturated monomer. Such monomers are, for example, styrene, vinyl toluene, 2- methylstyrene, alkyl (Ci to Cs) esters of acrylic acid, alkyl (Ci to Cs) esters of methacrylic acid, acrylonitrile, methacrylonitrile, and mono-olefins having 2 to 8 carbon atoms. The functionalised unsaturated polymer may comprise a copolymer of a diene and an alkene nitrile, such as propene nitrile. The copolymer may comprise more than 10 percent by weight, preferably more than 40% by weight, preferably more than 80% by weight, and more preferably more than 90% by weight of the polymer. The composition may comprise a copolymer of a diene and at least one monoethylenically unsaturated monomer, and a second polymer. Suitable comonomers for production of said polymers are listed in WO2015145175 (Al) and incorporated herein by reference. The resultant copolymer may be a block copolymer such as an AB diblock copolymer, an ABC triblock copolymer, an ABA or a BAB block copolymer; where A and B refer to the diene monomer and the unsaturated second monomer respectively. The unsaturated second monomer, C, may be a diene monomer different from the first diene monomer.

[0030] The functionalised unsaturated polymer comprises one or more functional groups. The functional group is for facilitating attachment of the polymer to the surface of the particles. Optionally, the functionalised unsaturated polymer may comprise an average of up to 5.0, optionally up to 3.0, optionally up to 2.0, optionally from 0.5-2.0 (and optionally an average of 0.8 to 1.5) of said functional groups per polymer molecule, for example, based on molecular weight Mn. The functional group may comprise carboxylic acid, anhydride or oxirane (epoxy), amine or acid chloride groups which may be introduced into the polymer by known techniques. A particularly favoured route is through a maleinisation reaction across the residual double bonds in a polymer or copolymer as disclosed in US3778418, and US3887527 for example. The teaching of US3778418 and US3887527 is incorporated herein by reference, particularly in so far as it related to maleinisation. Alternatively, or additionally, an adducted maleic group may comprise a half ester, formed by an esterification reaction with for example, methanol, ethanol, propanol, butanol, 2-ethylhexanol, or ethylinically unsaturated alcohols such as 2-hydroxyethyl (meth)acrylate etc. Those skilled in the art will realise that the precise nature and identity of the functional group will change when the functional group reacts with the surface of the particle. For example, it is thought that a maleic anhydride group will react with -OH groups on the surface of ATH to produce an ester linkage.

[0031] Optionally an oxirane (epoxy) group may be incorporated in to the functionalised unsaturated polymer, for example as disclosed in P.B. Latha, K. Adhinarayanan and R. Ramaswamy, Int. J. Adhesion and Adhesives, Vol 14, No. l, Jan 1994.

[0032] In these cases, the extent of functionalisation will depend on the number of sites (e.g. double bonds) which can readily be functionalised or, for example, in the case of copolymerisation, it will also be dependent upon the proportion of the diene component.

[0033] The extent of the thus incorporated functionalisation may be varied depending on the type of polymer, and may range from 1% to 75%, more probably from 1% to 50%, more probably 1 to 25%, preferably the extent of functionalisation is from 1 to 15% by weight, defined as the weight of the functionalising species (such as maleic anhydride) in grams per lOOgrams of the polymer being adducted.

[0034] Alternatively, or additionally an unsaturated group capable of polymerisation by any of free radical, controlled radical, anionic or cationic polymerisation may be introduced on to the polymer chain of the functionalised unsaturated polymer. For example, it is well known in the state of the art that a (meth)acrylate moiety may be introduced as a terminal functionality on to the optionally more than one chain end of the polymer. Such a modification may be introduced through the reaction of a suitable termination group on the polymer, such as a hydroxyl group with an acid, an anhydride or an acyl chloride for example. [0035] The w/w ratio of particles such as fire retardant particles to unsaturated polyester may be from 0.3: 1 to 10:1, optionally from 0.5: 1 to 8:1 and optionally from 1 :1 to 4:1. The w/w ratio of particles e.g. fire retardant parti cl esto the functionalised unsaturated polymer may be from 2:1 to 100:1 , optionally from 2:1 to 50:1, optionally from 2:1 to 25:1 , optionally from 4:1 to 25: 1 and optionally from 5:1 to 20:1. The w/w ratio of unsaturated polyester to the functionalised unsaturated polymer may be from 2:1 to 100: 1, optionally from 2:1 to 50:1, optionally from 2:1 to 25:1, optionally from 4:1 to 25:1 and optionally from 5:1 to 20:1.

[0036] The particles of material may be particles of aluminium hydroxide and/or magnesium hydroxide, and the functionalised unsaturated polymer may be a functionalised polybutadiene. The composition therefore optionally comprises one or both of aluminium hydroxide and magnesium hydroxide, a functionalised polybutadiene and an unsaturated polyester, optionally aluminium hydroxide, a functionalised polybutadiene and an unsaturated polyester.

[0037] The functionalised polybutadiene is optionally adducted with maleic anhydride, optionally with an average of up to 2.0 (and optionally up to 1.5) maleic anhydride groups per polymer molecule, based on the Mn of the polymer.

[0038] The particles of aluminium hydroxide and/or magnesium hydroxide are preferably coated with the functionalised polybutadiene.

[0039] The w/w ratio of the aluminium hydroxide and/or magnesium hydroxide to the unsaturated polyester is optionally from 0.5:1 to 2:1. The w/w ratio of the aluminium hydroxide and/or magnesium hydroxide to the functionalised polybutadiene is optionally from 30:1 to 3:1. The w/w ratio of the unsaturated polyester to the functionalised polybutadiene is optionally from 30: 1 to 3: 1.

[0040] According to a second aspect of the invention there is also provided a method of making a composition, the method comprising bringing an unsaturated polyester into contact with a functionalised unsaturated polymer in the presence of particles of material.

[0041] The particles of material may comprise particles of fire retardant material.

[0042] The method may comprise bringing the particles of material (optionally particles of fire retardant material) and the functionalised unsaturated polymer into contact with one another thereby forming coated particles, and contacting said coated particles with the unsaturated polyester.

[0043] The method may comprise bringing the functionalised unsaturated polymer and the unsaturated polyester into contact with one another to form a polymer blend and then contacting said blend with particles of material, such as particles of fire retardant material.

[0044] The method may comprise adding the functionalised unsaturated polymer, the unsaturated polyester and the particles of material (optionally particles of fire retardant material) and mixing the same.

[0045] The method of the second aspect of the present invention may be performed at any suitable temperature, but may be performed at no more than 35°C, optionally at no more than 30°C and optionally no more than 25°C.

[0046] The method of the second aspect of the present invention may be used to make a composition in accordance with the first aspect of the present invention. Accordingly, the features mentioned above in relation to the first aspect of the present invention may be incorporated into the method of the second aspect of the present invention. If particles of fire retardant material are present, then it is sometimes preferred to coat the fire retardant particles with functionalised unsaturated polymer to form coated particles, and then contact said coated particles with the unsaturated polyester.

[0047] The method of the second aspect of the present invention may incorporate those features described above in relation to the composition of the first aspect of the present invention.

[0048] According to a third aspect of the invention there is provided a composition made using the method of the second aspect of the present invention.

[0049] According to a fourth aspect of the invention there is provided a thermoset composition comprising a functionalised unsaturated polymer, a polyester and particles of material, such as particles of fire retardant material.

[0050] The thermoset composition is optionally a fire-retardant composition. The particles may be coated with functionalised unsaturated polymer. This may be preferred, for example, if the particles are particles of fire retardant material. [0051] The particles used may have the features of the particles described above in relation to the composition of the first aspect of the present invention. The functional unsaturated polymer may have the features described above in relation to the composition of the first aspect of the present invention. The polyester of the thermoset composition of the third aspect of the present invention may be based on the unsaturated polyester of the first aspect of the present invention, with the unsaturated polyester having reacted to form the polyester of the thermoset composition of the third aspect of the present invention.

[0052] According to a fifth aspect of the invention, there is provided a method of making a thermoset composition comprising curing a composition comprising a functionalised unsaturated polymer, an unsaturated polyester and particles of material.

[0053] Those skilled in the art will realise that such curing will typically provide a cross- linked polyester. The composition which is subjected to curing may comprise a composition in accordance with the first aspect of the present invention. The particles of material may be particles of fire retardant material. The functionalised unsaturated polymer, unsaturated polyester and particles may have the features described above in relation to the composition of the first aspect of the present invention.

[0054] The composition may be made using a method in accordance with the second aspect of the present invention.

[0055] According to a sixth aspect of the present invention, there is provided a use of a functionalised unsaturated polymer for facilitating dispersion of particles of material, optionally particles of fire retardant material, in an unsaturated polyester.

[0056] Those skilled in the art will realise that the functionalised unsaturated polymer, the particles and unsaturated polyester may have the features described above in relation to the composition of the first aspect of the present invention.

[0057] The use may comprise coating the particles with the functionalised unsaturated polymer, thereby forming coated particles. The use may comprise contacting the coated particles and the unsaturated polyester together.

[0058] The use may be further defined by the amounts of particles, functionalised unsaturated polymer and unsaturated polyester. Such amounts are described above in relation to the composition of the first aspect of the present invention. [0059] According to a seventh aspect of the present invention, there is provided a use of a functionalised unsaturated polymer for enhancing the thixotropic properties of an unsaturated polyester.

[0060] Those skilled in the art will realise that“enhancing” indicates an increase in the thixotropic index of the unsaturated polyester when the coating polymer is provided. The unsaturated polyester may or may not have thixotropic properties without coating polymer.

[0061] The use of the seventh aspect of the present invention may be use of a functionalised unsaturated polymer for enhancing the thixotropic properties of an unsaturated polyester, optionally in the presence of particles of material, optionally fire retardant material.

[0062] Those skilled in the art will realise that the functionalised unsaturated polymer, particles (if present) and unsaturated polyester may have the features described above in relation to the composition of the first aspect of the present invention.

[0063] The use may comprise coating the particles (if present) with the functionalised unsaturated polymer, thereby forming coated particles. The use may comprise contacting the coated particles and the unsaturated polymer together.

[0064] The use may be further defined by the amounts of particles (if present), functionalised unsaturated polymer and unsaturated polyester. Such amounts are described above in relation to the composition of the first aspect of the present invention.

[0065] The use may also comprise use of a functionalised unsaturated polymer for increasing viscosity, as well as for enhancing thixotropic properties. It is been found that the functionalised unsaturated polymer may increase the viscosity of the composition compared to when said polymer is not used.

[0066] For the uses of the sixth and seventh aspects of the present invention, an unsaturated polymer functionalised with one or more maleic anhydride groups is preferred, particularly with particles of material (particularly particles of fire retardant material) which have reactive OH groups on their surface, such as ATH and/or magnesium oxide. The unsaturated polymer may comprise a polymer of butadiene, isoprene and/or chloroprene, optionally a copolymer of butadiene, isoprene and/or chloroprene.

[0067] In accordance with an eighth aspect of the present invention, there is provided use of a composition in accordance with the first aspect of the present invention to enhance thixotropic properties.

[0068] In accordance with a ninth aspect of the present invention, there is provided a particulate composition comprising particles (optionally particles of a fire retardant material) coated with a functionalised unsaturated polymer.

[0069] The composition is a particulate (as opposed to particles distributed in carrier medium). The particles may be as described above in relation to the composition of the first aspect of the present invention. The functionalised unsaturated polymer may be as described above in relation to the composition of the first aspect of the present invention. In particular, the functionalised unsaturated polymer may be a polymer derived from butadiene monomers.

[0070] It will of course be appreciated that features described in relation to one aspect of the present invention may be incorporated into other aspects of the present invention. For example, the method of the invention may incorporate any of the features described with reference to the apparatus of the invention and vice versa.

[0071] Embodiments of the present invention will now be described by way of example only with reference to Figure 1.

DESCRIPTION OF DRAWINGS

[0072] Figure 1 shows the viscosity of an example of a composition in accordance with the present invention as a function of shear rate.

DETAILED DESCRIPTION

[0073] The effect of a quantity of maleinised polybutadiene on the properties of dispersions of ATH in various unsaturated polyesters was investigated. The maleinised polybutadiene used was Lithene® Ultra PM4-7.5MA (“PM4-7.5MA”), Synthomer (UK) Limited, Harlow, UK. PM4-7.5MA is liquid polybutadiene, adducted with 7.5 parts maleic anhydride, and has a viscosity of 20-60dPa.s at 25°C and Mn of about 1600. ATH was Huber Martinswerk, provided by Omya. Synolite polyesters were provided by Aliancys. Polipol polyesters were provided by Poliya. AOC polyesters were provided by AOC Aliancys. Intermediate and ULVA polyesters were provided by Biifa GmbH & Co. The general purpose polyester was provided by East Coast Resins. Crystic resins were provided by Scott Bader. Sarzyna polyesters were provided by Ciech. Polynt polyesters were provided by Polynt. All materials were used as supplied, without further treatment or purification.

[0074] Examples of compositions in accordance with the present invention were prepared in one of two ways, using Method A or Method B. The examples made using Method A are denoted Example A in Table 1 below. The examples made using Method B are denoted Example B in Table 1 below. In Example A, the PM4-7.5MA was mixed with the respective polyester denoted in the Example No. in Table 1 and ATH i.e. the three components were mixed together at the same time. In Example B, the ATH was mixed with the PM4-7.5MA, and then added to the respective polyester denoted in the Example No. in Table 1. For the compositions of Examples A and B, 100 parts ATH, 100 parts polyester and 5 parts PM4-7.5MA were used. In the Comparative Example, 100 parts ATH is mixed into 100 parts of the respective polyester, there being no PM4-7.5MA present.

[0075] The viscosity properties of each respective composition was determined at 2/s using a Haake Rheostress 600 viscometer with a C60/1 cone at 25 °C. The thixotropic index, denoted T in Table 1 below, is the ratio between the viscosity measured at 0.5/s and at 5.0/s.

Table 1 - viscosity properties of compositions

[0076] In Table 1 above, DCPD indicates a polyester comprising dicyclopentadiene, MMA is methyl methacrylate, “Iso” indicates isophthalic groups, NPG is neo-pentyl glycol and MA indicates methyl acrylate.

[0077] The examples of Table 1 demonstrate that addition of the PM4-7.5MA increases viscosity of the composition, but also increases the thixotropic index. This increase in thixotropic index facilitates easier handling/more effective mixing of the compositions.

[0078] Examples of further compositions were made in accordance with Method B mentioned above but using a greater amount of PM4-7.5MA. The ATH was mixed with the PM4-7.5MA, and then added to the respective polyester denoted m the Example No. in Table 2, with 100 parts ATH, 100 parts polyester and 20 parts PM4-7.5MA being used.

Table 2 - examples of compositions

[0079] As for the Examples of Table 1, Examples 7 to 15 of Table 2 demonstrate that addition of the PM4-7.5MA increases viscosity as 2/s, while also increasing thixotropic index T which was calculated from measurements taken at 0.5/s and 5.0/s.

[0080] The Examples also demonstrate that the PM4-7.5MA polymer acts to increase the viscosity of the composition relative to the composition without the PM4-7.5MA at low shear rates and/or enhance the thixotropic properties of the polyester. An increase in viscosity at low shear rates is desirable, especially in conjunction with enhanced thixotropic properties. In this connection, increased viscosity at low shear rates means that the composition may be easier to handle, less prone to dripping or running once it has been deposited. Enhanced thixotropic properties mean that the composition may be easier to apply or work with, becoming less viscous as it is sheared more quickly. Furthermore the PM4-7.5MA facilitates dispersion of the ATH particles in the polyester. Without wishing to be bound by theory, an explanation is proposed for the observation that the PM4-7.5MA disperses the ATH particles, but also increases viscosity. PM4-7.5MA comprises, on average, about 1 maleic anhydride group per polymer molecule. It is thought that one attachment point facilitates the attachment of the PM4-7.5MA to the ATH particles, and the polymer extends away from the ATH particle from said attachment point. The coating of the ATH particles produces a“hairy ball” which interacts more strongly with the unsaturated polyester than if the PM4-7.5MA was not present. It is believed that such an interaction may be easily broken by shearing, possibly explaining the thixotropic effect seen in the Examples.

[0081] The interaction between the ATH and the PM4-7.5MA was studied by IR spectroscopy. The peak at about 1800cm ¹ which is observed in the spectrum of PM4- 7.5MA and which is associated with the maleic anhydride group is not observed when the PM4-7.5MA is coated onto ATH particles. This indicates that the maleic anhydride group does not exist (or at the very least is significantly reduced in number) when the PM4- 7.5MA is coated onto the ATH. The presence of a peak at about 1720cm ¹ indicates the presence of an acid and/or ester group, indicating that the maleic anhydride group has been opened, most likely by reacting with the OH groups of the ATH.

[0082] Figure 1 shows how the viscosity of the composition of Example 14 varies with shear rate. This shows how the composition of Example 14 has good thixotropic properties, and how the incorporation of the PM4-7.5MA increases the viscosity at low shear rates compared to the control labelled ATH which is in the absence of PM4-7.5MA.

[0083] The applicant has demonstrated that compositions in accordance with the present invention can be made using a wide variety of unsaturated polyesters. The compositions of the Examples can easily be formed into thermoset polymer compositions by curing the compositions of the Examples using methods well known to those skilled in the art. In this connection, compositions of Example 1A, IB, 2A, 2B, 3 A and 3B were cured, and the hardness and flexural modulus studied. A noticeable decrease in hardness and flexural modulus were observed compared to the control, indicating that the PM4-7.5MA increases flexibility of the cured polyester. [0084] Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. By way of example only, certain possible variations will now be described.

[0085] The examples above illustrate the use of ATH particles. Those skilled in the art will realise that other particles may be used, for example, one or more of magnesium hydroxide, antimony trioxide, zinc stannate, magnesium sulphate, zinc sulphate, zinc hydroxystannate, ammonium polyphosphate and triethyl phosphate, or mixtures thereof. For example, a mixture of ATH and magnesium hydroxide may be used.

[0086] The examples above illustrate the use of polybutadienes. Those skilled in the art will realise that other polymers may be used. For example, polyisoprene and/or chloroisoprene may be used.

[0087] Without wishing to be bound by theory, it is believed that the -OH groups on the ATH react with the maleic anhydride groups of the maleinised LPBD - those skilled in the art will realise that other functionalised polymers may be used, and those skilled in the art will realise that the nature of the functional group will optionally depend on the nature of the corresponding functional groups present on the surface of the particle.

[0088] Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.