Homogeneous catalysts are used in many chemical processes, such as in esterifications for example. In particular esterifications based on transition metal catalysts such as Ti or Zn compounds are well known. One example is the use of titanium compounds, particularly titanium alkoxide for the manufacture of dioctyl phthalate and similar materials which are commercially important as plasticisers. However, the use of homogeneous catalysts makes separation of the catalyst from the reaction or product mixture difficult so that it is usual for the catalyst to remain within the product mixture. The use of heterogeneous catalysts overcomes this problem because the catalyst, being in a different phase from the reaction mixture may be separated therefrom by physical separation methods such as filtration.

When the catalyst can be separated from the reaction mixture, it may be re-used, sometimes after treatment or reactivation, bringing economic and environmental benefits.

Also when a catalyst remains within a reaction mixture it may promote further reaction to breakdown the desired product or to form undesirable side-products within the product mixture.

It is therefore desirable to provide a heterogeneous catalyst or a method of anchoring a homogeneous catalyst to a support to overcome the known disadvantages of homogeneous catalysis or the benefits of heterogeneous catalysis. It is an object of the present invention to provide such a heterogeneous catalyst and method. Some metal- containing catalysts based upon phosphonate-functionalised polyorganosiloxane are disclosed in WO-A-02055587.

According to the invention we provide a catalyst composition comprising the reaction product of (i) a phosphonate-functionalised polyorganosiloxane containing at least one P-OR group, where R is hydrogen, an alkyl, cycloalkyl, aryl or alkyl-aryl radical which may be substituted with hydrocarbyl or non-hydrocarbyl substituents or an optionally complexed metal ion, and (ii) a compound of a metal selected from the group consisting of titanium, zinc, tin, magnesium, germanium, zirconium, aluminium, hafnium, an alkali metal, alkaline earth metal, rhodium, palladium, platinum, gold and silver.

Preferably the metal is titanium, zirconium, aluminium, hafnium, rhodium, platinum, silver or gold. Optionally a further metal compound may be included. The further metal compound

may be selected from a compound of cobalt, copper, cerium, nickel, chromium or vanadium. The metal compound is not exclusively a compound of cobalt, copper, cerium, nickel, chromium or vanadium.

The metal compound may be a salt, alkoxide, oxo-alkoxide or halo-alkoxide of the metal.

Suitable metal salts include nitrates, sulphates, halides and salts of organic acids such as metal acetates, oxalates, citrates, lactates, stearates etc. Preferred metal salts include zinc acetate, magnesium acetate, tin halides, tin stearate, titanium tetrachloride. The alkoxide have the formula M (OR1) n where M is the metal, R1 is an alkyl group and n is the valency of the metal. Preferably, R'contains 1 to 10 carbon atoms and particularly suitable alkoxide include tetraisopropoxy titanium, tetra-n-butoxy titanium, tetra-n-propoxy zirconium and tetra-n-butoxy zirconium and tin octoate.

Condensed alkoxide (oxo-alkoxides) suitable for preparing the organometallic compounds used in this invention are typically prepared by careful hydrolysis of titanium or zirconium alkoxide. Titanium or zirconium condensed alkoxide are frequently represented by the formula a [M (O R') 20] R1 in which R1 represents an alkyl group and M represents titanium or zirconium. Preferably, n is less than 20 and more preferably is less than 10.

Preferably, R contains 1 to 12 carbon atoms, more preferably, R'contains 1 to 6 carbon atoms and useful condensed orthoesters include the compounds known as polybutyl titanate, polyisopropyl titanate and polybutyl zirconate.

By phosphonate-functionalised polyorganosiloxane containing at least one P-OR group, we mean a polysiloxane molecule containing a [POS]-CR22-PO (OR) (X) group, where X may be OH, H, OR, R or OM where M is a metal ion, R is a hydrogen atom, an alkyl, cycloalkyl, aryl or alkyl-aryl radical which may be substituted with hydrocarbyl or non-hydrocarbyl substituents, or an, optionally complexed, metal ion. [POS] represents a polyorganosiloxane moiety. The R2 groups may be selected from those listed for R but are normally H.

Preferred polyorganosiloxane compounds are of general Formula 1, wherein each R is, independently, hydrogen, a linear or branched C1. 40 alkyl, C2 40 alkenyl or C2-40 alkynyl group, an aryl or C1 40 alkylaryl group or an optionally complex metal ion Mn+/n wherein n is an integer from 1 to 8;

the free valences of the silicate oxygen atoms are saturated by one or more of: silicon atoms of other groups of Formula 1, hydrogen, a linear or branched C1 12 alkyl group or by cross-linking bridge members R³qM¹(OR²)mOk/2 or Al(OR4)3-pOp/2 or R³Al (OR4)2-rOr/2; where M1 is Si or Ti ; R4 is a linear or branched C1 12 alkyl group; and R3 is a linear or branched C1 6 alkyl group; k is an integer from 1 to 4 and q and m are integers from 0 to 2; such that m + k + q = 4 ; and p is an integer from 1 to 3; and r is an integer from 1 to 2; or other known oxo metal bridging systems; x, y and z are integers such that the ratio of x : y+z, varies from 0.00001 to 100,000 with the fragments [03/2SiCH (CH2PO (OR) 2) CH2CH2SiO3/2] x and [03/2SiCH2CH2PO (OR) 2] y always present whilst the integer z varies from 0 to 200y.

Formula 1 General Formula 1 can be abbreviated to XxYyZz where X represents [03/2SiCH (CH2PO (OR) 2) CH2CH2SiO3n], Y represents [03/2SiCH2CH2PO (OR) 2] and Z represents [03/2SiCH2CH2CH2PO (OR) 2].

Other phosphonate-functionalised polysiloxane materials may also be used in the invention.

The organopolysiloxanes containing sulphonic acids described in US 4,552, 700 require the presence of cross-linking agents containing Si, Ti or Al to provide the desired stability.

Unlike these systems, compounds of Formula 1 do not require these cross linking agents to possess the desired physical and chemical properties. The bridging unit [03/2SiCH (CH2PO (OR) 2) CH2CH2Si03/2] in Formula 1 provides the necessary cross-linking.

In the context of the present invention, CI-40 alkyl refers to a straight, branched or cyclic hydrocarbon chain having from one to forty carbon atoms. The C1 40 alkyl group may be substituted with one or more substituents selected from nitro, chloro, fluoro, bromo, nitrile, C1 6 alkoxy, amino, amino C1 40 alkyl or amino di (C1 40 alkyl). Examples include methyl, ethyl, isopropyl, n-propyl, butyl, t-butyl, n-hexyl, n-decyl, n-dodecyl, cyclohexyl, octyl, iso- octyl, hexadecyl, octadecyl, iso-octadecyl and docosyl. A Ci. alkyl group has from one to twelve carbon atoms.

In the context of the present invention, C2-40 alkenyl refers to a straight, branched or cyclic hydrocarbon chain having from one to forty carbon atoms and including at least one carbon-carbon double bond. The C2-40 alkenyl group may be substituted with one or more substituents selected from nitro, chloro, fluoro, bromo, nitrile, C1 6 alkoxy, amino, amino C 40 alkyl or amino di (C1 40 alkyl). Examples include ethenyl, 2-propenyl, cyclohexenyl, octenyl, iso-octenyl, hexadecenyl, octadecenyl, iso-octadecenyl and docosenyl.

In the context of the present invention, C2 40 alkynyl refers to a straight, branched or cyclic hydrocarbon chain having from one to forty carbon atoms and including at least one carbon-carbon triple bond. The C2-40 alkynyl group may be substituted with one or more substituents selected from nitro, chloro, fluoro, bromo, nitrile, Ci_6 alkoxy, amino, amino C 40 alkyl or amino di (C1 40 alkyl). Examples include ethynyl, 2-propynyl octynyl, iso-octynyl, hexadecynyl, octadecynyl, iso-octadecynyl and docosynyl.

C1 6 alkoxy refers to a straight or branched hydrocarbon chain having from one to six carbon atoms and attached to an oxygen atom. Examples include methoxy, ethoxy, propoxy, t-butoxy and n-butoxy.

The term aryl refers to a five or six membered cyclic, 8-10 membered bicyclic or 10-13 membered tricyclic group with aromatic character and includes systems which contain one or more heteroatoms, for example, N, O or S. The aryl group may be substituted with one or more substituents selected from nitro, chloro, fluoro, bromo, nitrile, C1 6 alkoxy, amino, amino C1 40 alkyl or amino di (C1 40 alkyl). Examples include phenyl, pyridinyl and furanyl.

The term C1 40 alkylaryl group refers to a straight or branched hydrocarbon chain having from one to forty carbon atoms linked to an aryl group. The C140 alkylaryl group may be substituted with one or more substituents selected from nitro, chloro, fluoro, bromo, nitrile, C1 6 alkoxy, amino, amino C1 40 alkyl or amino di (C1 40 alkyl). Examples include benzyl, phenylethyl and pyridylmethyl. In a C1 8 alkylaryl group, the alkyl chain has from one to eight carbon atoms

It is preferred that each R is independently hydrogen, C1 12 alkyl, C2 12 alkenyl, C2 12 alkynyl, aryl or C1 8 alkylaryl. Compounds in which each R is independently hydrogen, C1 4 alkyl, phenyl or C1 8 alkylaryl are especially preferred, particularly when each R is independently hydrogen, methyl, ethyl or phenyl.

The catalysts may contain an amount of metal which is selected to be appropriate for the intended use of the catalyst. Typically the amount of metal is between about 2 % and about 80% by total weight of the catalyst, for example 10-70% by weight. When the metal is of high atomic weight, the amount of metal in the catalyst may exceed 80%. The atomic ratio of P: metal in the catalysts is preferably in the range 1: 0.5 to 0.5 : 1. When the polyorganosiloxane backbone includes titanium-containing cross-links, the amount of metal in the catalyst may be higher, or the P: metal ratio may be lower than those mentioned when taking the total metal into account. In such cases, the total amount of metal may be up to 90% by weight and the P: total metal atomic ratio may be in the range 0.3 : 1-1: 0.5.

The catalysts of the invention are very preferably solid. They may take the form of powders, regular or irregular particles such as tablets, granules, extrudates or a massive form such as a coating or layer applied to a solid support, a block or monolith. When the catalyst in particulate form is intended to be recoverable from the reaction mixture it is conveniently provided in the form of particles having a size which is susceptible to removal from a fluid mixture by sedimentation, centrifugation or filtration. Preferably the average dimension of such particles is greater than about 50pm. When the catalyst is recovered in this way, it may be re-used in a similar or a different reaction, normally, but not necessarily, after washing, drying and/or another pre-treatment or pre-dispersion step. Alternatively, the catalyst may be provided as a stationary phase, e. g. as a coating on a reaction vessel or as a fixed catalyst bed through or over which the reactants may flow so that the need for a distinct separation step is avoided.

Alternatively, the catalyst may be intended to remain dispersed within the reaction mixture and the product (s) resulting therefrom. In this case the catalyst may be required to be of a particle size which is not readily detectable within the product, for example <50, um, more preferably <10Nm, especially 2Nm or less.

The catalysts of the invention may provide significant benefits over the use of homogeneous catalysts because they may be more hydrolytically and thermally stable than the corresponding homogeneous catalysts. The increased stability of the catalyst in turn offers the possibility of more selective reactions with fewer unwanted products so producing a final reaction product having more desirable properties (e. g. better colour, physical properties etc). When the stability of the catalyst is increased, less activity is lost through

decomposition and so the catalyst may retain its activity in the reaction mixture for a longer period, thereby reducing reaction times. Also the storage and handling of the catalysts of the invention may be easier when the catalyst is more stable.

The catalysts of the invention may be used in a reaction mixture in combination with one or more different homogeneous or heterogeneous catalysts or co-catalysts. For example various combinations of metal catalysts and stabilisers are used in the manufacture of polyesters, such as manganese or zinc transesterification catalysts, phosphorus-based stabilisers (e. g. phosphoric acid), titanium, antimony, germanium and/or cobalt polycondensation catalysts. The catalysts of the invention may be used to replace one or more of the components of the polyester catalyst system. Additional compounds such as dyes, stabilisers etc may also be present in the reaction mixture.

The catalysts are used in the reaction mixtures in amounts which provide an appropriate amount of metal for the desired reaction to occur. Normally the amount of catalyst used would be such as to provide a concentration of metal equivalent to between about 2 and about 1000 ppm by weight of final product.

The catalysts of the invention may be prepared by first reacting the corresponding acidic phosphonate-functionalised polyorganosiloxane with dilute base to a pH of approximately 8- 10. A solution containing the desired metal ion and/or complex is then added and the metal derivatives comprising the catalysts of the invention are subsequently separated, for example by filtration. When using metal alkoxide, the alcohol formed by reaction with the phosphonate-functionalised polyorganosiloxane may be removed by distillation or evaporation or by washing. Alternatively the alcohol may remain in the catalyst product. A wide range of bases and solvents, well known to those skilled in the art of chemistry, can be used in this reaction, for example sodium or potassium hydroxide, calcium hydroxide or ammonium hydroxide. Organic bases may be used instead of or in addition to inorganic bases. Suitable organic bases include quaternary ammonium compounds such as tetrabutyl ammonium hydroxide, tetraethyl ammonium hydroxide (TEAH), choline hydroxide (trimethyl (2-hydroxyethyl) ammonium hydroxide) or benzyltrimethyl ammonium hydroxide, or alkanolamines such as monoethanolamine, diethanolamine, triethanolamine and triisopropanolamine. The amount of base used should be sufficient to provide the required alkalinity, which is, as mentioned above, usually in the range 8-10. Thus the amount of base added depends upon the strength of the base and the acidity of the phosphonate- functionalised polyorganosiloxane. The catalysts may be prepared in aqueous media or in any of a range of non-aqueous solvents such as alcohols (e. g. isopropanol, iso or n- butanol, ethanol) or, more preferably, hydrocarbon solvents such as C5-C8 alkanes (e. g.

heptane or hexane), or aromatic solvents such as benzene or toluene. Preferably dry organic solvents are used.

The catalysts of the invention are especially useful in esterification reactions, including direct esterification, transesterification and interesterification. There are many examples of industrially useful esterification processes in which the catalysts may be used, for example the preparation of esters typically used in plastics manufacture such as phthalate esters (e. g. dioctyl phthalate), adipates and trimellitates. Examples of transesterification processes include the preparation of speciality acrylates and methacrylates, (for example for the preparation of 2, 2-dimethylaminoacrylate) and the preparation of polyesters from ester feedstocks such as dimethyl terephthalate. The preparation of triglycerides and interesterification of fatty acid esters derived from natural fats and oils is an example of industrial interesterification applications. The use of the catalysts for the amidation of fatty acids and esters with ammonia is also contemplated. Applications of the catalysts for polymerisation reactions include polycondensation to make polyesters (e. g. PET, PBT, PPT, PEN) and polyester resins, cure of polyurethanes, ring-opening of epoxides, lactones, lactams etc; preparation of polyolefins. Other uses may be found in coatings, as thixotropes or cross-linkers, adhesion promoters for inks and industrial coatings etc.

According to a further aspect of the invention we provide a method of carrying out an esterification reaction, a polycondensation, an olefin polymerisation, characterised in that the reaction is carried out in the presence of a solid catalyst which comprises the reaction product of a phosphonate-functionalised polyorganosiloxane containing at least one P-OR group and a metal compound.

According to a further aspect of the invention we provide an ink, coating, polyurethane or polyester composition containing particles of a solid catalyst, characterised in that the catalyst comprises the reaction product of a phosphonate-functionalised polyorganosiloxane containing at least one P-OR group and a metal compound.

The catalyst may be provided as a dry solid or alternatively it may be slurried in a liquid such as an alcohol. It may be convenient to provide the catalyst as a slurry in one of the reactants forthe reaction which it is intended to catalyse. For example, the catalyst may be slurried in an alcohol such as a glycol for use in polyester manufacture.

The invention is further illustrated in the following non-limiting examples.

Example 1 Preparation of Polyorganosiloxane A

A solution containing trimethoxy vinyl silane (19.0 g, 0.136 mol), diethyl phosphite (19.32 g, 0.136 mol) and di-tertbutyl peroxide (6 drops) was heated at about 120-130 ° C under an atmosphere of nitrogen. Heating was continued for 40 h and di-tert butyl peroxide (6 drops) was added every 4 h. Un-reacted starting material was removed by heating at 120 °C- bath temperature-under reduced pressure (2 mm Hg) to give a mixture of diethyl 2,4- di (trimethoxysilyl) butylphosphonate and diethyl 2-trimethoxysilyl ethylphosphonate as a colourless oil (30.1 g) in a ratio of 1.8 : 3.2.

The oil (30.1 g) was dissolved in methanol (125 ml) containing 1 M HCI (10 ml). The solution was left at ambient temperature for 48h and then at 55°C for 1 OOh. The resultant glass (16.0 g) was crushed and then added to concentrated HCI (150 ml). The mixture was gently refluxed with stirring for 1 Oh and then cooled to room temperature. The solid was filtered and first washed with distilled water till the washings were neutral and then with methanol and finally ether. After drying at 100°C at 0.1 mm of Hg a pale white solid was obtained (13.0 g)-Polyorganosiloxane (POS) A. DSC analysis-no thermal events were observed in heating a sample up to a temperature of 400°C under an atmosphere of nitrogen gas.

Example 2 Preparation of Polyorganosiloxane B A solution containing triethoxy vinyl silane (38.8 g, 0.204 mol), diethyl phosphite (28.17 g, 0.204 mol) and di tertbutyl peroxide (6 drops) was heated at 120-130 ° C under an atmosphere of nitrogen. Heating was continued for 40 h and di-tert butyl peroxide (6 drops) was added every 4 h. Un-reacted starting material was removed by heating at 120 °C- bath temperature-under reduced pressure (2 mm Hg) to give a mixture of diethyl 2,4- di (triethoxysilyl) butylphosphonate and diethyl 2-triethoxysilyl ethylphosphonate as a colourless oil (55.1 g) in a ratio of 1.1 : 1.8.

The oil (55.1 g) was dissolved in methanol (200 ml) and then 1 M HCI (20 ml) was added with stirring. The solution was left at ambient temperature for 48h and then at 55°C for 100h. The resultant glass (30.0 g) was crushed and then added to concentrated HCI (300 ml). The mixture was gently refluxed with stirring for 10h and then cooled to room temperature. The solid was filtered and first washed with distilled watertill the washings were neutral and then with methanol and finally ether. After drying at 100°C at 0.1 mm of Hg a white solid (23.0 g)-POS B-was obtained. DSC analysis-no thermal events were observed in heating a sample up to a temperature of 400°C under an atmosphere of nitrogen gas.

Example 3 Ti Catalyst A & B preparation

Catalysts A and B were prepared by refluxing a mixture of the respective POS (A or B as prepared in Examples 1 and 2) (0.12 g) and titanium (I\/) isopropoxide (0.07 g) in anhydrous benzene (10 mi) for 2h under an atmosphere of nitrogen. On cooling to room temperature the solvent was removed under reduced pressure. The solid was washed with dry ether (3 x 20 ml) and then dried under reduced pressure.

Example 4 Zn Catalyst preparation Sodium hydroxide (1 M) was added slowly over 2h to a mixture of POS A or B (0.6 g) in water (20 ml) to reach at pH of 9. An aqueous solution of zinc chloride (0.5 g) in water (20 ml) was added to give a white milky suspension which was stirred for 2h. The mixture was concentrated under reduced pressure. Water (50 ml) was added and the mixture was concentrated under reduced pressure. This was repeated a further three times. Water was then added and the solid was filtered off and washed well with water, then with ethanol and finally with ether. The catalyst was obtained as a white solid (0.6 g).

Example 5 Use of catalyst for esterification A mixture containing 2-ethyl hexanol (22.75 g, 0.175 mol), phthalic anhydride (10.37 g, 0.07 mol) and catalyst A (0.1 g) was heated at 180°C under an atmosphere of nitrogen with a modified Dean and Stark apparatus to collect the water. Reaction was complete within 1 h.

Diisooctylphthalate as a colourless liquid (25.2 g) was decanted from the catalyst and more 2-ethyl hexanol (22.75 g, 0.175 mol) and phthalic anhydride (10.37 g, 0.07 mol) was added.

After heating at 180°C for a further hour the reaction had gone to completion to give diiso- octylphthalate as a colourless liquid (25.0 g). This demonstrates that the catalyst of the invention may be recovered from a reaction mixture and re-used.

As a comparison a similar reaction was carried out using titanium tetraisopropoxide, conventionally used as a catalyst for this reaction. The reaction proceeded normally but the reaction product was coloured yellow.

Example 6 Transesterification (1) A mixture containing methyl methacrylate (3.8 ml, 40 mmol), 2-ethyl hexanol (7.8 g, 60 mmol) and catalyst A (0. 1 g) was stirred at 90°C for 12h under an atmosphere of nitrogen.

The catalyst was filtered off and washed with ether (20 ml). The combined organic liquids were concentrated under reduced pressure to give 2-ethylhexyl methacrylate as a colourless oil (3.8 g).

Example 7 Transesterification (2) A mixture of dimethyl terephthalate (15.5 g, 0.08 mol), ethylene glycol (5.0 ml, 0.089 mol) and catalyst (0.1 g) was heated at 160°C under an atmosphere of nitrogen using a modified Dean and Stark apparatus to collect the methanol. After 2h no more methanol was obtained and on cooling solid bis (hydroxyethyl) terephthalate was obtained in virtually quantitative yield.

Example 8 A mixture of methyl laurate (21. 44g, 0.1 mol), 2-ethyl hexanol (13. 02g, 0.1 mol) and catalyst B (0.68 g) was heated at 120 °C using a distillation apparatus to collect the methanol which was formed. 0. 1ml samples were taken every 30 minutes for 150 minutes and analysed by 1H NMR spectroscopy. Conversions were noted and are given in the table below. The catalyst was then recovered by filtration, added to new starting materials and the reaction repeated, this process was carried out until 5 repeats had been done. Table 1 shows the percentage conversion of methyl laurate to ethyl hexyl laurate for all 5 runs.

Table 1 Time (mins) 0 30 60 90 120 150 Run 1 0 38. 75 48. 33 56. 88 60. 79 62.735 Run 2 0 30. 67 60. 83 68. 26 70. 32 73. 05 Run 3 0 37. 94 56. 95 66. 85 72. 25 73. 89 Run 4 0 19. 83 36. 93 43. 69 54. 64 56. 98 Run 5 0 23. 26 40. 16 50. 28 63. 21 64. 47

Example 9 Example 8 was repeated using catalyst A instead of catalyst B. Table 2 shows the percentage conversion of methyl laurate to ethyl hexyl laurate for all 4 runs completed.

Table 2 Time (mins) 0 30 60 90 120 150 Run 1 0 21. 29 38. 08 49. 02 57. 27 60. 02 Run 2 0 10. 54 18. 35 24. 2 30. 97 33. 56 Run 3 0 6. 47 10. 35 14. 99 17. 23 20. 02 Run 4 0 2. 27 5. 46 8. 88 11. 12 12. 65

Example 10 Preparation of polyester 1. 317g of Catalyst B was added to a 15 litre oil-heated autoclave containing 4.555kg of pure terephthalic acid and 2.039kg of mono ethylene glycol. The contents of the autoclave was agitated and at an increased pressure of 2. 75bar heated to 260°C. At this temperature the direct esterification (DE) reaction takes place liberating water and the time taken to remove all water of reaction was measured. Once the DE was complete the temperature of

the autoclave was increased to 290°C and vacuum applied reducing the pressure to 1 mbar and the polycondensation (PC) reaction started. The torque required to maintain an agitator speed of 40 rpm was monitored and when this torque reached a predetermined level the resulting polymer was discharged into a water filled bath and chipped out through an industrial chipper. The direct esterification (DE) and polycondensation (PC) times were recorded together with the colour of the final polymer at the beginning and end of the discharge period from the reactor. The results are shown in Table 3.

Table 3 Catalyst concentration Reaction Colour at start of Colour at end of time (mins) discharge discharge DE PC L a b L a b Catalyst B 20ppm Ti 83 143 67.51-1. 08 4. 26 68. 42-2.57 7.25 TIPT* 20ppm Ti 74 110 71.92-2. 5 15. 64 68.59-1. 78 20.42 (comparison) * TIPT is titanium tetraisopropoxide