GB2191778A - Olefin polymerisation catalyst composition - Google Patents

Abstract

A composition is the reaction product of I) a solid magnesium compound and II) a derivative of a carboxylic acid having the formula <IMAGE> where R is a divalent residue; R<1>, R<2> and R<3> are the same or different and are monovalent substituted hydrocarbyl or hydrocarbyl groups, M is a Group IV element, other than carbon, x is 0, 1 or 2 and v is the valency of M, with the proviso that (v-1-x) is at least one. The magnesium compound may be a magnesium halide/alcohol adduct or a magnesium alkoxide. M may be silicon or titanium. The composition may be post-treated with a transition metal compound, for example titanium tetrachloride, and the transition metal composition thereby obtained can be used as a component of a catalyst to polymerise an olefin monomer. Examples are given in which the composition is prepared from I) magnesium ethoxide and II) the product of reacting titanium tetra n-butoxide, or titanium tetra 2-ethylhexoxide,with phthalic anhydride.

Description

SPECIFICATION Composition The present invention relates to compositions, the preparation of such compositions and the use of such compositions to prepare components of catalyst systems for the polymerisation of olefin monomers.

Transition metal compositions have been used as components of olefin polymerisation catalyst systems for many years. Compositions of this type containing titanium have been found to be especially useful, in particular for the production of polypropylene having a high stereoregularity. In recent years, considerable effort has been directed to the production of compositions which result in catalyst systems of high polymerisation activity coupled with high stereospecificity in the production of polypropylene. A catalyst system satisfying these requirements offers a propylene polymerisation process in which the removal of catalyst residues and undesirable atactic polymer is not necessary since the product of the the polymerisation process has a suitably low level both of catalyst residues and atactic polymer.To reduce the cost of the polymerisation process it has been proposed to effect the polymerisation in the essential absence of inert polymerisation diluents. In such processes, the polymerisation is effected with the monomer in the liquid phase or in the gas phase acting as the reaction medium.

Many of the recent developments in seeking improved catalyst performance have been directed to transition metal compositions in which a transition metal compound is reacted with a compound which may be regarded as functioning primarily as a support for the transition metal compound. There have been many proposals of systems in which titanium tetrachloride is reacted with magnesium chloride and a Lewis Base compound, the latter typically being an ester of an aromatic carboxylic acid. The reaction product thus obtained is then used, together with an organo-aluminium compound and optionally a Lewis Base compound to effect the polymerisation of propylene.In Japanese Laid-Open Patent Application (Kokai) No 54 (1979) 94590, and subsequently in European Patent Specifications No 45975,45976 and 45977, catalyst systems are disclosed in which the titanium chloride component of the catalyst system includes an organic ester of an aromatic carboxylic acid and the Lewis Base used with the organo-aluminium compound is a silane. We have now obtained a catalyst system having good polymerisation activity in which the titanium chloride component includes an inorganic Lewis Base complex.

According to the present invention there is provided a composition which is the reaction product of I) a solid magnesium compound and II) a derivative of a carboxylic acid having the formula

wherein R is a divalent hydrocarbon or substituted hydrocarbon residue; R7, R2 and R3, which may be the same or different, are monovalent hydrocarbon or substituted hydrocarbon residues; M is an element, other than carbon, from Group IV of the Periodic Table of the elements; visthevalencyofm; and x is 0, 1 or 2, with the proviso that (v-l-x) has a value of at least one.

As a further aspect of the present invention there is provided a process for the production of a composition which comprises reacting I) a solid magnesium compound with II) a derivative of a carboxylic acid having the formula

wherein R, R1, R2, R3, M, v and x are all as hereinbefore defined.

The solid magnesium compound may be a compound of the type MgX1X2yL, where X1 and X2, which may be the same or different, are halogen atoms or alkoxide groups; Lisa ligand; and y is a zero or has a value of up to 8 The groups X1 and X2 are conveniently the same. The ligand L, if present, may be, for example, an ether, an ester, an organic phosphate or an alkanol. The ligand L is conveniently an aliphatic alkanol containing from 1 to 10 carbon atoms, particularly ethanol. If the value of y is other than zero, it is typically from 2 up to 6.

Suitable solid magnesium compounds are magnesium dihalides, magnesium dihalide-alkanol complexes, magnesium halide alkoxides and magnesium dialkoxides. We have obtained useful products when the solid magnesium compound is a magnesium diethoxide.

In the carboxylic acid derivative, the group R may be an optionally substituted divalent aromatic, aliphatic or cycloaliphatic residue and may be saturated or unsaturated. The group R may contain substituent groups such as halogen or hydrocarbonoxy. The carboxylate groups may be attached to the same or different carbon atoms in the group R and, in particular, the carboxylate groups are attached to adjacent carbon atoms in the group R, as for example when the carboxylic acid derivative is based on phthalic acid, cyclohexane-1,2dicarboxylic acid, naphthalene-2,3-dicarboxylic acid, maleic acid or succinic acid.

The groups R1, R2 and R3 may be alkyl or aryl groups and it is preferred that R2 and R3 are alkyl groups, particularly alkyl groups containing from 1 to 8 carbon atoms. The groups R1, if present, are typically aryl groups, for example phenyl groups. When x has a positive value it is typically two.

The element M is any element, other than carbon, from Group IV of the Periodic Table and is typically silicon, germanium, zirconium, hafnium, tin or particularly titanium. Typically, if M can have more than one valency, the valency (v) is four. When M is titanium, the value of x is typically zero.

Thus, as a further aspect of the present invention there is provided a composition which is the reaction product of I) a solid magnesium compound and II) a derivative of a carboxylic acid having the formula

where R, R2 and R3 are as hereinbefore defined. In this composition R2 and R3 may be the same and may be, for example, and ethyl, n-butyl or 2-ethylhexyl group. The group R my be 1,2-phenylene.

The derivative of a carboxylic acid having the defined formula (hereinafter this material will be termed simply the "carboxylic acid derivative") may be obtained by any suitable technique. The carboxylic acid derivative may be a preformed material but may be obtained by a pre-reaction, which may be in situ, before the reaction with the solid magnesium compound.

The carboxylic acid derivative may be obtained by the reaction of an anhydride of a dicarboxylic acid with a compound containing at least one M-OR2 bond. This process can be used when the group R is such that a ring anhydride is formed. Thus, the carboxylic acid derivative may be a product obtained by the reaction of an anhydride such as phthalic anhydride, cyclohexane-1 ,2-dicarboxylic acid anhydride; naphthalene -2,3dicarboxylic acid an hydride, maleic anhydride or succinic anhydride with a compound containing at least one M-OR2 bond. The compound containing at least one M-OR2 bond is conveniently one containing only groups R1 and OR2 attached to M and specifically is a compound having the formula M R1X(oR2)(v-x) where M, R', R2, v and x are as defined.The carboxylic acid derivative which is obtained will be one in which R3 is the same as R2. The reaction between the anhydride of the dicarboxylic acid with the compound containing at least one M-OR2 bond is preferably effected at an elevated temperature of at least 60 C, and very preferably at a temperature of at least 1000C. It is especially preferred that the reaction is effected at a temperature which is close to or greater than the melting point of the anhydride. The reaction is preferably effected in the presence of an inert liquid preferably a liquid hydrocarbon or halohydrocarbon having a boiling point in excess of the reaction temperature. Preferred liquids for effecting the reaction are liquid aliphatic hydrocarbons, or mixtures of aliphatic hydrocarbons, containing at least 8 carbon atoms and especially containing at least 10 carbon atoms.The reaction is preferably effected using essentially stoichiometric proportions of the transition metal compound and the anhydride. A reaction time of at least 15 minutes is preferred and we have obtained essentially complete reaction in one hour.

Alternatively, the carboxylic acid derivative may be obtained by the reaction of an alkali metal salt of the mono-ester of the dicarboxylic acid (hereafter simply "alkali metal salt") with a compound containing a halogen atom and at least one M-OR2 bond (hereafter simply the "halide compound"). The alkali metal salt may be a sodium salt. The halogen atom is conveniently a chlorine atom. The halide compound is conveniently one containing one halogen, R1 and OR2 attached to M and specifically is a compound having the formula XMR1x(OR2)(v-l-x) where M, R', R2, v and x are as defined, and Xis a halogen atom.

If the carboxylic acid derivative is obtained by a pre-reaction stage, it is preferred to effect this pre-reaction using an anhydride of a dicarboxylic acid and a compound containing at least one M-OR2 bond since using this procedure the desired carboxylic acid derivative is the only reaction product and hence this pre-reaction may be effected in situ in the same reaction vessel as is subsequently used for the reaction with the solid magnesium compound.

The reaction of the solid magnesium compound with the carboxylic acid derivative is preferably effected at an elevated temperature in the presence of an inert liquid. The reaction temperature is preferably at least 60"C and very preferably at least 100"C. The inert liquid medium may be a liquid hydrocarbon of the same type as can be used for the production of the carboxylic acid derivative.

The magnesium compound is reacted with the carboxylic acid derivative in proportions which are conveniently in the range from 0.5 up to 20 moles of the magnesium compound for each mole of M which is present in the carboxylic acid derivative. The magnesium compound is preferably used in an amount of from 1 to 10 moles for example 6 moles for each mole of M.

The magnesium compound is reacted with the carboxylic acid derivative by stirring the reactants together under suitable reaction conditions, as hereinbefore described, for a time of at least 15 minutes, preferably at least 30 minutes. We have obtained satisfactory results by stirring the magnesium compound with the carboxylic acid derivative at a temperature of 1 20"C for a time of one hour.

The composition of the present invention can be used as a precursor in the preparation of a component of an olefin polymerisation catalyst system. More specifically, the composition is reacted with a compound of a transition metal, which compound does not contain any metal/OR2 bonds when the transition metal is one from Group IVA of the Periodic Table. The compound of a transition metal is preferably a transition metal halide, particularly a chloride. The transition metal is a metal of Group IVA, VA or VIA of the Periodic Table, referably a metal of Group IVA of the Periodic Table, and especially is titanium. It is particularly preferred that the transition metal compound is titanium tetrachloride.

Thus, as a further aspect of the present invention there is provided a transition metal composition which iS the reaction product of I) a solid magnesium compound II) a derivative of a carboxylic acid having a formula

,COOMR1 x(OR2)(v1x) R COOR3; and also IV) a compound of a transition metal, which compound does not contain any metal/OR2 bonds when the transition metal is one from Group IVA of the Periodic Table, where R, R1, R2, R3, M, v and x are all as hereinbefore defined.

According to a further aspect of the present invention there is provided a process for the production of a transition metal composition wherein a composition in accordance with the first aspect of the present invention is reacted with a compound of a transition metal, which compound does not contain any metal/OR2 bonds when the transition metal is one from Group IVA of the Periodic Table.

The compound of a transition metal is particularly titanium tetrachloride or a titanium tetrachloridecontaining material. For convenience "titanium tetrachloride" will be used hereafter to include the titanium tetrachloride-containing material.

The reaction with the transition metal compound may be effected in more than one stage, for example in two stages, but satisfactory results can be obtained by effecting the contacting in only one stage.

After effecting the reaction with the transition metal compound, the product obtained, which is a solid transition metal composition, is preferably separated from any excess quantity of any liquid phase which is present and the product may be washed to remove at least some soluble transition metal-containing species including adsorbed transition metal compounds, from the separated solid. However, we have found that It is not necessary to effect the washing of the solid product to remove all of the soluble transition metalcontaining species from the solid product.

The reaction with the transition metal compound may be effected using a liquid phase whch typically contains more than 25% by weight of the transition metal compound, and it is preferred that the liquid phase contains at least 45% by weight of the transition metal compound. It is especially preferred that the liquid phase consists solely of a liquid transition metal compound, particularly titanium tetrachloride. If a solution of the transition metal compound is used, the solvent is preferably an inert material, particularly an inert hydrocarbon or halohydrocarbon, especially an aliphatic hydrocarbon.

The transition metal composition may be prepared by suspending the composition of the present invention in an excess quantity of a liquid containing the transition metal compound and agitating the mixture, for example by stirring. In effecting contacting in this manner, the volume of the liquid is typically not less than the volume of the composition and typically there is used 1 to 10 especially 2 to 8 volumes of the liquid for each volume of the composition. Preferably the contacting of the composition with the liquid is effected, at least partially, at an elevated temperature which is conveniently at least 60"C up to the boiling temperature of the liquid phase, which is about 136"C when the liquid phase is undiluted titanium tetrachloride.Preferably, the foregoing process of contacting, the composition may be contacted with titanium tetrachloride in the range 800C up to 1300C. When effecting contacting with titanium tetrachloride when the latter is at the desired elevated temperature the composition may be added to the titanium tetrachloride at a lower temperature, which is conveniently ambient temperature, and the mixture is then heated to the desired elevated temperature.

As an alternative to suspending the composition in a liquid medium containing the transition metal compound, the contacting of the composition with transition metal compound may be effected by grinding.

Using a grinding process and titanium tetrachloride the volume of the titanium tetrachloride is preferably less than the volume of the composition. Preferably, during grinding, not more than one mole of the transition metal compound is present for each mole of solid magnesium compound used to prepare the composition, and the amount of the transition metal compound is typically from 0.01 up to 0.5, and especially from 0.2 up to 0.1, moles for each mole of the solid magnesium compound.

The grinding may be carried out in any suitable grinding apparatus such as, for example, a rotating ball mill or vibrating ball mill. The grinding is preferably carried out in the substantial absence of oxygen or moisture.

The grinding conditions will be dependent on the grinding technique and on the nature of the materials being ground. However, in general it is preferred to carry out the grinding for a period of from 1 hour up to 5 days particularly from 5 up to 50 hours. Any suitable temperature may be used for the grinding, for example, from - 50"C up to 100 C, especially from - 10 C up to 80"C, and, if desired, the temperature may be varied during the grinding operation. The grinding may be carried out without applying heating or cooling to the pulverising apparatus.However, the conditions of grinding are generally such that heat is generated during the grinding and hence, in order to operate at an essentially constant temperature, for example ambient temperature, which is the generally desired procedure, it may be necessary to apply cooling to the grinding apparatus. The need for cooling will be dependent on the mill size and the milling conditions.

The intensity of grinding will be dependent upon the type of grinding apparatus which is being used. Using a rotating ball mill, it is preferred that the mill is rotated at between 50% and 90% of the critical speed. By critical speed is meant the speed at which particles and balls are held by centrifugal force against the walls of the mill and do not tumble. Using a vibration mill, the mill is preferably operated to give an acceleration of between 12 and 200 metres per sec2. Since the vibration mill gives a more intensive grinding, a shorter time of grinding is generally possible using such a mill than when a rotating ball mill is used.

If reaction with the transition metal compound is effected in more than one stage, such a procedure may be effected by grinding the composition with the transition metal compound and thereafter suspending the product in a liquid medium which is, or which contains, the transition metal compound. We prefer to effect the reaction with the compound of a transition metal without using a grinding step.

If the composition is suspended in titanium tetrachloride to effect reaction, the reaction is conveniently effected for a period of time of from 0.25 hours up to 10 hours, for example 0.5 up to 5 hours. If reaction is effected by grinding, a longer period of time may be used such as up to 5 days, for example from 2 up to 80 hours, conveniently 5 up to 50 hours.

After the desired time of reaction with the transition metal compound, the solid transition metal composition obtained is preferably separated from any excess liquid phase which is present. The separation is effected by any suitable technique, for example by allowing the solid to settle and removing the supernatant liquid phase from the settled solid by a technique such as decantation, or using a siphon, or by using a technique such as filtration which gives essentially complete separation.Although filtration gives more complete separation than is readily achieved by settling and removing the supernatant liquid, the solid may include fine particulate material, for example at least 10% by weight of particles having a particle size of less than 5 microns and the presence of this fine particulate material can cause blockage of the filter which is undesirable to a commercial scale and outweighs any advantage of complete separation.

If the reaction with the transition metal compound is repeated, each repeat reaction may be effected under the conditions hereinbefore described. If more than one reaction step is effected, it is convenient, but not essential, for each step to be effected under essentially the same conditions of temperature and time.

After reacting the composition with the transition metal compound, the solid transition metal composition is preferably separated from any excess liquid phase which is present and thereafter washed at least once with an inert hydrocarbon or halohydrocarbon. Suitable inert liquids include hexane, heptane, octane, decane, dodecane and mixtures of the isomers thereof, aromatic liquids such as benzene and toluene, and halohydrocarbons such as 1,2-dichloroethane and chlorobenzene. The washing is conveniently effected by suspending the transition metal composition in the inert liquid hydrocarbon or halohydrocarbon medium and agitating the mixture for a period of time of at least 5 minutes up to 10 hours conveniently 10 minutes up to 5 hours.The number of washing steps used will depend on the quantity of the inert liquid hydrocarbon or halohydrogen used in each washing step and the time and temperature of each washing step. The washing step may be effected at ambient temperature but it is preferred that at least one washing step is effected under conditions such that the inert liquid hydrocarbon or halohydrocarbon attains an elevated temperature which is in the range 60"C up to 1300C, and especially at least 80"C.

The at least one washing step is believed to remove, from the transition metal composition, some complexes of the transition metal compound which remains. For the removal of the complexes, it is compound and also to remove any excess unreacted transition metal desirable that the at least one washing step, and particularly at least the first washing step when several washing steps are used, is effected at an elevated temperature of at least 60"C, particularly at least 80"C. However, if more than one washing step is used, the washing steps after the first step may be effected at a lower temperature. If the liquid medium is separated from the transition metal composition by a decantation process, or by using a siphon, some unseparated liquid, which typically includes unreacted transition metal compound, remains with the transition metal composition and if this unreacted transition metal compound is titanium tetrachloride, the proportion thereof can be reduced by washing at ambient temperature.

If the composition has been suspended in titanium tetrachloride at an elevated temperature, it is preferred to effect the washing step, or the first washing step, before any substantial cooling has occurred after separating the transition metal composition from the titanium tetrachloride. Thus, it is preferred to add the inert hydrocarbon or halohydrocarbon liquid to the separated solid transition metal composition within a few minutes, for example within one to 30 minutes, of removing the titanium tetrachloride. The at least one washing step is conveniently effected in a vessel containing heating means, such as an outer jacket for a heating fluid, and it is preferred to continue heating during the washing step or during at least the first of the washing steps.After the treatment with titanium tetrachloride, the washing may be effected without allowing any appreciable cooling of the separated solid transition metal composition to occur and adding the inert hydrocarbon or halohydrocarbon liquid at ambient temperature whilst still supplying heat to the solid, and the added liquid. The washing step, or each washing step, is effected by suspending the solid transition metal compound in the inert hydrocarbon or halohydrocarbon liquid and agitating the mixture for a period of time which may be from 5 minutes up to 10 hours, and which is preferably from 10 minutes up to 5 hours.

If the solid has been obtained by grinding the composition with titanium tetrachloride, or has been separated from a titanium tetrachloride containing liquid and allowed to cool appreciably, for example to ambient temperature, it is desirable that the at least one washing step, or at least the first washing step, is effected at an elevated temperature of at least 80"C, for example using heptane at reflux temperature, and that the elevated temperature is maintained for at least two hours, in order to ensure that materials which are insoluble at the initial low temperature may be dissolved in the hot inert hydrocarbon or halohydrocarbon liquid.

The quantity of the inert hydrocarbon or halohydrocarbon liquid used for the at least one washing step is conveniently in the range from 5 cm3 to 20 cm3 for each gramme of the transition metal composition, particularly from 8 cm3 to 12 cm3 for each gramme of the transition metal composition.

If the composition is suspended in undiluted titanium tetrachloride, if the washing step, or at least the first washing step, is effected before the separated transition metal composition has cooled appreciably, for example before the separated magnesium halide-transition metal composition has cooled below 70"C, and if heating is continued thoroughout the washing, we have found that satisfactory products can be obtained using not more than two washing steps at an elevated temperature of at least 60"C. Using such a procedure, adequate washing may be achieved by agitating the mixture of the separated transition metal composition and the inert hydrocarbon or halohydrocarbon liquid at the elevated temperature and continuing the agitation forfrom 10 minutes up to two hours, typically for 10 minutes up to one hour before either separating the solid from the liquid or allowing the solid to settle. After washing at the elevated temperature, if the liquid is separated by decantation or by using a siphon, further washes may be effected at a lower temperature, typically at ambient temperature, to reduce the proportion of unreacted titanium tetrachloride which remains with the solid transition metal composition.

After the, or each, washing step, the transition metal composition may be separated from the liquid phase by filtration, decantation or by means of a siphon. Using a siphon to effect separation of the transition metal composition from the liquid, we have obtained a satisfactory product by effecting a first washing step at a temperature of about 100 C, a second washing step with the temperature rising to be in the range 35 to 600C and two further washing steps at essentially ambient temperature.

The production of the transition metal composition has been described with particular reference to the use of titanium tetrachloride, which is a liquid under normal conditions of temperature and pressure, but it will be appreciated that other compounds of a transition metal can be used in a generally similar manner. However, using a solid compound of a transition metal, for example titanium trichloride, it is generally more convenient to effect reaction with the composition by grinding the two materials together.

According to a preferred aspect of the present invention, there is provided a process for the production of a transition metal composition which comprises A) effecting a pre-reaction to obtain a derivative of a carboxylic acid having the formula

B) contacting the pre-reaction product from A) with a solid magnesium compound; and C) reacting the product of B) with a compound of a transition metal which does not contain any metal/OR2 bonds when the transition metal is one from Group IV A of the Periodic Table.

The process is preferably effected without grinding. Thus, in pre-reaction step A), a solution of the carboxylic acid derivative is formed and step B) is effected by suspending the solid magnesium compound in this solution. Step C) may be effected by adding the compound of a transition metal to the mixture obtained in step B) or the product of step B) may be separated from the reaction medium prior to being reacted with the compound of a transition metal. The product of step C) may be separated from the reaction medium and washed once or several times with an inert liquid medium, particularly an aliphatic hydrocarbon or halohydrocarbon. Step C), and optionally the subsequent washing step or steps, may be repeated. However, we prefer that step C) is effected not more than twice.

The transition metal composition of the present invention may be used in combination with organic metal compounds, and optionally Lewis Base compounds, to give a polymerisation catalyst. This catalyst has a high activity and stereospecificity when used for the polymerisation of alpha-olefin monomers.

According to a further aspect of the present invention there is provided a polymerisation catalyst which comprises A. a transition metal composition as hereinbefore described; and B. an organic compound of aluminium or of a non-transition metal of Group IIA of the Period Table, or a complex of an organic compound of a non-transition metal of Group IA or IIA of the Periodic Table together with an organic aluminium compound.

Component B of the catalyst system may be an organic magnesium compound or a mixture or complex thereof with an organic aluminium compound. Alternatively, a complex of a metal of Group IA with an organic aluminium compound may be used, for example, a compound of the type lithium aluminium tetraalkyl.

However, it is preferred to use an organic aluminium compound and in particular it is preferred to use a tri-hydrocarbon aluminium compound such as an aluminium trialkyl compound, particularly one in which the alkyl group contains from 1 up to 10 carbon atoms, for example, aluminium triethyl, aluminium triisobutyl or aluminium trioctyl.

In addition to Components A and B, the catalyst system may also include a further Lewis Base compound.

The Lewis Base compound which is used as the additional component can be any organic Lewis Base compound which has been proposed for use in a Ziegler polymerisation catalyst and which affects either the activity or stereospecificity of such a catalyst system. Thus, the Lewis Base compound may be an ether, an ester, a ketone, an alcohol, an ortho-ester, a sulphide (a thioether), an ester of a thiocarboxylic acid (a thioester), a thioketone, a thiol, a sulphone, a sulphonamide, a fused ring compound containing a heterocyclic sulphur atom, an organic silicon compound such as a silane or siloxane, an amine, a urea, substituted ureas, thiourea, amines and derivatives thereof, and organic phosphorus compounds.

The Lewis Base component which is used as an additional component of the catalyst system may be an ester of the general formula R4a Ar (COOR5)b wherein Ar is a residue of an aromatic hydrocarbon; R4 is a hydrocarbon radical, a halohydrocarbon radical, a halogen atom or a group OR6; R5 its a hydrogen atom, a hydrocarbon radical ora halohydrocarbon radical; R6 is a hydrocarbon radical or a halohydrocarbon radical; a is 0 or an integer; and b is an integer.

The group Ar typically is a mono- or divalent residue derived from an aromatic hydrocarbon such as benzene or naphthalene. If the group Ar is a divalent residue it may be, for example, a divalent benzene residue wherein the unoccupied valencies are in the ortho- or para-position to each other.

The, or each, group R4, when present, is typically a hydrocarbon radical or a group OR6, especially an alkyl or alkoxy group, particularly one containing up to 10 carbon atoms, for example an alkyl or alkoxy group containing 1 to 6 carbon atoms such as a methyl, ethyl, butyl or methoxy group.

It is preferred that at least one of the groups R5 its a hydrocarbon radical. If the value of a is greater than one, the groups R5 may be the same or different, for example one group R5 may be a hydrogen atom and at least one group R5 is a hydrocarbon radical, particularly an alkyl group. The group R5 is preferably an alkyl group containing up to 10 carbon atoms and it is especially preferred that the alkyl group contains at least 4 carbon atoms, for example ethyl, n-propyl and especially n-butyl, iso-butyl or 2-ethylhexyl groups.

The value of b is at least one but preferably does not exceed two. The value of a can be zero and it is generally preferred that the value of (a+b) does not exceed two. Especially preferred are those compounds in which the value of b is two and the groups (COOR5) are in the ortho-position to each other. Compounds of the general formula Ra4 Ar(COOR5)b include methyl, ethyl and butyl benzoate, 4-methoxybenoic acid, ethyl 4-methoxybenzoate, methyl 4methylbenzoate and the mono- and diesters of phthalic acid such as diethyl phthalate, di-n-propyl phthalate, di-n-butyl phthalate, di-iso-butyl phthalate and di-2-ethylhexyi phthalate.

Preferably, the Lewis Base component is an organic silicon compound. Organic silicon compounds which may be present include compounds containing one or more Si-OR7, Si-OCOR7 or Si-NR7 bonds, wherein R7 is a hydrocarbon radical which may be substituted with one or more halogen atoms and/or oxyhydrocarbon groups.

Organic silicon compound which may be present as the Lewis Base compound include phenyltriethyoxy silane, diphenyl di-methoxy silane, diphenyl diisobutoxysilane and iso-butyl triethoxysilane.

In the polymerisation catalyst it is preferred to use at least one mole of the organic metal compound which is Component B for each mole of transition metal which is present in Component A of the catalyst system. In general at least 10 moles of the organic metal compound are used for each mole of transition metal but the proportion of Component B preferably does not exceed 250 moles per mole of Component B are from 10 up to 60 moles of the organic metal compound for each mole of transition metal.

The catalyst system may also include a Lewis Base compound and the proportion of Lewis Base compound should not exceed the proportion of Component B of the catalyst system. When the Lewis Base compound is an ester, preferably there is used from 0.05 up to 0.5 moles, especially from 0.1 up to 0.4 moles, of the ester for each mole of Component B. The Lewis Base compound is preferably a silicon compound, and it is preferred to use 0.02 up to 0.2, for example 0.1, moles of the silicon compound for each mole of component B.

The catalyst system of the present invention may be obtained by pre-mixing Components A, B and optional Component C before introducing the catalyst system into the polymerisation reactor. Alternatively, all the catalyst components may be introduced separately into the polymerisation reactor.

The catalyst systems of the present invention are suitable for the polymerisation or copolymerisation of unsaturated monomers, particularly ethylenically unsaturated hydrocarbon monomers such as the olefin monomers.

As a further aspect of the present invention there is provided a process for the production of a polymer or copolymer of an unsaturated monomer wherein at least one unsaturated hydrocarbon monomer is contacted under polymerisation conditions with a polymerisation catalyst as herein before described.

The monomer which may be used in accordance with the present invention has the formula CH2=CHR8 wherein R8 is a hydrogen atom or a hydrocarbon radical.

Thus, the monomers which may be polymerised by the process of the present invention include ethylene, propylene, butene-1, pentene-1, hexene-1, 4-methylpentene-1, styrene, 1,3-butadiene or any other monomer having the above formula. The monomer is preferably an olefin monomer, particularly an aliphatic mono-olefin monomer which contains from 2 up to 10 carbon atoms.

The monomers may be homopolymerised or may be copolymerised together. If a copolymerisation is being effected this may be done using a mixture of monomers which has essentially the same composition throughout the polymerisation process. Alternatively, a sequential polymerisation process, such as described in British patents 970478 and 970479 may be used, for example by polymerising propylene alone and thereafter polymerising a mixture of propylene and ethylene to give a polymer product which contains from 2 up to 20% by weight of ethylene.

The present invention is particularly suitable for the polymerisation of ethylene or propylene, and especially for the polymerisation or copolymerisation of propylene in the gas phase.

Thus, as a further aspect of the present invention there is provided a process for the polymerisation of propylene which comprises contacting gaseous propylene in the substantial absence of any liquid phase with a polymerisation catalyst of the type hereinbefore described and optionally thereafter contacting the polymer productwth a gaseous mixture of propylene and ethylene.

Using the process of the present invention, it is possible to obtain, as a direct product of polymerisation, a propylene polymer having a titanium content of not more than 10, especially less than 5, parts per million by weight. The preferred polymers also contain a low proportion of magnesium and chloride, particularly less than 20 parts per million by weight of magnesium and less than 50 per million by weight of chlorine. Preferred propylene homopolymers contain not more than 8%, and especially less than 5%, by weight of polymer which is soluble in boiling heptane. The low proportion of polymer which is soluble in boiling heptane indicates the high stereoregularity of the propylene polymers obtained.

The process of the present invention may also be used to sequentially polymerise propylene and ethylene to obtain sequential copolymers having a useful combination of properties.

If polymerisation is effected in the gas phase, propylene monomer may be introduced into the polymerisation vessel as a liquid with the conditions of temperature and pressure within the polymerisation vessel being such that major proportion of the liquid propylene vaporises, thereby giving an evaporative cooling effect, whereby the polymerisation vessel contains a solid phase which is the polymerisation catalyst and the polymer formed thereon and a gaseous monomer phase with only a minor proportion of liquid monomer.

Polymerisation in the gas phase may be effected using conditions which are such that the monomer is at a temperature and partial pressure which are close to the dew point temperature and pressure for that monomer, for example, as described in more detail in British patent specification 1532445. Polymerisation in the gas phase may be effected using any technique suitable for effecting a gas-solid reaction, such as a fluidised-bed reactor system, a stirred-bed reactor system or a ribbon-blender type of reactor.

It will be appreciated that the catalyst system hereinbefore described is of the type generally known as a Ziegler-Natta type of catalyst system. As is well known, Zeigler-Natta type catalysts are susceptible to the presence of impurities in the polymerisation system. Accordingly, particularly when a high yield of polymer is desired in relation to the transition metal component of the catalyst system, it is desirable to effect the polymerisation using reagents, that is monomer and possibly diluent, which have a high degree of purity, for example, a monomer which contains less than 5 ppm by weight of water and less than 1 ppm by weight of oxygen. Materials having a high degree of purity can be obtained by processes such as those described in British Patent Specification 1111493, 1226659 and 1383611.

The polymerisation may be effected either in a batch manner or on a continuous basis. The catalyst components may be introduced into the polymerisation vessel separately. When the monomer is propylene or a higher alpha-olefin monomer, the polymerisation may be effected in the presence of an additional Lewis Base compound.

The polymerisation can be effected in the presence of a chain transfer agent such as hydrogen in order to control the molecular weight of the polymer product. The proportion of chain transfer agent used will be dependent on the polymerisation conditions and on the particular monomer or monomer mixture which is being polymerised. Using hydrogen in the polymerisation of propylene, it is preferred to use hydrogen in an amount of from 0.01 up to 5.0%, particularly from 0.05 up to 2.0% molar relative to the monomer.However, when the monomer being polymerised is ethylene, or a mixture in which ethylene is a major polymerisable component (by moles), the amount of hydrogen used is typically much greater, for example, in the homopolymerisation of ethylene the reaction mixture may contain in excess of 50% molar of hydrogen, whereas if ethylene is being copolymerised, the proportion of hydrogen used is typically up to 35% molar of the total reaction mixture.

The polymerisation can be effected under any conditions which have been previously proposed for effecting the polymerisation of olefin monomers. Thus, ethylene polymerisation may be effected at pressures of up to 3000 kg/cm2, and at such pressures the polymerisation temperature may be as high as 300"C.

However, it is preferred to carry out the polymerisation at comparatively low pressures and temperatures, particularly for the production of polymers of the higher olefins (including propylene) which have a high stereoregularity. More specifically, the polymerisation is effected at pressures which are conveniently in the range from 1 up 100 kg/cm2, preferably at a pressure of up to 50 kg/cm2 and especially at pressures in the range from 5 up to 40 kg/cm2.

The polymerisation temperature used will be dependent in part on the particular polymerisation technique being used. Thus, it is possible to use polymerisation temperatures in excess of the melting point of the polymer and such conditions may be used in the polymerisation, or copolymerisation, of ethylene in the presence of a hydrocarbon liquid which can act as a solvent for the polymer formed. However, in general, it is preferred to use temperatures below the melting temperature of the polymer formed and in particular it is preferred to use temperatures of not more than 1 OO"C. The polymerisation temperature is typically in the range from 40"C up to 1000C.

It is generally preferred to effect all stages in the preparation of the composition and of the transition metal composition in an inert atmosphere such as water vapour. Very preferably the polymerisation process of the present invention should also be effected in the essential absence of such impurities since these can have a harmful effect on the polymerisation process.

The polymers obtained by the process of the present invention have a high molecular weight as indicated by the melt flow index of the polymer, which is typically in the range from 0.01 up to 1000. For propylene polymers, including copolymers, the melt flow index can be measured by ASTM Test Method D1238/70, using a temperature of 190"C and a weight of 10kg.

Various aspects of the present invention will now be described with reference to the following Examples which are illstrative of the invention. In the Examples, all operations are effected under an atmosphere of essentially oxygen- and water-free nitrogen unless otherwise indicated. All the glass apparatus was dried in air oven at 1 200C for at least one hour and purged with nitrogen before use.

In the propylene polymerisation examples, the propylene used for the polymerisation had been purified further by passing gaseous propylene of commercial purity through a column containing granules of Alcoa F1 alumina at ambient temperature.

Example 1 A) Reaction of titanium tetra n-butoxide with phthalic anhydride Into a Schlenk tube of capacity 200 cm3, provided with a magnetic stirrer, were placed 100 cm3 of an aliphatic hydrocarbon diluent consisting essentially of dodecane isomers and having a boiling point in the range 170"C to 1 800C (hereafter referred to simply as the "aliphatic hydrocarbon"). The contents of the tube were stirred and 2.96 g (about 20 millimoles) of phthalic anhydride were added. 6.8 cm3 (about 20 millimoles) of titanium tetra n-butoxide (obtained from BDH) were then added dropwise to the stirred suspension from a syringe. The Schlenktube containing the stirred mixture was placed in an oil bath and heated up to 1 100C, at which temperature a clear, essentially colourless solution was obtained.The temperature was maintained at 110for 15 minutes and the Schlenktube was removed from the bath and allowed to cool to ambient temperature with stirring. The product obtained at ambient temperature was a clear, aimost colourless (very pale yellow) solution.

B) Reaction with magnesium ethoxide Into a three necked 500 cm3 glass vessel having a sinter base, fitted with a mechanical stirrer and connected to a source of nitrogen were placed 6.64 (about 58.2 millimoles) of magnesium diethoxide (obtained from Dynamit Nobel). 50 cm3 of the solution obtained in Stage A) (this contained about 10 millimoles of titanium) were then added and the mixture was stirred at ambient temperature for 5 minutes.

The vessel was then placed in an oil bath and heated up to 120"C over a period of one hour whilst stirring the contents. The vessel was removed from the oil bath once a temperature of 120"C was attained and was allowed to cool to ambient temperature whilst continuing to stir the contents. 20 cm3 of the aliphatic hydrocarbon were then added and the mixture was allowed to stand, without stirring overnight.

Example 2 100 cm3 of titanium tetrachloride were added to the product mixture of Example 1 in the reaction vessel used in stage B). A pale yellow solid was formed and the mixture initially became quite sticky but was less sticky when the addition of titanium tetrachloride had been completed. The mixture was stirred and heated up to 11 00C over a period of one hour and was maintained, with stirring, at 11 00C for a period of one hour. Stirring was stopped and it was observed that a substantial proportion of the product showed little tendency to settle even after 5 minutes. Whilst maintaining the temperature at 1 100C, the excess liquid was removed through the sinter over a period of about one hour.

150 cm3 of titanium tetrachloride were added to the solid residue and the mixture was stirred for a further 1.25 hours. Stirring was stopped and the liquid withdrawn from the hot mixture through the sinter.

100 cm3 of the aliphatic hydrocarbon (at 1 100C) were then added, the mixture was stirred at 1 1 OOC for 10 minutes, stirring was stopped and the liquid withdrawn through the sinter. This step was repeated using 200 cm3 of the aliphatic hydrocarbon. 400 cm3 of the aliphatic hydrocarbon at 1 1 OOC were added, the vessel was removed from the oil bath and stirring was continued whilst the temperature fell to about 80"C. The liquid was then removed through the sinter. Two further washing steps were effected without heating and using 300 cm3 and 400 cm3 respectively of the aliphatic hydrocarbon at ambient temperature.

The solid obtained was finally suspended in 230 cm3 of the aliphatic hydrocarbon to give a suspension having a titanium content of about 11 millimoles/dm3.

Example 3 A) Reaction oftitanium tetra (2-ethyihexoxide) with phthalic anhydride The process of Example 1, stage A was repeated with the following modifications.

90 cm3 of aliphatic hydrocarbon were used together with 12.2 cm3 (about 20 millimoles) of titanium tetra (2-ethylhexoxide) and the mixture was heated to 85"C and maintained at 85"C for one hour.

B) Reaction with magnesium ethoxide The process of Example 1, stage B) was repeated with the following modifications.

7.1 g (about 62.1 millimoles) of magnesium diethoxide, 20 cm3 of the aliphatic hydrocarbon and 50 cm3 of the solution obtained in stage A) of this Example were placed in the vessel and heated to a temperature in the range 125" to 130"C over a period of 0.75 hour. Once at temperature, the bath heater was switched off and stirring was continued for 20 minutes. The vessel was then removed from the hot bath and allowed to cool overnight without stirring.

Example 4 The process of Example 2 was repeated with the following modifications.

The material treated with titanium tetrachloride was the product of Example 3.

During the washing stages, filtration became difficult and hence only about 80 cm3 of the hot aliphatic hydrocarbon was removed by filtration at the end of the first washing stage. After the second hot washing, the mixture was allowed to cool and settle overnight. The supernatant liquid was removed mainly by decantation with some filtration. The solid was then washed twice with the aliphatic hydrocarbon (200 cm3 for each wash) and the supernatant liquid was removed by decantation and some filtration.

The solid was finally suspended in the aliphatic hydrocarbon to give a total volume of about 150 cm3 with a titanium content of about 17 millimoles/dm3.

Example 5 The product of Example 3 was used to polymerise propylene.

A two dm3 polymerisation flask equipped with an efficient stirrer and a water jacket was dried carefully and one dm3 of the aliphatic hydrocarbon was introduced. The diluent was evacuated at 70"C and purged with nitrogen, this procedure being effected a total offourtimes, which treatment effectively reduced the water and oxygen contents of the diluent to below 10 ppm by weight. The diluent was then saturated with the purified propylene to one atmosphere pressure, the mixture was stirred and stirring was continued throughout the following stages. Ten millimoles of triethyl aluminium were introduced as one molar solution in the aliphatic hydrocarbon followed by one millimole of diphenyl dimethoxysilane as a 0.5 molar solution in the aliphatic hydrocarbon.After five minutes, 5 cm3 of the suspension obtained as described in Example 3 were introduced. The pressure in the reaction vessel was maintained at one atmosphere by supply of propylene from a cylinder. Hydrogen (25 cm3 at ambient temperature and pressure) was added after 8 and 70 minutes from the addition of the product of Example 3. After a period of two hours from the introduction of the product of Example 3 the run was termimated by removing the propyiene and passing nitrogen into the reaction vessel. The rate of addition of propylene was continuously monitored and from this it was determined that the rate of polymerisation during the second hour was 0.75 that of the rate of polymerisation during the first hour.

From the rate of addition of propylene it was calculated that the catalyst activity was 442 g/millimole/one atmosphere pressure/hour.

Example 6 The process of Example 5 was repeated using the product of Example 4.

The rate of polymerisation during the second hour was 0.69 that of the rate of polymerisation during the first hour. The catalyst activity was calculated to be 1 36g/millimole/one atmosphere pressure/hour.

Examples 7and8 The products of Examples 3 and 4 were used to effect the polymerisation of liquid propylene in the essential absence of any other liquids.

Polymerisation was carried out in a stainless steel autoclave, of total capacity 8 litres, which was fitted with a vertical anchor stirrer. The autoclave was heated to 70"C, evacuated, and the vacuum was released with nitrogen. The autoclave was then evacuated again and the procedure repeated 5 times. The autoclave was evacuated a further three times, the vacuum being released with propylene. The autoclave was then cooled to 20"C under propylene at a pressure of about 0.14 kg/cm2 gauge. A solution of aluminium triethyl (10 gm millimoles) in the aliphatic hydrocarbon was injected into the above-described autoclave containing propylene gas at 20"C and 0.14 kg/cm2 gauge. A further solution containing diphenyl dimethoxy silane (1 gm millimole) was also injected into the autoclave.A suspension of the product of Example 3 or Example 4 in 5 cm3 of the aliphatic hydrocarbon was injected into the autoclave and then 5 litres of liquid propylene were added over a period of 40 minutes, the stirrer being operated at 150 rpm. This propylene addition was effected by forcing 5.5 litres of liquid propylene to transfer under applied nitrogen pressure from a burette at ambient temperature to the autoclave. Hydrogen (200 gram millimoles) was then added and the temperature of the autoclave contents was raised at 700C. The hydrogen was commercially available hydrogen (99.9% pure) which had been further purified by passing through a column (8 inches by 4feet in length) containing a molecular sieve material (Union Carbide 3A) at 20 C. The hydrogen was stored in the sieve column and drawn off as required.Polymerisation was allowed to proceed at a temperature of 70"C and a pressure of about 31.6 kg/cm2 gauge. More hydrogen (20 gram millimoles on each occasion) was added at 15 minute intervals from the time of the first hydrogen addition. After polymerisation for 1.5 hours, (measured from the time the addition of the liquid propylene had been completed), the autoclave was vented over a period of 10 minutes to remove unpolymerised propylene, and a white powder was obtained. Further details are given in the Table.

TABLE Ex Tran Comp PolymerProperties No Type MFI Ti Al Cl Mg FM HHS (a) mM (b) (c) (c) (c) (c) (d) (e) 7 3 0.055 6.4 1.67 338 41.4 17.0 1.38 3.11 8 4 0.045 8.5 2.39 247 36.0 12.4 1.24 7.5 Notes to Table (a) 3 and 4 indicate the transition metal compositions obtained in accordance with Examples 3 and 4 respectively.

(b) MFI is the melt flow index measured byASTMTestMethod D 1238/70, using atemperatureof190 C and a weight of 10 kg.

(c) The titanium (Ti), aluminium (Al), chlorine (Cl) and magnesium (Mg) residues from the catalyst are given in parts per million by weight relative to the total polymer product (polymer+catalyst residues) and were measured by X-ray fluorescence on compression moulded discs.

(d) FM is the flexural modulus expressed in GN/m2. The flexural modulus was measured using a cantilever beam apparatus as described in Polymer Age, March 1970, pages 57 and 58. The deformation of a test strip at 1% skin strain after 60 seconds at 23"C and 50% relative humidity was measured. The test strip which had dimensions of approximately 150x19x1.6 mm, was prepared in the following manner.

23 g of the polymer were mixed with 0.1% by weight of an antioxidant ('Topanol' CA), and the mixture was added to a Brabender Plasticiser, at 190"C, 30 rpm and under a load of 10 kg to convert it to a crepe. The crepe was placed within a template, between aluminium foil and pressed by means of an electric Tangye press at a temperature of 250 C. The pressing was pre-heated for a period of 6 minutes, under just enough pressure to make the polymer flow across the template, that is an applied force of about 1 tonne. After the pre-heat period, the applied force was raised to 15 tonne in 5 tonne increments, degassing (that is releasing pressure) every 5 tonnes. After 2 minutes at 15 tonnes, the press was cooled by means of air and water for 10 minutes or until room temperature was reached. The plaque obtained was then cut into strips of dimensions 150x19x1.6 mm.

Duplicate strips of each polymer were placed into an annealing oven at 130"C and after 2 hours at this temperature the heat was switched off and the oven cooled to ambient temperature at 150C per hour.

(e) HHS is the proportion by weight of the polymer which is soluble in boiling heptane as determined from the weight loss of a sample of polymer after Soxhlet extraction with the heptane fraction for 24 hours.

Claims (36)

1. A composition which is the reaction product of I) a solid magnesium compound, and II) a derivative of a carboxylic acid having the formula

wherein R is a divalent hydrocarbon or substituted hydrocarbon residue; R1, R2 and R3, which may be the same or different, are monovalent hydrocarbon or substituted hydrocarbon residues; M is an element, other than carbon, from Group IV of the Periodic Table of the elements; v is the valency of M; and xis 0, 1 or 2, with the proviso that (v-l-x) has a value of at least one.

2. A composition as claimed in claim 1 wherein the solid magnesium compound is of the type MgX1X2yL where Xa and X2 may be the same or different and are halogen atoms or alkoxide groups; Lisa ligand; and y is zero or has a value of up to 8.

3. A composition as claimed in claim 2 wherein the solid magnesium compound is a magnesium dihalide, a magnesium dihalide-alkanol complex, a magnesium halide alkoxide or a magnesium dialkoxide.

4. A composition as claimed in any one of claims 1 to 3 wherein the group R is divalent aromatic, or saturated or unsaturated aliphatic or cycloaliphatic residue.

5. A composition as claimed in claim 4 wherein the group -COOMR1X (OR2)(v-Ix) and the group COOR3 are attached to adjacent carbon atoms in the group R.

6. A composition as claimed in any one of claims 1 to 5 wherein the group R1, if present, is an aryl group and the groups R2 and R3 are alkyl groups containing from 1 to 8 carbon atoms.

7. A composition as claimed in any one of claims 1 to 5 wherein M is silicon or titanium.

8. A composition as claimed in claim 7 wherein the derivative of a carboxylic acid has the formula

where R, R2 and R3 are as defined.

9. A composition as claimed in claim 8 whrein R is 1,2-phenylene and R2 and R3 are the same and are ethyl, n-butyl or 2-ethylhexyl groups.

10. A composition as claimed in any one of the claims 1 to 9 wherein the derivative of a carboxylic acid has been preformed in situ.

11. A composition as claimed in claim 10 wherein the derivative of a carboxylic acid is the in situ reaction product of an anhydride of a dicarboxylic acid with a compound containing at least one M-OR2 bond wherein the anhydride of a carboxylic acid has the formula

and the compound containing at least one M-OR2 bond has the formula MR1X(OR2)(v-x) where M, R, R1, R2, v and x are as defined.

12. A composition as claimed in any one of claims 1 to 11 containing 0.5 to 20 moles of the magnesium compound for each mole of the derivative of the carboxylic acid.

13. A process for the production of a composition which comprises reacting I) a solid magnesium compound with II) a derivative of a carboxylic acid having the formula

wherein R is a divalent hydrocarbon or substituted hydrocarbon residue; R1, R2 and R3, which may be the same or different, are monovalent hydrocarbon or substituted hydrocarbon residues; M is an element, other than carbon, from Group IV of the Periodic Table of the element, v is the valency of M; and x is 1 or 2, with the proviso that (v-l-x) has a value of at least one.

14. A process as claimed in claim 13 wherein the derivative of a carboxylic acid is prepared in situ in a pre-reaction stage.

15. A process as claimed in claim 14 wherein the derivative of a carboxylic acid is prepared from the anhydride of a carboxylic acid having the formula

and a compound having the formula MR1X(OR2)(VX) where M, R, R1, R2, v and x are as defined.

16. A process as claimed in claim 15 wherein the pre-reaction stage is effected at a temperature of at least 60"C and in the presence of an inert liquid hydrocarbon or halohydrocarbon.

17. A process as claimed in claim 16 wherein the solid magnesium compound is added to the reaction mixture obtained in the pre-reaction stage without isolating the derivative of a carboxylic acid.

18. A process as claimed in any one of claims 13 to 17 wherein the reaction with the solid magnesium compound is effected in the presence of an inert liquid and at a temperature of at least 60"C.

19. A process as claimed in any one of claims 13 to 18 wherein 0.5 up to 20 moles of the magnesium compound are used for each mole of the derivative of a carboxylic acid.

20. A process which comprises reacting Ti(OR2)4 with phthalic anhydride in an inert liquid hydrocarbon or halohydrocarbon at a temperature of at least 100"C and adding a solid magnesium dihalide, a solid magnesium dihalide-alkanol complex or a solid magnesium alkoxide to the product mixture and reacting further at a temperature of at least 1 OO"C; where R2 is a monovalent hydrocarbon or substituted hydrocarbon residue.

21. A transition metal composition which is the composition of any one of claims 1 to 12 or of the product of the process of any one of claims 13 to 20 with a compound of a transition metal which does not contain any metal/OR2 bonds when the transition metal is one from Group IVA of the Periodic Table.

22. A composition as claimed in claim 21 wherein the compound of a transition metal is a chloride.

23. A composition as claimed in claim 22 wherein the compound of a transition metal is titanium tetrachloride.

24. A process for the production of a transition metal composition which comprises reacting a composition as claimed in any one of claims 1 to 12 or a product obtained by the process of any one of claims 13 to 20 with a compound of a transition metal, which compound does not contain any metal/OR2 bonds when the transition metal is one from Group IVA of the Periodic Table.

25. A process as claimed in claim 24 wherein the compound of a transition metal is titanium tetrachloride.

26. A process as claimed in either claim 24 or claim 25 wherein reaction with the compound of a transition metal is effected in one or two stages.

27. A process as claimed in any one of claims 24 to 26 wherein the reaction is effected in a liquid phase which contains more than 25% by weight of the compound of a transition metal.

28. A process as claimed in claim 27 wherein the compound of a transition metal is a liquid and the liquid phase consists solely of the liquid compound of a transition metal.

29. A process as claimed either claim 27 or claim 28 which is effected at a temperature of at least 60"C up to the boiling temperature of the liquid phase.

30. A process as claimed in any one of claims 24 to 29 wherein the transition metal composition obtained is washed at least once at a temperature of 60"C up to 120"C using an inert hydrocarbon or halohydrocarbon.

31. A polymerisation catalyst which comprises A) a transition metal composition as claimed in any one of claims 21 to 23 or which is the product obtained by the process of any one of claims 24 to 30; and B) an organic compound of aluminium or of a non-transition metal of Group IIA of the Periodic Table, or a complex of an organic compound of a non-transition metal of Group IA or IlA of the Periodic Table together with an organic aluminium compound.

32. A catalyst as claimed in claim 31 which also includes C) a Lewis Base compound which is an ether, an ester, a ketone, an alcohol, an ortho-ester, a sulphide, an ester of a thiocarboxylic acid, a thioketone, a thiol, a sulphone, a sulphonamide, a fused ring compound containing a heterocyclic sulphur atom, an organic silicon compound, an amine, urea, a substituted urea, thiourea, or an organic phsophorus compound.

33. A catalyst as claimed in claim 32 where the Lewis Base compound is an organic silicon compound containing one or more Si-OR7, Si-OCOR7 or Si-NR7 bonds, wherein R7 is a hydrocarbon radical which may be substituted with one or more halogen atoms and/or oxyhydrocarbon groups.

34. A process for the production of a polymer or copolymer of an unsaturated monomer wherein at least one unsaturated hydrocarbon monomer is contacted, under polymerisation conditions, with a polymerisation catalyst as claimed in any one of claims 31 to 33.

35. A propylene polymer whenever obtained by the process of claim 34.

36. A propylene polymer as claimed in claim 35 which is a direct product of polymerisation and has a titanium content of less than 5 parts per million by weight, a magnesium content of less than 20 parts per million by weight and a chlorine content of less than 50 parts per million by weight.