GB2103627A

GB2103627A - Transition metal composition

Info

Publication number: GB2103627A
Application number: GB08124149A
Authority: GB
Inventors: Dr John William Kelland
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1981-08-07
Filing date: 1981-08-07
Publication date: 1983-02-23

Abstract

A titanium-containing composition is obtained by forming a magnesium halide-ester material, suspending this material in a liquid medium containing titanium tetrachloride, (preferably undiluted liquid titanium tetrachloride at elevated temperature) separating the solid from the liquid phase, repeating the treatment with titanium tetrachloride, and washing the solid product at least once to give a product in which the titanium level is in the range from 1 up to 5% by weight. The magnesium halide-ester material is conveniently produced by grinding together magnesium halide and an ester, such as magnesium chloride and ethyl benzoate. The titanium-containing composition may be combined with an organic metal compound such as aluminium triethyl and preferably a Lewis Base, particularly an ester such as ethyl benzoate, methyl p-methylbenzoate, or ethyl p-methoxy-benzoate, to give olefin polymerisation catalyst. The particle form of the titanium-containing composition can be improved by including a spray-drying step in the process of producing the composition or by spray- drying the composition when it has been produced.

Description

SPECIFICATION Transition metal composition production and use The present invention relates to the production of a transition metal composition, catalyst systems containing such transition metal compositions and the use of such catalyst systems to polymerise unsaturated monomers, particularly olefin monomers such as ethylene and propylene.

In recent years, considerable effort has been directed to the production of polymerisation catalysts which are highly active whereby there is no need to remove catalyst residues from the polymer at the end of the polymerisation. For the polymerisation of propylene and the higher olefin monomers it is also necessary that the catalyst system should be stereospecific. Considerable effort has been directed to producing catalysts which combine high activity with good stereospecificity and catalysts have been developed which are capable of giving high yields of propylene polymers which are more than 90% insoluble in boiling heptane.

Furthermore, the improvements in the catalyst system have made it possible to modify the polymerisation technique used. In particular, the polymerisation technique may be simplified to avoid the steps of post-treating the polymer product, which post-treatment has been necessary hitherto. To simplify the process even further, processes are now being used in which the polymerisation is carried out in the absence of any substantial quantity of inert hydrocarbon liquids in contrast to many prior art processes in which inert hydrocarbon liquids are as the suspension medium for the polymerisation process. One technique which avoids the use of any substantial quantity of inert hydrocarbon liquids carries out the polymerisation by using the monomer in the gaseous state and by contacting this gaseous monomer with growing polymer particles which contain active polymerisation catalyst.Using such a technique, the whole polymer product is recovered without separating any atactic polymer which may be formed. Hence, for use in such a process, it is necessary that the catalyst system should be particularly stereospecific. Whilst catalyst systems disclosed in the art, for example in British patent specifications 1 540 323 and 1 559 194, have high activity and good stereospecificity, we have found that these systems, when used in a gas phase polymerisation process, give a propylene polymer product the properties of which are not as good as the desired properties. Surprisingly however, we have found that by a modification of the processes of the prior art, the stereospecificity of the catalyst system produced is improved and the catalyst is then highly suitable for use in the gas phase polymerisation process to give propylene polymer products having useful properties.

According to the present invention there is provided a process for the production of a titanium containing composition which process comprises forming a solid material having the composition MgX2nR'COOR2, contacting the said solid material with a liquid phase containing titanium tetrachloride, separating a solid intermediate from the liquid phase, contacting this solid intermediate with a liquid phase containing titanium tetrachloride, separating a solid from this liquid phase, washing the separated solid at least once with an inert liquid hydrocarbon or halohydrocarbon and recovering a solid, titanium-containing material having a titanium content which is in the range from one up to 5% by weight, wherein Xis a halogen atom; R1 is a hydrocarbon radical which may be substituted with one or more halogen atoms and/or oxyhydrocarbon groups;; R2 is a hydrocarbon radical which may be substituted by one or more halogen atoms; and n has the value of from 0.1 upto 10.

In contrast previous process, we have found that it is not necessary to effect the washing of the separated solid to remove all of the soluble titanium-containing species from the separated solid. More specially, we have obtained satisfactory products wherein at least 25% by weight, and in some cases in excess of 50% by weight, of the titanium-containing species are capable of being removed by continued washing with a hot hydrocarbon or halohydrocarbon liquid such as for example heptane.

In the solid material it is preferred that Xis chlorine or bromine and is especially chloride. The groups R' and R2 may be the same or different and it is preferred that one, but not both, of the groups R1 and R2 includes an aryl group. The group R1 is conveniently an optionally substituted alkyl or aryl group, for example, a methyl, ethyl, or especially a phenyl, a tolyl, a methoxyphenyl, a fluorophenyl or a benzyl group.

The group R2 is preferably an alkyl group containing up to 6 carbon atoms, for example, a methyl, ethyl or butyl group. It is particularly preferred that R1 is, or contains, an aryl group and that R2 is an alkyl group. The solid material may be a magnesium chloride-ethyl benzoate composition, for example a material wherein the value of n is from 0.2 up to 2, and especially from 0.2 up to 1.

The solid material of composition MgX2nR1COOR2 may be prepared by any means suitable for the preparation of such composition. A convenient technique for preparing the composition is by grinding together a magnesium halide and a suitable proportion of an ester.

Thus, as a further aspect of the present invention, the magnesium halide-ester composition is obtained by grinding a magnesium halide and an ester of the formula R1COOR2 in the proportion of n moles of the ester for each mole of the magnesium halide, wherein R1, R2 and n are as hereinbefore defined.

The grinding may be carried out in any suitable grinding apparatus such as, for example, a rotating ball mill or a vibrating ball mill. The grinding is very 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 30 hours. Any suitable temperature may be used for the grinding, for example, from - 50"C u p to 1 000C, especially from -1 O"C up to am bient temperature, 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, which is the generally desired procedure, for example at ambient temperature, 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 using such a mill a shorter time of grinding is possible than when a rotating ball mill is used.

The magnesium halide-ester composition, once obtained, is contacted with a liquid phase which contains titanium tetrachloride. The liquid phase generally contains more than 25% by weight of titanium tetrachloride, and it is preferred that the liquid phase contains at least 45% by weight of titanium tetrachloride, and it is especially preferred that the liquid phase consists solely of liquid titanium tetrachloride. If a solution of titanium tetrachloride is used, the solvent is preferably an inert material, particularly an inert hydrocarbon or halohydrocarbon, especially an aliphatic hydrocarbon. The solid material may be agitated, typically by stirring, to form a suspension thereof in the titanium tetrachloridecontaining liquid.Preferably, the contacting of the solid material with the titanium tetrachloride-containing liquid is effected, at least partially, at an elevated temperature which is conveniently at least 600C up to the boiling temperature of the liquid phase, which is 137"C when the liquid phase is undiluted titanium tetrachloride. Preferably, the contacting is effected at a temperature in the range 80"C up to 1 20 C. The solid material may be contacted with the titanium tetrachloride-containing liquid when the liquid is at the desired elevated temperature or the solid material may be contacted with the liquid at a lower temperature, which is conveniently ambient temperature, and the mixture is then heated to the desired elevated temperature.

The solid material is contacted with the liquid titanium tetrachloride-containing phase for a period of time of from 0.25 hours up to 10 hours conveniently 0.5 up to 5 hours.

A solid intermediate is separated from the liquid phase, which contains titanium tetrachloride, 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, we have found that, when operating in accordance with the present invention, the solid may include fine particulate material, the presence of which can cause blockage of the filter and this is undesirable on a commercial scale and outweighs any advantage of complete separation.

The separated solid intermediate is then contacted with a liquid phase containing titanium tetrachloride.

The manner in which this contacting is carried out is as described for the contacting of the magnesium halide-ester composition with the titanium tetrachloride-containing liquid phase. Conveniently both stages in which a solid material is contacted with a titanium tetrachloride-containing liquid phase are effected under essentially the same conditions of temperature and time.

After contacting the solid intermediate with the liquid phase containing titanium tetrachloride, the separated solid thus obtained is washed at least once with an inert liquid hydrocarbon or halohydrocarbon.

Suitable liquids include hexane, heptane, octane, decane, dodecane and mixtures of the isomers thereof, and aromatic liquids such as benzene, toluene and chlorobenzene. The washing is conveniently effected by suspending the solid in the inert liquid hydrocarbon or halohydrocarbon medium and agitating the mixture for a period of time of at least 0.25 hours up to 10 hours conveniently 0.5 up to 5 hours. The number of washing steps used will depend on the quantity of the inert liquid hydrocarbon or halohydrocarbon 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 1 20 C, and especially at least 800C.

The at least one washing step is believed to remove complexes of titanium tetrachloride and the ester from the product and also to remove any excess unreacted titanium tetrachloride which remains after the contacting with the titanium tetrachloride. For the removal of the complexes, it is 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, although 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 solid by a decantation process, or by using a siphon, the solid contains unseparated liquid which typically includes unreacted titanium tetrachloride and the proportion of this unreacted titanium tetrachloride can be reduced by washing at ambient temperature.

It is preferred to effect the washing step, or the first washing step, before any substantial cooling has occurred after separating the solid from the liquid phase containing titanium tetrachloride. Thus, it is preferred to add the inert hydrocarbon or halohydrocarbon liquid to the separated solid within a few minutes, for example within one to 30 minutes, of removing the liquid phase containing 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.The washing may be effected without allowing any appreciable cooling of the separated solid 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 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 15 minutes up to 4 hours.If the separated solid intermediate is 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 usig heptane at reflux temperature, which 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 solid material, particularly from 8 cm3 to 12 cm3 for each gramme of solid material.

If the washing step, or at least the first washing step, is effected before the separated solid has cooled appreciably, for example before the separated solid has cooled below 70"C, and if heating is continued throughout the washing, we have found that satsfactory 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 solid and the inert hydrocarbon or halohydrocarbon liquid at the elevated temperature and continuing the agitation for from 5 minutes up to two hours, typically for 10 minutes up to 45 minutes 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 unreated titanium tetrachloride which remains with the solid.

If the separated solid has been allowed to cool to ambient temperature before effecting a washing step, it is preferred to effect the washing stpe, or the first washing step, at the elevated temperature using a higher temperature and/or for a longer period of time in order to ensure that materials which are insoluble at the initial low temperature, such as complexes of titanium tetrachloride and the ester, are dissolved and extracted by the washing step.

The solid may be separated from the liquid phase by filtration, decantation or by means or a siphon. The latter two techniques do not remove all of the liquid from the solid and hence more washing steps may be required to remove unreacted titanium tetrachloride from the solid. However, the solid may contain a significant proportion (for example at least 10% by weight) of particles having a particle size of less than 5 microns, and the presence of such small particles may adversely effect the efficiency of a filtration process.

Using a siphon to effect separation of the solid from the liquid, we have obtained a satisfactory product by effecting a first washing step at a temperature of about 1 00 C, a second washing step with the temperature rising to be in the range 35 to 60"C and one further washing step at essentially ambient temperature.

According to a preferred aspect of the present invention, it is not not necessary to remove all of the removable titanium materials by the washing steps. Indeed, we have obtained solid, titanium-containing materials which contain a substantial porportion of titanium species which can be removed by continued hot washing with an inert hydrocarbon or halohydrocarbon liquid, and we have found that such materials, when used as a catalyst component to polymerise propylene, give a high yield of a polymer having good stereoregularity (more than 90% is insoluble in boiling heptane). We have found that continued hot washing can reduce the titanium content of the final product to below one percent by weight but we prefer that the titanium content of the final product is in the range from 1.5 up to 3% by weight and particularly that the titanium content is not below 2% by weight.In the preferred products obtained by the process of the present invention, a substantial proportion of the titanium which is at least 25% and may be in excess of 50%, is capable of being removed by continued hot washing with an inert hydrocarbon or halohydrocarbon liquid.

However, the presence of such quantities of extractable titanium species does not detract from the characteristics of the product when used as a component of an olefin polymerisation catalyst which has high activity and high stereospecificity.

The magnesium halide-ester composition can be obtained by a grinding process. The product obtained by the grinding process typically contains a significant proportion, typically at least 10% by weight, or particles of a fine particle size of less than 5 microns. Furthermore, the ground product, in addition to having a poor particle size distribution, also has a particule form which is not ideal for a catalyst component. Since the particle form of the particles of the solid catalyst component may be replicated by the polymer product, for example when polymerising propylene the particle form, and in particular the powder flow, of the polymer product wil not be ideal. Furthermore, if the polymerisation is effected by a gas phase process, particularly a fluidised bed process, the fine particle size materials will be readily entrained in the circulating gas stream and removed from the polymerisation reactor. This could result in a highly active catalyst in the circulating gas stream causing continuing polymerisation with deposition of polymer in, and possibly blocking of, the circulating gas loop. To minimise these problems, it is desirable to improve the particle form of the solid titanium-containing material which is the product of the process of the present invention.

The particle form of the final product may be improved by suspending a solid material in an inert liquid medium, spray-drying the suspension formed and collecting a spray-dried solid material wherein the solid material is the magnesium halide-ester composition or the solid obtained in a subsequent stage of the process of the present invention, including the final product. Preferably, the solid material which is spray-dried is the magnesium halide-ester composition or the solid titanium-containing material which is the product obtained by the process of the present invention. If the magnesium halide-ester composition is spray-dried, the spray-dried product thereby obtained is thereafter contacted twice with titanium tetrachloride and washed at least once in accordance with the process of the present invention.

Thus, as a further aspect of the present invention, a spray-drying step may be incorporated either before the first stage, between two successive stages or after the final stage of the process hereinbefore described.

The spray-drying step can be effected using conventional spray-drying techniques. To effect spray-drying, the suspension is passed through a suitable atomizer which creates a spray or dispersion of droplets of the suspension, a stream of a hot gas is arranged to contact the droplets and cause evaporation of the liquid medium and the solid product which separates is collected. Suitable atomizers for producing the droplets of the supension include nozzle atomizers and spinning disc atomizers. The inert liquid medium used for the spray-drying may be any liquid medium which does not have a deleterious effect on the characteristics of an olefin polymerisation catalyst system which incorporates the spray dried material.Typically the inert liquid medium is a liquid hydrocarbon such as an aliphatic, aromatic or cycloaliphatic hydrocarbon or a halohydrocarbon such as chlorobenzene, but other materials such as titanium tetrachloride or polar materials such as esters may be used even though such materials are not normally regarded as inert when used in an olefin polymerisation process.

The product obtained by including a spray-drying stage in the process of the present invention typically contains a reduced proportion of fine particulate material and has a particle form which is generally spherical. The product obtained by using a spray-drying stage is suitable for effecting polymerisation in the gas phase.

Spray-drying of suspensions which include a transition metal compound, particularly where at least a part of the solid component of the suspension is, or contains, a transition metal compound, is the subject of our European Patent Application No. 81 300930.5. After contacting the mgnesium halide-ester composition at least once with titanium tetrachloride, the solid product contains a titanium chloride species and may be spraydried in accordance with European Patent Application No. 81 300930.5. However, the spray-drying step may be effected using a magnesium halide or the magnesium halide-ester composition and thereafter effecting the subsequent stages of the present invention using the spray-dried support material.

Spray-drying of catalyst supports such as silica, alumina and magnesium halide materials and subsequently contacting the spray-dried support material with a transition metal compound is the subject of our copending application of even date herewith entitled "Supported Transition Metal Composition".

The various solid materials obtained at different stages of the present invention typically include not only fine particles but also some coarser particles having a particle size which exceeds 50 microns. The presence of such coarser parties may cause blocking of a spray-drying apparatus or may result in the spray-dried material containing such coarser particles which have been essentially unaffected by the spray-drying and have an undesirable particle size and/or shape.

As a preliminary stage before spray-drying, a suspension of the solid in a liquid medium may be subjected simultaneously to vigorous agitation and shearing, for example using a device which is suitable for the production of a liquid-liquid emulsion, as is described in more detail in our copending application of even date herewith entitled "Dispersing transition metal compounds and Use". Suitable devices for this purpose are stirrers of the Ultra Turrax type (available from Janice and Kunkel KG IKA Werke) and high shear mixers such as are available from Silverson Machines Limited of Chesham, Buckinghamshire, England.The procedure of vigorous agitation and shearing may be applied to the solid material at any stage of the present invention and the thus-treated solid is then spray-dried and the spray-dried solid subjected to any remaining stages of the process of the present invention.

As an alternative preliminary stage before spraydrying, the solid may be mixed with a liquid medium and the mixture subjected to a grinding process and the ground mixture spray-dried as is described in more detail in our copending application of even date herewith entitled "Spraying Solid". This procedure may be applied to the solid material at any stage of the present invention but it is preferred to effect the grinding in the presence of the liquid medium using a magnesium halide or a magnesium halide-ester composition, spray-drying the mixture and subjecting the spray-dried solid to any remaining stages in the process of the present invention.

If a spray-drying step is included, the spray-dried solid is an agglomerate of smaller particles. In general, in using the spray-dried solid it will be subjected to shearing forces due to agitation or being circulated through pipe-work, and these shearing forces may cause at least some break-down of the spray-dried solid to smaller particles. To minimise such break-down it is preferred to incorporate into the spray-dried solid a material which renders the spray-dried solid more resistant to attrition and which may also assist in the agglomeration of the solid particles during the spray-drying step. For convenience hereafter, such a material will be referred to as an "attrition inhibitor".

The attrition inhibitor is conveniently present during the spray-drying stage and is typically present as a solution in the inert liquid medium in which the solid is suspended. The attrition inhibitor should be such that, or should be used in an amount such that, it does not have an appreciable adverse effect on the activity and stereospecificity of an olefin polymerisation catalyst system which includes a solid material obtained by including a spray-drying step in the process of the present invention. Off the material obtained by the use of a spray-drying step is subsequently to be suspended in a liquid medium, the attrition inhibitor preferably should be such as to at least minimise dispersion of the spray-dried solid material into smaller particles in the presence of the liquid medium in which the solid is to be suspended.Hence, the attrition inhibitor is preferably soluble in the liquid medium used for the spray-drying step but is insoluble, or of low solubility, in any liquid medium in which the solid is suspended after effecting the spray-drying step.

The attrition inhibitor may be, for example, polystyrene, polymethylmethacrylate, polyvinylacetate, atactic polypropylene, or an AB block copolymer for example of t-butylstyrene-styrene. It will be appreciated that not all attrition inhibitors will be equally effective. The use of an attrition inhibitor during the spray-drying or the suspension can result in the spray dried solid material being in the form of firmer agglomerates than a similar spray-dried solid material obtained without using an attrition inhibitor. The amount of the attrition inhibitor is preferably from 0.5% up to 10% by weight relative to the solid material present in the suspension.

The suspension containing the attrition inhibitor is spray-dried using conventional spray-drying techniques, for example such as are described in our European Patent Application No.81 300930.5.

We have found that the product obtained by the process of the present invention, with or without the spray-drying step, may be used in combination with organic metal compounds, and preferably Lewis Base compounds, to give a polymerisation catalyst and that 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. Atitanium-containing composition produced by a process as hereinbefore described; and B. An organic compound of aliminium 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 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, it is preferred that the catalyst system includes a Lewis Base compound.

The Lewis Base compound which is used in the additional stage 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 use of organic Lewis Base compounds has been disclosed, inter alia, in British patent specifications 803 198,809717,880998,896 509,920 118,921 954,933236,940 125,966025,969074,971 248, 1 013363, 1 017977, 1 049723, 1122010, 1 150 845, 1 208815, 1 234 657,1 1 324 173, 1 359 328,1 1 383 207, 1 387 890, 1 423 658, 1 423 659, 1 423 660, 1 495 031, 1 527 736,1 1 554574 and 1 559 194.

It is preferred to use, as the Lewis Base component, esters of the formula R1COOR2 as herein before described. It is particularly preferred to use an alkyl ester of a carboxylic acid containing an aromatic group such as, for example ethyl benzoate, butyl benzoate, methyl p-methylbenzoate, ethyl p-methoxybenzoate and ethyl phenylacetate.

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 titanium v hich is present in Component A of the catalyst system. It is particularly preferred to use at least 10 moles of the organic metal compound for each mole oftitanium but the proportion of Component b preferably does not exceed 250 moles per mole of titanium in Component A.

Especially preferred proportions of Component B are from 10 up to 60 moles of the organic metal compound for each mole of titanium.

The preferred catalyst systems 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 and preferably there is used from 0.1 up to 0.5 moles of the Lewis Base compound for each mole of Component B, especially from 0.25 up to 0.4 moles of the Lewis Base 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. A further alternative procedure is to add Component A of the catalyst system separately and to add Components B and C as a mixture. As disclosed in our co-pending application of even data herewith entitled "Olefin Polymerisation Process", when Component B is an aluminium trialkyl and Component C is an ester of a carboxylic acid containing an aromatic group, if Components B and C are premixed, it is particularly preferred to mix and to store the mixture in the presence of an olefin monomer.

The catalyst systems of the present invention are suitable for the polymerisation of 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 hereinbefore described.

The monomer which may be used in accordance with the present invention has the formula CH2=CHR3 wherein R3 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 970 478,970 479 and 1 014 944, may be used.

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

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 less than 5 parts per million by weight, a chlorine content of less than 150 parts per million by weight and containing less than 7% by weight of polymer which is soluble in boiling heptane.

Preferred polymers have a titanium content of less than 3 parts per million by weight. In the preferred polymers the chlorine content is less than 120 parts per million by weight, especially less than 100 parts per million by weight. Propylene polymers in accordance with the invention preferably contain not more than 5% by weight of polymer which is soluble in boiling heptane. The polymer may be formed into mouldings which have a flexural modulus of at least 1.40 GN 'm2, especially at least 1.50 GN/m2. The flexural modulus is determined from the deformation of a test strip at 1% skin strain after 60 seconds at 230C and 50% relative humidity measured using a cantilever beam apparatus as described in "Polymer Age", March 1970, pages 57 and 58, using a test strip prepared as described in the detail hereafter in Note (d) to Table One.

The low proportion of polymer which is soluble in boiling heptane and the high flexural modulus both indicate the high stereoregularity of the propylene polymers of the present invention.

Although the polymerisation process of the present invention is particularly suitable for gas phase polymerisation, it will be appreciated that this does not exclude the possibility of carrying out the polymerisation in the liquid phase where the liquid phase may be an inert hydrocarbon medium or a liquid olefine monomer. If polymerisation is effected in the gas phase, the 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 a major proportion of the liquid monomer 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 1 532445.

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 our a ribbon-blendertype 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, Ziegler-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 Specifications 1111 493, 1 226659 and 1 383 611.

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. It is preferred that the polymerisation is effected in the presence of a Lewis Base compound and that this Lewis Base compound is pre-mixed with the organic metal compound which is Component B of the catalyst system before the mixture of the two components is introduced into the polymerisation medium.

When carrying out polymerisation on a continuous basis, we have found that particularly useful effects are obtained if the organic metal compound and the Lewis Base compound are pre-mixed just before being introduced into the polymerisation reaction vessel, or if the pre-mixture has been stored in the presence of an olefine monomer.

Thus, as a preferred aspect of the present invention, polymerisation is carried out on a continuous basis using a catalyst system including a Lewis Base compound, the catalyst components are introduced into the intermittently, and Component B and the Lewis Base compound either a) are mixed together not more than one hour before being introduced into the polymerisation medium, or b) are mixed together and stored in the presence of an olefine monomer until introduced into the polymerisation medium.

Procedure b), is the subject of our copending application of even date herewith entitled "Olefin Polymerisation Process".

The polymerisation can be effected in the presence of a chain transfer agent such as hydrogen or a zinc dialkyl 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 olefine 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 olefines (including propylene) which have a high stereoregularity. More specifically, the polymerisation is effected at pressures in the range from 1 up to 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 100"C. The polymerisation temperature is typically in the range from 40"C up to 100 C.

It is generally preferred to effect all stages in the preparation of the titanium-containing composition in an inert atmosphere which is essentially free from oxygen-containing impurities such as water vapour. Very preferably the polymerisation process of the present invention should also be effected in the absence of materials which have a harmful effect on the polymerisation process.

Various aspects of the present invention will now be described with reference to the following Examples which are illustrative 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 1200C 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 by passing gaseous propylene in turn through a column (7.6 cm diameter, cm length) containing 1.58 mm granules of Alcoa Fl alumina at 50 to 60"C, and then through a similar column containing BTS catalyst (Cupric oxide reduced to finely divided metallic copper on a magnesium oxide support) at 40 to 50"C, condensing the issue gas and passing the liquid propylene through four columns (all 7.6 cm diameter; two of 90 cm in length, two of 1.8 m in length) at 25"C, each containing 1.58 mm pellets of Union Carbide 3A molecular sieves.

This treatment reduced the water content of the monomer from in the range of 5 to 10 ppm by volume down to < 1 ppm by volume and the oxygen content from in the range of 1 to 2 ppm by volume down to < 0.5 ppm by volume. The level of inert compounds (nitrogen, ethane, etc) was unchanged at 0.3% and the level of other unsaturated hydrocarbons (allene, methylacetylene etc) was unchanged at < 1 ppm.

EXAMPLE 1 A) Milling magnesium chloride and ethyl benzoate A Siebtechnik SM6 Vibromill chamber having a total usable volume of about 1.5 dm3 and containing 180 stainless steel balls of 25 mm diameter was sealed, evauated to a pressure of 0.2 mm of mercury, and purged with nitrogen, to give an atmosphere of nitrogen in the mill.

203 grammes of essentially anhydrous magnesium chloride (BDH technical grade) and 107 grammes of ethyl benzoate were introduced into the mill chamber. The mill chamber was then placed in the mill assembly, water at ambient temperature was passed through the jacket of the mill chamber, and the mill assembly was vibrated at a frequency of 1500 oscillations per minute and an amplitude of 2 mm. The vibration was continued for 24 hours whilst continuing to pass water at ambient temperature through the jacket of mill chamber.

After 24 hours, the mill chamber was inverted, and vibration was effected to remove the milled magnesium chloride-ethyl benzoate which was collected under nitrogen. The molar ratio of magnesium chloride to ethyl benzoate in the mill chamber was about 3 to 1.

B) Contacting with titanium tetrachloride A sample (108 grammes) of the milled product from stage A) was transferred to a two dm3 jacketted glass vessel which was provided with a stirrer. One dm3 of titanium tetrachloride was added to the vessel, the stirrer was started and heating was applied to the jacket. Heating was continued until a temperature of 1 30"C was attained, which took one hour 10 minutes. The temperature was maintained at 1300C and stirring was continued, for three hours. At the end of three hours, the stirrer was stopped, the heating was switched off and the solid was allowed to settle and cool over a period of 65 hours. The mixture was then heated up to 120"C, without stirring in order to dissolve crystals formed in the supernatant liquid.After a period of one hour at 1 20"C, the supernatant liquid was siphoned off from the settled solid, whilst continuing to heat.

The contacting with the titanium tetrachloride was repeated by adding 900 cm3 of titanium tetrachloride at ambient temperature to the hot residue remaining from the previous contacting, the mixture was stirred and heating was continued until a temperature of 1 20C was attained. Stirring at 1200C was continued for one hour, stirring was stopped, the solid was allowed to settle whilst continuing to heat and, after an hour, the supernatant liquid was siphoned off. Heating was terminated and the contents of the vessel were allowed to cool by standing for 20 hours.

C) Washing To the residue remaining from stage B) were added 1600 cm3 of a heptane fraction, at least 90% of which is n-heptane (hereafter referred to as the "n-heptane fraction"). The mixture was stirred and heated up to reflux temperature (about 100"C). Stirring at reflux temperature was continued for 25 minutes and the stirrer was then stopped. After a further 50 minutes, the supernatant liquid was siphoned off from the settled solid which was allowed to stand overnight without heating.

To the cold residue were added 1650 cm3 of the n-heptane fraction at ambient temperature. The mixture was stirred and heated up to reflux temperature. After 45 minutes the mixture was at reflux temperature and this temperature was maintained for 35 minutes with stirring. The stirrer was switched off and the solid allowed to settle whilst still maintaining the temperature. After 2 hours 40 minutes, the supernatant liquid was siphoned off from the settled solid and heating was ceased.

To the hot residue remaining from the previous washing step were added 1650 cm3 of the n-heptane fraction at ambient temperature. The mixture was stirred and heated up to reflux temperature which was attained after 25 minutes. Stirring at reflux temperature was continued for 40 minutes, the stirrer was switched off and the solid allowed to settle. After 20 minutes the supernatant liquid was siphoned off from the settled solid which was allowed to stand overnight without heating.

The cold residue was washed once more using the procedure as described for the previous washing stage.

The settled solid was finally diluted with the n-heptane fraction at ambient temperature to give a final volume of one dm3 and the mixture was transferred to a 2dim3 storage vessel under nitrogen.

A sample (5 cm3) of the mixture obtained was treated with 2N sulphuric acid and the aqueous layer was subjected to spectrophotometric analysis. The mixture was found to contain 2.10 milligramme atoms of titanium/dm3 and 134 milligramme atoms of chlorine/dm3. The solid component had a titanium content of 1.3% by weight.

EXAMPLE 2 A) Milling magnesium chloride and ethyl benzoate The procedure of stage A) of Example 1 was repeated using 204 grammes of the magnesium chloride.

B) Contacting with titanium tetrachloride The procedure of stage B) of Example 1 was repeated with the changes noted hereafter.

139 grammes of the milled product from stage A) of this example were used. cm3 of the n-heptane fraction and 500 cm3 of titanium tetrachloride were added to the reaction vessel. The mixture was stirred, heated up to 1 00"C, maintained at this temperature for three hours and the stirrer was stopped. After 2.25 hours, the supernatant liquid was siphoned off, the heating was switched off and the settled solid allowed to cool overnight.

The contacting with the n-heptane fractionititanium tetrachloride mixture was repeated with the exception that the mixture was stirred at 100 C for 4.5 hours, the solid was allowed to settle for 30 minutes and the settled solid was allowed to cool over a period of 90 hours.

C) Washing The procedure of stage C) of Example 1 was repeated with the changes noted hereafter.

In each washing stage, 1625cm3 of or the n-heptane fraction at ambient temperature were used.

In the first washing stage, the reflux temperature was maintained with stirring for one hour 10 minutes, the solid was allowed to settle for one hour and the hot supernatant liquid was then siphoned off.

The second washing stage was commenced 5 minutes after removing the supernatant liquid from the first washing stage. The reflux temperature was maintained for one hour, the solid was allowed to settle for 15 minutes without heating, the supernatant liquid was siphoned off and the settled solid was allowed to cool overnight.

The third washing stage was essentially the same as the first washing stage with the exceptions that the mixture was stirred at reflux temperature for one hour and the solid was allowed to settle for 45 minutes.

The fourth washing stage was essentially the same as the second washing stage but commenced 15 minutes after removing the supernatant liquid from the third washing stage, and the solid was allowed to settle for 30 minutes.

The washed solid was suspended and transferred to a storage vessel as in stage C) of Example 1.

The solid component had a titanium content of 1.44% by weight.

EXAMPLE 3 A) Milling magnesium chloride and ethyl benzoate The procedure of stage A) of Example 1 was repeated using 192 grammes of magnesium chloride, 97 grammes of ethyl benzoate and passing a mixture of water and ethylene glycol at OOC through the jacket of the mill chamber.

B) Contacting with titanium tetrachloride The procedure of stage B) of Example 2 was repeated with the changes noted hereafter.

90 grammes of the milled product from stage A) of this example, and one dm3 of titanium tetrachloride were used. The solid was allowed to settle for 1.5 hours, the supernatant liquid siphoned off, the heating switched off and the settled solid allowed to cool overnight.

The contacting with titanium tetrachloride was repeated as described for the previous stage with the exception that the solid was allowed to settle for two hours.

In each washing stage, 1600 cm3 of the n-heptane fraction at ambient temperature were used.

In the first washing stage, the reflux temperature was maintained with stirring for one hour, the solid was allowed to settle for 1.5 hours, the supernatant liquid was siphoned off, the heating switched off and the solid allowed to cool overnight.

The second washing stage was essentially a repeat of the first washing stage with the exception that the solid was allowed to settle for 4.25 hours and the settled solid was allowed to cool for 95 hours.

In the third washing stage, the mixture was stirred without heating for 0.5 hours, allowed to settle for 25 minutes and the supernatant liquid siphoned off.

The fourth washing stage was effected 10 minutes after the completion of the third washing stage and was essentially a repeat of the third washing stage with the exception that the solid was allowed to settle for 0.5 hours.

The solid component had a titanium content of 1.9% by weight.

EXAMPLE 4 A) Milling magnesium chloride and ethylbenzoate The procedure of stage A) of Example 1 was repeated with the changes noted hereafter.

224 grammes of magnesium chloride and 88.35 grammes of ethyl benzoate were introduced into the mill chamber and ground for 24 hours without applying cooling, or heating, to the jacket of the mill chamber.

A further 88.35 grammes of ethyl benzoate were introduced into the mill chamber and grinding was continued for a further 24 hours and the milled solid was then removed. The final molar ratio of magnesium chloride to ethyl benzoate in the mill chamber was 2:1.

BJ Contacting with titanium tetrachloride The procedure of stage B) of Example 3 was repeated with the changes noted hereafter.

136 grammes of the milled product from stage A) of this example, and 1.5 dm3 of titanium tetrachloride, were used for the first treatment. The mixture was stirred at 1 OO"C for 4.5 hours, then allowed to settle and cool overnight. The mixture was then heated up to 1 00'C with stirring. On attaining the temperature of 100 C, the stirrer was stopped and the solid was allowed to settle over a period of 35 minutes, whilst maintaining the temperature of 1 00"C. The supernatant liquid was then siphoned off.

The contacting with the titanium tetrachloride was repeated by adding one dm3 of titanium tetrachloride to the hot residue, stirring the mixture and maintaining the stirred mixture at 100"C for 3.5 hours. The stirrer was stopped, the solid allowed to settle for two hours, the supernatant liquid decanted off and the settled solid allowed to cool overnight.

C) Washing The procedure of stage C) of Example was repeated with the changes noted hereafter.

In the first washing stage, the mixture was stirred at the reflux temperature for one hour, the stirrer was stopped, the solid was allowed to settle for 1.25 hours, the supernatant liquid was decanted off and the settled solid allowed to cool overnight.

In the second washing stage, 1200cm3 of or the n-heptane fraction were added, the mixture was stirred without heating and then divided into two portions of equal volume (about 750 cm3). A further 1150 cm3 of the n-heptane fraction were added to one of the portions, the mixture was stirred and heated up to reflux temperature. The mixture was stirred at reflux temperature for one hour, the stirrer was stopped, the solid allowed to settle for one hour and the supernatant liquid siphoned off. The settled solid was allowed to cool overnight.

To the cold residue were added 850 cm3 of the n-heptane fraction and the mixture was stirred for one hour without heating. The solid was allowed to settle for one hour and the supernatant liquid was siphoned off.

Ten minutes after removing the supernatant liquid from the third washing stage, cm3 of the n-heptane fraction were added and the mixture was stirred for one hour without heating. The stirrer was stopped and the solid was allowed to settle overnight.

The supernatant liquid was siphoned off. The washed solid was suspended and transferred to a storage vessel as in stage C) of Example 1.

The solid component had a titanium content of 1.47% by weight.

EXAMPLE 5 A) Milling magnesium chloride and ethyl benzoate The procedure used was similar to that of stage A) of Example 4 with the changes as noted hereafter.

199 grammes of magnesium chloride and 78.37 grammes of ethyl benzoate were used in the first stage of the milling and a further 78.37 grammes of ethyl benzoate were added to effect the second stage of the milling. Throughout the milling, water at ambient temperature was passed through the jacket of the mill chamber. The final molar ratio of magnesium chloride to ethyl benzoate in the mill chamber was 2:1.

B) Treating with titanium tetrachloride The procedure of stage B) of Example 3 was repeated with the changes noted hereafter.

150 grammes of the milled product from stage A) of this example were used. Stirring at 100C was continued for 30 minutes, the stirrer was stopped, the solid was allowed to settle for two hours and the supernatant liquid was siphoned off.

One dm3 of titanium tetrachloride was added to the hot residue from the previous stage 10 minutes after removing the supernatant liquid. The mixture was stirred and heating was continued to raise the temperature of the mixture to 100"C. The mixture was stirred at 1 OO"C for 30 minutes, the stirrer was stopped, the solid allowed to settle for 1.5 hours, the supernatant liquid was siphoned off and the settled solid was allowed to cool overnight.

C) Washing The procedure of stage C) of Example 3 was repeated with the changes noted hereafter.

In each washing stage, 1500cm3 of or the n-heptane fraction were used.

In the first washing stage, the reflux temperature was maintained, with stirring, for five minutes and the solid was allowed to settle for 30 minutes. The settled solid was not allowed to cool.

The second washing stage commenced five minutes after the completion of the first washing stage. The reflux temperature was maintained, with stirring, for five minutes and the solid was allowed to settle for 85 minutes. The supernatant liquid was siphoned off and the settled solid was allowed to cool overnight.

In the third washing stage, the mixture was stirred for 15 minutes.

The fourth washing stage was effected directly after the third washing stage. The mixture was stirred for 15 minutes and allowed to settle for 1.25 hours.

The solid component had a titanium content of 1.14% by weight.

EXAMPLE 6 A) Milling magnesium chloride and ethyl ,oenzoate The procedure of stage A) of Example 1 was repeated using 190 grammes of magnesium chloride and 100 grammes of ethyl benzoate.

B) Contacting with titanium tetrachloride The procedure of stage B) of Example 3 was repeated with the changes noted hereafter.

284 grammes of the milled product from stage A) of this example, and 1.5 dm3 of titanium tetrachloride were used in a reaction vessel of 5 dm3 capacity. The solid was allowed to settle for four hours, the supernatant liquid was siphoned off and the settled solid allowed to cool overnight.

The contacting with the titanium tetrachloride was repeated in the manner described for the first contacting with the exception that the mixture was allowed to settle for three hours.

C) Washing The procedure of stage C) of Example 3 was repeated in the reaction vessel used in stage B) hereof with other changes as noted hereafter.

In the first washing stage, 2.2 dm3 of the n-heptane fraction were used. The solid was allowed to settle for 65 minutes and the supernatant liquid was siphoned off. The settled solid was not allowed to cool.

The second washing stage commenced 15 minutes after the completion of the first washing stage and 2 dm3 of the n-heptane fraction were used. The solid was allowed to settle for 2 hours 10 minutes, the supernatant liquid was siphoned off and the settled solid was allowed to cool overnight.

In the third washing stage, 2.3 dm3 of the n-heptane fraction were used, the mixture was stirred for one hour, the solid was allowed to settle for 68 hours and the supernatant liquid was siphoned off.

In the fourth washing stage, which was effected 10 minutes after the completion of the third stage, the procedure was essentially a repeat of the third washing stage, with the exception that the solid was allowed to settle for five hours.

The washed solid was suspended to give a total volume of 1.5 dm3 and transferred to a storage vessel as in stage C) of Example 1.

The solid component had a titanium content of 2.4% by weight.

EXAMPLE 7 A) Milling magnesium chloride and ethyl benzoate The procedure of stage A) of Example 1 was repeated using 263 grammes of magnesium chloride and 138 grammes of ethyl benzoate.

B) Contacting with titanium tetrachloride The procedure of stage B) of Example 6 was repeated with the changes noted hereafter.

145 grammes of the milled product from stage A) of this example, and one dm3 of titanium tetrachloride, were used. The solid was allowed to settle over a period of 1.5 hours.

The second contacting with titanium tetrachloride, was essentially the same as the first contacting with the exception the solid was allowed to settle for 80 minutes.

C) Washing The procedure of stage C) of Example 6 was repeated with the changes noted hereafter.

In each washing stage, 2dm3 of the n-heptane fraction at ambient temperature were used.

In the first washing stage, the solid was allowed to settle for 2.75 hours and the settled solid was allowed to cool overnight.

In the second washing stage, the solid was allowed to settle for 30 minutes.

In the third washing stage, the mixture was stirred for 10 minutes and the solid was allowed to settle for 50 minutes.

The fourth washing stage was effected seven days after the third washing stage and used the same procedure as the third washing stage.

The solid component had a titanium content of 1.8% by weight.

Comparative Example A 165 grammes of the product of stage A) of Example 7 were subjected to a single contacting with titanium tectrachloride, the conditions for this contacting otherwise being as described for stage B) of Example 7.

The product of the single contacting with titanium tetrachloride was subjected to a washing stage as described in stage C) of Example 7 with the exception that the fourth washing stage was effected 22 hours after the third washing stage.

The solid component had a titanium content of 2.5% by weight.

EXAMPLE 8 A) Milling magnesium chloride and ethyl benzoate A Siebtechnik SM10 Vibromill having a total volume of about 38dim3 and containing 119 keg of stainless steel balls of 25 mm diameter was sealed and purged with nitrogen to give a nitrogen atmosphere in the mill.

A mixture of water and ethylene glycol at OOC was passed through the jacket of the mill and the mill was vibrated at a frequency of 1500 oscillations per minute and an amplitude of 2 mm. Four kilogrammes of essentially anhydrous magnesium chloride (BDH technical grade) were introduced into the mill whilst the mill was being vibrated. After the addition of the magnesium chloride, the mill was vibrated for about 15 minutes and 2 dm3 of ethyl benzoate were added to the vibrating mill over a period of about 15 minutes. The mill was then vibrated for a further 24 hours whilst continuing to pass the mixture of water and ethylene glycol at 0"C through the jacket of the mill.

After 24 hours, the mill was inverted, the inverted mill was vibrated and the milled magnesium chloride-ethyl benzoate was collected under nitrogen. The molar ratio of magnesium chloride to ethyl benzoate in the mill was about 3 to 1.

B) Contacting with titanium tetrachloride A sample (371 grammes) of the milled product from stage A) was transferred to a 5 dm3, jacketted glass vessel which was provided with a stirrer. 3 dm3 of titanium tetrachloride was added to the vessel, the stirrer was started and heating was applied to the jacket. Heating was continued until a temperature of 100"C was attained, which took 1.75 hours. The temperature was maintained at 1 00"C, and stirring was continued, for three hours. At the end of three hours, the stirrer was stopped and the solid was allowed to settle whilst continuing to heat the contents of the vessel. 1.5 hours after terminating the stirring, the supernatant liquid was siphoned off from the settled solid. The heating was switched off and the settled solid allowed to cool over a period of 64 hours.

The contacting with the titanium tetrachloride was repeated by adding 3dim3 of titanium tetrachloride to the cold residue remaining for the previous contacting, the conditions of treatment being as previously described. The settled solid was allowed to cool overnight.

C) Washing To the residue remaining from stage B) was added a sufficient quantity of the n-heptane fraction at ambient temperature to give a total volume of 4.5 dm3. The mixture was stirred and heated up to reflux temperature. Stirring at reflux temperature was continued for an hour and the stirrer was then stopped. After a further 45 minutes, the supernatant liquid was siphoned off from the settled solid, which was still being heated.

After 30 minutes, a sufficient quantity of the n-heptane fraction at ambient temperature was added to give a total volume of 4.5 dm3. The mixture was stirred whilst continuing to heat. After 15 minutes, the mixture was at reflux temperature and this temperature was maintained for one hour with stirring. The stirrer was switched off and the solid allowed to settle whilst still maintaining the temperature. After 1.25 hours, the supernatant liquid was siphoned off from the settled solid, heating was ceased and the solid was left overnight to cool.

To the cold residue remaining from the previous washing steps, a sufficient quantity of the n-heptane fraction at ambient temperature was added to give a total volume of 4dim3. The mixture was stirred for 15 minutes without heating and allowed to settle. After 1.25 hours, the supernatant liquid was siphoned off from the settled solid.

After 15 minutes, the foregoing cold washing procedure was repeated.

The cold residue remaining from the two cold washing steps was diluted with the n-heptane fraction at ambient temperature to give a final volume of 1.5 dm3 and the mixture was transferred to a 2 dm3 storage vessel under nitrogen.

A sample of the mixture was subjected to analysis as described in Example 1. The mixture was found to contain 6.88 milligramme atoms oftitaniumidm3 and 395 milligramme atoms of chloride/dm3. The solid component had a titantium content of 1.8% by weight.

EXAMPLE 9 The milled product obtained in stage A) of Example 8 was used.

B) Contacting with titanium tetrachloride The procedure of stage B) of Example 8 was repeated with the changes noted hereafter.

240 grammes of the milled product of stage A) of ExampleS, and 1.5 dm3 of titanium tetrachloride, were used. The solid was allowed to settle for 2.25 hours. The settled solid was allowed to cool overnight.

The contacting with titanium tetrachioride was repeated as described for the first contacting with the exception that the solid was allowed to settle for 2 hours 40 minutes.

C) Washing Two dm3 of the n-heptane fraction were added to the 5 dm3 reaction vessel containing the residue remaining from stage B). The mixture was stirred and heated up to reflux temperature. Stirring was continued at reflux temperature for one hour, the stirrer was then stopped, the solid allowed to settle for 3.5 hours, the supernatant liquid decanted off, the heating ceased and the settled solid allowed to cool for 117 hours.

1.5 dm3 of the n-heptane fraction were added to the residue from the previous washing stage, the mixture was stirred and separated into two essentially equal portions, by volume. One of the portions was allowed to settle and the supernatant liquid was siphoned off. One dm3 of the n-heptane fraction was added and the mixture was stirred, without heating, for 10 minutes, allowed to settle for one hour and the supernatant liquid siphoned off.

The washed solid was suspended and transferred to a storage vessel as in stage C) of Example 1. The solid component had a titanium content of 4.0% by weight.

EXAMPLE 10 The milled product obtained in stage A) of Example 8 was used.

385 grammes of the milled product of stage A) of Example 8 were used. The solid was allowed to settle for 2 hours 20 minutes and the settled solid allowed to cool overnight.

The contacting with titanium tetrachloride was repeated with the exception the solid was allowed to settle for 2.5 hours and the settled solid was allowed to cool for 65 hours.

C) Washing The procedure of stage C) of Example 8 was repeated with the changes noted hereafter.

In the first washing stage, the solid was allowed to settle for 2.75 hours, the supernatant liquid was siphoned off, heating was ceased and the settled solid allowed to cool overnight.

In the second washing stage, sufficient of the n-heptane fraction was added to the cold residue from the first washing stage to give a total volume of 4 dm3.

The mixture was heated up to reflux temperature with sitrring, stirred at this temperature for one hour, the stirrer was stopped and the solid allowed to settle for 2.75 hours.

In the third washing stage, sufficient of the n-heptane fraction was added to give a total volume of 3.5 dm3.

The solid was allowed to settle for 3.75 hours.

After 30 minutes, the foregoing cold washing procedure was repeated with the exceptions that the mixture was stirred for 30 minutes and the solid allowed to settle for one hour.

The washed solid was suspended and transferred to a storage vessel as in stage C) of Example 8. The solid component had a titanium content of 1.7% by weight.

EXAMPLE 11 The milled product obtained in stage A) of Example 8 was used.

200 grammes of the milled product of stage A) of Example 8, and 2 dm3 of titanium tetrachloride, were used. The solid was allowed to settle over a period of 2.25 hours and the settled solid was allowed to cool overnight.

The contacting with titanium tetrachloride was repeated with the exception the solid was allowed to settle over a period of 1.5 hours.

C) Washing To the residue remaining from stage B) were added 2 dm3 of the n-heptane fraction at ambient temperature. The mixture was stirred and heated up to reflux temperature. Stirring at reflux temperature was continued for one hour and then ceased. The solid was allowed to settle for 2.5 hours and the supernatant liquid was siphoned off from the settled solid which was still being heated.

After 30 minutes, 2 dm3 of the n-heptane fraction at ambient temperature were added, the mixture was stirred for five minutes and then stirring and heating ceased. The solid was allowed to settle and cool for one hour 25 minutes and the supernatant liquid was then siphoned off.

After 30 minutes, to the residue remaining from the preceding washing step, which residue was at a temperature of 40"C, 2 dm3 of the n-heptane fraction were added. The mixture was stirred for five minutes, the stirrer was stopped and the solid allowed to settle for one hour 10 minutes. The supernatant liquid was then siphoned off from the settled solid.

After 40 hours, the cold residue remaining from the foregoing washing steps was diluted with the n-heptane fraction to give a final volume of one dm3 and the mixture was transferred to a 2 dm3 storage vessel under nitrogen.

The solid component had a titanium content of 2.3 % by weight.

EXAMPLE 12 A) Milling magnesium chloride and ethyl benzoate The procedure of stage A) of Example 1 was repeated with the changes noted hereafter.

205 grammes of magnesium chloride were introduced into the mill chamber which was then placed in the mill assembly and a mixture of water and ethylene glycol at -10"C was passed through the jacket of the mill chamber. The mill assembly was vibrated for one hour and then 103 cm3 of ethyl benzoate were added, using a syringe, whilst still vibrating the mill assembly. Vibration of the mill was continued for a further 36 hours whilst continuing to pass the water/ethylene glycol mixture at - 1 00C through the jacket of the mill chamber.

B) Contacting with titanium tetrachloride The procedure was essentially as described for stage B) of Example 8 with the changes noted hereafter.

204.6 grammes of the milled product from stage A) of this example, and 2 dm3 of titanium tetrachloride, were used. The settled solid was allowed to cool overnight.

The contacting with titanium tetrachloride was repeated as described for the preceding contacting with the exception that the solid was allowed to settle for 4 hours 10 minutes and the settled solid was allowed to cool for 21 hours.

C) Washing The procedure was similar to that used for stage C) of Example 11 with the changes noted hereafter.

In the first washing step, cm3 of the n-heptane fraction were used, the mixture was stirred at reflux temperature for two hours, the solid allowed to settle for 30 minutes and the settled solid allowed to cool overnight.

In the second washing step, 2 dm3 of the n-heptane fraction were added to the cold residue, the mixture was stirred for five minutes, without heating, and the solid allowed to settle for one hour 25 minutes.

After 30 minutes, this cold washing step was repeated.

After a further 2.5 hours, the washed solid was suspended and transferred to a storage vessel as in stage C) of Example 11.

The solid component had a titanium content of 1.9% by weight.

EXAMPLE 13 The milled product obtained in stage A) of Example 8 was used.

B) Contacting with titanium tetrachloride The procedure described in stage B) of Example 11 was repeated with the changes noted hereafter. 205 grammes of the product of stage A) of Example 8 were used. The solid was allowed to settle over a period of 1.5 hours.

In the second contacting, the solid was allowed to settle over a period of two hours. The settled solid was allowed to cool for about 162 hours.

C) Washing To the residue remaining from stage B) was added 3 dm3 of the n-heptane fraction at ambient temperature. The mixture was stirred and heated up to reflux temperature (about 1 00"C). Stirring at reflux temperature was continued for an hour and then ceased. After a further three hours 20 minutes, the supernatant liquid was siphoned off from the settled solid whilst still heating. Heating was then ceased and the settled solid was allowed to cool by standing for 67 hours.

Afurther washing step was effected by adding 3 dm3 of the n-heptane fraction at ambient temperature to the cold residue. The mixture was stirred and heated up to 70"C over a period of 40 minutes. The stirrer was switched off and the solid allowed to settle while maintaining the temperature at about 60"C. After two hours 20 minutes, the supernatant liquid was siphoned off from the settled solid, heating was ceased and the residual material was allowed to cool by standing for about 68 hours.

To the cold residue remaining from the previous washing step was added 2.5 dm3 of the n-heptane fraction at ambient temperature. The mixture was stirred for five minutes without heating and allowed to settle. After two hours, the supernatant liquid was siphoned off from the settled solid. This washing procedure was repeated twice.

The cold residue remaining from the fifth washing step was diluted with the n-heptane fraction to give a final volume of one dm3 and the mixture was transferred to a 2 cm3 storage vessel under nitrogen.

The solid component had a titanium content of 1.9% by weight.

The following two Examples illustrate the incorporation, into the process of the present invention, of dispersion and spray-drying stages, as disclosed in more detail in our copending application of even date herewith entitled "Dispersing Transition Metal Compounds and Use".

EXAMPLE 14 In this Example, some of the milled product obtained in stage A) of Example 8 was dispersed, spray-dried, contacted with titanium tetrachloride and washed.

A) Dispersion of milled magnesium chloride-ethyl benzoate A one dm3 three-necked glass flask having a heating 'cooling jacket, was fitted with a high shear homogeniser of the Ultra Turrax T45 type (available from Janke and Kunkel KG IKA Werke). Into the flask were introduced 630g of nitrogen sparged toluene, 245 g of the milled product of stage A) of Example 8 and 1.62 g of polystyrene ('Lustrex' HF66 - available from Monsanto Limited). Water at ambient temperature was passed through the heating/cooling jacket. The mixture was then subjected simultaneously to vigorous agitation and shearing by operating the homogeniser for five minutes at maximum power (an initial rate of stirring of 10,000 rpm). During the agitation and shearing, the temperature of the mixture rose but did not exceed 50"C.

The dispersion was then transferred to a storage vessel (a 2 dm3 three-necked glass flask fitted with a stirrer) and, whilst stirring, a further 0.8 g of polystyrene was added. The mixture was stirred for a further 30 minutes.

B) Spray drying of magnesium chloride-ethyl benzoate dispersion The dispersion obtained in stage A) was spray dried using a glass laboratory scale spray-drying apparatus similar to that illustrated in Figure 3 of European patent application 81300930.5. The spray-drying apparatus had a diameter of 15 cm, a length of 0.7 metres and a generally hemispherical bottom section. A conduit from the bottom section was connected directly to a cyclone provided with a catch-pot in which the solid material was collected. A spray nozzle was located at the top of the apparatus and this was a 1/4 JAU Automatic Air Atomizing Nozzle obtained from Spraying Systems Co. of the USA and having a 0.52 mm diameter nozzle.

Spraying was effected under nitrogen by passing a stream of nitrogen, preheated to a temperature of 130"C, into the spray-drying apparatus at a rate of 190 dm3/minute. Nitrogen at a pressure of about 0.5 kg/cm2 gauge was introduced into the spray nozzle. The suspension obtained in stage B) was fed from the 2 dm3 three-necked glass flask to the spray nozzle by the application of an excess nitrogen pressure of 5 cm of mercury to this flask.

C) Contacting with titanium tetrachloride 100 grammes of the spray dried product from stage B) were transferred to a 2 dm3 jacketted glass vessel which was provided with a stirrer. One dm3 of titanium tetrachloride were added to the vessel, the stirrer was started and heating was applied to the jacket. Heating was continued until a temperature of 1 00 C was attained, which took 0.5 hours. The temperature was maintained at 1 000C, and stirring was continued, for three hours. At the end of three hours, the stirrer was stopped and the solid was allowed to settle whilst continuing to heat the contents of the vessel. 2.0 hours after terminating the stirring, the supernatant liquid was siphoned off from the settled solid. The heating was switched off and the contents of the vessel allowed to cool by standing overnight.

The contacting with the titanium tetrachloride was repeated by adding one dm3 of titanium tetrachloride to the cold residue remaining from the previous contacting, the conditions of treatment being as previously described.

D) Washing To the residue remaining from stage C) was added 1.5 dm3 of the n-heptane fraction at ambient temperature. The mixture was stirred and heated up to reflux temperature (about 100"C). Stirring at reflux temperature was continued for an hour and then ceased. After a further 30 minutes, the supernatant liquid was siphoned off from the settled solid whilst still heating.

A further 1.5 dm3 of the n-heptane fraction at ambient temperature was added to the hot residue, the mixture was heated up to 1 00 C and was stirred at that temperature for one hour. The stirrer was switched off and the solid allowed to settle. After 1.00 hours, the supernatant liquid was siphoned off from the settled solid. The heater was switched off and the settled solid allowed to cool overnight.

To the residue remaining from the previous washing step was added 1.0 dm3 the n-heptane fraction at ambient temperature. The mixture was stirred for 15 minutes without heating and allowed to settle. After 0.45 hours, the supernatant liquid was siphoned off from the settled solid. This procedure was repeated once.

The cold residue remaining from the fourth washing step was diluted with the n-heptane fraction to give a final volume of 1.0 dm3 and the mixture was transferred to a 2 dm3 storage vessel under nitrogen.

A sample (5 cm3) of the mixture was treated with 2N sulphuric acid and the aqueous layer was subjected to spectrophotometric analysis. The mixture was found to contain 2.7 milligramme atoms of titanium/dm3, 72 miligramme atoms of magnesium and 160 milligramme atoms of chloride/dm3. The solid compenent had a titanium content of 1.64% by weight.

EXAMPLE 15 A) Dispersing magnesium chloride-titanium tetrachloride product A sample containing about 200 grammes of the product of stage C) of Example 13 was allowed to settle and the supernatant heptane was siphoned off. 1.5 dm3 of toluene was added, the mixture was stirred for five minutes at ambient temperature, allowed to settle and the supernatant liquid was siphoned off. This procedure was repeated twice to leave a settled solid in some residual toluene.

The residual mixture (about 600 cm3) from the third washing with toluene was introduced into the flask fitted with the Ultra Turrax homogeniser as described in stage A) of Example 14. A further 100 cm3 of toluene was used to rinse out residues from the storage vessel to the flask. 2.5 g of polystyrene ('Lustrex' HF66) were added to the flask.

Water at ambient temperature was passed through the heating/cooling jacket. The homgeniserwas operated for about 2.5 minutes at maximum power. After 1.5 minutes, and again after 2.0 minutes, extra toluene (100 cm3) was added. When the agitation had been completed, a further 100 cm3 of toluene was added to assist in transfer of the dispersion to a 2 dm3 three-necked glass flask fitted with a stirrer and, whilst stirring, a further 2.0 g of polystyrene were added.

B) Spray drying of magnesium chloride-titanium tetrachloride dispersion The dispersion obtained in stage A) was spray dried using essentially the same procedure as used in stage B) of Example 14 with the following exceptions.

The diameter of the spray nozzle was 0.72 mm. The pre-heated nitrogen was at a temperature in the range 140 to 145"C. The nitrogen introduced into the spray nozzle was at a pressure of about 0.56 kg/cm2 gauge.

Initially, the excess nitrogen pressure applied to the mixture in the 2 dm3 three-necked glass flask was 8 cm of mercury. The product collected will be referred to hereafter by the reference 15L.

Since the initial rate of spraying was low, the pressure in the flask containing the dispersion was increased to 18 cm of mercury. The product obtained using this higher applied pressure will be referred to hereafter by thereferencel5H.

The following Example illustrates the incorporation, into the process of the present invention of the wet-milling and spray-drying stages disclosed in more detail in our copending application, of even date herewith, entitled "Spraying Solid".

EXAMPLE 16 A) Milling magnesium chloride and ethyl benzoate The procedure of stage A) of Example 1 was repeated using 207 grammes of the magnesium chloride and 52 cm3 of ethyl benzoate and passing a mixture of water and ethylene glycol at OC through the jacket of the mill chamber. The molar ratio of magnesium chloride to ethyl benzoate in the mill chamber was about 6 to 1.

B) Milling with toluene After 24 hours, 400 cm3 of toluene were added to the mill chamber whilst continuing to vibrate the mill.

Milling was continued in the presence of the added toluene at ooh for a further 30 minutes.

After 30 minutes, the mill was inverted, the inverted mill was vibrated and the milled magnesium chloride-ethyl benzoate in toluene was collected under nitrogen. The mill chamber was washed out with a further 200 cm3 of toluene, which was added to the suspension previously removed.

After standing overnight, the milled mixture was still fluid but was viscous. The mixture was stirred and 39 cm3 of a 10% weight volume solution of polystyrene ('Styron' 6867 - available from Dow Chemical Company) in toluene was added to provide 1.5% by weight of polystyrene relative to the milled magnesium chloride - ethyl benzoate. A further 100 cm3 of toluene was then added and this mixture had a solid content of about 29% by weight.

C) Spray drying magnesium chloridelethyl benzoate suspension All of the suspension obtained in step B) was spray dried using essentially the same procedure as used in stage B) of Example 14 with the following exceptions. A 0.72 mm diameter nozzle was used. The preheated nitrogen was at a temperature of 142"C and was introduced into the spray-drying apparatus at a rate of 190 dm3/minute. Nitrogen at a pressure of about 1.35 kgícm2 absolute was introduced into the spray nozzle. The suspension obtained in step B) was fed from a stirred storage flask to the spray nozzle by the application of an excess nitrogen pressure of 9 cm of mercury to the storage flask.

D) Contacting with titanium tetrachloride A sample (25 grammes) of the spray dried product from stage C) was transferred to a 800 cm3 jacketted glass vessel which was provided with a stirrer. cm3 of titanium tetrachioride were added to the vessel, the stirrer was started and heating was applied to the jacket. Heating was continued until a temperature of 100 C was attained. The temperature was maintained at 100"C, and stirring was continued, for three hours.

At the end of three hours, the stirrer was stopped and the solid was allowed to settle whilst continuing to heat the contents of the vessel. 50 minutes after terminating the stirring, the supernatant liquid was siphoned off from the settled solid. The heating was switched off and the contents of the vessel allowed to cool by standing overnight.

The contacting with the titanium tetrachloride was repeated by adding 250 cm3 of titanium tetrachloride to the cold residue remaining from the previous contacting, the conditions of treatment being as previously described with the exception that the solid was allowed to settle for 70 minutes and the supernatant liquid was removed but the mixture was not allowed to cool.

E) Washing To the hot residue remaining from stage D) were added 300 cm3 of the n-heptane fraction at ambient temperature. The mixture was stirred and heated up to reflux temperature (about 100"C). Stirring at reflux temperature was continued for an hour and then ceased. After a further 65 minutes, the supernatant liquid was siphoned off from the settled solid whilst still heating. The heating was switched off and the contents of the vessel allowed to cool by standing overnight. cm3 of the n-heptane fraction at ambient temperature were added to the cold residue and the mixture was stirred and heated to reflux temperature. The mixture was stirred at reflux temperature for one hour then the stirrer was switched off and the solid allowed to settle. After one hour, the supernatant liquid was siphoned off from the settled solid and the heating was ceased.

To the hot residue remaining from the previous washing step were added 300 cm3 of the n-heptane fraction at ambient temperature. The mixture was stirred for 15 minutes without heating and allowed to settle. After one hour, the supernatant liquid was siphoned off from the settled solid. The residue was again washed without heating in the manner described.

The cold residue remaining from the fourth washing step was diluted with the n-heptane fraction to give a final volume of 250 cm3 and the mixture was transferred to a storage vessel under nitrogen.

EXAMPLE 17 TO 24 Polymerisation was carried out in an 8 dm3 stainless steel autoclave.

3 dm3 of an aliphatic hydrocarbon diluent consisting essentially of dodecane isomers and having a boiling point in the range 17000 to 18500 (hereafter referred to simply as the "aliphatic hydrocarbon") were charged into the autoclave and degassed at 70"C for 15 minutes at a pressure of 50 millimetres of mercury. Propylene was then admitted to the vessel in an amount to give a pressure of 1.1kg/cm2 absolute. The aliphatic hydrocarbon was stirred and stirring was continued throughout the following procedures. cm3 of a solution in the aliphatic hydrocarbon containing 20 millimole of aluminium tri-isobutyl were added to the autoclave followed by 40 cm3 of a solution in the aliphatic hydrocarbon containing 7 millimoles of methyl p-methylbenzoate.The titanium halide composition obtained in one of Examples 1 to 16 was then added as a suspension in the n-heptane fraction.

The autoclave was maintained at 700C while propylene was passed into the autoclave to achieve a pressure of 11.5 kg/cm2 absolute. 10 millimoles of hydrogen were then added. The pressure was maintained at 11.5kg/cm2 absolute by feeding propylene. 10 millimole quantities of hydrogen were added to the autoclave 0.5 and 1.0 hours after pressurising to 11.5 kg/cm2 absolute. After 2 hours, the propylene feed was terminated and the autoclave was vented to atmospheric pressure. The polymer suspension was passed into a receptacle and the polymer was filtered off in air. A sample of the polymer was washed with petroleum ether (boiling point 60-80 C) and the polymer was dried at 10000 in a fluidised bed using nitrogen as the fluidisig gas.Further details of the polymerisation conditions, and the properties of the products obtained, are given in Table One.

TABLE ONE Ti Example composition Polymer properties or Comp.

Example Type Amount MFI FM Ti Al CI HHS (a) (b) (mM) (c) (d) (e) (e) (e) (%) (f) 17* 1 0.042 69 1.13 5 190 207 8.9 18 2 0.055 4.7* 1.25 5 192 229 5.6 19 3 0.0258 4.6* 1.35 3 192 109 4.4 20 5 0.0261 2.2* 1.35 14 271 326 4.1 B A 0.0684 18 1.10 7 253 260 10.2 21&num; 14 0.058 25.5 1.47 5 197 186 ND 22&num; 15L 0.15 20.2 1.57 4 167 112 ND 23&num; 15H 0.15 20.3 1.46 8 155 337 ND 24 16 0.08 7.0 1.43 5 285 195 ND Notes to Table One (a) * In this Example, 4 millimoles of methyl p-methylbenzoate were used.

&num; in these examples, the pressure was raised to, and maintained at, 10kg/cm2 absolute.

(b) Type refers to the Example, or Comparative Example, in which the production of the titanium composition is described, and includes specific references noted in the Examples.

(c) MFI is the melt flow index measured by ASTM Test Method D1238/70, Condition N (190"C and 10 kg).

In those measurements marked *, the MFI was measured using a temperature of 230"C and a weight of 2.16 kg.

(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 150 x 19 x 1.6 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 tonnes 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 150 x 19 x 1.6 mm. Duplicate strips of each polymer were placed into an annealing oven at 13000 and after 2 hours at this temperature the heat was switched off and the oven cooled to ambient temperature at 15"C per hour.

(e) The titanium (Ti), aluminium (Al) and chlorine (Cl) 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.

(f) 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 heptane for 24 hours.

ND indicates that this property was not determined.

EXAMPLE 25 A 2 dm3 glass polymerisation flask having three necks and equipped with an efficient stirrer and a water jacket was dried carefully and one dm3 ofthe aliphatic hydrocarbon used in Examples 17 to 24 was introduced. Whilst heating, the liquid was vigorously stirred, evacuated, purged with nitrogen and evacuated, which treatment effectively reduced the water and oxygen contents of the aliphatic hydrocarbon to below 10 ppm by weight. The evacuation and purging was completed during the heating and before a temperature of 70"C had been attained.

Whilst still stirring the aliphatic hydrocarbon and maintaining the temperature at the polymerisation temperature (70 C), the aliphatic hydrocarbon was saturated with the purified propylene. 8 millimoles of triethyl aluminium and then 2.67 millimoles of ethyl anisate, both as a solution in the aliphatic hydrocarbon were added. Finally one cm3 of the suspension obtained in Example 13 were added. Polymerisation was continued at 70"C for two hours whilst maintaining a pressure of 1 atmosphere by the addition of further propylene. Polymerisation was terminated by the addition of 10 cm3 of isopropanol and an aliquot portion of the diluent was taken and the proportion of polymer dissolved in this aliquot was determined by evaporation to dryness.The polymer was filtered, washed three times with 200 cm3 of petrol ether for each wash and dried in an oven at 1200C and 0.1 mm of mercury pressure. By analysis, the polymer was found to contain 22 parts per million by weight of titanium. The portion of the polymer dissolved in the polymerisation diluent under the polymerisation conditions was 0.25% by weight relative to the total (soluble + insoluble) polymer formed.

EXAMPLES 26 TO 40 Propylene was polymerised continuously in the gas phase as described hereafter. To initiate the polymerisation, the reaction vessel initially contained about 5 kg of polypropylene powder having a flexural modulus of 1.45 GNlm2, and containing 4% by weight of polymer soluble in boiling heptane by Soxhlet extraction for 24 hours.

Polymerisation was effected in a 25 dm3 stainless steel autoclave fitted with a stirrer. Initially, the polypropylene powder was placed in the autoclave, the stirrer was rotated at 60 rpm and stirring was continued throughout the following procedure. The autoclave was purged at 70"C with nitrogen, then evacuated to a pressure of 0.1 mm of mercury. Liquid propylene was added to the autoclave and vaporised to raise the pressure to 28 kg/cm2 gauge. Hydrogen was added separately in the proportion of 1.5% by weight relative to the propylene.

Solutions of a trialkyl aluminium compound and an ester in the aliphatic hydrocarbon were separately fed to a "T" piece and the mixture was then passed immediately into the autoclave. A suspension containing a titanium composition obtained by the process of one of Examples 3, 4, 6, 7, 8, 9 or 10 was also introduced into the autoclave. The trialkyl aluminium compound, the ester and the titanium composition were added until polymerisation was observed to start. Liquid propylene was being introduced, and gaseous propylene vented off, whilst the catalyst was being added.

Once polymerisation had started, venting of the autoclave was stopped, liquid propylene at 20"C was introduced into the autoclave at a rate to maintain a pressure of 28 kg/cm2 gauge, (about 2 kg/hrfor a dwell time of 2.5 hours) and polypropylene, saturated with propylene, was intermittently withdrawn from the autoclave at a desired rate, typically about 2 kg of polymer per hour. The temperature and pressure were maintained at 70"C and 28 kg/cm2 gauge respectively. The trialkyl aluminium solution, the ester solution and the suspension of the titanium composition were continuously introduced into the autoclave at the rates set out in Table Two hereafter.

The rate of adding the suspension of the titanium composition was adjusted to maintain the rate of polymer production at the desired rate. During the operation of the autoclave, the nature of the titanium composition, the aluminium trialkyl compound and the ester were changed and operation of the autoclave was continued using various different catalyst systems.

Further details of the polymerisation conditions are set out in Table Two. Properties of the polymer products removed at various times during the polymerisations are set out in Table Three.

TABLE TWO Ti Al composition compound Ester DT Example (hours) (h) Type Amount Type Amount Type Amount (k) (b) (mM/h) (i) (mM/h) (j) (mM/h) 26 3 0.1 TEA 20 EA 6.6 3 27 3 0.1 TEA 20 EA 6.6 3 28 4 0.18 TEA 20 EA 6.6 2.5 29 6 0.25 TEA 20 EA 6.6 3 30 6 0.25 TBA 15 MT 5.0 2 31 6 0.15 TBA 15 MT 5.0 2 32 7 0.22 TEA 10 MT 3.3 2.5 33 7 0.2 TEA 10 MT 3.3 2.5 34* 7 0.15 TEA 10 MT 3.3 2 35 8 0.1 TBA 10 MT 3.3 3 36 8 0.1 TBA 10 MT 3.3 3 37 9 0.25 TBA* 15 MT 5.0 2.5 38 9 0.15 TBA* 15 MT 5.0 2.5 39 10 0.15 TEA* 10 EA 3.3 2 40 10 0.2 TEA* 10 EA 3.3 2 Notes to Table Two (b) is as defined in Notes to Table One.

(h) * The polymerisation temperature was 75"C.

(i) TEA is triethyl aluminium.

TBA is tri-isobutyl aluminium.

* The trialkyl aluminium compound and the ester were premixed, in the molar ratio of 3:1, as solutions in the aliphatic hydrocarbon, and stored for at least 12 hours, both premixing and storage being under propylene at a propylene pressure of one atmosphere and at ambient temperature before the use of the mixture was commenced. This procedure is the subject of our copending application, of even data herewith, entitled "Olefin Polymerisation Process".

(j) EA is ethyl p-methoxybenzoate.

MT is methyl p-methylbenzoate.

(k) DT is dwell time and corresponds to: Average weight of polymer bed Weight of polymer removed per hour TABLE THREE Polymer properties Time Example (hours) MFI FM Ti Al Cl HHS (1) (c) (d) (e) (e) (e) (%) (f) 26 26.5 21.6 1.53 3 256 133 4.1 27 28.5 22.3 1.52 3 250 112 4.1 28 5.5 20.6 1.47 6 209 199 4.9 29 14.5 22.5 1.50 8 209 128 6.0 30 36 16.5 1.62 8 159 175 3.3 31 38 10.2 1.60 5 129 153 2.5 32 7.5 5.4 1.43 7 105 154 4.8 33 8.5 5.6 1.51 6 85 192 ND 34 34 39.5 1.44 4 115 131 8.6 35 11 33.4 1.45 3 98 99 7.6 36 13 32.7 1.50 3 101 96 8.0 37 18.5 1.0* 1.46 8 148 111 6.4 38 22.5 0.5* 1.34 5 153 117 5.8 39 30 3.0* 1.49 5 95 150 7.2 40 32 2.9* 1.41 6 86 155 6.8 Notes to Table Three (c) to (f) are all as defined in Notes to Table One.

(I) The time is the time, in hours from the commencement of using the specified catalyst system under the specified operating conditions.

EXAMPLES 41 TO 44 Polymerisation was effected in a 100 dm3 stainless steel autoclave fitted with a stirrer. To initiate polymerisation 36 kg of polypropylene powder having a flexural modulus of 1.45 GN/m2, and 4.0% by weight of which was soluble in boiling heptane as determined from the weight loss after Soxhlet extraction for 24 hours, were placed in the autoclave. The stirrer was rotated at 60 rpm and stirring was continued throughout the following procedure. The autoclave was purged at 73"C with nitrogen, then evacuated to a pressure of 0.1 mm of mercury. Liquid propylene was added to the autoclave and vaporised to raise the pressure to 28 kg/cm2 gauge. Hydrogen was added separately in the proportion of 1.5% by weight relative to the propylene.

A solution of a trialkyl aluminium compound, and an ester, in the aliphatic hydrocarbon and a suspension containing a titanium composition obtained as described herein were introduced into the autoclave until polymerisation was observed to start. Liquid propylene was being introduced, and gaseous propylene vented off, whilst the catalyst components were being added.

Once polymerisation had started, venting of the autoclave was stopped, liquid propylene at 20"C was introduced into the autoclave at a rate to maintain a pressure of 28 kg/cm2 gauge (about 15 kg/hr for a dwell time of 2.5 hours) and polypropylene, saturated with propylene, was intermittently withdrawn from the autoclave at a desired rate, typically about 10 to 12 kg of polymer per hour. The temperature and pressure were maintained at 70"C and 28 kg/cm2 gauge respectively. The trialkyl aluminium compound solution, the ester solution and the suspension of the titanium composition were continuously introduced into the autoclave at a rate to maintain the rate of polymer production at the desired rate of 10 to 12 kg/hr of polymer.

After polymerisation had been proceeding for a sufficient time to establish steady operating conditions, the product of Example 11, and subsequently the product of Example 12, were used as the titanium composition. Further details of the polymerisation conditions are given in Table Four.

Properties of the polymer products removed at various times during the polymerisations are set out in Table Five.

TABLE FOUR Ti Al composition compound Ester DT Example (hours) Type Amount Type Amount Type Amount (k) (b) (mM/h) (i) (mM/h) (j) (mM/h) 41 11 1.0 TBA* 60 MT 22 2.5 42 11 1.1 TBA* 60 MT 22 2.5 43 12 1.1 TEA* 100 EA 37 2.5 44 12 1.2 TEA* 100 EA 37 2.5 Notes to Table Four (b) is as defined in Notes to Table One.

(i), (j) and (k) are all as defined in Notes to Table Two.

TABLE FIVE Polymer properties Time Example (hours) MFI FM Ti Al CI HHS (1) (c) (d) (e) (e) (e) (%) (f) 41 2 3.5 1.55 4 93 94 ND 42 4 3.3 1.49 5 112 114 5.7 43 16 4.5 1.58 5 179 131 6.2 44 18 4.8 1.65 6 188 129 6.3 Notes to Table Five (c) to (f) are all as defined in Notes to Table One.

(I) is as defined in Notes to Table Three.

EXAMPLE 45 The milled product obtained in stage A) of Example 8 was used.

105.8 grammes of the milled product of stage A) of Example 8 were used. After removing the supernatant liquid, a further one dm3 of titanium tetrachloride was added immediately, the mixture was stirred and the temperature was raised to 100"C again. Stirring at 1 00'C was continued for three hours, stirring was stopped, the solid was allowed to settle for 1.5 hours, the supernatant liquid was removed, the heating switched off and the settled solid allowed to cool overnight.

In each washing stage, sufficient of an isoparaffin fraction, essentially all of which had a boiling point in the range 117"C to 135"C (hereafter referred to simply as the "isoparaffin fraction") was added to give a total volume of 2 dm3.

In the first washing stage, the settled solid plus residual titanium tetrachloride was stirred and heated up to 100C. The isoparaffin fraction was then added and stirring at 1 OO"C was contin ued for one hour. Stirring was then stopped, the solid was allowed to settle for 1.5 hours, the supernatant liquid was removed and the heating was then switched off.

Three further washes were then carried out, without heating, by adding the isoparaffin fraction at ambient temperature to the settled solid from the previous wash. For each wash, the mixture was stirred for one minute, the solid allowed to settle for 30 minutes and the supernatant liquid removed.

After the fourth wash, sufficient of the n-heptane fraction was added to give a total volume of one dm3.

EXAMPLE 46 A portion of the product of Example 45 was mixed with a polymer powder, as described hereafter.

Mixing with polymer powder A powder of a copolymer of ethylene and butene-l having a melt flow index (measured at 190"C with a weight of 2.16 kg) of one and a density (measured as in ASTM 1928/70, Method A, using a density gradient column at 23"C) of 920 kg/m3 was sieved and the fraction passing through a 425 micron sieve was retained.

The copolymer powder was mixed with solid carbon dioxide and milled through a 250 micron brass screen.

The copolymer powder was dried overnight in an air oven at 60"C and the powder was again sieved and the fraction passing through a 212 micron sieve and caught on a 106 micron sieve was retained. The retained fraction was dried overnight in an air oven at 60"C.

A 500 cm3 flask was evacuated to less than 1 mm of mercury and purged with nitrogen, this procedure being effected three times. To the flask was added the sieved and dried copolymer powder fraction. The flask was evacuated to 1 mm of mercury and the copolymer powder fraction was dried for seven hours at 60"C.

The final weight of the dried copolymer powder fraction was 45.5 grammes.

A 100 cm3 round bottom tube was dried overnight in an air oven at 160"C, evacuated to 1 mm of mercury and purged with nitrogen, this procedure being effected three times. A 60 cm3 sample of the suspension obtained in stage C) of this example was transferred to the tube and allowed to settle. The supernatant liquid was removed to give a settled solid.

The copolymer powder fraction was stirred and the settled solid added gradually thereto over a period of 15 minutes.

A further 60 cm3 sample of the suspension from stage C) were allowed to settle, the supernatant removed and the settled solid added to the copolymer powder fraction, this addition being effected over a period of three minutes. The product obtained was dried at a pressure of 1 mm of mercury for three hours at 60"C. The dried product was passed through a 250 micron sieve.

EXAMPLES 47 AND 48 A 20 cm internal diameterfiuldised bed reactor vessel, operated in a continuous manner, was used to produce a series of ethylene/butene-1 copolymers. A reaction mixture comprising ethylene, butene-1 and hydrogen was circulated continuously through the bed at a superficial velocity estimated to be about five times the minimum necessary for fluidisation. In the fluidised bed, the reaction temperature was controlled at 80"C by adjusting the temperature of the gas fed to the fluidised bed reactor vessel using a heat exchanger in the circulating gas loop. Aluminium triethyl was pumped continuously into the reactor as a 0.25 molar solution in the n-heptane fraction at a rate of 6.25 millimoles per hour.The product of Example 45 or 46 was blown into the reactor as a dry powder at frequent intervals so as to maintain a rate of polymer production of about 1.5 Kg/hr, which corresponds to a mean residence time of four hours. The reaction pressure was maintained automatically at 15 Kg/cm2 absolute by admitting an ethylene/hydrogen mixture through a control valve. Liquid butene-1 was pumped into the circulating gas stream so as to maintain a constant composition as determined by Gas Liquid Chromotography.

The polymer formed was removed periodically so as to maintain an essentially constant level in the reactor vessel. The polymer collected was degassed in a stream of nitrogen which had been passed over a bath of water at ambient temperature, and then through a steam jacket. The use of this warm, moist nitrogen removed monomers and also de-activated the catalyst and alkyl residues.

Further details, together with some characteristics of the polymers obtained, are set out in Table Six.

TABLE SIX Ti Compn. Gas Composition Rate of Polymer Polymer Ex Type Rate Mole % (p) Polymer MFI Density No. (b) (mM/hr) Eth B-l Hy Production (r) Kg/m3 (m)(n) Kg/hr (s) (q) 47 45 0.026 62.8 20.8 16.4 2.1 1.0 919 48 46 0.08 57.2 22.8 20.0 1.2 1.1 920 Notes to Table Six (b) Is as defined in Notes to Table One.

(m) The amount is given as millimoles of titanium contained in the product of the Examples and added to the autoclave.

(n) The titanium composition is added as a solid using a solid metering device of known volume capacity.

(p) Eth is ethylene B-1 is butene-1 Hy is hydrogen Mole % is calculated from the relationship (Mole ofgas)x100 (Mole of ethy) + (Mole of B-1) + (Mole of Hy) (q) This is the rate at which polymer is removed from the reactor vessel in order to maintain an essentially constant level in the reactor vessel.

(r) MFI masured by ASTM Method D 1238/70 at 190"C using a 2.16 kg weight.

(s) Density was measured as described in ASTM 1928/70, Method A, using a density gradient column at 23"C.

Claims

1. A process for the production of a titanium containing composition which process comprises forming a solid material having the composition MgX2nR'COOR2, contacting the said solid material with a liquid phase containing titanium tetrachloride, separating a solid intermediate from the liquid phase, contacting this solid intermediate with a liquid phase containing titanium tetrachloride, separating a solid from this liquid phase, washing the separated solid at least once with an inert liquid hydrocarbon or halohydrocarbon and recovering a solid, titanium-containing material having a titanium content which is in the range from one up to 5% by weight, wherein X is a halogen atom; R1 is a hydrocarbon radical which may be substituted with one or more halogen atoms and/or oxyhydrocarbon groups; R2 is a hydrocarbon radical which may be substituted by one or more halogen atoms; and n has the value of from 0.1 up to 10.

2. A process as claimed in claim 1 wherein, in the solid, titanium-containing material which is recovered, at least 25% of the titanium-containing species are capable of being removed by continued washing with a hot hydrocarbon or halohydrocarbon liquid.

3. A process as claimed in claim 1 or claim 2 wherein Xis chlorine.

4. A process as claimed in any one of claims 1 to 3 wherein the group R1 is an optionally substituted alkyl or aryl group.

5. A process as claimed in claim 4 wherein the group R1 is a phenyl, a tolyl, a methoxyphenyl, a fluorophenyl or a benzyl group.

6. A process as claimed in any one of claims 1 to 5 wherein the group R2 is an alkyl group containing up to 6 carbon atoms.

7. A process as claimed in any one of claims 1 to 6 wherein R1 is an aryl group and R2 is an alkyl group.

8. A process as claimed in claim 7 wherein the solid material is a magnesium chloride-ethyl benzoate composition wherein the value of n is from 0.2 up to 2.

9. A process as claimed in any one of claims 1 to 8 wherein the solid material of composition MgX2nR'COOR2 has been prepared by grinding together a magnesium halide and a suitable proportion of an ester.

10. A process as claimed in claim 9 wherein the grinding has been carried out in a rotating ball mill or a vibrating ball mill.

11. A process as claimed in claim 9 or claim 10 wherein the grinding has been carried out from 5 up to 30 hours.

12. A process as claimed in any one of claims 9 to 11 wherein the grinding has been carried out at a temperature of from -50 C up to 100"C.

13. A process as claimed in any one of claims 1 to 12whereinthe magnesium halide-estercomposition is contacted with a liquid phase which contains at least 45% by weight of titanium tetrachloride.

14. A process as claimed in claim 13 wherein the liquid phase consists solely of liquid titanium tetrachloride.

15. A process as claimed in any one of claims 1 to 14 wherein the solid material is contacted with the titanium tetrachloride-containing liquid at an elevated temperature which is at least 60"C up to the boiling temperature of the liquid phase.

16. A process as claimed in claim 15 wherein the contacting is effected at a temperature in the range 80"C upto 120 C.

17. A process as claimed in any one of claims 1 to 16 wherein the solid material is contacted with the liquid titanium tetrachloride-containing phase for a period of time of from 0.5 up to 5 hours.

18. A process as claimed in any one of claims 1 to 17 wherein both stages in which a solid material is contacted with a titanium tetrachloride-containing liquid phase are effected under the same conditions of temperature and time.

19. A process as claimed in any one of claims 1 to 18 wherein after contacting the solid intermediate with the liquid phase containing titanium tetrachloride, the separated solid thus obtained is washed at least once with an inert liquid hydrocarbon or halohydrocarbon by suspending the solid in the inert liquid hydrocarbon or halohydrocarbon medium and agitating the mixture for a period of time of at least 0.5 hours up to 5 hours.

20. A process as claimed in claim 19 wherein more than one washing step is effected and at least the first washing step is effected at a temperature of at least 60"C.

21. A process as claimed in any one of claims 1 to 20 wherein the quantity of the inert hydrocarbon or halohydrocarbon liquid used for the at least one washing step is in the range from 5 cm3 for each gramme of solid material.

22. A process as claimed in claim 20 where the first washing step is effected before the separated solid has cooled appreciably, heating is continued throughout at least the first washing step, not more than two washing steps are effected at the elevated temperature and not more than a further two washing steps are effected without heating.

23. A process as claimed in any one of claims 1 to 22 wherein the solid titanium-containing material recovered has a titanium content in the range from 1.5 up to 3% by weight.

24. A process as claimed in any one of claims 1 to 23 which includes a spray-drying stage in which a solid material is suspended in an inert liquid medium, the suspension formed is spray-dried and a spray-dried solid material is collected wherein the solid material is the magnesium halide-ester composition or solid material obtained in a subsequent stage, including the solid titanium-containing material.

25. A process as claimed in claim 24 wherein the solid material which is subjected to the spray-drying is the magnesium halide-ester composition or the solid titanium-containing material.

26. A process as claimed in claim 24 or claim 25 wherein the magnesium halide-ester composition is subjected to spray-drying, the spray-dried product thereby obtained is thereafter contacted twice with titanium tetrachloride and then washed at least once.

27. A process as claimed in any one of claims 24 to 26 wherein the inert liquid medium in which the solid material is suspended is a liquid hydrocarbon or halohydrocarbon.

28. A process as claimed in any one of claims 24 to 27 wherein spray-drying is effected by passing the mixture through an atomizer to form a spray of droplets, contacting the droplets with a stream of a hot gas to cause evaporation of the liquid medium and collecting a separated solid product.

29. A process as claimed in claim 28 wherein the hot gas is essentially oxygen- and water vapour-free and is at a temperature of at least 80"C.

30. A process as claimed in any one of claims 24 to 29 wherein the spray-drying step is effected in the presence of an attrition inhibitor which renders the spray-dried solid more resistant to attrition.

31. A process as claimed in claim 30 wherein the attrition inhibitor is polystyrene, polymethylmethacrylate, polyvinylacetate, atactic polypropylene, or a t-butylstyrene-styrene AB block copolymer.

32. A process as claimed in claim 30 or claim 31 wherein the attrition inhibitor is present in an amount of from 0.5% up to 10% by weight relative to the solid material present in the suspension.

33. A transition metal composition whenever obtained by the process of any one of claims 1 to 32.

34. A polymerisation catalyst which is the product obtained by mixing together 1) a transition metal composition as claimed in claim 33; and 2) an organic compound of aluminium or of a metal of Group IIA of the Periodic Table or a complex of an organic compound of a metal of Group IA or Group IIA of the Periodic Table together with an organic aluminium compound.

35. A catalyst as claimed in claim 34 wherein Component 2) is an aluminium trihydrocarbyl compound and the catalyst also includes an ester of a carboxylic acid which contains an aromatic group.

36. A process for the production of a polymer of copolymer of an unsaturated monomer wherein at least one ethylenically unsaturated hydrocarbon monomer is contacted, under polymerisation conditions, with a polymerisation catalyst as claimed in claim 34 or claim 35.

37. A process as claimed in claim 36 wherein the monomer which is contacted with the catalyst system is one having the formula: CH2=CHR wherein R is a hydrogen atom or a hydrocarbon radical.

38. A propylene polymer which is a direct product of polymerisation and which has a titanium content of less than 5 parts per million by weight, a chlorine content of less than 150 parts per million by weight and wherein less than 7% by weight of the polymer is soluble in boiling heptane by Soxhlet extraction for 24 hours.

39. A polymer as claimed in claim 38 which has a chlorine content of less than 100 parts per million by weight.

40. A polymer as claimed in claim 38 or claim 39 wherein less than 5% by weight of the polymer is soluble in boiling heptane.

41. A polymer as claimed in any one of claims 38 to 40 which is capable of forming mouldings having a flexural modulus of at least 1.40 GN/m2.

42. A polymer as claimed in claim 41 which is capable of forming mouldings having a flexural modulus of at least 1.50 GN/m2.