WO2001002446A1 - Catalytic system based on rare earth and magnesium. novel neodymium alcoholate, use for polymerising unsaturated compounds - Google Patents

Abstract

The invention concerns a catalytic system based on rare earth and magnesium and its use for polymerising unsaturated compounds. The inventive catalytic system is characterised in that it comprises a compound consisting of the reaction product between: a rare earth alcoholate; an organo-magnesium. The alcoholate can be prepared in particular by reacting a rare earth halide with an alkaline or alkaline-earth alcoholate. The invention also concerns a neodymium alcoholate characterised in that the alcoholate is a tert-butylate or a tert-amylate and it does not contain chlorine in its structure. The inventive system can be used more particularly for polymerising methyl ethylene or methacrylate and for copolymerising them.

Description

 CATALYTIC SYSTEM BASED ON RARE EARTH AND MAGNESIUM, NOVEL NEODYME ALCOOLATE, USE FOR THE POLYMERIZATION OF

UNSATURATED COMPOUNDS

The present invention relates to a catalytic system based on rare earth and magnesium, a new neodymium alcoholate and their use for the polymerization of unsaturated compounds.

The polymerization of compounds containing vinyl (olefins, dienes (meth) acrylates) such as ethylene or methyl methacrylate or the copolymerization of the latter with olefins is currently an important industrial issue. therefore catalysts or initiators for these polymerization reactions which are always more competitive in cost and efficiency. In particular, an improvement in tacticity and homodispersity efficiency is sought. Thus, initiators of the metallocene type are known which are effective but which have the disadvantage of being difficult to prepare and of being expensive

The object of the invention is therefore the development of an efficient and simple preparation catalytic system

For this purpose, the catalytic system according to the invention is characterized in that it comprises a compound constituted by the product of the reaction between

- a rare earth alcoholate,

- an organo-magnesian

The system of the invention is efficient and allows, according to preferred embodiments, to obtain unimodal polymers, if necessary homodispersed and with a high rate of syndiotacticity.

The invention also relates to a neodymium alcoholate which is characterized in that the alcoholate is a tert-butylate or a tertioamylate and in that it does not contain a neodymium-chlorine covalent bond

Other characteristics, details and advantages of the invention will appear even more completely on reading the description which follows, as well as various concrete but nonlimiting examples intended to illustrate it.

For the whole of the description, the term “rare earth” is understood to mean the elements of the group constituted by yttπum and the elements of the periodic classification with atomic number included inclusively between 57 and 71 As indicated above, the catalytic system of the invention comprises a compound consisting of the product of the reaction of two reagents which will be described more precisely below The first reagent is a rare earth alcoholate. By alcoholate is meant the products corresponding to the general formula (1) (TR) _x (OR ¹ ) _y (X) _z (S) _t in which R ¹ denotes an organic group, X a halogen and S a coordinating solvent and where x> 1, y> 1, z> 0 and t> 0. The term alcoholate also applies, in the context of the present invention, to alcoholates of formula (1) comprising several different radicals R ¹ . The rare earth of the alcoholate can be more particularly yttrium, lanthanum, cerium, neodymium or samarium. Neodymium is preferred.

plus particulièrement en C₄-C₈. On peut mentionner tout particulièrement les alcoolates ou polyalcoolates tertiaires, par exemple le tertiobutylate ou le tertioamylate.The alcoholate is more particularly an alcoholate of an alcohol or of a polyol derived from an aliphatic or cyclic hydrocarbon and in particular from an aliphatic hydrocarbon, linear or branched, in

more particularly in C ₄ -C ₈ . Mention may very particularly be made of tertiary alcoholates or polyalcoholates, for example tert-butylate or tertioamylate.

The alcoholate can also be a phenate, that is to say a derivative of a compound of phenolic or polyphenolic type. According to a preferred embodiment of the invention, the alcoholate is prepared by specific methods which will be described more precisely below.

A first method implements a reaction of a rare earth halide with an alkali or alkaline earth alcoholate. The halide can more particularly be a chloride and the alkali can be in particular sodium and potassium. The reaction is carried out in an anhydrous solvent medium and protected from air. The solvent medium is constituted by tetrahydrofuran (THF) or comprises tetrahydrofuran in mixture with another solvent. As other solvent, mention may be made of liquid hydrocarbons of 3 to 12 carbon atoms such as heptane, cyclohexane, cyclic or aromatic hydrocarbons such as benzene, toluene or even xylenes. We can also mention ethers.

The reaction generally takes place at a temperature which can be between ambient (20 ° C.) and 100 ° C. over a period which can vary between approximately 12 hours and approximately 96 hours. In the case of the preparation of a phenate, the reaction mixture is brought to reflux over a period of the same order of magnitude. At the end of the reaction, the reaction medium is allowed to settle, the supernatant is evaporated and a solid product is thus obtained, in the form of a powder, which constitutes the rare earth alcoholate.

A second specific process consists in reacting with an alkali or alkaline earth alcoholate an adduct of a rare earth halide and THF (TRX ₃ , xTHF). What has been said above as to the nature of the alcoholate and the halide also applies here. The adduct can be obtained by heating a rare earth halide in THF, for example at 50 ° C., then evaporation of the solvent. This evaporation can be done under vacuum at 20 ° C. The reaction with the alcoholate also takes place in an anhydrous solvent medium and away from air. and under the same conditions as those described for the previous process The solvents are of the same type as those given above and mention may be made very particularly of toluene

Another specific process can be mentioned. This process consists in reacting an alcohol with a rare earth amide. The alcohol can be an alcohol, a polyol or a phenolic or polyphenolic compound as defined above. The amide is a compound. of formula TR (N (SιR ² ₃ ) ₂ ) ₃ , R ² denoting an alkyl radical, for example methyl The reaction is also carried out in an anhydrous solvent medium and protected from air The solvent medium consists of tetrahydrofuran (THF) or comprises tetrahydrofuran in admixture with another solvent. As other solvent, mention may be made of liquid hydrocarbons of 3 to 12 carbon atoms such as heptane, cyclohexane, cyclic or aromatic hydrocarbons such as benzene, toluene or xylenes can also be mentioned ethers The reaction temperature can be between -20 ° C and 100 ° C, but generally one works at room temperature The reaction time can be short t vary between 15 minutes and 96 hours, it can be for example 24 hours

Finally, a last specific process can be described. II consists in reacting an alcohol as defined above with an adduct of a rare earth amide as defined above and of THF. The preparation of the adduct can be done in the same way. manner as that given for the adduct described previously The rest of the process is also of the same type as that which was described previously for the amide

The present invention also relates, as a new product, to a neodymium alcoholate. This neodymium alcoholate has as specific characteristic the fact that it does not contain chlorine in its structure. It will be noted that the known rare earth alcoholates, by their mode of preparation, present either chlorine which belongs to their atomic structure even, or a liganded solvent, or both at the same time In addition, for this product, the alcoholate is a tert-butylate or a tertioamylate The neodymium alcoholate of the invention can correspond to the formula Nd ₃ (μ3-O ^t Bu) ₂ (μ ₂ -O ^t Bu) ₃ (μ- O ^t Bu) ₄ (THF) ₂ nTHF or Nd ₃ (μ ₃ -O ^t Am ) ₂ (μ ₂ -O ^t Am) ₃ (μ-O ^t Am) ₄ (THF) ₂ nTHF, where n can be 0 or 1

The absence of chlorine can be demonstrated by X-ray analysis. The neodymium alcoholate of the invention can be prepared by implementing the specific methods which have been described above, in particular using tert-butylate or a tertioamylate or else the tertiobutanol or tertiobutyl alcohol The second reagent used in the reaction, the product of which constitutes the compound of the catalytic system of the invention, is an organomagnesium

By organo-magnesium is meant a product which is either a dialkyl-magnesian or a Gπgnard reagent In the case of a dialkyl-magnesian, that is to say the compounds of formula (2) R-Mg-R 'where R and R' denote alkyl radicals, R and R 'can be in particular radicals CC ₈ , linear or branched, identical or different, R and R 'may more particularly be n-hexyl Mention may also be made more particularly of the product of formula (2) in which R and R' are respectively butyl and ethyl The alkyl radicals R and / or R 'can also carry a heteroatom such as Si Mention may in particular be made of the radical -CH ₂ -Sι (CH ₃ ) ₃

The organomagnesium can also be a Gπgnard reagent, that is to say a compound of formula (3) R-Mg-X in which X denotes a halogen, the halogen can be bromine, chlorine or iodine, but use is more particularly made of those for which the halogen is bromine The nature of R may be any R may in particular be a saturated or non-ahcyclic or aromatic aliphatic radical R may more particularly be an alkyl radical, such as the ethyl radical, another phenyl radical

The rare earth alcoholate and the magnesium compound can be reacted in respective variable proportions This proportion can be expressed by the ratio TR / Mg This ratio (molar ratio) is generally between 0.5 and 5 It can be more particularly equal to 1 It would not, however, depart from the scope of the present invention to use a ratio outside the above-mentioned range. This ratio may vary in particular as a function of the unsaturated compounds which it is desired to polymerize. It will be noted that the use of 'an organo-magnesian of formula (2) above in which R and R' are respectively butyl and ethyl makes it possible to work with TR / Mg ratios which can vary within a fairly wide range

The product of the reaction of the two reactants which have just been described therefore constitutes the compound of the catalytic system of the invention. By "consists of the product of the reaction of the two reactants" it is meant that there is no other compounds or elements which participate, as a reagent, in this reaction

The catalytic system of the invention is usually in the form of a solution which is generally obtained by mixing and then reacting a first solution of the first reagent with a second solution of the second reagent then stirring These solutions are in solvents of the same type as those which were mentioned above The mixture obtained from the two aforementioned solutions can be maintained and stirred, before its use, at a temperature which can be between -80 ° C and 110 ° C for a period of a few minutes a few hours, for example for an hour The system of the invention can be used for the polymerization or copolymerization of unsaturated compounds of the type of those described in the introduction to this description (olefins, dienes, (meth) acrylates) As compound of this type, mention may more particularly be made of ethylene, butadiene. The system of the invention is preferably used for the polymerization of ethylene. Mention may also be made of the polymerization of polar monomers of the (meth) acrylate type, iactone or lactide, preferably methyl methacrylate It will be noted that the system of the invention is suitable for block block copolymerization of ethylene with a polar monomer, in particular methyl methacrylate

The polymerization is carried out under known conditions The polymerization temperature can be between -80 ° C. and 110 ° C. It is preferably worked at atmospheric pressure but it is also possible to work under pressure The reaction is usually carried out in the presence of a solvent which can be chosen in particular from aliphatic hydrocarbons or their mixtures such as butane, hexane, cyclohexane, aromatic hydrocarbons such as toluene

In the case of the polymerization of ethylene, it is possible to work in the presence of hydrogen as a transfer agent, which makes it possible, in particular, to control the length of the chains of the polymers formed. Examples will now be given

Example 1 This example relates to the preparation of tert-butylates of different rare earths

The procedure is given below in the case of neodymium. In a glove box, are weighed and placed in two Schlenk tubes of 100 ml, on the one hand sodium tertiobutylate (30mmol) and on the other hand anhydrous neodymium (III) (10mmol) These are then placed under argon and 40mL of THF are added to them respectively (distilled over K and degassed according to the freezing point technique) A solution of sodium tertiobutylate and a suspension are thus obtained of neodymium chloride The suspension of NdCI3 is transferred to a Schlenk tube with a minimum capacity of 300mL then the tBuONa solution is added to it. The two small Schlenk tubes are rinsed with 20mL of THF which will be added to the previous 80mL The mixture is maintained for 72 hours at room temperature with vigorous stirring and then the residual NaCl is left to settle overnight before filtering the solution which allows a clear blue solution to be obtained. the solvent for this solution is then evacuated under vacuum (10 ² mmHg) at room temperature for 5 to 6 hours. A light blue granular powder very soluble in toluene, is obtained with a yield of between 80 and 90%.

The powdery product obtained can be re-installed in a solvent such as toluene or a toluene / pentane mixture (1/1) at -5 ° C. The X-ray diffraction analysis correlated by NMR analysis of the proton establishes that the compound has a formula like Nd ₃ (μ3-O ^t Bu) ₂ (μ ₂ -O ^t Bu) ₃ (μ-O ^t Bu) ₄ (THF) ₂ THF The compound therefore does not contain chlorine This compound crystallizes in the orthorhombic system in the group Pbcn with the mesh parameters a = 17.0538 (10) A, b = 20.0343 (12) A, c = 17.7400 (11) A

The light blue powdery product and the crystallized product have the same catalytic properties

We proceed in the same way for the tertiobutylates of cerum, yttnum, lanthanum and samanum

The examples which follow illustrate the use of the system of the invention in the polymerization of different compounds. The meanings of the different abbreviations used in these examples are given below n (TR) number of milhmoles of rare earth used

Tmel temperature at which the reaction between the alcoholate and the organo-magnesium was carried out

T polym temperature at which the polymerization was carried out t polym duration of the polymerization

Tm melting temperature of the polymer (determined by ATD)

Yield of polymerization

% rr percentage of syndiotacticity (determined by 1 H NMR)

% mr percentage of atacticity (determined by 1 H NMR)% mm percentage of isotacticity (determined by 1 H NMR)

IP polymolecularity index (determined by GPC)

Mn molar mass in number (determined by GPC)

Cπst (%) percentage of crystallinity (determined by ATD)

Examples 2 to 10

These examples illustrate the use of the system of the invention in the polymerization of methyl methacrylate (MAM)

In a glove box, place in a Schlenk tube the rare earth tert-butylate obtained in Example 1 (1 mmol) and in a second tube the magnesium compound in 20% solution in heptane These being under argon, 10 ml of toluene are added to them respectively (distilled over Na and degassed) and the solutions thus obtained are placed at the desired alkylation temperature. The solution of rare earth tert-butylate is then added to that of the magnesium compound. obtained is maintained for one hour at the desired temperature and then injected into another Schlenk tube in which 80 ml of toluene are found at the polymerization temperature. Immediately, the MAM (50 mmol) is injected and the mixture is left stirring for one hour. reaction by adding a small amount of ethanol (1 to 2 ml) and the polymer in an acidified ethanol solution. The polymer obtained is filtered and washed again with acidified ethanol, filtered and dried for 24 hours in an oven at 60 ° C.

The nature of the compounds of the catalytic system used and the polymerization conditions are given in table 1 below.

Table 1

The results of the polymerization and the properties of the polymers obtained are given in table 2 below. Table 2

insoluble polymer

Examples 11 to 18

These examples relate to the use of the system of the invention in the polymerization of ethylene.

The procedure is carried out using the same method as that described for Examples 2 to 10, but by injecting the mixture of rare earth tert-butoxide and the magnesium compound in 80 ml of toluene under 1 bar of ethylene placed at the desired reaction temperature. The consumption of ethylene is monitored by an instantaneous flowmeter and a totalizer. The polymer is precipitated in an acidified methanol solution (5% HCl). It is then filtered on a frit and dried in an oven at 60 ° C for 24 hours.

The nature of the compounds of the catalytic system used and the polymerization conditions are given in table 3 below. In all cases, the alkylation temperature is 0 ° C.

Table 3

The results of the polymerization and the properties of the polymers obtained are given in table 4 below. Table 4

^* several peaks

The polyethylenes prepared in the examples in the presence of Nd at low temperature (0 ° C) advantageously have a higher melting temperature than those of the polymers usually obtained. Physico-chemical analyzes (NMR, GPC and solubility) show that the polymers obtained in these conditions are highly linear polymers with high molecular weights. For example, the GPC analysis of the sample of example 11 reveals an Mn of 390000 and an IP of 2.1

Example 19

This example illustrates the biblock copolymerization of ethylene and methyl methacrylate

Neodymium tertiobutylate and dι (n-hexyl) magnesium are used in an Nd / Mg ratio of 1. The procedure is as described for Examples 2 to 10 with, however, the following modifications The mixing of the solutions which has been maintained for 1 hour at a temperature of 0 ° C. is injected into another Schlenk tube containing 80 ml of toluene saturated with ethylene (1 bar) at the polymerization temperature (0 ° C.) The polymerization of ethylene is carried out for 12 minutes On then stop the arrival of ethylene, the medium is purged with argon and the MAM is injected (50 mmol) The mixture is left stirring for one hour at 0 ° C. The reaction is stopped by adding a small amount of ethanol (1 to 2 ml ) and the polymer is precipitated in heptane The copolymer obtained is then filtered on filter and dried in an oven at 60 ° C for 24 hours 6.0g of the latter undergo extraction with acetone (at its point of boiling) for 48 hours in a Ku agawa apparatus. HomoPMMA is thus separated from homoPE and from the copolymer. Only 1.0 gram was dissolved in acetone, which amounts to saying that there is only 17%. homoPMMA in the polymer obtained

The results obtained are given in table 5 below.

Table 5

Examples 20 to 22

These examples illustrate the polymerization of ethylene in the presence of hydrogen as a transfer agent. The procedure is carried out using the same method as that described for Examples 11 to 18 but by injecting a mixture of ethylene / hydrogen (1.0 atm). at different hydrogen concentration

The nature of the rare earth of the catalytic system used and the polymerization conditions are given in table 6 below. In all cases, the organomagnesium used is Mg (n-Hex) and the temperature at which the reaction between the alcoholate and the organo-magnesian is 0 ° C

Table 6

On donne dans le tableau 7 ci-dessous des résultats de la polymérisation et les propriétés des polymères obtenus

The results of the polymerization and the properties of the polymers obtained are given in table 7 below.

Table 7

insoluble polymer

Example 23

This example relates to the preparation of the trιs (phenate) of neodymium Nd (O (2,6-'Bu-4- Me-C ₆ H ₂ ) ₃ ) and its use in the polymerization of ethylene

The neodymium tπs (phenate) is prepared as in Example 1 using sodium phenate in place of sodium tertiobutylate The other difference is that the reaction mixture is maintained for 72 hours at THF reflux. A fine powder is obtained purplish with a yield of 80-90%

For the polymerization, the procedure is as in Example 2 The mixing temperature of neodymium trιs (phenate) and the magnesium compound is 20 ° C. The polymerization temperature is also 20 ° C. and the reaction time is d 'one o'clock

During this reaction, 750 mg of ethylene are consumed and after precipitation and filtration 450 mg of polyethylene are obtained

Claims

1- Catalytic system, characterized in that it comprises a compound consisting of the product of the reaction between: - a rare earth alcoholate; - an organo-magnesian. 2- catalytic system according to claim 1, characterized in that the rare earth is yttrium, lanthanum, cerium, neodymium or samarium. 3- catalytic system according to claim 1 or 2, characterized in that the alcoholate comes from a compound of phenolic or polyphenolic type or also from an alcohol or a polyol derived from an aliphatic hydrocarbon, linear or branched, in C _r C ₁₀ , more particularly in C ₄ -C ₈ 4- Catalytic system according to one of the preceding claims, characterized in that the alcoholate comes from an alcohol or a tertiary polyol. 5- Catalytic system according to one of the preceding claims, characterized in that the organomagnesium is a dialkyl-magnesian of formula R-Mg-R 'where R and R' denote linear or branched alkyl radicals, identical or different , more particularly CC ₈ radicals. 6- Catalytic system according to claim 5, characterized in that R and R 'are n-hexyl or in that R and R' are respectively butyl and ethyl. 7- Catalytic system according to claim 5, characterized in that at least one of the radicals R or R 'carries a heteroatom, which may be more particularly silicon 8- Catalytic system according to one of claims 1 to 4, characterized in that the organomagnesium is a Grignard reagent. 9- Catalytic system according to one of the preceding claims, characterized in that the alcoholate and the organomagnesium are reacted with respective amounts such that the rare earth / Mg molar ratio is between 0.5 and 5 . 10- Catalytic system according to one of the preceding claims, characterized in that the rare earth alcoholate was obtained by reaction of a rare earth halide with an alkali or alkaline earth alcoholate in an anhydrous solvent consisting of or comprising tetrahydrofuran or of a rare earth amide with an alcohol in an anhydrous solvent constituted by or comprising tetrahydrofuran 11- Catalytic system according to claim 10, characterized in that the rare earth alcoholate was obtained by reaction of a rare earth chloride with an alkali or alkaline earth alcoholate 12- Catalytic system according to claim 10 or 11, characterized in that the alkaline alcoholate is a sodium or potassium alcoholate 13- Catalytic system according to one of claims 1 to 9, characterized in that the rare earth alcoholate was obtained by reaction in an anhydrous solvent of an alkali or alkaline earth alcoholate with an adduct of rare earth halide and tetrahydrofuran or an alcohol with an adduct of a rare earth amide and THF 14- Neodymium alcoholate, characterized in that the alcoholate is a tert-butylate or a tertioamylate and in that it does not contain a neodymium-chlorine covalent bond 15- Process for the polymerization or copolymerization of an unsaturated compound, characterized in that a catalytic system according to one of claims 1 to 13 is used 16- Process according to claim 15, characterized in that the unsaturated compound is ethylene, butadiene or methyl methacrylate 17- The method of claim 16, characterized in that copolyméπse ethylene and methyl methacrylate