EP1322677A1

EP1322677A1 - Olefin polymerisation catalyst

Info

Publication number: EP1322677A1
Application number: EP01969906A
Authority: EP
Inventors: Jérôme CLAVERIE; Rémi SOULA; Roger Spitz
Original assignee: Atofina SA
Current assignee: Total Petrochemicals France SA
Priority date: 2000-09-19
Filing date: 2001-09-17
Publication date: 2003-07-02
Also published as: JP2004509990A; AU2001290035A1; KR20030032041A; CN1458939A; US7078363B2; US20040097672A1; FR2814169B1; WO2002024763A1; FR2814169A1

Abstract

The invention concerns a catalyst for olefin polymerisation, of formula (I) wherein: E is an oxygen or sulphur atom; X is a phosphorus, arsenic or antimony atom; M is a nickel, palladium or platinum atom comprising a non-attributed valency; a is 1 or 2; R1, R2, R3, identical or different can be selected among hydrogen, alkyl, cycloalkyl, aryl, alkylaryl, arylalkyl radicals, the hydroxyl radical, the alkoxide radicals (with 1 to 20 carbon atoms), the groups -C(O)OR'-, -SO3Y; and Z represents a hydrocarbon radical comprising 2 to 3 carbon atoms; R represents a hydrocarbon radical of valency a, provided that at least one of the radicals Z or R bears at least an electroattractive substituent.

Description

CATALYST FOR OLEFIN POLYMERIZATION

The present invention relates to the polymerization of olefins, a catalyst for the polymerization of olefins, a process for the preparation of such a catalyst, as well as a process for the polymerization of olefins.

Polymers of ethylene and other olefins have significant commercial appeal. The applications of these polymers are extremely numerous, ranging from products with low molecular weights for lubricants and greases, to products with higher molecular weights for the manufacture of fibers, films, molded objects, elastomers, etc. In most cases, the polymers are obtained by catalytic polymerization of olefins using a compound based on a transition metal. The nature of this compound has a very strong influence on the properties of the polymer, its cost, its purity. Given the importance of polyolefins, there is a permanent need to improve the catalytic systems and to propose new ones.

There are a variety of homogeneous or heterogeneous catalysts for the polymerization or copolymerization of ethylene. Among the most well-known families, mention may be made, for example, of "Ziegler" type catalysts using organometallic complexes of metals from groups III and IV or "Philipps" type catalysts involving chromium complexes. But there are also nickel-based catalysts used in particular for many years for the production of α-olefins. Some systems also have a certain tolerance for polar media.

Among the many catalytic systems exposed in the literature, it has been described for example the association between a nickel complex, such as bis-1, 5-cyclooctadiene, with benzoic acid derivatives such as 2- mercaptobenzoic or acid 3,5-diaminobenzoic acid (US-A-3,637,636) or with tertiary chelating organophosphorus ligands (US-A-3,635,937, US-A-3,647,914) or with glycolic, thioglycolic or thiolactic acids (US-A-3,661,803). In US-A-3,686,159, the use of a zero degree nickel complex is described, such as bis-1,5-cyclooctadiene again, with a phosphorus ylide ligand. The above inventions have in common the formation in if you in the polymerization medium of the active species. Other methods, such as in US patent US-A-4,716,205 or the Bulgarian patent BG 60319, claim nickel catalytic systems which can be isolated, but it is necessary to introduce an acceptor compound into the polymerization medium. capable of extracting one of the ligands from the nickel complex to make it active. The in technique if you do not allow to isolate the catalytic system so as to identify precisely its structure but the approach has the merit of being simple and it limits the handling of the catalysts, which is a source of pollution.

US Pat. Nos. 4,293,727, 4,301,318 and 4,529,554 relate to processes for the oligomerization of ethylene comprising contacting the ethylene with nickel ylides having sulfonated substituents. These ylures have the particular disadvantage of being difficult to synthesize.

US Patent No. 4,716,205 relates to the polymerization of ethylene in the presence of certain catalysts containing nickel. In the article entitled “Ethylene Homopolymerization ith P, 0-Chelated Nickel Catalysts” by U. KLABUNDE, et al., Journal of Polymer Science, Part A: Polymer Chemistry, Vol. 25, 1989-2003 (1987), as well as in the article “Nickel catalysis for ethylene homo- and co-polymerization”, by U. KLABUNDE and SD ITTEL, Journal of Molecular Catalysis, 41 (1987) 123-134 are described phosphorus and nickel based catalysts. The article entitled “Coordination polymerization of ethylène in water by Pd (II) and Ni (II) catalysts” by A. HELD, FM BAUERS and S. MECKING, Chem. Comm. , 2000, 301-302 reports the polymerization of ethylene in water using nitrogen complexes of palladium (II) and sulfonated complexes of nickel (II).

French patent application published under number 2 784 110 relates to a process for the polymerization of at least one olefin in the presence of at least one catalyst comprising at least one E - M - X chain in which E represents an oxygen atom or sulfur, M represents a nickel or palladium or platinum atom, X represents a phosphorus, arsenic or antimony atom, in a medium comprising a continuous liquid phase which comprises more than 30% by weight of water. As an example of a catalyst, the structure represented by formula (1) is cited in this document.

in which the radicals R, R, R ³ , R ⁴ and R ⁵ , which may be identical or different, may be chosen from hydrogen, alkyl, cycloalkyl, aryl, alkylaryl, arylalkyl, halogen, hydroxyl radical , the alkoxide radicals, - C (0) OR 'in which R represents a hydrocarbon radical which may comprise from 1 to 15 carbon atoms, - SO Y in which Y is chosen from Li, Na, K, NH ₄ ®, NR " ₄ ® in which R "represents a hydrocarbon radical which can comprise from 1 to 15 carbon atoms.

The structure represented by the formula is also cited as a catalyst in this document.

in which the radicals R ⁶ , R ⁷ , R ⁸ , R ⁹ , R 10 R 11 and R, 1- ¹ -3 ⁰ , which may be identical or different, can be chosen from the same list of radicals as R ¹ to R ⁵ above, E'— M'— X ^* and E "—M" —x "being two sequences of type E — M — X and may be identical or different, R being a bivalent hydrocarbon radical. The invention has aim of proposing a new catalyst for the polymerization of olefins, having an improved activity and productivity, even in the presence of a polar medium, the polar mediums generally considerably reducing the activity of the catalysts.

The invention also proposes to provide a catalyst which can be prepared in situ.

This catalyst has the following formula:

in which :

E is an oxygen or sulfur atom;

X is a phosphorus, arsenic or antimony atom;

M is a nickel, palladium or platinum atom having an unallocated valence; a is 1 or 2;

Ri, R ₂ , R ₃ , identical or different, may be chosen from hydrogen, alkyl radicals cycloalkyls, aryls, alkylaryls, arylalkyls, each generally having from 1 to 20 carbon atoms, the hydroxyl radical, the alkoxide radicals (with from 1 to 20 carbon atoms), —C (0) OR ′ in which R represents a hydrocarbon radical which can comprise from 1 to 15 carbon atoms, -S0 ₃ Y in which Y is chosen from Li, Na, K, NH ^ ®, NR " ₄ ® in which R" represents a hydrocarbon radical which can comprise from 1 to 15 carbon atoms; and

Z represents a hydrocarbon radical comprising from 2 to 3 carbon atoms;

R represents a hydrocarbon radical of valence a; provided that at least one of the radicals Z and R carry at least one electron-withdrawing substituent.

Such a catalyst therefore makes it possible to obtain a polyolefin such as polyethylene or a copolymer of ethylene, of high molecular weight, with very high activity even in the presence of a polar medium.

The subject of the invention is also a process for preparing the catalyst according to the invention, comprising the following reaction, in which L is a ligand:

where E, X, M, Rf and Ri, R ₂ , R ₃ , and R ₄ , have the meanings given above.

Another object of the present invention is a process for the polymerization of at least one olefin, including nant contacting said olefin (s) with a catalyst according to the invention.

DETAILED DESCRIPTION OF THE INVENTION Catalyst according to the invention

The catalyst according to the invention corresponds to the following formula:

in which :

E is an oxygen or sulfur atom;

X is a phosphorus, arsenic or antimony atom;

Ri, R ₂ , R ₃ , identical or different, may be chosen from hydrogen, alkyl, cycloalkyl, aryl, alkylaryl or arylalkyl radicals, each generally having from 1 to 20 carbon atoms, the hydroxyl radical, the alkoxide radicals ( with 1 to 20 carbon atoms), —C (0) 0R 'in which R' represents a hydrocarbon radical which may comprise from 1 to 15 carbon atoms, -S0 ₃ Y in which Y is chosen from Li, Na, K , NH ₄ ®, NR " ₄ ® in which R" represents a hydrocarbon radical which can comprise from 1 to 15 carbon atoms; and

Z represents a hydrocarbon radical comprising from 2 to 3 carbon atoms;

Advantageously Z has 2 carbon atoms and R is chosen from alkyl, cycloalkyl, aryl, alkylaryl or arylalkyl radicals, each generally having from 1 to 20 carbon atoms, preferably from 1 to 10 carbon atoms,

Z is preferably unsaturated. Preferably, the catalyst corresponds to the following formula:

in which :

E, X, M, a, Ri, R ₂ and R ₃ have the same definitions as above;

Rf represents a hydrocarbon radical of valence a and carrying said electron-attracting substituent (s); and

R ₄ , just like R _x , R ₂ and R ₃ , can be chosen from hydrogen, alkyl, cycloalkyl, aryl, alkylaryl, arylalkyl radicals, each generally having from 1 to 20 carbon atoms, the hydroxyl radical, the alkoxide radicals (with from 1 to 20 carbon atoms), —C (0) 0R 'in which R represents a hydrocarbon radical which may comprise from 1 to 15 carbon atoms, -S0 ₃ Y in which Y is chosen from Li, Na , K, NH ₄ ®

NR " ₄ ® in which R" represents a radical hydrocarbon which can comprise from 1 to 15 carbon atoms.

The Applicant has surprisingly found that the substituent Rf allows the catalyst according to the invention to be significantly more active than the catalytic systems of the prior art.

The hydrocarbon radical Rf may be a radical chosen from alkyl, cycloalkyl, aryl, alkylaryl or arylalkyl radicals, generally having from 1 to 20 carbon atoms, preferably from 1 to 10 carbon atoms.

The electro-attractant substituent carried by Rf can be chosen from halogens and groups -CN, N0 ₂ , NH ³⁺ , C≡Cr, CH = CR ''' ₂ , COR''', S0 ₂ R "', NR ''' ₃ ⁺ , SR''' ₂ ⁺ , S0 ₂ Ar, R '''representing an alkyl group having from 1 to 20, and preferably from 1 to 7 carbon atoms and Ar representing an aryl group, from preferably a phenyl group, preferably the electron-withdrawing substituent is chosen from the group consisting of fluorine, chlorine, bromine, iodine and the nitro group.

Even more preferably, the electron-withdrawing substituent is a fluorine atom. Advantageously, the radical Rf is perfluorinated.

The radicals R ₁₇ R ₂ , R ₃ , R ₄ , which may be identical or different, may be chosen from hydrogen, the alkyl, cycloalkyl, aryl, alkylaryl or arylalkyl radicals, each generally having from 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, halogens, hydroxyl radical, alkoxide radicals (with from 1 to 20, preferably 1 to 10 carbon atoms), —C (0) 0R 'in which R represents a hydrocarbon radical which may include from 1 to 15, preferably 1 to 6 carbon atoms, - S0 ₃ Y in which Y is chosen from Li, Na, K, NH ₄ ®, NR " ₄ ® in which R" represents a hydrocarbon radical which may comprise from 1 15 carbon atoms, preferably 1 to 7 carbon atoms. Advantageously, the radicals Ri, R ₂ , R ₃ are chosen from aryl groups, in particular phenyl. Advantageously, the radical R ₄ , is a group —C (O) OR ′ in which R represents a hydrocarbon radical which may comprise from 1 to 6 carbon atoms.

According to one embodiment of the invention at least one of the radicals R _x , R ₂ , R ₃ , R ₄ , may optionally be a radical such as the radical Rf defined above.

Preferably, M is a nickel atom.

Preferably E is an oxygen atom.

Preferably X is a phosphorus atom.

The catalysts can be in the form of bimetallic complexes. Mention may be made in particular of those in which a is 2 and R ₄ is the group - COOR, R being an alkyl having from 1 to 7 carbon atoms. Such catalysts have the formula:

The catalysts which have proved to be the most interesting are those for which a is equal to 1, the groups Ri, R ₂ and R ₃ are a phenyl group, R ₄ is the group -COOR ', with R' which is an alkyl having

1 to 7 carbon atoms or an aryl radical; X is a phosphorus atom, E is an oxygen atom, and Rf is a fluorinated alkyl or aryl radical.

Advantageously: R 'is an ethyl, tert-butyl or benzyl group, Rf is then a pentafluorophenyl; or

R 'is an ethyl group and Rf is a trifluoromethyl group; or

R 'is an ethyl group and Rf is a heptafluoropropyl group.

Preparation of the catalyst according to the invention

The catalyst according to the invention can be prepared according to a process comprising a step in which a compound corresponding to the following formula (component A) is reacted with a metal derivative M as defined above (in state 0 ), represented M (0), (component B), so as to obtain the catalyst. When the metal M is nickel, it is then possible to use NiCOD (in fact Ni (COD) ₂ ) as the derivative of the metal M, the term COD representing cis, cis-1, 5-cyclooctadiene. The diagram is then as follows:

L is a ligand generally chosen from phosphines of formula PR ¹⁴ R ¹⁵ R ¹⁶ in which R ¹⁴ , R ¹⁵ , R ¹⁶ , which may be identical or different, may represent alkyl, aryl, alkylaryl, arylalkyl radicals, or from oxides phosphine, ethers, esters, nitriles, ketones, amines, pyridine, substituted pyridines, alcohols.

According to a variant, the ligand L is an olefin.

It is possible to prepare the catalyst according to the invention in two main ways.

The first route involves separation of the catalytic species before the polymerization is carried out. This approach is described in document US Pat. No. 4,716,205. The catalytic species can be isolated either complexed with a Lewis base (ligand L = phosphine of formula PR ¹⁴ R ¹⁵ R ¹⁶ as defined above or pyridine) or under form of dimer.

If the ligand is strongly coordinated on the metal (PPh3), it is desirable to polymerize to use a "phosphine sponge" in order to avoid any possible competition between the ligand and the monomer. If the ligand is more weakly coordinated (pyridine or dimer), this "phosphine sponge" is not preferred. This term "phosphine sponge" covers the corresponding "scavengers" in the English language.

The second way uses the in si tu catalyst preparation.

The catalytic species is formed "in situ" by introducing the ylide, the Ni (O) complex, into the reactor in the presence of an olefin.

Polymerization process according to the invention

The catalyst according to the invention is intended to be used for the polymerization of at least one olefin.

Preferably, the olefin (s) is (are) non-cyclic (s). In particular, ethylene or propylene is polymerized.

The polymerization medium can comprise a liquid aqueous phase.

The catalyst according to the invention can advantageously be used in a medium comprising more than 30% in water.

According to a first variant, ^'prepares the catalyst then one proceeds to a (co) polymerization takes place at a temperature between 0 and 300 ° C, prefer- ence between 25 and 250 ° C and at a total absolute pressure ranging from 1 to 200 bars, preferably from 1 to 100 bars. Variants of this embodiment (solvent, temperature, additives, etc.) are given in the description following, given with regard to the second preferred embodiment of the invention.

According to this second embodiment, the method comprises: - in a first step, each of the constituents (A) and (B) being in solution in an inert solvent, as well as the medium, are introduced into a reactor, separately or simultaneously reaction; and - in a second step, the olefin (s) are introduced, the (co) olymerization taking place at a temperature between 0 and 300 ° C, preferably between 25 and 250 ° C, and at an absolute total pressure ranging from 1 at 200 bars, preferably from 1 to 100 bars.

The inert solvent in which the components (A) and (B) are found for the first step is a solvent compatible with the operations to be carried out. Examples of such solvents that may be mentioned are all those compatible with the polymerization of olefins by organometallic catalysis, in particular saturated aliphatic, saturated alicyclic, aromatic hydrocarbons, such as isobutane, butane, pentane, hexane, heptane, isododecane, cyclohexane, cycloheptane, methylcyclohexane, methylcycloheptane, benzene, toluene, orthoxylene, paraxylene and any mixture of the above compounds.

The inert solvents of each of components (A) and (B) may be the same or different. The reaction medium of the process according to the invention may consist of an organic medium, or else it may comprise a continuous liquid aqueous phase, which comprises more than 30% by weight of water. In the latter case, the aqueous phase may be the only liquid phase of the reaction medium (except the solutions of constituents (A) and (B)). Also in this case, the medium can comprise a liquid organic phase. The concentration of component (A) in the inert solvent is preferably between 0.1 micromole and 100 millimoles per liter of solution; and the concentration of component (B) in the inert solvent is preferably between 0.1 micromole and 200 millimoles per liter of solution.

The process according to the invention is generally carried out under an inert atmosphere.

In a preliminary step, the constituents (A) and (B) can be brought into contact in solution in their inert solvent, for a period of less than 15 minutes, before their introduction into the reaction medium, this precontact step also being carried out under inert atmosphere, at a temperature between 0 and 100 ° C, in particular between 10 and 70 ° C.

The constituents (A) and (B) which are in solution in their inert solvent, can also be introduced separately without preferential order into the reaction medium, the latter being maintained at a temperature of 0 to 100 ° C., particular from 10 to 70 ° C.

The polymerization medium (organic medium) or the organic phase of a polymerization medium comprising a liquid aqueous phase can be chosen from: saturated aliphatic hydrocarbons, saturated alicyclic hydrocarbons, aromatic hydrocarbons and their mixtures, in particular from isobutane, butane, pentane, hexane, heptane, isododecane, cyclohexane, cycloheptane, methylcyclohexane, methylcycloheptane, benzene, toluene, 1 'orthoxylene, paraxylene and any mixture of these compounds; and insofar as the polymerization conditions keep them in liquid form, the α-olefins, such as propylene, butene, hexene or 4-methyl pentene-1, the non-conjugated dienes, such as 1, 9-decadiene, 1, 5-hexadiene, 1,13-tetradecadiene, biscyclo (, 2, 1) -hepta-2, 5-diene, and mixtures thereof. In the case where the polymerization medium comprises an aqueous phase, during the polymerization, the polymerization medium comprises said liquid aqueous phase, a solid phase constituted by the solid polymer resulting from the polymerization, and also comprises, depending on the state physical nature of the olefin to be polymerized, at least one other gas phase and / or another liquid phase. If an olefin to be polymerized is liquid under the conditions of temperature and pressure of the polymerization, this olefin may be part of a liquid organic phase distinct from the liquid aqueous phase. Such a liquid organic phase can also comprise an organic solvent, such as those indicated above, of said olefin. The constituents of the possible liquid organic phase are sufficiently insoluble in water that, taking into account its quantity involved, the aqueous phase contains more than 30% of water.

In the case where the polymerization medium comprises two distinct liquid phases, the latter may for example be present so that the phase different from the aqueous phase represents 1 to 50% of the volume of the aqueous phase.

The aqueous phase can comprise at least 40%, or even at least 50%, or even at least 60%, even at least 70%, or even at least 80% by weight of water.

The aqueous phase may comprise, in dissolved form, an organic compound which may be an alcohol or a ketone or a diol such as a glycol, for example ethylene glycol, or propane diol or butane diol. This organic compound may have the function of increasing the solubility of the olefin to be polymerized in the aqueous phase.

The polymerization medium is preferably stirred. The stirring is preferably sufficient to distribute the different phases uniformly in the reactor. At least one dispersing agent can be added to the polymerization medium. Such a dispersing agent can in particular be used when the polymerization medium comprises a liquid organic phase, in which case it helps the dispersion of said liquid organic phase in the form of droplets surrounded by the continuous aqueous phase. In this case, the constituents (A) and (B) having been mainly dissolved in the liquid organic phase, the polymerization takes place mainly in the droplets, the latter generally having an average diameter of between 100 μm and 3 millimeters.

The dispersing agent can be one of those known to have this function, such as for example a polyvinyl alcohol, methylcellulose, gelatin, kaolin, barium sulphate, hydroxyapatite, magnesium silicate, tricalcite phosphate , or a combination of several of these dispersing agents.

The dispersing agent can be introduced into the polymerization medium up to 10% by weight relative to the water used and preferably from 0.01% to 5% by weight relative to the weight of water used.

At least one emulsifying agent can be added to the polymerization medium. The use of such an emulsifying agent is particularly recommended when it is desired that the polymerization leads to a latex, that is to say to a set of polymer particles having a number average diameter less than 1 micrometer , said particles being dispersed in the aqueous phase. When an emulsifying agent is used, it is generally not necessary for the polymerization medium to contain a dispersing agent.

As the emulsifying agent, any of the known surface-active agents may be used, whether anionic, non-anionic or even cationic. In particular, the emulsifying agent can be chosen from anionics such as the sodium or potassium salts of fatty acids, in particular sodium laurate, sodium stearate, sodium palmitate, sodium oleate. sodium, mixed sodium or potassium sulfates and fatty alcohol, especially sodium laurysulfate, sodium or potassium salts of sulfosuccinic esters, sodium or potassium salts of alkylaryl sulfonic acids, especially dodecylbenzene sodium sulfonate, and the sodium or potassium salts of monosulfonates of fatty monoglycerides, or also among nonionic surfactants such as the reaction products between ethylene oxide and alkylphenols. It is of course possible to use mixtures of such surfactants.

The emulsifying agent can be introduced into the polymerization medium up to 10% by weight relative to the weight of water, and preferably from 0.01% to 5% by weight relative to the weight of water.

In such a process comprising an emulsifying agent and a liquid organic phase, the constituents (A) and

(B) having been mainly dissolved in said liquid organic phase, the emulsifying agent being in an amount greater than the critical micelle concentration, the polymerization takes place in the droplets of liquid organic phase, which generally have an average diameter of between 1 mm and 1000 mm, and in the micelles which generally have an average diameter between 1 nanometer and 100 nanometers. Such a process is similar to the so-called “radical emulsion polymerization” process except that it is not radical. When in such a process, the concentration of emulsifying agent is increased, the relative importance of the polymerization taking place in the micelles is increased and the formation of a latex at the end of polymerization is favored. In this case of the presence of a liquid organic phase, when the amount of emulsifying agent is such that all of the liquid organic phase is present in the micelles, the process is similar to the process known as “radical polymerization in microemulsion” except that the polymerization is not radical. In the case where the polymerization medium comprises a liquid organic phase and an emulsifying agent, it is possible to add a co-surfactant to the medium as is done for the polymerization processes in miniemulsion. Such a co-surfactant generally has a solubility in water of less than 1 × 10 ⁻³ mole per liter at 20 ° C. Such a co-surfactant can, for example, be hexadecane or alcohol It can be present up to 10% by weight relative to the weight of water and preferably the ratio of the mass of emulsifying agent to that of co-surfactant ranges from 0.5 to 2. The presence of this co-surfactant also makes it possible, thanks to sufficient shearing of the medium, to obtain droplets of liquid organic phase of less than 1 mm and promotes the formation of a latex at the end of polymerization. be obtained by ultrasound or by a homogenizer (such as an apparatus of the ultraturax or diax 600 type from the company Heidolph). Once the characteristic droplet size (<1 mm) has been obtained, the stirring can be continued with less vigorous shearing, of the type of shears used for the processes polymerization dice in suspension.

Preferably, the polymerization is carried out in mini-emulsion.

In the case where an organic solvent has been used, this can, if desired, be removed by evaporation.

The method according to the invention leads to polymer particles whose diameter can range from 10 nanometers to 5 millimeters.

For the case where the polymerization comprises an emulsifying agent, a latex is obtained. At the end of the polymerization carried out in the presence of an emulsifying agent, the latex optionally contains particles which tend to decant and it may be desired to carry out a separation, for example by filtration so as to remove these particles which do not part of the latex. The polymerization conditions, namely quantity of the ingredients in the polymerization medium and degree of conversion from monomer to polymer, can be adapted so that the latex has a solid content ranging from 0.1 to 50% by weight.

The olefin intended to be polymerized is introduced with sufficient stirring of the polymerization medium, for example stirring ranging from 10 to 10,000 revolutions per minute. The olefin can be introduced in liquid or gaseous form, depending on its physical state.

The polymerization temperatures and pressures have been indicated above.

For the case where only ethylene is polymerized, a high density homopolyethylene is obtained. The polymerization of ethylene with at least one olefin other than ethylene leads to the production of an ethylene polymer of lower density than the high density homopolyethylene mentioned above. Depending on the quantity and the nature of the ethylene comonomer (s), it is therefore possible to obtain a polymer of high density ethylene (high density polyethylene), or a polymer of medium density ethylene (polyethylene medium density) or, at a high comonomer level, a polymer of low density ethylene (low density polyethylene). As is customary for polymers of ethylene, the term "high density" means that the density is greater than 0.940, by medium density the fact that the density ranges from 0.925 to 0.940 and by low density does the density is less than 0.925. The polymerization can therefore lead to a latex of at least one olefin, that is to say to a polymer comprising polymerized units of at least one olefin, optionally with other units of polymerized monomer. In particular, if at least one olefin is ethylene, a latex of a polymer of ethylene can be obtained.

The process according to the invention can therefore lead to a latex of a high density ethylene polymer or to a latex of a polymer of ethylene medium density, even of a polymer of ethylene low density.

In the context of the present application, the term polymer must be taken in its general sense, so that it covers copolymer homopolymers, interpolymers and mixtures of polymers. The term polymerization should also be taken in an equivalent general sense.

The set of olefins includes that of the alpha-olefins. As olefins, mention may be made of ethylene, propylene, cyclopentene, 1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1, 4-hexadiene, 1.9 - decadiene, 1-octene, 1-decene, and cyclic olefins such as cyclohexene. The set of olefins also includes the compounds of formula CH ₂ = CH (CH ₂ ) _n G in which n represents an integer ranging from 2 to 20, and G represents a radical which can be chosen from the following list:

OH, CHOHCH ₂ OH, OT, CF ₃ , COOT, COOH, Si (OH) ₃ , Si (OT) ₃ , T representing a hydrocarbon radical containing from 1 to 20 carbon atoms. Particular mention is made of cases where at least one olefin is ethylene.

The process according to the invention can be carried out batchwise, semi-continuously or continuously.

Examples.

The following examples illustrate the present invention without, however, limiting its scope. In these examples, the synthesis scheme is as follows:

The following compounds are prepared

Examples 1 to 4: preparation of the compounds (ligands 1b to le)

Example 1

Synthesis of the ethyl ester of 6, 6, 6, 5, 5, 4, 4 - heptafluoropropyl - 3 - oxo - 2 - (triphenyl -phosphoranylidene) hexanoic acid.

A suspension of carbethoxymethyl triphenyl phosphonium bromide (3.4 g, 7.9 mmol) in 25 ml of anhydrous THF is cooled in an ice bath and treated with triethylamine (2.4 ml, 17.2 mmol) . After 15 minutes of stirring, the mixture is treated by adding dropwise heptafluoro chloride butyryl (1.28 ml, 8.6 mmol). The temperature is allowed to rise to room temperature and left to stand for another hour. The reaction mixture is then filtered and the precipitate is washed three times with cold THF, and the filtrate is dried under vacuum. The powder obtained is recrystallized from methanol. The yield is 63%.

1H NMR (ppm, in CDC1 ₃ ): C ₆ H ₅ 7.4-7.8, 15H, m; OCH ₂ , 3.78, 2H, q; CH ₃ , 0.9, 2H, t (3JH-H = 7 Hz). 13C (ppm, in CDC1 ₃ ) 13.6, 60.3, 72.6 (1JC-P = 115 Hz), 124 (1JC-P = 100 Hz), 129.9 (2JC-P = 13 Hz), 132.6 (4JC-P = 3 Hz), 133.4 (3JC-P = 10 Hz), 165.7 (2JC-P = 13.5 Hz), 175.2 (2JC-F = 27 Hz, 2JC-P = 6 Hz).

19F NMR (ppm, in CDC1 ₃ ) COCF ₂ -124.9, s; CF ₂ - 113.7, q (3JF-F = 1.5 Hz); CF ₃ -80.7, t (3JF-F = 1.5 Hz).

31 P NMR (ppm, in CDC1 ₃ ), 20, s.

IR (10% KBr granulated): 3062, 2981, 1709, 1682, 1579, 1571, 1486, 1437, 1330, 1251, 1234, 1200, 1157, 1105, 968, 935, 757, 692, 556, 516 cm ^"1 .

Elementary analysis: C calculated: 57.36%, found 57.61%; H calculated: 3.70%, found 3.87%.

EXAMPLE 2 Synthesis of the ethyl ester of pentafluorobenzyl-3 -oxo-2 - (triphenylphosphoranylidene) propanoic acid

The procedure is as in Example 1, with (ethoxycarbonylmethyl) triphenyl phosphonium bromide (0.8 g, 2.0 mmol), triethylamine (0.6 ml, 4.2 mmol) and pentafluorobenzoyl chloride ( 0.3 ml, 2.1 mmol).

The yield is 52%.

1 H NMR (ppm, in CDC1 ₃ ) C ₆ H ₅ 7.5-7.6 and 7.7-7.8,

15H, m; OCH ₂ , 3.65, 2H, q; CH ₃ , 0.58, 2H, t (3JH-H = 7 Hz). 13C (ppm, in CDC1 ₃ ) 13.5, 58.9, 74.2 (1JC-P = 110

Hz), 124.7 (1JC-P = 94 Hz), 128.8 (2JC-P = 13 Hz), 132.4 (4JC-P = 3 Hz), 133.5 (3JC-P = 10 Hz) , 166.7 (2JC-P = 13

Hz), 178.7 (2JC-P = 7 Hz). 19F NMR (ppm, in CDC1 ₃ ) C ₆ F ₅ -145.2, dd (3JF-F = 22 Hz, 4JF-F = 6.7 Hz), -157, 8, t (3JF-F = 22 Hz ), -163, 7, td (3JF-F = 22 Hz, 4JF-F = 6.7 Hz).

31 P NMR (ppm, in CDC1 ₃ ), 18.3, s. IR: 1661, 1562, 1517, 1496, 1437, 1369, 1341, 1293, 1244, 1103,

1087, 983, 940, 692, 542 cm ^"1. Elemental analysis: C calculated: 64.21%, found: 64.49%. H calculated 3.72%, found 3.84%.

Example 3

Synthesis of the tert-butyl ester of pentafluorobenzyl -3 - oxo -2 - (triphenylphosphoranyl i dene) propa - no ï

The procedure is as in Example 1, with (tert-butoxycarbonylmethyl) triphenylphosphonium bromide (1.65 g, 4.0 mmol), triethylamine (1.3 ml, 8.2 mmol) and pentafluorobenzoyl chloride (0 , 6 ml, 4 mmol). The yield is 62%.

1H NMR (ppm, in CDC1 ₃ ) C ₆ H _S 7.4-7.9, 15H, m; CH ₃ , 0.96, 9H, s., 13C (ppm, in CDC1 ₃ ) 13.5, 58.9, 74.2 (1JC-P = 110 Hz), 124.7 (1JC-P = 94 Hz ), 128.8 (2JC-P = 13 Hz), 132.4 (4JC-P = 3 Hz), 133.5 (3JC-P = 10 Hz), 166.7 (2JC-P = 13 Hz), 178.7 (2JC-P = 7 Hz), 19F NMR (ppm, in CDC1 ₃ ) C ₆ F ₅ -145.2, dd (3JF-F = 22 Hz, 4JF-F = 7.4 Hz), -158, 0, t (3JF-F = 22 Hz), -163, 8, td (3JF-F = 22 Hz, 4JF-F = 7.4 Hz).

31 P NMR (ppm, in CDC1 ₃ ), 18.1, s.

IR: 1666, 1552, 1516, 1495, 1437, 1359, 1303, 1247, 1167, 1108, 988, 941, 692, 543, 521 cm ^"1. Elemental analysis: C calculated: 65.27%, found 65.28 % H calculated 4.24%, found 4.31%.

Example 4

Synthesis of the benzyl ester of pentafluorobenzyl -3-oxo -2- (triphenylphosphoranyl idene) propanoic acid

The procedure is as in Example 1, with (benzyloxycarbonylmethyl) triphenylphosphonium bromide (0.98 g, 2.0 mmol), triethylamine (0.58 ml, 4.2 mmol) and pentafluorobenzoyl chloride (0.3 ml, 2.1 mmol). The yield is 32%.

1H NMR (ppm, in CDC1 ₃ ) C ₆ H _S , 20H, m; CH ₂ , 2H, s. 13C (ppm, in CDC1 ₃ ) 65.7, 74.4 (1JC-P = 112 Hz), 124.5

(1JC-P = 94 Hz), 128.0, 128.2, 128.5, 128.8 (2JC-P = 13

Hz), 132.4 (4JC-P = 3 Hz), 133.5 (3JC-P = 10 Hz),

135.6, 166.3 (2JC-P = 13 Hz), 178.7 (2JC-P = 7 Hz), NMR

19F (ppm, in CDCl ₃ ) C ₆ F ₅ -145.7, dd (3JF-F = 23 Hz, 4JF-F = 7 Hz), -157, 4, t (3JF-F = 23 Hz), - 163, 8, td (3JF-F = 23 Hz, 4JF-F = 7 Hz).

31 P NMR (ppm, in CDC1 ₃ ), 18.6, s.

IR: 1648, 1554, 1519, 1487, 1440, 1341, 1288, 1274, 1066, 986, 754, 690, 545, 510.501cm ^"1. Elemental analysis: C calculated: 67.55%, found 67.32 % H calculated 3.67%, found 3.95% Example 5 a) Preparation of the polymerization catalyst la In a Schlenk tube, 23.5 mg of Ni (COD) ₂ are dissolved in 8.5 ml of toluene 4 ml of the solution obtained are added to 8.9 mg of ethyl ester of trifluoromethyl-3-oxo-2- (triphenylphosphoranylidene) hexanoic acid (la). The solution is stirred for 15 minutes and added 0.6 ml of this solution to 400 ml of toluene in a glass reactor.

b) Polymerization

The solution obtained above is introduced into a 1 liter stainless steel reactor equipped with a mechanical magnetic induction stirrer, a thermocouple, a sampling orifice and a double jacket and heated to 70 ° C.

Ethylene is immediately introduced at a pressure of 3 bars. The introduction of ethylene is continued without interruption under a pressure of 3 bars from a 1 liter tank under high pressure.

The pressure drop in the tank is recorded, so as to assess activity and measure productivity. The reaction medium (approximately 400 ml) is added to approximately 600 ml of methanol and approximately 70 g of polymer are then recovered by filtration. Another polymerization test was carried out with a larger amount of catalyst la. The characteristics of the polymerization are given in Table 1.

Example 6

As described in Example 5, in a), polymerization catalysts 1b to 1c are prepared from the ligands of Examples 1 to 4, respectively.

In addition, lf and lg polymerization catalysts are prepared in the same way according to the aforementioned French patent application No. 2 784 110, from ethyl ester of methyl-3-oxo-2- acid. (triphenylphosphoranylidene) hexanoic acid and ethyl ester of benzyl-3-oxo-2- (triphenylphosphoranylidene) propanoic acid, respectively. These two acids have been found commercially.

Polymerizations no. 1 to 13 are then carried out, following the procedure described in example 5, in b). The characteristics of these polymerizations 1 to 13 are given in Table 1 below.

Unless otherwise indicated in Table 1, the polymerizations were carried out with the catalyst in 400 ml of toluene under 3 bars of ethylene and at 70 ° C.

b: the reactions were carried out in 400 ml of heptane c: values determined by gel permeation chromatography by comparison with polyethylene standards d: the solvent was a toluene / water mixture 300 ml / 100 ml e: if acts of a polymerization of propylene and not of ethylene

Example 7: Emulsion and Mini-Emulsion Polymers a) Preparation of the polymerization catalyst 2a In a Schlenk tube, 33 mg of Ni (COD) ₂ are dissolved in 10 ml of toluene. To the solution is added 13.3 mg of ethyl ester of trifluoromethyl-3-oxo-2- (triphenyl-phosphoranylidene) hexanoic acid. The solution is stirred for 15 minutes. b) Polymerization

The solution obtained above is added to 300 ml of water containing 5 g / l of sodium lauryl sulfate (surfactant) in a Teflon flask. To carry out a mini-emulsion polymerization, hexadecane (10 g / per liter of water) is added to the biphasic mixture obtained and the mixture is emulsified using an ultrasonic device such as a Branson 600 W for 2 minutes, with magnetic stirring and under argon. Alternatively, homogenization can be performed for 10 minutes using a device called Ultraturrax.

Then, the reaction medium (fine dispersion in the case of a mini-emulsion and biphasic mixture in the case of an emulsion) is introduced into a 1 liter stainless steel reactor, equipped with a mechanical (magnetic) stirrer, a thermocouple, a sampling port, and a double jacket heated to 70 ° C. Ethylene is immediately introduced at a pressure of 20 bars. The introduction of ethylene is continued without interruption at a pressure of 20 bars from a 5.5 liter tank under high pressure. The pressure drop in the tank is recorded, in order to assess the activity and measure the productivity. The reaction medium (300 ml) is recovered after having removed the remaining ethylene slowly enough to avoid the flocculation of a latex by creamy sedimentation. The latex is filtered to determine the floc content and the liquid residue is analyzed by dynamic light scattering (DLS) and gravimetry. ^" . - - Example 8

As described in Example 7, in a), polymerization catalysts 2b to 2e are prepared from the ligands of Examples 1 to 4, respectively.

In addition, polymerization catalysts 2f and 2g are prepared in the same way according to the state of the art, from ethyl ester of methyl 3-oxo-2- (triphenylphosphoranylidene) hexanoic acid and benzyl-3-oxo-2- (triphenylphosphoranylidene) propanoic acid ethyl ester, respectively.

The polymerizations are then carried out by following the procedure described in Example 7, in b), the polymerizations 14 to 19 being carried out in emulsion and the polymerizations 20 to 36 in mini-emulsion.

The characteristics of these polymerizations 14 to 26 are given in Table 2 below.

b: benzene is used in place of toluene c: values determined by dynamic light scattering (DLS) after dilution d: solid content determined by gravimetry of the latex after filtration e: the catalyst used is 2b f: emulsification made with an Ultraturax, at low speed g: not measurable (less than 3% of polymer) h: productivity in the aqueous phase without taking the floc into account

Example 9

In this example, the productivities of prior art catalysts with those of the catalysts according to the invention la to le and 2a to 2e are presented for comparison. The data is shown in the following table

(1): Catal is the catalyst n ° 2a of the article entitled "Coordination polymerization of ethylène in water by Pd (II) and Ni (II) catalysts" by A. HELD, F. M. BAUERS and S. MECKING, Chem. Comm. , 2000, 301-302;

Cata2 is the catalyst n ° 6 of the article entitled "Ethylene Homopolymerization with P, 0-Chelated Nickel Catalysts" by U. KLABUNDE, et al., Journal of Polymer Science, Part A: Polymer Chemistry, Vol. 25, 1989-2003 (1987);

Cata3 is the catalyst No. 8 of the article entitled “Ethylene Homopolymerization with P, 0-Chelated Nickel Catalysts” by U. KLABUNDE, et al., Journal of Polymer Science, Part A: Polymer Chemistry, Vol. 25, 1989-2003 (1987); Cata4 is the catalyst n ° 2 of Table 1 ("Table 1") of the aforementioned US patent 4,529,554.

It can therefore be seen that the productivity of the catalysts according to the invention is at least twice as high as that of the catalysts of the prior art.

Claims

1. Catalyst for the polymerization of olefins, corresponding to the following formula:

in which :

E is an oxygen or sulfur atom;

X is a phosphorus, arsenic or antimony atom;

M is a nickel, palladium or platinum atom having an unallocated valence; a is 1 or 2; Ri, R ₂ , R ₃ , identical or different, may be chosen from hydrogen, alkyl, cycloalkyl, aryl, alkylaryl or arylalkyl radicals, each generally having from 1 to 20 carbon atoms, the hydroxyl radical, the alkoxide radicals ( with 1 to 20 carbon atoms), —C (0) OR 'in which R' represents a hydrocarbon radical which may comprise from 1 to 15 carbon atoms, —S0 ₃ Y in which Y is chosen from Li, Na, K , NH ₄ ®, NR " ₄ ® in which R" represents a hydrocarbon radical which can comprise from 1 to 15 carbon atoms; and

Z represents a hydrocarbon radical comprising from 2 to 3 carbon atoms;

2. Catalyst for the polymerization of olefins according to claim 1, corresponding to the following formula:

in which :

E, X, M, a, Ri, R ₂ and R ₃ have the same definitions as in claim 1;

R ₄ may be chosen from hydrogen, alkyl, cycloalkyl, aryl, alkylaryl or arylalkyl radicals, each generally having from 1 to 20 carbon atoms, the hydroxyl radical, the alkoxide radicals (with from 1 to 20 carbon atoms) , —C (0) OR 'in which R represents a hydrocarbon radical which can comprise from 1 to 15 carbon atoms, —S0 ₃ Y in which Y is chosen from Li, Na, K, NH ₄ ®, NR " ₄ ® in which R "represents a hydrocarbon radical which can comprise from 1 to _ 15 carbon atoms.

3. Catalyst according to claim 1 or claim 2, characterized in that the electro-attractant substituent is chosen from halogens and groups -CN, N0 ₂ , NH ³⁺ , C≡Cr, CH = CR ''' ₂ , COR

S0 ₂ R "', NR'" ₃ , SR '" ₂ , S0 ₂ Ar, R"' representing a alkyl group having from 1 to 20, and preferably from 1 to 7 carbon atoms and Ar representing an aryl group, preferably a phenyl group.

4. Catalyst according to claim 3, characterized in that the electron-attracting substituent is chosen from the group consisting of fluorine, chlorine, bromine, iodine and the nitro group.

5. Catalyst according to claim 4, characterized in that the electron-withdrawing substituent .is a fluorine atom.

6. Catalyst according to one of claims 2 to 5, characterized in that Rf is an alkyl or aryl radical, having from 1 to 20 carbon atoms.

7. Catalyst according to one of the preceding claims, characterized in that M is a nickel atom.

8. Catalyst according to one of the preceding claims, characterized in that E is an oxygen atom.

9. Catalyst according to one of the preceding claims, characterized in that X is a phosphorus atom.

10. Catalyst according to one of the preceding claims, characterized in that the radicals Ri, R ₂ , R ₃ , are chosen from aryl groups, in particular phenyl.

11. Catalyst according to one of the preceding claims, characterized in that the radical R ₄ is a group —C (0) 0R 'in which R represents a radical hydrocarbon which can comprise from 1 to 7 carbon atoms.

12. Catalyst according to claim 11, characterized in that R 'is an ethyl, ter-butyl or benzyl group, Rf is then a pentafluorophenyl; or R 'is an ethyl group and Rf is a trifluoromethyl group; or R 'is an ethyl group and Rf is a heptafluoropropyl group.

13. Catalyst according to one of the preceding claims, characterized in that it is in the form of a bimetallic complex.

14. A method of polymerizing at least one olefin comprising bringing said olefin (s) into contact with a catalyst according to one of the preceding claims.

15. The method of claim 14, wherein the olefin is non-cyclic.

16. The method of claim 15, wherein the olefin is ethylene or propylene.

17. Method according to one of claims 14 to 16, wherein the polymerization medium comprises a liquid aqueous phase.

18. Method according to claim 17, characterized in that the medium comprises more than 30% in water.

19. Method according to one of claims 14 to 18, characterized in that: - in a first step, are introduced into a reactor, separately or simultaneously, each of the constituents (A) and (B) being in solution in a inert solvent, as well as the reaction medium, component (A) corresponding to formula II below, while component (B) is a metal derivative M (0);

where E, X, M, Rf and Ri, R ₂ , R ₃ , and R ₄ , have the meanings according to one of claims 1 to 13; in a second step, the olefin (s) are introduced, the (co) polymerization taking place at a temperature between 0 and 300 ° C, preferably between 25 and 250 ° C, and at an absolute total pressure ranging from 1 to 200 bars, preferably from 1 to 100 bars.

20. Process for the preparation of a catalyst according to one of claims 1 to 13, characterized in that it comprises the following reaction, where L is a ligand:

where E, X, M, Rf and Ri, R ₂ , R ₃ , and R ₄ , have the meanings according to one of claims 1 to 13.

21.- Method according to claim 20, characterized in that L is an olefin.