FI93967C - Method for copolymerizing ethylene and 1-alkene - Google Patents

Description

93967

Process for the copolymerization of ethylene and 1-alkene - For the copolymerization of ethylene and 1-alkene

The invention relates to a process for the copolymerization of ethylene and 1-alkene by the catalytic action of an ir-cyclopentadienyl transition metal compound and an alumoxane compound.

For the polymerization of ethylene, a Ziegler-Natta catalyst system consisting of the so-called procatalyst and cocatalyst. The procatalyst is based on a transition metal compound belonging to Groups IVA - Vili (Hubbard) of the Periodic Table of the Elements and the cocatalyst is based on a metal compound belonging to Groups 1 (A) to III (A) (Hubbard) of the Periodic Table of the Elements. A separate group of procatalysts are metallocene-type transition metal compounds, i.e., compounds in which one or more unsaturated rings, such as a cyclopentadienyl ring, are attached to the transition metal by a 7r bond.

U.S. Patent No. 3,242,099 discloses a catalyst system for the polymerization of olefins in which bis-cyclopentadienyl titanium dichloride is combined with an oligomeric alumoxane compound.

U.S. Patent No. 4,404,344 discloses a process for preparing homopolymers and copolymers of ethylene and propylene by polymerizing one or more monomers with a catalyst system formed by bis-cyclopentadienyl zirconium dimethyl and lower alkyl alumoxane. The publication mentions that ethylene can be copolymerized with propylene, 1-butene, 1-hexene or o, ω-dienes.

EP-69951 and US-4,542,199 disclose the polymerization of C 1 -C 10 olefins in the presence of a catalyst system consisting of bis-cyclopentadienylzirconium dichloride or 93967 2 bis-cyclopentadienylzirconium monomethyl monocyclyl monohydride The publication also mentions that the catalyst system is well suited for controlling the density of polyethylene by copolymerizing up to 10% by weight of longer chain α-olefins such as propylene, 1-butene and 1-hexene in the polyethylene chain. No correlation between the alkyl chain length of the or-olefins and the activity and monomer selectivity of the catalyst system has been shown.

EP-260 999 discloses a process for the homo- or copolymerization of ethylene with a cyclopentadienyl transition metal compound and an alumoxane compound. The transition metal may be a Group IVB or VB transition metal, the cyclopentadienyl ring may be either unsubstituted or substituted, and in addition, one or more organic groups and one or more halogen atoms may be attached to the transition metal compound. The alumoxane may be a linear or cyclic lower alkyl substituted alumoxane oligomer. According to the publication, olefin copolymers and in particular copolymers of ethylene and C3-C8-α-olefins can also be prepared with the catalyst system. The comonomer content of the polymer is also adjustable by selecting the appropriate type of cyclopentadienyl transition metal compound. There is no mention of any correlation between the alkyl chain length of the α-olefin and the activity or monomer selectivity of the catalyst.

In JP publications 09,092,621, 1,045,406, 1,101,315, 1,198,608, 2,084,405 and 2,218,706, ethylene is copolymerized with C3-C10-α-olefins using bis-cyclopentadienylzirconium dichloride and alumoxane as the polymerization catalyst. . The first five use either an inorganic oxide or a granular polymer as a support for the catalyst system. In the latter publication, the cocatalyst is a mixture of alumoxane and trialkylaluminum. The publications do not show a correlation between the alkyl chain length of the α-olefin comonomer and the activity or monomer selectivity of the 93967 3 catalyst system.

It is an object of the invention to provide a process for the copolymerization of ethylene and 1-alkene by the catalytic action of a 7R-cyclopentadienyl transition metal compound and an alumoxane compound in which said catalyst system has the highest possible activity. The invention also seeks to provide a process for the copolymerization of ethylene and 1-alkene in which the catalyst system used has the highest possible selectivity, especially when long alkyl-chain and monomer units are desired in the copolymer. The invention further relates to a copolymerization system of ethylene and 1-alkene in which, when said catalyst system is used, the polymerization can be carried out at a relatively low temperature and pressure and preferably in the presence of an alkane solvent. The invention also seeks to provide terpolymers of ethylene in which the thermonorers are ethylene, a C3-C10-α-olefin and an ethylenically unsaturated monomer having at least 8 carbon atoms in its side chain.

The above objects have now been achieved by a new process for the homo- or copolymerization of ethylene by means of a 7r-cyclopentadienyl transition metal compound and an alumoxane compound / catalytic action, which is mainly characterized by what is stated in the characterizing part of claim 1. Thus, it is understood that the copolymerization of ethylene and 1-alkene can be improved by using said catalyst system if the polymerization is allowed to involve a compound of formula (I) CH 2 = CHR (I) wherein R represents a hydrocarbon group having at least 8 to 20 carbon atoms. Thus, said long-chain ethylenically unsaturated compound improves the activity of the catalyst system formed by the π-cyclopentadienyl transition metal compound and the alumoxane compound 93967 4 and increases its monomer selectivity when ethylene is copolymerized (di- or terpolymerized) with a formula. Compared to the lower molecular weight ethylenically unsaturated compounds, this compound gives clearly better activity values and selectivity values for the catalyst system.

It is preferred that in the group R of the compound of formula (I) there are 10 to 20 and most preferably 14 to 20 carbon atoms. It is further preferred that the compound of formula (I) is 1-alkene. Useful alkenes include decene, undecene, dodecene, tridecene, tetradecene, pentadecene, hexadecene, heptadecene, octadecene, nonadecene and non-cosene. Their branched isomers may also be considered.

According to an important embodiment of the invention, the compound of formula (I) is used in higher amounts in the polymerization mixture to obtain an ethylene copolymer having a higher proportion of monomer units corresponding to the compound of formula (I). By the word greater is meant that the catalyst system used in the invention favors the incorporation of the comonomer of formula (I) into the resulting ethylene copolymer chains in copolymerization than conventional catalyst systems based on a TiCl 4 / MgCl 2 procatalyst and a trialkylaluminum cocatalyst.

Such selectivity based on the length of the monomer chain of the catalyst system is used eo. in the invention • e.g. by adding a compound of formula (I) to a solution or bulk polymerization mixture of 0.10 to 1.00, preferably 0.20 to 1.00 and most preferably about 0.40 to 1.00 mol / l to provide an ethylene copolymer which the proportion of monomer units corresponding to the compound of formula (I) is respectively more than 6, preferably more than 13 and most preferably more than. about 30% by weight.

5,95967

As already mentioned, one advantage of the compound of formula (I) is its activating effect on the catalyst system formed by the ir-cyclopentadienyl transition metal compound and the alumoxane compound. If it is only desired to activate the catalyst, it is advisable to use small amounts of the compound of formula (I) to enhance the copolymerization of ethylene. In one embodiment, the solution or bulk polymerization of ethylene uses about 0.01 to 0.10 mol / L of a compound of formula (I). In a system with a polymerization temperature of 70 ° C, an ethylene pressure of 3.8 bar, a reaction time of 10 min and an Al / Zr 1000 ratio, a doubling of the activity of 0.05 mol / l and a tripling of the activity of more than 0.10 mol / l are obtained. -hexadecene also achieves considerable catalyst activation. With both 1-decene and 1-hexadecene, the catalyst system is activated more than with 1-butene. Thus, there is clear experimental evidence that a compound of formula (I) in which R has at least 10 carbon atoms achieves surprising activity with respect to smaller 1-alkenes.

The polymerization parameters of the process according to the invention can in principle be of any kind, as long as the copolymer produces an ethylene copolymer and the compound of the formula (I) participates in one way or another in the polymerization. For example, the polymerization temperature may be about -50 to + 200 ° C. and preferably about +50 to + 100 ° C. The polymerization time may be about 5-40 minutes and preferably about 10-20 minutes.

It is preferred if the polymerization is carried out in a solvent or as a bulk polymerization. The preferred solvent is my liquid time, the most preferred is my C6-C12 time.

The molar ratio of metals of the alumoxane compound to the 7r-cyclopentadienyl transition metal compound can vary widely. In general, the rule is that aluminum is used considerably more than the transition metal compound. According to one embodiment 6,93967, said molar ratio of metals is between 100,000: 1 and 10: 1, preferably between 2000: 1 and 200: 1.

By 7r-cyclopentadienyl transition metal compound is meant a catalytically active transition metal compound having at least one π-bonded cyclopentadienyl ligand in the transition metal. Such a ligand is very stable and can be considered to form the six-electron aromatic anion C5Hg. Due to its aromatic stability, it can also be substituted. These compounds are also called metallocenes.

According to one embodiment, the 7r-cyclopentadienyl transition metal compound has the following general formula (II)

CPmMR ^ o HD

wherein Cp is π-cyclopentadienyl or substituted ir-cyclopentadienyl, R1 is an organic group, Y is halogen and m is an integer from 1 to 3, n is an integer from 0 to 3 and o is an integer from 0 to 3.

It is preferred that Cp is 7r-cyclopentadienyl, i.e. unsubstituted. When R 1 is used, the group is preferably lower alkyl and most preferably methyl. Accordingly, Y is preferably chlorine. M is preferably zirconium Zr or titanium Ti, preferably zirconium Zr. It is also preferred that m is 2, n is 0 or 1 and o is 1 or 2. Preferred 7r-cyclopentadienyl transition metal compounds are bis-7r-cyclopentadienyl-zirconium monomethyl monochloride and bis-7r-cyclopentadienyl-zirconium dichloride and the most preferred br-7r-cyclopentadienyl -cyclopenta-dienyylizirkoniumdikloridi.

Although the above is the most advantageous we consider. 35 7r-cyclopentadienyl transition metal compounds, other similar compounds can also be used. Such compounds are listed e.g. From page 3, line 59 to page 4, line 31 of EP application 303 519 and lines 14-30 of page 93 of page 7 of EP 93 999. Both applications are hereby incorporated by reference into eo. application.

Another catalyst component of the polymerization process of the invention is an alumoxane compound. It preferably has the following general formula (III) (Al (R 2) O) p (IIIa) 10 or R 2 (Al (R 2) 0) pAIR 2 (IHb) wherein R 2 represents an organic group and p is an integer from 1 to 50. Formula (purple) is valid when the alumoxane compound has an annular structure and formula (IIIb) is valid when the structure of the alumoxane compound is linear.

The group R 2 of the alumoxane compound of the formula (III) is preferably an alkyl group having 1 to 5 carbon atoms, and most preferably methyl. The formula p is preferably such that the alumoxane is at least an oligomer and is most preferably a size i of 4-20.

The alumoxane used in the invention can be prepared in a number of ways, for example, by contacting water with trialkylaluminum or by contacting trialkylaluminum with a hydrated salt such as hydrated copper sulfate or ferrous sulfate. When aiming to prepare oligomers of at least 30 alumoxanes, the alumoxane is preferably prepared with hydrated ferrous sulfate or hydrated copper sulfate. In this case, a dilute solution of trialkylaluminum in toluene, benzene or xylene is treated with FeSO 4 * 7H 2 O or CuSO 4 5H 2 O. The molar ratio of hydrated sulfate to trialkylaluminum is generally 1: 5 to 1:10 and the reaction temperature is between -40 and + 60 ° C, releasing methane gas in the reaction. The result is generally both linear and annular alumoxane having a degree of oligomerization of about 6 or more upon successful reaction.

The catalyst system used in the process of the invention may be homogeneous or heterogeneous. In a heterogeneous system, a carrier can be used for both the π-cyclopentadienyl transition metal compound and the alumoxane compound, or a π-cyclopentadienyl transition metal compound and an alumoxane-treated, e.g. impregnated, carrier can be added to the polymerization mixture. Suitable carriers include silica, alumina, magnesium oxide, zirconia, magnesium silicate, alkylated silicates, and some polymers such as granular polyethylene.

However, it is preferred if eo. the invention uses a homogeneous catalyst system of a π-cyclopentadienyl transition metal compound and an alumoxane compound, wherein the polymerization and catalysis are preferably carried out in a hydrocarbon solvent.

Although the catalyst system used in the process of the invention is based on a π-cyclopentadienyl transition metal compound and an alumoxane compound, it may also contain other catalyst components and catalytic auxiliaries. These include other transition metal compounds and aluminum compounds, as well as potential electron donors. In one embodiment, a mixture of an alumoxane compound and a trialkylaluminum is used as the cocatalyst.

The invention has also realized that it is particularly advantageous to carry out terpolymerization based on ethylene monomer, i.e. copolymerization of three comonomers, if the compound of formula (I) participates in the reaction. According to a preferred embodiment, terpolymerization of ethylene, a C 3 -C 10 -o-olefin and a compound of formula (I) is carried out. The advantage is based in part on the fact that there is an effect between the compound of formula (I) and the catalyst system used in the invention in favor of the compound of formula (I) as a comonomer.

Γ At the same time, the compound of formula (I) also has an active effect on the catalyst system, producing more terpolymer.

In said terpolymerization, it is preferable to keep the pressure of ethylene 5 at 3.0 to 4.5 bar and most preferably at 3.6 to 4.0 bar. In this case, the terpolymerization is preferably carried out in solution or by bulk polymerization, the initial concentration of the C3-C10-α-olefin being between 0.10 and 0.50 mol / l and the initial concentration of the compound of the formula (I) being between 0.05 and 0.50 mol / l. glycol / 1. When the initial content of the C3-C10-α-olefin is between 0.10 and 0.20 mol / l and the initial content of the compound of formula (I) is between 0.37 and 0.45, a terpolymer is formed which has a corresponding content of the compound of formula (I). the proportion of monomer units is of the order of about 25% by weight. Such a high proportion of the monomer unit corresponding to the compound of formula (I) is not achieved with a conventional TiCl4 / MgCl2 / R3Al catalyst system.

The following are a few examples to illustrate the invention.

Examples 1-21

Materials 25 Bis-7T-cyclopentadienylzirconium dichloride (Cp2ZrCl2) and methylalumoxane (MAO) were of commercial grade and were not separately purified. Polymerization grade ethylene, 1-butene, 1-decene and 1-hexadecene as well as medium n-heptane were purified by passing them through a series of columns 30 to remove moisture and oxygen residues. The MgCl 2 / TiCl 4 catalyst system used as a reference was a typical supported Ziegler-Natta catalyst with a titanium content of 7% by weight. The aluminum alkyl compounds used as reference cocatalysts were used as a 10% by weight solution of n-heptane (Schering AG).

93967 10

Polymerization

Bi- and terpolymerizations of ethylene, 1-butene, 1-decene and 1-hexadecene were performed in a 500 ml autoclave at 70 ° C for 10 minutes using n-heptane as the reaction medium. The comonomers and catalysts were fed to the reactor at the beginning of the polymerization. The reactor pressure was maintained at the desired level by means of a continuous ethylene feed, the reactor ethylene pressure being 3.8 bar. The molar ratio Al / Zr was 1000. The comonomer conversions were 16-45% for dipolymerization and 19-48% for terpolymerization when using 1-butene as comonomer and 24-32% for dipolymerization and 25-41% for terpolymerization when using 1-decene as comonomer.

Characterization of Polymers Figures 1-4 show graphical representations of the experimental results of the examples.

Figure 1 shows a typical 13 C-NMR spectrum of a terpolymer of ethylene, 1-butene and 1-decene (Example 14), Figure 2 shows the total copolymerization activity as a function of comonomer concentration, Figure 3 shows the function of the 1-decene content of the polymer as a function of the 1-decene content. where the filled square points represent the Cp2ZrCl2 catalyst and the 25 unfilled square points represent the reference catalyst, i.e. the TiCl4 / MgCl2 catalyst, and Figure 4 shows the dependence of the total activity on the reactor 1-decene butene / 1-ethylene content dekeeniterpolymeroinnissa.

3 0

The compositions of ethylene / butene, ethylene / 1-decene and ethylene / 1-hexadeene dipolymers and ethylene / 1-butene / 1-decene terpolymers were determined by 13 C NMR spectrometry using a Jeol SGX-14 type NMR spectrometer. A typical terpolymer spectrum (Example 14) is shown in Figure 1.

93967 11

Melting points and enthalpies were determined from the peak of the DSC curve measured with a PL-DSC instrument. DSC measurements were made at a heating rate of 10 ° C / min. Molecular weights, i.e. molecular weights and molecular weight distributions (MWD), were measured on a Waters-type ALC / GPC150 instrument equipped with 2 Schodex mixed bed columns with a polystyrene barrier of 5x10 7 and 1 Schodex column with a polystyrene barrier of 200 ° C. 1,2,4-Trichlorobenzene with a flow rate of 1.0 ml / min was used as a solvent.

Ethylene / 1-butene, ethylene / 1-decene and ethylene / 1-hexadecene polymerizations were performed using a Cp2-ZrCl2 / MAO combination as a catalyst. The polymerization results and the basic chemical and physical properties of the polymers obtained are shown in Tables 1, 2 and 3. Table 1 and Figure 2, which show the total polymerization activity as a function of feed comonomer concentration, show a significant increase in catalyst activity when ethylene is polymerized. 1-butene or l-de-kene. In addition, it is found that even at very low concentrations, i.e. at a concentration of about 0.1 mol / l, a significant increase in activity is achieved with 1-decene. It has not been previously observed or shown that the longer the comonomer chain, the higher the activity of the Cp2Zr-Cl2 / MAO catalyst.

* »•

When moving to an even longer comonomer chain, the activity increases very sharply and according to Table 3, the catalyst activity given by 1-hexadecene at a comonomer concentration of 0.10 mol / l is about three times that of the 1-butene comonomer shown in Table I. At the same time, it is seen that the activating effect of the longer-chain 1-alkene is high, especially at low feed comonomer concentrations.

It can be seen from Figure 3 that the proportion of 1-decene in the copolymer increases continuously as the 1-decene content of the feed increases. When the concentration of 1-decene is 0.4 mol / l, the proportion of decene in the copolymer reaches about 30% by weight.

93967 12

As a reference, polymerization was carried out under the same conditions using the previously known MgCl2 / TiCl4-Et3Al catalyst system, whereby with the same 1-decene content in the feed (0.4 mol / l), only a 6% by weight 1-decene content in the copolymer was achieved. Thus, it appears that the Cp2ZrCl2 / MAO catalyst system can be used to increase the proportion of longer chain α-olefins in the copolymers and, correspondingly, by using a Cp2ZrCl2 / MAO catalyst in the copolymerization to provide longer amounts of longer chain α-olefins which can be added in larger amounts. the proportion of olefins is high.

Terpolymerization of ethylene with 1-butene and 1-decene was also studied using the same catalyst under the same polymerization conditions. Figure 5 shows that the same phenomena occur in terpolymerization as in dipolymerization, i.e. the activity of the catalyst increased as the feed concentration of 1-decene increased, which occurred at different 1-butene concentrations. It can also be seen that with a lower 1-butene content of 20 (0.1 mol / l), the activity of the catalyst increased substantially as the feed 1-decene content increased, but with a higher 1-butene content (0.4 mol / l) the corresponding activity growth is lower.

25 Table 2 shows some properties of terpolymers. Terpolymers exhibit the same phenomena as dipolymers, i.e., with Cp2ZrCl2 / MAO catalysts, comonomer chain elongation increases activity at low concentrations, and that the catalyst system can incorporate larger amounts of α-olefin and especially long chain into the terpolymer.

t 93967

Table 1 Polymerization conditions and results

Comonomer conc. in feed Activity Polymers Eg l-butene 1-decene x10-6 physical mol / 1 mol / 1 g / mol Zr.h form3 dipolymerization_ _1__0__0__5_j_5__I_ _2__0__0,05__12,1__I_ _3__0__0,10__17,6__I_

_4__0__0,20__21.4 '__I + S

_5__0__0,30__22,9__I + S

_6__0,10__0__11,9__I_ _7__0,20__0__19,2__I_

_8__0,30__0__21,8__I + S

terpolymerointi_

_9__0,40__0,05__25,5__I + S

10 __0.40__0.10__26.0__S_ 11 __0.40__0.20__26.8__S_ 12 __0.40__0.30.3028.5__S_ 13 __0.10__0.40__28.5__S_ 14 __0.20__0.40__28.8__S_ 15 __0.30__0.40__29.6__S_ 16 __ , 40__0.40__30.4__S_. polymerization temperature = 70 ° C, ethylene pressure = 3.8 bar, [Zr] = 6.8 μιη, [Al] / [Zr] = 1000, reaction time 10 min, a: I = insoluble polymer during polymerization, S = soluble polymer • · 93967

Table 2 Basic properties of some di- and terpolymers Polymer composition

Eg 1-butene-1-dece- Mw110'3 MWD T ° C

ni p-% ni p-% g / mol peak range J / g dipolymer_ 1 0__0__98.4 3.3__139 115-145 166.3 2 0__4.6 43.6 4.2__130 105-142 147.3 3 0__5 / 7__25 .3 3.0__127__95-140 126.0 4 0__12.2__13.6 3.0__117__75-130 112.1 5 0__15.8__11.1 2.8__113__65-125 83.6 6 1.6 0__35.9 2.3 125 95 -135 141.6 7 3.6__0__29.7 2.8__123__75-135 127.3 8 8.3__0__10.6 2.7__117 100-130 87.9 terpolymen_ 13 0.85 25.8__7.7 2.9__102a 60-120 60.3 14 3.1 25.0__7.8 3.0__97a 40-118 54.0 15 4.3 24.1__7.3 2.8__87a 35-105 43.3 16 8.7 22.3__3.7 3, 0__81a 30-105 13.1 a = average value of several peaks is 93967 o

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Claims (24)

93967 A process for the copolymerization of ethylene and 1-alkene by the catalytic action of a tert-cyclopentadienyl transition metal compound and an alumoxane compound, characterized in that a polymerizing 1-alkene of formula (I) CH 2 = CHR (I) is used in which R represents a hydrocarbon group in which 8-20 carbon atoms. Process according to Claim 1, characterized in that the group R of the compound of formula (I) has about 14 to 20 carbon atoms. Process according to Claim 1 or 2, characterized in that the compound of the formula (I) is used in larger amounts in the polymerization mixture to obtain an ethylene copolymer having a higher proportion of monomer units corresponding to the compound of the formula (I). Process according to Claim 3, characterized in that the compound of the formula (I) is added to the solution or bulk polymerization mixture in an amount of 0.10 to 1.00, preferably 0.20 to 1.00 and more preferably about 0.40 to 1.00 mol / l. 1 to provide an ethylene copolymer having a proportion of monomer units corresponding to the compound of formula (I) of more than 6, preferably more than 13 and most preferably more than about 30% by weight, respectively. Process according to Claim 1 or 2, characterized in that the compound of the formula (I) is used in small amounts to enhance the polymerization of ethylene. Process according to Claim 5, characterized in that the compound of the formula (I) is used in solution or bulk polymerization in an amount of about 0.01 to 0.10 mol / l. • - 93967 Process according to one of the preceding claims, characterized in that the polymerization temperature is from about -50 to + 200 ° C, preferably from about +50 to + 100 ° C and / or the polymerization time is from about 5 to 40 minutes, preferably from about 10 to 20 minutes. min. Process according to one of the preceding claims, characterized in that the polymerization is carried out in a solvent which is preferably my liquid time, most preferably C 6 -C 12 time. Process according to one of the preceding claims, characterized in that the molar ratio of the metals of the alumoxane compound and the ττ-cyclopentadienyl transition metal compound is between 100,000: 1 and 10: 1, preferably between 2000: 1 and 200: 1. Process according to any one of the preceding claims, characterized in that the β-cyclopentadienyl transition metal compound has the following general formula (II): is an integer from 1 to 3, n is an integer from 0 to 3 and o is an integer from 0 to 3. Process according to Claim 10, characterized in that Cp is unsubstituted 7r-cyclopentadienyl. Process according to Claim 10 or 11, characterized in that R 1 is lower alkyl, preferably methyl. Process according to Claim 10, 11 or 12, characterized in that Y is chlorine. Method according to one of Claims 10 to 13, characterized in that M is Zr or Ti, preferably Zr. 93967 Method according to one of Claims 10 to 14, characterized in that m is 2, n is 0 or 1 and o is 1 or 2. Process according to one of Claims 10 to 15, characterized in that the π-cyclopentadienyl transition metal compound is bis-7r-cyclopentadienylzirconium monomethyl monochloride, bis-Tr-cyclopentadienylzirconium dichloride, preferably bis-7r-cyclopentadienylzirconium zirconium. Process according to one of the preceding claims, characterized in that the alumoxane compound has the following general formula (III) (A1 (R 2) O) p (IIIa) or R 2 (A 1 (R 2) O) pAlR 22 (IHb) in which R 2 represents an organic group and p is an integer from l to 50. Process according to Claim 17, characterized in that R 2 is an alkyl group having 1 to 5 carbon atoms, preferably methyl. Method according to Claim 17 or 18, characterized in that p is an integer from 4 to 20. Process according to one of the preceding claims, characterized in that terpolymerization of ethylene, a C 3 -C 10 α-olefin and a compound of the formula (I) is carried out. Process according to Claim 20, characterized in that terpolymerization of ethylene, a C 3 -C 8 α-olefin and a compound of formula (I) is carried out. 93967 Process according to Claim 20 or 21, characterized in that the ethylene pressure is kept at 3.0 to 4.5 bar, preferably about 3.6 to 4.0 bar. Process according to Claim 20, 21 or 22, characterized in that the terpolymerization is carried out in solution or by bulk polymerization, the initial content of the C 3 -C 10 α-olefin being between 0.10 and 0.50 mol / l and the formula (I) the initial concentration of the compound is between 0.05 and 0.50 mol / l. Process according to Claim 23, characterized in that the initial content of the C 3 -C 10 α-olefin is between 0.10 and 0. 20 mol / l and the initial content of the compound of the formula (I) is between 0.37 and 0.45, to give a terpolymer in which the proportion of monomer units corresponding to the compound of formula (I) is of the order of about 25% by weight.