WO1994021692A1

WO1994021692A1 - Ethylene-propylene copolymer and method for manufacturing the same

Info

Publication number: WO1994021692A1
Application number: PCT/FI1994/000081
Authority: WO
Inventors: Jari KOIVUMÄKI; Jukka Seppälä
Original assignee: Neste Oy
Priority date: 1993-03-18
Filing date: 1994-03-08
Publication date: 1994-09-29
Also published as: JPH08508057A; NO953674L; FI931194A0; NO953674D0; CA2158464A1; EP0689554A1; FI95582B; FI931194A; FI95582C

Abstract

The present invention is related to an elastomeric copolymer produced from ethylene, propylene and optionally diolefin, said copolymer having a weight-average molecular weight Mw of 10 000 - 250 000 g/mol, intrinsic viscosity of 0.8 - 4.0 dl/g, and an ethylene unit content of 65 - 95 wt.%, preferably 80 - 90 wt.%, in said copolymer, and said copolymer further having a homogeneous comonomer unit distribution, whereby the product is free from blocks formed by ethylene homopolymer in the copolymer. The Random Index value characterizing this property is approx. 50 - 90. The invention further concerns a method for producing said copolymer using a catalyst system formed by an alkadiene-metallocene compound and an alumoxane compound in a slurry phase containing either liquid propene or a hydrocarbon, or alternatively, in gas phase, at a temperature of 0 - 100 °C, preferably 10 - 50 °C. The copolymer thus produced is elastomeric yet easy flowing, easily melt-workable, and soluble in hydrocarbon solvents or swelling in hydrocarbons.

Description

Ethylene-propylene copolymer and method for manufacturing the same

5 The invention is related to an elastomer formed by the copolymer of ethylene and propylene, and further, to a manufacturing method thereof by means of a metallocene compound and an alumoxane catalyst.

Copolymers with elastomeric, that is, rubberlike elasticity characteristics have been o manufactured from ethylene and propylene.

An important characterizing property of elastomers is their rubberlike behavior, and particularly, as wide as possible operating range of such a property, or alternatively, a controlled and desired change of the elastic properties with variations in the operating 5 ' conditions and also in the raw materials of the elastomer, that is, the monomers. Besides by varying the additives of the elastomer, the desired goal can be attained by controlling the properties of the basic component, the elastomer, which can be imple¬ mented by altering, in addition to the reaction conditions (temperature, pressure, media, reactor type, etc.), particularly the catalyst utilized in the polymerization 0 process.

A copolymer can be produced by means of different catalyst systems, e.g., ethylene and propylene have been copolymerized into an elastomeric product utilizing a catalyst system formed by a procatalyst composition comprising a compound of a transition 5 metal of the IN-NI subgroup of the Periodic Table of Elements, particularly titanium, zirconium and/or vanadium, and a cocatalyst formed by an organic compound of a metal of the I— III major group of the Periodic Table of Elements, particularly an organic aluminium compound. Several other catalyst system components, e.g., electron donor compounds, and other additives required in polymerization reactions such as 0 different kinds of media can be utilized. Besides monor r (in bulk polymerization), the reaction met ^: urn can be a compound which will be incorporated in the product in its entirety or )art, or alternatively, a molecular- weight controlling compound (chain transfer agent). Suited for controlling the molecular weight and its distribution only, hydrogen is a chain transfer agent which 5 can be introduced to the polymerization reaction with the significant benefit of not bringing along any unwanted atoms to the produced polymer. Obviously, a great number of other additives may be employed to the end of improving different properties of the product.

ι o While the production of an ethylene-propylene elastomer is conventionally carried out utilizing a catalyst system of chiefly dual-component nature, a great number of such components are known in practice today, and the catalyst composition can be prepared by means of a wide selection of methods which sometimes involve a plurality of steps and complex procedures. Typical compositions of Ziegler-Natta catalysts are disclosed

15 in patent publications US 3,789,036 and DE 2,505,825.

An essential component of the procatalyst composition may be a compound of a transi¬ tion metal, termed as metallocene, in which the metal has aromatic rings joined to it, typically hydrocarbons which can further be substituted, as well as halogen groups. 0 The substituent may also contain heteroatoms. The halogen group joining to the metal typically is a simple halogen atom, advantageously chlorine, and the number of halogen atoms is two if the transition metal has a valence state of 4. Typically, the transition metal is titanium or zirconium, and the aromatic ring is five-membered and two rings join to one metal atom. Most commonly, said rings are bis-pentadienyl or bis-indenyl 5 derivatives, which can be substituted as mentioned above. The cocatalyst used with such a procatalyst is an alumoxane compound in which two or a greater number of aluminium atoms join via the oxygen atom to each other, and the aluminium atoms can further have a variety of substituents which typically are hydrocarbon groups, advantageously alkyl groups. 0

The copolymer is principally produced from ethylene and propylene, while additionally multi-unsaturated compounds can be used, chiefly polyene hydrocarbons, particularly diolefins. Then, unsaturated bonds remain within the polymer chain that can be useful with a greater or lesser reactivity when other chemical groups are desiredly joined to the polymer by a chemical bond or when the polymer is desiredly bridged or vulcan¬ ized, the latter being a traditionally typical process for treating rubber to the end of achieving a structure most suited to different applications. The proportion of the polyenes is small, e.g., 0.5 - 2 mol-% .

Generally, the proportion of ethylene units in the elastomeric ethylene-propylene copolymer is relatively high, however, rarely in excess of 80 %, and even more rarely in excess of 95 % . The molecular weight of the copolymer is typically rather low, not greater than a few thousands with a theoretical maximum at approx. 10 000 g/mol if the elastomeric properties of the copolymer are desiredly retained.

Patent application EP 223,394 discloses the production of an elastomeric ethylene- propylene copolymer having a low molecular weight (number-average molecular weight in the range 1800 - 4400 g/mol) using a catalyst system formed by bis-cyclopenta- dienyl-Zr-dichloride and methylalumoxane. The intrinsic viscosity of such a polymer is 0.025 - 0.6 dl/g determined in tetraline at 135 °C. The ethylene content in the product is 20 - 80 % , according to the examples 54-69 % .

Patent application EP 273,654 is related to an unsaturated copolymer made from ethylene and nonconjugated diene; also propylene being proposed as a possible comonomer, while no experimental proof is given. The catalyst system used is a com¬ position formed by bis-cyclopentadienyl-Zr-dichloride and methylalumoxane. The ethylene content of the product is high, in the range 96 - 99 %, and the rest is essentially at least a diene. The molecular weight range of the product is disclosed in a broad manner: not less than 500, advantageously in excess of 10 000 and even up to 2 000 000 g/mol, and according to the examples in the range 60 000 - 120 000 g/mol. The viscosity values of the product are not given.

Recently, an unexpected observation has been made that, using a catalyst system formed by bis-cyclopentadienyl-Zr-dichloride and methylalumoxane, a copolymer of ethylene and propylene, and optionally of a diene, can be produced that is characterized by its elastomeric properties, easy flowability, excellent workability due to its low value of melt viscosity and solubility in aliphatic hydrocarbon solvents whereby swelling occurs, said product having a high molecular weight. The weigh- average molecular weight is in the range 10 000 - 250 000 g/mol, advantageously 40 000 - 90 000 g/mol. The product has a narrow molecular weight distribution MWD = M_w/M_n, advantageously only approx. 2.0 - 2.5. The intrinsic viscosity is over 0.8 dl/g in decaline at 135 °C when the ethylene content of the copolymer is approx. 65 wt-%. The limiting viscosity number is determined using an apparatus comprising, e.g. , a Lauda UD15 heating bath and Schott timer, using the Ubbelohde capillary. The sample from which the limiting viscosity number was determined weighed 30 mg and it was dissolved in 50 ml decaline at 135 °C, and the limiting viscosity number computed on the basis of one measurement point as proposed by Solomon, O.F., Ciuta, I.Z., J. Appl. Polvm. Sci. 6(1962), p. 683.

Important factors characterizing the quality of the product are also the Mooney viscosity MV, the glass transition point T_g and the loss factor tan δ_mtx. MV characterizes the processability of the product and it is determined from a polymer melt. The glass transition point and the loss factor, which correlate with the low- temperature properties such as the low-temperature impact strength, can be determined by thermal analysis methods such as DTMA. The subsequent examples and comparative examples indicate that these values of the elastomers according to the invention are essentially commensurate with those of the comparative examples; so the quality of the product is in this respect fully equivalent to that of elastomers obtained by using other types of catalyst systems.

The ethylene content of the product is high, in excess of 65 wt-%, advantageously 80 - 90 wt-% . Yet, the product is elastomeric and the different monomers are homogeneously distributed over the molecule chain, that is, blocks consisting of ethylene alone have not been formed and then mixed with copolymer blocks. This homogeneity can be seen from, e.g., the Random Index (RI) value which characterizes the proportion of monomer units not incorporated in homopolymer blocks comprising at least three identical monomer units. The index is computed from triad distributions obtained from the C¹³ NMR spectrum:

(PPE +EPE + PEP + EEP)/(PPP + PPE + EPE + PEP + EEP + EEE),

where E and P are ethylene and propylene monomer units, while PPE, EPE, etc., denote the molar proportions of the triads in the polymer product. In elastomers made using titanium- and vanadium-based catalysts, this distribution of comonomer units is clearly more inhomogeneous indicating that the number of homopolymer blocks is greater, which is evidenced by the RI values given in the tables of comparative examples.

The copolymer made by a slurry process, whereby the medium can be either a liquid polymer, namely propylene, or a hydrocarbon solvent, advantageously aliphatic paraffin such as hexane, heptane, etc. The polymerization temperature herein is rather low, typically less than 50 °C, advantageously 0 - 30 °C. Gas phase polymerization can also be used, whereby a desired amount of propylene, and optionally also a diene, is mixed with gaseous ethylene in, e.g., a fluid-bed reactor in liquid droplet form, because a relatively low temperature must be used also herein.

The catalyst used is a compound of bis-cycloalkadiene and a transition metal. The tran¬ sition metal is advantageously titanium or zirconium. The cycloalkadiene is advanta¬ geously 5-membered, that is, cyclopentadiene which can be substituted with a hydro¬ carbon group such as an alkyl group, that is, a methyl-, ethyl-, propyl-, etc. -cyclo- pentadiene, or alternatively, with a hydrocarbon group containing also a heteroatom such as, e.g., a silyl or silanylene group. The cycloalkadiene can also be indene.

The cocatalyst used is an alumoxane compound. Methylalumoxane has been found suitable, while also other, more complex alumoxane compounds can be used of which alkylalumoxanes and their polymerized compounds deserve mentioning. A metallocene compound and alumoxane were used to produce the catalyst in amounts having the mole ratio of aluminium-to-zirconium in the range 1500 - 5000, advantageously 3000 -4200.

In the following, examples are given on the utilization of the catalyst according to the invention, as well as comparative examples on ethylene-propylene elastomers obtained with conventional Ti- and N-based catalyst systems.

Example 1 6.9 mg bis-cyclopentadienyl-Zr-dichloride catalyst was weighed into a flask in a nitro¬ gen chamber having an oxygen content of less than 15 ppm and dissolved in toluene. The solution was transferred from the flask to a metal funnel into which 4200 mg methylalumoxane (MAO) was transferred after storage for approx. half a year in a nitrogen atmosphere cabinet, said alumoxane being a 30 wt-% toluene solution by Schering AG, whereby the Al-to-Zr mole ratio became 3000. The funnel was installed permanently onto a 2 1 polymerization reactor. The reactor was vacuumed prior to purging with nitrogen, and it was equipped with an anchor-shaped agitator. The reactor was cooled to -5.0 °C and 430 g liquid propylene was introduced to the vacuumed reactor. The reactor temperature was next raised to 15 °C and the catalyst system in which the catalyst and the cocatalyst had been contacted for 7 min with each other was flushed with compressed nitrogen gas from the funnel to the reactor. Ethylene was introduced to the reactor under 10.7 bar (gauge) pressure. The rotation speed of the agitator was consistently 500 r/min. The reactor temperature was adjusted by rotating water-ethanol mixture in the heat jacket of the reactor, while the reactor pressure was controlled automatically by a solenoid valve. After 30 min of reaction, the unreacted propylene was evaporated away and 74 g of the product, that is, ethylene-propylene copolymer was obtained. The product properties are given in Table 1.

Example 2 The polymerization was carried out as in Example 1 except that 6.0 mg catalyst was used and 460 g propylene was introduced to the reactor. The absolute pressure in the reactor was now 11.1 bar. 58 g the product was obtained. The product properties are given in Table 1.

Example 3 The polymerization was carried out as in Example 1 except that 7.9 mg catalyst was used and 470 g propylene was introduced to the reactor. The absolute pressure in the reactor was now 11.4 bar. 50 g the product was obtained. The product properties are given in Table 1.

Example 4

The polymerization was carried out as in Example 1 except that 6.4 mg catalyst was used, and 5600 mg cocatalyst was added, whereby the Al-to-Zr mole ratio was 4200. The absolute pressure in the reactor was now 11.4 bar. 49 g the product was obtained. The product properties are given in Table 1.

Example 5

The polymerization was carried out as in Example 1 except that 3.0 mg catalyst was used, and 1400 mg cocatalyst (as 10 wt-% MAO solution) was added, whereby the Al-to-Zr mole ratio was 3300. 350 g propylene was added to the reactor. The absolute pressure in the reactor, whose volume in this example was 1 1, was 15.0 bar. 32 g the product was obtained. The product properties are given in Table 1.

Example 6

The polymerization was carried out as in Example 1 except that the reactor volume was 0.5 1 and 200 g propylene was introduced into it. 1 mg catalyst was used, and 290 mg cocatalyst (as 10 wt-% MAO solution) was added, whereby the Al-to-Zr mole ratio was 2000. The temperature in the reactor was 29 °C and the absolute pressure was 18.9 bar. 10 g the product was obtained after processing for 25 min. The product properties are given in Table 1.

Example 7 The polymerization was carried out as in Example 1 except that the reactor volume was 1 1 and 350 g propylene was introduced into it. 3 mg catalyst was used, and 1400 mg cocatalyst (as 10 wt-% MAO solution) was added, whereby the Al-to-Zr mole ratio was 2000. The temperature in the reactor was 14 °C and the absolute pressure was 19.0 bar. 10 g the product was obtained after processing for 20 min. The product properties are given in Table 1.

Example 8

A 0.5 1 polymerization reactor equipped with a propeller agitator was vacuumed and purged with nitrogen. Then, 207 g heptane was introduced to the reactor and 220 mg

MAO solution (as 10 wt-% toluene solution by Schering AG, stored approx. half a year in nitrogen atmosphere cabinet) was added to the reactor, and the monomer mixture feed to the reactor was turned on. The ethylene flow rate was 2.0 1/min and the propylene flow rate was 0.2 1/min (gas flow rates are given referenced to NTP); the flow was maintained constant during the entire polymerization process in accordance with the so-called semi-flow method. After five minutes from the start of the reaction, 0.6 mg bis-cyclopentadienyl-Zr-dichloride, whereby the Al-to-Zr mole ratio was 2000. The temperature in the reactor was 50 °C and the absolute pressure

5.0 bar. The reactor pressure was controlled by a solenoid valve and the temperature was adjusted by circulating thermostatted water in the heat jacket of the reactor. The agitator rotational speed was 800 r/min. The polymerization time was 10 min, after which 8.8 g the product was obtained. The product properties are given in Table 1.

Example 9 The polymerization was carried out as in Example 8 except that the propylene flow rate was 0.05 1/min. The product yield was 7.9 g. The product properties are given in Table 1.

Example 10 The polymerization was carried out as in Example 8 except that the propylene flow rate was 0.4 1/min. The product yield was 9.7 g. The product properties are given in Table 1. To obtain comparative results, a series of reactions were carried out to copolymerize ethylene and propylene into an elastomeric product using both a titanium- and a vanadium-based catalyst system. A similar polymerization procedure and apparatus as in the above examples was used, with the exception that hydrogen acting as a chain transfer agent was added to the reactant mixture during polymerization, which step was not included in the reaction carried out using the catalyst system according to the invention.

The titanium catalyst system comprised TiCl₄ procatalyst on MgCl₂ support and of triethylaluminium cocatalyst, in which system the Al-to-Ti mole ratio was 200 and the titanium content was 7.2 wt-% . The vanadium catalyst system comprised NOCl₃ and diethylaluminiumchloride (DEAC), in which system the V-to-Cl mole ratio was 4200. The results of the comparative examples are given in Table 2.

Table 1. Ethylene-propylene elastomer according to the invention.

Example Ethylene Intrinsic Random Weight-av. Mol. wt. Degree of Mooney Glass Loss factor content viscosity index molecular distribution crystallinity viscosity transition tan δ_m„ [mol-%] η [dl/g] RI weight MWD = [%] [V] point

1) M_w MJM→ 2) T_ε [°C] 4) [kg/mol] 5) 4)

1 64 0.85 79 46 2.4 - - - -

2 68 1.25 67 76 2.5 1 15 -43 0.566

3 74 1.06 62 71 2.3 3 12 - -

4 76 1.08 59 64 2.7 2 21 -42 0.299

5 77 2.52 - 210 2.6 8 - - -

6 68 1.16 - 74 3.4 7 - - -

7 87 3.70 - 197 2.4 21 - - -

8 98.4 2.55 - 113 3.8 55 - - -

9 99.4 2.82 - 226 3.6 50 - - -

10 95.5 0.99 - 63 4.1 48 - - -

1) Determined in decaline at 135 °C.

2) Determined from DSC-measured enthalpy of fusion referenced to 290 J/g being enthalpy of fusion for a polymer of 100 % crystallinity.

3) Determined from IR transmission spectrum absorbances at 720 cm^"1 and 1150 cm^-1.

4) Determined by DMTA, 4 °C/min, 1 Hz.

5) According to ISO 667-1981 standard, using a large rotor, 1 min preheating, 4 min measurement at 100 °C.

Table 2. Elastomers made with comparative catalyst systems.

Comparative Ethylene Hydrogen M_w Intrinsic Mooney Glass transi¬ Loss Random example content pressure [kg/mol] viscosity viscosity tion point factor Index no. [%] [bar] η [dl/g] MV T_g [°C] n δ_^ RI

Titanium catalyst

1 39 0.3 182 1.53 17 - - 71

2 49 0.3 250 2.09 32 -40 0.559 69

3 55 0.3 279 2.28 33 - - 65 I 4 64 0.3 314 2.59 45 - - 62 I

5 67 0.3 289 2.73 50 - - 57 )

6 73 0.3 210 3.00 78 -38 0.299 49 I

Vanadium catalyst

7 46 0.7 113 1.51 8 - - 82

8 65 2.0 116 1.37 13 - - 67

9 62 2.0 198 1.67 20 - - 71

10 54 0.5 344 2.62 44 -44 0.687 79

11 75 2.1 486 2.95 53 -43 0.322 49

12 69 0.3 949 7.08 63 - - 66

Table 2. Elastomers made with comparative catalyst systems.

Comparative Ethylene Hydrogen M_w Intrinsic Mooney Glass transi¬ Loss Rando example content pressure [kg/mol] viscosity viscosity tion point factor Index no. [%] [bar] V [dl/g] MV T_g [°C] tan δ_max RI

Titanium catalyst

1 39 0.3 182 1.53 17 - - 71

2 49 0.3 250 2.09 32 -40 0.559 -J9

3 55 0.3 279 2.28 33 - - 65

10 4 64 0.3 314 2.59 45 - - 62

5 67 0.3 289 2.73 50 - - 57

6 73 0.3 210 3.00 78 -38 0.299 49

Vanadium catalyst

7 46 0.7 113 1.51 8 - - 82

15 8 65 2.0 116 1.37 13 - - 67

9 62 2.0 198 1.67 20 - - 71

10 54 0.5 344 2.62 44 -44 0.687 79

11 75 2.1 486 2.95 53 -43 0.322 49

12 69 0.3 949 7.08 63 - - 66

20

Claims

1. An elastomeric copolymer produced from ethylene, propylene and, optionally, diolefin, characterized by being produced by contacting a monomer mixture containing ethylene, propylene and, alternatively, diolefin, under polymerizing conditions with a catalyst system comprising an alkadiene-metallocene compound and an alumoxane compound to the end of obtaining such an elastic copolymer which is soluble in hydro¬ carbon solvents, or swelling therein, and is melt-workable, said copolymer having a weight-average molecular weight M_w of 10 000 - 250 000 g/mol, intrinsic viscosity of 1 - 4.0 dl/g determined in decaline at 135 °C, and an ethylene unit content of 65 - 95 wt-%, and said copolymer further having a homogeneous comonomer unit distribution.

2. A copolymer as defined in claim 1, characterized by having an ethylene unit content of 80 - 90 wt-% in said copolymer.

3. A copolymer as defined in claim 1 or 2, characterized by being polymerized using an alkadiene-metallocene compound containing zirconium.

4. A copolymer as defined in any of claims 1 - 3, characterized by being polymerized using an alkadiene-metallocene compound which is a bis-cyclopentadienyl- zircono compound.

5. A copolymer as defined in any of claims 1 - 4, characterized by being polymerized using an alkadiene-metallocene compound which is bis-cyclopentadienyl-

Zr-dichloride.

6. A copolymer as defined in any of claims 1 - 4, characterized by being polymerized using an alumoxane compound which is methylalumoxane.

7. A method for producing an elastomeric copolymer from ethylene, propylene and, possibly, diolefin, characterized in that ethylene is contacted with propylene and, optionally, diolefin, in a slu phase or, alternatively, gas phase containing liquid propene or a hydrocarbon in th-, presence of a catalyst system formed by an alkadiene- metallocene compound and an alumoxane compound at a temperature of 0 - 100 °C, advantageously 10 - 50 °C, using such a partial pressure of ethylene which gives the copolymer thus obtained an ethylene unit content of 65 - 95 wt-%, preferably 80 - 90 wt-%.

8. A method as defined in claim 7, characterized in that said alkadiene-metallocene compound is a bis-cyclopentadienyl-zircono compound.

9. A method as defined in claim 7 or 8, characterized in that said alkadiene- metallocene compound is bis-cyclopentadienyl-Zr-dichloride.

10. A method as defined in any of claims 7 - 9, characterized in that said alumoxane compound is methylalumoxane.