WO1997011098A1

WO1997011098A1 - Olefin polymers which contain polar groups, and a method for their manufacture

Info

Publication number: WO1997011098A1
Application number: PCT/FI1996/000494
Authority: WO
Inventors: Barbro LÖFGREN; Päivi Aaltonen; Pekka Knuuttila
Original assignee: Borealis A/S
Priority date: 1995-09-21
Filing date: 1996-09-19
Publication date: 1997-03-27
Also published as: FI954475L; FI954475A0; AU6989996A

Abstract

An olefin copolymer prepared by polymerizing an olefin which contains 2-5 carbon atoms with a monomer which contains a functional group, the functional monomer being 9-methyl decenoate.

Description

Olefin polymers which contain polar groups, and a method for their manufacture

The invention relates to novel olefin copolymers which contain functional groups and to a method for their manufacture.

The linking of monomers which contain functional groups to a hydrocarbon polymer chain signifies the creating of a usable method for the modification of the chemical and physical properties of olefins. By using monomers containing functional groups it is possible to improve properties such as adhesion, dyeability, printability and permeability. Furthermore, a functional group provides a possibility for graft polymerization and thereby for uses such as compatibilization of blends containing polyolefins.

The Ziegler-Natta catalyst system is commonly used in the polymerization and copolymerization of olefins, but one of the major limitations of these conventional catalysts is that they are not suited for use in conjunction with monomers containing polar groups. Ziegler-Natta catalysts rather form a complex with the electron pair of a heteroatom, and thus in polymerization they rapidly deactivate the active centers by forming a stable complex with the functional group.

The more a polar monomer resembles alpha-olefin, the greater is its potential for becoming polymerized by the same active centers as olefins. The inventors have shown that comonomers which contain heteroatoms can be used for the polymerization of polyolefin. It is known that Lewis acid components (Zr, Al) present in the catalyst tend to form a complex with the unbound electron pairs of heteroatoms, thus causing deactivation of the catalyst. In practice this non-desirable interaction can be minimized by certain methods, such as (a) by isolating the double bond from the heteroatoms by means of a longer hydrocarbon chain; (b) by adding a steric barrier around the heteroatom; (c) by decreasing the electron donor character of the heteroatom, for example, by linking to it or in its vicinity a group which attracts electrons; (d) by selecting catalyst components which are inert to functional groups; (e) by precomplexing the functional monomer by using a Lewis acid; or (f) by using a polar solvent which becomes polarized with the active center but allows the polymerization of the vinyl monomer.

If deactivation can be successfully prevented by one or several of the above-men¬ tioned methods, the copolymerization of functional monomers will become more popular than it is today.

US patent publication 5, 286, 800 discloses the polymerization, with alpha-olefins, of comonomers containing functional groups. In these polymerizations there are used borane monomers which are converted, by reactions after the polymerization step, into polyolefins which contain functional groups.

In Japanese patent publication 61 72 447, the comonomer used is 10-undecen-l-ol which has been pretreated with tri-isobutyl aluminum for 3 hours at room tempera¬ ture before polymerization.

An object of the present invention is to provide novel copolymers of olefins and monomers containing functional groups. Furthermore, one object of the invention is a method in which the catalyst system has as high an activity as possible in the presence of a polar group. One object of the invention is also to provide for the copolymerization of olefins a method in which the copolymerization with a polar comonomer takes place in one step, without any pretreatment or postmodif ication. A further object according to the invention is to provide functional polyolefins in which the molar masses remain relatively high and the molar mass distributions are wide. In the Applicant's previous application FI 951970, this object was achieved by using as the functional monomer 2-methyl-3-buten-l-ol, 3-methyl-3-buten-l-ol and 5- hexen-1-ol.

The olefin copolymer according to the invention, prepared by polymerizing an olefin which contains 2—5 carbon atoms with a monomer which contains a functional group, is characterized in that the functional monomer is 9-methyl decenoate.

The olefin used in the manufacture of copolymers according to the invention consists of olefins containing 2—6 carbon atoms. Preferably, ethylene or propylene is used, but olefins having a longer carbon chain, such as l-butene, pentene and 1 -hexene, may be used just as well.

The catalyst used is a metallocene-type catalyst. The metallocene may be a metallocene of any type. Thus, suitable metallocene compounds include compounds having the formula (Cp)_mR_nMR'₀X_p, where Cp is an unsubstituted or substituted and/or fused homo- or heterocyclopentadienyl, R is a group containing 1-4 carbon atoms and serving as a bridge between two Cp rings, M is a transition metal belonging to group 4A, 5A or 6A (Hubbard), R' is a C_j-C₂ hydrocarbyl or hydroxy- carbyl group, and X is a halogen, m being 1—3, n being 0 or p being 0—3, and the sum m+n+p corresponding to the state of oxidation of the transition metal M. The transition metal is preferably zirconium or hafnium, most preferably zirconium.

Examples of suitable metallocene compounds include bis(n-butylcyclopentadienyl) zirconium dichloride, 1 ,2-ethylene-bis(indenyl) zirconium dichloride, and 1,2- ethylene-bis(indenyl) hafnium dichloride.

The polymerization activity of the catalyst can also be increased by using activators such as alumoxane. One method is to add the alumoxane to the metallocene compo¬ nent either before, simultaneously or after the metallocene. Another method is to add the activator directly into the polymerization reactor. Suitable activators include alumoxane compounds having the formula R-(Al(R)-O)_n- A1R2 or (-Al(R)-O-)_m,where n is 1-40, m is 3-40, and R is a C_rC₈ alkyl group. Preferably R is a methyl group.

The support used may be any porous or inert support, such as silica or alumina or mixtures thereof.

The polymerization may be carried out by any method, for example by slurry polymerization or gas phase polymerization. Thus the polymerization may be carried out, for example, at a temperature of 60-100 °C and under a pressure of 1-100 bar. The partial pressure of olefin in the reactor may vary within the range 1-3 bar and the amount of comonomer within the range 0.5—10 mmol.

The invention is described below in greater detail, with reference to the accompany - ing examples.

Materials

Bis(n-butylcyclopentadienyl) zirconium dichloride (n-butCp)₂)ZrCl₂, dicyclopenta- dienyl zirconium dichloride Cp₂ZrCl₂, l,2-ethylene-bis(indenyl) zirconium di¬ chloride Et(Ind)₂ZrCl₂, (dimethylsilyl-bis(lH-indenyl)) zirconium dichloride Me Si(Ind)₂ZrCl₂ and methylalumoxane (MAO) were of a commercial grade and were not purified separately. Polymerization-grade ethylene and propylene and the n-heptane and toluene serving as the medium were purified by feeding them through a column series to eliminate any moisture and oxygen residues. The comonomer methy 1-9-decenoate was of own production.

Polymerization

Ethylene copolymerizations were carried out in a 0.5 dm³ autoclave at a temperature of 60 °C for 40 minutes, and the reaction medium used was n-heptane. The medium n-heptane (350 cm³) was fed into a vacuumized reactor, blanketed with nitrogen and equipped with a stirrer. The rotation velocity of the stirrer was con¬ stantly 400 rotations per minute. The comonomer was added in one batch under nitrogen blanket, and the cocatalyst MAO (Al/Zr = 3000 mol/mol) was added at the beginning of the polymerization by using a pump. After the polymerization tempera¬ ture had been reached, ethylene was fed into the reactor. The consumption of ethylene was monitored by means of a mass flow controller. After equilibrium had been reached, polymerization was started by pumping the catalyst into the reactor. The partial pressure of ethylene or propylene was maintained constant (2.5 bar ethylene overpressure) by means of an electronic pressure controller and a solenoid valve, and the reactor temperature was maintained constant (±0.1 °C). The conver¬ sion was maintained low in order that it could be assumed that the concentration in the reactor remained constant. At 40 minutes, reactor pressure was released and the obtained polymer product was washed with a solution of ethanol and hydrochloric acid, and was dried.

Propylene copolymerizations were carried in the same manner as ethylene copolymerizations except that the medium used was toluene in an amount of 300 cm³, the polymerization time was 60 minutes and the polymerization tempera- ture was 30 °C, and the propylene overpressure was 3.0 bar. The catalyst used was l,2-ethylene-bis(indenyl) zirconium dichloride.

Characterization of the polymers

The compositions of the copolymers of ethylene and the functional monomer were determined by using a Jeol NMR spectrometer.

The melting points and enthalpies were determined from the peak of the DSC curve by using a Perkin Elmer DSC-7 instrument. The DSC measurements were carried out by reheating the sample to 180 °C at heating rates of 2 and 10 °C/min. The molar masses and the molar mass distributions were measured using a Waters- type ALC/GPC 150 instrument in which there had been installed 3 TOSOH mixed- bed columns in which the polystyrene barrier limit was 4 x 10⁸ at a temperature of 135 °C. The solvent used was 1,2,4-trichlorobenzene having a flow rate of 1.0 ml/min.

Examples

Ethylene was copolymerized with methyl-9-decenoate. The catalysts used were combinations (n-butCp)₂ZrCl₂/MAO, Cp₂ZrCl₂/MAO, Et(Ind)₂ZrCl₂/MAO and Me₂Si(Ind)₂ZrCl₂/MAO. The polymerization conditions and some product properties are shown in Table 1.

Table 1

Ex. Catalyst Comonomer Activity Molar mass Mv/Mn Tm

No. 2 mg amount kg/g cat h M_w 10^"3 °C mmol

1 (n-butCp)₂ZrCl₂ 1 5,0 98 3, 1 131 ,5

2 ^» 2 4, 1 139 3,8 134,5

3 ^» 3 2, 1 131 3,9 134,0

* 4 ^« 4 0,2 60 5,2 133,3

5 Cp₂ZrCl₂ 1 2,5 120 4,6 130,4

6 Et(Ind)₂ZrCl₂ 1 1.9 265 4,8 130,8

7 Me₂Si(Ind)₂ZrCl₂ 1 1 , 1 104 2,9 128, 1

polymerization temperature 60 °C polymerization time 40 min ethylene pressure 2.5 bar

Zr = 4.94 x IO^"2 mol

Al (as MAO) = 1.98 x IO^"2 mol

* Composition of the ethylene copolymer Comonomer Comonomer feed In the copolymer mmol % wt. molar %

methyl-9-decenoate 4 1.1 0.2

Activity decreases as the amount of comonomer fed in increases.

Copolymerizations of propylene and methyl-9-decenoate were carried out by using the combination l ,2-ethylene-bis(indenyl) zirconium chloride/MAO. The polymerization conditions and some properties of the product are shown in Table 2.

Table 2

Ex. Catalyst Comonomer Activity Molar mass Mv/Mn Tm No. 2 mg amount kg/g cat h M_w- 10^"3 °C mmol

8 Et(Ind)₂ZrCl₂ 0,5 3,9 33 1 ,8 135,5

Al/Zr 4000 mol/mol

MAO solution 12.4 ml (7.0 cm) from burette

Propylene 3.0 bar

30 °C

300 ml (261 g) toluene

400 rpm

60 min

Claims

1. An olefin copolymer prepared by polymerizing an olefin containing 2—5 carbon atoms with a monomer containing a functional group, characterized in that the functional monomer is 9-methyl decenoate.

2. An olefin copolymer according to Claim 1, characterized in that the olefin has been selected from the group ethylene and propylene.

3. An olefin copolymer according to Claim 1—2, characterized in that it has been prepared by using a metallocene catalyst.

4. An olefin copolymer according to any of the above claims, characterized in that the metallocene is selected from the group bis(n-butylcyclopentadienyl) zirconium chloride (n-butCp)₂)ZrCl₂, dicyclopentadienyl zirconium dichloride Cp₂ZrCl₂, 1,2- ethylene-bis(indenyl) zirconium dichloride Et(Ind)₂ZrCl₂, (dimethylsilyl-bis(lH- indenyl) zirconium dichloride Me₂Si(Ind)₂ZrCl₂.

5. An olefin copolymer according to Claim 4, characterized in that the polymerization has been carried out using methylalumoxane (MAO) as an activator.