NL8300457A - ETHYLENE POLYMERS WITH A LINEAR STRUCTURE AND METHOD FOR THEIR PREPARATION. - Google Patents

Description

833006 / vdKl / dw *

Short designation: Ethylene polymers with a linear structure and method for their preparation.

The invention relates to special polymers of ethylene with a linear structure (i.e. virtually without long side chains) with a density of less than 0.9450 g / cm 2. More particularly, the invention relates to copalymers of ethylene with at least one other alpha olefin having densities from 0.9150 g / cm 2 to 0.9450 g / cm 2 and also to processes for preparing such polymers.

It is already known (for example, German Patent Application No. 2,609,889, British Patent No. 1,131,528, U.S. Patent 4,067,882 and German Patent Application No. 2,014,172) that linear poly-ethylene can be obtained with a low or medium density by low-pressure polymerization processes, in which ethylene is copolymerized with another alpha-olefin, preferably butene-1 or octene-1, in the presence of Ziegler catalysts or, in any case, in the presence of catalytic systems commonly used for the production of poly alpha olefins. 15 are applied.

Such linear low-density copolymers differ from the known low-density polyethylene (obtained by free-radical high-pressure processes) not only because of their linear structure rather than branched structure, but mainly because of the significant improvement of some properties such as the modulus and elongation at break, as shown is in the following table:

Density Melt Flow Bend Elongation at Tensile index modulus fracture g / cm ^ g / 10 Min MPa ft Mpa 25 Linear LDPE 0.9213. 2.0. 278 617. 14.9

Known LDPE 0.9230 2.0 214 545 10.0 LDPE = Low density Polyethylene 8 300 457, - ï. . r -2-

The linear low density polyethylene has a greater mechanical resistance than the known low density polyethylene and the $; property, for example, in processes for obtaining films, it is possible to save up to 30% of the product, while noticeable advantages are obtained in injection molding and in the manufacture of fibers and cables due to the improved mechanical properties at low temperatures, such as resistance to shock. The properties of the copolymers are a function of the distribution of the comonomer in the polymer chain.

Applicant has now found, and this is the subject of the present invention, that it is possible to prepare polymers with a differentiated distribution of the comonomer by employing catalytic systems of the high yield class, which are already known for the preparation of high density and medium density polyethylene, as described in Dutch patent applications 77.01005, 78.07137, 81.00477, 82.03012 by changing the production method or introducing changes itself / in the plasticizing method.

The catalytic systems concerned contain components consisting mainly of an organoaluminum compound and a second compound which may be the reaction product of metal vapors with a titanium compound and a halogen donor or the like, modified by a subsequent reaction with an organo-aluminum compound or with a alcohol.

In the former case, the catalyst can be represented by a formula such as TiX2. m'MXn, where X is a halogen atom, M is a metal selected from Mg, Al, Ti, V, Mn, Cr, Mo, Ca, Zn, n represents the dignity of M and m 'is equal or greater then 1: n. Such a compound is obtained by a process consisting of evaporating in vacuo at least one of the above-mentioned metals and reacting the vapors thus obtained with the titanium compound in the presence of a compound capable of producing halogen atoms. As explained above, such a composition can be used as such or modified by reacting it with an organoaluminum compound to yield a compound of the type TiX ^ .mM'Y ^ qM''Y'p.cAlY'sRs wherein X are a halogen atom, M 'and M "different from each other and selected from the above-mentioned metals Y, Y', and YM, which may or may not be different, represent halogen atoms and in turn may or may not be the same are at X, m and q equal to 0 or different from 0 but not simultaneously equal to 0, 8300457 f -3- '. * c is always different from O, n and p and the values of M' and M 'respectively *, s can assume any value between 0 and 3, R 'is a hydrocarbon group, preferably having a number of carbon atoms less than or equal to 10. On the other hand, the catalyst may be the reaction product of a titanium compound selected from the halides and the alkoxide, with da of an electrically positive metal, with reducing properties, condensed at a low temperature, an organic halogen compound or an inorganic halogen compound and an alcohol.

In any case, as a co-catalyst, a compound of aluminum of the formula Al R''p is always used, in which R 'represents a hydrocarbon group, X a halogen atom and p' a number from 1 to 3. In addition to the above said compositions, the catalyst system can be obtained from (a) the reaction product of a titanium compound selected from the halides and the alcoholates, with vapors of magnesium, condensed at low temperatures, an organic or an inorganic halogen compound and an alcohol, (b) an aluminum trialkyl and an aluminum halide corresponding to the formula AIR '' X, wherein X represents chlorine or bromine and s is between 0 and 2.

The use of the aforementioned catalytic compositions makes it possible to obtain low density polyethylene and more particularly linear low density polyethylene by allowing the polymerization of ethylene to take place in the presence of at least another alpha-olefin having 3 to 10 carbon atoms. The alpha-25 olefins, especially butene-1, have been observed to improve the activity of the catalytic systems used.

Quite special advantages have been obtained by using butene-1, hexene-1, and octene-1: the final crystalline copolymers have a comonomer content of 1 mole S to 7 mole ft, melting point between 115 and 130 ° C, a crystallinity (X-rays) of from 39 to 55% depending on the amount of comonomer present, and a melt flow index according to the ASTM D-1238 method) between 0.1 and 50 g per 10 minutes - (g / 10 min. ), the density always being less than 0.9450 g / cm 2 and preferably between 0.9150 and 0.9450 g / cm 2.

The distribution of the comonomer in the polymer chain is different depending on the process used for the preparation and this fact is demonstrated by the different amounts of substances which can be extracted by boiling heptane γ 8300457 1 f -4- when the density is equal and the melt flow index is the same.

The polymerization can be carried out, without difference, in suspension, in solution, and in gaseous phase, and, if necessary, the reaction medium can consist of linear or branched hydrocarbons with 4-10 carbon atoms, cyclic hydrocarbons , halogenated hydrocarbons, or a C4 fraction from reforming, in accordance with the method to be used.

Obviously, the procedures also change according to the process used: the gas phase polymerization is therefore carried out by adding the above catalytic system to the gas mixture consisting of ethylene, an alpha olefin, preferably propylene or butene-1, and hydrogen as a means, to adjust the molecular weight in variable amounts in accordance with the product to be obtained, at a temperature which can be selected between 10 ° C and 100 ° C, preferably between 60 ° C and 90 ° G under a pressure between 5 and 50 bar, preferably 10-30 bar. The products thus obtained are characterized by a quantity of substances to be extracted by density ranging between 0.9150 and 0.9450 g / cm and by boiling heptane, which for the products with the same melt flow index is between 65%. and 5.9%.

The slurry polymerization is carried out in straight or branched chain aliphatic hydrocarbon solvents having 4-10 carbon atoms, preferably butane or isobutane, or with halogen substituted hydrocarbons using alpha-olefins of 3 to 10 carbon atoms, the comonomer being 25 those with 3 to 6 carbon atoms are preferred, and one of the catalytic systems described above.

The polymerization is carried out at a temperature which can be selected between 20 ° C and 90 ° C, preferably between 50 ° C and 80 ° Cr, under a pressure between 1 to 60 bar, preferably between 13 and 30 bar. The polymerization can be carried out as a one-step process or in multiple steps with series-placed reactors and by feeding the gas phase with different compositions.

The finishing of the product can be carried out by either evaporating the solvent in the case of low boiling solvents, or by centrifuging and drying the powder, or by stripping.

The products obtained from a one-step process and having a density between 0.9150 and 0.9450 g / cm 5 have an amount of boiling heptane extractable substances between 43% and 3%, while the. 830 0 45 7

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-5- »samples obtained in a two-stage process have an amount of substances to be extracted between 50¾ 603.5¾.

For the solution polymerization process, it is necessary to work with solvents whose critical temperature is above the polymerization temperature, which is preferred in the range of 130-250 ° C. The cyclic hydrocarbons such as cyclohexane and methylcyclohexane and mixtures of n- and iso-hydrocarbons, the boiling point of which is between 120 ° C and 180 ° C, provided they have a good solubility for the copolymers to be formed, the best results being obtained by the concentration of the polymer in the reaction mixture not exceeding 40 wt. , ¾ relative to the solvent.

The molecular weight of the copolymers formed is adjusted in a known manner by using hydrogen in an amount between 0.003 and 0.5 moles per mole of ethylene.

The polymerization can be carried out by introducing ethylene, hydrogen, an alpha-olefin (03-010 ^ preferably C6-C1Q or branched) into the reaction medium, and any of the above catalytic systems, stirring the reaction mixture to release of the polymerization and obtain a hotter homogeneity of the system. The residence times of the polymer solution can change according to the polymerization conditions, from 1 min to 24 hours, preferably from 5 min to 4 hours, the polymerization pressures are comparatively low and are between 5 and 100 bar.

The copolymers are recovered by removing the unreacted monomers and the solvent from the polymerization mixture and inactivating the catalytic system with suitable reaction mixtures.

The products thus obtained, with a density of between 0.9150 and 0.9450 g / cm 2, have an amount of 50 substances between 56¾ and 5¾ by boiling heptane to be extracted.

In order to demonstrate the difference of the products, Table A shows the data of the substances that can be extracted with n-heptane at the boiling point, as well as some technological properties of the films obtained therewith.

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The invention will be further elucidated by means of the following non-limiting examples.

EXAMPLE I

Preparation of the Catalyst. A rotary evaporator is used with a spiral tungsten wire centrally located in the flask connected to an electricity source. A cooling bath is placed horizontally under the flask.

The device is connected via a three-way valve to a vacuum line and the nitrogen supply lines.

For the suitably protected tungsten resistance, a 1 g magnesium wire is wound and placed in the 500 ml flask, under a nitrogen blanket, 250 ml anhydrous and deaerated heptane, 15 ml 1-chlorhexane, ml / corresponding to 105 mmcL , and 0.23 TiCl2, corresponding to 2.1 mmol.

The flask is cooled to -70 ° C, vacuum of 10 Torr is formed and the tungsten coil is heated to evaporate the metal wound around it. After the evaporation is complete, nitrogen is introduced into the apparatus and the flask is brought to room temperature with stirring, and the flask is heated at 88 ° G for 1 hour (Catalyst A).

70 g of polyethylene powder with a controlled particle size are placed in a 500 ml flask, dried under vacuum for 30 minutes, after which the flask is filled with nitrogen and the suspension obtained in the flask is still charged in such an inert atmosphere. The solvent is removed under vacuum by heating the flask to 50 ° C to 60 ° C with vigorous stirring.

After the solvent has evaporated, the flask is refilled with nitrogen.

The catalyst thus obtained (Catalyst B) is a free-flowing powder of hazelnut color.

Analysis provides:

Ti = 0.029 milligrams / g, Mg = 0.532 milligrams / g, and Cl = 1.12 milligrams / g.

EXAMPLE II

A 5 1 autoclave equipped with an anchor-shaped stirrer is vented under vacuum and charged with 1.3 liters of isobutane, and the temperature is allowed to rise to 60 ° C, after which 120 g of butene-1.7 mM aluminum tri-35 isobutyl , hydrogen to a pressure of 1.55 bar, ethylene to a total pressure of 13 bar and 0.5 g of catalyst (B), equivalent to 0.0145 milligrams of Ti.

8300457 -8- 1 «I 1

The temperature is maintained at 60 ° C and ethylene is added. to keep the total pressure constant.

After a polymerization of 2 hours, the reaction is stopped with 20 ml of ethanol and the solvent is evaporated. 310 g of polymer, corresponding to a yield of 430 kg of polymer per gram of Ti, are obtained, the polymer having the following properties:

Density 0.9210 g / cm ^

Butene content (NMR) 6.8 wt. % CH3 / 10Q C (number) 1.70 10 Melt flow index (MFI) 1.2 g / 10 min.

at 2.16 kg

Melting point 122 ° C

X-rays - crystallinity 42? Ó

Apparent density 0.33 g / cm ^ 15 Average diameter of the 350 micron powder

Boiling C7 extract 33.8%

EXAMPLE .III

The same device and method as in Example II are used, but with a different amount of butene, i.e. 80 g. 260 g of polymer, corresponding to a yield of 360 kg of polymer per gram of titanium, are obtained, the polymer having the following properties: 8300457 * t -9-

Density 0.9284 g / cm ^ Buten content 4.8 wt. % CH3 / 100 C (number) 1.1 MFI (Melt flow index) 0.4 g / 10 min.

5 Apparent density 0.30 g / cnr *

Melting point 124.5 ° C

EXAMPLE IV

The same device and method as in Example II are used, but with an amount of butene-1 of 140 g.

350 g of polymer, corresponding to a yield of 480 kg of polymer per gram of titanium, are obtained, the polymer having the following properties:

Density 0.9152 g / cm ^

Butene content 10.3 wt. % 15 CH3 / 100 C 2.5 MFI (2.16 kg) 1.2 g / 10 min.

Apparent density 0.25 g / cm ^

Melting point 120 ° C

Heptane extract (boiling) 52¾

EXAMPLE V

The same device as in Example 2 is used, but the method of operation is changed as follows: 1.3 liters of isobutene, which has been brought to 60 ° C, are introduced into the device, after which 40 g of butene-1 mM (mmol) are added. aluminum tri-isobutyl, hydrogen up to a pressure of 1.70 bar, ethylene 8300457 I 6 V- -10- up to first pressure (total) of 14 bar and 0.5 g of catalyst (B) of example _I which is equivalent to 0.0145 milligrams atom of Ti. The temperature is maintained at 60 ° C and ethylene is added to keep the total pressure constant. After a polymerization time of 15 minutes (about 30-5 of the total polymer is formed), 140 g of butene is added and the polymerization is continued while the total pressure is maintained at 14 bar by adding ethylene again.

After a total polymerization time of two hours, polymerization 3 is terminated with 19 cm ethanol and the solvent is evaporated. 320 g of polymer are obtained, which corresponds to a yield of 445 kg of polymer per gram of titanium, the polymer having the following properties:

Density 0.9204 g / cm ^

Butene content 7.0% by weight 15 Melt flow index 1.1 g / 10 min.

Apparent density 0.33 g / cm ^

Melting point 122 ° C

Extract from boiling C7 39¾

EXAMPLE VI

20 A 5-liter autoclave equipped with an anchor-shaped stirrer. under vacuum and filled with 2 liters of anhydrous and deaerated hexane and brought to 60 ° C, after which 130 g of butene-1,6 mM (mmol) aluminum tri-isobutyl, hydrogen to a partial pressure of 2.2 bar, ethylene to a total overpressure of 6 bar and 0.5 g of catalyst (B) of Example I, corresponding to 0.0145 milligrams of titanium.

The temperature is maintained at 60 ° C and ethylene is added to keep the total pressure constant. After 2 hours of polymerization, the reaction is stopped with 10 ml of ethanol, the autoclave is allowed to cool, the gases are removed and the polymer suspension is stripped from the solvents.

The dried polymer, 250 g, corresponding to a yield of 350 kg of polymer per gram of titanium, is a free-flowing powder and has the 8300457 ^ -9 -11-

S

following properties:

Density 0.9213 g / cm ^

Butene content 6.2 wt. %

Melt flow index 0.9 g / 10 min.

5 Apparent density 0.23 g / cm ^

Boiling C7 extract 50.1%

EXAMPLE VII

They use the apparatus and apply the method of Example 2, but use anhydrous n-butane as the reaction medium and the same polymerization components in the same proportions, so that the total overpressure is 11.5 bar.

The polymer is obtained in an amount of 280 g, corresponding to a yield of 385 kg of polymer per gram of titanium, and with the following properties: Density 0.9215 g / cm 3

Butene content 6.5 wt. % CHj / 10QfC (number) 1.65

Melt flow index 0.90 g / 10 min.

X-rays crystallinity 41¾

20 Apparent density 0.34 q / cnP

EXAMPLE VIII

The same apparatus and method as in Example VI are used using 300 g of anhydrous and deaerated hexene. 240 g of polymer having the following properties are obtained: 8300457 SA X- <t -12-

Density 0.9290 g / cm3 CH3 / 100 C (number) 0.90 Hexene content 5.4 wt. ?O

Melt flow index 1.1 g / 10 min.

3 5 Apparent density 0.25 g / cm

EXAMPLE IX

2 g of catalyst (B) and 6 milligrams of aluminum triisobutyl dissolved in 15 ml of hexane are stirred into a test tube with a tail section, which has been previously dried and placed in an inert atmosphere, stirred with a magnetic stirrer, and hexane is stirred stirring evaporates until the sample is thoroughly dry.

1 g of catalyst, equivalent to 0.013 milligrams of titanium, is placed under a nitrogen blanket in a 2-liter autoclave equipped with a stirrer, dried and kept under an inert atmosphere.

The autoclave is sucked empty to remove nitrogen, heated to 70 ° C, and a gas stream of the following composition is added to a pressure of 10 bar: ethylene 80 vol. S, butene 15%, hydrogen 5%.

After a polymerization time of 1 hour, 100 g of a powdered polymer with the following properties is obtained: Density 0.9198 g / cm

Butene-1 content 6.9 wt. % MFI 1.30 g / 10 min.

Melting point 121.5 ° C

Extract from cracking C7 58¾

EXAMPLE X

An autoclave of 5 liters, with a stirrer, is filled with 2 liters of anhydrous and deaerated cyclohexane containing 1 mmol Al (n-oct) 3, the temperature is raised to 150 ° C. 100 g of actene-1, hydrogen to a pressure of 0.5 bar, ethylene to a total overpressure of 10 bar and 1.5 cm @ 5 of catalyst (type A) of Example I, corresponding to 0.012, are then added. milligrams of titanium, add. The pressure is kept constant by adding ethylene for 30 minutes. After the polymerization is complete, the reaction is stopped, the autoclave is allowed to cool and the gases are removed. The product thus obtained consists of 140 g of polymer, corresponding to a yield of 230 kg of polymer per gram of titanium.

The polymer thus obtained has the following properties: Density 0.9210 g / cm 2

Octene content 7.2 wt. %

Cttj / IOQ C 0.96

Melting point 122 ° C

15 Melt flow index 1.0 g / 10 min.

C7 extract (boiling) 44.5% 8300457

Claims (16)

1. Ethylene copolymers with at least one other alpha-olefin with the amount of comonomer present, densities between 0.9150 g / cm 2 and 0.9450 g / cm 2, melting point between 115 ° C and 130 ° C, an X-ray crystallinity of between 39 ° and 55 °, a melt flow indicator according to the. ASTM D-1238 method between 0.1 and 50 g / 10 min., And an amount of comonomers ranging from 1 mole. % to 7 mol%. Copolymers according to claim. 1, characterized in that the other alpha-olefin is selected from butene-1, hexene-1, and octene-1. Process for preparing copolymers of ethylene according to claims 1 or 2, characterized in that ethylene is contacted with at least one other alpha-olefin in the presence of a catalytic system consisting of an organo-aluminum compound and a composition selected from the reaction product of metal vapors with a titanium compound and a halogen donor or the product obtained from the previous reaction * previously modified by an organoaluminum compound or an alcohol. Processes for the preparation of copolymers of ethylene according to claim 3, characterized in that the catalyst consists of a compound of the formula TiX, .m, .MX, wherein X is a halogen atom, M20 a metal selected from Mg, Al, Ti, V, Mn, Cr, Mo, Ca and Zn, n represent the dignity of M and m 'is equal to or greater than 1 / n. Process for the preparation of copolymers of ethylene according to claim 3, characterized in that the catalyst consists of a compound of the formula TiX, .mM'Y .qM ^ Y '«cAlY ,, r, R', wherein X a 3 np 3-ss 25 halogen atom, M 'and M "metals which are different from each other and are selected from the metals mentioned in claim 4, Y, Y', and YM, which may or may not be different, represent halogen atoms and whether or not different from X, m and q are equal to or different from 'te-0, but not equal to 0 at the same time, c is always different from 0, n and p the values are respectively M' and M " s can assume any value from 0 to 3, R 'is a hydrocarbon group with a number of carbon atoms of 10 or less. 6. Process for preparing copolymers of ethylene according to claim 3, characterized in that the polymerization is carried out by adding at least one other alpha-olefin and hydrogen to a gas mixture containing ethylene. 8300457 * * f -15- 7. Process for preparing ethylene copolymers according to claim 6, characterized in that the reaction is carried out at a temperature between 200C and 100C and under a pressure between 5 and 50 bar. 8. Process for preparing ethylene copolymers according to claim 7, characterized in that the reaction is carried out at a temperature between 60 and 90 ° C and under a pressure between 10 and 30 bar. 9. Process for the preparation of ethylene copolymers according to claim 3, characterized in that the polymerization reaction is carried out in suspension. 10. Process for the preparation of ethylene copolymers according to claim 9, characterized in that the reaction is carried out in the presence of a solvent selected from the aliphatic hydrocarbons with 4 to 10 carbonoms or from the halogen-substituted hydrocarbons. . Process for the preparation of ethylene copolymers according to claim 9 or 10, characterized in that the reaction is carried out at a temperature between 20 ° C and 90 ° C and under a pressure between 1 and 60 bar. 12. Process for the preparation of ethylene copolymers according to claim 2011, characterized in that the reaction is preferably carried out at a temperature between 50 ° C and 80 ° C and under a pressure between 13 and 30 bar. 13. Process for the preparation of varethylene copolymers according to claim 3, characterized in that the polymerization is carried out in solution. Process for the preparation of ethylene copolymers according to claim 13, characterized in that the reaction is carried out at a temperature between 130 and 250 ° C. Process for the preparation of ethylene copolymers according to claim 3013 or 14, characterized in that the reaction is carried out in the presence of a solvent with a critical temperature higher than the polymerization temperature. 16. Process for the preparation of ethylene copolymers according to claim 15, characterized in that the solvent is selected from the cyclic hydrocarbons and hydrocarbon mixtures. 8300457