LU84641A1 - ETHYLENE POLYMERS WITH LINEAR STRUCTURE AND PROCESS FOR THEIR PREPARATION - Google Patents

Description

I 1 1 Ethylene polymers with a linear structure and their preparation process.

The present invention relates to particular ethylene polymers having a linear structure (that is to say substantially devoid of lateral branches) having

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1 · a density less than 0.9450 g / cm. More particularly, the present invention relates to copolymers of ethylene with at least one other alpha-olefin before densities included! * 2 d | between 0.9150 and 0.9450 g / cm and it also concerns j | processes for preparing these polymers.

It is already known (for example from German patent application No. 2,609,889, British patent |! No. 1,131,528, US patent No. 4,067,882 and German patent application No. ° 2 014 172) which can be obtained a linear poly- *, low density or medium density, by i: low pressure polymerization, during which the ethylene: = 15 is copolymerized with another alpha-olefin, butene-1 or. octene-1, preferably in the presence of catalyst of the type | - Ziegler or, in any case, in the presence of catalytic systems; of the type usually used for the preparation of 'poly-alpha-olefins.

These low density linear copolymers differ from these; conventional low density polyethylenes * (as obtained with high pressure radical processes) not only by their linear structure rather than by their ramifications, but above all by the considerable improvement in some properties such as the modulus and 1 elongation at break as shown in the table below.

Density Index of elongation- Modulus of Extension- Kesistat-, in bending mas- tion so that at the melt the rupture! 30 g / in? g / 10 min MPa% MPa. t "Linear LDPE 0.9213 2.0 278 617 14.9 | Classic LDPE 0.9230 2.0 214 545 10.0 LDPE = Low density polyethylene, Linear low density polyethylene has a mechanical strength greater than that of low polyethylene

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i 2! . conventional density and this property, for example in the J * treatment cycles to obtain films, can save up to 30% of the product and obtain j | * appreciable advantages with regard to injection molding and the manufacture of filaments and cables, of! fact that the mechanical properties are improved at low temperatures such as impact resistance and the properties of the copolymers are a function of the distribution <ju j * · comonomer in the polymer chain.

The authors of the present application have now discovered, which is the object of the present invention, that polymers having a different distribution of the comonomer can be prepared using catalytic systems of the high yield class which are already known for the preparation of high density and medium density polyethylenes, as disclosed in French patent applications Nos. 7702334, 7818763, 8101605 and 82/12867, by modifying the preparation process or by introducing variants in the process itself.

The catalytic systems in question comprise constituents which are mainly constituted by an organometallic compound of aluminum and a second compound which can be the product of the reaction of metal vapors 1 i ques with a titanium compound and a halogen donor, or a compound of this kind modified by a subsequent reaction with an organometallic aluminum compound or with an alcohol.

In the first case, the catalyst can be represented by a formula such as TilU.m'MX, in which X is a halogen, M a metal chosen from Mg, Al, Ti, Y, Mn,

Cr, Mo, Ca, Zn; n is the valence of M and m 'is equal or * - 20 greater than 1: n. This formula is obtained by a process which consists in vaporizing under vacuum at least one of the metals mentioned above, and reacting the vapors thus obtained with the titanium compound in the presence of a compound capable of giving halogen atoms. As indicated above, a composition of this kind can be used as it is or it can be modified by reacting it with an organometallic aluminum compound, so that a formula of the type is obtained. TiX .mM'Y .qM "Y '.cA1Y" 7 R' / fr 3 nnp 3-ss in which X is a halogen; M 'and M "are metals different from each other and chosen from those mentioned above. Y, Y' and Y" identical, or different from each other, are halogens and, in turn, may be the same as X or different from X; m and q can be 0 or different from 0 but cannot simultaneously be 0; c is always different from 0; n and p are the valences of M 'and M ", respectively; s can take any value between • 0 and 3; R' is a hydrocarbon radical, preferably having a number of carbon atoms less than or equal to 10. As a variant, the catalyst can be the product of the reaction between a titanium compound chosen from halides and alcoholates Vapors of an electro-positive meta 15, having reducing properties, condensed at low temperatures , a halogenated organic compound or a halogenated mineral compound and an alcohol.

As a co-catalyst, in any case, an aluminum derivative before the formula Al R ″, X-, is always used Ρ -> - p se, formula in which R ″ is a carbon radical; 20 ′ X is a halogen, and p 'is a number varying from 1 to 3. In

in addition to the above-mentioned compositions, the catalytic system can be obtained starting from (a) the product of the reaction between a titanium compound chosen from halides and alcoholates, magnesium vapors condensed at low temperature, an organic or inorganic halogen compound and an alcohol, (b) an aluminum-trialbyle and an aluminum hsénénure corresponding to the formula AIR '"gX__ in which X

is Cl or Br, and s ^ is between 0 and 2.

The adoption of the catalytic compositions mentioned above makes it possible to obtain a low density polyethylene and more particularly a linear low density polyethylene by the fact that the polymerization of ethylene takes place in the presence of at least one other alpha-olefin. the number of carbon atoms of which is between 3 and 10. It has been observed that alpha-olefins, particularly butene-1, improve the yield of the catalytic systems used.

Very special advantages have been | obtained using butene-1, hexene-1 and] 'octene-1.

! · 4 i; The final crystalline copolymers have a comonomer content of between 1¾ and 7 mol%, a melting point of between 115 ° C and 130 ° C, a crystallinity (at Xjvariant from 39¾ to 55¾ depending on] a quantity of 5 comonomer which is present, and a melt flow index (according to the method ASTM D-1238) of between! 0.1 and 50 g for 10 minutes (g / 10 min), the density being

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if always less than 0.9450 g / cm and preferably included; I between 0.9150 and 0.9450 g / cm-3.

, J 10 The distribution of the comonomer in the polymer chain varies according to the preparation process used and this fact is proven by the different content of the substances which can; can be extracted with boiling heptane if the density is - the same and the melt flow index is the same.

I ^; The polymerization can be carried out, in any manner I, in suspension, in solution and in the gas phase i. and, if necessary, the reaction medium can be formed; by linear or branched hydrocarbons having 4 to 10 carbon atoms, cyclic hydrocarbons, halogenated hydro-carbides or C4 cuts originating from reforming according to the process to be used.

Also, the process varies markedly depending on the operating mode which is adopted: thus the vaporization in the gas phase is carried out by feeding the above-mentioned catalytic system in a gas mixture consisting of ethylene, a alpha-o] efine, preferably propylene or butene-1, and hydrogen as molecular weight regulator, in variable proportions depending on the product to be obtained, at a temperature which can be chosen from 10 ° C. and 100 ° C, preferably between 60 ° C and 90 ° C, under a pressure between 5 and 50 bars, preferably between 10 and 30 bars. The products thus obtained are characterized by a density comprised between 0.9150 and 0.9450 g / cm 3, and by a content of substances extractable by boiling heptane 35 which goes, for products having the same index melt flow, from 65¾ to 5.9¾.

- The suspension polymerization is carried out in aliphatic hydrocarbon solvents before 4 to 10 carbon atoms, - straight or chain chain, preferably 5! . butane or isobutane, or halogenated hydrocarbons, in! * using as comonomer alpha-olefins having 3 to 10! | carbon atoms, those preferably having 3 to 6 carbon atoms, and any of the catalyst systems described! i! 5 above.

The polymerization is carried out at a temperature which can be chosen between 20 ° C and 90 ° C, preferably between? 50 ° C and 80 ° C, under a pressure between 1 and 60 bars, preferably between 15 and 30 bars. Polymerization can! 10 be performed in a single operation, or in several stages,! . with reactors arranged in series and by supplying the gas phase with a different composition.

The product can be finished either by evaporation of the solvent in the case of low boiling point solvents or by centrifugation and drying of the powder or by rectification.

The products obtained from the one-step process add a new process / having a density of between 0.9150 and 0.9450 g / cm 2 f / w have a level of extractable substances by boiling hep-20 'tane between 43 “and 3rd, while the samples obtained from the two-step process | have a level of extractable substances between 50¾ and 3.5¾.

For the solution polymerization process, it is necessary to operate with solvents whose critical temperature is higher than the polymerization temperature, the latter being chosen between T30 ° and 250 ° C; cyclic hydrocarbons such as cyclohexane and methvl-cyclohexane, and a mixture of normal hydrocarbons and iso hydro-carbides whose boiling point is between 120 ° C. and 180 ° C. have proved to be particularly advantageous in the measurement where they have good dissolving power towards the copolymers to be prepared, the best results being obtained by maintaining the concentration of the polymer in the reaction mixture at a value not exceeding 40% by weight relative to the solvent.

The molecular weight of the copolymers obtained is adjusted in a conventional manner using i · 6 hydrogen in an amount between 0.003 and 0.5. mole per mole of ethylene.

The polymerization can be carried out by introducing into the reaction medium ethylene, hydrogen, an alpha-olefin (C - C.JQ, preferably C6-C10, straight or branched chain I) and a any of the catalytic systems! ques described above, while maintaining the agitation of the reaction mixture in order to promote the elimination of cha- I | their polymerization and to obtain improved homogeneity there 10 of the system. The residence time of the polymer solution can i? vary, depending on the polymerization conditions, from 1 minute to 24 hours, the preferred range being between 5 minutes! nutes and 4 hours, the polymerization pressures are i if i | relatively low and are between 5 and 100 bars.

The copolymers are recovered by removing me-, ·! polymerize the unreacted monomers and solvent, and deactivate the catalytic system with suitable reagents.

The products thus obtained having a density of between 0.9150 and 0.9450 g / cm have a rate of substances extractable by boiling heptane of between 660 and 5%.

In order to highlight the difference between the products which can be obtained with the various processes, Table 1 gives the results concerning the substances which can be extracted with normal heptane (nC7) at the boiling point, as well as some technological properties of the films obtained as a result.

J, j L · - $ t • t 1 7 J TABLE 1 | Example Process Medium Density Tempera- Extrac Index- Rate of j | - revelation of listening comono-! polymerically per mother 4 5 masonry sation C7 ä

melts 98 ° C

! due o T b 'i g / cro0 ° C g / 10min. % by weight ^ 21-operation- I 10 ration J isobu- 0.9210 122 1.2 33.8 6.8 tane i suspension 5 2-operations isobu- syspen- Tane 0.9204 122 1.1 39 ~ 7.0 s ion 6 1-operat ion

Nor.

hexane 0.9215 122.5 0.9 50-, 1 6.2 “u suspension 9 Gas phase ------ 0.9198 121.5 1.3 58 6.9 25 10 ^ clo_ 0.9210 124 1.0 44: 6.0 hexane * *

The present invention is illustrated by the following descriptive and nonlimiting examples.

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8 EXAMPLE 1 I —--! "Preparation of the catalyst ä * A rotary evaporator whose balloon I" is used has a tungsten filament placed in the center, which is "5 wound in a spiral and connected to a source of electricity. Under> | the flask finds a cooling bath arranged horizontally.

! ! By means of a three-way tap, the device is connected

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i | _ vacuum and a nitrogen supply line.

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1 I ·] 0 Around the tungsten resistance which is pro-; ’Suitably teged, a 1 g magnesium wire is wound and introduced into the 500 ml flask, under a nitrogen atmosphere, 250 ml of anhydrous and deaerated heptane, 15 ml; | of 1-chlorohexane, corresponding to 105 millimoles (mM) and ': 1 0.23 ml of TiCl., corresponding to 2.1 mM. Cool the: - flask to -70 ° C, establish a vacuum of 1.33 x 10 “" millibar and heat the tungsten spiral in order to vaporize the metal wound around this spiral. At the end of the vaporization stage , nitrogen is sent to the apparatus and the flask 20 is brought back to room temperature while maintaining the agitation of the mixture, after which the flask is heated for 1 hour at 80 ° C. (catalyst A ).

70 g of polyethylene powder having a set particle size are introduced into a 500 ml flask, dried under vacuum for 30 minutes, after which the flask is filled with nitrogen and, while remaining under a inert atmosphere, the suspension obtained above is introduced into the flask. The solvent is removed in vacuo while stirring: I vigorously by heating the flask to 50 ° C-60cC.

Once the solvent has evaporated, the flask is again filled with nitrogen. The catalyst thus obtained (catalyst B) is a hazelnut-colored powder which does not agglomerate.

The analysis gives: 35 Ti = 0.029 atom-mill igram / g - Mg = 0.552 atom-mi 11 i gram: r and Cl = 1.12 atom-mil 1igram / g.

if /. * _____ '9' EXAMPLE 2

A 5 liter autoclave equipped with an anchor-shaped stirrer is vacuum-purged and charged with 1.3 liters of isobutane, the temperature is raised to 60 ° C., after which 120 g of butene-1 are added , 7 mM aluminum-tri-isobutyl, de | hydrogen under a pressure of 1.55 bar ', ethylene under! ; a total pressure of 15 bars and 0.5 g of catalyst (B) ΐ equivalent to 0.0145 atom-milligrams of Ti.

1 - Maintain the temperature at 60 ° C and feed; 10 in ethylene while keeping the overall pressure constant.

! After polymerization for 2 hours, the reaction | is stopped with 20 ml of ethanol, after which the solvent is; expelled by evaporation. 510 g of polymer are obtained, corresponding. î corresponding to a production of 450 kg of polymer per gram of; ’15 Ti, this polymer having the following specifications:

Itensity 0.9210 g / cm ^

Butene content (NMR) 6.8 l by weight CH ^ / 100 C (number) 1.70! Melt flow index (MF1) at 2.16 kg 1.2 g / 10 min

; 20 Melting point 122 ° C

f X-ray crystallinity 42 I 7: Bulk density at 0.33 g / cm I Average diameter of the powder 350 microns | Extracted by boiling C7 33.8 l 25 EXAMPLE 3

The same apparatus and the same process are used as in Example 2, but with a different amount of butene, that is to say 80 g. 260 g of polymer are obtained, corresponding to a production of 360 kg of nar g of titanium polymer, this polymer having the following specifications:

Density 0.9284 g / cnf ’

Butene content 4.8 i by weight CH ^ / IOO C (number) 1.1 | Melt flow index (MFI) 0.4 g / 10 min 7 * 7 • Bulk density 0.30 g / cm

75 Melting point 124.5 c

„£>" i Ta 10 · '·' * EXAMPLE 4 I * The same apparatus and the same method i i are used as in Example 2, but with an amount of butene-1 equal to 140 g.

5 350 g of polymer are obtained, corresponding to a production of 480 kg of polymer per g of Ti, this polymer having the following specifications: 1 ,; * Density 0.9152 g / cm3

Butene content 10.3 ”by weight 10 CH3 / 100 C 2.5 f - MFI (2.16 kg) 1.2 g / 10 min 1 3! Bulk density 0.25 g / cm

: | Melting point 120 ° C

i ;! Extract with heptane (boiling) 52 I

j! 15 EXAMPLE 5

The same apparatus is used as in Example 2 but with a different procedure, that is to say that I i introduce 1.3 liters of isobutene, which is brought to 60 ° C. / after | 1 which is added 40 g of butene-1.6 mM (millimoles) of aluminum! ;; tri-isobutyl, hydrogen under a pressure of 1.70 barx; i ethylene up to a pressure (total) of 14 bar and 0.5 g of the catalyst (B) of Example 1, which is equivalent to 0.0145 atom-milligrams of Ti. The temperature I is maintained at 60 ° C and ethylene is introduced while keeping the total pressure constant. After 15 minutes of polymerization (approximately 30% of the total polymer are obtained) 140 g of butene are introduced and the polymerization is continued while maintaining the total pressure e at 14 bar by sending

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j ·! . new ethylene.

; After an overall polymerization time of 2:; hours, the polymerization is stopped with 19 circles of ethanol; f after which the solvent is removed by evaporation. We obtain

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320 320 »g of polymer, which corresponds to a production of 445 kg of polymer per g of Ti, this polymer having the prc-; «Following properties: f: ί jf?

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s - • Oi_!; I "., 11 • Density 0.9204 g / cm ^"

Butene content 7.0% by weight j | Melt flow index 1.1 g / 10 min ί 1 »3 | ij Bulk density 0.53 g / cm

N 5 Melting point 122 ° C

, î Extracted by boiling C7 39 ¾ dd EXAMPLE 6 d | A 5-liter autoclave equipped with a stirrer in the form of a Ti anchor is purged under vacuum and loaded with 2 liters and 10 liters of anhydrous and deaerated hexane and brought to 60 ° C., after which one; | ij adds 130 g of butene-1, 6 mM of aluminum-tri-isobutyl,; i of hydrogen at a partial pressure of 2.2 bars, of ethylene under a total gauge pressure of 6 bars / and 0, 5 g of the catalyst (B) of Example 1 corresponding to 0.0145 -15 atom-milligrams of Ti.

The temperature is maintained at 60 ° C and the ethylene is sent while keeping the total pressure constant.

added a ° ng hours / P ° lym ^ rization, the reaction is stopped with 10 cm "5 ethanol, after which the autoclave is allowed to cool, the gases are removed and the polymer suspension is freed of solvents.

The dried polymer, 250 g, corresponding to a production of 350 ikg of polymer per gram of Ti, is a powder which does not agglomerate and shows the following specifications: 25 Density 0.9213 g / cm ~ _

Butene-1 level 6.2 l by weight

Melt melt index 0.9 g / 10 min 3

Bulk density 0.23 g / cm

Extracted by boiling C7 50.1% 30 EXAMPLE 7

The same apparatus and the same process are used as in Example 2, but using anhydrous nor.butane as the reaction medium and the same constituents for the polymerization in the same quantities, so that the overall manometric pressure is 11.5 bars.

280 g of polymer are obtained, corresponding to a ί production of 385 kg of polymer per g of Ti which has the following properties: \ 'k: i 112

Density 0.9215 g / cm3

Butene content 6.5 ç0 by weight ICHj / 100 C (number) 1.65

Mass flow index 5 melt 0.90 g / 10 min 1 X-ray crystallinity 41% | Bulk density 0.34 g / cm3 i y Ί EXAMPLE 8

The same apparatus and the same method are used as in Example 6, but with 300 g of deaerated anhydrous hexene. 240 g of polymer having the specifications i are obtained; '' following: i 7

Density 0.9290 g / cnT

CH ^ / 100 C (number) 0.90 * 15 Hexene content 5.4% by weight

Melt flow index 1.1 g / 10 min

Bulk density 0.25 g / cm '"1: example 9

2 g of the catalyst (B) and 6 atom-milligrams of Al-iso-Bu- dissolved in 15 ml of liquid are introduced into a test tube having a bottom part which has been dried beforehand and placed in an inert atmosphere. hexane, stir with a magnetic stirrer after which the hexane is removed by evaporation, while stirring, until the sample-25

Ion be completely dry.

1 g of the catalyst, equivalent to 0.013 atom - milli-7 - gram of Ti, is introduced under a nitrogen atmosphere into a 2-liter autoclave, equipped with a stirrer, dried and maintained under an inert atmosphere. A vacuum is created in the autoclave to expel the nitrogen, it is heated to 70 C after which a gas stream is introduced having the following composition: ethylene 80% by volume, butene 15¾, -hydrogen 51, under a pressure of 10 bars.

After one hour of polymerization, 100 g of a powder polymer having the following properties are obtained: __: 3_ 9 f ♦ · ji * 13 I Density 0.9198 g / cm3 '1! * j t Rate of butene-1 6.9% by weight 'I MFI 1.30 g / 10 min? |

; 3 »Melting point 121.5 ° C

i 5 Extracted by boiling C7 58 1.

i a: fl II EXAMPLE 10! | A 5 liter autoclave with an agitator is loaded with 2 liters of anhydrous and deaerated cyclohexane j | -. containing 1 millimole of Al (nor.Oct) _, the temperature is raised! ^ ture at 150C after which 100 g of octene-1, of hydro- are added: | gene under a pressure of 0.5 bar, ethylene under a total manometric pressure of 10 bar, and 1.5 cm of catalyst II of the type (A) of example ^ corresponding to 0.01 2 atom - mg of titanium.

|! The pressure is kept constant by sending ethylene i 1 ^ for 30 minutes. Once the polymerization is complete, we | the reaction is stopped, the autoclave is allowed to cool and evacuated; got the gas. The product thus obtained consists of 140 g of polymer, corresponding to a production of 230 kg of polymer per g of titanium.

The polymer thus obtained has the following properties; Density 0.9210 g / cm3

Octene level 7.2% by weight CH ^ lOO C 0.96

Melting point 122 ° C

Melt flow index 1.0 g / 10 min '/ Extracted by C7 (boiling) 44.5% -' S>? t /

Claims (9)

3. Process for the preparation of ethylene copolymers according to the preceding claims, characterized; By bringing ethylene into contact with at least one other alpha-olefin, in the presence of a catalytic system comprising an organo-metallic aluminum compound and a composition chosen from the reaction product of metal vapors with a titanium compound and a halogen donor / or the product obtained from the previous reaction modified beforehand with an organometallic aluminum compound or an alcohol. 4. Process for the preparation of ethylene copolymers according to the preceding claim, characterized in that the catalyst consists of a compound having the formula TiX ^ .m'ND ^ in which X is a halogen; M is a metal chosen from Mg, Al, Ti, V, Mn, Cr, Mo, Ca and Zn; n is 'the valence of M, and m' is at least 1 / n. . 5. Process for the preparation of ethylene copolymers according to claim 3, characterized in that the * catalyst consists of a compound before the formula TiX ^ .mM'Yn.qM "Y'p. CA 1Y "2_SR's in which X is a halogen; M ’and M” are metals different from each other and chosen * r from those mentioned in the preceding claim; Y, Y '35 and Y "identical to each other, or different from each other, are halogens and can be the same as X or different from X; m and £ can be 0 or different from zero, but they 3 g J are not both equal to zero simultaneously; £ is - i% *. 15 j, always different from zero; n and £ are the valences of M ': ί j and M ”, respectively; £ can take a any value j between 0 and 3; R 'is a hydrocarbon radical having a number * of carbon atoms equal to a maximum of 10,! 6. Process for the preparation of ethyl- copolymers; lene according to claim 3, characterized in that the polymerization is carried out by sending a gas mixture comprising ethylene at least one other alpha-olefin and hydrogen. 7. Process for the preparation of copolymers: of ethylene according to the preceding claim / characterized in that the reaction is carried out at a temperature between 20 ° C and 100 ° C, and under pressure between 5 and 50 bars. 8. Process for the preparation of ethylene copolymers according to the preceding claim, characterized in that the reaction is preferably carried out at a temperature between 60 ° C and 90 ° Cret under a pressure between 10 and 30 bars. 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-2ς lene copolymers according to the preceding claim, characterized in that the reaction is carried out in the presence of a solvent chosen from aliphatic hydrocarbons having 4 to 10 carbon atoms or from hydrocarbons halogens. 11. Process for the preparation of ethylene copolymers according to any one of claims 9 and 10, characterized in that the reaction is carried out at a temperature between 20cC and 90 ° C / and under pressure between 1 and 60 bars. 1 12. Process for the preparation of ethylene copolymers according to the preceding claim. Rare characterization that the reaction is preferably carried out at a temperature between 50 ° C and 80 ° Cy and under a pressure 'i between 13 and 30 bars. It is a process for the preparation of copolymers; The ethylene according to claim 3, characterized in that the polymerization is carried out in solution. * 14. Process for the preparation of ί 5 ethylene copolymer according to the preceding claim, characterized 1 il j by the fact that the reaction is carried out at a temperature: I 0 ô, I between 130 Ç and 250 C. 15. Process for the preparation of ethylene copolymers according to any one of claims 13 and 14! ! - 10 characterized in that the reaction is carried out in I | presence of a solvent having a critical temperature which is higher than the polymerization temperature, day 16. Process for the preparation of ethylene copolymers according to the preceding claim, characterized in that the solvent is chosen from cyclic hydrocarbons and mixtures of cyclic hydrocarbons. ; \; ; i? T