NZ201200A

NZ201200A - Ethylene/alpha-olefin copolymers

Info

Publication number: NZ201200A
Application number: NZ201200A
Authority: NZ
Inventors: J P Machon; F Raviola; M Hert
Original assignee: Charbonnages Ste Chimique
Priority date: 1981-07-10
Filing date: 1982-07-07
Publication date: 1986-01-24
Also published as: TR21453A; DD203730A5; FI75581B; ES8400756A1; IL66280A0; IL66280A; FI822421A0; EG15623A; ZA824379B; JPH0448804B2; MA19523A1; IE821656L; DK162940C; FR2509315B1; CS235952B2; KR840000590A; AU8578382A; AR241538A1; ATE18566T1; DK162940B

Description

<div class="application article clearfix" id="description"> New Zealand Paient Spedficaiion for Paient Number £01 200 201 ZOO Priority Date(s): ■ •■■•••■■••••••(•••■■••••■•••■••■•••■a Complete Specification Filed: .. Class: £-.0.if?.. .j,. Q- Publication Date: ..f". P.O. Journal, No: NO DRAWINGS Patents Form No.). Patents Act 1953 COMPLETE SPECIFICATION "HETEROGENEOUS COPOLYMERS OF ETHYLENE FOR MAKING FILMS" WE, SOCIETE CHIMIQUE DES CHARBONNAGES S.A., a company organised and existing under the laws of France, of Tour Aurore - Place des Reflets, F-920&0 Paris La Defense, Cedex 5, France, hereby declare the invention, for which we pray that a patent may be granted to us, and the method b'y which it is to be performed, to be particularly described in and by the following statement:- - 1 - 201 20 0 The invention relates to copolymers and terpolymers of ethylene capable of being made into films, and to a method of production of the said copolymers and terpolymers. The literature offers a great number of examples of copolymers of ethylene and of ano(-olefin. The catalysts capable of polymerizing ethylene are generally capable of copolymerizing ethylene with ano^-olefin. However, the result's, of such copolymerization are very much dependent upon the catalyst employed and above all, as far as the quality of the products is concerned, upon the nature of the «?C-olefin. The copolymers most suitable for making into films are those in which the oL -olefin comprises at least 4 atoms of carbon. P.L.E.&A, U3. 3<><tS<WZ y For such copolymers the F-ron.eh Patent No.l. 604- 9^0 teaches p5n~£^a..c- * I & I ss firstly the importance of a narrow distribution of the molecular masses and secondly the importance of the distribution of the comonomer between the molecules of the copolymer. In considering this latter factor it teaches that homogeneous copolymers offer better properties for the manufacture of films than heterogeneous copolymers. Hence, it is known that a copolymer of ethylene and of an ei.-olefin, intended for a certain method of transformation into a finished object, is fully defined only by giving simultaneously the following seven characteristics: l) the bulk density, 2) the nature of the comonomer, 3) the melt index, 4) the molar content of comonomer, 5) the average molecular weight, 6) the index of polydispersity which measures the distribution of the molecular weights and is defined below, and 7) the index of homogeneity of distribution of the comonomer. - 2 - ao 1-2 oo When in the presence of copolymers which offer equal or equivalent values for six of the seven foregoing characteristics, one fMs distinctly different values with respect to the seventh characteristic, one must expect that these copolymers will have distinctly different aptitudes for a given method of transformation into finished objects, and hence these finished objects also will have distinctly different properties. It has just been discovered that it is possible to obtain heterogeneous copolymers of ethylene and of oC-olefins comprising at least 4 atoms of carbon which, contrary to the F. L. B. & A. U-Ji 36^59^2, ieriEv<£d<^" teachinS tlie Fr°nah Patent Mo. 11 604» 9^0, offer properties GI 8"^ suitable for their transformation into films. In the following description, the word * copolymer' is used to mean both binary polymers comprising one od-olef in and ternary polymers comprising two ot-olefins in addition to ethylene. The present invention also applies to polymers comprising more than two oL -olefins in addition to ethylene. A first object of the present invention consists in the provision of heterogeneous copolymers having a base of' ethylene and of o<L-olefins comprising at least 4 atoms of carbon, capable of being transformed into films which have a. set of properties at least technically equivalent to, and preferably superior to, that of similar or analogous polymers of ethylene. By a "superior set of properties" it must be understood that in the set of properties being considered, not all of the properties are necessarily simultaneously improved, . but certain of these properties are substantially improved for the benefit of the employment of films, the other properties being either simply preserved or reduced without this reduction - 3 - / / > • ~ ": 201200 cancelling out the favourable effects of the first properties. "Similar or analogous polymers of ethylene" means not only those of the copolymers of ethylene the suitability of v/hich for being transformed into films is noted in the literature but also and above all the homopolymers of ethylene known as "low-density polyethylenes" produced by the method under high pressure in the presence of free radical initiators. Other aims of the present invention consist on the one hand of providing films of improved properties manufactured from the said copolymers and on the other hand of a method of production of the said copolymers. The present invention provides copolymers of ethylene pip oa and ofC^-olefin. comprising at least 4 atoms ' J' foP»LyneRj carbon^having a bulk density between 0.905 and 0.940 g/cm , a index between 0.2 and 2 dg/mn, and an average content'of o(. -olefin units between 1 and Bfo by moles; wherein the distribution of the o(-olefin units in the copolymer is heterogeneous, the said copolymer comprising crystalline fractions and amorphous fractions, and the content of -olefin units in the copolymer varying between 0.2 times and 5 times their average content according to said fractions. Preferably, the copolymers in accordance with the invention are such that their crystalline fractions exhibit a single melting peak between 116° and 130° and represent from 20 to 50$ by weight of the total copolymer. Preferably, also the copolymers in accordance with the ion are characterized by an average molecular weight - 4 - PATENT OFFICE 2? OCT 1985 r; EceiVED 01200 of between 15000 and 60000 and/or an index of polydispersity of between 3 and 9 for binary polymers, and between 4 and 12 for ternary polymers. In the foregoing definition, in the way conventional in polymer technique, the average molecular weight must be understood as being the number average molecular weight Mn, and the index of polydispersity as being the radio Mw/Mn of the weight average molecular weight to the number average molecular weight. The o(-olefins which may enter •" r into the constitution of the heterogeneous" copolymers in accordance with the invention are, for example, butene-1, hexene-1, methyl-4,pentene-l, octene-1. When twoo^-olefins are simultaneously present in the copolymer according to the' invention (i.e. terpolymer) , their total .average content lies, as described hereinabove, between 1 and 8?o by moles, and, moreover, the ratio between their respective average contents is preferably between 0.25 and 4. Thus, for example, a terpolymer ethylene/butene-l/hexene-1 according to the invention comprising, as an average proportion, 95 mole percent of ethylene units, will comprise an average content of 1 to 4 mole percent of butene-1 units and an average content of 4 to 1 mole percent of hexene-1 units. The copolymers in accordance with the invention, thus defined, are endowed with remarkable properties and are capable of being transformed into films having a set of properties technically superior to the polymers of ethylene at present recognized as able to be made into films. The chief improved properties are the elongation at break and the resistance to tearing. Thus the copolymers in accordance with the invention generally exhibit for a film of 50 Urn thickness, an elongation 2 012 00 at break between about 600$ and 1100$, a resistance to tearing (measured in accordance with the standard ASTM D 1922-67), between approximately 150 and 900 grammes (depending upon whether in the longitudinal sense or in the transverse sense), an industrial stretchability less than or equal to 10 microns under the conditions of measurement specified in the examples below, a gloss (measured in accordance with the standard ASTM D-2457) higher or equal to 70$, and an impact resistance (measured in accordance with the iandard NF T 54 109) of up to 400 grams. It should be observed that as far as the properties in the longitudinal sense are concerned, the thickness of the test sample must always be stated because these , properties increase considerably when the thickness increases. The present invention also provides a process for producing copolymers according to any one of claims 1-7 consisting of copolymerizing ethylene and ol_-olefins having at least 4 atoms of carbon in at least one reactor including at least one zone, at a temperature between 160° and 320°C and under a pressure between 300 and 2500 bars, by means of a catalytic system of Ziegler type comprising an activator selected from the hydrides and the organometallic compounds of the metals of groups I to III of the Periodic Table and at least one halogenated compound of transition metal, the atomic ratio of the metal of the activator to the transition metal lying between 1 and 10 and the average dwell time of the catalytic system in the polymerization reactor being between 2 and 100 seconds; wherein the flow of gas feeding the reactor consists of steady operation of 10 to 80$ by weight of ethylene and of 20 to 90$ by weight of o(.-olefin, and the catalytic - 6 - 2131 system exhibits a reactivity, with respect to the ethylene which is very much higher than its reactivity with respect to the cC~olefin. A non-restrictive example of such compounds has the formula: (TiCl3,l/3AlCl3) (MX3) x (MgCl2)y in. which 0.3^: x —3> 0^ y 1=z 20, M is a transition metal ■v selected from groups VB, V1B and VIII in the Periodic Table and X is. a halogen. When the metal M is selected from groups VB and VIB, then these catalysts have a Ti-M binary solid solution-structure which may be characterized by the dimension - of its crystallites. It has been found that from the point of view of the efficacy .of these catalysts, this dimension, - determined by the method of radiocrystallographic analysis (Sherrer's Law) in the direction perpendicular to the ]3ane (300) o must be preferably less than or equal to 100 angstroms (A). As may be understood from their developed formula, these catalysts may if the occasion arises (when y^O) be attached to an inert support consisting of an anhydrous magnesium halide. Amongst the metals M, vanadium chromium and nickel are preferred but molybdenum and tungsten may be employed. The halogen in the magnesium halide and that in the halide of the metal M may be identical or different and are chosen from fluorine, chlorine, bromine and iodine. A method of manufacture of such compounds consists of contacting titanium trichloride syncrystallized with aluminium chloride, the halide of the metal M, and eventually the anhydrous magnesium halide, for a sufficient period of time. This may be - 7 - 201200 obtained efficiently by subjecting the aforesaid halides to a grinding stage in which the grinding energy should be at least equal to 3kWh per kg of solid matter treated. More precisely, it has been observed -that the efficacy of these compounds is the greater, the higher this energy of grinding.. However, in order to bring this efficacy to an optimum, taking into account the operative cost and the necessity of economizing power, it is generally unnecessary for the grinding energy to be higher than about 25 kWh per kg of solid matter treated. * The proportions of the activator and of the halogenated compound of transition metal will be chosen so that the atomic ratio of the metal of the activator to the transition metal (or, in the case described above to the sum : Ti + M) lies between 1 and 10. The average dwell time of the catalytic system in the polymerization reactor generally lies between 2 and 100 seconds. This dwell time depends upon the temperature in the reactor in the sense that it is the longer, the lower-the temperature. The preferred activators are firstly the trialkyl .aluminiums and secondly the alkylsilosalanes such as those described in the U.S.Patent No.3.969.332. The composition of the flow of gases feeding the reactor in steady operation which characterizes the method of the invention, must be understood as an average composition over the whole of the reactor, it being clearly understood that this composition is not uniform and. may vary along the reactor, particularly when the latter includes several zones. This composition varies in accordance with the nature of the -olefin being considered. Thus for a binary polymer the content by weight of°C-olefin in this flow of gas preferably - 8 - 201200 lies between 15 and 70$ for butene-1 and between 35 and 90$ for hexene-1. When the reactor used in the process according to the invention comprises several zones, it is often preferred to inject substantially all the o(- olefins into the first zones, which operate at temperatures between 1#0° to 2LQ °, whereas the last .zone operates at a temperature between 240° and 320° without substantial complementary injection of ^(.-olefins. The method in accordance with the invention is carried out continuously in an autoclave of in tubular reactors as is known in the technique of polymerization of ethylene under high pressure. In order to control accurately the melt index of the copolymer it may also be advantageous to carry out the copolymerization in the presence of up to 2/o by moles of hydrogen. As indicated previously the heterogeneous copolymers in accordance with the invention find are especially suitable for the manufacture of films of improved performance and of thickness between 5 and 200 microns, in particular less than or equal to 20 microns, i.e. less than that of low-density polyethylene films obtained by a process involving radicals. These films are obtained in accordance with the customary techniques of either extrusion-blowing with a blow ratio between 1.5 and 4, or extrusion through a flat die, and offer the exceptional advantage of providing the same wear and the same solidity as films of radical polyethylene with a much lower weight. Films thus obtained have numerous uses e.g. bags of high capacity, rigid films for automatic packing, and agricultural films. The following examples are given by way of illustration / - 9 - 2 012 0 0 and are not intended to restrict the invention. EXAMPLE. 1 Ethylene and hexene-1 are copolymerized in an autoclave reactor of cylindrical shape operating under a pressure of 1000 bars and equipped internally with a stirrer and metal screens which define three zones of identical volume. Zone 1, kept at a temperature of 220°C and fed by a flow of 49 kg/h ' of hexene-1 and of 24 kg/h of ethylene, receives a catalytic system comprising dimethyl ethyldi ethyl siloxal ane anda compound of formula: TiCl3, 1/3A1C13, 2YC13 in amounts respectively such that the atomic ratio.Al/Ti is equal to 3« The zone 2 kept at a temperature T^ (expressed in °C) is fed by a flow of 24 kg/h of ethyleneand receives the same catalytic system as previously. Finally the zone 3, at the output from which the mixture from the reaction, containing the copolymer, is discharged towards a separation and recycling device, is kept at the temperature T3 (expressed in °G) and receives neither monomer nor catalyst. Hence the average content by weight of hexene-1 in the reactor is.50c5$-The copolymerization is carried out in the presence of 0.12$ by moles of hydrogen. The average dwell time of the catalytic system in the reactor is equal to 80 seconds. The copolymer obtained is characterized by the following properties: a) Melt index (MI) measured in accordance with .the standard ASTM D 123&-73 expressed in dg/min. - 10 - -.a 20120 0 b) Bulk density P expressed in g/cm . : ) c) Number average molecular weight Mn measured by gel-permeation chromatography and expressed in thousands. d) Index of polydispersity determined from Mn and from the weight average molecular weight Mw measured in accordance with the same method.. e) Average content of hexene-1 units in the copolymer, expressed in molar percent and determined from the proportion of methyl groups per 1000 atoms of carbon in the molecule, by analysis of the absorption of infrared P. L. B. & A. radi^ion in accordance with the standard ASTM D 2238-64 T -described in the Fronoh Patent No. 1: 604' 9&0 c2(13 j (O f) Index of homogeneity (IH) in the distribution of the comonomer, determined by a fractionation test of the polymer and expressed as multiple and sub-multiple of the average content between which the content of hexene-1 units varies. g) Melting point (MP) of the crystalline fraction of the copolymer, expressed in °C and determined by differential enthalpic analysis. The values of these properties are assembled with the values of T^ and T^ in Table I below. EXAMPLE 2 Ethylene and hexene-1 are copolymerized, the pressure being - kept at 1000 bars in the same reactor in Example I and under identical conditions apart from the following exceptions:-Zone 1 is fed by a flow of 6l Kg/h of hexene-1 and 25 Kg/h of - - 11 - Z 012 00 ethylene; and Zone 2 receives a flow of 25 Kg/h of.ethylene. Hence the average content by weight of hexene-1 in the reactor is 55$. The copolymerization is carried out in the absence of hydrogen. The catalytic yield Rc expressed in kilogrammes of copolymer per milliatom of transition metal, as well as the properties of the copolymer obtained, appear in Table I below. EXAMPLE 3 Ethylene and hexene-1 are copolymerized, the pressure being kept at 600 bars in the same reactor as in Example I and under identical conditions apart from the following exceptions:-' The zones 1 and 2 are each fed with a flow of 27-5 kg/h of ethylene and 2S.5 kg/h of hexene-1. Hence the average content by weight of. hexene-1 in the reactor is 50.9$. The copolymerization is carried out in the presence of 0.06$ by moles of hydrogen. The catalytic yield and the properties of the copolymer obtained appear in Table I below. TABLE I Example T 2 T3 ■ Rc MI i : ^ : V; 1 225 270 5,1 0,6 0,929 2 210 255 7,6 0,9 0,920 : 3" 220 245 6,1 1,2 0,934 - 12 _ 201200 TABLE I (continuation) Exaimpl e Mn Mw/Mn • Hexene-1 IH MP 1 21,3 7,5 !,7 0,36-3,4 126 2 46,4 3,4 4,5. 0,22-1,6 125 3 id ,6 S,2 2,0 0,20-2,5 127 EXAMPLE 4 - Ethylene and octene-1 are copolymerized, the pressure being kept at 1000 bars in the same reactor and under the same conditions as in Example 3, apart from the following exceptions:-the zones 1 and 2 are each fed with a flow of 24 kg/h of ethylene and 29 kg/h of octene-1. Hence the average content by weight of octene-1 in the reactor is 55%. The copolymerization is carried out in the absence of hydrogen, the temperatures in the zones 2 and 3 being respectively Tg = 200 °C and T^ =-250°C. The copolymer, obtained with a catalytic yield R = 7 kilogrammes per milliatom of transition metal, has the 0 following properties: M.I. = 0.25 £ = 0.933 g/cm3 Mn ' =57-000 Mw/Mn =3-3 Octene-1 = 1.1$ (Moles) MF = 127°C EXAMPLE 5 Ethylene and butene-1 are copolymerized in an autoclave reactor - 13 - 2 01200 of cylindrical shape operating under a pressure of 900 bars and equipped internally with a stirrer and metal screens which define three zones. Zone 1 is kept at a temperature of 210°C, has a volume double that of each of the two following zones, is fed with a flow of 200 kg/h of a mixture comprising 36$ by weight of butene-1 and 64$ by weight of ethylene and receives a catalytic system comprising dimethylethyldiethyl'siloxalane and a compound of formula:. TiCly 1/3A1C13, VC13 in amounts respectively such that the atomic ratio Al/Ti is equal to 3« The zone 2 kept at the temperature of 240°C, is fed with a flow of 55 kg/h of the same mixture as previously, and receives the.same catalytic system. Finally the zone 3 at the output from which the reaction mixture containing the copolymer is discharged towards a separation and recycling device, is kept at the temperature of 2$0°C and receives neither monomer nor catalyst. The average dwell time of the catalytic system in the reactor is equal to 43 seconds. The catalytic yield as well as the properties of the copolymer obtained appear in Table II below. EXAMPLE 6 Ethylene, butene-1 and hexene-1 are terpolymerized, in the absence of hydrogen, in the reactor described in Example 1 operating under a pressure of 1000 bars. Zone 1, maintained at a temperature of 1&0°C and fed by a flow of 13 kg/h of hexene- - 14 - 20120 14 kg/h of ethylene and 6 kg/h of butene-1, receives a catalytic system comprising dimethylethyldiethylsiloxalahe and a compound of formula: TiCl3, 1/3 AlCl^, 6 MgCl2, 1/2 NiCl2 in amounts respectively such that, the atomic ratio Al/Ti is equal to 3• The. Zone 2, maintained at a temperature of 225°C, is fed by a flow of 14 kg/h of ethylene and 6 kg/h of butene-1 and receives the same catalytic system. Finally the zone 3, at the output from which the reaction mixture comprising the terpolymer is discharged towards a separation and recycling device, is maintained at the temperature of 245°C and receives neither monomer nor catalyst. Hence the average contents by weight in the reactor are 53$ for ethylene, 24$ for hexene-1 and 23$ for butene-1. The average dwell time of the catalytic system in the reactor is equal to 85 seconds. The catalytic yield as well as the properties of the terpolymer obtained appear in Table II below. EXAMPLE 7 Ethylene, butene-1 and hexene-1 are terpolymerized, in the presence of 0,15$ by moles of hydrogen, in the reactor described in Example 1 operating under a pressure of 800 bars. Zone 1,' maintained at a temperature of l80°C and fed by a flow of 27.1 kg/h hexene-1, 18.4 kg/h ethylene and 1.6 kg/h butene-1, receives the catalytic system described in example 5*' Zones 2 and 3, respectively maintained at temperatures of 220°C and 260°C, are each fed by a flow of 18.4 kg/h ethylene and 1.6 kg/h butene-1. The average dwell time of the catalytic system in the reactor is equal to 100 seconds. The catalytic yield as - 15 - 2 012 '0 $ well as the properties of the terpolymer obtained appear in Table II below. EXAMPLE 8 Ethylene and butene-1 are copolymerized, in the presence of 0.1% by moles of hydrogen, in the reactor described in Example 1 which is fed by a flow of gas consisting of 35% by weight of ethylene and 65% by weight of butene-1. Zones 1, 2 and 3 operate at temperatures of respectively 200°C, 210°C and 235°C and the catalytic system used is that described in Example 1. The average dwell time of the catalytic system in the reactor is equal to 45 seconds. The catalytic yield as well as the properties of the copolymer obtained appear in Table II below. TABLE II Example Rc Mi e Mn VMn " 5 6,2 . 0,8 0., 919 43 3,6 . ' 6 - 4,5 0,5 0,915 1-5 ' i°, 5 7 .4,9 0,6 0,933 ■ 21,5 7,6 8 6,8 0,8 0,908 25 ■: 5,4 -It- 201200 TABLE II (Continued) Example Butene-1 Hexene-1 IH F 5 3,2 - 0,5-2,2 122 6 2,6 °,9 0,3-3,0 121 7 0,4 1>3. . 0,2-1,8 128. 8 6,0 - 0,5-2,0 ■ 117- EXAMPLES 9 to 14 The copolymers from Examples 1 to 3, 4, 5 and 7 are transformed by extrusion-blowing into films of thickness 50 Um under the following conditions: temperature of the resin: 230°C . speed of ratation of the extrusion screw: 80 r.p.m. . - degree of inflation: 2.0 The properties that are measured on these films are: a) The elongation at breaking AR (expressed in °/o) in the longitudinal, sense L and transverse sense T, determined in accordance with the standard ASTM D 882-67; b) The resistance to tearing RT (expressed in grammes) in the longitudinal sense L and transverse sense T, determined in accordance with standard ASTM D 1922-67. - 17 - 2 012 0 The results of these measurements appear in Table III in which it must be understood that the Examples 9 to 11 correspond respectively to the copolymers of Examples 1 to 3» and the Examples 12 to 14 correspond respectively to the copolymers of the Examples 4, 5 and 7. TABLE III Example ? 10 11 12 13' 14 L . 750 635 635 630 910 760 A.R T 860 805 610 660 1060 850 L RT T 190 ■ 775 680 900 160 430 150 500 300 64O 200 440 Moreover the film of example 10 shows an impact resistance (measured according to standard NF T 54 109) equal to 300 grams. All of the copolymers studied above exhibit ah industrial. stretchability, defined as the thickness of film which envies continuous manufacture by extrusion-blowing for a period of 2 hours without disturbance, equal to 5 Um. EXAMPLE 15 The copolymer of example 8 is transformed by extrusion-blowing, under the conditions described hereinabove, into a film 50 microns thick. The following properties are measured on this film: impact resistance : 400 grams longitudinal resistance to tearing : 600 grams transverse resistance to tearing:- $00 grams - 18 - </div>

Claims

<div class="application article clearfix printTableText" id="claims"> 201200 EXAMPLE 16 The optical properties of the films obtained in examples 10, 13 and 14 were measured: gloss (according to the standard ASTM D-2457) and haze (according to the standard ASTN D-1003). These properties, expressed in percentage, show the values indicated in Table IV. TABLE IV Film Ex.10 Ex. 13 ; Ex.14.., Gloss 95 80 Haze 10,5 IS' - 19 - 201200 WHAT WE CLAIM IS: I

1. Copolymers of ethylene and ofod-olefin "• B. & A. t o n«r r-S comprising at least 4 atoms of carbonT") having a bulk density P«r ^ / ^between 0.905 and 0.940 g/cm3, a melt index between 0.2 and 2 dg/mn, and an average content ofo6-olefin units between 1 and 8fo by moles; wherein the distribution of theoC-olefin units in the copolymer is heterogenous, the said copolymer comprising crystalline fractions and amorphous fractions, and the content of oL-olefin units in the copolymer varying between 0.2 times and 5 times their average content according to said fractions.

2. Copolymers according to Claim 1, wherein the crystalline fractions exhibit a single melting peak between 116° and 130°C and represent from 20 to 50fo by weight of the total copolymer.

3. Copolymers according to either of claims 1 and 2, wherein their average molecular weight lies between 15000 and 6000C

4. Copolymers according to any one of claims 1 to 3, wherein said copolymers comprise a single o£-oleiin and the index of polydispersity lies between 3 and 9.

5. Copolymers according to any one of claims 1 to 3, wherein said copolymers comprise two °(-olefins and the ratio (fotntMT between their respective averageNis between 0.25 and 4.

6. Copolymers according to claim 5, wherein their index of N.2. PATENT OFFfCE , —— p-oiryd 2 9 OCT 1985 RECEIVED Lspersity is between 4 and 12. - 20 - 201200 i

7. Copolymas according to any one of claims 1 to 6, wherein the oC-olefiris are selected from butene-1, hexene-1, methyl-4-pentene-1 and octene-1.

8. Application of copolymers according to any one of claims 1 to 7 to the manufacture of films having a thickness between 5 and 200 microns.

9. A process for producing copolymers according to any one of claims 1 to 7 consisting of copolymerizing ethylene and oi. -olefins having at least 4 atoms of carbon in at least one reactor including at least one zone, at a temperature between l80° and 320°C and under a pressure between 300 and 2500 bars, by means of a catalytic system of Ziegler type comprising an activator selected from the hydrides and the organometallic compounds of the metals of groups I to III of the Periodic P. L. B. & A. ^ Table and at least one halogenated compound of^transition metal, the atomic ratio of the metal of the activator to the transition metal lying between 1 and 10 and the average dwell time of the catalytic system in the polymerization reactor being between 2 and 100 seconds; wherein the flow of gas feeding the reactor consists of steady operation of 10 to BOfo by weight of ethylene and of 20 to 90$ by weight of °£-olefin, and the catalytic system exhibits a reactivity with respect to the ethylene which is very much higher than its reactivity with respect to the oC-olefin. i©v<t A process according to claim 9, wherein the ratio of N.Z.

PATDjJ 0:-F;"g reactivity of the catalytic system with respect to the ethylene 15 AUG 1985 - 21 - 20!200 to its reactivity with respect to the ©(.-olefin lies between 5 and 15.

11. A process according to claim 9 or claim 10,wherein the halogenated compound of transition metal has the formula: (TiCl3, 1/3 A1C13) (MX3)* (MgCl2)Y;in which 0.3 x "^3, 0 — Y — 20, Misa transition metal selected from groups VB, V1B and VIII of the Periodic Table and X is a halogen.;12. A process according to any one of Claims 9 to 11 wherein the reactor comprises several zones and substantially all the o(,-olefins are injected in the first zones operating at temperatures between 1$0° and 240°C, and the last zone operates at a temperature between 240° and 320°C without substantial complementary injection of o(.-olefins.;13. A process according to any one of claims 9 to 12, wherein the activator is selected from trialkyfeluminiums and alkylsiloxalanes.;14. A process according to any one of claims 9 to 13, wherein copolymerization is effected in the presence of up to 2fo by moles of hydrogen.;15. A process according to any one of claims 9 to 14,;..wh.e.r.eijp the o(,-olefin is butene-1 and the flow of gas feeding;T; );t'lTe-"reactor comprises, in steady operation, from 15 to 70$;f by weight butene-1.;1200;16. A process according to any one of claims 9 to;14, wherein the <3(.-olefin is hexene-1 and the flow of gas feeding the reactor comprises, in steady operation, from 35 to 90$ by weight hexene-1.;17. A copolymer of ethylene and o^-olefin, substantially as hereinbefore described with reference to any one of the Examples.;18. A process for producing copolymers as claimed in Claim 1 and substantially as hereinbefore described, with reference to any one of the Examples.;SOCIETE CHIMIQUE PES CHARBONNAGES S.A. by their authorised agents:;P.L.BERRY & ASSOCIATES;per: If;,•j'-V-"VT.;-•7 v w--< i: .;' \\ .■ . :;' V: : ■. V'-v* V: ■'■■ ■ '■ Q'H1 ■ v- ' - 23 - - - — </div>