MXPA00000269A - Polyolefin compositions and films obtained therefrom - Google Patents

Abstract

Polyolefin compositions comprising from 70 to 99 parts by weight of a composition (A) comprising:(i) from 75 to 95%by weight of a copolymer of ethylene with an&agr;-olefin CH2=CHR, wherein R is an alkyl radical having from 1 to 10 carbon atoms;and (ii) from 5 to 25%by weight of a copolymer of propylene with ethylene and/or an&agr;-olefin CH2=CHR1, wherein R1 is an alkyl radical having from 2 to 10 carbon atoms and from 1 to 30 parts by weight of a polyolefin component (B) comprising crystalline polybutene-1. The polyolefin compositions of the invention are endowed with an improved processability while the films obtained therefrom show improved mechanical properties with respect to those of the prior art.

Description

POLYOLEFINE COMPOSITIONS AND FILMS OBTAINED FROM THE SAME DESCRIPTIVE MEMORY The present invention relates to polyolefin compositions endowed with improved treatment properties. In addition, the present invention relates to films obtained from said compositions showing very good mechanical and optical properties. The compositions according to the present invention comprise a first composition (A) comprising an ethylene copolymer (LLDPE type) and a copolymer of propylene with ethylene and / or an α-olefin CH2 = CHR1, wherein R1 is an alkyl radical having from 2 to 10 carbon atoms, said propylene polymer having a relatively high insolubility in xylene, said first composition (A) being mixed with (B), a crystalline 1-polybutene. Compositions comprising an ethylene copolymer (LLDPE type) and a copolymer of propylene with ethylene and / or α-olefin are already known from WO93 / 03078 and WO 95/20009. Such compositions show improved treatment properties with respect to conventional LLDPE polymers. As a consequence, some of the problems related to the use of LLDPE have been related, such as the need to widen the gap or increase the temperature of the heads of the extruders in order to maintain productivity unaltered.

However, it would be desirable, in order to save energy when the polymer is processed, to have available polyolefin composition, suitable for the preparation of films, which have still improved treatment properties. An improvement in the treatment properties of the LLDPE polymers is generally achieved by mixing them with low density polyethylene (LDPE) obtained by high pressure polymerization. In this way, however, the improvement of the treatment properties is obtained to the detriment of the mechanical properties of the films obtained from these compositions. In effect, said mechanical properties decrease proportionally with the amount of LDPE used. It would therefore be desirable to have polyolefin compositions with improved treatment properties and which are capable, at the same time, of giving films that maintain very good mechanical and optical properties. It has been unexpectedly discovered that compositions obtained by mixing crystalline 1-polybutene with compositions comprising an ethylene copolymer (LLDPE type) and a copolymer of propylene with ethylene and / or an α-olefin are endowed with high processing properties and They are capable of giving films that retain very good mechanical properties. It is therefore an object of the present invention to provide polyolefin compositions comprising from 70 to 99 parts by weight of a composition (A) comprising (i) from 75 to 95% by weight of a copolymer of ethylene with an a- olefin CH2 = CHR1, wherein R is an alkyl radical having from 1 to 10 carbon atoms, said copolymer containing up to 20 mol% of α-olefin and (ii) from 5 to 25% by weight of a copolymer of propylene with ethylene and / or an α-olefin CH2 = CHR1, wherein R is an alkyl radical having from 2 to 10 carbon atoms, said copolymer containing from 80 to 98% by weight of propylene and being characterized by its insolubility in xylene more than 70%; and from 1 to 30 parts by weight of a polyolefin component (B) comprising crystalline 1-polybutene. It is very surprising that, unlike what is observed when LDPE is used, the increase of the treatment properties is obtained, manifested by the reduction of the molten bath pressure in the extruder, without detriment to the mechanical properties of the films. Conversely, the presence of 1-polybutene provides an improvement of the mechanical properties with respect to the film obtained from composition A. The crystalline 1-polybutene used as component (B) of the composition of the invention can be any of the homo- 1-polybutene copolymer with other olefins, having a predominantly isotactic structure. Such polymers are known in the art. The isotactic copolymers of 1-polybutene can be prepared by polymerizing 1-butene in the presence of TiCl 3 -based catalyst components together with alkylaluminium halides (such as diethylaluminum chloride-DEAC) as a catalyst. Copolymers of 1-polybutene can also be obtained by polymerizing the monomers in the presence of a stereospecific catalyst comprising (a) a solid component comprising a Ti compound and an electron donor compound supported on MgCl 2.; (b) an alkylaluminum compound and, optionally, (c) an external electron donor compound. A method of this type is disclosed, for example, in EP-A-017296. Preferably, the 1-polybutene used has an isotacticity (expressed in terms of pentads mmmm%) higher than 80%, more preferably higher than 85% and still more preferably higher than 90%. The melt index (MIÉ) is generally in the range of 0.01 to 100, preferably 0.1 to 50 and more preferably 0.1 to 20. When a copolymer of butene is used with one or more additional olefins, the olefin may be selected preferably from the group consisting of ethylene, propylene, 1-pentene, 1-hexen, 1-ketene. Particularly preferred are random copolymers with ethylene or propylene containing up to 20% by weight of units derived from ethylene or propylene or both. The component (B) in the composition of the invention is present in amounts comprised between 1 and 30 parts by weight, preferably 5 to 25 and more preferably 5 to 20 parts by weight. In component (A) of the present invention, the xylene insolubility of component (i) is preferably higher than 75%, more preferably higher than 85%. The insolubility is determined according to the method described below. Preferably in said copolymer (ii), the propylene content varies between 85 and 96% by weight and the content of ethylene and / or α-olefin varies between 4 and 15% by weight. When the copolymer (ii) is a terpolymer of the ethylene / propylene / α-olefin type, and this constitutes a preferred embodiment, the ethylene content ranges from 2 to 8% by weight while the content of the α-olefin CH2 = CHR1 it varies between 2 and 7% by weight. However, the ethylene content may be higher than that of the α-olefin CH2 = CHR1. The content of the various components is determined by IR and NMR analysis. The α-olefin CH 2 = CHR 1 can be selected, for example, from 1-butene, 1 -hexene, 1-ketene, 4-methyl-1-pentene, and is preferably 1-butene or 1 -hexene. The melting enthalpy of copolymer (ii) is generally higher than 50 J / g, preferably 60 J / g, more preferably higher 70 J / g. The melting temperature of the copolymer (b) is less than 140 ° C and preferably between 120 and 140 ° C. The melt index (determined according to the method ASTM D-1238, condition L) of the copolymer (ii) has values generally varying between 5 and 1000, preferably between 5 and 100, more preferably between 5 and 30. It can be prepared suitably the component (ii) of the polyolefin composition of the invention, using a highly stereospecific catalyst, of the type described in the patent application EP-A-395083. The copolymer (i) used in the component (A) of the invention has a density comprised between 0.88 and 0.945 g / cm3. Preferably, these values are between 0.89 and 0.94, more preferably between 0.90 and 0.935.

The melt index (determined by the method ASTM D-1238, condition E) of the copolymer (i) has values generally comprised between 0.01 and 100 g / 10 minutes, preferably comprised between 0.1 and 10 g / 10 minutes, more preferably between 0.2 and 5 g / 10 minutes. The α-olefin CH2-CHR can be selected, for example, from propylene, 1-butene, 1 -hexene, 1-ketene, 4-methyl-1-pentene; preferably 1-butene or 1 -hexene are used. In the preparation of component (i) of the composition of the invention, even olefins CH2 = CHR can be used as a mixture. The copolymer (i) is prepared by copolymerization of ethylene with an α-olefin CH2 = CHR in the presence of a Ziegler-Natta type catalyst obtained by the reaction of an organometallic compound of a metal of groups II and III of the periodic table with a catalytic component comprising a transition metal belonging to groups IV, V or VI of the periodic table. Preferably, the transition metal compound is supported on a solid carrier comprising magnesium halide in active form. Examples of catalysts usable in the preparation of copolymer (a) are described in the U.S.A. No. 4,218339 and the patent of E.U.A. No. 4,472,520. Catalysts can also be prepared according to the methods described in the U.S. Patents. No. 4,784,221 and 4,803,251. Particularly preferred are catalysts comprising components having regular morphology, for example spherical or spheriform.

Examples of such catalysts are described in patent applications EP-A-395083, EP-A-553805 and EP-A-553806. The polymeric compositions of the invention preferably comprise from about 75 to about 95% by weight of copolymer (i) and from about 5 to about 25% by weight of copolymer (ii); preferably, the content of copolymer (i) is between 75 and 90% by weight and the content of copolymer (i) between 10% and 25% by weight. As explained above, component (i) is preferably a copolymer of ethylene with 1-butene and / or 1-hexene, and component (ii) is preferably a copolymer of propylene with ethylene and 1-butene. In the compositions of the invention, component (A) is preferably present in amounts of 75 to 95 and more preferably 80 to 95 parts by weight. The component (A) of the invention can be prepared by mixing the components (i) and (ii) in the molten state, for example in a single or double worm extruder. The components of the mixture can be fed directly to the extruder or can be remixed in the solid state. Preferably, said component (A) is prepared directly in polymerization by operating at least two reactors in series in which, whatever the order and using the same catalyst in the several reactors, one of the reactors is synthesized copolymer (A ) and in the other reactor the copolymer (b) is synthesized. The polymerization is conveniently carried out in the gas phase, using a fluidized bed reactor. In particular, the component (A) can be prepared directly by polymerization of the monomers in gas phase, in the presence of a catalyst obtained from the reaction between: (i) a solid catalyst component comprising a titanium compound which contains minus a titanium-halogen bond supported on a magnesium halide in active form and optionally an electron donor compound; (ii) an Al-alkyl compound; (iii) optionally, an electron donor compound; operating in two or more reactors in series gas phase in which, in any order and using the same catalyst of the several reactors: (I) in a reactor a mixture of ethylene is polymerized with an α-olefin CH2 = CHR, wherein R is an alkyl radical having from 1 to 10 carbon atoms to obtain a copolymer of ethylene with said olefin containing up to 20 mol% of α-olefin; (II) in another reactor a mixture of propylene, ethylene and / or an α-olefin CH2 = CHR1 is polymerized, wherein R1 is an alkyl radical having from 2 to 10 carbon atoms to obtain the component (i) in amounts between 5 and 25% by weight with respect to the total polymer obtained in (I) and (II). The polyolefin compositions of the invention can be prepared by mixing the components (A) and (B) in the molten state, for example in a single or double worm extruder. The components of the mixture can be fed directly to the extruder or they can be premixed in the solid state. Alternatively, said compositions can be prepared by sequential polymerization operating in at least three reactors in series in which, whatever the order and using the same catalyst in the reactor means, in one of the reactors the copolymer is synthesized (i). ), in another reactor the copolymer (ii) is synthesized, thus obtaining the component (A) and the other reactor the component (B) is synthesized. Also in this case, the polymerization is conveniently carried out in the gas phase, using fluidized bed reactors. The films obtained from the compositions of the invention have impact resistance (Dart test) generally higher than that of the films obtained from the corresponding component (A) alone. In addition, an improvement in the tear strength, determined by the Elmendorf method, is also observed. However, as can be seen from the following examples, greater improvement of the treatment properties of the composition is obtained. In effect, using the compositions of the invention, it is possible to save energy to an extent even higher than 30% with respect to the use of component (A) alone. It is worth mentioning that this improvement of the treatment properties is obtained, without substantial worsening of the mechanical properties. Due to its high characteristics of treatment properties and mechanical strength, the compositions of the invention find applications in various sectors such as: blown films and cast films both single layer and multiple layer; films and coextruded rolled products in which at least one layer consists of the composition of the invention and at least one layer consists of a thermoplastic polymer, such as for example polypropylene homopolymer, copolymers of propylene with ethylene and / or -olefin having 4-12 carbon atoms, such as polyethylene polymers (both LDPE and HDPED), copolymers of ethylene with α-olefin having 3-12 carbon atoms, copolymers of ethylene and vinyl acetate, polyvinylidene chloride; extrusion covers for substrates and electric cables, injection molding; blow molding, thermoforming. The weight ranges described for the components of the present invention relate to the relative weight ratios of the components A [(i) and (i i)] and B. Obviously, according to what is known to the experts in the technique or as can be easily determined by routine tests, additional polymeric components, additives (such as, for example, adhesives, stabilizers, antioxidants, anticorrosion agents, etc.) and fillers, of nature already organic or inorganic can be added , which are capable of imparting specific properties to the films of the invention. The following examples are given to illustrate and not to limit the invention.

Characterization Determination of the isotactic index (mmmm%). Per 13C NMR Measurement is performed by dissolving the sample in C2CI4D2 and recording the spectra at a temperature of 120 ° C with a 500 MHz DRX instrument, operating at 125.7 MHz under proton decoupling in Waltz16 in FT mode, with a spectral width of 10 Khz, 90 ° pulse angle and pulse repetition of 16 seconds and 3600 scans.

Determination of melt index ASTM D 1238, condition "E" Comonomer content Percent by weight of the comonomer determined by NMR spectroscopy. Xylene Insolubility 2.5 grams of copolymer and 250 cm3 of o-xylene were placed in a glass flask equipped with a condenser and magnetic stirrer. The temperature was increased to the boiling point of the solvent for 30 minutes. The transparent solution is thus formed with reflux with stirring for another 30 minutes. The closed flask is then placed in an ice-water bath for 30 minutes and thermostatically adjusted in a water bath at 25 ° C for 30 minutes. The formed solid is then filtered off on filter paper at high cooling speed. 100 cm 3 of liquid obtained by means of the filtration is poured, a container of previously weighed aluminum, which is placed on a hormone to evaporate the liquid under a stream of nitrogen. The container is placed in an oven at 80 ° C and kept under vacuum until a constant weight is obtained. Turbidity: ASTM D 1003: Dart Test: ASTM D 1709; Tear strength of Elmendorf ASTM D 1922, determined in machine direction (DM) as in transverse direction (DT).

EXAMPLE 1 Three polymeric compositions according to the invention were prepared by mechanically mixing the amounts of the component (A) (obtained by sequential copolymerization carried out according to the process described in the procedure in example 3 of WO 95/2009) and the component (B) (random copolymer of 1-butene with ethylene marketed by Shell under the name of PB-8640), presented in table 1. The characteristics of the components used were the following: COMPONENT (A) -MIÉ 0.95 -F / E 30 -Density 0.9187 -% of component (i) 85 -% of component (ii) 15 COMPON ENTE (B) MIÉ 0.8% by weight of C "2 0.75 Density 0.908 The composition was prepared by mixing in an extruder of flag type TR60. The mixture thus obtained was subsequently shaped as a film, through a COLLIN-25 blow-film apparatus. The properties of the films are shown in Table 2.

EXAMPLE 2 Three polymeric compositions according to the invention were prepared by mechanically mixing the amounts of component (A) (obtained by sequential copolymerization carried out according to the procedure described in the procedure in example 3 of WO 95/2009) and the component (B) (1-butene homopolymer sold by Shell under the name of PB-0110), presented in table 1. The characteristics of the components used were the following: COMPONENT (A) -MIÉ 0.95 -F / E 32 -Density 0.917 -% of component (i) 85 -% of component (ii) 15 COMPON ENTE (B) -MIÉ 0.4 -isotactic index (%) 91.

Or a < or THE TABLE 2 01

Claims (23)

NOVELTY OF THE INVENTION CLAIMS

1. - Polyolefin compositions comprising from 70 to 99 parts by weight of a composition (A) comprising (i) from 75 to 95% by weight of an ethylene copolymer with an α-olefin CH2 = CHR, wherein R is a alkyl radical having from 1 to 10 carbon atoms, said copolymer containing up to 20 mol% of α-olefin and (i) from 5 to 25% by weight of a copolymer of propylene with ethylene and / or a olefin CH2 = CHR ?, wherein R1 is an alkyl radical having from 2 to 10 carbon atoms, said copolymer containing from 80 to 98% by weight of propylene and being characterized by its insolubility in xylene of more than 70%; and from 1 to 30 parts by weight of a polyolefin component (B) comprising 1-crystalline polybutene.

2. Polyolefin compositions according to claim 1, further characterized in that the component (B) is present in amounts of 5 to 25 parts by weight.

3. Polyolefin compositions according to claim 2, further characterized in that the component (B) is present in amounts of 5 to 20 parts by weight.

4. Polyolefin compositions according to claim 1, further characterized in that component (B) is 1-polybutene having a predominantly isotactic structure.

5. - Polyolefin compositions according to claim 4, further characterized in that 1-polybutene has an isotacticity (expressed in terms of pentads mmmm%) higher than 80%.

6. Polyolefin compositions according to claim 5, further characterized in that 1-polybutene has an isoctacity higher than 90%.

7. Polyolefin compositions according to any of claims 1-6, further characterized in that 1-polybutene is a 1-butene copolymer with one or more additional olefins.

8. Polyolefin compositions according to claim 7, further characterized in that the olefins are selected from the group consisting of ethylene, propylene, 1-petene, 1 -hexene and 1-ketene.

9. Polyolefin compositions according to claim 8, further characterized in that the olefin is ethylene or propylene.

10. Polyolefin compositions according to claim 7, further characterized in that the 1-polybutene is a random copolymer containing up to 20% by weight of units deriving from ethylene or propylene or both.

11. Polyolefin compositions according to claim 1, further characterized in that the component (A) is present in amounts of 75 to 95.

12. - Polyolefin compositions according to claim 1, further characterized in that the component (A) is present in amounts of 80 to 95 parts by weight.

13. Polyolefin compositions according to claim 1, further characterized in that component (i) has a density of 0.88 to 0.945 g / cm3.

14. Polyolefin compositions according to claim 1, further characterized in that the component (i) has a melting index "E" in the range between 0.01 and 100 g / 10 minutes.

15. Polyolefin compositions according to claim 14, further characterized in that the component (i) has a melting index "E" in the range between 0.1 and 10 g / 10 minutes.

16. Polyolefin compositions according to claim 1, further characterized in that component (i) is selected, the α-olefin between propylene, 1-butene, 1-hexene, 1-ketene, 4-methyl-1-pentene .

17. Polyolefin compositions according to claim 1, further characterized in that the xylene insolubility of component (ii) is higher than 75%.

18. Polyolefin compositions according to claim 1, further characterized in that in said copolymer (ii) the content of propylene varies between 85 and 96% by weight, and the content of ethylene and / or α-olefin varies between 4 and 15% by weight.

19. - Polyolefin compositions according to claim 1, further characterized in that the copolymer (ii) is a terpolymer of ethylene, propylene and an α-olefin and the content of ethylene varies from 2 to 8% by weight while the content of a -olefiona varies between 2 and 7% by weight.

20. Polyolefin compositions according to claim 19, further characterized in that component (i) is a copolymer of ethylene with 1-butene and / or 1-hexene, and component (ii) is a copolymer of propylene with ethylene and 1 -butene.

21. Polyolefin compositions according to claim 19, further characterized in that the α-olefin is 1-butene or 1-hexene.

22. Single or multiple layer films comprising at least one layer of a polyolefin composition according to any of the preceding claims. 23.- Shaped articles that are obtained from the polyolefin compositions according to any of the preceding claims.