Abstract: It is possible to prepare in high yield and purity the racemic and meso forms of bridged chiral metallocenes with a stereoselective method, by synthesizing the sylil-, germyl- or stannyl-substituted ligands. These compounds can be prepared in their racemic and meso forms, and then selectively transformed in the corresponding metallocenes.

Abstract: Embossed sheets having improved grain retention can be made from a polyolefin composition containing a propylene polymer material and a partially crosslinked thermoplastic olefin elastomer composition that includes (1) 20-80 parts by weight of a thermoplastic elastomer containing (a) from 20 to 70% of a propylene homopolymer having an isotactic index greater than 90, or a crystalline propylene copolymer with ethylene and/or a 4-8 C alpha-olefin having a polymerized propylene content greater than 85% and an isotactic index of greater than 85%; (b) from 30 to 75% of an amorphous ethylene-propylene or ethylene-butane-1 copolymer, which is xylene soluble at room temperature and contains from 30 to 70% polymerized ethylene, and (c) from 3 to 30% of a semi-crystalline ethylene-propylene or ethylene-butene-1 copolymer that is xylene insoluble at room temperature and contains greater than 90% polymerized ethylene, and (2) 80-20 parts by weight of an ethylene/propylene/diene terpolymer rubber containing 1 to 10% of a

Abstract: Amorphous propylene polymers are disclosed having the following characteristics:(a) intrinsic viscosity ?.eta.!>1 dl/g;(b) % (r)-% (m)>0, wherein % (r) is the % of syndiotactic diads and % (m) is the % of isotactic diads;(c) less than 2% of the CH.sub.2 groups contained in sequences (CH.sub.2).sub.n, with n.gtoreq.2;(d) Bernoullianity index (B)=1.+-.0.2;(e) melting enthalpy value lower than 10 J/g; and (f) Mw/Mn being less than 5.

Abstract: Catalysts component of the (co)polymerization of alpha-olefins CH.sub.2 .dbd.CHR, wherein R is hydrogen or an alkyl radical having from 1 to 8 carbon atoms, comprising a product of the composition:VCL.sub.y.z(b)wherein (b) represents an organic compound selected from alkyl, aryl and acyl halides, y is a number higher than 2 and lower than 4, and preferably comprised between 2.5 and 3.5 and z is a number higher than zero and lower than or equal to 2, and preferably between 0.002 and 1. Components can be obtained as products of the reaction, carried out at temperatures higher than 10.degree. C., between VCl.sub.4 and the compound (b). Particularly preferred among compounds (b) are benzoyl chloride, p-methoxybenzoyl chloride and p-chloro benzoyl chloride. From the components of the invention, either supported or not, catalysts having high activity particularly useful for the production of ethylene polymers showing broad molecular weight distribution can be prepared.

Abstract: A catalyst for the polymerization of olefins comprises the product obtained by contacting:(A) a titanium, zirconium or hafnium mono- or bis-cyclopentadienyl compound, this latter optionally containing a bridging group which links the two cyclopentadienyl compounds;(B) an alkyl aluminium wherein at least one alkyl is different from a straight alkyl; and(C) water.The molar ratio aluminium/water is higher than 1:1 and lower than 100:1.

Abstract: It is possible to modify the rac/meso ratio of a rac/meso mixture in a stereorigid, bridged metallocene compound by subjecting a rac/meso isomeric mixture directly obtained from the synthesis to selective decomposition of the undesired isomer in the presence of compounds having either acidic hydrogen atoms or reactive halogen atoms. This process allows to prepare chiral metallocenes in their pure racemic or meso isomeric form.

Abstract: Homo- and copolymers of ethylene endowed with very high molecular weights and narrow molecular weight distributions are obtainable by carrying out the polymerization reaction in the presence of a metallocene-based catalyst wherein the metallocene is stereorigid and it is in its meso isomeric form.

Abstract: Polymers and copolymers of propylene are modified by grafting with polyalkenylenes having a trans double bond content of higher than 30%. The preparation is carried out via thermic treatment of the propylene (co)polymer with said polyalkenylene at a temperature comprised between 200.degree. and 350.degree. C. an the presence of a free radical initiator other than peroxide.

Abstract: Catalysts for the polymerization of olefins are disclosed, which comprise the reaction product of:(A) a bridged and/or substituted cyclopentadienyl compound of titanium, zirconium or hafnium;(B) an organometallic aluminum compound of the formula (II):Al(CH.sub.2 --CR.sup.4 R.sup.5 R.sup.6).sub.w R.sup.7.sub.y H.sub.z(II)wherein in the (CH.sub.2 --CR.sup.4 R.sup.5 R.sup.6) groups, which are the same or different, R.sup.4 is an alkyl, alkenyl or arylalkyl group having from 1 to 10 carbon atoms, R.sup.5 is an alkyl, alkenyl, aryl, arylalkyl or alkylaryl group having from 3 to 50 carbon atoms which is different from a straight alkyl or alkenyl group and, optionally, R.sup.4 and R.sup.5 fused together can form a ring having from 4 to 6 carbon atoms, R.sup.6 is hydrogen or an alkyl, alkenyl or arylalkyl group having from 1 to 10 carbon atoms, the R.sup.

Abstract: Thermoplastic polymer compositions are disclosed which comprise the following components:(A) 1 to 99% by weight of an amorphous propylene polymer having the following characteristics:?.eta.!>1 dl/g,% of syndiotactic dyads (r)-% of isotactic dyads (m)>0,less than 2% of the CH.sub.2 groups contained in (CH.sub.2).sub.n sequences wherein n.gtoreq.2,Bernoullianity index=1.+-.0.2; and(B) 1 to 99% by weight of a propylene polymer having an essentially syndiotactic structure, optionally containing from 0.1 to 30% by moles of units deriving from .alpha.-olefins of formula CH.sub.2 .dbd.CHR in which R is an hydrogen atom or an alkyl group having from 2 to 10 carbon atoms.The compositions of the invention are endowed with good elasto-mechanical properties and are suitable for the production of low-temperature-heat-sealing films.

Abstract: Metallocene compounds of a Group 4 or 5 metal having two fluorenyl ligands bridged with a single silicon or germanium atom, said atom having two substituent groups containing a total of at least four carbon atoms, are useful as catalyst components for the polymerization of olefins. Particularly, it is possible to prepare high molecular weight atactic polypropylene with improved yields with respect to the known catalysts.

Abstract: The present invention relates to components of catalysts for the polymerization of olefins comprising the product that can be obtained by bringing a compound of a transition metal M, containing at least one M--.pi. bond, into contact with an olefinic prepolymer obtained by polymerization of one or more olefins with a coordination catalyst comprising a compound of Ti or V supported on a magnesium halide.

Abstract: Fractionable, reactor blend polypropylenes, directly obtainable from the polymerization reaction of propylene, having:(a) content of isotactic pentads (mmmm) comprised between 25 and 85%;(b) ratio M.sub.w,/M.sub.n <5;containing from 10 to 70% by weight of a fraction soluble in boiling diethyl ether, said fraction having a content of isotactic pentads (mmmm) comprised between 5 and 25%, and from 30 to 90% by weight of a boiling n-heptane-insoluble fraction, soluble in xylene at 135.degree. C., said fraction having a content of isotactic pentads (mmmm) comprised between 50 and 99%, are disclosed. These polymers are suitable as thermoplastic-elastomeric materials. A process for the preparation of these polymers and a process for the preparation of 2-aryl-substituted indenyl metallocene ligands is also disclosed.

Abstract: Process for the gas-phase polymerization of ethylene and ethylene mixtures with .alpha.-olefins CH.sub.2 .dbd.CHR in the presence of a high activity catalyst comprising a titanium compound containing at least one Ti-halogen bond, supported on magnesium dichloride in active form said process comprising the steps of: (a) contacting the catalyst component; (b) prepolymerizing ethylene or ethylene mixtures with .alpha.-olefins in order to produce a polymer amount of from approximately 5 g per g of solid component, up to an amount corresponding to about 10% of the final catalyst yield; (c) polymerizing ethylene or ethylene mixtures with .alpha.-olefins in the gas-phase, in the presence of the prepolymer-catalyst system obtained in (b), while maintaining in the gas phase a molar concentration concentration of the alkane comprised between 20 and 90% with respect to the total gases.

Abstract: The present invention relates to spherical solid components of catalysts for the polymerization of olefins comprising, supported on a magnesium dihalide in active form, a titanium compound containing at least one Ti-halogen bond and one OR group, said OR group being bonded to Ti in an amount such that the OR/Ti molar ratio is greater than or equal to 0.5; optionally the component also comprises an electron donor compound. The spherical solid components of the invention are characterized by having a porosity comprised between 0.35 and 0.7 cm.sup.3 /g and by a pore size distribution such that at least 50% of the porosity is due to pores having an average radius greater than 800 .ANG..

Abstract: The present invention relates to components of catalysts for the polymerization of olefins comprising a metallocene compound and a magnesium halide which have particular values of porosity and surface area. In particular the components of the invention have surface area (BET) greater than about 50 m.sup.2 /g, porosity (BET) greater than about 0.15 cm.sup.3 /g and porosity (Hg) greater than 0.3 cm.sup.3 /g, with the proviso that when the surface area is less than about 150 m.sup.2 /g, the porosity (Hg) is less than about 1.5 cm.sup.3 /g. The components of the invention are particularly suitable for the preparation of catalysts for the gas-phase polymerization of .alpha.-olefins.

Abstract: Multi-layer heat-shrinkable films in which at least one layer (A) is based on a polyolefin composition comprising a propylene copolymer and having particular crystallinity characteristics, and at least one layer (B) comprises a linear compolymer of ethylene with one or more .alpha.-olefins (LLDPE). The films are characterized by an optimum balance of physicomechanical properties, processability and sealability at low temperatures.

Abstract: Multistage process for the polymerization of one or more olefins of the formula CH.sub.2 .dbd.CHR, in which R is hydrogen or an alkyl, cycloalkyl or aryl group having from 1 to 10 carbon atoms, comprising:(A) a first stage of polymerization, in which a first olefin polymer is prepared in the presence of titanium catalyst or vanadium catalyst;(B) a treatment stage in which the catalyst used previously is deactivated and in which a metallocene compound is supported on the olefin polymer produced in stage (A); and(C) a second stage of polymerization in which one or more olefins are polymerized in the presence of the product obtained from stage (B).

Abstract: Isospecific and/or syndiospecific catalysts and processes for the propagation of an isotactic and/or syndiotactic polymer chain derived from an ethylenically unsaturated monomer which contains 3 or more carbon atoms or is a substituted vinyl compound. The catalysts comprise a stereorigid, stereodirected and stereolocked metallocene and/or metallocene cation catalysts, characterized by having .beta. stereodirecting substituents and .alpha. stereolocking substituents such that the catalysts have overall either C.sub.s or C.sub.2 (or pseudo-C.sub.s or C.sub.2) symmetry and such that the substituents define the orientation of the growing polymer chain end and resulting in tactioselectivity of successive monomer additions. Methods are also described for the preparation and use of these unique catalysts.

Abstract: Shaped articles for biomedical use characterized by a good transparency and flexibility also at low temperatures are prepared starting from elastomeric copolymers of ethylene with propylene and/or other alpha-olefins having a unique set of mechanical properties and thermoplastic processability. Of particular interest are devices for containing, administering, draining and transport of blood and biological and physiological fluids, syringe seals and similar applications.