摘要:
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).
摘要:
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.
摘要:
Spherical components of catalysts for the polymerization of olefins comprising:(a) a vanadium compound selected from the compounds of formula VOX.sub.2 Y or VX.sub.n Y.sub.n-4n, where X is Cl or Br and Y is Cl, Br OR or NR.sup.I.sub.2(b) MgCl.sub.2 in spherical form.Said components have an average diameter greater than 1 .mu.m, a surface area of at least 10 m.sup.2 /g, a porosity of at least 0.1 g/cm.sup.3 and an X-ray spectrum having particular characteristics.
摘要:
Copolymers of ethylene with comonomers selected from (a) alpha-olefins, (b) cycloolefins and/or (c) dienes, characterized by the fact that:the molar percentage of the comonomer (% .alpha.) and the density of the copolymer (D) satisfy the relation % .alpha.+150D.ltoreq.141.
摘要:
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.
摘要:
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.
摘要:
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
摘要:
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..
摘要:
A process for the preparation of an ethylene/1-butene or ethylene/1-butene/diene elastomer by slurry polymerization of the monomers in a polymerization medium consisting mainly of an excess of the 1-butene maintained in liquid form, performed in the presence of a catalyst based on a metallocene compound of Ti, Zr or Hf. This process is exempt from occurrence of reactor fouling and enables the recovery of the polymer without the use of steam as a stripping agent.
摘要:
Process for gas-phase polymerization carried out in two interconnected polymerization zones, to which one or more null-olefins CH2nullCHR are fed in the presence of catalyst under reaction conditions and from which the polymer product is discharged. The process is characterized in that the growing polymer flows through a first polymerization zone under fast fluidization conditions, leaves said first zone and enters a second polymerization zone through which it flows in a densified form under the action of gravity, leaves said second zone and is reintroduced into the first polymerization zone, thus establishing a circulation of polymer around the two polymerization zones. The novel process allows olefins to be polymerized in the gas phase with high productivity per unit volume of the reactor without incurring the problems of the fluidized-bed technologies of the known state of the art.