Abstract: A polymerization process may include: polymerizing a monomer having 4 or less carbons and a comonomer having 6 or more carbons in the presence of an inert isomer/saturate of the comonomer to yield a product stream comprising a polymer, unreacted monomer, unreacted comonomer, and the inert isomer/saturate of the comonomer; separating the product stream into (a) a polymer stream and (b) an unreacted components stream; and separating the unreacted components stream in a distillation column into (a) an overhead stream comprising the unreacted monomer and (b) a bottoms stream comprising the comonomer and the inert isomer/saturate of the comonomer, wherein a concentration of C5? hydrocarbons in the overhead stream is higher than a concentration of the C5? hydrocarbons in the unreacted components stream, and wherein a concentration of C6+ hydrocarbons in the bottoms stream is higher than a concentration of the C6+ hydrocarbons in the unreacted components stream.

Abstract: The present invention relates to an inner-plasticized vinyl chloride-based copolymer resin not requiring plasticizers and a preparation method thereof. Specifically, the vinyl chloride-based copolymer resin is prepared by a suspension polymerization method of initiating the polymerization of vinyl chloride monomer, feeding a certain amount of butyl acrylate continuously or discontinuously thereinto and carrying out the additional polymerization at the temperature higher than the polymerization initiation temperature so as to prepare a core-shell type vinyl chloride-based random copolymer resin. The vinyl chloride-based copolymer resin of core-shell structure prepared by the present invention includes vinyl chloride-butyl acrylate copolymer, and it can provide a vinyl chloride-butyl acrylate copolymer product which can be processed without plasticizers positively necessary to produce a soft product.

Abstract: The present invention relates to a process for preparing a bimodal polyethylene product in a single loop reactor, comprising polymerizing ethylene monomer and optionally one or more olefin co-monomers in the presence of a single heterogeneous polymerization catalyst consisting of a metallocene-alumoxane catalyst immobilized on a porous support wherein said metallocene comprises only one transition metal. Said polymerization catalyst consists of two physically different fractions of support particles onto which said metallocene-alumoxane catalyst is immobilized.

Abstract: The invention relates to a process for the preparation of a particulate bimodal polyethylene product having a median particle diameter of less than 300 ?m in a serially connected double loop reactor, wherein said polymerization catalyst applied in the polymerization process comprises a particulate metallocene-alumoxane catalyst immobilized on a porous silica support, wherein said polymerization catalyst has a median particle diameter of less than 50 ?m; and whereby the ratio of the median particle diameter of the obtained bimodal polyethylene product to the median particle diameter of the applied polymerization catalyst is less than 30.

Abstract: A process for producing high-quality polymer microparticles having uniform particle size of the order of several micrometers to tens of micrometers by inverse suspension polymerization at high productivity while keeping excellent dispersion stability without causing aggregation among particles. The inverse suspension polymerization involves a vinyl monomer and is performed in at least two steps. A water-soluble oxidizing agent and a water-soluble reducing agent are used as a polymerization initiator, and the water-soluble reducing agent is fed after the water-soluble oxidizing agent is fed.

Abstract: In the present invention, a tubular flow reactor can maintain a plug flow property even though the tubular flow reactor is downsized, and provided is the tubular flow reactor with which uniform resin fine particles exhibiting a narrow particle size distribution and a narrow molecular weight distribution can be prepared when the tubular flow reactor is used for preparation of the resin fine particle via emulsion polymerization or the like. Disclosed is a tubular flow reactor possessing a stirring blade and a cylindrical channel, wherein a ratio d/D is 0.3-0.9 when a diameter of the stirring blade is represented by d and an inner diameter of the cylindrical channel is represented by D, and a ratio Lb/La is 0.80-0.99 when a length of the stirring blade is represented by Lb and a length of the cylindrical channel is represented by La.

Abstract: Process comprising polymerizing in a loop reactor of a continuous tubular construction an olefin monomer optionally together with an olefin comonomer in the presence of a polymerization catalyst in a diluent to produce a slurry comprising solid particulate olefin polymer and the diluent, wherein the average internal diameter of at least 50% of the total length of the continuous tubular loop reactor is at least 700 mm wherein the HMW polymer is produced in a reactor upstream of the LMW polymer reactor and the ratio of the average internal diameter of the HMW reactor to the average internal diameter of the LMW reactor is between 0.8 and 1.4.

Abstract: A process comprising polymerising in a loop reactor of a continuous tubular construction an olefin monomer optionally together with an olefin comonomer in the presence of a polymerisation catalyst in a diluent to produce a slurry comprising solid particulate olefin polymer and the diluent wherein the average internal diameter of at least 50% of the total length of the reactor is at least 650 millimeters, the solids concentration in the reactor is at least 15 volume % and having a particle size distribution such that (D90?D10)/D50 is less than 2.

Abstract: A process for controlling a slurry phase (co-) polymerisation process in the presence of a polymerisation catalyst, which comprises maintaining the density SPAN of the polymer powder particles (defined as the absolute value of the density difference in g/cm3 between the average density of the polymer particles exiting the reactor with particle size above D90 and the average density of the material with particle size below D10) below 0.005, preferably below 0.003, more preferably below 0.0026, most preferably below 0.0023.

Abstract: Rubber composition based on at least one diene elastomer, a polymeric filler as reinforcing filler and a coupling agent for bonding between the polymeric filler and the elastomer. The polymeric filler includes nanoparticles of a polyvinylaromatic (PVAr) carrying a functional group denoted by Z of formula a ?Si—X, X representing a hydroxyl or hydrolyzable group. The PVAr is especially a copolymer of styrene, ethylvinylbenzene, divinylbenzene and trimethoxysilylpropylacrylate or trimethoxysilylpropylmethacrylate, being in the form of nanobeads, the diameter of which is between 10 and 100 nm. Also described is a method of obtaining such a composition, and use of such a rubber composition for the manufacture of rubber articles, in particular tires or rubber semi-finished products intended for these tires, as well as a masterbatch including at least one diene elastomer and such a polymeric filler, and a method of obtaining such a masterbatch.

Abstract: A process for the polymerisation of olefins is disclosed wherein at least part of a stream, preferably a catalytically active stream, withdrawn from a polymerisation reactor is passed through a fractionator so as to remove hydrogen and active fines.

Abstract: A process for the polymerisation of olefins is disclosed wherein at least part of a stream, preferably a catalytically active stream, withdrawn from a polymerisation reactor is passed through a fractionator so as to remove hydrogen and active fines.

Abstract: Process for polymerising an olefin monomer in at least one continuous tubular loop reactor of a multiple reactor system, optionally together with an olefin comonomer, in the presence of a polymerisation catalyst in a diluent, to produce a slurry containing solid particulate olefin polymer and diluent. The average internal diameter of at least 50% of the total length of the continuous tubular loop reactor is at least 700 mm. A high molecular weight (HMW) polymer is made in a first reactor and a low molecular weight (LMW) polymer is made in a second reactor, the first (HMW) reactor having a space time yield (defined as production of polymer in kg/h per unit volume of reactor) greater than 100 kg/m3/h, and the ratio of space time yield in the first (HMW) reactor to the second (LMW) reactor is greater than 1.

Abstract: The present invention discloses an olefin polymerisation process carried out in the presence of a Ziegler-Natta catalyst in two liquid full loop reactors connected in series wherein different molecular weight fractions are produced to form a polyolefin, said process being characterized in that the Ziegler-Natta catalyst has a particle size distribution d50 of less than 20 ?m and greater that 5 ?m.

Abstract: The present invention relates to a polyethylene resin comprising A) a first ethylene homo- or copolymer fraction, and B) a second ethylene homo- or copolymer fraction, wherein fraction (A) has a lower molecular weight than fraction (B), characterized in that the polymer resin powder obtained directly after the final polymerisation step has a particle size distribution PSD95/5 equal to or smaller than 12. Furthermore, the invention relates to a process for the production of a polymer composition comprising: (i) a step in which ethylene monomers, and optionally further alpha-olefin-comonomers, are polymerised in liquid phase in the presence of a polymerisation catalyst, (ii) a step in which ethylene monomers, and optionally further alpha-olefin comonomers, are polymerised in the gas phase in the presence of a polymerisation catalyst, and (iii) obtaining a polymer resin powder after the final polymerisation step wherein the powder has a particle size distribution PSD95/5 equal to or smaller than 12.

Abstract: The present invention provides a process for producing a resin powder containing a radical polymer having a volume-average primary-particle diameter of 1 nm to 300 nm and containing no impurities such as surfactants by a simple procedure without via multistage reactions. The process for producing a resin powder (J) comprising a radical polymer obtained by polymerizing a bifunctional radical-polymerizable monomer (A) with a ter- or higher functional radical-polymerizable monomer (B) in the presence of 15 mol % to 170 mol % polymerization initiator (C), based on the sum of monomers (A) and (B).

Abstract: Ion exchange resins are described that are hydrophilic, crosslinked (meth)acrylic copolymers. The ion exchange resins are macroporous, have a surface area of at least 50 m2/g, and an average particle size of at least 20 micrometers. Additionally, chromatographic columns containing the ion exchange resins, composite materials containing the ion exchange resin, filtration elements containing the ion exchange resin, methods of preparing the ion exchange resins, and methods of separating or purifying negatively or positively charged materials with the ion exchange resins are described.

Abstract: To provide moisture absorptive and desorptive ultrafine particles having high moisture absorptive and moisture desorptive properties and particularly having an excellent moisture absorptive rate and also a product using said ultrafine particles. Moisture absorptive and desorptive ultrafine particles, characterized in that, the said particles consist of a cross-linked polymer containing 1.0 to 10.0 meq/g of a salt-type carboxyl group as a polar group where an average primary particle size is not more than 0.2 ?m and saturated moisture absorptive ratios at 65% RH and 90% RH at 20° C. are not less than 20% by weight and not less than 40% by weight, respectively.

Abstract: The present invention relates to a process for preparing a catalyst, a novel polymer and a process for preparing the polymer. In particular, the invention provides a process for preparing a homopolymer and/or copolymer having an irregular particle structure and a melt flow index (MFR 190/15) of from 1.3 g/10 min to 10 g/10 min, a molecular weight distribution Mw/Mn of from 3 to 30, a bulk density of from 0.05 g/cc to 0.4 g/cc and a particle size of from 5 ?m to 300 ?m, which comprises polymerizing the monomers in the presence of a mixed catalyst comprising a titanium component and an organic aluminum compound and the presence of a molar mass regulator.

Abstract: The present invention provides a method of producing porous spherical particles, which includes suspension polymerization of a multifunctional monomer having two or more vinyl groups and a vinyl monomer having one vinyl group in an aqueous medium in the presence of a porogen and a distribution stabilizer, wherein the distribution stabilizer is polyvinyl alcohol having a saponification degree of 75 to 85 mol %. According to the method of the present invention, generation of particle agglomerates and large particles can be suppressed and porous spherical particles having a desired average particle size and a narrow particle size distribution can be conveniently produced.

Abstract: Ion exchange resins are described that are hydrophilic, crosslinked (meth)acrylic copolymers. The ion exchange resins are macroporous, have a surface area of at least 50 m2/g, and an average particle size of at least 20 micrometers. Additionally, chromatographic columns containing the ion exchange resins, composite materials containing the ion exchange resin, filtration elements containing the ion exchange resin, methods of preparing the ion exchange resins, and methods of separating or purifying negatively or positively charged materials with the ion exchange resins are described.

Abstract: An objective of the invention is to provide a rubber composition which has satisfactory processability and dimension stability, and the like, gives a vulcanized rubber exhibiting excellent wearing resistance and tensile strength, and the like, and thus is useful in a belt, a hose and a tire and the like, as well as a crosslinked rubber particle for obtaining such rubber composition. A rubber composition of the invention comprises [1] a crosslinked rubber particle comprising as repeating units (a) 30 to 94.89% by weight of a conjugated diene unit, (b) 5 to 69.89% by weight of an aromatic vinyl unit, (c) 0.01 to 10% by weight of a monomer unit having at least two polymerizable unsaturated group, (d) one polymerizable unsaturated group and an amino group, a hydroxyl group and an epoxy group and (e) 0.

Abstract: The present invention concerns large spherical polymer particles with a narrow size distribution and a procedure for producing such particles. The procedure is characterized in that a seed polymerization is performed in which the start particles have a very high ability to absorb new monomer so that finished particles are obtained after only one stage of polymerization even if the finished particles are to be as large as in the range 10 to 100 ?m. The procedure is also characterized in that, when porous particles are produced, a porous structure can be formed in which the fraction of micropores is insignificant. Another characteristic feature of the procedure is that the size distribution of the finished particles is narrow and in some cases narrower than in the start particles.

Abstract: The present invention provides a process to create without mechanical agitation a zone of low shear, low turbulence flow pattern within a continuous liquid phase contained in a vessel and comprising a dispersed phase consisting of particles or immiscible liquid droplets which have a density different from and should be distributed within the continuous phase without excessive agglomeration or breakups in order to largely preserve the initial particle size distribution, by a continuous or periodic re-circulation of at least a part of the continuous phase which is preferably free of dispersed particles or droplets.

Abstract: Provided are improved coatings, polymeric dispersions, and polymeric composites, which include crosslinked polymeric nanoparticles (hereafter “PNPs”). Also provided are methods for forming improved coatings, polymeric dispersions, and polymeric composites, which include PNPs. The PNPs have polymerized units of at least one multi-ethylenically-unsaturated monomer have a mean diameter of from 1 to 50 nanometers. PNPs having polymerized units of at least one multi-ethylenically-unsaturated monomer and at least one surface-active monomer are also provided.

Abstract: The present invention relates to novel crosslinked bead polymers having an average particle size of 1 to 1000 ?m containing specific, halogen-free phosphorus compounds including triphenyl phosphate as the halogen-free phosphorus compound, and to a process for the production of these bead polymers and to the use thereof as flame retardants in thermoplastics.

Abstract: The present invention relates to a process for producing monodisperse anion-exchanger gels with high stability, purity and coarse particle size greater than 800 ?m starting from a monodisperse bead polymer with a swelling index of from 2.5 to 7.5 and more than one subsequent feed procedure without any separation between the polymerization steps and then modifying to give the anion exchanger.

Abstract: A bioadhesive composition is disclosed which includes copolymer particles containing as polymerized units, terminally unsaturated acid-containing oligomers and ethylenically unsaturated nonionic monomers. A method of preparing the bioadhesive composition and a method of using the bioadhesive composition are also disclosed.

Abstract: The invention is directed to amphipathic polymeric particles that serve as both the dispersant and the binder in water based inks, ink compositions containing these particles, and methods for making the particles. The polymeric particles contain both hydrophilic and hydrophobic moieties with a pre-determined structure, and have an average diameter of 50 to 500 nm. The amphipathic polymeric particles may be prepared by a side-chain conversion method or a polymerization process involving an ATRP step, with or without a cross-linking agent. This invention improves the stability of polymer and inks by both ionic and steric stabilization of the suspended polymer particles.

Abstract: The present invention relates to an emulsion free high solids process for preparing crosslinked polymeric nanoparticles of 1-200 nm in diameter.

Abstract: The invention relates to cross-linked acrylic microparticles, a method for the production thereof by polymerization in a dispersion in a non aqueous medium and to the uses thereof in covering or moulding compositions involving a favourable compromise between hardness, flexibility and adhesion. The micropparticles are obtained from a composition comprising: 50-99% mols of a constitutent (A) consisting of Cardura E 10 (meth)acrylate and optionally alkyl (meth)acrylate in C2-C8; a compound (B) consisting of at least one monomer or oligomer having at least 2 ethylenic unsaturations; a compound (C) consisting of at least one monomer or oligomer having in addition to one ethylenic unsaturation at least one second function (F1) with the possibility of at least partial chemical modification of the initial functions f1 into final functions f2.

Abstract: A method has been described of preparing monodisperse polymer particles by free radical polymerization or copolymerization of hydrophobic monomers in a water-based system in the presence of cyclodextrin, characterized in that said free radical polymerization is performed with semi-continuous addition of monomer, wherein said monomer is absent before initiating polymerization, and in that a total solid contents of less than 30% by weight is present in said water-based system, in order to provide monodisperse polymer particles which are very suitable for use in many applications as e.g. in inks or toners, in photonic crystal films, in thermal printing plates for computer-to-plate or computer-to-press applications, in inkjet media, in displays, in photographic films, or as a spacing agent.

Abstract: Subjects of the present invention are to provide resin particles having high ability and suitable for various purposes and to provide preparation method thereof. This invention provides resin particles each of which is formed by two curved surfaces or by one curved surface and one plane surface, has a boundary line between these two surfaces and satisfies the relationships: 0.1 &mgr;m≦D≦500 &mgr;m  (I) 0.05≦d/D≦0.8  (II) wherein D is particle diameter in horizontal direction and d is the maximum height in longitudinal direction in a side view in which the boundary line is placed in horizontal direction.

Abstract: Tetrafluoroethylene (TFE) thermoprocessable copolymer microspheres having a substantially spherical shape for at least 95% by weight, the average size of the microspheres being in the range 25 &mgr;m and 2 mm, the bulk density being in the range 0.5 and 1.1 g/cm3.

Abstract: A prepolymerization catalyst for use in a gas phase polymerization of an olefin or combinations of olefins which comprises (A) a solid catalyst component comprising magnesium, halogen, titanium and an electron donor and having a weight-average particle diameter of 15 to 45 &mgr;m, (B) at least one organoaluminum compound and (C) a prepolymer of an ethylene and/or at least one &agr;-olefin, wherein the molar ratio of aluminum to titanium in the prepolymerization catalyst (Al/Ti ratio) is 3 to 11 (mol/mol), the weight ratio of the prepolymerization catalyst to the solid catalyst component (prepolymerization catalyst/solid catalyst component) is 2 to 35 (g/g), the content of volatile materials (VM) in the prepolymerization catalyst is 2.0% by weight or less, and the intrinsic viscosity [&eegr;] measured in tetralin at 135° C. is 2.0 dl/g or less, and a process for a production thereof.

Abstract: Vinylidene fluoride polymers, characterized in that they are thermoplastic vinylidene fluoride/chlorotrifluoroethy-lene/hexafluoropropylene terpolymers and in that they contain at least 70% vinylidene fluoride, process for obtaining them and use thereof.

Abstract: A device for producing disperse mixtures by ultrasound, containing a housing, and a reaction chamber within the housing and at least one sonotrode having a free emitting surface which is directly in effective connection with the reaction chamber and whose end remote from the free emitting surface is coupled to an ultrasonic transducer, wherein the sonotrode is designed as a rod-shaped, axially emitting longitudinal oscillator with the emitting surface corresponding essentially to the surface of the reaction chamber, and wherein the reaction chamber depth which is essentially vertical with respect to the emitting surface is lower than a maximum effective depth of the sonotrode.

Abstract: There is provided a polyvinyl chloride dispersion resin from which a product having excellent clarity and heat resistance can be obtained, and which has improved pulverization efficiency and increased recovery percentage in the production process, a plastisol composition and a plastigel composition using the same. The polyvinyl chloride dispersion resin of the present invention is obtained by polymerization using 0.1 to 5.0 parts by weight of an ammonium salt emulsifier based on 100 parts by weight of a vinyl chloride monomer, wherein the polyvinyl chloride dispersion resin has a specific surface area of 5 to 10 m2/g and comprises (A) 10 to 60% by weight of a particle having a particle diameter distribution of less than 0.5 &mgr;m and having at least one peak diameter of the distribution in the range of at least 0.1 &mgr;m to less than 0.5 &mgr;m and (B) 40 to 90% by weight of a particle having a particle diameter distribution of at least 0.

Abstract: A continuous process for the preparation of inorganic and organic bead polymers using a static micromixer is disclosed. The bead polymers obtainable by the process according to the invention have a very uniform particle size distribution, which can be set in a range of between 0.1 and 300 &mgr;m.

Abstract: Microspheres comprise a polymer or copolymer including one or more of 1) a plurality of C3 or larger alpha-olefin units wherein the polymer has an average number of branch points less than one per monomer unit, and 2) a plurality of C2 alpha-olefin units wherein the polymer has an average number of branch points greater than 0.01 per monomer unit, the microspheres having an average diameter in the range of 1 to 300 micrometers. Optionally, the polymer of the microspheres can be crosslinked. The microspheres can be prepared by suspension or dispersion polymerization processes using aqueous or organic reaction media.

Abstract: Tetrafluoroethylene (TFE) thermoprocessable copolymer microspheres having a substantially spherical shape for at least 95% by weight, the average size of the microspheres being in the range 25 &mgr;m and 2 mm, the bulk density being in the range 0.5 and 1.1 g/cm3.

Abstract: The present invention is directed to an acrylic resin composition obtained by adding a non-crosslinked polymer powder having a bulk density within the range from 0.1 to 0.7 g/ml, an oil absorption based on linseed oil within the range from 60 to 200 ml/100 g and a degree of swelling by methyl methacrylate of 16-fold or more as a thickening agent to acrylic syrup; and acrylic premix obtained by mixing an inorganic filler with this composition; and acrylic premix obtained by extruding constituent components by a kneading extruder to continuously form the mixture; and a method for producing an acrylic artificial marble in which these acrylic premixes are cured.

Abstract: Process for the preparation of tetrafluoroethylene (TFE) polymer-based dispersions having diameter average sizes in the range 0.005-0.06 &mgr;m, which comprises: a) preparation of an aqueous perfluoropolyether (PFPE) microemulsion; b) microemulsion feeding into the polymerization reactor, in such amounts so that the microemulsion perfluoropolyetheral oil phase is present in a concentration higher than 2 ml for liter of reaction medium; c) reaction medium feeding in the gaseous TFE polymerization reactor, optional addition of surfactants, stabilizers, comonomers, transfer agents; d) addition of the initiator, stabilizers, comonomers and transfer agents; e) discharge from the reactor of the polymeric latex.

Abstract: Microspheres comprise a polymer including one or more of 1) a plurality of C3 or larger alpha-olefin units wherein the C3 or larger alpha-olefin units are incorporated into the polymer so as to give an average number of less than one branch point per C3 or larger alpha-olefin unit, 2) a plurality of C2 alpha-olefin units wherein the C2 alpha-olefin units are incorporated so as to give an average number of branch points greater than 0.01 per C2 alpha-olefin unit, and 3) cyclopentene or substituted cyclopentene, the microspheres having an average diameter in the range of 1 to 300 micrometers. Optionally, the polymer of the microspheres can be crosslinked. The microspheres can be prepared by suspension or dispersion polymerization processes using aqueous or organic reaction media. Powder coatings can be prepared from the microspheres.

Abstract: A process for producing a microporous oil sorbent polymer comprising the steps of: dissolving a polyunsaturated monomer in a silicone organic solvent to provide a monomer mixture containing more than 90% by weight polyunsaturated monomer; polymerizing said monomers by precipitation polymerization, under an inert atmosphere to precipitate microporous, micro-particles in the form of micro-particles, agglomerates and aggregates having a bulk density of about 0.02 gm/cm3 to about 0.01 gm/cm3 and capable of adsorbing at least about 20% by weight organic materials based on the total weight of polymer plus adsorbed organic material.

Abstract: The invention provides a process for the preparation of a particulate polymer having a mode particle size of at least 200 &mgr;m, the improvement comprising the use of substantially monodisperse polymeric particles as polymerization seeds in a suspension polymerization preparation of said particulate polymer.

Abstract: A procedure for the production of PVC particles with a narrow size distribution in the range 10-50 &mgr;m, preferably 10-30 &mgr;m, in which, in a first stage, a vinyl monomer or a mixture of monomers is polymerised to form a polymer/oligomer seed particle in the range 1-10 &mgr;m. In a second stage, another vinyl monomer or mixture of monomers is swelled into the polymer/oligomer seed particles and polymerisation takes place in such a way that they grow into polymer particles of the desired size. It is preferable to use aromatic vinyl monomers or acrylates as the monomer in the seed particles. The seed particles in the first stage can be produced in a two-stage swelling process or by dispersion polymerisation.

Abstract: A method for separating poly(vinyl acetate) particles having various particle sizes, which have been prepared by suspension polymerization of vinyl acetate monomers, into respective microspheric poly(vinyl acetate) particles with uniform particle size distribution by the use of inorganic salt as a dispersing and antistatic agent, a method for preparing the microspheric embolic particles of a dual structure consisting of poly(vinyl acetate) core/poly(vinyl alcohol) shell by suspending the separated poly(vinyl acetate) particles into an aqueous alkali solution and subjecting the suspended particles to a heterogeneous surface saponification and the microspheric embolic particles prepared.

Abstract: An aqueous microemulsion polymerization procedure is described in which very small colloidal polymer particles are produced from tetrafluoroethylene monomer. The polymerization procedure involves adding a free-radical initiator to a mixture of a microemulsion of at least one liquid saturated organic compound; and tetrafluoroalkyl ethylene.

Abstract: Process for the preparation of a catalyst component for the polymerization and copolymerization of ethylene to give ultrahigh-molecular-weight ethylene polymers. Reaction of a Grignard compound with a halogenating agent, a titanium compound, a perhalogen compound and an electron-donor compound and subsequent comminution of the resultant solid to a mean particle size of from 0.5 to 5 .mu.m gives a catalyst component which, together with an organoaluminum compound, results, in the polymerization and copolymerization of ethylene, in ultrahigh-molecular-weight ethylene polymers having a mean particle diameter of from 50 to 200 .mu.m and a viscosity index of greater than 2,000 cm.sup.3 /g. The mean particle diameter can be adjusted by means of the catalyst particle diameter and by means of the catalyst productivity.