Abstract: Aqueous dispersions of water-soluble polymers of N-vinylcarboxamides contain, based on 100 parts of water, (A) from 5 to 80 parts by weight of water-soluble polymer containing N-vinylformamide units and/or N-vinylacetamide units and having particle sizes of from 50 nm to 2 ?m and (B) from 1 to 50 parts by weight of at least one polymeric dispersant which is incompatible with the water-soluble polymers (A) in aqueous solution, which dispersions are prepared by polymerizing (A) from 5 to 80 parts by weight of N-vinylformamide and/or N-vinylacetamide, if desired together with other monoethylenically unsaturated monomers which form water-soluble polymers therewith, and (B) from 1 to 50 parts by weight of at least one polymeric dispersant which is incompatible with the polymers, formed from the monomers (A), in aqueous solution, in 100 parts by weight of water, at from 30 to 95° C. in the presence of from 0.001 to 5.

Abstract: The invention pertains to a method for making a block or gradient final (co)polymer comprising a step of radically polymerizing a mixture of ethylenically unsaturated monomers in the presence of a) a radical precursor and b) an iodine atom-containing intermediate polymer or a mixture of iodine atom-containing intermediate polymers, wherein the iodine atom-containing intermediate polymer comprises at least 50 mole % of methacrylate monomers and is obtainable from a polymerization of ethylenically unsaturated monomers.

Abstract: The present invention relates to the use of an aqueous polymer dispersion comprising dispersed particles of at least one polymer A1 having a glass transition temperature, Tg, of from ?20° C. to +35° C. and obtainable through free-radical emulsion polymerization in the presence of a polymer A2 synthesized from from 50 to 99.5% by weight of at least one ethylenically unsaturated monocarboxylic and/or dicarboxylic acid whose carboxylic groups can form an anhydride group, or mixtures thereof, from 0.5 to 50% by weight of at least one ethylenically unsaturated compound selected from the esters of ethylenically unsaturated monocarboxylic acids and the monoesters and diesters of ethylenically unsaturated dicarboxylic acids with an amine containing at least one hydroxyl group, and up to 20% by weight of at least one further monomer as binder for producing abrasive material.

Abstract: The invention relates to a latex that may be utilized as a binder for nonwoven applications to form a permeable sublayer of personal hygiene articles. The latex is prepared by a process including the steps of (1) polymerizing a monomer mixture comprising styrene, itaconic acid, surfactant and water soluble free radical initiator to form a seed; (2) sequentially adding equal increments of a monomer mixture of styrene, butadiene and acrylic acid to the seed under emulsion polymerization conditions to form a styrene-butadiene-acrylic acid copolymer; and then (3) neutralizing the styrene-butadiene-acrylic acid copolymer to a pH of about 4.5 to 7 to form the latex.

Abstract: A process for the preparation of amine-functionalized vinyl polymer particles which process comprises suspension polymerizing aminostyrene together with at least one other vinylic monomer and optionally a crosslinking agent.

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 relates to a polymer microsphere comprising at least one polymer and at least one bound latent colorant, wherein the microsphere is stabilized by at least one stabilizing polymer. The invention also includes a method of preparing polymer microspheres comprising combining latent colorant, ethylenically unsaturated monomer, stabilizing polymer, and an initiator in solvent and initiating polymerization to form a polymeric microsphere stabilized by a stabilizing polymer bound to the surface of the polymeric microsphere.

Abstract: The present invention relates to powdered, crosslinked polymer compositions, containing a) 55-99.9 wt.-% of at least one polymerized, ethylenically unsaturated, polymerizable monomer which contains acid groups neutralized to at least 25 mole-%, b) 0-40 wt.-% of polymerized, unsaturated monomers copolymerizable with a), c) 0.01-5.0 wt.-%, preferably 0.1-2.0 wt.-% of one or more crosslinking agents, d) 0-30 wt.-% of a water-soluble polymer, the weight amounts a) through d) being based on anhydrous polymer composition, and the sum of these components always being 100 wt.-%, which compositions can be obtained by continuous polymerization wherein at least one parameter biasing the polymerization is varied according to a recurring pattern. The present invention also relates to a process for their production and to their use.

Abstract: An aqueous semi-continuous emulsion polymerization process for producing bimodal polymer particles in volumes large than a single batch size is provided. A bimodal polymer composition prepared by the process of carrying out an aqueous semi-continuous emulsion polymerization is also provided.

Abstract: A water dispersible polymer particle stabilized by a hydrophobically capped oligomeric acrylamide dispersant or a heterogeneous method for forming polymer particles comprising providing a water immiscible organic phase comprising at least one monomer dispersed in a continuous water phase and a hydrophobically capped oligomeric acrylamide, and polymerizing the organic phase to yield polymer particles stabilized with hydrophobically capped oligomeric acrylamide. Also, a heterogeneous method for forming polymer particles comprising providing a water immiscible organic dispersed in a continuous water phase, polymerizing the organic phase, and adding hydrophobically capped oligomeric acrylamide to yield polymer particles stabilized with hydrophobically capped oligomeric acrylamide.

Abstract: Processes for transitioning among polymerization catalyst systems, preferably catalyst systems that are incompatible with each other. In particular, the processes relate to transitioning among olefin polymerization reactions utilizing Ziegler-Natta catalyst systems, metallocene catalyst systems and other MAO-based single site catalyst systems.

Abstract: The present invention relates to a process for the gas-phase (co-)polymerization of olefins in a fluidised bed reactor using a late transition metal catalyst characterised in that the polymerization is performed in the presence of a process aid additive.

Abstract: The invention describes a process for the preparation of a particulate polymer, said process comprising: i) forming an aqueous dispersion comprising a particulate polymer seed material and a first organic compound; ii) allowing said first organic compound to diffuse into said seed material to produce a pre-swollen seed material; iii) contacting said pre-swollen seed material in aqueous dispersion with said first organic compound and a second organic compound, preferably one which is soluble in said first organic compound; iv) allowing or causing said first and second organic compounds to pass into said pre-swollen seed material to produce an activated seed material; v) contacting said activated seed material with a monomer and effecting suspension polymerization thereof.

Abstract: Compositions for use in optical fiber coatings and optical fibers and optical fiber arrays using these coatings are disclosed, as are methods for making the same. The compositions comprise a combination of two different radiation curable urethane oligomers, and can further comprise one or more reactive monomers. One of the oligomers has at least three functional groups that can undergo radiation cure.

Abstract: A removable pressure-sensitive adhesive which, even when applied to metal sheets or to metallic members which have undergone a coating treatment, is inhibited from increasing in adhesive force with the lapse of time and can be easily removed therefrom and which has satisfactory weatherability and satisfactory pot life contains 100 parts by weight on a solid basis of an aqueous dispersion type acrylic copolymer obtained by polymerizing a monomer mixture in an aqueous medium in the presence of a nonionic surfactant and/or an anionic surfactant each having an ethylenic double bond and 0.1 to 3 parts by weight of a hindered-amine light stabilizer having a piperidine ring in which the nitrogen atom has a tertiary amine structure; and an adhesive sheet is produced with the adhesive.

Abstract: The present invention relates to a method of preparing an impact-reinforcement agent for polyvinylchloride (PVC) resin having superior anti-stress whitening properties, and specifically to a method for preparing a graft copolymer of methyl-methacrylate-butadiene-styrene (MBS) comprising 3 steps of graft-copolymerizing monomers such as alkylmethacrylate, acrylate, and an ethylene-unsaturated aromatic compound to a rubber latex, in sequence.

Abstract: A process is presented for the preparation of a latex by the emulsion polymerization at a temperature of between 30 and 90 C. of at least one ethylenically unsaturated monomer in the presence of at least one surfactant and of a seed of polymer particles with a diameter of between 200 and 450 nm. The seed particles represent from 5-25% by weight of the total weight of the monomer and seed. The polymerization is initiated by a mixed water-soluble/fat-soluble system. Also included are lattices obtained from this process.

Abstract: In paper coating slips containing, as a binder, a copolymer which is obtainable by free radical polymerization of ethylenically unsaturated compounds, at least one of the ethylenically unsaturated compounds is a polymer having at least one copolymerizable ethylenically unsaturated group, a number average molecular weight of from 500 to 50000 g/mol and at least one carboxyl group (referred to below as ethylenically unsaturated polymer for short).

Abstract: A droplet polymerization process is provided to create efficacious molecularly imprinted polymers (MIPs). Such imprinted polymers have increased surface area for adsorptive or catalytic reactions. This method provides for monomer-template interactions in the absence of a suspending medium, thereby permitting formation of MIPs with increased template selectivity and substantial processing advantages. The process is particularly useful for separating isoflavones from soy whey.

Abstract: Metal alkyl borohydrides are used as initiators of polymerisation, particularly in adhesive compositions for bonding a wide range of substrates including low surface energy substrates such as polyolefins. As described, the metal alkyl borohydrides are of the formula I or II. wherein R1 is C1-C10 alkyl, R2 and R3, which may be the same or different, are H, D, C1-C10 alkyl or C3-C10 cycloalkyl, phenyl, or phenyl-substituted C1-C10 alkyl or C3-C10 cycloalkyl, provided that any two of R1-R3 may optionally be part of a carbocyclic ring, and M+ is a metal ion. In particular, alkali metal trialkyl borohydrides are used, the alkali metal salt being selected from: Lithium triethylborohydride, Sodium triethylborohydride, Potassium triethylborohydride, Lithium tri-sec-butylborohydride, Sodium tri-sec-butylborohydride, Potassium tri-sec-butylborohydride, and Lithium triethylborodeuteride. Other exemplified compounds which are less effective on low surface energy substrates include Lithium 9-borabicyclo [3.3.

Abstract: The present invention relates to a dispersion of polymer particles, the particle containing, on average, more than 1 living radicals each, the radicals not being chemically protected. The invention is also directed to a free radical polymerization process resulting in a dispersion containing polymer particles having on average one or more living radicals. The process involves carefully regulating the polymerization conditions to produce small size particles under monomer-starved conditions containing, on average, more than one living radical in every particle. These living polymer radicals can be further reacted to form polymers with a controlled architecture.

Abstract: A modified supported olefin polymerization catalyst modified by prepolymerization with an olefin or an olefin mixture different from the olefin or olefin mixture of the subsequent olefin polymerization. The polymerization catalyst is a metallocene, and the melting or softening point of the polyolefin made using the catalyst is at least 20° C. lower than that of the prepolymerized polyolefin.

Abstract: A subject-matter of the present invention is a process for the preparation of a latex by radical aqueous emulsion polymerization in the presence of at least one ethylenically unsaturated monomer, of at least one radical polymerization initiator and of at least one surface-active block copolymer comprising at least one hydrophilic block and at least one hydrophobic block which is prepared by a “living” or “controlled” preparation process, the said copolymer exhibiting a number-average molecular mass of between 2 000 and 20 000, preferably between 4 000 and 16 000, a glass transition temperature of the hydrophobic block of less than 30° C., preferably of less than 25° C., and greater than −100° C., and a surface tension of less than 60 millinewtons per metre (mN/m), preferably of less than 50 mN/m, measured at a concentration in demineralized water of less than or equal to 10−4 mol/l at 20° C.

Abstract: The invention is directed to an improvement in a process for preparing an aqueous emulsion of pressure-sensitive adhesive based upon acrylic esters having a good balance of adhesive and cohesive properties and to the resulting emulsion. In the basic process, a pressure-sensitive adhesive formulation comprised of at least one ester of acrylic or methacrylic acid is polymerized in the presence of water and an emulsifier thereby forming an emulsion polymerized pressure-sensitive adhesive. The improvement resides in effecting the polymerization of said pressure-sensitive adhesive formulation comprised of at least one ester of acrylic or methacrylic acid in the presence of from 5 to 30 percent by weight of a styrene containing polymer containing at least 80 percent by weight styrene.

Abstract: Disclosed herein are methods for producing polymeric materials which are normally tenacious in their character to such degree that their processing by conventional means is not possible, for example substantially-amorphous polyolefins. By introducing a second catalyst capable of producing a powdery polymer into the polymerization system during production of the sticky polymers, these normally sticky, tenacious polymers are rendered into a form which may be processed using conventional means and equipment.

Abstract: The present invention relates to preparation of fluorinated core-shell particles with water and oil repellency, and more particularly, to preparation of emulsion-type coating material with good water and oil repellency using only small amount of expensive fluorinated monomers, which comprise a shell wherein a large amount of hydrophobic fluorinated monomers are included and a core wherein no fluorinated monomers are included.

Abstract: The invention is the use of a glycolic acid adduct of sodium sulfite as the reducing agent in the redox couple for polymerization of vinyl acetate polymer based emulsions for nonwoven binders which contain formaldehyde, primarily from the self-crosslinking co-monomer N-methylolacrylamide.

Abstract: A solid catalyst component comprises a transition metal-containing metallocene compound, a non-cyclopentadienyl transition metal compound, a magnesium compound and a polymeric material which acts as a support. The catalyst component is combined with co-catalyst organoaluminum compound or a mixture of organoaluminum compounds to provide a catalyst composition useful for olefin polymerization, e.g., to produce linear low, medium and high density polyethylenes or copolymerization of ethylene with alpha-olefins. Product polyolefin polymers have a varied range of molecular weight distributions. The catalyst composition is prepared by a process comprising combining polymer support particles, magnesium compound, transition metal-containing metallocene compound, and non-cyclopentadienyl transition metal compound to provide a solid catalyst component, and, combining the solid catalyst component with a cocatalyst compound to provide a polyolefin polymerization catalyst composition.

Abstract: An aqueous polymerization method for preparing graft copolymers is disclosed. Copolymer compositions produced therefrom are also disclosed. The method of the present invention includes (a) forming a macromonomer aqueous emulsion containing water insoluble macromonomer particles; (b) forming a monomer composition containing at least one ethylenically unsaturated monomer; and (c) combining at least a portion of the macromonomer aqueous emulsion and at least a portion of the monomer composition and polymerizing the resulting polymerization reaction mixture in the presence of an initiator to form a copolymer composition. The copolymer composition produced contains water insoluble particles of graft copolymer.

Abstract: Supported catalysts for the polymerization of olefins comprise the following components: (A) a porous organic support functionalised with groups having active hydrogen atoms; (B) an organo-metallic compound of aluminium containing heteroatoms selected from oxygen, nitrogen and sulphur; and (C) a compound of a transition metal selected from those of groups IVb, Vb or VIb of the Periodic Table of the Elements, containing ligands of the cyclopentadienyl type. These supported catalysts, obtainable in the form of spherical particles, can be used in the polymerization reaction of olefins either in liquid or in gas phase, thus producing polymers endowed with a controlled morphology and with a high bulk density.

Abstract: The application relates to a foamable copolymer resin and a process for preparing the same, which comprises firstly adding an organic peroxide initiator, a modifying aid and a foaming agent to a mixed monomers of methyl methacrylate and styrene so as to constitute a homogenous mixture; at the same tine charging a deionized water into a polymerization reactor and adding a dispersant hydroxy ethyl cellulose or hydroxylpropyl cellulose ether with stirring to produce a homogenous mixture, then sealing the reactor and introducing N2 gas to purge the reactor before the above homogenous monomer mixture is added; after the completion of the reaction the residue is washed with water and dewatered and dried, obtaining foamable pellets.

Abstract: An aqueous semi-continuous emulsion polymerization process for producing bimodal polymer particles in volumes large than a single batch size is provided. A bimodal polymer composition prepared by the process of carrying out an aqueous semi-continuous emulsion polymerization is also provided.

Abstract: A lens-fitted photo film unit of a waterproof type comprises a unit body covered with a case body and a lid member. A front window and a top window of the case body are made of transparent plastic. The lid member is also made of the transparent plastic. Methacrylate styrene resin is utilized as the transparent plastic, which is used for a taking lens, a viewfinder lens, and an underwater case constituted of the case body and the lid member. This transparent plastic is hardly clouded even if cosmetics of suntan lotion and so forth adhere thereto. Moreover, a poisonous gas causing photographic-film fog is prevented from rising so that photographic properties are not damaged.

Abstract: The invention relates to a process for the preparation of aqueous dispersions of latex particles having a heterogeneous morphology by a semicontinuous emulsion polymerization, comprising the emulsion polymerizing of ethylenically unsaturated (co)monomers, accompanied by, the addition of cationic and/or anionic and/or nonionic emulsifiers and/or protective colloids as stabilizers, which are directly used as such or synthesized in situ, the semicontinuous emulsion polymerization being performed in the presence of the stabilizer or stabilizers with a monomer mixture, which a) contains at least one nonionic, ethylenically unsaturated monomer with a glass transition temperature Tg above about 30° C. in a quantity of about 10 to 70 wt. %, based on the total weight of ethylenically unsaturated (co)monomers and b) at least one hydrophilic, ethylenically unsaturated monomer in a quantity of about 5 to 30 wt. %, based on the total weight of ethylenically unsaturated (co)monomers.

Abstract: The invention is directed to an improvement in a process for preparing an aqueous emulsion of pressure-sensitive adhesive based upon acrylic esters having a good balance of adhesive and cohesive properties and to the resulting emulsion. In the basic process, a pressure-sensitive adhesive formulation comprised of at least one ester of acrylic or methacrylic acid is polymerized in the presence of water and an emulsifier thereby forming an emulsion polymerized pressure-sensitive adhesive. The improvement resides in effecting the polymerization of the pressure-sensitive adhesive formulation comprised of at least one ester of acrylic or methacrylic acid in the presence of from 5 to 30 percent by weight of a styrene containing polymer containing at least 80 percent by weight styrene.

Abstract: Non-Newtonian fluids, such as partially polymerized monomers or solutions of polymer in monomer may be pressure atomized below the surface of an immiscible continuous liquid phase to produce a dispersed phase having a uniform particle size distribution. A dual or customized size distribution can be obtained by imposing a controlled pressure pulsation on a flowing fluid upstream the atomizer inlet. Such dispersion may be further polymerized to produce a uniform or customized bead size product.

Abstract: A catalyst composition useful for catalyzing the polymerization of olefinic monomers is disclosed, along with a polymerization method using those catalyst compositions to prepare a variety of polyolefins from olefinic monomers. A method for preparation of the catalyst composition by combining an epoxy functional porous organic polymer, a catalytic component, and an activator component is also disclosed.

Abstract: The present invention provides aqueous polymer dispersions comprising at least one particulate polymer P having a glass transition temperature Tg of less than 0° C. which is composed of ethylenically unsaturated monomers M including: i. from 60 to 94.9% by weight, preferably from 75 to 89.5% by weight, of n-butyl acrylate as monomer M1, ii. from 5 to 39.9% by weight, preferably from 10 to 24.5% by weight, of at least one monomer M2 selected from esters of methacrylic acid with C1 to C4 alkanols, tert-butyl acrylate, and vinylaromatic monomers, and iii. from 0.1 to 5% by weight, preferably from 0.5 to 2% by weight, of at least one monomer M3 selected from ethylenically unsaturated compounds having at least one acid group; the proportions of said monomers M1 to M3 being based on 100% by weight of monomers M, obtainable by free-radical aqueous emulsion polymerization of monomers M in the presence of at least 0.

Abstract: There are disclosed: (i) a first solid catalyst component (A1) obtained by contacting (a) a carrier of carboxyl group-carrying polymer particles having an average particle size of from about 1 to 200 &mgr;m, (b) an organometallic compound of the number 1, 2 or 13 group of metals in the periodic table of elements, and (c) a transition metal compound of the number 4 group of metals of the periodic table of elements, and a second solid catalyst component (A2) obtained by contacting (a), (b), (c) and (d) a phenol compound, and production processes of the solid catalyst components (A1) and (A2), (ii) a catalyst obtained by combining the solid catalyst component (A1) or (A2) with an organoaluminum compound (B); and (iii) a process for producing an olefin polymer with a catalyst of the invention, wherein the polymer produced is extremely low in its content of lower molecular weight components and low crystallinity components, and superior in its powder properties.

Abstract: The present invention provides an aqueous polymerization method for preparing graft copolymers, and copolymer compositions produced therefrom. The method of the present invention includes (a) forming a macromonomer aqueous emulsion containing water insoluble macromonomer particles; (b) forming a monomer composition containing at least one ethylenically unsaturated monomer; and (c) combining at least a portion of the macromonomer aqueous emulsion and at least a portion of the monomer composition and polymerizing the resulting polymerization reaction mixture in the presence of an initiator to form a copolymer composition. The copolymer composition produced contains water insoluble particles of graft copolymer.

Abstract: The invention relates to a method for producing caoutchouc particles (K) by means of emulsion polymerisation in the presence of an emulsifier and a polymerisation initiator. Said particles contain A) 80 to 100 wt. % of one or more conjugated diene monomers (A) in relation to (K) and B) 0 to 20 wt. % of one or more monoethylenically unsaturated comonomers (B) in relation to (K) in the polymerised form. The inventive method is characterised in that 1) a mixture (M1) containing water and an emulsifier is provided, 2) a mixture (M2) containing one or more monomers in the monomer or polymerised form selected from styrole, &agr;-methylstyrole, butadiene, n-butylacrylate, MMA and acrylnitrile and optionally comonomers is added, 3) polymerisation of the obtained mixture starts in the presence of a polymerisation initiator at temperature of 5 to 95° C., 4) a mixture (M3) containing 0 to 100 wt. % of the comonomers (B) in relation to (B) and 0 to 25 wt.

Abstract: Non-Newtonian fluids, such as partially polymerized monomers or solutions of polymer in monomer may be pressure atomized below the surface of an immiscible continuous liquid phase to produce a dispersed phase having a uniform particle size distribution. A dual or customized size distribution can be obtained by imposing a controlled pressure pulsation on a flowing fluid upstream the atomizer inlet. Such dispersion may be further polymerized to produce a uniform or customized bead size product.

Abstract: An aqueous semi-continuous emulsion polymerization process for producing bimodal polymer particles in volumes large than a single batch size is provided. A bimodal polymer composition prepared by the process of carrying out an aqueous semi-continuous emulsion polymerization is also provided.

Abstract: The present invention relates to a process for polymerizing &agr;-olefins in at least two stages, the first stage comprising at least one bulk reactor and optionally at least one gas phase reactor for forming the &agr;-olefin polymer matrix and the second stage comprising at least one additional gas phase reactor for copolymerization of ethylene with said polymer matrix. In the second stage an antifouling composition is fed into said gas phase reactor(s) for preventing fouling in the second stage.

Abstract: A process for producing an acrylic polymer capable of providing a polymer controlled in molecular weight and free of colorization, and a heterogeneous polymerization catalyst used in the process for producing an acrylic polymer are provided. The heterogeneous polymerization catalyst contains (A) a radical generating substance, (B) a metallic halide containing a metallic element selected from the group consisting of the Group 4 to Group 12 elements and a halogen element selected from the group consisting of chlorine, bromine and iodine, and (C) a carrier carrying a ligand capable of forming a coordination bond with the metallic halide (B). The process for producing an acrylic polymer contains a step of polymerizing a monomer containing at least an acrylate and/or a methacrylate in the presence of the heterogeneous polymerization catalyst.

Abstract: Composition comprising an oil phase, an aqueous phase, at least one emulsifying agent of water-in-oil (W/O) type and at least one emulsifying agent of oil-in-water (O/W) type in the form of a self-invertible inverse latex comprising from 20% to 70% by weight, and preferably from 25% to 50% by weight of a branched or crosslinked polyelectrolyte, characterized in that the said polyelectrolyte is either a homopolymer based on a monomer having a partially or completely salified strong acid functional group or a copolymer based on at least one monomer having a partially or completely salified strong acid functional group copolymerized with acrylamide and characterized in that the constituent solvent of the oil phase is chosen from white mineral oils, squalane, hydrogenated polyisobutene, isohexadecane or isododecane. Cosmetic, dermocosmetic, dermopharmaceutical or pharmaceutical composition comprising them.

Abstract: A process for the continuous gas-phase (co-)polymerisation of olefins in a fluidised bed reactor using a Ziegler-Nata type catalyst wherein the polymerisation is performed in the presence of a process aid additive selected from at least one of (1) a polysulphone copolymer; (2) a polymeric polyamine or (3) an oil-soluble sulphonic acid.

Abstract: The present invention concerns a process for producing homogeneous polyethylene compositions and processes for making high density, medium density and low density films therefrom. The process comprises carrying out the polymerization in the presence of an ethylene-polymerizing catalyst system in a multistage reaction sequence of successive polymerization stages, at least one of which is a loop polymerization stage, and at least one of which is a gas phase polymerization stage. According to the invention, said loop polymerization stage is operated using a diluent selected from the group of linear and branched C4-C6 hydrocarbons and/or mixtures thereof. The reactor sequence is operated with different amounts of hydrogen and comonomers to produce a high molecular weight portion in one of the polymerization stages and a low molecular weight portion in another, so as to provide bimodal polyethylene composition with a low molecular weight part having an MFR2 of 250 g/10 min or more.

Abstract: A process for the gas-phase (co-)polymerization of olefins in a fluidized bed reactor using a chromium oxide catalyst. The polymerization is performed in the presence of a process aid additive.

Abstract: This invention relates to a method to start up an olefin polymerization process comprising: a. calculating a trajectory, from elements including catalyst deactivation rate constants (kd), for the rate of introduction of a catalyst system, into a reactor, said catalyst system comprising two different metal catalyst compounds (A and B) and at least one activator, wherein the ratio of the deactivation constants of the two different metal catalyst compounds kdA/kdB is not 1; and b. introducing olefin monomer, a catalyst system, optional co-monomer, and optional chain transfer or termination agents into a polymerization reactor in a manner such that the catalyst system introduction rate is manipulated to follow the trajectory until a desired production rate is achieved.