Abstract: An olefin polymerization process is disclosed. The process comprises polymerizing olefins in the presence of a supported indenoindolyl catalyst system and an organoboron or organoaluminum-treated solid. The supported indenoindolyl catalyst system comprises a support, an organometallic complex comprising a Group 3 to 10 transition or lanthanide metal, M, and at least one indenoindolyl ligand that is &pgr;-bonded to M, and an activator. Performing the process in the presence of the organoboron or organoaluminum-treated solid surprisingly leads to an increased activity compared to polymerization processes performed without the treated solid.

Abstract: Prealkylation of a supported catalyst system comprising a transition metal or inner transition metal complex precatalyst and a bulky, non-coordinating anion on an inorganic support by treatment with a solution of metal alkyl in a ratio of metal of metal alkyl to transition metal or inner transition metal of precatalyst less than 20:1, and in an amount of solution insufficient to form a paste or dispersion provides supported catalysts of high olefin polymerization activity which promote production of polyolefins of low polydispersity and improved morphology.

Abstract: A novel loop/slurry olefin polymerization process is provided which produces ultra high molecular weight ethylene homopolymers and ultra high molecular weight ethylene copolymers. Catalyst systems used are selected from the group consisting of inorganic oxide supported titanium-containing catalyst systems, inorganic oxide supported organo-zirconium catalyst systems and inorganic oxide supported organo-hafnium catalyst systems.

Abstract: Olefin polymerization may be catalysed by a wide range of catalytic materials. Described herein is a heterogeneous olefin polymerization catalyst comprising a porous paniculate support material having impregnated therein a metallocene catalyst the metal atom whereof is bound to an amide group which is not bound to an &eegr;-ligand of the metallocene, or the reaction product of a said metallocene catalyst and a co-catalyst.

Abstract: A process for the production of an ionic transition metal catalyst in supported form than is highly productive under gas phase olefin polymerization conditions. In the process a an aluminum alkyl is added to a suitable solvent after which a neutral metallocene compound is added to the solution under stirring in a quantity that provides for a ratio of Al to transition metal of at least 25:1. To this metallocene-aluminum alkyl solution is next added an ionic compound the anionic portion of which is a non-coordinating anion under stirring until all materials are dissolve. The ionic compound is added in a quantity that provides for a ratio of NCA to transition metal of at least 1:1. Next the support particles are added to the solution and thereafter the solution is heated to at least 40° C. and held at this elevated temperature for at least 0.5 hour. Thereafter the solvent is removed and the supported catalyst is dried under vacuum.

Abstract: There is provided a process for producing an olefin polymer, which comprises a step of polymerizing an olefin in a gas phase in the presence of a homogeneous solid catalyst having a content of particles having a particle size of not more than 180 &mgr;m of not more than 15% by weight based on 100% by weight of the total weight of the homogeneous solid catalyst.

Abstract: The present invention relates to a process for the copolymerization of conjugated diolefins with non-conjugated olefins in the presence of rare earth metal catalysts. The advantages of the process according to the invention are in particular the high selectivity, good space-time yield and the possibility of being able to vary the reaction conditions within a wide range.

Abstract: A process for the production of an ionic transition metal catalyst in supported form than is highly productive under gas phase olefin polymerization conditions. In the process a an aluminum alkyl is added to a suitable solvent after which a neutral metallocene compound is added to the solution under stirring in a quantity that provides for a ratio of Al to transition metal of at least 25:1. To this metallocene-aluminum alkyl solution is next added an ionic compound the anionic portion of which is a non-coordinating anion under stirring until all materials are dissolve. The ionic compound is added in a quantity that provides for a ratio of NCA to transition metal of at least 1:1. Next the support particles are added to the solution and thereafter the solution is heated to at least 40° C. and held at this elevated temperature for at least 0.5 hour. Thereafter the solvent is removed and the supported catalyst is dried under vacuum.

Abstract: A coordination catalyst system comprising at least one metallocene or constrained geometry pre-catalyst transition metal compound, (e.g., rac-ethylene bis(indenyl)zirconium dichloride), at least one non-metallocene, non-constrained geometry, bidentate transition metal compound or tridentate transition metal compound (e.g., tridentate 2,6-diacetylpyridine-bis(2,4,6-trimethylanaline)FeCl2), at least one support-activator (e.g., spray dried silica/clay agglomerate), and optionally at least one organometallic compound (e.g., triisobutyl aluminum), in controlled amounts, and methods for preparing the same. The resulting dual transition metal catalyst system is suitable for addition polymerization of ethylenically and acetylenically unsaturated monomers into polymers; for example, polymers having a broad molecular weight distribution, Mw/Mn, and good polymer morphology.

Abstract: A copolymer of ethylene and a higher alpha olefin, preferably 1-hexene, can be produced using an activated chromium containing catalyst system and a cocatalyst selected from the group consisting of trialkylboron, trialkylsiloxyalutninum, and a combination of trialkylboron and thalkylaluminum compounds. The polymerization process must be carefully controlled to produce a copolymer resin having an exceptionally broad molecular weight distribution, extremely high PENT ESCR values, and a natural branch profile that impacts branching preferably into the high molecular weight portion of the polymer. The resulting copolymer resin is especially useful in high stiffness pipe applications.

Abstract: A process to produce a polymer is provided. The process comprising contacting a treated solid oxide compound, an organometal compound, and an organoaluminum compound in the presence of an alpha olefin under polymerization conditions to produce the polymer.

Abstract: The invention relates to supported ligands and catalysts for use in the polymerization of olefinically unsaturated monomers such as vinylic monomers, comprising the use of a compound attached to support, the compound being capable of complexing with a transitional metal. Preferably the compound capable of complexing with a transition metal is a diimine such as a 1,4-diaza-1,3-butadiene, a 2-pyridinecarbaldehyde imine, an oxazolidone or a quinoline carbaldeyde. Preferably the catalysts are used in conjunction with an initiator comprising a homolytically cleavable bond with a halogen atom. The application also discloses processes for attaching ligands to supports, and processes for using the catalysts disclosed in the application.

Abstract: Prealkylation of a supported catalyst system comprising a transition metal or inner transition metal complex precatalyst and a bulky, non-coordinating anion on an inorganic support by treatment with a solution of metal alkyl in a ratio of metal of metal alkyl to transition metal or inner transition metal of precatalyst less than 20:1, and in an amount of solution insufficient to form a paste or dispersion provides supported catalysts of high olefin polymerization activity which promote production of polyolefins of low polydispersity and improved morphology.

Abstract: The present invention relates to a composition of carboxylate metal salt and a flow improver useful in combination with a polymerization catalyst to improve the flowability and bulk density of the catalyst. The invention also relates to a polymerization process using the catalyst.

Abstract: A novel loop/slurry olefin polymerization process is provided which produces ultra high molecular weight ethylene homopolymers and ultra high molecular weight ethylene copolymers. Catalyst systems used are selected from the group consisting of inorganic oxide supported titanium-containing catalyst systems, inorganic oxide supported organo-zirconium catalyst systems and inorganic oxide supported organo-hafnium catalyst systems.

Abstract: A clay-filled polyolefin composition and process for making it are disclosed. The process involves treatment of a non-acid-treated smectite clay with a Ziegler-Natta catalyst in the presence of a hydrocarbon and subsequent polymerization of an olefin in the presence of the treated clay and an organoaluminum cocatalyst. Results indicate that filled compositions produced by this process contain exfoliated clay.

Abstract: The invention relates to a catalyst support and to a method for the production of the catalyst support comprising the following steps: a) production of a silicic acid hydrogel having a solids content of from 10 to 25% by weight (calculated as SiO2) whose particles are substantially spherical, b) extraction of the hydrogel particles with an alcohol until at least 60% of the water present in the hydrogel has been removed, c) drying of the resultant hydrogel until the residual alcohol content is less than 10% by weight (xerogel formation) at temperatures of ≧160° C. at atmospheric pressure using an inert entraining gas, d) setting of the desired particle size of the resultant xerogel, in which the hydrogel particles have a particle size of ≧8 mm before the extraction, and to a catalyst and to a method for the production of the catalyst by loading the catalyst support with a chromium compound. The invention also relates to a method for the production of polyolefins using the catalyst.

Abstract: This invention relates to olefin polymers particularly suited to satisfying the dielectric properties required in electrical device use. The olefin polymers can be prepared by contacting polymerizable olefin monomers with catalyst complexes of Group 3-11 metal cations and noncoordinating or weakly coordinating anion compounds bound directly to the surfaces of finely divided substrate particles or to polymer chains capable of effective suspension or solvation in polymerization solvents or diluents under solution polymerization conditions. Thus, the invention includes polyolefin products prepared by the invention processes, particularly ethylene-containing copolymers, having insignificant levels of mobile, negatively charged particles as detectable by Time of Flight SIMS.

Abstract: A process comprising polymerizing ethylene, or polymerizing ethylene and at least one other olefin, to produce a polymer is provided.

Abstract: The present invention is directed to homo-polymers and copolymers of mono-1-olefins, a method of making such polymers, and uses of such polymers. Polymers of the present invention are formed by contacting at least one mono-1-olefin having from 2 to about 20 carbon atoms per molecule and at least one mono-1-olefin co-monomer having from 2 to about 10 carbon atoms per molecule in a reaction zone under polymerization conditions in the presence of a hydrocarbon diluent, a catalyst system, and a cocatalyst. The catalyst system of the present invention comprises a chromium source on an aluminophosphate support which has a phosphorous to aluminum mole ratio of less than about 0.3. Further, the catalyst system is treated with less than about 7 weight percent fluoride based on the weight of the support and is calcined. Cocatalyst are selected from trialkylboron compounds, triarylboron compounds, alkylaluminum compounds, and combinations thereof.

Abstract: An ethylene/&agr;-olefin copolymer having a density of 0.900 to 0.965 g/cm3; having an MI of 0.01 to 100 g/10 minutes; in a chromatogram with the use of Rayleigh ratio obtained by extrapolating GPC-MALLS data at a scattering angle of 0°, showing an average {overscore (Mc)} obtained by measuring five times of 0.5% or more and a standard deviation <&sgr;> from the average of 35% or less, wherein Mc stands for the chromatographic area ratio of the components having molecular weight of 1,000,000 or more calculated on the basis of the above measurement; and having a W30 (weight fraction of the portion eluted below 30° C.) in CFC measurement of 1 (% by weight) or less; and a film thereof.

Abstract: A process for preparing pillared chromium phyllosilicate clay &agr;-olefin catalysts is disclosed. This process utilizes palygorskite and sepiolite clays. The pillaring of said clays comprises the steps of: (a) preparing a hydrolyzed first solution by dissolving a chromium salt and a base in water, heating said first solution to a temperature in the range of about 20° C. to about 100° C. while stirring continuously until the solution reaches a pH in the range of about 1.5 to about 2.5 and thereby producing a master batch; (b) diluting said master batch with water to produce a diluted second solution and heating said diluted second solution to produce a heated second solution; (c) adding a solid clay selected from the group consisting of sepiolites and palagorskites to said heated second solution, and continuing heating; (d) recovering said pillared chain silicate clay; and (e) drying said pillared chain silicate clay to form first product.

Abstract: A copolymer of ethylene and a higher alpha-olefin having broadened melt processing windows and reduced melt fracture can be produced using a chromium-containing catalyst system and a trialkyl boron cocatalyst. The polymerization process must be carefully controlled to produce a copolymer resin that easily can be made into articles of manufacture.

Abstract: The invention provides for compositions that are useful for polymerizing at least one monomer to produce a polymer, wherein the composition comprises a post-contacted organometal compound, a post-contacted organoaluminum compound, and a post-contacted solid oxide compound treated with boron and fluoride.

Abstract: Supported metal halides and metal halide solid acids are used as catalysts for the polymerization of a feed stream containing at least one of pure monomer, C5 monomers, and C9 monomers to produce hydrocarbon resins. Freely-associated water may be removed from the solid acid catalyst prior to use. Resins with softening points (Ring and Ball) in the range of about 5° C. to 170° C. can be prepared. These catalysts offer advantages over the traditional Friedel-Crafts polymerization catalysts since the acid sites are an integral part of the solid. The solid acid catalysts are relatively nonhazardous, reusable catalysts which eliminate or at least reduce contamination of the resulting resin products with acid residues or by-products.

Abstract: The invention relates to a method for producing supported chromium catalysts for the polymerisation of olefins by loading a xerogel support with chromium by adding to the xerogel support a volume of a 0.025 to 15% by weight solution of a chromium compound or a volume of a solution comprising from 0.025 to 7.8% by weight of Cr which is essentially converted into a chromium(VI) compound on heating in a water-free stream of gas under oxidizing conditions at temperatures in the range from 300 to 1100° C. for a period of from 10 to 1000 minutes in a solvent which comprises a maximum of 20% by weight of water, and subsequently evaporating the solvent, where the volume of the chromium salt solution employed is smaller than the pore volume of the xerogel support.

Abstract: A clay-filled polyolefin composition and process for making it are disclosed. The process involves treatment of a non-acid-treated smectite clay with a Ziegler-Natta catalyst in the presence of a hydrocarbon and subsequent polymerization of an olefin in the presence of the treated clay and an organoaluminum cocatalyst. Results indicate that filled compositions produced by this process contain exfoliated clay.

Abstract: This invention relates to a composition of matter comprising the catalyst compound comprising a transition metal complexed with a facially coordinating tridentate bisamide ligand. The invention is also directed to a catalyst system or a supported catalyst system comprising this compound and an activator and to a process for using the catalyst system or supported catalyst system in a process for polymerizing olefin(s).

Abstract: This invention relates to olefin polymers particularly suited to satisfying the dielectric properties required in electrical device use. The olefin polymers can be prepared by contacting polymerizable olefin monomers with catalyst complexes of Group 3-11 metal cations and noncoordinating or weakly coordinating anion compounds bound directly to the surfaces of finely divided substrate particles or to polymer chains capable of effective suspension or solvation in polymerization solvents or diluents under solution polymerization conditions. Thus, the invention includes polyolefin products prepared by the invention processes, particularly ethylene-containing copolymers, having insignificant levels of mobile, negatively charged particles as detectable by Time of Flight SIMS.

Abstract: The present invention is directed to producing a resin which, when formed into a film, has excellent gas barrier and/or moisture barrier (low MVTR) properties. Further, the resin has a relatively high molecular weight distribution, preferably above 6, and has excellent processability/extrudability. The resin is produced using a cyclopentadienyl chromium compound, preferably a mono CpCr compound, on a support, preferably a silica support. A particularly preferred catalyst for use in the present invention comprises pentamethylcyclopentadienyidimethylchromiumpyridine. Preferably, the catalyst is used in a slurry polymerization process.

Abstract: Method of preparation of ethylene copolymers suitable for manufacturing films or pipes so characterized that for the initiation of polymerization of ethylene and 1-alkene monomer a substantially innovated catalyst system containing silyl chromate compound is used. The catalyst system, containing a high yield structure A, is prepared by a sequential interaction of the following components: a) a silyl chromate compound completely freed from water and oxygen prior to its contact with the porous support, b) a support containing a suitable type and optimum concentration of hydroxyl groups, and c) an alkylating agent, being a combination of organometal compounds of aluminum (RO)AlR2 and magnesium (R1MgR2), the ratios between the components in the catalyst vary in the following ranges: content of silyl chromate on the support varies from 0.05 to 0.35% of the support weight, ratio between the total amount of organometals (ORG) to silyl chromate (expressed in terms of ORG/Cr) varies between 0.

Abstract: This invention relates to olefin polymerization processes suitable for limiting or eliminating aromatic solvents or diluents. The invention processes can be conducted by contacting polymerizable olefin monomers with catalyst complexes of Group 3-11 metal cations and noncoordinating or weakly coordinating anions bound directly to the surfaces of finely divided substrate particles or to polymer chains capable of effective suspension or solvation in polymerization solvents or diluents under polymerization conditions. These processes minimize problems associated with using largely insoluble organometallic or organometalloid catalysts and cocatalysts in aliphatic, solution, or diluent polymerization processes.

Abstract: Alpha-olefins are manufactured in high yield and with very high selectivity by contacting ethylene with an iron complex of a selected 2,6-pyridinedicarboxaldehyde bisimine or a selected 2,6-diacylpyridine bisimine, and in some cases a selected activator compound such as an alkyl aluminum compound. Novel bisimines and their iron complexes are also disclosed. The &agr;-olefins are useful as monomers and chemical intermediates.

Abstract: A copolymer of ethylene and a higher alpha olefin, preferably 1-hexene, can be produced using an activated chromium containing catalyst system and a cocatalyst selected from the group consisting of trialkylboron, trialkylsiloxyaluminum, and a combination of trialkylboron and trialkylaluminum compounds. The polymerization process must be carefully controlled to produce a copolymer resin having an exceptionally broad molecular weight distribution, extremely high PENT ESCR values, and a natural branch profile that impacts branching preferably into the high molecular weight portion of the polymer. The resulting copolymer resin is especially useful in high stiffness pipe applications.

Abstract: Alpha-olefins are manufactured in high yield and with very high selectivity by contacting ethylene with an iron complex of a selected 2,6-pyridinedicarboxaldehyde bisimine or a selected 2,6-diacylpyridine bisimine, and in some cases a selected activator compound such as an alkyl aluminum compound. Novel bisimines and their iron complexes are also disclosed. The &agr;-olefins are useful as monomers and chemical intermediates.

Abstract: The invention relates to alteration of a linear low density polyethylene which is ordinarily free of long chain branching to introduce long chain branching into the polymer.

Abstract: Supported metal halides and metal halide solid acids are used as catalysts for the polymerization of a feed stream containing at least one of pure monomer, C5 monomers, and C9 monomers to produce hydrocarbon resins. Freely-associated water may be removed from the solid acid catalyst prior to use. Resins with softening points (Ring and Ball) in the range of about 5° C. to 170° C. can be prepared. These catalysts offer advantages over the traditional Friedel-Crafts polymerization catalysts since the acid sites are an integral part of the solid. The solid acid catalysts are relatively nonhazardous, reusable catalysts which eliminate or at least reduce contamination of the resulting resin products with acid residues or by-products.

Abstract: The present invention relates to a composition of carboxylate metal salt and a flow improver useful in combination with a polymerization catalyst to improve the flowability and bulk density of the catalyst. The invention also relates to a polymerization process using the catalyst.

Abstract: The present invention relates to a chromium/silca-aluminophosphate catalyst, titanated under specific conditions and used for the homopolymerisation or the copolymerisation of ethylene. The polyethylene obtained with this catalyst has a high melt potential and a high shear resistance. The catalyst has a high level of activity.

Abstract: The present invention is a nanocomposite which is a dispersion of nanofiller particles derived from layered metal oxides or metal oxide salts. The nanocomposite is advantageously prepared by first swelling an untreated clay in water, then removing the water to form an organophilic clay that is dispersible in non-polar organic solvents. The organophilic clay can then be treated with an alkyl aluminoxane and subsequently a catalyst to form a complex that promotes olefin or styrenic polymerization and platelet dispersion. The nanocomposite can be prepared directly by in situ polymerization of the olefin or the styrene at the nanofiller particles without shear, without an ion exchange step, and without the need to incorporate polar substituents into the polyolefin or polystyrene.

Abstract: An ethylene-&agr;-olefin copolymer which is a copolymer of ethylene with a C3-20 &agr;-olefin and which satisfies the following conditions (a) to (c): (a) the density (D) is from 0.850 to 0.950 g/cm3, (b) the relation between the melt tension (MT) and the melt flow rate (MFR) at 190° C. satisfies the following formula (1): log(MT)≧−0.91×log(MFR)+0.06   (1), and (c) the following three formulae (2), (3) and (4) are satisfied: Tmax≦972D−813   (2) logW60≦−0.114 Tmax+9.48   (3) logW90≧0.0394 Tmax−2.95   (4) where D is the density, Tmax is the elution peak temperature (°C.) by the cross fractionation measurement, W60 is the weight percentage (wt %) of a soluble content at 60° C. or lower, and W90 is the weight percentage (wt %) of a soluble content at 90° C. or higher.

Abstract: A particulate phyllosilicate mixture comprising a mixture containing a phyllosilicte belonging to the smectite group and a phyllosilicate belonging to the mica group, the phyllosilicate particle having a content of the phyllosilicate belonging to the smectite group of 0.1 to 50% by weight and optionally satisfying the following requirements (a) to (c): (a): the average particle diameter is 20 to 1000 &mgr;m with not more than 20% of the total number of particles being accounted for by particles having a particle diameter of not more than 10 &mgr;m; (b): the crushing strength of the particle is not less than 0.5 MPa as measured with a microcompression tester and (c): the bulk density of the particle of not less than 0.6 g/cm3.

Abstract: A process for preparing halogen-free, reactive polyisobutene having a terminal double bond content of more than 50 mol % and an average molecular weight Mn of 280-10000 dalton by the cationic polymerization in the liquid phase of isobutene or hydrocarbon mixtures comprising isobutene comprises polymerizing at from −30° C. to +40° C. in the presence of a heterogeneous polymerisation catalyst comprising one or more oxides of the elements of transition groups V and VI of the Periodic Table of the Elements or in the presence of a heterogeneous polymerization catalyst comprising one or more oxidic compounds of one or more elements of transition groups V and VI of the Periodic Table of the Elements supported on a non-zeolitic oxidic support material which is not an oxygen-containing zirconium compound, the catalyst not containing a technically effective amount of halogen.

Abstract: A process for the polymerisation of olefins in the gas phase is carried out in the presence of a supported transition metal catalyst. The process involves a prepolymerisation step which may be performed in-situ and in particular the prepolymer may be prepared in the dry phase. The catalyst may for example comprise a constrained geometry transition metal complex supported on silica and used in the presence of an activator. The prepolymerisation step enables the activity of the catalyst to be improved.

Abstract: A process for the polymerization of olefins in a gas phase reactor operating in a non-condensed mode, in which the process is carried out in the presence of a catalyst system containing (a) a metallocene supported on a solid support and (b) an activator, and adding a lower alkane to the gas phase reactor.

Abstract: The invention provides new olefin(s) polymerization catalyst systems, including controlled pore glass support.

Abstract: The invention is directed to organometallic catalysts prepared by a process comprising a) combining nucleophilic group-containing particulate support material with an arylboron or arylaluminum Lewis acid compound in the presence of a Lewis base compound; b) contacting the product of a) with a trialkylaluminum compound before combining said product with a metal precursor compound capable of activation for olefin polymerization by said product a); and, c) combining the product of b) with said metal precursor compound. These catalyst compositions are suitable for addition reactions of ethylenically and acetylenically unsaturated monomers. The invention includes a polymerization process of combining or contacting olefinically unsaturated monomers with the invention catalyst composition. Use of the invention catalyst to polymerize &agr;-olefins is exemplified.

Abstract: A catalyst system comprising a) at least one support, b) at least one metallocene and c) at least one compound of the formula (I)  where M1 is an element of group IIa, IIIa, IVa or Va of the Periodic Table of the Elements, x is 0 or 1, y is 0 or 1, z is 0 or 1, A is a cation of group Ia, IIa, IIIa of the Periodic Table of the Elements, a carbenium, oxonium, phosphonium or sulfonium cation or a quaternary ammonium compound, Q1, Q2, Q3 are each a ligand system based on a biphenyl framework bound to M1 via the positions 2 and 12 and having the formula (II)  where R1, R2, R3, R4, R5, R6, R7 and R8 are identical or different and are each a hydrogen atom, a halogen atom, a C1-C40 group, or an OSiR39 group, where R9 are identical or different and are each a hydrogen atom, a halogen atom, a C1-C40 group and two or more radicals R1 to R8 may be joined to one another so as to form a monocyclic or polycyclic ring system which may be substituted.

Abstract: An improved chromium oxide-based catalyst supported on a granular or microspherical refractory oxide for the gas phase polymerization of at least one alpha olefin containing from 2 to 12 carbon atoms, wherein the supported chromium oxide-based catalyst has been subjected to a sole calcination/activation step consisting of a single thermal treatment performed at a temperature ranging from 200° to 450° C. under an oxygen containing atmosphere, and an olefin polymerization process employing such catalyst.

Abstract: The present invention relates to a process of preparing syndiotactic styrenic polymers with a high conversion rate in the form of fine powder, which comprises (a) preparing styrenic polymers in a solid state by reacting a mixture consisting of styrenic monomers, a metallocene catalyst, a cocatalyst and inert organic solvent in a polymerization reactor, (b) separating a portion of the styrenic polymers from the reactor, (c) recycling the portion of the styrenic polymers in the reactor, and (d) reacting the recycled styrenic polymers with styrenic monomers. The styrenic monomers may include olefinic monomers. The monomers can be introduced to a single inlet or multiple inlets of the reactor. A single reactor or a plural number of reactors can be operated in the present invention. The plural numbers of reactors are arranged in series or in parallel. In the present invention, a self-cleaning mono- or twin-axis reactor can be employed to prevent the polymers from agglomerating on the inner wall or the axis.