Abstract: A method for quenching an active polymerization mixture, the method comprising introducing a polyhydroxy compound to an active polymerization mixture.

Abstract: Processes for reducing the ultra high molecular weight polymeric material content of a high density polyethylene produced with a bis-triarylsilyl chromate catalyst system are provided. Processes for reducing the gel content of articles produced from high density polyethylene are also provided. The gel content of the articles is reduced by using the high density polyethylene with reduced ultra high molecular weight polymeric material content to produce the articles. The processes described reduce the content of ultra high molecular weight polymeric material in comparison to conventional high density polyethylene by introducing at least one catalyst deactivator into a recycle gas line containing a recycle gas stream associated with the fluidized bed reactor. The at least one catalyst deactivator has a boiling point lower than the maximum temperature within the recycle gas line.

Abstract: The present invention relates to a method for terminating anionic polymerization using phosphate ester/water mixture, more particularly to a novel method for terminating anionic polymerization using phosphate ester/water mixture as a polymerization terminator in a living polymer solution prepared by the anionic polymerization, so that the polymerization can be terminated effectively, without coupling or discoloration and with less production of basic materials that affect the antioxidant, thereby enabling control of acidity without necessitating a further neutralization process.

Abstract: A method of deactivating a polymerization catalyst system comprising contacting the catalyst system with a catalyst deactivation agent wherein the catalyst system comprises an alkyl aluminum cocatalyst and the reaction of the catalyst system and catalyst deactivation agent produces reaction products that are noncorrosive, nongelatinous, or both. A method of inhibiting the polymerization of propylene comprising contacting a polymerization catalyst system with a catalyst deactivation agent wherein the catalyst system comprises an alkyl aluminum cocatalyst and the reaction of the cocatalyst and the catalyst deactivation agent produces reaction products that are noncorrosive, nongelatinous, or both. A method of deactivating a polymerization catalyst system having an alkyl aluminum cocatalyst, comprising contacting the catalyst system with an alcohol, a carboxylic acid, an alkylene glycol, or combinations thereof.

Abstract: There is provided a process for producing a polymer comprising the steps of (a) adding at least one low-reactivity monomer to a reaction vessel with a decreasing rate of addition, (b) adding at least one high-reactivity monomer to said reaction vessel, (i) wherein less than 1% of all of said high-reactivity monomers, by weight of high reactivity monomers, based on the weight of all said high-reactivity monomers, is added to said reaction vessel before the beginning of said step (a), and (ii) wherein at least half of all of said high-reactivity-monomers, by weight of high reactivity monomers, based on the weight of all of said high-reactivity monomers, is added to said reaction vessel before the completion of said step (a), and (c) adding at least one chain regulator to said reaction vessel prior to the completion of said step (a), wherein said steps (a), (b), and (c) are performed while conditions in said reaction vessel will cause polymerization of said low-reactivity monomer and said high-reactivity

Abstract: The present invention relates to methods for controlling fouling in the reaction zone of slurry-type olefin polymerization reactors by measuring a process operating parameter and by responding to said process operating parameter, e.g., by introducing a gaseous poison for the polymerization catalyst in response to a comparison between said measured parameter and a fouling parameter limit for said measured parameter.

Abstract: A multi-functional admixture for simultaneously providing specified characteristics to hydraulic cement compositions such as concrete contains one or more of specified reaction mixtures obtained by specified two processes as well as partially or completely neutralized substances obtained from such a reaction mixture through a specified third process. The specified two processes include initiating a radical copolymerization process of a radical polymerizable monomer mixture containing maleic anhydride and a monomer of a specified kind in a non-aqueous system in the presence of a non-aqueous radical initiator and stopping the radical copolymerization reaction in its midst while the inversion rate of polymerization is at a specified level by adding water to the reaction system to thereby obtain a reaction mixture. The specified third process is for partially or completely neutralizing the reaction mixture.

Abstract: A dispersing agent suitable for suspension polymerization of vinyl compounds, comprising a polyvinyl alcohol resin containing carbonyl groups in its molecule and having a block character of remaining fatty acid ester groups of at least 0.5 and an absorbance of at least 0.1 measured at each of wavelengths of 215 nm, 280 nm and 320 nm with respect to a 0.1% by weight aqueous solution of the polyvinyl alcohol resin, wherein the ratio of absorbance at 320 nm to absorbance at 280 nm is at least 0.3. The dispersing agent has an excellent surface activity and can suppress foaming which may occur in the suspension polymerization of vinyl compounds.

Abstract: In a process for preparing water-absorbent resins based on acrylic acid, crude acrylic acid is firstly isolated from the reaction gases from the catalytic gas-phase oxidation of propane, propylene and/or acrolein. This is treated with an aldehyde scavenger and pure acrylic acid is separated by distillation from the treated crude acrylic acid, and this pure acrylic acid can be subjected directly to a free-radical polymerization.

Abstract: The invention relates to a process for the preparation of poly(?-methylstyrene) by anionic polymerization of the ?-methylstyrene monomer, said process successively comprising the following stages: a) a stage of preparation of a solution comprising the ?-methylstyrene monomer and a nonpolar aprotic solvent; b) a stage of neutralization of the solution prepared in a) comprising the addition, to this solution, of an effective amount of at least one monofunctional organometallic initiator, so as to neutralize the proton sources of the solution prepared in a); c) a stage of cooling the solution obtained in b) to a temperature of less than 0° C.

Abstract: A catalyst for bulk polymerization of a polymerizable unsaturated compound of the invention comprises a compound having at least one thiol group and a secondary hydroxyl group and represented by the following formula (I): wherein R1 to R5 are each a hydrogen atom or an alkyl group, and R6 is a hydroxyl group, an alkyl group or the like. Also a process for bulk polymerization of the invention comprises polymerizing a polymerizable unsaturated compound in an inert gas atmosphere substantially in the absence of a solvent using, as a catalyst, a compound having at least one thiol group and a secondary hydroxyl group and represented by the above formula (I). According to the catalyst or the process of the invention, bulk polymerization can be carried out in one-component catalyst system in a high yield without suffering a runaway reaction.

Abstract: Provided are a preparation process of a copolymer for semiconductor lithography, suited for a film forming composition used for the formation of minute patterns necessary for semiconductor fabrication, which comprises carrying out radical polymerization of at least two monomers having an ethylenic double bond in the presence of a polymerization initiator in a polymerization solvent, while causing to exist, in the solution containing the monomers, a polymerization inhibitive component; and a copolymer for semiconductor lithography prepared by the above-described process, and contains no high polymer, has excellent storage stability and generates remarkably less defects in resist pattern when used for semiconductor lithography.

Abstract: A process is provided that produces polyolefins. The process comprises mixing a first stream, which comprises at least one catalyst deactivating agent, with a second stream, which comprises at least one polyolefin, at least one catalyst, at least one diluent, and at least one monomer, to produce a third stream, which comprises at least one polyolefin, at least one deactivated catalyst, at least one diluent, and at least one monomer. By utilizing the deactivating agent, polymerization can be slowed, or substantially stopped, when downstream equipment is being repaired or process control problems are being corrected. Later, polymerization can be restarted without the use of scavengers to remove poisons from the slurry polymerization reactor, and polyolefin production can be resumed.

Abstract: A metallocene catalyst may be temporarily and reversibly passivated by contact with an effective amount of a passivating compound selected from the group of oxygen, oxygen-containing compounds, and nitrogen-containing compounds.

Abstract: Processes for transitioning among polymerization catalyst systems, preferably catalyst systems that are incompatible with each other. In particular, the processes relate to transitioning from olefin polymerizations utilizing metallocene catalyst systems to olefin polymerizations utilizing traditional Ziegler-Natta catalyst systems.

Abstract: A diene rubber (A) having a weight average molecular weight (Mw) of 100,000 to 3,000,000, an Mw/number average molecular weight (Mn) ratio of 1.30 to 2.50, and an Mw/peak top molecular weight (Mp) ratio 0.70 to 1.30. A rubber composition comprising the diene rubber (A) and a diene rubber (B) having an Mw of 2,000 to 90,0000 and/or an oil extender for rubber has good processability and can give a rubber vulcanizate having high tensile strength and good abrasion resistance. The diene rubber (A) is produced by conducting a living polymerization of diene monomer in a hydrocarbon solvent; adding a polymerization stopper to a polymerization mixture at a conversion of 5 to 98% to deactivate 10 to 90% by mole of active terminals present as of the initiation of polymerization; and finally adding a polymerization stopper to completely terminate the polymerization reaction.

Abstract: A process is provided that produces polyolefins.

Abstract: The present invention relates to the preparation of syndiotactic 1,2-polybutadiene polymer using a catalyst containing a carbon disulfide in which the polymerizate thereof is treated with hydrogen peroxide, to preparation of a composite of conjugated diene-based elastomer and syndiotactic 1,2-polybutadiene polymer using a catalyst containing a carbon disulfide which the polymerizate thereof is treated with hydrogen peroxide, a rubber composition containing said syndiotactic 1,2-polybutadiene polymer and/or said composite and a tire having at least one rubber component thereof.

Abstract: Processes for transitioning among polymerization catalyst systems, preferably catalyst systems that are incompatible with each other. In particular, the processes relate to transitioning from olefin polymerizations utilizing metallocene catalyst systems to olefin polymerizations utilizing traditional Ziegler-Natta catalyst systems.

Abstract: Continuous gas-phase polymerization process for preparing ethylene and propene homopolymers and copolymers, in which ethylene, propene or mixtures comprising ethylene or propene and C3-C8-?-monoolefins are polymerized in the polymerization zone of a gas-phase polymerization reactor at from 30 to 125° C. and pressures of from 1 to 100 bar in the gas phase in a bed comprising finely divided polymer in the presence of a catalyst. To remove the heat of polymerization, the reactor gas is circulated and firstly passes through a cyclone after leaving the reactor. To prevent polymer deposits in the circulating gas system, a catalyst poison having a boiling point above the maximum temperature within the circulating gas system is fed into this circulating gas system at a position between the reactor and the cyclone.

Abstract: A process for the preparation of linear polymers or block copolymers of styrene by anionic polymerization comprises carrying out the chain termination with an n-alkyl glycidyl ether or a dialkyl ketone.

Abstract: A polymer scale preventive agent for use in the polymerization of a monomer containing an ethylenic double bond is provided. The agent includes (A) a condensation reaction product obtained by reacting an aldehyde compound and a hydroxynaphthalene-based compound in the presence of a reducing agent, and (B) a polymer compound containing a nitrogen atom. This agent is capable of forming a coating with satisfactory scale prevention properties on inner wall surfaces of a polymerization vessel with a single-stage application, enabling the production process time to be shortened and the productivity and quality of polymeric products improved.

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 is a process for transitioning from a first polymerization reaction to a second polymerization reaction incompatible with the first polymerization reaction in a gas-phase reactor. The novel process comprises conducting multiple polymerization reactions, capturing and storing a substantially contaminant-free polymerization product from each multiple polymerization reaction for use as a selected substantially contaminant-free seedbed in a second polymerization, wherein the polymerization product from each multiple polymerization reaction is rendered substantially contaminant-free by stripping or venting reactants and contaminants and is maintained as substantially contaminant-free by storage under an inert atmosphere.

Abstract: Processes for transitioning among polymerization catalyst systems, preferably catalyst systems, which are incompatible with each other. Particularly, processes for transitioning among olefin polymerization reactions utilizing silyl-chromate catalyst systems and metallocene catalyst systems.

Abstract: A process of transitioning from a first polymerization reaction conducted in the presence of a mixed catalyst system to a second polymerization reaction conducted in the presence of a chrome-based catalyst system is disclosed, the polymerization reactions being conducted in one embodiment in a polymerization zone of a gas phase fluidized bed reactor which contains a fluidized bed of polymer particles by the essentially continuous passage of monomer gases through the polymerization zone, comprising: a) discontinuing the introduction of the mixed catalyst system into the reactor; b) maintaining polymerization conditions in the reactor and permitting polymerization to continue for a period of time to allow the components of the mixed catalyst system present in the reactor to produce additional polymer particles; c) introducing a deactivating agent into the fluidized bed in an amount sufficient to deactivate the mixed catalyst system; d) establishing optimal conditions within the reactor for the chrome-based

Abstract: A process of transitioning from a first polymerization reaction conducted in the presence of a mixed catalyst system comprising to a second polymerization reaction conducted in the presence of a chrome-based catalyst system is disclosed, the polymerization reactions being conducted in one embodiment in a polymerization zone of a gas phase fluidized bed reactor which contains a fluidized bed of polymer particles by the essentially continuous passage of monomer gases through the polymerization zone, comprising:

Abstract: A catalyst for bulk polymerization of a polymerizable unsaturated compound comprises a compound having at least one thiol group and a secondary hydroxyl group and represented by the following formula (I): wherein R1 to R5 are each a hydrogen atom or an alkyl group, and R6 is a hydroxyl group, an alkyl group or the like. Also a process for bulk polymerization of the invention comprises polymerizing a polymerizable unsaturated compound in an inert gas atmosphere substantially in the absence of a solvent using, as a catalyst, a compound having at least one thiol group and a secondary hydroxyl group and represented by the above formula (I). According to the catalyst or the process, bulk polymerization can be carried out in one-component catalyst system in a high yield without suffering a runaway reaction.

Abstract: Processes for chemically-modifying the surface of an emulsion polymer particle are provided which include providing an aqueous emulsion polymer, a monomer at a level of at least 0.5% by weight based on the weight of the emulsion polymer and a, surface-modifying chemical capable of bonding with the monomer, under conditions where there is no substantial polymerization of the monomer, and then reducing the level of the monomer by at least 50%.

Abstract: A method for forming a fluoropolymer comprises providing a reaction mixture comprising carbon dioxide, at least one fluoromonomer, and an initiator; and reacting the at least one fluoromonomer in the reaction mixture to form a fluoropolymer. The fluoropolymer has a multimodal molecular weight distribution.

Abstract: The present invention is to provide a continuous anion polymerization method for preparing transparent high impact vinyl aromatic polymer comprising the steps of: i) charging and polymerizing vinyl aromatic monomers and initiator to obtain vinyl aromatic polymer in the presence of solvent and polar organic compounds in the first reactor (1a); ii) continuously charging and polymerizing vinyl aromatic monomers and conjugated diene monomers to the vinyl aromatic polymer obtained in the first reactor to obtain tapered vinyl aromatic polymer chain in the presence of organic solvent in the second reactor (1b); iii) continuously charging and polymerizing vinyl aromatic monomers and multi-functional compounds to the vinyl aromatic polymer chain obtained in the second reactor to obtain high impact vinyl aromatic polymer in the presence of organic solvent in the third reactor (1c); and iv) terminating the reaction with terminator and removing the remaining hydrocarbon solvent and unreacted monomers to obtain transparen

Abstract: This invention relates to a process for the synthesis of addition polymers containing branches upon branches and having a polymerizable olefin end group by a convenient one-pot polymerization of selected vinyl monomers with chain polymerization initiators and a method to provide olefinic end groups by chain termination agents; and polymers produced thereby characterized by branch-on-branch structure and lower inherent viscosity than heretofore possible.

Abstract: The present invention includes a bimodal polyethylene polymerization process wherein metallocene catalyst to is used to adjust the hydrogen response of a Ziegler-Natta catalyst. The polymerization may be carried out in a single reactor or in two or more reactors in series, preferably two or more continuously stirred tank reactors in series. In an embodiment having two or more reactors, the Zeigler-Natta catalyst is added to a first reactor and the metallocene catalyst is added to a downstream reactor. In another embodiment having two or more reactors, the Zeigler-Natta catalyst and metallocene catalyst are added to the same reactor, preferably an upstream reactor. A preferred Zeigler-Natta catalyst comprises TiCl4, and a preferred metallocene catalyst comprises bis(cyclopentadienyl) titanium dichloride.

Abstract: A method for forming a fluoropolymer comprises providing a reaction mixture comprising carbon dioxide, at least one fluoromonomer, and an initiator; and reacting the at least one fluoromonomer in the reaction mixture to form a fluoropolymer. The fluoropolymer has a multimodal molecular weight distribution.

Abstract: The present invention relates to a polymerizable composition comprising a) at least one ethylenically unsaturated monomer and b1) at least one multifunctional triazinyl based 2,2,6,6 tetramethylpiperidine-1-oxyl and a free radical initiator or b2) at least one multifunctional triazinyl based 2,2,6,6 tetramethylpiperidine-1-oxyl-ether. Further aspects of the present invention are a process for polymerizing ethylenically unsaturated monomers, the (co)polymers obtainable by this process and the use of multifunctional triazinyl based 2,2,6,6 tetramethylpiperidine-1-oxyls in combination with a free radical initiator, or a multi-functional triazinyl based 2,2,6,6 tetramethylpiperidine-1-oxyl-ethers for controlled polymerization. In a particularly preferred embodiment at least one additional heating step at a temperature from 140 to 280° C. is applied after polymerization is completed.

Abstract: A process for the preparation of polyisobutylenes by cationic polymerization of isobutylene or isobutylene-containing hydrocarbon streams in the liquid phase in the presence of boron trifluoride acting as catalyst, the catalytic activity of boron trifluoride being partially or completely stopped by means of a solid deactivator following a given timelapse, which deactivator is an inorganic, anhydrous or hydrous oxygen compound of aluminum which is insoluble in the reaction mixture.

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: The present invention is to provide a continuous anion polymerization method for preparing transparent high impact vinyl aromatic polymer comprising the steps of: i) charging and polymerizing vinyl aromatic monomers and initiator to obtain vinyl aromatic polymer in the presence of solvent and polar organic compounds in the first reactor (1a); ii) continuously charging and polymerizing vinyl aromatic monomers and conjugated diene monomers to the vinyl aromatic polymer obtained in the first reactor to obtain tapered vinyl aromatic polymer chain in the presence of organic solvent in the second reactor (1b); iii) continuously charging and polymerizing vinyl aromatic monomers and multi-functional compounds to the vinyl aromatic polymer chain obtained in the second reactor to obtain high impact vinyl aromatic polymer in the presence of organic solvent in the third reactor (1c); and iv) terminating the reaction with terminator and removing the remaining hydrocarbon solvent and unreacted monomers to obtain transparen

Abstract: A method of producing a vinyl-based polymer is provided in which the blocking of piping resulting from solidification of a reaction inhibitor does not occur even if the operation of supplying the reaction inhibitor is conducted at a low temperature. This method involves the polymerization of a vinyl monomer via a radical reaction, wherein a reaction inhibitor formed from a compound represented by a general formula (1), shown below, is added to the polymerization system in the form of an aqueous dispersion, either prior to commencement of the polymerization, during the polymerization, or following completion of the polymerization, depending on the effect desired. R represents an alkyl group of 3 to 6 carbon atoms.

Abstract: Zirconocene compounds with two indenyl ligands linked in the 2 position by means of a two-carbon-atoms divalent bridging group can be suitably used as components of catalysts for the polymerization of olefins. Particularly it is possible to prepare, with high yields, ethylene (co)polymers having low molecular weights and narrow molecular weight distributions, without the need of using considerable amounts of molecular weight regulators, such as hydrogen.

Abstract: It has been discovered that the polymerization of unsaturated compounds, such as butadiene, may be inhibited by the addition of a diene and/or alkanolamine inhibitor. The inhibitor is believed to catalytically destroy peroxides present, such as hydrogen peroxide, which may be present in trace amounts. Particularly useful inhibitors include, but are not limited to, ethylenediamine (EDA) and monoethanolamine (MEA).

Abstract: The present invention relates to a polymerizable composition comprising a) at least one ethylenically unsaturated monomer and b1) at least one multifunctional triazinyl based 2,2,6,6 tetramethylpiperidine-1-oxyl and a free radical initiator or b2) at least one multifunctional triazinyl based 2,2,6,6 tetramethylpiperidine-1-oxyl-ether. Further aspects of the present invention are a process for polymerizing ethylenically unsaturated monomers, the (co)polymers obtainable by this process and the use of multifunctional triazinyl based 2,2,6,6 tetramethylpiperidine-1-oxyls in combination with a free radical initiator, or a multi-functional triazinyl based 2,2,6,6 tetramethylpiperidine-1-oxyl-ethers for controlled polymerization.

Abstract: A stable continuous production of a propylene-based block copolymer can proceed for a long time without causing accumulation of particles having a small diameter by a process having the following steps: (1) polymerizing an &agr;-olefin containing liquid propylene as a main component in the presence of hydrogen and a stereoregular polymerization catalyst in one or more polymerization reactors to obtain a polymer slurry; (2) feeding the polymer slurry to a copolymerization reactor; and (3) copolymerizing propylene and an &agr;-olefin other than propylene substantially in a gaseous phase in the presence of the stereoregular polymerization catalyst, the polymer slurry and a deactivating compound in the copolymerization reactor to obtain a propylene-block copolymer powder.

Abstract: A high-quality protective film for a dry film resist is provided. A film of a polyethylene is used as the protective film, the polyethylene being prepared by pressurizing ethylene with use of an ultra-high pressure compressor and then polymerizing the ethylene at a reaction temperature of 190° to 300° C. and a reaction pressure of not lower than 167 MPa in the presence of a radical polymerization initiator, or by pressuring ethylene with use of an ultra-high pressure compressor and then polymerizing the ethylene at a reaction temperature of 190° to 300° C. in the presence of a radical polymerization initiator while allowing a radical polymerization inhibitor to be present in the reaction system.

Abstract: The problem addressed by the invention was to find an anionic polymerization inhibitor for cyanoacrylate adhesives containing one or more cyanoacrylates, stabilizers against anionic and radical polymerization and auxiliaries typically used in such adhesive systems which, besides a reliable inhibiting effect, would counteract any increase in the setting time after storage. This problem was solved by using 2-oxo-1,3,2-dioxathiolanes as inhibitors.

Abstract: A production process for a vinyl-based polymer is provided. The production process comprises a step for polymerizing a vinyl-based monomer by a radical reaction within an aqueous medium in a polymerization vessel, and a step for supplying a reaction inhibitor with a melting point of no more than 40° C. from a reaction inhibitor supply tank to the polymerization vessel via a reaction inhibitor supply pipe. The reaction inhibitor supply tank and the reaction inhibitor supply pipe are heated, and the reaction inhibitor is added to the polymerization vessel in a liquid state with a viscosity of no more than 200 mPa·s. The reaction inhibitor can be added to the polymerization mixture without the use of an organic solvent even at low temperatures, and problems such as the solidification of the reaction inhibitor inside the supply tank or piping, and subsequent blocking of the piping do not occur.

Abstract: Methods and compositions for inhibiting the polymerization of vinyl monomers are disclosed. Combinations of aminophenol compounds and nitroxyl radical compounds are effective at inhibiting vinyl monomer polymerization under both processing and storage conditions.

Abstract: A process is disclosed for a continuous, high temperature polymerization process for preparing a free radically polymerized epoxy-functional polymeric product. The process comprises continuously charging into a reactor at least one epoxy-functional acrylic monomer, and optionally at least one non-functional free radical polymerizable monomer. An optional free radical polymerization initiator may also be added. The reactor is maintained at an effective temperature for an effective period of time to cause polymerization of the monomers into a polymeric product, such that the polymeric product is formed substantially free of gel particles. A clear coating is also disclosed incorporating polymers of the present invention, such that the clear coating has a low Delta b value at standard conditions.

Abstract: The invention relates to a process for the preparation of an organic solution of dialkyl peroxydicarbonate which is particularly suited for use in the aqueous suspension polymerization of halogenated monomers. The dialkyl peroxydicarbonates are employed in the aqueous suspension polymerization of halogenated monomers in the form of an organic solution in a water-insoluble organic solvent chosen from conventional chain-regulating agents for halogenated polymers.

Abstract: Provided is a continuous vapor-phase polymerization method for producing polyolefins. In the method, polymer agglomerates and aggregates are prevented from being formed, and polymer deposition on the wall of reactors and around stirring blades is prevented. The method enables continuous and stable production of high-quality polyolefins, with no pipe line clogging. The method is characterized by a specific supply mode of feeding a catalyst activity retardant such as alcohol into polymerization reactors. Specifically, the retardant is fed into the vapor phase in a polymerization reactor and into the powder phase therein through its side wall. Preferably, the retardant is fed into the powder phase through a plurality of sites of the side wall of the reactor.