Abstract: Novel ultrahigh molecular weight linear polyethylene (UHMWLPE) in the form of a shaped article, exhibiting a unique combination of properties making the material useful as a bearing surface, in general, but particularly useful as a prosthetic hip joint cup and as other prosthetic shapes for replacement of other joints of the human body. A novel process for preparing this article is also disclosed.

Abstract: This invention relates to a process for transitioning between incompatible polymerization catalyst systems. Particularly, the invention relates to a process for transitioning from an olefin polymerization reaction utilizing a traditional Ziegler-Natta catalyst system to a metallocene-olefin polymerization reaction.

Abstract: In the preparation of polyolefin in a vapor phase polymerization using catalysts comprising a solid catalyst component containing titanium and/or vanadium; and magnesium and an organoaluminum compound, when the reaction is stopped for a certain period of time, the restarting of reaction is possible by feeding in the first place an organoaluminum compound into the reaction system with retaining of polymer particles in the reactor.

Abstract: Method for the shortstopping of polymerizations of conjugated dienes possibly mixed with vinyl-substituted aromatic products in a radicalic emulsion polymerization process using a redox initiator, in particular radicalic emulsion polymerizations of butadiene possibly mixed with styrene or acrylonitrile, a method which enables the production of polymers without nitrosamines (NA) and/or their precursors.

Abstract: An advanced control method is disclosed for the polymerization of an alpha-olefin in a substantially horizontal, quench-cooled, stirred bed reactor.

Abstract: A process for the preparation of an ethylenic polymer composition having excellent physical properties such as high impact properties, environmental stress cracking resistance, pinch-off fusing characteristics and having an intrinsic viscosity ranging from 3.2 to 4.5 dl/g and a density ranging from 0.943 g/cm.sup.3 to 0.958 g/cm.sup.3.

Abstract: A process for producing a polymer of a monomer having an ethylenically unsaturated double bond is described, wherein the monomer is polymerized in a polymerization vessel having a coating on its inner wall surfaces of a specific three-component polymer scale preventive agent, these three components are a naphthoquinone dimer, a water soluble polymer, and an inorganic colloid, whereby polymer scale is prevented from being deposited on the inner wall surfaces of the polymerization vessel.

Abstract: The color of hydrocarbon resins having carbon-carbon double bonds and containing color bodies is lightened by a hydrotreating process comprising contacting a resin having a weight average molecular weight Mw of 250-10,000 with hydrogen in the presence of a catalyst that promotes the hydrogenation of the color bodies without substantially changing the content of carbon-carbon double bonds in the resin. The preferred catalysts are copper chromite and copper/zinc.

Abstract: A polymer scale preventive process for use in polymerization of a monomer having an ethylenically unsaturated double bond, comprising (A) a water-soluble basic polysaccharide and (B) a phenothiazine. The process is used for forming a coating on the inner wall, etc. of a polymerization vessel, and highly safe for operators. Deposition of polymer scale can be effectively prevented, and polymeric product with high whiteness or a low initial coloration is obtained.

Abstract: A polymer scale preventive process for use in polymerization of a monomer having an ethylenically unsaturated double bond, comprising an alkaline solution containing a condensation product of (A) an aromatic amine compound having at least two amino groups and (B) an aromatic tetracarboxylic acid anhydride. This process is used for forming a coating on the inner wall, etc. of a polymerization vessel. Such a vessel is effective in preventing polymer scale deposition and useful in producing a polymer that shows very few fish eyes and good whiteness when formed into sheets or the like.

Abstract: A polymer scale preventive process for use in polymerization of a monomer having an ethylenically unsaturated double bond, comprising an alkaline solution containing (A) a condensation product of (A-1) an aromatic compound having at least two amino groups with (A-2) an aromatic tetracarboxylic acid anhydride, and (B) at least one member selected from the group consisting of (B-1) a water-soluble polymeric compound and (B-2) an inorganic colloid. The scale preventive process is low in virulence or the like, and high in safety. The process is used for forming a coating on inner wall surfaces of a polymerization vessel. Where such a polymerization vessel is used to carry out the polymerization, polymer scale deposition can be effectively prevented, not only on areas in the liquid-phase region but on areas around the gas-liquid interface in the vessel, and the resulting polymeric product shows few fish eyes and good whiteness when formed into sheets or the like.

Abstract: A process for the polymerization of at least one olefin is a suspension process employing a hydrocarbon diluent such that at least 70% of the polymer formed is insoluble therein, and employs at least two polymerization reactors. The process includes introducing a first portion of the at least one olefin and a catalyst into a first reactor. The catalyst is composed of bis(cyclopentadienyl)chromium, which may be substituted, supported on an inorganic oxide support and is supplied solely into the first reactor. The at least one olefin is polymerized in the first reactor to provide a first composition composed of a polymer and the catalyst. The first composition is then drawn off from the first reactor and the first composition and another portion of the at least one olefin are introduced into a second reactor and the another portion of the at least one olefin is polymerized in the second reactor in the presence of the first composition.

Abstract: Novel ultrahigh molecular weight linear polyethylene (UHMWLPE) in the form of a shaped article, exhibiting a unique combination of properties making the material useful as a bearing surface, in general, but particularly useful as a prosthetic hip joint cup and as other prosthetic shapes for replacement of other joints of the human body, A novel process for preparing this article is also disclosed.

Abstract: A process for removing unpolymerized monomers from a solid olefin polymer containing the monomers by countercurrently feeding an inert purge gas through a bed of polymer in a cylindrical purge vessel having tapered walls wherein the vessel has a height to bottom diameter ratio of 0.5:1 to 10:1 and the walls have a tapered angle based on a vertical axis of 0.5 to 15 degrees. An apparatus for removing unpolymerized monomers from a solid olefin polymer containing the monomers which comprises, a cylindrical purge vessel having tapered walls wherein the vessel has a height to bottom diameter ratio of 0.5:1 to 10:1 and the walls have a tapered angle based on a vertical axis of 0.5 to 15 degrees; a solids inlet disposed in an upper portion of the vessel; a solids discharge disposed in a lower portion of the vessel; gas entry means disposed within or below a bed of solids, and gas discharge means disposed in the upper portion of the vessel.

Abstract: An ethylene stream which contains ethane as an impurity or a propylene stream which contains propane as an impurity is contacted with a polymerization catalyst thereby producing a polymer product containing unreacted ethylene or propylene and the corresponding alkane. A gas mixture containing ethylene or propylene and the corresponding alkane is separated from the polymer product and subjected to adsorption at a temperature of 50.degree. to 200.degree. C. in a bed of adsorbent which selectively adsorbs alkenes, thereby adsorbing substantially all of the propylene or ethylene from the gas mixture. The ethylene or propylene is desorbed from the adsorbent and recycled to the polymerization zone. The process is operated on a low per pass conversion with recycle of unreacted monomer. In the system of the invention the adsorption unit may be upstream or downstream of the polymerization reactor.

Abstract: A polymerization apparatus equipped with a circuit made up of a polymerization vessel, a heat exchanger placed outside said polymerization vessel, and a circulation pipeline extending from said polymerization vessel and returning to said polymerization vessel through said heat exchanger, a branch pipeline being connected to said circulation pipeline through a ball valve comprising a spherical valve element and a valve body for housing said spherical valve element, wherein the valve body of said ball valve is joined directly to said circulation pipeline, and a method of producing a polymer of a monomer having an ethylenically unsaturated double bond by using said apparatus. Scale and polymers in the form of blocks can be prevented from mixing with the reaction mixture.

Abstract: The aqueous dispersions from the polymerization of fluorinated thermoplastics can be worked up to a high value product (e.g., substantially purified of cations resulting from the polymerization) in a continuous manner, if the cations are first removed from the aqueous dispersion, the dispersion is then compressed and decompressed through small openings, thereby being coagulated, the coagulated phase is washed on a filter and partially dewatered, subsequently broken up to give a free-flowing product and this is dried to the desired residual moisture content. Qualitatively high value products, which can be directly fed to a melt extruder, are thus obtained with high throughputs.

Abstract: An improved method for polymerizing one or more polyolefins in the presence of a transition metal catalyst in at least one gas phase fluidized bed reactor, the improvement comprises generating at least one low frequency, high pressure sound wave inside a reactor system, which wave has sufficient frequency and pressure to dislodge and/or prevent particle build-up on interior surfaces of the reactor system.

Abstract: The temperature of the polymerization medium of vinyl chloride with the involvement of oil-soluble initiators is controlled essentially by direct and modified injection of an effective amount of a strong inorganic inhibitor of radical polymerization or of a precursor advantageously chosen from iodine and nitrogen monoxide, as well as from alkali metal iodides and nitrites, which are the respective precursors of iodine and of nitrogen monoxide.

Abstract: The content of spherulites of polyethylene resins is reduced by contact of the polyethylene resin while it is molten with lithium carbonate which is in a subdivided form and is dispersed in the molten polyethylene resin or which is in a form of a block and is removed from the polyethylene resin after the contact. The dispersed lithium carbonate can be removed with the reduced spherulite content preserved.