Abstract: An objective of the invention is to provide a conjugated diene-based rubber having a specific composition and a method of producing the same, an oil extended rubber using the same, as well as a rubber composition capable of being converted into a vulcanized rubber which has a low rolling resistance, an excellent wearing resistance and the like, and is useful, for example, as a tire or the like. A conjugated diene-based rubber in the invention has a glass transition point of −60 to 0° C., an olefinically unsaturated nitrile monomer unit randomly contains in its molecular chain, its repeating units consists of 9 to 30% by mass of an olefinically unsaturated nitrile monomer unit such as acrylonitrile, 10 to 50% by mass of an aromatic vinyl monomer unit such as styrene and 20 to 81% by mass of a conjugated diene monomer unit such as 1,3-butadiene, and its Mooney viscosity [ML1+4(100° C.)] is 20 to 200.

Abstract: A process for producing an isobutylene block copolymer, which comprises performing cationic polymerization of a monomer component containing isobutylene as a major monomer and a monomer component whose major monomer is not isobutylene in the presence of an initiator, wherein the polymerization is carried out in a mixed solvent containing a monohalogenated hydrocarbon solvent and a non-halogenated hydrocarbon solvent the monohalogenated hydrocarbon solvent containing a primary monohalogenated hydrocarbon having three to eight carbon atoms and/or a secondary monohalogenated hydrocarbon having three to eight carbon atoms, the non-halogenated hydrocarbon solvent containing an aliphatic hydrocarbon and/or an aromatic hydrocarbon.

Abstract: An objective of the present invention is to provide an unsaturated nitrile-conjugated diene-typed rubber capable of giving a vulcanized rubber which exhibits is well-balanced in terms of the mechanical strength, the oil resistance and the like, as well as a process for the production of the same, and a rubber composition which is containing such rubber and exhibits an excellent processability as well as a process for the production of the same. The unsaturated nitrile-conjugated diene-typed rubber in the invention is produced by polymerizing using certain amounts of an olefinically unsaturated nitrile monomer such as acrylonitrile and a conjugated diene monomer such as butadiene at first, and continuing by supplying a remainder of the monomers at a certain ratio continuously or stepwise to proceed the polymerization.

Abstract: It is possible to provide the heat resistant material and coating material for OA equipments which comprise a fluorine-containing multi-segment polymer having heat resistance, abrasion resistance, non-sticking property against toner and oil resistance in addition to flexibility and are used particularly on surfaces of fuser roll and belt. Those materials comprise a fluorine-containing multi-segment polymer having an elastomeric fluorine-containing polymer chain segment A and a non-elastomeric fluorine-containing polymer chain segment B, and the elastomeric fluorine-containing polymer chain segment A comprises not less than 90% by mole of perhaloolefin unit as a recurring unit and imparts flexibility to the whole polymer.

Abstract: &agr;-Olefins are polymerized in the gas phase at from 30 to 150° C. and a pressure of from 5 to 80 bar using a catalyst or a catalyst mixture containing as antistatic agent from 0.1 to 5% by weight of ZnO and/or anhydrous MgO, based on the total amount of the catalyst mixture, except for a process in which the catalyst mixture comprises a chromium catalyst and MgO-supported Ziegler catalyst which is modified with an alkene and with alkylaluminum hydride and also comprises free MgO and the total amount of the MgO is not less than 2% by weight of the catalyst mixture.

Abstract: A hydrogenated block copolymer has at least two polymer blocks A each having an aromatic vinyl hydrocarbon compound monomer unit and at least two hydrogenated polymer blocks B each having a hydrogenated butadiene monomer unit. At least 90% of olefinically unsaturated double bonds in the polymer blocks mainly having a butadiene monomer unit before hydrogenation have been hydrogenated. At least one of the locks at the terminal of the hydrogenated block copolymer is the polymer block B. The proportion of the terminal polymer blocks B in the hydrogenated block copolymer is 0.1 wt % to 9.1 wt %. The proportion of the aromatic vinyl hydrocarbon compound in the hydrogenated block copolymer is 25 wt % to 80 wt %. The 1,2-bond content of the polymer blocks having a butadiene monomer unit before hydrogenation averages 60 mol % to 99 mol %. The resulting resin composition improves the balance among the appearance of its molded article, tensile elongation at break and moldability.

Abstract: The present invention provides: an acrylic acid-maleic acid copolymer (or its salt) which is excellent in performances, such as Mg2+ scavengeability, clay dispersibility in the presence of Mg2+, inhibitability upon Mg(OH)2 scale, and inhibitability upon CaCO3 scale; and a production process for such a copolymer (or its salt). The present invention further provides a production process for an aqueous maleic salt solution with a low impurity content which has the advantage of easily giving the above copolymer (or its salt). The present invention still further provides uses of the above copolymer (or its salt) having the above excellent properties.

Abstract: A block copolymer comprising at least three consecutive conjugated diene/monovinylarene tapered blocks is provided. Other aspects of this invention include a polymerization process for preparing the block copolymer and polymer blends comprising the block copolymer. The block copolymer and polymer blends exhibit excellent optical and mechanical properties.

Abstract: An objective of the present invention is to provide an unsaturated nitrile-conjugated diene-typed rubber capable of giving a vulcanized rubber which exhibits is well-balanced in terms of the mechanical strength, the oil resistance and the like, as well as a process for the production of the same, and a rubber composition which is containing such rubber and exhibits an excellent processability as well as a process for the production of the same. The unsaturated nitrile-conjugated diene-typed rubber in the invention is produced by polymerizing using certain amounts of an olefinically unsaturated nitrile monomer such as acrylonitrile and a conjugated diene monomer such as butadiene at first, and continuing by supplying a remainder of the monomers at a certain ratio continuously or stepwise to proceed the polymerization.

Abstract: A process for reducing the odor emission of aqueous vinylaromatic/1,3-diene copolymer dispersions and of redispersion powders obtainable therefrom by drying, is by emulsion polymerization of a mixture containing at least one vinylaromatic and at least one 1,3-diene in the presence of one or more surfactant substances and optionally drying of the polymer dispersion obtained thereby. There are 0.01% to 15.0% by weight of one or more monomers of the branched or straight-chain alkyl esters having 1 to 8 C atoms in the alkyl radical of monounsaturated monocarboxylic or dicarboxylic acids and 0.01% to 15.0% by weight of one or more monomers based upon the vinyl esters of branched or straight-chain aliphatic carboxylic acids having 1 to 10 C atoms which are added in one step or in two successive steps toward the end of the polymerization, when the total content of free monomers in the aqueous copolymer dispersion is in the range from ≧0 to ≦20% by weight.

Abstract: An aqueous crosslinkable coating composition suitable for the provision of thick coatings without incurring carbon dioxide bubble formation comprising: (A) an aqueous dispersion of at least one hydroxyl- and acid-functional vinyl polymer having a hydroxyl value of 8 to 250 mg KOH/g of polymer and an acid value of 2 to 55 mg KOH/g of polymer, where the contribution of at least 30% of the acid value results from a monocarboxylic acid(s) of formula: CH2—CR1—Q—CO2H  (1) where R1 is H or lower alkyl of 1 to 5 carbon atoms and Q is a spacer group of formula: [—C(═O)—X—(CH2)m—]k  (2) where X is —O— or —NH—, m is at least 1, preferably 2 or 3, and k is at least 1, preferably 2, 3, 4 or 5; and (B) at least one organic polyisocyanate. The acid of formula (1) preferably comprises &bgr;-carboxyethyl acrylate.

Abstract: A process for production of diene rubber polymers wherein, during production of a diene rubber polymer by emulsion polymerization, the polymerization is initiated using a portion of the starting material and the polymerization is continued with either continuous or intermittent dropwise addition of the remainder of the starting material during the polymerization, and wherein at least ½ of the total amount of the water and of the monomer in the starting material used is added dropwise during the polymerization, and the temperature of the dropwise added water and monomer is kept to at least 20° C. below the polymerization temperature. The process can produce industrially useful diene rubber polymer latexes at a high productivity rate.

Abstract: The invention pertains to a process wherein peroxides are dosed to a polymerization mixture, with essentially all of the organic peroxide that is used in the polymerization process having a half-life from 0.05 hour to 1.0 hour at the polymerization temperature. The dosing of such peroxide allows for accurate control of the polymerization rate, and the process will render a polymer with a low residual peroxide level.

Abstract: This invention relates to a method to introduce multiple catalysts into a gas or slurry phase reactor comprising: (a) introducing one or more olefins and a first catalyst and an activator into the reactor and allowing the olefins to polymerize, (b) obtaining a polyolefin, (c) introducing a second catalyst and an optional activator into the first catalyst/activator composition and thereafter introducing the combination into the reactor and allowing the olefins to polymerize. This invention further relates to a method to introduce multiple catalysts into a gas or slurry phase reactor comprising: (a) introducing one or more olefins, a first catalyst and an activator, and a second catalyst and an optional activator into the reactor, wherein the all the catalysts and activators are combined together prior to being introduced into the reactor.

Abstract: The present invention provides: an acrylic acid-maleic acid copolymer (or its salt) which is excellent in performances, such as Mg2+ scavengeability, clay dispersibility in the presence of Mg2+, inhibitability upon Mg(OH)2 scale, and inhibitability upon CaCO3 scale; and a production process for such a copolymer (or its salt). The present invention further provides a production process for an aqueous maleic salt solution with a low impurity content which has the advantage of easily giving the above copolymer (or its salt). The present invention still further provides uses of the above copolymer (or its salt) having the above excellent properties.

Abstract: The present invention provides a method for substantially continuously polymerizing olefins comprising: introducing into a first reaction zone a fresh olefin polymerization catalyst; contacting said fresh olefin polymerization catalyst in said first reaction zone with a first vent mixture at a first feed rate and under conditions sufficient to form and avoid melting a polyolefin, wherein first vent mixture comprises unreacted olefins and a diluent vented from a second reaction zone; withdrawing a vent product of unreacted olefins and diluent from said first reaction zone; withdrawing from said first reaction zone a first product mixture comprising said catalyst and said polyolefin; passing said first product mixture to said second reaction zone; contacting said first product mixture in said second reaction zone with a second vent mixture at a second feed rate and under conditions sufficient to form and avoid melting said polyolefin, wherein said second vent mixture comprises a material selected from the group

Abstract: A device and method allow a dry catalyst to be delivered to a liquid-filled polymerization reactor, thus avoiding problems associated with catalyst-liquid contact or with undesired addition of gases to the reactor. A quantity of dry catalyst is transferred from a catalyst reservoir maintained under dry conditions to a catalyst chamber. An inert fluid then enters the chamber to flush the catalyst charge toward the reactor. Optional embodiments include means for precontacting the dry catalyst with a modifier and for removing gas from the fluid line.

Abstract: A device and method allow a dry catalyst to be delivered to a liquid-filled polymerization reactor, thus avoiding problems associated with catalyst-liquid contact or with undesired addition of gases to the reactor. A quantity of dry catalyst is transferred from a catalyst reservoir maintained under dry conditions to a catalyst chamber. An inert fluid then enters the chamber to flush the catalyst charge toward the reactor. Optional embodiments include means for precontacting the dry catalyst with a modifier and for removing gas from the fluid line.

Abstract: Fluoroelastomers having copolymerized units of vinylidene fluoride major monomer, at least one other fluorinated major monomer, and at least one cure site monomer are prepared in an aqueous suspension polymerization process using an initiator consisting essentially of a solution of an oil soluble peroxide in a water-soluble hydrocarbon solvent.

Abstract: A method for producing poly(p-t-butoxystyrene) by a polymerization reaction of p-t-butoxystyrene characterized in that p-t-butoxystyrene or a solution thereof is added little by little to a mixture of the reaction solvent and the polymerization initiator, and water content of the p-t-butoxystyrene or a solution thereof is in a range of 5-70 ppm, and according to the method, poly(p-t-butoxystyrene) having narrow molecular weight distribution can be produced securely, with easy reaction temperature control.

Abstract: Process for the synthesis of block polymers, homopolymers and copolymers of narrow polydispersity having formula (1) by contacting selected vinyl monomer(s), vinyl-terminated compound(s) and free radicals in which effective control of production of polymer is achieved by controlling the mole ratio of vinyl monomer(s), vinyl-terminated compound(s) and free radicals relative to one another; and polymers produced thereby

Abstract: A polymer dispersion is prepared by free radical polymerization of an aqueous monomer emulsion by a process in which the monomer emulsion is prepared continuously at the rate of consumption.

Abstract: A method for making viscosity index improving copolymer includes polymerizing a monomer mixture including a first (meth)acrylate monomer, a second (meth)acrylate monomer and a styrenic monomer in an oil soluble diluent and in the presence of a polymerization initiator to form a polymerization intermediate and then polymerizing an additional amount of the first (meth)acrylate monomer, the second (meth)acrylate monomer or a mixture thereof in the presence of the polymerization intermediate to provide a solution of a viscosity index improving copolymer in the diluent wherein the solution includes less than or equal to 1000 parts by weight residual styrene monomer per one million parts by weight solution.

Abstract: A process for producing a monodisperse polymer which has a number-average molecular weight from 1,000 to 100,000 and a molecular weight distribution Mw (weight-average molecular weight)/Mn (number-average molecular weight)=1.00 through 1.50 is disclosed. This process comprises: homopolymerizing or random copolymerizing an anionic polymerizable compound by living anionic polymerization using an organic alkali metal and/or an alkali metal as a polymerization initiator, wherein a target molecular weight is obtained by adding the compound divided into multiple steps.

Abstract: A process for the preparation of resin particles comprising: adding a mixture of at least one free radical reactive monomer continuously to a heated aqueous solution of a water soluble free radical initiator and a water soluble salt to form latex emulsion particles and aggregates thereof; and wherein the rate of continuous addition of said monomer is greater than the rate at which monomer is consumed by polymerization.

Abstract: A process for forming a hydrophobically modified water soluble or water dispersible polymer by utilizing a micellar polymerization technique comprising the steps of: (1) providing a reaction medium including one or more water soluble or water dispersible monomers and one or more surface active agents or protective colloids; (2) incrementally adding one or more ethylenically unsaturated monomers having hydrophobic properties to said reaction medium; (3) initiating polymerization of said one or more water soluble or water dispersible monomers with said one or more ethylenically unsaturated monomers having hydrophobic properties; and (4) continuing polymerization of said one or more water soluble or water dispersible monomers with said one or more ethylenically unsaturated monomers having hydrophobic properties while incrementally adding said one or more ethylenically unsaturated monomers having hydrophobic properties to said reaction medium is provided.

Abstract: Solvent-free, fine white powders of high molecular weight copolymers of maleic anhydride and C1-C4 alkyl vinyl ethers, which are particularly useful as starting materials for denture adhesives. A solvent-free process for making such copolymers also is described.

Abstract: This invention relates to copolymers which contain hydroxyl groups and which are based on vinyl esters of monocarboxylic acids, wherein the copolymers which contain hydroxyl groups have an OH number of 110-170 mg KOH/g, an acid number of 5-35 mg KOH/g and a number average molecular weight M.sub.n of 1500-8000 g/mole and are obtainable by the polymerisation of A) 5-20% by weight of one or more vinyl esters of saturated monocarboxylic acids, B) 10-30% by weight of one or more aromatic vinyl hydrocarbons, C) 41-55% by weight of hydroxy-functional, polymerisable, unsaturated monomers, and D) 0-40% by weight of further polymerisable, unsaturated monomers, wherein component C) contains C1) 40-70% by weight of one or more hydroxyalkyl esters of .alpha.,.beta.-unsaturated monocarboxylic acids, C2) 1-10% by weight of one or more lactones, and C3) 30-55% by weight of one or more reaction products of an .alpha.,.beta.-unsaturated monocarboxylic acid with a glycidyl ester of a saturated .alpha.,.alpha.

Abstract: An olefin polymerization process in which at least two introductions of hydrogen are made during the olefin polymerization reaction. Suitable catalysts include metallocenes of the general formula (Cp).sub.m TiX.sub.n, wherein Cp is a substituted or unsubstituted cyclopentadienyl ring, X is a halogen, m=1-2, n=2-3, and wherein m+n=4, and conventional Ziegler-Natta catalysts blended with or modified by such metallocenes.

Abstract: A process for the preparation of continuously variable-composition copolymers by effecting gradual changes in monomer composition during the polymerization is disclosed. Poly(meth)acrylate copolymers made by the process of the present invention have improved lubricating oil additive properties, for example, as pour point depressants, when compared to related polymer additives made by conventional means.

Abstract: This invention relates to graft copolymers containing polydiorganosiloxane and polybutylene grafts. More particularly this invention relates to a graft copolymer having a backbone and two or more polymeric side chains, the copolymer formed from the copolymerization of at least one acryloxyalkyl-functional polydiorganosiloxane macromonomer, at least one acryl-terminated, carboxyl-functional polybutylene macromonomer, and at least one ethylenically unsaturated monomer which is copolymerizable with the polydiorganosiloxane and polybutylene macromonomers. This invention also relates to a method of making graft copolymers containing polydiorganosiloxane and polybutylene grafts.

Abstract: Repulpable PSA compositions and constructions that exhibit high adhesive performance on a wide range of substrates are provided. In one embodiment, a PSA composition comprises a blend of two emulsion acrylic copolymers. The first type is a repulpable, emulsion acrylic copolymer that passes TAPPI UM 213. Preferably, the copolymer is prepared by sequential polymerization. The second type of copolymer is a non-repulpable, gpp or removable, repositionable, emulsion acrylic copolymer, also preferably prepared by sequential polymerization. The PSA compositions are inherently tacky and can be used in labels and tapes. In addition, they can be added to other PSAs as external tackifiers.

Abstract: A process for forming a hydrophobically modified water soluble or water dispersible polymer by utilizing a micellar polymerization technique comprising the steps of: (1) providing a reaction medium including one or more water soluble or water dispersible monomers and one or more surface active agents or protective colloids; (2) incrementally adding one or more ethylenically unsaturated monomers having hydrophobic properties to said reaction medium; (3) initiating polymerization of said one or more water soluble or water dispersible monomers with said one or more ethylenically unsaturated monomers having hydrophobic properties; and (4) continuing polymerization of said one or more water soluble or water dispersible monomers with said one or more ethylenically unsaturated monomers having hydrophobic properties while incrementally adding said one or more ethylenically unsaturated monomers having hydrophobic properties to said reaction medium is provided.

Abstract: A polymeric material comprising at least first and second polymer parts, which first part has a number average molecular weight higher than that of the second part and which first and second polymer parts each comprise a respective polymer part derived from at least one ethylenically unsaturated monomer, is prepared by a process which comprises the steps of (1) preparing, by aqueous suspension polymerisation the first, higher molecular weight polymer part in the presence of a free radical initiator, but in the absence of a chain transfer agent to form a suspension of the first, higher molecular weight part and thereafter (2) preparing by aqueous suspension polymerisation the second, lower molecular weight part, which preparation step (2) is carried out in the presence of the suspension of the first, higher molecular weight part, a free radical initiator and a catalytic chain transfer agent (CCTA).

Abstract: A method for preparing a polymer composite material comprises a step in which a monomer which forms a rigid polymer is compounded with a flexible polymer or a monomer which forms a flexible polymer to form a mixture which is polymerized in a further step by kneading in a molten state. The monomer which forms the rigid polymer is added several times to the polymerized mixture in a repeated series of compounding steps followed by a further polymerization. The compounding amount of the rigid polymer polymerized in the matrix of the polymer composite material can be increased while preventing the agglomeration and enlargement of fibers of the rigid polymer.

Abstract: The invention relates to a method of surface sizing cellulose based products such as paper, board and paper board. The method comprises applying to the surface of said products an aqueous dispersion of a copolymer obtainable by free-radical emulsion polymerization of a monomers mixture comprising at least one monomer selected from the group consisting of styrene and derivatives thereof; at least one monomer selected from the group consisting of esters of ethylenically unsaturated carboxylic acids and alkanols; and at least one monomer selected from the group consisting of ethylenically unsaturated carboxylic and sulfonic acids and salt thereof; optionally in combination with other ethylenically unsaturated copolymerizable monomers.

Abstract: The present invention provides a method for substantially continuously polymerizing olefins comprising: introducing into a first reaction zone a fresh olefin polymerization catalyst; contacting said fresh olefin polymerization catalyst in said first reaction zone with a first vent mixture at a first feed rate and under conditions sufficient to form and avoid melting a polyolefin, wherein first vent mixture comprises unreacted olefins and a diluent vented from a second reaction zone; withdrawing a vent product of unreacted olefins and diluent from said first reaction zone; withdrawing from said first reaction zone a first product mixture comprising said catalyst and said polyolefin; passing said first product mixture to said second reaction zone; contacting said first product mixture in said second reaction zone with a second vent mixture at a second feed rate and under conditions sufficient to form and avoid melting said polyolefin, wherein said second vent mixture comprises a material selected from the group

Abstract: Disclosed is a method for controlling or reducing the amount of powder fines present in a polyethylene fluidized bed reactor. The method uses hydrocarbons that are inert with respect to the polymerization reaction, as well as using reactive olefins. The reduction of powder fines provides significant operating benefits in the fluid bed process, including reduced formation of powder agglomerates in the reactor and reduced fouling of equipment in the recycle gas stream.

Abstract: In a process for producing a vinylidene fluoride resin by polymerizing vinylidene fluoride or a mixture of vinylidene fluoride and a vinyl monomer copolymerizable with vinylidene fluoride, a portion of an iodide compound represented by the formula: X-R.sub.f -X wherein R.sub.f is a divalent organic group containing at least two divalent fluoroalkyl ether groups: and X's are independently an iodine atom or a fluorine atom, provided that at least one of the X's is an iodine atom; is added to start the polymerization, and the remainder of the iodide compound is further added dividedly at least twice in the course of the polymerization. This process enables to obtain a vinylidene fluoride resin having a viscosity-average molecular weight of 150,000 or more and also having a superior water repellency. This resin has good mechanical strength and release properties and also can be well processed into films.

Abstract: The synthesis and characterization of novel linear polymers and multi-arm star polymers comprising polyisobutylene arms connected to a well-defined calixarene core are described. The polymers are directly telechelic. They synthesis has been achieved using the "core first" method wherein multifunctional calix?n!arene (where n=4 to 16) derivatives or their monofunctional analogues are used as initiators which, in conjunction with certain Freidel-Crafts acids as co-initiators, induce the living polymerization of isobutylene or a similar carbocationic polymerizable monomer. Novel initiators suitable for inducing the polymerization are also described.

Abstract: Monodisperse crosslinked polymers prepared by seed/feed polymerization have less tendency to tack when a microencapsulated monodisperse crosslinked polymer has been used as seed. Compared with the seed used, the seed/feed polymer obtained exhibits substantially less broadening of the particle size distribution when microencapsulated seed has been used.

Abstract: Process with two or more steps for the preparation in suspension of mixtures of ethylene-propylene (EPM) elastomer homopolymers or ethylene-propylene-diene (EPDM) elastomer terpolymers in the presence of a catalytic system essentially consisting of a compound of Vanadium and a cocatalyst essentially consisting of an Aluminum alkyl and in the presence of an activator, the above process being characterized in that:a) in the first step a first polymerization of the monomers is carried out in the presence of the Vanadium based catalyst;b) in the second or subsequent steps further polymerizable monomers and activator are added to the suspension of the polymer obtained in step (a).

Abstract: A process for the free radical initiated polymerization of unsaturated species characterized by the use of compound of Formula (I) as chain transfer agents: ##STR1## wherein: X is selected from hydrogen; CN; optionally substituted aryl; COOH; COOR; C(O)NHR.sup.6 ; C(O)NR.sup.7 R.sup.8 ; and halogen;Q is selected from COOR.sup.1 ; CN; and C(O)NR.sup.7 R.sup.8 ;Y is selected from hydrogen; C.sub.1 to C.sub.6 alkyl; C.sub.1 to C.sub.6 alkyl substituted with one or more substituents selected from hydroxy, amino, C.sub.1 to C.sub.6 alkoxy, C.sub.1 to C.sub.6 alkoxycarbonyl, halogen, CN and optionally substituted aryl; C.sub.1 to C.sub.6 alkenyl; and C.sub.1 to C.sub.6 alkynyl;Z is selected from COOR.sup.2 ; CN; and optionally substituted aryl;R.sup.3 and R.sup.4 are the same or different and are selected from hydrogen C.sub.1 to C.sub.4 alkyl and halogen; or R.sup.3 and R.sup.

Abstract: A free radical polymerization process for the preparation of a polymer comprising heating a mixture of a free radical initiator, a stable free radical agent, a metal catalyst, or a metal stable free radical complex catalyst, and at least one polymerizable monomer; cooling said mixture; and optionally isolating said polymer.

Abstract: A vinyl chloride polymer is prepared through suspension polymerization of a vinyl chloride monomer in the presence of a polymerization initiator in a reactor. The reactor is charged with up to 4/5 of the overall monomer charge to initiate polymerization. Polymerization is carried out under a certain saturated vapor pressure of P1 kgf/cm.sup.2 at a preset polymerization temperature. When the internal pressure of the reactor declines to P2 kgf/cm.sup.2, the remainder of the overall monomer charge is continuously fed to the reactor so as to maintain the internal pressure within the range of (P1-.DELTA.P) wherein .DELTA.P=P1-P2 ranges from 0.1 to 2.0 kgf/cm.sup.2. A vinyl chloride polymer having a high degree of polymerization is efficiently produced while alleviating the load of heat removal.

Abstract: An olefin polymerization process in which at least two introductions of hydrogen are made during the olefin polymerization reaction. Suitable catalysts include metallocenes of the general formula (Cp).sub.m TiX.sub.n, wherein Cp is a substituted or unsubstituted cyclopentadienyl ring, X is a halogen, m=1-2, n=2-3, and wherein m+n=4, and conventional Ziegler-Natta catalysts blended with or modified by such metallocenes.

Abstract: A maleic acid-based copolymer is provided which has a weight-average molecular weight of 1,000 to 100,000, a calcium ion-capturability of 300 mgCaCO.sub.3 /g or higher calculated as calcium carbonate, and a clay-dispersibility of 1.2 or higher. Another maleic acid-based copolymer is also provided which has a level of adsorption to clay within the range of 20 to 90% and a calcium ion-stabilization degree constant of 4.0 or larger.

Abstract: A bimodal latex having high printing strength, reduced residue and a controlled polymer gel content which can be utilized for paper coating compositions and to a process for making the bimodal latex. The high strength bimodal latex, prepared by emulsion polymerization, includes in polymerized form open chain conjugated diene monomer, alkenyl aromatic monomer and at least one ethylenically unsaturated monomer selected from the group consisting of ethylenically unsaturated carboxylic acid and derivatives thereof.

Abstract: An saturated nitrile-conjugated diene copolymer obtained by copolymerizing acrylonitrile with butadiene in the presence of a free radical initiator and an alkylthiol compound as a molecular weight modifier. A part of the monomers is incorporated in a monomer charge before polymerization, and the remainder thereof is added in a polymerization mixture during polymerization. The alkylthiol compound has 12 to 16 carbon atoms, which include at least three tertiary carbon atoms, and further has a sulfur atom directly bound to at least one of the tertiary carbon atoms. The copolymer has a Mooney viscosity of 15 to 450 and a bound nitrile content of 10 to 60% by weight. The breadth (.DELTA.AN) of compositional distribution of the unsaturated nitrile in the copolymer is 3 to 20. The copolymer is used in combination with a sulfur-containing vulcanizer.

Abstract: A method for making a polymer includes adding a first portion of a colloidal stabilizer to an aqueous medium, adding a monomer mixture, said monomer mixture including a monomer charge and a second portion of colloidal stabilizer and said monomer charge including from about 40 parts by weight to about 70 parts by weight of a vinyl ester monomer per 100 parts by weight monomer charge and from about 30 parts by weight to about 60 parts by weight of a (C.sub.1 -C.sub.12)alkyl (meth)acrylate monomer per 100 parts by weight monomer charge, to the aqueous medium and polymerizing the monomers to form an emulsion of the polymer in the aqueous medium.