Radiation-induced polymerization of ethylene in a pilot plant. II. Development of wet-wall process

Radiation-induced polymerization of ethylene using tert-butyl alcohol aqueous solution as a medium was carried out in a pilot plant with 10 liter reactor at pressures of 100 to 400 kg/cm², ethylene feed rates of 1.2 to 11.8 kg/hr, medium feed rates of 0 to 100 liter/hr, dose rates of 0.6 × 10⁵ to 1.4 × 10⁵ rad/hr, and at room temperature. The space-time yield and molecular weight of polymer were in the range of 1.2 to 16.7 g/liter hr and 6 × 10³ to 2 × 10⁵, respectively. The space-time yield and molecular weight increased with pressure and mean residence time. The space-time yield was the maximum at an ethylene molar fraction of 0.5. The produced polymer was continuously taken out from the high-pressure system as a slurry. The amount of deposited polymer to the reactor wall was markedly decreased, and five full days continuous operation was successfully performed with the space-time yield of 13.5 g/liter hr.     

Radiation-induced polymerization of ethylene in pilot plant. III. Heavy-phase recycling process

Radiation-induced polymerization of ethylene using aqueous tert-butyl alcohol as medium was carried out in a large-scale pilot plant with a 50-liter central source-type reactor at a pressure of 105 to 395 kg/cm², temperature of 30° to 80°C, mean dose rate of 4.5 × 10⁴ to 1.9 × 10⁵ rads/hr, ethylene feed rate of 5.5 to 23.5 kg/hr, and medium feed rate of 21 to 102 l./hr. The space–time yield and molecular weight of the polymer were in the range of 4.7 to 16.8 g/l.-hr and 1.3 × 10⁴ to 8.9 × 10⁴, respectively. The space–time yield and molecular weight increased with mean residence time at 30°C, whereas at 80°C they became almost independent of the time. The space–time yield increased with pressure and dose rate, slightly decreased with temperature, and was maximum at ethylene molar fraction of 0.5. The polymer molecular weight increased with pressure and ethylene molar fraction, and decreased with dose rate and temperature. The total amount of deposited polymer on the reactor wall, source case wall, and scraping blades was usually less than 1 kg, which was negligibly small for the analysis of polymerization. Continuous discharge of the polymer slurry and production of fine-powder polyethylene were successfully carried out. In the central source-type reactor, a dose rate of 1.9 × 10⁵ rads/hr was obtained with a ⁶⁰Co source of ca. 12 kCi.     

Structure and properties of polyethylene produced by γ-radiation polymerization in flow system

The radiation-induced polymerization of ethylene was carried out by use of a benchscale plant with a flow-type reactor of 1 liter capacity under the following conditions: pressure, 200–400 kg/cm²; temperature, 30–90°C; irradiation intensity, 3.8 × 10⁵ rad/hr; and ethylene flow rate, 300–3000 nl/hr. The molecular weight of polymer formed was shown to decrease with increasing reaction temperature and to increase with increasing pressure. When the ethylene flow rate increases, the molecular weight decreases in the polymerization at 30–60°C, but it does not change in the polymerization at 75–90°C. Methyl group content, which is a measure of short-chain branching of the polymer, increases with increasing reaction temperature, i.e., ca. 1 CH₃/1000 CH₂ at 30°C and ca. 9 CH₃/1000 CH₂ at 90°C. Methyl content is independent of the ethylene flow rate. The changes in the melt index of polymer with reaction conditions corresponds to the change of the molecular weight. The density, crystallinity, and melting point of polymer decrease with the reaction temperature as the short-chain branching increases, and they are almost independent of ethylene flow rate and pressure.     

Effect of fluid motion on radiation-induced polymerization of ethylene in a tubular reactor

The influence of the turbulence of reactant on the radiation-induced polymerization of ethylene in 40 mole-% Freon-114 (C₂Cl₂F₄) was studied using a tubular reactor at 400 kg/cm² and 25°C with a dose rate of 1.3 × 10⁵ rad/hr. At constant linear velocity and tube diameter, the polymer concentration was shown to increase linearly with the reactor tube length. This indicates that the polymerization is in a stationary state. By changing the linear velocity from 3.5 to 42.7 cm/sec and the tube diameter from 5 to 14 mm, the space time yield and the molecular weight of polymer were found to vary between 0.21 and 0.46 mole ethylene/1.-hr and from 5.0×10³ to 10.5×10³, respectively. The space time yield and molecular weight decreased sharply to about one half those in the static polymerization with increasing fluid turbulence and then slowly increased in the highly turbulent state. Similar effects were observed in a tank reactor when the stirring speed was changed.     

Radiation-induced emulsion polymerization of tetrafluoroethylene

The radiation-induced emulsion polymerization of tetrafluoroethylene was carried out with the use of ammonium perfluorooctanoate as an emulsifier at an initial pressure of ca. 30–35 Kg/cm². The polymerization rate was shown to be proportinal to about the 0.8 power of the dose rate in the range of 2 × 10⁴ to 10⁵ R/hr and to be almost independent of emulsifier concentration. The molecular weight of the polymer lies in the range of 10⁴ to 10⁵, increases with reaction time at the initial stage, and decreases with emulsifier concentration, but is independent of the dose rate from 2 × 10⁴ to 6 × 10⁴ R/hr. If the emulsifier is not used, a polymer with a molecular weight as high as 1.8 × 10⁶ to 2 × 10⁷ is obtained. Apparently, the emulsifier and its radiolysis products act as chain transfer agents. Postirradiation polymerization was found to take place with the formation of products with increased molecular weight.     

Emulsion polymerization of tetrafluoroethylene: effects of reaction conditions on the polymerization rate and polymer molecular weight

The emulsion polymerization of tetrafluoroethylene (TFE) was carried out in a semibatch reactor using a chemical initiator (ammonium persulfate) and a fluorinated surfactant (FC-143). The effects of the reaction condition were investigated though the polymerization rate, molecular weight of polytetrafluoroethylene (PTFE), and stability of the dispersion. The emulsion polymerization of TFE was different from conventional emulsion polymerization. The polymerization rate was suppressed when the polymer particles were significantly coagulated. The polymerization rate increased with operating temperature, surfactant concentration, and agitation speed, due to the enhanced stability of the polymer particles. However, once the parameter value was reached, the rate decreased due to the coagulation of the particles. Stable PTFE dispersion particles were obtained when the surfactant concentration was in the range between 3.48 × 10⁻³ and 32.48 × 10⁻³ mol/liter, which is below critical micelle concentration (CMC). The molecular weight of the PTFE obtained was a function of the surfactant and initiator concentrations, and the polymerization temperature. The molecular weight increased as each parameter decreased. This is against the phenomena observed in a conventional emulsion polymerization. A stable PTFE dispersion polymer having a high molecular weight was obtained by optimizing the reaction conditions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 777–793, 1999     

Radiation-induced seeded copolymerization of tetrafluoroethylene with propylene. I. Effects of agitation and dose rate

Seeded copolymerization of teterafluoroethylene with propylene by radiation was studied by semibatch experiment at a constant pressure of 25 kg/cm², a temperature of 40°C, and at various dose rates and monomer compositions in polymer particles. The polymerization rate and polymer molecular weight are in the ranges of 5.6–58.7 g/h.L-H₂O and 4.6 × 10⁴–1.6 × 10⁵, respectively. The polymerization rate increases with agitation speed up to 300 rpm and slightly decreases above 500 rpm. The polymer molecular weight is the highest at 300 rpm. The polymerization rate and polymer molecular weight increase with tetrafluoroethylene fraction. At lower tetrafluoroethylene fraction, the polymerization rate is proportional to the 0.7–0.9 power of the dose rate and the polymer molecular weight is almost independent. The dose rate effects are explained by considering that first-order termination by degradative chain transfer to propylene is predominant at a lower tetrafluoroethylene fraction. Decrease in the dose rate dependence of the polymerization rate and increase in that of the polymer molecular weight with the tetrafluoroethylene fraction are due to the increase in second-order termination by recombination.     

Synthesis of high molecular weight polyacrylamide flocculant by radiation polymerization

The radiation-induced polymerization of acrylamide was studied to prepare a high molecular weight and highly effective polyacrylamide flocculant. Among various solvents, mixtures of water–tert-butyl alcohol and water–acetone were found to be suitable for the synthesis of the high molecular weight polyacrylamide. For polymerization in acetone–water mixtures, the molecular weight of polymer increases with monomer concentration; but at the high concentration, intermolecular imidation of amide groups tends to take place during the polymerization to from crosslinked and water-insoluble polymer. The water-soluble polymer with the largest molecular weight of 6.7 × 10⁶ is produced in the polymerization with monomer concentration of 2.91 moles/1. at 0°C at a dose rate of 6.2 × 10² rad/hr in acetone–water mixture containing 60 vol-% water. The crosslinking of polymer of the formation of water-insoluble polymer could be avoided by the addition of K₂CO₃ or NaOH to raise the pH of the reaction mixture above 6.5. The flocculation effects were evaluated from sedimentation speed of kaolin suspension and transparency of the separated water. The sedimentation speed is proportional to the intrissic viscosity of the polymer in the range of 4 to 23 dl/g. The polymers prepared in this study show much higher sedimentation speed than commercial polyacrylamide flocculants. The transparency of the separated water is higher than 93%, similar to the results with commercial flocculants.     

Gas‐phase olefin polymerization over supported metallocene/MAO catalysts: influence of support on activity and polydispersity

Three catalysts obtained by supporting bis(n‐butylcyclopentadienyl)zirconium dichloride/methylaluminoxane on: (1) porous crosslinked poly(2‐hydroxyethylmethacrylate‐co‐styrene‐co‐divinylbenzene) particles (CAT1); (2) swellable crosslinked poly(styrene‐co‐divinylbenzene) particles (CAT2); and (3) by evaporating the catalyst precursors solution to dry powder, CAT3 were used in gas‐phase polymerization of ethylene, and ethylene/1‐hexene in a 2 L semi‐batch reactor at 80 °C and 1.4 MPa. The average polymerization activities of the three catalysts were 12.3–15.5, 4.2–10.1, and 14.3–62.9 ton PE (mol Zr h)^?1 respectively. CAT1 and CAT3 produced polyethylenes with a polydispersity range of 2.3–2.7, while that of CAT2 was 3.5–6.4. The supported catalysts produced polyolefin particles with bulk density of 0.36–0.43 g ml^?1, and essentially no fines. Ethylene/1‐hexene co‐polymerization (7 mol m^?3 initial 1‐hexene concentration in the reactor) increased polymerization activities and produced lower‐molar‐mass co‐polymers. At 21 mol m^?3 1‐hexene the polymerization activities decreased, but the relative amount of the low‐molar‐mass co‐polymer for CAT2 increased, leading to higher polydispersity. Copyright © 2006 Society of Chemical Industry     

Radiation-induced polymerization of water-saturated styrene in a wide range of dose rate

Radiation-induced polymerization of water-saturated styrene (water content 3.5 × 10^-2 mole/liter) was carried out in a wide range of dose rate between 1.2 × 10³ and 1.8 × 10⁷ rad/sec, and compared with the polymerization of the moderately dried styrene (water content 3.2 × 10^-3 mole/liter). Molecular weight distribution curves of the polymerization products showed that they were generally consisted of four parts, namely, oligomers, radical, cationic, and super polymers. Contributions of the four constitutents to the polymerization and the number average degrees of polymerization (DP) of the four kinds of polymers were calculated by the graphical analysis of the curves. The rate of radical polymerization and DP of radical polymers are independent of the water content; the dose rate dependences of the polymerization rate and DP agree with the well known square root and inverse square root laws, respectively, of the radical polymerization of styrene. The rate of ionic polymerization is directly proportional to the dose rate, but it decreases, at a given dose rate, inversely proportional to the water content of styrene. DP of ionic polymer is independent of the dose rate but decreases with increasing water content. The super polymer of DP about 10⁴ is not formed in the case of the moderately dried styrene. G values for the initiating radical and ion formation are calculated to be, independently of the dose rate and water content, 0.66 and 0.027, respectively. It was suggested that oligomer was formed in the early stage by the interaction of cation with anion and only those cations which had survived underwent polymerization.     

Late Transition Metal Catalyst Based on Cobalt for Polymerization of Ethylene

The late transition metal catalyst of [2,6-diacethylpyridinebis(2,6-diisopropylphenylimine)]cobalt(II) dichloride was prepared under controlled conditions and used for polymerization of ethylene. Methylaluminoxane (MAO) and triisobuthylaluminum (TIBA) were used as a cocatalyst and a scavenger, respectively. The highest activity of the catalyst was obtained at about 30°C; the activity decreased with increasing temperature. At polymerization temperatures higher than 50°C not only was a sharp decrease in the activity observed but also low molecular weight polyethylene product that was oily in appearance was obtained. The polymerization activity increased with increasing both of the monomer pressure and [MAO]:[Co] ratio. However, fouling of the reactor was strongly increased with increasing both of the monomer pressure and the amount of MAO used for the homogeneous polymerization. Hydrogen was used as the chain transfer. The activity of the catalyst and the viscosity average molecular weight (M_v) of the polymer obtained were not sensitive to hydrogen concentration. However, the viscosity average molecular weight of the polymer decreased with the monomer pressure. The (M_v), the melting point, and the crystallinity of the resulting polymer at the monomer pressure of 1 bar and polymerization temperature of 20°C were 1.2 × 10⁵, 133°C, and 67%, respectively. Heterogeneous polymerization of ethylene using the catalyst and the MAO/SiO₂ improved morphology of the resulting polymer; however, the activity of the catalyst was also decreased. Fouling of the reactor was eliminated using the supported catalyst system.     

Polymerization of olefins through heterogeneous catalysis. XIV. The influence of temperature in the solution copolymerization of ethylene

The influence of temperature variation on the kinetics and the polymer properties in the homo- and copolymerization of ethylene in a solution reactor is discussed. The Polymerization is conducted in a semibatch mode at 320 Psig total reactor pressure for 10 min polymerization time. Temperature variations in the range 145–200°C in both home-and copolymerization of ethylene with 1-octene shows that the highest catalyst yield was obtained at temperature of 165–175°C. At the optimal temperature, a high initial maximum in the rate of ethylene consumption is attained in a few seconds followed by a relatively slow decay when compared with polymerization conducted at higher temperatures. Polymerization at temperatures ≥ 185°C resulted in a lower peak in the consumption rate of ethylene accompanied by a rapid decay with time. In the case of ethylene/1-Octene copolymerization, a rather low comonomer incorporation level is obtained at the conditions employed; the 1-octene incorporated was only 0.2–0.7 mol %. Higher M_w values, of about 350,000 at 145°C, are obtained in homopolymerization in comparison to M_w values obtained in copolymerization, of about 195,000 at the same temperature. Over the temperature range of 145–200°C, both M_w and M_n values vary by about 40%. © 1993 John Wiley & Sons, Inc.     

Sorption studies of propylene in polypropylene. Diffusivity in polymer particles formed by different polymerization processes

Propylene was polymerized in gas phase and liquid phase by using a novel nonporous Ziegler–Natta‐catalyst system. The polymer particles formed at different polymerization times were used for sorption measurements. In both cases it was found that the effective diffusion coefficient is increasing with increasing size of polymer particles and the effective diffusion coefficients of polymer particles formed by liquid‐phase polymerization are larger than those of polymer particles produced by gas‐phase polymerization. The effective diffusion coefficients of polymer particles are in the range of 2 × 10^?11 to 1.6 × 10^?10 m²/s with activation energies from 34 to 22 kJ/mol. The analyzed polymer particles have average diameters between 250 and 875 μm. The solubility of propylene in polypropylene particles can be described by the law of Henry at conditions studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2642–2648, 2006     

Reactions catalyzed by soda lime glass. II. Polymerization of methyl methacrylate

Rates of sodium bisulfite-initiated polymerization of methyl methacrylate (MMA) in water were determined in the presence and absence of colorless and colored soda lime glass (amber glass). The rate of polymerization increased in the presence of glass. For example, the rate of polymerization increased from 1.3 × 10^?5 mole/(1.sec) to 3.9 × 10^?5 mole/(1.sec) when amber glass (200 mesh) concentration was varied from 0 to 30 g/l. of the reaction mixture at 40°C. It was found that the finer the particle size of the soda lime glass, the higher was the conversion percentage of monomer to polymer. A glass–polymer combination containing 20 g glass was prepared and subjected to Soxhlet extraction with benzene; the insoluble polymer part was found to increases as initiator concentration was decreased.     

Radiation-induced polymerization of ethylene in pilot plant. IV. Kinetic analysis

The kinetics of the radiation-induced polymerization of ethylene in a flow system using tert-butyl alcohol aqueous solution as a medium were studied. The polymerization was carried out in a large-scale pilot plant with a 50-liter central source-type reactor at various mean residence times and does rates under constant pressure of 300 kg/cm², temperature of 30°C, and ethylene molar fraction of ca. 0.4. The reaction mixture in the reactor was back-mixed flow from the residual polymer concentration in the reactor. The results of the polymerization were analyzed by kinetic treatment based on a reaction mechanism with both first-and second-order terminations for the propagating radical. The apparent rate constants, except for that of second-order termination (k_t2), were consistent with those determined by small-scale batch experiments. The k_t2 is 20 to 40 times larger than that in the batch experiments. The k_t2 increases with decrease in mean residence time and with agitation, probably because of mobility of the propagating radical.     

Characterization of poly(methyl methacrylate) from radiation-induced polymerization in the presence of a kaolin clay substrate

Two types of polymer are formed in the radiation-initiated polymerization of methyl methacrylate (MMA)–kaolin clay complexes. Homopolymer can be extracted from the complex by the use of organic solvents. Inserted polymer must be removed by dissolution of the polymer–clay complex with hydrofluoric acid. The polymers formed show no differences in structure (as determined by infrared analysis), had high molecular weights (1–5 × 10⁶), and had similar molecular weight distributions (as determined by GPC). The molecular weights of the homopolymer increased as temperature increased (25°–75°C), and dose rate decreased (24.9–7.35 rads/sec). The isotacticity of the polymers when compared to irradiated bulk polymer decreased as follows: inserted > homo > bulk. The compressive properties of the irradiated composite compared well with those of commercial bulk polymers. Degradation temperatures were 20° to 30°C higher for the composite than for the commercial chemically initiated bulk polymer.     

Emulsion polymerization of methyl methacrylate in the presence of burnt mazote boiler deposit

The emulsion polymerization of methyl methacrylate (MMA) using different initiators was carried out in the absence and presence of burnt mazote boiler deposit (BMBD). When sodium persulfate or potassium persulfate was used, the initial rate of polymerization was found to decrease with increase of the burnt mazote boiler deposit concentration but to increase when sodium bisulfite was used as initiator. The initial rate of polymerization was found to be higher in nitrogen atmosphere than in air. The apparent activation energy (E_a) was found to be 12.4 × 10⁴ J/mol and 16.3 × 10⁴J/mol in the absence and presence of burnt mazote boiler deposit when potassium persulfate was used as initiator and 5.9 × 10⁴ J/mol and 5.1 × 10⁴ J/mol when sodium bisulfite was used as initiator, respectively. The mean average molecular weights for PMMA were found to increase with increase of the burnt mazote boiler deposit when sodium bisulfite was used as initiator.     

Initiator‐fragment incorporation radical polymerization of ethylene glycol dimethacrylate in the presence of 1,1‐diphenylethylene: synthesis and characterization of soluble hyperbranched polymer nanoparticles

The polymerization of ethylene glycol dimethacrylate (EGDMA) as crosslinker was carried out at 70 and 80 °C in benzene using dimethyl 2,2′‐azobisisobutyrate (MAIB) as initiator at concentrations as high as 0.50–0.70 mol l^?1 in the presence of 1,1‐diphenylethylene (DPE), where the concentrations of EGDMA and DPE were 0.50–0.70 and 0.25–0.50 mol l^?1, respectively. The polymerization proceeded homogeneously, without gelation, to give soluble polymers. The yield and molecular weight of the resulting polymers increased with time. The homogeneous polymerization system involved ESR‐observable DPE‐derived radicals of considerably high concentration (3.6–5.3 × 10^?5 mol l^?1). The methoxycarbonylpropyl groups as MAIB‐fragments were incorporated as a main constituent (35–50 mol%) into the polymers (initiator‐fragment incorporation radical polymerization). The polymers also contained DPE units (15 mol%) and EGDMA units with double bonds (10–25 mol%) and without double bonds (20 mol%). Results from gel permeation chromatography (GPC)–multiangle laser light scattering (MALLS), transmission electron microscopy (TEM) and viscometric measurements revealed that the individual polymer molecules were formed as hyperbranched nanoparticles. Copyright © 2004 Society of Chemical Industry     

Effective promotion of tetrahydrofuran polymerization initiated with heteropolyacid

Tetrahydrofuran was polymerized using the heteropolyacid H₃PW₁₂O₄₀ as the initiator and ethylene oxide as the promoter, which effectively increased the rate and conversion of the polymerization. Water and butylene glycol were used to control the molecular weight of the product in the range of 1000–3000. The polymer was found to be polyether glycol containing 10–22 mol % oxyethylene moieties with hydroxyl groups at both chain ends. The melting point was ∼ 10°C lower compared to polytetramethylene ether glycol having the same molecular weight. The concentration of active species remained unchanged in the main period of the polymerization, indicating the absence of chain termination. The values of the chain propagation rate constant of tetrahydrofuran polymerization at 0 and 20°C were found to be 3.78 × 10⁻³ and 1.98 × 10⁻² L mol⁻¹ s⁻¹, respectively, which are close to the rate constant of chain propagation of tetrahydrofuran on ionic active species. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2303–2308, 1999     

A novel polymer chain growing mode and styrene copolymer prepared with low molecular weight copolymer of α‐methylstyrene and styrene as macroinitiator

A new polymer chain growth mode, having multiple potential chain propagation sites, initiated by oligomer of α‐methylstyrene (AMS) and styrene (St) (PAS) is presented in this article. The effects of PAS content, AMS fraction in PAS and reaction temperature on bulk polymerization of St have been investigated. It is demonstrated that the PAS performed as macroinitiator in the polymerization of St. The average molecular weights of products increase significantly with the evolution of the polymerization, which is different from conventional free radical polymerization. With 20 wt % macroinitiator, the molecular weights increase from 1.21 × 10⁵ to 3.00 × 10⁵ with the monomer conversion increasing from 15.3 to 83.0%. This unique feature is tentatively attributed to both the reversible polymerization–depolymerization of AMS segments at high temperature which could generate more than one propagation sites in a polymer chain and the combination termination of St free radical polymerization. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41460.