Abstract  In this work, the effects of two silane type external donors, Ph2Si(OCH3)2 (DPDMS) and dicyclopentyldimethoxysilane (DCPDMS) on propylene slurry polymerisation in the presence of hydrogen with a MgCl2/TiCl4/DIBP - Al(C2H5)3 catalyst system were investigated, and the tacticity distribution and molecular weight distribution (MWD) of polypropylene (PP) were further regulated by using silane/ether (ROCH3, R = n-Bu, i-C8H17) composite external donors. The tacticity distribution of PP, as revealed by successive self-nucleation and annealing (SSA) thermo analysis of the polymer, is markedly changed by the external donors. DCPDMS shows much stronger effects than DPDMS. Addition of the ether as an auxiliary external donor in MgCl2/TiCl4/DIBP-TEA/silane (DPDMS or DCPDMS) lead to further increase in catalytic activity and isotacticity of PP, and changes in tacticity distribution. By using the composite external donors, PP with both higher isotacticity index, lower molecular weight or narrower molecular weight distribution was prepared at high activity. Effects of the external donors on the active centre distribution were discussed based on the results of deconvoluting the MWD curve with multiple Flory 'most-probable' distributions, and possible mechanism of the external donor effects was proposed. 17 Refs.

Abstract  The solubility of 1-hexene was measured for linear low-density polyethylenes (LLDPEs) produced over a heterogeneous Ziegler-Natta catalyst, Mg(OEt)(2)/DIBP/TiCl4-TEA (ZN), and over a homogeneous metallocene catalyst, (2-MeInd)(z)ZrCl2-MAO (MT). The 1-hexene solubility in LLDPEs was well represented by the Flory-Huggins equation with a constant value of chi. ZN-LLDPEs dissolved a larger amount of 1-hexene and thus showed a lower value of chi compared to MT-LLDPEs. The Flory-Huggins interaction parameter chi, or the solubility of 1-hexene at a given temperature and pressure, was suggested as a sensitive measure for the composition distribution of LLDPEs. (C) 2002 Wiley Periodicals, Inc.

Abstract  A new generation of magnesium chloride supported Ziegler-Natta catalysts that contain dialkyl propane diethers as internal donors produced highly stereospecific PP even without any external donor being present. Results from three different catalysts containing 2,2-diisobutyl-1,3-dimethoxypropane, 2,2-dicyclopentyl-1,3-dimethoxypropane, and 2-ethyl-2-butyl-1,3-dimethoxypropane as internal donors are compared. The same donors were also studied by using them as external donors with a catalyst containing diisobutyl phthalate as internal donor. Data are shown for isotacticity index, isotactic productivity and isotactic fraction. The present results, along with previously obtained findings on traditional supported Ziegler-Natta catalysts, permit a general comprehension of the role of internal and external donors. 10 refs. (Presented at STEPOL'94, Int. Symp. on Synthetic, Structural and Industrial Aspects of Stereospecific Polymerisation, Milan, Italy, 6th-10th June 1994).

Abstract  Magnesium chloride supported vanadium/titanium bimetallic Ziegler-Natta catalysts with di-i-butyl phthalate as internal donor for copolymerisation of ethylene and propylene were prepared. The effects of reaction temperature, ethylene/propylene molar ratio, aluminium/vanadium (Al/V) molar ratio and titanium/vanadium molar ratio on the catalytic activity were investigated. The molecular weight, molecular weight distribution, sequence composition and crystallinity of the products were measured by gel permeation chromatography, 13C-NMR and differential scanning calorimetry analysis, respectively. In comparison to the vanadium and titanium catalysts, the bimetallic catalyst showed higher catalytic activity and better copolymerisation performance. The obtained ethylene/propylene copolymers have high molecular weight (105), broad molecular weight distribution, high propylene content with random or short blocked sequence structures (rErP = 1.919), low melting temperatures and low crystallinities (Xc

Abstract  The direct oxidation of n-heptane to ester using air as the oxidant under mild conditions assisted by sulfated tin oxide (SO(4)(2-)/SnO(2)) and Co modified sulfated tin oxide (SO(4)(2-)/SnO(2)-Co(2)O(3)) prepared by chemical co-precipitation method and characterized by means of SEM, XRD, FT-IR and XPS techniques was studied. From the results it was found that the catalytic activity of SO(4)(2-)/SnO(2)-Co(2)O(3) is higher than that of SO(4)(2-)/SnO(2) in this target reaction, and two asymmetric esters: diisobutyl phthalate and cyclohexylmethyl tridecyl oxalate that have not been reported in the directly oxidation of n-heptane by traditional method have been obtained. The possible mechanism was also discussed.

Abstract  (Paper given at the 10th Adhesion Seminar at Rosenheim,27-29th Jan.1988). The bonding of bodywork components in the early stages of construction is frequently undertaken, but the assembled parts must then pass through a pre-treatment before spraying, which may cause debonding if the adhesive is not fully gelled. Thermal gelling is often used, particularly with PVC plastisol adhesives; this process is described in detail. Heat stabilisers to improve performance are described, and the use of fillers to control viscosity. The use of heating ovens and induction heating are compared, as are the use of PVC plastisols, acrylate plastisols, epoxy resins and rubber adhesives. 1 ref.

Abstract  The phyto-toxic problems which have occurred through use of plasticised PVC glazing strip in greenhouses and other horticultural applications of PVC are described. It is suggested that the use of diisobutyl phthalate as plasticiser in PVC is the cause of the problems.

Abstract  Three types of polymerisation catalysts (donor-free, diisobutyl phthalate (DIBP), 2,4-pentadiol dibenzoate (PDDB) as internal donor) and a polymerisation catalyst with DIBP/PDDB as internal donor were investigated. The effects of mixed catalyst on polymer yield, isotacticity, relative molec.wt., and MWD were evaluated and the isotactic fraction of PP characterised by crystallisation analysis fractionation and Carbon-13 NMR spectroscopy. The results obtained were interpreted on the basis of a mathematical model. 10 refs.

Abstract  A catalyst component is made by chlorinating magnesium ethoxide followed by treating the solid with an electron donor, particularly diethyl phthalate or diisobutyl phthalate, at a relatively low donor level and then with a titanating agent, such as titanium tetrachloride. It is activated with an aluminium alkyl cocatalyst and produces a polymer having a broad MWD. An organosilane compound can be added as a stereoselectivity control agent.

Abstract  The effect of ethyl benzoate, diisobutyl phthalate, dibutyl ether and triethoxy(phenyl)silane as third components on propylene polymerisation with the above catalyst systems was investigated. The influence of external donors on the isotacticity, catalytic activity and average molec.wt.(Mv) was examined. If external donors were used, Mv decreased, the insoluble fraction in boiling isooctane increased and the catalytic activity was strongly influenced by the mole ratio of external donor to titanium trichloride. The results indicated that all the external donors studied had the same qualitative effect on catalytic active centres. 16 refs.

Abstract  A range of Ziegler-Natta catalysts, prepared with and without diisobutyl phthalate (DIBP) as internal donor and modified by an alkylaluminium and a methoxysilane external donor, were characterised using X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure analysis (EXAFS). EXAFS indicated a more ordered structure around the titanium atom in systems containing DIBP. Different titanium-chlorine distances were found and discussed, and the effect this has on binding energy was noted. 33 refs.

Abstract  Polymerisation of propene by magnesium chloride/titanium tetrachloride/diisobutyl phthalate catalysts,using 2,2,6, 6-tetramethylpiperidine as external donor was studied. The fraction of atactic polymer formed increased with decreasing ester content in the catalyst. The stereoregularity of the isotactic polymer increased. Absence of the external donor gave lower yield and lower stereoregularity. Analysis showed changes in the ester composition due to transesterification reactions during catalyst preparation. 12 refs.

Abstract  16 refs.

Abstract  The results of experiments with a supported Ziegler-Natta catalyst were interpreted by a two-site model of the active sites, in order to enhance the understanding of multiple types of catalyst active sites and in particular the role of the external donor. The applicability of the two-site model is discussed and the stochastic parameters of the model are correlated with both the experimental and molecular modelling data. The two-site model satisfactorily explains the major part of the active sites of this highly isospecific catalyst and is a suitable model for analysing the effects of the donors on catalyst active sites. This study also supports the earlier suggestion that some of the changes in the population of active sites can be explained only through the formation of new sites, and more specifically through the existence of fluctuating sites that can be stabilised by external donors. The stability of these new sites depends on both the structural and electronic properties of the external donors. Fifteen alkoxysilane compounds were tested in conjunction with a typical high-activity supported catalyst of the type magnesium chloride/titanium tetrachloride/diisobutyl phthalate-triethylaluminium/external donor. Catalytic activity and productivity data for PP production are given. 19 refs.

Abstract  Propylene was polymerised using a magnesium-supported titanium chloride catalyst (with diisobutyl phthalate as an internal donor) in the presence and absence of hydrogen as a chain transfer agent. Alkylaluminiums with different structures were used as cocatalysts. The effects of the size of the alkyl group of the cocatalyst, hydrogen feed and the feed time on the propylene polymerisation behaviour were studied. With increasing alkyl group size in the cocatalyst, the activity of the catalyst decreased significantly and the molecular weight and polydispersity index (PDI) of the PP increased. In the presence of hydrogen, the catalyst activity increased significantly but the molecular weight and PDI of the PP decreased. The molecular weight distribution curve was bimodal for short polymerisation times in the presence of hydrogen and the molecular weight distribution of PP could be controlled by changing the polymerisation time in the presence of hydrogen. 28 refs.

Abstract  Measurement of the solubility of 1-hexene in linear low density polyethylene (LLDPE) obtained by catalytic synthesis using a heterogeneous Ziegler-Natta (ZN) catalyst, Mg(OEt)2/DIBP /TiCl4-TEA(ZN) and a homogeneous metallocene catalyst, (2-MeInd)ZrCl2-MAO (MT) showed that it was well described by the Flory-Huggins equation with a constant value of the interaction parameter X. ZN-LLDPE dissolved more 1-hexene and thus had a lower value of X than MT-LLDPE. It was suggested that the parameter X or the solubility of 1-hexene at a given temperature and pressure could be a sensitive measure of the composition distribution of LLDPE. 12 refs.

Abstract  Application of pervaporation process on silica hydrophilic membranes with the reaction of synthesis of diisobutyl phthalate ester has been investigated. The experimental study on reaction kinetics and pervaporation process were performed. The mathematical model describing the integrated process (reaction and pervaporation) was formulated. Several computer simulations were performed in order to compare the efficiency of ester production of the reactor integrated with the module of a different membrane area.

Abstract  The treatment of gaseous effluents containing hydrophobic volatile organic compounds (VOCS) can be carried out by absorption with the use of a heavy hydrophobic solvent. These solvents must be regenerated in order to be reused in the absorption process. A possible solution to continuously regenerate the absorbent is a hybrid absorption-pervaporation process, with the pervaporation step serving to regenerate the solvent. This piece of research examines the feasibility of that regeneration step. The VOC used was toluene and three high temperature boiling absorbents were considered: di(2-ethylhexyl) adipate (DEHA), diisobutyl phthalate (DIBP) and polyethylene glycol 400 (PEG 400). Bibliographical research and a preliminary theoretical evaluation led to the choice of PDMS for separating the toluene/absorbent mixture, whatever the absorbent. Experiments using various absorbents showed that toluene passed through the membrane. The extracted toluene flows from DEHA were considerably higher that those measured using diisobutyl phthalate or polyethylene glycol. Therefore, di(2-ethylhexyl) adipate would be the most easily regenerable absorbent. No absorbent was found in the permeate, but a slow accumulation of DEHA was observed in the porous support. This point is of interest and could decrease the separation efficiency. The predominant effect of the liquid boundary layer was highlighted. The resistance-in-series theory allowed the impact of the boundary layer to be quantified. The flow rates of toluene extraction from a DEHA solution were low and require improving the pervaporation regeneration performance to use this kind of separation in an industrial hybrid process.

Abstract  Spherical MgCl2-supported Ziegler-Natta catalysts containing internal donors, such as diethyl phthalate, diisobutyl phthalate, and di-n-octyl phthalate, have been prepared. The effects of external donors, phenyltrimethoxysilane, phenyltriethoxysilane, and diphenyldimethoxylsilane, on the propylene polymerization catalyzed by these catalysts were studied. The results indicate that the external donors not only led to an increase in the isotactic index, but also affected the morphology of resultant polymer particles. (C) 2004 Wiley Periodicals, Inc.

Abstract  The penta-ether compound was synthesized by the reaction of di(trimethylolpropane) with sodium hydride as the strong base and methyl iodide as the alkyl halide. This compound was characterized by NMR, FTIR, and GC techniques. The MgCl2-supported titanium catalysts were incorporated with varying amounts of penta-ether compound as the internal donor and also the catalysts without the internal donor were synthesized. The synthesized catalysts and the conventional Ziegler- Natta catalyst were characterized. The titanium contents were determined by spectrophotometry, magnesium by complexometric titration and chloride by argentometric titration. The effects of the new internal donor on propylene polymerization with the prepared MgCl2-supported Ziegler-Natta catalysts were investigated and then these results were compared to the results obtained using the conventional diisobutyl phthalate-besed-Ziegler-Natta catalyst. The highest crystallinity degree, melting temperature, and isotacticity of polypropylene were obtained using the catalyst with a penta-ether/Mg molar ratio equal to 0.21.

Abstract  Studies were made of the effects of tributyl phosphate, ethyl benzoate and diisobutyl phthalate as second internal bases on the Ziegler-Natta catalysts prepared by the reduction of titanium tetrachloride with diethylaluminium chloride in the presence of n-butyl ether as a first internal base. These catalysts were evaluated in propylene polymerisation in the presence or absence of external bases. The effects of internal and external bases on the catalyst activity and stereospecificity were investigated. 15 refs.

Abstract  Propylene polymerizations were conducted in slurry phase batch process using different dialkyldimethoxysilanes as an external donor with magnesium dichloride (MgCl₂) supported titanium tetrachloride (TiCl₄) catalyst having diisobutylphthalate (DIBP) as an internal donor. The dialkyl group of the external donors like dimethyldimethoxysilane (DMDMS), diisopropyldimethoxysilane (DIPDMS) and dicyclopentyldimethoxysilane (DCPDMS) were found to influence on the microstructure and the molecular weight characteristics of synthesized polypropylene in addition to the initial rate of polymerization and decay index. DCPDMS gave highest productivity and high molecular weight polypropylene with improved kinetics while DMDMS gave lowest productivity in comparison. The molar equivalent combination of DCPDMS with DIPDMS and DMDMS respectively, resulted in producing polypropylene with tacticity pattern and molecular weight characteristics in between the individual alkoxysilane based system indicating the effect of alkyl group on the catalyst performance.

Abstract  Propylene polymerisations were conducted in slurry phase batch process using different dialkyldimethoxysilanes as an external donor with magnesium dichloride (MgCl2) supported titanium tetrachloride (TiCl4) catalyst having diisobutylphthalate (DIBP) as an internal donor. The dialkyl group of the external donors like dimethyldimethoxysilane (DMDMS), diisopropyldimethoxysilane (DIPDMS) and dicyclopentyldimethoxysilane (DCPDMS) were found to influence on the microstructure and the molecular weight characteristics of synthesised polypropylene in addition to the initial rate of polymerisation and decay index. DCPDMS gave highest productivity and high molecular weight polypropylene with improved kinetics while DMDMS gave lowest productivity in comparison. The molar equivalent combination of DCPDMS with DIPDMS and DMDMS respectively, resulted in producing polypropylene with tacticity pattern and molecular weight characteristics in between the individual alkoxysilane based system indicating the effect of alkyl group on the catalyst performance. 28 Refs.

Abstract  Investigations in an isothermal, semibatch reactor have been conducted to find out kinetic parameters for the synthesis of dibutyl phthalate (DBP) and diisobutyl phthalate (DIBP) from phthalic anhydride and butyl alcohol or isobutyl alcohol,. The first stage, the formation of monoester, is very fast and irreversible. The second stage of the process, the esterification of monoester to diester, is slow. This reaction rate appears to be first-order with respect to the monoester and the rate does not depend on the concentration of alcohol.