- Experimental and theoretical studies on ethylene polymerization using SiO2-supported silyl chromate type catalysts prepared by a green method
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SiO2-supported silyl chromate catalyst (UCC S-2 catalyst) is an important catalyst for the commercial production of polyethylene. Cann first reported a possible green synthesis route for the preparation of S-2 catalyst through transformation from Phillips catalyst by addition of triphenylsilanol (TPS) to avoid the use of toxic bis(triphenylsilyl) chromate (BC). In this work, this green synthesis route was further investigated by the combination of experimental and theoretical methods. The obtained catalyst was named as PS catalyst based on the incomplete conversion of Phillips catalyst to S-2 catalyst. Polymerization activity of PS1.5 catalyst was higher than that of S-2 catalyst with either TEA or MAO as cocatalyst. The existence of the simultaneously formed hydroxyl group and its coordination to the reduced Cr site was favorable to the PS catalyst, and this might attribute to the higher polymerization activity of PS catalyst than that of S-2 catalyst. A further modification of PS catalyst by a series of alkyl chlorosilane compounds showed that the role of the electron-withdrawing group only limited at a certain distance away from Cr active site. This preliminary study provided a solid basis for a further innovation of PS catalysts and final substitution of S-2 catalyst in commercial processes.
- Li, Xiaofang,Cheng, Ruihua,Luo, Jun,Dong, Qi,He, Xuelian,Li, Liuzhong,Yu, Yongling,Da, Jianwen,Liu, Boping
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Read Online
- The crystal structure of (HOMe2Si)2O
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X-Ray crystallography shows that in the solid state, molecules of (HOMe2Si)2O are extensively hydrogen bonded together to form zig-zag double chains with no bonding between the chains.
- Lickiss, Paul D.,Redhouse, Alan D.,Thompson, Robin J.,Stanczyk, Wlodzimierz A.,Rozga, Krystyna
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Read Online
- Silanol Compound, Composition, and Method for Producing Silanol Compound
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The purpose of the present invention is to provide silanol compounds that can be used as raw materials of siloxane compounds and the like, and a composition of the silanol compounds, as well as to provide a production method that makes it possible to produce silanol compounds at excellent yield. A composition comprising 5 mass % to 100 mass % of a silanol compound represented by Formulas (A) to (C) can be prepared by devising to produce silanol compounds under water-free conditions, to produce silanol compounds in a solvent having the effect of suppressing the condensation of silanol compounds, and to perform other such processes, the composition being able to be used as a raw material or the like of siloxane compounds because the silanol compounds can be stably present in the resulting composition.
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Paragraph 0224-0230
(2017/07/14)
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- The complex compound and its manufacturing method org. tantalum
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Disclosed is an organotantalum complex compound, which is easily cured by ultraviolet (UV) light, enables patterning, provides a coating film having excellent uniformity when being formed into a coating film, and is formed into a cured product having high resistance to etching using an etching gas. Also disclosed are a method for producing the organotantalum complex compound and a photocurable composition comprising the organotantalum complex compound. The organotantalum complex compound is obtained by reacting a ?-diketone compound (A) having at least one organic group with a photopolymerizable carbon-carbon unsaturated bond with a tantalum alkoxide compound (B) at a specific ratio to obtain a reaction product, and then, reacting the reaction product with a disiloxanediol compound (C) using a specific amount of the disiloxanediol compound (C).
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Paragraph 0146-0156
(2016/10/07)
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- Copper-catalyzed formic acid synthesis from CO2 with hydrosilanes and H2O
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A copper-catalyzed formic acid synthesis from CO2 with hydrosilanes has been accomplished. The Cu(OAc)2?H 2O-1,2-bis(diphenylphosphino)benzene system is highly effective for the formic acid synthesis under 1 atm of CO2. The TON value approached 8100 in 6 h. The reaction pathway was revealed by in situ NMR analysis and isotopic experiments.
- Motokura, Ken,Kashiwame, Daiki,Miyaji, Akimitsu,Baba, Toshihide
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experimental part
p. 2642 - 2645
(2012/08/13)
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- Formation of silicones mediated by the sponge enzyme silicatein-α
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The sponge-restricted enzyme silicatein-α catalyzes in vivo silica formation from monomeric silicon compounds from sea water (i.e. silicic acid) and plays the pivotal role during synthesis of the siliceous sponge spicules. Recombinant silicatein-α, which was cloned from the demosponge Suberites domuncula (phylum Porifera), is shown to catalyze in vitro condensation of alkoxy silanes during a phase transfer reaction at neutral pH and ambient temperature to yield silicones like the straight-chained polydimethylsiloxane (PDMS). The reported condensation reaction is considered to be the first description of an enzymatically enhanced organometallic condensation reaction. The Royal Society of Chemistry.
- Wolf, Stephan E.,Schlossmacher, Ute,Pietuch, Anna,Mathiasch, Bernd,Schroeder, Heinz-C.,Mueller, Werner E. G.,Tremel, Wolfgang
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experimental part
p. 9245 - 9249
(2011/01/11)
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- Synthesis of poly(dimethyldiphenylsiloxane) α,ω-diol copolymers by acid-catalyzed polycondensation
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Polycondensation of diphenylsilanediol (DFSD) and 1,3-bis(hydroxy)-tetramethyldisiloxane (D2) was carried out in solution in order to obtain low-molecular weight poly(dimethyldiphenylsiloxane)s with OH terminal groups. A cation-exchanger, Vionit CS-34C, with SO3H groups was used as catalyst for polycondensation. The copolymers obtained from two different feed ratios were analyzed by IR, 1H-NMR, DSC and POM.
- Vlad, Angelica,Cazacu, Maria,Marcu, Mihai,Racles, Carmen
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p. 919 - 924
(2007/10/03)
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- Cyclotrisiloxanes, new siloxane polymers and their preparation
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This invention relates to methods for the preparation of hyperbranched siloxane polymers by anionic polymerization of a cyclotrisiloxane having the functional group Si—OH, and for the preparation of linear siloxane polymers by cationic or anionic polymerization of a cyclotrisiloxane having a vinylterminated functional group. Furthermore, this invention concerns novel cyclotrisiloxanes useful for the preparation of the aforementioned polymers.
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- Decomposition of Some Organosilicon Compounds under the Action of Concentrated Sulfuric Acid in the Presence of an Oxidant
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Chemical transformations of some organosilicon compounds of the siloxane and silazane series under the action of concentrated sulfuric acid in the presence of an oxidant were studied, varying the amounts and the order of addition of the reactants. Conditions ensuring the most complete decomposition of the substrates were found. The chemical oxygen demand factors for 21 organosilicon compounds were determined for the first time.
- Varezhkin,Mikhailova,Vokin
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p. 570 - 574
(2007/10/03)
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- Hydrolysis of oligodimethylsiloxane-α,ω-diols and the position of hydrolytic equilibrium
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The hydrolysis of tetramethyldisiloxane-1,3-diol and hexamethyltrisiloxane-1,5-diol in aqueous solutions has been studied. The position of equilibrium of the system including these compounds, dimethylsilanediol, and water has been determined. Concentrations of these compounds in dilute aqueous solutions were determined by coupling HPLC to ICP analysis for Si and also by extraction into ethyl acetate followed by triethylsilylation and GC analysis. It was found that the siloxanediols hydrolyze to the equilibrium mixture at environmentally significant rates and that dimethylsilanediol dominates the equilibrium in dilute aqueous solution, even at concentrations orders of magnitude above that expected in the environment. The hydrolysis of tetramethyldisiloxane-1,3-diol in water was found to be first order in [H+] and in [phosphate buffer] by studying the rates at pH 3 and 6. The hydrolysis of a mixture of higher oligodimethylsiloxane-α,ω-diols as a suspension in water is also described. The first observation of dimethylsilanediol in an environmental sample is reported. The hydrolysis of tetramethyldisiloxane-1,3-diol and hexamethyltrisiloxane-1,5-diol in aqueous solutions has been studied. The position of equilibrium of the system including these compounds, dimethylsilanediol, and water has been determined. Concentrations of these compounds in dilute aqueous solutions were determined by coupling HPLC to ICP analysis for Si and also by extraction into ethyl acetate followed by triethylsilylation and GC analysis. It was found that the siloxanediols hydrolyze to the equilibrium mixture at environmentally significant rates and that dimethylsilanediol dominates the equilibrium in dilute aqueous solution, even at concentrations orders of magnitude above that expected in the environment. The hydrolysis of tetramethyldisiloxane-1,3-diol in water was found to be first order in [H+] and in [phosphate buffer] by studying the rates at pH 3 and 6. The hydrolysis of a mixture of higher oligodimethylsiloxane-α,ω-diols as a suspension in water is also described. The first observation of dimethylsilanediol in an environmental sample is reported.
- Spivack,Dorn
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p. 2345 - 2352
(2007/10/03)
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- Procedures for the preparation of silanols
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Two procedures are described for the preparation of silanols and silanediols from the corresponding chlorosilanes.The first procedure, a two-phase hydrolysis-extraction process, is- particularly convenient and suited to the preparation of a wide range of mono-silanols.Hydrolysis of dichlorosilanes by this procedure gives varied results depending on the structure of the dichlorosilane and specific reaction conditions.The second procedure, a modification of a published procedure, is especially beneficial for the preparation of silanols and silanediols prone to undergo self-condensation. Key words: Silicon; Hydrolysis; Self-condensation; Silanols
- Cella, James A.,Carpenter, John C.
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- Disproportionation of oligodimethylsiloxanols in the presence of a protic acid in dioxane
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The kinetics of the acid-catalyzed disproportionation of α,ω-dihydroxyoligodimethylsiloxanes HOnH, n = 2, 5, and their analogues having one hydroxyl function replaced by methyl MenH, n = 2, 5, were studied in dioxane in the presence of water.The formation of the primary disproportionation products was monitored by gas-liquid chromatography.The reaction in dioxane solution can compete with the condensation process only in the presence of water.It is of first order with respect to the substrate, catalyst, and water.The results are interpreted in terms of a stepwise mechanism involving rate determining cleavage of the terminal siloxane unit by water, followed by condensation of transiently-formed dimethylsilanediol with the substrate.The unzipping mechansim involving the dimethylsilanediol intermediate is suggested to operate in hydrolytic cleavage of polydimethylsiloxane exposed to water or water vapour.
- Cypryk, M.,Rubinsztajn, S.,Chojnowski, J.
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- Rate studies of the acid-catalyzed solvolysis of eight-membered cyclosilazoxanes
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The solvolysis of N-phenyl-1,1,3,3,5,5,7,7-octamethyl-1,3,5,7-tetrasila-2-aza-4,6,8-trioxacyclooctane (1) and N,N'-diphenyl-1,1,3,3,5,5,7,7-octamethyl-1,3,5,7-tetrasila-2,6-diaza-4,8-dioxacyclooctane (II) in methanol/water in the presence of an acetate buffer is a pseudo-first-order process, subject to general acid-catalysis.The catalytic rate constants have been determined spectrophotometrically for the solvolysis of I.The ring cleavage is slower than that of analogous six-membered cyclosilazoxanes, but the catalytic mode and the solvent isotope effect indicate a close mechanistic similarity between the solvolyses of six- and eight-membered rings.
- Lasocki, Zygmunt,Witekowa, Malgorzata
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- Novel n[meth)allyloxy(meth)allylphenyl]maleimides and thermosetting imido copolymers prepared therefrom
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Novel N-[(meth)allyloxy-mono-/di(meth)allylphenyl]maleimides, in admixture with at least one N-[(meth)allyloxyphenyl]maleimide, are reacted with at least one bismaleimide, and optionally a hydroxylated organosilicon compound, in the presence of an imidazole compound, to obtain mechanically improved thermosetting imido copolymerizates well adapted for the production of, e.g., coatings, adhesive bondings, laminates and composites.
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