Showing papers on "Vinyl acetate published in 1994"
TL;DR: In this article, the effect of the composition of the initiating system and its aging is described, as well as its effect on the aging of the AL(iBu)3:DPy:TEMPO system.
Abstract: : Synthesis of well-defined poly(vinyl acetate) in 'living' radical polymerization is reported. Straight lines in semilogarithmic plots up to >90% conversion indicate internal first order in monomer and a constant concentration of growing species. Molecular weights increase linearly with conversion. The initiating system might involve persistent radicals formed by the ternary complexes of organoaluminum compounds with Lewis bases and stable radicals. This article focuses on Al(iBu)3:DPy:TEMPO system. The effect of the composition of the initiating system and its aging is described.
120 citations
TL;DR: In this paper, various methods which lead to the control of molecular weight and polydispersities, and which allow for the preparation of block copolymers by radical polymerization are discussed.
Abstract: Various methods which lead to the control of molecular weight and polydispersities, and which allow for the preparation of block copolymers by radical polymerization are discussed. Thermal polymerizationof styrenes in the presence of stable radicals, polymerization of vinyl acetate and methyl methacrylate in the presence of chromium complexed by macrocyclic ligands polymerization of vinyl acetate initiated by organoaluminum compounds complexed by dipyridyl and activated by stable radicals, as well as in the presence of phosphites, are described in detail.
104 citations
TL;DR: In this article, the pulsed-laser polymerization (PLP) technique for determination of free radical propagation rate coefficients (k p ) by GPC analysis has been extended to systems with rapid chain growth.
Abstract: The pulsed-laser polymerization (PLP) technique for determination of free radical propagation rate coefficients (k p ) by GPC analysis has been extended to systems with rapid chain growth. A mathematical model is developed to gain a better understanding of the relative importance of propagation, termination, and transfer events on the leer-generated molecular weight distributions. Insights from the model are used to define appropriate PLP experimental conditions for vinyl acetate (VAc), for which measured k p values are an order of magnitude higher than values measured for styrene and methyl methacrylate at the same temperature
92 citations
Patent•
15 Aug 1994TL;DR: In this article, a reusable and compostable coated paper stock comprising a substrate coated on at least one surface with a primer coat and a top coat both of which are water-based dispersions is described.
Abstract: Recyclable and compostable coated paper stock comprising a substrate coated on at least one surface with a primer coat and a top coat both of which are water based dispersions. The primer coat comprises a water based dispersion of a polymer selected from the group comprising acrylic polymers, acrylic copolymers, polyvinyl acetate, polyvinyl alcohol, poly-ethylene vinyl acetate, poly-ethylene vinyl chloride, styrene butadiene copolymers, polyvinylidiene chloride or starch. The top coat comprises a water based dispersion of a polymer selected from the group comprising acrylic polymers, acrylic copolymers, styrene butadiene copolymers or polyvinylidiene chloride. In another embodiment the top coat further includes a wax component comprising 15-90 wt. % of the polymer and 5-85 wt. % of the wax. The substrate is coated with a primer coat prior to the application of the top coat to seal the substrate surface. The top coat forms a film over the primer coat and imparts water and grease resistant properties to the coated paper stocks. The invention also includes processes for making and using the invented coated paper stocks.
86 citations
TL;DR: In this paper, the synthesis of mesoporous MCM-41 type materials based on transition metal oxides and the polymerization of several monomers within MCM41 is presented with the aim to specifically investigate the effects of the interface and confinement on host-guest interactions.
Abstract: The synthesis of mesoporous MCM-41 type materials based on transition metal oxides and the polymerization of several monomers within MCM-41 is presented with the aim to specifically investigate the effects of the interface and confinement on host-guest interactions. In addition to standard MCM-41, material based on transition metal oxides is obtained although template removal has been unsuccessful for such compounds until now. In situ polymerization of styrene, methyl methacrylate and vinyl acetate is possible within the mesopore system. The properties of some of the encapsulated polymers differ markedly with those obtained in the bulk.
72 citations
TL;DR: The correlation between hydrogen-bonding self-association and sequence distribution in different polyvinyl acetate-co-vinyl alcohol copolymers of different degrees of hydrolysis and sequence distributions has been studied by infrared and NMR spectroscopy as discussed by the authors.
Abstract: The correlation between hydrogen-bonding self-association and sequence distribution in different poly(vinyl acetate-co-vinyl alcohol) copolymers (ACA) of different degrees of hydrolysis and sequence distributions has been studied by infrared and NMR spectroscopy. For ACA copolymers, quasi-random distributions are obtained by acid alcoholysis, blocker distributions by saponification, and intermediate distributions by acombined method, as shown by 13 C NMR. FTIR spectroscopy has pointed out that hydrogen-bonding distribution in ACA copolymers strongly depends on sequence distribution. For block copolymers, hydroxyl-hydroxyl self-association is preferred
57 citations
TL;DR: In this article, the in situ compatibilization of poly(ethylene terephthalate) (PET) copolymer (PETG) with ethylene vinyl acetate (EVA) via catalysed transesterification reactions was examined through rheological, morphological and mechanical studies.
53 citations
TL;DR: In this paper, three well-defined pyrolysis stages have been observed which occur over the temperature ranges 250-350°C, 350-550°C and above 550°C.
Abstract: Homopolymeric polyacrylonitrile and fibre-forming copolymers containing either vinyl acetate or methyl acrylate comonomer have been studied by thermal analysis (DSC, TGA and DTG) at various heating rates (10–100 K min−1) and under air and nitrogen. Three well-defined pyrolysis stages have been observed which occur over the temperature ranges 250–350°C, 350–550°C and above 550°C. Each stage involves a competition between volatilisation and cyclisation or char-forming reactions which depends on heating rate and the presence or absence of oxygen.
The well-established dominance of cyclisation in the 250–350°C temperature range obtained during carbon fibre production from acrylic precursors occurs only at low heating rates. At high heating rates, volatilisation dominates and this explains why acrylic polymers have high flammabilities when heating rapidly.
The full pyrolysis mechanism has been semi-quantitatively analysed and the role that comonomers play discussed. This has enabled a fuller understanding of the potential burning behaviour of these polymers to be developed.
53 citations
Patent•
11 Jul 1994
TL;DR: In this paper, the authors describe the use of Pd/K/Au, Pd-K/Ba and PdK/Cd supported catalysts for the preparation of vinyl acetate from ethylene, acetic acid and oxygen in the gas phase.
Abstract: The invention relates to Pd/K/Au, Pd/K/Ba and Pd/K/Cd supported catalysts constructed in a shell-shape, their production and their use for the preparation of vinyl acetate from ethylene, acetic acid and oxygen in the gas phase. The said catalysts are produced by impregnating the support particles with a solution of salts of the corresponding elements and then drying them, the dynamic viscosity of the solution being at least 0.003 Pa.s and the solution volume during impregnation being more than 80% of the pore volume of the support particles and the duration of impregnation and the time until the beginning of drying being selected to be short enough so that after drying is completed, a shell of 5% to 80% of the pore volume of the support particles contains the said metal salts.
52 citations
TL;DR: In this paper, the isotopic transient kinetics technique has been used to characterise the surface species of Pd/Cd/silica (Pd/Au/Silica) and Pd/(Cd)/silica catalysts for vinyl acetate synthesis, and the major byproduct, CO2 was derived equally from ethylene and acetic acid under these conditions.
51 citations
TL;DR: In this paper, the kinetics of high solids content emulsion terpolymerization of vinyl acetate, methyl methacrylate, and butyl acrylate were investigated.
Abstract: The kinetics of the high solids content emulsion terpolymerization of vinyl acetate, methyl methacrylate, and butyl acrylate were investigated. The effect of feed flow rate, total amount of emulsifier, distribution of emulsifier between the initial charge and the feed, concentration of initiator, and solids content on the time evolution of the conversion, terpolymer composition, and total number of polymer particles were investigated. The experimental results were analyzed by means of a mathematical model that incorporated the main features of the system. © 1994 John Wiley & Sons, Inc.
TL;DR: In this article, the free radical copolymerization of O-D vinyl alcohol and maleic anhydride was investigated and the polymerization was determined to be first order in both anhydrous and vinyl alcohol.
Abstract: Vinyl alcohol was generated through the hydrolysis of ketene methyl vinyl acetal I. In general, we have observed that room temperature addition of 0.9 mol equiv of I to a 1% (v/v) D[sub 2]O solution in acetone-d[sub 6], made such that the concentration of the overall solution is 10[sup [minus]4]M in DCl, yields 90% O-D vinyl alcohol which tautomerizes to acetaldehyde only very slowly at ambient temperature (k[sub t] [approx] 10[sup [minus]6] M/s, vide infra). The remaining 10% of I is converted into vinyl acetate, a side product in the hydrolysis, as well as to a small amount of acetaldehyde from tautomerization. Spectroscopic data for the vinyl alcohol were identical to previously reported data. Our observations suggest that the key to generating persistent vinyl alcohol solutions is to drive the system toward an anhydrous state through use of nearly stoichiometric amounts of water in the rapid hydrolysis step. By taking advantage of stabilizing electron donor-acceptor interactions, the free radical copolymerization of O-D vinyl alcohol and maleic anhydride proved successful. The polymerization was determined to be first order in both maleic anhydride and vinyl alcohol. Since the rate of polymerization is far greater than that of tautomerization under the conditions (ca.more » 30 times faster at [minus]10[degree]C), there is no significant increase in acetaldehyde concentration during polymerization. 20 refs., 1 fig.« less
TL;DR: In this article, the effect of the fractal morphology of the alumina surface surface has been investigated in the gas phase production of vinyl acetate from ethylene and acetic acid on a Pd/Al2O3 catalyst.
TL;DR: In this article, the in situ polymerization of tetraethoxysilane (TEOS) in polyvinyl acetate (PVAc) yields homogeneous and transparent nanocomposite materials.
Abstract: The in situ polymerization of tetraethoxysilane (TEOS) in poly(vinyl acetate) (PVAc) yields homogeneous and transparent nanocomposite materials. It was shown that covalent bonds occur between the organic chains and the inorganic clusters, preventing macroscopic phase separation. For an initial amount of TEOS higher than a critical value, gel formation is observed. Up to this critical TEOS content, improved mechanical properties, which persist at high temperatures, are obtained.
TL;DR: In this paper, the structural development during radical polymerization of a mixture of methyl methacrylate (MMA) and poly(ethylene-co-vinyl acetate) (EVA) was investigated by light scattering and optical microscopy.
TL;DR: In this article, the dependence of thermal degradation behavior on vinyl acetate (VA) content of EVA copolymers was studied by thermogravimetric analysis (t.g.a.).
TL;DR: In this article, the conversion of hydroxycarboxylic acids with primary or secondary hydroxy functions into the corresponding vinyl esters was successfully achieved under basic conditions in presence of vinyl acetate and palladium(II) acetate as catalyst.
Abstract: The conversion of hydroxycarboxylic acids with primary or secondary hydroxy functions into the corresponding vinyl esters was successfully achieved under basic conditions in presence of vinyl acetate and palladium(II) acetate as catalyst. Side reactions, which were previously frequently interfering with these transformations, have been studied and reaction conditions optimised to reach maximum product yield
TL;DR: In this paper, the surface chemistries of semi-crystalline copolymers of ethylene (CH2CH2) and vinyl acetate (CH 2CHCO2CH3) (EVAs) and blends of them with low-density polyethylene (LDPE) have been examined critically for the first time using angle-resolved XPS and time-of-flight SIMS (ToF-SIMS) analyses.
Abstract: The surface chemistries of semi-crystalline copolymers of ethylene (CH2CH2) and vinyl acetate (CH2CHCO2CH3) (EVAs) and blends of these copolymers with low-density polyethylene (LDPE) have been examined critically for the first time using angle-resolved XPS and time-of-flight SIMS (ToF-SIMS) analyses. Specimens were fabricated using a variety of methods (commercial extrusion, spin coating and thermal compression) to determine the influence of processing conditions on EVA surface chemistry. The XPS and ToF-SIMS analysis of these specimens has provided techniques for identifying surface EVA (also thermal oxidation), has provided both XPS and ToF-SIMS methods for quantitative EVA analysis and has revealed the details of EVA surface chemistry. The XPS core-level spectra indicate the presence of the ester (VA) and ether (surface oxidation) species, but do not provide positive EVA identification. The ToF-SIMS spectra show features specific to both the ethylene and vinyl acetate portions of the polymer. Both XPS and ToF-SIMS analyses have been calibrated to provide quantitative VA (error 20 A depth) is dominated by a VA-poor (ethylene-rich) layer. This region is covered by a thin (⩽20 A thick) VA-enriched layer.
TL;DR: In this article, the stability of vinyl acetate miniemulsions employing polyvinyl alcohol (PVOH) as the surfactant, and hexadecane and/or various polymers as the cosurfactant, were studied.
Abstract: The stability of vinyl acetate miniemulsions employing polyvinyl alcohol (PVOH) as the surfactant, and hexadecane and/or various polymers as the cosurfactant, were studied. Shelf lives (to phase separation) and monomer droplet sizes were measured. The results indicate that it is possible to prepare stable miniemulsions using a nonionic surfactant (PVOH) and hexadecane as the cosurfactant. Polymeric cosurfactants do not create stable miniemulsions but retard Ostwald ripening to an extent that allows predominant droplet nucleation. The polymerization behavior of these miniemulsion systems was investigated using on-line conductance measurements to differentiate droplet versus micellar/homogeneous nucleation. The effect of cosurfactant concentration on the reaction rate was compared for hexadecane and polymeric cosurfactants. © 1994 John Wiley & Sons, Inc.
Patent•
11 Jul 1994
TL;DR: The Pd/K/Au/Cd supported catalysts were used for the preparation of vinyl acetate from ethylene, acetic acid and oxygen in the gas phase.
Abstract: The invention relates to Pd/K/Au, Pd/K/Ba and Pd/K/Cd supported catalysts constructed in a shell-shape, their production and their use for the preparation of vinyl acetate from ethylene, acetic acid and oxygen in the gas phase. The said catalysts are produced by impregnating the support particles, intimately mixing them with a solution of salts of the corresponding elements and then immediately drying them, the dynamic viscosity of the solution being at least 0.003 Pa.s and the solution volume during impregnation being 5 to 80% of the pore volume of the support particles.
TL;DR: In this paper, a new simulation model for the kinetics of long-chain branching formed via chain transfer to polymer and terminal double bond polymerization that was proposed in Part 1 of this series is extended to a continuous stirred tank reactor.
Abstract: A new simulation model for the kinetics of long-chain branching formed via chain transfer to polymer and terminal double bond polymerization that was proposed in Part 1 of this series is extended to a continuous stirred tank reactor. The present model is applied to the free radical polymerization of vinyl acetate in a micromixed continuous stirred tank reactor, and various information on branched structure such as the molecular weight distribution, distribution of branch points, and branching density of the largest polymer molecule are calculated. Based on the present simulation model, it was found that the method of moments used successfully to predict various average properties in a batch polymerization cannot be applied to a continuous stirred tank reactor without accounting for the outflow of polymer radicals and the existence of polyradicals. The present model has given an excellent agreement with the experimental results of Chatterjee, Park, and Graessley (1977) for a solution polymerization of vinyl acetate in a continuous stirred tank reactor. © 1994 John Wiley & Sons, Inc.
Patent•
18 Nov 1994
TL;DR: In this paper, a barium salt additive is added to the catalyst after reduction to reduce the tendency of the catalyst to deactivate with use, which is a technique used for the preparation of palladium and palladium/gold shell type catalysts for vinyl acetate production.
Abstract: In a process for the preparation of palladium and palladium/gold shell type catalysts for vinyl acetate production, the improvement comprises using a barium salt to precipitate water-insoluble palladium and optional gold compounds onto a support prior to reduction with a reducing agent. A barium salt additive may also be introduced to the catalyst after reduction to reduce the tendency of the catalyst to deactivate with use.
TL;DR: In this article, polyvinyl acetate (PVAc) was incorporated into silica gel using the sol-gel process involving tetraethoxysilane (TEOS), and the physical properties of the resulting two sets of hybrids were compared.
Abstract: Poly(vinyl acetate) (PVAc) was incorporated into silica gel using the sol–gel process involving tetraethoxysilane (TEOS). In order to prepare silica-gel microhybrids, two different processes were employed, and the physical properties of the resulting two sets of hybrids were compared. In the first method, PVAc was first mixed with TEOS in an acetone solution and then cured using HCI and H2O. In the second method, an acetone solution of a copolymer composed of vinyl acetate (VAc) and vinyl triethoxysilane (VTES) was first mixed with TEOS and then cured. This copolymer contained 10 mol % of VTES component and was bound covalently to silica-gel molecules. When comparing the properties of the hybrids, the dynamic modulus, E′, increased with increasing amounts of TEOS over a wide temperature range: −20–120°C. E′ of a hybrid from PVAc was lower than that of a hybrid from the VAc/VTES copolymer. A sharp peak in the loss modulus, E″, of a PVAc hybrid occurred at 40°C, and its position did not change with TEOS content. In contrast, the E″, peak of a copolymer hybrid was broad and its position also shifted to a higher temperature as the TEOS content increased. The tensile strength of a PVAc hybrid increased as the amount of mixed TEOS increased, reaching a maximum of 30 MPa at 50 wt % of TEOS. However, the strength of a copolymer hybrid reached a maximum of 50 MPa at 50 wt % of TEOS. The differences in the physical properties between a PVAc hybrid and a copolymer hybrid arise from the difference in their structure. Organic polymer molecules in a copolymer hybrid combine covalently with silica-gel molecules through the VTES component, while a PVAc hybrid has no bounding between PVAc and silica-gel molecules. © 1994 John Wiley & Sons, Inc.
TL;DR: In this article, Inductive and resonance effects are stated to be the cause of the ν(CO) frequency differences exhibited by the three esters included in this study.
TL;DR: Reduction of protected α-vinyl amino acids produces “neopentyl” alcohols that may be enriched in the L-antipode by lipase-mediated acylation with vinyl acetate and subsequent deacetylation, oxidation and hydrolysis yields enantiomerically enriched L-α-vinYL amino acids.
TL;DR: In this article, the inclusion and 60 Co γ-ray-initiated polymerization of vinylic and acrylic monomers within the clathrate tunnels formed by tris(o-phenylenedioxy)cyclotriphosphazene is described.
Abstract: The inclusion and 60 Co γ-ray-initiated polymerization of vinylic and acrylic monomers within the clathrate tunnels formed by tris(o-phenylenedioxy)cyclotriphosphazene is described. Methacrylonitrile, methacrylic acid, ethyl acrylate, butylacrylate, hexyl acrylate, allyl methacrylate, vinyl acetate, and vinylanisole monomers were included by direct contact imhibition. Varying degrees of stereoregularity were obtained from the inclusion polymerization of the monomers listed above. For example, poly(methacrylonitrile) synthesized within the host adduct showed an enhanced isotactic microstructure
TL;DR: In this paper, the effects of two low profile additives (LPA), namely poly(vinyl acetate) and poly(methyl methacrylate), on the rheokinetics and morphological changes up to gelation in the cure of unsaturated polyester (UP) resins at 110°C were investigated by using a Haake viscometer, a differential scanning calorimeter, a Fourier-transform infra-red spectrometer and a scanning electron microscope.
Patent•
28 Dec 1994
TL;DR: In this paper, a polyamide thermoplastic elastomer, e.g., a polyetheresteramide, and at least one modified polyolefin, is defined.
Abstract: Polyblend compositions well adopted for the production of a wide variety of useful shaped articles having improved physical/chemical properties, e.g., fibers, films, sheets, composites, and the like, comprise (a) at least one polyamide thermoplastic elastomer, e.g., a polyetheresteramide, and (b) at least one modified polyolefin, e.g, an optionally maleized copolymerizate of ethylene and vinyl acetate, a copolymerizate of ethylene and (meth)acrylic acid, a copolymerizate of ethylene, vinyl acetate and (meth)acrylic acid and/or an alkyl (meth)acrylate, a copolymerizate of ethylene, an alkyl (meth)acrylate and, optionally, maleic anhydride, or maleized SBS, SIS or SEBS.
TL;DR: In this article, a kinetic resolution of racemic pyridyl and bipyridylethanols was performed by Candida antarctica lipase with vinyl acetate in diisopropyl ether, in which (R)-alcohol was acetylated stereoselectively, and both the acetate 2 and the remaining (S)-alcohol 1 were obtained with high enantiomeric excesses.
TL;DR: In this paper, the authors investigated the differentiaal scanning calorimetry (DSC) results of poly(4-vinyl pyridine) (P4VP) with different copolymer compositions and found that P4VP is immiscible with PVAC, PVA, and their copolymers over the whole composition range.
Abstract: Miscibility of poly(4-vinyl pyridine) (P4VP) and poly(2-vinyl pyridine) (P2VP) with poly(viny acetate) (PVAc), poly(vinyl alcohol) PVA and poly(vinyl acetate-co-alcohol) (ACA copolymers) has been investigated over a wide composition range. Differentiaal scanning calorimetry (DSC) results indicate that P2VP is immiscible with PVAC, PVA, and their copolymers over the whole composition range. In turn, P4VP appears to be immiscible with PVAC and PVA, but miscible with some ACA copolymers in certain range of composition. The P4VP-ACA phase diagram for different copolymer compositions has been determined. The variation of the glass transition temperature with composition for miscible mixtures was found to follow the Gordon-Taylor equation, with the parameter κ dependent upon copolymer composition. FTIR analysis of blends reveal the existence of specific interactions via hydrogen bonding between hydroxyl groups and the nitrogen of the pyridinic ring, which appear to be decisive for miscibility. © 1994 John Wiley & Sons, Inc.