Showing papers on "Vinyl acetate published in 2000"

Dithiocarbamates as universal reversible addition-fragmentation chain transfer agents

Abstract: Control of the radical polymerization of acrylates, styrene and vinyl acetate has been achieved by using novel dithiocarbamates as reversible addition-fragmentation chain transfer agents. The key parameter for the control with N,N-disubstituted (A) or cyclic (B) dithiocarbamates was found to be the conjugation of the lone pair of electrons of the nitrogen atom with carbonyl or aromatic groups.

Preparation and characterization of poly(vinyl acetate)-intercalated graphite oxide nanocomposite

Abstract: Graphite oxide, a pseudo-two-dimensional solid in bulk form, was synthesized from natural graphite powder by graphite oxidation with KMnO4 in concentrated H2SO4. Poly(vinyl acetate) intercalated graphite oxide nanocomposite was prepared by an in situ intercalative polymerization reaction, in which an n-octanol–graphite oxide intercalation compound was first obtained, vinyl acetate monomer was then dispersed into the interlayer of the modified graphite oxide, followed by thermally polymerizing the monomer. It was experimentally shown that the c-axis spacing increased to 1.152 nm when poly(vinyl acetate) was intercalated into the interlayer space of the graphite oxide. Thermal analysis and FT-IR spectrometry were also used to characterize the nanocomposite. The extractability of the intercalated poly(vinyl acetate) and the electrical properties of the nanocomposite were evaluated.

Temperature and strain rate independence of critical strains in polyethylene and poly(ethylene-co-vinyl acetate)

Abstract: True stress−strain curves measured during uniaxial tensile deformations of polyethylene generally show four characteristic points where the differential compliance and the recovery properties change. They can be associated with the onset of isolated inter- and intralamellar slip processes (point A), a change into a collective activity of slips (B), the beginning of crystallite fragmentation (C), and chain disentanglement (D). Experiments were carried out for high density polyethylene, low density polyethylene, and an ethylene−vinyl acetate copolymer, with variation of the temperature and the strain rate. While the stresses at the critical points change remarkably, the related strains turn out as constant. The only exception is point D, which shifts to lower strains on heating. Observations correspond with the previously found independence of the critical strains on the crystallinity.

Vinyl Acetate Emulsion Polymerization and Copolymerization With Acrylic Monomers

Abstract: INTRODUCTION EMULSION POLYMERIZATION Emulsion Polymerization of Hydrophobic Monomers Inverse and Emulsifier Free Emulsion Polymerizations Vinyl Acetate Emulsion Polymerization Radiation Induced Vinyl Acetate Emulsion Polymerization THE ROLE OF INGREDIENTS IN VINYL ACETATE EMULSION Monomer Quality and Inhibitors Initiators Emulsifiers Protective Colloids PH and Ionic Strength Controllers Others THEORY AND KINETICS OF VINYL ACETATE HOMOPOLYMERIZATION Effect of Monomer Concentration Effect of Initiator Concentration and Type Effect of Emulsifier Concentration and Type Particle Nucleation Mechanisms Thermodynamics and Kinetics of Particle Morphology Control VINYL ACETATE COPOLYMERIZATION WITH ACRYLIC MONOMERS Reactivity Ratios Propagation Rate in Copolymerization Controlled Monomer Addition The Effect of the Type of the Acrylic Monomer The Effect of the Vinyl Acetate/Acrylic Monomer Feed Ratio COLLOIDAL STABILITY OF VINYL ACETATE HOMO AND COPOLYMERS Basic Phenomena Steric Stabilization Coagulation Ionic Effects EXPERIMENTAL DETERMINATION OF LATTICE PROPERTIES Viscosity Solids Content Free Monomer Content Mean Molecular Weight and Molecular Weight Distribution Graft and Cross-Linked Polymer Content Monomer Sequence Distribution Mean Particle Size and Particle Size Distribution Chemical Composition of Copolymers Scattering of Colloids Surfactant Adsorption on Latex/Water Interface Colloidal Stability Drying and Film Forming Properties of Latices Surface Tension of Dried Latex Films Dynamic Mechanical Properties of Latex Films Aging Properties FACTORS AFFECTING THE FINAL P ROPERTIES OF THE POLYVINYL ACETATE-BASED LATICES The Role of the Type and the Quality of the {Polyvinyl Alcohol Protective Colloids on PVAc Homopolymers The Role of Emulsifiers on the Mean Particle Size and Colloidal Stability The Stabilization of PVAc Latices by Monomeric Carboxylic Groups The Role of the Duration of Polymerization Reaction The Role of Acrylic Comonomers The Role of Monomer Addition Methods and Propagation Rates on Copolymer Composition in Semi-Batch Reactor Operations The Role of the Shapes of Reactor Stirrers and Baffles and Stirring Rate The Role of Antifoaming Agents Seed Latex Preparation and Use Emulsion Polymerization in Continuous Reactors Scale-Up Problems OVERVIEW OF THE USES OF POLYVINYL ACETATE-BASED LATICES SOME NEW APPLICATIONS IN INDUSTRY Ultrasound Sensor Monitoring of Emulsion Polymerization Loop Reactor Continuous Emulsion Polymerization

Properties of Hot-Melt Extruded Theophylline Tablets Containing Poly(Vinyl Acetate)

Abstract: The objectives of this study were to investigate the properties of poly(vinyl acetate) (PVAc) as a retardant polymer and to study the drug release mechanism of theophylline from matrix tablets prepared by hot-melt extrusion. A physical mixture of drug, polymer, and drug release modifiers was fed into the equipment and heated inside the barrel of the extruder. The cylindrical extrudates were either cut into tablets or ground into granules and compressed with other excipients into tablets. Due to the low glass transition temperature of the PVAc, the melt extrusion process was conducted at approximately 70°C. Theophylline was used as the model drug in this study. Theophylline was present in the extrudate in its crystalline form and was released from the tablets by diffusion. The Higuchi diffusion model and percolation theories were applied to the dissolution data to explain the drug release properties of the matrix systems. The release rate was shown to be dependent on the granule size, drug particle size, a...

Catalyst and method for producing vinyl acetate

Abstract: The invention relates to a supported catalyst which contains palladium and/or compounds thereof, gold and/or compounds thereof, alkali metal compounds and also vanadium and/or compounds thereof. The invention also relates to the use of said supported catalyst for producing vinyl acetate from acetic acid, ethylene and oxygen, or gases containing oxygen.

Cellulose degradation in an acetic acid environment

Abstract: Gas chromatography-mass spectrometry was used to analyse off-gassing from three archival boxes that had an acidic smell. A number of volatile organic compounds were found, including acetic (ethanoic) acid, likely to be generated by Jade 403, a poly (vinyl acetate/ethylene) adhesive that had been used in the boxes. The aim of this study was to assess the effect of acetic acid vapour on pure cellulose paper using cold extraction pH and viscometric determination of the average degree of polymerization (DPv) of cellulose dissolved in cadoxen. Whatman No. 1 paper samples were exposed to 200, 20 and 3mgm–3 of acetic acid vapour for 40 and 80 days. The degree of degradation both immediately after exposure and following artificial aging at 80°C and 65% RH for 30 and 60 days was significant in all samples except those exposed for 80 days at 3mgm–3. The results suggest that the effect of acetic acid on paper most likely occurs over the long term after the exposure. Concerns about acid-emitting materials bei...

Grafting of hyperbranched polymers onto ultrafine silica: postgraft polymerization of vinyl monomers initiated by pendant initiating groups of polymer chains grafted onto the surface

Abstract: The grafting of polymers having pendant peroxycarbonate groups onto ultrafine silica surface and the radical postgraft polymerization of vinyl monomers initiated by the initiating groups of polymer chains grafted onto silica surface were investigated. The grafting of polymers having pendant peroxycarbonate groups onto the silica surface was achieved by the copolymerization of vinyl acetate (VAc) with t-butylperoxy-2-methacryloyloxyethylcarbonate (HEPO) initiated by azo groups introduced onto silica surface: the introduction of azo groups onto silica surface was achieved by the reaction of 4,4′-azobis(4-cyanopentanoic acid) with amino groups previously introduced onto the surface. The percentage of grafting (the proportion of grafted polymer to silica) of poly(VAc–co-HEPO) onto the surface was about 51% at 80.0°C after 3 h. The amount of pendant peroxycarbonate groups of grafted chain was determined to be 0.55 mmol/g. Radical postgraft polymerization of various vinyl monomers, such as methyl methacrylate, glycidyl methacrylate, 2-hydroxyethyl methacrylate, vinyl acetate, and N-vinyl-2-pyrrolidinone was initiated by the pendant peroxycarbonate groups of grafted poly(VAc–co-HEPO) to give the corresponding hyperbranched polymer-grafted silica. It was found that the grafting of hydrophilic or hydrophobic polymers readily controls the surface wettability to water.

Biodegradable starch-based polymeric materials

Abstract: The effects of low-molecular-weight additives, temperature and mechanical action on the structure and properties of starch are discussed. Special attention is given to mixtures of starch with synthetic polymers, e.g., co-polymers of ethylene with vinyl acetate, vinyl alcohol, acrylic acid, cellulose derivatives and other natural polymers. These mixtures can be used in the development of novel environmentally safe materials (films, coatings, packaging materials) and various articles for short-term use. The bibliography includes 105 references.

Flame retardant resin composition

Abstract: An olefinic flame-retardant resin composition which exhibits excellent mechanical strengths, scuff resistance and processability in spite of its containing an inorganic compound, and is excellent in flame retardance as well as in shell-forming properties at burning This composition comprises 100 parts by weight of a base resin composition comprising 95 to 5 wt% of a copolymer (A) prepared from ethylene, vinyl acetate and, if necessary, other polar monomer, 5 to 95 wt% of a copolymer (B) prepared from an olefin, an unsaturated carboxylic acid ester and, if necessary, other polar monomer, and 0 to 49 wt% of a thermoplastic resin (C) other than the above copolymers, and 25 to 250 parts by weight of a flame retardant inorganic compound (D)

Investigation of flame retardancy in EVA

Abstract: Strategies for fire retarding ethylene vinyl acetate copolymer (EVA) in electrical cable insulation by means of halogen-free systems were explored. Attempts to increase char yield, promoting crosslinking of double bonds either created by deacetylation of vinyl acetate units or by dehydrogenation of ethylene sequences in EVA were carried out. Pd catalysed dehydrogenation was unsuccessful, whereas oxidative dehydrogenation seems promising as shown by using thermally decomposing KMnO4. On the other hand organic peroxides failed to increase the rate of crosslinking of deacetylated units. Better results were obtained with the addition to EVA of an intumescent system which is a combination of melamine phosphate and phosphate-phosphonate substituted trimethylamine. EVA was shown to play a substantial role in the intumescence phenomenon. Copyright © 2000 John Wiley & Sons Ltd.

Process for the production of vinyl acetate.

Abstract: The present invention describes contacting in a first reaction zone a gaseous feedstock comprising essentially ethane with a molecular oxygen-containing gas in the presence of a catalyst to produce a first product stream comprising acetic acid; contacting in a second reaction zone a gaseous feedstock comprising essentially ethane with a molecular oxygen-containing gas in the presence of a catalyst to produce a second product stream comprising ethylene; contacting in a third reaction zone the first gaseous product stream and the second gaseous product stream with a molecular oxygen-containing gas in the presence of a catalyst to produce a fourth product stream comprising vinyl acetate; separating the product stream from step (3) and recovering vinyl acetate from said product stream from step (3).

Ethylene/Vinyl Acetate Copolymers via Acyclic Diene Metathesis Polymerization. Examining the Effect of “Long” Precise Ethylene Run Lengths

Abstract: Tandem acyclic diene metathesis (ADMET) polymerization/catalytic hydrogenation has been exploited to synthesize copolymers modeling ethylene/vinyl acetate (EVA) materials. A series of four sequence...

Ink jet recording sheet

Abstract: PROBLEM TO BE SOLVED: To improve a surface strength and a water resistance and to eliminate a stain of an image by providing a coating layer containing an ethylene vinyl acetate copolymer, an amphoteric starch and a pigment at least on one surface of a base material. SOLUTION: If an ethylene vinyl acetate copolymer contained in a coating layer provided on one or each of both surfaces of a base material is a copolymer containing at least an ethylene and a vinyl acetate as monomer components, it is not particularly limited. In this case, a monomer ratio of the ethylene: the vinyl acetate is preferably about 10:90 to about 30:70. About 40 to 55 wt.% of the copolymer is contained in the coating layer so that a film is made transparent and an adhesive force of its pigment can be made rigid. As the starch, a phosphate group is preferably contained as an anionic group, and a quaternary ammonium salt is preferably contained as a cationic group. As the pigment used for the layer, if a pigment which contributes to an absorption of an aqueous ink, it is not particularly limited. Of them, a fine particle silica of an inorganic pigment having high oil absorbency and high specific surface area is good.

Radical telomerization of vinyl acetate with chloroform. Application to the synthesis of poly(vinyl acetate)-block-polystyrene copolymers by consecutive telomerization and atom transfer radical polymerization

Abstract: This paper demonstrates that radical telemerization and atom transfer radical polymerization (ATRP) can be combined in a two-step procedure to prepare poly-(vinyl acetate)-block-polystyrene (PVOAc-b-PSt) diblock copolymers. The first step consists in telomerizing VOAc with chloroform, leading to trichloromethyl-terminated VOAc telemers CC1 3 (VOAc) n H. A detailed 1 H NMR analysis shows that nearly pure telomer structures are obtained over a broad range of DP n values (up to at least 60 units). When ATRP of styrene is initiated with a model telomer adduct (CC1 3 CH 2 CH 2 OAc), molecular weights increase linearly with monomer conversion and match theoretical values. Moreover, polydispersities are consistently low (1.22 < M w M n < 1.38) throughout polymerization. Similarly, VOAc telomers (DP n = 9 and 62) are good ATRP macroinitiators. The hight purity of the resulting diblock copolymers is confirmed by GCP using RI/UV dual detection.

Static and Dynamic Fluorescence of Pyrene as Probes of Site Polarity and Morphology in Ethylene-co-(Vinyl Acetate) (Eva) Films

Abstract: Static and dynamic fluorescence of pyrene has been used to study the polarity of microenvironments of ethylene-co-(vinyl acetate) copolymers of varying compositions. The polarity of these copolymers, defined by the Py-scale, has been compared with low-density polyethylene and poly(vinyl acetate). Linear correlations between vinyl acetate content and either the vibronic ratio, I/III, of the pyrene fluorescence spectra or the fluorescence decay constants, τF, have been obtained. We have also studied the photophysical properties of pyrene sorbed on the polymer surface by vapor deposition or incorporated within the polymer by swelling with a solvent. The photophysical parameters determined by both experiments are virtually the same, demonstrating that pyrene senses the same type of environment throughout the polymer film. Furthermore, in each of the copolymers, the probes experience an average polarity rather than one from domains enriched in either ethylene or vinyl acetate.

Surface photografting polymerization of vinyl acetate (VAc), maleic anhydride, and their charge transfer complex. I. VAc(1)

Abstract: On the basis of our earlier work, extensive experiments were conducted to further investigate grafting vinyl acetate onto different films (10 types of films and 20 kinds of film combinations), using various photoinitiators, for example, BP, AQ, ITX, XAN, Irgacure 651 and 184, acetone, and cyclohexanone, irradiated by UV radiation. Several means were applied to confirm the grafted PE-g-PVAc film. The results showed that increasing UV radiation intensity is favorable for grafting polymerization and the far UV radiation plays a decisive role. Among the photoinitiators tested, BP is the best one, because it was found that BP initiates the grafting copolymerization efficiently, and other initiators are less effective. To various combined substrates, the affinity between the monomer and films, the reactivity of hydrogens on the substrates, and the transparence of the top film to UV radiation are main factors affecting polymerization. Both direct method (FTIR) and indirect methods (contact angle, color reaction, absorption of dye and water) verified the true product PE-g-PVAc. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1522–1531, 2000

Plastification of poly(vinyl chloride) by polymer blending

Abstract: Blends of poly(vinyl chloride) (PVC) with different copolymers have been studied to obtain a plasticized PVC with improved properties and the absence of plasticizer migration. The copolymers used as plasticizers in the blends were acrylonitrile butadiene rubber, ethylene vinyl acetate (EVA), and ethylene-acrylic copolymer (E-Acry). Blends were studied with regard to their processing, miscibility, and mechanical properties, as a function of blend and copolymer composition. The results obtained were compared with those of equivalent compositions in the PVC/dioctyl phthalate (DOP) system. Better results than PVC/DOP were obtained for PVC/acrylonitrile butadiene rubber blends. The plasticizing effect on PVC of EVA and E-Acry copolymers was similar to that of DOP. It is shown that crosslinking PVC/E-Acry blends or increasing the vinyl acetate content in PVC/EVA blends, are alternatives that can increase the compatibility and mechanical properties of these blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1303–1312, 2000

Hair dye composition

Abstract: A one-pack aerosol type hair dye composition which comprises an oxidation color and an oxidase, characterized in that at least one water-soluble high-molecular compound selected from hydroxypropyl cellulose, carboxymethyl cellulose, xanthan gum, gum guaiac, locust bean gum, gum arabic, tragacanth gum, karaya gum, gellan gum, pectin, carrageenan, furcellaran, alginic acid and salts thereof, hyaluronic acid and salts thereof, chondroitin sulfuric acid and salts thereof, ethylene oxide polymer, polyacrylic acid and salts thereof, acrylic copolymers and salts thereof, polyvinyl pyrrolidone, vinyl pyrrolidone copolymers, polyvinyl acetate, vinyl acetate copolymers, carboxy vinyl polymer is formulated.

Enzymatic resolution of racemic secondary alcohols by lipase B from Candida antarctica

Abstract: Chiral intermediates S-(+)-2-pentanol and S-(+)-2-heptanol were prepared by a lipase-catalyzed enzymatic resolution proces. Among various lipases evaluated for the stereoselective acylation of racemic alcohols, lipase B from Candida antarctica catalyzed the acylation of the undesired enantiomer of racemic alcohols leaving the desired S-(+)-alcohols unreacted. A reaction yield of 43–45% and an enantiomeric excess (e.e.) of >99% were obtained for S-(+)-2-pentanol or S-(+)-2-heptanol when the reaction was carried out using vinyl acetate or succnic anhydride as acylating agent. In an alternative process, an enantioselective hydrolysis of 2-pentyl acetate was demonstrated using lipase B giving S-(+)-2-pentyl acetate and R-(−)-2-pentanol. A reaction yield of 45% and an e.e. of 98.6% were obtained for S-(+)-2-pentyl acetate.

Improvement of the water resistance of poly(vinyl acetate) emulsion wood adhesive

Abstract: Four different approaches were taken to improve the water resistance of poly(vinyl acetate) (PVAc) emulsion adhesives. The improved wood adhesives were tested according to the ISO 9020 standard. Tensile storage modulus (E’) and glass transition temperature of the polymer films were measured using dynamic mechanical thermal analysis to quantify the influence of different approaches on those variables. Gel fraction and swelling ratio of the polymer film were measured to evaluate internal crosslink density. The experimental results showed that blending melamine/urea/formaldehyde (MUF) resin with PVAc emulsions modified the water resistance considerably and the film had a high E’ since an interpenetrating network‐type structure was formed in the polymer. The advantages and limitations of each modification were assessed on the basis of comparison of the results.

Method for producing vinyl acetate monomer from ethane or ethylene oxidation

Abstract: Methods for the catalytic production of vinyl acetate monomer from ethane, ethylene or an ethane/ethylene mixture using a first catalyst containing MoVNbPd, MoVLaPdNbX (where X is Al, Ga, Ge or Si) or MoVNbX (where X is P, B, Hf, Te, As or mixtures thereof) in the first step of oxidation and using a conventional VAM catalyst for the second step. The method produces high yields to acetic acid and vinyl acetate without the coproduction of carbon monoxide. Furthermore, the ethylene and acetic acid produced in the first step may be utilized in the second step for VAM production.