Showing papers on "Vinyl acetate published in 1975"

Drug-delivery device comprising certain polymeric materials for controlled release of drug

Abstract: Drug-delivery device for releasing a drug at a continuous and controlled rate for a prolonged period of time is comprised of a shaped body of polymeric material containing a pharmaceutically acceptable drug and permeable to passage of the drug by diffusion. The polymeric material is an ethylene-vinyl acetate copolymer having a vinyl acetate content of about 4 to 80% by weight and a melt index of about 0.1 to 1000 grams per 10 minutes.

Vaginal drug dispensing device

Abstract: Drug-delivery device for releasing a drug at a continuous and controlled rate for a prolonged period of time is comprised of a shaped body of polymeric material containing a pharmaceutically acceptable drug and permeable to passage of the drug by diffusion. The polymeric material is an ethylene-vinyl acetate copolymer having a vinyl acetate content of about 4 to 80% by weight and a melt index of about 0.1 to 1000 grams per 10 minutes.

Gas permeation of polymer blends. I. PVC/ethylene–vinyl acetate copolymer (EVA)

Abstract: The transport behavior of O2 and N2 were studied for series of physical blends of PVC with EVA having different vinyl acetate (VAc) contents in the EVA (45 and 65 wt-%) and using different milling temperatures (160° and 185°C). The polymer blends were further characterized by dynamic mechanical measurements, density measurements, and x-ray diffraction. At higher VAc content in EVA and with higher milling temperature, the rate of permeation (P) and the rate of diffusion (D) decrease, and the activation energy of D (from Arrhenius plots) increases. Furthermore, the experimental density values of PVC/EVA-45 blends agree well with calculated values, assuming volume additivity of the two components, while those of PVC/EVA-65 blends are higher than the calculated densities. These results are interpreted as due to denser packing of polymer molecules and increased PVC-EVA interaction at higher VAc content and with higher milling temperature, indicating better compatibility between the blend components. The x-ray diffraction data give no evidence of crystallinity. Sharp increases in P and D values at about 7.5% EVA (by weight) are found for PVC/EVA-45 blends (in agreement with our previous work) but not for PVC/EVA-65 blends. This is interpreted as due to a phase inversion at increasing EVA content in the former blends but not in the latter blends. The dynamic mechanical measurements show that the PVC/EVA-65 blends milled at 160°C behave largely as semicompatible systems with maximum interaction between the two polymers at compositions of about 50/50 by weight.

Polymers comprising vinyl esters-crotonic acid

Abstract: Copolymers of vinyl acetate, crotonic acid and an unsaturated ester or ether are employed in cosmetic compositions for the hair.

Kinetics of vinyl chloride and vinyl acetate emulsion polymerization

Abstract: The kinetics of vinyl chloride and vinyl acetate emulsion polymerization are reexamined. The validity of Ugelstad's model for systems with high desorption rate is confirmed by simulating conversion histories for both systems at different initiator concentrations and particle numbers. On the basis of the model, it is shown that at ordinary initiation rates, termination reactions are unimportant with respect to molecular weight development in both systems, and as a consequence, molecular weight development is independent of number and size distribution of polymer particles and of initiator and emulsifier level. Based on this conclusion, it is shown that in accordance with experimental facts, the molecular weight distribution obtained in vinyl chloride emulsion polymerization is the most probable distribution, and it is concluded that the number of long-chain branch points per repetition unit is less than 2 × 10−4 at high conversions. In vinyl acetate emulsion polymerization, an almost logarithmic normal distribution is obtained. The distribution is strongly broadened by branching reactions with the number of long-chain branch points increasing rapidly with monomer conversion. The increase of Mn with increasing conversion is due to terminal double-bond polymerization, while the increase in Mw is due mainly to transfer to polymer.

Method of producing vinyl acetate

Abstract: Vinyl acetate is produced through reaction of ethylene, oxygen and acetic acid in vapor phase employing a catalyst which comprises 0.3 to 3.0 weight % of palladium metal, 0.0157 to 1.8 weight % of gold metal and 1 to 30 weight % of an alkali metal acetate, all based on the weight of the carrier or catalyst support therefor. These components are supported on said carrier or support under such conditions that (1) at least 90% by weight of each of the supported palladium and gold metals is distributed proximate the external surfaces of the carrier particles, extending to depths no greater than about 30% of the radius of each particle as measured from the external surface of each particle to the center of said particle, and (2) the proportion of gold to palladium ranges from about 5 to 60% by weight, based upon the total weight of the gold and palladium.

Mechanism of Alternating Copolymerization of Vinyl Acetate and Maleic Anhydride

Abstract: Vinyl acetate and maleic anhydride are known to give 1:1 alternating copolymerization regardless of the monomer feed composition. The existence of a charge transfer complex between the comonomers has been shown and its equilibrium constant determined. The mechanism has been discussed, starting from a study of the copolymerization rate when varying the solvent, the temperature, and the concentration of comonomers.

Process for the continuous production of an ethylene/vinyl acetate copolymer dispersion

Abstract: A process for the continuous manufacture of an aqueous ethylene/vinyl acetate copolymer dispersion which comprises continuously copolymerizing ethylene and vinyl acetate and optionally other α-olefinically unsaturated monomers, in an aqueous emulsion in the presence of an emulsifier and/or a protective colloid, and in the presence of a free-radical-forming redox catalyst system of a reducing agent and an oxidizing agent as well, optionally, as a heavy metal salt, and recovering said ethylene/vinyl acetate copolymer dispersion, characterized by (a) the presence of a molar excess of at least 3 times, preferably from 3 to 10 times, said reducing agent over said oxidizing agent dosed into the reaction medium and (b) adding the monomers continuously to the reaction mixture at such a rate that the concentration of unreacted monomers at no place in the reaction zone exceeds 15% by weight of the total weight of the reaction mixture.

Aqueous emulsion copolymers of vinyl alkanoates, alkyl, acrylates, and acrylic modified alkyds

Abstract: Aqueous polymeric emulsions are formed by the inter-polymerization reaction product of at least one monomer having a reactive CH 2 =C< group (e.g., vinyl acetate and alkyl acrylates) and an alkyd resin which is modified by the incorporation therein of certain ethylenically unsaturated monomers.

Interaction of inorganic salts with polar polymers. II. Infrared studies of polymer–inorganic nitrate systems

Abstract: Certain inorganic nitrate salts are quite soluble in the polymers studied, namely, cellulose acetate, poly(vinyl acetate), poly(vinyl alcohol), poly(methyl methacrylate), and poly(methyl acrylate). Large effects upon the glass-transition temperature were observed in those systems where the transition could be readily measured. Large shifts in the infrared spectra of both the inorganic nitrate salts and in the polymer carbonyl and ester ether frequencies have been observed. These observations have been interpreted in terms of complex formation between these polymers and salts in the solid state. The proposed structure of the complex explains the nature of the infrared shifts both for the nitrate salts and the polymers as well as explaining the concentration effects observed. Effects of the solvating environment upon the salt and polymer spectra remain unexplained. The large glass-transition effects are a result of the degree of solubility of the salts in the polymers and the interactions between them. However, the reason why, in some cases, the change in the transition temperature as a function of concentration goes through a maximum is unclear.

Processes for coating films

Abstract: Substrate layers comprising an acrylic or methacrylic copolymer or a copolyester on a polyester film support are coated with an aqueous latex or solution comprising an acrylic or methacrylic copolymer, an unhydrolyzed or partially hydrolyzed polymer or copolymer of vinyl acetate or a copolymer of vinylidene chloride together with a crosslinking component. The coated films may be used in a variety of end uses, including drafting films.

Flexible collapsible blood freezing containers

Abstract: Improved, flexible, collapsible containers are provided for the storage of frozen blood and the like at cryogenic temperatures. The containers are defined by plastic walls consisting essentially of a biaxially-oriented ethylene-vinyl acetate copolymer containing from ten to thirty-five percent by weight of vinyl acetate units. The container wall thickness is typically from 0.01 to 0.025 inch.

Method of conducting drilling operations

Abstract: A method for reducing the loss of fluid through the walls of a well penetrating a permeable subterranean formation during completion, workover and other operations. The method provides for the use of a fluid comprising an aqueous dispersion of finely divided, slowly oil-soluble, water-insoluble solid particles in an aqueous salt solution containing chrome lignite, hydroxyethyl cellulose and xanthan gum. The density of the fluid is controlled by varying the concentration of salt dissolved in the solution. The finely divided solid particles consist of a homogeneous solid solution of (1) wax; (2) an oil-soluble surface active glyceryl or sorbitan partial ester of a saturated higher fatty acid; and (3) a water-dispersible surface active polyethylene glycol monoester of a saturated higher fatty acid. The particles may optionally include an ethylene/vinyl acetate copolymer, and/or a fatty alcohol.

Determination of crystallinity of olefin copolymers and polyolefin powders by inverse gas chromatography

Abstract: Studies of olefin copolymers by inverse gas chromatography show that the method is suitable for determining the crystallinity of compositions where a linear extrapolation of density determinations is not applicable. Satisfactory estimates of crystallinity were obtained on ethylene copolymers with carbon monoxide and vinyl acetate and on an emulsifiable polyethylene wax. Studies were also made in which the columns were packed with physical mixtures of GC support and polyolefin powders, either obtained direct or ground from film samples. It was shown that good estimates of crystallinity could be obtained if suitable allowance is made for variance in peak retention time with flow rate, due to the relatively slow rate of diffusion of the probe molecule in polymer particles of large diameter (>100 μm). If smaller particles are used it is usually unnecessary to correct for flow rate effects. This extends the usefulness of the “molecular probe” technique to any polyolefin sample which can be ground to a fine particle size and eliminates the need for solution coating of the column packing.

Production of lactic acid

Abstract: Lactic acid is synthesized by a process in which a vinyl ester is hydroformylated to an α-substituted propionaldehyde by reacting the vinyl ester with carbon monoxide and hydrogen in the presence of a hydroformylation catalyst and by further converting the α-substituted carbonyl intermediate via oxidation and hydrolysis to lactic acid. A preferred embodiment of the invention utilizes vinyl acetate as the feed.

A New Thermo-Dielectric Loss Measurement for Estimating Polymer Compatibility

Abstract: The thermo-dielectric loss measurement is a technique whereby the change of dielectric loss is measured under a definite temperature program. In this method, dielectric loss is determined by the DTA method, since dielectric loss is finally transformed to heat. The contour maps of loss∼logf∼1/T are easily drawn from the DTA curves of polymers and their mixtures.The results obtained from these maps provide new and interesting information about the estimation of polymer compatibility. The compatible pairs poly(vinyl nitrate) (PVN)—poly(vinyl acetate) (PVAc) and PVN—ethylene vinyl acetate copolymer (86-wt% vinyl acetate) (EVAc) are quite different from the incompatible pair PVAc—EVAc in the topographical shape of these contour maps. In these maps, it was found that the maps of compatible and incompatible mixture corresponded well to the maps of random copolymer and of graft copolymer, respectively. And judging by the sharpness of the temperature and frequency dispersion curves of normalized dielectric loss, it was found that even among these compatible pairs, the PVN—PVAc mixture could be presumed more homogeneous than PVN—EVAc mixture.

Structural irregularities in poly(vinyl alcohol)

Abstract: Poly(vinyl alcohols) derived from the product of polymerization of vinyl acetate in methanol have been characterized by various physical and chemical methods before and after NaIO4 cleavage. The 220-MHz 1H-NMR spectra confirm the reliability of NaIO4 titrimetry for estimating 1,2-glycol content and help explain the tendency for viscometry to grossly underestimate the 1,2-glycol content for low molecular weight polymers. The spectra and related chemical evidence indicate that the major endgroups are HOCH2CH2 and CH3CH(OH)CH(OH)CH2. s-Hydroxyethyl groups also occur as short chain branches, mainly attached to α carbon atoms in the normal head-to-tail polymer chain sequence. The concentrations of the branch and endgroups depend on polymerization conditions and help explain polymerization “solvent” effects on physical properties.

Epoxy resin powder including ethylene vinyl acetate

Abstract: Stable, free-flowing epoxy resin powder which fuses to and cures upon striking an object which has been preheated to the curing temperature of the composition to provide a tough protective coating. The composition of the powder differs from the prior art in that it includes 3-30 parts of a copolymer of 2-50% vinyl acetate and 5-75% ethylene per 100 parts of the epoxy resin. The copolymer improves the flexibility of the cured coatings.

Mechanism of thermal degradation of poly(vinyl acetate)

Abstract: The thermal degradation of poly(vinyl acetate) was investigated under dynamic atmosphere of helium up to 400° with a thermobalance. The volatile products were analyzed by a gas chromatograph.

Foreign-body tumorigenesis by vinyl chloride vinyl acetate copolymer: no evidence for chemical cocarcinogenesis.

Abstract: We investigated whether vinyl chloride monomers, released from implants of vinyl chloride vinyl acetate copolymer (VCA), exerted cocarcinogenic activity and added thereby to the mechanism of foreign-body (FB) tumorigenesis. CBA/H and CBA/H-T6 mice were used. No evidence was found to indicate that chemical carcinogenic activity partakes in tumorigenesis by VCA implants. Hence it was concluded that VCA plastic is not suitable for the study of the combined process of FB/chemical cocarcinogenesis. Furthermore, experimental results obtained with VCA film implants were representative of FB tumorigenesis in the absence of demonstrable chemical carcinogenic activity.

Process for the controlled alcoholysis of ethylene-vinyl ester interpolymers

Abstract: Process for controlling the degree of alcoholysis of ethylene-vinyl acetate and other ethylene-vinyl ester interpolymers, by regulating the initial water content of the materials utilized to make up the reaction medium within predetermined limits in order that partially hydrolyzed polymers may be obtained having substantially constant, predetermined residual vinyl acetate or other vinyl ester contents. The partially hydrolyzed products so prepared have uniform, predetermined properties making them particularly useful in film, adhesive, fluidized bed coating, and like applications.

Hair-care composition containing a thermoplastic polymer

Abstract: The hair-care composition broadly comprises an ethanolic cosmetic vehicle and between about 1 and 20% by weight, based on the total weight of the composition, of film-forming thermoplastic resinous polymeric material which in dried condition is resistant to softening by humidity, insoluble in water alone but dispersible in water having a cosmetic pH, fully soluble in ethanol, and consists essentially of the addition free-radical polymerization product formed by polymerizing a monomeric mixture consisting essentially of, by weight percent: 1 to 20% of 1,1 dimethyl-1,(2-hydroxypropyl) amine methacrylimide; 8 to 45% of N-vinyl pyrrolidone; and 35 to 89% of vinyl acetate.

Some aspects of the emulsion polymerisation of vinyl acetate

Abstract: The present status of work on the mechanism of the emulsion polymerisation of vinyl acetate initiated by potassium persulphate is critically reviewed. In addition, some new data illustrating the effect of adding electrolytes is presented. The polymerisation proceeds by a mechanism different from that of most vinyl monomers. In particular, the rates are approximately zero order on monomer from 20 to 85% conversion with only a minor dependence on the soap concentration and the number of particles. The dependence of the rate on the initiator concentration varies with different investigators from 0.5–1.0 order. The results are discussed in terms of various current theories and an attempt is made to rationalise them in a reasonable way.

Polyvinyl chloride terpolymer powder coating composition

Abstract: A powder coating composition of powder particles having a size range of about 1-100 microns in which the powder particles are a blend of A. a polyvinyl chloride terpolymer of vinyl chloride/vinyl acetate/maleic acid and B. a polymer of ethylene/vinyl acetate/carbon monoxide; The powder can contain in addition to the above polymers a heat stabilizer such as a organometallic mercaptide, an epoxy resin, pigments, plasticizers, ultraviolet light-absorbing agents, polyethylene wax and a hard polymer such as an acrylic polymer; the powder coating composition is useful as a finish for metals such as tubing, wires, fence posts, lawn furniture, play equipment and the like.

Palladium(II) Catalyzed Exchange Reactions. XI. Vinyl Propionate Exchange with Acetic Acid Catalyzed by Palladium(II) Acetate

Abstract: The kinetics of the palladium(II) acetate catalyzed exchange of vinyl propionate with acetic acid solvent to give vinyl acetate has been studied in the sodium acetate concentration range from 0 to 1 M. The exchange rate first sharply increases as [NaOAc] increases, reaches a maximum at about 0.2 M and then gradually decreases as the sodium acetate concentration is in-creased to 1.0 M. Using previous results on the equilibrium between palladium(II) acetate and sodium acetate in acetic acid it can be shown that the rate expression for exchange is: rate = (ko + kt[Pd3(OAc)6] + kd[Na2Pd2(OAc)6]) [CH2=CHO2CC2H5] where ko = 2 × 10−4 s−1, kt = 0.045 M−1 s−1, and kd = 0.089 M−1 s−1. A monomeric palladium(II) species, Na2Pd(OAc)4, formed at high [NaOAc] is unreactive. Since the rate expression does not contain a term in [NaOAc], the sodium acetate serves only to convert one palladium(II) species to another. The lack of a [NaOAc] term in the rate expression for the Na2Pd2(OAc)6 catalyzed reaction is believed to res...