Showing papers on "Vinyl acetate published in 1990"

Blends of polyactic acid

Abstract: An environmentally degradable composition comprising blends of a physical mixture of poly(lactic acid), and a polymer selected from the group consisting of poly(ethylene terephthalate), a polymer or copolymer of styrene, ethylene, propylene, vinyl chloride, vinyl acetate, alkyl methacrylate, alkyl acrylate, and physical mixtures thereof; plasticized with D-lactic acid, L-lactic acid, racemic D,L-lactic acid, D-lactide, L-lactide, meso D,L-lactide, racemic, D,L-lactide, oligomers of lactic acid, oligomers of lactide, derivatives of oligomers of lactic acid, or various mixtures thereof.

Polymer compositions containing destructurized starch

Abstract: A thermoplastic polymer composition comprising: (a) a destructurized starch, and either (b) an effective amount of at least one compound selected from the following: (1) a polymer which contains at least two different types of functional groups, one of said types of these groups being hydroxyl groups; (2) at least one polymer which does not contain hydroxyl groups and is selected from the group consisting of polymers which contain at least two types of functional groups bound to the same molecule one type of these groups being carboxylate groups; (3) at least one polymer selected from the group consisting of polymers which contain tertiary amino groups and/or salts thereof and/or quaternary ammonium groups; (4) at least one polymer selected from the group of polysaccharides which have been chemically modified to contain added hydroxyalkyl groups and/or contain alkyl ether groups, and/or contain ester groups; (5) at least one compound selected from the group consisting of copolymers of vinyl pyrrolidone; (6) at least one compound selected from the group consisting of cationically modified polysaccharides; (7) at least one compound selected from the group consisting of anionically modified polysaccharides; (8) at least one polymer selected from the group of copolymers containing vinyl alcohol units together with aliphatic chain units as are obtained by copolymerization of vinyl esters, preferably vinyl acetate, with unsaturated monomers containing no functional group with subsequent hydrolysis of the vinyl ester group; (9) at least one compound selected from the group consisting of polysaccharide graft copolymers and graft copolymers of polysaccharide derivatives; (10) at least one compound selected from the group consisting of polyalkyleneimine polymers and polyalkyleneimine copolymers; (11) at least one compound selected from the group consisting of styrene sulfonic acid polymers, styrene sulfonic acid copolymers, and salts thereof; and (12) at least one compound selected from the group consisting of polymers and copolymers which contain carboxylic groups which partially or wholly are present in the form of their salts and wherein said polymers or copolymers do not contain further functional groups; or (c) At least one substantially water-insoluble thermoplastic polymer. combinations of (a), (b) and (c) are also disclosed.

Cement admixture and cement composition

Abstract: A cement admixture comprising a polymer latex and a water reducing agent as effective components, wherein the polymer latex comprises a copolymer of monomers comprising ethylene, vinyl acetate and an acrylic ester, and an emulsion stabilizer, said emulsion stabilizer being a surfactant.

Flame retardant polymer composition

Abstract: A flame retardant polymer composition which is substantially free of halogen compounds and of organometallic salts comprises (A) an organic polymer, at least 40% by weight of which is a copolymer of ethylene with one or more comonomers selected from the group consisting of alkyl acrylates, alkyl methacrylates, acrylic acid, methacrylic acid and vinyl acetate, (B) a silicone fluid or gum and (C) an inorganic filler which is a compound of a metal of Group II A of the Periodic Table of Elements but which is neither a hydroxide nor a substantially hydrated compound. Suitable inorganic fillers are magnesium oxide, magnesium carbonate and calcium carbonate, the latter being the most preferred. The compositions are particularly suitable for use in wire and cable applications.

Enzymatic acylation using acid anhydrides: Crucial removal of acid

Abstract: An efficient enzymatic resolution of 7,7-disubstituted 1,4,5,6-tetrachlorobicyclo [2.2.1]hept-5-en-2-ols was accomplished by means of lipase AY-30 from Candida cylindracea in toluene. When acid anhydrides were used as acyl donors, the enantioselectivity was found to depend strongly on the reaction conditions: Whereas low selectivity (E 200). Alternatively, adsorption of the biocatalyst onto Celite was equally effective (E > 300). Complete specificity was obtained when vinyl acetate was used as acyl donor (E ∼ 1000).

Effect of the way of addition of the reactants in the graft copolymerization of a vinyl acetate–methyl acrylate mixture onto cellulose

Abstract: In order to graft a vinyl acetate–methyl acrylate mixture onto cellulose, an exploration of the way of addition of the reactants has been made. The influence of several factors on the grafting parameters was studied, i.e., the order of addition of the ceric ion initiator and the monomer mixture, the removal of the ceric ion solution after a cellulose-ceric ion contact time, and the delayed addition along the polymerization period of the more reactive monomer (methyl acrylate) towards the cellulosic radicals. Some grafting parameters were determined: grafting yield, grafting efficiency, cellulose conversion, molecular weight, ceric ion consumption, grafting frequency, number of grafted chains, and synthetic copolymer composition. After a short period (ca. 15 min) for the ceric adsorption on cellulose, a fast formation of cellulosic radicals arises in the initial stages of the polymerization. These initial cellulosic radicals should be trapped by a sufficiently reactive monomer if high grafting yield and high number of grafted chains are to be reached. A portion of the synthetic polymer chains anchored to cellulose that are formed in the first stages of the polymerization, which are generated from cellulosic hemiacetal groups, should constitute block copolymer.

Mouth guard compositions

Abstract: An improved mouth guard composition comprises an ethylene/vinyl acetate copolymer and a thermoplastic polycarprolactone having a molecuar weight of 10,000-100,000, optionally with polyvinyl acetate, colorants and perfumes.

Process for producing microcapsules

Abstract: In producing microcapsules using the amino resin as a capsule wall in a system in which hydrophobic core material is dispersed or emulsified in an aqueous acidic solution containing an anionic colloidal substance, said anionic colloidal substance comprises an anionic, water-soluble copolymer consisting of at least three monomers including acrylic acid, hydroxyalkylacrylate or hydroxyalkylmethacrylate and styrenesulfonic acid. The process of the present invention provides a good emulsification against the variation of the emulsifying condition, a good stability of emulsion between the encapsulating reaction, an excellent stability against the variation of the encapsulating conditions and a superior capsule slurry. More desirable results may be obtained when an anionic, water-soluble copolymer which is obtained by copolymerizing one or more components selected from alkyl acrylate, methacrylic acid, alkyl methacrylate, acrylamide, methacrylamide, succinic ester of hydroxyalkyl acrylate, succinic ester of hydroxyalkyl methacrylate, vinyl acetate and acrylonitrile as fourth and further components in addition to the above-mentioned three components, is used.

A novel synthetic procedure of vinylacetamide and its free radical polymerization

Abstract: The pyrolysis of N-(α-methoxyethyl) acetamide, which was obtained by one-step reaction of acetamide, acetaldehyde, and methanol, gave N-vinylacetamide (NVA) in a good yield. The polymerizability and copolymerizability of NVA were studied. Free radical polymerization was carried out in the presence of radical initiator or by γ-ray irradiation. The monomer reactivity ratios of NVA were estimated in the copolymerization with acrylamide, vinyl acetate, and methyl methacrylate. The solvents were found to influence the monomer reactivity ratio. NVA showed a typical copolymerizability as nonconjugated vinyl monomer, and Q and e values were obtained in DMF as 0.16 and −1.57, respectively.

Quantitative measurement of chain contraction in a solid blend of two incompatible polymers: poly(methyl methacrylate)/poly(vinyl acetate)

Abstract: Electronic excitation transport among naphthyl chromophores in low concentration on isolated chains of poly(2-vinylnaphthalene-co-methyl methacrylate) dispersed in both PMMA and PVAc is monitored by time-resolved fluorescence depolarization spectroscopy. Analysis of the results with a theory for excitation transport in finite volume systems allows the quantitative determination of the root-mean-square radius of gyration ((R g 2 ) 1/2 ) of PMMA in the two hosts. The results for bulk PMMA agree with expected values for PMMA in a θ solvent. A significant decrease in (R g 2 ) 1/2 for isolated PMMA chains is observed in the PMMA/PVAc blend

Flow-induced mixing of blends of poly(ethylene-vinyl acetate) and solution chlorinated polyethylene

Abstract: A rheooptical device was constructed to monitor phase changes in polymer blends undergoing simple shear flow. Light scattering experiments during shear flow of blends of EVA and SCPE indicated that stress improves the miscibility of the two polymers. This is interpreted in terms of a stress-dependent phase diagram in which the phase boundary of a polymer mixture that exhibits a lower critical solution temperature is shifted upward in temperature due to the application of stress

Simulation of the latex particle morphology

Abstract: A model is presented for the simulation of the structuration of polymer particles under conditions in which the new polymer chains are compatible with the polymer previously formed. The model involves the calculation of the monomer concentration gradients within the particles due to discrepancies in thermodynamic interactions between the monomer and the different polymers present in each part of the polymer particle. In addition, the distribution of free radicals in the latex particle is taken into account. This distribution results from the anchoring of the hydrophilic end-group of the growing polymer chain on the surface of the particle. The model was applied to the simulation of the polymerization of vinyl acetate on a butyl acrylate–vinyl acetate copolymer seed. It was found that the development of the particle morphology was mainly due to the profile of concentration of radicals in the particle. On the other hand, the effect of the monomer–polymer thermodynamic interactions on the particle morphology was found to be negligible. However, it has to be pointed out that this is because, for the system studied, the interaction parameters of vinyl acetate with polyvinyl acetate and polybutyl acrylate are nearly identical.

The use of activated benzyl vinyl ethers to control molecular weight in free radical polymerizations

Abstract: The vinyl ethers, α-benzyloxyacrylonitrile (4), methyl α-benzyloxyacrylate (5), and α-benzyloxy-acrylamide (6), act as sulfur-free chain transfer agents in the polymerization of methyl methacrylate (chain transfer constant Cx = 0,081–047), styrene (Cx = 0,036–0,14), methyl acrylate (Cx = 0,3–1,1), and vinyl acetate (Cx = 12–20) initiated by AIBN at 60°C With methyl methacrylate and styrene, the conversions of the polymerizations are relatively unaffected by the vinyl ethers With methyl acrylate and vinyl acetate, however, some retardation occurs The activity of the compounds is compared with that of α-benzyloxystyrene (1), which undergoes chain transfer by a novel free radical addition-fragmentation pathway

Process for the isolation of vinyl acetate by distillation

Abstract: The invention relates to a process for the isolation of vinyl acetate which involves not combining the bottom product of the recylced gas washings with the water-saturated vinyl acetate but rather introducing it to further multiple distillation columns from the gas mixture formed in the reaction of ethylene with acetic acid and oxygen over catalysts containing palladium or palladium compounds in the gas phase.

Electro-Optic Studies on Polymer Dispersed Liquid Crystal Films Prepared by Solvent- Induced Phase Separation Technique

Abstract: The electro-optic performance characteristics of PDLC films using two different polymers, namely, poly (methyl methacrylate) (PMMA) and poly (vinyl chloride:vinyl acetate 17%) (PVC:VAC-17) and liquid crystal mixture E-8 (BDH, England) have been studied. It is found that the PMMA-based PDLC films have more superior mechanical and electro-optical properties than the PVC:VAC-17-based PDLC films. The performance characteristics of PDLC films, in general, improve significantly with increasing temperature. An optimum weight fraction of liquid crystal mixture is to be added in the polymer for good performance of the PDLC films. The finite solubility of liquid crystal mixture in the polymer affects the properties of the polymer matrix and hence the electro-optic performance characteristics significantly.

Emulsion polymerization of vinyl acetate initiated by potassium persulfate-cyclohexanone sodium bisulfite redox pair system

Abstract: The emulsion polymerization of vinyl acetate using potassium persulfate and cyclohexanone sodium bisulfite as redox pair initiation system was studied. The rate of polymerization, maximum conversion, and the number of polymer particles produced were found to change with redox initiator, monomer and emulsifier concentrations, and temperature variation. The rate of polymerization was found to be dependent on the initiator, the monomer, and the emulsifier concentrations to the 0.88, 0.22, and 0.20 powers, respectively. The K2S2O8–NaHSO3 redox system was found to decrease maximum conversion and doesn't form a stable emulsion. The apparent arrhenius activation energy (Ea) estimated for the polymerization system was 65.6 kJ/mol. The viscosity average molecular weights for some obtained poly(vinyl acetate) were determined.

Probe diffusion in poly (vinyl acetate) / toluene solutions

Abstract: The technique of forced Rayleigh scattering has been used to examine the tracer diffusion of probe photochromic dyes, azobenzene and methyl red, in poly (vinyl acetate)/ toluene solutions, as a function of polymer concentration (0–96% by weight) and temperature (5–45°C). It is demonstrated that the dye diffusivity can be quantitatively scaled to the solvent diffusivity, thus permitting direct application of predictions for two-component systems. The results have been interpreted using the free volume theories of Fujita and Vrentas and Duda. While both approaches are able to describe the concentration dependence extremely well, the Vrentas-Duda expression has the virtue of being employed without any freely adjustable parameters. However, neither theory is particularly successful in predicting the observed temperature dependence.

Siliconized emulsion based pressure-sensitive adhesives.

Abstract: There is provided inherently tacky pressure-sensitive adhesive polymers prepared by emulsion polymerization and containing an interpolymerized amount of a reactive silicone acrylate polymer, an unsaturated carboxylic acid one or more alkyl acrylates, preferably a mixture of butyl acrylate and 2-ethylhexyl acrylate. Methyl acrylate and vinyl acetate are optionally present. The polymers have initial repositionability, long term permanence and excellent water resistance.

Degradation of vinyl acetate by soil, sewage, sludge, and the newly isolated aerobic bacterium V2.

Abstract: Vinyl acetate is subject to microbial degradation in the environment and by pure cultures. It was hydrolyzed by samples of soil, sludge, and sewage at rates of up to 6.38 and 1 mmol/h per g (dry weight) under aerobic and anaerobic conditions, respectively. Four yeasts and thirteen bacteria that feed aerobically on vinyl acetate were isolated. The pathway of vinyl acetate degradation was studied in bacterium V2. Vinyl acetate was degraded to acetate as follows: vinyl acetate + NAD(P)+----2 acetate + NAD(P)H + H+. The acetate was then converted to acetyl coenzyme A and oxidized through the tricarboxylic acid cycle and the glyoxylate bypass. The key enzyme of the pathway is vinyl acetate esterase, which hydrolyzed the ester to acetate and vinyl alcohol. The latter isomerized spontaneously to acetaldehyde and was then converted to acetate. The acetaldehyde was disproportionated into ethanol and acetate. The enzymes involved in the metabolism of vinyl acetate were studied in extracts. Vinyl acetate esterase (Km = 6.13 mM) was also active with indoxyl acetate (Km = 0.98 mM), providing the basis for a convenient spectrophotometric test. Substrates of aldehyde dehydrogenase were formaldehyde, acetaldehyde, propionaldehyde, and butyraldehyde. The enzyme was equally active with NAD+ or NADP+. Alcohol dehydrogenase was active with ethanol (Km = 0.24 mM), 1-propanol (Km = 0.34 mM), and 1-butanol (Km = 0.16 mM) and was linked to NAD+. The molecular sizes of aldehyde dehydrogenase and alcohol dehydrogenase were 145 and 215 kilodaltons, respectively.

Heat-laminatable, high-gloss multilayer films

Abstract: An improved heat-laminatable, high-glass and high-slip, at least monoaxially stretched multilayer film comprises at least one base layer I consisting essentially of polypropylene, an outer layer II which is thin by comparison with layer I and which consists essentially of polypropylene and an addition of an anti-blocking additive and a heat-activatable, heat-laminatable layer III containing an ethylene/vinyl acetate copolymer A and an ethylene/ethyl acrylate copolymer B1 and/or an ethylene/acrylic acid copolymer B2, the base layer I containing no anti-blocking additives.

Subbing layer for dye-donor element used in thermal dye transfer

Abstract: A dye-donor element for thermal dye transfer comprising a poly(ethylene terephthalate) support having thereon, in order, a subbing layer and a dye layer comprising a dye dispersed in a cellulosic binder, and wherein said subbing layer comprises a copolymer of vinyl alcohol and an alkyl ester of vinyl alcohol, such as vinyl acetate.

Palatable solid pesticidal compositions of ethylene and vinyl acetate copolymer

Abstract: The invention comprises compositions in solid form of ethylene/vinyl acetate copolymer with an effective amount of bioactive agent, a protein/carbohydrate-lipid source, 0 to 20% of an edible oil and optionally an attractant, dye, preservative, adversive agent and biomarker and the use, thereof, to control pests.

Copolymer composition control during the seeded emulsion copolymerization of vinyl acetate and methyl acrylate

Abstract: The effect of various monomer addition policies on the copolymer composition during the seeded copolymerization of methyl acrylate and vinyl acetate in a semicontinuous reactor was investigated. Four policies were considered. In the first, which is called optimal policy, the reactor was initially charged with all of the less reactive monomer (vinyl acetate) plus the amount of the more reactive monomer (methyl acrylate) needed to initially form a copolymer of the desired composition. Then, the addition of the remaining methyl acrylate was made at a flow rate that ensured the formation of a copolymer of the desired composition. In the second, the initial charge is the same as in the previous case but the time dependent addition rate of methyl acrylate was decomposed into three periods of constant feed rate. In the third, the initial charge is the same as in the previous policies but the remaining methyl acrylate was added at a constant feed rate. In the forth, both monomers were added under starved conditions. In order to calculate the optimal addition policy, the time evolution of the average number of radicals per particle, n, is required. The calculation of n involves rate parameters which values are usually unknown. Therefore, a semi-empirical method for the calculation of the time evolution of n was developed. It was found that n was always greater than 2. For the experimental conditions used in this work, this result suggested that termination in the polymer particles was affected by gel effect. A gel effect function was estimated and then the optimal addition policy was calculated. Comparison between the different processes showed that, for a fixed process time, the copolymer obtained through the optimal addition policy was more homogeneous than that formed when the methyl acrylate was fed in three periods of constant feed rate and even better than the one obtained using a constant feed rate throughout the process. The copolymer quality of the later process is similar to that of the copolymer formed by means of the starved process. Nevertheless, a more homogeneous copolymer composition can be obtained through the starved process when longer process times are used.

Vinyl acetate/ethylene/NMA copolymer emulsion for nonwoven binder applications

Abstract: A process for making an aqueous vinyl acetate/ethylene/N-methylolacrylamide copolymer emulsion comprising: (a) adding an initial charge containing all the vinyl acetate monomer to be polymerized and an effective amount of an emulsifying system consisting essentially of an anionic surfactant, especially a salt of an alkylphenoxy poly(ethyleneoxy) sulfate containing about 3-5 ethyleneoxy units, (b) pressurizing the reactor with sufficient ethylene to yield a copolymer having the desired Tg, (c) initiating polymerization at a temperature from 45° to 85° C., and (d) continuing polymerization at a temperature from 45° to 85° C., while continuously adding N-methylolacrylamide over a period of time such that the free vinyl acetate monomer content of the reaction medium is about 2-4% upon completion of the N-methylolacrylamide addition.

Flame retardant and smoke suppressed polymeric composition and electric wire having sheath made from such composition

Abstract: A flame retardant and smoke suppressed polymeric composition comprising a radiation curable copolymer of ethylene and vinyl acetate containing 50-85% by weight of vinyl acetate having intimately admixed therewith a flame retarding and smoke suppressing amount of a finely divided filler mixture consisting essentially of a first filler selected from hydroxides and carbonate of di- and tri-valent metals and a second filler which is zinc borate, the composition may be shaped into a desired article, such as a sheath of an electric wire, which may be radiation cured.

Method of producing heat-resistant and shape memory formed products

Abstract: A method of forming a heat-resistant product, produced from a polymer composition comprising 40-70 weight % of a thermoplastic elastomer containing a repeating unit derived from ethylene and a repeating unit derived from propylene and 60-30 weight % of an ethylene-vinyl acetate copolymer containing 7.5 weight % or more of a vinyl acetate repeating unit, which comprises blending the polymer composition at a temperature of 160° C. or less, molding it at a temperature of 180° C. or less, and then cross-linking the resulting molded product by irradiating it with an electron beam or by heating to produce a foamed product which has good shape memory characteristics.