Showing papers on "Vinyl acetate published in 1993"

Poly(vinyl acetate)/silica-filled materials: material properties of in situ vs fumed silica particles

Abstract: Composites of poly(vinylacetate) (PVAc) and silica were prepered from the in situ polymerization of acid-catalyzed tetraethoxysilane. The physical properties of these composites were compared with those of PVAc/fumed silica (of 7-nm nominal perticle size) composites prepered by both melt-milling and solution-casting from THF or CCl 4 . Their morphologies were examined by TEM and SAXS revealing that, although all the materials were optically transparent, differences in the primery perticle size and interfacial regions exist. IR data showed that substantially more hydrogen bonding occurs in the in situ prepared composites.

Rate constants for the gas‐phase reactions of ozone with unsaturated alcohols, esters, and carbonyls

Abstract: The kinetics of the gas-phase reaction of ozone with unsaturated alcohols, carbonyls, and esters in air have been investigated at atmospheric pressure, ambient temperature (285–295 K), and in the presence of sufficient cyclohexane to scavenge the hydroxyl radical which forms as a product of the ozone-unsaturated compound reaction. The reaction rate constants, in units of 10−18 cm3 molecule−1 s−1, are 0.26 ± 0.05 for acrolein, 1.07 ± 0.05 for 2-ethyl acrolein, 6.0 ± 0.4 for ethyl vinyl ketone, 4.9 ± 0.4 for 3-buten-1-ol, 14.4 ± 2.0 for allyl alcohol, 105 ± 7 for cis-3-hexen-1-ol, 7.5 ± 0.9 for methyl methacrylate, 2.9 ± 0.3 for vinyl acetate, 4.4 ± 0.3 for methyl crotonate, and 8.1 ± 0.3 for the 1,1-disubstituted alkene 2-ethyl-1-butene. Substituent effects on reactivity are discussed by comparison with alkenes and indicate that the reactivity of unsaturated alcohols is the same as that of alkene structural homologues and that the —C(O)OR, —C(O)R, and —CHO groups decrease the reactivity towards ozone as compared to alkyl groups. Estimates are made of the atmospheric persistence of these unsaturated compounds using the kinetic data obtained in this study as input to structure-reactivity and linear free-energy relationships. © 1993 John Wiley & Sons, Inc.

Stabilized pulverulent active agents, compositions containing them, process for obtaining them and their applications

Abstract: Stabilized pulverulent active agents, compositions containing them and also a process for obtaining them. Such stabilized active agents enable dry and stable pharmaceutical, dietary, nutritional or cosmetic compositions to be obtained, in which the properties of the said active ingredients are neither modified nor impaired. Such stabilized active ingredients are stabilized by coating with a composition comprising: at least one film forming agent, in proportions of between 2 and 25% by weight of the final mass, selected from polyvinylpyrrolidones (povidone), polyvinyl alcohols, vinylpyrrolidone/vinyl acetate copolymer, vinylpyrrolidone/polyvinyl alcohol copolymer, cellulose derivatives such as cellulose acetate, cellulose acetate phthalate, cellulose butyrate, ethylcellulose and methylcellulose, acrylic and methacrylic polymers and copolymers, and vegetable, animal or synthetic waxes; and, at least one pore-forming agent, in proportions of between 0 and 5%, preferably of between 0.5 and 5%, by weight of the final mass, selected from microcrystalline lactose, low molecular weight polyethylene glycols, calcium carbonate, calcium phosphate, sucrose, sodium chloride and potassium chloride. The stabilized pulverulent active product, in the form of microparticles, possesses a particle size of between 50 and 1000 um, and preferably between 200 and 500 um.

Hydrogen bonding in poly(4-vinylpyridine)/poly(vinyl acetate-co-vinyl alcohol) blends. An infrared study

Abstract: The specific interactions between poly(vinylpyridine) and copolymers of vinyl alcohol/vinyl acetate of different compositions have been studied by FTIR. Hydrogen bonding between both polymer components leads to significant spectral modification in hydroxyl, carbonyl, and pyridine rings spectral bands. Minor modifications in other spectral modes have also been detected. The spectral results indicate at least three competing equilibrium processes in the blends: copolymer self-association (hydroxyl-hydroxyl and hydroxyl-carbonyl) and hydroxyl-pyridine interassociation. The Punter-Coleman association model for three interacting units was successfully applied

Studies on the swelling and shrinking kinetics of chemically crosslinked disk-shaped poly(vinyl acetate) gels

Abstract: The kinetics of swelling and shrinking of disk-shaped poly(vinyl acetate) networks swollen in isopropyl alcohol is measured at different temperatures. The cooperative diffusion coefficient and the ratio of the shear modulus over the longitudinal osmotic modulus have been determined by using a theory developed by Li and Tanaka. The macroscopic swelling and deswelling experiments show good agreement with other experimental results as well as with the theoretical predictions

Vinyl Acetate Catalyst Preparation Method

Abstract: A method is provided to manufacture a palladium-gold catalyst by separately impregnating and fixing the palladium and gold and reducing the fixed solids to free metal on a suitable support useful for vinyl acetate manufacture from ethylene and acetic acid.

Exchange and free radical grafting reactions in reactive extrusion

Abstract: The potential of two types of reactions for reactive extrusion was evaluated in our laboratory: exchange reactions of copolyesters and free radical grafting of monomers onto polyolefins. Specifically, the alcoholysis of ethylene and vinyl acetate copolymers, the transesterification of ethylene and alkyl acrylate copolymers (EAA) and the aminolysis of alkyl acrylate copolymers were investigated as the exchange reactions while the grafting of maleic anhydride (MA) onto polypropylene (PP) as the free radical reactions. The exchange reactions are very slow without catalysts. Tin derivatives, such as dibutyl tin dilaurate (DBTDL) and dibutyl tin oxide (DBTO), are good catalysts for the alcoholysis and the transesterification, but not for the aminolysis. For the latter, tautomeric compounds, such as 2-pyridone and 2-mercaptopyridone, are efficient. Comparative kinetic studies showed that, for all the three exchange reactions, the reacting medium (solution or the homogeneous melt) does not affect their reaction mechanisms nor their intrinsic rate constants. Additionally, mechanical mixing does not contribute to the overall reactions. As for the free radical grafting of MA, the presence of electron-donating monomers and styrene (ST) in particular was shown to be very effective in improving the grafting yield while minimising the degradation of PP. This was proven to be due to the formation of a charge transfer complex between MA and such a monomer.

Dental impression method and composition

Abstract: A dental impression composition, dental impression pre-form and/or pre-mold and method for taking a dental impression that includes a pre-form made of an ethylene vinyl acetate copolymer mixed with a second polymer selected from vinyl acetate, a second ethylene vinyl acetate and a vinyl acetate vinyl alcohol ester. The pre-form softens at a temperature of about 120° F. to 170° F. The composition and method may also include a second pre-form made of a thin separator film sheet of a high molecular weight polycaprolactone, sandwiched between two ethylene vinyl acetate pre-forms.

Thermodynamic properties of poly(vinyl alcohol) and poly(vinyl alcohol-vinyl acetate) hydrogels

Abstract: Osmotic and light scattering observations are reported for chemically cross-linked poly(vinyl alcohol) and poly(vinyl alcohol-vinyl acetate) hydrogels and the corresponding semidilute polymer solutions. The osmotic contribution of the network polymer is obtained from swelling pressure and shear modulus measurements. The free energy of mixing in the cross-linked polymer is found to be significantly smaller than that of the polymer solution at the same concentration. SANS and static light scattering measurements indicate the presence of large-scale static structures in the systems

Fluorine containing copolymers and aqueous dispersions prepared therefrom

Abstract: Finishers for texthes, leather, paper and mineral substrates consisting of fluorine-containing copolymers and aqueous dispersions prepared therefrom are characterized by the following percentages by weight of the comonomers, relative to the total weight of the copolymers: a) 60 to 90% by weight of perfluoroalkyl-containing (meth)acrylates of the formula Cn F2n+1 --X--0--CO--CR1 ═CH2 (I), b) 1 to 35% by weight of monomers of the formula CH2 ═CR4 --COO--R5 (II) and/or styrene, acrylonitrile, vinyl acetate or vinyl propionate, c) 4 to 25% by weight of monomers of the formula ##STR1## d) 1 to 15% by weight of monomers of the formula CH2 ═CR11 --COOCH2 CH2 --N(R9,R10)(IVa) or [CH2 ═CR11 --COO--CH2 CH2 --N(R9,R10,R12)].sup.⊕ Y.sup.⊖ (IVb) or ##STR2##

Modeling and experimental studies of aqueous suspension polymerization processes. 2. Experiments in batch reactors

Abstract: The results from extensive studies of aqueous suspension homo- and copolymerizations with methyl methacrylate, styrene, and vinyl acetate in a lab-scale batch reactor are presented. Simulation results from homogeneous and two-phase free-radical polymerization kinetics models, using physical and kinetic parameter values from the bulk and solution polymerization literature were found to be in good agreement with batch suspension experimental results. The evolution of the particle size distribution was also observed and measured. The results suggest that polymerization kinetics and liquid-liquid dispersion phenomena can be decoupled in the cases of low dispersed phase fraction (O<0.25)

Calorimetric monitoring of emulsion copolymerization reactions

Abstract: An approach for monitoring both the overall conversion and the cumulative copolymer composition in emulsion copolymerization systems via calorimetric measurements was developed. The approach was checked by carrying out batch emulsion copolymerization of methyl methacrylate/n-butyl acylate, n-butyl acrylate/vinyl acetate, and methyl mthacrylate/vinyl acetate and comparing calorimetric based estimations with off-line determinations of both of the overall conversion and the cumulative copolymer composition. A good agreement was achieved for most of the cases studied

Oral sustained release drug delivery device

Abstract: This invention pertains to a sustained release delivery device for delivering a beneficial agent into the oral cavity of a patient. More particularly, the invention relates to a device comprising about 0.1% to about 20% by weight beneficial agent, about 40% to about 95% by weight ethylene vinyl acetate copolymer having a vinyl acetate content of about 4% to about 80% and about 1% to about 60% by weight polyvinyl pyrrolidone.

Sensitivities of droplet size and stability in monomeric emulsions

Abstract: The stability of a monomeric emulsion is directly dependent on the size of the monomer droplets. The droplet diameter is in turn significantly influenced by a variety of parameters. Both size and stability are important when emulsions consisting of small droplets are polymerized. These parameters were studied for the monomer methyl methacrylate, although the monomers styrene and vinyl acetate were also considered. Conductance was developed as a predictive tool for providing a measurement of emulsion stability. These indications were verified by shelf life stabilities and droplet size measurements. The key parameters which affect size and stability were found to be cosurfactant concentration and monomer water solubility. Coalescence was found to play an important role in stability as well.

Aqueous dispersions of fluorescent pigments

Abstract: An aqueous dispersion of a fluorescent pigment comprising: a water insoluble polymer; fluorescent dye; emulsifiers; and water. The polymer comprises: a water insoluble vinyl monomer free of polar groups; vinyl nitrile; a vinyl monomer containing sulfonate groups; and a polar vinyl monomer from the group consisting of: polar acrylate esters; vinyl acetate; polar methacrylate esters and a substituted acrylamide containing hydroxyl or carboxylic ester groups. The invention also relates to a fluorescent pigment and method for preparing the dispersion and pigment.

Crosslinking aqueous pigment dispersion

Abstract: A crosslinking aqueous pigment dispersion is disclosed, comprising (A) an aqueous resin dispersion, (B) a pigment, (C) a carbonyl-containing copolymer resin having an aldo group or a keto group, and (D) a hydrazine derivative having at least two hydrazino groups (-NHNH₂) per molecule, in which said carbonyl-containing copolymer resin (C) is a copolymer resin obtained by copolymerizing a monomer mixture consisting of (a) from 1 to 30% by weight of a carbonyl-containing unsaturated monomer having an aldo group or a keto group, (b) from 10 to 65% by weight of an ethylenically unsaturated carboxylic acid monomer, (c) from 5 to 89% by weight of at least one unsaturated monomer selected from the group consisting of an alkyl acrylate or alkyl methacrylate having from 1 to 10 carbon atoms in the alkyl moiety thereof, an aromatic vinyl monomer, acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, a vinyl halide, a vinylidene halide, butadiene, and ethylene, and (d) not more than 50% by weight of an unsaturated monomer other than the unsaturated monomers (a) to (c), and said carbonyl-containing copolymer resin (C) is present in an amount of from 0.1 to 10% by weight based on said pigment (B) and has been solubilized to a degree of at least 90% by weight by addition of an alkali and/or an organic solvent. The pigment dispersion provides a dry film excellent in gloss, water resistance, alkali resistance and weather resistance in good balance and is useful as an aqueous coating compound, a sealing compound, an adhesive, a paper coating, etc.

Lipase-catalyzed resolution of racemic 2-alkyl substituted 1-alkanols

Abstract: R)-2-alkyl-1-alkanols (R)-1 with high optical purities were obtained by lipase-ca- talyzed esterification of the racemic substrates (Rs)-1 with vinyl acetate in dichloromethane. The alcohols (R)-1 were oxidized without racemization to the corresponding carboxylic acids (R)-4. The enriched Q-acetates (q-3 either were saponified to the alcohols (Q-1 which are substrates for a second lipase-catalyzed transesterification to give (Q-1 in high optical purity or were racemized and applied once again in the kinetic resolution to prepare (R)-1. Optically active 2-alkyl carboxylic acids as well as the corresponding primary alcohols are important intermediates in the synthesis of biologically active compounds and for the preparation of liquid crystals. (n-ZMethyl-1-hexanol and (Q-2-methyl-ldecanol, for example, have been used as chiral building blocks for the synthesis of the pheromones of the european pine saw fly3 and of the peach leaf miner moth.4 Q-2- Methyl pentanoic acid was used for the synthesis of (5')-4-methyl-3-heptanone, the pheromone of the leaf- cutting ant Atta texana.skb (&(+)-Manicone and (S')-(-)-normanicone, the mandibular gland constituents of myrmicine ants, were prepared starting from Q-Zmethyl-1-butano1.k For the preparation of chiral ferroelectric liquid crystals, 2-methyl-lcarboxylic acids and the corresponding primary alcohols were used in recent times.6

Controlled antibody release from a matrix of poly(ethylene-co-vinyl acetate) fractionated with a supercritical fluid

Abstract: A new method is presented for controlling the rate of antibody (Ab) release from an inert matrix composed of poly(ethylene-co-vinyl acetate) (EVAc), a biocompatible polymer that is frequently used to achieve controlled release. Using supercritical propane, a parent EVAc sample (Mn = 70 kDa, Mw/Mn = 2.4) was separated into narrow fractions with a range of molecular weights (8.7 90% of the incorporated Ab was released from low molecular weight fractions (Mn 160 kDa) during 14 days of release. No significant differences in polymer composition, glass-transition temperature, or crystallinity were identified in the different molecular weight fractions of EVAc. Mechanical properties of the polymer did depend on the molecular weight distribution, and correlated directly with Ab release rates. Because it permits rapid and reproducible fractionation of polymers, supercritical fluid extraction can be used to modify the performance of polymeric biomaterials. © 1993 John Wiley & Sons, Inc.

Structural analysis of anisometric colloidal iron(III)-hydroxide particles and particle-aggregates incorporated in poly(vinyl-acetate) networks

Abstract: Anisometrical colloidal iron(III)hydroxide particles and particle aggregates were incorporated in elastic poly(vinyl acetate) networks. A novel method has been developed to fix the colloidal structure of deformed samples. Digitalized image analysis has been applied in order to evaluate the micrographs. The rod-like particles allow for studying the local deformation and orientation due to uniaxial and triaxial deformations. The density correlation function as well as the micrographs show that the structure of aggregates is not influenced by the strain. Due to strong attractive interactions between the colloidal particles the developing strain is not enough to destroy the aggregate structure. The orientation behavior of the model filled networks can be satisfactorily described by using the affinity principle.

Synthesis and emulsion copolymerization of amphiphilic poly(2‐oxazoline) macromonomer possessing a vinyl ester group

Abstract: The present article describes the synthesis and emulsion copolymerization of a block-type amphiphilic poly(2-oxazoline) macromonomer possessing a polymerizable vinyl ester group. The macromonomer was synthesized by one-pot two-stage block copolymerization of 2-oxazolines using vinyl iodoacetate as initiator. 2-Methyl- and 2-n-butyl-2-oxazolines were employed for the construction of hydrophilic and hydrophobic segments, respectively. The surface activities evaluated by the surface tension of the macromonomer in water were fairly good. Emulsion copolymerization of vinyl acetate with the macromonomer was carried out. The macromonomer acted as a polymeric surfactant, as well as a comonomer. The resulting copolymer latex particles were spherical and their diameter was in the sub-micron range. The effects of the composition of the macromonomer on the emulsion copolymerization and the resulting latex particles were examined. © 1993 John Wiley & Sons, Inc.

Supported catalyst, preparation process thereof and use thereof for preparing vinyl acetate

Abstract: The invention relates to improved Pd/K/Au, Pd/K/Ba and Pd/K/Cd supported catalysts, the preparation thereof, and the use thereof for preparing vinyl acetate from ethylene, acetic acid and oxygen in the gas phase. These catalysts are prepared by atomising a solution of the corresponding metal salts by means of ultrasound and then applying it in such limited amounts and within such a limited time to the support particles and commencing the drying thereof, that the catalytically active metal salts cannot penetrate the support particles as far as their core but only an outer part of greater or lesser size.

Kinetics of nasal carboxylesterase-mediated metabolism of vinyl acetate

Abstract: Vinyl acetate vapor has been shown to produce tumors of the nasal cavity in rats, but not mice, exposed by the inhalation route. Carboxylesterase-mediated hydrolysis of vinyl acetate produces acetic acid and vinyl alcohol, which rearranges to form acetaldehyde, another nasal carcinogen that could be the ultimate carcinogenic metabolite of vinyl acetate. The purpose of this study was to define the kinetics of hydrolysis of vinyl acetate in nasal respiratory and olfactory mucosa of male and female rats and mice. The results showed few differences in kinetic parameters between male and female rats or mice. Differences were observed between mucosae. In respiratory mucosa, Vmax ranged from approximately 22-46 mumol/min/mg protein. In olfactory mucosa, Vmax was significantly higher and ranged from 89 to 165 mumol/min/mg protein. Substrate inhibition was apparent at high substrate concentrations in some cases and for those, a kinetic model that accounted for substrate inhibition fit the data better than a Michaelis-Menten model. The substrate inhibition model yielded Vmax values for olfactory tissues that ranged from 113 to 254 mumol/min/mg protein. The second-order rate constant for binding and catalysis, V/K, ranged from 52 to 79 mumol/min/mg/mM for respiratory tissue and from 270 to 469 mumol/min/mg/mM for olfactory tissue. KM derived from the best-fit models was similar for most tissues and ranged from 0.30 to 1.07 mM. These data demonstrate the high capacity of nasal tissue to metabolize vinyl acetate to acetaldehyde and may explain, in part, vinyl acetate-induced nonneoplastic nasal lesion distribution. However, the data do not account for the species difference in susceptibility to the carcinogenic effects of vinyl acetate.

Modeling poly(vinyl alcohol)-stabilized vinyl acetate emulsion polymerization. I. Theory

Abstract: A mathematical model for particle nucleation and growth in the isothermal semibatch emulsion polymerization of vinyl acetate stabilized with poly(vinyl alcohol) is presented. In addition to the particle nucleation and growth mechanisms governing ionically stabilized polymerizations of relatively water-soluble monomers, the model accommodates grafting onto the poly(vinyl alcohol) backbone during nucleation, and polymeric stabilization. The user supplies the emulsion recipe, process conditions and kinetic parameters, and the model predicts the various species concentrations, along with the conversion and particle size and number profiles. In part II, model predictions are discussed. © 1993 John Wiley & Sons, Inc.

Sequential kinetic resolution of (±)-2,3-butanediol in organic solvent using lipase from Pseudomonas cepacia

Abstract: Lipase from Pseudomonas cepocia (PCL, Amano FS) catalyzed the enantioselective diacetylation of (±)-23-butanediol in vinyl acetate. Both acetylation steps favored the (R)-enantiomer (E1 = 12, E2 = 34), thus the reaction is a sequential kinetic resolution. The enantioselectivities of the two steps reinforced one another because both steps proceeded at comparable rates (S = 3) yielding an overall enantioselectivity of approximately 200. A synthetic-scale resolution starting from 2.7 g of (±)-2,3-butanediol yielded the diacetate ester of (R)-(−)-butanediol with 96% ee (1.6 g, 30% yield) and (S)-(+)-butanediol with 99% ee (0.63 g, 23% yield). This preparation is carried out entirely in organic solvent, thereby avoiding the difficult and low yield extraction of 2,3-butanediol from aqueous aolution.

Hot melt adhesive

Abstract: The foregoing and other objects and advantages of the present invention are accomplished by a hot melt adhesive comprising a blend of a low molecular weight polyolefin, olefin-carboxylic acid graft polymer or olefin-maleic anhydride graft polymer or blend thereof; a propylene-ethylene copolymer or propylene-ethylene-butene terpolymer; and a tackifying resin or blend of tackifying resins. The blend can include an antioxidant or blends of antioxidants, a high molecular weight or functionalized polyolefin or a copolymer or terpolymer of a vinyl monomer (e.g., ethylene/vinyl acetate).

Pretreatment of palladium-gold catalysts useful in vinyl acetate synthesis

Abstract: A method for pretreatment of a palladium-gold catalyst useful in the synthesis of vinyl acetate. A virgin catalyst, following reduction to the metallic palladium and gold, is first heated at elevated temperatures in the presence of an oxidizing agent such as air. The oxidizing agent is withdrawn and an inert gas such as nitrogen is introduced. The catalyst is heated again at a temperature up to 500 °C in the presence of a reducing agent such as hydrogen or ethylene. Improvements in selectivity and yield are obtained.