Showing papers on "Vinyl acetate published in 1991"

Vinyl acetate-ethylene copolymer emulsion and process for producing the same

Abstract: A vinyl acetate-ethylene copolymer emulsion is disclosed, comprising a vinyl acetate-ethylene copolymer composed of from 10 to 40% by weight of an ethylene unit and from 90 to 60% by weight of a vinyl acetate unit and an emulsifying dispersant in an amount of from 2.5 parts by weight or more but less than 5.0 parts by weight per 100 parts by weight of the vinyl acetate unit, and having a mean particle size of not larger than 0.9 μm and a solids content of from 65 to 75% by weight, wherein the emulsifying dispersant contains from 1.0 to 1.9 parts by weight of partially saponified polyvinyl alcohol prepared so as to have an average polymerization degree of from 300 to 1,000 and from 1.0 to 3.0 parts by weight of a polyoxyethylene nonionic surface active agent having an HLB of from 16.5 to 17.5 per 100 parts by weight of the vinyl acetate unit. A process for producing the vinyl acetate-ethylene copolymer is also disclosed.

Macroscopic and microscopic thermodynamic observations in swollen poly(vinyl acetate) networks

Abstract: Chemically cross-linked poly(vinyl acetate) (PVAc) networks swollen in toluene are compared with un-cross-linked polymer solution. The swelling pressure data are described by a two-term equation consisting of a separable elastic and mixing contribution. The mixing term for the gel is smaller than for the solution, but both exhibit a similar concentration dependence. The scattering signal of the gel is separated into a static and a solution-like part. The latter is compared with the swelling pressure of the gel obtained from the macroscopic osmotic measurements

Thermal degradation of EVA and EBA—A comparison. I. Volatile decomposition products

Abstract: This is the first in a series of papers in which structural changes during thermal degradation of ethylene-vinyl acetate (EVA) and ethylene-butyl acrylate (EBA) copolymers are compared. EVA, containing 11.4 mol% vinyl acetate (VA) and EBA, containing 5.4 mol% butyl acrylate (BA), were pyrolyzed at 280°C in nitrogen for 30 min. In another series of pyrolysis, EVA containing 1.2, 2.2, and 11.4 mol% VA were treated at 150–190°C for 3 h. The volatile decomposition products were collected in cooled traps respectively gas bags and then analysed with GC-MS and ion-chromatography. EVA is rather labile. The main volatile decomposition product is acetic acid. A linear decomposition rate was found already at the lowest investigated pyrolysis temperature, 150°C. After 30 min at 280°C every 15th of the acetate side groups had been eliminated. EBA is much more stable to pyrolysis. Thirty minutes at 280°C resulted in a decomposition of one out of 1500 BA groups. Butene is the main volatile decomposition product. Ester pyrolysis is supposed to account for the degradation of both types of polymers. The big difference in reactivity is presumably due to conformational differences. The ester pyrolysis mechanism will result in random unsaturations in EVA and carboxylic groups in EBA. To a minor extent acetaldehyde is formed when EVA is degraded. According to the mechanisms suggested, carbonyl groups remain in the main chain. Contrary to what is reported for poly(butyl acrylate), no alcohol was formed when pyrolysing EBA. This indicates that adjacent acrylate groups are needed for alcohol formation. For both types of polymer, scissions of the main chain results in hydrocarbon fragments mainly. In addition, acrylate containing fragments are observed when EBA is degraded. EVA, however, does not give any acetate-containing fragments.

Copolymer composition control of emulsion copolymers in reactors with limited capacity for heat removal

Abstract: A method for the determination of the optimal monomer addition strategy to produce a homogeneous copolymer under conditions in which the reactor has a limited capacity for heat removal is presented. The method allows for the calculation of the monomer addition profiles for both constant and time-dependent heat removal rates. The approach was successfully applied to the emulsion co-polymerization of vinyl acetate and methyl acrylate carried out in a laboratory reactor that had been transformed to reduce its capacity for heat removal to the level of a large-scale reactor

Preparation of microlatex dispersions using oil-in-water microemulsions

Abstract: The preparation of microlatex dispersions from microemulsions of a monomer (styrene, methylmethacrylate or vinyl acetate) is described. A simple method for preparing the microemulsion has been devised. This consists of forming a water-in-oil (w/o) emulsion using a low (HLB) surfactant (nonylphenol with 5, 6 or 7 moles ethylene oxide) and then titrating with an aqueous solution of a high HLB surfactant (nonylphenol with 15 or 16 moles ethylene oxide). A small amount of anionic surfactant (sodium lauryl sulphate, sodium dodecyl benzene sulphonate or dioctyl sulphosuccinate) was also incorporated to enhance the stability of the w/o emulsion and facilitate the inversion to an o/w microemulsion. The droplet-size distribution of the resulting microemulsion was determined using photon-correlation spectroscopy.

‘Immunization’ of lipase against acetaldehyde emerging in acyl transfer reactions from vinyl acetate

Abstract: Immobilization of Candida cylindracea lipase by covalent linkage involving the Iµ-amino residues of lysine leads to a five-fold increase of selectivity which is entirely preserved against deactivation caused by acetaldehyde, an unavoidable by-product in acyl transfer reactions with vinyl acetate.

Ethylene copolymer-modified dynamically vulcanized alloys

Abstract: A dynamically vulcanized composition is provided which comprises a polyolefin resin, an elastomer, and an ethylene copolymer resin such as a copolymer of ethylene and vinyl acetate or an alkyl acrylate. A process for producing the dynamically vulcanized composition is also provided, which process includes the addition of the ethylene copolymer resin after the dynamic vulcanization step. The resulting composition comprises the ethylene copolymer resin predominantly in the polyolefin resin phase. The compositions have improved surface appearance and softness.

Packaging thermoplastics from lactic acid

Abstract: A first general embodiment includes environmentally biodegradable compositions of poly(lactic acid) intimately plasticized with derivatives of oligomers of lactic acid, and mixtures such as lactic acid. A second general embodiment includes biodegradable polymer comprising polymerized lactic acid where the number of repeating lactic acid units n is an integer between 450 and 10,000 and the alpha carbon is a mixture of L- and D-configurations with a preponderance of either D- or L-units. A third general embodiment includes an environmentally degradable composition of 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. A fourth general embodiment includes an environmentally degradable composition that comprises blends of a physical mixture of a poly(lactic acid), comprising about 1 to 99 weight percent of the composition, and an elastomeric blend compatible polymer.

Increase in thermal stability of vinyl polymers through radical copolymerization with N‐cyclohexylmaleimide

Abstract: It was found that radical polymerization of N-cyclohexylmaleimide (CHMI) occurred readily under various polymerization conditions, and that the resulting poly(CHMI) had excellent thermal stability; i.e. the onset of decomposition was 362°C and the maximum rate of decomposition was observed at 430°C by thermogravimetric analysis in nitrogen. Subsequently, radical copolymerizations of CHMI with various vinyl monomers were performed, and the monomer reactivity ratios were determined from the copolymer composition curves obtained. It was found that CHMI copolymerized alternatingly with electron-donating monomers such as styrene and isobutene. It was also discovered that facile copolymerizations proceeded with methyl acrylate and methyl methacrylate as electron-accepting monomers, and with vinyl acetate and vinyl chloride as non-conjugated monomers. It was verified that the introduction of the CHMI unit increased the thermal stability of common vinyl polymers.

Polymer foams containing gas barrier resins

Abstract: An improved closed cell polymer foam and foaming agent involving the use of a halocarbon blowing agent (eg, HCFC-22, HCFC-123, HCFC-123a, and HCFC-141b) in combination with an effective amount of a gas barrier resin (eg, an ethylene/vinyl acetate copolymer, ethylene/acrylic ester copolymer or acrylic ester polymer) uniformly dispersed in the continuous polymeric phase The presence of the gas barrier resin is shown to significantly reduce the escape of blowing agent from and/or entry of air into the foam resulting in low thermal conductivity over a longer period of time and improved thermal insulation value

Hot-melt composition that have good open time and form creep-resistant bonds when applied in thin layers

Abstract: A hot-melt composition comprising an ethylene/vinyl acetate copolymer, an ethylene/n-butyl acrylate copolymer, and a tackifying resin can be spread into a thin layer that has a limited open time of at least 5 seconds. The composition eventually crystallizes to form a creep-resistant bond.

Compatibilized blends of crystalline propylene polymers and styrenic copolymers

Abstract: Thermoplastic resin compositions having good toughness and resistance to heat deformation are obtained by blending crystalline propylene polymers, elastomeric olefin polymers, random styrenic copolymers, and epoxy group-containing copolymers. For example, the composition may be a blend of polypropylene, ethylene-propylene or ethylene-propylene-diene monomer rubber, styrene/maleic anhydride copolymer, and ethylene/glycidyl methacrylate or ethylene/glycidol methacrylate/vinyl acetate copolymer. Physical properties are enhanced by the use of a two step blending procedure.

Thermal degradation of EVA and EBA—A comparison. III. Molecular weight changes

Abstract: This is the third in a series of papers in which the thermal degradation of ethylene-vinyl acetate (EVA) and ethylene-butyl acrylate (EBA) copolymers are compared. The EBA samples contained 0.8, 1.6, and 5.4 mol % butyl acrylate (BA), respectively, and the EVA samples 1.2 and 6.7 mol % vinyl acetate (VA). The samples were heated in nitrogen in a tubular oven at 285–390°C, for 6–120 min. The molecular weight distribution (MWD), long chain branching, and gel content were analyzed with size exclusion chromatography (SEC). The columns were connected to refractive index, viscometric, and light scattering detectors. EVA gave a pronounced molecular enlargement at all degradation temperatures. In EVA-6.7, gel was formed at all degradation levels, whereas the low content sample, EVA-1.2, did not form any visible amount of gel. The strong tendency to molecular enlargement is due to allyl radicals formed after thermal deacetylation and the formation of internal double bonds. These macroradicals will combine or, less frequently, add to double bonds. The EBA copolymers show a more polyethylenelike degradation behavior. At 285°C molecular enlargement dominates, but already at 333°C a net reduction in molecular size is observed. At high temperatures, ester pyrolysis of the BA groups give carboxylic groups and anhydrides. Alkaline treatment will not give any appreciable change in MWD, showing that the anhydride formation is mainly intramolecular. The chain scission increases with the BA content. This is probably due to β-cleavage of tertiary macroradicals formed in the chain at the acrylate or carboxylic side groups.

Kinetic resolution of rac-3-(2-methylphenoxy)propane-1,2-diol (mephenesin) by sequential lipase-catalyzed transesterification

Abstract: The kinetic resolution of rac-3-(2-methylphenoxy)propane-1,2-diol ( rac-1 , Mephenesin) by sequential lipase-catalyzed transesterification with vinyl acetate in tetrahydrofuran/triethylamine in the presence of lipase Amano PS is described.

Vinyl acetate polymer with wet adhesion

Abstract: Wet adhesion properties comparable or superior to all-acrylic latexes for vinyl acetate copolymers and other low cost polymers, such as EVA-vinyl chloride copolymers, is achieved by blending a minor proportion, usually about 5 to 15%, of a small particle size copolymer containing copolymerized wet adhesion monomer which is a cyclic ureido. Very low quantities of the wet adhesion monomer, less than 0.25 wt% of total monomers, only are required to achieve excellent results.

An Improved Procedure for the Regioselective Acetylation of Monosaccharide Derivatives by Pancreatin-Catalyzed Transesterification in Organic Solvents

Abstract: A series of pyranosidic and furanosidic monosaccharide derivatives were monoacetylated in the 6-position with high regioselectivity and good to excellent yields by the pancreatin-catalyzed transesterification with vinyl acetate in the solvent system tetra- hydrofuran/triethylamine.

Process for repairing exposed or damaged parts of a plastic coatings on metal tubing by coating or patching the area with an adhesive polymer composition

Abstract: Disclosed is a process for repairing removed or damaged parts of plastic coating on metal tubing characterized in that the coating material or the adhesive for patches or bands is an adhesive polymer composition comprising by weight: A) from 59% to 94% of polypropylene, propylene/ethylene random copolymer, propylene/ethylene/1-butene random copolymer or mixtures thereof with one or more plastomeric polymers selected from the group consisting of ethylene/vinyl acetate copolymers, LDPE, HDPE, polyamides and polyurethane; B) from 5% to 40% of a polymer or a mixture of elastomeric polymers selected from the group consisting of EPR, EPDM, SEBS block copolymers, SBS block copolymers and ethylene/ethyl acrylate copolymers; C) from 1% to 10% of polypropylene modified with from 1 to 10% of maleic anhydride, isophorone bismaleamic acid or acrylic acid; and D) from 0% to 3% of carbon black.

Interpolymer association between poly(acrylic acid) and vinyl alcohol-vinyl acetate copolymers in dilute aqueous solutions

Abstract: Interpolymer association and complexation between poly(acrylic acid) and vinyl alcohol-vinyl acetate copolymers (PVAL-AC) in dilute aqueous solutions were investigated by means of reduced viscosity and pH measurements. The influence of the degree of saponification of PVAL-AC and of the molecular weight of both polymers on complexation were examined. The viscosity measurements show the formation of gel-like or compact complexes and that association is strongly increased by the presence of acetate units in the PVAL-AC copolymer. The degree of complexation was calculated from the results of pH measurements. Some special aspects of the two different experimental approaches are discussed.

Controlled morphology barrier elastomers made from blends of syndiotactic 1,2-polybutadiene and ethylene-vinyl acetate-vinyl alcohol terpolymers

Abstract: An elastomer barrier composition comprises a melt blend of syndiotactic 1,2-polybutadiene, a terpolymer of ethylene, vinyl acetate and vinyl alcohol, and a compatibilizing agent. The melt blend is formed under suitable mixing and shear conditions such that the terpolymer exists as a separate domain in generally a flat or plate-like form. The elastomer barrier material can be utilized in rubber compositions such as in the innerliner of the tire.

Stock for labels and tapes utilizing siliconized emulsion based pressure-sensitive adhesives

Abstract: There is provided stock for labels and tapes having in the surface of a self supporting substrate and 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-ethylehexyl acrylate. Methyl acrylate and vinyl acetate are optionally present.

Method for improving scrub resistance

Abstract: A method of improving the scrub resistance of a paint is provided. The method involves adding to a paint containing at least one polymeric binder having a glass transition temperature greater than about 20° C. and an average particle size diameter of from about 70 nanometers to about 150 nanometers when said binder is formed from at least one acrylic monomer or from about 100 nanometers to about 50 nanometers when said binder is formed from at least 50% by weight of vinyl acetate, at least one coalescent at a concentration of at least about 10% by weight based on the weight of the polymeric binder and where said coalescent is a solvent for the polymeric binder. The method is particularly useful for improving the scrub resistance of flat latex paints.

Polymerization photoinitiated by pyrene in the presence of triethylamine :interaction between monomers and pyrene-derived reaction intermediates

Abstract: The effect of vinyl monomers (styrene vinyl acetate, methyl methacrylate) on the transients involved in the pyrene-triethylamine system is studied. The results show that the photoinitiation of vinyl polymerization is due to the reaction of the pyrene radical anion with the monomers; since this process results in the regeneration of pyrene, the monomers effectively prevent the photobleaching of pyrene

A molecular model for the strength of the dielectric β relaxation in methyl acrylate and vinyl acetate polymers

Abstract: As a test of the supposition that flexible side-group motion is responsible for subglass relaxation in some polymers, a molecular model based on a RIS treatment for the overall relaxation, α glass-rubber relaxation+β process, has been developed for poly (methyl acrylate) and poly (vinyl acetate) homopolymers and their copolymers with ethylene. A good account of the experimental behavior was obtained throughout the subglass temperature range for the β processes in both PMA and PVAc homopolymers

Thiohydroxamic esters : a new class of polymerization regulator

Abstract: N-Hydroxypyridine-2-thione esters and N-hydroxy-4-methylthiazole-2(3H)-thione esters act as chain transfer agents in free radical polymerizations of methyl methacrylate (Cx=0.6-4.3), styrene (Cx=0.32-3.9), methyl acrylate (Cx=3.1-20), and vinyl acetate (C x =9.7-80) at 60 o C. Some retardation occurs with vinyl acetate and methyl acrylate. One of these compounds also has the property of initiating the polymerization of methyl methacrylate photochemically, while another one acts as a thermal initiator