Latex Emulsion Research Articles

Comparison of Trends in Latex Emulsions for Nonwovens and Textiles: China and the United States

The U.S. and Chinese markets for synthetic latex polymers in the nonwoven and textile markets reached 337,000 dry tons (or 744 million dry pounds) in 1996. Overall, the demand for latex polymers in these two market segments will grow to 377,000 dry tons (or 831 million dry pounds) in 2001. Latex usage in nonwovens in these two regions will reach an estimated 202,000 dry tons (or 445 million dry pounds) in 2001, representing average annual growth of 2.2% a year. Likewise, demand in the textile market will grow to 175,000 dry tons (or 386 million dry pounds) in 2001. It is critical to understand that the demand for latex polymer in both markets in the United States will follow that of a more mature market, growing at approximately 2% a year. Demand in China, however, will grow by an estimated 6% a year, but from a very small base. Future demand for latex polymers in the nonwovens market will be driven by such factors as: • Consumer discretionary income and preference • The continued development of specialty niche applications • Capacity changes in nonwoven products

Effects of sulphonic and phosphonic acrylic monomers on the crosslinking of acrylic latexes with cycloaliphatic epoxide

Two model acrylic latexes were synthesized using methyl methacrylate (MMA) and butyl acrylate (BA) with methacrylic acid (MAA) or 2-hydroxyethyl methacrylate (HEMA). The MAA or HEMA were incorporated to provide the latexes with carboxyl and hydroxyl functionality, respectively. A cycloaliphatic diepoxide (3, 4-epoxycyclohexyl methyl-3′, 4′-epoxycyclo-hexane carboxylate) was used as a crosslinker for both the latexes. The crosslinking of the latexes with the diepoxide was catalyzed using a copolymerizable or free sulphonic or phosphonic acids. The copolymerizable acids (2-sulfoethyl methacrylate (SEM) and acid phosphoxyethyl methacrylate (PEM)) were added during the latex synthesis. The free acids ( p-toluene sulphonic acid (TsOH) and phenylphosphonic acid (PPA)) were added into the latex emulsion shortly before crosslinking. The crosslinked coatings were evaluated in terms of water absorption, gel content, and pull-off adhesion. The crosslinking of the hydroxyl functional latex coatings with the cycloaliphatic epoxide required an acid catalyst, whereas the crosslinking of the carboxyl latex coatings did not need an acid catalyst. Sulphonic and phosphonic acrylic acid monomers not only functioned as catalysts for the crosslinking reactions, but also improved the adhesion and freeze–thaw stability of the latex coatings. In addition, neutralization of the acid catalysts led to reduction of the crosslinker hydrolysis, and consequently enhanced the overall coating properties.

Reactive surfactants in heterophase polymerization. XXIV. Emulsion polymerization of styrene with maleate- and succinate-containing cationic surfactants

A series of alkyl pyridinium bromide maleate and succinate diester surfactants has been used as stabilizers in the free radical emulsion polymerization of styrene. High conversions of styrene were achieved readily with the maleate surfactants, but the succinates gave rise to varying levels of retardation. In two of the latter cases, use of the surfactant at a concentration below its crucial micelle concentration appears to be a key factor, but the other retardations are difficult to account for. Little difference in reactivity and latex properties was found with the maleate surfactants despite the position of the maleate group being very different in the series of molecules examined. Chemical incorporation of the maleate surfmers into the polymer particles appears to occur early on in the polymerizations, but a sufficiently high proportion of groups is on the surface to yield stable latex emulsions. The surface tensions of the final latices produced with both the maleate and succinate surfactants are high, suggesting a large proportion of succinate species are also surface adsorbed. However, the surface tensions of these latices are a little lower than those of latices produced with the maleates, suggesting the proportion of solubilized succinate surfactant is a little higher. This seems to be important in terms of the robustness of the stability of the latices to the addition of electrolytes, the succinate-stabilized species being consistently more tolerant. This suggests that while chemically bound surfactants can improve some of the properties of latices, e.g. the hydrophobicity of films, this might be at the expense of latex stability.

Transverse magnetic birefringence of poly(tetrafluoroethylene) latex emulsion particles

The magnetic analogue to electric field orientation has been studied for the more general class of predominantly diamagnetic, rather than para- or ferromagnetic, colloidal media. With a carefully designed and constructed conventional apparatus, measurable signals were obtained at relatively low magnetic fields (<2 T) using a suitably modified electromagnet. Pulsed data were recorded on latex emulsions of poly(tetrafluoroethylene). Analysis of the decay region yielded 0.18 s −1 for the experimental rotary diffusion coefficient 〈 D〉 from which the mean size of 320 nm was calculated. By comparing the rise and decay amplitude rates of the transient signal, the ratio of the permanent dipole component ( P) to the induced one ( Q) was found to be 0.05 for this material. This is consistent with literature data. Advantages of the magnetic method over the more popular transient electro-optic procedure are discussed for colloidal media.

塗料の保水性が塗工紙物性に与える効果 （第２報） 塗料中のラテックス浸透

The water retention of coating color on base paper is one of the most important properties that affect the sheet properties of coated paper. However, we do not have any standard to evaluate water retention of coating color even though some methods have been suggested to evaluate water retention of coating color. We divided “Water Retention” into static water retention and dynamic water retention and evaluated coating runnability by the two kinds of water retention.In this study, we measured water loss rate of actual coatings and dilute latex emulsions, a common part of typical coatings. We suggested a new concept “Interactive Water Retention”, which is calculated from these water loss rates. Interactive Water Retention and water loss ratio were used as an index to evaluate the coating properties.Binder in a coating color penetrates into base paper when the coating color is applied. Binder in coating goes through a filter and also penetrated into filter papers when water loss ratio is measured under pressure. This binder (SB-latex) penetration is measured by reflected ultraviolet absorption. We suggested new concepts “Total Latex Loss” and “Penetrating Latex Loss”, which are calculated from these signals and the depth of latex penetration. We also suggested new concepts “Interactive Latex Retention I”, which is calculated from a “Total Latex Loss” of a coating and a latex solution, and “Interactive Latex Retention II”, which is calculated from a “Penetrating Latex Loss” of a coating and a latex solution. Total Latex Loss, Penetrating Water Loss, Interactive Latex Retention I and II were used as an index to evaluate the coating properties.Water Loss Rate, Interactive Water Loss, Total Latex Loss, Penetrating Latex Loss, and Interactive Latex Retention I and II were different from each other and apposite to evaluate coating color.

Examination of Rheological Properties of Fine Particle Dispersions as Carriers for Controlled Drug Release

The rheological characteristics of various systems made by mixing blood, blood serum, and drug carriers. as liposomes, lipid emulsion and polymer latex (model system for nano- particles) are reported as function of shear rate and volume fraction of solid. The diversity of system behaviour (pseudoplasticity, dilatancy and tixotropy), is detected: some are Newtonian and some non-Newtonian. Attention is directed especially to viscosity of the systems developing theoretical models to forecast drug carrier behaviour under different conditions in some part of living organisms and testing models by viscosity measurement in HAAKE Rotovisco CV100 which provide extreme sensitivity for differentials between fine particles, as drug carriers.

Kinetics and polymerization characteristics for some polyvinyl acetate emulsions prepared by different redox pair initiation systems

The emulsion polymerization of vinyl acetate was carried out using different sodium bisulfite adducts (containing the same weight equivalent of bisulfite anion) as reducing agents with potassium persulfate as an oxidising agent at low temperature. The polymerization evaluation was followed by taking samples at regular intervals. The average volume diameters, the areas and the number of polymer particles per unit volume of water ( Nt) for some prepared emulsion latices were calculated with the aid of transmission electron microscopy and image analyzer techniques. Also, it was found that the rate of emulsion polymerization decreases in the following order: acetone sodium bisulfite (AcSBS) > methyl propyl ketone sodium bisulfite (MpKSBS) > octyl aldehyde sodium bisulfite (OASBS) > acetaldehyde sodium bisulfite (ASBS) > benzaldehyde sodium bisulfite (BSBS) > salicylaldehyde sodium bisulfite (SSBS) > cyclohexanone sodium bisulfite (ChSBS), while the particle size of the prepared emulsions increases in the following order: (OASBS)<(SSBS)<(BSBS)<(ChSBS)<(MpSBS)<(AcSBS)<(ASBS). Finally, the D z, D v/ D s, number of particles per cm 3 and D w/ D n were calculated for polymer latices obtained.

Paper Sheets Treated by Polymeric Substances

Poly(vinyl acetate) (PVAc) and vinyl acetate with butyl acrylate (VAc-BuA) copolymer latices are prepared by semicontinuous emulsion polymerization technique. The prepared latices are used in paper treatment using two different techniques. In the first technique, the latices are added during the paper sheet formation, but in the second one the untreated paper sheets are dipped in either the polymer or acetone polymer solution of different concentrations. The effect of different concentrations of the prepared emulsion latices by using different emulsifier and initiator concentrations on the paper sheet is studied. Increasing the initiator concentration in the preparation of PVAc latex decreases the retained polymer on the treated paper sheets. Also, increasing the butyl acrylate percentage in the copolymer latices improves the mechanical properties. The water uptake of the treated paper sheets is decreased by increasing the retained polymer. The effect of thermal treatment of the treated paper sheets is investigated.

Cross-flow filtration of latex emulsion on a pilot scale using organic and inorganic membranes with different cut-off values

The aim of the following project was to increase the concentration of a ca. 1 wt% styrene butadiene latex emulsion (also termed ‘white-water streams’) resulting from industrial production using cross-flow filtration, and to investigate the process performance using different types of membranes. The permeate flux lie in the range 2.36×10 −5−0.14×10 −5 m s −1 when the emulsion was concentrated up to ∼40 wt%. Although three different membrane types, one organic and two inorganic, with varying cut-off values (20 000, 50 000 and 0.2 μm) were used, no significant differences in average permeate flow were observed. The concentration of the latex emulsion was seen to have the greatest effect on the permeate flux, and with increasing concentration, the flux was observed to drop to ∼0. In contrast to this, during continuous testing over a period of nearly two months, using two emulsions of 15 wt% and 1 wt%, respectively, the permeate flow rate remained practically stable.

Preparation and characterization of polystyrene and styrene-butyl acrylate copolymer latices

Emulsion polymerization of styrene (S) and emulsion copolymerization of styrene with butyl acrylate (BuA) using potassium persulfate (KPS)/different aromatic aldehydic sodium bisulfite adducts as developed redox pair initiation systems were investigated at variable initiator, emulsifier concentrations and feed monomer compositions for studying the morphological characteristics of the obtained latices. It was found that the developed redox pair initiation system increased the number of polymer particles per unit volume of water ( Nt) more than the classical system. Also, N t , decreased with increasing initiator concentration, but increased with increasing emulsifier concentration for both the classical and developed ones. The volume-average particle diameter D ̄ v was found to be dependent on the different redox initiators: potassium persulfate/methylbenzaldehyde sodium bisulfite (KPS/MeBSBS), potassium persulfate/chlorobenzaldehyde sodium bisulfite (KPS/CBSBS), potassium persulfate/methoxybenzaldehyde sodium bisulfite (KPS/MBSBS), potassium persulfate/benzaldehyde sodium bisulfite (KPS/BSBS) and potassium persulfate/sodium bisulfite (KPS/SBS) to the powers 0.15, 0.27, 0.30, 1.80 and 0.70, respectively, while N t , is dependent on emulsifier concentration to the powers 0.48, 1.00, 2.08, 3.33 and 4.41 with respect to the different redox systems KPS/SBS, KPS/MBSBS, KPS/CBSBS, KPS/BSBS and KPS/MeSBSB. The polydispersity index ( D w D w ) for the emulsion latices prepared using different emulsifier concentrations was found to be in the range 1.00–1.29, i.e. they are relatively narrow. This means that the emulsion polymerization of styrene was not in the so-called induction period. Increasing BuA ratio in the feed monomer composition of the prepared S/BuA copolymer lattices led to a decrease in N t .

Copolymerization of Styrene with Nonionic Surfactants: Poly(Ethylene Oxide) Macromonomers

Abstract A series of macromonomers of ω-methoxy poly(ethylene oxide)n undecyl-α-methacrylate (PEO-R-MA-n, where n = 10, 15, 40) was synthesized. The copolymerization of styrene (M1) with the macromonomers (M2) was carried out in benzene solution and in an emulsion. The apparent reactivity (1/r1) of the macromonomer decreased with an increase of its PEO chain length. The results are discussed in terms of the incompatibility between PEO macromonomer and polystyryl radicals. Stable emulsion latices with monodisperse particles were obtained from the copolymerization of styrene with PEO-R-MA-40. The particle sizes ranged from about 30 to 300 nm in diameter depending on the amount of styrene used and the PEO chain length of the macromonomer. The molecular weights of the copolymers produced by the emulsion copolymerization of PEO-R-MA-40 with styrene were around half a million, and their molecular weight distributions ( M w/ M n) were relatively narrow (1.6–1.9) as determined by gel-permeation chromatography.

Emulsion polymerization of vinyl propionate using a newly developed redox pair initiation system

The kinetics of emulsion polymerization of vinyl propionate (VP) using the redox system potassium persulfate (KPS)/acetone-sodium bisulfite (ASBS) as redox pair initiation system is studied at 25°C. The effect of different initiator concentrations on the rate of polymerization and on the number and size of particles of the formed emulsion latices is established. The polymerization proceeded smoothly till high conversion and yielded stable emulsion latices. The rate of polymerization was found to be dependent on the initiator concentration to the 2 5 power.

Characterization of gel layer formed during ultrafiltration of latex emulsion waste waters

The results of investigations of the ultrafiltration of latex waste waters, carried out with and without stirring, have been presented. The dependence of the permeate flux versus time profiles, transmembrane pressure and latex particle concentration for three polyacrylonitrile membranes of differing compactness, have been worked out. The basic parameters of the gel layer formed on the membrane surface, i.e., the resistance of the gel layer ( G g ), specific resistance (a) and mass of gel per unit area of the membrane ( m g / A m ) have been calculated based on the data of ultrafiltration without stirring.

A newly developed polyvinyl acetate emulsion latex adhesive made by the semicontinuous process

A newly developed polyvinyl acetate (PVA) emulsion latex for adhesive has been prepared by the semicontinuous process using a newly developed octyl aldehyde sodium bisulphite‐potassium persulphate redox pair initiation system. In this work the amount of polyvinyl alcohol (PVA) as a protective colloid has been changed and it was found that only a little amount of (PVA) together with the newly developed adduct could cause a stable latex with excellent mechanical properties for bonding wood which favours this redox system in large industrial applictions. Also monodisperse latex particles with low polydispersity index can be prepared by using 1% PVA coupled with the newly developed redox system. Finally the developed latex has been incorporated and the corresponding shear strength were measured.

Advances in emulsion polymerization and latex technology

Advances in emulsion polymerization and latex technology

High‐conversion emulsion polymerization

SUMMARY The four important factors that determine the rate of emulsion polymerization are the propagation rate coefficient, the latex-particle concentration, the monomer concentration in the latex particles, and the free-radical concentration in the latex particles. Both theoretical considerations and experimental evidence suggest that the important factors that may reduce the rate of emulsion polymerization at high conversion are the propagation rate coefficient and the monomer concentration in the latex particles, and not the free-radical concentration in the latex particle, if the initiator is not depleted. Various approaches for increasing the rate of emulsion polymerization at high conversion are suggested. One of the important considerations in any industrial application of the emulsion polymerization process is residual monomer in the final emulsion latex product. Often it is very difficult to remove the last few percent of monomer during the polymerization reaction, since the rate of an emulsion polymerization can become relatively slow at high weight fractions of polymer in the latex particles. It should be noted that the problem of slow rates of emulsion poiymerization at high conversions apply for both continuous and batch processes, since in continuous and semi-continuous reactors residual monomer is normally removed by reaction in a post (batch) reactor. In this paper theories of emulsion polymerization are considered in an attempt to show the causes of the often slow rate of emulsion polymerization at high conversions of monomer. Case studies are presented for the emulsion polymerizations of methyl methacrylate and butadiene. The aim of this paper is to distinguish the effect of high conversion upon those factors that determine the rate of an emulsion polymerization. Specifically, we wish to determine why the rate of emulsion polymerization of a specific system may become (uneconomically) slow at high conversion. Having isolated some of the major difficulties, some techniques for circumventing the slow rates of emulsion polymerization at high conversion are suggested. 2. Theory In the following discussions we consider, for simplicity, emulsion homo-polymerization, i.e. the emulsion polymerization of one monomer. However, most of the theoretical description can be easily extended to account for two or more monomers. The rate of any free-radical polymerization can be written as:

Final Report on the Safety Assessment of Polyvinyl Acetate

Polyvinyl Acetate, as used in cosmetic products, is a latex emulsion known as the homopolymer of ethenyl acetate. It is used as a binder, emulsion stabilizer, and hair fixative at concentrations less than 25%. Polyvinyl Acetate was nonmutagenic in the Ames assay, with and without activation, and in the Chinese Hamster fibroblast cell assay. Carcinogenic implantation studies using mice gave negative results. It is concluded that the data available are insufficient to support the safety of Polyvinyl Acetate as currently used in cosmetic products. The types of data needed to complete the safety evaluation are listed in the report.

Advances in emulsion polymerization and latex technology

Advances in emulsion polymerization and latex technology

Matrix inhomogeneity in crosslinked rubber and rubber emulsions

The radiation induced crosslinking of a polymer can be greatly affected by its environment and morphology. This is examined for rubber of identical source, but irradiated as (1) nonpurified, (2) purified rubber and (3) as an emulsion where the rubber particles are separated. Measurements include solubility, swelling and ESR studies using spin probe whose penetration into the denser parts of rubber network can be inhibited in the more crosslinked form. An apparent discrepancy between solubility and swelling data in irradiated emulsion is ascribed to a bimodal structure in the rubber emulsion, with dense rubber particles linked together by more extended chains. The use of spin probe technique allows an estimate of the penetrability of these small molecules in both irradiated latex emulsion and dry latex. The slow component of the ESR spectra is ascribed to spin probes in regions of high crosslink density, whereas the fast component is identified with spin probes in lightly crosslinked regions. According to the ratio of slow and fast ESR component latex irradiated in emulsion reveals different morphology as compared with the irradiated dry latex.

Fiber optic dynamic light scattering from concentrated dispersions 3: Particle sizing in concentrates

We describe measurements of particle size during the course of a latex emulsion polymerization reaction using fiber optic dynamic light scattering (FODLS). These measurements are compared to results from dynamic light scattering (DLS) measurements performed in the usual way on diluted samples. It is shown that the FODLS measurements follow the DLS results and reliably track the growth of the latex particles throughout the reaction. It thus appears that the FODLS technique is useful for the measurement of particle size in highly concentrated samples, such as is found in latex production.