Jaromír Šňupárek

Nontoxic anticorrosion pigments of the spinel type compared with condensed phosphates

The spinel-type compounds of a general formula corresponding to AB2O4 containing as A the ions Mg2+ or Zn2+ and as B the ions Fe3+ or Al3+ or combination of both the A and B given were prepared and investigated with respect to their anticorrosive activities as pigments used in organic coatings. For comparative purposes pigments known for their efficiency as metal-corrosion-inhibiting ingredients in similar formulations were used. Condensed phosphates were also evaluated as anticorrosion pigments. The results obtained shown high anticorrosion activities of the spinel-type pigments.

Principles and limits of polymer latex tailoring

Abstract The preparation of a synthetic latex is a very complex process that is affected by the monomers selected, surfactants, initiators and the polymerization process. The semi-continuous process is the most frequent as it enables the control of the polymerization heat removal as well as the control of the composition of the copolymers comprising several types of monomer units. Some aspects of copolymerization in emulsion and particle growth in the case of the semi-continuous process are discussed. Copolymers usually comprise 4–5 comonomers, some of them with functional groups. Functional groups serve as loci for crosslinking, improve colloid stability, increase polarity, improve adhesion, cause alkali-solubility and/or alkali-swellability. High value polymer latices with special particle morphology, composition and other characteristics can be tailor-made by using special polymerization recipes that are still mostly empirical.

Thickening of butyl acrylate/styrene/2-hydroxyethyl methacrylate/acrylic acid latices with an HEUR associative thickener

Thickening of acrylate copolymer latices containing various amount of 2-hydroxyethyl methacrylate (HEMA) by commercial associative thickener SER-AD FX 1070 (CONDEA Servo BV), based on hydrophobic ethoxylated urethane (HEUR), showed that the thickening efficiency decreases with the HEMA content in the latex copolymer. The strongest increase in viscosity occurred in the latex without HEMA comonomer suggesting formation of the network space structure due to the bridging of the latex particles by adsorption of hydrophobic ends of the thickener. When HEMA was incorporated into the latex copolymers, the particle surface became more hydrophilic and the association of the thickener was more significant. In this case thickening was much lower and was only a result of the hydrodynamic interaction between swollen latex particles and the thickener macromolecules or their aggregates (clusters, micelles).

Effect of alkalinization on carboxylated latices prepared with various amount of a non-ionogenic hydrophilic comonomer 2-hydroxyethyl methacrylate

Abstract Six latices of carboxylated styrene/butyl acrylate copolymers with 0–25% of 2-hydroxyethyl methacrylate (HEMA) were prepared by semicontinuous non-seeded emulsion polymerization and investigated by photon correlation spectroscopy and viscometry. Although HEMA is non-ionogenic, it profoundly affects the latex behavior after alkalinization: both methods revealed that HEMA promotes an increase in hydrodynamic dimensions of dispersed particles. The increase in viscosity due to incorporation of 10% of HEMA into the copolymers can make more than one order of magnitude at high volume fractions.

INVERSE SUSPENSION POLYMERIZATION OF THE HYDROPHILIC ACRYLIC MONOMERS IN THE STATIC CONTINUOUS PHASE

ABSTRACT A new polymerization technique for the synthesis of the high molecular weight hydrophilic polymers was developed. This new method of inverse suspension polymerization is based on the principle of the gradually polymerization of the initiated water solution monomer droplets during their fall through no stirring continuous oil phase which is filled in a long vertical reactor. This technique was used for the preparation of spherical polymeric beads of high molecular weight sodium salt of polyacrylic acid Polymeric particles were separated, dried and tested as a waterabsorbing material for baby diapers napkins.

Thickening of butyl acrylate/styrene/2-hydroxyethyl methacrylate/acrylic acid lattices with dispersion of crosslinked ethyl acrylate/methacrylic acid copolymer

Abstract Thickening of lattices of styrene–acrylic copolymers containing a small amount of acrylic acid and various amounts of 2-hydroxyethyl methacrylate (HEMA) with alkali-swellable dispersion of crosslinked ethyl acrylate/methacrylic acid copolymer has been studied using capillary viscometry and dynamic and steady shear measurements. The higher the amount of HEMA incorporated into the latex copolymers, the stronger the thickening effect is. A comparison of flow behavior of thickened systems with those of neat lattices confirmed a significant influence of the effective volume fraction of alkalinized swollen latex particles on the thickening process. Under these conditions, to obtain the same rheological properties, the necessary amount of thickener was lower for the latex copolymers with higher amounts of HEMA because a part of the thickener volume fraction was replaced by an increased volume fraction of swollen latex particles. These findings indicate weakly interacting dispersion systems without strong compression of particle domains.

Anticorrosive pigments for chemically and thermally resistant coatings

The present state in the field of organic coatings requires such an anticorrosive pigment, which is adapted in its properties to the binder concerned and will contribute to the overall protection properties of the pigmented coating film at max. The paper presents as an example of thermally and chemically stable pigments the compounds based on mixed metal oxides. Other pigments exhibiting prospective results for the coating applications comprise the pigments of lamellar shape, which in addition to their alkalizing properties contribute to increasing the barrier and simultaneously inhibition mechanism by protective action ofthe coating.

The effect of (2-hydroxypropyl)-β-cyclodextrin on rheology of hydrophobically end-capped poly(ethylene glycol) aqueous solutions

(2-Hydroxypropyl)-β-cyclodextrin (HPBCD), a modified cyclic oligosaccharide, changes the flow behavior of aqueous solutions of a model telechelic associative polymer, hydrophobically end-capped poly(ethylene glycol) (ODU-12), because the inclusion complexation of HPBCD and octadecyl end-capping groups interferes with aggregation of the polymer end groups. The HPBCD-induced decrease in the high-frequency modulus can be well described assuming a 1:1 binding isotherm, but cannot fully explain the decrease in the low shear rate Newtonian viscosity, because HPBCD also strongly decreases the relaxation time. Consequently, besides decreasing low shear rate Newtonian viscosity, HPBCD also extends the Newtonian behavior to higher shear rates as predicted by the free-path version of the transient network theory [Marrucci et al., Macromolecules 26, 6483–6488 (1993)].(2-Hydroxypropyl)-β-cyclodextrin (HPBCD), a modified cyclic oligosaccharide, changes the flow behavior of aqueous solutions of a model telechelic associative polymer, hydrophobically end-capped poly(ethylene glycol) (ODU-12), because the inclusion complexation of HPBCD and octadecyl end-capping groups interferes with aggregation of the polymer end groups. The HPBCD-induced decrease in the high-frequency modulus can be well described assuming a 1:1 binding isotherm, but cannot fully explain the decrease in the low shear rate Newtonian viscosity, because HPBCD also strongly decreases the relaxation time. Consequently, besides decreasing low shear rate Newtonian viscosity, HPBCD also extends the Newtonian behavior to higher shear rates as predicted by the free-path version of the transient network theory [Marrucci et al., Macromolecules 26, 6483–6488 (1993)].

Synthesis and some properties of functionalized film-forming latexes

Semi-continuous emulsion copolymerization was used for preparation different colloid copolymers containig hydroxyl, carboxyl and amide functional groups. Copolymerization of hydroxyethyl methacrylate with styrene and butyl acrylate was investigated. Molecular weight increase in the copolymerization of methacrylamide indicated an extensive branching of macromolecules. Functionalized latexes have been used as binders in water borne paints. In addition to the crosslinking ability the hydrophilic functional monomers positively affect the film formation. The effect of dissociated carboxylic groups on lowering the minimum film forming temperature was much more pronounced if the polymer chains were more polar and softer. Some relationships between the latex flow properties and the film forming ability have been illustrated in this paper.

Thickening Effect of Commercial Associative Thickeners on the Latices of Copolymers of Acrylic Monomers Carrying Hydrophilic Reactive Groups

Abstract Investigation of flow properties of butyl acrylate/styrene/2‐hydroxyethyl methacrylate/acrylic acid latices thickened by commercial associative thickeners based on hydrophobic ethoxylated urethane (HEUR) or hydrophobically modified alkali‐soluble emulsions (HASE) showed that the apparent viscosity, at a constant medium shear rate, increased with the increasing content of 2‐hydroxyethyl methacrylate (HEMA). In contrast, the relative change in latex viscosity after the thickener addition (thickening efficiency), expressed as the ratio of viscosities of the thickened and untreated latices, decreased. This indicates that the increase in viscosity of the thickened latex with a higher HEMA content is caused by the increasing viscosity of the untreated latices due to rising hydrodynamic volume of alkalinized latex particles and not by higher particle bridging with the thickener macromolecules. The HEMA monomer clearly increases hydrophilicity of the particle surface which reduces adsorption of hydrophobic ends of the thickener on latex particles and the thickening efficiency decreases.