Hitoshi Maruyama

Preparation of polymer emulsions using a poly(vinyl alcohol) as protective colloid

Abstract We have prepared poly(vinyl acetate) (PVAc) emulsions using a new modified fully hydrolyzed poly(vinyl alcohol) (PVOH) with hydrophobic groups (RS-POLYMER) as a protective colloid. The stability of emulsion polymerization was excellent and the emulsion concurrently resulted in a good viscosity stability at low temperatures and high water resistant film; which could not be achieved by using a conventional PVOH. The features of the emulsion are ascribed to the characteristics of RS-POLYMER, which are stable at low temperatures and have a high water resistance. The emulsion has the advantage that it can be applied in high wet strength adhesives for paper and wood use.

Physical properties of acrylic copolymer emulsions using poly(vinyl alcohol) as a protective colloid in comparison with those using surfactants

Properties of copolymer emulsions of methyl methacrylate and butyl acrylate prepared using poly(vinyl alcohol) (PVA) as a protective colloid have been studied and compared with those prepared using anionic and anionic/non-ionic surfactants. The emulsions with PVA revealed a Newtonian flow, while those with surfactants had a thixotropic flow. Cast films of the emulsions with PVA afforded much larger tensile strengths, higher Youngs moduli, and poorer resistance to water compared with those with surfactants. Adhesive layer composed of the copolymers with PVA revealed markedly higher creep resistance to shearing stress, while that with surfactants had poor resistance; these phenomena appear to arise from the canal-like morphology of PVA in the former cast films, while the surfactants in the latter existed in island morphology. © 2000 Society of Chemical Industry

Effect of poly(vinyl acetate/vinyl alcohol) copolymer with a thiol end group as a steric stabilizer on dispersion polymerization of styrene

In dispersion polymerization of styrene in ethanol, effects of a reactive steric stabilizer, poly(vinyl acetate/vinyl alcohol) copolymer with a thiol end group (P(VAc/VA)-SH), were investigated. In the absence of the thiol end group, the dispersion coagulated at the middle stage of the polymerization, while in the presence of the thiol end group, the polymerization proceeded successfully to result in close to monodisperse particles. The reactive thiol group acts as a site of formation of the block copolymer, that is, polystyrene-b-P(VAc/VA), which is utilized as an effective dispersant. From the measurement on molecular weights during the course of polymerization, two polymerization loci were realized. Addition of butyl methacrylate to styrene affected markedly not only rate of polymerization but also particle size.

Effects of Poly(vinyl alcohols) Modified with Copolymerization as a Binder on Green Strengh of Pressed Compacts of Alumina Powder.

アルミナ粉体のプレス成形に及ぼす結合剤としてのポリビニルアルコール(PVA)の影響を,プレス成形物の曲げ強度,曲げ弾性率および密度から検討した.成形時の,穎粒中の水分率が高いほど曲げ強度などは高かった.このことはPVAのガラス転移温度(Tg)が吸水により成形温度よりも低くなることが重要であることを示している.PVAは成形時には水により十分に可塑化されることが必要であるが,成形後は水などの可塑剤は存在しない方が強度は高かった.次に各種共重合変性PVAの影響を調べた.炭素数10のカルボン酸のビニルエステルとイタコン酸を共重合したPVAで顕著な成形物のグリーン強度の増加,および密度の上昇が認められたので,これらの変性度の影響をやや詳細に調べた.最適組成では通常のPVAの系に比べて成形物の曲げ強度で3倍,タフネスで4倍大きかった.パラフィン鎖による滑剤効果によって穎粒の変形および緻密化が起こりやすくなることがその理由であろうと推定した.