Poly polymeric suspending agent

Suspension polymerization of VDE in water are batch processes in autoclaves designed to limit scale formation (91). Most systems operate from 30 to 100°C and are initiated with monomer-soluble organic free-radical initiators such as diisopropyl peroxydicarbonate (92—96), tert-huty peroxypivalate (97), or / fZ-amyl peroxypivalate (98). Usually water-soluble polymers, eg, cellulose derivatives or poly(vinyl alcohol), are used as suspending agents to reduce coalescence of polymer particles. Organic solvents that may act as a reaction accelerator or chain-transfer agent are often employed. The reactor product is a slurry of suspended polymer particles, usually spheres of 30—100 pm in diameter they are separated from the water phase thoroughly washed and dried. Size and internal stmcture of beads, ie, porosity, and dispersant residues affect how the resin performs in appHcations. 

The suspension polymerization is conducted using monomer-soluble per-oxy initiators. Water-soluble polymers, such as poly(vinyl alcohol), are typically used as suspending agents to reduce the coalescence of the polymer particles [ 17]. A slurry of polymer particles 30-100 pm in diameter is formed during the polymerization. The particles are washed and dried before further processing. 

A number of important commercial resins are manufactured by suspension polymerization, including poly(vinyl chloride) and copolymers, styrene resins [general purpose polystyrene, EPS, high impact polystyrene (HIPS), poly(styrene-acrylonitrile) (SAN), poly(acrylonitrile-butadiene-styrene) (ABS), styrenic ion-exchange resins], poly(methyl methacrylate) and copolymers, and poly(vinyl acetate). However, some of these polymers rather use a mass-suspension process, in which the polymerization starts as a bulk one and, at certain conversion, water and suspending agents are added to the reactor to form a suspension and continue the polymerization in this way up to high conversions. No continuous suspension polymerization process is known to be employed on a... 

Typical suspending agents for the vinyl acetate polymerization are poly(vinyl alcohol) [particularly a grade represented as approximately 88% hydrolyzed poly(vinyl acetate)], gum arabic, hydroxyethyl cellulose, methyl cellulose, starches, sodium polyacrylate or sodium polymethacrylate, gelatin, and an equimolar copolymer of styrene and maleic anhydride neutralized with either sodium hydroxide or aqueous ammonia. Water-insoluble dispersing agents or... 

Sodium thiosulfate interfered with the polymerization in the aqueous phase. This manifested itself in a decrease in the overall rate of polymerization (cf. Table XVII). In this woric, substantial additions of sodiiun chloride were made to the aqueous phase to reduce further the unwanted emulsion polymerization. The suspending agent used in these experiments was a partially saponified poly(vinyl acetate) whose trade designation is Rhodoviol HS 100. This poly-(vinyl alcohol) was normally added to the reaction system as a 6% aqueous... 

One interesting aspect of this method of producing a suspension polymer is the fact that this method produces beads of poly(vinyl acetate) which may be loosely coated with poly(vinyl alcohol). This coating may be removed much more readily than the poly(vinyl alcohol) used in a conventional polymerization procedure. In the conventional process, a fair amoimt of the suspending agent probably forms a graft copolymer with vinyl acetate and is, therefore, permanently bound to the polymer bead. The properties of the two types of bead polymers are expected to be somewhat different since the graft copolymer with poly(vinyl alcohol) is present only in one and not the other polymer. 

Polyacrylamide ipa-le-o- kri-b- mld (1944) n. Poly(2-Propenamide) A non-ionic, water-soluble polymer prepared by the addition polymerization of acrylamide (CH2=CHC0NH2). The white polymer is readily soluble in cold water but insoluble in most organic solvents. It is used as a thickener, suspending agent, and as an ingredient in adhesives See image). 

The most commonly used suspending agents are cellulose derivatives, poly-aciylate salts, starch, poly(vinyl alcohol), gelatin, talc, and clay derivatives (95). The important function these agents must serve is to prevent the coalescence of monomer droplets during the course of the polymerization (114). Thickeners can also be added to improve suspension quality (95). Other additives such as lauryl alcohol, stearyl acid or cetyl alcohol lubricants and di- or trivinyl benzene, dial-lyl esters of dibasic acids, and glycol dimethacrylates cross-linkers are used to improve bead imiformity and bead performance properties. 

The styrene monomer first may be polymerized to about 65% conversion in the absence of water, and then the blowing agent (cyclopentane) may be added with additional peroxide. This solution is suspended in water in the presence of potato starch, and the polymerization is finished (74). By another modification a styrene solution of waste polystyrene and peroxide is suspended by poly (vinyl alcohol) in water, and pentane is added to the suspension after the solids content of the oil phase is greater than 70% (133). Polystyrene particles may also be suspended in water by a mixture of poly (vinyl alcohol) and a phenyl sulfonate and then a mixture of equal parts of pentane and catalyzed styrene (8% each on polymer) is diffused into the polymer. The temperature is elevated, and the polymerization is completed (23). 

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