Viscosity plastisols

The effect of various plasticizers was studied for a number of plastisols prepared both from emulsion and suspension PVC 2>6,7,37 42 46 4% Judging from the published data 48), the most viscous plastisols are formed with mesamole, low-viscosity plastisols with dioctyladipate taken as a base, irrespectively of PVC type. Plastisol viscosity may be controlled by certain additives small smounts of certain solvents may lower plastisol viscosity by as much as an order of magnitude37,41>, the use of bentonites makes pastes more dense 40,48>. Thermoplastic polyethylene may also be used as a thickening agent6,42). 

It is clear that in order to produce a low initial viscosity plastisol with good viscosity stability, the drying conditions need to be optimized for two factors ... 

High speed dispersion vertical mixers which are fitted with a variable speed drive and a toothed disc at the end of the vertical shaft. This type suits the lower viscosity plastisols used in wall and floor coverings. 

Based on low-toxicity polymeric plasticisers, new formulations of PVC plastisols were proposed and characterised. The study used propyleneglycol adipate as the polymeric plasticiser and compared its properties with two conventional phthalates DEHP and DINP. Mechanical and optical properties were examined, together with the determination of the optimum processing conditions for the higher viscosity plastisols using the polymeric plasticiser. 21 refs. 

In practice, the latexes resulting from emulsion polymerization most often contain particles within a wide size range. In fact, a broad particle size distribution (PSD) with a substantial amount of large size particles (dp > 1000 nm) is often required for low-viscosity plastisols. The relative growth of each particle size is determined by principles of competitive growth. Due to the complexi of a syston with a broad PSD, most woik dealing with this problem has been carried out with a bimodal system of two well-defined particle sizes. 

General Purpose, Low Temperature/Flexibility, Low Volatility Miscellaneous Low viscosity, plastisols... 

Plastisols of modest viscosity are commonly filtered through stainless steel mesh to remove tramp contaminants, often from the use of low-cost fillers. For thin-film applications, organosols and low-viscosity plastisols are pressure-filtered through cartridge or bag filters. Organosols may also be refined on three-roll paint mills for improved dispersion and ejection of contaminants. 

Recommended for products adhesives, blood bags, cellular rubber goods, film sheeting, gaskets, general purpose film, industrial hose and tubing, low viscosity plastisols, packaging, sealants, PVC film, vinyl foam ... 

A type of physical stabili2ation process, unique for poly(vinyl chloride) resias, is the fusion of a dispersion of plastisol resia ia a plastici2er. The viscosity of a resia—plastici2er dispersioa shows a sharp iacrease at the fusioa temperature. Ia such a system expansioa can take place at a temperature corresponding to the low viscosity the temperature can then be raised to iacrease viscosity and stabili2e the expanded state. 

Additives. Because of their versatility, imparted via chemical modification, the appHcations of ethyleneimine encompass the entire additive sector. The addition of PEI to PVC plastisols increases the adhesion of the coatings by selective adsorption at the substrate surface (410). PEI derivatives are also used as adhesion promoters in paper coating (411). The adducts formed from fatty alcohol epoxides and PEI are used as dispersants and emulsifiers (412). They are able to control the viscosity of dispersions, and thus faciHtate transport in pipe systems (413). Eatty acid derivatives of PEI are even able to control the viscosity of pigment dispersions (414). The high nitrogen content of PEIs has a flame-retardant effect. This property is used, in combination with phosphoms compounds, for providing wood panels (415), ceUulose (416), or polymer blends (417,418) with a flame-retardant finish. 

Plastisol Viscosity and Viscosity Stability. After the primary contribution of the resin type in terms of its particle size and particle size distribution, for a given PVC resin, plastisol viscosity has a secondary dependence on plasticizer viscosity. The lower molecular weight and more linear esters have the lowest viscosity and hence show the lowest plastisol viscosity, ie, plastisol viscosity for a common set of other formulation ingredients... 

Plastisols are often mixed and then stored rather than processed immediately (Fig. 5). It is of great importance in this case for the plasticizer to show htde or no paste thickening action at the storage temperature, and clearly it is not advisable to use a plasticizer of too great an activity, since grain sweUing, leading to plastisol viscosity increase, can occur at low temperatures for some active plasticizer systems. 

Fig. 5. Viscosity aging of plastisols at 23°C where A is BBP/DIPB B, DOP C, FllO and D, 911P.

Plasticizers for acryhcs include all common phthalates and adipates. There has been interest in the development of acryUc plastisols similar to those encountered with PVC. Clearly the same aspects of both plastisol viscosity and viscosity stabiUty are important. Patents appear in the Hterature (32) indicating that the number of available plasticizers that show both good compatibiHty with acryHc resins and satisfactory long-term plastisol stabiHty may be fewer than those showing equivalent properties with emulsion PVC resins. 

By selection of those chlorinated paraffins specifically developed for the PVC industry to match the properties of primary plasticizers, reductions in costs can be achieved without significant change in properties. However, certain aspects can be improved by the inclusion of chlorinated paraffin such as flame resistance, chemical and water resistance, low temperature performance, and the viscosity aging stabiUty in plastisols. 

Random copolymers of vinyl chloride and other monomers are important commercially. Most of these materials are produced by suspension or emulsion polymerization using free-radical initiators. Important producers for vinyl chloride—vinyUdene chloride copolymers include Borden, Inc. and Dow. These copolymers are used in specialized coatings appHcations because of their enhanced solubiUty and as extender resins in plastisols where rapid fusion is required (72). Another important class of materials are the vinyl chloride—vinyl acetate copolymers. Principal producers include Borden Chemicals Plastics, B. F. Goodrich Chemical, and Union Carbide. The copolymerization of vinyl chloride with vinyl acetate yields a material with improved processabihty compared with vinyl chloride homopolymer. However, the physical and chemical properties of the copolymers are different from those of the homopolymer PVC. Generally, as the vinyl acetate content increases, the resin solubiUty in ketone and ester solvents and its susceptibiUty to chemical attack increase, the resin viscosity and heat distortion temperature decrease, and the tensile strength and flexibiUty increase slightly. 

The first four types are most conveniently distinguished by reference to formulations A to D in Table 12.5. Formulation A is a conventional plastisol. The viscosity of the paste is largely controlled by the choice of type and amount of polymer and plasticiser. In order to achieve a sufficiently low viscosity for processing, large quantities of plasticiser must be added, thereby giving a product of lower hardness, modulus, tensile strength and other mechanical properties than would be the case if less plasticiser could be used. In many applications this is not a serious problem and plastisols are of some considerable importance commercially. 

P.V.C. plastisols P.V.C. plastisols are liquids which contain little or no solvent/diluent. They consist of a blend of polyvinyl chloride (p.v.c.) resins, plasticisers, stabilisers, viscosity depressants, pigments and sometimes fillers. 

The plasticizer-range alcohols are largely used as feedstock for production of high molecular weight diesters of phthalic, adipic, azelaic, and sulftiric acids. All these are used primarily in plasticizers for polyvinyl chloride (PVC) and other plastics. The plastics industry also uses them as additives for heat stabilization, to control the viscosity of PVC plastisols, ultraviolet absorbers, flame retardants, and antioxidants. They are also found in synthetic, lubricants, agricultural chemicals, and defoamers. 

In the plastisol propellant process, it is essential that the resin particles not solvate too rapidly at processing temperature since a rapid increase in viscosity of the propellant mix interferes with the mixing and casting operation. There must be adequate pot life of the mixed propellant. The resin-plasticizer system itself is the dominating influence on pot life, and for this reason certain combinations cannot be used in the plastisol process. 

The upper limit depends quantitatively on the viscosity that can be processed through the casting fixtures in reasonable time. Too high a viscosity may also lead to problems under certain flow conditions as, for example, when propellant folds over on itself to form a void space which may remain as a defect in the cured grain. If the propellant grain is to be formed and cured by screw extrusion, however, somewhat higher viscosities can be handled. A viscosity of 1600 poise has been reported (9) for a PVC plastisol propellant processed this way. 

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