Synthetic latexes

Latex technology encompasses coUoidal and polymer chemistry ia the preparation, processing, and conversion of natural and synthetic latices into useful products. 

Many synthetic latices exist (7,8) (see Elastomers, synthetic). They contain butadiene and styrene copolymers (elastomeric), styrene—butadiene copolymers (resinous), butadiene and acrylonitrile copolymers, butadiene with styrene and acrylonitrile, chloroprene copolymers, methacrylate and acrylate ester copolymers, vinyl acetate copolymers, vinyl and vinyUdene chloride copolymers, ethylene copolymers, fluorinated copolymers, acrylamide copolymers, styrene—acrolein copolymers, and pyrrole and pyrrole copolymers. Many of these latices also have carboxylated versions. 

Most synthetic latices contain 5—10 wt % of nonelastomeric components, of which more than half is an emulsifier or mixture of emulsifiers. One reason for this relatively high emulsifier concentration as compared with natural latex is that emulsifier micelles containing solubiHzed monomer play a principle role in the polymerization process. A high emulsifier concentration is usually necessary to achieve a sufficiently rapid rate of polymerization. Secondly, a considerable fraction of the surface of the polymer particles must be covered by adsorbed soap or equivalent stabilizer to prevent flocculation... 

The most commonly used emulsifiers are sodium, potassium, or ammonium salts of oleic acid, stearic acid, or rosin acids, or disproportionate rosin acids, either singly or in mixture. An aLkylsulfate or aLkylarenesulfonate can also be used or be present as a stabilizer. A useful stabilizer of this class is the condensation product of formaldehyde with the sodium salt of P-naphthalenesulfonic acid. AH these primary emulsifiers and stabilizers are anionic and on adsorption they confer a negative charge to the polymer particles. Latices stabilized with cationic or nonionic surfactants have been developed for special apphcations. Despite the high concentration of emulsifiers in most synthetic latices, only a small proportion is present in the aqueous phase nearly all of it is adsorbed on the polymer particles. 

Neutral or alkaline salts, eg, KCl, K SO, K CO, or Na PO, are often present in synthetic latices in quantities of - <1%, based on the weight of the mbber. During emulsion polymerization the salts help control viscosity of the latex and, in the case of alkaline salts, the pH of the system. Many polymerizations are carried out at high pH, requiring the use of fixed alkaH, eg, KOH or NaOH. Very small amounts of ferrous salts can be employed as a component of the initiator system, in which case a sequesteriag agent, eg, ethyldiaminotetraacetic acid (EDTA) may be iacluded to complex the iron. Water-soluble shortstops, eg, potassium dithiocarbamate, may also be iacluded ia very small amounts (ca 0.1 parts). 

Styrene—butadiene latexes generally are quite stable mechanically because of the presence of relatively large amounts of emulsifying and stabilizing agents, and therefore require addition of less stabilizer in compounding. The apphcations of SBR latex are classified in Table 21. This classification indicates the scope of the industry and illustrates the large number of diverse applications in which synthetic latices are employed. The latex types previously found most suitable for particular applications are also listed. 

Neoprenes. Of the synthetic latices, a type that can be processed similarly to natural mbber latex and is adaptable to dipped product manufacture, is neoprene (polychloroprene). Neoprene latices exhibit poor initial wet gel strength, particularly in coagulant dipped work, but the end products can be made with high gum tensile strength, oil and aUphatic solvent resistance, good aging properties, and flame resistance. There are several types of neoprene latex, available at moderately high (ca 50 wt %) and medium soHds content. Differences in composition between the types include the polymer s microstmcture, eg, gel or sol, the type of stablizer, and the total soHds content (Table 22). 

Alkylphenol ethoxylates are chemically stable and highly versatile surfactants that find appHcation in a large variety of industrial products including acid and alkaline metal cleaning formulations, hospital cleaners, herbicides (qv) and insecticides, oil-weU drilling fluids, synthetic latices, and many others (see Disinfectants AND antiseptics Elastop rs, synthetic Insect control technology Metal surface treati nts Pesticides Petroleum, drilling fluids). 

Finally brief reference should be made to the stabilization of synthetic latices, particularly high solids latices of the GR-S type and the improvement of the cold GR-S polymerization by a synthetic emulsifying agent known as EMCOL K-8300, which is a sulfosuccinic acid ester (sodium salt) of the isopropanolamide of oleic acid ... 

Synthetic latices, 14 707 Synthetic linalool, 24 501 Synthetic lubricants, 13 687-688 Synthetic lubricating oil base stocks,... 

Is a water-soluble emulsifier and solubilizing agent. It is used as a component in dyeing assistants and as a low-foaming solvent emulsifier in textile dye carriers. It acts as a stabilizer in natural and synthetic latices, and is used as a wax emulsifier in coatings for citrus fruits. 

Is a strongly hydrophilic emulsifier, dispersant, solubilizer and detergent. It is used as a stabilizer and anticoagulant for natural and synthetic latices and dye pastes, as a dyeing assistant for wool/acrylic blends, and as a detergent and lubricant for fiber/fabric scouring. TRYCOL 5972 is also used as an emulsifier for waxes used in coating citrus fruits. HLB 15.8... 

Is a highly water-soluble, strongly hydrophilic surfactant used as a wetting agent in high electrolyte solutions and as a stabilizer in synthetic latices. 

Is an 80% aqueous solution of a strongly hydrophilic emulsifier that is used as an antistatic additive for commercial carpet maintenance. It is also used as a dyeing assistant and as a stabilizer for natural and synthetic latices to prevent coagulation by acids. 

All of the following are recommended for thickening synthetic latices, particularly RHOPLEX acrylic emulsions for standard backcoating, flocking, and laminating applications. They can be Incorporated directly into the binder system thickening begins with the addition of base to the proper pH. 

Use Lubricant stabilizer its potential uses include corrosion inhibitor, plasticizer, and textile auxiliary. Phenylstearic acid and its quaternary and ethoxylat-ed derivatives are used in synthetic latices, as mineral oil emulsifiers, and in invert systems. 

Phenolic resins Chlorinated rubber Synthetic latices Chlorinated paraffin Polyisocyanates Reactive monomers Phenolic varnishes Natural resins... 

NR was the original latex polymer. NR co-exists with a range of synthetic latices, each of which has a defined... 

Macromolecular Symposia Vol. 155, April 2000, p.171-80 ADSORBENT USAGE FOR VOC REMOVAL IN SYNTHETIC LATICES... 

A review is presented of topics covered at the Evolving Latex Market meeting organised by the Belgium Plastics and Rubber Institute, in which problems of volatile organic compounds in carpets, extractable proteins in foam mattresses and gloves, and aniline content in mattresses, were discussed. Papers presented demonstrated that suppliers of synthetic latices have successfully modified their materials to tackle environmental problems. BELGIAN PLASTICS RUBBER INSTITUTE... 

Information is given on methods of applying coatings (air-knife coaters, lock coalers, roll coalers and blade coalers) and the development of synthetic latices from SB, NB and AN for coating paper. 24 refs. Articles from this journal can be requested for translation by subscribers to the Rapra produced International Polymer Science and Technology. 

Mechanical stability of natural and synthetic latices - ASTM ATS FAAR Model 10.67000... 

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