Process Aids and Lubricants

Lubricants are widely used in PVC because, besides smoothing out processing problems, they improve produetivity and help to disperse the additives. They are often used in preference to external mould releases, some of which adversely affeet surface quality. There have not been many changes in the type of substance used, many of which have already been mentioned in Chapter 4. 

Lubricants have to be compatible with the main heat stabiliser systems, otherwise their sales will obviously be severely restricted. Clariant s Licowax OP is described as suitable for either lead or mixed metal systems. 

Crompton has developed a combined lubricant and heat stabiliser, called Mark 2910, for extruded PVC pipe. The special feature of this liquid product is that profile extruders do not have to buy a separate lubricant such as paraffin wax and add it by a further metered operation. 

Peter Greven manufactures calcium, zinc, lead and barium stearates as well as glycerine-based and ester lubricants. Its latest products are marketed under the Ligalub name, and are offered in a dust-free form for improved hygiene. 

Certain lubricants and slip agents are vegetable-based, because avoidance of the usual animal sources is essential in certain food packaging markets. Chemax offers vegetable-based stearate additives called Maxomer Lube , and Kemamide ELO from Crompton is a vegetable-based GMO-free erucamide, used in bottle closures where odour and taste are particularly important. It is a mould release agent for polyolefins and is said to be fairly resistant to oxidation. 

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A C Copolymer. [Allied-Signal] EVA and ethylaie-acrylic acid copolymers plastics lubricant and processing aid, pigment dispersant... 

AluibrasoKB. [PPG/Specialty Chem.] Fiber lubricant and processing aid for... 

Genseke. [McIntyre] Rubber lubricants and processing aids. 

Starwax . [Petrolite/Polymers] Hard microcrystalline wax for coatings, adhesives, paper, printing inks, plastic modification (as lubricant and processing aid), lacquers, paints, varnishes, as binder in ceramics, for potting/impreg-nant in elecyelectronic components, rubber, cosmetics. 

Syncrolube. [Croda Universal Ltd. Croda Surf. 1 ] Intonalaitd external lubricants and processing aids. 

Lubricants and process aids can be either (a) internal, whereby they act in the resin phase to increase melt flow and throughput, prevent shear burning, and resist melt fracture (by reducing viscosity at high shear rate), or (b) external, whereby they act at the interface between resin and other materials to improve release of the composite, promote dispersion of fillers, resist melt fi"acture, and/or reduce friction between resin and process equipment. 

Flame Retardants Impact Modifiers Lubricants and Processing Aids... 

Uses Plastics lubricant and processing aid pigment dispersant internal lubricant for PVC, nylon 6, nylon color cones. for adhesives, floor finishes, personal care, plastics, wax blends gellant for oils in personal care prods., pharmaceuticals film-former oil or fragrance encapsulator nonirritating abrasive emollient heat stabilizer food pkg. adhesives, coatings, paper/paperboard, cellophane, rubber articles, lubricants, textiles food-contact defoamer... 

Uses Plasticizer, processing aid for extrusion of PVC, urethanes lubricant and processing aid for filled PS, PC reactive diluent and flow promoter for epoxy powd. coatings... 

Uses Surfactant emulsifier, lubricant used in fiber lubricants and processing aids emulsifier in finish formulations Trade Name Synonyms Ethox MI-14 [Ethox http //www.ethox.com]] Trydet ISA-14 t[Cognis/Chems. Group http //www.cognis-us.com]... 

Lubricants and process aids are often dual-purpose additives, fulfilling both roles to varying extents and sometimes acting as impact modifiers as well. The primary purpose of a lubricant is to improve the flow behaviour of the resin, but it will often affect the physical and optical properties of the final product. 

While the plasticizers sector (which is almost totally bound up with PVC) has been dominated in recent years by controversy over the use of phthalates, there has been significant development in systems based on other materials, such as polymeric plasticizers. Lubricants and processing aids also come into this classification, where the trend is towards adaptation to other plastics compounds, both standard and engineering plastics, and new systems that reduce or overcome migration, for use especially in food contact and medical/ healthcare applications. 

This can come from other solids or liquids with which the surface has been in contact, as well as from the atmosphere. Thus the surface of a metal, which, outside the realms of surface science might be described as clean, will be covered by complex layer including an oxide, probably partly hydrated, perhaps carbonated, adsorbed water, residual lubricant, and processing aids. Such a layer, in molecular terms, will be thick. It is unlikely to have good wetting properties and is likely to be cohesively weak. Unless removed by pretreatment, it is likely to form a weak boundary layer and to give poor practical adhesion. A successful pretreatment is very unlikely to produce a molecularly clean surface, but the surface produced will not suffer from the same cohesive weakness and lyophobicity of the original. Polymers are also likely to require pretreatment, because their surfaces usually carry complex layers, chemically different from the bulk material. The formation of these layers is now considered. 

Uses Wetting agent, dye solvent, wax plasticizer, stabilizerfor textile, household, and cosmetic appiics., iipsticK rewetting dried skins secondary plasticizer, lubricant, and processing aid for vinyl resins grinding medium for pigment dispersions Features Recommended for low viscosity and non-exudation in PVC plastisols ... 

Uses Pigment dispersant for use in most polyolefins lubricant and processing aid for plastics and robber antislaL mold release agent in polymeric resins in confect with food... 

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