Use as processing aid

Fluoroplastics. Conventional plasticizers are used as processing aids for duoroplastics up to a level of 25% plasticizer. However, certain grades of Kel-E (chlorotriduorethylene) contain up to 25 wt % plasticizer to improve elongation and increase softness the plasticizers used are usually low molecular weight oily chloroethylene polymers (5). 

The majority of food enzymes are used as processing aids, and they have no function in the final food. Eor that reason, they do not need to be declared on the label, and will not be present in the final food in any significant amount. A few enzymes, however, are used both as processing aids and as food additives. When used as additives, they must be declared on the food label using the appropriate class name, eg, preservative or antioxidant ... 

Natural rubber displays the phenomenon known as natural tack. When two clean surfaces of masticated rubber (rubber whose molecular weight has been reduced by mechanical shearing) are brought into contact the two surfaces become strongly attached to each other. This is a consequence of interpenetration of molecular ends followed by crystallisation. Amorphous rubbers such as SBR do not exhibit such tack and it is necessary to add tackifiers such as rosin derivatives and polyterpenes. Several other miscellaneous materials such as factice, pine tar, coumarone-indene resins (see Chapter 17) and bitumens (see Chapter 30) are also used as processing aids. 

The specific allergenic ingredients must be labeled even in cases of carryover conditions or when used as processing aids. Labeling of the 18 subspecific allergenic ingredients in Table 4.1 is recommended as much as possible. 

Resins resulting from the polymerisation of one of the fractions of coal tar. Used as processing aids, tackifiers and as non-black organic reinforcing agents in mbber compounding. 

There are certain exemptions from these rules. Some food ingredients need only be identified by a generic term, and additives used in such ingredients need not be named. Additives contained in ingredients of a food need not be listed, provided that they do not perform a technological function in the final foodstuff, and additives used as processing aids need not be hsted. The constituents of compound ingredients that constitute less than 25% of the product need not be... 

There are also hundreds of additives used as process aids to improve such things as air release, cure rate, thickening, viscosity reduction, mold release, wetting and dispersion of fillers, thixotropy, shrinkage and static reduction. 

Many applications of enzymes exist today in many, veiy different industries. In this chapter, first a short description is given of the various industries where enzymes are used as processing aids or processed into final products. Further in this chapter examples from the detergent, feed, textile and food industiy are worked out in detail, highlighting technical, commercial and social aspects to reckon with when developing and applying enzymes for these purposes. 

Cyclodextrins can also be used as process aids to remove specific compounds from a mixture of materials.79 81 A precipitate forms as the compound or compounds of interest are complexed. The complex is collected by centrifugation or filtration. 

The previous sections are an attempt to illustrate the diversity of surfactants, their many properties and the factors influencing their selection for a specific application. Practically everything that has an impact on our everyday life has a connection with surfactants, whether from a detergent and hygiene aspect or their use as process aids in the production of the objects around us. 

Enzymes are currently applied across many industries and are used as processing aids, incorporated into final products, and used in biocatalysis for chemical production. The global market for industrial enzymes will continue to expand as enzymes find their way into new markets and attract greater interest from the chemical industry at large. Several factors will contribute to this growth ... 

Process oils are not typical lubricants and are mostly used as processing aids in manufacture. They are generally additive-free mixtures of crude oil hydrocarbons and include products such as (i) medicinal white oils, (ii) technical white oils, (iii) bright process oils and (iv) dark process oils. Medicinal white oils are composed exclusively of isoparaffins and alkylnaphthenes. Technical white oils are less refined products than medicinal white oils and are composed of saturated hydrocarbons, though they may also contain a slight amount of aromatic compounds. Bright process oils include both yellow raffinates and brown distillates. Dark process oils are extracts from solvent refining of mineral base oils. 

Paraffin waxes, of melting point approximately 55 °C, are used as processing aids. They bloom to the surface and protect ozone sensitive elastomers against cracking under static stress. 

In the processing of fruit and vegetables exogenous enzymes are used as processing aids to improve or maintain the quality characteristics of traditional products. The use of enzymes further provides possibilities for product and process development (1). Table I summarizes present uses and Table II shows the quality aspects involved. 

The strength of the acid HX plays a decisive role in the fate of HAS. Salts of weak acids, like carboxylic acids formed in oxidized PO or used as processing aids, benzoic acid or carbonic acid are evidently not dangerous from the point of view of HAS depletion [228]. This was also envisaged in mechanistic studies dealing with the conversion of Af-methylated HAS into the salt of formic acid and secondary HAS 122, not depleting the photo-antioxidant effect. 

Fluoropolymers have been used as processing aids because small quantities can reduce signih-cantly the overall viscosity and thus facilitate extrusion. Feng et al. [1996] examined the mechanism of viscosity reduction in the capillary flow of HDPE/fluoroelastomer blends. X-ray photoelectron spectroscopy, used to characterize the composition of the extmdates surface, indicated only very small traces of the fluoroelastomer on the extrudate, pointing to the fact that the viscosity reduction is due to adhesive failure between the fluoropolymer layer and HOPE. 

Usually, and for obvious reasons, stability is discussed in terms of its benefits. Any such discussion would, however, be incomplete without some mention of commercial situations where stability is undesirable, or even dangerous. Enzymes are used in many food manufacturing processes, mainly in the form of lyases (amylases, phosphorylases, lipases, etc ). Health and safety considerations demand that they must have been removed entirely before the hnished products reach the marketplace. In a similar manner, any extraneous enzymes used as processing aids in protein purihcation protocols have to be removed prior to freeze-drying. 

Ester plasticizers (phthalates and phosphates) that are used to plasticize PVC (see Chapter 1) are also used as process aids, particularly with NBR and CR. Polymerizable plasticizers such as ethylene glycol dimethacrylate are particularly useful for peroxide curing rubbers. They act as plasticizers or tackifiers during mixing and undergo polymerization by peroxide initiation during cure. 

Alkane sulfonates are applied in a widespread manner in emulsion polymerization. They are used as processing aids, in particular in the emulsion polymerization of vinyl chloride, vinyl acetate, styrene and acrylonitrile. Because they possess no double bonds, alkane sulfonates do not act as radical chain stoppers. Well-known lattices derived from emulsion polymerization are poly(vinyl chloride), ethylene-vinylacetate copolymers, polyacrylates, and butadiene and chloroprene rubbers. Alkane sulfonates also offer good stabilizing effects in lattices against coagulation by fillers. 

Rubber Compounding. Specialty phenolic resins are used as processing aids, tackifiers, adhesives to fabric, and for reinforcement. 

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