Acetal extrusion

Extrusion Processes. Polymer solutions are converted into fibers by extmsion. The dry-extmsion process, also called dry spinning, is primarily used for acetate and triacetate. In this operation, a solution of polymer in a volatile solvent is forced through a number of parallel orifices (spinneret) into a cabinet of warm air the fibers are formed by evaporation of the solvent. In wet extmsion, a polymer solution is forced through a spinneret into a Hquid that coagulates the filaments and removes the solvent. In melt extmsion, molten polymer is forced through a multihole die (pack) into air, which cools the strands into filaments. 

The solvent used to form the dope is evaporated during the extrusion process and must be recovered. This is usually done by adsorption on activated carbon or condensation by refrigeration. For final purification, the solvent is distilled. Approximately 3 kg of acetone, over 99%, is recovered per kg of acetate yam produced. Recovery of solvent from triacetate extmsion is similar, but ca 4 kg of methylene chloride solvent is needed per kg of triacetate yam extmded. 

Because of its high cold flow, poly(vinyl acetate) is of little value in the form of mouldings and extrusions. However, because of its good adhesion to a number of substrates, and to some extent because of its cold flow, a large quantity is produced for use in emulsion paints, adhesives and various textile finishing operations. A minor proportion of the material is also converted into poly(vinyl alcohol) and the poly(vinyl acetal)s which, are of some interest to the plastics industry. 

Acetal resins may be processed without difficulty on conventional injection moulding, blow moulding and extrusion equipment. The main points to be considered are ... 

The most important of the esters is cellulose acetate. This material has been extensively used in the manufacture of films, moulding and extrusion compounds, fibres and lacquers. As with all the other cellulose polymers it has, however, become of small importance to the plastics industry compared with the polyolefins, PVC and polystyrene. In spite of their higher cost cellulose acetate-butyrate and cellulose propionate appear to have retained their smaller market because of their excellent appearance and toughness. 

Acetal Resins 1960 pb P P G<= Injection, blow or extrusion molded Plumbing, appliance, automotive industries... 

Cellulosic They are tough, transparent, hard or flexible natural polymers made from plant cellulose feedstock. With exposure to light, heat, weather and aging, they tend to dry out, deform, embrittle and lose gloss. Molding applications include tool handles, control knobs, eyeglass frames. Extrusion uses include blister packaging, toys, holiday decorations, etc. Cellulosic types, each with their specialty properties, include cellulose acetates (CAs), cellulose acetate butyrates (CABs), cellulose nitrates (CNs), cellulose propionate (CAPs), and ethyl celluloses (EC). 

Among the more than several uses for polyethers in ordn application is as a binder for extrusion cast expls (Ref 3), and in a caseless propint charge where the charge is used as an ammo element (Ref 5). Also, some development work on the use of Poly acetal resins (polyform aldehyde)1 as a fuel has been done by Singhal T ien yief 7)... 

It is likely that some devolatilization occurred during the extrusion step, possibly aided by the acetic acid, since it is doubtful that there could be sufficient residence time in the final 180°C tower section to drive the conversion to 99.5%. 

ISO 4613-1 1993 Plastics - Ethylene/vinyl acetate (E/VAC) moulding and extrusion materials - Part 1 Designation and specification ISO 4613-2 1995 Plastics - Ethylene/vinyl acetate (E/VAC) moulding and extrusion materials - Part 2 Preparation of test specimens and determination of properties ISO 8985 1998 Plastics - Ethylene/vinyl acetate copolymer (EVAC) thermoplastics -Determination of vinyl acetate content... 

S.E. Barnes, E.C. Brown, M.G. Sibley, H.G.M. Edwards and P.D. Coates, Vibrational spectroscopic and ultrasound analysis for the in-process monitoring of poly(ethylene vinyl acetate) copolymer composition during melt extrusion, Analyst, 130, 286-292 (2005). 

Both compounds 190 and 193 are reduced to 9,10-diphenylanthracene (205) by zinc and acetic acid. However, more interest attaches to the formation of anthracenes from anthracen-9,10-imines in nonreducing conditions. The iV-ethoxycarbonyl derivative (192) decomposed at 215° in cyclohexane to 33% of 205, although curiously this product was not obtained if the solvent was previously degassed. Whether or not the reaction involves simple extrusion of ethoxycarbonyl nitrene could not be established, since the expected iV-cyclohexylurethane was not detected. The 9,10-epithioanthracene (194) loses sulfur thermally to give 205. ... 

VAE, a copolymer of vinyl acetate with minor amounts of ethylene is used as an adhesive for paper, plastics and leather and as a binder for different paints. Shoes, tubes, toys and other articles of daily use also contain VAE polymers. The hydrolysis product of VAE polymers, EVOH, is a thermoplast and can therefore be processed by extrusion and injection moulding and is used as barrier polymer for O2 and CO2 (e.g. in packaging applications). 

Lastly, Corey has developed B LA species 65, derived from zwitterionic oxazaboro-lidine 64 and tri-n-butyltin trifalte, as a novel catalybc system for the enanboselec-bve synthesis of P-lactones from ketene and aldehydes (Scheme 5.81) [152]. The reaction of B LA 65 with ketene generates intermediate A. The subsequent addition of the ketene acetal unit to the coordinated aldehyde (intermediate B) followed by extrusion of the P-lactone completes the catalybc cycle. 

Schkeryantz and Pearson (59) reported a total synthesis of ( )-crinane (298) using an intramolecular azide-alkene cycloaddition (Scheme 9.59). The allylic acetate 294 was first subjected to an Ireland-Claisen rearrangement followed by reduction to give alcohol 295, which was then converted into the azide 296 using Mitsunobu conditions. Intramolecular cycloaddition of the azide 296 in refluxing toluene followed by extrusion of nitrogen gave the imine 297 in quantitative yield. On reduction with sodium cyanoborohydride and subsequent reaction with... 

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