Polymerization grade

Tetrafluoroethylene of purity suitable for granular or dispersion polymerizations is acceptable for copolymerization with ethylene. Polymerization-grade ethylene is suitable for copolymerization with tetrafluoroethylene. Modifying termonomers, eg, perfluorobutylethylene and perfluoropropylene, are incorporated by free-radical polymerization. 

The ethynylation reaction takes place at 10—40°C and 2 MPa (20 atm) and hquid ammonia is the solvent. The methylbutynol is converted into methylbutenol by selective hydrogenation and then is dehydrated over alumina at 250—300°C. Polymerization-grade isoprene is obtained. 

C to give the expected 2-methyl-1-butene in high selectivites (24). The AI2O2 catalyzed process can be optimized to give di- -pentyl ether as the exclusive product (23). Dehydration of 1-pentanol over an alkah metal promoted AI2O2 catalyst at 300—350°C provides 1-pentene at selectivities of 92% (29,30). Purification produces polymerization grade (99.9% purity) 1-pentene. A flow chart has been shown for a pilot-plant process (29). 

Table 5. Specifications for Typical Polymerization-Grade Styrene Monomer Product...

Polymerization-grade vinyl chloride should not contain more than the amounts of impurities Hsted in Table 6 (145). 

Polymerization-grade chloroprene is typically at least 99.5% pure, excluding inert solvents that may be present. It must be substantially free of peroxides, polymer [9010-98-4], and inhibitors. A low, controlled concentration of inhibitor is sometimes specified. It must also be free of impurities that are acidic or that will generate additional acidity during emulsion polymerization. Typical impurities are 1-chlorobutadiene [627-22-5] and traces of chlorobutenes (from dehydrochlorination of dichlorobutanes produced from butenes in butadiene [106-99-0]), 3,4-dichlorobutene [760-23-6], and dimers of both chloroprene and butadiene. Gas chromatography is used for analysis of volatile impurities. Dissolved polymer can be detected by turbidity after precipitation with alcohol or determined gravimetrically. Inhibitors and dimers can interfere with quantitative determination of polymer either by precipitation or evaporation if significant amounts are present. 

The experimental semibatch apparatus and procedure have been described in several places through the text of Wisseroth s publications ( 1, 7-9). so the details will not be repeated here. For nearly all of his work the reactor volume was one liter, temperature was 80 C, pressure was 30 atm (441 psia), and the feed was polymerization grade I assume that the reactor gas composition was 99% CsHgand 1% inerts. The range of catalyst loading was from 11 to 600 mg of TiCils per batch. The reaction time was varied from 0.5 to 6 hours. The weight ratio of alkyl-to-TiC 3 in the catalyst recipe was varied from 0.5 to 32. No data are reported from a continuous gas phase reactor. 

Alternatively, acrylic acid can be obtained in a two-step reactor in which glycerol is catalytically dehydrated with an acid catalyst like H3PO4 on a-alumina [67]. The obtained acrolein is then oxidized with a commercially available oxidation catalyst, viz. Mo/V/W/Cu-oxide on a-alumina, yielding up 55% polymerization grade acrylic acid (Scheme 11.8) [68]. 

The chlorotrifluoroethylene used was inhibited polymerization grade, supplied by the Kinetic Chemicals Division, Organic Chemicals Department, E. I. du Pont de Nemours and Company, Wilmington, Delaware. 

Butadiene is available commercially as a liquefied gas underpressure. The polymerization grade has a minimum purity of 99%, with acetylene as an impurity in the parts-per-million (ppm) range. Isobutene, 1-butene, butane and cis-l- and Zrc//7.s-2-butcnc have been detected in pure-grade butadiene (Miller, 1978). Typical specifications for butadiene are purity, > 99.5% inhibitor (/c/V-butylcatecliol). 50-150 ppm impurities (ppm max.) 1,2-butadiene, 20 propadiene, 10 total acetylenes, 20 dimers, 500 isoprene, 10 other C5 compounds, 500 sulfur, 5 peroxides (as H2O2), 5 ammonia, 5 water, 300 carbonyls, 10 nonvolatile residues, 0.05 wt% max. and oxygen in the gas phase, 0.10 vol% max. (Sun Wristers, 1992). Butadiene has been stabilized with hydroquinone, catechol and aliphatic mercaptans (lARC, 1986, 1992). 

Chloroprene is available commercially on a restricted basis in the United States as crude P-chloroprene with a minimum purity of 95% (Lewis, 1993 DuPont Dow Elastomers, 1997). The principal impurities are dichlorobutene and solvents, with smaller amounts of 1-chlorobutadiene (a-chloroprene), chlorobutenes and dimers of both chloroprene and butadiene. Due to its reactivity, chloroprene is stored at 0°C or below under nitrogen and contains significant quantities of inhibitors, such as phenothiazine, tert-butylcatechol, picric acid and the ammonium salt of A -nitroso-N-phenylhydroxy lamine, to prevent degradation and polymerization (Stewart, 1993). Generally within six weeks of manufacture, crude chloroprene is distilled to produce polymerization grade, which is used within approximately 24 h of distillation. 

A simplified flow sheet of the industrial process is shown in Fig. 5.1-1. In the first section fresh ethylene is mixed with the low-pressure recycle at 5 MPa and is compressed to 15 -35 MPa by means of a five-stage piston compressor. Fresh ethylene should have a high purity of above 99.9 vol.%. Further specifications of polymerization-grade ethylene are given in Table 5.1-1. 

The costs assume the production of pellets on 1997 German prices. Polymerization-grade ethylene is available at 5 MPa. The on-stream time is 8,000 h/a. The tubular reactors equipped with multiple feeds of ethylene and peroxide initiators are operated at 200 MPa. The initiators are a mix of dicyclohexyl peroxy dicarbonate, /-butylperoxy pivalate, /-butylperoxy 2-ethylhexanoate, and di(/-butyl)peroxide, which is fed in after the heating zone and at two further locations downstream. 

Materials. Styrene and butadiene monomers were polymerization grade, available from Dow Chemical Company. Acrylic acid was a technical grade monomer from Dow Badische. The polymeriza-tion surfactant was sodium dodecyldiphenyl oxide sulfonate available from Dow. The polymerization initiator was sodium persulfate, and bromoform and carbon tetrachloride the chain transfer agents. 

The first commercial application of olefin disproportionation was in 1966 87) Shawinigan Chemicals Ltd. at the Varennes complex near Montreal, Quebec brought onstream the Phillips Triolefin Process88) for converting propylene into polymerization-grade ethylene and high-purity butenes. Pilot plant development, reported by Johnson 89), showed that during a 20-hour test propylene conversion remained nearly constant at 43 per cent and efficiency of converted propylene to ethylene and n-butenes increased from 93 to 99 per cent. 

In this project the raw materials are ethylene and chlorine of high purity. The design refers to a capacity of 300kton/year VCM polymerization grade. Information about technology used in this project can be found in encyclopaedic works [1-3], review papers [4—6], patents, as well as on the websites of leading producers. Table 7.1 shows quality specifications, namely regarding key impurities [2],... 

Table 10.1 presents typical specifications for a polymerization-grade product, as well as some physical properties. Prohibited impurities refer to inhibitors (croton-aldehyde, vinyl acetylene), chain-transfer agents (acetic acid, acetaldehyde, acetone) and polymerizable species (vinyl crotonate), while methyl and ethyl acetate impurities are tolerated. 

All the emulsions appeared to have similar particle sizes, estimated to be in the range of 0.1-0.5/. The monomers were all polymerization grade and polymerized without purification since no significant difference in induction period or rate was observed with distilled monomer. 

Materials. Polymerization grades of propylene and ethylene, obtained from Sun Oil Co., were used without further purification. Vinyl-pyridines were obtained from Borden Chemical Co. Before use, the monomers were purified by vacuum distillation to remove inhibitors. Acrylonitrile, from Distillation Products Industries, was purified by distil-... 

Removal of catalyst residue and amorphous polymer is not required. Unreacted monomer is flashed in a two-stage pressure system (2, 4) and recycled back to the reactors. This improves yield and minimizes energy consumption. Dissolved monomer is removed from the polymer by a steam sparge (5). The process can use lower-assay chemical-grade propylene (94%) or the typical polymerization-grade (99.5%). 

Description Ethylene feedstream (plus recycle ethylene) and butenes feedstream (plus recycle butenes) are introduced into the fixed-bed, metathesis reactor. The catalyst promotes reaction of ethylene and 2-butene to form propylene and simultaneously isomerizes 1-butene to 2-butene. Effluent from the metathesis reactor is fractionated to yield high-purity, polymerization-grade propylene, as well as ethylene and butenes for recycle and small byproduct streams. Due to the unique nature of the catalyst system, the mixed C4 feed stream can contain a significant amount of isobutylene without impacting performance of the OCT process. A variation of OCT—Automet Technology—can be used to generate ethylene, propylene and the comonomer—hexene-1—by metathesis of n-butenes. 

The process can use lower-assay chemical-grade propylene (94%) or the usual polymerization grade (99.5%). 

As shown by Table 3 commercial specifications for polymerization grade butadiene are extremely severe, especially concerning acetylene derivatives, which are present at the rate of 0.5 to 0.7 per cent weight in the initial cu. ... 

Typical commercial spsancATioNS of polymerization grade butadiene... 

This operation is essential for the extraction of butadiene contained in a steam-cracked C4 cut by means of cuprous ammonium. It is not absolutely necessary in the case of extractive disrillation. In this case, however, hydrogenation pretreatment significantly improves the operating conditions of the separation step, and helps to raise the recovery rate of polymerization grade butadiene. Indeed, this leads to a reduction of its losses as a diluent for acetylenic compounds in the effluent rich in these compounds and separated by extraction. Energy costs are reduced simultaneously ... 

A schematic flow chart of this process is shown in Fig. 6. The feed is composed of 25-35 wt% purified isobutene and the required amount of isoprene (0.4-1.25 wt%), dissolved in cooled liquid methyl chloride. Purity of supplied isobutene is variable and preliminary drying and fractionation in a two-tower system remove water, n-alkenes, f-butanol, and diisobutenes. The polymerization grade (>99.5%) fresh isobutene is then mixed in a feed blend drum with isoprene (purity >98%) and a recycle stream of diluent and unreacted monomers. A concentrated catalyst solu-... 

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