Highly Saturated Nitrile ,

Highly saturated nitrile elastomers (HSN) have become available. These mbbers are prepared by (nearly complete) hydrogenation of the nitrile mbber copolymer. The resulting product has better heat and oxidation resistance than conventional nitrile mbber but still retains some double bonds for vulcanization. Trade names for HSN are Zetpol (Nippon Zeon), Therbar (Bayer), and Tormac (Polysar). HSN has been used, and is being developed, for oil field chemical, automotive, power station, aerospace, military, and industrial appHcations (66). 

Y. Kubo, K. Hashimoto, and N. Watanabe, "Stmcture and Properties of Highly Saturated Nitrile Elastomers," paper presented at theH.CA. 

K. Hashimoto and co-workers, "Highly Saturated Nitrile Elastomer, A Review," paper presented at theH.CA. Energy Rjibber Group, Dallas, Tex., Jan. 19,1989. 

HNBR Hydrogenated acrylonitrile-butadiene rubber (highly saturated nitrile... 

The relative speed with which hydrogenated or highly saturated nitriles have appeared on the market commercially has highlighted the need for polymers that fill the performance gap between standard NBRs and the high-performance fluorinated elastomers. This is an area of polymer and technology development that is in a rapid state of change and more candidates for this market, defined by the automobile and oil exploration industries, are sure to appear. 

Klingender RC, Oyama M, Saito Y (1990) High-strength compound of highly saturated nitrile and its applications. Rubber World 202(3) 26-31... 

It is claimed that the development of a nitrile rubber-based compound for battle tank track pads could save the US Army million of dollars in maintenance costs. Researchers at the Army Materials Research Laboratory and Belvoir Research Development Engineering Centre developed a highly saturated nitrile rubber compound in 1987 in an attempt to make the pads, currently moulded in SBR, wear longer. Details are given. 

HNBR—Highly Saturated Nitrile is moderately priced and is available in acrylonitrile levels similar to NBR. It has excellent strength and is generally used with a mechanical restraint or reduced extrusion gap. It has good general chemical and very good temperature compatibility, up to 175°C or 200°C. HNBR is unusual in that it does not lose hardness and modulus as the temperature increases to nearly the same extent as other elastomers. 

Homogeneous hydrogenation of nitriles, Saturated nitriles are hydrogenated to primary amines in 67-100% yield with 1 as catalyst in THF. The catalytic activity of 1 for aromatic nitriles is not so high as for hydrogenation of aliphatic nitriles. The C=C bond of unsaturated nitriles is reduced more readily than the C=N bond. This catalyst is also eflective for dehydrogenation of amines (benzylamine — benzonitrile, 27% yield). 

Zetpol Hydrogenated, nitrile elastomer (HNBR), highly saturated for fuel and solvent resistance Nippon Zeon Co., Ltd. 

An alternative, high-yield synthesis of y<5-unsaturated esters is provided by reaction of ethoxycarbonylmethylcopper with allylic halides (Scheme 18) similar reaction with cyanomethylcopper leads to the analogous y5-un-saturated nitriles. 

These polymers are produced by hydrogenation of the butadiene units of Nitrile polymers and are available with different amounts of unsaturation. As the number of double bonds is reduced, the elastomer becomes more highly saturated and the polymers have better heat resistance. They require peroxide cures to develop optimum properties. 

The as-spun acrylic fibers must be thermally stabilized in order to preserve the molecular structure generated as the fibers are drawn. This is typically performed in air at temperatures between 200 and 400°C [8]. Control of the heating rate is essential, since the stabilization reactions are highly exothermic. Therefore, the time required to adequately stabilize PAN fibers can be several hours, but will depend on the size of the fibers, as well as on the composition of the oxidizing atmosphere. Their are numerous reactions that occur during this stabilization process, including oxidation, nitrile cyclization, and saturated carbon bond dehydration [7]. A summary of several fimctional groups which appear in stabilized PAN fiber can be seen in Fig. 3. 

Nitriles show an intense and easily recognizable C=N bond absorption near 2250 cm-1 for saturated compounds and 2230 cm-1 for aromatic and conjugated molecules. Since few other functional groups absorb in this region, IR spectroscopy is highly diagnostic for nitriles. 

The formation of unsaturated cyanohydrins (from a, -unsaturated aldehydes) is of further advantage as these products possess an additional synthetic potential. As in the saturated cyanohydrins (above in Scheme 6) they possess the same opportunities for elaboration of the hydroxyl or nitrile moiety, although the presence of the carbon-carbon double bond offers the possibility for additional transformations to be performed such as additions [108], oxidative cleavage [117,118] and epoxidation [119] (Scheme 7). Thus, these highly functionalised chiral units can be of greater importance to an organic chemist. 

This and other similar cycloadditions, however, when unactivated hydrocarbons without heteroatom substituents participate in Diels-Alder reaction, are rarely efficient, requiring forcing conditions (high temperature, high pressure, prolonged reaction time) and giving the addition product in low yield. Diels-Alder reactions work well if electron-poor dienophiles (a, p-un saturated carbonyl compounds, esters, nitriles, nitro compounds, etc.) react with electron-rich dienes. For example, compared to the reaction in Eq. (6.86), 1,3-butadiene reacts with acrolein at 100°C to give formy 1-3-cyclohexene in 100% yield. 

Note Highly polar solvent sweet, ethereal odor soluble in water flammable, burns with a luminous flame highly toxic by ingestion, inhalation and skin absorption miscible with water, methanol, methyl acetate, ethyl acetate, acetone, ethers, acetamide solutions, chloroform, carbon tetrachloride, ethylene chloride, and many unsaturated hydrocarbons immiscible with many saturated hydrocarbons (petroleum fractions) dissolves some inorganic salts such as silver nitrate, lithium nitrate, magnesium bromide incompatible with strong oxidants hydrolyzes in the presence of aqueous bases and strong aqueous acids. Synonyms methyl cyanide, acetic acid nitrile, cyanomethane, ethylnitrile. 

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