Cellulose nitrates

Cellulose nitrate or pyrolyxin was the first synthetic thermoplastic of industrial significance, and was first discovered in 1833 by H. Bracconof after the nitration of wood flour and paper and later by Friedrich Schonbein in 1846. In 1870 the American chemist J.W. Hyatt invented its gelification in order to find a substitute for ivory. It is obtained by nitration of purified 

The doyen of the ester polymers is cellulose nitrate. Camphor-modified cellulose nitrate has been known for over 120 years and still retains its use in a few specialised applications. 

Degree of nitration Nitrogen content (%) Typical usage 

It will be observed from Table 22.1 that industrial cellulose nitrates or nitrocellulose (as they are often erroneously called) have a degree of substitution somewhere between 1.9 and 2.7 and that materials with lower degrees of substitution are used for plastics applications. 

Before nitration the moisture content of the purified linters is reduced to well below 5% since the presence of water will modify the progress of the reaction and tends to produce undesirable products. The drying operation is carried out by breaking open the cotton linters and passing along a hot air drier. 

The nitration bath normally contains sulphuric acid as a condensing agent and a typical bath for producing a cellulose nitrate with a nitrogen content of 11% would be 

The following plasticizers are/weie used in the plasticization of cellulose nitrate 

The following are the main functions played by plasticizers in cellirlose nitrate  

Measurements of the saturated vapor pressures of plasticizers over plasticized cellulose nitrate were used for calculation of chemical potentials of plasticizers and partial enthalpies and entropies of mixing.  

Phthalate plasticizers were fonnd to be stable in cellulose nitrate film, which, tested after 41 years of storage, retained all initial amonnt of 20 wt% of plasticizers. Camphor is known to be slowly lost from cellnloid. After 30-40 years it reaches a concentration of 15 wt% (initial concentration 33 wt%) and this remains quite stable.  

The loss of plasticizer may be accelerated by the decomposition of cellulose nitrate which produces nitrous oxides that then combine with water to form nitrous and nitric acids. Acids affect the stability of plasticizers and their interaction with the polymer. 

This material may be readily joined to itself with acetone. To obtain high optical clarity, use medium-boiling ketones and esters, or mesityl oxide (isopropylidene acetone). Ethyl acetate, methyl acetate, butyl acetate, ethyl lactate, diacetone alcohol, and methyl ethyl ketone are also used. A dope-type cement made with 10% by weight of cellulose nitrate and 90% by weight of diacetone alcohol has also been suggested.  

---

CH3CH(0H)C(0)0Et. A colourless liquid with a pleasant odour, b.p. 154 C. Manufactured by distilling a mixture of ( )-lactic acid, ethanol and benzene in the presence of a little sulphuric or benzenesulphonic acid. It is a solvent for cellulose nitrate and acetate and also for various resins. Used as a lacquer solvent. 

Glycerol ct-dichlorohydrin, sym-dichloroiso-propyl alcohol, 1,3-dichloro-2-hydroxypropane, CH2CI-CHOH-CH2C1. Colourless liquid with an ethereal odour b.p. 174-175" C. Prepared by passing dry HCl into glycerin containing 2% elhanoic acid at 100-1 lO C. Converted to x-epichlorohydrin by K.OH, Used as a solvent for cellulose nitrate and resins. 

C5H10O2, CHjCOOPr. Colourless liquid with a fragrant odour b.p. 88 C. Manufactured by leading propene into hot ethanoic acid containing sulphuric acid, or by heating isopropyl alcohol with ethanoic and sulphuric acids. Used as a solvent for cellulose nitrate and various gums. 

Me2C = CHCOCH= CMca- Yellow liquid having a camphor-like odour m.p. 28 C, b.p. 198-5°C. It is formed when propanone is saturated with HCl and allowed to stand. Resembles camphor in many of its properties and is a solvent for cellulose nitrate. Used to prepare diisobutyl ketone (reduction). 

Cellulose nitrate resin Poly(aryl ether)... 

Cellulose Nitrate. Cellulose nitrate is prepared according to the following reaction ... 

Key properties of cellulose nitrate are good dimensional stability, low water absorption, and toughness. Its disadvantages are its flammability and lack of stability to heat and sunlight. 

Properties molding resin, molding cellulose nitrate polyether reinforced filled... 

Figure 10.12 shows data for cellulose nitrate in acetone measured at Xo = 436 nm, and plotted in the manner suggested in Eq. (10.89). The following example completes the analysis of these data. 

Figure 10.12 Light-scattering data in the limit of C2 = 0 plotted according to Eq. (10.89) for cellulose nitrate in acetone. [Data from H. Benoit, A. M. Holtzer, and P. Doty,/. Phys. Chem. 58 635 (1954).]...

Interpret the slope and intercept values of the line in Fig. 10.12 in terms of the molecular weight and radius of gyration of cellulose nitrate in this solution. At 436 nm the refractive index of acetone is 1.359. 

Benoit et al.f prepared a mixture of two different fractions of cellulose nitrate and determined the molecular weight of the mixture by light scattering. The mixture was 25.8% by weight fraction A and 74.2% fraction B, where the individual fractions have the following properties ... 

Cellulosics. CeUulosic adhesives are obtained by modification of cellulose [9004-34-6] (qv) which comes from cotton linters and wood pulp. Cellulose can be nitrated to provide cellulose nitrate [9004-70-0] which is soluble in organic solvents. When cellulose nitrate is dissolved in amyl acetate [628-63-7] for example, a general purpose solvent-based adhesive which is both waterproof and flexible is formed. Cellulose esterification leads to materials such as cellulose acetate [9004-35-7], which has been used as a pressure-sensitive adhesive tape backing. Cellulose can also be ethoxylated, providing hydroxyethylceUulose which is useful as a thickening agent for poly(vinyl acetate) emulsion adhesives. Etherification leads to materials such as methylceUulose [9004-67-5] which are soluble in water and can be modified with glyceral [56-81-5] to produce adhesives used as wallpaper paste (see Cellulose esters Cellulose ethers). 

E. D. Miles, Cellulose Nitrate, Interscience PubHshers, New York, 1945. 

Sir Joseph Swan, as a result of his quest for carbon fiber for lamp filaments (2), learned how to denitrate nitrocellulose using ammonium sulfide. In 1885 he exhibited the first textiles made from this new artificial sHk, but with carbon fiber being his main theme he failed to foUow up on the textile possibihties. Meanwhile Count Hilaire de Chardoimet (3) was researching the nitrocellulose route and had perfected his first fibers and textiles in time for the Paris Exhibition in 1889. There he got the necessary financial backing for the first Chardoimet silk factory in Besancon in 1890. His process involved treating mulberry leaves with nitric and sulfuric acids to form cellulose nitrate which could be dissolved in ether and alcohol. This collodion solution could be extmded through holes in a spinneret into warm air where solvent evaporation led to the formation of soHd cellulose nitrate filaments. 

Cellulose nitrate also has widespread use as an adhesive and coating material. Whereas stabilizers are added to products, eg, sodium carbonate as a neutralizer, many conservators are hesitant to use cellulose nitrate materials because of the inherent instabiUty and the dangers to the object from nitric acid, formed when the nitric oxide combines with moisture. 

Aryl Phosphates. Aryl phosphates were introduced into commercial use early in the twentieth century for flammable plastics such as cellulose nitrate and later for cellulose acetate. CeUulosics are a significant area of use but are exceeded now by plastici2ed vinyls (93—95). Principal appHcations are in wire and cable insulation, coimectors, automotive interiors, vinyl moisture barriers, plastic greenhouses (Japan), furniture upholstery, conveyer belts (especially in mining), and vinyl foams. 

Triphenyl phosphate [115-86-6] C gH O P, is a colorless soHd, mp 48—49°C, usually produced in the form of flakes or shipped in heated vessels as a hquid. An early appHcation was as a flame retardant for cellulose acetate safety film. It is also used in cellulose nitrate, various coatings, triacetate film and sheet, and rigid urethane foam. It has been used as a flame-retardant additive for engineering thermoplastics such as polyphenylene oxide—high impact polystyrene and ABS—polycarbonate blends. 

Cellulose acids, cellulose esters, cellulose nitrates, cellulose ethers, cellulose xanthogenates... 

MiscelUneous. Mahc acid is used in pharmaceuticals (qv), cosmetics (qv), dentifrices (qv), metal cleaning, electroless plating (46), wash-and-wear textile finishing (47—49), for stabilization of heat-sensitive copying paper (50), as an inhibitor of gelation, livering, and agglomeration in cellulose nitrate Hqueurs, and in many other appHcations. 

---