Cellulose alkali concentration

Use of a high concentration of sodium hydroxide117 in water (about 5 M) permits the formation of a 1 1 adduct of cellulose. Lower concentrations lead to adducts having a lower content of alkali. 

The most important alternative crystalline form is cellulose II. This form can result from treatment of cellulose in concentrated alkali, such as 23% NaOH, followed by rinsing in water. This is also the main form that results from crystallization of dissolved cellulose, such as regeneration of rayon. Supercritical water can also effect the transformation [216]. The treatment of cotton in milder alkali, for industrial mercerization, amounts mainly to disruption and decrystallization rather than transformation to crystalline II. Cellulose II can occur as the native state when the normal biosynthesis and subsequent crystallization is disrupted [217-219]. 

The discrepancies among reported data, besides possibly being caused by different analytic techniques employed, may be partly attributed to variations in the alkali concentration used as shown in Fig. 1. Rammas and Samuelson [197] also demonstrated that the reactivity of the 2-OH and 6-OH with ethylene oxide was quite comparable in dilute alkali and that the C6 hydroxyethylation was preferentially promoted by an increase in the alkali concentration. In etherification of cotton cellulose with sodium 2-aminoethyl sulfate [192], sodium allyl sulfate [193], or acrylamide [194], the 6-OH group was generally found to be more reactive than the 2-OH group. 

The only other noticeable effect of variation of the experimental parameters shown (Table I) is a negative effect of high alkali concentration on oil yield, when the sodium carbonate concentration is raised to 2.37 N (12.6%) at 270-343 C. This is counter to Elliott and Giacoletto s results (10). The effect of alkali on cellulose chain peeling and cleavage was found to be directly proportional to alkali concentration at lower temperatures (185 C) (47). Since high alkali concentrations favor the hydride- transfer mediated Cannizzaro reaction to yield acid salts and alcohols from aldehydes and some ketones, we suggest that perhaps the lower oil yield may be due to removal of carbonyl intermediates from the reaction. 

The conclusions from this series of experiments are also clear Alkali concentration has little effect on the liquefaction reaction over the range 0.07 to 0.6 N. The reaction proceeds to the same products at concentrations as low as 0.07 N. The presence of some alkali is necessary for the reaction to proceed, even though in all of our experiments, the pH at the conclusion of the experiment dropped to the acid side (5-6 on average). Results obtained by Lai and Sarkanen ( 7) showed that the rate of cellulose degradation is directly proportional to the alkali concentration. 

Regardless of the vehicle used, it appears that the alkali concentration used at Albany is too high. Our results with cellulose indicate that a reduction of up to 13x may be possible without interfering with product composition (not yield), while Elliott and Giacoletto s results (JO) indicate that a 2x reduction is possible without affecting oil y/e/cf from wood. 

Of cellulose ethers only ethyl cellulose has found application as a molding material. Methyl cellulose, hydroxyethyl cellulose, and sodium carboxymethyl cellulose are usefiil water-soluble polymers. The first step in the manufacture of each of these materials is the preparation of alkali cellulose (soda cellulose) by treating cellulose with concentrated sodium hydroxide. Ethyl cellulose is made by reacting alkali cellulose... 

Alkali hydroxide solutions possess some of these requirements and dissolve the biopolymer of rather low DP after swelling in aqueous 8-9 per cent NaOH, subsequently freezing, thawing, and then diluting to a 5 per cent alkali concentration. Urea enhances the solubility due to the fact that it is able to weaken intermolecular hydrogen bonds [3]. However, the base will consume most of the estaifying agent before it reacts with the cellulose and therefore these systems cannot be employed in this context. 

The results above achieved may be attributed to partial merceri-zation which accompanies treatment of bagasse with high concentrations of alkali, namely, 12,5 and 25% ammonium hydroxide and which may lead to the transofrmation of cellulose I into the more hygroscopic cellulose II. Increased mercerization is known to accompany increased mercerizing alkali concentrations. 

Byproducts give an orange-yellow color yellow crumbs are formed. The degree of xanthation (of cellulose) is low fewer than 0.5 hydroxyl groups need be derivat-ized to accomplish dissolution in dilute alkali. The polymer concentration for a textile yarn would be around 9% and the alkali concentration 5-6%. Eor a tire cord the polymer/alkali ratio is lower, both concentrations being 7%, for example. The... 

Obtained by reacting methylchloride at 95-100°C with alkali cellulose (pulp, linter pulp as raw material) under pressure. If the alkali concentration is high the reaction time is long. 

The effectiveness of the treatment, of course, depends on the alkali treatment condition adopted. Uses of excessive alkali concentration, extended time, and high temperature can accelerate the extent of treatment but may depolymerize the cellulose component and damage the pristine natural fibers, resulting in the deterioration of the fiber strength [4j. 

Hydroxyethyl cellulose (HEC), a nonionic thickening agent, is prepared from alkali cellulose and ethylene oxide in the presence of isopropyl alcohol (46). HEC is used in drilling muds, but more commonly in completion fluids where its acid-degradable nature is advantageous. Magnesium oxide stabilizes the viscosity-building action of HEC in salt brines up to 135°C (47). HEC concentrations are ca 0.6—6 kg/m (0.2—21b/bbl). 

With each of these materials the first step is the manufacture of alkali cellulose (soda eellulose). This is made by treating eellulose (either bleaehed wood pulp or eotton Enters) with concentrated aqueous sodium hydroxide in a niekel vessel at elevated temperature. After reaetion excess alkali is pressed out, and the resultant eake is then broken up and vacuum dried until the moisture content is in the range 10-25%. The moisture and eombined alkali contents must be carefully eontrolled as variations in them will lead to variations in the properties of the resultant ethers. 

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