Cotton linters hydrolysis

Results with newsprint are roughly intermediate between those for wood and cotton linters. Hydrolysis of the delignified chemical pulp component (about 20% of the total newsprint furnish) and of the accessible carbohydrates of the groundwood component is accomplished with about 4 days of digestion. Further hydrolysis of the groundwood carbohydrate is then stymied by lignin as in the case of red oak and Douglas fir. 

A recent modification of the hydrolysis-oxidation technique19 has produced strong support for the acid hydrolysis results already mentioned. In this instance samples of purified cotton linters were treated for varying times with boiling 2.5 N hydrochloric acid or with 2.5 N hydrochloric acid- 0.6 M ferric chloride. The latter was necessary where the hydrolysis extended over periods longer than 12 minutes and acted to hinder the formation of humic materials. By filtration and washing, a series of hydrocelluloses was obtained which corresponded to times of hydrolysis varying from 0 to 7 hours. 

Fig. 3.—Effects of varying amounts of hydrolytic pretreatment on hydrolysis of cotton linters.

Inspection of the data in Table IV shows that fine grinding causes a substantial increase in the rates of hydrolysis of all four substrates— nearly nine-fold for cotton linters and about five-fold for newsprint and Douglas fir after 120 min of milling. Red oak is somewhat less responsive, requiring 240 min of milling for a five-fold rate increase. 

The effect of ball milling on the dilute acid hydrolysis of cellulose is similar in many ways to the effect electron irradiation has on enhancing saccharification (18). In the case of cotton linters, for example, maximum irradiation lO d) resulted in a half life of hydrolysis of about 7 min... 

The relative influence of vibratory milling on the course of enzymatic and dilute acid hydrolysis of four cellulosic substrates was investigated. The four substrates—cotton linters, newsprint, Douglas fir, and red oak— were vacuum-dried and then milled for various time periods ranging up to 240 min. Assays were then made of rate and extent of hydrolysis, maximum yield of reducing sugar, and cellulose crystallinity. 

Vibratory milling also yields substantial increases in the rates of dilute acid hydrolysis of all four substrates nearly nine-fold for cotton linters and roughly five-fold for the three lignocelluloses. Increases in maximum sugar yields under simple batch conditions ranged from 60% to 140% over the yields for the unmilled materials. 

Most experiments were performed with cotton or cotton linters as highly crystalline celluloses. Table I shows conditions leading to complete dissolution. A minimum amount of an acid which forms a cellulose ester (sulfuric or trifluoromethylsulfuric acid) (Entries 5 7-14) is necessary for the reaction. The dissolution is accelerated by a temperature increase (Entries 10-12 13, 14) and leads to water-soluble cellulose acetate hydrogensulfate. Whereas this primary hydrolysis can be achieved within 1-5 min, the deesterification and complete hydrolysis of the soluble cellulose derivative proved to be much more difficult. This is in contrast to the generally accepted view that the main resistance to the hydrolysis of cellulose lies in the crystalline nature or low accessibility determining the heterogeneous first step of the reaction. 

FIGURE 5.23 Relationship between residue weight and time of hydrolysis at 100°C with 6 M HCl for cotton linters. (From Nelson, M.L., J. Polym. Sci., 43, 351, 1960.)... 

Depolymerization of cellulose fibers during irradiation is accompanied by a reduction in crystallinity, and, at high doses, extensive decomposition occurs. A dose of 5 X 10 equivalent roentgens brings about marked degradation and is sufficient to convert cotton linters into water-soluble materials. After irradiation, cellulose is more susceptible to acid hydrolysis and exhibits an after-effect. When irradiation is terminated, the intrinsic viscosity of cupriethylenediamine solutions of the irradiated cellulose continues to decrease. This behavior is initiated by oxygen and terminated by water. A similar effect is encountered with pectins after irradiation. 

Figure 5. Effect of acid hydrolysis on the CP-MAS spectrum of cotton linters. A Original material, B subjected to 2.5N HCl for 30 min, and C a renormalized linear combination spectrum [4x(a-.72B)]. Spectrum A and B are normalized to the same total intensity.

The composites with cotton linter showed a quicker onset of biodegradation and a higher degree of biodegradation after 90 d than the maple wood fiber based composites. This is possibly due to a quicker thermal hydrolysis during processing and composting. 

FIGURE 4 J Qualitative comparison of mechanistic model predictions (top row, from Griggs et al. (2012b)) with experimental results (bottom row, from Srisodsuk et al. (1998)) for the changing DP distribution of cellulose during enzymatic hydrolysis by EG, and CBH,. The left column compares resnlts for bacterial microcrystalline cellulose (BMCC) with a relatively low initial DP, and the right column compares results for cotton linter with a relatively high initial DP. For a color version, see the color plate section.)... 

Cellulose acetate (CA) is the acetic acid ester of cellulose. It is obtained by the action, under rigidly controlled conditions, of acetic acid anhydride on purified cellulose usually obtained from cotton linters. All three available hydroxyl groups in each glucose unit of the cellulose can be acetylated. However, in the material normally used for plastics, it is usual to acetylate fully and then to lower the acetylate value (expressed as acetic acid) to 52-56 percent by partial hydrolysis. When compounded with suitable plasticizers, this gives a tough thermoplastic material. Cellulose acetate is mainly an extrusion (film and sheet) material, but injection applications include premium toys, tool handles, appliance housings, shields, lenses, and eyeglass frames. 

Cellulose secondary acetate fibres are manufactured from cotton linters by steeping in glacial acetic acid and sulphuric acid-catalysed reaction with acetic anhydride. The reaction is exothermic and the final product in a maximum of 20 hours is cellulose triacetate, which is converted to secondary acetate by adding sufficient water. The hydrolysis is stopped when 1/6 of the acetate groups have been randomly changed to hydroxyl groups. The precipitated polymer flakes are dissoluted in acetone containing small amounts of water or alcohol. The chemical formula of cellulose triacetate and the diacetate fibre production chart are shown in Fig. 4.5. 

Figure 11.9 Pathway of H SO hydrolysis process on cotton linter [116].

NOTE The results of a non-linear least squares fitting of the C4 region of the CP/MAS C-NMR spectrum recorded on cellulose isolated from cotton linters by HCl(aq) hydrolysis (Reproduced with permission from reference 16. Copyright 1999). 

Figure 3. Fitting the C4 region of a CP/MAS C-NMR spectrum recorded on cellulose / isolatedfrom cotton linters by HCl(aq) hydrolysis (2.5MHCl(aq) 100 C 17h, yield about 80 %. After hydrolysis the cellulose is a colloidal sol). The experimental spectrum is shown as a broken line. The fttted spectral lines and their superposition are shown as solid lines. The broken line of the experimental spectrum is partialfy hidden by the superimposedfttted curves. See Table I for...

Cotton linters have been subjected to acid hydrolysis for various times and the products converted into samples of cellulose tricarbanilate (weight-average mol. wt. 0.21—1.1 X 10 ).Measurements of the intrinsic viscosities of dilute solutions of the derivatives in p-dioxan and butanone showed that the environment is well displaced from the normal 0-state and is closer to that at the lower critical solution temperature (234 °C in / -dioxan). 

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