Depolymerized cellulosic material with low crystallinity obtaine

Details Depolymerized cellulosic material with low crystallinity obtaine Depolymerized cellulosic material with low crystallinity obtaine

1980-06-20

1982-11-02

Clingman, A. Lionel

Organic compounds -- part of the class 532-570 series

Organic compounds

Carbohydrates or derivatives

424362, 426658, 536 57, C08G 1808

Patent

active

043574670

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention concerns a depolymerized cellulose powder and, as a matter of consequence, the controlled depolymerization of cellulose and, namely, its conversion into a depolymerized cellulose powder with a high degree of amorphicity.
Microcrystalline cellulose is known which is obained from a combination of chemical and physical treatments. Thus, the amorphous portions of cellulose are preferentially hydrolyzed by diluted acids; then, the undissolved crystalline portions thereof are recovered and disintegrated mechanically. The product from this heterogeneous acid hydrolysis is a depolymerized cellulose which has a "limited degree of polymerization" ("level-off degree of polymerization" or "DP-cellulose"). This product is thereafter milled and dried such as to obtain a finely ground powder of microcrystalline depolymerized cellulose.


THE PRIOR-ART

The prior-art relative to micro-crystalline cellulose can be illustrated by the following publications:
U.S. Pat. No. 2,978,446;
An article entitled: "Microcrystalline Cellulose" published in Industrial & Engineering Chemistry 5 (9), 20-29, September (1962).
An article entitled "Microcrystalline Cellulose Powders, Properties and Possible Application in Nutrition" published in the Tappi review 61 (5), May (1978).
The particles of the microcrystalline cellulose powder obtained as disclosed have lost the initial fibrous structure of cellulose, however, there was noted that they nevertheless have an acicular microcrystalline structure which can be undesirable for some applications, namely in the field of food chemistry, because such crystalline cellulose can possibly cause damages to the body cells.
However, these known processes for fabricating microcrystalline cellulose are not capable to achieve a controlled depolymerization, the latter intendedly reaching well determined polymerization degrees, which degrees would be below the limits obtainable from heterogeneous acid hydrolysis.
Other references concerning the depolymerization of cellulose can be cited, e.g.:
East German Patent No. DD No. 91.974 discloses the treatment of cellulose with gaseous HCl below 40.degree. C. without any solvent, which provides a product suitable for manufacturing mycrocrystalline cellulose.
East German Patent No. DD 71.282 discloses a process for hydrolyzing cellulose fibers down to about 150 .mu.m sizes, after which this product is ground in an air-jet mill, which provides particles of 5-20 .mu.m and a degree of polymerization (DP) of about 180. It is however not mentioned that such a cellulose is amorphous.
Geman Patent DAS No. 1.470.825 discloses the preparation of cellulose microcrystallites by the hydrolysis of amorphous portions of cellulosic fibers, then grinding in the presence of water and freeze-drying of the aqueous suspension thus obtained.
Geman Patent DAS No. 1.123.460 discloses the hydrolysis of cellulosic materials, namely viscose, by means of boiling in 2.5 N HCl. The product thus obtained is washed, neutralized and ground in the presence of water, so as to obtain a suspension of cellulose microparticles of 0.5-1 .mu.m.
Austrian Pat. No. 288.805 concerns a method rather similar with that mentioned above, as does U.S. Pat. No. 2,978,446. The following Chemical Abstract publication can be further cited: CA 66, 9991w (1967); CA 66, 77156a (1967); CA 67, 118346d (1967); CA 72, 123397p (1970); CA 73, 51582 (1970); CA 73, 67850c (1970); CA 82, 87960c (1975); CA 83, 130305c (1975) and CA 84, 6765j (1976).
Other references exist in which cellulose is fully dissolved in a concentrated acid and the dissolved product is thereafter separated and isolated by precipitation. Thus, ELLEFSEN et al. disclose in Norsk Skog Industri 1959, p. 411, the dissolving of cellulose at 20.degree. C. in aqueous 38-40.3% HCl and, after variable periods, the reprecipitation of the dissolved cellulose by adding water. This publication indicates that the products obtained were crystalline and not amorphous.
French Pat. No. 471.479 discloses dissolving cellulose in aqueous H

REFERENCES:
patent: 2305833 (1942-12-01), Warth
patent: 2978446 (1961-04-01), Battista et al.
patent: 3278519 (1966-10-01), Battista et al.
patent: 3345357 (1967-10-01), Cruz
patent: 3397198 (1968-08-01), Greidinger et al.
patent: 3954727 (1976-05-01), Toshkov et al.
patent: 4058411 (1977-11-01), Bellamy et al.
Sharkov, V. I. et al., Chemical Abstracts, 1972, 76, (No. 16), 87379w.

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