CS238884B1 - Method of processing of cation active hemicellulose - Google Patents

Abstract

The invention relates to the preparation of cationic hemicellulose. The essence of the preparation lies in that sawdust is activated from 3.5 to 25 % aqueous hydroxide solution sodium or 5 to 30% aqueous solution potassium hydroxide at 15 ° C up to 30 ° C for 30 to 120 minutes; alkylate with a 10 to 50% aqueous solution 3-chloro-2-hydroxypropyltrimetylamóniumchloridu at 40 to 70 ° C for 1 hour up to 4 h at a weight ratio of sawdust: Sodium hydroxide or potassium hydroxide: alkylating agent 1: 0.3 to 1.5: 0.7 to 3.0 a the modified sawdust is obtained by extraction with water followed by 5 to 10% aqueous sodium hydroxide solution or potassium hydroxide. The invention has utility in the pulp-paipier, textile, chemical and pharmaceutical.

Description

The invention relates to a process for the preparation of cationic hemicelluloses.

Alkaline amine and epichlorohydrin modified hemicellulosic processes, isolated from various sources, provide cationic preparations with film-forming and flocculating properties (US Pat. 3,833,512; US Pat. 3,832,313). In practice, these processes have not yet been used because of the lack of commercial availability of the starting material hemicelluloses whose production is not satisfactorily solved economically.

Isolation of hemicelluloses from effluents resulting from the batch of wood, bleaching, refining and mercerization of pulp is energy intensive due to their low concentration in said solutions. Hemicelluloses are isolated from the wood mass by extraction with dilute alkali solutions only in very small yields, substantially contaminated with lignin. Higher yields and purity of hemicelluloses are only achieved after prior delignification, thereby increasing the cost of production of hemicelluloses.

The above-mentioned disadvantages are substantially eliminated by the method of preparation of cationic hemicelluloses, which is based on the use of wood sawdust as starting material, which after activation with a 3.5 to 25% aqueous sodium hydroxide solution or a 5 to 30% aqueous potassium hydroxide solution at 15 to 30 ° C and for 30 to 120 minutes while stirring the alkyl is treated with a 10 to 50% aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride at a weight ratio of sawdust: sodium or potassium hydroxide: alkylation reagent 1: 0.3 to 1.5: 0.7 to 3.0 at 40 to 70 ° C for 1 to 4 h.

The reaction is stopped by the addition of 0-90% aqueous ethyl alcohol and the modified sawdust is washed with water or 70-90% aqueous ethyl alcohol until neutral, optionally neutralized with dilute hydrochloric acid. From the aqueous wash solutions, hemicelluloses are obtained by clotting in a double volume of 96% ethyl alcohol, washing the precipitate with 70-90% aqueous ethyl alcohol, and drying.

From the modified ethanol-washed sawdust they are obtained by extraction with water or 5-10% aqueous sodium or potassium hydroxide solutions. They are isolated from the extracts by precipitation in an excess of ethyl alcohol as described above.

An advantage of the proposed method of preparing cationic hemicelluloses over other methods is that the present method is more economically efficient because it uses hemicelluloses in their native form as a raw material without prior isolation from lignocellulosic materials.

In this way it is possible to utilize wastes from mechanical and chemical processing of wood mass in the form of sawdust, fly, pulp as well as waste of agricultural plants (straw, corn husk, etc.). 40 to 75% of the hemicelluloses present in the wood are obtained in the form of water- and alkali-soluble cationic hemicelluloses.

If deciduous trees and annual plants are used, cationic xylan-type hemicelluloses are obtained. The lignocellulosic residue after hemicellulose extraction has the properties of a strong basic ion exchanger with an exchange capacity of 0.1 to 0.5 mmol / g. Example 1 kg of air-dry beech sawdust was activated with 41.3 L of a 3.5% aqueous sodium hydroxide solution with stirring at 15 ° C for 30 minutes. Then, while stirring, the sawdust is alkylated with 7.5 L of a 50% aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride at 50 ° C for 2 hr.

The modified sawdust was washed with water until neutral to phenolphthalein, 96% ethyl alcohol, and air dried. After concentrating it to one-tenth of the original volume, hemicelluloses are precipitated from the aqueous solution by adding twice a volume of 96% ethyl alcohol and dried at 3 kPa and 60 ° C. 7.8% of water-soluble cationic hemicelluloses are obtained with a nitrogen content of 0.85 percent.

Treatment of modified sawdust with 15 L of a 5% aqueous sodium hydroxide solution extracts alkali-soluble cationic hemicelluloses. They are obtained from the extract after dialysis of the alkali by lyophilization in a yield of 4.6% with a nitrogen content of 0.61%.

The lignocellulose residue after extraction in a yield of 51.0 o / ₀ has a nitrogen content of 0.10%. Example 2

The procedure is as in Example 1 except that the wood is used as the starting material for sawdust, sawdust is used as the starting material, 4.7 liters of a 25% aqueous sodium hydroxide solution for 120 minutes and alkylation 37.5 1 10% - % aqueous 3-chloro-2-hydroxypropyltrimethylammonium chloride solution at 60 ° C for 4 h. The reaction is stopped by adding a 5% aqueous hydrochloric acid solution to the neutral reaction and the modified sawdust is washed with water. *

The yield of water-soluble cationic hemicelluloses is 5.6% with a nitrogen content of 0.46 percent and alkali-soluble 12.0% with a nitrogen content of 0.35%.

Example 3

The procedure is as in Example 1, except that spruce sawdust is used as the starting material to activate 28 1% aqueous potassium hydroxide solution at 30 ° C for 2 h. For alkylation, 31 L of a 50% aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride was used at 70 ° C for 1 h.

The reaction is stopped by adding 36 L of 96% ethyl alcohol. The modified sawdust was washed with 70% aqueous ethyl alcohol until neutral to phenolphthalein. Water-soluble cationic hemicelluloses are obtained by extracting modified sawdust with water at a hydromodule 1:10 for 2 ih in an 11.8% yield with nitrogen content, 1.9% and alkali-soluble cationic hemicelluloses by extracting the residue with a 10% aqueous potassium hydroxide solution. 9% with a nitrogen content of 0.95%.

The lignocellulose residue has a nitrogen content of 0.21%.

Example 4

The procedure is as in Example 3 except that a mixture of foliar and coniferous sawdust is used as the starting material to activate 19.5 L of a 30% aqueous potassium hydroxide solution at 30 ° C for 30 minutes and to alkylate using temperature 40 ° C and time 4 h.

The yield of water-soluble cationic hemicelluloses is 10.6% with a nitrogen content of 2.08% and alkaline-soluble 14.7% with a nitrogen content of 0.66%.

The lignocellulose residue has a nitrogen content of 0.56%.

Cationic hemicelluloses are soluble in water and dilute alkaline solutions and have a nitrogen content of 0.8 to 2.0%, corresponding to a exchange capacity of 0.6 to 1.4 mmol per gram. They are characterized by the properties of a strong basic ion exchanger, by flocculated and adhesive properties. This allows them to be widely used in various technical applications, in the pulp, paper, textile, chemical and pharmaceutical industries.

Cationic hemicelluloses are useful as an additive in the manufacture of paper to improve some of the physicochemical and mechanical properties, to enhance the retention of fillers, glues, short fibers and anionic additives. They have reactive ink adsorbent properties and increased resistance to biodegradation.

Claims (1)

SUBJECT A process for the preparation of icathionic hemicelluloses, characterized in that the sawdust is activated with a 3.5 to 25% aqueous solution of sodium hydroxide or a 5 to 30% aqueous solution of potassium hydroxide at a temperature of 15 to 30 ° C for 30 to 120 minutes. Alkyl is a 10-50% aqueous solution of 3-chloro-2-hydroxypropyltrimethylvinylcarbonic ammonium chloride at 4a to 70 ° C for 1-4 hours at a sawdust weight ratio of sodium hydroxide or potassium hydroxide: alkylating agent of 1: 0, 3 to 1.5: 0.7 to 3.0 and from modified sawdust are obtained by extraction with water followed by a 5 to 10% aqueous sodium or potassium hydroxide solution.