CS240181B1 - A method of preparing cationic hsmicelluloses - Google Patents

Abstract

The invention relates to the preparation of cationically active hemicelluloses. The essence of the preparation is that the delignified wood material is activated with a 3.5 to 25% aqueous sodium hydroxide solution or a 5 to 3θ% aqueous potassium hydroxide solution at a temperature of 15 to 30 for a period of 3θ to 120 min. 40 to 70 °C for 1 to 4 h at a weight ratio of delignified wood material: sodium hydroxide or potassium hydroxide: alkylating agent 1: 0.3 to 1.5: 0.7 to 3.0 and are obtained from the modified material by extraction with water and a 5. to 10% aqueous solution of sodium or potassium hydroxide. The invention has applications in the pulp and paper, textile, chemical and pharmaceutical industries.

Description

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

The prior art processes for the preparation of cationic hemicelluloses are based on the interaction of alkanolamines and epichlorohydrin in an alkaline environment on hemicellulose preparations isolated from various sources such as waste liquors in a batch of wood, pulp processing / V3 pat. 3,832,313; US Pat. 3. Isolation of hemicelluloses from wood-based effluents, bleaching and pulp refinement, and pulp mercerization in the process of producing viscose fibers is energy intensive because of their low concentration in said solutions. Hercellulose is isolated from the wood mass by impregnating dilute alkali solutions only in very low yields, largely contaminated with lignin. Higher yields and purely hemicelluloses are only achieved after previous delignification. Of these reasons, hemicelluloses are not commercially available on a wider scale, their cost is many times higher compared to cellulose and starch and therefore disadvantageous for the preparation of derivatives.

The above-mentioned disadvantages are substantially eliminated by the proposed process for the preparation of cationic hemicelluloses, which is based on the use of a delignified wood material as starting material, which, after activation with a 3-5% aqueous sodium hydroxide solution or a 5-30% intrusion. with a solution of potassium hydroxide at a temperature of 15 to 30 ° C for 30 to 120 minutes, with stirring, alkylating with 10 to 50% aqueous or ethanolic solution of 3-Chloro-2-hydroxypropyltrimethylammonium chloride at a weight ratio delignified wood material or sodium hydroxide or potassium hydroxide: reagent 1: 0.3 to 1.5: 0.7 to 3.0 at 40 ° C and for 1 to 4 h. The reaction is stopped by adding 0 to 96% aqueous alcohol and the modified material is washed with water or 70 to 90% aqueous alcohol until neutral, optionally neutralized with dilute aqueous hydrochloric acid.

- 2 240 181 wash solutions are concentrated to one tenth after concentrating. of an initial volume of cationic hemicellulose precipitated in a double volume of 96% ethyl alcohol and further washed with 70-90% aqueous ethyl alcohol and dried. Extraction with water and a 5 to 10% aqueous solution of sodium or potassium hydroxide is obtained from the modified wood material washed with ethyl alcohol.

An advantage of the proposed method of preparing cationic hemicellulosic pulp compared to other methods is that the present method is economically more efficient because it uses non-insulated hemicelluloses, present in holocellulosic-type pulp and other high-yield pulp, delignified cellulosic-delignified wood pulp. E. Timell: Adv. Carbohydrate Chem. 255 (1964)], yielding 70 to 90% of the present hemicelluloses with strong basic ion-exchange properties having a exchange capacity of 0.5 to 1.5 mmol / g by extraction with water and dilute alkali. , 1 to 0.5 mmol / g. The method allows the use of wastes from chemical and mechanical processing of wood, wastes from pulp production and from the processing of annual plants (corn cob, straw, etc.).

Example 1

Air-dry holocellulose beech sawdust (5 kg) with a hemicellulose content of 46.2% is activated by multiplying 41.3 l of a 3.5% aqueous sodium hydroxide solution with stirring at 15 ° 0 for 30 minutes. Then, with stirring, 7.5 L of a 50% aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride is alkylated at 40 ° C for 4 h. After this time, the modified holocellulose is filtered off and washed with water of the post-neutral reaction, followed by 96% ethyl alcohol and free air drying. Cationic water-soluble hemicelluloses are precipitated from the aqueous solution after concentration to one-tenth of the original volume by addition of twice a volume of 96% ethyl alcohol, which is further washed with 70 to 90% aqueous ethanol and dried over phosphorus pentoxide. Their yield is 19.7% with a nitrogen content of 0.86%. Subsequent extraction with 5% aqueous sodium hydroxide in a 1: 10 hydromodule for 2 h gives alkali-soluble cationic hemicelluloses in a yield of 11.2% with a nitrogen content of 0. , 64% · Cellulose residue has a nitrogen content of 0.15% ·

Example 2 240 ιβι

The procedure is as in Example 1 except that a semi-pulp having a hemicellulose content of 14.0% is used as the starting material, which is activated with 6.4 1 of 5% aqueous potassium hydroxide solution at 30 ° C for 120 minutes and subsequently alkylated 37.5 L of a 10% aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride at 60 ° C for 4 h. The reaction is stopped by adding a 5% aqueous hydrochloric acid solution to the neutral reaction. The yield of water-soluble cationic hemicelluloses is 9.6% with a nitrogen content of 1.04% and alkali-soluble 2.5% with a nitrogen content of 0.74% · The cellulose residue has a nitrogen content of 0 30

Example 3

The procedure is as in Example 1 except that the starting material is holocellulose spruce sawdust with a haemicellulose content of 45.9% which is activated with 4.9 l of a 25% aqueous sodium hydroxide solution at 15 ° C for 2 h and alkylated 31 L of a 50% ethanolic solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride at 70 ° C for 1 h. The reaction is stopped by adding 65 L of 96% ethyl alcohol, washing the modified material to neutral with 80% aqueous ethyl alcohol. hydromodule 1: 10 for 2 h to obtain water-soluble cationic hemicelluloses in the extract

21.5% and a nitrogen content of 2.3%, followed by extraction with 10% aqueous potassium hydroxide solution, after alkali dialysis and lyophilization, 14.4% of alkali-soluble cationic hemicelluloses are obtained, with a nitrogen content of 0.85% · The cellulose residue has a nitrogen content of 0, 45% ·

Example 4

The procedure is as in Example 4 except that the starting material used is holocellulosic wood sawdust mixture with a hemicellulose content of 43.8% which is activated with 19.5 L of a 30% aqueous potassium hydroxide solution at 30 ° C for 30 minutes and alkylated at 60 ° C for 2 h. The yield of water-soluble cationic hemicelluloses is 20.8% with a nitrogen content of 1.43% and the alkali-soluble cationic hemicelluloses are 19.8% with a nitrogen content of 0.78%. The cellulose residue has a nitrogen content of 0.32% ·

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The cationic hemicelluloses are soluble in water and dilute alkaline solutions and have a nitrogen content of 0.5 to 2.0%, corresponding to a exchange capacity of 0.3 to 1.5 mmol / g. They are characterized by strong base ion exchangers, flocculation and adhesion properties. This allows them to be widely used in various technical applications in the pulp and paper, textile, chemical and pharmaceutical industries. Cationic hemicelluloses are useful as an additive in the manufacture of paper to improve some of the physical-mechanical properties, to increase the retention of fillers, glues, short fibers and anionic additives. They have the properties of reactive ink adsorbents and have increased resistance to biodegradation.

Claims (1)

The process for preparing cationic hemicelluloses, characterized in that the delignified wood material is activated with 3.5 to 25% aqueous sodium hydroxide solution or 5 to 30% aqueous potassium hydroxide solution at 15 to 30 ° C for 30 to 30 ° C. 120 minutes of alkyl is 10 to 50% aqueous or ethanolic solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride at 40-70 ° C for 1-4 hours at a weight ratio of delignified wood material: sodium hydroxide or hydroxide potassium: alkylating agent 1: 0.3 to 1.5: 0.7 to 3.0 and from the modified material are obtained by extraction with water and 5 to 10% aqueous solution of sodium or potassium hydroxide ·