US1998389A - Process for improving cellulose - Google Patents

Description

P 16, 1935 I Q 1,998,389

UNITED STATES PATENT OFFICE Emil Scheller, Lorsbach in Taunus, Germany No Drawing. Application November 12, 1930, 'fgrgal No. 495,301. In Germany November 23,

4 Claims. (Cl. 8-2) In my previous patent application S. N. 477,191 white it is necessary to carry out a more energetic I have applied for a process for improving cellualkali treatment in order to produce a high conloses, which allows of obtaining products having tent of alpha cellul se- The Working eenditlens particular properties, such as for instance a high should, therefore, be naturally arranged to obdegree of bleach, high or adjustable content .of tain the most suitable action according to the na- 5 undecomposed alpha-cellulosesmall content of ture of the cellulose employed. ash, and low copper number. Following the caustic alkali boil, the material The process of my invention SerialNo. 477,191 is washed out thoroughly and then subjected to consists essentially in this that the cellulose to be the oxy bleaeh- It has been found that the 10 treated is subjected successively to a treatment. quality of the product obtained, and more par- 10 with chlorine, an alkaline treatment at increased ticularly the viscosity of Solutions of this product temperature, preferably with exclusion of elewhich are made, for example, by dissolving the mentary oxygen and a treatment with active oxy- P u t a ter treatment in carbon bisulphide p en or with or without unrestricted admission of Sodium hydroxide in emmenieeal pp 80111- air, whereupon the process is terminated by acidie, y be varied to a considerable extent y 15 tying the material. By elemental oxygen 7 is regulating the amount of molecular or elemental meant oxygen in the gaseous state. By active xy n P nt dur n he l h n process, as oxygen is meant oxygen existing in combined by x ludin m al xy tir y or ad tform in oxidizing agents, such as metal peroxides, ting Varying quantities theIeOf- This regulation hydrogen peroxide and other well known oxidizhe oxy n pr i pe l y imp nt d r- 20 ing agents. This combined oxygen is readil ing the bleaching with the alkali metal peroxides.

leased from the oxidizing agent during the course If h l m y xy n is n irely absent durofthe process, and is available for use in the ing this treat Stage, a P c giving Solutions process. Active oxygen is sometimes known as of V y h Viscosity is produced, 011 the Other nascent oxygen. hand, to obtain solutions of varying viscosity, as 25 According to the process of my earlier'appllcais sometimes desired, measured amounts of oxytion, Serial No. 477,191, the cellulose is subjected s n may be nt n a y t du d. to a treatment which is, in brief, as follows: Alkaline solutions of y n p oxide-ob- The cellulose material is first bleached in the ta d om Sodium p roxide, are the most adusual manner by the use of a chlorine bleach. Ventegeeus Sources active y The'amount 30 v The quantity of chlorine here employed can adof S m peroxide employed Will in al range vantageously be less than that which is usual in from 1 t0 0f the Weight 01 the goo the art. This results in obtaining an article which, This is a summary of the process dieeleeedin, is bleached from to whit my earlier. application. I have now made fur- The material is then thoroughly washed, and ther investigations and have improved this earlier 35 afterward is subjected to a treatment with an P ss. These subsequent experiments have alkaline solution at ordinary or increased presshown that it is advantageous to precede the sums and 'at high temperatur Air should be treatment of the material with chlorine, by an excluded during this treatment, for example, the ,alkaline treatment at increased teknpele-ture 40 prgcess may be carried out, in an autoclave. In which in this'case also is carried out with or 40 general, the highest content. of alpha cellulose is Without the exclusion of e ent y oxy en. This obtained by the use of sodium hydroxide, o preliminary treatment may I consist in boiling can, however, use sodium carbonate, lime, or a e material at Ordinary 0 increased Pressure 5 mixture of the two. The quantity of alkali emin alkaline lye, preferably a caustic alkali lye.

ployed will depend upon the quality of the cello- The subsequent treatment with chlorine is preflose and is preferably so limited that immediately erably i the form of Partial h, for an e after the boiling process the liquor still gives an in such a way that the quantities of chlorine actalkaline reaction. Ordinarily, 5 to 10% of caustic ing upon the material are so restricted that for I alkali, based on the dry weight of the cellulose instance the bleach is only to whitef 5 will prove satisfactory. Boiling for longer periods I have also found that with this method of and at increased pressure increases the quantity treatment, an intermediate alkaline boiling, such i of alpha cellulose. In case the pre-treatment with as takes place according to the'said previous patchlorine has been longer than, is recommended, ent application Serial No. 477,191 between the [66 Le. if the goods are bleached more than V2 to chlorine treatment and the treatmentof the material with active oxygen, can if desired be dispensed with.

The present process enables the carrying out of the process with a smaller expenditure of bleaching media, products being obtained, which are equal to those of the said previous patent application or in some cases even have better properties. In other respects the working conditions of the previous patent application apply for carrying out the present process. This applies more especially as regards the exclusion or admission of oxygen from the air. For instance according to the desired viscosity properties of the finished cellulose, elementary oxygent may either be completely excluded or restricted or even unrestricted access given thereto.

According to the nature of the initial material and the particular requirements to be satisfied by the end product, one boiling in alkali may be sufficient or, if necessary, in addition to the alkaline preliminary treatment preceding the chlorination, a further boiling in alkali will be interposed between the treatment with chlorine and the oxygen bleach.

After bleaching, the goods are washed and acidified. This acidification is preferably carried to a point where the solution is weakly acid, as indicated by the Congo red acid reaction. This has a favorable effect in decreasing the ash content, provided the goods are subjected to a careful and thorough washing out afterwards. The latter part of this washing out is generally conducted in the presence of small quantities of alkali or ammonia.

It will be understood that the matter of regulating the time of bleaching, the temperature and the alkalinity will vary considerably according to the quality of the material with which one starts, and also according to the qualities which one desires to impart to the final product, and I, therefore, do not desire to be limited to the specific disclosures of this kind which have been given here largely by way of example. It must be understood that in art of this kind one necessarily must determineexperimentally certain features of the process which are inherently subject to variation.

By following the method herein described, I have obtained as an example a. cellulose with a content of 96.26% alpha-cellulose.

The improvement obtainable by the present Percent Consumption oi chlorine NmO, consumption-..

What I claim is:

1. A process for improving cellulose which comprises treating such cellulose with alkali at increased temperatures, thereupon partially bleaching the same with chlorine, subsequently completing the bleaching with an active oxygen containing substance capable of yielding hydrogen peroxide under the conditions of the process and then acidifying the material.

2. A process for improving cellulose which comprises treating such cellulose with alkali at increased temperatures in the presence of definite quantities of oxygen, thereupon partially bleaching the same with chlorine, subsequently completing the bleaching with an active oxygen containing substance capable of yielding hydrogen peroxide under the conditions of the process and then acidifying the material.

3. A process for improving cellulose which comprises treating such cellulose with alkali at increased temperatures, thereupon partially bleaching said cellulose with chlorine, then treating said cellulose again with alkali at increased temperatures, subsequently completing the bleaching with an active oxygen containing material capable of yielding hydrogen peroxide uncontaining substance capable of yielding hydrogen peroxide under the conditions of the process while regulating the quantity of elemental oxygen present, and then acidifying the material.

- EMIL SCHELLER.