US 2231953 A
Description (OCR text may contain errors)
Patented Feb. 18, 1941 UNITED STATES PROCESS FOR THE TREATMENT OF ORGANIC FIBROUS MATERIALS Charles Ruzicka, London, England, assignor to Celec Corporation Limited, London, England 7 No Drawing. Application July 9, 1938, Serial No. 218,479. In Great Britain April 13, 1938 2 Claims. (Cl. 92-17) This invention relates to a process for the treatment of cellulosic materials, for example, wood sawdust, shavings, esparto grass, jute, hemp, linseed straw, coconut fibre, bamboo, soya 5 bean stalks and like cellulosic materials, and it has for its object to produce a bleached cellulose product composed of cellulosic fibres by releasing the fibres of such materials by the removal of the contained binding agents such as resins and waxes so that a product is obtained consisting of loose cellulosic fibres and suitable for use in manufactures, for example, in spinning, in the manufacture of artificial silk, for plastics, transparent paper, and similar products.
The present invention is wholly concerned with a process which will separate the fibres composing a fibrous ceilulosic material, such as those set forth above, into a filamentary or like degree of fineness from which substantially all colouring matter has been removed and with little or no injury to the resulting fibres. Such process must not therefore be confused with processes used for the production of fibre pulp.
It is an essential in a process according to the present invention that the separation of the fibres shall be eifected in two stages without boiling in either stage, partial separation being effected in the first stage and final separation in the second stage, so that the dissolving of the 80 resins, waxes and other binding agents shall be effected without destroying the fibrous form of the main bulk of the fibres.
It is also an essential that the final removal of colouring matter shall be efiected after the 86 final separation of the fibres has been completed asby this means such removal will be facilitated, and, in consequence, damage to the fibres during this final stage may be obviated by reducing the time of subjection and/or the strength of the 4o oxidising agent which would otherwise be required for this purpose.
The process according to the present invention in its broadest aspect consists in firstly, eifecting partial separation of the fibres by the removal 45 of some of the resins, waxes and other binding agents by immersing the material in an alkaline salt in solution, for example, sodium carbonate 7 or caustic potash, said solution being at a temperature which is always below its boiling point, the
50 strength of the solution and the period of immersion being predetermined to produce the required' partial separation of the fibres without injuring the fibres, and then washing the partially fibres in water to free the same from the alkaline solution, secondly, immersing the washed and partially separated fibres in a dilute solution of sulphurous acid to complete the separation of the fibres by the removal therefrom of all remaining resins, waxes, and other binding agents, said solution also being kept at 5 a temperature which is below its boiling point the strength of the solution and the period of immersion being again predetermined to produce the required complete separation of the fibres without injuring the fibres, and again 10 washing the separated fibres in water to free the same from the sulphurous acid solution, thirdly subjecting the washed and separated fibres to an oxidising agent to effect final removal therefrom of colouring matter, and then 16 washing the oxidised fibres in water to free the same from the oxidising agent, the oxidised fibres being, if desired, afterwards dried. Referring more specifically to the temperature of each of the solutions it is to be noted that in practice 20 this temperature is maintained as close as possible to 100 C. without the solution being allowed actually to boil.
The material resulting from the third step in the process is, after washing in water and where a dry product is required, centrifuged to remove excess moisture and finally de-hydrated at suitable temperatures.
During each stage in the treatment the material is preferably gently agitated and the period of treatment in each stage is determined by several factors such as-the type of material which is used, the strength of the solutions employed, and as to whether a soft or a hard final product is required. The period of the second or intermediate stage, where an acid solution is employed, may be shortened by operating under pressure.
The following is an example of one way in which the process according to the present invention may be carried out in the treatment of wood or sawdust:
The raw material is treatedffirstly with a 7%% solution of sodium carbonate, and then by any suitable means freed as far as possible from the sodium carbonate solution adhering to it, after which it is washed, and either partly or completely dried by centrifugal machine at a moderate temperature. It is then treated at an increased temperature of about 80-100' C., with a 5% solution of sulphurous acid, and afterwards, again by any suitable means freed as far as possible from any of the solution still adhering to it. It is then once more washed and partly or completely dried at a moderate teml6.
perature. Finally, at the ordinary normal temperature, the material is treated with a solution of sodium hypochlorite following which it is again thoroughly washed and then carefully dried at a moderate temperature.
In the treatment of fibrous materials other than wood such,-for example, as esparto grass or-fiax straws I the following method may be adopted:
'A suitable crude fibre, such as esparto grass -or flax straws is treated for 9 hours with a 3% solution of caustic potash at a temperature of about 90-95 C., after which the mass is freed from thezliquor, washed and dried. The mass is then put into a saturated solution of sulphurous acid and heated at about 801-90" 0., for
16-18 hours when the same is again freed from alladhering liquor, washed and dried. The partially treated mass is then put into a 5% solution of sodium hypochlorite and left in it at the ordinary air temperature for 48 hours, after which it is again freed'from all adhering liquor, washed and dried.
What I claim is:
1. Process for-the production of a bleached cellulosic product, composed of separated fibres,
from wood in the form of sawdustor shavings which consists in firstly, efiecting partial separation of the fibres by the"removal of some "of the resins, waxes, and other bindingagents.
by immersing the material for approximately 9 hours in a il /2% solution of sodium carbonate,
said solution being at a temperature Just below its boiling point, and then washing the partially separated fibres in water to free the same from the alkaline solution, secondly, immersing the washed and partially separated fibres in a dilute solution of sulphurous acid for a period of 16-18 hours to complete the separation of the fibres by the removal therefrom of all remaining resins, waxes, and other binding agents, said solution also being at a temperature just below its boiling point, and again washing the separated fibres in water to free the same from the sulphurous acid solution, thirdly subjecting the washed and separated fibres to a bleaching agent to eflect' at a temperature of 90-95 C., washing the partially treated material in water to free the partially separated fibres from the caustic liquor,
immersing the mashed material for 16-18 hours in a saturated solution of sulphurous acid heated to a temperature of 80-90? 0., again washing the now'separated fibres in waterto free the same from the acid solution, then bleaching the separated fibres by. immersing the same in an unheated 5% solution of sodium hypochlorite for approximately 48 hours and flnallywashing and drying the bleached fibres.