DE1103282B - Process for bleaching natural or regenerated cellulose fibers or products made from them - Google Patents

Description

GERMAN

Patent 1,005,038 describes a process for bleaching cellulose-containing material with sodium chlorite. It is characterized in that the bleached material is treated for 3 to 25 minutes with a warm or hot aqueous solution of alkali or alkaline earth metal chlorites, which removes the excess solution, e.g. B. by pressing, and the bleached material is then expediently bleached without further supply of heat for a period of at least 20 minutes, advantageously 1 to 3 hours, in an expediently thermally insulated chamber. Another embodiment of this method is described in patent 1,008,701. It is characterized in that the impregnation of the bleaching material is made with the bleaching solution at ordinary or moderately elevated temperature and that the bleach goods after removal of the excess bleaching solution by steam heated to 100 ⁰ C and further bleached in this state in a thermally insulated chamber .

In the further development of this process it has been found that it is useful in bleaching natural or regenerated cellulose fibers, e.g. B. pulp, cotton, rayon or rayon, or made from them Products, e.g. B. fabrics, knitted fabrics or the like. It is advantageous that the temperature in the bleaching chamber to be kept at 95 to 100 ° C for the entire duration of the bleaching time. The bleached material should here are densely packed. Such a tight packing can be made, for example, by placing in regular Loop position can be achieved. But you can also wind the goods to be bleached into a roll and treat in this form in the chamber. This makes it possible to bleach with very good results to be completed in a short time without causing fiber damage despite the high temperature.

Maintaining the high temperature can be achieved by a good thermal insulation of the milling chamber. In most cases, however, it is advantageous to keep the temperature in the thermally insulated chamber at the desired level by briefly steaming.

The process can be carried out batchwise. It has particular advantages with continuous Working in which the material to be bleached is continuously passed through a suitable device.

It is known to mix cellulose-containing material, in particular paper, cellulose or cotton, with aqueous To bleach solutions of chlorites, this material first with an inactive solution of the Chlorite is added, whereupon the solution is activated by adding acids or by heat. The material to be bleached is not treated in the form of a block of goods or a fiber pack.

Method of bleaching

of natural or regenerated

Cellulose fibers or made from them

manufactured products

Applicant:
German gold and silver separator

formerly Roessler,
Frankfurt / M., Weißfrauenstr. 9

Wilhelm Hundt and Heinrich Hundt, Frankfurt / M.,
have been named as inventors

It is also known when bleaching cellulosic! Textile material to soak the bleached material with a solution of sodium chlorite, the excess To squeeze off the liquid and then to spend the textile material in a closed chamber, where it is in loose form is continuously treated with steam until the bleaching is done. The procedure of Invention differs from this known method in that a treatment with steam takes place at most intermittently and that the bleached material is present in dense form. This comes about you can use significantly lower amounts of steam and make better use of what is used

. · Chlorite.

example 1

Desized cotton fabric is passed in continuous strand or in continuous wide web by an apparatus, per the same with a cold or moderately heated, to a _pH value from 3.8 to 4.0 adjusted aqueous solution of 8 to 10 g sodium chlorite Liter, 2 g neutral sodium pyrophosphate per liter, 1 g fatty alcohol sulfonate per liter evenly soaked and

4-5 then by pressing or the like. Of the excess Liquid is freed in such a way that the wet content of the fabric after pressing 110% of the Dry weight of the same.

The fabric so impregnated with the chlorite solution then runs continuously over a Insertion device in a dust container insulated against heat radiation, in which there is a well-ordered and forms a densely layered block of goods that continuously moves through the dust container

109 538/530

and at its outlet end by peeling off the fabric is dissolved again.

This moving block of goods is in the first and second half or in the first, second and third third of its pack length by blowing into it heated by steam to a temperature between 95 and 100 ° C. The duration of the run of the block of goods is 30 to 60 minutes. An excellent bleaching effect is achieved during this time. The bleached material is then treated with cold or hot, possibly also alkaline Water washed out and this washing operation can also be carried out in a continuous way will.

Example 2

100 kg of a twisted raw cotton yarn to be impregnated uniformly with a cold or warmed and at a _pH value from 3.8 to 4.2 adjusted solution containing 10 g of sodium chlorite, 2 g of neutral sodium pyrophosphate and 2 g of a chlorite against resistant Contains wetting agent, and then dehydrated by pressing or suction down to a wet content of 100 to 120% of the dry weight of the bleached material. Immediately thereafter, the bleached material is placed in a container, suitably insulated against heat radiation, and arranged therein in such a way that it forms a block of goods that is as evenly dense as possible. Steam is blown into this block of goods for a short time, either centrally at one point or distributed over several points, so that the yarn pack or fiber block is heated to 95 to 100 ° C.

The brief flow of steam is triggered when the temperature inside falls of the fiber block to about 90 ° C one or more times within a total bleaching time of Repeated for 30 to 60 minutes. After a total exposure time of those in the yarn material If the chlorite is soaked for not significantly more than 60 minutes, the bleaching process has ended. The bleached goods, which show a very good bleaching effect, are then rinsed and dried in the usual way.

Example 3

Unbleached sulfate cellulose is continuously in a suitable device, for example a Dutch, with a cold or warmed solution of 10 to 15 g of sodium chloride per liter, which also with an addition of 1.5 g of neutral sodium pyrophosphate and with acetic acid on one pH is set to 4.0, mixed well and then to a moisture content of about 150 per cent pressed off. The one in this way with chlorite solution soaked pulp is then continuous

5. From the Dutchman such a bleach tower above ^ fed and discharged again at the bottom of the conical outlet part that there is always a large in the tower relatively dense pack of moist pulp located in passage from top to bottom. This fiber pack will

ίο on its way from top to bottom roughly in the middle. of the upper third, further flows through in approximately the center of the middle third and, if necessary also in approximately the center of the lower third with expanded steam concentrically such that the fiber pack has by and by a temperature of 100 ⁰ C.

This steam flow can be brought about by steam rings at suitable points are attached around the mantle of the tower

ao and from which the steam is blown concentrically towards the interior of the tower.

The passage time of the fiber material through the tower and thus the heat development should be 30 to 60 minutes. During this time, the pulp is bleached to a pure one and beautiful full white without damaging the cellulose material of the pulp.

Claims (2)

Patent claims: 1. Process for bleaching natural or regenerated cellulose fibers or made from them Products by soaking with aqueous activated, cold or possibly heated Solutions of alkali or alkaline earth chlorites and subsequent removal of the excess Bleached liquid, characterized in that the moist material is packed tightly passes through a damming device in which it is at one temperature for 30 to 60 minutes from 95 to 99 ° C, especially 98 to 99 ° C, is held. 2. \ ^r experience according to claim 1, characterized in that the temperature in the thermally insulated chamber is kept at 95 to 100 ⁰ C by brief steam treatment. Considered publications:
German Auslegeschriften No. 1005 038, 1 008 701; U.S. Patent Nos. 2,194,956, 2,195,302,
■ 2,395,305; British Patent No. 552 711.