DE1794251C3 - Process for the production of threads and fibers matted with titanium dioxide from copper oxide ammonia cellulose solutions - Google Patents

Description

over 160 160 10 - 144 to 144 10 - 128 to 128 10 - 112 to 112 20th 20th 96 to 96 20th 10 80 to 80 40 60 64 to 64 40 70 48 to 48 120 60 32 to 32 120 110 16 to 420 240

It is known that the TiO.yPigment used for matting purposes of spinning solutions should have a grain size of about 0.5 μ; so one uses the finest possible grain. Grain size fluctuations from 0.1 to 1 u are still permitted. The reasons for these requirements lie on the one hand in achieving perfect spinning solution filtration and on the other hand in the task of avoiding capillary thread breaks and the resulting defects such as poor running, reduced tear strength and increased wear of thread guides, take-off rollers and deflection rollers, etc. For these purposes the TiCX pigment must be able to be dispersed well in the spinning solution; flocculations, which for whatever reasons lead to the formation of the highly undesirable TiO ₂ conglomerates, are to be avoided as completely as possible. For viscose spinning solutions, a wide variety of methods have been proposed to achieve these goals. B. the pigment can be added during the defibration, or a TiO ₂ suspension can be prepared in water, which is then added to the spinning solution before the spinning process, and the pigment can first be dispersed in voscosis and this suspension can be used as a so-called s.- use, or the degree of dispersion of the pigment can also be improved by using ethylene oxide adducts as dispersants.

If you apply the known methods to the matting of copper oxide ammonia cellulose solutions in a corresponding manner, you will in most cases have to find that a more or less large proportion of the TiO ₂ pigment, despite all possible caution, is again in the form of the undesired TiO ₂ conglomerates are present. This also applies in particular to the method of working with an aqueous TiOy suspension which, in a certain phase of the preparation of the Cuoxam solution, e.g. B. is added to the solution before the addition of the activating liquor.

So were in an unfiltered spinning solution prepared according to a conventional procedure as well In the regenerated fiber, the following loads of coarse titanium particles per g of cellulose are counted:

By filtering the spinning solution before it is spun, only the coarsest particles are removed, while most of the mean particle sizes are retained in the rayon.

It has now been found that the deficiencies described above can be found in a surprising manner can be completely avoided if the pigmentation with TiOo in the production of the copper

carries out oxidammoniacceilulose spinning solutions in the following way:

The TiO ₂ pigment powder is kneaded in a weakly ammoniacal medium at pH lü.4 to 11.4, the resulting TiCX paste is whipped while adding electrolyte-free water to the "TiCX cream" at pH 9.9 to 10.6, which is then whipped decanted after a certain sedimentation time immediately before further use, then immediately diluted with soft water (about 300 mg / 1 NaHCO ^) to 5 to 25 times its volume and the very dilute "TiO ₂ milk" obtained with pH 9.2 up to 9.9 is added to the prepared solution in the stage »before the activation of the activating liquor«, this solution is then stirred at pH values above 13, the required activating liquor is added and the solution is further treated in a manner known per se. The spinning solutions matted in the manner described now differ in an advantageous manner from the spinning solutions matted by known processes in the unfiltered and filtered state due to the absence of the troublesome Ti0 ₂ conglomerates.

The distribution of the titanium pigment is so fine that the matted solution almost achieves the number of thread breakages of non-pigmented glossy solution. Furthermore, the running times of the filter presses covered with fine screen meshes are extended by a factor of 2 to 3 due to the lack of coarse agglomerates. This often eliminates the discontinuous and labor-intensive process of opening, cleaning and reloading the filter presses. In addition, every change of the filter press is associated with a deterioration in the spinning condition.
The following process example is intended to characterize the method more precisely.

example

8.3 kg of titanium dioxide powder (finely grained anatase modification) are kneaded with 2.701 electrolyte-free water (condensate) and 0.351 ammonia water (225 g / l NH ₃ ) in a Werner Pfleiderer kneader for at least 8 hours at pH 11.4 , where-

at the temperature in the closed kneader can rise to 60 ° C. The total amount of the paste obtained (11.2 kg) is then whipped with 40 liters of electrolyte-free water using a grinding intensive stirrer for 45 minutes at pH 10.6 to form a homogeneous "TiCX cream", which is placed in the V2A sedimentation vessel (clear width 400 mm, clear height 600 mm) for 480 minutes. After this time, an amount of 0.1 kg of coarse TiO ₂ conglomerates has deposited on the bottom of the vessel, from which the conglomerate-free TiGy cream is carefully separated by decanting and made up to 250 _{liters with soft water (approx. 300 mg / 1 NaHCO 3) immediately before further use} and mixed thoroughly. The highly diluted "., - milk" with pH 9.9 obtained in this way is then added to a prepared CuoxamcelluIose solution containing 820 kg of cellulose before the addition of the so-called activating liquor (80% sodium hydroxide solution) while the solution is continuously stirred with the help of a long funnel tube added so that the diluted TiO., - Mikh gets directly into the Cuoxamansatz. After a total stirring time of 6.5 hours at pH 13.4, the dissolution process of the cellulose is then completed in a manner known per se by adding the activating liquor to the batch with continued stirring; the subsequent working processes for the preparation of the solution are also known.

The following statistical observation material comparatively shows the qualitative improvements achieved according to the method described above on.

Particle size Number of coarse TiOi particles b) in copper per g of cellulose rayon - a) in unnoticed 10 μ Dope 18th 80 to 96 10 96 64 to 80 10 48 to 64 20th 32üis48 40 16 to 32 140

Compared to the values reported above, a very considerable reduction in coarse particles was achieved with the method of operation described in the example. The remaining coarse particles can be removed by simple filtration of the highly diluted ΤίΟ., - milk, e.g. B. by using a V ₁ AS fabric ^ .s No. 350, can be further reduced. By further diluting the TiO ₂ milk to z. B. 1000 instead of the 2501 given in the example above, an even greater improvement could be achieved.

In a corresponding experiment, only 14 TiO., - Tcilchen in the range from 16 to 32 μ were obtained counted. Öifenbar shows a more thinned ΤίΟ., - milk when it meets the strong one Electrolyte content of the alkaline spinning solution hardly

still tendency to flocculation and conglomerate bilijuimen.

Claims (1)

Claim
τ / -_ * ~ u. ~ .— -..- Ua ^ cfaiii ^ nf »ιτλγι TiO -mattier- V CU (UItUI 2.Ul llblSlvuuug »Sj» * ~. ~~ 2- ^loul th threads or fibers from copper oxide moniac cellulose solutions, characterized in that the spinning solution during Titanium dioxide pigment to be incorporated in their production in a weakly ammoniacal medium kneaded, whipped with water, sedimented and decanted and immediately before further use is diluted 5 to 25 times, the resulting titanium dioxide dispersion before the addition of the activating liquor to the spinning solution added and the spinning solution is spun into threads in a known manner. Particle size Number of coarse titanium particles
per g cellulose or 10 mg TiOs
a) in unfiltered b) in copper-> Ä Spinning solution Kunstselde W