CS205368B1 - Manufacturing process of viscose - Google Patents

Description

It is an object of the present invention to provide a process for preparing a reduced sulfur content of viscose, thereby substantially reducing the amount of sulfur-containing exhalates during processing of viscose to fibers, films, bast fibers, tapes and other products.

It is known that in the sulphidation process a significant proportion of the carbon disulfide used binds to the upper alkali of the alkali cellulose on a different sieve of the compound which is released as harmful sulfur pollutants during the coagulation and regeneration of the cellulose.

A conventional method for preparing viscose is generally known.

PodTa Dr. H. Sihtoíu and B. Nizovská, In the SI-NI process, a new process for the preparation of viscose is proposed by means of a multi-stage alkalinization process, the latter being carried out by adolescent sulphide, after previous pulping and pre-maturation of the alkali cellulose. The second alkalization is carried out with 9 to 1Γ wt. % sodium hydroxide solution to reduce the sodium hydroxide content of the alkali celluloses from the original 15.5 16.0 wt. % to 11.6 to 12.3 wt.

Similarly, the content of low molecular weight moieties, expressed as solubility number —NS (nwnber solubility), from 4.9-5.8 wt.% To 2.4-3.2 wt. in 10N NaOH solution.

205 368

205 368

Alkallo-cellulose of the stage SI-NI prooes allows to reduce the amount of carbon disulphide used in the sulphidation of alkali cellulose by 30 to 40% by weight. This is due to the fact that the prepared alkalio-cellulose after the second degree of alkalization has a lower NaOH content of up to 25% by weight, and the content of low molecular weight fractions is similarly reduced. Low molecular weight fractions. It is substantially more reactive than the other alkaline cellulose and, as a result, these proportions bind your peroxygen carbonate sulfide. The sulfidation process must therefore be conducted at higher temperatures and requires a shorter reaction time.

Viscose with a lower NaOH content can also be prepared with single-phase alkalization, but this possibility is related to the amount of carbon disulphide used. the lower the NaOII content of the alkali cellulose, the higher the amount of carbon disulphide used to prepare the xanthate to achieve the desired yiskose properties and be a good viscose filter.

Thus, the essence of the SI-NI process is a two-step alkalinization of the cellulose, whereby. dhuhý stu-. The foam, using a lower concentration of lye, is converted into a slurry of alkalicellulose, which is refined by pulping and subsequent pre-maturing of the products from the first alkalization step.

According to the present invention, the process for preparing viscose by two-stage alkalinization comprises providing alkali cellulose after the first alkaline pulp in the form of leaves is directly alkalinized in a second stage using an aqueous sodium hydroxide solution of 90-120 g / liter conentration without pre-pulping and pre-heating or other handling. The alkali cellulose is molded, pulped and preheated only after the second alkalization stage, and the pre-matured is sulfidated with a reduced amount of carbon disulfide and finally dissolves viscose.

The advantage of the proposed process for the preparation of viscose is that it is possible to use a conventional device, i.e. a viscose. The press is also applied in the second step of alkalization and the handle in the coating press needs to be handled. In the further processing of alkalloellulose, lower amounts of carbon disulphide are used and, as a result, viscose processing results in a proportional lower amount of exhalates.

If the method of the invention is used in a continuous alkali furnace, for example of the SUNDS type, the process is simplified because the compacted alkali cellulose after the first non-pulping is subjected to a further alkalization in the second stage and then sulphided after the stripping.

The first alkalinization is carried out in a batch molding machine in a conventional conventional manner, i. using a 210 to 240 g / l NaOH liquor solution at 18 to 22 ° C for 45 to 60 minutes. The prepared alkali cellulose is compressed and after the leaves have been reprocessed in the press, a second alkalization and a mixing bottle of 90-120 g / l NaOH are carried out at a temperature of up to 22 ° C for 15-45 minutes. After pressing and pulping, alkalloellulose is left

0 5 3 β 8 can be pre-matured in a conventional manner and the degraded alkalicellulose to the desired average degree of polymerization -PPS is sulfidated with a substantially lower carbon disulphide content at higher temperatures and in a relatively shorter reaction time.

In sulfidation, 17 to 40% by weight of carbon disulphide is then used at a temperature of 25 to 50 ° C. Sulfidation lasts up to 90 minutes, which is very advantageous especially in continuous sulfidation processes.

As mentioned above, the reduction in the amount of carbon disulphide used is conditioned by a lower NaOH content in the alkali cellulose after the second alkalization step after the corresponding alkalicellulose pre-maturation.

However, the results of the tests have shown that the alkali cellulose fractions are reduced only to a minor extent in order to reduce the content of carbon disulfide as well as to shorten the course of the sulfidation. This fact is also confirmed by the analytical values of alkalicellulose expressed in terms of hemicelluloses, resp. with an NS number of 2.4 to 3.2 wt.%, the alkalicellulose after double alkalization and after the corresponding pre-maturation has an NS of 3.2 to 3.8 wt. 6 to 2.4% by weight.

The alkali cellulose thus prepared is sulfidated with an amount of carbon disulphide corresponding to 18 to 27% by weight to alpha-cellulose at 30 to 45 ° C for 30 to 120 minutes.

In the following, several examples are given where the process of the present invention has been used.

Example 1

20 x 16 mm sheets of sulphite spruce pulp VL and V-2 containing 92% by weight alpha-cellulose were alkalinized at 20 ° C by dipping 230 g NaOH per liter for 60 minutes and then pressed to yield.

- The alkaline sample V-1 was pre-matured at 32 ° C for 25 hours in sheets in a sealed box. After pre-maturing, the alkalio-cellulose was alkalinized in a second step with a solution of 110 g of NaOH per liter at 20 ° C for 30 minutes. After pressing and pulping, the alkalicellulose had the following values:

alpha cellulose content 33.5% by weight

Na OH 12.1 wt.%

Sample V-2 was treated identically to Sample V-1, but immediately after the first alkalization was immediately followed by a second alkalization under the same conditions. The alkali cellulose was pulverized and pre-matured to achieve the following values:

*

205 300 alpha cellulose Ka OK

34,2 luno t. (by 12.0 ^l mass #.

After pre-maturing both samples were sulfidated using 22% by weight of carbon disulphide - calculated on alpha-cellulose - at 30 ° C for 90 minutes. Prepared samples of vasculosis mail these values:

sample number alkalicellulose solubility number before after fuzzing viscose viscosity in sec. gamma Value filtering factor KW V-L 2.77 76 49 126 V-2 1.97 3.49 91 44 237

Example 2

A sample of sulphite pulp V-1 to V-6 containing 92% by weight of alpha-oellulose was alkalized in a soaking liquor with a NaOH concentration of 280 g / liter at 20 ° C for 60 minutes.

Samples V-1 to V-4 after compression were pre-matured in leaf form at 30 ° C for 25 hours. Then, in the second stage, they were basified at the following concentration of NaOH:

V-1 90 g / l V-2 100 g / l V-3 lio g / 1 V-4 120 g / l

Sample V-5 and V-6 were basified immediately after the first alkalization in the second step in accordance with Example 1.

Samples V-1 and V-2 were sulfidated using 22 wt% carbon disulfide at 30 ° C for 60 minutes. Sample V-5 and V-6 were sulfidated under the same conditions but for 90 minutes. Prepared viscose from these samples mail 8.05% w / w alpha-oellulose and 6.47% w / w NaOH and the following values:

sample number alkalioellulose after pre-maturation of NaOH in% by weight NS vis viscosity in sec. k ó Sir wt.% z a gamma Value KW V-L 11.2 2.68 89 1.5 37 960 V-2 11.5 2.82 95 1.52 4 l 470 V-3 11.8 2.90 79 1.55 42 195 V-4 12.4 3.11 71 1.57 46 189 V-5 11.9 3.50 99 1.49 44 190 V-6 12.0 3.70 91 1.51 42 192

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Example 3

Sulfite spruce pulp samples V-1 to V-4 as in Example 1. were alkalinized according to Example 8.1. Samples V-1 and V-2 were pre-matured in the form of leaves, while samples V-3 and V-4 were pre-matured in the pad after the previous second alkalinization. The course of the second alkalization was the same as in Example 8.1. Sample V-1 and V-2 were sulfidated for 45 minutes and Sample V-3 and V-4 for 90 minutes. Other conditions of preparation were identical. The viscose obtained had an alpha-oellulose content of 8.10 wt% and a NaOH of 6.37 wt%. Fibers of the prepared viscose were prepared by conventional spinning and had a titer of 133 dtex.

Alkalicellulose had the following values:

sample number alkalicellulose after pre-maturation of NaOH in w / w NS v i s viscosity in sec. k ó Sir w. ^ z a gamma Value KW V-L 11.87 2.76 65 1.47 38 130 V-2 11.93 2.93 71 1.50 40 125 in-3 12.01 3.50 87 1.49 43 170 V-4 11.97 3.40 80 1.50 45 160

Fibers prepared from of these viscoses these parameters: sample 8islo titre in dtex fpk in cN / dtex rpm in $ fpm in cN / dtex cpm in V-L 134.2 1.82 17.7 0.70 22.0 V-2 133.7 1.87 17.2 0.74 21.0 V-3 135.1 1.80 15.8 0.69 20.7 in-4 135.3 1.72 16.7 0.66 21.2

Fpk is the strength of the conditioned fiber Fpm is the strength of the wet fiber £ pk is the ductility of the conditioned fiber Cpm is the ductility of the wet fiber

Example 4

Sulfite spruce pulp sample V-1 and leaf bucsulfate pulp sample V-2 were basified as described in Example 8.1. Both samples after the first alkalization were basified for the second time with the lamb, and after pressing they were pre-matured for 25 hours at 32 ° C. The alkali cellulose obtained had the following values:

V-1 alpha-cellulose 34.5 wt%, NaOH 12.0 wt%

V-2 alpha-cellulose 35.0% by weight, NaOH 12.1% by weight.

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The samples were sulfidated with an amount of 22% by weight of carbon disulfide, calculated on the alpha-cellulose content.

The sulfidation time in both cases was 90 minutes and the temperature was 32 ° C. The viscose of the classical composition was evaluated and spun as in the previous example. The following viscose and fiber values were obtained:

sample number alkalioellulose after decomposition of NaOH in wt. ⁰ / NS vis viscosity in sec. k ó sulfur hraot.% z a gamma Value KW V-L 12.0 3.5 99 1.51 43.5 170 V-2 12.1 2.7 63 1.50 37.7 375 Values obtained for fibers: sample titer dtex YPK he / dtex Cpk % BPM cN / dtex cpm % V-L 135.2 1.81 17.2 0.69 21.3 V-2 136.7 1.73 15.1 0.66 17.2

Example 5

The leaf samples of S-1 to V-8 from sulphite spruce pulp as in the previous examples were alkalinized two times in succession under the same conditions as in Example 3. From 29 to 21% by weight of carbon disulphide was used for alkali cellulose sulphide. The sulphidation was carried out for 90 minutes at 30 ° C. From the prepared xanthate, a viscose was prepared having a different composition of NaOH content in the viscose, but a constant alpha-oellulose content of 8.10 wt.%.

The following values have been obtained for viscose:

sample number consumption CS 'for sulphidation in mass% vis Sir wt. $ k ó NaOH bmot. ^ z a . KW the number of insoluble fibers in viscose in M / ml V-L 29 1.86 6.47 132 2-6 V-2 21 1.48 6.48 216 5-8 in-3 29 1.76 6.03 158 3-7 in-4 21 1.42 6.00 314 9-12 V-5 29 1.72 5.47 262 4-18 V-6 21 l, 4l 5.51 434 9-15 V-7 29 1.76 4.97 306 9-13 V-8 21 and, 4l 5.05 637 12-16

Example 6

On a pilot scale, viscose items were prepared using spruce sulphite pulp in the form of 30x40 sheets containing 92% by weight of alpha-oellulose, alkalinized in two stages in a conventional soaking press. The course of the first alkalinization was classical, consistent with Example 8 * 1. The alkali cellulose so prepared was subjected to the second stage alkalysis under the conditions of Example 8.1. In sulfidation, 22 wt. 5g CSg-translated for alpha-cellulose content. It was sulfidated at 30 ° C for 45 to 105 minutes. From the cellulose xanthate thus prepared, viscose was prepared and subjected to filter pans on a filter press using a commonly used lining, namely 2x flannel, 1x molino, 1x lawn. Viscoses had the following values:

sample number sulfur sulfide period gamma M e / h KW F number kg / m ⁴ M / ITA in minutes in weight% V-L 105 1.44 39.8 150 230 83.1 17-21 V-2 90 1.42 40.6 261 121 144.7 7-9 V-3 75 and, 4o 37.5 172 144 140.0 10-13 V-4 ⁶⁰ 1.36 36.8 143 312 80.1 18-24 V-5 45 1.30 34.7 114 463 52.3 22-30

M in g / hour is the flow rate of viscose

K Number of filter frit test in kg / m ²

M / ml is the number of undissolved fibers per ml. viscose

The filterability of the viscose from the filter press in said coating at a pressure of 0.6 MPa and an amount of viscose prepared from 6 kg of cellulose was in all cases below 30 minutes.

Claims (1)

SUBJECT OF THE INVENTION Process for the production of viscose by two-stage pulping of the pulp, followed by pre-maturing of alkali cellulose, sulphide and dissolving the prepared xanthate, characterized in that the second stage alkali cellulose is treated with an aqueous sodium hydroxide solution at a concentration of 0 to 190 g / liter.