JPS6189201A - Sedimentation of cellulose carbaminate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to a method for precipitating cellulose carbamate from an aqueous alkaline solution.

(Prior Art) Cellulose carbamate is an alkaline, water-soluble cellulose derivative that is a compound of cellulose and isocyanic acid. Cellulose carbamate! An alkaline solution of cellulose carbamate that can be spun or made into a film can be prepared using a precipitant bath in which the salt is precipitated from an aqueous alkaline solution.

(Problem to be solved by the invention) A solution containing sulfuric acid is usually used as the precipitant bath.

Cellulose carbamate is stable under acidic conditions and does not decompose during precipitation. Contacting an alkaline solution of cellulose carbamate with sulfuric acid causes the cellulose carbamate to precipitate while simultaneously neutralizing the sodium hydroxide and producing sodium sulfate.

Thus, the cellulose carbamine spinning process produces sodium sulfate as a by-product, which is low in price and does not bring benefits to the manufacturing process. Another major drawback is that it is extremely difficult to return the sodium hydroxide neutralized by lIJ acid to the manufacturing process.

Therefore, sodium hydroxide accounts for most of the raw material cost for this process. Accordingly, there has been a need for a precipitation process that does not produce undesirable by-products. In such a precipitation process, it is particularly desirable to be able to economically recover at least a substantial portion of the hydroxide tremes without the use of sintered mineral acids.

At the same time, the process must meet certain requirements regarding the quality of the fiber or film.
For example, the initial strength of the fibers produced by precipitation must be sufficient to withstand the strong external mechanical forces to which the resulting product is subjected during processing. In the fiber manufacturing process, for example, stretching gA fibers during the spinning process is an essential processing condition in order to obtain desired strength properties.

(Means and Effects to Solve the Problems) According to the present invention, fibers or Regarding the film 'JJ Q, 12) it was possible for rerose carbamate to precipitate from an alkaline solution in a very satisfactory manner.

According to the invention, therefore, it is possible to precipitate cellulose carbamate in a solution completely free of mineral acids. According to the method of the invention, salts are not produced which give rise to sodium hydroxide (NaOH), a by-product which is extremely difficult to regenerate economically. In summary, the present invention provides a method for easily recovering and reusing sodium hydroxide used for dissolving cellulose carbamate.

The method according to the invention for precipitating cellulose carbamates from alkaline solutions is characterized in that the precipitation is carried out in a solution containing an inorganic salt.

The use of a salt solution as a precipitant bath allows the recovery and reuse of the sodium hydroxide contained in the spinning solution. On the contrary, if ljf M is used, sodium hydroxide must be converted to sodium sulfate and etc. a must be introduced into the process. Sodium hydroxide occupies a high proportion of the raw material 1'i+cost, so the present invention has the effect of increasing the economic efficiency of the process.

Another feature and advantage of the present invention is that the chemicals described above can be recycled and recovered with great ease. especially,
The use of carbamate solutions is highly effective due to the easy recovery and recycling of the sodium hydroxide used to dissolve the carbamate. In principle, there is no need to be concerned about the high content of sodium hydroxide at the precipitation temperature. This can be achieved by withdrawing a source of sodium hydroxide from the precipitation side temperature and using it to prepare the cellulose carbamine M salt solution. In principle, no sodium hydroxide is consumed during the process, nor are other salts used.

In the method of this invention, the salt contained in the precipitation side temperature is non-salt. Almost all salts have some precipitating effect, but best results are obtained with carbonates, bicarbonates, chlorides, and sulfates. Acid salts such as can be effectively used as precipitants.

From the two points of view of fiber properties and chemical recovery, the best results are obtained when carbonates or sodium carbonate are used as the salt.

The salt requirement is determined, for example, by the salt used and its solubility characteristics at the temperature of use. If the salt content is too low, the precipitation rate of cellulose carbamate will be slow and the strength properties will be impaired.

When using sodium carbonate, the appropriate amount of salt at the precipitation side temperature is 10 to 300 to 30% by weight, or 20% by weight.
Above and most preferred is about 25% by weight.
When using a chloride as a salt, the suitability of the chloride at the precipitation side temperature is 1 to 30% by weight, preferably 20 to 30% by weight.
It is in the range of 30 times Q'lχ. When using sulfuric acid jn, the mDk of the sulfuric acid salt at the precipitation side temperature is 1 to 30%. Most preferably, it is in the range of 20 to 30 times ω2.

The salt grains are usually chopped to the required ω for the precipitation to take place very rapidly, and the resulting film or film can be spun and withstand the stretching process.
)9 The precipitant bath may contain, in addition to the inorganic salt, sodium hydroxide. If the content of sodium hydroxide is too high, the precipitation characteristics of the precipitation side temperature will be reduced, so care must be taken. Therefore, in the case of continuous processing, it is necessary to control the amount of sodium hydroxide so that it does not exceed a predetermined value, and it is necessary to constantly remove the excess amount of sodium hydroxide that enters with the spinning bath in which precipitation is carried out. .

In this invention, the temperature on the precipitation side is set to 6% by weight of sodium hydroxide or less, preferably to 4% by weight to prevent deterioration of the precipitation properties.

According to the present invention, in order to produce cellulose carbamine fibers by the conventional method and means of the Scouse method, both the fibers (1 & 1t) and the film are mixed, the cellulose carbamate solution is heated to the precipitation side temperature through the spinning protrusions. In the case of spinning and film production, the solution is extruded through a sulin-shaped nozzle to the precipitation side temperature. In this invention, since no acid is used at all, a low-cost material can be used for the ¥L holder.

In the process of the invention, the cellulose carbamate solution in which the precipitation is carried out contains 4 to 15 times a range of cellulose carbamate, and the suitable viscosity of the spinning bath is, as a rule, 5 to 5 ONs/m@2.

A suitable concentration of sodium hydroxide is 5-12% by weight.
is within the range of

After the precipitation is completed, the fiber or film is subjected to post-treatments such as washing and drying in a conventional manner, but since this point is not relevant to the gist of the present invention, the explanation thereof will be omitted.

Regeneration of the precipitation side temperature can be carried out in various ways.

For example, methods such as those disclosed in Finnish Patent Application No. 843813 and Finnish Patent Application No. 843814 can be used.

The method of this invention is described in detail in the Examples below.

(Example) In the examples described below, cellulose carbamate is a nitrogen-containing ω2. IX SDP approximately 300 is used.

Solutions A-D were prepared from cellulose carbamate. Its composition is shown in Table 1. The solution was filtered and deaerated by vacuum treatment.

The solution prepared in this manner was subjected to a spinning experiment.

Table 1 Solution Cellulose NaOH2nO Carbamine Carbonate Content Butrate Content % % Neem% Content % A 7.1 9 - -B
6.5 g □0g
-C6,59-- D6.8 9 2 E 7.4 9 1 -1
Solution E was spun into a precipitant bath containing 8% sulfuric acid and 20% sodium sulfate at room temperature. Experimental scale spinning equipment a (5
The spinning was carried out in a 100-hole nozzle with a diameter of 0.0 utl. The physical properties of the fiber thus obtained were as follows.

Titer 1.1 dtex, strength (
air conditioned) 2.2cN/d
tex, elongation 8%.

Wet module 11.4 cN/dtex 0 Example 2 Solutions A-D were spun at room temperature in an experimental scale spinning apparatus (50 um size 1 (with to-hole nozzle). The physical properties of the fibers obtained were as shown in Table II below.

Table [1 (Part 1) Solution Carbamate solution Cellulose Na011 ZnONa2CO3 Carbamate % % % % A 7.1 9--A 7
．． 1 9 - -8 6.5
9 0.9 -8 6.5
9 0.9 -0 6.5
9 - - [) 6.8
,．． 9 2E 7.4
9 1 - (continued) fill (part 2) Solution Precipitant bath Na2CO3% NaOH% Temperature ℃A
22.5 0.1 20A
20 20B 20
20B 24
0.4 72C203, 4-20 D 23 3-20E
25 2G (next page) 肚(Part 3) Solution Characteristic potency strength of carbamate
Degree of elongation Web 1- (air conditioned) 7dur dtex cN/dtex % cN/
dtexA 2.1 2.1 8
9A 2.3 1.9 9 4
．． 7B 1.5 2.0 8 6
．． 4B 3.0 1.8 7 5
．． 1C1,72,0711,4 [) 1.0 1.8 10-
-E 1.1 2.0 7 8.
7 The test was carried out in Example 1, in which the method of the present invention was carried out by acid precipitation.
11. Results comparable to those of the product were obtained.
It shows.

Cellulose carbamate 10. lfi%, NaO
A carbamate solution containing 1% H9i was prepared.

Precipitation was carried out in a laboratory scale spinning apparatus similar to Examples 1-2 at a temperature of 42-44°C. The precipitant bath contained 26% sodium chloride.

This is how it was obtained! ! The physical properties of miscellaneous objects are as follows. Titer 2.7 d
tex.

Strength 1.5 cN/dtex, elongation 7%, wet module 8.1 c14/dtex 0 Example 4 A carbamate solution containing 7.4 mff1X of cellulose carbamate Ju and 10 parts of sodium hydroxide was prepared. Fibers were spun from the solution using a pilot plant of a spinning device (spinning projections were 5 (jum size, 100 holes). Spinning was carried out at room temperature in a precipitant bath containing 25% by weight of bisulfate. The physical properties of the fiber thus obtained were as follows: Titer 2.8 dtex;
Strength 2.1cN/dtex, elongation 4%, wet module 14 CM/dtex.

Example 5 Cellulose carbamate 6.5% by weight, Na0t
A carbamic acid 1N solution containing 19 fl, 2nOO, 9wt.X was prepared. From this solution, mm was spun at room temperature into an aqueous solution (containing 15.4% by weight of Ha Co and 3.1% by weight of Na1lCO ). The physical properties of the fiber thus obtained were as follows. Titar 0.99 dtex, strength 1.0 (l cN/dtOX, degree of concentration 11%, wet 7 Joules 12.4 cN/dtex 0) Example 6 A carbamate solution according to Example 5 was prepared, mm from the solution is aqueous solution (Na2CO3 12.9IfaX
, 4.4% Na1lCO, respectively). The physical properties of the fiber thus obtained were as follows.

Titer: 0.99 dtex, strength: 0.
86 CN/dteX.

Elongation 7%, wet module 12.5cN/dte
x 0 Example 7 Cellulose carbamate 6.6% by weight, NaOH 9%
A cellulose carbamate solution was prepared containing: From the solution the fibers were dissolved in an aqueous solution (NaHCo 3 7.0
%). ra obtained in this way
The physical properties of the fibers were as follows.

Titer: 1.08 dtex, strength: 0.
74 CM/dt (iX.

Elongation 11%, wet module 6.7cN/dte
x.

Claims (4)

[Claims] (1) A method for precipitating cellulose carbamate, which comprises, in precipitating cellulose carbamate from an alkaline solution, bringing the solution into contact with a solution containing an inorganic salt to precipitate cellulose carbamate. (2) The cellulose carbamate solution is spun into a solution containing one or more inorganic salts selected from the group consisting of carbonate, bicarbonate, chloride, sulfate, sulfite, and bisulfite. Claim 1 characterized in that
Method for precipitating cellulose carbamate as described in Section 1. (3) Cellulose carbamate according to claim 1 or 2, characterized in that the precipitant bath does not contain sodium hydroxide or contains up to 6% by weight of sodium hydroxide. precipitation method. (4) Claims 1 to 3 characterized in that the precipitant bath contains up to 30% by weight of sodium carbonate and up to 6% by weight of sodium hydroxide.
The method for precipitating cellulose carbamate according to any one of paragraphs.