JPH0340806A - Production of cellulosic fiber or film - Google Patents

Abstract

PURPOSE:To industrially and advantageously obtain the subject fiber or film by coagulating a cellulosic discharged substance dissolved in an alkaline aqueous solution into a fibrous form, etc., in an alkaline aqueous solution flowing in a specific direction, then washing and removing the alkali with hot water. CONSTITUTION:Alkali-soluble cellulose is dissolved in an alkaline aqueous solution (e.g. aqueous solution of NaOH) in 1.5-2.6N concentration to provide a discharged substance, which is then discharged into an alkaline aqueous solution in 0.01-1.0N and 4.0N to the saturation concentration flowing in substantially the same direction as the running direction of the aforementioned discharged substance at a temperature of 10 deg.C to the ice point and coagulated into a fibrous or filmy form. The alkali is then washed and removed with hot water at >=60 deg.C to afford the objective fiber or film. Furthermore, the alkali eluted with the hot water can be concentrated and reutilized as a solvent and the coagulant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an industrially advantageous cellulose spinning or film forming method.

[Conventional technology]

Cellulose has a regular structure and has as many as three hydroxyl groups per structural unit, forming strong hydrogen bonds. Therefore, it is easy to obtain a solution of cellulose with a high concentration suitable for spinning and film production. could not. Therefore, instead of dissolving cellulose as it is, a method has been adopted in which the hydroxyl groups are substituted to turn cellulose into a derivative, and the substituted groups increase the affinity with the solvent, thereby dissolving the cellulose. Typical spinning and film-forming methods include the viscose method using cellulose xanthate, and
This is a copper ammonia method via a cellulose copper ammonia complex. Spinning or film formation is possible by discharging a spinning stock solution in which these cellulose derivatives are dissolved in an alkaline aqueous solution into a non-solvent to form a filament or film. However, in spinning or film formation from these solutions, However, it is not sufficient to simply coagulate and mold the cellulose derivative; it is necessary to further regenerate it into cellulose using a regenerating agent. For regeneration, a regenerant such as sulfuric acid is unavoidably required in the spinning bath, but the acid used here and caustic soda as a solvent react irreversibly and are consumed. Such conventional methods for producing re-salted cellulose are extremely disadvantageous from an economical point of view.

In order to avoid the use of regenerants, a technique has been proposed in JP-A-60-42401 and JP-A-62-116601 in which a cellulose solution in which cellulose is dissolved without being derivatized is used as a spinning dope. Here, an alkaline aqueous solution of cellulose is used as a spinning dope. In this stock solution, cellulose is stably dissolved in an alkaline aqueous solution, and cellulose can be rapidly coagulated and precipitated only when it comes into contact with an acid such as sulfuric acid or hydrochloric acid or a concentrated inorganic salt aqueous solution. It has also been confirmed that cellulose coagulates when this aqueous solution comes into contact with an alkaline aqueous solution of an appropriate concentration.

However, the rate of coagulation by an alkaline aqueous solution is extremely slow, and therefore films can be formed by contacting with an alkaline aqueous solution in this concentration range for a long period of time in a stationary state, but it is not possible to form films continuously, such as by spinning or continuous film forming. It is extremely difficult to form fibers or films.

In addition, in JP-A No. 62-240328, a cellulose molded product with developed intramolecular hydrogen bonds is produced by coagulating cellulose dissolved in an alkaline aqueous solution in water, an alkali, or a neutral salt, and then neutralizing it in an acidic bath. It has been shown that it can be obtained. Although this publication refers to coagulating an alkaline aqueous solution of cellulose in an alkali, it is an essential condition that the coagulation is then neutralized in an acidic bath.

This is because not only a good molded product cannot be obtained by coagulation with alkali alone, but also stable molding itself is impossible. In the neutralization step using an acidic bath, the alkali used as a solvent and the acid in the acidic bath are consumed as salts. Therefore, recovery of alkali is not possible in this method.

As mentioned above, cellulose dissolved in alkali can be coagulated in alkali at a specific concentration and temperature range, but coagulation in alkali proceeds slowly, and coagulated cellulose immediately after coagulation is not yet sufficiently mechanized. It has no objective strength.

Therefore, in this state, if stress due to winding is applied,
Coagulated cellulose breaks due to its tensile stress or liquid resistance in the coagulation bath, making it impossible to continuously form it into fibers or films. To solve this problem, acids or salts have conventionally been used as coagulants to impart mechanical strength to coagulated cellulose that can withstand stress and bath resistance.

[Problem to be solved by the invention]

The object of the present invention is to use an alkaline aqueous solution of cellulose as a stock solution for spinning or film forming, and to use only the alkaline aqueous solution as a coagulant to produce fibers and films in an industrially advantageous manner without wasting alkali or acid. This is to provide a way to do so.

[Means to solve the problem]

The above purpose is to coagulate the extruded material of cellulose dissolved in an alkaline aqueous solution into fibers or films in an alkaline aqueous solution flowing in substantially the same direction as the traveling direction, and then wash and remove the alkali with hot water. This is achieved by a method characterized by:

Cellulose coagulated in an aqueous alkaline solution initially does not have sufficient mechanical strength, but by using a fluid aqueous alkaline solution as a coagulation bath, the liquid resistance applied to the coagulated cellulose is significantly greater than when using a static coagulation bath. small,
Moreover, since the tensile force from the winding part is not transmitted and is carried to the winding part together with the fluidized coagulation bath, almost no stress is applied to the cellulose at the beginning of solidification. It is inevitable that a certain amount of stress will be applied during the transition process from the coagulation bath to the winding section, but at that point coagulation has already progressed and the coagulated cellulose has the strength to withstand the stress.

As a normal wet coagulation bath, a static coagulation bath is used for -m, in which the yarn runs in a stationary coagulation bath and coagulation progresses. In this case, the discharged and coagulated yarn is pulled by the drive of the winding section, so as the traveling speed of the yarn increases, the liquid resistance acting between it and the coagulating liquid increases, and the winding Tensile stress acts. On the other hand, in the fluidized coagulation bath used in the present invention, the coagulating liquid itself flows from the discharge section to the winding section, and the discharged material flows along this flow to the winding section. Therefore, almost no tension is applied from the pick-up section to the yarn that is coagulating. moreover,
Since the solution flows in the same direction as the thread running direction, the relative speed difference between the running thread and the coagulating liquid is small and has little to do with the thread running speed. Therefore, the shear stress applied to the yarn is much smaller than the liquid resistance stress caused by the static coagulation bath.

Various types of fluidized coagulation baths are conceivable; for example, a vertical tubular coagulation bath that uses gravity to flow, which has been conventionally used in the production of regenerated cellulose, can be used.

The concentration of the alkaline aqueous solution that is the solvent is preferably 145 to 2.6N, and at this concentration, cellulose can be stably dissolved in a relatively high concentration. Further, as the aqueous alkali solution as a coagulant, an aqueous solution of an alkali metal hydroxide of the same type as that used as a solvent is used, and an aqueous solution of 0.01 to 1. O
N and 4. It is preferable to have a concentration equal to or higher than ONM and up to saturation concentration. At concentrations other than this, cellulose coagulation is slow;
Spinning and film forming speeds are severely limited.

It is desirable that the alkaline aqueous solution of natural cellulose be brought into contact with the coagulant at a temperature below 10°C and above the freezing point. Spinning and film formation are possible even when exceeding IO゛C, but the cellulose solution lacks spinning stability and thread breakage easily occurs at the nozzle.
The transparency of the film surface becomes poor. On the other hand, when the fiber is brought into contact with a coagulant (aqueous alkaline solution) at a temperature below io'c, stable spinning and film formation are possible for a long period of time, and the physical properties of the fiber and film are good.

The alkalis used in the present invention are sodium hydroxide, ligram hydroxide, potassium hydroxide and mixtures thereof.

To the alkaline aqueous solution as a solvent, add a small amount of acrylonitrile, carbon disulfide, urea derivatives, dithiocarboxylic acid or its alkali salt, etc. as a dissolution aid to the extent that it does not adversely affect the quality of the filament, in order to promote the dissolution of cellulose. There is no problem with that. However, in that case, it is necessary to measure and correct these residual concentrations when reusing the recovered alkali as a solvent.

The cellulose used in the present invention is so-called alkali-soluble cellulose that dissolves in alkali at high concentration at low temperatures, and is
Cellulose disclosed in No. 16601, for example, cellulose with type 2 crystals obtained by dissolving natural cellulose in a cupric ammonia solution, evaporating the ammonia, and then regenerating it with acid, natural cellulose is treated with a hydrogen bond-cleavable solution at high temperature and high pressure. Examples include type I crystal cellulose, which is obtained by holding the cellulose at the bottom and then rapidly releasing it into the atmosphere.

The cellulose concentration in the alkaline aqueous solution is preferably as high as possible from an economic point of view, but if the concentration is too high, it will cause handling problems such as increased viscosity and gelation, so it is usually 30 to 150 g/f. Used within the range of

In spinning or forming a film according to the present invention,
Ordinary wet spinning or film-forming technology can be used, and the cellulose solution is continuously discharged into a coagulation bath from a spinning hole or a film-like slit using a metering pump such as a gear pump or a metering extruder to form a fibrous or A method of coagulating into a film can be adopted.

The fiber or film coagulated in the fluid aqueous alkaline solution is washed with hot water to remove the alkaline content prior to winding. The higher the temperature of the hot water used, the more effective it is in removing alkali and cleaning.

Specifically, a temperature of 60°C or higher is used. The alkali dissolved in hot water can be concentrated and reused as a solvent or a coagulant.

〔Effect of the invention〕

According to the method of the present invention, the alkali solvent can be easily recovered, its loss is extremely small, and no other coagulant is consumed, making it extremely economically advantageous. In addition, the manufacturing process is also greatly simplified.

Further, the coagulated cellulose will not be broken due to liquid resistance in the coagulation bath.

The fibers and films obtained by the present invention have physical properties comparable to those obtained by acid coagulation, and also have thread physical properties close to those of recycled fibers obtained from viscose.

〔Example〕

Hereinafter, the method of the present invention will be specifically explained with reference to Examples.

Definitions of terms used in each Example and Comparative Example and their measurement methods are as follows.

The degree of polymerization was expressed as the viscosity average degree of polymerization calculated from the intrinsic viscosity number [η] measured value in a cadoxene solution using the W, Brown formula.

Solubility Sa is defined as follows. 10g cellulose
190g of 10% by weight sodium hydroxide aqueous solution of O″C
Stir to dissolve and leave at 0°C for 15 to 20 hours.
It is diluted 5 times with a sodium hydroxide aqueous solution containing 0° CIO weight %, and then the insoluble matter is separated and collected using a centrifuge, and its dry weight w (g) is calculated.

W.

Wo: Total amount (g) of cellulose contained in the 5-fold diluted solution applied to the centrifuge.

Polymerization degree 3 exploded using 30 kg/cJ of saturated steam
00 alkali-soluble cellulose (solubility index 5a = 98
%) 8g in a 2.25N NaOH aqueous solution 92°C at 4°C.
(concentration 8-14%) and filtered through two 350 mesh stainless steel screens at 4°C.
The solution was stored in a storage room and used as a spinning stock solution. Place the stock solution within 2 days of storage into a 400 d capacity cylinder kept at 4°C, and flow the alkaline aqueous solution at a constant rate of 30 m/r@in through the spinneret attached to the tip of the cylinder using a plunger. The mixture was discharged into a vertical tubular coagulation bath with a length of 1.0 m and spun. The coagulated cellulose fibers were separated from the alkaline aqueous solution at the outlet of the coagulation bath, wound around a metal roll with a diameter of 100 m, and washed by pouring hot water at 80'C. After washing, the yarn was pulled out from the three metal rolls, dried through a hot air zone, and then wound up.

The coagulating liquid discharged from the tubular coagulating bath was collected in a recovery tower, and after adjusting the alkali concentration, it was repeatedly used as a coagulant.

Spinning conditions: Spinning hole: pore diameter 0. lO φ x number of holes 50 Discharge linear speed: 30m/win Winding speed: 30m/rain Coagulation bath: 6.75N NaOH aqueous solution coagulant flow rate at 15°C: 30m/m1n (tubular coagulation bath length 1.om) Spinning and winding is carried out stably, and the obtained yarn has a tensile strength of 1.
It had an elongation of 5 g/d and an elongation of 12%, which was comparable to commercially available rayon.

A stock solution was prepared and spinning was carried out in the same manner as in Example 1. However, spinning was carried out by changing the coagulation bath NaOH concentration, the polymerization degree of cellulose, and the cellulose concentration in the solution over a wide range. Good spinnability and yarn properties were confirmed. The results are shown in Table 1.

Table 104 The same alkali-soluble cellulose 6 used in Example 1
g was cooled to 4'C to 2,5N Li01!
It was dissolved in 94 g of an aqueous solution, filtered and cooled in the same manner as in Example 1, and spun under the following conditions.

Spinning conditions: Spinning hole: hole diameter 0.08 mmφ x number of holes 100 Discharge linear speed: 5
m/min Winding speed: 5 m/min Coagulation bath: 8N Li aqueous solution coagulant flow rate at 15'C: 5 m/m1n (Length of tubular coagulation bath 1.0m) Physical properties of the obtained yarn include tensile strength 1. 5g/d, elongation 10
%Met.

1. Ammonia was released from a copper ammonia solution in which earthen cotton linter for sweetfish was dissolved, and then 4 g of cellulose (degree of polymerization 450), which was regenerated in sulfuric acid and washed with water, was added to 2. ON NaO
It was dissolved in 96 g of H aqueous solution at 4°C to obtain a stock solution for film formation. This stock solution was put into a 400ml plunger type extruder, and a length of 40mm and a width of 0.10M was attached to the tip of the extruder.
7, ON NaOH flows down in the form of a film from a nozzle with a slit-shaped opening into a vertical tubular coagulation bath with a length of 1 m.
While coagulating into a film, it was passed through a hot water washing bath and a hot air dryer and rolled up onto a roll.

The obtained film was strong and highly transparent, similar to cellophane.

The method of Example 1 was repeated. However, instead of the vertical tubular coagulation bath, a 1-length tube made of 6.75N caustic soda aqueous solution
The stock solution was directly discharged into the static coagulation bath of m. The discharged material was coagulated in the coagulation bath, but when the coagulated filament was applied to a wind-up roll in order to wind it up, the filament was immediately cut in the coagulation bath.

Claims (1)

[Claims] (1) The discharge material of cellulose dissolved in an alkaline aqueous solution is coagulated into a fiber or film form in an alkaline aqueous solution flowing in substantially the same direction as the traveling direction, and then the alkali is washed away with hot water. A method for continuously producing cellulose fibers or films.