JPH0324497B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to fibers and films made using cellulose dope. More specifically, the present invention relates to a novel method for dissolving cellulose, the resulting dope, and fibers or films produced by spinning the dope.

It is well known that fibers and films used in fields such as clothing, medical and industrial materials are manufactured from dope obtained by dissolving cellulose. Particularly representative are the viscose method and the copper ammonia rayon method. However, these methods have problems, such as the chemicals used are extremely harmful to the human body, and the waste causes pollution, requiring special treatment for disposal. This is extremely concerning.

On the other hand, cellulose is a naturally occurring abundant resource, and its usefulness is expected to increase in the future, unlike petrochemical industrial products for which it is expected that it will be difficult to supply raw materials in the future. Therefore, it is currently most desired to establish a novel method for producing cellulose fibers and films that is non-polluting and industrially suitable in place of the viscose method and the copper ammonia rayon method.

In order to use cellulose to produce fibers and films, it is necessary to dissolve the cellulose into a solution suitable for spinning. In addition to the viscose method and copper ammonia method, which are currently used industrially,
One of the methods known for a long time to dissolve cellulose is to use a hot solution of salts. However, hot solutions of these salts have not been adopted industrially for reasons such as hydrolysis of cellulose and inability to dissolve cellulose at a high concentration that would provide good properties suitable for molding. do not have.

The inventors believe that these salts are non-toxic and
Furthermore, we have completed the present invention as a result of intensive studies based on the viewpoint that if the above-mentioned problems can be solved, it can be fully adopted industrially by taking advantage of the advantage of being inexpensive.

That is, the gist of the present invention is as follows.

A dope exhibiting optical anisotropy composed of 5 to 20% by weight of cellulose and 95 to 80% by weight of a zinc chloride aqueous solution, and characterized in that zinc chloride accounts for at least 50% by weight in the zinc chloride aqueous solution. cellulose dope.

While maintaining a mixture of cellulose and an aqueous solution containing at least 67% by weight of zinc chloride at a temperature of 80 to 105°C, add water in an amount necessary to maintain the concentration of the aqueous zinc chloride solution at least 50% by weight. A method for producing cellulose dope, characterized by dropping it.

It is a dope composed of 5-20% by weight of cellulose and 95-80% by weight of zinc chloride aqueous solution,
Fibers and films obtained by wet spinning or aerial discharge wet spinning a cellulose dope in which zinc chloride accounts for at least 50% by weight in an aqueous zinc chloride solution.

An object of the present invention is to provide a cellulose dope that is suitable for molding and is economically superior, a method for producing the same, and a fiber or film made using the dope.

Although zinc chloride solutions of cellulose and their dissolution methods are known, cellulose solutions containing 5% by weight or more of cellulose, which has a relatively high degree of polymerization, are not known. Furthermore, regarding the dissolution method, since an aqueous solution containing 60% by weight or more of zinc chloride is dissolved while being maintained at 110°C or higher, depolymerization of cellulose occurs and the solution takes on a brown color. Since undissolved cellulose remains, it is unsuitable as a molding dope, and the amount of dissolved cellulose is usually as low as 2 to 3% by weight, making it extremely uneconomical for molding. The present inventors studied the above-mentioned concept and the drawbacks of the above-mentioned conventional techniques, and discovered a method for producing a colorless and transparent dope suitable for molding, which contains no undissolved cellulose and contains 5% by weight or more of cellulose, and has achieved the present invention. It has been reached.

That is, in the present invention, a mixture consisting of at least 67% by weight aqueous zinc chloride solution and cellulose is heated at 80 to 105°C.
Cellulose is dissolved by dropping an amount of water necessary to maintain the zinc chloride concentration of the aqueous zinc chloride solution at least 50% by weight while maintaining the temperature at .

In addition to _ZnCl2 , salts known to dissolve cellulose include LiI, LiCNS, and Ca.
(CNS) ₂ , Mg(CNS) ₂ KCNS, etc. Although aqueous solutions of these salts can also dissolve cellulose by the method of the present invention, economic efficiency and
ZnCl ₂ aqueous solution is the most suitable solution since it can dissolve cellulose at a higher concentration and provide a solution suitable for spinning. Preferably, the concentration of the aqueous ZnCl ₂ solution used in the first stage of cellulose dissolution is at least 67% by weight. If a ZnCl ₂ aqueous solution with a concentration lower than this concentration is used, dissolution with cellulose by subsequent addition of water will be insufficient, a large amount of undissolved matter will remain, and the resulting solution will lack stringiness suitable for molding, and undissolved matter will remain. It is extremely difficult to filter and is not suitable for spinning. A more preferably used concentration range is 75 to 85% by weight.

Next, cellulose is added to the prepared ZnCl ₂ aqueous solution. As the cellulose, natural cellulose such as cotton or pulp is preferably used, but regenerated cellulose or the like may also be used, and the cellulose is not particularly limited. The weight fraction of cellulose in the final spinning solution obtained by adding water to the mixture of 67% by weight aqueous ZnCl ₂ solution and cellulose is between 5 and 20%.
A solution with a concentration lower than this can naturally be easily prepared, but it is unsuitable as a dope for spinning because it lacks the spinnability and coagulation ability necessary for spinning. Moreover, at high concentrations, undissolved cellulose increases, making it unsuitable for spinning. In some cases, centrifugal force is used to uniformly permeate cellulose with a ZnCl ₂ aqueous solution, and in other cases, cellulose is immersed in a large amount of ZnCl ₂ aqueous solution and squeezed to a suitable concentration. The proportion of cellulose in the solution is determined by the average degree of polymerization of the cellulose used, and generally, the higher the degree of polymerization, the lower the concentration used. Especially when using cellulose with a number average degree of polymerization of 600 or more, the cellulose content is 5% by weight.
Flow birefringence appears in the above solution. This flow birefringence can be easily detected by placing the solution on a slide glass under the crossed nicols of a polarizing microscope, placing a cover glass on top of it, and applying shear stress by lightly pressing the cover glass. can be observed. Since this flow birefringence easily appears, the fibers obtained from the solution of the present invention are oriented without a drawing step, and fibers with suitable physical properties can be obtained. The appearance of flow birefringence at such a low concentration is also a feature of the present invention, and this is because there is almost no decomposition or deterioration of cellulose when it is dissolved. It is expected that the directionality will increase and flow birefringence will also occur more easily.

The most important feature of the present invention regarding cellulose dissolution is that the mixture of cellulose and an aqueous ZnCl ₂ solution of 67% by weight or more is maintained at a temperature range of 80 to 105° C., and then water is added dropwise. The holding temperature is preferably in the range of 90 to 100°C. At temperatures lower than this, it becomes difficult to dissolve cellulose,
If it is high, cellulose decomposition and deterioration will occur.
Further, the holding time at this temperature is usually between several minutes and 30 minutes. Extending the holding time may accelerate the decomposition and deterioration of cellulose. While maintained at this temperature, the morphology of the cellulose remains in the initially charged morphology. Partial dissolution may occur if the holding time is increased.

Next, water is added dropwise to a ZnCl ₂ aqueous solution containing cellulose maintained at a temperature range of 80 to 105° C., and the cellulose is rapidly dissolved by stirring.
The temperature of the water dropped is not particularly limited. The amount of water dripping excludes cellulose.
The concentration of _ZnCl2 aqueous solution is at least 50% by weight after dropping water, assuming no evaporation of water due to heating.
It should be done so that If the amount of water is large, cellulose cannot be completely dissolved.
A suitable amount of water to be dropped is set so that the concentration of the ZnCl ₂ aqueous solution excluding cellulose after dropping water is 60 to 75% by weight. By dropping this water, the cellulose is rapidly dissolved and a uniform, highly concentrated solution suitable for spinning is obtained.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 This example shows that a homogeneous solution can be obtained from commercially available cellulose.

A zinc chloride aqueous solution was prepared by dissolving 11 g of zinc chloride in 3 g of water. Add 1g of commercially available Leonia pulp to this
(DP=1200) was added and heated with a heater to raise the temperature to 98°C. After 3 minutes, 4 g of water at room temperature was added dropwise while stirring. Cellulose rapidly dissolved into a homogeneous solution. When this solution was observed under crossed nicol white light using a polarizing microscope, the visual field was dark and there was no undissolved material. They then applied shear force to the solution by pressing the coverslip with their fingers, causing the field to glow brightly and exhibit fluid birefringence.

Example 2 This example shows that a highly concentrated and uniform solution can be obtained by using centrifugal force.

Dissolve 11 g of zinc chloride in 3 g of water, add 12 g of commercially available Leonia pulp (DP = 1200), then put it into a centrifuge to uniformly penetrate the zinc chloride aqueous solution into the cellulose, and centrifuge for 10 minutes at a centrifugal effect of 1000. , applied centrifugal force. removed from the centrifuge
The mixture of ZnCl ₂ aqueous solution and cellulose was heated to 90° C. and held at this temperature for 5 minutes, after which 4 g of water at 25° C. was added dropwise with stirring. A clear, non-brown, homogeneous solution was obtained. This solution also showed flow birefringence under crossed Nicols under a polarizing microscope.

Example 3 This example shows that an aqueous ZnCl ₂ solution can be uniformly infiltrated into cellulose by squeezing to obtain a homogeneous solution.

A ZnCl ₂ aqueous solution was prepared by dissolving 100 g of ZnCl ₂ in 20 g of water. 2 g of commercially available Leonia pulp was opened and immersed in this. After standing for 1 hour, the cellulose was pulled up, excess ZnCl ₂ aqueous solution was removed by filtration, and the cellulose was sandwiched between filter papers and pressed at 50 kg/cm ² for 5 minutes using a tabletop press machine. Ta. When the cellulose was taken out and weighed, the weight ratio of cellulose/ZnCl ₂ aqueous solution was approximately 1/9. This was heated to 100° C. and maintained at this temperature for 3 minutes, and then 8 g of water was added dropwise while stirring to dissolve the cellulose and obtain a homogeneous solution.

Example 4 This example uses commercially available microcrystalline cellulose (DP=
250) shows that a highly concentrated homogeneous solution can be obtained.

10 g of ZnCl ₂ was dissolved in 2 g of water. 4 g of powdered microcrystalline cellulose was added to this aqueous solution. Next, this was heated to 95° C., and after being left for 3 minutes, 4 g of water at room temperature was added dropwise while stirring to dissolve the cellulose. The resulting solution was clear and homogeneous.

Example 5 This example demonstrates the production of fibers from solutions prepared from commercially available cellulose.

A zinc chloride aqueous solution was prepared by dissolving 110 g of ZnCl ₂ in 30 g of water. To this, 10 g of commercially available Leonia pulp (DP=1200) was opened and introduced. It was then heated and the temperature was maintained at 93°C. After this state was maintained for 5 minutes, 30 g of water at 25° C. was gradually added dropwise while stirring to dissolve the cellulose. A clear and homogeneous cellulose solution was obtained. From the weight measurement at this time, it was found that 20g of water evaporated during the dissolution process, and the weight fraction of cellulose relative to the total weight was
It had become 6.25%. When this solution was observed under crossed nicols using a polarizing microscope, the field of view glowed brightly when shearing force was applied, confirming flow birefringence. In the absence of shear force, the field of view was dark and there was almost no undissolved material.

Next, this solution was put into a screw-type small test spinning machine and spinning was performed. The spinning conditions were air discharge wet spinning with a winding speed of 20 m/min, a draft of 40, and an air gap of 3 cm. The coagulation bath used alcohol for primary coagulation and water for secondary coagulation, both at room temperature. The temperature of the spinneret and spinneret was also room temperature. The obtained fibers were oriented without a drawing step and had a birefringence Δn=0.0035. The tensile strength was 1.5 g/d and the elongation was 18%.

Example 6 10 g of an aqueous solution containing 95% by weight of K CNS was added to
Wood pulp prepared to 300% (gelatinization degree of 95% or more) 1
g were mixed and stirred at 85°C for 20 minutes. This and water
When 3.2 g was added and stirred, the cellulose rapidly dissolved. On the other hand, in a 72% aqueous solution of K CNS
Mix 1g of cellulose with 13.2g and heat to 120℃ for 30 minutes.
Although it was held for a minute, it swelled to a high degree, and some of it turned brown and became low in molecular weight and dissolved, but it was not possible to obtain a uniform dope.

Comparative Example 1 This comparative example shows that hot solutions of salts are unable to adequately dissolve cellulose at high concentrations without decomposing the cellulose.

This solution of 11g of zinc chloride dissolved in 3g of water is
It was heated to 100°C and 1 g of commercially available Leonia pulp was added, but no dissolution occurred. When the temperature was further increased to 120°C, cellulose decomposed and dissolved, forming a brown solution. However, the viscosity of the solution was extremely low, and significant cellulose decomposition and deterioration occurred, so that it could not be used as a raw material for spinning. This solution did not exhibit flow birefringence even when shearing force was applied under crossed nicols under a polarizing microscope.

Comparative Example 2 This comparative example shows that a solution cannot be prepared when the concentration of the initially prepared ZnCl ₂ aqueous solution is low.

A ZnCl ₂ aqueous solution was prepared by dissolving 8 g of ZnCl ₂ in 4 g of water. 1 g of commercially available Leonia pulp was added to this, and the temperature was maintained at 95°C. After 5 minutes, 4 g of water was added dropwise while stirring, but almost no cellulose was dissolved.

As described above, according to the present invention, a cellulose solution suitable for spinning can be obtained from a non-toxic and non-polluting salt aqueous solution, and fibers and films useful for various purposes can be produced, which will contribute to the future textile industry. It is very useful for the development of

Claims (1)

[Scope of Claims] 1. A dope exhibiting optical anisotropy composed of 5 to 20% by weight of cellulose and 95 to 80% by weight of a zinc chloride aqueous solution, and in which zinc chloride accounts for at least 50% by weight of the zinc chloride aqueous solution. % cellulose dope. 2. The amount of water necessary to maintain the concentration of the zinc chloride aqueous solution at least 50% by weight or more while maintaining the mixture of cellulose and an aqueous solution containing at least 67% by weight zinc chloride at a temperature of 80 to 105°C. A method for producing cellulose dope, which comprises dropping a cellulose dope. 3 A dope composed of 5 to 20% by weight of cellulose and 95 to 80% by weight of zinc chloride aqueous solution, and the zinc chloride in the zinc chloride aqueous solution is at least
Fibers and films obtained by wet spinning or aerial discharge wet spinning of 50% by weight cellulose dope.