JPS5826372B2 - Mesophase dope made of cellulose acetate and inorganic acid - Google Patents

Description

Detailed Description of the Invention The present invention provides a mesophase dope composed of cellulose acetate and an inorganic acid as a solvent for the mesophase dope, and a mesophase dope that loses its mesophase characteristics due to the hydrolysis action of the inorganic acid as a component of the dope. The present invention relates to a memphase dope in which the degree of polymerization and the degree of acetylation are lowered without reducing the degree of polymerization and the degree of acetylation and the dope viscosity is adjusted to a range suitable for forming into a spinning film, etc., and fibers and films produced from such a dope.

An object of the present invention is to provide a cellulose-based mesophase dope useful for producing novel mechanically excellent fibers and films and fibers and films having a novel structure.

Here, mesophase dope refers to a dope that is fluid with respect to the movement of the center of gravity of the molecules forming the dope, but exhibits elastic properties with respect to changes in the orientation of the molecules. This is different from dope, which exhibits flow birefringence due to shear force when a velocity gradient is applied, for example.

In other words, the dope exhibits clear interference colors even when observed with the naked eye without any external stimulation, or has the properties of a liquid and a solid that exhibits a bright field under crossed Nicols under a polarizing microscope. Dope, liquid crystal, optically anisotropic liquid, ordered liquid
is synonymous with

Therefore, fibers spun from such dopes will provide highly oriented yarns without going through a drawing process. polyamide hydrazide,
Many examples are known in which solutions or melts of aromatic polyesters, polyazomethines, etc. form mesophases.

flow! J (Flory), Proceedings
Of the Loiselle Society Series ((Pr.
oc, R, Soc, 5er), A234, 73 (19
56), l performs statistical treatment on hard particles and calculates the free energy of mixing by the number of moles, the axial ratio of solute molecules, and the disorientation.
We proposed a general expression as a function of coefficients and predicted the separation of optically isotropic and anisotropic phases at a critical concentration.

This phase separation is said to occur as a result of particle asymmetry, and the relatively small positive interaction energy significantly increases the concentration of the anisotropic phase.

In addition, polymers whose molecular chains have a certain degree of flexibility (Sem
For i-flexible polymers, the solution properties are said to be determined primarily by the length of the rigid segments between the bonds.

While it can be said that it is practically and theoretically supported that a specific solution of a polymer with a rigid molecular chain forms a mesophase, the flexibility of the molecular chain of a cellulose derivative is ,
This has been discussed since the time of Flo'J (Flory) and others.

However, these arguments could not be called accurate because they did not properly consider the effects of solvent removal.

Recently uploaded etc. 1J7-. Journal (Polym, Jo
urnal, 10, 4.409 (1978)) more accurately analyzed the solution physical property data of many cellulose derivatives and concluded about the flexibility of their molecular chains.

What should be noted is that, unlike vinyl polymers, cellulose derivatives have polar OH groups and Peter oxygen atoms in their molecules, depending on the degree of substitution, so the expansion of the molecular chain in an unperturbed state, and even The hardness varies significantly depending on the solvent used, and the hardness of its molecular chain is sufficiently stiffer than that of vinyl polymers.

Thus, it is fully expected that cellulose derivatives have the potential to form memphaze dopes in combination with specific solvents.

It has already been recognized that chitin, which has a similar structure to cellulose derivatives, forms a birefringent gel.
ture), Ldan'', supplementary 9.632 (1959)),
One proof of the foregoing is given.

JP-A-52-96230 also states that an optically anisotropic dope can be obtained by combining a cellulose derivative with a degree of substitution of 1 or more and a specific solvent therefor.

In this publication, it is stated that the selection of a solvent is the most important for forming an optically anisotropic dope, and organic solvents are mainly disclosed as such solvents. This is a natural consequence of the fact that the degree of substitution of the cellulose derivative disclosed in the publication is 1.0 or more.

According to what is known about cellulose chemistry, substituents,
In particular, it is well known that when the substitution of hydrophobic groups such as alkyl groups and ester groups with hydrogen atoms in the hydroxyl groups of cellulose increases, the cellulose becomes more soluble in organic solvents.

However, when dissolving cellulose derivatives using organic solvents, it is often difficult to obtain a homogeneous solution with partial gel formation, not to mention a high polymer concentration ( The above points become a major problem in the mesophase formation process that requires 15 weight φ or more, and not only is it extremely difficult to obtain a homogeneous molded product from such a dope, but it is also difficult to completely remove the organic solvent from the final molded product. It is difficult to do so, and it is common to experience quality problems.

On the other hand, the publication does not mention the memphase-forming properties of cellulose derivatives using inorganic acids as solvents, but does list several examples using inorganic solvents.

For example, hydroxypropyl cell o-7, (RPC
)/water, sodium salt of carboxymethyl cellulose (
CMCNa7 water, CMCNa/loading soda aqueous solution, C
MCNa/sodium chloride aqueous solution, cellulose sulfate sodium salt/water, etc. are listed.

However, most of these require a solid weight of polymer on a 50-weight plate for mesophase dope formation, and are completely unsuitable for actual molding.

Further, even when the solid weight is about 30 weight φ and the membrane phase dope is formed, the whole becomes pasty, and problems occur in spinnability and the like.

When a salt solvent or an alkaline solvent is used, in addition to the problems mentioned above, there is a possibility that fatal problems such as residual metal in the molded product and drainage may occur.

On the other hand, inorganic acids, which are not mentioned at all in the publication, are
Utilizing the depolymerization effect on cellulose, it has been applied to the production of pulp with various degrees of polymerization, but in general, the use of inorganic acids as solvents for cellulose derivatives is difficult from both an industrial and academic standpoint. It has been shunned.

Due to the sulfuric acid added as a catalyst during the production of cellulose acetate and cellulose nitrate, significant depolymerization of the polymer and residual SO ions in the resulting raw materials may cause gel formation in organic solvent solutions. In my experience in the cellulose industry, the use of inorganic acids has been frowned upon, and I have read Cellulose Parts I to M, which is a good summary of cellulose chemistry in general.
tJ~■,) Cellulose and Cellulose Derivatives Part IV + V (Celulosea
nd Ce1lulose Derivativecs
Part I%', V) [The above, E.Otto.

5purlin), co-edited by Interscience (Inte
Regarding the solubility of cellulose derivatives, even in the literature, most of the descriptions are about whether it is alkali-soluble, water-soluble, or organic solvent-soluble, but about the solubility of cellulose derivatives in inorganic acids. There is no debate at all.

It is no exaggeration to say that there has been no effort to discover the benefits of using inorganic acids in cellulose derivatives.

The basic principle of the present invention is the expansion of the molecular chains of various cellulose derivatives in their unperturbed state in various solvents;
Furthermore, based on a detailed analysis of stiffness, it is based on the truth that the molecular chain extension of polar polymers increases in a polar solvent in an unperturbed state, and when organic solvents and inorganic salts are used as solvents. Considering the disadvantages when using
As a result of intensive studies on the mesophase expression properties of cellulose and cellulose derivatives and solvents, we were surprised to find that, despite the difficulty of applying inorganic acids to cellulose derivatives, cellulose acetate dope using an inorganic acid/water system as a solvent has been widely used. The inventors have discovered that an extremely stable mesophase dope can be formed in a wide range of doping concentrations and a wide range of acid concentrations, leading to the present invention.

That is, the present invention provides an inorganic acid aqueous solution containing at least 5 weight φ of one or more inorganic acids, and at least one inorganic acid in this aqueous solution.
This dope is composed mainly of cellulose acetate present in an amount of 0 weight φ and exhibits mesophase properties without applying any external hydrodynamic force.

The cellulose acetate useful in the dope of the present invention can be prepared using Methods in Carbohydrate Chemistry.
Chem 1stry) Roy L. Leistler (
Roy.

Edited by L. Whistler, Academic Press, New York.
The amount of bound acetic acid defined by R.K., 1963) is 61.3%.
(DS=2.9) or less, and is essentially soluble in an aqueous inorganic acid solution.

The degree of substitution DS can be calculated from the amount of bound acetic acid (in %) D8-
It is displayed as 2,77× combined acetic acid ■102.4 one-mouth phase change 1.395.

Hereinafter, to simplify the explanation, the DS defined by the above equation will be used.

Since the solvent is an inorganic acid, a mesophase dope can be formed even if the degree of substitution of cellulose acetate is small (DS<1.0).

This fact is a feature not found in the mesophase system described in JP-A-53-96230.

The solubility of cellulose acetate in inorganic acid systems depends on its degree of polymerization and especially on its degree of substitution.

DS=2.9 is the upper limit of solubility in inorganic acids.

Moreover, it only dissolves in concentrated acids.

Furthermore, when the DS is 0.5 or less, it dissolves in acid aqueous solutions with a wide range of concentrations, from dilute acids to concentrated acids.

The degree of substitution of cellulose acetate is preferably 2.7 to 0.3 from the viewpoint of solubility of cellulose acetate in acids and ease of forming memphase dope.

The high solubility of cellulose acetate in inorganic acid systems is important in the production of mesophase dope, and it is necessary that cellulose acetate be dissolved at a concentration of at least 10 weight plates.

When the degree of substitution increases with cellulose acetate of the same degree of polymerization,
The concentration of polymers that exhibit mesophase in combination with certain types of inorganic acids generally decreases.

When using cellulose acetate with the same degree of substitution, as the degree of polymerization increases, the concentration of the polymer forming memphase decreases.

For example, for cellulose acetate with DS = 2.56, 65
When heavy duty nitric acid is used as a solvent, with DP=600,
The minimum polymer concentration for mesophase development is 10% by weight, whereas at DP=250, it is 30% by weight or more.

The average degree of polymerization (DP) of cellulose acetate is preferably 100 or more for use in molding from the dope of the present invention.

Inorganic acids useful in forming the mesophase dope of the present invention include nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, metaphosphoric acid, pyrophosphoric acid, hypophosphoric acid, sulfite, fluorosulfuric acid, chlorosulfuric acid, chloric acid,
hypochlorous acid, chlorous acid, perchloric acid, bromic acid, perbromic acid,
Hypobromous acid, hydrofluoric acid, thiocyanic acid, thiosulfuric acid, etc. are used, and nitric acid, sulfuric acid, phosphoric acid, hydrochloric acid, etc. are particularly preferably used from the point of view of economy, operability, etc.

In actual use, an aqueous solution containing at least 5 parts by weight of these acids is used.

However, the more preferred acid concentration is determined by the degree of substitution of cellulose acetate, the type of acid, and the memphase forming properties of the system.

For example, 1) in the case of cellulose acetate with S=2.57, a 25 to 75 weight φ aqueous solution of nitric acid and a 40 to 85 weight φ aqueous solution of sulfuric acid are suitably used as the solvent.

When using cellulose acetate with DS = 0.35,
5-75 weight with nitric acid, 20-98 weight with clear water solution φ
Aqueous solutions are suitable as solvents.

In general, in a mixture of an inorganic acid and water, the components present in the system change depending on its composition, and are not simply dissociated by water in their extreme state.

This point is considered to be different from a system in which water is mixed with an organic acid, and is probably one of the important factors for converting cellulose acetate having various degrees of substitution into mesophase.

In the present invention, the inorganic acid has a memphase forming ability either alone or as a mixture of two or more acids.

Since an inorganic acid is used as a solvent, the dope viscosity and degree of substitution can be adjusted as appropriate under certain temperature conditions without changing the characteristics of the existing mesophase dope.

For example, cellulose acetate (DP=300, DS2.
45)/Nitric acid (65% by weight) based mesophase dope containing 40% cellulose acetate has an initial viscosity of /2
It is possible to maintain the Menphase characteristic even if the temperature is reduced to .

Furthermore, since the degree of substitution can be adjusted, cellulose acetate having a different solubility from the cellulose acetate initially used can be molded.

For example, it is possible to produce a molded article having a novel structure and exhibiting organic solvent resistance from a mesophase dope made of acetone-soluble cellulose acetate and a 65 weight aqueous nitric acid solution.

The properties of mesophase doping can be determined by various methods.

Most of the dope of the present invention has a pearl-like appearance, which can be seen with the naked eye.

Moreover, when this is placed between a slide glass and a cover glass and observed under a polarizing microscope under crossed Nicols, a bright field is displayed without applying any shearing force, so it can be easily confirmed.

The concentration range of the polymer that characterizes the mesophase dope is determined from the viscosity-concentration plot of the dope.

FIG. 1 shows the behavior of cellulose acetate-65 weight polynitric acid system A with DP250 and D82.57 as a representative example, and the same cellulose acetate-acetone system B as a comparative example.

The dope viscosity was measured using a cone-plate rotational viscometer at a shear rate of 20 seconds and 1.5°C.

In system A, the dope viscosity begins to decrease rapidly in the concentration range where the menphase phase separation begins, and the dope viscosity increases again at the concentration where the separation is completed.

On the other hand, in the case of system B which does not form memphazes, the dope viscosity increases almost linearly.

Also, the visible transmittance-concentration plot qualitatively gives the mesophase formation concentration range, and it is observed that the dope transmittance increases once in the mesophase formation region.

The dope of the present invention can be produced in a gel-free, uniform state in a short time by stirring an aqueous solution of cellulose acetate and a suitable inorganic acid at room temperature or while cooling.

It is also possible to depolymerize and desubstitute the cellulose acetate in the memphaze dope thus obtained under appropriate acid species and temperature conditions to adjust the cellulose acetate to a desired memphaze dope.

In this way, the effects of memphaze dope, which is made of cellulose acetate and inorganic acid, are as follows: (1) The solvent is inexpensive and economical; (2) The hydrolysis action of the acid allows the dope to maintain its viscosity within a range that maintains the characteristics of memphase dope. Can be adjusted and is advantageous for molding. ■Relaxation time of the men phase is very long.
When stored under appropriate temperature conditions, it usually exists stably for several days to several weeks or more. ■Easy to handle and easy to recover the solvent because it basically has the ability to form mesophase with a single solvent. ■Fibers and films. When molded into molded products, the amount of solvent remaining in the molded product is much lower than that of organic solvent systems, and as a result, the purity and self-sufficiency of the molded fibers are excellent. Memphase dope can be produced, and new molded products with various performances can be produced. (2) New fibers and films with excellent mechanical properties (for example, strength) can be produced.

Fibers spun from such dopes can be obtained into highly oriented yarns without going through a drawing process.

A wide variety of things. These mesophase dopes can be formed into films and fibers with useful novel structures.

Air gap spinning is suitable for producing high strength cellulose acetate fibers.

In this method, the spinneret is placed 2±1 points above the coagulation bath on the horizontal plane.
．． The yarn is held at a position of 8 cr 11, and the yarn discharged from the spinneret is passed vertically into a coagulation bath, and then the yarn is run on pins in the bath and wound.

The coagulation bath temperature is preferably in the range of 0 to 15°C.

The coagulant is appropriately selected depending on the degree of substitution of the polymer and the type of acid, but alcohol, ether, water, acetone, and mixtures of these with inorganic acids and inorganic salts are preferably used.

Further, a film constructed from the dope of the present invention can be easily formed in a bath containing the above-mentioned coagulant.

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

Example 1 This example describes a polymerization degree of about 250 to 3 with various degrees of substitution.
Table 1 illustrates a mesophase dope made of a combination of No. 00 unfractionated cellulose acetate and an acid.

In this example, the dope was adjusted at 0° C. in order to maintain the degree of polymerization of the polymer.

In the table, the mark x means that the polymer is insoluble, the mark x means that the polymer is dissolved but does not form a mesophase, and the flow birefringence reaches a state extremely close to the formation of a mesophase.

Among those with high DS (22, 93), there were only examples showing flow birefringence, and none showing complete mesophase.

Example 2 This example uses commercially available cellulose diacetate (DS=2
．． Cellulose diacetate with various degrees of polymerization obtained by fractionating 56) using an acetone/ethanol system exhibits mesophase forming property.

Table 2 shows the minimum polymer concentrations required for mesophase formation using various acids.

Example 3 This example uses acetone-soluble cellulose acetate (DP
250, DS=2.57) and 60 wt.

In a 1 ton reaction vessel, 325 g of 60 weight polynitric acid and 175 g of cellulose acetate were stirred at room temperature to produce memphaze dope (35 weight).

The obtained dope was kept at 50°C for 30 minutes and then left at 0°C for one day and night.

After that, the spinning dope, which has been defoamed under reduced pressure, is
Dilute nitric acid/sodium nitrate aqueous solution (0 to 4℃) through a 0.5CrIL air gap from a 50-hole nozzle.
) was used as a coagulation bath for spinning.

The resulting yarn was wound up at 6077 Z/min, thoroughly washed with water as a bobbin, and then air-dried.

The physical properties of the obtained yarn are Den/T, S/T, E/Mi
-142/4.4/8.5/73.

Furthermore, the obtained fibers were insoluble in the cellulose diacetate and triacetate solvents examined for their organic solvent resistance.

Example 4 This example describes a fiber having a new structure than the mesophase dope made of a combination of cellulose heptanoacetate (water soluble) with a degree of substitution of 0.35 and 60 weight plate chloric acid described in Example 1. The manufacturing method is shown below.

The air gap (0
, 5CIfL), thoroughly washed with methanol/ethyl ether, and air-dried.

The obtained monofilament fibers had streaks almost perpendicular to the fiber axis, unlike conventional cellulose fibers.

Figure 2 shows a polarized light micrograph of the characteristic fiber (magnification: 52
0 times).

The physical properties of the obtained yarn are T-8/TE/M1
== 4.1/4/92.

(S'/d) (%) (S'/d) On the other hand, as a comparative example, spinning was carried out under the same conditions using 60% water instead of perchloric acid. No structure was observed.

The physical properties of the obtained yarn were T, S/T, E/Mi = 1.3 g/d/6%/17 P/d.

Furthermore, as a comparative example, the same operation was carried out using 100 weight φ trifluoroacetic acid as the organic solvent for the cellulose heptanoacetate.

However, 60 weight or more polymer was required to obtain the memphaze dope, and even after stirring for 15 to 20 hours, there was a large amount of undissolved portion, making it completely unsuitable as a spinning dope.

[Brief explanation of drawings]

FIG. 1 shows the relationship between the dope viscosity and the dope concentration that forms the mesophase. In the figure, A and B are cellulose acetate/65 weight eunitric acid system with DP=2501DS=2.57, and the same polymer/acetone system, respectively. FIG. 2 is a polarized light micrograph (side view) of a monofilament obtained from the cellulose heptanoacetate/perchloric acid system of Example 3.

Claims (1)

[Scope of Claims] A fluid comprising an inorganic acid aqueous solution containing at least 5 by weight of 11 or more types of inorganic acids, and cellulose acetate present in this aqueous solution in an amount of at least 10% by weight, and A molding dope that exhibits mesophase properties without applying any external mechanical force. 2 Inorganic acids include hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, metaphosphoric acid,
Pyrophosphoric acid, hypophosphoric acid, sulfurous acid, fluorosulfuric acid, chlorosulfuric acid, chloric acid, hypochlorous acid, chlorous acid, perchloric acid, bromic acid, perbromic acid, hypobromous acid, hydrofluoric acid, thiocyanic acid The molding dope according to claim 1, which is thiosulfuric acid.