JPS6340213B2 - - Google Patents

Description

Detailed Description of the Invention The present invention provides an acetoxymethylcellulose compound selected from acetoxymethylcellulose and acetoxymethylcellulose acetate;
The invention relates to a mesophase dope containing an inorganic acid, which reduces the degree of polymerization of an acetoxymethyl cellulose compound without losing the characteristics of mesophase by the hydrolysis action of the inorganic acid in the dope, and reduces the viscosity of the dope for spinning or manufacturing. Mesophase dope adjusted to a region suitable for forming membranes, etc., and
Fibers and films made from such dopes are also within the scope of this invention. An object of the present invention is to provide a cellulose-based mesophase dope useful for producing novel fibers and films with excellent mechanical properties. The term "mesophase dope" as used herein refers to a state in which the dope is fluid with respect to the movement of its center of gravity, but exhibits elastic properties with respect to changes in the orientation of the molecules. This means a dope that exhibits flow birefringence due to its flow characteristics when a shear force is applied to the dope in a hydrodynamic field, for example, to create a velocity gradient. different. In other words, mesophase dope means that the dope clearly shows interference color even when observed with the naked eye without applying any external stimulus, or shows a bright field under crossed Nicols under a polarizing microscope. It means a dope that has the properties of a liquid and a solid, and is synonymous with liquid crystal, optically anisotropic liquid, and ordered liquid. Therefore, fibers spun from such dopes provide highly oriented yarns without undergoing any drawing process. Many examples have been known in which solutions or melts of polymers with rigid molecular chains, such as synthetic polypeptides, aromatic polyamides, aromatic polyamide hydrazides, aromatic polyesters, and polyazomethines, form mesophases. Flory
Proceedings of the Royal Society Series [(Proc, R, Soc.Ser),
A234, 73 (1956)] conducted a statistical treatment of hard particles and proposed a general expression of the free energy of mixing as a function of the number of moles, the axial ratio of solute molecules, and the disorientation coefficient, At a critical concentration, we predicted separation of optically isotropic and anisotropic phases. 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 (semi-flexible
Polymer), the properties of the solution are said to be determined primarily by the length of the rigid segments between the bonds. In the case of polymers with rigid molecular chains like this,
It can be said that it is practically and theoretically supported that the specific solution forms mesophases. On the other hand, the flexibility of the molecular chains of cellulose derivatives has been discussed since the time of Flory et al. However, these arguments could not be called accurate because they did not properly take into account the effect of solvent leakage. Recently, etc.
Polym.Journal, 10 , 4409 (1978) more accurately analyzed the solution physical property data of many cellulose derivatives and reached conclusions about the flexibility of their molecular chains. What is noteworthy about this conclusion is that
Unlike vinyl polymers, cellulose derivatives have polar OH groups and heterooxygen atoms in their molecules, depending on the degree of substitution, so the spread of their molecular chains in an unperturbed state and, ultimately, their stiffness are affected by their use. It differs markedly depending on the solvent in which it is used, and the stiffness 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 mesophase 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 [Merche-sault et al., Nature, et al.
184, Suppl. 9, 632 (1959)], this provides one basis for the above conjecture. 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. The above-mentioned publication also states that the selection of a solvent is most important for forming an optically anisotropic dope, and mainly discloses organic solvents as such solvents. However, 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. That is, according to general knowledge of cellulose chemistry, it is well known that as the degree of substitution of substituents, especially hydrophobic groups such as alkyl groups and ester groups increases, solubility in organic solvents increases. However, when a cellulose derivative is dissolved using an organic solvent, it is generally difficult to obtain a uniform solution, often accompanied by the formation of a partial gel. Furthermore, in the process of forming a mesophase dope that requires a high polymer concentration (15% by weight or more), the above-mentioned gelation becomes a major problem. Therefore, it is not only extremely difficult to obtain homogeneous molded products from such dopes, but also difficult to completely remove the organic solvent from the final molded products, which often causes quality problems. By the way. On the other hand, the above-mentioned publication does not mention anything about the mesophase forming properties of cellulose derivatives when an inorganic acid is used as a solvent, but several examples using an inorganic solvent are given. For example, hydroxypropylcellulose (HPC)/
Water, carboxymethylcellulose sodium salt (CMCNa)/water, CMCNa/caustic soda aqueous solution,
Combinations such as CMCNa/sodium chloride aqueous solution and cellulose sulfate sodium salt/water are exemplified. However, in most of these combinations, the solid weight of the polymer must be greater than 50% by weight for the formation of the mesophase dope, and therefore, in practice, the production of molded articles from the dope requires no at all.
It is not suitable. Further, even when a mesophase dope is formed with a solid weight of about 30% by weight, the entire dope has a pasty appearance and has poor spinnability. Furthermore, when forming a dope using a salt-based solvent or an alkaline solvent, in addition to the problems pointed out above, there is a risk of residual metal problems in the obtained molded product and associated deterioration of the polymer. There is. On the other hand, inorganic acids, which are not taught or suggested at all in the above-mentioned publications, are applied to control the degree of polymerization of cellulose in pulp production and the like by utilizing their depolymerization effect on cellulose. However, in general, the use of inorganic acids as solvents for cellulose derivatives has been avoided from both an industrial and academic standpoint. For example, sulfuric acid added as a catalyst during the production of cellulose acetate and cellulose nitrate causes significant polymer depolymerization, and
SO ^2-4 ions remain in _the raw material thus obtained,
For this reason, there are problems such as gel formation in the organic solvent solution of the polymer. In the cellulose industry, which has had such experience, the use of inorganic acids for cellulose and cellulose derivatives has been considered to be avoided. In addition, Cellulose Part ~ Cellulose and Cellulose Derivatives Part ~ describes cellulose chemistry in general in extremely detail.
As mentioned above, even in Interscience co-edited by E. Otto and Spurlin, regarding the solubility of cellulose derivatives, whether it is alkali-soluble or water-soluble is discussed. , or all descriptions of whether it is soluble in organic solvents,
There is no discussion about solubility in inorganic acids. It is no exaggeration to say that there has been no effort to discover the benefits of using inorganic acids in cellulose derivatives. The inventors,
We conducted a detailed analysis of the molecular chain spreading and, ultimately, the stiffness of various cellulose derivatives in various solvents in their unperturbed state. Based on the truth that the spread of molecular chains increases, and considering the disadvantages of using organic solvents or inorganic salts as solvents, we conducted intensive studies on the mesophase development of cellulose and cellulose derivatives with solvents. As a result, surprisingly, a cellulose derivative dope with an acetoxymethyl group using an inorganic acid/water system as a solvent forms an extremely stable mesophase dope over a wide range of cellulose derivative concentrations and a wide range of acid concentrations. This discovery led to the present invention. That is, the Mesophase Dope of the present invention contains at least 10% by weight of acetoxymethylcellulose and at least one compound selected from acetoxymethylcellulose acetate (hereinafter referred to as an acetoxymethylcellulose compound), and 90% by weight or less of at least one compound selected from acetoxymethylcellulose and acetoxymethylcellulose acetate. Both contain an aqueous solution containing 5% by weight or more of one kind of inorganic acid, and are characterized by exhibiting mesophasic properties without applying external hydrodynamic force. The acetoxymethyl cellulose compound useful in the dope of the present invention is obtained by treating cellulose with a dimethyl sulfoxide/paraformaldehyde solvent at high temperature (60 to 60°C).
After introducing methylol groups into cellulose, acetic anhydride,
By carrying out a homogeneous reaction using methylene diacetate, ethylene diacetate, etc., and further using pyridine, sodium acetate, etc. as a reaction promoting catalyst,
It can be easily prepared. The degree of substitution of the obtained acetoxymethylcellulose compound (herein, it refers to the total number of acetoxymethyl groups and acetyl groups per pyranose ring of cellulose.Hereinafter, for the sake of brevity, it will be referred to as DS):
Method in Carbohydrate Chemistry
Roy. L. Whistler (Roy.L.Whistler)
Edited by Academic Press, New York.
(Academic press, New York, 1963) based on the evaluation method (neutralization titration method). The acetoxymethylcellulose compound usable in the dope of the present invention has a DS of 0.3 to 0.8 and is essentially soluble in an aqueous inorganic acid solution. The solubility of acetoxymethylcellulose compounds with a DS of 0.3 or less in inorganic acids decreases significantly,
Formation of mesophases is difficult. more than
Those with DS essentially form mesophases. However, if ideal mechanical strength of a molded article is expected, a material with a low degree of substitution as close to cellulose as possible is desirable. Furthermore, in consideration of ease of post-processing and regeneration, it is desirable to use an acetoxymethylcellulose compound that is economical and can use water as a solvent, and therefore is preferably hydrophilic. Furthermore, in the true sense, acetoxymethyl cellulose means one that essentially contains an acetoxymethyl group with DS≦1.0, and in other cases, the acetoxymethyl cellulose compound is acetoxymethyl cellulose acetate. In this sense, in the preparation of the dope of the present invention, the DS of an acetoxymethyl cellulose compound suitable for the present invention is determined from the solubility in inorganic acids, ease of formation of mesophase dope, and ease of post-processing and regeneration. is preferably within the range of 0.3 to 0.8. The high solubility of these acetoxymethylcellulose compounds in inorganic acids is extremely important in the production of mesophase dope. That is, in the present invention, the acetoxymethylcellulose compound must be dissolved in the dope at a concentration of at least 10% by weight. When acetoxymethylcellulose compounds having the same degree of polymerization are used, the range of polymer concentration that causes mesophases does not change much depending on the degree of substitution (0.3<DS<0.8), but largely depends on the type of inorganic acid. Also, when the degree of polymerization is changed, as the degree of polymerization increases, the range of polymer concentrations in which mesophases can be formed decreases. The range of polymer concentration at which mesophases develop in the dope varies depending on various factors and cannot be unambiguously determined, but it should be determined that at least 10 Polymer concentrations of % by weight or higher are preferred. More preferably, the polymer concentration is preferably 15% by weight in view of the production efficiency of molded products such as fibers and films and the degree of polymerization of the polymer used. On the other hand, considering the use of molding the dope of the present invention, it is desirable that the average degree of polymerization (DP) of the acetoxymethylcellulose compound is at least 100 or more. Also, if your DP is 1500 or more,
The expression concentration of mesophase dope varies depending on the degree of substitution of the polymer and the type of acid, but in most cases
Although the dope content is 15% by weight or less, the viscosity of the dope is as high as 20,000 poise or more.
It is difficult to use it for manufacturing molded products. Therefore, the DP of acetoxymethylcellulose compounds useful in the dope of the present invention ranges from 100 to 1500. 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, hypophosphorous acid, sulfurous acid, fluorosulfuric acid, chlorosulfuric acid, chloric acid, hypochlorous acid, chlorous acid, perchloric acid, bromic acid, perbromic acid, hypobromous acid,
It can be selected from hydrofluoric acid, thiocyanic acid, thiosulfuric acid, etc., especially nitric acid, sulfuric acid, phosphoric acid,
Hydrochloric acid and the like are preferably used in terms of economy, operability, and the like. In actual use, an aqueous solution containing at least 5% by weight of these acids is used. but,
A more preferable acid concentration is determined by the degree of polymerization of the acetoxymethylcellulose compound, the degree of substitution, the type of acid, and the mesophase forming property of the system. In general, in a mixture of an inorganic acid and water, the presence of acid components in the system changes depending on its composition, and the mixture is not always in its ultimate dissociated state in water. This point is considered to be different from a system in which water is mixed with an organic acid, and is also considered to be one of the important factors for converting an acetoxymethylcellulose compound with a relatively low degree of substitution into mesophase. In the dope of the present invention, the inorganic acid can be used alone or as a mixture of two or more kinds. In the present invention, since an inorganic acid aqueous solution is used as a solvent, the dope viscosity can be adjusted as appropriate under certain temperature conditions without changing the mesophase properties of the existing mesophase dope. For example, in a mesophase dope made of 45% by weight acetoxymethylcellulose acetate (DP = 580, DS = 0.63) and a 72% sulfuric acid aqueous solution, even if the viscosity of the dope is reduced to half of its initial value, Mesophase properties can be maintained. The mesophase properties of mesophase dope are as follows:
It can be determined by various methods. Most of the dope of the present invention exhibits pearl-like luster, which can be confirmed by visual observation. Furthermore, when this dope is placed between a slide glass and a cover glass and observed under a polarizing microscope with crossed Nicols, a bright field is observed without applying any shearing force, making it possible to easily confirm the development of mesophase characteristics. The concentration range of the polymer that characterizes the mesophase dope can be determined from the viscosity-concentration plot of the dope. In this case, the dope viscosity is
Shear rate using a cone-plate rotational viscometer
Measured at 200sec ^-1 and 5°C. In a system that expresses mesophases, the dope viscosity begins to decrease rapidly in the concentration range where the mesophase phase begins to separate.
At the concentration where separation is completed, the dope viscosity increases again. On the other hand, in systems that do not form mesophases, the dope viscosity increases almost linearly. Also, visible transmittance -
The concentration plot also gives the mesophase formation concentration range. That is, an increase in dope transmittance is observed in the mesophase phase formation region. The mesophase dope of the present invention can be produced by stirring an acetoxymethylcellulose compound and an aqueous solution of an appropriate inorganic acid at room temperature or while cooling.
It can be manufactured in a uniform state without gel in a short time.
It is also possible to depolymerize the acetoxymethylcellulose compound in the Mesophase dope thus obtained using an appropriate type of acid under appropriate temperature conditions to convert it into a Mesophase dope having a desired viscosity. . As described above, the mesophase dope made of an acetoxymethyl cellulose compound and an inorganic acid has a wide variety of advantages as described below. The solvent is cheap and economical. Due to the hydrolytic action of the acid, the viscosity of the dope can be adjusted to a desired value while maintaining the mesophase properties, which is advantageous in terms of molding. The relaxation time of mesophases is very long, and when stored under appropriate temperature conditions, the mesophase state usually exists stably for several days to several weeks or more. Since it basically has the ability to form mesophases with a single solvent, it is easy to handle and recover the solvent. When molded into fibers, films, etc., the amount of solvent remaining in the molded product is much lower than that of organic solvent systems, which improves the purity of the molded fibers, etc.
Excellent whiteness etc. Since it essentially uses water-soluble polymers, post-processing such as crosslinking and regeneration can
New molded products with various performances can be manufactured. The mesophase dope of the present invention can be formed into films and fibers having useful and novel structures.
Air gap spinning is suitable for producing high strength, high modulus fibers. In this method,
The spinneret is held at a position 2 ± 1.8 cm above the liquid level of the coagulation bath, and the yarn discharged from the spinneret is introduced vertically into the coagulation bath, and then the solidified yarn flows along the pins in the coagulation bath. Run the row and wind it up. Coagulation bath temperature is 0~15℃
A range of is preferred. Coagulant depends on the degree of substitution of the polymer,
Although it is appropriately selected in consideration of the type of acid, etc., alcohol, ether, acetone, a mixture of these and an inorganic salt, or an aqueous alkali solution is preferably used. Further, the film formed from the dope of the present invention can be easily solidified and 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 relates to a method for producing acetoxymethyl cellulose acetate with a degree of substitution of 0.6, and the production of mesophase dope by combining the obtained compound with various acids. 162 g of wood pulp with a degree of polymerization (DP = 900, evaluated from the intrinsic viscosity number [η] in cadoxene) was dispersed in a kneader with an internal capacity of 15 containing 5 dimethyl sulfoxide, 150 g of paraformaldehyde was added, and after sealing, 70 ~ Stirring was carried out at 90°C for 18 hours to obtain a clear homogeneous solution. The temperature of this solution was lowered to 40°C, 153 g of acetic anhydride and 118.5 g of pyridine were added thereto, and the mixture was reacted for 60 minutes. Next, 5 methanol was gradually added to the reaction mixture to stop the reaction. The resulting solution was mixed with 15 methanol under stirring, and the resulting white precipitate was separated and air-dried.The resulting solid was dissolved in water, reprecipitated with methanol, and air-dried separately. The desired acetoxymethyl cellulose acetate was obtained. The degree of substitution (DS) of this polymer is 0.60
The intrinsic viscosity [η] in formamide at 25℃ and the weight average molecular weight determined by light scattering method are
The Mw of the above compound determined from the relational expression with Mw is approximately
It was 400,000. The obtained polymer in heavy water
The C ¹³ -NMR diagram is shown in Figure 1. In this graph, there is a peak related to methylenedioxy groups at 85 to 91 ppm and a peak related to carbonyl groups around 170 ppm, indicating that the obtained polymer is acetoxymethyl cellulose acetate. The resulting polymer was dissolved at 0° C. in various acids at various concentrations as shown in Table 1 to form dopes. [Table] All of the obtained dopes exhibited mesophase properties. Example 2 Mixtures of acetoxymethylcellulose and acetoxymethylcellulose acetate with various degrees of substitution (DS) were synthesized by changing the amount of acetic anhydride added and the reaction time using the method described in Example 1 (the degree of polymerization DP of the raw material cellulose) 500) Dopes were prepared in combination with various acids as shown in Table 2. All the obtained dopes showed mesophase properties. [Table] Example 3 This example describes a mesophase dope of acetoxymethyl cellulose acetate (DS = 0.60, Mw = 400,000) that can yield high-strength, highly oriented regenerated cellulose fibers, and a method for producing the fiber. For example,
At the same time, comparison results are shown between the case where an inorganic acid is used as a solvent (the present invention) and the case where an organic solvent (comparative example) is used. 1, 350g of 73.5% by weight nitric acid and 150g of acetoxymethylcellulose acetate (DS = 0.60, Mw = 400,000) were dissolved at -5℃ for 6 to 7 hours.
Stir for an hour to dissolve. This solution was transferred to an extruder, filtered through a cloth placed inside the extruder, and subjected to primary defoaming. After the obtained dope was left at a temperature of 0 to -5°C for a day and night, it was defoamed again under reduced pressure, and then passed through an extruder (inner diameter 12
mmφ) and 0.07mmφ while keeping it at 0-5℃.
Discharges from a 50-hole nozzle at a rate of 2.5cc/min, air gap (distance between coagulation bath surface and nozzle 0.5cm)
The mixture was then subjected to a coagulation step using a 5% aqueous sodium hydroxide solution at 0 to 5°C as a primary coagulation bath and a 2% aqueous sodium hydroxide solution maintained at 25°C as a secondary coagulation bath.
The obtained fiber was wound onto a bobbin at 60 m/min.
This bobbin was washed by immersing it in water for a day and night, and then air-dried. The obtained fibers were completely regenerated into cellulose. Table 3 shows the performance of the obtained fibers. On the other hand, for comparison, we investigated the ability of the same polymer to form mesophases using dimethylacetamide (DMAc), a type of organic solvent described in JP-A No. 52-96230, and found that it formed mesophases. I didn't. Therefore, an acetoxymethyl cellulose acetate/DMAc (150 g/350 g) dope that does not substantially form mesophases was prepared, and regenerated cellulose was obtained in exactly the same manner as described above. During the formation of the dope, the polymer aggregated and exhibited a so-called "mamako" state, and the mixture had to be stirred for 15 to 18 hours or more to obtain a uniform dope. Table 3 shows the physical properties and whiteness of the comparative fibers obtained. Table 3 As is clear from Table 3, the tensile strength and initial Young's modulus of the fibers obtained by the method of the present invention are much higher than those obtained by spinning from a comparative dope that does not form a mesophase dope. Moreover, the whiteness is measured by calibration at a wavelength of 400 mm using a Hitachi colorimeter EPR-type, and is shown by the reflectance. This whiteness can be considered to reflect the difference in residue content in the relative fibers. As is clear from Table 3, the whiteness of the fibers obtained in this example is higher, and therefore the purity is also higher. Example 4 This example shows a method for producing acetoxymethylcellulose with a degree of substitution of 0.35, and the formation of a mesophase dope by combining the obtained compound and various acids as shown in Table 4. It is. 162 g of wood pulp with a degree of polymerization (DP = 650, evaluated from the intrinsic viscosity number [η] in cadoxene) was dispersed in a kneader with an internal capacity of 15 containing 5 dimethyl sulfoxide, and 150 g of paraformaldehyde was added.
After sealing, the mixture was stirred at 70 to 90°C for 18 hours to obtain a transparent and homogeneous solution. The temperature of this solution was lowered to 30° C., 153 g of acetic anhydride and 39 g of pyridine were added, and the reaction was carried out for 120 minutes. The reaction was stopped by gradually adding 5 methanol to the reaction mixture. This solution was poured into 15 methanol with stirring, and the white precipitate formed was separated, air-dried, dissolved in water, reprecipitated with methanol, and air-dried separately to obtain the desired product. The degree of substitution of this polymer was 0.35, and the Mw determined according to the method of Example 1 was about 290,000. The results of infrared absorption spectrum (IR) and C ¹³ -NMR measurements of this polymer revealed that no acetyl group was found in the polymer molecule, indicating that it was a complete acetoxymethylcellulose. The obtained polymer was dissolved in inorganic acids of various concentrations as shown in Table 4 at 0° C. to prepare mesophase dopes. All the obtained dopes showed clear mesophase characteristics. 【table】

[Brief explanation of the drawing]

FIG. 1 is a C ¹³ -NMR diagram of acetoxymethylcellulose acetate obtained in Example 1.

Claims (1)

[Scope of Claims] 1 At least 10% by weight of at least one compound selected from acetoxymethylcellulose and acetoxymethylcellulose acetate, and 90% by weight or less of at least one inorganic acid, at least 5% by weight 1. A mesophase dope which contains an aqueous solution containing an aqueous solution and which exhibits mesophase properties without applying an external hydrodynamic force. 2 The inorganic acid is hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid,
Metaphosphoric acid, pyrophosphoric acid, hypophosphorous acid, sulfite,
Fluorosulfuric acid, chlorosulfuric acid, chloric acid, hypochlorous acid,
The dope according to claim 1, which is selected from the group consisting of chlorous acid, perchloric acid, bromic acid, perbromic acid, hypobromous acid, hydrofluoric acid, thiocyanic acid and thiosulfuric acid. 3. The dope according to claim 1, wherein the acetoxymethyl cellulose compound has a sum of degrees of substitution of acetoxymethyl groups and acetyl groups in the range of 0.3 to 0.8. 4. The dope according to claim 1 or 3, wherein the inorganic acid is nitric acid or sulfuric acid.