JPH0218342B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an aliphatic polyamide dope having a novel optical anisotropy useful for producing fibers and films. Conventionally, aromatic polyamides (US Pat. No. 3,671,542) and cellulose derivatives (Japanese Patent Laid-Open No. 52-96230) have been known as dopes having optical anisotropy useful for producing fibers and films. Dopes having optical anisotropy can be expected to improve the mechanical properties of fibers and films, and are very useful in the production of fibers and films. However, optically anisotropic doping for aliphatic polyamides has not been known at all. Conventionally, as common knowledge among those skilled in the art, in order to obtain a dope with optical anisotropy, it is necessary to have a rigid structure such as a benzene ring or a pyranose ring in the main chain of the polymer material constituting the dope. This is because it was considered necessary for the unit to be included. In other words, it was thought that it would be impossible to obtain a dope with optical anisotropy with aliphatic polyamides that do not have such a structure. However, the present inventors believe that optical anisotropy is an intermediate or transition process in the process of changing from a liquid structure to a solid structure in the process of forming fibers from a solution. He had a strong belief that a dope with optical anisotropy could be obtained by combining them, and he conducted extensive research. As a result, it was found that even in aliphatic polyamides, optical anisotropy appears if an appropriate solvent and conditions are selected, leading to the completion of the present invention. From the dope of the present invention, it is possible to obtain fibers and films with excellent mechanical properties.
Furthermore, it is fully expected that the performance of fibers and films will be improved by mixing with other polymeric materials that are soluble in the solvent used. The dope with excellent moldability according to the present invention is composed of an aliphatic polyamide and a halogenated aliphatic carboxylic acid or a halogenated aliphatic carboxylic acid and a solvent compatible therewith, and the weight fraction of the aliphatic polyamide is at least 15 % and exhibits optical anisotropy. As the aliphatic polyamide, nylon 6 and nylon 66 are preferably used here. There is no problem even if these are copolymers. As the solvent, halogenated acetic acid or a mixture of halogenated acetic acid and a solvent compatible therewith is used. As the halogenated acetic acid, monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, dibromoacetic acid, tribromoacetic acid, monoiodoacetic acid, diiodoacetic acid, triiodoacetic acid, monofluoroacetic acid, difluoroacetic acid, and trifluoroacetic acid are used. Considering the ease of liquid crystallization of the aforementioned polyamide in the mixed system, monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monofluoroacetic acid, difluoroacetic acid, and trifluoroacetic acid are preferably used. Considering economy and ease of handling, monochloroacetic acid and dichloroacetic acid are particularly preferred. Further, a mixture of a halogenated acetic acid and a solvent compatible therewith may be used to prepare a dope having optical anisotropy. It is also possible to use two or more of these solvents in combination. As compatible solvents, water, alcohols, ketones, carboxylic acids, amides, sulfoxides and amines are used, and particularly preferred are water, methyl alcohol, formic acid, acetic acid, dimethylformamide,
Dimethylacetamide, dimethylsulfoxide, etc. are used. Generally, the mixing ratio of halogenated acetic acid and these solvents is not limited, but when water and alcohol are used, the content of water and alcohol in the mixed solvent is preferably 30% by weight or less. The dope of the present invention is obtained by mixing polyamide and a suitable solvent, usually at around room temperature, and stirring the mixture. If the solvent is solid at room temperature,
Prepared at a temperature above the melting point of the solvent. When the solvent is solid at room temperature, the prepared dope is solid at room temperature, which is convenient for storage and transportation of the dope. The weight fraction of polyamide in the dope is at least
Should be 15%. Dopes useful in the production of fibers and films contain 20-40% by weight polyamide. A particularly preferred dope contains 25 to 35% by weight polyamide. When the weight fraction of polyamide in the dope is less than 15%, no optical anisotropy is exhibited, the dope lacks spinnability, and it cannot be used for producing fibers or films. Moreover, even if it can be formed into fiber or film, it will not be able to withstand use due to poor physical properties. 40
% or more, the viscosity increases significantly, making it difficult to prepare dope at temperatures below 100°C, which is the temperature usually used for dope. Another feature of the dope of the present invention is that it is very stable, shows little change over time, and can be stored for a long period of time. The preferred combination of polyamide and solvent is that the polyamide is nylon 6 or nylon.
66, the solvent is monochloroacetic acid or dichloroacetic acid. The optical anisotropy of these dopes can be confirmed using a polarizing microscope. The dope is sealed between a slide glass and a cover glass, and placed under a crossed Nicols polarizing microscope. Normally, in this state, no light transmission is observed, and the visual field may be dark. However, when the cover glass is pressed to apply shear force to the dope, light transmission is observed, and the transmission lasts for several seconds to several minutes, and optical anisotropy appears. The appearance of optical anisotropy is generally influenced by the molecular weight of the polyamide, the temperature of the dope, and the concentration of the dope. The higher the molecular weight, the lower the doping temperature, or the higher the doping concentration, the more optical anisotropy tends to appear. Additionally, the solvent used to prepare the dope of the present invention can dissolve other polymeric materials such as cellulose derivatives, polyvinyl alcohol, polyesters, polyacrylic acid, polyacrylamide, polyvinylpyrrolidone, polypeptides, polyurethanes, etc. Therefore, by mixing it with these polymeric materials and applying an appropriate molding method, it is expected that their performance will be improved or that completely new functions will be imparted. Generally, the mixing ratio of these polymeric materials and polyamide and the mixing partner are not limited and should be selected depending on the purpose. For example, to improve the dyeability and hygroscopicity of cellulose acetate, a polyamide mixing ratio of about 10% may be sufficient, and if you want to manufacture porous polyamide molded products, polyvinyl alcohol, polyvinylpyrrolidone, polyamide, etc. It can be produced by preparing a mixed dope with polyamide containing 5 to 50% by weight of a water-soluble polymer such as acrylamide, and removing the water-soluble polymer using water as a coagulant, for example. From the optically anisotropic dope of the present invention, fibers with excellent mechanical properties such as strength and elongation and Young's modulus can be obtained. In particular, satisfactory mechanical properties can be obtained without the stretching step. The present invention will be explained in more detail below using Examples. The relative viscosity (VR) described in the examples is a value measured by a conventional method at 25° C. by dissolving 8.4% by weight of nylon 6 or nylon 66 in a 99% by weight formic acid solution. Example 1 This example shows a method for preparing an optically anisotropic dope from commercially available nylon 6 chips. 30 g of commercially available nylon 6 chips (VR=32) and 70 g of dichloroacetic acid were mixed and stirred at room temperature for 5 hours. The obtained dope exhibited good stringability, and pearl-like luster was observed with the naked eye under stress. This dope was sealed between a slide glass and a cover glass, and observed under crossed nicols using a polarizing microscope. When shear force was applied, the field of view glowed brightly, and light transmission was observed for several tens of seconds. Example 2 This example shows a method for preparing an optically anisotropic dope from commercially available nylon 66 chips. 30 g of commercially available nylon 66 chips (VR=36) and 70 g of dichloroacetic acid were mixed and stirred at room temperature for 5 hours. The obtained dope exhibited good spinnability and optical anisotropy as in Example 1. This dope was put into a small screw-type test spinning machine, and air discharge wet spinning was performed to obtain fibers. Winding speed is 10m/min.
The draft was 2.5, the air gap was 2 cm, the primary coagulation bath was water containing 2% NaCl and 3% Na ₂ CO ₃ , the secondary coagulation bath was methanol, and spinning was performed at room temperature. Example 3 This example shows how to obtain an optically anisotropic dope from commercially available nylon 66. 65 g of monochloroacetic acid was placed in a beaker and heated to adjust the temperature to 65°C. 35 g of nylon 66 chips (VR=36) were added to this and stirred. A uniform dope was obtained in about 1 hour. The dope solidified when cooled to room temperature. When the temperature was further increased, it melted and exhibited good stringability. When this dope was observed under a crossed Nicol microscope with a polarizing microscope equipped with a heating stage, it showed optical anisotropy under shear force at 65°C, but no optical anisotropy was observed at around 100°C even when shear force was applied. I didn't show it. Example 4 This example shows a method for obtaining an optically anisotropic dope from a mixed solvent of commercially available nylon 6, trichloroacetic acid, and water. Aqueous solutions of 90, 80, 70, 60, and 50% by weight of monochloroacetic acid were prepared, respectively. When the solubility of nylon 6 (VR=32) was checked, it was found to dissolve in a monochloroacetic acid aqueous solution of 80% by weight or more, but was difficult to dissolve at 70% by weight, and did not dissolve in the bath at 60 and 50% by weight. Next, 30 g of nylon 6 chips were added to 70 g of a 90% by weight aqueous monochloroacetic acid solution, and the mixture was heated to adjust the temperature to 60°C. A uniform dope was obtained after stirring for about 2 hours, and exhibited good spinnability and optical anisotropy at 60°C. Example 5 An experiment similar to Example 4 was conducted using a mixed solvent of dichloroacetic acid and water. A nylon 6 dope with good spinnability and optical anisotropy that can be formed into fibers or films with an 80% by weight or more dichloroacetic acid aqueous solution was obtained. Example 6 This example shows a method for obtaining an optically anisotropic dope of nylon 6 using a mixed solvent of monochloroacetic acid and acetic acid. A solution with a weight ratio of monochloroacetic acid to acetic acid of 2/1 was prepared. 60 g of nylon 6 chips (VR=32) were added to 140 g of this solution, and the mixture was stirred at room temperature for 3 hours. The obtained dope exhibited good stringability at room temperature and exhibited optical anisotropy. Example 7 This example describes a blend dope of the optically anisotropic nylon 6 dope of the present invention and cellulose acetate, and fibers obtained from this dope. 40 g of commercially available cellulose acetate (DS2.5) was dissolved at room temperature in 60 g of a mixed solvent consisting of monochloroacetic acid and acetic acid at a weight ratio of 2/1. Add 9g of nylon 6 (VR=32) to 21g of the same mixed solvent.
The dissolved dope was blended. When this blend dope was observed under crossed nicols using a polarizing microscope, it showed optical anisotropy. Further, in this state, the individual presence of nylon 6 and cellulose acetate was not observed, and no phase separation was observed. Next, this blended dope was put into a screw-type small test spinning machine, and air discharge wet spinning was performed at room temperature to obtain fibers. The winding speed at this time is 10m/
min, the draft was 4.5, the air gap was 10 mm, and the coagulation bath was water, methanol, ethanol, n-propanol, or isopropanol. Example 8 The mixed solvent system that showed optical anisotropy when 30 g of nylon 6 used in Example 1 was dissolved in 70 g of a mixed solvent of monochloroacetic acid and a third solvent is shown in the table.

[Table] Comparative Example Nylon 6 used in Example 1 was dissolved in formic acid and DMF, which are known as solvents for nylon, but it was not possible to obtain a dope with optical anisotropy. As described above, the dope of the present invention has spinnability and optical anisotropy suitable for manufacturing molded products such as fibers and films, and can be easily blended with other polymers, making it suitable for producing molded products such as fibers and films. It can be used to improve films, and furthermore, it is also possible to add new functionality, so its value is extremely high.

Claims (1)

[Scope of Claims] 1 Consisting of an aliphatic polyamide and a halogenated acetic acid or a halogenated acetic acid and a solvent compatible therewith, the weight fraction of the aliphatic polyamide is at least
An aliphatic polyamide dope with excellent moldability that is characterized by having an optical anisotropy of 15% and exhibiting optical anisotropy. 2 Halogenated acetic acid is monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, dibromoacetic acid, tribromoacetic acid, monoiodoacetic acid, diiodoacetic acid, triiodoacetic acid, monofluoroacetic acid,
The dope according to claim 1, which is at least one selected from difluoroacetic acid and trifluoroacetic acid. 3. The dope according to claim 1 or 2, wherein the compatible solvent is at least one selected from water, alcohol, ketone, carboxylic acid, amide, sulfoxide, and amine. 4 The compatible solvent is water or alcohol, and water or alcohol is present in the mixture with halogenated acetic acid.
The dope according to any one of claims 1 to 3, containing 30% by weight or less.