Dry spinning of nylon 3 was investigated for two samples of molecular weight of 90, 000 and 240, 000, using formic acid as solvents. With the polymer having molecular weight of 90, 000 filaments could not be wound continuously, while for the polymer of molecular weight of 240, 000 dry spinning was possible, and filaments could wound continuously. Thus the spinnability of spinning dope is thought important for dry spinning of nylon 3. Even for the maximum draft ratio (ratio of the winding speed to extrusion velosity), about 20 no chain orientation. was observed. Formic acid content in fibers was mainly controlled by spiuning temperature and by output of the dope, and was not affected by winding speed. Cross section of the fibers was dogbone-shaped for the polymer having molecular weight of 90, 000 and was extra-ordinal-shaped for the polymer of molecular weight of 240, 000. Dry-spun fibers could be drawn in such media as silicone oil and hot air, which were thought to have no interaction with polyamides, but in such media as hot water, steam and hot glycerine, which were thouget to have some interaction with polyamides, drawing was impossible, Relations between spinning conditions and properties of fibers are discussed.

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Dyeability and miscellaneous properties of nylon 3 fibers were investigated, and following results were obtained. Nylon 3 fibers have good dyeability with acid dyeing metal-complex dyes, and the degrees of color fastness are also good. Nylon 3 fibers have some different properties from those of other ordinary polyamides. The glass transition temperature of nylon 3 fibers is higher by about 70°C than ordinary aliphatic polyamide fibers. The sorption behavior of nylon 3 fibers is similar to that of silk. Its modulus and birefringence are also higher than those of ordinary polyamide fibers. These properties are due to the high amide group concentration of nylon 3.

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In order to improve the mechanical properties of nylon 3 fibers, especially to increase tensile elongation, the heat treatment were investigated. By treating drawn nylon 3 fibers in such media as hot silicone oil and hot air which were thought to have no interaction with polyamides, elongational properties were not improved. However, by treating the drawn nylon 3 fibers in such media as hot water, steam and hot glycerine which were thought to have some interaction with poly amides, elongational properties were improved. Further, the effects of spinning conditions, especially drawing conditions on the elongational properties of heat treated fibers were investigated. With increased drawing temperature and draw ratio, shrinkage of nylon 3 in boiling water was decreased. From these results a mechanism of hot water treatment of nylon 3 fibers was proposed. Mechanical properties of nylon 3 fibers obtained by heat treatment were as follows: strength; 2-3g/d, elongation; 20-30% Young's modulus; 800-1200kg/mm².
The copolymerization of nylon 3 and its wet spinning were also investigated to improve the mechanical properties. Relations between mechanical properties of nylon 3 fibers and its copolymer composition of nylon 3 fibers were discussed.

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The fiber forming process of nylon 3 in the wet spinning process was investigated, using formic acid as the solvent and alcohols, esters and ethers as the coagulants. Following results were obtained:
As for the mass transportation in the wet spinning of nylon 3, the solvent (formic acid) diffuses into the coagulant while the coagulant does not permeate into proto-fibers. Thus homogeneously deswelled proto-fibers were obtained.
The maximum draft ratio is mainly affected by three factors, that is to say, coagulation power of a coagulant, molecular weight of the polymer and polymer concentration of the spinning dope. The highest value of the maximum draft ratio is attained in a definite range of the coagulation power of coagulants. By decreasing polymer concentration and molecular weight of the polymer the maximum draft ratio is increased.
Cross sectional shapes of the proto-fibers are mainly affected by coagulation power of the coagulants. When coagulation power is strong, the cross sectional shape of the fibers is changed and when coagulatian power is weak, the cross sections of the fiber were dog-bone-shaped.
As proto-fibers are already crystallized, it is not possible to orientate the prato-fibers by drawing in a coagulation bath.

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Properties of nylon 3 formic acid solution were investigated and compared with those of dichloroacetic acid. The effects of dope properties on spinnability were also examined.
Of the properties of dilute solution, especially solution viscosity was examined. Nylon 3 behaves as a polyelectrolyte in formic acid and in dichloroacetic acid, and this behavior was affected by the addition of salts or water.
Properties of concentrated formic acid solution of nylon 3 were also investigated. The results obtained are as follows: Viscosity in formic acid is much lower than that obtained in dichloroacetic acid. This suggests the poorer interaction between formic acid and nylon 3. The result is in accordance with that of an infrared spectrometry. When polymer concentration is low, the solution in dichloroacetic acid shows much better spinnability, whereas when polymer concentration is high, the spinning solution in formic acid shows much better spinnability. Dope viscosity, using. formic acid as the solvent, is unstable and the solution gelled when polymer concentration exceed 36%. Fiber formation of nylon 3 in the wet spinning process is seriously effected by gellation.

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Choosing α methyl nylon 3, β methyl nylon 3, α, α, dimethyl nylon 3, and β, β, dimethyl nylon 3 as the nylon derivatives, the effects of substituents on the properties and structures were investigated by the methods of X-ray diffraction, infra-red spectra, and thermal analysis, and following results were obtained. Melting points of the polymer increase with in following order. α, α, dimethyl<β, β, dimethyl<α methyl≤β mthyl_??_no substituent. The NH streching absorptions were observed at 3380cm^-1 in α, α, dimethyl nylon 3, at 3340cm^-1 in β, β, dimethyl nylon 3, and at 3300cm^-1 in other nylons. NH--O distances of the derivatives are estimated, and melting point of the polymers and location of the NH streching absorptions were found to be mainly determined by the NH-O distances. Though nylon 3 derivatives belong to short methylene polyamides, a distort of molecular chain occurs around amide groups. This may be due to the favorable NH-O hydrogen bond distances under the steric hinddrances of the substituents.

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Nylon 3 was-spun in the ethyl acetate coagulation bath, using formic acid as the dope solvent. Spinning conditions, especially the drawing conditions were investigated.
Boiling water, steam and glycerine, which are well-known drawing medias for ordinary polyamides were not suitable as the drawing media for nylon 3 fibers. While in such media as silicone oil, wood's metal or hot air, which are thought to have no interaction with polyamides, nylon 3 fibers were able to be stretched above the glass transition temperature (170_??_180°C). The drawn nylon fibers thus obtained showed fairly good mechanical properties as textile fibers, i. e. strength, 2_??_3g/d, elongation; 10_??_20%.
Relations between mechanical properteis and spinning conditions were also investigated. Mechanical properties of drawn nylon 3 fibers thus obtained were not so much affected by coagulation conditions and spinning dope conditions, but remarkably affected by drawing conditions.

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Fiber-forming properties of nylon 3 in the wet spinning process were investigated, using formic, dichloroacetic, trifluoroacetic, sulfuric, nitric acids, aqueous phenol, aqueous calcium thiocyanate, aqueous zinc chloride, aqueous chloral hydrate, aqueous formaline and water as the typical solvents for nylon 3. Film-forming properties of these nylon 3 solutions were also investigated. Following results were obtained.
Nylon 3 solutions in formic acid, trifluoroacetic acid and aqueous phenol have film-forming ability in the dry process. The spinning dopes using sulfric acid, nitric acid, and aqueous chloral hydrate have little ability of fiber-forming in the wet and dry spinning process. The spinning solution of nylon 3 in formic acid as the solvent shows excellent fiber-forming property in the wet spinning process, using ethers, esters and alcohols as the coagulants. Thus the fiber forming mechanism of nylon 3 in the wet spinning process using formic acid as the solvent is discussed. Cohesive energy density, strength of hydrogen bonding and proton accepting power of coagulants are found important factors in the wet spinning process of nylon 3.

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