Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
  • D01F6/02—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D01F6/18—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds from polymers of unsaturated nitriles, e.g. polyacrylonitrile, polyvinylidene cyanide
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
  • D01F6/28—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D01F6/38—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds comprising unsaturated nitriles as the major constituent

Definitions

• a method of producing acrylonitrilic polymer fibers comprises coagulating a spinning solution so as to form coagulated gel fibers, treating such fibers in a hot medium, stretching the fibers, and water-washing and drying them.
• the present invention relates to a method of producing polyacrylonitrile-ty-pe fibers and particularly to a Wetspinning method of producing dense polyacrylonitrile-type fibers having smooth surfaces, circular cross-sections and a silk-like touch and luster.
• Fibers composed of acrylonitrile polymers are normally produced by either a dry-spinning or a wet-spinning method using an appropriate spinning solution which comprises the acrylonitrile-type polymer dissolved in either an organic solvent or a concentrated aqueous solution of inorganic salt.
• wet-spinning particularly when an aqueous coagulation bath is used, the solvent is diffused outwardly from the fibers being coagulated and at the same time the water in the coagulation bath penetrates into the fibers. This results in such fibers having spongelike porous structures. In some cases opaque gel fibers are obtained through devitrification. Such porous structures cannot be entirely collapsed in the subsequent processing and are carried through into the final fibers thereby adversely affecting the strength, wear-resistant properties and luster of the fibers.
• An object of the present invention is to provide a method of producing fibers having properties adapted to various fiber applications by making dense the porous structures inherent as above-stated to the wet-spinning of acrylonitrile polymers, without the necessity of subsequent slackening treatment.
• Another object of the present invention is to provide a method of producing acrylonitrile polymer fibers having smooth surfaces, circular cross-sections and a silk like touch and luster.
• the above-stated objects may be achieved by a process comprising the steps of (1) extruding a spinning solution containing (a) acrylonitrile polymer and (b) organic solvent or concentrated aqueous solution of inorganic salt, into an aqueous coagulation bath so as to coagulate it in the form of swelling gel fibers containing water and a small amount of solvent (the above-stated organic solvent or inorganic salt), (2) drying the resultant fibers thereby evaporating the water in the gel fibers, (3) subjecting the same to stretching in a hot medium, (4) washing in water to extract the solvent, and (5) final drying.
• the fibers thus obtained are excellent in strength and wear-resistant properties and have smooth surfaces without any perceptible surface irregularity of grooves extending axially of the fibers as would be seen in the conventional wet-spun fibers. Further, the cross-sections of the novel fibers are of substantially perfect circle, and such configurational features are substantially maintained even in case of fibers of 50 to deniers or more. It is impossible not only for the conventional wet-spinning process but also for the conventional dry-spining process to obtain such desirable results.
• the fibers made according to the present invention are desirably dense and compact.
• their minute voids (larger than 0.1 in magnitude) will be observed as being small shining spots because they reflect the light, while the other portions of the fibers will look black.
• many shining spots i.e., voids
• the fibers made according to the present invention have very few voids, which fact is evidence that these fibers have practically perfectly uniform structures.
• the acrylonitrile polymers employed in the invention include polyacrylonitrile (homopolymer), a copolymer, a copolymer of acrylonitrile and at least one kind of other monoolefin monomer, block polymers, graft polymers and mixtures of said polymers.
• the polymers used in the invention contain at least 40% of acrylonitrile.
• vinyl acetate vinyl esters of other monocarboxylic acids, acrylic acid, acrylic esters such as methyl acrylate and ethyl acrylate, methacrylic acid, methacrylic esters such as methyl rnetharylate, vinyl chloride, vinylidene chloride, styrene, methacrylonitrile, vinylidene cyanide, vinyl pyridine and its substituted derivatives, other vinyl substituted nitrogen-containing heterocyclic compounds such as vinyl imidazole, aliphatic and ⁇ acromatic sulfonic acids having unsaturated bond such as styrene sulfonic acid, allyl sulfonic acid and methallyl sulfonic acid, and fonoolefin monomers capable f0 copolymerizing with acrylonitrile.
• vinyl acetate vinyl esters of other monocarboxylic acids
• acrylic acid acrylic esters such as methyl acrylate and ethyl acrylate
• Solvents used in the present invention would include organic solvents having higher boiling point than water as N,N dimethyl formamide, N,N dimethylacetamide, ethylene carbonate and dimethyl sulfoxide, and concentrated aqueous solutions of such inorganic salts as thiocyanates, e.g., sodium thiocyanate and calcium thiocyanate, perchlorates, e g., sodium perchlorate and calcium perchlorate, zinc chloride and lithium chloride.
• organic solvents having higher boiling point than water as N,N dimethyl formamide, N,N dimethylacetamide, ethylene carbonate and dimethyl sulfoxide
• concentrated aqueous solutions of such inorganic salts as thiocyanates, e.g., sodium thiocyanate and calcium thiocyanate, perchlorates, e g., sodium perchlorate and calcium perchlorate, zinc chloride and lithium chloride.
• the spinning solutions obtained by dissolving the abovementioned acrylonitrile polymers in these solvents are transparent, viscous solutions, and the suitable concentration of polymer varies according to the kinds of solvents and the molecular weight of polymers, but preferably is generally more than 7%.
• the gel fibers after coagulation is complete are trans ferred to a drying process while they still contain a fixed amount :of solvent (e.g., the aforementioned organic solvent or inorganic salt) in an amount by weight not exceeding 1.5 times the dry weight of the polymer.
• a fixed amount :of solvent e.g., the aforementioned organic solvent or inorganic salt
• the purpose of this drying process is to evaporate the water contained in the gel fibers and thereby correct the gel from a porous structure type form into a transparent and compact form. It is important that such a fixed amount of solvent should be contained in the gel fibers at the outset of this drying step. This permits the gel fibers to be again dissolved and to be converted into a transparent and uniform gel and finally results in the subsequent stretching process becoming easier to manage.
• the polymer content in the dried gel fibers be more than 30% but if it becomes higher than about 90% the stretching step is rendered difiicult.
• the amount of solvent to be contained in the dried gel fibers varies according to the kinds of solvents and the conditions of stretching. For example, where an inorganic salt such as a thiocyanate is used as the solvent, it is desirable that the ratio ofthe weight of solvent contained in the dried gel fibers to the weight of polymer is less than 1.521 and that the ratio of the weight of water to the weight of solvent is less than 1.5 :1. Also, where an organic solvent is used, it is necessary to dry the gel fibers until a condition is attained wherein solvent alone remains in the gel fibers with no substantial water contained therein. If the drying temperature is higher a shorter drying time is required, but if the temperature is too much higher, uniform drying is hard to effect. A temperature range of about 40-80 C. is suitable.
• the gel fibers made dense by the aforesaid drying step are now stretched in a medium that will not extract the solvent.
• Suitable stretching conditions vary according to the compositions of gel fibers, the kinds of solvents and the physical properties of the intended final fibers. Generally, with higher polymer content in the dried gel fibers, stretching becomes more difficult with the result that high stretching temperatures are necessary, and if it is desired to have a higher ratio of stretching, then higher stretching temperatures are required. If the stretching temperatures are very low, the stretched fibers will considerably be devitrified and if the stretching temperatures are still lower, the fibers will be broken, whereupon it is impossible to continue the stretching operation. Therefore, when certain compositions and stretching ratio are given, there will exist the lowest temperature at which the stretching may be successfully carried out.
• This temperature may vary from room temperature up to about 100 C. depending upon the gel compositions and the stretching ratio. There is a close relationship between the stretching conditions and the final fibers, i.e., generally, the higher the stretching ratio, the higher the strength and the lower the elongation. Also, the higher the stretching temperaures the lower the strength, the higher the elongation and the more the tenacity is increased. Therefore, it is necessary to select suitable conditions according to the intended properties.
• Any stretching medium may be employed so far as it is inactive with respect to the dried gel fibers, but such a medium as will extract the solvent is not preferable.
• the most generally used medium is air.
• the heat source may be air itself (i.e., heated air).
• Sources such as heating by the radiant heat such as from an infrared lamp or a heated plate, heating by high frequency or heating by many other known methods, may also be utilized.
• Liquid mediums such as will not extract the solvent may be used. Heating by hot water or water vapor is not suitable. In practice, it is convenient to operate the stretching successively at the end of the preceding drying process.
• the stretched gel fibers are immediately washed in a water bath to extract the solvent is contained in the fibers.
• the washing temperature used may be room temperature, but in some cases Washing at high temperature is operated.
• the washed fibers are then, if necessary, passed through such subsequent processes as crimping process, finishing agent-applying process, cutting process, etc. and thereafter are dried to produce the final fibers.
• the fibers after washing are still of suitable density and their water content is remarkably low. Consequently they can be dried at a higher speed and lower temperature than the ordinary wet-spun fibers.
• the method of the invention it is also possible to produce considerably heavy denier fibers of more than 50 deniers.
• heavy denier fibers are to be spun by the ordinary wet-spinning process, it is very hard to effect the collapsing of the swelling porous structure for making the fibers dense or compact. Even if it is effected, there would result grooves and irregularity on the surfaces thereby providing irregular cross-sections.
• the rate of evaporation would be low due to the fibers being thick, thus causing difiiculties. Since according to the present invention compacting is easily effected before stretching, the drawbacks in the conventional wet-spinning process are eliminated.
• the method of the present invention is suitable also for the production of thick fibers.
• customary additives such as coloring pigments, anti-coloring agents, stabilizer, plasticizers and the like.
• acryl sulfonic acid 10/ 0.75 is dissolved in a 46% aqueous solution of sodium thiocyanate to prepare a spinning solution having a polymer concentration of 9%.
• This spinning solution is extruded through a spinnerette provided with 50 fine holes each having a diameter of 0.065 mm. into a 12% aqueous solution of sodium thiocyanate kept at 20 C. and is permitted to coagulate therein.
• the coagulated gel fibers are then immersed in a bath containing a 4% aqueous solution of sodium thiocyanate to permit the sodium thiocyanate concentration of the gel fibers to establish its equilibrium and thereafter are taken out from said bath. After the removal of excessive solution from the thus-treated gel fibers, these fibers are dried in the air at 50 C. for 6 minutes.
• the gel fibers obtained by said drying step have a composition consisting of about 70% of polymer, 15% of sodium thiocyanate and 15% of water.
• the dried gel fibers are stretched in heated air at various stretching ratios and stretching temperatures and immediately thereafter are washed under tension in water at room temperature to remove the sodium thiocyanate therefrom and finally are dried at C.
• the yarn properties of the fibers thus obtained are shown in Table 1.
• the properties of the fibers re- EXAMPLE 3 markably vary according to the stretching conditions.
• the higher the stretching ratio the higher the dry strength and the lower the dry elongation, the knot strength and the knot elongation.
• the stretching temperature becomes higher the dry strength gradually diminishes through its maximum value, the dry elongation increases to some degree and the knot strength and elongation considerably increase. It is, therefore, possible to obtain any desired set of fiber properties by suitably selecting the stretching ratio and stretching temperature.
• the microscopic observation of these samples under dark field will prove that they are very uniform in structure, with very few voids found in the fibers.
• the samples of Nos. 1, 5, 9 and 12 are devitrified since local fracture takes place in the fibers due to their lower stretching temperatures. At temperatures still lower than these, it would be impossible to stretch the fibers because of their breakage.
• EXAMPLE 2 The coagulated gel fibers obtained by the same operation as in Example 1 are immersed in a 5% aqueous solution of sodium thiocyanate and thereafter are dried overnight to obtain gel fibers having a composition consisting of about 65% of polymer, 18% of sodium thiocyanate and 17% of water.
• the gel fibers thus obtained are stretched in heated air, are Washed in hot water and are A copolymer of acrylonitrile/methyl acrylate (/10) is dissolved in a 50% aqueous solution of sodium thiocyanate to prepare a spinning solution having polymer concentration of 12%. This spinning solution is extruded through a spinnerette provided with a hole having a diameter of 0.5 mm.
• the coagulated gel fibers are taken out from the bath. After the removal of the excessive coagulated solution from the gel fibers, these fibers are dried at 50 C. under non-tension and thereby converted into transparent gels, the composition of which consists of 67% of polymer, 20% of sodium thiocyanate and 13% of water.
• the gels are stretched by 7.1 times in heated air at 105 C., immediately thereafter are washed in water at room temperature to remove the solvent therefrom and are dried at 105 C. to provide fibers of 98 deniers. It is astonishing that in spite of being as thick as 100 deniers, these fibers have no such irregularity on the fiber surfaces as is seen in the usual conventionally wet-spun fibers and are very smooth with their cross-sections almost perfect circles.
• the gel fibers when being stretched contain a slightly more amount of solvent than in Example 1, so that the stretching is easily operated. Though the fibers were subjected to the same stretching conditions, the dry strength is somewhat lower but the knot strength is higher.
• a method of producing acrylonitrilic polymer fibers by Wet-spinning a spinning solution containing an acrylonitrilic polymer dissolved in a concentrated aqueous solution of a thiocyanate as solvent comprising coagulatin said spinning solution in an aqueous coagulating bath so as to form coagulated gel fibers containing the thiocyanate in an amount of not more than 1.5 times the dry weight of the polymer, treating such coagulated fibers in hot air at a temperature of 40 to 80 C. in order to reduce the water content in said fibers to not more than 1.5 times the amount of thiocyanate contained in said fibers, stretching the fibers at a temperature of above 40 C. in a medium which will not extract said thiocyanate from the fibers, and subsequently Water-wash- ]5 ing and drying the fibers.
• Themethodaccording t0 q lw l q fiil l fiq unstretched fibers contain equal parts of water and sodium thiocyanate and at least 30% by weight of the polymer.

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Citations (7)

• 1964
  • 1964-04-17 BE BE646691D patent/BE646691A/xx unknown
  • 1964-05-20 NL NL6405582A patent/NL6405582A/xx unknown
  • 1964-05-27 LU LU46167D patent/LU46167A1/xx unknown
  • 1964-05-27 US US370722A patent/US3399260A/en not_active Expired - Lifetime
  • 1964-05-28 GB GB22174/64A patent/GB1006040A/en not_active Expired
  • 1964-06-03 FR FR976953A patent/FR1397075A/fr not_active Expired
  • 1964-06-04 DE DE19641494623 patent/DE1494623A1/de active Pending

Patent Citations (7)

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