SU705013A1 - Method of producing synthetic ultrathin fibers - Google Patents

Description

 . I

The invention relates to the production of ultrafine synthetic fibers (microvopos), which are widely used in the manufacture of filters for the most precise clean (trapping particles with a diameter of 0.010, 001 micron) {high-quality paper, nonwovens, etc.

A known method for producing mikro fibrils of ethylene terephthalate with a length of 100 microns to several millimeters and a diameter of OD to 2 microns when processing a dispersion of polyethylene terephthalate in a polycaproamide melt (IJ.

The resulting oriented microfibrils are obtained (after washing polycaproamide ™) in the form of entangled felt.

The disadvantages of the method include the fact that microfibers have a very small length (length to diameter ratio of 50), a wide size distribution is obtained in the form of entangled felt.

A known method for producing synthetic ultrathin fibers by melt extrusion blends a mixture of two polymers, one of which is a matrix, and the second is a fiber-forming material, cooling the newly formed fiber to room temperature, extracting the matrix. from them and thermo-orientation drawing .2.

According to this method, fibrils (in the form of a non-continuous beam) are formed using a dispersion of 80% of the fiber-forming component and 2O% of the matrix. The best beam is obtained when 75-50% of the fiber-forming polymer is dispersed in the melt 25-50% of the matrix. The tape is formed from the dispersion through a slit die, followed by some axial orientation (spin drawing) and taking the tape into water at room temperature. The additional orientation of the belt (due to drawing) can be carried out in any way. The following 370 fiber-forming polymers are used: polyamides, stereoregular polyolefins, polyvinyl chloride, polyethylene gephteralag; polyethylene or copolymers of ethylene with N. are used as a matrix — vinylcyclic lactates, acrylic, Meteicrylic, and other acids, vinyl acetate. Taking into account the necessary thermodynamic incompatibility of mixed potmeter, it is extremely difficult to finely disperse, for example, 80% of fiber-forming polymer in 20% of the matrix, therefore, a complex (b-zone) double-scrubbing extruder is used for mixing polymers, and then further additional dispersion occurs in the Bruender extruder pad with three zones. Further, the variances of these equations are extremely unstable in the absence of. VII mixing, the aggregation of the fiber-forming Polymer areas begins immediately, and the degree of dispersion deteriorates until the system is divided into 2 phases. The resulting ribbon (and pu4ok fibrils) from polymer dispersion is characterized by uneven properties along the length and a wide distribution of microfibrils produced by diameter (heterogeneity of microfibers by diameter). In the first place, this is manifested in the low values of the physicomechanical properties of the tape and fibril bundle. The strength of the ultrathin fibrils washed from the matrix does not exceed 0.5–4 g / denier (5–40 kg / mm) even after additional thermal orientation of the belt. The individual microfibrils (microfibres n: a) included in the bundle are interlaced with each other and are not separated from each other, so count the number of fibers or; measure the length of an individual fiber is impossible. The diameter of the resulting fibrils (fibers) is 10 microns, preferably 2 microns. The purpose of the invention is to increase the uniformity of the fiber structure and the improvement of the physicomechanical parameters of the complex yarn obtained from them. The goal is achieved by extruding a mixture containing 5-45 wt.% Of a fiber-forming polymer with a degree of crystallinity of 50-90% with a difference, crystallization of the latter and a ZO-100% matrix and a ratio of viscosities of polymer melts 0,, 0, and cooling freshly formed fibers are carried out at O- (-70) C. 3 The invention is illustrated by the following examples and tables: Example. Powdered polyoxymethylene (POM) with an average particle size of 50 microns. mixed with a 20% solution of copolyamide 548 (SPA) in ethanol. The alcohol is evaporated (-t 60 ° C) with vigorous stirring, and the mixture is dried under vacuum (t 60 ° C) to constant weight. The POM / SPA ratio is 20/80; The characteristics of the polymers used are given in Table. 1. The resulting polymer dispersion is sufficiently kinetically stable. Therefore, in the process of melting and tempering, the degree of dispersion of the fiber of the formative component remains almost unchanged, which makes it possible to obtain an extrudate (vein) with properties that are unchanged and relatively uniform in length. the distribution of ultrafine fibers by diameter. . The melt mixture is exhausted into the vein at t 200 ° C and P 32 kgf / cm ––. cut the die plate 3 0.8 mm, 1O. The vein is received in a liquid with t. R4 (7 ° C with a draw die of 800%. The ratio of the melt viscosities of the POM and SPA under these conditions is 0.7: 1, the time of melting and tempering the mixture before pressing is 6 minutes. According to X-ray data, the degree of crystallinity (SC) of a powdered PMT is 75%, the degree of crystallinity of the SPA is 548-5%., The difference in degree of crystallinity (RA) of this polymer pair is 93%. From the resulting vein is extracted with polyamide at t 75 ° C, whereupon poly oxymethylene remains as a continuous multifilament yarn containing 10,000 oriented microfibers with an average diameter of 0.8 m1 s Processing the quantitative results on the distribution of fibers by diameter (building a differential distribution curve) shows that 90% of all the fibers obtained have a diameter, i.e. a complex thread consists of fibers that are almost uniform in diameter, Kinetic stability of the melt the mixture obtained by the described method from 2% of the fiber-forming component and 80% of the matrix is very high: within 30 minutes the change in the degree of diopersity (at t 200 ° C) is practically insignificant. 570 The obtained continuous complex polyoxymethyl thread is stretched 11 times at t 145 ° C, while the number of fibers in the thread remains almost unchanged, and their average diameter decreases to 0.2 microns. The breaking strength of the microfibers yarn thus obtained was 13 ~ 140 kg / mm with an elongation of 10%, the specific surface determined by the sorption method -vlOO. These microfibers are highly oriented (the misorientation angle of the crystals was 6), but they are uniformly colored, have a soft softness, bulkiness, good adherence. Breaking strength, initial module, percentage of strength retention in the knot and loop (elasticity characteristics a) for a thread of ultrafine fibers, respectively 13rkg / mm 1600 kg / mm 80%, 90%. The same characteristics for the yarn from the initial PEM are 100 kg / mm, 900 kg / mm, 15% and 20%, respectively. Example 2. A mixture of POM and SPA of composition 30% POM + 70% SPA prepared according to Example 1 is extruded into the flesh at -t, P 94.5 kgf / cm through 1 pms diameter of 1 mm, 5. The difference in the degrees of crystallinity of polymers is 93%, and the ratio in the ratio and melt of POM to SPA viscosity is 0.2. A microscopic analysis of the structure of extra dates and residues after extraction of copolyamide showed that when the pressure is above 45 kgf / cm and the indicated ratio of viscous melt, polyoxymethylene forms not fibers in the copolyamide matrix, but located concentrically fibrous cylindrical layered structures that, after removal of the SPA, on the day a ready multilayer, infinite membrane permeable at the micron level. Such structures can be of direct interest from the point of view of their application for iltratsii and separation of the different systems. PRI me R. 3. From POM, a highly dispersed powder is obtained (with an average particle size of 2 microns) by precipitating the polymer from a 1% dimethylformamide solution with hot water. Fine powder POM: (2O ar.%) Is mixed with SPA (VO wt.%) As described in example 1. The mixture is extruded through a die of b 0.8 mm, 10 at -t 200 C and P 32 kgf / mm into the vein which is taken with a phiperineal stretch of 2000% in a mixture of water and ice (0 ° С). The difference in the SC of the mixed polymers is 85%, and the ratio of the melt viscosity is 0.57. Copolyamide is extracted from the resulting vein, after which the polyoxymethylene remains in the continuous complex filament yarn of uniform ultrathin fibers. The thread is pulled 8 times at -t 145 C. A polyoxymethylene thread is obtained, the fineness of the fibers in which goes beyond the resolution of optical microscopes and is one hundredth of a micron (according to electron microscopy), and the strength reaches 100 kg / mm% P p and meper 4. A mixture of 5% POM and 95% SPA is prepared as described in Example 1, a vein is extruded from the mixture at t 190 ° C, P 10 kgf / cm through a 0.5 mm capillary va 5 with a spinneret stretching 2000% in a ct 70 C liquid medium. Copolyamide is extracted and the thread is stretched under the conditions of Example 3. A high strength polyoxymethylene n is obtained. of homogeneous fibers with an average diameter of one hundredth micron, Example 5: A mixture of 30% PEM and 7O% copolymer of ethylene and 25% vinylpyrrolidone (CEAT) is prepared as in Example 1, but as a solvent for TEWGEN (t 100 ° C) is used as an EVA. The melt index of SEVPrI at 2 00 ° C was 5. The melt viscosity of the POM refers to the viscosity of the UEMP under extrusion conditions, as 0.6: 1. The difference in degrees of crystallinity of these polymers is 100%. The mixture is extruded under the conditions of Example 1, extracted from the VEFT vein, then the complex polyoxymethylene yarn is pulled (Example l), after which its strength is 130 kg / mm and the average diovietTp fibers are O 4 microns. Example Mix powdered polypropylene (PP) with an average particle size of 30 μs 2 0% solution of copolyamide 548 in ethanol. The PP / SPA ratio is 40/60. Polypropylene has the following characteristics: the characteristic viscosity in decalin is 1. 1.2 ° C at 1.2, the melting point is 169 ° C, the content of the atactic fraction is 5%, CK-90%. The alcohol from the mixture evaporates with stirring, then the mixture is evacuated to constant weight at t (;) O ° C. Said composite composite is forced at i and P 1.6 kgf / cm through the capillary tube of 3 8 m 1 to produce a vein, which is taken in a liquid medium at 40 ° C and with a 200% filter stretch. Relatively, the melt viscosity of PP to viscosity SPA 548 under extrusion conditions is 1: 1, the difference in degrees of crystallinity is 90%. Copolyamide is extracted from the vein with ethyl alcohol. The resulting non-convertible complex thread made of ultrathin polypropylene fibers of the Syut V. Uraz stretch at i 120 ° C, after which its breaking strength was 70 kg / m at an elongation of 23%. If, however, the vein from the PP-SPA mixture is first pulled out, and then the extraction of SPA is performed, a polypropylene filament with a lower strength (SOCg / mm), containing many short filaments, is obtained, while the orientation of the polypropylene microfibers is much less than in the case when extraction precedes pulling. With an increase in the molecules of the pn weight of the PP used and with assembly. In determining all the conditions of the proposed method, the strength of the multifilament yarn of ultra-thin polypropylene fibers exceeds 100 kgf / mm. Example. The powdered POM of example 1 is subjected to granulation on a screw extruder at t 200 ° С to obtain granules with a diameter of 3 mm. In a ball mill, granules of POM (30% wt.%) And polycaproamide PKA (dried,%, weight) dried to a constant weight are mixed. The dispersion of POM n PKA is carried out by extruding this mixture on a screw extruder under nitrogen atmosphere to obtain granules of the mixture, which are evacuated at i: 6 ° C for 14 days. PKA has the following characteristics: average molecular weight 28000, low molecular weight compounds 1.4%, moisture 0.08%, melt viscosity at T 24 ° C and a shear stress of 6, 10.10 dyne / cm 5500 poise. The difference in the power of CRP personality of POM and PKA is 30%, and the ratio of POM / SPA melts is 0.9: 1. The dried mixture is extruded under the conditions of Example 1 (but at 24 ° C) a vein is obtained, from which the formic acid is extracted with PKA (t-20 ° C), washed with water and alcohol. The remaining complex polyoxymethylene yarn is stretched 8 times with .i. 145 ° C, after which its strength is 110 kgf / cm and the average fiber diameter is ~ 5 micron. Example 8. PKA granules are mixed on an extruder at 230 ° C with ethylene-vinyl acetate copolymer granules. (CMEA). The ratio of PKA: SEV is. 45:55. In order to confirm the determining effect of the melt ratio of the fiber-forming polymer to the matrix viscosity (i POM: 7 CMEA), the degree of crystallinity (SC) of the fiber of the forming component and the difference in degrees of crystallinity (RC), the various PKA and CMEA are used. (tab. 2). Melt viscosity is controlled by the use of polymers of different molecular weights. The degree of crystallinity of the CMEA is altered by using a copolymer with different vinyl acetate contents. For mixture No. 3, conventional Industrial PKA with a crystallinity of 30% is used. All other characteristics of PKA are given in Example 7. To obtain a complex high-strength polycaproamide yarn and uniform ultrathin PKA fibers of such a low SC, it is unsuitable. Therefore, PKA specimens with increased SC (50%} due to annealing by known methods are specially obtained. In the case of mixture No. 2, the same ratio of viscosities of the mixegaembix polymers was achieved as in the prototype. The granulated mixture of the indicated 2 polymers is evacuated for 14 days at 60. C to remove moisture and volatile compounds and extruded into the vein at t. And P 20 kgf / cm through a die of 3 0.8 mm; / d 5. The vein is taken in liquid from -70 ° C with a spin nozzle of 1OOO%. the veins are extracted with CMOS benzene, after which the PKA remains as a multifilament yarn, with of ultrathin polycaproamide fibers or in the form of short fibers (mixture 2) .The yarns obtained are pulled at t 180 C. The properties of the threads are presented in Table 2. It can be seen that the high-strength multifilament yarn consisting of homogeneous thin fibers is obtained only from mixture No. 1, for which the fiber-forming component of a high SC is used, the desired values of RK and ratios of melt viscosities are achieved. If at least one of the listed parameters does not fall within the limits of this method, the fiber uniformity in the nigi and durability or no continuous thread at all (mixture No. 1 to 2) is obtained, even if all the molding parameters are observed. PRI me R 9, Powdered POM (characteristics in π-reamer l) are mixed with a 20% solution of polystyrene (PS) in benzene. Benzene is evaporated (lb 6 O ° C) with vigorous stirring, and the mixture is dried in vacuum (t 60 ° C) to constant weight. The ratio of POM / PS as 30/70. PS block is applied, with a monomer content of 0.9% and a melt viscosity at 190 ° C and a dyn / cm -15000 shear yield of 6.0.10. The mixture melt is extruded into the vein at t 190 ° C and P 20 kgf / cN through a spinneret (, 8 mm, 5. The ratio of the viscosity of the melt POM to the viscosity of PS under extrusion conditions of 0.6: 1, and the difference in degrees of crystallinity is 100%. The vein is taken in a mixture of water and ice (0 ° C) with a spinnerette extract of 2000%. From the obtained vein, PS is extracted with benzene, and the remaining complex polyoxnmethylene thread from ultrafine fibers is pulled 6 10 times at 145 C and a high strength is obtained polyoxymethylene yarn Example 10. Powdered polyethylene of low pressure mixed 20% solution of copolyamide 54 (SPA-54) in ethanol as with yew is used in example 1. The characteristics of the polymers used are given in Table 3. Soda} polyanide mixture in a mixture of 35%, SPA-54 - 65 weight The% viscosity of the PE and SPA-54 melts is 1: 1, and the difference in degree of crystallinity is 84%. 3 The dried mixture is extruded into the vein at t 190 ° C and P 35 kgf / cm; through a spinneret 9 0.8 mm, / 3 Yu. The vein is taken and the SPA-54 is extracted under the conditions of Example 2. A complex polyethylene thread is pulled 6 times at t 80c and a high-strength thread is obtained from homogeneous ultrathin polyethylene fibers. Example I. Powdered POM (characteristics are given in example l) are mixed with a 20% solution of a copolymer of ethylene and vinyl acetate (CMEA) in benzene under the conditions of Example 1. The characteristics of the CMEA are given in Example 11 (Table 2, Mixture No. 1). The ratio POM / CMEA 25-75. The mixture, dried to constant weight, is extruded into the vein, as in Example 1 (the ratio of the melt viscosities of POM and CMEA is 1: 3), extracted with benzene | SEI, and the resulting polyoxymethylene naphite is stretched 11 times at Tt 145 ° WITH. The strength of the multifilament yarn of ultra-fine polyoxymethylene fibers (average fiber diameter / 0.3 m ") is 13 O kgf / mm, an elongation of 11%. Thus, this invention allows to obtain a continuous high-strength complex thread (when formed through one hole) consisting of tens and hundreds of thousands of homogeneous, ultrathin diameters up to tenths and hundredths of microns) of highly oriented synthetic fibers that have specific properties - high strength (HU kg / mm and above, high specific surface area - more than 10 O, high hygroscopicity, painted over by a tew, good adhesion, soft, soft n neck.

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7O5013

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"In; N Characteristics of the mixed polymers from PKA microfibers

Characteristics, polymers

Polyethylene

Powder with average. particle size 80 microns

Capralactam copolymer (5O%) and AG salts (5O%)

granules

Claims (2)

1. US patent number 3546063, cl. 161-176, published. 1970. 2.Patent UK No. 1280676, cl. In 5 In, pub. 1972 (prototype).