JP2017160586A - Multifilament yarn consisting of high density fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multifilament yarn consisting of a high density fiber having high density and high strength, hardly generating fuzz by cut of the fiber and capable of continuous operation with improved productivity.SOLUTION: There is provided a multifilament yarn consisting of a core sheath type composite fiber containing high density particles in a core component and having density of 1.50 or more, strength of the multifilament yarn is 4.7 cN/dtex or more and fuzz number is 20/1,000,000 m or less. It is preferable that a polymer constituting the core component is copolymer polyester having crystal melting point of 200 to 220°C and glass transition temperature of 70 to 80°C and a polymer constituting a sheath component is polyethylene terephthalate.SELECTED DRAWING: None

Description

  The present invention relates to a high specific gravity fiber, and particularly relates to a multifilament yarn having a high specific gravity and high strength suitable for marine material use, and comprising a high specific gravity fiber having a small number of fluffs.

  Conventionally, since synthetic fibers such as polyester and polyamide have high strength, they are used as nets for fishery materials such as fishing nets and fibers for land nets such as civil engineering materials. In addition, a technique for adding functional particles to a synthetic fiber at a high concentration is an effective technique as a means for imparting a function in an affordable manner without impairing the properties of the synthetic fiber.

  Among the fibers for marine products, the fibers used for stationary nets must have high specific gravity to increase the sedimentation rate in water and improve the shape of the fishing net against tidal currents. It has been. As described in Patent Document 1 and Patent Document 2, a high specific gravity yarn in which the core component of the core-sheath composite fiber contains high specific gravity particles and the specific gravity is 1.5 to 1.7 or more has been proposed. Yes.

JP-A-8-311721 JP-A-8-144125

  In the composite fiber in the above-described technology, when high specific gravity particles are contained in the core component at a high concentration, uniform dispersion tends to be difficult, and as a result, the portion where the high specific gravity particles are contained at a high concentration when drawing is drawn. It is inferior in properties, and voids (voids) are generated in the core component, which makes it difficult to obtain a fiber having a specific gravity corresponding to the content of high specific gravity particles in the fiber, or due to cutting of the core component. Stretch fluff may occur. When such a multifilament yarn having a fluff formed by cutting some fibers is applied to a Russell net or the like, there is a problem that the mesh of the net is blocked due to the fluff. For this reason, a warping test is simultaneously performed at the time of beam cutting to remove fluff, and there is a problem that production efficiency is poor.

  The present invention solves the above-described problem, and without obtaining a void in the core component, obtains a high specific gravity fiber having a high specific gravity commensurate with the content of the high specific gravity particles, and obtains a high strength fiber. It is an object of the present invention to provide a multifilament yarn composed of high specific gravity fibers that simultaneously satisfies the requirements of obtaining a multifilament yarn that is less prone to fluff due to fiber cutting and improving productivity and enabling continuous operation.

  The present inventors have intensively studied to achieve the above-mentioned problems. In particular, we were investigating a variety of polymers to be distributed to the core component containing high specific gravity particles. By using a specific copolymer polyester with crystallinity, production efficiency was improved and continuous operation was possible. However, the present inventors have found that a multifilament having high strength and high specific gravity and hardly causing fluff can be obtained. And based on this knowledge, it further examined and reached the present invention.

  That is, the present invention is a multifilament yarn comprising a core-sheath type composite fiber containing high specific gravity particles in the core component and having a specific gravity of 1.50 or more, and the strength of the multifilament yarn is 4.7 cN / dtex or more. The gist of the present invention is a multifilament yarn made of high specific gravity fibers, characterized in that the number of fluffs is 20 / million m or less.

  The feature of the present invention is that the strength of the multifilament yarn composed of this fiber is 4.7 cN / dtex or more while the specific gravity is 1.50 or more, and the number of fluff is 20/100. At the same time, it satisfies the performance of 10,000 m or less, and the continuous operability and the continuous productivity are improved both in the production process of the multifilament yarn and in the knitting network using the obtained multifilament yarn. .

  In order to obtain fibers with a high specific gravity of 1.50 or more, the core component polymer as a matrix holds the high specific gravity particles blended in the core component well, and there is a gap between the polymer and the high specific gravity particles. And cracks (voids) should be avoided as much as possible.

  Here, the generation of a void which is a problem occurs in the drawing process in the fiber manufacturing process. That is, the polymer and the high specific gravity particles are not compatible, and a large amount of the high specific gravity particles are contained in the polymer. Therefore, when stretching stress is applied, voids are generated at the interface between the polymer and the particles. Therefore, the inventors considered that if the core component polymer has fluidity during stretching, voids are less likely to be generated at the interface between the polymer and the high specific gravity particles. And in order to make the core component polymer in the state which maintains fluidity | liquidity in extending | stretching, it decided to raise the heating temperature before extending | stretching. As a result, the fluidity of the core component polymer is increased, but it is difficult to control the set temperature range, and when the heating temperature exceeds a certain level, the core component polymer begins to crystallize and conversely the fluidity decreases. Crystallization will also begin, sufficient stretching will not be performed, the strength of the resulting fiber will be low, and the fluidity of the core component polymer will decrease, so voids will occur in the core component polymer and from there The fibers are easily cut, and the cut fibers become fluff in the multifilament yarn and are generated in large quantities. Therefore, when the setting range of the heating temperature is small as described above, the desired multifilament yarn having high specific gravity, high strength and less fluff cannot be obtained stably, and continuous operability and productivity are improved. Absent.

  Therefore, it was possible to increase the setting range of the heating temperature, and while investigating the core component polymer capable of maintaining the fluidity during stretching, the relationship between the glass transition temperature and the melting point of the core component polymer was investigated. Pay attention. That is, when the glass transition temperature (Tg) is low, crystallization is likely to occur, so that the generation of voids and poor stretching as described above are likely to occur. On the other hand, if the melting point is high, the heating temperature is increased to increase the fluidity during stretching. In this case, the sheath polymer is crystallized, and sufficient stretching cannot be performed. Therefore, as a result of examining various polymers, the glass transition temperature of the core component polymer can be set in the range of 70 to 80 ° C., and the crystal melting point can be set in the range of 200 to 220 ° C., thereby increasing the setting range of the heating temperature. It has been found that it is possible to maintain the fluidity of the core polymer during stretching.

As a copolymer polyester having a glass transition temperature of 70 to 80 ° C. and a crystal melting point of 200 to 220 ° C., an ethylene terephthalate unit, isophthalic acid and an ethylene oxide adduct of bisphenol A as copolymer components are represented by the following molar fraction: It is preferable to use a copolyester obtained by copolymerization with.
0.0 ≦ A ≦ 10.0
5.0 <B ≦ 15.0
(In the above formula, A is the molar fraction (%) of isophthalic acid to the total acid component of the copolyester, and B is the molar fraction (%) of the ethylene oxide adduct of bisphenol A to the total glycol component of the copolyester. .)

  Here, the mole fraction is the mole fraction A (mol%) of isophthalic acid to the total acid component of the polyester of the core component, and the mole fraction B of the ethylene oxide adduct of bisphenol A to the total glycol component of the polyester of the core component. (Mol%). By copolymerizing the isophthalic acid component and the ethylene oxide adduct component of bisphenol A in the above-described molar fraction, a low-melting polyester having a crystalline melting point with good heat resistance can be obtained.

  In the present invention, the composition of the copolyester is determined based on the following. That is, the copolyester resin was dissolved in a mixed solvent having a volume ratio of deuterated hexafluoroisopropanol and deuterated chloroform of 1/20, and 1H-NMR was measured with an LA-400 NMR apparatus manufactured by JEOL Ltd. Then, from the integral intensity of the proton peak of each component of the obtained chart, the type and content of the copolymer component are obtained.

  The above-mentioned copolymer polyester is less likely to be thermally decomposed during melting during melt spinning, and can hold high specific gravity particles well in the melting stage, so that clogging of the spinning pack is less likely to occur, and continuous spinning productivity is improved. Greatly improved. In the case of a polymer that is easily thermally decomposed when melted, the viscosity is lowered and the melted polyester becomes difficult to retain high specific gravity particles, and the high specific gravity particles that could not be retained gradually remain in the spin pack upstream of the spinneret. As a result, a problem of spinnability due to clogging of the pack occurs, so that the pack needs to be replaced, so that continuous operation cannot be performed, and productivity is lowered. The same applies to the case where an amorphous polymer is used as the core component. In the case of an amorphous polymer, fluidity is easily ensured at the time of drawing, so that fibers satisfying specific gravity and strength are easily obtained. However, during melt spinning, the melted polyester is difficult to hold high specific gravity particles, and as above, continuous operation is difficult and productivity is lowered.

  Also, by copolymerizing the ethylene oxide adduct component of bisphenol A at a specific molar fraction, the glass transition temperature can be made relatively high compared to the case of copolymerizing only the isophthalic acid component, and the core component By delaying crystallization, it is possible to suppress a decrease in stretching fluidity during stretching and to suppress voids generated in the core component.

  Furthermore, by copolymerizing the ethylene oxide adduct component of bisphenol A and the isophthalic acid component at the specific molar fraction described above, the glass transition temperature is relatively high as described above, while the melting point is lowered (200 to 220). C.), it is possible to prevent the heating temperature from being raised excessively before stretching and maintain the fluidity of the core component polymer. Here, when the melting point is 230 ° C. or higher, the fluidity of the core component polymer is lowered. Moreover, when the melting point is less than 200 ° C., thermal decomposition tends to occur, and continuous operation cannot be performed as described above.

  In the present invention, as a guide for continuous operation in the fiber production process, it is preferable that continuous operation can be performed for 20 hours or more without clogging, and more preferably 24 hours or more.

  The intrinsic viscosity [η] of the core component polymer is preferably 0.5 to 0.8 in consideration of the fluidity of the core component polymer during stretching.

  Examples of the high specific gravity particles contained in the core component include metal particles such as barium, titanium, aluminum and tungsten, and metal compounds such as titanium dioxide, zinc oxide and precipitated barium sulfate. Of these, barium sulfate is preferred because of its high specific gravity, excellent dispersibility of the core component in polyester, and difficulty in inhibiting stretchability.

  In addition, the maximum particle diameter (diameter) of the high specific gravity particles is preferably 4.0 μm or less, and more preferably 3.0 μm or less in consideration of stretchability.

  The content of the high specific gravity particles to be contained in the core component is preferably 30 to 70% by mass in the core component. When the content of the high specific gravity particles is less than 30% by mass in the core component, it is necessary to increase the composite ratio of the core component in order to increase the fiber specific gravity. It is difficult to obtain the fibers. On the other hand, when the content of the high specific gravity particles in the core component is 70% by mass or less, the core component can be uniformly kneaded, voids are hardly generated, and stretching fluidity is improved.

  In addition, as a method of incorporating the high specific gravity particles into the core component polymer, a copolymer polyester used for the core component is kneaded into arbitrary high specific gravity particles in advance to form a chip as it is at the time of melt spinning. It is preferable to use it as a component.

  Next, the sheath component in the core-sheath composite fiber will be described. In the present invention, the sheath of the core-sheath composite fiber bears the strength of the multifilament yarn. In the present invention, it is preferable to use a polyester having ethylene terephthalate as a main repeating unit in consideration of strength and yarn-making property, and is inexpensive, relatively high in specific gravity, and excellent in dimensional stability. , Referred to as PET). The intrinsic viscosity [η] of PET is preferably 0.9 to 1.3. If the intrinsic viscosity is lower than 0.9, it may be difficult to obtain a fiber having high strength. On the other hand, if the intrinsic viscosity is higher than 1.3, stretchability may be deteriorated.

  The core-sheath composite fiber core-sheath composite ratio is preferably 50/50 to 20/80 in terms of mass ratio (core: sheath). When the ratio of the core component is smaller than 20/80, the ratio of the core component becomes small, so that it is difficult to obtain a high specific gravity fiber. On the other hand, when the ratio of the core component is larger than 50/50, the ratio of the sheath component is decreased, and the strength of the fiber tends to be lowered.

  In addition, as long as the core component and the sheath component do not impair their effects and properties, matting agents such as titanium oxide, antioxidants such as hindered phenol compounds, ultraviolet absorbers, light stabilizers, pigments, flame retardants, An antibacterial material, a conductivity imparting agent, or the like may be blended.

  The cross-sectional shape of the conjugate fiber in the present invention may be an irregular shape such as a polygonal shape or a multilobal shape for both the core component and the sheath component, and the center point of the core component and the sheath component is not the same. A core-sheath composite that has a circular cross-section with a concentric core-sheath that has a circular cross-sectional shape, because the center point of the core component and the sheath component are approximately the same, because it is likely to be high strength. Fiber is particularly preferred.

  The multifilament yarn of the present invention has a fluff number of 20 / 1,000,000 m or less, particularly preferably 10 / 1,000,000 m or less. The fluff of the multifilament yarn is one in which some of the composite fibers constituting the multifilament yarn are cut and present on the surface of the multifilament yarn as fluff. When the number of fluff exceeds 20 million / 1,000,000 m, if fluff is present when the multifilament yarn is applied to the braided net before beaming, the machine is stopped and the fluff is repaired. Work (work to join the cut parts of the composite fiber) is required, and the greater the number of fuzz, the greater the number of machine stand stops and the worse the production efficiency. In addition, if there is a fluff that misses the presence of fluff and cannot be removed without repairing at the time of beam cutting, the fluff is taken up by the adjacent net yarn during knitting, and the mesh is closed. Therefore, it is necessary to expand the closed mesh in the obtained net. Therefore, the smaller the number of fluffs, the better, preferably 10 / million m or less, and more preferably 5 / million m or less. In addition, in the present invention, the number of fluffs of 20/1 million m or less could be achieved because, as described above, in the stretching after melt spinning, the core component can be stretched while maintaining fluidity. It is presumed that the fiber is less likely to be cut due to the cutting of the core component.

  The specific gravity of the core-sheath type composite fiber in the present invention is 1.50 or more, and particularly preferably 1.51 or more. When the specific gravity of the composite fiber is less than 1.50, when the multifilament yarn of the present invention is used for, for example, a stationary net, the sedimentation and shape retention of the fishing net are insufficient. The upper limit of the specific gravity is preferably about 1.80. That is, it is considered that the specific gravity increases as the content of the high specific gravity particles contained in the core component increases. However, as the content of the high specific gravity particles increases, it becomes more difficult to increase the strength of the fiber. Therefore, in order to obtain a fiber having a high strength of 4.7 cN / dtex or more in consideration of the content of high specific gravity particles contained in the core component, the upper limit of the fiber specific gravity is preferably 1.80.

  The strength of the multifilament yarn of the present invention is 4.7 cN / dtex or more. By setting the strength to 4.7 cN / dtex or more, the strength is sufficient for use in fishery resources. In addition, considering the fiber specific gravity as described above, the upper limit of the strength is preferably 5.5 cN / dtex.

  Further, in consideration of wear resistance and yarn production, it is preferable that the core-sheath composite fiber obtained in the present invention has a single fiber fineness of 10 to 30 dtex and an elongation of 15 to 30%.

  As described above, the multifilament yarn made of the high specific gravity fiber of the present invention has a high specific gravity and high strength, and has achieved the number of fluffs of 20 pieces / 1,000,000 m or less. It can be applied well to the net obtained.

  Next, the preferable aspect of the manufacturing method of the multifilament yarn which consists of high specific gravity fiber of this invention is demonstrated.

  As the core component polymer, prepare a copolyester having an intrinsic viscosity of 0.5 to 0.8 obtained by a conventional polymerization method, high specific gravity particles, and additives such as pigments as necessary, and weigh each. It is obtained by melt-kneading with a twin-screw extruder or the like by a conventional method, and then extruding from a nozzle and cutting into pellets. The copolymerized polyester containing the high specific gravity particles formed into chips is dried and subjected to spinning.

  On the other hand, the sheath component polymer is prepared by solid-phase polymerization of polyethylene terephthalate obtained by a conventional polymerization method to increase the viscosity. In this case, the polyethylene terephthalate of the sheath is preferably PET having an intrinsic viscosity of 0.9 or more, more preferably 1.3 or more in consideration of high strength and the number of fluff. In addition, matting agents such as titanium oxide, antioxidants such as hindered phenol compounds, ultraviolet absorbers, light stabilizers, pigments, flame retardants, as long as they do not affect the strength, specific gravity, and number of fluff of the fiber In addition, a master batch containing an antibacterial material, a conductivity imparting agent, or the like can be mixed.

  Next, a core-sheath composite type spinneret is attached to a composite type melt spinning apparatus, and a core component and a sheath component containing high specific gravity particles are respectively introduced to perform melt spinning. After passing the spun fiber through a heating cylinder with a wall surface temperature of 200-500 ° C. installed directly under the die, cooling air is blown with a cooling air at a temperature of 10-30 ° C. and a speed of 0.5-1 m / sec. Cool and apply oil.

  After that, it is taken up by a non-heated first roller, and subsequently drawn by a second roller having a surface temperature of 120 to 170 ° C., and is aligned 1.01 to 1.10 times, and a third having a surface temperature of 130 ° C. to 200 ° C. First-stage stretching is performed with the roller. Subsequently, a steam processor is installed between the fourth roller and the third roller having a surface temperature of 200 to 260 ° C, and the total draw ratio is 4.0 to 6.0 times while spraying steam of 300 ° C or higher. Thus, the second stage stretching is performed at a stretching ratio of 1.2 to 1.6 times. Thereafter, a relaxation heat treatment of 2 to 5% is performed between the fifth roller having a surface temperature of 100 to 200 ° C., wound around a winder at a speed of 1500 to 3500 m / min, and the number of fluff is 20 / 1,000,000 m or less. A multifilament yarn having a strength of 4.7 cN / dtex or more and a specific gravity of 1.50 or more is obtained.

  According to the present invention, it is possible to provide a multifilament yarn having high specific gravity and high strength, in which fuzz due to fiber cutting is less likely to occur, with good continuous operability and improved production efficiency. Since the multifilament yarn is less prone to fluff, the production efficiency can be improved even when the multifilament yarn is used for knitting.

Next, an embodiment of the present invention will be specifically described. In addition, evaluation of each physical property in this invention was performed with the following method.
(A) Intrinsic viscosity Measured at a concentration of 0.5 g / dl and a temperature of 20 ° C. using an equal mass mixture of phenol and ethane tetrachloride as a solvent.
(B) Composition of polyester The polyester resin was dissolved in a mixed solvent having a volume ratio of deuterated hexafluoroisopropanol and deuterated chloroform of 1/20, and 1H-NMR was measured with an LA-400 NMR apparatus manufactured by JEOL Ltd. From the integrated intensity of the proton peak of each component of the obtained chart, the type and content of the copolymer component were determined.
(C) Strong Elongation According to JIS L-1013, a standard test of tensile strength and elongation, Shimadzu Autograph DSS-500 was used and measured at a sample length of 25 cm and a tensile speed of 30 cm / min.
(D) Specific gravity of fiber Measured according to JIS 1-1013 specific gravity (floating and sinking method).
(E) Number of fluff Using a Kasuga Denki fluff detector F9-AN type, measurement was performed at a take-up speed of 300 m / min.
(F) Melting point (° C)
A differential scanning calorimeter DSC-7 manufactured by Perkin Elmer was used, and the temperature was measured at a heating rate of 20 ° C./min.
(G) Glass transition temperature (° C)
A differential scanning calorimeter DSC-7 manufactured by Perkin Elmer was used, and the temperature was measured at a heating rate of 20 ° C./min. The extrapolated glass transition start temperature (T _ig ) was _defined as the glass transition temperature.
(H) Operability The following three stages were evaluated according to the continuous operation time per base.
○: 20 hours or more Δ: 10 hours or more, less than 20 hours ×: less than 10 hours

Example 1
As a sheath component, a master batch containing a high concentration of carbon black in PET having an intrinsic viscosity of 1.2 and a regular PET (ultimate viscosity of 1.2) are mixed, and the concentration of carbon black in the sheath component is 0.8 mass. %, Blended chips were used. On the other hand, an average particle size of 0 is used as a core component in a copolyester having an intrinsic viscosity of 0.58, an isophthalic acid copolymerization rate of 8.0 mol%, and an ethylene oxide adduct copolymerization rate of bisphenol A of 6.5 mol%. A chip (chip) prepared by melting and mixing precipitated barium sulfate having a maximum particle size of 2.0 μm and a specific gravity of 4.3 in a core component to 65% by mass and carbon black to 1.5% by mass was used. .

  The core component and the sheath component are introduced into a composite melt spinning apparatus, and the temperature is 286 ° C., the core-sheath mass ratio (core: core: from the core-sheath composite spinneret having a diameter of 0.6 mm and a number of holes of 64. Sheath) Melt spinning at 26:74.

  The spun fiber was passed through a heating cylinder having a wall surface temperature of 450 ° C., and then cooled by blowing cooling air at a temperature of 16 ° C. and a speed of 0.8 m / sec using a horizontal cooling device to give an oil agent. Subsequently, the film is taken up by a non-heated first roller, aligned 1.01 times with a second roller having a surface temperature of 150 ° C., and then placed with a third roller having a surface temperature of 160 ° C. The film was stretched 7 times (first stage). Then, using a steam processing machine, while blowing steam at a temperature of 450 ° C. and a pressure of 0.5 MPa onto the fiber, the fiber is stretched 1.4 times (second stage) with a fourth roller having a surface temperature of 240 ° C. 2% relaxation heat treatment with a fifth roller at a surface temperature of 190 ° C. and a speed of 1840 m / min, wound around a winder of 1800 m / min and wound from a concentric core-sheath composite fiber with 1230 dtex / 64 filament A multifilament yarn was obtained.

Comparative Examples 1-4
The same procedure as in Example 1 was carried out except that the isophthalic acid copolymerization rate (A) and the ethylene oxide adduct copolymerization rate (B) of bisphenol A in the core component were changed as described in Table 1.

Comparative Example 5
In Example 1, a copolymerized polyester having an isophthalic acid copolymerization ratio (A) of 8.0 mol% was used as the core component, and the amount of precipitated barium sulfate mixed in the core component was 50% by mass. This was carried out in the same manner as in Example 1 except that melt spinning was performed with a core-sheath mass ratio (core: sheath) of 36:64.

Comparative Examples 6-9
The same procedure as in Example 1 was conducted except that the diol component in the core component was changed to the components described in Table 2 instead of the bisphenol A ethylene oxide adduct.

  The evaluation results of the composite fibers are shown in Tables 1 and 2.

Example 1 had 2 fluffs / 1,000,000 m, and had high strength (strength 4.7 cN / dtex) and high specific gravity (specific gravity 1.50 or more) defined by the present invention. In addition, the frequency of changing the spinneret was low, and the continuous productivity was excellent.

  On the other hand, in Comparative Examples 1 and 4, the molar fraction of the copolymer component was low, the melting point was 230 ° C. or higher, the core component had low stretching fluidity, and the specific gravity was low. In Comparative Example 4, the specific gravity was 1.46, which was very low, so no other performance evaluation was performed.

  In Comparative Examples 2 and 3, since only the isophthalic acid component was copolymerized, the glass transition temperature was low, the thermal stability was poor, the replacement frequency of the spinneret was increased, and the continuous productivity was poor.

  In Comparative Example 5, the intended strength was not obtained, and there was much fuzz. This result is considered to be due to the low molar fraction of the copolymer component in the core component and the melting point of 230 ° C., and the low draw fluidity of the core component.

  In Comparative Examples 6 to 8, 1,4-butanediol was used as a copolymerization component, but the heat stability was poor, the frequency of changing the spinneret was greatly increased, and the continuous productivity was poor. In Comparative Example 9, 1,4-cyclohexanedimethanol was used as the copolymer component, but the melting point exceeded 230 ° C., the core component had low stretching fluidity, and the resulting fiber had a specific gravity of 1.46. Since it was extremely low, no other performance evaluation was performed.

  In Comparative Examples 2, 3, and 6 to 8, since the continuous operability was not good, fluff evaluation was not performed.

  Table 3 shows the results of the following wear resistance evaluation for Example 1 and Comparative Examples 1 and 5, which have good continuous operability. It can be seen that the result of Example 1 is the best and has practical wear resistance.

<Abrasion resistance>
Eight braids were made using the obtained multifilament yarn and used as a sample. The sample was attached to the test apparatus using an abrasion resistance test apparatus (manufactured by Yonekura Seisakusho). That is, a weight of 300 g is hung on one end of the sample, and the other end is placed over a round file (Tsubomiya's excellent ironwork file, round-medium), and the sample is repeated at a speed of 30 ± 1 times / min. The sample was reciprocated at a width of 230 ± 30 mm, the sample and the peripheral surface of the round file were brought into contact with each other at an angle of about 90 degrees, and the reciprocating friction was performed.
The measurement was evaluated as “dry wear” when the abrasion resistance was evaluated at room temperature, and “wet abrasion” when the sample was immersed in industrial water for 5 minutes and then taken out and evaluated for abrasion resistance. “Wet wear” was measured by dropping 1 cc of water just before the start of the test and every 100 wears.

Claims (4)

  It is a multifilament yarn comprising a core-sheath type composite fiber containing high specific gravity particles in the core component and having a specific gravity of 1.50 or more, the strength of the multifilament yarn is 4.7 cN / dtex or more, and the number of fluff is 20 Multifilament yarn made of high specific gravity fibers, characterized in that the number is 1 million or less.   The core-sheath ratio (mass ratio) is a core component / sheath component = 30-20 / 70-80, and the polymer constituting the core component and the sheath component is a polyester-based polymer. Multifilament yarn made of high specific gravity fiber.   The polymer constituting the core component is a copolyester having a crystal melting point of 200 to 220 ° C and a glass transition temperature of 70 to 80 ° C, and the polymer constituting the sheath component is polyethylene terephthalate. A multifilament yarn comprising the high specific gravity fiber described. The net | network comprised by the multifilament yarn of any one of Claims 1-3.