JP7048060B2 - Manufacturing method of multifilament yarn made of high density fiber - Google Patents

Description

The present invention relates to a high density fiber, and more particularly to a multifilament yarn made of a high density fiber having a high density and high strength suitable for use in marine products and having a small number of fluffs.

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

Among the fibers for fishery materials, the fibers used for fixed nets are required to have a high specific density in order to increase the settling speed in water and to improve the shape retention of fishing nets against tidal currents. Has been done. As described in Patent Document 1 and Patent Document 2, a high-density yarn in which high-density particles are contained in the core component of a core-sheath type composite fiber and the specific density is 1.5 to 1.7 or more has been proposed. There is.

Japanese Unexamined Patent Publication No. 8-311721 Japanese Unexamined Patent Publication No. 8-144125

In the composite fiber in the above-mentioned technique, if the core component contains high-density particles at a high concentration, uniform dispersion tends to be difficult, and as a result, the portion containing the high-density particles at a high concentration during stretching tends to flow. The properties are inferior, voids (voids) are generated in the core component, and it is difficult to obtain a fiber having a specific density corresponding to the content of high specific density particles in the fiber, or it is considered that the core component is cut. Stretched fluff may occur. When a multifilament yarn having fluff due to cutting of some of such fibers is applied to a Russell net or the like, there arises a problem that the mesh of the net is blocked due to the fluff. Therefore, the current situation is that a warping test is performed at the same time as the beam is wound to remove fluff, and there is a problem that the production efficiency is inferior.

The present invention solves the above-mentioned problems, and obtains high-density fibers having a high specific density commensurate with the content of high-density particles without generating voids in the core component, and obtains high-strength fibers. It is an object of the present invention to obtain a multifilament yarn which is less likely to cause fluff due to cutting of the fiber, and to provide a multifilament yarn made of high density fiber which simultaneously satisfies that productivity is improved and continuous operation is possible.

The present inventors have conducted diligent studies in order to achieve the above-mentioned problems. In particular, when various polymers were studied as the polymer to be arranged in the core component containing high specific density particles, the production efficiency was improved and continuous operation was possible by using a specific copolymerized polyester having crystallinity. However, it has been found that it is possible to obtain a multifilament having high strength and high specific density and less likely to cause fluff. Then, based on this finding, further studies were carried out to reach the present invention.

That is, the present invention is a method for producing a multifilament yarn composed of 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.
Copolymerized polyester having a crystal melting point of 200 to 220 ° C. and a glass transition temperature of 70 to 80 ° C. was used as the polymer constituting the core component, and polyethylene terephthalate was used as the polymer constituting the sheath component.
A core component containing high specific gravity particles and a sheath component are introduced into a composite type melt spinning device to cool the fibers spun by melt spinning, and then heat stretching in the first and second stages is performed. By winding at a speed of 1500 to 3500 m / min.
The gist is a method for producing a multifilament yarn, which is characterized by obtaining a multifilament yarn made of high density fibers having a strength of 4.7 cN / dtex or more and a fluff number of 20 pieces / 1 million m or less. do.

The features of the present invention are that the fiber has a high specific gravity of 1.50 or more, the strength of the multifilament yarn composed of this fiber is 4.7 cN / dtex or more, and the number of fluffs is 20/100. The performance of 10,000 m or less is satisfied at the same time, and continuous operability and continuous productivity are improved both in the manufacturing process of multifilament yarn and in knitting and knitting using the obtained multifilament yarn. ..

In order to obtain a fiber having a high specific density of 1.50 or more, the polymer of the core component as a matrix grips the high specific density particles blended in the core component well, and a gap is formed between the polymer and the high specific gravity particles. It is necessary to prevent the generation of cracks (voids) as much as possible.

Here, the problematic void generation occurs in the drawing step in the fiber manufacturing process. That is, since the polymer and the high-density particles are incompatible with each other and a large amount of the high-density particles are contained in the polymer, voids are generated at the interface between the polymer and the particles when stretching stress is applied. Therefore, the inventors thought that if the core component polymer had fluidity during stretching, voids would be less likely to occur at the interface between the polymer and the high-density particles. Then, in order to maintain the fluidity of the core component polymer during stretching, it was decided to raise the heating temperature before stretching. Then, the fluidity of the core component polymer increases, but it is difficult to control the set temperature range, and when the heating temperature exceeds a certain level, the core component polymers start to crystallize and the fluidity decreases, and further, the sheath polymer. Crystallization of materials will also start, sufficient stretching will not be applied, the strength of the obtained fiber will be low, and the fluidity of the core component polymer will decrease, so voids will be generated in the core component polymer, and from that point. The fibers are easily cut, and the cut fibers become fluff in the multifilament yarn and are generated in large quantities. Therefore, if the setting range of the heating temperature is small in this way, it is not possible to stably obtain the desired multifilament yarn having a high specific density, high strength, and little fluff, and continuous operability and productivity are improved. not.

Therefore, while studying a core component polymer that can increase the setting range of the heating temperature and maintain the fluidity during stretching, the relationship between the glass transition temperature and the melting point of the core component polymer was investigated. I paid attention to it. That is, when the glass transition temperature (Tg) is low, crystallization is likely to occur, so that voids and stretching defects as described above are likely to occur, while when the melting point is high, the heating temperature is increased in order to increase the fluidity during stretching. It becomes necessary to raise the temperature, which leads to crystallization of the sheath polymer and prevents sufficient stretching. 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 and it is possible to maintain the fluidity of the core polymer during stretching.

As a copolymerized polyester having a glass transition temperature of 70 to 80 ° C. and a crystal melting point of 200 to 220 ° C., an ethylene oxide adduct of isophthalic acid and bisphenol A as a copolymerization component is added in ethylene terephthalate units to the molar fraction of the following formula. It is preferable to use a copolymerized polyester obtained by copolymerizing with.
0.0 ≤ A ≤ 10.0
5.0 <B ≦ 15.0
(In the above formula, A is the mole fraction (%) of isophthalic acid with respect to the total acid component of the copolymerized polyester, and B is the mole fraction (%) of the ethylene oxide adduct of bisphenol A with respect to the total glycol component of the copolymerized polyester. .)

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

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

The above-mentioned copolymerized polyester is less likely to cause thermal decomposition at the time of melting during melt spinning, and can hold high specific gravity particles well at the melting stage, so that the spinning pack is less likely to be clogged and the continuous productivity of spinning is improved. It will improve dramatically. In the case of a polymer that is easily pyrolyzed during melting, the viscosity decreases and it becomes difficult for the melted polyester to retain the high density particles, and the high density particles that could not be retained gradually remain in the spinning pack upstream of the spinneret. This causes a problem of spinnability due to clogging of the pack, so that continuous operation cannot be performed because the pack needs to be replaced, and the productivity is lowered. This is the same even when an amorphous polymer is used as the core component. In the case of an amorphous polymer, it is easy to secure fluidity at the time of stretching, so that it is easy to obtain a fiber satisfying the specific gravity and strength. However, during melt spinning, the molten polyester is difficult to retain high specific gravity particles, and as in the above, continuous operation is difficult and productivity is lowered.

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

Further, by copolymerizing the ethylene oxide adduct component and the isophthalic acid component of bisphenol A at the above-mentioned specific mole fraction, the glass transition temperature is relatively high as described above, but the melting point is low (200 to 220). Since the temperature can be set to (° C.), it is possible to prevent the heating temperature from being excessively raised before stretching and to 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 becomes low. Further, when the melting point is less than 200 ° C., thermal decomposition is likely to occur, and continuous operation cannot be performed as described above.

In the present invention, as a guideline for continuous operation in the fiber manufacturing process, continuous operation for 20 hours or more without clogging is preferable, and more preferably 24 hours or more.

Further, the ultimate 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. Among them, barium sulfate is preferable because it has a high specific gravity, has excellent dispersibility of the core component in polyester, and does not easily hinder stretchability.

Further, the maximum particle diameter (diameter) of the high specific density 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 density particles contained in the core component is preferably 30 to 70% by mass in the core component. When the content of 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. Therefore, when the composite ratio of the sheath component is lowered, the strength becomes high. It tends to be difficult to obtain the fibers of. On the other hand, when the content of the high specific density particles in the core component is 70% by mass or less, it is possible to knead the particles uniformly into the core component, voids are less likely to occur, and the stretching fluidity is also good.

In addition, as a method of incorporating high-density particles into the core component polymer, a product obtained by uniformly kneading arbitrary high-density particles into a copolymerized polyester used as a core component in advance to form chips is used as it is during melt spinning. It is preferable to use it as an ingredient.

Next, the sheath component in the core-sheath type composite fiber will be described. In the present invention, the strength of the multifilament yarn is borne by the sheath portion of the core-sheath composite fiber. In the present invention, in consideration of strength and yarn-making property, it is inexpensive, has a relatively high specific gravity, and is excellent in dimensional stability. Therefore, it is preferable to use polyester having ethylene terephthalate as a main repeating unit, and polyethylene terephthalate (hereinafter referred to as polyethylene terephthalate). , PET) is more preferable. The ultimate 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, while if it is higher than 1.3, the stretchability may be lowered, which is not preferable.

The core-sheath composite ratio of the core-sheath type composite fiber 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 fiber having a high specific density. On the other hand, when the ratio of the core component is larger than 50/50, the ratio of the sheath component is small and the strength of the fiber tends to be low.

As long as the effects and characteristics of both the core component and the sheath component are not impaired, matting agents such as titanium oxide, antioxidants such as hindered phenolic compounds, ultraviolet absorbers, light stabilizers, pigments, flame retardants, etc. An antibacterial material, a conductivity-imparting agent, or the like may be blended.

The cross-sectional shape of the composite fiber in the present invention may be a variant such as a polygonal shape or a multi-leaf shape for both the core component and the sheath component, and the eccentric core sheath in which the center points of the core component and the sheath component do not match. Although it may be of a mold, it tends to have high strength, so that the center points of the core component and the sheath component are substantially the same, and the concentric core sheath having a circular cross-section and the core-sheath composite having a circular cross section. Fibers are particularly preferred.

The multifilament yarn obtained by the present invention has 20 fluffs / 1 million m or less, and more preferably 10 fluffs / 1 million m or less. The fluff of this multifilament yarn is one in which some of the plurality of composite fibers constituting the multifilament yarn are cut and the fluff is present on the surface of the multifilament yarn. When the number of fluffs exceeds 20 pieces / 1 million m, if fluff is present when the beam is wound before the knitting net when applying the multifilament yarn to the knitting net, the machine base is stopped and the fluff is repaired. Work (work to join the cut parts of the composite fiber) is required, and as the number of fluffs increases, the number of machine stand stops increases and the production efficiency deteriorates. In addition, if there is fluff that cannot be removed without repairing when the beam is wound because the presence of fluff is overlooked, the fluff is taken by the adjacent net thread during knitting and the mesh is closed. Therefore, it is necessary to widen the closed mesh in the obtained net. Therefore, the smaller the number of fluffs, the more preferable, 10 pieces / 1 million m or less, and more preferably 5 pieces / 1 million m or less. In the present invention, the number of fluffs of 20 pieces / 1 million m or less can be achieved because, as described above, the core component can be stretched while maintaining the fluidity during stretching after melt spinning. It is presumed that this is because the cutting of fibers due to the cutting of the core component is less likely to occur.

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, the sedimentation property and shape retention property of the fishing net become insufficient when the multifilament yarn obtained by the present invention is used, for example, for a fixed net application. 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-density particles contained in the core component increases, but it becomes more difficult to increase the strength of the fiber as the content of the high-density particles increases. Therefore, in order to consider the content of high specific density particles contained in the core component and to obtain a fiber having a high strength of 4.7 cN / dtex or more, the upper limit of the fiber specific gravity is preferably 1.80.

The strength of the multifilament yarn obtained by the present invention is 4.7 cN / dtex or more. By setting the strength to 4.7 cN / dtex or more, the strength becomes sufficient for use in fishery resource applications. 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 silk reeling property, the single fiber fineness of the core-sheath type composite fiber obtained in the present invention is preferably 10 to 30 dtex, and the elongation is preferably 15 to 30%.

As described above, the multifilament yarn made of high specific density fibers obtained by the present invention has a high specific density and high strength, and has a fluff number of 20 pieces / 1 million m or less. It can be applied well to the net obtained by netting.

Next, a preferred embodiment of the method for producing a multifilament yarn made of high-density fibers of the present invention will be described.

As the core component polymer, a copolymerized polyester having an intrinsic viscosity of 0.5 to 0.8 obtained by a conventional polymerization method, high specific gravity particles, and, if necessary, additives such as pigments are prepared and weighed respectively. It is obtained by melt-kneading with a twin-screw extruder or the like by a conventional method, extruding from a nozzle, and cutting into pellets. A copolymerized polyester containing high-density particles that have been chipped is dried and used for spinning.

On the other hand, as the sheath component polymer, polyethylene terephthalate obtained by a conventional polymerization method is subjected to solid phase polymerization to increase the viscosity. At this time, the polyethylene terephthalate of the sheath is preferably PET having a limit viscosity of 0.9 or more in consideration of high strength and the number of fluffs, and more preferably 1.3 or more. In addition, as long as it does not affect the strength, specific gravity, and number of fluffs of the fiber, it is a matting agent such as titanium oxide, an antioxidant such as a hindered phenol compound, an ultraviolet absorber, a light stabilizer, a pigment, and a flame retardant. , An antibacterial material, a masterbatch containing a conductivity-imparting agent, etc. can be measured and mixed.

Next, a core-sheath composite-type spinneret is attached to the composite-type melt-spinning apparatus, and a core component and a sheath component containing high-density particles are introduced to perform melt-spinning. After the spun fibers are passed through a heating cylinder with a wall surface temperature of 200 to 500 ° C. installed directly under the mouthpiece, a cooling device is used to blow cooling air at a temperature of 10 to 30 ° C. and a speed of 0.5 to 1 m / sec. Cool and add oil.

After that, it is picked up by a first roller that is not heated, and subsequently, it is hung on a second roller having a surface temperature of 120 to 170 ° C. to align 1.01 to 1.10 times, and a third roller having a surface temperature of 130 ° C. to 200 ° C. is performed. The first step of stretching is performed between the rollers and the rollers. Subsequently, a steam processing machine is installed between the 4th roller and the 3rd roller having a surface temperature of 200 to 260 ° C., and the total draw ratio becomes 4.0 to 6.0 times while spraying steam of 300 ° C. or higher. As described above, the second-stage stretching is performed at a stretching ratio of 1.2 to 1.6 times. After that, a relaxation heat treatment of 2 to 5% is performed between the fifth roller having a surface temperature of 100 to 200 ° C., the winding is wound on a winder at a speed of 1500 to 3500 m / min, and the number of fluff is 20/1 million 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 density and high strength, which is less likely to cause fluff due to fiber cutting, and which has good continuous operability and improved production efficiency. Since the multifilament yarn is less likely to cause fluff, the production efficiency can be improved even when knitting and knitting using this multifilament yarn.

Next, it will be specifically described with reference to Examples of the present invention. The evaluation of each physical property in the present invention was carried out by the following method.
(A) Extreme 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 carried out by a LA-400 type NMR apparatus manufactured by JEOL Ltd. Was measured, and the type and content of the copolymerized components were determined from the integrated intensity of the proton peaks of each component in the obtained chart.
(C) Strong elongation JIS L-1013 According to the standard time test of tensile strength and elongation, the sample length was 25 cm and the tensile speed was 30 cm / min using Shimadzu Autograph DSS-500.
(D) Specific gravity of fiber Measured according to JIS l-1013 specific gravity (floating and sinking method).
(E) Number of fluffs Measured at a pick-up speed of 300 m / min using a fluff detector F9-AN type manufactured by Kasuga Electric.
(F) Melting point (° C)
Measurement was performed at a heating rate of 20 ° C./min using a differential scanning calorimeter DSC-7 manufactured by PerkinElmer.
(G) Glass transition temperature (° C)
Measurement was performed at a heating rate of 20 ° C./min using a differential scanning calorimeter DSC-7 manufactured by PerkinElmer. The extrapolated glass transition start temperature ( _Tig ) was defined as the glass transition temperature.
(H) Operability The evaluation was made on the following three stages based on the continuous operating hours per mouthpiece.
◯: 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 extreme viscosity of 1.2 and a regular PET (extreme viscosity 1.2) are mixed, and the carbon black concentration in the sheath component is 0.8 mass. A blended chip adjusted to% was used. On the other hand, as a core component, the average particle size of the copolymerized polyester having an ultimate 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% is 0. A melt-mixed product (chip) containing 65% by mass of precipitated barium sulfate having a maximum particle size of 2.0 μm and a specific gravity of 4.3 in the core component and 1.5% by mass of carbon black was used. ..

The above core component and sheath component are introduced into the composite melt spinning device, and the core-sheath composite spun spout having a diameter of 0.6 mm and a number of holes of 64 has a temperature of 286 ° C. and a core-sheath mass ratio (core: Sheath) was melt-spun at 26:74.

After the spun fiber was passed through a heating cylinder having a wall surface temperature of 450 ° C., it was cooled by blowing a cooling air having a temperature of 16 ° C. and a speed of 0.8 m / sec using a horizontal cooling device, and an oil agent was applied. Subsequently, it was taken up by a first roller that was not heated, and 1.01 times aligned with the second roller having a surface temperature of 150 ° C., and then with a third roller having a surface temperature of 160 ° C. Stretching was performed 7 times (first step). Then, using a steam processing machine, while spraying steam at a temperature of 450 ° C. and a pressure of 0.5 MPa onto the fibers, stretching 1.4 times (second stage) between the fibers and the fourth roller having a surface temperature of 240 ° C. is performed. , Surface temperature 190 ° C., 2% relaxation heat treatment with a 5th roller at a speed of 1840 m / min, winding on a winder at a speed of 1800 m / min, from a concentric core-sheath composite fiber with 1230 dtex / 64 filament. A multifilament yarn was obtained.

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

Comparative Example 5
In Example 1, a copolymerized polyester having an isophthalic acid copolymerization rate (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. The same procedure as in Example 1 was carried out except that the core-sheath mass ratio (core: sheath) was 36:64 for melt-spinning.

Comparative Examples 6-9
The same procedure as in Example 1 was carried out except that the diol component in the core component was changed to the component shown in Table 2 in place of the ethylene oxide adduct of bisphenol A.

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

実施例１は、毛羽数２個／１００万ｍであり、本発明が規定する高強度（強度４．７ｃＮ／ｄｔｅｘ）、高比重（比重１．５０以上）のものであった。また、紡糸口金の交換頻度も低く、連続生産性に非常に優れていた。

Example 1 had two fluffs / 1 million m, and had a high strength (strength 4.7 cN / dtex) and a high specific density (specific gravity 1.50 or more) specified by the present invention. In addition, the frequency of replacement of the spinneret was low, and the continuous productivity was very excellent.

On the other hand, in Comparative Examples 1 and 4, the molar fraction of the copolymer component was low and the melting point was 230 ° C. or higher or exceeded, the stretch fluidity of the core component was low, and the specific gravity was low. In Comparative Example 4, the specific gravity was 1.46, which was extremely 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 and the thermal stability was inferior, the frequency of replacement of the spinneret increased, and the continuous productivity was inferior.

In Comparative Example 5, the desired strength was not obtained and there was a lot of fluffing. It is considered that this result is due to the fact that the molar fraction of the copolymerized component in the core component is low, the melting point is 230 ° C., and the stretching fluidity of the core component is low.

In Comparative Examples 6 to 8, 1,4-butanediol was used as the copolymerization component, but the thermal stability was inferior, the frequency of replacement of the spinneret was significantly increased, and the continuous productivity was inferior. In Comparative Example 9, 1,4-cyclohexanedimethanol was used as the copolymerization component, but the melting point exceeded 230 ° C., the draw fluidity of the core component was low, and the specific gravity of the obtained fiber was 1.46. Since it was extremely low, no other performance evaluation was performed.

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

Table 3 shows the results of the following wear resistance evaluations for Example 1 and Comparative Examples 1 and 5 having good continuous operability. It can be seen that the results of Example 1 are the best and have practical wear resistance.

<Abrasion resistance>
An eight braid was prepared using the obtained multifilament yarn, and this was used as a sample. The sample was attached to the test device using a wear resistance test device (manufactured by Yonekura Seisakusho). That is, a weight with a mass of 300 g is hung on one end of the sample, and the other end is placed over a round file (a round file for excellent ironwork manufactured by Tsubomiya Co., Ltd.), and the sample is repeated at a speed of 30 ± 1 time / minute and a stroke. The sample was reciprocated with a width of 230 ± 30 mm, and 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 rubbed back and forth, and the number of reciprocating times leading to breakage was measured.
In the measurement, the one evaluated for wear resistance at room temperature was defined as "dry wear", while the sample was immersed in industrial water for 5 minutes and then taken out and evaluated for wear resistance as "wet wear". The "wet wear" was measured by dropping 1 cc of water immediately before the start of the test and every 100 times of wear.

Claims (2)

It is a method for producing a multifilament yarn composed of a core-sheath type composite fiber containing high specific density particles in the core component and having a specific gravity of 1.50 or more.
Copolymerized polyester having a crystal melting point of 200 to 220 ° C. and a glass transition temperature of 70 to 80 ° C. was used as the polymer constituting the core component, and polyethylene terephthalate was used as the polymer constituting the sheath component.
A core component containing high specific gravity particles and a sheath component are introduced into a composite type melt spinning device to cool the fibers spun by melt spinning, and then heat stretching in the first and second stages is performed. By winding at a speed of 1500 to 3500 m / min.
A method for producing a multifilament yarn, which comprises obtaining a multifilament yarn made of high-density fibers having a strength of 4.7 cN / dtex or more and a fluff number of 20 pieces / 1 million m or less. The first aspect of claim 1, wherein the core-sheath ratio (mass ratio) is core component / sheath component = 30 to 20/70 to 80, and the polymer constituting the core component and the sheath component is a polyester-based polymer. Method for manufacturing multifilament yarn.