JPH10325018A - Conjugate filament having high specific gravity and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a conjugate filament capable of producing in good yarnproducing property, having high specific gravity and strength and suitable for marine raw materials, especially fishing nets. SOLUTION: This conjugate filament having high specific gravity comprises a core layer composed of a polyester resin composition having 1.9-3.5 specific gravity and containing a polyester resin, <=40 vol.% inorganic fine particles and a melting viscosity-lowering agent in an amount of 0.5-10.0 wt.% based on the polyester resin and a sheath layer composed of a polyester resin having >=1.5 relative viscosity, and has <=40/60 volume ratio of the core layer to the sheath layer and >=4 g/d linear strength and >=15% linear breaking elongation and >=1.5 specific gravity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high specific gravity and high strength composite filament suitable for marine materials, particularly for fishing nets, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, polyvinylidene chloride fibers used in fishing nets have a problem that they emit gases harmful to the environment when incinerated. In recent years, many fishing nets have been replaced by polyester fibers.

[0003] Polyester fiber is a synthetic fiber having a relatively high specific gravity, but has a high sedimentation speed in water and has a higher specific gravity in order to improve the shape retention of the fishing net against the tide. .

[0004] In recent years, in order to improve productivity, a fishing net of Russell knitting capable of high-speed net-making has become mainstream, and polyester fibers for fishing nets having high strength capable of withstanding high-speed net-making have been desired. .

Hitherto, various types of high-specific-gravity core-sheath composite filaments in which a core layer contains inorganic particles having a high specific gravity have been proposed. However, in the conventional composite filament, since the core layer contains a large amount of inorganic fine particles, there is a problem that a small space (void) is generated around the inorganic fine particles by stretching and the specific gravity cannot be sufficiently increased. In addition, the core layer containing a large amount of inorganic fine particles has a problem that the fluidity during melting and stretching is poor, and the spinning property is poor.

[0006]

DISCLOSURE OF THE INVENTION The present invention aims to provide a composite filament which can be produced with good yarn-making properties, has a high specific gravity and a high strength, and is suitable for marine materials, particularly for fishing nets, and a method for producing the same. Is what you do.

[0007]

The present invention solves the above-mentioned problems, and the gist is as follows. 1. A polyester resin composition having a specific gravity of 1.9 to 3.5 in which a core layer contains 40% by volume or less of inorganic fine particles in a polyester resin and a melt viscosity reducing agent of 0.5 to 10.0% by weight based on the polyester resin; Made of the above polyester resin, the volume ratio of the core layer to the sheath layer is 40/60 or less, the linear strength is 4 g / d or more, the linear elongation at cut is 15% or more, and the specific gravity is 1.5 or more. And a high specific gravity composite filament.

[0008] 2. The core layer is less than 40% by volume of inorganic fine particles in polyester resin and 0.5-10.0% in polyester resin.
1.9 to 3.5 specific gravity containing a melt viscosity reducing agent in a weight percent
Polyester resin composition, the sheath layer is made of a polyester resin having a relative viscosity of 1.5 or more, and the volume ratio of the core layer and the sheath layer is 40.
/ 60 or less composite monofilament spinning speed 20 ~ 10
Melt spun at 0 m / min and the obtained undrawn yarn is 80-120 ° C
The first step stretching 3.0 to 5.5 times while heating to
While heating to 0 to 200 ° C, the second stage stretching is performed 1.0 to 2.0 times,
2. The high specific gravity composite monofilament according to the above item 1, wherein the total draw ratio is 5.0 to 6.0 times, and subsequently, a relaxation heat treatment is performed at a temperature of 200 ° C. or more at a relaxation rate of 5 to 10%. Method.

3. The core layer is less than 40% by volume of inorganic fine particles in polyester resin and 0.5-10.0% in polyester resin.
1.9 to 3.5 specific gravity containing a melt viscosity reducing agent in a weight percent
Polyester resin composition, the sheath layer is made of a polyester resin having a relative viscosity of 1.5 or more, and the volume ratio of the core layer and the sheath layer is 40.
Spinning speed of 200/60 or less composite multifilament
Melt spinning at ~ 1000m / min and the obtained undrawn yarn is 80 ~ 13
After heating to 0 ° C, heat-treating at a temperature of 150 ° C or more
2. The high specific gravity composite multifilament according to the above item 1, wherein the multifilament is stretched at a draw ratio of 5.0 to 6.5 times and then subjected to a relaxation heat treatment at a temperature of 150 ° C. or more at a relaxation rate of 5 to 15%. Method.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

[0011] As described above, the marine material filament is required to have not only a high specific gravity but also a high strength. The sheath layer is responsible for the strength of the filament. In the present invention, a polyester resin having a high specific gravity and exhibiting high strength by stretching is used as the sheath layer.

As the polyester resin used in the present invention, polyethylene terephthalate, polybutylene terephthalate, aliphatic polyester and copolymerized polyester mainly composed of these are used, but polyethylene terephthalate is most preferable in consideration of filament strength and economy.

In the present invention, the polyester resin used for the sheath layer preferably has a relative viscosity of 1.60 to 1.75. If the relative viscosity is less than 1.60, high-strength filaments cannot be obtained and the relative viscosity of the filaments
It is difficult to adjust to 1.5 or more, and stable spinnability for a long time cannot be obtained. On the other hand, if the relative viscosity exceeds 1.75, there is a problem that melting spots are caused, the flowability of the molten polymer is deteriorated, and the fiber surface becomes rough, and the melting temperature is required to completely melt the polymer. However, when the value is too high, the polymer is thermally decomposed, and the effect of the high-viscosity polymer is lost.

As the polyester resin for the sheath layer, a resin substantially free of inorganic fine particles for increasing the specific gravity is used. (A small amount of inorganic fine particles as a coloring agent, matting agent, leveling agent, etc. may be contained.)

On the other hand, for the core layer, a resin composition containing inorganic fine particles and a melt viscosity reducing agent in a polyester resin is used.

As the inorganic fine particles, those having a small secondary aggregation between the fine particles, excellent dispersibility in the polyester resin, and high safety and high specific gravity are used. Specifically, titanium, zirconium, barium, and the like are used. What consists of various metals, such as tungsten, and the compound of these metals is used. Particularly preferred is sedimentable barium sulfate in view of dispersibility in polyester resin, spinnability, stretchability and safety.

The inorganic fine particles have an average particle size of 1.0 μm.
m or less, and those containing substantially no particle size of 6.0 μm or more are preferred. If such inorganic fine particles are used, they are uniformly dispersed in the polyester resin, and a filament having good spinning properties and high strength can be obtained. If the particle size of the inorganic fine particles is too large, it will be difficult to uniformly disperse the particles in the polyester resin, and the spinning properties will deteriorate, and a high-strength filament cannot be obtained. Further, the inorganic fine particles are preferably nearly spherical.

The amount of the inorganic fine particles contained in the polyester resin of the core layer must be 40% by volume or less. When the content of the inorganic fine particles exceeds 40% by volume, the processability in producing the polyester resin composition is remarkably reduced, and a composition having a uniform specific gravity cannot be obtained, and the spinnability and stretchability are reduced. It is impossible to obtain a filament having high strength and uniform specific gravity.

The specific gravity of the polyester resin composition containing the inorganic fine particles must be 1.9 to 3.5. If the specific gravity of the polyester resin composition is attempted to be larger than 3.5, the processability during the production of the polyester resin composition is significantly reduced, and it is difficult to obtain a polyester resin composition having a uniform specific gravity and shape, and the melt spinnability is deteriorated. It is not preferable because it may cause On the other hand, if the specific gravity of the polyester resin composition is less than 1.9, it becomes difficult to obtain a filament having a high specific gravity and high strength.

In general, when a melt-spun yarn using a polyester resin composition containing a large amount of inorganic fine particles is drawn, the polyester resin is gradually drawn, but the inorganic fine particles themselves remain without being drawn. In addition, there is a problem that voids are generated around the inorganic fine particles and the specific gravity of the filament is reduced. In some cases, even if inorganic fine particles are added to increase the specific gravity, the specific gravity may be lower than the specific gravity of the polyester resin.

In the present invention, in order to solve the above problems, the melt viscosity reducing agent is contained in the polyester resin composition of the core layer in an amount of 0.5 to 10.0% by weight based on the polyester resin. The melt viscosity reducing agent acts to reduce the melt viscosity of the polyester resin, thereby improving the dispersibility of the inorganic fine particles in the polyester resin, promoting plastic deformation, and suppressing the generation of voids around the inorganic fine particles. In addition, it is possible to suppress a decrease in specific gravity. Further, by containing a melt viscosity reducing agent, the spinning property is improved, and the strength of the obtained filament is also increased.

As the melt viscosity lowering agent, a bisphenol compound represented by the following formula is preferably used.

[0023]

Embedded image

Specific examples of the melt viscosity reducing agent include the following compounds.

[0025]

Embedded image

The amount of the melt viscosity reducing agent to be added to the polyester resin in the core layer is 0.5 to 10.0% by weight, preferably 1.5 to 8.0% by weight, more preferably 1.5 to 8.0% by weight, based on the polyester resin.
It is necessary to be 2.5-6.0% by weight, and if this condition is not satisfied, the target performance is not exhibited. That is, if the amount is less than 0.5% by weight, a sufficient effect cannot be obtained, and if it exceeds 10.0% by weight, the spinnability deteriorates, which is not preferable.

The polyester resin composition of the core layer is
It is desirable that the polyester resin, the inorganic fine particles, and the melt viscosity reducing agent are mixed and melt-kneaded to form chips, whereby the workability is good and the inorganic fine particles can be uniformly dispersed in the polyester resin.

The ratio between the core layer and the sheath layer must be 40/60 or less by volume, preferably 10/90 to 40/60. When the ratio of the core layer is larger than this, it is difficult to obtain a high-strength filament even when using a polyester resin having a high relative viscosity as the polyester resin of the sheath layer, and it is difficult to obtain stable spinnability for a long time. Become.

Next, a method for producing the composite monofilament of the present invention will be described. First, using the polyester resin composition as the core layer and the polyester resin as the sheath layer, melt spinning is performed at a spinning speed of 20 to 100 m / min by a conventional method to obtain a composite undrawn monofilament. The spinning temperature at this time is suitably from 230 to 350 ° C., preferably from 250 to 310 ° C. If the spinning temperature is too low, it is difficult to completely melt the polymer. It is unfavorable.

The spun yarn is cooled and solidified by a liquid bath at 0 to 100 ° C., preferably 10 to 90 ° C. If the cooling temperature is too low, it is difficult to control the temperature and the workability deteriorates. If the cooling temperature is too high, the solidification of the cooling becomes incomplete, which is not preferable.

The undrawn yarn solidified by cooling is drawn after being wound once or without being wound.

The stretching can be carried out in one stage or in two or more stages. In the present invention, a two-stage stretching method is employed. That is, using a liquid bath and / or an oven, the temperature of the yarn is set to 80 to 120 ° C., and the first-stage drawing is performed at a draw ratio of 3.0 to 5.5 times.
Using a 200 ° C liquid bath and / or oven, draw ratio
Stretching in the second stage at 1.0 to 2.0 times, the total stretching ratio is 5.0 to 6.5
Make it double.

When the yarn temperature in the first-stage drawing is lower than 80 ° C., a high-strength monofilament can be obtained, but the generation of voids cannot be suppressed, and the target high specific gravity and high strength Monofilament cannot be obtained. On the other hand, if the temperature of the yarn exceeds 120 ° C., superdraw occurs, and although the specific gravity of the monofilament does not decrease, a high-strength monofilament cannot be obtained.

In the second-stage stretching, since the crystals are oriented to some extent during the first-stage stretching, it is necessary to stretch at a higher temperature than in the first-stage stretching. If the yarn temperature in the second-stage drawing is lower than 120 ° C., it becomes difficult to suppress generation of voids as in the first-stage drawing, and it is not possible to obtain a target monofilament having a high specific gravity. On the other hand, if the temperature of the yarn exceeds 200 ° C., superdraw occurs, and a high-strength monofilament cannot be obtained.

On the other hand, if the draw ratio of the first step is less than 3.0 times, uneven drawing occurs, the drawability in the second step is deteriorated, and the desired high-strength monofilament can be obtained. On the other hand, if the ratio exceeds 5.5 times, the film is excessively stretched, a large amount of voids are generated, and a monofilament having a high specific gravity cannot be obtained.

Further, the stretching ratio in the second stage is set to 1.0 to 2.0.
And the total draw ratio must be 5.0 to 6.5. If the total draw ratio is less than 5.0 times, the desired high-strength monofilament cannot be obtained.On the other hand, if the total draw ratio exceeds 6.5 times, voids are generated due to excessive drawing and the specific gravity is increased. Can not do.

The drawn yarn is subjected to a relaxation heat treatment at a relaxation rate of 5 to 15% using a liquid bath at 200 ° C. or higher and / or an oven.

When the relaxation heat treatment temperature is lower than 200 ° C., it is difficult to make the linear cut elongation 15% or more,
Workability decreases.

On the other hand, if the relaxation rate exceeds 15%, excessive relaxation treatment causes unevenness in the properties of the fibrous material and causes deterioration in workability. On the other hand, if the relaxation rate is less than 5%, it is difficult to make the linear elongation at break 15% or more.

It is appropriate that the fineness of the monofilament after drawing and heat treatment be 50 to 1500 d.

Next, a method for producing the composite multifilament of the present invention will be described. First, using the core layer polyester resin composition as described above as a core layer and a polyester resin as a sheath layer, at a spinning temperature similar to that of a monofilament, melt spinning at a spinning speed of 200 to 1000 m / min by a conventional method, Obtain a composite undrawn multifilament.

The spun yarn is cooled and solidified by blowing gas (air) at 0 to 100 ° C., preferably 10 to 90 ° C. If the cooling temperature is too low, it is difficult to control the temperature and the workability deteriorates. If the cooling temperature is too high, the solidification of the cooling becomes incomplete, which is not preferable.

The cooled and solidified yarn is stretched after winding once or without winding. Stretching can be performed in one step or in two or more steps. In the present invention, a one-step drawing method is employed. That is, after the temperature of the yarn is adjusted to 80 to 130 ° C. using a heating roller and / or an oven, the yarn is heated using an oven and / or a contact heater.
Stretch at a stretching ratio of 5.0 to 6.5 while heating to 150 ° C or higher.

The drawn yarn is subjected to a relaxation heat treatment at a relaxation rate of 5 to 15% using a heating roller and / or an oven at 150 ° C. or higher.

If the stretching and heat treatment conditions are not satisfied, as in the case of the monofilament, voids are generated and a multifilament having a high specific gravity cannot be obtained, or a superdraw occurs and a multifilament having a high strength can be obtained. The elongation at straight section cannot be increased to 15% or more, unevenness in the thread properties occurs, and workability is poor.

It is appropriate that the fineness of the multifilament after drawing and heat treatment be 4 to 50 d for single yarn and 100 to 2000 d for total fineness.

In the present invention, the content of the inorganic fine particles in the core layer, the amount of the melt viscosity reducing agent added to the polyester resin in the core layer, the relative viscosity of the polyester resin in the sheath layer, the ratio between the core layer and the sheath layer, Appropriate spinning, drawing and heat treatment conditions are selected to obtain filaments with stable continuous spinnability, specific gravity of 1.5 or more, linear strength of 4 g / d or more, and linear cut elongation of 15% or more. To be able to

By maintaining such characteristics, high-speed netting can be achieved, and the fishing net has the necessary strength as a fishing net, has a high sedimentation speed in water, and has excellent shape retention against tidal currents. It is a filament that can be used.

When producing the filament, a chain extender or a terminal blocking agent can be added, and various additives such as a stabilizer and a soaking agent are contained as long as the performance of the filament is not impaired. You can also.

[0050]

Next, the present invention will be described in detail with reference to examples. In addition, the measuring method and the evaluation method are as follows. (a) Relative viscosity of polyester The measurement was carried out at a concentration of 0.5 g / dl and a temperature of 20 ° C. using an equal weight mixture of phenol and ethane tetrachloride as a solvent. (b) Strength and elongation Sample length 25c using Shimadzu Autograph DSS-500
m at a tensile speed of 30 cm / min. (c) Specific gravity 1 mm or less of the resin composition or a 10 mm long fiber piece was pulverized with 1,1-dichloro-2,2,3,3,3-pentafluoropropane and 1,3-dichloro-1,1 , 2,2,3-pentafluoropropane and a solution obtained by mixing at a ratio of 45/55 by volume and a chlorofluoroethylene low-polymer solution were immersed in a solution obtained by mixing so as to have an arbitrary specific gravity, After defoaming, it was measured by a float-sink method. (d) Operability Twenty-four hours of spinning was performed, and the number of yarn breaks during spinning (spinnability) and the number of yarn breaks during stretching (drawability) were evaluated in the following five stages. A: 0 times B: 1 time C: 2 to 3 times D: 4 times or more E: Difficulty of spinning or drawing or impossible to wind

Example 1 Polyethylene terephthalate (PET) having a relative viscosity of 1.41
67.5 parts by volume of resin, average particle size 0.5 μm, maximum particle size 2.0 μm
, Specific gravity 4.3 barium sulfate fine particles (BaSO ₄ )
32.5% by volume based on volume and polyester resin
Was melt-kneaded to obtain a high specific gravity chip for a core layer having a specific gravity of 2.30. In addition, the above formula as a melt viscosity reducing agent
The bisphenol S-based compound represented by (a) was used. On the other hand, a PET chip having a relative viscosity of 1.68 was prepared for the sheath layer. High specific gravity chip for core layer and PET for sheath layer
The chips are fed to separate melt extruders and
Four concentric composite monofilaments having a core / sheath composite volume ratio of 20/80 were spun from a spinneret having four spinning holes having a diameter of 1.3 mm heated at 295 ° C and heated to 295 ° C. Spun yarn
After cooling and solidifying through a 70 ° C hot water bath, the yarn is taken up at a speed of 40 m / min, the yarn is heated to 100 ° C using a glycerin bath, stretched at a draw ratio of 4.5 times in the first stage, and then drawn at 150 ° C. Using an oven, stretch the film in the second stage at a draw ratio of 1.2 times, so that the total draw ratio becomes 5.4 times, and then heat-treat it at a relaxation rate of 10% using an oven at 250 ° C. A sheath-type composite monofilament was obtained. In addition, PET for sheath layer
The monofilament obtained by melt-spinning using only the chips at the same temperature and residence time as described above has a relative viscosity of 1.55.
Met.

Examples 2 to 10 The content of the melt viscosity reducing agent in the core layer (Examples 2 to 3), the temperature of the first stage stretching (Examples 4 to 5), and the temperature of the second stage stretching (Example 6) 7), stretching ratio (Examples 8 to 9) or P for sheath layer
A composite monofilament was obtained in the same manner as in Example 1 except that the relative viscosity of the ET chip (Example 10) was changed as shown in Table 1.

Example 11 As a high specific gravity chip for a core layer, 88.3 parts by volume of a PET resin, 11.7 parts by volume of fine particles of tagustene having an average particle diameter of 0.6 μm, a maximum particle diameter of 2.0 μm and a specific gravity of 19.3, and 5.0% by weight of the PET resin were used. A composite monofilament was obtained in the same manner as in Example 1, except that a chip having a specific gravity of 3.45 obtained by melt-kneading the melt viscosity reducing agent was used.

Table 1 shows the yarn properties and the like of the monofilaments obtained in Examples 1 to 11.

[0055]

[Table 1]

Comparative Examples 1 to 10 The content of the melt viscosity reducing agent in the core layer (Comparative Examples 1 and 2), the first stage stretching temperature (Comparative Examples 3 and 4), and the second stage stretching temperature (Comparative Example 5) -6), and the production of a composite monofilament was attempted in the same manner as in Example 1 except that the stretching ratio (Comparative Examples 7 to 8) or the relaxation rate (Comparative Examples 9 to 10) were changed as shown in Table 2. .

Table 2 shows the yarn properties and the like of the composite monofilament obtained in the above comparative example.

[0058]

[Table 2]

In Comparative Example 2 in which a core layer chip containing a large amount of the melt viscosity reducing agent was used, in Comparative Example 8 in which the spinning property was poor, good monofilaments could not be obtained, and the distribution of the draw ratio was not appropriate. , The yarn is cut during the second stage drawing,
In Comparative Example 10 in which the relaxation rate was increased, the yarn was loosened during the relaxation heat treatment, and could not be wound.

Comparative Example 11 As a high specific gravity chip for a core layer, 85.7 parts by volume of a PET resin, 14.3 parts by volume of fine particles of tagustene having an average particle diameter of 0.6 μm, a maximum particle diameter of 2.0 μm, and a specific gravity of 19.3, and 5.0% by weight based on the PET resin were used. An attempt was made to obtain chips having a specific gravity of 3.90 by melt-kneading. However, the workability was extremely poor, and the specific gravities and shapes of the obtained chips were not uniform. Further, melt spinning of the composite monofilament was attempted using this, but the spinnability was poor and an undrawn monofilament could not be obtained.

Comparative Example 12 An attempt was made to produce a monofilament in the same manner as in Example 1 except that the core / sheath composite volume ratio was changed to 45/55. The spinnability was poor, and it was difficult to take off the undrawn monofilament.

Comparative Example 13 A high specific gravity chip for a core layer was obtained by setting the content of BaSO ₄ to 50% by volume. However, the workability was poor and the specific gravity and shape of the obtained chip were not uniform. Further, melt spinning of the composite monofilament was attempted using this, but the spinnability was poor and it was difficult to take off the undrawn monofilament.

Example 12 The same high specific gravity chip for the core layer and the PET chip for the sheath layer as in Example 1 were fed to separate melt extruders, melted at 295 ° C., respectively, and heated to 295 ° C. with a diameter of 0.6. A concentric composite multifilament having a core-sheath composite volume ratio of 20/80 was spun from a spinneret having 48 spinning holes of mm. After the spun yarn is cooled and solidified by blowing air at 20 ° C., a spinning oil is applied,
It is drawn at a speed of 400 m / min with a heating take-off roller at 105 ° C, stretched 5.6 times while contacting a hot plate at 200 ° C between the take-off roller and the stretching roller. The film was wound after being subjected to relaxation heat treatment at a relaxation rate of 10% to obtain a composite multifilament of 1000d / 48f. The multifilament obtained by melt spinning using only the sheath layer PET chip at the same temperature and residence time as above had a relative viscosity of 1.58.

Examples 13 to 26 Content of melt viscosity reducing agent in core layer (Examples 13 to 14), temperature of take-up roller (Examples 15 to 16), temperature of hot plate (Example
17-18), stretching ratio (Examples 19-20), temperature of relaxation heat treatment (Examples 21-22), relaxation rate (Examples 23-24) or relative viscosity of PET chip for sheath layer (Examples 25-20) 26) in Tables 3-4
A composite multifilament was obtained in the same manner as in Example 12, except for the following changes.

Example 27 A composite multifilament was obtained in the same manner as in Example 12 except that the high specific gravity chip for the core layer was changed to the same high specific gravity chip for the core layer as in Example 11.

Tables 3 and 4 show the yarn properties and the like of the composite multifilaments obtained in Examples 12 to 27.

[0067]

[Table 3]

[0068]

[Table 4]

Comparative Examples 14 to 23 The content of the melt viscosity reducing agent in the core layer (Comparative Examples 14 to 15), the temperature of the take-up roller (Comparative Examples 16 to 17), and the temperature of the hot plate (Comparative Example)
18), stretching ratio (Comparative Examples 19 to 20), temperature of relaxation heat treatment
(Comparative Example 21) An attempt was made to produce a composite multifilament in the same manner as in Example 12, except that the relaxation rate (Comparative Examples 22 to 23) was changed as shown in Table 5.

Table 5 shows the yarn properties of the composite multifilament obtained in the above comparative example.

[0071]

[Table 5]

In Comparative Example 15 in which a core layer chip containing a large amount of a melt viscosity reducing agent was used, the spinning property was poor, a good composite multifilament was not obtained, and Comparative Example 22 in which the relaxation rate was increased. In this case, the yarn was loosened during the relaxation heat treatment, and could not be wound.

[0073]

According to the present invention, a composite filament having a high specific gravity and a high strength can be produced with a good spinning property. If a fishing net is manufactured using this composite filament, a fishing net with excellent sedimentation properties, low net shaking in water, excellent fishing operability, and excellent durability can be obtained.

Claims (5)

[Claims] 1. A polyester resin composition having a specific gravity of 1.9 to 3.5, wherein a core layer contains 40% by volume or less of inorganic fine particles in a polyester resin and 0.5 to 10.0% by weight of a melt viscosity reducing agent based on the polyester resin. The layer is made of a polyester resin having a relative viscosity of 1.5 or more, and the volume ratio between the core layer and the sheath layer is 40 /
A high specific gravity composite filament having a linear strength of 4 g / d or more, a linear elongation at break of 15% or more, and a specific gravity of 1.5 or more. 2. The high specific gravity composite filament according to claim 1, wherein the inorganic fine particles are precipitated barium sulfate. 3. The high specific gravity composite filament according to claim 1, wherein the melt viscosity reducing agent is a compound represented by the following formula. Embedded image 4. A polyester resin composition having a specific gravity of 1.9 to 3.5, comprising a core layer containing 40% by volume or less of inorganic fine particles in a polyester resin and a melt viscosity reducing agent in an amount of 0.5 to 10.0% by weight based on the polyester resin. The layer is made of a polyester resin having a relative viscosity of 1.5 or more, and the volume ratio between the core layer and the sheath layer is 40 /
Spinning speed of the composite monofilament which is 60 or less is 20 to 100
melt-spun at a rate of m / min, and the resulting undrawn yarn is stretched 3.0 to 5.5 times in the first stage while heating to 80 to 120 ° C.
2nd stretching to 1.0 to 2.0 times while heating to 200 ° C, making the total stretching ratio 5.0 to 6.0 times, followed by relaxation heat treatment at a temperature of 200 ° C or more at a relaxation rate of 5 to 10%. The method for producing a high specific gravity composite monofilament according to claim 1, characterized in that: 5. A polyester resin composition having a specific gravity of 1.9 to 3.5, comprising a core layer containing 40% by volume or less of inorganic fine particles in a polyester resin and a melt viscosity reducing agent in an amount of 0.5 to 10.0% by weight based on the polyester resin. The layer is made of a polyester resin having a relative viscosity of 1.5 or more, and the volume ratio between the core layer and the sheath layer is 40 /
Spinning speed of 200 ~
Melt spinning at 1000 m / min.
After heating to 150 ℃, heat-treat at a temperature of 150 ℃ or more.
The method for producing a high specific gravity composite multifilament according to claim 1, wherein the multifilament is stretched at a draw ratio of up to 6.5 times, and then subjected to a relaxation heat treatment at a temperature of 150 ° C or higher at a relaxation rate of 5 to 15%.