JPH10121331A - Conjugate filament for fishery material and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a conjugate filament suitable for fishery materials, especially for dishing nets, excellent in safety, and having a high density and a high strength. SOLUTION: This conjugate filament for marine materials comprises a core layer comprising a polyester resin composition containing 40-65wt.% of precipitated barium sulfate particles and 0.1-1.0wt.% of a metal soap and a sheath layer comprising polyethylene terephthalate resin, and has a specific gravity of >=1.5, a linear strength of >=4.0g/d, and a linear breaking elongation of >=15%.

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, high-strength composite filament excellent in safety and suitable for fishery materials, particularly fishing nets, and a method for producing the same.

[0002]

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 In recent years, many fishing nets have been replaced by polyester fibers.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

Conventionally, various types of core-sheath composite fibers having a high specific gravity in which a core layer component contains high specific gravity fine particles have been proposed. However, when the fiber is drawn, the core layer contains a large amount of high specific gravity fine particles. A small space (void) is created around the high specific gravity fine particles,
There is a problem that the specific gravity is reduced, and it has been difficult to obtain a conjugate fiber having a high specific gravity and high strength.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a composite monofilament for fishery materials having excellent safety and high specific gravity and high strength, and a method for producing the same.

[0007]

The present invention solves the above-mentioned problems, and the gist is as follows. 1. A core-sheath type composite fiber having a core layer of a polyethylene terephthalate resin composition containing 40 to 65% by weight of precipitated barium sulfate fine particles and 0.1 to 1.0% by weight of a metal soap, and a sheath layer of polyethylene terephthalate resin. A composite filament for marine materials, characterized in that the linear filament has a linear strength of at least 1.5, a linear elongation of at least 4.0 g / d and a linear elongation of at least 15%. 2. A polyethylene terephthalate resin composition containing 40 to 65% by weight of precipitated barium sulfate fine particles and 0.1 to 1.0% by weight of metal soap as a core layer, and a relative viscosity of 1.60 as a sheath layer.
A composite monofilament is melt-spun at a spinning speed of 20 to 100 m / min using a polyethylene terephthalate resin of from 1.75 to 1.75 m, and the obtained undrawn yarn is heated to 80 to 120 ° C. and heated to 3.0 to
First-stage stretching at a stretch ratio of 5.5 times, then 120-200
2nd stretching to 1.0-2.0 times while heating to ℃, so that the total stretching ratio is 5.0-6.5 times, and then 200 ℃
2. The method for producing a composite monofilament for a marine material according to claim 1, wherein the relaxation heat treatment is performed at a relaxation rate of 5 to 10%. 3. A polyethylene terephthalate resin composition containing 50 to 65% by weight of precipitated barium sulfate fine particles and 0.1 to 1.0% by weight of metal soap as a core layer, and a relative viscosity of 1.60 as a sheath layer.
The composite multifilament is melt-spun at a spinning speed of 200 to 1000 m / min using a polyethylene terephthalate resin of ~ 1.75, and the obtained undrawn yarn is heated to 80 to 130 ° C.
2. The marine material composite according to claim 1, wherein the heat treatment is performed at a stretching ratio of 5.0 to 6.5 times while being heat-treated at 150 ° C. or more, and then a relaxation heat treatment is performed at 150 ° C. or more at a relaxation rate of 5 to 15%. A method of manufacturing a multifilament.

[0008]

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

As described above, the marine material fiber 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 fiber, and in the present invention, a polyethylene terephthalate (PET) resin that develops high strength by stretching is used as the sheath layer.

In the present invention, the PET 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 fibers cannot be obtained. On the other hand, if the relative viscosity exceeds 1.75, there is a problem of causing unevenness of melting, causing the deterioration of the flowability of the molten polymer, and causing the fiber surface during the fiber formation process,
In addition, when the melting temperature is increased to completely melt the polymer, the polymer is thermally decomposed, and the effect of the high-viscosity polymer is lost.

The polyester resin contains copolymer components such as dicarboxylic acids such as isophthalic acid, naphthalenedicarboxylic acid and diphenylcarboxylic acid, and diol components such as ethylene glycol, propylene glycol and butylene glycol as long as their properties are not impaired. May be included.

On the other hand, for the core layer, a resin composition containing PET resin containing high specific gravity fine particles and metal soap is used. As the high specific gravity fine particles, secondary aggregation between fine particles is small, and Precipitated barium sulfate, which has excellent safety and high safety, is used.

The high specific gravity fine particles have an average particle size of 1.0
Those having a size of not more than μm and substantially not containing not less than 6.0 μm are preferable. When such fine particles are used, they are uniformly dispersed in the resin, and a fiber having good spinning properties and high strength can be obtained. If the particle size is too large, it is difficult to uniformly disperse the resin in the resin, and the spinnability deteriorates, so that high-strength fibers cannot be obtained. Further, the high specific gravity fine particles are preferably spherical.

Next, the amount of the precipitated barium sulfate fine particles contained in the PET resin of the core layer needs to be 40 to 65% by weight. When the content of the sedimentable barium sulfate is less than 40% by weight, the specific gravity of the high specific gravity composition is not sufficient, and the ratio of the sheath layer which bears the strength is reduced, so that it is difficult to obtain the desired high strength fiber. Becomes On the other hand, when the content of the sedimentable barium sulfate exceeds 65% by weight, the processability in producing a high specific gravity composition is remarkably reduced, and a composition having a uniform specific gravity cannot be obtained. However, it is impossible to obtain fibers having high strength and uniform specific gravity.

In general, when a melt spun yarn using a PET resin containing a large amount of fine particles is drawn, the PET resin is gradually drawn, but the fine particles themselves are not drawn and remain in place, so that There is a problem that voids are generated around the fiber and the specific gravity of the fiber is reduced. In some cases, the specific gravity may be lower than that of the PET resin even though fine particles are contained in order to impart a high specific gravity.

In the present invention, in order to solve the above problem, the dispersibility of the fine particles in the PET resin is improved by adding 0.1 to 1.0% by weight of a metal soap in the high specific gravity composition of the core layer. It promotes plastic deformation, suppresses the generation of voids around fine particles, and suppresses a decrease in specific gravity.

Specific examples of the metal soap include barium stearate, magnesium stearate, calcium stearate, lithium stearate, aluminum stearate, zinc stearate and the like. In the present invention, since barium sulfate is used as the high specific gravity fine particles, it is particularly preferable to use barium stearate as the metal soap.

The amount of the metal soap added to the high specific gravity composition of the core layer must be 0.1 to 1.0% by weight. If this condition is not satisfied, the target performance will not be exhibited. That is, if the addition amount is less than 0.1% by weight, a sufficient effect of addition cannot be obtained, and if it exceeds 1.0% by weight, the spinnability deteriorates, which is not preferable.

The high specific gravity composition of the core layer is prepared by mixing and melting and kneading a PET resin, precipitated barium sulfate fine particles and metal soap in advance, and forming chips. Can be uniformly dispersed in the PET resin.

The high specific gravity composition of the core layer has a relative viscosity of 1.
Must be 20 or more. If the relative viscosity of the core layer is small, the continuity of the core layer in the spun filament is poor, causing composite spots.If the spinning temperature is lowered to increase the melt viscosity, it causes the melt spots and uniform filaments. Can not be obtained.

The ratio between the core layer and the sheath layer is 15/85 to
A value of 45/55 is appropriate. If the ratio of the core layer is too small, it is difficult to obtain the desired high specific gravity fiber, the difference between the discharge amount of the core layer and the sheath layer is too large,
On the other hand, if the ratio of the core layer is too large, the desired high-strength fiber cannot be obtained.

Next, a method for producing the composite monofilament of the present invention will be described. First, high specific gravity PE
Using the T resin composition as the core layer and the PET resin as the sheath layer, melt spinning is carried out 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. Stretching can be performed in one stage or in two or more stages, but in the present invention, a two-stage stretching method is particularly employed. That is, the temperature of the yarn is adjusted to 80 to 120 ° C. using a liquid bath and / or an oven.
First stretching at a stretching ratio of 3.0 to 5.5 times, and then using a liquid bath and / or oven at a temperature of 120 to 200 ° C. higher than the first stretching, the total stretching ratio becomes 5.0 to 6.5 times. Stretch in two steps at a magnification of 1.0 to 2.0 times. If the yarn temperature in the first-stage drawing is lower than 80 ° C., high-strength fibers can be obtained, but the generation of voids in the fibers cannot be suppressed, and the target high specific gravity and high strength Fiber 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 fiber does not decrease, high-strength fibers cannot be obtained.

In the second-stage drawing, since the crystals in the fibers are oriented to some extent during the first-stage drawing, it is necessary to perform the drawing at a higher temperature than in the first-stage drawing. If the yarn temperature in the second-stage drawing is lower than 120 ° C, it becomes difficult to suppress the generation of voids in the fiber as in the first-stage drawing, and it is not possible to obtain a target fiber having a high specific gravity. . On the other hand, when the temperature of the yarn exceeds 200 ° C., superdraw occurs, and high-strength fibers 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 fiber can be obtained. On the other hand, when the ratio exceeds 5.5 times, excessive drawing occurs, a large amount of voids are generated around the fine particles, and it becomes impossible to obtain a fiber having a high specific gravity.

Further, it is necessary to set the second stage stretching ratio to 1.0 to 2.0 times, so that the total stretching ratio is 5.0 to 6.5 times. If the total draw ratio is less than 5.0 times, the desired high-strength fiber cannot be obtained.On the other hand, if the total draw ratio exceeds 6.5 times, voids will be generated in the fiber due to excessive drawing and the specific gravity must be high. Can not. In addition, the second stage stretching ratio is 2.
If the magnification is more than 0, the stretching will be excessive regardless of the first-stage stretching magnification, so that the generation of voids cannot be suppressed.

The drawn yarn is subjected to relaxation heat treatment at a relaxation rate of 5 to 15% using a liquid bath at 200 ° C. or higher and / or an oven. If the relaxation heat treatment temperature is lower than 200 ° C., it is difficult to increase the linear elongation at break to 15.0% or more, and the workability decreases. On the other hand, if the relaxation rate exceeds 15%, excessive relaxation treatment results in fibers having irregularity in the thread properties 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 15.0% or more.

It is suitable 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, the high specific gravity P
Using the ET resin composition as the core layer and the PET resin as the sheath layer,
Melt spinning is performed at a spinning temperature similar to that of the monofilament at a spinning speed of 200 to 1000 m / min by a conventional method to 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 once or without winding. Stretching can be performed in one stage or in two or more stages, but in the present invention, a one-stage stretching method is particularly employed. That is, the temperature of the yarn is adjusted to 80 to 130 using a heating roller and / or an oven.
After the temperature is raised to 150 ° C., the yarn is drawn at a draw ratio of 5.0 to 6.5 while heating the yarn to 150 ° C. or higher using an oven and / or a contact heater.

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 of 150 ° C. or higher.

If these drawing and heat treatment conditions are not satisfied, as in the case of the monofilament, voids are generated and a fiber having a high specific gravity cannot be obtained, or a super draw occurs and a fiber having a high strength cannot be obtained. In addition, the linear elongation at break cannot be set to 15.0% or more, the yarn properties are uneven, or the workability is poor.

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

In the present invention, the content of the precipitated fine barium sulfate particles in the core layer, the ratio of the core layer to the sheath layer, the spinning, drawing and heat treatment conditions are appropriately selected so that the specific gravity is 1.5 or more and the linear strength is The filament should be 4.0 g / d or more and the straight-line elongation at 15% or more. By retaining such characteristics, high-speed netting can be achieved, and the fishing net has the necessary strength as a fishing net, has a high sedimentation rate in water, and has excellent shape retention against tides. Become fibers.

In producing the filament, a chain extender and 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.

[0038]

Next, the present invention will be described in detail with reference to examples. In addition, the measuring method is 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) Resin composition crushed to a specific gravity of 1 mm or less or a piece of fiber having a length of 10 mm was mixed with 1,1-dichloro-2,2,3,3,3-pentafluoropropane / 1,3-dichloro-1,1 , 2,2,3-pentafluoropropane mixed at a ratio of 45/55 and a chlorofluoroethylene low polymer solution were immersed in a mixed solution of any specific gravity and defoamed. Thereafter, the measurement was performed by the floatation / sink method.

Example 1 39.7 parts by weight of a PET resin having a relative viscosity of 1.50, 0.3 parts by weight of barium stearate (metal soap) and an average particle size of 0.5 μm,
60 parts by weight of precipitated barium sulfate fine particles having a maximum particle size of 2.0 μm and a specific gravity of 4.3 are mixed and melt-kneaded to obtain a relative viscosity of 1.27 and specific gravity.
2.30 high specific gravity chips for core layer were obtained. On the other hand, a PET resin chip having a relative viscosity of 1.68 was prepared for the sheath layer. The high specific gravity chip for the core layer and the PET resin chip for the sheath layer are supplied to separate extruders and melted at 295 ° C.
Four concentric composite monofilaments having a core / sheath composite volume ratio of 30/70 were spun from a spinneret having four 1.3 mm diameter spinning holes heated to ° C. The spun yarn is cooled and solidified through a hot water bath at 70 ° C., taken up at a speed of 40 m / min, and heated to 100 ° C. using a glycerin bath to obtain a draw ratio of 4.5%.
1st stretching at 1 ×, then 2nd stretching at a stretching ratio of 1.2 times using an oven at 150 ° C., and then relaxing using an oven at 250 ° C. so that the total stretching ratio is 5.4 times. Relaxation heat treatment was performed at a rate of 10% to obtain a core-sheath composite monofilament of 500 d.

Examples 2 to 10 The content of the metal soap 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), a composite monofilament was obtained in the same manner as in Example 1 except that the draw ratio (Examples 8 to 9) or the relative viscosity (Example 10) of the PET resin for the sheath layer was changed as shown in Table 1. .

Table 1 shows the yarn properties of the monofilaments obtained in Examples 1 to 10.

[0042]

[Table 1]

Comparative Examples 1 to 10 The content of the metal soap in the core layer (Comparative Examples 1 and 2), the temperature of the first stage stretching (Comparative Examples 3 and 4), and the temperature of the second stage stretching (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 of the composite monofilament obtained in the above comparative example. In Comparative Example 2 in which the core layer chip containing a large amount of metal soap was used, the spinning property was poor, a good monofilament was not obtained, and in Comparative Example 8 in which the distribution of the stretching ratio was not appropriate, the second stage In Comparative Example 10 in which the yarn was cut during stretching and the relaxation rate was increased, the yarn was loosened during the relaxation heat treatment and could not be wound.

[0044]

[Table 2]

Comparative Example 11 A monofilament was obtained in the same manner as in Example 1 except that a high specific gravity chip for a core layer having a relative viscosity of 1.30 and a specific gravity of 1.78, in which the content of precipitated barium sulfate fine particles was 35% by weight, was used. .
The resulting composite monofilament has a specific gravity of 1.45 and a linear strength.
The product had a low specific gravity of 4.58 g / d and a linear cut elongation of 19.7%.

Comparative Example 12 A composite monofilament was produced in the same manner as in Example 1 except that a high specific gravity chip for a core layer having a relative viscosity of 1.13 and a specific gravity of 2.60, in which the content of precipitated barium sulfate fine particles was 70% by weight, was used. Tried to do. The yarn-forming properties were poor, and it was difficult to take off the undrawn monofilament.

Comparative Example 13 An attempt was made to produce a composite monofilament in the same manner as in Example 1 except that a high specific gravity chip for a core layer having a relative viscosity of 1.07 and a specific gravity of 2.26 was used. The yarn-forming properties were poor, and it was difficult to take off the undrawn monofilament.

Example 11 The same high specific gravity chip for the core layer and the same PET resin chip for the sheath layer as in Example 1 were fed to separate extruders and melted at 295 ° C., respectively, and heated to 300 ° C., with a diameter of 0.6. A concentric composite multifilament having a core / sheath composite volume ratio of 30/70 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 pulled at a speed of 400 m / min with a heating take-off roller at 105 ° C, stretched 5.5 times while contacting a hot plate at 200 ° C between the take-off roller and the stretching roller. A heat treatment for relaxation was carried out at a relaxation rate of 5% between the above and wound to obtain a composite multifilament of 1000d / 48f.

Examples 12 to 25 Content of metal soap in core layer (Examples 12 to 13), temperature of take-up roller (Examples 14 to 15), temperature of hot plate (Examples 16 to 1)
7), stretching ratio (Examples 18-19), temperature of relaxation heat treatment
(Examples 20 to 21), the relaxation rate (Examples 22 to 23) or the relative viscosity (Examples 24 to 25) of the PET resin for the sheath layer were changed as shown in Tables 3 and 4, and the results were the same as those in Examples 11 and 12. Similarly, a composite multifilament was obtained.

Tables 3 and 4 show the yarn properties of the composite multifilaments obtained in Examples 11 to 25.

[0051]

[Table 3]

[0052]

[Table 4]

Comparative Examples 14 to 23 Content of metal soap in core layer (Comparative Examples 14 to 15), temperature of take-up roller (Comparative Examples 16 to 17), temperature of hot plate (Comparative Example 1)
8), stretch ratio (Comparative Examples 19-20), temperature of relaxation heat treatment
(Comparative Example 21) An attempt was made to produce a composite multifilament in the same manner as in Example 11, 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. In Comparative Example 15 using a core layer chip containing a large amount of metal soap, the spinning property was poor, a good composite multifilament could not be obtained, and in Comparative Example 22 in which the relaxation rate was increased, The strip became loose and could not be wound.

[0054]

[Table 5]

Comparative Example 24 A composite multifilament was obtained in the same manner as in Example 11, except that the PET having a relative viscosity of 1.55 was used as the PET resin for the sheath layer. The obtained composite multifilament has a specific gravity of 1.6.
3, linear strength 3.87 g / d, linear cutting elongation 17.8%,
It was of low strength.

Comparative Example 25 An attempt was made to produce a composite multifilament in the same manner as in Example 11 except that a PET having a relative viscosity of 1.80 was used as the PET resin for the sheath layer. The yarn-forming properties were poor, and good composite multifilaments could not be obtained.

Comparative Example 26 A composite multifilament was prepared in the same manner as in Example 11, except that a high specific gravity chip for a core layer having a relative viscosity of 1.30 and a specific gravity of 1.78 was used with the content of precipitated barium sulfate fine particles being 35% by weight. Obtained. The resulting composite multifilament has a specific gravity of 1.45,
The linear strength was 4.46 g / d, the linear breaking elongation was 18.1%, and the specific gravity was low.

Comparative Example 27 A composite multifilament was prepared in the same manner as in Example 11 except that a high specific gravity chip for a core layer having a relative viscosity of 1.13 and a specific gravity of 2.60 was used with the content of precipitated barium sulfate fine particles being 70% by weight. Tried to manufacture. Poor spinnability and difficulty in taking up undrawn multifilaments.

[0059]

According to the present invention, a high specific gravity and high strength composite filament for marine material is provided. And the fishing net using this composite filament is excellent in sedimentation property, has little net shaking in water, is excellent in fishing operability, and is excellent in durability.

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[Procedure amendment]

[Submission date] October 18, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

Claims (3)

[Claims] A core-sheath type composite fiber comprising a polyethylene terephthalate resin composition containing 50 to 65% by weight of precipitated barium sulfate fine particles and 0.1 to 1.0% by weight of a metal soap as a core layer and a polyethylene terephthalate resin as a sheath layer. And a specific gravity of 1.5 or more, a linear strength of 4.0 g / d or more, and a linear cut elongation of 15% or more. 2. Precipitating barium sulfate fine particles are used as a core layer.
Polyethylene terephthalate resin composition having a relative viscosity of 1.20 or more containing 40 to 65% by weight and metal soap of 0.1 to 1.0% by weight, and using a polyethylene terephthalate resin having a relative viscosity of 1.60 to 1.75 as a sheath layer to spin a composite monofilament at a spinning speed of 20 to Melt-spinning is performed at 100 m / min.
First-stage stretching at a stretching ratio of 3.0 to 5.5 times while heating to 80 to 120 ° C, and then 1.0 to 2.
2. The method according to claim 1, wherein the film is stretched in the second step to 0 times so that the total stretching ratio becomes 5.0 to 6.5 times, and subsequently, the film is subjected to a relaxation heat treatment at 200 ° C. or more at a relaxation rate of 5 to 10%. A method for producing composite monofilaments for marine materials. 3. Precipitating barium sulfate fine particles as a core layer.
Polyethylene terephthalate resin composition having a relative viscosity of 1.20 or more containing 40 to 65% by weight and metal soap of 0.1 to 1.0% by weight, and using a polyethylene terephthalate resin having a relative viscosity of 1.60 to 1.75 as a sheath layer, spinning a composite multifilament 200 The resulting unstretched yarn is heated to 80 to 130 ° C., stretched at a stretching ratio of 5.0 to 6.5 times while being heat-treated at 150 ° C. or higher, and then stretched at a stretch ratio of 5.0 to 6.5 times. The method for producing a composite multifilament for a marine material according to claim 1, wherein the relaxation heat treatment is performed at a relaxation rate of ~ 15%.