JPH09228151A - High-specific gravity and high-strength conjugate fiber and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a conjugate fiber having a combination of high sinkability with enough mechanical strength to cause no problem in its net making process, and having such high durability and weatherability as not to cause its mechanical strength drop-off even after used as a fishnet for a long period. SOLUTION: This fiber >=1.5 in specific gravity, >=60 in toughness and >=3.5g/d in tenacity, is composed of core component with a thermoplastic polymer >=1 in specific gravity incorporated with 50-85wt.% of non-lead-based inorganic fine particles >=3 in specific gravity and sheath component consisting of a polyester in the weight ratio of core/sheath of (20:80) to (70:30).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite fiber having both high specific gravity and high strength, which is suitable for use in industrial materials, and particularly to a composite fiber which is free from the problem of marine environmental pollution and is suitable for fishing nets having excellent durability. .

[0002]

2. Description of the Related Art Conventionally, as a material for marine products represented by fishing nets, fishing ropes, etc., it is superior to natural fiber products in terms of water resistance, corrosion resistance, strength, abrasion resistance, durability, etc. Synthetic resin fiber products exhibiting the above properties have been used. However, its moisture content is lower than that of natural fiber products, and its specific gravity is relatively small, so its settability in seawater and shape retention against tidal current are unsatisfactory, and its use is subject to many restrictions. It was

Various proposals have been made to overcome such difficulties, but the technique of increasing the specific gravity of the fibers and the ropes themselves to increase the sedimentation property in water has received the most attention.
As a means for increasing the specific gravity of the fibers and the ropes themselves, there is a technique of kneading metallic lead or its compound into the fibers. There is a possibility that it may fall off from the ground or may be eluted into seawater during use as a fishing net and lead pollution problems may occur. Further, even when the used fishing net is discarded, there is a possibility that the same pollution problem may occur as a harmful component including lead remains after the waste is incinerated, so that it cannot be easily disposed of. On the other hand, as a means not using a lead compound, for example, vinylidene chloride-based fibers having a relatively large specific gravity have been used, but with the development of net-making technology, high-strength fibers that can be stably supplied to high-speed nets have As a result of the demand, vinylidene chloride fibers have a problem of insufficient strength. Further, a fishing net made of vinylidene chloride fiber also has a problem that it is difficult to incinerate because hydrogen chloride gas is generated during incineration. in this way,
Not only high specific gravity but also high strength and pollution-free properties are required.

Various proposals have been made to meet such demands, and as one means therefor, fibers made of a combination of a resin exhibiting high strength by a stretching treatment and a high specific gravity powder are considered. Specifically, (1) a fiber obtained by uniformly dispersing high specific gravity powder such as zinc or lead in a synthetic filament (for example, Japanese Patent Publication No. 51-37378, Japanese Patent Publication No. 56-61936, Japanese Patent Publication No. 61-61936). -613), (2) a fiber obtained by mixing and dispersing high specific gravity powder in a resin having a low softening point, and further mixing this mixture with a resin for imparting strength (for example, Japanese Patent Publication No. 57-20407). , (3) cored fibers having a mixture of a low softening point resin and high specific gravity powder as a core layer and a strength imparting resin as a sheath layer (for example, JP-A-58-4819). .

However, the proposal (1) has a drawback that if the specific gravity of the fiber is sufficiently increased, the amount of the powder added increases, and the strength of the fiber itself decreases in inverse proportion to the improvement of the specific gravity. . Further, in the proposal of (2), the low softening point resin mixed with the powder extends in the drawing direction of the fiber to become a fiber which is partially and irregularly embedded unevenly, and therefore the production of the fiber is complicated. In addition, there is a restriction that the amount of high specific gravity powder contained in the same fiber diameter as compared with the proposal of the above (1) is naturally small, and the degree of increase in specific gravity is significantly limited. Further, the proposal of (3) not only has drawbacks such as a decrease in yarn quality and a decrease in durability due to an increase in interfacial strain due to the incompatibility at the interfaces of different resins, but also in the low softening point resin. Since the high specific gravity powder of 1) is not uniformly dispersed, it has a drawback that only powders with high fiber fineness can be obtained.

[0006]

The object of the present invention is to have a high settling property and a sufficient fiber strength that does not cause any problems in net-making processing, and has excellent durability that does not decrease even when used as a fishing net for a long period of time. , To provide fibers having weather resistance.

[0007]

That is, the present invention provides a core component comprising a thermoplastic polymer having a specific gravity of 1 or more and 50 to 85% by weight of lead-free inorganic fine particles having a specific gravity of 3 or more. And a sheath component made of polyester covering the core component, wherein the composite weight ratio of the core component and the sheath component is core /
Sheath = 20/80 to 70/30, fiber specific gravity of 1.5 or more,
A composite fiber having a toughness of 60 or more and a strength of 3.5 g / denier or more.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The conjugate fiber of the present invention has a specific gravity of 1.5 or more, a toughness of 60 or more, and a strength of 3.5 g / denier.
It has more than just When the specific gravity of the composite fiber is less than 1.5, it is difficult to achieve high sedimentation in seawater and shape retention of the fishing net, and when the strength is less than 3.5 g / denier, high speed is achieved. Not practical because the fibers are damaged during netting. Toughness is represented by the product of strength and elongation, but when the value is less than 60, that is, when elongation is low, fatigue resistance and durability against tidal currents and waves are low, and it is not useful as a fishing net. From this point of view, it is desired that the fiber has a specific gravity of 1.55 or more, a strength of 4.0 g / denier or more, and a toughness of 80 or more.

In the present invention, it is essential to contain lead-free inorganic fine particles having a specific gravity of 3 or more in order to increase the specific gravity of the fiber. When using inorganic fine particles having a specific gravity of less than 3, the content of the inorganic fine particles in the fiber must be increased and the composite ratio of the core component in the composite fiber must be increased in order to achieve the target fiber specific gravity. , Even if the fiber of the target fiber specific gravity is obtained, the spinnability,
It is unsuitable for use as a fishing net because it has poor processability such as drawability and only fiber strength is low.

Examples of the type of the inorganic fine particles include fine particles of a lead-free metal or fine particles of a compound thereof. The "lead-free metal" means a metal other than a metal such as lead or tin that is extremely susceptible to environmental problems, and specifically, titanium, iron, copper, zinc, silver, barium, zirconium,
Examples thereof include metals such as manganese, antimony, and tungsten, and oxides and salts thereof. In the present invention, the inorganic fine particles can be appropriately selected from such metals, their oxides, and salts as desired, but the specific gravity of the fine particles, the dispersibility of the fine particles in the polymer, and the thermal decomposition of the polymer can be selected. Titanium dioxide, iron oxide, barium sulfate and the like are preferably used from the viewpoint of non-catalytic property which is not promoted. Further, the inorganic fine particles may be used not only in one kind but also in a mixture of two or more kinds.

The content of the inorganic fine particles in the core component is 5
It is necessary to be 0 to 85% by weight. The content is 5
If it is less than 0% by weight, the core component ratio in the composite fiber must be increased in order to obtain the target fiber specific gravity, and only a fiber having a low fiber strength can be obtained. On the other hand, when the content exceeds 85% by weight, the polymer melt flowability during spinning is deteriorated and the yarn breaks frequently.

Regarding the particle size of the inorganic fine particles, the average particle size of the primary particles is preferably 5 μm or less. Particle size is 5
If it exceeds μm, yarn breakage or fluffing is likely to occur during spinning and drawing. If the particle size is too small, when the fine particles are added to the polymer, thermal agglomeration occurs due to the heat during the molding process, which causes coarse particles on the contrary, or heat of the fine particles in the pipe of the polymer melting line during spinning. Trouble such as agglomeration is likely to occur and the line is often clogged. Therefore, the average particle diameter of the primary particles of the inorganic fine particles is 0.
It is preferably at least 05 μm.

First, the case where iron oxide is used as the inorganic fine particles will be described. Iron oxide includes magnetite with a black color, that is, magnetite (Fe ₃ O ₄ ), brown γ-type hematite, reddish-brown α-type hematite, and the like. Since no vigilance is given, it is preferable to use black magnetite, which can give a favorable result to the catch and is black. When magnetite is used in combination with other inorganic fine particles, dyeing treatment or the like can be simplified or omitted by using magnetite in an amount of 20% by weight or more of the whole inorganic fine particles to be used. It does not make any difference to use polyester.

The particle shape of iron oxide includes spherical, octahedral, hexahedral and polyhedral shapes, and any shape can be used. Is preferable because it has the best dispersibility. In particular, when a large amount of inorganic fine particles are added to the polymer, the use of spherical fine particles exerts a remarkable effect, the filter clogging during spinning due to agglomeration is less likely to occur, and yarn breakage occurs during spinning / drawing. Also few.

Further, the iron oxide may be subjected to a surface coating treatment with an organic or inorganic compound such as silica or ferrite. When fine particles subjected to the surface coating treatment are used, the heat of the polymer is reduced. Decomposition is suppressed,
It is preferable because the dispersibility of fine particles can be further improved.

Iron oxide may be used alone as the inorganic fine particles contained in the core component, but when the content exceeds 50% by weight in the core component, iron oxide having an appropriate particle shape and particle size is obtained. Even if it is used, contamination may occur due to thermal agglomeration in the line during melt extrusion, and in severe cases, trouble such as pipe clogging may occur. Iron oxide is used as the inorganic fine particles contained in the core component, and it is preferable to use iron oxide in combination with other fine particles in order to achieve a content rate exceeding 50% by weight. Especially when producing fine denier yarns, the residence time in the molten polymer line becomes long,
It also causes troubles such as line clogging.

Other fine particles used in combination with iron oxide have a specific gravity of 3
As described above, it is preferable to select the primary particles having an average particle size of 5 μm or less, having little thermal agglomeration, and being inexpensive in terms of cost. Suitable examples include titanium dioxide, zinc oxide, barium sulfate, alumina, ferrite,
Examples thereof include lithopone, copper oxide, and magnesium oxide. Among them, titanium dioxide is particularly preferable in terms of dispersibility of inorganic fine particles in the core component. When iron oxide and titanium dioxide are used in combination, the mixing ratio is such that the total content relative to the core component is 50 to 8
If the amount is within the range of 5% by weight, the desired fiber can be obtained without any serious troubles such as good spinnability and drawability even if arbitrarily changed. An example of a suitable mixing ratio is iron oxide / titanium dioxide = 20/80 to 70/30 (weight ratio). For example, the total amount of fine particles in the core component is 7
In the case of 0% by weight, iron oxide is 30% by weight and titanium dioxide is 40% by weight. When the total amount is 60% by weight, iron oxide is 30% by weight and titanium dioxide is 30% by weight.
The hue of the resulting fiber becomes preferred.

As described above, when the content of the fine particles in the core component is as high as 50% by weight or more, and when iron oxide is added to the core component at a high content, titanium dioxide is added together. The fact that there is no trouble such as line clogging during melt extrusion, the dispersibility in the core component is good, the number of yarn breakage during the process is small, and the target fiber can be obtained in a state with a high A rating is This was first discovered by the inventors after various examinations.

Next, the case where titanium dioxide is used as the inorganic fine particles will be described. It is an object of the present invention to provide a fishing net fiber having both excellent mechanical properties and high specific gravity, and at the same time provide a fishing net fiber capable of coping with various hues. However, as described above, when colored fine particles such as iron oxide are used at a high content rate as the inorganic fine particles, it becomes difficult to freely change the hue. Is white, and such a white fine particle is added to the core component, and the desired hue is obtained without being disturbed by the color of the core component by adding a pigment of a desired color to the polyester that is the sheath component. Can be expressed.

Titanium dioxide has three forms of anatase type (Anatase), rutile type (Rutile) and brookite type (Brookite) depending on the crystal form.
Generally used as pigments are anatase type and rutile type. In particular, the anatase type is mainly used for synthetic fibers due to the relationship of hardness affecting wear resistance in the process and the problem of dispersibility in a solvent or dispersion medium, but it has a high specific gravity and is excellent in light resistance. In this respect, the rutile type is preferably used in the present invention. in this case,
Although the motile hardness of the rutile type is larger than that of the anatase type, there is a concern that troubles such as abrasion in the process may occur, but in the composite fiber of the present invention, the core component containing inorganic fine particles is sheathed. Since it is substantially covered with the components, there are no problems such as abrasion of the nozzle die during spinning and abrasion damage of guides and rollers during the processing step.

Titanium dioxide is less likely to cause thermal coagulation during melt extrusion of the polymer even if it is added to the polymer at a high content ratio as compared with other inorganic fine particles, and this is caused by contamination in the melt polymer line. Clogs are less likely to occur, filter clogging during spinning is less, and yarn breakage during spinning and drawing is less likely to occur. The surface of such titanium dioxide may be subjected to a coating treatment with an inorganic or organic compound such as titanium, alumina, silica, etc. When the fine particles subjected to the surface coating treatment are used, heat resistance and fine particle dispersibility are obtained. Is more preferable because it can be further improved.

Titanium dioxide may be used alone or
It may be used in combination with other fine particles having a specific gravity of 3 or more and an average particle diameter of 5 μm or less. Further, even if the fine particles to be used in combination are those which easily cause the problem of thermal aggregation as described above, improvement in dispersibility can be expected by using titanium dioxide in an amount of 15% by weight or more, particularly 40% by weight or more. As other fine particles, for example, zinc oxide, alumina, barium sulfate, lithopone, magnesium oxide, etc., which have less toxicity than tin oxide (tin stone), etc. can be used. Since titanium dioxide easily promotes deterioration of the thermoplastic polymer constituting the core component by exciting titanium atoms with ultraviolet rays, it is preferable to use an antioxidant together.

In the present invention, the thermoplastic polymer constituting the core component must have a specific gravity of 1 or more. If the specific gravity of the thermoplastic polymer is less than 1, the content of the fine particles must be increased in order to increase the specific gravity of the fiber, which further disturbs the process condition.

Further, in general, when a polymer containing a high content of inorganic fine particles is melt-spun, there is a problem that the spinning tone is extremely deteriorated due to a peculiar viscous behavior. Such viscous behavior means so-called thixotropic property, in which melt viscosity is high under low shear, while melt viscosity becomes low under high shear. The shear rate is 10 ⁰ sec ^{-1 order} at the introduction part where the polymer containing a high content of inorganic fine particles is supplied to the spinning pack, but it is 10 ² at the flow distribution plate distributed to the nozzle holes. A sec ^{-1 order} , and further, a nozzle which is extruded by merging with a polymer which is a sheath component, reaches 10 ³ sec ^{-1 order} . The polymer flow having a remarkable thixotropic property has a large variation in the melt viscosity under this large change in the shear rate, the discharge amount per nozzle single hole fluctuates, and the balance of the core-sheath is lost, resulting in extremely spinning. It will be difficult. In the present invention, as a result of studying such points, it was found that the melt viscosity of the polyester, which is a core component and a sheath component containing a large amount of inorganic fine particles, is important. That is, the shear rate at 300 ° C is 1.0 x 1
In the entire range of 0 ^{1 to} 5 × 10 ² sec ^-1 , the ratio (a / b) of the melt viscosity a of the core component to the melt viscosity b of the polyester that is the sheath component is in the range of 5.0 to 0.05. It is desirable to have one. Only when the melt viscosity ratio of the core component and the sheath component is in this range, the core component and the sheath component containing a large amount of inorganic fine particles can be smoothly joined, and the operability such as the composite spinning / drawability is also improved. . Moreover, the inorganic fine particles are uniformly dispersed in the thermoplastic polymer that constitutes the core component, and it has become possible to manufacture the target composite fiber with good operability. A preferable melt viscosity ratio (a / b) is 1.5 to
0.8.

In order to adjust the melt viscosity ratio (a / b), it is desirable to first suppress the thixotropy of the core component as much as possible and then set the intrinsic viscosity of the polymer of the sheath component. As means for suppressing the thixotropy of the core component,
Select spherical particles to increase the particle size to reduce the surface area of the inorganic particles, or select particles with a high specific gravity as much as possible to reduce the addition rate of the inorganic particles; the molecular weight and melting point of the core component polymer The addition of a coupling agent in order to improve the affinity between the core component polymer and the inorganic fine particles.

The above-mentioned conditions, that is, specific gravity, melting point,
As the thermoplastic polymer satisfying the melt viscosity, polyamides such as nylon 6, nylon 66, nylon 610, nylon 11 and nylon 12; polyethylene terephthalate
And polyester such as polybutylene terephthalate and polyhexamethylene terephthalate.

When a large amount of inorganic fine particles are added as in the present invention, the wettability between the inorganic fine particles and the polymer and the dispersibility in the polymer are good, and the spinnability and the drawability are the best. It is preferable to use a thermoplastic polymer, and from this viewpoint, it is preferable to use a polyamide, particularly a polyamide containing nylon 6 as a main component. Nylon 6 used as a suitable example has a number average molecular weight of about 22,000 or less, especially 20,000 or less.
It is preferably at least 000. If the degree of polymerization is too high, the melt viscosity of the core component to which a large amount of inorganic fine particles is added becomes too high, and troubles are likely to occur or the inorganic fine particles may be poorly dispersed. Further, when a polymer having a high content of inorganic fine particles is actually melt-extruded to form a fiber, if the melt viscosity is too high, equipment troubles are likely to occur frequently and, at the same time, yarn breakage occurs frequently, which is not preferable. On the other hand, if the degree of polymerization is too low, the melt viscosity becomes too low relative to the sheath component, making it difficult to form the core-sheath interface.

In addition, when polyamide is used as the thermoplastic polymer constituting the core component, the moisture content of the core component is preferably 500 ppm or less, more preferably 300 ppm or less. When a large amount of inorganic fine particles are contained in a water-absorbing polymer such as polyamide, when the water content is high,
There is a problem that the fluidity is extremely lowered during melting and the process condition is significantly impaired. In general, polyamide is used with a water content of about 500 to 1000 ppm, but in the present invention in which a large amount of inorganic fine particles are contained, special consideration must be given. Further, the polyamide may be copolymerized with a small amount of the third component, and may contain a small amount of additives, stabilizers and the like.

The main purpose of using the composite fiber of the present invention is for fishing. However, since the fishing net is used outdoors, the weather resistance over time is an important issue, and the strength of the fishing net remains strong during long-term use. It is not possible to use a material that causes deterioration and is a practical problem. When a polyamide to which a large amount of inorganic fine particles as described above is added is used as a core component, there is a possibility that fiber strength may decrease when used as a fishing net for a long period of time. 0.01
Addition of a copper salt such as copper iodide as a heat stabilizer in a range of not less than 0.1% by weight, particularly not less than 0.1% by weight and not more than 2% by weight makes it possible to reduce the fiber strength over time to a level at which practically no problem occurs. Be improved.

In the present invention, the polyester as a sheath component is preferably a polyester containing polyethylene terephthalate or polybutylene terephthalate as a main component. Further, a small amount of a third component may be copolymerized with the polyester, and examples thereof include isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid, 4,4′-diphenyletherdicarboxylic acid, 4,
4'-diphenylmethane dicarboxylic acid, 4,4'-diphenyl sulfone dicarboxylic acid, 4,4'-diphenyl isopropylidene dicarboxylic acid, 1,2-diphenoxyethane-4 ', 4 "-dicarboxylic acid, anthracene dicarboxylic acid, 2, 5-pyridinedicarboxylic acid, diphenoxyketone dicarboxylic acid, 5-sodium sulfoisotalic acid, dimethyl 5-sodium sulfoisophthalate, 5
-Aromatic dicarboxylic acids such as tetrabutylphosphonium sulfoisophthalic acid; malonic acid, succinic acid, adipic acid,
Aliphatic dicarboxylic acids such as azelaic acid and sebacic acid; alicyclic dicarboxylic acids such as decalin dicarboxylic acid and cyclohexanedicarboxylic acid; hydroxy such as β-hydroxyethoxybenzoic acid, p-oxybenzoic acid, hydroxypropionic acid and hydroxyacrylic acid Carboxylic acids; carboxylic acids derived from these ester-forming derivatives; aliphatic lactones such as ε-caprolactone; aliphatic diols such as trimethylene glycol, hexamethylene glycol, neopentyl glycol, diethylene glycol, polyethylene glycol; hydroquinone catechol , Naphthalenediol, resorcin, bisphenol A, bisphenol A ethylene oxide adduct, bisphenol S, bisphenol S ethylene oxide adduct, etc. Examples thereof include aliphatic diols such as cyclohexanedimethanol. These 3rd components may be copolymerized by 1 type (s) or 2 or more types.

Further, the polyester of the present invention contains trimellitic acid within a range where the polyester is substantially linear,
Polyvalent carboxylic acids such as trimesic acid, pyromellitic acid and tricarballylic acid; glycerin, trimethylolethane,
A polyhydric alcohol such as trimethylolpropane or pentaerythritol may be contained. The polyester may contain additives such as a fluorescent whitening agent and a stabilizer. In particular, in order to maintain the weather resistance of the composite fiber as a whole, that is, the strength retention rate over time at a better level, a key is
Bonblack may be contained in polyester which is a sheath component.

The intrinsic viscosity [η] of the polyester is preferably 0.7 or more. The intrinsic viscosity is 3 in a mixed solvent of equal weight of phenol / tetrachloroethane.
It is a value measured at 0 ° C. In ordinary clothing fibers,
The intrinsic viscosity of polyethylene terephthalate is 0.60
Whereas those having a degree of polymerization of about 0.65 are used, the present invention uses a polyester having a degree of polymerization higher than the ordinary degree of polymerization in order to express the desired fiber strength. When the intrinsic viscosity is less than 0.7, the fiber specific gravity is 1.5 or more, the fiber strength is 3.5 g / denier or more, and the toughness is 6
It is difficult to satisfy all of 0 or more, and if the composite ratio of the sheath component and the core component is changed to make the sheath component rich, the fiber specific gravity cannot reach the target level, and conversely the core component is rich. The result is that the fiber strength and toughness do not reach the target levels. That is, by using polyester having an intrinsic viscosity of 0.7 or more as the sheath component, it was possible to obtain the one satisfying all of the fiber strength, toughness and specific gravity for the first time.

The intrinsic viscosity in the present invention is the intrinsic viscosity of polyester which is a sheath component in the fiber after spinning. That is, it is needless to say that when the degree of polymerization is lowered due to thermal decomposition or hydrolysis during spinning, it is necessary to use the polyester having a slightly higher degree of polymerization to make it into fibers.

By the way, in the present invention, a colorant can be added to polyester which is a sheath component to give a hue suitable for use in fishing nets as described above, and heat resistance of the polyester that can withstand the melt spinning temperature. An organic pigment or an inorganic pigment that it has can be appropriately used. Specifically, carbon black, anthraquinone brown colorant, anthraquinone purple colorant, benzoquinone red colorant, and ordinary underwear colorant may be used, and these colorants may be used alone or in combination of two kinds. Addition rate of 0.1-5% by weight
Can be incorporated into the Porie ester within the range. When the amount of the colorant added is less than 0.1% by weight, it is difficult to obtain a spun yarn for fishing nets exhibiting sufficient "hue" and "luster", and the amount added exceeds 5% by weight. If this is the case, the strength is greatly reduced, which is not preferable.

In particular, most of the hues of the currently required primary yarn for fishing nets are black. In such a case, carbon black is added to the polyester as the sheath component in an amount of 1 to 3% by weight.
It is preferred to add. Carbon black has an effect of absorbing ultraviolet rays and preventing deterioration of polyester, can prevent weather resistance of fibers, that is, decrease in fiber strength over time, and can exert a synergistic effect. Further, it is also possible to dye a desired color after fiber formation.

The composite fiber of the present invention has a cross-sectional shape in which the core component containing the above-mentioned inorganic fine particles is substantially covered with the polyester as the sheath component. Here, "substantially covered cross-sectional shape" means that 60% or more, preferably 80% or more, of the fiber surface perimeter is occupied by the sheath component. In the present invention, the core component is completely covered with the sheath component in order to further prevent friction and yarn breakage of guides and rollers in the spinning / drawing process and to solve the problem of interfacial peeling between the core component and the sheath component. The cross-sectional shape may be a concentric core-sheath type, an eccentric core-sheath type, or the like, and the number of cores may be 1 to 4.

The composite weight ratio of the core component and the sheath component is the former /
The latter = 20/80 to 70/30, preferably the former / latter = 20/80 to 50/50. If the composite weight ratio of the sheath component is too small, the fiber strength will decrease. On the other hand, if the composite weight ratio of the sheath component is too large, the effect of increasing the fiber specific gravity cannot be sufficiently exerted.

The method for obtaining the conjugate fiber of the present invention is not particularly limited, but the polyester, which is the sheath component, and the core component are heated and melted in separate melting systems, and each is prepared by a usual extrusion spinning device. To the spinneret, and immediately before the spinneret, both components are brought together according to a desired core-sheath type composite shape, and the yarn obtained by extrusion is wound up, further stretched and heat-treated. Further, there can be used a method in which the material is extruded from the spinneret and then immediately stretched without being wound, or a method in which the material is extruded from the spinneret and then wound at high speed to obtain a product as it is.

Specifically, the so-called POY or FOY stretching method in which the material is drawn at a speed of about 4000 m / min or less, and is once wound and then stretched, or the spin-draw method in which the material is stretched without winding, and further 4000 m / min. The above-mentioned DSY method for drawing at a high speed, or a method of installing a heater between a nozzle and a drawing roller in the DSY method and drawing while drawing is adopted. Among them, 300 to 4000 m / min is preferable, and 600 to 600 is more preferable.
This is a method in which the film is drawn and drawn at 2000 m / min (either FOY or spin-draw may be used) and then heat treated. If the speed is less than 300 m / min, the degree of orientation of the undrawn yarn is low, and it is necessary to increase the draw ratio in order to obtain the desired fiber strength. As a result, many voids are generated in the fiber and In some cases, high specific gravity cannot be achieved. On the other hand, in the case where the drawing is carried out in a so-called DSY region where the speed exceeds 4000 m / min, the target physical properties may be obtained without carrying out the drawing heat treatment operation, but the drawing draw heat treatment is carried out at the above-mentioned drawing speed. It is unavoidable that the fiber strength is reduced as compared with the method.

The stretching may be one-stage stretching or two-stage stretching. Further, the draw ratio cannot be uniquely specified because it varies depending on the spinning speed, but it is preferable to adopt a draw ratio of about 75 to 85% of the break ratio. Particularly, the characteristic point in the production of the fiber of the present invention is the heat treatment after drawing.
That is, the melting point of the thermoplastic polymer constituting the core component is not less than (melting point −80) ° C.
5) It is characterized in that it is heat-treated at a temperature of not higher than 0 ° C., and when the heat-treatment temperature is set higher within the range where fluff does not occur, a fiber having a higher fiber specific gravity and a higher strength and toughness can be obtained. By heating at a temperature close to or higher than the melting point of the thermoplastic polymer constituting the core component, the voids around the inorganic fine particles in the fiber generated during stretching while the fiber shrinks are restored to some extent. It is presumed that this is because the crystallization of the sheath component that expresses the mechanical properties of the fiber is promoted by increasing the heat treatment temperature.

When the heat treatment temperature exceeds (melting point-5) ° C of the polyester which is the sheath component, yarn breakage occurs frequently, and when the temperature is less than (melting point-80) ° C of the thermoplastic polymer which constitutes the core component, the above-mentioned is used. It is difficult to sufficiently repair the voids around the inorganic fine particles. A preferable heat treatment temperature is (melting point -60) ° C or higher of the thermoplastic polymer constituting the core component and (melting point -10) ° C or lower of polyester which is the sheath component. As a specific example, when the thermoplastic polymer constituting the core component is nylon 6, the heat treatment temperature is 160 ° C. or higher and 255 ° C.
It is desirable to make the following.

Further, in order to stabilize the stretching and suppress the generation of voids around the inorganic fine particles, heating at the time of stretching is performed by a contact heating method such as a heat roll, and also by non-heating such as steam jet or air heating. It is preferable to use the contact heating method together. This is intended to be stretched in a state where the fluidity of the core component is enhanced at a temperature sufficiently higher than the melting point of the thermoplastic polymer constituting the core component. For example, the thermoplastic polymer constituting the core component is made of nylon 6 350 ° C or higher,
It is preferable to heat draw using a temperature steam jet of preferably 400 ° C. or higher, more preferably 430 ° C. or higher. The temperature of the steam jet does not indicate the heat treatment temperature itself in the present invention,
The heat treatment temperature in the present invention means a contact heating temperature. From these findings, it is necessary that the melting point of the thermoplastic polymer that constitutes the core component is higher than the melting point of the polyester that is the sheath component by 20 ° C. or higher, especially 30 ° C. or higher, and the melting point of the thermoplastic polymer is inevitably high. 200 ° C or higher is required.

The composite fiber of the present invention can be used in a wide variety of applications either alone or in combination with other fibers. When mixed with other fibers, any means such as mixed fiber, mixed yarn, combined twist, mixed woven, mixed knit, and the like can be used, and the obtained fabric may be subjected to various post-processing treatments if necessary. It can be used for various purposes. Preferable uses of the conjugate fiber of the present invention include unprecedented high specific gravity, fiber strength that can withstand practical use, and gill nets, towing nets, lathes, and constructions that maximize the characteristics of polyester fibers having toughness. It is suitable for various fish nets such as nets and nets. Especially, it is most suitable for the set net such as salmon, yellowtail, tuna, horse mackerel, mackerel, sardine, sea bass, squid.

In addition to the above-mentioned fish net applications, it can be applied to various industrial material applications such as a silt protector used in civil engineering work and the like, as a polyester fiber having a high specific gravity performance that has never been seen. In addition to industrial materials, it is also suitable for non-clothing fields such as curtains and blackout curtains.

[0045]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples. In addition, each physical-property value in an Example is measured by the following method. (1) Intrinsic viscosity [η] of polyester: Measured at 30 ° C. using an equal weight mixed solvent of phenol and tetrachloroethane. (2) Number average molecular weight of nylon: HL manufactured by Waters Co., Ltd.
It was measured by a GPC chromatogram according to C-510. (3) Average particle size of inorganic fine particles: Measured by a centrifugal automatic particle size distribution analyzer CAPA-500 manufactured by Horiba Ltd. (4) Fiber specific gravity: Measured at 20 ° C. by a density gradient method using carbon tetrachloride and normal hexane. (5) Fiber strength, elongation and toughness: 2 using a tensile tester (Autograph IM-100) manufactured by Shimadzu Corporation
It was measured at 0 ° C. and 65 RH%. The toughness is indicated by the product of the strength at break and the elongation. (6) Melt viscosity of polymer (poise) It was measured at 300 ° C. using Capirograph 1C type manufactured by Toyo Seiki Co., Ltd.

Example 1 Nylon 6 powder having a number average molecular weight of 11,000 (P1011F manufactured by Ube Industries, Ltd.) was used as a thermoplastic polymer constituting a core component, and an average particle diameter of 0.2 μm was used as inorganic fine particles of the core component. Spherical magnetite powder [Toda Industry Co., Ltd.
Surface ferrite coated product, specific gravity 5.0] 30% by weight, and titanium dioxide having an average particle diameter of 0.35 μm (Rutile type, specific gravity 4.2) 40% by weight, manufactured by Titanium Industry Co., Ltd. The mixture was melt-kneaded as a core component with a twin-screw kneader and extruded into a strand, and the strand was cut into pellets and vacuum dried at 90 ° C. to a water content of 180 ppm. On the other hand, polyethylene terephthalate having an intrinsic viscosity [η] = 0.80 containing 0.08% by weight of titanium dioxide was used as a sheath component, and the polyester was melt-polymerized and pelletized by a conventional method.

The core component and the sheath component are melt-extruded by separate melt extruders, and the same core-sheath type having a spinning temperature of 295 ° C. and a composite weight ratio (core component / sheath component) of 1/2 is formed in the nozzle portion. They were merged, discharged using a nozzle having a nozzle aperture of 0.4 mmφ and 8 holes, and wound at a speed of 1000 m / min. The intrinsic viscosity [η] of the polyethylene terephthalate as the sheath component forming the composite fiber obtained at this time was 0.7.
It was 5.

The obtained spun raw yarn was heated at a hot roller temperature of 80.
At a hot plate temperature of 140 ° C. and a draw ratio of 4.0, followed by heat treatment at a hot roller temperature of 180 ° C. while adding 3% of over feed, and then 75 deniers.
A multifilament of 8/8 filaments was wound up. When the cross-sectional shape of this multifilament yarn was observed with a microscope, the core-sheath composite ratio was almost constant in all fibers and in the length direction, and there was no fluff. In addition, no trouble was observed in the spinning / drawing process. The fiber specific gravity of the drawn yarn was 1.58, the strength was 4.5 g / denier, and the toughness was 67.5.

The drawn yarns were combined to form a net, and the net was put into the sea and observed. As a result, the settling property was good, there was little shaking of the net in the sea, and the durability was excellent. Was confirmed.

It was also found that the fiber specific gravity of the drawn yarn obtained by changing the heat treatment temperature during drawing was different. As a result of drawing the spun raw yarn obtained under the above spinning conditions under the following conditions, a drawn yarn having the following physical properties was obtained.

Stretching Temperature Conditions Fiber Properties HR ₁ HP HR ₂ ρ DT Toughness Fluff 80 ° C. 140 ° C. 180 ° C. 1.58 4.5g / d 67.5 ○ 80 140 140 160 1.53 4.3 55.9 ○ 80 140 140 230 1.60 4.7 72.0 ○ 80 180 180 230 1.60 4.6 69.0 × Note: HR ₁ = hot roller (first roller), HP = hot plate HR ₂ = hot roller (second roller), ρ = specific gravity, DT = strength

The higher the treatment temperature at the time of the shrinking treatment, the more excellent the fiber properties are. However, if the treatment temperature is extremely high, the drawn fluff will frequently occur, which is not preferable.

Further, instead of the above magnetite powder, magnetite powder not surface-coated (manufactured by Toda Kogyo Co., Ltd., specific gravity 5.0) was used for fiberizing in the same manner. As a result, the fiber specific gravity of the drawn yarn was 1.53, which was slightly lower than that when the surface-coated article was used.

Example 2 A composite fiber (drawn yarn) was produced in the same manner as in Example 1 except that 0.2% by weight of copper iodide was added to the core component, and the strength retention of the obtained drawn yarn was obtained. Was measured. As an evaluation means, the strength retention ratio after carbon fade irradiation for 400 hours at 83 ° C. and the xenon weather irradiation at 83 ° C. 4
The strength retention after irradiation for 00 hours was examined. As a result, the average strength retention of n = 5 after 400 hours of carbon-fade irradiation was about 86%, and the average strength retention of n = 5 after 400 hours of xenon weather irradiation was about 84%. On the other hand, the composite fiber (drawn yarn) obtained in Example 1 has an average strength retention of about 42% at n = 5 after 400 hours irradiation with carbon fade, and n after 400 hours irradiation with xenon weather. = 5, the average strength retention rate was about 36%.

Examples 3 to 6 Magnetite powder 5 was used as the inorganic fine particles contained in the core component.
A mixture of 0% by weight and 20% by weight of titanium dioxide in a total of 70% by weight (Example 3), 20% by weight of magnetite powder and a mixture of 50% by weight of titanium dioxide in a total of 70% by weight (Example 4), magnetite powder 10% by weight, titanium dioxide 60% by weight
70% by weight of the mixture (Example 5), magnetite powder 3
A composite fiber was obtained in the same manner as in Example 2 except that a total of 50% by weight of 0% by weight and 20% by weight of titanium dioxide was used (Example 6). In both cases, there are no process problems.
Moreover, fibers having good fiber properties were obtained. The hue of the conjugate fiber obtained in Example 4 was gray and was at a level slightly different from black. The hue of the conjugate fiber obtained in Example 5 was whitish gray.

Examples 7 to 8 In Example 2, except that the intrinsic viscosity [η] of polyethylene terephthalate, which is a sheath component, was 0.85 (Example 7), the composite weight ratio of the core component and the sheath component was set. A composite fiber was obtained in the same manner except that (core component / sheath component) = 1/1 (Example 8). In all cases, fibers having good processability and good fiber properties were obtained. Various physical properties of the conjugate fiber in each example are shown in Tables 1 and 2.

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[Table 1]

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[Table 2]

Examples 9 to 10 In Example 2, zinc oxide having an average particle size of 1.0 μm (specific gravity 5.5) was used in place of titanium dioxide (Example 9), and alumina having an average particle size of 2.0 μm was used. (Specific gravity 3.98)
A composite fiber was obtained in the same manner except that was used (Example 10). In each case, the processability was good except that some fluff was generated during spinning, and the fiber physical properties were also good (see Tables 1 and 2).

Examples 11 to 12 Composite fibers were obtained in the same manner as in Example 2, except that the number of cores was 3 (Example 11) and the number of cores was 4 (Example 12). All of them had good processability and good fiber properties.

Example 13 Nylon 6 having a number average molecular weight of 22000 is used instead of nylon 6 having a number average molecular weight of 11,000 in Example 2.
A composite fiber was obtained in the same manner except that [P1022 manufactured by Ube Industries, Ltd.] was used. Various physical properties of the obtained conjugate fiber are shown in Tables 1 and 2.

Example 14 Polyethylene terephthalate having an intrinsic viscosity [η] = 0.70
Is used as a thermoplastic polymer constituting the core component, 70% by weight of barium sulfate (specific gravity 4.35) having an average particle diameter of 0.5 μm is used as the inorganic fine particles of the core component, and melted by a biaxial kneader as the core component. The mixture was kneaded and extruded into a strand, and the strand was cut into pellets. On the other hand, the intrinsic viscosity [η] containing 0.08% by weight of titanium dioxide as a sheath component
= 0.80 polyethylene terephthalate was used, and the polyester was melt-polymerized and pelletized by a conventional method.

The core component and the sheath component are melt-extruded by separate melt extruders, and the spinning temperature is 295 ° C. and the composite weight ratio (core component / sheath component) is 1/2. They were merged, discharged using a nozzle having a nozzle aperture of 0.4 mmφ and 8 holes, and wound at a speed of 1000 m / min. The intrinsic viscosity [η] of the polyethylene terephthalate as the sheath component forming the composite fiber obtained at this time was 0.7.
It was 5.

The obtained spun raw yarn was heated at a hot roller temperature of 80.
At a hot plate temperature of 140 ° C. and a draw ratio of 4.0, followed by heat treatment at a hot roller temperature of 180 ° C. while adding 3% of over feed, and then 75 deniers.
A multifilament of 8/8 filaments was wound up. When the cross-sectional shape of this multifilament yarn was observed with a microscope, the core-sheath composite ratio was almost constant in all fibers and in the length direction, and there was no fluff. In addition, no trouble was observed in the spinning / drawing process. The fiber specific gravity of the drawn yarn was 1.52, the strength was 4.1 g / denier, and the toughness was 61.5.

The drawn yarns were combined to form a net, which was put into the sea and observed. As a result, the settling was good, the net was not shaken in the sea, and the durability was excellent. Was confirmed.

Comparative Example 1 A polyethylene terephthalate chip having an intrinsic viscosity [η] of 0.65 before spinning was used as a sheath component, and spinning was performed so that the intrinsic viscosity [η] after spinning was 0.60. A composite fiber was obtained in the same manner as in Example 2 except for the above. as a result,
The fluff was slightly generated during spinning and stretching, and the fiber strength was low at 2.5 g / denier due to the low viscosity of the sheath component.
It was inferior to the fiber obtained in.

Comparative Example 2 15% by weight of magnetite mineral and titanium dioxide 1 as inorganic fine particles
A composite fiber was obtained in the same manner as in Example 2 except that 5% by weight of the mixture was used. The spinning / drawing process was good and the fibers could be formed, but the fiber specific gravity was 1.45, which was inferior to the fibers obtained in Example 2.

Comparative Examples 3 to 4 In Example 2, silicon dioxide particles having an average particle size of 0.1 μm and a specific gravity of 2.2 were used in place of titanium dioxide (Comparative Example 3), and an average particle size of 1.0 μm and a specific gravity of 2 were used. A composite fiber was obtained in the same manner as in Example 2 except that the kaolin particles of 0.5 (Comparative Example 4) were used. In each case, many fluffs were generated, spinning was not possible, and the drawability was not so good. The specific gravity of each of the obtained conjugate fibers was also inferior to that of the fiber obtained in Example 2.

Comparative Examples 5 to 6 The same as Example 2 except that the composite weight ratio (core component / sheath component) was 15/85 (Comparative Example 5) and 15/85 (Comparative Example 6). Then, composite spinning was performed. In Comparative Example 5, fiberization was good, but the level of fiber specific gravity was poor. In Comparative Example 6, the spinnability and drawability were poor, fluff and yarn breakage occurred frequently, and it was not possible to obtain fibers at a level at which performance could be evaluated. The results of these comparative examples are shown in Tables 1 and 2.

Example 15 Nylon 6 powder having a number average molecular weight of 11,000 (P1011F manufactured by Ube Industries, Ltd.) was used as a thermoplastic polymer constituting a core component, and an average particle diameter of 0.35 μm was used as inorganic fine particles of the core component. Titanium dioxide [Titanium Industry Co., Ltd.
Manufactured by K.K., specific gravity 4.2] 70% by weight, melt-kneaded as a core component in a twin-screw kneader and extruded into a strand, and the strand is cut into pellets, and the moisture content is 460 ppm by circulating nitrogen at 100 ° C. I chose On the other hand, the intrinsic viscosity [η] = 0.80 containing 1.5% by weight of carbon black (manufactured by Tegusa) having an average particle diameter of 0.03 μm as a sheath component.
Polyethylene terephthalate was used, and the polyester was melt-polymerized and pelletized by a conventional method.

The core component and the sheath component were spun and drawn in the same manner as in Example 2 to obtain a composite fiber. The intrinsic viscosity [η] of polyethylene terephthalate, which is the sheath component of the composite fiber, was 0.75. The fiber specific gravity is 1.57,
The strength was 4.6 g / denier and the elongation was 18%, and it had excellent performance for fishnet applications.

Example 16 A composite fiber was obtained in the same manner as in Example 15 except that the content of titanium dioxide was changed to 55% by weight. The specific gravity of the obtained composite fiber is 1.53, the strength is 5.2 g / denier, and the elongation is 2.
It was 0% and was excellent in both spinnability and stretchability.

Example 17 In Example 15, titanium dioxide 5 was used as the inorganic fine particles.
A composite fiber was obtained in the same manner except that a mixture of 0% by weight and 20% by weight of zinc oxide having an average particle size of 1.0 μm and a specific gravity of 5.5 was used. The specific gravity of the obtained composite fiber was 1.58, the strength was 4.5 g / denier, and the elongation was 15%. Although some fluff was generated during spinning, it was excellent in stretchability and was excellent as a fishing net application. Had performance.

Example 18 In Example 15, titanium dioxide 5 was used as the inorganic fine particles.
A composite fiber was obtained in the same manner except that a mixture of 0% by weight and 20% by weight of alumina having an average particle diameter of 2.0 μm and a specific gravity of 3.9 was used. The specific gravity of the obtained conjugate fiber was 1.56, the strength was 4.5 g / denier, and the elongation was 15%. Although some fluff was generated during spinning, it was excellent in stretchability and was excellent for fishing net use. Had performance.

Example 19 In Example 15, titanium dioxide 5 was used as the inorganic fine particles.
A composite fiber was obtained in the same manner except that a mixture of 0% by weight and 20% by weight of barium sulfate having an average particle size of 0.6 μm and a specific gravity of 4.3 was used. The specific gravity of the obtained conjugate fiber is 1.57,
The strength was 4.5 g / denier and the elongation was 14%, and although some fluff was generated during spinning, it was excellent in stretchability and had excellent performance for fishing net applications. Examples 15-19
Table 3 and Table 4 show the composition of each component, the fiber physical properties, etc. of the conjugate fiber obtained in the above.

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[Table 3]

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[Table 4]

Example 20 Nylon 6 powder having a number average molecular weight of 11,000 was used as a thermoplastic polymer constituting the core component, and 60% by weight of titanium dioxide having an average particle diameter of 0.35 μm was used as the inorganic fine particles of the core component. (Moisture content 100 ppm), and an intrinsic viscosity [η] of 0.08 wt% titanium dioxide = 0.
95 polyethylene terephthalate is used as a sheath component and melt-extruded by a separate extruder, and a nozzle is formed so as to form a concentric core-sheath type with a spinning temperature of 300 ° C. and a composite weight ratio (core component / sheath component) of 1/1. Merged at the nozzle, nozzle diameter 0.5 mmφ, 20
It was ejected using a 0-hole nozzle. The discharged yarn is passed through a heating zone of 20 cm long and 380 ° C. provided directly under the nozzle, and then cooled with a cooling air of 25 ° C. and 7 Nm ³ per minute,
A spinning oil is applied with an oiling roller, and the spinning speed is 600.
Withdrawn at m / min.

Subsequently, drawing and heat treatment were carried out in the following manner without winding the yarn, and the yarn was wound. Stretching: After being heated by a heat roll of 110 ° C., it is stretched by 4.3 times while injecting heated steam of 400 ° C. Heat treatment: 3% between heat roll and relaxation roll at 220 ° C
Heat shrink treatment. As a result, the process stability was good, and a highly practical fiber as a fishing net fiber having a denier of 1004, a strength of 4.0 g / denier, an elongation of 18% and a specific gravity of 1.62 was obtained.

Example 21 Nylon 6 powder having a number average molecular weight of 12000 was used as a thermoplastic polymer constituting the core component, and 25% by weight of titanium dioxide having an average particle size of 0.35 μm and an average particle size of 0 were used as the inorganic fine particles of the core component. Carbon black (manufactured by Tegusa) was used as a core component (moisture content of 200 ppm) by using a mixture of 50% by weight of α-hematite powder of 2 μm [manufactured by Toda Kogyo KK, specific gravity 5.2]. Polyethylene terephthalate containing 0% by weight of intrinsic viscosity [η] = 1.0 was used as a sheath component and melt-extruded by separate extruders, and the spinning temperature was 300.
℃, combined weight ratio (core component / sheath component) of 1/2, concentric core-sheath type to join to form a nozzle with a nozzle diameter of 0.6 m
Discharge was performed using a nozzle of mφ and 100 holes. The discharged yarn was passed through a heating zone of 20 cm long and 380 ° C. provided directly below the nozzle, then cooled with a cooling air of 25 ° C. and 7 Nm ³ per minute, and a spinning oil was applied with an oiling roller, and the spinning speed was increased. It was collected at 600 m / min.

Successively, without winding the yarn, drawing and heat treatment were carried out according to the following procedure. Stretching: After being heated by a heat roll of 110 ° C., it is stretched 4.8 times while injecting heated steam of 450 ° C. Heat treatment: 4% between 210 ° C. heat roll and relaxation roll
Heat shrink treatment. As a result, the process stability was good, and a highly practical fiber as a fishing net fiber having a denier of 1002, a strength of 5.5 g / denier, an elongation of 19% and a specific gravity of 1.62 was obtained.

Comparative Example 7 A composite fiber was produced in the same manner as in Example 20 except that the temperature of heated steam was 300 ° C., and as a result, the strength was 3.3.
A fiber having a fiber strength of less than the present invention was obtained, which was as small as g / denier, elongation 20%, and specific gravity 1.54.
This was probably due to the insufficient fluidity of the thermoplastic polymer constituting the core component during drawing, and many yarn breakages occurred during drawing.

Examples 22 to 23 and Comparative Example 8 The heat treatment temperature after stretching was 245 ° C. (Example 22), 160.
A composite fiber was produced in the same manner as in Example 20 except that the temperature was changed to 0 ° C (Example 23) and 256 ° C (Comparative Example 8). As a result, in Example 22, a composite fiber having a strength of 4.2 g / denier, an elongation of 21%, a specific gravity of 1.63 and a high strength and a high specific gravity could be obtained. In Example 23, the strength was 3.
A composite fiber having 7 g / denier, an elongation of 15% and a specific gravity of 1.53 was obtained. In Comparative Example 8, some fibers were fused and broken.

Comparative Example 9 In Example 1, when the moisture content of the core component was set to 650 ppm, screws dropped from the nozzle holes, and spinning was not possible at all.

Comparative Example 10 In Example 5, the particle diameter of titanium dioxide was 0.02 μm.
Except for the above, chips were prepared in the same manner as in Example 5, and composite spinning was tried. When the shear rate is 1 × 10 ¹ sec ^-1 ,
The melt viscosity of the core component is 30 × 10 ³ poise, the melt viscosity of the sheath component is 7.0 × 10 ³ poise, and the shear rate is 5 × 1.
At 0 ² sec ^-1 , the melt viscosity of the core component is 0.08 × 10.
The melt viscosity of ³ poise and the sheath component was 7.0 × 10 ³ poise. That is, a / b has a shear rate of 1 × 10 ¹ sec
When it is ^-1 , it is 4.3 and the shear rate is 5 × 10 ² sec.
It was 0.02 at ^-1 . At this time, single yarn breakage frequently occurred on the nozzle surface, and spinning was impossible.

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EFFECTS OF THE INVENTION According to the present invention, by obtaining a composite fiber having a core component highly added with specific inorganic fine particles and a sheath component made of polyester, it has both high strength and high specific gravity, which have never been seen before, and is for stationary netting. It is possible to provide a composite fiber which has no pollution problem as a fiber and has a suitable hue.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masao Kawamoto Inventor, Masao Saijo City, Ehime Prefecture, 892 Sakusui City, Kuraray Co., Ltd. (72) Inventor, Eiichi Sasakawa 1-1239, Umeda, Kita-ku, Osaka Kuraray Co., Ltd.

Claims (4)

[Claims] 1. A sheath made of a thermoplastic polymer having a specific gravity of 1 or more containing 50 to 85% by weight of lead-free inorganic fine particles having a specific gravity of 3 or more, and a polyester covering the core component. The core component and the sheath component have a composite weight ratio of core / sheath = 20/80 to 70/30, fiber specific gravity of 1.5 or more, toughness of 60 or more, and strength of 3.5.
A composite fiber having a g / denier or more. 2. The lead-free inorganic fine particles are iron oxide fine particles B and at least one fine particle A selected from the group consisting of titanium dioxide, zinc oxide, alumina and barium sulfate.
2. The composite fiber according to claim 1, which is mixed fine particles obtained by mixing in a weight ratio of / B = 10/0 to 3/7. 3. The shear rate at 300 ° C. is 1.0 × 10.
^In the entire region of ^{1 to} 5 × 10 ² sec ⁻¹ , the ratio (a / b) of the melt viscosity a of the core component and the melt viscosity b of the sheath component is 5.
It is 0-0.05, The composite fiber of Claim 1 or Claim 2 characterized by the above-mentioned. 4. A lead-free inorganic fine particle having a specific gravity of 3 or more is 50 to 8
A thermoplastic polymer containing 5% by weight and having a specific gravity of 1 or more is used as a core component, polyester is used as a sheath component for composite spinning, and after heat drawing, the thermoplastic polymer of the core component has a melting point or softening point of -80 ° C. As described above, the method for producing a conjugate fiber is characterized in that the heat treatment is carried out at a temperature of (melting point or softening point −5) ° C. or lower of the sheath component polyester.