JP5662262B2 - Core-sheath type composite yarn - Google Patents

Description

  The present invention relates to a core-sheath type composite yarn having a core yarn containing para-type wholly aromatic copolyamide fiber. More specifically, the present invention relates to a core-sheath type composite yarn having high heat resistance and simultaneously satisfying both high tensile strength and high breaking elongation.

Conventionally, so-called high-strength fibers such as para-type wholly aromatic copolyamide fibers, para-type wholly aromatic polyamide fibers, and polyparaphenylene benzobisoxazole fibers have characteristics such as high tensile strength, high elastic modulus, and high heat resistance. Therefore, it is widely used in various applications.
However, high-strength fibers have high mechanical properties and therefore have a low elongation at break. Since the dimensional change of the reinforcing fiber is obviously small with respect to the dimensional change, there has been a problem that the resin is distorted or cracked.

On the other hand, meta-type wholly aromatic polyamide fibers, polyester fibers such as polyethylene terephthalate and polyethylene naphthalate, nylon fibers, and rayon fibers are known to have high elongation. And taking advantage of the high elongation, it is widely used in industrial materials and clothing.
However, fibers having such a high elongation have a problem that they are not suitable for applications requiring high heat resistance and reinforcing effect because their mechanical properties themselves are small and generally their melting point and thermal decomposition starting temperature are low. It was.

Accordingly, development of composite yarns combining two or more types of fibers has been underway in search of fibers having high heat resistance and simultaneously satisfying both high tensile strength and high elongation at break.
For example, Patent Documents 1 and 2 report core-sheath type composite yarns for rubber reinforcement or resin reinforcement by combining various fibers. These composite yarns have high heat resistance and high tensile strength due to the combination of the core and the sheath, but have not yet been satisfactory for high breaking elongation.

  Patent Document 3 reports a para-type wholly aromatic amide fiber having characteristics of high elongation and low elastic modulus. Since the fiber described in Patent Document 3 is formed from para-type wholly aromatic polyamide, it has high heat resistance. However, since it was not stretched or the like, the fiber had extremely low tensile strength.

Japanese Patent Laid-Open No. 2005-199580 JP 2006-161225 A JP 2011-001666 A

  The present invention has been made against the background of such prior art, and its object is to provide a composite yarn that is excellent in heat resistance and simultaneously satisfies both high tensile strength and high elongation at break. is there.

  The present inventor has intensively studied to solve the above problems. In addition, the para-type wholly aromatic copolyamide fiber obtained after the drying process or after one-stage stretching has a high heat resistance, but has a low elastic modulus. It was found that the above-mentioned problems can be solved by combining a high-strength fiber having a tensile strength with a core-sheath type composite yarn, and the present invention has been completed.

  That is, the present invention is a core-sheath type composite yarn having a core yarn containing a para-type wholly aromatic copolyamide fiber, having a melting point and / or thermal decomposition starting temperature of 450 ° C. or higher and a tensile strength of 10 to 10. This is a core-sheath type composite yarn having 30 cN / dtex, an elongation at break of 5 to 30%, and an initial elastic modulus of 40 cN / dtex or less.

  The core-sheath type composite yarn of the present invention is excellent in heat resistance and becomes a fiber satisfying both high tensile strength and high breaking elongation at the same time. For this reason, the fiber of the present invention is very useful in the use of reinforcing materials such as rubber and various other industrial materials.

Hereinafter, embodiments of the present invention will be described in detail.
<Para-type wholly aromatic copolyamide>
In the core-sheath type composite yarn of the present invention, the para-type wholly aromatic copolyamide constituting the core yarn is one or two or more divalent aromatic groups directly linked by an amide bond at the para position. Polymer. As the aromatic group, two aromatic rings may be bonded through oxygen, sulfur, or an alkylene group. Furthermore, these divalent aromatic groups may contain a lower alkyl group such as a methyl group or an ethyl group, a halogen group such as a methoxy group, a chloro group, or the like.

<Method for producing para-type wholly aromatic copolyamide>
In the core-sheath type composite yarn of the present invention, the para-type wholly aromatic copolyamide used for the core yarn can be produced according to a conventionally known method. For example, a polymer solution of an aromatic copolyamide can be obtained by reacting an aromatic dicarboxylic acid chloride component and an aromatic diamine component in an amide polar solvent.

[Raw material of para-type wholly aromatic copolyamide]
(Aromatic dicarboxylic acid dichloride component)
The aromatic dicarboxylic acid dichloride component used as a raw material for the para-type wholly aromatic copolyamide used in the present invention is not particularly limited, and generally known compounds can be used. Examples thereof include terephthalic acid dichloride, 2-chloroterephthalic acid dichloride, 3-methylterephthalic acid dichloride, 4,4′-biphenyldicarboxylic acid dichloride, 2,6-naphthalenedicarboxylic acid dichloride, and the like. Of these, terephthalic acid dichloride is most preferably used from the viewpoints of versatility and mechanical properties of the fiber.

  These aromatic dicarboxylic acid dichlorides can be used not only in one type but also in two or more types, and the composition ratio is not particularly limited. In the present invention, a small amount of a component such as isophthalic acid dichloride that forms a bond other than the para position may be contained.

(Aromatic diamine component)
Examples of the aromatic diamine component used as a raw material for the para-type wholly aromatic copolyamide used in the present invention include paraphenylenediamine, 3,4'-diaminodiphenyl ether, parabiphenylenediamine, and 5-amino-2- (4- Aminophenylene) benzimidazole, 1,4-dichloroparaphenylenediamine, and the like, but are not limited thereto. Aromatic rings may have a substituent or other heterocyclic rings may be present. Moreover, these can use not only one type but 2 or more types, The composition ratio is not specifically limited. In addition, in this invention, components, such as metaphenylenediamine which forms a bond other than para position, may be contained in a small amount.

  Two or more of these are used as raw materials for the para-type wholly aromatic copolyamide used in the present invention. The combination is most preferably a combination of paraphenylenediamine and 3,4'-diaminodiphenyl ether from the viewpoints of versatility and mechanical properties of the fiber. Further, when paraphenylenediamine and 3,4'-diaminodiphenyl ether are used in combination, the composition ratio is not particularly limited, but is 30 to 70 mol% with respect to the total aromatic diamine amount. 70 to 30 mol%, more preferably 40 to 60 mol% and 60 to 40 mol%, respectively, and most preferably 45 to 55 mol% and 55 to 45 mol%, respectively.

(Raw material composition ratio)
The ratio of the aromatic dicarboxylic acid chloride component to the aromatic diamine component is preferably in the range of 0.90 to 1.10 as the molar ratio of the aromatic dicarboxylic acid chloride component to the aromatic diamine component, 0.95 More preferably, it is in the range of ˜1.05. When the molar ratio of the aromatic dicarboxylic acid chloride component is less than 0.90 or exceeds 1.10, the reaction with the aromatic diamine component does not proceed sufficiently and a high degree of polymerization cannot be obtained, which is not preferable.

[Polymerization of para-type wholly aromatic copolyamide]
(Polymerization conditions)
The polymerization conditions for the aromatic dicarboxylic acid chloride component and the aromatic diamine component are not particularly limited. The reaction between the acid chloride and diamine is generally rapid, and the polymerization temperature is preferably in the range of -25 ° C to 100 ° C, and more preferably in the range of -10 ° C to 80 ° C.

(Polymerization solvent)
Examples of amide solvents used for the production of para-type wholly aromatic copolyamide include N-methyl-2-pyrrolidone (hereinafter also referred to as NMP), N, N-dimethylformamide, N, N-dimethylacetamide, dimethylimidazo. Examples include lysinone. These solvents can be used alone or as a mixed solvent of two or more. Note that the solvent used is preferably dehydrated.
In the production of the para type wholly aromatic copolyamide used in the present invention, N-methyl-2-pyrrolidone (from the viewpoints of versatility, harmfulness, handleability, solubility in the para type wholly aromatic copolyamide polymer, etc. Most preferably, NMP) is used.

(Neutralization reaction)
After completion of the polymerization, it is preferable to carry out a neutralization reaction by adding a basic inorganic compound such as sodium hydroxide, potassium hydroxide, calcium hydroxide, calcium oxide or the like, if necessary.

(Post-polymerization treatment, etc.)
The para-type wholly aromatic copolyamide obtained by polymerization can be put into a non-solvent such as alcohol or water, precipitated, and taken out as a pulp. The taken para-type wholly aromatic copolyamide can be dissolved again in another solvent and then used for fiber molding, but the polymer solution obtained by the polymerization reaction is directly adjusted to a spinning solution (dope). It can also be used. The solvent used for once taking out and then dissolving again is not particularly limited as long as it dissolves the para-type wholly aromatic copolyamide, but is preferably a solvent used for the above-described polymerization.

<Core yarn>
The core yarn of the core-sheath type composite yarn of the present invention contains para-type wholly aromatic copolyamide fiber. The content of the para-type wholly aromatic copolyamide fiber in the core yarn is preferably 90% by mass or more, more preferably 95% by mass or more, and 100% by mass with respect to the total mass of the core yarn. Most preferred. When the amount is less than 90% by mass with respect to the total mass of the core yarn, it is difficult to obtain a core-sheath type composite yarn having target elongation and heat resistance.

Examples of fibers other than the para-type wholly aromatic copolyamide fiber and constituting the core yarn of the core-sheath type composite yarn of the present invention include meta-type wholly aromatic polyamide fibers. Such a fiber is inferior in heat resistance as compared to para-type wholly aromatic copolyamide fiber, but there is no problem when it is contained in a small amount of less than 10% by mass.
The mixing method of the para-type wholly aromatic copolyamide fiber and the other fibers is not particularly limited, and examples thereof include a method of aligning or twisting both long fibers.

<Physical properties of core yarn>
[Melting point and thermal decomposition temperature]
It is essential that the melting point and / or the thermal decomposition temperature of the core yarn be 450 ° C. or higher. When the melting point and / or thermal decomposition temperature of the core yarn is lower than 450 ° C., the melting point and / or thermal decomposition temperature of the resulting composite yarn cannot be made 450 ° C. or higher. In order to set the melting point and / or the thermal decomposition temperature of the core yarn to 450 ° C. or higher, fibers having a melting point and / or a thermal decomposition temperature of 450 ° C. or higher are used for the core yarn.

<Manufacture of para-type wholly aromatic copolyamide fiber constituting core yarn>
The production of the para-type wholly aromatic copolyamide fiber constituting the core yarn of the core-sheath type composite yarn is not particularly limited, and examples thereof include the following methods. As the core yarn, fibers collected after the drying step or fibers collected after one-stage hot drawing can be used.

[Process for adjusting spinning solution (polymer dope)]
In producing the fiber, first, a spinning solution (polymer dope) for forming the fiber is prepared. The spinning solution (dope) contains para-type wholly aromatic copolyamide and a solvent, and the adjusting method is not particularly limited. As the solvent used for preparing the spinning solution (dope), it is preferable to use the solvent used for the polymerization of the para-type wholly aromatic copolyamide. In addition, the solvent used may be one type alone or a mixed solvent obtained by mixing two or more types of solvents. In the production method of the present invention, the polymer can be used as it is without being isolated from the polymer solution obtained by the production of the para-type wholly aromatic copolyamide.

  Furthermore, an inorganic salt can also be used as a solubilizing agent for the purpose of increasing the solubility of the para-type wholly aromatic copolyamide in the solvent. Examples of the inorganic salt include calcium chloride and lithium chloride. Although the amount of the inorganic salt added to the polymer dope is not particularly limited, it is 1 to 10% by mass with respect to the polymer dope mass from the viewpoint of the effect of improving the polymer solubility and the solubility of the inorganic salt in the solvent. It is preferable that

  Moreover, you may mix | blend other arbitrary components, such as an additive, in the range which does not exceed the summary of this invention in order to provide functionality etc. to a fiber. When an additive or the like is blended, it can be introduced in adjusting the dope. The method of introduction is not particularly limited, and for example, it can be introduced into the dope using a ruder or a mixer.

  The polymer concentration in the spinning solution (dope), that is, the concentration of the para-type wholly aromatic copolyamide is preferably in the range of 0.5 mass% to 30 mass%. When the polymer concentration in the spinning solution (dope) is less than 0.5% by mass, the entanglement of the polymer is small, so that the viscosity necessary for spinning cannot be obtained, and the ejection stability during spinning decreases. . On the other hand, when the polymer concentration exceeds 30% by mass, the viscosity of the dope increases abruptly, so that the discharge stability at the time of spinning decreases, and stable spinning becomes difficult due to the sudden increase in pressure in the spinning pack. Cheap.

[Spinning and coagulation process]
In the spinning / coagulation step, fibers are formed by a wet method, a semi-dry semi-wet method, or the like. For example, in the semi-dry semi-wet method, a spinning solution (dope) is discharged from a spinneret and solidified in a coagulation bath made of a poor solvent to obtain an undrawn yarn. The spinneret used in the present invention is not particularly limited as long as the final fineness of the composite yarn is adjusted to 100 to 5000 dtex.
The temperature of the polymer dope when passing through the spinneret and the temperature of the spinneret are not particularly limited, but are preferably 80 to 120 ° C. from the viewpoint of spinnability and polymer dope discharge pressure. .

Next, the polymer dope discharged from the spinneret is solidified in a coagulating liquid. At this time, when the temperatures of the spinneret and the coagulating liquid are greatly different, when the spinneret and the coagulating liquid come into contact with each other, the respective temperatures change, and as a result, it becomes difficult to control the spinning process. Therefore, when the temperatures of the spinneret and the coagulating liquid are greatly different, it is preferable to perform semi-dry semi-wet spinning provided with an air gap. The length of the air gap is not particularly limited, but is preferably in the range of 5 to 15 mm from the viewpoints of temperature controllability, stringiness, and the like.
The coagulating liquid used here is, for example, an NMP aqueous solution, and its temperature and concentration are not particularly limited. As long as there is no problem in the solidified state of the formed yarn and the subsequent process passability, it can be adjusted as appropriate.

[Washing process]
Next, the coagulated yarn obtained above is washed with water. The purpose of the water washing step is to diffuse NMP in the yarn using water and remove it from the yarn. If NMP can be sufficiently removed from the yarn, washing conditions such as temperature and washing time are not particularly limited.

[Drying process]
Next, the dried yarn is subjected to a drying process. The drying conditions are not particularly limited, and there is no problem as long as moisture attached to the fibers can be sufficiently removed. However, in consideration of workability and deterioration of the fibers due to heat, the temperature is in the range of 150 to 250 ° C. It is preferable. Moreover, drying can use any of contact-type drying apparatuses, such as a roller, and non-contact-type drying apparatuses, such as passing a fiber through a drying furnace.
In the core-sheath type composite yarn of the present invention, the dried fiber obtained after this drying step can be used as the core yarn of the composite yarn. Or you may use the fiber after implementing the below-mentioned heat | fever stretching as needed, such as physical properties.

[Hot drawing process]
Next, the dried fiber is hot-drawn. The purpose of this step is to improve the physical properties by applying heat to the fibers to densify the molecular structure and by promoting the molecular orientation by stretching. In order to obtain the para type wholly aromatic copolyamide fiber used for the core yarn of the present invention, the heat drawing temperature is preferably 400 ° C. or less, more preferably 380 ° C. or less, and most preferably 350 ° C. or less. When the heat stretching temperature exceeds 400 ° C., the molecular structure is excessively densified, so that a para-type wholly aromatic copolyamide fiber having the desired physical properties cannot be obtained. In order to set the heat stretching temperature to 400 ° C. or lower, the atmospheric temperature for performing the heat stretching is adjusted to 400 ° C. or lower.

  In the heat stretching step, heat is applied and stretching is performed. The draw ratio at this time is preferably in the range of 1.00 to 1.40 times, more preferably in the range of 1.05 to 1.3 times, and most preferably in the range of 1.10 to 1.30 times. . When the draw ratio exceeds 1.4 times, the orientation of molecules is promoted too much, and para-type wholly aromatic copolyamide fibers having the desired physical properties cannot be obtained. On the other hand, since it is difficult to shrink the fiber, the draw ratio cannot be less than 1.00 times. Examples of the method of setting the draw ratio in the range of 1.00 to 1.40 times include a method of setting the ratio between the feed speed before and after the draw and the take-up speed in the range of 1.00 to 1.40 times.

<Physical properties of para-type wholly aromatic copolyamide fiber constituting core yarn>
The physical properties of the para-type wholly aromatic copolyamide fiber constituting the core yarn are preferably such that the tensile strength is 0.5 to 5 cN / dtex, the breaking elongation is 3 to 30%, and the initial elastic modulus is 40 cN / dtex or less. More preferably, the tensile strength is 1.0 to 4.5 cN / dtex, the elongation at break is 3.5 to 27%, the initial elastic modulus is 35 cN / dtex or less, and most preferably, the tensile strength is 1.5 to 4 cN. / Dtex, the elongation at break is 4 to 25%, and the initial elastic modulus is 30 cN / dtex or less.

[Tensile strength]
If the tensile strength of the para-type wholly aromatic copolyamide fiber constituting the core yarn is less than 0.5 cN / dtex, the strength is too weak and it is difficult to use as the core yarn of the core-sheath composite yarn. On the other hand, in order to obtain a fiber having a tensile strength exceeding 5 cN / dtex, it is necessary to further promote molecular orientation in the hot drawing process. The fiber manufactured under such conditions is the core-sheath type of the present invention. Other physical properties necessary for forming the core yarn of the composite yarn cannot be satisfied.
Examples of the method for setting the tensile strength in the range of 0.5 to 5 cN / dtex include a method of performing heat stretching in the heat stretching step within the range of the temperature and the stretching ratio described above.

[Elongation at break]
When the breaking elongation of the para-type wholly aromatic copolyamide fiber constituting the core yarn is less than 3%, a composite yarn having a target breaking elongation of 5 to 30% cannot be obtained. On the other hand, in the case of para-type wholly aromatic copolyamide fibers, it is difficult to obtain fibers having a breaking elongation exceeding 30%. Therefore, the higher the breaking elongation of the para-type wholly aromatic copolyamide fiber used as the core yarn, the better.
Examples of the method for setting the breaking elongation in the range of 3 to 30% include a method of thermally stretching in the thermal stretching step within the range of the temperature and the stretching ratio described above.

[Initial elastic modulus]
When the initial elastic modulus of the para type wholly aromatic copolyamide fiber constituting the core yarn exceeds 40 cN / dtex, a composite yarn having a target initial elastic modulus of 40 cN / dtex or less cannot be obtained. In order to set the initial elastic modulus to 40 cN / dtex or less, for example, in the heat stretching step, a method of performing heat stretching within the range of the temperature and the stretching ratio described above can be used.

<Sheath thread>
The fiber used for the sheath yarn of the core-sheath type composite yarn of the present invention is not particularly limited as long as a composite yarn having the desired physical properties can be obtained. In order to set the melting point and / or thermal decomposition start temperature of the composite yarn to 450 ° C. or more and the tensile strength to 10 to 30 cN / dtex, for example, para-type wholly aromatic copolyamide fiber, para-type wholly aromatic polyamide fiber, poly It is preferably at least one selected from the group consisting of paraphenylene benzobisoxazole fibers.
The fineness of the sheath yarn is not particularly limited as long as the fineness of the composite yarn can be in the range of 100 to 5000 dtex.

<Composite yarn>
[Production method of composite yarn]
The core-sheath type composite yarn of the present invention is produced using the core yarn and sheath yarn described above. For the production of the composite yarn, a known method for producing a core-sheath composite yarn can be used as it is. For example, a method in which a sheath yarn is covered with a single yarn so as to be Z-twisted or S-twisted with respect to a core yarn to form a single covering yarn, or after a single twist is applied to a yarn that becomes a sheath yarn, this and the core yarn For example, a method may be used in which the yarns are aligned with each other and twisted in a direction opposite to the twisting direction of the sheath yarn to form a wall yarn covering the core yarn with the sheath yarn.

  At this time, the core yarn needs to be arranged in a straight line, and the sheath yarn needs to be arranged in a curved shape. When the core yarns are arranged in a curved line, the load cannot be received when a load is applied to the composite yarn. On the other hand, when the sheath yarns are arranged in a straight line, the sheath yarn having high physical properties is immediately subjected to a load, so the elongation of the core yarn cannot be utilized, and as a result, the intended breaking elongation is not achieved. A composite yarn of 5 to 30% cannot be obtained.

  In order to arrange the core yarn in a straight line and the sheath yarn in a curved shape, a method of supplying the sheath yarn to the linearly arranged core yarn in the production stage of the core-sheath type composite yarn is mentioned. It is done. The degree of curve of the sheath yarn arranged in a curved shape is not particularly limited as long as the composite yarn has the desired physical properties.

  In addition, it is desirable to use twisted yarns for the core yarn and the sheath yarn in order to fully express the uniformity and performance of physical properties. The number of twists is not particularly limited, but the twist is most preferably applied so that the twist coefficient = 1. Here, the twist coefficient and the number of twists are numerical values calculated from the following formula (1).

[Proportion of core yarn and sheath yarn in composite yarn]
The ratio of the core yarn to the sheath yarn in the composite yarn is not particularly limited as long as a composite yarn having the desired mechanical properties is obtained, but the ratio of the fineness of the core yarn to the fineness of the composite yarn is not limited. A range of 10 to 50% is preferable.

[Physical properties of composite yarn]
The composite yarn of the present invention has a melting point and / or thermal decomposition starting temperature of 450 ° C. or higher, a tensile strength of 10 to 30 cN / dtex, a breaking elongation of 5 to 30%, and an initial elastic modulus of 40 cN / dtex or less. It is a thread.
The fineness is preferably in the range of 100 to 5000 dtex. When the fineness of the composite yarn is less than 100 dtex, each of the core yarn and the sheath yarn becomes further finer, and it becomes very difficult to produce the core yarn and the sheath yarn having such a fineness. On the other hand, when the fineness of the composite yarn exceeds 5000 dtex, each of the core yarn and the sheath yarn has a large fineness, so that workability for producing the composite yarn is remarkably deteriorated.

  EXAMPLES Hereinafter, although an Example etc. demonstrate this invention further more concretely, this invention is not limited to these, unless the summary is exceeded.

<Measurement and evaluation method>
In Examples and Comparative Examples, the following items were measured and evaluated by the following methods.
(1) Fineness of fiber and composite yarn The obtained fiber was wound up 100 m using a known measuring machine, and its mass was measured. A value obtained by multiplying the obtained mass by 100 was calculated as a mass per 10,000 m, that is, a fineness (dtex).
(2) Tensile strength, breaking elongation, elastic modulus of fibers and composite yarns Using a tensile tester (manufactured by INSTRON, trade name: INSTRON, model: 5565 type), using the yarn test chuck, the procedure of ASTM D885 Based on this, the measurement was performed under the following conditions.
[Measurement condition]
Temperature: Room temperature Test piece: 75cm
Test speed: 250 mm / min Chuck distance: 500 mm
(3) Melting point of composite yarn or thermal decomposition start temperature Using a thermal analyzer (TAS-200, manufactured by Rigaku Corporation), measurement was performed under the following conditions.
[Measurement condition]
Measurement start temperature: Room temperature Temperature rise: 10 ° C / min Measurement atmosphere: In air

<Example 1>
[Production of para-type wholly aromatic copolyamide]
By a known method, 100 parts by mass of terephthalic acid dichloride is added to 50 parts by mass of paraphenylenediamine and 50 parts by mass of 3,4'-diaminodiphenyl ether dissolved in NMP, and a polycondensation reaction is performed. , 4'-oxydiphenylene terephthalamide polymer solution (dope) was obtained.
[Manufacture of para-type wholly aromatic copolyamide fiber as core yarn]
A spinneret having a hole diameter of 0.3 mm and a hole number of 10 is heated to 105 ° C., and then the polymer solution (dope) obtained above is heated to 105 ° C. and discharged through an air gap of 10 mm. Was passed through a coagulation bath filled with 30% by mass of an aqueous solution at 50 ° C. to obtain a fiber bundle in which the polymer was coagulated.
Next, the coagulated fiber bundle was passed through a water washing bath adjusted to 55 ° C., followed by water washing, followed by drying with a 200 ° C. drying roller. Subsequently, it was hot-drawn 1.12 times at 300 ° C. to obtain a para-type wholly aromatic copolyamide fiber to be a core yarn.
The physical properties of the obtained fiber were fineness = 138 dtex, tensile strength = 3.00 cN / dtex, elongation at break = 4.74%, initial elastic modulus = 15.7 cN / dtex.
[Scabbard thread]
As the sheath yarn, Technora (manufactured by Teijin Techno Products), which is a commercially available para-type wholly aromatic copolyamide fiber, was used.
The physical properties of the fiber used were as follows: fineness = 220 dtex, tensile strength = 24.7 cN / dtex, elongation at break = 4.05%, initial elastic modulus = 599 cN / dtex.
[Manufacture of composite yarn]
After twisting the core yarn and the sheath yarn so that the twist coefficient = 1, respectively, the sheath yarn is Z-twisted with respect to the core yarn that is linearly oriented using a known single covering device. A composite yarn was obtained by coating at a rate of 200 T / m.
Table 1 shows the fineness, tensile strength, breaking elongation, initial elastic modulus, and decomposition start temperature of the obtained composite yarn.

<Example 2>
In the process of producing a para-type wholly aromatic copolyamide fiber to be the core yarn of Example 1, except that the yarn drawn after drying with a drying roller was used as the core yarn without carrying out the heat stretching step. A composite yarn was obtained in the same manner as in Example 1.
The physical properties of the dried yarn used as the core yarn were fineness = 154 dtex, tensile strength = 2.08 cN / dtex, elongation at break = 19.6%, and initial elastic modulus = 8.7 cN / dtex.
Table 1 shows the fineness, tensile strength, elongation at break, initial elastic modulus and decomposition start temperature of the obtained composite yarn.

<Example 3>
A composite yarn was obtained in the same manner as in Example 1 except that a commercially available polyparaphenylene benzobisoxazole fiber (trade name: Zylon, manufactured by Toyobo Co., Ltd.) was used as it was for the sheath yarn.
The physical properties of the polyparaphenylene benzobisoxazole fiber used as the sheath yarn were fineness = 110 dtex, tensile strength = 37.2 cN / dtex, elongation at break = 3.63%, initial elastic modulus = 1134 cN / dtex.
Table 1 shows the fineness, tensile strength, elongation at break, initial elastic modulus and decomposition start temperature of the obtained composite yarn.

<Comparative Example 1>
In the process for producing a para-type wholly aromatic copolyamide fiber to be the core yarn of Example 1, except that a yarn having a heat drawing condition of 2.3 times stretched at 380 ° C. was used as the core yarn. A composite yarn was obtained by the same method as in No. 1.
The physical properties of the hot drawn yarn used as the core yarn were fineness = 67 dtex, tensile strength = 6.37 cN / dtex, breaking elongation = 2.41%, and initial elastic modulus = 93 cN / dtex.
Table 1 shows the fineness, tensile strength, elongation at break, initial elastic modulus and decomposition start temperature of the obtained composite yarn.

<Comparative example 2>
A composite yarn was obtained in the same manner as in Example 1 except that a commercially available polyester fiber (trade name: Tetron, manufactured by Teijin Fibers Ltd.) was used as it was for the core yarn.
The physical properties of the polyester fiber used as the core yarn were fineness = 110 dtex, tensile strength = 7.82 cN / dtex, elongation at break = 11.7%, and initial elastic modulus = 83 cN / dtex.
Table 1 shows the fineness, tensile strength, elongation at break, initial elastic modulus and decomposition start temperature of the obtained composite yarn.

<Comparative Example 3>
Only the para-type wholly aromatic copolyamide fiber that becomes the core yarn in Example 1 was evaluated as it was, not the core-sheath type composite yarn. Table 1 shows the fineness, tensile strength, elongation at break, initial elastic modulus and decomposition start temperature of the para-type wholly aromatic copolyamide fiber.

<Comparative Example 4>
Only the para-type wholly aromatic copolyamide fiber that becomes the sheath yarn in Example 1 was evaluated as it is, not the core-sheath type composite yarn. Table 1 shows the fineness, tensile strength, elongation at break, initial elastic modulus and decomposition start temperature of the para-type wholly aromatic copolyamide fiber.

  The composite yarn of the present invention is a composite yarn that is excellent in heat resistance and simultaneously satisfies both high tensile strength and breaking elongation. Therefore, the composite yarn of the present invention is useful as various industrial materials, and is particularly useful for use as a reinforcing material such as rubber.

Claims (5)

A core-sheath type composite yarn having a core yarn containing a para-type wholly aromatic copolyamide fiber,
A core-sheath composite yarn having a melting point and / or thermal decomposition starting temperature of 450 ° C. or higher, a tensile strength of 10 to 30 cN / dtex, a breaking elongation of 5 to 30%, and an initial elastic modulus of 40 cN / dtex or less. .   The core-sheath type composite yarn according to claim 1, wherein the para-type wholly aromatic copolyamide fiber is a copolyparaphenylene 3,4'-oxydiphenylene terephthalamide fiber.   The core according to claim 1 or 2, wherein the para-type wholly aromatic copolyamide fiber has a tensile strength of 0.5 to 5 cN / dtex, a breaking elongation of 3 to 30%, and an initial elastic modulus of 40 cN / dtex or less. Sheath type composite yarn.   The sheath yarn is at least one fiber selected from the group consisting of para-type wholly aromatic copolyamide fibers, para-type wholly aromatic polyamide fibers, and polyparaphenylene benzobisoxazole fibers. Core-sheath type composite yarn.   The core-sheath type composite yarn according to any one of claims 1 to 4, having a fineness of 100 to 5000 dtex.