JPH02145813A - Conjugate fiber having high strength and production thereof - Google Patents

Abstract

PURPOSE:To obtain the subject fiber having high strength, heat-resistance, adhesivity and durability and useful for rubber-reinforcing material, etc., by carrying out conjugate spinning using a high-polymer polyester as the core and a high-polymer polyamide as the sheath, passing the spun fiber through a high-temperature atmosphere, quenching and solidifying the fiber and passing the product through an apparatus for promoting the crystallization of the surface layer. CONSTITUTION:Conjugate spinning is carried out by using a high-polymer polyethylene terephthalate having a intrinsic viscosity [eta] of >=0.80 as a core and a high-polymer polyamide having a relative viscosity etar (in sulfuric acid) of >=2.8 as a sheath. The ratio of the core part to the sum of the core and the sheath is 30-90wt.%. The melt-spun fiber is passed through an atmosphere of >=200 deg.C in a zone having a length of >=10cm under the spinneret and the treated fiber is quenched and solidified. The fiber is passed through an apparatus to promote the crystallization of the surface layer of the fiber, applied with a lubricant, taken up at a high speed (>=1,000m/min) and drawn in multiple stages (>=2 stages) to obtain the objective sheath-core conjugate fiber having a birefringence n of 160X10<-3>-190X10<-3> at the core part and >=50X10<-3> at the sheath part. A number of ridges having a width of 0.01-1mum and a length of 0.1-10mum and extended in the direction of fiber axis are uniformly distributed over the whole area on the surface of the filament.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-strength conjugate fiber with excellent durability suitable for industrial material use, particularly as a rubber reinforcing material. More specifically, it has excellent mechanical properties such as high strength, high modulus, and improved dimensional stability, and has excellent adhesion to rubber, especially heat-resistant adhesion, heat resistance in rubber, and fatigue resistance. The object of the present invention is to provide an improved composite fiber for industrial materials.

[Conventional technology]

Polyester fibers, typified by polyethylene terephthalate fibers, have high strength and high modulus of elasticity, and are therefore widely used in various industrial material applications. It is particularly useful as a rubber reinforcing material for tire cords, transmission belts, conveyor belts, etc.

However, polyester fibers generally have poor heat resistance in rubber. That is, at high temperatures, the ester bonds of polyester fibers are broken due to the action of moisture and amine compounds in the rubber, causing a decrease in strength. Furthermore, the adhesion to rubber is also poor, and there is a problem in that the adhesion to rubber decreases markedly especially when repeatedly exposed to a high temperature atmosphere for a long time.

Tire cords made of polyester fibers have high strength and high modulus, and have been widely used as carcass materials for radial tires for passenger cars.

However, when used for larger light trucks, trucks, and buses, the heat generated during driving tends to accumulate in the tires, causing thermal deterioration and strength reduction, and the tires also lose adhesive strength with rubber and peel off. There was a problem. Therefore, there has been a need to improve the heat resistance of polyester fibers in rubber and to improve their adhesive properties at high temperatures.

Many attempts have been made to improve the adhesiveness, which is a drawback of polyester fibers, and one known method is to coat the surface of polyester with polyamide. For example, Japanese Patent Application Laid-open No. 49-85315 describes a method for manufacturing a composite fiber having a polyester core and a nylon 6 sheath, specifies the degree of polymerization of each component polymer and the proportion of the core polymer, and also describes a spinning method. A method of directly spinning and drawing with non-hydrous oil supply is disclosed.

JP-A-56-140128 also describes a rubber reinforcing material made of fibers with a core-sheath type composite structure in which the core is made of polyester and the sheath is made of polyamide.
~30% by weight, and a rubber reinforcement material whose surface is adhered with an epoxy adhesive is described.

[Problem that the invention seeks to solve]

The above-mentioned JP-A-49-85315 and JP-A-56-1
The fiber with a core-sheath composite structure proposed by the method of Publication No. 40128 was intended to improve adhesion to rubber by using a polyamide component in the sheath, and maintain modulus and dimensional stability by using a polyester component in the core. . Although adhesion is certainly improved sufficiently by this method, the modulus and dimensional stability decrease as the nylon component of the sheath increases, and it is difficult to sufficiently maintain the modulus and dimensional stability of the polyester core component. I couldn't do it,
On the other hand, it was not possible to fully utilize the heat resistance and fatigue resistance of nylon in rubber.

FIG. 2 is a photograph in place of a drawing showing the surface shape of a conventional composite fiber consisting of a polyamide sheath component and a polyester core component. As shown in the figure, no streak-like irregularities are formed on the surface of the conventional composite fiber made of a polyamide sheath component and a polyester core component.

Ordinary polyesters such as polyethylene terephthalate and ordinary polyamides such as nylon 6 and nylon 66 have poor compatibility with each other, so when they are manufactured by ordinary yarn-making methods, the interface between the two polymers in a core-sheath composite structure The lid does not have enough durability to be used in practical use because it easily peels off and breaks. In particular, the polymer interface is destroyed by the stretching process, tire cord processing process such as twisting, dipping, tire vulcanization process, and repeated stretching/compression fatigue during tire running.
The performance expected of core-sheath composite fibers could not be obtained.

By overcoming the above problems, the present invention has excellent adhesion to rubber, high modulus and dimensional stability on the same level as polyester, and has improved heat resistance and fatigue resistance in rubber. The object of the present invention is to provide a composite fiber suitable for In particular, a composite that has high modulus, improved dimensional stability, and improved heat resistance in rubber that could not be achieved with conventional technology, and has sufficient durability against peeling of the polymer at the core-sheath composite interface. The aim is to provide fiber.

[Means and effects for solving the problems] The present invention has the following features: (1) A core-sheath type composite structure in which the core component is polyester containing ethylene terephthalate units as the main component and the sheath component is polyamide. The fiber has a ratio of the core component to the core component and sheath component of 30 to 90% by weight.
It is made of a high-strength composite fiber characterized by having each of the following properties (a) to (c).

(a) The intrinsic viscosity ([η]) of the polyester core component in the composite m1tt is 0.8 or more, and the birefringence (Δn) is 160.
It should be between X 10-3 and 190X 10-3.

(b) The sulfur relative viscosity (ηr) of the polyamide sheath component in the composite fiber is 2.8 or more, and the birefringence (Δn) is 50X10-
Must be 3 or higher.

(c) The width is 0.01-1μ over the entire surface of the filament.
, a large number of unevenness with a length of 0.1 to 10μ are uniformly distributed, and the unevenness extends in the direction of the lli fiber axis blade axis.

It is a high-strength composite fiber characterized by being formed in a striped shape, (2) and
In high-strength composite fibers, the density of the polyester core component (
ρ) is 1.395 g/cm3 or more, and the density (ρ) of the polyamide sheath component is 1.135 g/cm3 or more,
3) Furthermore, in the high-strength composite m-fiber, the polyester core component fiber has an initial tensile resistance (Ml) of 90 g/tenee or more, and a terminal modulus (Mt) of 20 g/tenee 11 or less. ) High-strength composite listed in! (4) Furthermore, the high-strength composite fiber according to the present invention has a strength (T/
D) is 7.5g/chineael or more, initial tensile resistance (
Mi) is 60 g/denier or more, and the dry heat shrinkage rate (ΔS 150) measured at 150° C. is 7% or less.

(5) Furthermore, in the high-strength composite fiber according to the present invention, the core is formed of a polymer substantially made of highly polymerized polyethylene terephthalate having an intrinsic viscosity ([η]) of 0.80 or more, and the relative viscosity of sulfuric acid is A high polymerization degree polyamide polymer of 2.8 or more forms the sheath, and the ratio of the core to the sheath is 30.
In melt-spinning of core-sheath type high-strength composite fibers with a concentration of ~9% by weight, the melt-spun yarn is passed through an atmosphere in which at least 10 cm below the spinneret is at a high temperature of 200°C or higher, and after rapid cooling and solidification, m-fibers are formed. Pass through a surface layer crystallization accelerator. After that, an oil agent is applied and the yarn is taken up at a high spinning speed of 1000 m/min or more, so that the birefringence of the polyamide part of the sheath of the undrawn yarn is 25.
XIO-' to 40X10-3, and the polyester core portion has a birefringence of 20X10-3 to 70X10-3, and can be produced by stretching in two or more stages.

The composite fiber of the present invention has the above-mentioned structure, but in particular maintains the same level of high modulus and dimensional stability as polyester, which is the objective of the present invention, and which has not been achieved with the prior art.
Improvements in the heat resistance and fatigue resistance in the rubber, as well as the peeling durability of the polymer at the core-sheath composite interface, were achieved by the combination of the specified birefringence, density, etc. of the polyester core component and the polyamide fiber of the sheath. Invention complex! The unique surface layer structure of Ii male confirms that the fiber structure targeted by the present invention is complete.

The contents and effects of each element constituting the present invention will be explained in detail below.

The core component of the composite fiber of the present invention is essentially polyester containing ethylene terephthalate units as a main component. The copolymer component may be contained to an extent that does not substantially reduce the physical and chemical properties of the polyethylene terephthalate polymer, for example, less than 10%. Copolymerization components include isophthalic acid,
It may contain dicarboxylic acids such as naphthalene dicarboxylic acid and diphenyl dicarboxylic acid, diol components such as propylene glycol and butylene glycol, and ethylene oxide. The strength of the composite fiber of the present invention is 7.5 g.
/denier or more, the core component polyethylene terephthalate fiber has a high intrinsic viscosity ([η]) of 0.8 or more, preferably 0.9 or more. In addition, in order to obtain excellent heat resistance in rubber of the composite fiber of the present invention, the concentration of carboxyl terminal groups of the polyester, which is the main component of the core, is 20 eq.
/106g or less is preferable.

The polyamide used as the sheath component is composed of ordinary polyamides such as polycabramide, polyhexamethylene adipamide, polytetramethylene adipamide, polyhexamethylene dodecamide, and polyhexamethylene dodecamide, and is a blend or a part of the above polymers. Although copolymerized polymers can also be used, polyhexamethylene adipamide is particularly preferred.

The polyamide sheath component polymer also needs to have a high degree of polymerization in order to obtain the high-strength conjugate fiber of the present invention, and has a sulfuric acid relative viscosity (ηr) of 2.8 or more, preferably 3.0 or more. It is preferable that the polyamide component contains a copper salt and other organic or inorganic compounds as a thermal oxidative deterioration inhibitor. Usually, copper salts such as iodized steel, copper acetate, steel chloride, and copper stearate are used in an amount of 30 to 500 ppm as copper, and alkali metal halides such as potassium iodide, sodium iodide, and potassium bromide are added in an amount of 0.01 to 0.0 ppm. 5% by weight, and/or organic,
An inorganic phosphorus compound is contained in an amount of 10 to 500 ppm as phosphorus.

The proportion of the core component of the composite fiber of the present invention is 30 to 90% by weight. If the core component is less than 30% by weight, it is difficult to achieve the desired modulus and dimensional stability of the composite fiber at the level of polyester.

On the other hand, if the polyester core component exceeds 90% by weight, the adhesion between the composite fiber and the rubber, the heat resistance in the rubber, etc. will not be sufficiently improved, and the effects of the present invention will be insufficient.

The composite fiber of the present invention is characterized in that both the polyester core component fiber and the polyamide sheath component fiber are highly oriented and crystallized. That is, the birefringence (Δ
n) is 160X10-3 to 190X10-3. 1
If it is less than 60X10-3, the strength (T/D) of the composite fiber is 7
．． It is not possible to make the initial tensile resistance dust (Mi) more than 60 g/y. On the other hand, if it exceeds 190×10 −3 , dimensional stability and fatigue resistance cannot be improved. According to the novel method for producing composite fibers of the present invention, which will be described later, the birefringence usually does not exceed 190×10 −3 .

On the other hand, the birefringence (Δn
) has a high orientation of 50X10-3 or more, usually 55X10-3 or more. If the birefringence is less than 50XlO-3, a composite fiber having high strength and high initial tensile resistance cannot be obtained.

The birefringence (Δn) of the core-sheath composite fiber can be measured as follows. That is, the sheath was directly measured using a transmission interference microscope, and the core was measured using hydrochloric acid. l
! ! By dissolving with acid, sulfuric acid, fluorinated alcohol, etc., only the core polyester component fibers are sampled.
Measure using a transmission interference microscope or the standard Berek compensator method.

The density (ρ) of the composite fiber of the present invention is 1.395 g/cm3 or more for polyester, which is the main component of the core, and 1.135 g/cm3 or more for the polyamide sheath component, which is the main component of the sheath, and is highly crystallized. There is.

Unless the density is above the above-mentioned specific values, the dimensional stability, fatigue resistance, and heat resistance in rubber of the composite fiber will not be improved.

The density (ρ) of the polyester core component is measured by dissolving and removing the polyamide component with hydrochloric acid, formic acid, sulfuric acid, fluorinated alcohol, or the like. The density of polyamide, which is the main component of the sheath, can be calculated from the density of the composite fiber, the density of the polyester component, and the composite ratio.

Furthermore, since the composite fiber of the present invention has a unique surface layer structure, its fatigue resistance, heat-resistant adhesion, and heat resistance in rubber are significantly improved. Figure 1 is a photograph in place of a drawing showing the surface shape of a composite fiber comprising a high-strength polyamide sheath component and a polyester core component with good fatigue resistance according to the present invention, and the photograph shows the surface of the fiber magnified 5000 times. This is a scanning electron micrograph.

As shown in FIG. 1, a large number of streak-like irregularities extending in the axial direction of the fiber are uniformly formed on the entire surface of the composite fiber consisting of a polyamide sheath component and a polyester core component. That is, the numerous streak-like irregularities extending in the m1tt axis direction on the entire surface of the fiber of the present invention shown in FIG. 1 are characterized by having a width of 0.01 to 1 μm and a length of 0.1 to 10 μm. , observed using a scanning electron microscope. The unevenness of this fiber surface is approximately 2
Polarized light microscopy of the cross-section of the fiber reveals a crystalline layer having a thickness of ~10μ, typically 3-6μ. If this unevenness is not present, stress concentration occurs on the fiber surface when subjected to compression fatigue, which tends to cause cracks, resulting in insufficient fatigue resistance, as well as insufficient adhesion at high temperatures and heat resistance in rubber. It is. Further, even if unevenness is formed, if the size is large or uneven, a high strength yarn cannot be obtained.

The composite fiber of the present invention characterized by the above fiber structure has a high strength of 7.5 g/y-11 or more, an initial tensile resistance of 60 g/y-11 or more, and a dry heat shrinkage rate ( ΔS, so) exhibits fiber properties of 7% or less. More preferable composite fiber properties include a strength of 8 g/F" or more, an initial tensile resistance of 70 g/F" or more, and a dry heat shrinkage rate (ΔSt'so) of 5% or less. This can be achieved by combining.

The composite fiber according to the present invention having the above-mentioned characteristics is produced by the novel method shown below.

In order to obtain the polyester fiber physical properties of the core, a polymer consisting essentially of polyethylene terephthalate and having an intrinsic viscosity ([η]) of 0.80 or more, usually 0.85 or more is used. Furthermore, in order to obtain fibers with excellent heat resistance, it is preferable to spin a polymer having a low concentration of carboxyl end groups. For example, techniques such as employing a low temperature polymerization method or adding a sequestering agent during the polymerization process or the spinning process are applied. Examples of the capping agent include oxazolines, epoxies, carbodiimides, ethylene carbonate, oxalic acid esters, and malonic acid esters.

The polyamide polymer used as the sheath component is a high polymerization degree polymer having a sulfuric acid relative viscosity of 2.8 or more, usually 3.0 or more. The antioxidant is usually added during the polymerization or spinning process.

It is preferable to use two extruder type spinning machines for melt spinning each of the above-mentioned polymers. The polyester for the core component melted by one extruder and the polyamide polymer for the sheath component melted by the other extruder are introduced into a composite spinning pack, and passed through a composite spinning nozzle to place the polyester in the core and the polyamide in the sheath. The fibers are then spun into composite fibers.

The spinning speed is 1000 m/min or more, preferably 1500 m/min.
The speed should be at least 1/min. Immediately below the spinneret, a temperature of 200°C or higher, preferably 260°C, is applied for a distance of 10cm or more and within 1m.
The high-temperature atmosphere is set to be at least .degree. After the spun yarn passes through the above-mentioned high-temperature atmosphere, it is rapidly cooled and solidified with cold air, and then the crystallization of the fiber surface layer is promoted by low-pressure steam for a short period of time, and then a non-aqueous oil is applied, and a fiber surface layer crystallization accelerator is applied. A cylindrical heating device filled with steam is desirable. The water vapor used is so-called 50% even when it is saturated.
Superheated steam with a moisture content of 5 or more may be used, but the pressure is
Low pressures of 0-400 mmH2O are preferred. Furthermore, it is necessary to control the atmospheric temperature within the cylinder while blocking the airflow accompanying the yarn, and it is preferable to attach an accompanying airflow exclusion plate or the like to the upper part of the fiber surface layer crystallization promoting device.

Further, the atmospheric temperature within the apparatus is preferably 80 to 120°C. Then, after applying an oil agent, the fiber is taken up by a take-up roll that controls the spinning speed. Control of the high-temperature atmosphere immediately below the spinneret is extremely important in maintaining stringiness during high-speed spinning of the present invention. The taken-off undrawn yarn is usually drawn continuously without being wound up, but it can also be drawn in a separate step after being wound up. The birefringence of the undrawn yarn immediately after passing over the take-up roll is 25×10
-3 to 40X10-3, the birefringence of the polyester fiber in the core is 20X10-3 or more, usually 30X10-3 to 70
X10-3 and is relatively highly oriented.

The adoption of high-speed spinning according to the present invention increases the modulus of the composite fiber,
This has a great effect on improving dimensional stability and fatigue resistance, and also has the effect of improving peel durability at the core-sheath composite interface. This is probably due to the fact that unlike the conventional low-speed spinning method, in which a slightly crystallized polyamide component and an amorphous polyester component are combined, in the high-speed spinning method, both the polyamide component and the polyester component have oriented crystals. It is thought that the following factors contribute to the improvement of the peeling durability of the composite interface: the fact that the polyester fibers are in a state where the carbonization is progressing, and the stretching ratio after spinning can be reduced.

Next, the undrawn yarn is heated at 180°C or higher, preferably at 210°C.
Hot-stretched at a temperature of ~240°C. Stretching is performed in two or more stages, usually three or more stages, and the stretching ratio is 1.4 to 3.5.
This is twice the range. The adoption of such high-temperature hot stretching according to the present invention also greatly contributes to improving the peel durability of the composite interface. For example, the stretching temperature in the final stage during stretching is low, 160°C.
If it is less than that, peeling at the core-sheath interface often occurs due to stretching. Furthermore, it has been confirmed that when stretched at a temperature lower than 180°C, interfacial peeling occurs during the tire cord processing process, tire vulcanization process, or tire running process when used as a tire cord. High temperature drawing is extremely important as a method of obtaining fibers.

The fiber thus obtained has the characteristics of the composite fiber of the present invention.

Next, it will be explained based on Examples, but the main text of the present invention specification,
and definitions of fiber properties and cord properties described in the examples,
And the measurement method is as follows.

◎Characteristics of Polyester Core Component Fiber For the sample, the core component polyamide was dissolved and removed with formic acid, and the polyester core fiber portion was taken out and subjected to measurement.

(a) Intrinsic viscosity ([η]): A sample was dissolved in an orthochlorophenol solution and measured at 25°C using an Ostwald viscometer.

(b) Birefringence (Δn): Measured by the usual Berek compensator method using sodium D line as a light source.

(c) Density (ρ): Measured at 25°C using a density gradient tube prepared using carbon tetrachloride as a heavy liquid and n-hebutane as a light liquid.

(d) Initial tensile resistance (Mi), terminal modulus (Mt): The initial tensile resistance was defined and measured according to JIS L1017. The specific conditions for the tensile test to obtain the load-elongation curve are as follows.

Take a cotton sample and leave it in a room with temperature and humidity control at 20℃ and 65% RH for more than 24 hours.
-4L" type tensile testing machine (manufactured by Orientic Co., Ltd.), the test length was 25 cm, and the tensile speed was 30 cm/min.

Terminal modulus is the value (g/denier) obtained by dividing the stress increment between the point on the load-elongation curve, which is 2.4% less than the cutting elongation, and the cutting point by 2.4X10-2. .

◎Characteristics of polyamide sheath component wAf11t (e) Relative viscosity of sulfuric acid (ηr): A sample was dissolved in formic acid, and the dissolved portion was reprecipitated by a conventional method, washed and dried, and used as a measurement sample.

1 g of the sample was dissolved in 25 cc of 98% sulfuric acid and measured at 25° C. using an Ostwald viscometer.

(f) Birefringence (Δn): Using a transmission quantitative interference microscope manufactured by Carls Ikuyena Co., Ltd., only the polyamide sheath portion was measured by the interference fringe method at 2 lt intervals from the side of the fiber toward the center. The average value was calculated.

(g) Density (ρ): The density of the composite fiber and polyester core fiber component was measured, and the density of the polyamide fiber component was calculated using the composite ratio.

◎Characteristics of composite fiber (H) Strength (T/D), elongation (E), initial tensile resistance (Mi): Strength and initial tensile resistance were determined according to the definition and measurement method of JIS L1017. Note that the conditions for obtaining the load-elongation curve are the same as in the case of the polyester core component fiber.

(S) Dry heat shrinkage rate (ΔS, 5o): Take a sample in the form of cotton, leave it in a temperature and humidity controlled room at 20°C and 65% RH for more than 24 hours, and then apply a load equivalent to the O0Ig/denier of the sample. Measured length. The sample is processed in an oven at 150° C. for 30 minutes under no tension. The sample after treatment was air-dried, left in the temperature and humidity control room for 24 hours or more, and the load was applied again to calculate the measured length Ll using the following formula.

Dry heat shrinkage rate (%) = ((Lo Lt) /Lo)
×100 (N) Scanning electron microscope: Using a field emission scanning electron microscope, model S-800 manufactured by Hitachi ■, the side surface of the fiber was observed at an accelerating voltage of 6 KV.

◎Characteristics of composite 1-fiber cord: Strength (T/D), elongation (E), initial tensile resistance (Mi), and intermediate elongation (ME): Measured in the same manner as in the case of the fibers. The intermediate elongation was the elongation at which the strength was determined by the following formula.

(6,75XDXn) / (1500X2)kgHowever,
D: Drawn yarn fineness n: Number of twisted yarns For example, cord 1500/2, which is made by combining and twisting two yarns with a drawn yarn fineness of 1500 denier, has an intermediate elongation when weighing 6.75 kg.

(2) Dry heat shrinkage rate (ΔS1□7): Measured in the same manner as the composite fiber in item (2) above, except that the heat treatment temperature was 177°C.

(W) GY fatigue life: JIS L1017-1.3.2. Compliant with IA law. However, the bending angle was 90'.

(Force) GD fatigue: Based on JIS L1017-1.3.2.2. However, the expansion was 6.3% and the compression was 12.6%.

(Y) Adhesiveness: JIS L1017-3.3. According to IA method.

(ri) Heat-resistant adhesiveness The above (
It was evaluated using the same method as in section y).

(I) Heat resistance in rubber: The dip cord arranged on a rubber sheet was sandwiched between separately prepared rubber sheets and heat-treated under a pressure of 50 kg/cm2 for 3 hours in a press heated to 170°C. The cord strength before and after heat treatment was measured, and the strength retention rate was determined, which was used as a measure of heat resistance.

[Example] <Examples-1 to -2, Comparative Examples-(1) to (6)> Intrinsic viscosity ([η)) 0.96, carboxyl terminal group concentration 9. O
eq/106g polyethylene terephthalate (PET
) as a core component, and a nylon 66 (N66: sulfuric acid relative viscosity ηr3.6) polymer containing 0.02% by weight of iodized steel, 0.1% by weight of potassium iodide, and 0.1% by weight of potassium bromide as a sheath component. After each was melted using a 40φ Ktruder-type spinning machine, it was introduced into a composite spinning pack, and a mixed polymer of PET in the core and N66 and PET in the sheath was spun as a composite fiber from a core-sheath composite spinneret. The proportions of the core and sheath components were varied as shown in Table 1. The hole diameter of the cap is 0.4
mmφ and 120 holes were used. Polymer temperatures were as follows: PET in the core was melted at 295°C, and N66 in the sheath was melted at 290°C, and the spinning pack was spun at a temperature of 295°C.

A 15 cm heating cylinder was attached directly below the mouthpiece, and the atmosphere inside the cylinder was heated to 290°C. Ambient temperature is a position 10 cm below the mouth surface and 1 cm below the outermost thread.
This is the ambient temperature measured at a position cm away. A horizontal uniflow chimney with a length of 120 cm was attached below the heating cylinder, and cold air at 20° C. was blown at a speed of 30 m/min from a direction perpendicular to the yarn to rapidly cool it. After that, while maintaining the temperature at 105°C, the yarn is passed through a 200 cm crystallization promotion cylinder filled with the water vapor pressure shown in Table 1, and then a non-aqueous oil agent is applied to the yarn by 1 weight per weight using a roller oiling device arranged in two stages. % was given.

Then, after controlling the yarn speed with a take-up roll rotating at the speed shown in Table 1, the yarn was drawn continuously without being wound up. The film was stretched in three stages using five pairs of Nelson type rolls, then subjected to a relaxation heat treatment with 3% relaxation, and then wound up. The stretching conditions were a take-up roll temperature of 60'C5.
The temperature of the first stretching roll was 110°C, the temperature of the second stretching roll was 190°C, the temperature of the third stretching roll was 230°C. The tension adjustment roll after stretching was not heated, and the first stage stretching ratio was 70 of the total stretching ratio. %, and the remainder was distributed in two stages for stretching. The yarn was produced by varying the spinning speed, total draw ratio, etc., and the discharge amount was changed in accordance with the spinning speed and draw ratio so that the fineness of the drawn yarn was about 500 denier. Three of the obtained drawn yarns were combined to have a denier of 1,500.

For comparison, fibers were obtained by separately spinning the polyamide used in the production of the composite fibers. The spinning and drawing conditions were the same as those for the composite fiber of the present invention.

The yarn spinning conditions are shown in Table 1, and the obtained drawn yarn properties and fiber structure parameters are as shown in Examples -1 to -2 and Comparative Examples -(1) to -(4) in Table 2. . In addition, commercially available N66 fiber for tire cord (1260D-20
4f i l-1781) (comparative example-(5)) and P
Table 2 shows the measurement results regarding the characteristics of the ET fiber (1500D-288fil-702C) (Comparative Example-(6)).

It can be seen that the composite fibers according to the present invention (Examples 1 to 2) exhibit dynamic elastic modulus and creep rate characteristics similar to those of polyester fibers, even though they contain a particularly large amount of N66 component, and are extremely unique. .

In addition, the composite fibers according to the present invention (Examples-1 to -2)
, Comparative Examples - (1) to - (2)) and PET fiber (Comparative Example - (6)) were used to create a raw cord of 1500D/2 by applying first and second twists of 407/10 cm in opposite directions, respectively. did. However, N66! ! - fiber (comparative example - (3) ~ -
(5)) The number of twists is 397/10cm, and the number of twists is 1260D/
2 raw code.

The raw cord made of the composite fiber according to the present invention was made into a dip cord by applying an adhesive and heat-treating it in a conventional manner using a dipping machine manufactured by Riller.

The adhesive component contained 20% resorcinol, formalin, and latex, and was adjusted so that about 4% of the adhesive component adhered to the cord. The heat treatment was carried out at 225° C. for 80 seconds while stretching the dip cord so that the intermediate elongation was about 5%.

N66 fiber (comparative examples -(3) to -(5)) The raw cord was heat treated under the same conditions as the composite fiber according to the present invention, and the intermediate elongation was about 9, which is applied to normal N66 tire cord.
%, stretched and processed.

In addition, the PET fiber (comparative example - (6)) raw cord was subjected to a two-bath adhesive treatment using a conventional method, and heat treatment was performed at 240°C for 120 seconds, resulting in an intermediate elongation of approximately 5%, which is applied to ordinary PET tire cord. Set and stretched and processed.

The dip cord thus obtained was simultaneously evaluated for tire cord properties such as heat resistance in rubber, adhesion, and fatigue resistance, and the results are shown in Table 3.

Of the composite fibers obtained, all of the composite fibers obtained in Examples 1 and 2 satisfy the respective constituent requirements of the present invention, and as shown in FIG. The width of the numerous streak-like irregularities extending in the axial direction is 0.01 to 1μ,
The length was within the range of o, i to 10μ. Furthermore, none of the composite fibers obtained in Comparative Examples 1 and 2 satisfy the respective constituent requirements of the present invention. For example, the surface of the composite fiber obtained in Comparative Example 1 has the shape shown in FIG. Therefore, the numerous streak-like irregularities extending in the axial direction of the fibers are not uniformly formed.

Furthermore, some of the comparative examples had unevenness formed on the surface of the fibers, but the unevenness was non-uniform and did not satisfy the requirements of the present invention.

The composite fiber dip cord according to the present invention has a modulus and dimensional stability equivalent to or higher than conventional dip cords made of PET fibers, and has significantly improved heat resistance in rubber.
This shows that it is a high-strength dip cord that has heat-resistant adhesion and fatigue resistance.

〔Effect of the invention〕

Compared to conventional polyester, the composite fiber of the present invention has significantly improved heat resistance and adhesion in rubber, especially heat resistant adhesion after high temperature history, and fatigue resistance, which could not be achieved with polyamide fiber. The present invention provides a highly durable, high-strength composite fiber that has both high modulus and dimensional stability. Therefore, when used as a tire cord, for example, the durability during tire running is extremely good. Therefore, it is ideal as a tire cord for relatively large light trucks, trucks, and buses, and as a cord material for tire types that require high-speed durability, such as racing cars and high-speed passenger cars.

Furthermore, since the composite fiber of the present invention has the above-mentioned excellent characteristics, it can of course be used as rubber reinforcing materials other than tire cords, such as power transmission belts, conveyor belts, rubber hoses, air springs, etc.
It can be useful for general industrial materials such as sewing thread, seat belts, fishing nets, car seats, slings, cables, robes, etc.

[Brief explanation of the drawing]

Figure 1 is a photograph in place of a drawing showing the surface shape of a composite fiber comprising a high-strength polyamide sheath component and a polyester core component with good fatigue resistance according to the present invention, and the photograph shows the surface of the fiber magnified 5000 times. This is a scanning electron micrograph. FIG. 2 is a photograph in place of a drawing showing the surface shape of a conventional composite fiber comprising a polyamide sheath component and a polyester core component, and this photograph is a scanning electron micrograph magnifying the surface of an m-male 5000 times.

Claims (5)

[Claims] (1) A high-strength composite fiber having a core-sheath type composite structure in which the core component is polyester containing ethylene terephthalate units as a main component and the sheath component is polyamide, wherein the core component and the sheath component are A high-strength conjugate fiber characterized in that the ratio of the core component to the fiber is 30 to 90% by weight, and has each of the following properties (a) to (c). (a) The intrinsic viscosity ([η]) of the polyester core component in the composite fiber is 0.8 or more, and the birefringence (Δn) is 160 x 10^-^3 to 190 x 10^-^
3.Be. (b) The sulfur relative viscosity (ηr) of the polyamide sheath component in the composite fiber is 2.8 or more, and the birefringence (Δn) is 50×10^-^3 or more. (c) The width is 0.01 to 1 μ over the entire surface of the filament.
, a large number of unevenness having a length of 0.1 to 10μ are uniformly formed, and the unevenness is formed in a long striped shape in the fiber axis direction. (2) The high-strength composite fiber is characterized in that the density (ρ) of the polyester core component is 1.395 g/cm^3 or more, and the density (ρ) of the polyamide sheath component is 1.135 g/cm^3 or more. A high-strength conjugate fiber according to claim (1). (3) In the high-strength composite fiber, the polyester core component fiber has an initial tensile resistance (Mi) of 90 g/denier or more and a terminal modulus (Mt) of 20 g/denier or less. ) High-strength conjugate fiber described in section 2. (4) In high-strength composite fibers, the strength (T/D) is 7.
5g/denier or more, initial tensile resistance (Mi) 60
g/denier or more, dry heat shrinkage rate (Δ
The high-strength conjugate fiber according to claim (1), characterized in that S_1_5_0) is 7% or less. (5) A polymer consisting essentially of highly polymerized polyethylene terephthalate with an intrinsic viscosity ([η]) of 0.80 or more forms the core, and a high polymerized polyamide polymer with a sulfuric acid relative viscosity of 2.8 or more forms the sheath. In the melt spinning of core-sheath type high-strength composite fibers in which the ratio of the core to the core and sheath is 30 to 90% by weight, the melt-spun yarn is heated at a temperature of 200°C or higher for at least 10 cm below the spindle. The fiber is passed through a high-temperature atmosphere, rapidly cooled and solidified, and then passed through a fiber surface layer crystallization accelerator. After that, an oil agent is applied and the yarn is taken up at a high spinning speed of 1000 m/min or more, so that the birefringence of the polyamide part of the sheath of the undrawn yarn is 25 x 10^-^3 to 40 x 10^-^3,
The birefringence of the polyester core part is 20×10^-^3
Peeling durability of a core-sheath composite interface obtained by multi-stage stretching of ~70×10^-^3 and satisfying the following characteristics (a) to (c). A method for producing a core-sheath type high-strength composite fiber with improved properties. (a) The intrinsic viscosity ([η]) of the polyester core component in the composite fiber is 0.8 or more, and the birefringence (Δn) is 160 x 10^-^3 to 190 x 10^-^
3.Be. (b) The sulfur relative viscosity (ηr) of the polyamide sheath component in the composite fiber is 2.8 or more, and the birefringence (Δn) is 50×10^-^3 or more. (c) The width is 0.01 to 1 μ over the entire surface of the filament.
, a large number of unevenness having a length of 0.1 to 10μ are uniformly formed, and the unevenness is formed in a long striped shape in the fiber axis direction.