JPH03146713A - Sheath-core conjugated fiber - Google Patents

Abstract

PURPOSE:To provide the subject sheath-core type conjugated fiber composed of polyethylene-2,6-naphthalate as the core component and a polyamide as the sheath component, respectively having a specified viscosity, birefringence and density, excellent in heat resistance and fatigue resistance, having a high strength and a high elasticity and suitable for a reinforcing material for rubber, etc. CONSTITUTION:Polyethylene-2,6-naphthalate mainly composed of ethylenenaphthalene-2,6-dicarboxylate is used as the core component and a polyamide is used as the sheath component. Both the components are melted, discharged through a sheath-core conjugated fiber spinning nozzle, cooled and, after application of an oil agent, stretched to obtain the objective conjugated fiber having 30-90wt.% core component ratio occupying in the total fiber, >=0.5 intrinsic viscosity [eta], 230X10<-3>-350X10<-3> birefringence, >=1.340g/cm<3> density respectively in the core component, >=2.8 sulfuric acid-based relative viscosity [etar], >=45X10<->3 birefringence, 1.135g/cm<3> density respectively in the sheath component and a structure where the core and sheath components are highly orientated and highly crystallized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to high-strength, high-modulus fibers suitable for industrial material applications, particularly for rubber reinforcing materials.

More specifically, it has excellent mechanical properties such as high strength, high modulus, and improved dimensional stability, and has improved rubber reinforcement such as adhesion to rubber, heat resistance in rubber, and fatigue resistance. Our goal is to provide composite fibers.

[Prior art] Polyethylene-2,6-naphthalate (hereinafter referred to as 2.6-PE
Fibers consisting of N) have high strength, high modulus, and high heat resistance in rubber, and are being used as rubber reinforcing materials for various industrial materials, especially tire cords, power transmission belts, and conveyor belts. be.

Many attempts have been made to improve the adhesion to rubber, which is a drawback of polyester fibers such as polyethylene terephthalate and polyethylene naphthalate, and one of them has recently been proposed to cover the surface layer of polyester with polyamide. For example, it is disclosed in Japanese Patent Application Laid-Open No. 1-97211. Further, JP-A No. 1-97211 describes a yarn spinning method in which the degree of polymerization of each component polymer and the proportion of the core polymer are specified for a composite fiber having a core of polyester and a sheath of nylon 66.

[Problems to be Solved by the Invention] Although the composite fiber described in JP-A-1-97211 has improved adhesiveness, durability, etc., it cannot be used for high-speed passenger cars, trucks, buses, off-road cars, etc. This is not satisfactory for tires used under such severe conditions, and still requires improved durability and ride comfort.

In addition, the core-sheath type fiber described in JP-A-1-97211 has a polyamide component in the sheath to provide improved adhesion to rubber, and a polyester component in the core to maintain modulus and dimensional stability. That's what I did. Although this method certainly improves adhesion, it has the problem that the modulus and dimensional stability of polyester fibers cannot be sufficiently maintained.

On the other hand, the above-mentioned 2.6-PEN fiber has poor adhesion to rubber, and especially when repeatedly exposed to a high temperature atmosphere for a long time, the adhesion to rubber decreases significantly.

Especially when used as a tire cord, automobile driving 1,! f
The heat generated in the tire builds up inside the tire and becomes hot, causing the tire to lose its adhesive strength with the rubber and peel off.Additionally, the tire cord can break due to the repeated compression and stretching that the tire undergoes. was.

The object of the present invention is to overcome the problems in the prior art as described above, thereby achieving excellent adhesion to rubber, significantly improved dimensional stability, high modulus, and heat resistance in rubber compared to conventional composite fibers. The object of the present invention is to provide a composite fiber suitable for rubber reinforcement with improved fatigue resistance.

[Means and effects for solving the problems] The structure of the present invention is as follows: (1) In the core-sheath composite fiber, the core component is polyethylene-2,6-dicarboxylate whose main component is ethylenenaphthalene-2,6-dicarboxylate. It is a core-sheath composite fiber consisting of naphthalate and a sheath component consisting of polyamide, the proportion of the core component in the fiber is 30 to 90% by weight, and the intrinsic viscosity of the core component [
η] is 0.5 or more, birefringence is 230 x 10-8 to 350
X10-3, the density is 1.340 g/cm3 or more, the sulfuric acid relative viscosity ηr of the polyamide sheath component is 2.8 or more, the birefringence is 45×1()-8 or more, and the density is 1.135 g/cm” or more. A core-sheath composite fiber, characterized in that the core component and the sheath component form a highly oriented, highly crystalline fiber structure.

(2) In the core-sheath composite fiber described in (1) above,
A core-sheath composite fiber characterized in that the composite fiber has a strength of 6.0 g/d or more, an elongation of 20% or less, an initial tensile resistance of 150 g/d or more, and a dry heat shrinkage rate of 3% or less.

It is in.

The core-sheath composite fiber according to the present invention has a core component of 2.6-P.
EN, the sheath component is polyamide, and by combining the proportions of these core and sheath components and the characteristics of the core and sheath components within a specific range, significant improvements have been achieved that could not be achieved with conventional composite fibers. A fiber for industrial use, particularly for rubber reinforcement, which is excellent in dimensional stability, high modulus, heat resistance, fatigue resistance, and peeling durability of the polymer at the core-sheath composite interface can be obtained.

2゜6-PE serving as the core component of the core-sheath composite fiber according to the present invention
N is essentially ethylenenaphthalene-2゜6-dicarboxylate as a main component, and if necessary, it may be added to an amount that does not substantially reduce the physical and chemical properties of 2.6-PEN, for example less than 10%. It may also contain a polymeric component. As copolymerization components, dicarboxylic acids such as isophthalic acid and diphenyl dicarboxylic acid, diol components such as ethylene oxide, propylene glycol, butylene glycol, and other components are used.

2゜6-PEN used in the core-sheath composite fiber according to the present invention
By setting the intrinsic viscosity [η] of 0.5 or more, the strength of the obtained core-sheath composite fiber can be made 6.0 g/d or more.

On the other hand, the polyamides used as the sheath component of the core-sheath composite fiber according to the present invention include polycapramide, polyhexamethylene adipamide, polytetramethylene adipamide, polyhexamethylene dodecamide, polyhexamethylene dodecamide, and polyhexamethylene dodecamide. These include xamethylene terephthalamide, polyhexamethylene isophthalamide, etc. Among them, polyhexamethylene adipamide-based polymers are preferably used. In addition, the polyamide may contain, for example, less than 10% of ε-cabramide, tetramethylene adipamide, hexamethylene dodecamide, etc., to the extent that physical properties such as strength are not substantially reduced. Components such as hexamethylene dodecamide, polyhexamethylene terephthalamide, and polyhexamethylene isophthalamide may be copolymerized or blended.

In addition, the above-mentioned polyamide may optionally contain thermal oxidative deterioration inhibitors, matting agents, pigments, light stabilizers, heat stabilizers, etc. that add other properties to the extent that the physical properties such as strength of the fibers of the present invention are not reduced. Agents, antioxidants, antistatic agents, dyeability improvers, adhesion improvers, etc. can be added. In particular, copper salts and other organic and inorganic compounds can be added as thermal oxidative deterioration inhibitors. When used for industrial purposes, in particular, copper salts such as iodized steel, copper acetate, copper chloride, and copper stearate should be used in an amount of 30 to 500 ppm as copper, and alkali metal halides such as potassium iodide, sodium iodide, potassium bromide, etc. 0.01
~0.5% by weight and/or 0 organic or inorganic phosphorus compounds
．． It is preferable to contain 01 to 0.1% by weight.

The ratio of the core component consisting of 2) 6-PEN in the core-sheath composite fiber according to the present invention is 30 to 90% by weight. 2.6-
If the PEN component is less than 30% by weight, the dimensional stability and modulus cannot be improved to the desired values,
Heat resistance is also not improved. When the 2.6-PEN core component accounts for 90% by weight or more, the flexibility of the composite fiber is lost and fatigue resistance is reduced.

The core-sheath composite fiber according to the present invention is characterized in that both the 2.6-PEN core component and the polyamide sheath component are highly oriented and crystallized.

In other words, the birefringence of the 2.6-PEN core component is 230XIO
-"~350X10-". Birefringence is 230X10
-'', the composite yarn cannot achieve a strength of 6.0 g/d or more and an initial tensile resistance of 150 g/d or more.

On the other hand, the birefringence of the polyamide sheath component is 45x1o-8 or more, which is highly oriented. By setting the birefringence to 45×40 −3 or more, a composite fiber having high strength and high initial tensile resistance can be obtained. If the birefringence is 40 x 10-'', even if the other requirements of the present invention are satisfied, a core-sheath composite fiber having high strength and high initial tensile resistance cannot be obtained.

The density of the 2.6-PEN core component is 1,340 g/am" or more, and the polyamide sheath component is 1,135 g/cm" or more, and is highly crystallized.

By setting the density to each of the above values or more, the dimensional stability, fatigue resistance, and heat resistance in rubber of the core/sheath composite fiber are improved.

As described above, the core-sheath composite fiber according to the present invention has a high strength of 6°0 g/d or more, an initial tensile resistance of 150 g/d or more, and an elongation of 20% or less. More preferable composite fiber properties are a strength of 7.0 g/d or more and an initial tensile resistance of 2.
00 g/d or more, the elongation is 8-16%, which can be achieved by appropriately combining the above conditions.

The composite fiber according to the present invention is produced by a novel method detailed below.

2) In order to obtain the physical properties of the 6-PEN core component,
A polymer consisting essentially of ethylenenaphthalene-2,6-dicarboxylate having an intrinsic viscosity [η] of 0.5 or more, usually 0.6 or more is used.

The polyamide sheath component polymer has a sulfuric acid relative viscosity of 2°8 or more,
Usually, a polymer with a high degree of polymerization of 3.0 or higher is used for melt spinning.

Two extruder type spinning machines are used for melt spinning the polymer. Core component 2.6-PEN polymer is 300-3
It is melted in one extruder at a melting temperature of 30°C, and the polyamide polymer of the sheath component is melted in the other extruder at a melting temperature of 280-310°C. Each polymer was introduced into a composite spinning device at a temperature of 300 to 310°C, and 2.6-PEN was added to the core through a composite spinning nozzle.

Spun as a composite fiber with polyamide in the sheath.

The spinning speed is 1000 m/min or more, preferably 1500 m/min.
The speed should be at least 1/min. 10cm or more directly below the spinneret,
200°C or more, preferably 260°C within 1 m
The above heating atmosphere is created by providing a heat retaining cylinder and a heating cylinder.

After passing through the above-mentioned heating atmosphere, the spun yarn is quenched and solidified with cold air, and then, after being applied with an oil agent, it is taken off by a take-off roll that controls the spinning speed.

Control of the heating atmosphere directly below the spinneret is important in order to maintain stringiness during high-speed spinning of the present invention.

The taken-off undrawn yarn is usually drawn continuously without being wound up or drawn in a separate step after being wound up. In order to understand the physical properties of the undrawn yarn before drawing, the birefringence of the undrawn yarn sampled after passing over a take-up roll is such that the polyamide sheath portion is 20X10-'' or more, preferably 30X10-'' or more, 2.6- PEN core is also 70X
It is highly oriented with an orientation of IO"" or more, preferably 80X10-' or more.

Adoption of high-speed spinning improves the dimensional stability and durability of the composite fiber at high temperatures, but surprisingly, the peeling durability of the core-sheath composite interface is significantly improved. Unlike the conventional low-speed spinning method, in which a highly hygroscopic and crystallized polyamide component is combined with the amorphous 2.6-PEN component, in the high-speed spinning method, the polyamide component and the 2.6-PEN component are combined.
It is thought that the progress of oriented crystallization of both the PEN component and the fact that the stretching ratio after spinning is small contributes to the peel durability of the composite interface.

Next, the undrawn yarn has a temperature of 180°C or higher, preferably 200°C.
It is hot stretched at a temperature of ℃ or higher. The stretching is carried out in two or more stages, usually three or more stages, and the stretching ratio is in the range of 1.1 to 4.0.

The use of such high-temperature hot stretching according to the present invention also contributes to improving the peel durability of the composite interface.

When the stretching temperature in the above stretching is low, for example, 160°C
If it is less than
Furthermore, it has been confirmed that when stretched at a temperature lower than 180°C, interfacial peeling occurs during the tire cord processing process, vulcanization process, or tire running when used as a tire cord, for example.

The fiber thus obtained has the characteristics of the core-sheath composite fiber according to the present invention described above.

Next, explanations will be given based on Examples, and the definitions and measurement methods of the fiber characteristics and cord characteristics described in the main text of the specification and Examples of the present invention are as follows.

2. Characteristics of 6-PEN core fiber (a) Intrinsic viscosity [η]: A sample was dissolved in a mixed solvent of phenol and orthodichlorobenzene (mixing ratio 6:4), and measured at 25°C using an Ostwald viscometer.

(o)? uljlui: Fiber U[
The average birefringence observed from the side was determined. The polyamide component of the sample was dissolved and removed with formic acid, and the 2.6-PEN core fiber component was measured.

(c) Density: Measurement was performed at 25° C. using a density gradient tube prepared using carbon tetrachloride as a heavy liquid and n-hebutane as a light liquid. The sample was prepared by dissolving and removing the polyamide component with formic acid.
The PEN core fiber component was measured.

Characteristics of polyamide sheath fibers (a) Relative viscosity of sulfuric acid ηr: 0.25 g of a sample was dissolved in 25 cc of 98% sulfuric acid, and measured at 25° C. using an Ostold viscometer.

(B) Birefringence: Similar to the 2.6-PEN core fiber component, only the polyamide fiber portion in the surface layer was measured from the side using the interference fringe method using a transmission constant loss interference microscope.

(c) Density: Composite fiber density and 2.6-PEN core composition It was calculated from the density of minutes.

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

(b) Strength, elongation, and initial tensile resistance Strength, elongation, and initial tensile resistance were in accordance with the definition and measurement method of JI S L1017. In addition, SS
The specific conditions for the tensile test to obtain the curve are as follows.

A sample was taken into a general shape, and after being left in a temperature- and humidity-controlled room at 20°C and 65% RH for more than 24 hours, it was tested using a "Tensilon UTL-4L" type tensile tester (manufactured by Orientic Co., Ltd.) with a test length of 25. cm-, tensile speed 30
Measured in cm/min.

(c) Dry heat shrinkage rate: A sample was taken in a general shape, left in a temperature and humidity controlled room at 20°C and 65% RH for 24 hours or more, and then measured by applying a load equivalent to O, Ig/d of the sample. length L
The sample is processed in an oven at 150° C. for 30 minutes under no tension. The treated sample was air-dried, left in the above-mentioned temperature and humidity control room for 24 hours or more, and then the above-mentioned load was applied again, and the measured length Lo was calculated using the following formula.

Dry heat shrinkage rate = (L-LO) /LX100 Characteristics of composite fiber cord (a) Strength, elongation, initial tensile resistance, and intermediate elongation: Measured in the same manner as in the case of the fibers. Intermediate elongation refers to the elongation at which strength is shown as determined by the formula below.

(4,5X D X n ) / (1000X2)
K g However, D = drawn yarn fineness n: number of yarns combined and twisted. For example, CORDE 500/2, which is made by combining and twisting two yarns with a drawn yarn fineness of 1500 denier, is 6.75 kg.
The elongation at the time is the intermediate elongation.

(b) Dry heat shrinkage rate: Same as before except that the processing temperature was 177℃. Measurements were made in the same manner as for the composite fiber.

(c) GY fatigue life: JIS L1017-1.3, 2. Compliant with IA law. However, the bending angle was 90°.

(d) GD fatigue life Compliant with JIS L1017-1.3.2.2. However, the expansion was 6.3% and the compression was 12.6%.

(e) Adhesiveness: According to JIS 1017-3.3.1A.

(f) Heat-resistant adhesion: Heat treatment during vulcanization at 170℃ for 60 minutes Evaluation was made in the same manner as in section (e) above, except that

(G) Heat resistance in rubber: Dip cords lined up on a rubber sheet are sandwiched between separately prepared rubber sheets.
Heat treatment was performed for 3 hours under a pressure of 50 kg/am2 using a press heated to 170°C. The cord strength before and after treatment was measured, and the strength retention rate was determined, which was used as a measure of heat resistance.

[Example] Example 1 2.6-PEN with intrinsic viscosity [η] 0.8 and iodized steel 0
．． Hexamethylene adipamide with a relative viscosity ηr of 3.3 containing 0.02% by weight of potassium iodide and 0.1% by weight of potassium iodide was melted in a 40φ xtruder-type spinning machine, guided into a composite spinning bag, and then passed through a core-sheath composite spinneret. 2.6-PE twisted core
N.

It was spun as a composite fiber with hexamethylene adipamide in the sheath. The proportions of the core component and sheath component were varied as shown in Table 1. The cap used had a hole diameter of 0.4 mmφ and 120 holes. The polymer temperature was 2.6-PEN and hexamethylene adipamide were melted at 305°C and 290°C, respectively, and spun at a spinning back temperature of 300°C. 15 directly below the base
A cm heating cylinder was attached and the cylinder was heated to an atmospheric temperature of 300°C. The atmosphere temperature inside the cylinder is 10% from the mouth surface.
This is the atmospheric temperature measured at a position 1 cm below the outermost thread and 1 cm away from the outermost thread. There is a length of 40 mm under the heating cylinder.
Attach a circular chimney of 20cm in diameter and
The yarn was cooled by blowing cold air at 40 m/min perpendicularly to the yarn at °C. After applying an oil agent, the yarn speed was controlled with a take-up roll rotating at the speed shown in Table 1, and then the yarn was continuously stretched 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 are: take-up roll temperature of 60°C, first stretching roll temperature of 120°C, second stretching roll temperature of 190°C, and third stretching roll temperature of 220°C.
After stretching, the tension adjustment roll was not heated, the first stage stretching ratio was 70% of the total stretching ratio, and the remainder was divided into two stages for stretching.

Silk production was carried out by changing the discharge amount in accordance with the spinning speed and the draw ratio, and the discharge amount was varied in accordance with the spinning speed and the 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.

The spinning conditions, the obtained drawn yarn properties, and the fiber structure parameters were determined using commercially available nylon 66 fiber for tire cords (12
60-204-1781), and polyethylene terephthalate (PET)! Wi (1500-288-702C)
, and those of 2) 6-PEN monocomponent fibers that were experimentally spun are shown in Table 1.

Example 2 Using the drawn yarn obtained in Example 1, the first twist and the second twist were applied in opposite directions at a rate of 40T/10cm, and the yarn was twisted at a rate of 1500/10cm.
2 raw code. However, N66 of Comparative Example 5 had a twist number of 39T/10cm and was made into a raw cord of 1260/2. This raw cord was applied with an adhesive and heat-treated using a dipping machine manufactured by Riller Co., Ltd. to obtain a dip cord.

The dip liquid contained an adhesive component consisting of 20% resorcinol, formalin, and latex, and was adjusted so that 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%.

Nylon 66 was stretched under the same heat treatment conditions so that the intermediate elongation was approximately 9%.

In addition, PET and 2.6-PEN monocomponent fibers were prepared using a conventional method.
Bath adhesion treatment was performed, heat treatment was performed at 240°C for 120 seconds,
It was stretched and processed so that the intermediate elongation was about 5%.

The dip cord thus obtained was evaluated for heat resistance in rubber, adhesiveness, fatigue resistance, etc., and the results are shown in Table 2.

The composite fiber dip cord of the present invention has dimensional stability equal to or higher than conventional polyester dip cord, and has significantly improved modulus, heat resistance in rubber, heat resistant adhesiveness,
This shows that it is a high-strength deep dip cord with excellent fatigue resistance.

[Effect of the invention] The composite fiber of the present invention has significantly improved dimensional stability, modulus, and heat resistance in rubber compared to conventional composite fibers,
In addition, adhesion properties, particularly heat-resistant adhesion properties and fatigue resistance after being subjected to high-temperature history, are significantly improved. Therefore, when used as a tire cord, for example, it has extremely good durability against repeated fatigue during tire running and heat generation during running. Therefore, it can be useful as a tire cord for relatively large passenger cars, light trucks, trucks, and buses. It is especially suitable as a carcass cord for large radial tires.

Moreover, since the composite fiber of the present invention has the above-mentioned excellent physical properties, it can be useful not only as a rubber reinforcing material other than tire cords, but also for general industrial material applications.

Claims (2)

[Claims] (1) A core-sheath composite fiber in which the core component is made of polyethylene-2,6-naphthalate whose main component is ethylene-naphthalene-2,6-dicarboxylate, and the sheath component is made of polyamide, The proportion of the core component in the fiber is 30 to 90% by weight, and the core component has an intrinsic viscosity of [
η] is 0.5 or more, birefringence is 230×10^-^3~3
50 x 10^-^3, density is 1.340 g/cm^3 or more, sulfuric acid relative viscosity ηr of polyamide sheath component is 2.8 or more, birefringence is 45 x 10^-^3 or more, density is 1.135
g/cm^3 or more, and wherein the core component and the sheath component form a highly oriented, highly crystalline fiber structure. (2) In the core-sheath composite fiber described in claim 1, the composite fiber has a strength of 6.0 g/d or more, an elongation of 20% or less, and an initial tensile resistance of 150 g/d or more,
A core-sheath composite fiber characterized by a dry heat shrinkage rate of 3% or less.