JPH04174720A - Multi-core sheath-core type conjugate yarn for reinforcing rubber - Google Patents

Abstract

PURPOSE:To obtain the title yarn useful for tire cord, having excellent hydrolysis resistance, comprising multi-core sheath-core conjugate yarn wherein a polyester component is divided into plural parts by a polyamide component existing in the direction of section of yarn and the ratio of both the components is a specific weight ratio. CONSTITUTION:The objective yarn comprising multi-core sheath-core conjugate yarn wherein a polyester component such as polyethylene terephthalate is divided into plural parts by a polyamide component such as nylon 6 continuously existing in the direction of section of yarn and the ratio of the polyester component and the polyamide component is 30/70-75/25 by weight.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a multi-core sheath-type composite fiber for rubber reinforcement made of polyester and polyamide.

(Prior Art) Fibers made of polyamides such as nylon 6 and nylon 66 and polyesters such as polyethylene terephthalate are widely used as fibers for reinforcing rubber such as tire cords, but these fibers have advantages and disadvantages. be. That is, while polyamide fibers have the advantage of being excellent in fatigue resistance and impact resistance, they have the disadvantages of high shrinkage rate, easy occurrence of flat spots, high water absorption, and low modulus. Additionally, polyester fibers do not have the problem of flat spots.

While it has the advantage of having a high modulus, it has the disadvantage of being easily hydrolyzed in rubber and having poor adhesion to rubber.

Therefore, in order to take advantage of the advantages of polyamide and polyester, Japanese Patent Application Publication No. 49-85315 and Japanese Patent Publication No. 62-420
61, JP 1-97212, JP 2-74
No. 610, No. 2-74612, etc. propose composite fibers containing polyester as a core component and polyamide as a sheath component. However, in composite fibers made of components with completely different molecular structures, phase separation occurs, and the core component and sheath component tend to shift, resulting in separation between the two components, and when used for tire cords, etc. There was a problem in that fatigue resistance was poor due to friction between component phases.

In order to solve this problem of peeling between image components and provide a high-strength composite fiber, JP-A-1-97211 uses nylon 66/6T, which is made by copolymerizing nylon 66 with terephthalic acid, as a polyamide. Composite fibers have been proposed. However, the problem of peeling cannot be satisfactorily solved simply by using such a copolyamide.

Incidentally, multi-core sheath-type composite fibers having polyamide as a sheath component and polyester as a core component are known, but there are no examples of them being applied to rubber reinforcement.

(Problems to be Solved by the Invention) The present invention provides a core-sheath composite fiber for rubber reinforcement, which has polyester as a core component and polyamide as a sheath component, which has excellent properties for rubber reinforcement in which peeling of three stroke components is suppressed. The aim is to provide fibers with

(Means for Solving the Problems) As a result of various studies to solve the above problems, the present inventors arranged the core component in a number of islands in the sheath component, and brought the polyamide and polyester interface into contact with each other. The present invention was achieved by discovering that peeling can be suppressed by increasing the area.

That is, one aspect of the present invention is a multicore-sheath type composite fiber in which a polyester component is divided into a plurality of pieces in which a polyamide component exists continuously in the cross-sectional direction of the fiber.

The gist of the present invention is a multicore-sheath type composite fiber for rubber reinforcement, characterized in that the ratio of polyester component to polyamide component is 30/70 to 75/25 by weight.

The present invention will be explained in detail below.

First of all, in the present invention, the core component polyester is polyethylene terephthalate (including that which is substantially recombined as polyethylene terephthalate, and 10% by mole).
Other components may be copolymerized or mixed to a certain extent. ) is used.

Further, as the polyamide of the sheath component, nylon 6, nylon 66, nylon 46, and copolyamide or mixed polyamide containing these as main components are used. Specific examples of copolyamides or mixed polyamides include nylon 6, nylon 66, or nylon 46 in which part of the acid component and/or diamine component is replaced with terephthalic acid, isophthalic acid, p-phenylenediamine, or m-phenylenediamine. copolyamide and nylon 6,
Examples include mixed polyamide of nylon 66 or nylon 46 and polymethaxylylene adipamide. and,
Polyamide is required to be melt-spun at a melting temperature of 200 to 330° C. in order to perform composite melt-spinning with polyester.

Polyester and polyamide have a high degree of polymerization in order to provide high-strength fibers for rubber reinforcement.The polyester uses a mixture of equal weights of phenol and tetrachloroethane as a solvent, and has a concentration of 0.5 g/a.

Those with a relative viscosity of 1.5 or more when measured at a temperature of 20°C.

Polyamide uses 96% sulfuric acid as a solvent and has a concentration of 1.0 g/a.
, those having a relative viscosity of 2.0 or more when measured at a temperature of 25° C. are preferably used. In addition, in order to improve heat resistance, a terminal carboxyl group blocking agent such as an epoxy compound, a carbodiimide compound, or an oxazoline compound is added to polyester, and a heat stabilizer such as a copper compound and potassium iodide is added to polyamide. It is preferable.

The most important point in the composite fiber of the present invention is that it is a multicore sheath-core composite fiber (sea-island fiber) in which the polyester core is divided into many pieces.

The number of cores is also related to the weight ratio of the core to the sheath.

2 to 11 are preferred. Further, the arrangement of the cores is not particularly limited, but it is more preferable that the cores are arranged symmetrically in the cross-sectional direction of the fiber. FIG. 1 shows a typical example of the cross-sectional shape of the composite fiber of the present invention. In addition.

The weight of the core component can be increased the most by using the cross-sectional shape (2) which allows a so-called close-packed structure.

In addition, in the composite fiber of the present invention, the ratio of polyester to polyamide is 30/7.0 to 75/25 in terms of weight ratio.
must be within the range of Of course, the weight ratio is limited by the number of cores, but if the amount of the core is less than this range, the high Young's modulus, which is a characteristic of polyester, will be lost; If more,
A portion of the core is exposed from the sheath 61, and only composite fibers with poor adhesive performance or hydrolysis resistance can be obtained.

The conjugate fiber of the present invention can be produced by subjecting the above-mentioned core component and sheath component to conjugate spinning and drawing in a conventional manner. Stretching may be performed after the undrawn yarn is once wound up, or may be performed continuously after spinning. In order to produce the fibers of the present invention with good productivity, a method is preferably employed in which highly oriented undrawn yarn is obtained by a direct spinning drawing method or a high speed spinning method and then drawn.

Although the physical properties of the composite fiber of the present invention vary depending on the primary blending ratio and spinning conditions, it is desirable that the fiber has a strength of 7 g/d or more, an elongation of 10 to 30%, and a Young's modulus of 65 g/d or more.

The composite fiber of the present invention can be used for tire cords, belts,
Used as rubber reinforcing fiber for conveyor belts, etc.

(Function) The conjugate fiber of the present invention has a core component arranged in a large number of islands, and the contact area at the interface between polyamide and polyester is large, so even if a part of the fiber is peeled off.

Since the majority can maintain a bonded state, it is considered to be a special silicone that is excellent as a rubber reinforcing fiber.

(Examples) - The present invention will be explained in more detail below using examples.

Note that the elongation at 1 strength and Young's modulus are as per JIS L 2511.
According to the above, Autograph DSS-500 manufactured by Shimadzu Corporation was used.

The measurement was performed under the conditions of a sample length of 30 cm and a tensile speed of 30 cm/min.

The hydrolysis resistance of the composite fiber was evaluated by treating it in heated steam at 130° C. for 48 hours and determining the strength retention rate at that time.

Examples and Comparative Examples Polyethylene terephthalate with a relative viscosity of 1.60 as the core component, nylon 66 with a relative viscosity of 3.60 as the sheath component
Composite yarns with the number of cores of 4 [(a) in Fig. 1] and 1 were spun using the same.

At this time, the spinning temperature was set to 305°C, and the discharge ratio (weight ratio) of the nine fraction components was changed as shown in Table 1, and the spinning was carried out.After being cooled and solidified and oiled, it was taken up by a take-up roller at a speed of 2000 m/min. A first stage of stretching is performed between this take-up roller and a pair of first stretching rollers at a temperature of 160°C at a stretching ratio of 1.3 while spraying heated steam at 450°C. A second stage of drawing was carried out at a drawing ratio of 2.0 between the second drawing roller and the yarn was wound at a speed of 5050 m/min to obtain a composite yarn of 250 d/36 f.

Next, the above composite yarn was formed into a dip cord in a 9-order manner, and the adhesive strength of the dip cord with rubber was measured and a fatigue test was conducted.

Combine 4 of the above composite yarns to make 1000 d/144
The raw yarn of f is twisted 49 times/1 in the Z direction by a ring twisting machine.
Apply a first twist of 0c+n, then double the two yarns and make 4 yarns in the S direction.
It was twisted 9 times/10 cm to obtain a raw cord.

Next, using a Ritzler dipping machine, 3.5 to 4.0% by weight of RFL liquid with a solid content of 15% was applied, followed by drying zone 120°C x 120 seconds and heat treatment zone 230°C x 36 seconds. The sample was processed under normal zone conditions of 230° C. for 36 seconds to form a dip cord.

In addition, the adhesive strength with rubber is determined by embedding the dip cord in rubber according to JIS L 1017 and at a temperature of 155°C.
.

Vulcanization was performed at a pressure of 100 kg/c for 30 minutes, and the force required to pull the cord from the rubber was expressed.

Further, the fatigue test was carried out by adopting the Gutdeyer method and Mallory tube test method described in JIS L 1 () 17, and measuring the time until the tube bursts at an angle of 80''.

Composite yarn strength, elongation, Young's modulus, and tenacity retention (hydrolysis resistance), dip cord adhesive strength and bursting time (
Fatigue resistance) is shown in Table 1.

As is clear from Table 1, five examples of the present invention are N.

In No. 2, No. 3, and No. 3, the composite fibers had good yarn characteristics and also had excellent hydrolysis resistance and fatigue resistance.

On the other hand, in comparative example No. 4, the proportion of polyester in the core component was too large, so the cross-sectional shape of the fiber collapsed, and some of the polyester in the core was exposed on the fiber surface.
The hydrolysis resistance and adhesive performance were poor. Further, in No. 1, in which the proportion of polyamide in the sheath component was too high, the Young's modulus was low. Furthermore, in No. 4, which is a single-core sheath-type composite fiber, the yarn properties of the raw yarn were good, but the fatigue resistance of the dip cord was poor.

(Effects of the Invention) According to the present invention, there is provided a rubber reinforcing fiber that takes advantage of the characteristics of polyamide and polyester, has a high modulus, is excellent in hydrolysis resistance, and has good fatigue resistance.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing a specific example of the cross-sectional shape of a composite fiber of the present invention.

Claims (1)

[Claims] (1) A multicore-sheath type composite fiber in which the polyamide component that exists continuously in the cross-sectional direction of the fiber is a polyester component divided into a plurality of pieces, and the ratio of the polyester component to the polyamide component is 30/30 by weight. 70 to 75/25 multicore sheath type composite fiber for rubber reinforcement.