JPH0376840A - Tire reinforcing fiber - Google Patents

Abstract

PURPOSE:To obtain the subject fiber having excellent adhesion with rubber and high-speed durability, etc., comprising filament of a core-sheath double structure to have mutually corresponding hooking uneven inversely at the outer surface of the core part and the inner surface of the sheath part and tightly engaging mutually. CONSTITUTION:For instance, a core part 1 is constructed with polyethylene naphthalate, etc., and sheath part 2 is constructed with a different polymeric material such as nylon 66, then the outer surface of the core part 1 and the inner surface of the sheath part 2 have mutually hooking uneven inversely so as to mutually tightly engage to afford the objective fiber. Besides, preferably, the height (a) of the protruding part measured in the direction to the center of said fiber is 5-30% of the fiber breadth (d) between the farthest two points on contour of the fiber and the hooking length (b) of the overhang breadth to the side direction of the protruding part is 5-30% of the fiber maximal breadth (d), and further the breadth of the bottom part (c) is 10-20% of the fiber maximal breadth (d).

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to industrial materials, particularly high-strength tire reinforcing fibers suitable as rubber reinforcing materials. More specifically, we use composite fibers for rubber reinforcement, which have excellent adhesion to rubber, heat resistance and fatigue resistance in rubber, and are particularly useful for improving the high-speed durability and retreading durability of pneumatic radial tires. This is what we provide.

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

However, polyester fibers generally have poor heat resistance in rubber. In other words, at high temperatures, the ester bonds in polyester fibers are broken due to the action of moisture and amine compounds in the rubber, causing a decrease in strength and poor adhesion to rubber, especially when exposed repeatedly for long periods of time in high-temperature atmospheres. When this happens, there is a problem in that the adhesive strength with the rubber decreases.

Many attempts have been proposed to improve the adhesiveness, which is a drawback of polyester, and one known method is to coat the surface of polyester with polyamide. For example, in Japanese Patent Application Laid-Open No. 49-85315,
Japanese Patent Publication No. 62-42061 describes a method for producing composite fibers with a polyester core and a nylon 6 sheath, which characterizes the degree of polymerization of each component polymer and the proportion of the core polymer. Regarding the rubber reinforcing material made of fibers with a core-sheath type composite structure, the boria rod-sheath component is 70 to 30.
% by weight and a rubber reinforcement whose surface is adhered with an epoxy adhesive is described.

In JP-A-1-97211, the core is made of polyester,
66/6T copolyamide is used for the sheath, and the copolymerization ratio of hexamethylene diammonium terephthalate in the 66/6T copolyamide is 5% by weight or more, preferably 10% by weight.
It is stated that the boundary adhesion between the core polyester and the sheath 66/6T copolyamide can be improved if the amount is 40% by weight.

JP-A-1-97212 describes that by making the core polyester and the sheath hexamethylene diammonium terephthalate boriagodo have a highly oriented, highly crystalline fiber structure, the adhesion at the interface can be improved and improved. .

Special Publication No. Sho 49-85315, Special Publication No. Sho 62-4206
Publication No. 1 describes that the adhesion with rubber, which is a disadvantage of polyester, can be improved by using boria in the sheath, and furthermore, it has the effect of suppressing amine decomposition. In JP-A-1-97211 and JP-A-1-97212, the boundary adhesion between the core polyester and the sheath polyamide is improved, but a sufficient improvement effect is not recognized.

Therefore, with conventional composite fibers, the core-sheath polymer interface is destroyed and the sheath is then separated and fractured due to repeated elongation and compression fatigue during tire running, so the original performance of core-sheath composite fibers is lost. It's not being demonstrated.

(Problems to be Solved by the Invention) The present invention has excellent adhesion to rubber, as well as Young's modulus and
The purpose is to provide high-strength composite fibers that have excellent dimensional stability, heat resistance and fatigue resistance in rubber, and are suitable as rubber reinforcing materials. The present invention provides a composite fiber made of a composite polymer that has sufficient durability against peeling between the core and sheath polymers due to stress, fully exhibits its properties over a long period of time, and has excellent high-speed durability.

(Means for Solving the Problems) As a result of extensive research to solve the above problems, the present inventors have found that the deterioration of fiber properties due to peeling of the core-sheath interface of fibers having a core-sheath type composite structure is The inventors have confirmed that this can be prevented by having the sheath part and the sheath part have opposing hooking protrusions on their boundary surfaces and fitting into each other, and have completed the present invention.

That is, the present invention provides a tire reinforcing fiber consisting of a double-structured filament having a core-sheath structure consisting of a core and a sheath of different polymers wrapped around the core. This tire reinforcing fiber is constructed such that its inner surface has opposite hooking irregularities that correspond to each other so that the core part and the sheath part fit tightly together.

(Function) An example of the tire reinforcing fiber of the present invention is shown in cross-sectional view in FIG. 1a. This fiber consists of a core 1 (the area indicated by the horizontal line) and a sheath 2 that encloses it and is made of a polymeric material different from the core, and as seen in the cross-sectional view, the outer surface of the core and the inner surface of the sheath. The core part 1 and the sheath part 2 have recesses and recesses that are opposite to each other and fit into each other in close contact with each other.

In this case, the tips of the respective protrusions 3 on the outer surface of the core and the inner surface of the sheath protrude to both sides and fit tightly into the correspondingly shaped recesses of the mating partner, and the shape of the protrusions on the inner surface of the sheath is such that the filament The height of the protrusion (a) measured toward the center of the filament is 5 to 30% of the maximum width of the filament (d), which is the length connecting the two furthest points on the filament outline.
The hooking length (b), which is indicated by the lateral width of the protrusion, is 5 to 30% of the maximum filament width (d), and the width of the base (c) is the maximum filament width (d). 5
It is preferable that it is 30%.

Furthermore, the height (a) of the protrusion, the hook length (b), and the width (c) of the base are each 10% of the filament maximum width (d).
More preferably, it is 20%.

It is preferable that the number of protrusions is two or more.

In the present invention, for example, in a fiber having a core-sheath type composite structure in which the core component is polyester containing polyethylene terephthalate as the main component and the sheath component is polyamide, the core-sheath fiber is improved in the peeling durability of the polymer at the core-sheath composite interface. The polymer at the composite interface is formed with irregularities as shown in Figures 1 and 2.
It is a distant relative due to its structure that causes it to catch when a force is applied in a direction perpendicular to the fiber axis direction. The size of this catch is the maximum width (d) of the cross section of the filament.
5 to 30% for a, 5 to 30% for b, and 5 for C.
The range of a and b is preferably 30%.

If C is less than 5%, there will be little catching and the peeling durability of the polymer at the core-sheath composite interface will be poor. a, b for d
, c is more preferably in the range of 10 to 20%.

For example, when examining the durability of a tire cord made of filaments with a, b, and c"0%, that is, concentric core-sheath cross sections, peeling failure occurred between the core-sheath interface polymers during running. It was confirmed that

Secondly, as a core material, it is more thermally stable than polyester,
High modulus polyethylene naphthalate (PEN
) was used, and the core-sheath interface was also found to have a catching effect in the same manner as described above, even in fibers having a core-sheath type composite structure in which polyamide was used as the sheath material. Further, as the sheath material, 6.6-nylon and 4°6-nylon are preferably used.

The cross-sectional shape of the core-sheath type structural cord is not limited to the circular cross section shown in FIG. 1a, but may also be triangular (FIG. 1b) or elliptical (FIG. 1c).

Furthermore, the shape parameters a, b, c of the protrusion 3 can suitably vary in the range of 5 to 30% with respect to the maximum width d, but a = b = c = 5% as shown in Figure 2a. , a=b=20%, c=25% as shown in FIG. 2b, and a=b=c=10% as shown in FIG. 2c.

(Examples) Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Creation of organic fiber filaments Polyethylene terephthalate (PET) chips with an intrinsic viscosity (r, v, ) of 0.9 measured in orthochlorophenol (25°C) and relative viscosity in sulfuric acid Polyhexamethylene adipamide (6°6-
Special Publication No. 4418369 using nylon chips as raw materials
Using equipment similar to the spinning equipment described in the publication, PE
A core-sheath filament with a total denier of 1500 deniers was prepared, with T as the core and 6,6-nylon as the sheath. In this case, the weight ratio of PET/6.6-nylon was controlled by adjusting the diameter of the spinneret hole and the amount of polymer discharged. PET No. 1 of the obtained filament. The weight ratio of V and PET/6.6-1-I 1 ml was measured by the following method. PET 1. V.

The measurement was performed after dissolving and removing the 6.6-nylon layer (sheath) from the filament using formic acid. V.

was measured in orthochlorophenol (25°C).

At the same time, the weight of each core and sheath was also measured to determine the weight ratio. Confirmation of core-sheath structure and a of FIGS. 1 and 2.

The values of b, c, and d were calculated by measuring a photograph of a cross section of the filament taken with a scanning electron microscope (SEM).

The code created in this way is 195/70 R14
It was used as a cord for the yaw 18 layer of a radial tire of the same size. As shown in FIG. 3, this tire has a cord A layer 13 as a belt layer on a carcass cord layer 12, which is further reinforced with a yaw layer 14. The number of cords embedded in the 18th yaw layer was 50 and 15 cm, and a steel cord (1 x 5 x O, 23 mm) was used as code A. In addition, the carcass cord layer (ply layer) is made of polyethylene terephthalate (PUT) cord (1500d/
It had a single layer structure of 3.30 x 30).

Furthermore, the yaw 18 layer is the prototype 12 shown in Tables 1 and 2.
Seed filament (core PET/sheath 6,6-nylon = 6
0/40) was used.

The properties of the parts and tire performance (high-speed test) of the prototype tires were evaluated using the methods shown below. The results obtained are shown in Tables 1 and 2.

Table 3 ml N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylene 2 2,2,4-trimethyl-L2-dihydroquinone polymer *3 Dibenzothiazyl disulfide $4N -Oxydiethylene-2-benzothiazylsulfenamide As shown in Example 1, when a, b, and c of the protrusion are 3%, the adhesion is higher than that of Comparative Example 1 (conventional example) which does not have a protrusion. Improvements in strength and high-speed durability were noted, albeit on a small scale. Adhesive strength and high-speed durability increased as the values of a, b, and c increased. In Example 6, a and b are 30% and C
In the case of 10%, the tread-B delamination occurred in about 15 minutes at 20km/h. Overall, when the proportions of these protrusions a, b, and c are within the range of 5 to 30%, improvements in adhesive strength and high-speed durability can be seen compared to Comparative Example 1.
The above improvement is significant at ~20%.

Next, as shown in Table 2, the relationship with the number of protrusions is 193 km 20 minutes for the one with the number O (Comparative Example 1), and as the number increases, the adhesive strength and high-speed durability improve. However, when the number of protrusions exceeds 16, b of the protrusions must be made smaller, and the adhesive force and high-speed performance tend to worsen (although it is still better than Comparative Example 1). A range is preferred.

(Effects of the Invention) The tire reinforcing fiber of the present invention is a core-sheath type composite fiber in which the outer surface of the core and the inner surface of the sheath have opposite hooking irregularities that correspond to each other. By configuring the core and sheath polymers to fit tightly into each other, peeling of the core-sheath polymer interface is suppressed and the adhesive strength is improved.When used as a tire cord, durability, especially high-speed durability, can be significantly improved. has.

[Brief explanation of drawings]

Figures 1a to 1c are cross-sectional views showing examples of various cross-sectional shapes of the tire reinforcing fiber of the present invention, and Figures 2a to 2c are various arrangement examples of protrusions of the tire reinforcing fiber of the present invention. FIG. 3 is a schematic cross-sectional view of a radial tire shown as an example to which the tire reinforcing fiber of the present invention is applied. DESCRIPTION OF SYMBOLS 1... Core part 2... Sheath part 3... Protrusion part 11... Bead 12... Carcass cord layer 13... Cord A layer 14... Yaw 18 layer
a... Height of protrusion b... Hooking length
C...Base width d...Filament maximum width

Claims (1)

[Claims] 1. A tire reinforcing fiber consisting of a double-structured filament having a core-sheath structure consisting of a core and a sheath of different polymers wrapped around the core, comprising: the outer surface of the core and the sheath; 1. A tire reinforcing fiber, characterized in that the inner surfaces of the parts have opposite hooking irregularities corresponding to each other so that the core part and the sheath part are fitted into each other in close contact with each other. 2. In the cross section of the filament, the tips of the protrusions on the outer surface of the core and the inner surface of the sheath protrude to both sides and fit tightly into the correspondingly shaped recesses of the other, and the tips of the protrusions on the inner surface of the sheath The height (a) of the protrusion measured toward the center of the filament is 5 to 30% of the filament maximum width (d), which is the length connecting the two furthest points on the filament outline, and the protrusion The hooking length (b), which is indicated by the lateral overhang width of the filament, is the maximum width of the filament (
d), and the base width (c) is 5 to 30% of the filament maximum width (d). 3. The height of the protrusion (a), the length of the hook (b), and the width of the base (c) are each 10 to 10 times the maximum width of the filament (d).
The tire reinforcing fiber according to claim 2, wherein the fiber content is 20%. 4. Claim 2 or 3, wherein the number of protrusions is two or more
The tire reinforcing fibers described.