JPH09257161A - Hose - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hose with light weight and high durability. SOLUTION: A hose 1 is constituted in such a way that a reinforcing layer 3 made of PBO fiber cord is formed on an inner pipe 2 comprising tube rubber, an intermediate rubber layer 4 is arranged on the reinforcing layer 3, and the outermost reinforcing layer 5 made of PPTA fiber cord is formed on the intermediate rubber layer 4, then cover rubber 6 is arranged on the reinforcing layer 5 as the outermost layer. By arranging PBO fiber cord in the inner layer reinforcing layer and PPTA fiber cord in the outer reinforcing layer, weight is remarkably reduced while burst pressure and durability the same as those of the conventional steel cord are kept.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hose provided with a reinforcing layer, and more particularly to a high pressure hose which is lightweight, has a high breaking pressure resistance and is excellent in durability.

[0002]

2. Description of the Related Art Conventionally, hoses for pressurized fluid such as rubber hoses for automobiles, hoses for construction machinery, hydraulic hoses for aircraft, etc.
Inner tube made of tube rubber such as acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR) and hydrogenated NBR, and cover rubber such as CR, chlorosulfonated polyethylene rubber (CSM) and chlorinated polyethylene rubber (CPE) The reinforcing layer is formed by braiding a reinforcing cord in a blade shape or a spiral shape between the outer layer and the outer layer.

Conventionally, as such a reinforcing cord, rayon fiber, vinylon fiber, nylon 6 fiber and nylon 66 are used.
Organic fibers such as fibers are used. However, as a fiber reinforcing layer for hoses used under higher pressure or high temperature, these organic fibers have the problems of lack of heat resistance, decrease in strength due to temperature rise, and decrease in tensile modulus, and thus steel wire. Had to use.

However, the steel wire has a problem that its specific gravity is large and therefore its weight is increased, and that the corrosion of water or corrosive gas causes the life of the hose to be greatly reduced. It was As a method for solving such a problem, for example, poly-P-phenylenebenzbisoxazol having a tensile elastic modulus per cross-sectional area similar to that of a steel wire and a tensile strength per weight significantly higher than that of the steel. There has been proposed a method of using a reel fiber in a hose (Japanese Patent Laid-Open No. 6-300169).

[0005]

The poly-P-phenylenebenzbisoxazol fiber (hereinafter abbreviated as PBO fiber) has a tensile strength of about 42 g / d and a tensile elastic modulus of 200.
It has 0 g / d and is a material with a very high potential as a weight-reducing material to replace steel. However, as disclosed in the above-mentioned application, it has become clear that there is a problem that sufficient durability cannot be ensured by simply using PBO fibers.

That is, when it is simply used as a reinforcing layer of the hose, the reinforcing cord of the reinforcing layer formed on the outermost layer of the hose is caulked at the metal fitting tightening portion by caulking when the hose fitting is attached. It was found that it fractured and could not withstand repeated impact pressure during actual use, resulting in hose breakdown with a short life. The reason for this is PB
O-fiber has very high tensile strength and tensile modulus, but J.Ma
As disclosed in ter.Sci, 22, 853 (1987), it is considered that the compressive strength is low, and when local bending is applied, it easily buckles and causes stress concentration fracture. The present invention has been devised in view of such conventional problems, and an object thereof is to provide a hose which is lightweight and has excellent durability.

[0007]

In order to achieve the above object, the present invention comprises an inner tube made of an elastomer composition, a reinforcing layer made of a plurality of reinforcing cords, and an elastomer composition covering the outside thereof. In a hose composed of an outer tube, at least the outermost reinforcing layer is composed of a reinforcing cord made of poly-P-phenylene terephthalamide fiber, and a reinforcing cord forming a reinforcing layer arranged inside thereof. The gist is a hose made of poly-P-phenylenebenzbisoxazole fiber.

Here, the reinforcing cord forming the reinforcing layer disposed inside is composed of PBO fiber cord.
PBO fiber is a fiber material capable of exceeding the tensile strength per unit area and the tensile modulus per unit area of weight of the steel, and by using the fiber to prepare an appropriate fiber cord. When the steel wire is replaced with a steel wire, the weight can be reduced without impairing the tensile strength and the tensile elastic modulus, that is, without damaging the breaking pressure and pressure response of the hose.

A method for producing such a PBO fiber is disclosed in US Pat. Nos. 4,533,692, 4,533,693, and 4,53.
3,724, JP-A-6-173113, The Materials
Science and Engineering of Rigid-Rod Polymers Vol.
Although disclosed in 134 Materials Research Society 1989, a polymer obtained by polymerizing diaminoresorcinol and terephthalic acid dichloride in a polyphosphoric acid solvent is usually produced by wet spinning.

When such a PBO fiber is used as a fiber cord, if twist is applied, the tensile strength and the tensile elastic modulus decrease. Therefore, the tensile strength of PBO fiber is 35 g /
It is necessary to use one having a tensile modulus of elasticity of d or more and 1500 g / d or more. Twist is imparted using such a PBO fiber to produce a PBO fiber cord, and it is preferable to add twist so that the twist coefficient K _b represented by the following formula is in the range of 150 to 700.

K _b = T _b √D _b K _b : PBO fiber cord twist coefficient, T _b : PBO fiber cord twist number (times / 10 cm), D _b : PBO fiber cord total When the number of denier and the twist coefficient K _b are less than 150, the convergence of the fiber cord is deteriorated, and the fiber filament is apt to be broken in the adhesion reduction or the braiding work for forming the hose reinforcing layer. Also, 700
When it exceeds, the tensile strength and the tensile elastic modulus are largely decreased.

The tensile strength produced in this way is 30
A PBO fiber cord having a tensile modulus of 650 g / d or more is used. When the tensile strength is less than 30 g / d and the tensile elastic modulus is less than 650 g / d, the hose finally obtained has the pressure response and the puncture resistance characteristic of the conventional hose made of steel wire reinforcement. It will be difficult to achieve weight reduction while maintaining.

In the present invention, it is essential that the outermost reinforcing layer is formed of a reinforcing cord made of poly-P-phenylene terephthalamide fiber (hereinafter referred to as PPTA fiber). PPTA fiber is J. Mater. Sci, 22,8
As disclosed in 53 (1987), the compressive strength is higher than that of PBO fiber, the fracture resistance against caulking at the time of mounting the hose fitting is also high, and the cord breakage at the fitting mounting portion can be suppressed.

The PPTA fiber has a tensile strength of about 23 g.
/ D is about 1/2 of PBO fiber, but the pressure load in each layer of the hose having a plurality of reinforcing layers is
Since there are few outer layers, sufficient fracture pressure resistance can be secured even if PPTA fibers are used. On the contrary, when the PPTA fiber cord is used as the inner reinforcing layer and the PBO fiber cord is used as the outermost reinforcing layer, not only the cord breaks in the metal fittings but also the inner layer PPTA having low tensile strength is used. The internal pressure load on the fiber cord reinforcing layer is also increased, and not only the breaking pressure is lowered but also the durability against repeated impact pressure is significantly lowered.

The PPTA fibers used here include:
Kevlar (trade name of DuPont) or Twaron (trademark of Akzo) is used. Since PPTA fiber has a characteristic that it has a high tensile elastic modulus among aromatic polyamide fibers (aramid fiber), PB fiber having a higher tensile elastic modulus is used.
It is also suitable for compounding with O fibers. The PPTA fiber cord is manufactured by applying twist to the PPTA fiber. The twist is more preferably added so that the twist coefficient K _t represented by the following formula is in the range of 150 to 600. When it is less than 150, the convergence of the cord is low and the adhesion is lowered, and the fiber filament is apt to break when braided into the reinforcing layer.

On the other hand, if it exceeds 600, the tensile strength and the tensile elastic modulus are greatly reduced, and the hose puncture resistance is lowered. In addition, the twist coefficient K _b of the PBO fiber cord and PP
It is more preferable that the ratio K _b / K _t of the twist coefficient K _t of the TA fiber cord is 1 or more. If less than 1, PPTA fiber core
The difference between the tensile elastic moduli of the cord and the PBO fiber cord is further increased, and the breakdown pressure resistance of the hose is further reduced.

K _t = T _t √D _t K _t : twisting coefficient of PPTA fiber cord, T _t : twisting number of PPTA fiber cord (times / 10 cm) D _t : total denier of PPTA fiber cord According to the present invention, the outermost reinforcing layer is made of PPTA fiber cord and the inner reinforcing layer is made of PBO fiber cord. It is possible to provide a hose having excellent pressure transmission characteristics.

[0018]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a partially cutaway perspective view showing an embodiment of a hose of the present invention. The hose 1 is made of PBO fiber cord on an inner tube 2 made of tube rubber. The reinforcing layer 3 is formed.

Further, an intermediate rubber layer 4 is arranged on this,
Furthermore, the outermost reinforcing layer 5 located thereon is a PPTA fiber core.
It is formed from do. Further, a cover rubber 6 is arranged as an outermost layer on the reinforcing layer. The rubber elastomer used for the inner tube rubber 2, the intermediate rubber layer 4 and the outer cover rubber 6 is not particularly limited, but NBR, CR, hydrogenated NBR, CSM, etc. are used, and heat It may be a plastic elastomer or resin.

Further, the reinforcing layer formed of the reinforcing cord may have a blade shape or a spiral shape, and FIG. 1 shows a blade structure. Also, PB
Although an example of one reinforcing layer made of O fiber cord is shown in FIG. 1, a plurality of layers may be used. In the case of a plurality of layers, an intermediate rubber layer may be arranged between the layers. PBO fiber core
As shown in FIG. 1, it is preferable to arrange one layer of PPTA fiber cords on the outer side of the reinforcing layer made of cords, but a plurality of layers may be arranged. It is necessary to form a reinforcing layer made of fiber cord.

The embodiments of the present invention will be specifically described below. As an inner tube tube rubber for hoses, hydrogenated NBR,
NBR as the middle layer rubber and CSM as the outer layer cover rubber
Was used. As the hose structure, the structure having the blade reinforcing layer shown in FIG. 1 is used, and the reinforcing layer is two layers. Also,
Each reinforcing layer was braided using 24 reinforcing cords with three cords aligned. The following reinforcing cords were used.

The PBO fiber cord is disclosed above.
2 pieces of PBO fiber 1000D manufactured by the method
Aligned 10 times / 10 cm (twist coefficient K_b= 450)
A single twist cord was created. Tensile strength of the reinforcing cord
The length was 76 Kgf and the tensile modulus was 750 g / d.
Kevlar as a PPTA fiber cord (made by DuPont,
Title) 2 times 1000D, 8 times / 10cm
Added twist (twist coefficient K_t= 360, K_b/ K _t= 1.
25) The code was prepared. The tensile strength of one of the cords is 4
It is 0 Kgf. The tensile modulus is 440 g / d.
You.

Also, as a reinforcing code of the conventional example, 0.5 m
A steel wire of m diameter was used. The tensile strength of one steel wire is 58 Kgf. Tensile elastic modulus is 300g /
d. The tensile test of the fiber cord is JIS L1.
017. The tensile elastic modulus of the fiber cord is 1.0 g / d to 4.5 g / d of the stress-strain curve of the fiber cord.
It was calculated from the slope at d load. The tensile test of the steel wire was in accordance with JIS Z2241. A hose was manufactured by using these reinforcing cords, and the following items were tested.

The total tensile strength of the reinforcing cords used for each hose was the same except for Comparative Example 2. In Comparative Example 2, since the PBO fiber cord is used for the inner layer and the outermost reinforcing layer, the total tensile strength is 30% higher than the other examples. . Damage condition of the reinforcing cord when the metal fitting is attached: The compression ratio is 55 with respect to the wall thickness of the hose by the eight-way tightening method.
After tightening the metal fittings as%, the metal fittings were divided into two and the inside was checked to check the damage state of the reinforcing cord.

[0025] Impact pressure test: JIS K6349.
An impact pressure test according to paragraph 7.7 was carried out. The test oil temperature was 100 ° C., and a pressure of 133% of the design normal pressure was set as the maximum pressure, which was repeatedly applied as a rectangular wave, and the number of times of breaking was measured. In addition, the test was aborted for those that were not destroyed by applying impact pressure up to 1,000,000 times. . Breaking pressure test: JIS K6330 4.2.1
The measurement was performed according to the test method according to the item (2), and the breaking pressure of the conventional example was set as 100 and displayed as an index. The higher the value, the better.
. Reinforcement layer weight index: In order to show the weight reduction of the hose, the weight of the reinforcement cord actually used in the hose is compared with that of the conventional product.
It was indexed against the lure weight. The smaller the value, the lighter the weight. The test results are shown in Table 1 below.

[0026]

[Table 1] As is clear from Table 1, as shown in the examples of the present invention, P
By arranging the BO fiber cord in the inner reinforcement layer of the hose and the PPTA fiber cord in the outer reinforcement layer, the breaking pressure and durability equivalent to those of the conventional steel cord can be maintained, while greatly improving the durability. It can be seen that it is possible to reduce the weight significantly.

On the other hand, when the arrangement is reversed, the PBO fiber cord of the outer reinforcing layer breaks at the metal fitting, resulting in a lower breaking pressure and a significantly worse impact pressure test. Further, even when PBO fiber cords are arranged in both reinforcing layers, the breaking pressure is lowered only by the cord breakage in the metal fitting portion, although the total tensile strength of the cords used is high. In addition, durability against repeated impact pressure is also reduced.

[0028]

As described above, according to the present invention, at least the outermost reinforcing layer is composed of a reinforcing cord made of poly-P-phenylene terephthalamide fiber, and the reinforcing layer disposed inside the reinforcing cord is formed. Since the cord is a hose made of poly-P-phenylene benzbis oxazole fiber, it is effective in that it can be made into a high-pressure hose which is lightweight, has a high breaking pressure resistance and is excellent in durability. .

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing an embodiment of a hose of the present invention.

[Explanation of symbols] 1 hose 2 inner tube 3 reinforcing layer 4 intermediate rubber layer 5 outermost reinforcing layer 6 cover rubber

Claims (1)

[Claims] 1. A hose composed of an inner tube made of an elastomer composition, a reinforcing layer made of a plurality of layers of reinforcing cords, and an outer tube made of an elastomer composition covering the outer side of the hose, at least the outermost layer. Is composed of a reinforcing cord made of poly-P-phenylene terephthalamide fiber, and the reinforcing cord forming the reinforcing layer disposed inside thereof is poly-P-phenylene benzbisoxazole. A hose characterized by being made of fibers.