JPH0331958B2 - - Google Patents

Description

[Detailed description of the invention]

<Technical Field> The present invention relates to a reinforced rubber hose in which a reinforcing layer is formed of polyamide fiber, and a rubber layer in contact with the reinforcing layer is formed of an ethylene propylene terpolymer (abbreviated as EPDM) compound. It is suitable as a water-based hose. <Prior art> The configuration of a cooling water system hose for an automobile is, for example, a first
As shown in the figure, a reinforcing layer 3 (usually made of braid; spiral or knitting is also acceptable) is arranged between an inner layer 1 and an outer layer made of EPDM. The reinforcing thread that forms this reinforcing layer is
Heat-resistant polyamide fibers are now being used in place of conventional rayon fibers due to the need for maintenance-free fibers (usually requiring no replacement after 10 years or 150,000 km). However, when polyamide fibers come into contact with EPDM rubber compounds, their deterioration accelerates, leading to a decrease in hose bursting pressure, making it difficult to meet the requirement for maintenance-free use. At this time, it is possible to improve the deterioration resistance of the polyamide fiber itself, but this would be expensive and impractical. Therefore, the present inventors believe that the above-mentioned problems can be resolved.
As a result of extensive research into EPDM formulations, we discovered that it is effective to incorporate specific metal oxides into EPDM. The reason for this is not clear, but it is presumed that the agent contained in EPDM that accelerates the deterioration of polyamide fibers reacts with CaO, reducing the deterioration effect. <Purpose of the invention> The present invention provides a reinforced rubber hose in which the reinforcing layer is made of polyamide fibers and the rubber layer in contact with the reinforcing layer is made of an EPDM compound, which reduces the deterioration accelerating effect of EPDM on the polyamide fibers. The purpose is to extend the service life of the product. <Summary of the Invention> The present invention provides a reinforced rubber hose in which the reinforcing layer is formed of polyamide fibers and the rubber layer in contact with the reinforcing layer is formed of an EPDM compound.
It is characterized by blending the required amount into the EPDM formulation. <Embodiment> The reinforced rubber hose to which this invention can be applied is not limited to the structure shown in FIG. Or multi-layered ones with three or more layers, etc.
The rubber layer in contact with the reinforcing layer may have any structure as long as it is made of an EPDM compound. Polyamide fibers are usually nylon.
6, nylon 6,6, aromatic polyamide (Kepler), etc. are used. In addition to conventional auxiliary materials such as carbon black, process oil, stearic acid, sulfuric acid, and vulcanization accelerator, the EPDM formulation contains a required amount of CaO in this invention. This required amount is such that the deterioration promoting effect of EPDM on polyamide fibers can be reduced to the required level, and the vulcanized rubber (inner/outer layer 1,
2) refers to the blending amount at which the compression set does not exceed a predetermined value. Specifically, in order to achieve the above maintenance-free condition, CaO5~35PHR (preferably 10~35PHR) is required, as is clear from the examples and comparative examples described below.
25PHR). <Examples/Comparative Examples> The basic formulations of the EPDM formulations used in each of the Examples and Comparative Examples are as shown below, and the amount of CaO blended is shown in Table 1. EPDM basic formulation (unit: PHR) Polymer (third component ethylidene norbornene) Carbon black (FEF) 140 Process oil (paraffinic) 80 Stearic acid 1 Zinc white 5 Sulfur 1 Vulcanization accelerator 3 CaO Variable Using each EPDM formulation After extrusion molding a cooling water hose (inner diameter 16φ, inner thickness 4.0mm, nylon cord insertion pitch 50mm) as shown in Figure 1, steam vulcanization was performed under vulcanization conditions: 150℃ x 30min. was used as the test material for the hose enclosure deterioration test. Here, the nylon cord is made of nylon-6,6, 2
It had a real twist of 840D and an initial strength of 14 kgf/cord, and was coated with an adhesive (resorcinol formaldehyde type). In the hose-enclosed deterioration test, cooling water (containing 50 wt% of long-life coolite) was circulated in an atmosphere of 120°C, and the burst pressure was measured every 500 hours until 3000 hours. The results are shown in Table 1 and Figure 2. In addition, the yarn deterioration test was conducted as shown in Figure 2.
The same nylon cord 5 as above was sandwiched between 2 mm vulcanized rubber sheets 6 formed using each EPDM compound (vulcanization conditions: 150°C x 30 min. steam vulcanization), and Close the opening of container 7, which is almost filled with the same cooling water, and turn it over.
The test was conducted at 150°C for 168 hours. The results are shown in Table 1. The compression set test was conducted according to JISK6301 (vulcanization conditions: 120°C x 22 hours). In order for the cooling water hose to meet the requirement of maintenance-free operation, in the hose enclosure deterioration test, the bursting pressure of the hose after 3000 hours must be 5.25 kg/
cm ² or more, 7.65 Kgf/cord or more in the yarn deterioration test, and compression set of approximately 65% or less. Judging by this standard, as mentioned above, CaO
It can be seen that the appropriate amount is 5 to 35 PHR.

[Table] <Effects of the Invention> As described above, the reinforced rubber hose of this invention has the following properties:
By simply incorporating the required amount of CaO into the EPDM formulation, the effect of EPDM on accelerating yarn deterioration on polyamide fibers can be easily reduced. Therefore, when the present invention is applied to a cooling water system hose, the requirement for maintenance-free hoses can be satisfactorily met. In addition, the inventors of the present application have investigated the effect on yarn deterioration when MgO is added instead of CaO.
Tests were conducted in the same manner as in the examples. Sample No. in Table 1
From the test results shown in columns 7 to 10, it can be seen that the effect of MgO in reducing the acceleration of yarn deterioration is small, and in order to obtain the same effect of inhibiting yarn deterioration, it is necessary to mix more than twice as much as CaO. Incidentally, an increase in the blending amount is undesirable because the compression set resistance of the rubber vulcanizate decreases (see the compression set column in Table 1). This also shows that CaO in the EPDM formulation has a remarkable effect of inhibiting yarn deterioration.

[Brief explanation of drawings]

Fig. 1 is a partially cutaway perspective view showing an example of a reinforced rubber hose, Fig. 2 is a data graph of hose deterioration tests of examples and comparative examples of the present invention, and Fig. 3 is a cross section of a model showing the method of yarn deterioration test. It is a diagram. 1...inner layer, 2...outer layer, 3...reinforcement layer.

Claims (1)

[Scope of Claims] 1. A reinforced rubber hose in which the reinforcing layer is formed of polyamide fibers, and the rubber layer in contact with the reinforcing layer is formed of an ethylene propylene terpolymer (abbreviated as EPDM) compound, comprising: A reinforced rubber hose characterized by containing 5 to 35 PHR of CaO.