JPS5811461B2 - Rubber hose inner tube forming material for fuel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inner tube forming material for a rubber fuel hose, which is used mainly for connecting metal pipes in the engine room of an automobile.

In recent years, the automobile industry has developed significantly, and the temperature inside the engine compartment varies over a wide range from over 100 degrees Celsius at the top to below -40 degrees Celsius at the bottom, and gasoline is oxidized at high temperatures (hereinafter referred to as sour gasoline). Because of this, harsh conditions are now required for the inner tube forming material of this type of rubber hose.

For this reason, acrylonitrile rubber compounds, which have traditionally been used as the inner tube forming material of fuel rubber hoses as a material that is inexpensive and has the best oil resistance and gasoline resistance, gradually harden when immersed in the sour gasoline for a long period of time. Eventually, the hose lost its elasticity and cracked due to repeated internal pressure inside the hose, resulting in fuel leakage.

This invention was devised in view of this point, and as a result of various experiments, it was found that with regard to leakage caused by hardening with sour gasoline, the absolute value of elongation after deterioration even after being immersed in sour gasoline for a long time is After further research, we discovered that this problem could be solved if the inner tube rubber was made of acrylonitrile rubber that could hold more than 30 cm.
It has been discovered that a blend of mixed polymers of 35-60% by weight of acrylonitrile rubber and 40-65% by weight of polyvinyl chloride is optimal.

The reason for limiting the amount of polyvinyl chloride in the mixture of acrylonitrile rubber and polyvinyl chloride to 40% by weight or more is that if the amount of polyvinyl chloride is less than 30% by weight, the absolute elongation after deterioration in sour gasoline will be value is 3
If it is 65% by weight or more, it is possible to maintain an absolute elongation of 30% or more, but the cold resistance and compression set properties decrease, which is the cause of fuel leakage from the connection. This is because.

Figure 1 shows a mixture of vulcanized polymers with varying mixing ratios of nitrile rubber and polyvinyl chloride mixed into a solution of 2 g of benzoyl peroxide dissolved in 98 g of gasoline (a gasoline almost similar to sour gasoline) at 60°C for 72 hours. The elongation was measured using the JISK 6301 method after 4 cycles of soaking (replace the liquid with a new one every 72 hours), based on the total 100% by weight of nitrile rubber and polyvinyl chloride. When the amount of polyvinyl chloride was 40% by weight or less, the absolute value of elongation was 30% or less.

The formulation contents, mixing conditions, and vulcanization conditions used were as follows.

Ingredients Contents Ingredients Polymer to tolyl rhodium polyvinyl chloride 10σ modified part Zinc white 5 Stearic acid 1 Sulfur 0.5 Accelerator
3.0 total 109.5 *1 Nitrile rubber product name: JSRN220S with trile content 40%) *2 PVC product name: Mitsui Toatsu Vinicron 3000L Mixing conditions The mixed polymer of nitrile rubber and polyvinyl chloride is mixed with a Banbury mixer. -Or, after high-temperature blending in a closed type mixer such as a kneader, other ingredients are mixed using a mixing roller or the like.

Vulcanization conditions: Press vulcanization at 150°C for 30 minutes.
0°C x 72 hours) This shows the relationship between compression set and the amount of polyvinyl chloride mixed.The larger the amount of polyvinyl chloride mixed, the worse the compression set tends to be, and the larger the compression set. As the temperature increases, the force with which the rubber hose tightens the fittings becomes weaker.

FIG. 3 also shows JISK6 in the mixed polymer.
This shows the relationship between cold resistance (impact embrittlement temperature) according to the 301 method and the amount of polyvinyl chloride mixed.It shows that the higher the weight ratio of polyvinyl chloride, the worse the cold resistance and the lack of resilience. ing.

Next, an inner tube was formed using the above compounded material, and a rubber hose was actually manufactured and tested.The results are shown below.

8.8 m diameter near the end of a metal pipe with an outer diameter of 7.5 mm
Two metal pipes with a chevron-shaped enlarged part of m are installed with their axes aligned, and a length of 80 m is attached to the end of these two metal pipes.
Insert the following rubber hoses with an inner diameter of 7 mm beyond the ampulla to 25 mm from the end, tighten near the ends of the rubber hoses with a band, and cross them to form a connected conduit. Sour gasoline heated to 60℃ is repeatedly circulated in the tube at a pressure range of 0 to 5 and 9 layers cm2, causing the inner tube rubber to harden and lose its elongation. The time required for gasoline to leak from the hose was measured.

In addition, the entire pipeline was heat treated at 115°C for 72 hours, and then -
Gasoline was sealed at 35° C. and a leak pressure test was conducted to measure the pressure at which gasoline leaked from the connection. The results are shown in the table below.

The configuration of the rubber hose used in the test consists of three layers: inner tube rubber, reinforcing layer, and outer rubber, and the wall thickness of the inner tube rubber is 1.
The 5 μm reinforcing layer is a braided layer of one layer of vinylon yarn, and the outer tube rubber is 1 to 2 mm made of chloroprene rubber or shrimp chlorohydrin rubber, which has excellent weather resistance, heat resistance, and cold resistance.
This shows a rubber hose with a total wall thickness of 2.7 mm consisting of a rubber coating layer, in which only the inner tube rubber forming material was changed.

As described above, the fuel rubber hose inner tube forming material of the present invention is made of a mixed polymer mixture of acrylonitrile rubber and polyvinyl chloride containing 40 to 65% by weight of polyvinyl chloride. Even if the tube rubber is immersed in sour gasoline for a long time, it can maintain elasticity above a certain level, and will not crack due to repeated internal pressure and will not cause fuel to leak from the inner tube.

Furthermore, in addition to the above effects, the elastic force that tightens the connecting pipe from the outside can be maintained constant even under repeated high and low temperatures, and even if gasoline is circulated at high pressure, leakage from the joint can be prevented for a long time. .

[Brief explanation of the drawing]

Figure 1 shows the change in the elongation of the mixed vulcanizate after immersion in sour gun rins as a result of the change in the mixing ratio of nitrile rubber and polyvinyl chloride, and Figure 2 shows the change in the mixing ratio of nitrile rubber and polyvinyl chloride. Regarding changes, JIS of mixed vulcanizate
Diagram showing the change in compression set by K6301 method, Part 3
The figure also shows the change in impact embrittlement temperature of the mixed vulcanizate according to the JIS K6301 method.

Claims (1)

[Claims] 1. A fuel rubber hose inner tube forming material made of a mixed polymer blend of 35 to 60% by weight of acrylonitrile rubber and 40 to 65% by weight of polyvinyl chloride.