JPH1054485A - Fuel hose and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a hose with ease and at a low cost, by laminating, heat treating and integrally forming a polyamide resin inner layer on the inner circumferential surface of an acrylonitrile-butadiene rubber outer layer without an adhesive. SOLUTION: In the manufacture of a fuel hose, a rubber composition is prepared by mixing a rubber material for forming a rubber outer layer, carboxyl containing NBR, a divalent to tetravalent metallic compound, a vulcanizing agent, a vulcanization accelerator and a plasticizer, and a tubular rubber outer layer is formed by being injection molded or being vulcanized after molding. Next, polyamide resin powder is charged and stuck on the inner circumferential surface of the outer layer so as to electrostatically coat the inner circumferential surface of the outer layer, however, a powder fluidizing/clipping/coating method and a spray atomizing method can be used. Then, heat treatment that polyamide resin powder and the rubber outer layer are integrated, is executed under a condition of a temperature of 200 to 220 deg.C and time of 10 to 30 minutes. By this treatment, it is considered that NBR activated by the divalent to tetravalent compound and fused polyamide are bonded each other. Therefore, a complex-shaped hose can be manufactured without increasing a cost to a large extent and deteriorating environment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel hose used for transferring a liquid organic compound or a liquid composition containing the same, particularly a liquid fuel for an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, as a fuel hose used for a fuel pipe of an automobile or the like, NBR / PVC rubber (acrylonitrile) having excellent gasoline resistance and gasoline permeability resistance has been used.
Rubber single-layer hoses using a mixture of butadiene rubber and polyvinyl chloride) are well known. However, in recent years, regulations on gasoline permeation have become strict, and the rubber single-layer hose as described above cannot respond to the above regulations. Therefore, as a hose satisfying more severe conditions, a hose in which an inner layer made of fluororubber is formed on the inner peripheral surface of the rubber layer has been developed and used in part.

[0003]

However, the hose having the fluororubber inner layer has high performance,
It has the disadvantage of high cost, and has not been widely used. On the other hand, it has been proposed to form the inner layer with a less expensive polyamide resin instead of the fluororubber.

[0004] The above polyamide resin has excellent performance in terms of gasoline resistance and gasoline permeation resistance.
However, since the adhesiveness with the rubber outer layer is poor, it is necessary to apply an adhesive to the inner peripheral surface of the rubber outer layer and bond both layers in order to laminate and integrate. This is particularly problematic for filler hoses that connect the hose end to another member. That is, the filler hose may be formed into a smooth curved tube shape as shown in FIG. 1 or a bellows tube shape as shown in FIG. Many, but when molding into such a special shape, not only is it difficult to apply the adhesive evenly,
There is also a problem that a drying step is required after the application of the adhesive, and the step becomes complicated. Further, there is a concern that the environment may be deteriorated due to the solvent of the adhesive. Therefore, on the inner peripheral surface of the rubber outer layer,
It is strongly desired to establish a method for manufacturing a fuel hose simply and inexpensively by integrally forming a polyamide resin inner layer without using an adhesive.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and a fuel hose in which a polyamide resin inner layer is integrally formed directly on the inner peripheral surface of a rubber outer layer without using an adhesive. The purpose is to provide the manufacturing method.

The carboxyl group-containing NBR to be used is obtained by using a carboxyl group-containing monomer as a third component monomer together with an acrylonitrile monomer and a butadiene monomer, and polymerizing them.

Examples of the carboxyl group-containing monomer include acrylic acid and methacrylic acid. These may be used alone or in combination of two or more. The content ratio is preferably set to 1 to 15 ephr (gram equivalent number of potassium hydroxide / 100 parts by weight of rubber). The carboxyl group content is determined by titrating a rubber solution dissolved in chloroform with an alcoholic potassium hydroxide solution. When the carboxyl group content is less than 1 ephr, the effect of improving the adhesive strength is small, and when the content exceeds 15 ephr, the adhesive strength is high, but there is a tendency that the set properties of the rubber deteriorate and the sealing property tends to deteriorate.

The mixing ratio of the carboxyl group-containing NBR to the rubber composition is preferably set to 2 to 15 parts by weight based on 100 parts by weight of the rubber material. If the amount is less than 2 parts by weight, the effect of improving the adhesive strength is small, and if the amount exceeds 15 parts by weight, the effect of improving the adhesive force is high, but the settability of the rubber tends to deteriorate, and the sealing property tends to deteriorate.

The rubber outer layer is made of NBR from the viewpoint of gasoline resistance.
-PVC rubber is optimal, but need not be limited to this. For example, acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR) and the like can be used.

When the ozone resistance is required to be high, the rubber outer layer may be composed of two layers. In this case, the above rubber is used for the inner layer of the rubber outer layer, and ethylene propylene rubber (EPD) is used for the outer layer of the rubber outer layer.
M, EPM), chlorosulfonated polyethylene rubber (C
SM), epichlorohydrin rubber (CO, ECO), chlorinated polyethylene (CPE) and the like are used.

Examples of the divalent to tetravalent metal compound used include hydroxides and oxides of divalent to tetravalent metals. Among them, aluminum hydroxide and calcium hydroxide are preferably used.

The mixing ratio is preferably set to 5 to 25 parts by weight with respect to 100 parts by weight of the rubber material. If the amount is less than 5 parts by weight, the effect of improving the adhesive strength is small, and if it exceeds 25 parts by weight, the effect of improving the adhesive force is high, but the mechanical strength of the compounded rubber is deteriorated.

In order to further improve the adhesion between the rubber outer layer and the polyamide resin inner layer, it is preferable that the rubber outer layer has a polysulfide bond density of 4 × 10 ⁻⁵ mol / cm ³ or more.

[0014]

In the present invention, the polysulfide bond density in the vulcanized rubber is determined by a chemical reagent treatment method ("DETERMINA").
TION OF CROSSLINK DENSITY
AND VULCANIZATE Structur
E "MONSANTORUBBER CHEMICA
LS JULY 1983) and the swelling compression method ("Structural analysis of crosslinked structure by swelling compression method [1] Test method development""Bridgestone Japan Rubber Association Vol. 60 No. 5
1987).

The method for increasing the polysulfide bond density is not particularly limited, but it is preferable to use a thiazole vulcanization accelerator. The same effect can be obtained by blending the thiazole-based vulcanization accelerator as a main component with a non-thiazole-based accelerator.

On the other hand, polyamide resins for forming the inner layer include nylon 6, nylon 11, nylon 12, nylon 6.10, nylon 6.12, nylon 6/66 copolymer, nylon 6/12 copolymer and the like. Although it is not particularly limited, nylon 11 is preferred in view of the balance between gasoline permeability and flexibility. It is also possible to use a mixture of the polyamide resin with a plasticizer or an elastomer, or a copolymer of the polyamide resin with a polyether or polyester.

The fuel hose of the present invention has a polyamide resin inner layer directly formed integrally with the inner peripheral surface of the rubber outer layer without the use of an adhesive, and can be manufactured, for example, as follows. That is, first, a rubber composition is prepared by mixing a rubber material for forming a rubber outer layer, a carboxyl group-containing NBR, a divalent to tetravalent metal compound, a vulcanizing agent, a vulcanization accelerator, a plasticizer, and the like. A tubular rubber outer layer is formed by applying to a molding machine or vulcanizing after extrusion molding. Next, the polyamide resin powder is melted on the inner peripheral surface of the rubber outer layer to bond and integrate the two layers. Thus, the desired fuel hose is obtained.

In the above-mentioned production method, the molding conditions for molding the tubular rubber outer layer depend on the shape and thickness of the tube, but when using an injection molding machine, the molding temperature is usually 150 to 170.
C. and a molding time of about 3 to 10 minutes are preferable. Moreover, when using a steam vulcanization can, 150-160
It is preferable to set the temperature to about 20 to 40 minutes.

Further, as a method of laminating the polyamide resin powder on the inner peripheral surface of the molded rubber outer layer, a method of charging the polyamide resin powder to a positive charge or a negative charge and attaching it to the inner peripheral surface of the outer layer by electrostatic attraction is used. Electrocoating is preferred, but other than that, various coating methods such as powder fluidized immersion coating, spray spraying, inner surface liquid coating immersion, and electrodeposition coating can be used.

The heating treatment for melting the above-mentioned polyamide resin powder and bonding and integrating it with the rubber outer layer may be performed by any heating means, but for example, an oven can be used. And the heating temperature is 200 ~
It is preferable to set the temperature at 220 ° C. and the heating time at about 10 to 30 minutes.

It is considered that the heat treatment causes the carboxyl group-containing NBR activated by the divalent to tetravalent compound to adhere to the molten polyamide by a chemical action.
Further, the polysulfide bond in the rubber outer layer is decomposed by the heat treatment, and the decomposed residue chemically acts on the molten polyamide, thereby further increasing the adhesive strength.

The fuel hose obtained by the above method is
Although any shape may be used, according to the manufacturing method of the present invention, it is not necessary to apply an adhesive to the inner peripheral surface of the rubber outer layer and bond the polyamide resin layer to each other, as shown in FIG. This is convenient when forming into a complicated shape such as a curved tube shape or a bellows tube shape as shown in FIG.

Further, in particular, according to the above-mentioned electrostatic coating, it is necessary to apply a coating to a part other than the joint part without coating a part of the inner peripheral surface of the rubber outer layer instead of the entire circumference, for example, a maintenance part at both ends of the hose. Thereby, it is possible to sufficiently secure the sealability of the joint portion, and it is possible to obtain a hose having excellent sealability.

[0024]

Examples 1 to 9 and Comparative Examples 1 and 2 First, the rubber components shown in Table 1 were prepared and subjected to steam vulcanization at 150 ° C. for 30 minutes.
35mm inner diameter, 4mm thickness, 300mm length shown in FIG.
The bent rubber hoses A to J were manufactured.

[0025]

[Table 1]

Next, the ten types of rubber hoses (A to A)
J) was used as an outer rubber layer, and the inner peripheral surface thereof was electrostatically coated with a 0.2 mm-thick polyamide resin powder. 60k for electrostatic painting
The polyamide resin powder was charged positively by v / 10 μA corona discharge. Further, this laminate was subjected to a heat treatment at 210 ° C. for 20 minutes to obtain a target fuel hose. The materials of the rubber hoses (A to J) and the inner layer of the polyamide resin used in Examples 1 to 9 and Comparative Examples 1 and 2 are as shown in Table 2.

[0027]

[Table 2]

[0028]

[Measurement of Peeling Strength] The hose was cut into a ring shape with a width of 25 mm in the axial direction, then cut open in the axial direction, and the peeling force in the circumferential direction was measured.

With respect to the fuel hoses of the examples and comparative examples,
The measurement results of the polysulfide bond density and the outer layer / inner layer peel strength are as shown in Table 2.

[0030]

As described above, by using the method according to the present invention, it is possible to form a complicated shape at the same time without significantly increasing the cost and without using an adhesive so that the environment is not deteriorated by a solvent. Also, a fuel hose can be conveniently manufactured. In addition, since the electrostatic coating is used to form the inner layer, the inner peripheral surface of the rubber outer layer is not entirely coated, but is not partially coated, for example, the maintenance portions at both ends of the hose are not coated, and the coating can be applied to portions other than the joint portion. It is possible to ensure sufficient sealing performance of the part. On the other hand, the resulting fuel hose also has good adhesion between the inner and outer layers, and has excellent performance in terms of gasoline resistance and gasoline permeation resistance.

[Brief description of the drawings]

FIG. 1 is a perspective view of a general bent tube-shaped fuel hose.

FIG. 2 is a perspective view of a general bellows tube-shaped fuel hose.

Claims (5)

[Claims] 1. A fuel hose comprising a polyamide resin inner layer laminated on an inner peripheral surface of an acrylonitrile-butadiene rubber outer layer, and both layers are adhered by heat treatment. 2. The fuel hose according to claim 1, wherein the rubber outer layer contains acrylonitrile-butadiene rubber and a divalent to tetravalent metal compound. 3. The fuel hose according to claim 2, wherein the divalent to tetravalent metal compound is aluminum hydroxide or calcium hydroxide. 4. The fuel hose according to claim 1, wherein the rubber outer layer is cross-linked so as to have a polysulfide bond density of 4 × 10 ⁻⁵ mol / cm ³ or more. 5. An acrylonitrile containing a carboxyl group.
Preparing a rubber outer layer containing butadiene rubber and a divalent to tetravalent metal compound, laminating a polyamide resin powder on the inner peripheral surface of the rubber outer layer, and heating the laminated product to form a polyamide resin inner layer. And bonding the rubber outer layer and the polyamide resin layer to each other.