JPH085151B2 - Rubber hose resistant to methanol - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a methanol resistant rubber hose with improved fiber deterioration and metal deterioration for reinforcement.

(Prior art and its problems) Chlorinated polyethylene, especially chlorinated polyethylene produced by a process including a chlorination process near the melting point of polyethylene crystals, is a useful substance as a rubber material and should be sufficiently crosslinked. It is known that among these various synthetic rubbers, excellent mechanical properties, heat resistance, oil resistance, chemical resistance, and weather resistance can be exhibited. Furthermore, in recent years, chlorinated polyethylene has superior methanol resistance compared to other rubber materials, so it has been developed for applications such as lining of fuel feed hoses for automobiles, fuel tanks or methanol storage tanks. However, it has been proposed by two of the applicants that it is effective to use a specific chlorinated polyethylene for this purpose (Japanese Patent Application No. 60-220768).

Normally, not only for methanol fuel but also for gasoline fuel, physical properties that are especially problematic when using rubber material as a fuel hose include swelling resistance, extraction resistance, etc. against the used fuel in the inner layer, as well as joints and caps. It has metal deterioration resistance in the contact part, and weather resistance, ozone resistance, wear resistance, lubricating oil resistance, etc. in the outer layer.

In recent years, the physical properties required for hoses have become more severe,
Furthermore, since the usage has expanded, the shape of the hose has become complicated, and the number of laminated structures made of different rubber materials has increased from that of a single layer. In terms of strength and shape retention, a fibrous reinforcing layer with a reinforcing system woven between the rubber layers has been used. Many are used. Therefore, it is one of the important physical properties that the rubber material does not deteriorate the reinforcing yarn.

Generally, many polymers deteriorate under some use conditions in which they come into contact with metals. However, in the case of chlorine-containing polymers such as chlorinated polyethylene, the deterioration of the metal, especially zinc, tin, iron, etc. , Copper, etc., or their alloys, or their compounds at high temperature, or dehydrochlorination may occur during long-term contact in a liquid containing them at a high temperature, resulting in significant deterioration of the polymer itself. Are known.

Furthermore, the problem is that the hydrochloric acid desorbed from the chlorinated polyethylene deteriorates the reinforcing yarn braided between the hose layers, and the pressure resistance and strength of the hose deteriorate.

Polyvinyl alcohol fibers, polyamide fibers, polyester fibers, etc. are generally used as the reinforcing yarns, but among them, polyvinyl alcohol fibers and polyamide fibers are easily hydrolyzed in an acidic atmosphere, so that deterioration is remarkable. In particular, polyvinyl alcohol fibers are now often used as reinforcing yarns for fuel liquid supply hoses, and it is not easy to change them to other yarns in view of their physical properties.

(Means for Solving Problems) As a result of repeated studies in view of the above points, the present inventors have found that a crosslinked composition of chlorinated polyethylene to which a specific amount of hydrotalcites has been added is used for a spinneret, a reinforcing thread, etc. We have succeeded in obtaining a methanol-resistant rubber hose with improved resistance to metal deterioration and resistance to reinforcing yarn by using it in the parts that come into contact with other materials.

That is, according to the present invention, a plurality of layers of crosslinked rubber are formed through a fibrous reinforcing layer, and at least the inner layer of the crosslinked rubber contains 5 to 50 parts by weight of hydrotalcites and 100% by weight of chlorinated polyethylene and a crosslinking agent. A methanol-resistant rubber hose, which is a crosslinked product of a rubber composition containing the rubber hose.

The methanol-resistant rubber hose of the present invention refers to a fuel hose for a methanol engine and a rubber hose used when transferring methanol to a tank.

Further, the methanol resistance includes resistance to not only methanol but also monovalent lower aliphatic alcohols such as ethanol, propyl alcohol, isopropyl alcohol, n-butyl alcohol, and tert-butyl alcohol. In addition, not only pure methanol but also fuel containing gasoline added to methanol may be practically used. Therefore, similar resistance to gasoline-added methanol prepared by mixing gasoline up to 20% by volume is also applicable. Required to have. As substantial test conditions and standards, when the rubber product is immersed in methanol or gasoline-added methanol at 40 ° C. for 48 hours, the volume swelling degree is required to be 20% by volume or less, preferably 10% by volume or less. When the volume swelling degree is higher than this value, metals, sulfur, etc. in the rubber are easily extracted. The evaluation method is shown in JIS K6301 and is compared by measuring the tensile strength after elongation of alcohol and the reduction rate of elongation.

The chlorinated polyethylene used for the inner layer component of the hose of the present invention is a chlorinated polyethylene having an arbitrary chlorine content, crystallinity and molecular weight distribution.
It is preferable to use high-temperature chlorinated polyethylene of 00 or more near the melting point by an aqueous suspension method. When the weight average molecular weight of the raw material polyethylene is less than 50,000, it is insufficient in strength when used as a rubber hose, and it is usually preferable that the average molecular weight is large, but if it is too large, moldability, especially extrusion workability due to high viscosity, etc. Therefore, it is appropriate to use a raw material polyethylene having a weight average molecular weight of less than 300,000.

The chlorinated polyethylene used in the present invention is a substantially amorphous rubber, and powdered polyethylene, preferably high density polyethylene having a particle size of 20 to 300 mesh by a low pressure method, is suspended in an aqueous suspension at 100 to 140 ° C under pressure. Chlorine content of 20
Obtained by chlorinating to -50% by weight, preferably 25-45% by weight.

The hydrotalcites used in the present invention are hydrous double salt compounds of the following general formula [I] consisting of magnesium and aluminum.

Mg _1-x Al _x (OH) ₂ A _{x / 2} · mH ₂ O [I] (In the above formula, X is a real number in the range of 0 <X ≦ 0.5, and A is C
Indicates O ₃ or SO ₃ , and m indicates a real number. ) The amount of the above hydrotalcites used is 5 to 50 parts by weight, preferably 7 to 40 parts by weight based on 100 parts by weight of chlorinated polyethylene.
Parts by weight, more preferably 15 to 40 parts by weight. If the blending amount is less than 5 parts by weight, the metal deterioration resistance and reinforcing yarn deterioration resistance are not sufficiently improved, and if it is more than 50 parts by weight, the above properties are not so improved and the workability is deteriorated. Become.

In the present invention, hydrotalcites are presumed to act as a stabilizer for metallic materials and reinforcing yarns, so it is conceivable to directly treat metal surfaces or reinforcing yarns with hydrotalcites. Is a powder, and its handling is difficult and uniform treatment is not easy.

The method of adding hydrotalcites at the time of kneading a rubber composition is simple and industrially useful.

It is already known to use hydrotalcites as a cross-linking acid acceptor for chlorinated polyethylene, and there is no practical problem if it is not used in combination with other acid acceptors. When used in combination with the agent, the metal deterioration resistance and the yarn deterioration resistance may be further improved. In this case, the total amount of hydrotalcites and other acid acceptors is preferably 20 to 40 parts by weight with respect to 100 parts by weight of chlorinated polyethylene. Examples of such acid acceptors and stabilizers include magnesium oxide, magnesium hydroxide, calcium oxide, calcium hydroxide,
Calcium silicate, calcium carbonate, magnesium stearate, barium stearate, cadmium oxide, cadmium stearate, tin stearate, dibutyltin malate, lead monoxide, red lead, lead white, dibasic lead phosphite, dibasic Lead sulfate etc. are mentioned. Also 3-amino-1,2,4
Triazole derivative, polymethylene dicarboxylic acid-di-
It is also possible to add a metal deterioration preventing agent such as a hydrazine derivative.

For the crosslinking of the rubber composition, a thiourea derivative, a thiuram sulfide, or a trithiol triazine compound can be used. Furthermore, in order to fully exert the effect of the present invention,
Preference is given to using organic peroxides. Such organic peroxides include dicumyl peroxide and di-t-
Butyl peroxide, 1,3-bis (t-butylperoxyisopropyl) benzene, 4,4-di-t-butylperoxyvaleric acid-n-butyl ester, 1,1-di-t-butylperoxy- 3,3,5-trimethylcyclohexane,
There are α, α'-bis (t-butylperoxy) -p-diocypropylbenzene, 2,5-dimethyl-2,5-di- (t-butylperoxy) hexyne-3, and chlorinated polyethylene. It is used in the range of 1 to 15 parts by weight based on 100 parts by weight.

Other reactive mixtures such as diallyl phthalate, triallyl cyanurate, and triallyl isocyanurate are added to chlorinated polyethylene 100 for the purpose of promoting processability and crosslinking.
20 parts by weight or less can be added to the parts by weight.

As other compounding agents, various fillers, reinforcing agents, plasticizers, processing aids, antiaging agents, pigments, flame retardants, foaming agents, etc., which are commonly used in this technical field, may be arbitrarily compounded. You can

It is also possible to use chlorinated polyethylene as a rubber material by blending acrylonitrile-butadiene rubber, styrene-butadiene rubber, ethylene-propylene rubber or the like.

In order to produce the hose of the present invention, any means conventionally used in the field of rubber processing, for example, mixing rolls, Banbury mixers, various kneaders, and the like are blended, an inner layer is formed by an extruder, and then a reinforcing yarn is added. It is knitted to form a fiber layer, and then an extruder is used to cover it with an outer layer. After that, heat crosslinking is performed with a steam can, an air bath, a microwave, or the like. Crosslinking is usually at 120-200 ° C
It is performed by heating for 0.5 to 60 minutes.

In the hose of the present invention, the liquid contact portion of the inner layer may be a chlorinated polyethylene cross-linked composition containing the above hydrotalcites, and the outer layer may be made of any rubber. However, the chlorinated polyethylene cross-linked composition containing hydrotalcites has excellent weather resistance, impact resistance and other physical properties, and thus can be used as it is as an outer layer.

Furthermore, it is possible to obtain a hose having the effect of the present invention also with a hose having three or more layers, and for that purpose, in the layer which is in direct contact with the mouthpiece and the reinforcing yarn, the chlorinated polyethylene containing the above hydrotalcites is blended. It is necessary to use a crosslinking composition.

Examples and comparative examples will be shown below, but in the examples,% and parts are by weight.

Examples 1 to 9, Comparative Examples 1 to 5 Chlorine chlorinated to a chlorine content of 30 to 43% in an aqueous suspension at 125 to 130 ° C under pressure, using polyethylene powder by a low pressure method having a weight average molecular weight of 150,000 and a density of 0.947. Polyethylene rubber was used in each example and comparative example.

Each composition shown in Table 1 was mixed with a mixing roll at 60 ° C for 15 minutes.
Kneading for a minute and making into a sheet is put in a mold at 160 ℃, 100K
Each crosslinked product was obtained by heating at g / cm ² for 30 minutes. Table 2 shows the results.

Also, using the extruder with L / D = 15, diameter 20mm, each of the above sheets has a screw set temperature of 70 ° C and an extrusion set temperature of 90 °.
Extruded under conditions of ℃, screw rotation speed 30 rpm,
An inner layer rubber hose having an outer diameter of 11 mm and an inner diameter of 7 mm was obtained. After providing a fiber layer in which a reinforcing yarn made of polyvinyl alcohol fiber is woven in a net-like manner on the surface of the rubber hose molded in this way, an outer layer having the same composition as the inner layer is similarly provided on the surface to have a thickness of 1.5 mm. A rubber hose having a reinforcing fiber layer with an outer diameter of 14 mm and an inner diameter of 7 mm was molded. 2 this hose at 160 ℃
After cross-linking with a steam can for 0 minutes, cut to a length of 60 mm and cut the outer diameter to 1
After inserting about 30 mm into a 0 mm test metal tube and leaving it in a gear oven at 135 ° C for 360 hours, the contamination state of the metal tube surface and the presence or absence of cracks on the metal contact surface of the rubber tube were examined. The material of the metal pipe used for the test is a steel pipe subjected to nickel plating treatment and a steel pipe subjected to zinc chromium plating. The evaluation criteria for the contamination state of the metal tube surface are as follows.

◎ No change.

○ The surface is slightly discolored.

△ Slightly corroded.

× Very corroded.

 The cracks on the rubber surface are as follows.

○ No crack.

× There is a crack.

In addition, the deterioration state of the reinforcing yarn in the portion in contact with the metal surface was examined. The initial thread color is white, and the evaluation criteria are as follows.

○ No change.

△ The yarn is slightly discolored to brown.

× The color of the reinforcing yarn has changed to brown, and the reinforcing yarn has shrunk.

From Tables 1 and 2, it is apparent that Comparative Examples 3 to 5 containing no hydrotalcites have lower metal deterioration resistance and reinforcing yarn deterioration resistance than the Examples. In addition, Examples 4, 5 and 6 in which magnesium oxide, hydroxide and calcium hydroxide are used in combination are considerably superior in metal deterioration resistance to the case where these are not used. Further, Comparative Examples 1 and 2 with a small content of hydrotalcites have lower metal deterioration resistance than each Example, and the Comparative Examples generally have a large volume expansion purity after immersion in methanol / fuel oil C. Is recognized.

(Effect of the invention) The rubber hose of the present invention has a cross-linked product obtained by cross-linking chlorinated polyethylene with hydrotalcites in the inner layer, so that not only methanol resistance but also metal deterioration resistance and fiber deterioration resistance are excellent. , Corrosion of metal parts such as joints and caps and damage of fiber reinforced layer are less likely to occur, and the life of the hose can be extended. Further, since it has excellent properties such as weather resistance and impact resistance required as a rubber hose, it can be sufficiently used not only as an inner layer but also as an outer layer of the rubber hose.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kaiho Akihiko 330 Naganumacho, Chiba City, Chiba Prefecture Kinugawa Rubber Co., Ltd.

Claims (2)

[Claims] 1. A plurality of layers of crosslinked rubber are formed via a fibrous reinforcing layer, and the crosslinked rubber of at least the inner layer is 5 to 50 parts by weight of hydrotalcites based on 100 parts by weight of chlorinated polyethylene.
A methanol-resistant rubber hose, which is a crosslinked product of a rubber composition containing parts by weight and a crosslinking agent. 2. The rubber hose according to claim 1, wherein the fibrous reinforcing layer is a braided layer of polyvinyl alcohol fibers or polyamide fibers.