JPH0631659B2 - Silicone rubber hose - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a silicone rubber hose, and more particularly to a silicone rubber hose attached to a mandrel so that it can be vulcanized.

(Prior Art) In recent years, in the field of rubber hoses for automobiles, it has been desired to develop a rubber hose having more heat resistance and cold resistance than ever before.

Currently, EP (D) M is mainly used as a rubber material in water-based hoses such as radiator hoses and heater hoses.
[Ethylene-propylene (diene) rubber] is generally used. In addition, hydrin rubber, acrylic rubber and the like are used for air hoses and the like which are required to have heat resistance. The high temperature limit of the operating temperature of these rubber materials is EPD.
M and hydrin rubber are about 150 ° C, and acrylic rubber is about 170 ° C. At such temperature limits, it may not be possible to withstand the heat-resistant required properties that are becoming severer year by year due to engine performance improvement and engine room space reduction. .

Also, regarding the use limit at low temperature, EP (D) M hose is -40 ° C to -60 ° C, and hydrin rubber and acrylic rubber are about -20 ° C to -30 ° C depending on the rubber compounding technique. The cold resistance requirements such as sealability have almost reached the limit.

Therefore, development of a silicon rubber hose having rubber characteristics in a very wide temperature range of -90 ° C to 300 ° C is expected. If such a silicone rubber hose is obtained as an automobile hose, it prevents the deterioration of functionality such as sealability, vibration absorption, or rubber destruction due to rubber deterioration due to high temperature, and prevents liquid leakage due to rubber curing in cold regions. It can be lost.

Conventionally, many products using silicone rubber materials are molded by compression molding, injection molding, transfer molding, etc., and in some areas, in the fields of medical care and food, taking advantage of the hygienic safety of silicone rubber. Extrusion tubes are used.

However, silicone rubber has weaker raw rubber strength than the above-mentioned generally used organic rubbers, and extrusion-molded hoses (tubes) have problems such as shape retention and being easily damaged by external force, making storage difficult. Therefore, it cannot be inserted into the mandrel for vulcanization, and it is common to vulcanize with hot air immediately after extrusion. Therefore, the silicone rubber hose (tube) currently used is a single layer of silicone rubber and is usually a straight pipe. According to Japanese Examined Patent Publication No. 1-36779, a method of fitting the extruded hose into an outer mold and vulcanizing it in order to manufacture a bent hose of silicone rubber has been proposed, but the manufacture of the mold is troublesome, Can't get financially.

On the other hand, radiator hoses, heater hoses, hoses that require a certain level of pressure resistance, such as air hoses, often require a reinforcing layer such as fibers, but as mentioned above, the technique of making hoses from silicone rubber is Since it has not been established, radiator hoses made of silicone rubber materials have not been put to practical use in general.

Conventionally, a blade method, a spiral method, and a knitting method are generally well known as methods for producing a medium-reinforced hose, but these methods are one in which an inner surface rubber is extruded into a hose shape by an extruder and then a die is used. Then, a reinforcing yarn is knitted on the inner rubber hose to form a reinforcing layer, and an outer rubber is further covered on the inner hose to form a hose having a three-layer structure or a multi-layer structure of four or more layers.

However, the above method is possible because the rubber material is a general-purpose rubber as described above and has a shape-retaining function even in an unvulcanized state after extrusion. Since the material is deformed by a slight external force, the above method cannot be adopted. That is, the tightening force when braiding the reinforcing thread causes the thread to bite into the silicone rubber, resulting in uneven thickness and difficulty in maintaining the shape of the rubber inside the hose. In addition, even if the extruded inner rubber layer is formed, or even if the reinforcing layer can be braided thereto, it is easily deformed in the previous step of covering with the outer rubber, which causes an increase in the defective rate. Further, even when the outer surface rubber is covered, since it does not have a shape retaining function, it is difficult to press the inner surface rubber and the outer surface rubber by applying sufficient pressure.

Various methods can be considered for solving them, but it is considered difficult to put them into practical use for the reasons described below.

For example, when it is attempted to solidify the extruded inner surface rubber with liquid nitrogen or the like, the silicone rubber may not be sufficiently solidified, water droplets may adhere, and the extrusion line may become long.

Further, in the case where the mandrel is passed through the inner rubber, the problem that the reinforcing thread is caught in the inner rubber cannot be solved, and a problem such as mold release between the inner rubber and the mandrel newly occurs.
In other words, due to the low plasticity of the silicone rubber, it is difficult to remove it from the mandrel in the unvulcanized state, and molding vulcanization of various bent shapes cannot be performed.

Further, in the method of vulcanizing the inner rubber immediately after extrusion and braiding a reinforcing thread on the inner rubber to cover the outer rubber, the adhesion between the inner rubber and the outer rubber may not be sufficient.

(Problem to be Solved by the Invention) In view of the above circumstances, an object of the present invention is to provide a silicone rubber hose which has a shape retaining function even in an unvulcanized state and can be vulcanized by using a mandrel.

(Means for Solving the Problem) According to the present invention, the above object is to provide a rubber hose in which the rubber layer is made of a silicone rubber material with a reinforcing layer in which fibers or the like are braided between an inner rubber layer and an outer rubber layer. When the inner rubber layer and the outer rubber layer are extruded, the reinforcing layer is extruded at the same time, and the reinforcing layer is a strip and is rounded so as to surround the inner rubber layer along the axial direction of the hose, The edges are overlapped with each other, and the inner rubber layer and the outer rubber layer are integrated by the pressure during extrusion through the mesh of the reinforcing layer, and the reinforcing layer is fixed in the rubber hose by vulcanization. Can be achieved with a silicone rubber hose.

In order to extrude the inner rubber layer and the outer rubber layer and at the same time to extrude the reinforcing layer to the middle portion thereof, for example, an extrusion head as shown in FIG. 1 can be used. In the figure, an extrusion head main body 1 has a supply port 2 of a silicone rubber material supplied in a molten state by an extruder, and the supply port 2 has an inner side which substantially contributes to formation of an inner rubber layer 3. The flow path 4 and the outer flow path 6 that substantially contributes to the formation of the outer rubber layer 5 are open. A die 8 having an annular extrusion opening 7 is provided at the tip of the head body 1, and the inner flow passage 4 and the outer flow passage 6 communicate with each other at an inner inlet portion 9 of the extrusion opening. The silicone rubber material that has passed through the inner flow path 4 and the outer flow path 6 becomes integrated at the inlet portion 9 and is extruded in the form of a hose (tube) from the outlet side of the extrusion opening 7.

A reinforcing cloth supply port 11 which contributes to the formation of the reinforcing layer 10 is also opened at this inward entrance of the extrusion opening. Reinforcing cloth 1
Although 2 is made of a glass fiber material as a measure against high temperature, it may be made of polyester, nylon, rayon or the like, and is woven or knitted to form a belt-like body having an appropriate mesh. When the reinforcing cloth is subjected to a texture treatment with an epoxy resin or the like to have a certain degree of rigidity, it is further useful for maintaining the shape of the rubber hose in an unvulcanized state. However, if it is too hard, it will be difficult to maintain the fibers in the middle part of the hose. When the dry adhesion treatment is performed with the silicon-based treatment liquid, the adhesion with the rubber layer can be improved in the subsequent step.

The reinforcing cloth is put into the head main body 1 through the insertion opening 13 and fed to the reinforcing cloth supply opening 11 through the guide means 14. The guide means is formed so as to round the reinforcing cloth in a circumferential shape along the axial direction, but other suitable structures can be adopted. At this time, the edges of the reinforcing cloth need to be wound so as to sufficiently overlap each other.

Since the silicone rubber material supplied from the supply port 2 of the extrusion head body 1 has a lower plasticity than general-purpose rubber,
Extrusion is easy, but maintaining a stable process is difficult. That is, when the plasticity is lower than necessary, adhesion occurs, the extruded hose surface is easily damaged, rubber remains in the extruder, and the number of steps such as cleaning increases.

Also, if the plasticity is too high, the surface of the extruded hose will become rough, reducing the commercial value, leaving traces of the spider flange supporting the mandrel of the extruder in the direction of the hose and causing cracks when stress is applied. Will also be. Moreover, plasticity tends to increase with time and must therefore be controlled by accelerated testing. It is important to control the linear shrinkage of the silicone rubber material when it is not vulcanized or vulcanized. That is, rubber is shrunk in the extruding direction after extruding, but, for example, glass fiber shrinks less than that, so that the fiber may protrude from the end of the hose. Further, such a phenomenon is likely to occur even during vulcanization.

It was confirmed from the results of the experiment that the plasticity satisfying the above-mentioned conditions is 320 to 380 after 10 minutes by Williams, and the accelerated plasticity is 500 or less after Williams at 40 ° C. for 72 hours. Was given.

It is desirable that an extruder (not shown) connected to the supply port 2 of the extrusion head is equipped with a forced cooling device inside the extruder body and the screw to suppress the heat generation in order to prevent the silicone rubber from softening due to heat generation. In addition, it is better that the screw has a single groove and the pitch becomes shorter toward the tip and the shaft diameter be constant, and the spider flange that supports the mandrel in the extruder may cause cracks, so its shape is It needs to be devised.

Regarding the supply of the silicone rubber material to the extruder hopper, when a band-shaped endless one is used, since the silicone rubber has a weak strength, it is preferable that the cross-sectional shape is circular or elliptical so that the material does not run out. Further, talc or a silica-based filler is sufficient as a release agent used for release.

According to the method and apparatus of the present invention as described above, the reinforcing cloth 12 is rolled so as to surround the inner rubber layer 3, the edges are overlapped, and the inner rubber layer is passed through the mesh of the reinforcing layer 10. 3 and the outer rubber layer 5 are integrated by the pressure at the time of extrusion (3rd
(Fig.) After extrusion, a silicone rubber hose having a shape-retaining function even in an unvulcanized state can be obtained, and this can be inserted into a mandrel such as a bending mold and vulcanized to obtain a desired product.

In the above description, the rubber layer of the hose is composed of two layers, the inner rubber layer and the outer rubber layer, but it may be formed in a plurality of rubber layers.

(Example 1) One layer of glass fiber cloth made of a silicone rubber material having a Williams plasticity of 320 to 380 was extruded into the following inner diameter and outer diameter by using the above-mentioned apparatus as a reinforcing layer, and then hot air vulcanization at room temperature was carried out to hydrate water. A hose bent tube was formed.

As can be seen from the above table, the burst pressure is
The strength was not inferior to that of a PDM hose, and it was excellent in heat resistance and cold resistance.

Example 2 The following bent tube of an air hose was manufactured under the same conditions as in Example 1 above.

In each case, an air hose excellent in heat resistance and cold resistance was obtained.

(Effect of the present invention) The present invention is configured as described above, and when a reinforcing cloth in which fibers or the like are braided in advance is used as the reinforcing layer, and when the reinforcing cloth is extruded simultaneously with the inner rubber layer and the outer rubber layer, Since it is provided so as to be rolled around the inner rubber layer and surround the inner rubber layer, it is possible to prevent the reinforcing cloth from biting into the inner rubber layer, and further, the reinforcing cloth is appropriately treated by resin treatment. Since the silicone rubber has a rigidity of 320 to 380 (Williams plasticity), it has a sufficient shape-retaining function even in the unvulcanized silicone rubber hose extruded from the die, and the surface is simple. There is no risk of being damaged or deformed, and there is no rough surface on the hose surface, nor is there a trace of the spider flange that causes cracking.
Therefore, even if it is forcibly inserted into a mandrel having various bent shapes, it can be securely inserted without damaging or deforming it, and then using a vulcanizing can or the like that is generally used, An accurate silicon rubber hose can be obtained economically.

[Brief description of drawings]

Drawing shows an embodiment of the present invention, Fig. 1 is a sectional view showing an example of an extrusion head, and Fig. 2 is a perspective view showing the structure of a hose.
FIG. 3 is a partially enlarged sectional view of the hose. 1 ... Extrusion head body, 3 ... Inner rubber layer 5 ... Outer rubber layer, 10 ... Reinforcing layer 12 ... Reinforcing cloth

Claims (2)

[Claims] 1. A rubber hose made of a silicone rubber material, which has a reinforcing layer in which fibers or the like are braided between the inner rubber layer and the outer rubber layer, and when the inner rubber layer and the outer rubber layer are extruded, The reinforcing layer is extruded at the same time, and the reinforcing layer is formed into a strip shape and is rolled up so as to surround the inner rubber layer along the axial direction of the hose, and the edges thereof are overlapped with each other and pass through the mesh of the inner layer to form the inner rubber layer. The outer rubber layer and the outer rubber layer are integrated by the pressure during extrusion, and the reinforcing layer is fixed in the rubber hose by vulcanization. The reinforcing layer is formed of a reinforcing cloth having an appropriate rigidity by a resin treatment. A silicone rubber hose whose material has a plasticity (Williams plasticity) of 320 to 380. 2. The silicone rubber hose according to claim 1, wherein the reinforcing cloth is a glass fiber cloth that is texture-treated with an epoxy resin.