Method for manufacturing brake hose

Abstract

To suppress deterioration of adhesiveness between a reinforcement layer and a rubber layer of a brake hose.SOLUTION: A method for manufacturing a brake hose that includes an inner surface rubber layer, a reinforcement layer containing polyethylene terephthalate and an outer surface rubber layer disposed from the inner side in this order includes: a first vulcanization process of performing steam vulcanization of a laminate having an unvulcanized inner surface rubber layer, a reinforcement layer containing polyethylene terephthalate and an unvulcanized outer surface rubber layer from the inner side in this order at 115°C or higher and 140°C or lower and 0.07 MPaG or more and 0.26 MPaG or less of gauge pressure to convert the inner surface rubber layer and the outer surface rubber layer into a half-vulcanized state; and a second vulcanization process of vulcanizing the laminate at 180°C or higher and 190°C or lower by using hot air or warm air following the first vulcanization process to completely vulcanize the inner surface rubber layer and the outer surface rubber layer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a brake hose. [Background technology]

[0002] Many vehicles, such as automobiles, employ hydraulic brake systems that apply pressure to brake fluid to activate the brakes. Hydraulic pressure is generally transmitted to the brakes via a brake hose. Patent Document 1 discloses a hydraulic brake hose having, in this order from the inside, an inner rubber layer, a first reinforcing thread layer, a second reinforcing thread layer, and an outer rubber layer. Patent Document 1 also discloses a brake hose in which the inner rubber layer is formed from an ethylene-propylene-diene rubber (EPDM) composition, the first reinforcing thread layer and the second reinforcing thread layer are formed from reinforcing threads made of polyvinyl alcohol (hereinafter referred to as PVA), and the outer rubber layer is formed from an ethylene-propylene-diene rubber (EPDM) composition. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6851619 Summary of the Invention [Problem to be solved by the invention]

[0004] When each layer of a brake hose expands, hydraulic pressure is not transmitted to the brakes quickly, resulting in reduced brake response. Brake hoses also tend to expand more at high temperatures. Therefore, it is desirable to improve the low expansion properties of each layer of a brake hose at high temperatures.

[0005] The present inventors have discovered that, in the brake hose disclosed in Patent Document 1, low expansion at high temperatures can be improved by using reinforcing yarns containing polyethylene terephthalate (PET) instead of PVA for the first and second reinforcing yarn layers. However, they have also found that when reinforcing yarns containing PET are used, the adhesion between the reinforcing yarn layers (first reinforcing yarn layer, second reinforcing yarn layer) and the adjacent rubber layers (inner rubber layer, outer rubber layer) is poorer than when the reinforcing yarns made of PVA as disclosed in Patent Document 1 are used. Poor adhesion between the reinforcing yarn layer and the adjacent rubber layer tends to degrade hose performance. In particular, the rubber layer and the reinforcing yarn layer are more likely to become misaligned when the hose is bent. Misalignment between the rubber layer and the reinforcing yarn layer can easily cause cracks to form in the reinforcing yarn layer, potentially reducing durability.

[0006] In the brake hose disclosed in Patent Document 1, the rubber layers (inner rubber layer and outer rubber layer) are vulcanized during the manufacturing process. When the rubber layer is vulcanized, the rubber layer and the adjacent reinforcing thread layer are bonded together. Vulcanization methods include immersing the hose in a heat medium such as oil to vulcanize the rubber layer, and vulcanizing the rubber layer with steam. In these methods, the hose is coated with resin before vulcanization, and the resin-coated hose is vulcanized, and the resin is removed from the hose after vulcanization, with the aim of preventing damage to the outer rubber layer during vulcanization and ensuring close contact between the layers. However, in recent years, there has been a demand for vulcanization without resin coating, due to considerations such as disposal of the resin after use.

[0007] The present inventors fabricated a brake hose disclosed in Patent Document 1 in which the first and second reinforcing thread layers were made of reinforcing threads containing polyethylene terephthalate (PET), which improves low expansion at high temperatures. The hose was then vulcanized without being coated with resin. As a result, the resulting brake hose had poor adhesion between the reinforcing thread layers (first reinforcing thread layer, second reinforcing thread layer) and the adjacent rubber layers (inner rubber layer, outer rubber layer). While the cause of this is unclear, it is speculated that the use of PET, which has low adhesiveness, as the reinforcing threads and the vulcanization without being coated with resin allowed a heat transfer medium or steam to penetrate from the outermost layer to the interior during vulcanization, resulting in poor adhesion.

[0008] The object of the present invention is to provide a method for manufacturing a brake hose in which the reinforcing layer uses reinforcing yarn containing polyethylene terephthalate (PET), which has low adhesion to the rubber layer, and further in which the adhesion between the rubber layer and the reinforcing layer is good even when the hose is vulcanized without being coated with resin. [Means for solving the problem]

[0009] The method for manufacturing a brake hose disclosed in this specification is a method for manufacturing a brake hose having, in order from the inside out, an inner rubber layer, a reinforcing layer containing polyethylene terephthalate, and an outer rubber layer, and includes a first vulcanization step in which a laminate having, in order from the inside out, an unvulcanized inner rubber layer, a reinforcing layer containing polyethylene terephthalate, and an unvulcanized outer rubber layer is steam vulcanized at 115°C or higher and 140°C or lower and a gauge pressure of 0.07 MPaG or higher and 0.26 MPaG or lower, thereby semi-vulcanizing the inner rubber layer and the outer rubber layer; and a second vulcanization step in which, after the first vulcanization step, the laminate is vulcanized at 180°C or higher and 190°C or lower using hot or warm air, thereby fully vulcanizing the inner rubber layer and the outer rubber layer.

[0010] The inner rubber layer and the outer rubber layer may each contain an ethylene propylene rubber.

[0011] Furthermore, the above manufacturing method may further include a mandrel being present inside the laminate before vulcanizing the laminate in the first vulcanization step, steam vulcanizing the laminate with the mandrel present in the laminate in the first vulcanization step, vulcanizing the laminate with the mandrel present in the laminate in the second vulcanization step, and removing the mandrel from the laminate after the second vulcanization step. [Effects of the Invention]

[0012] It is possible to provide a method for manufacturing a brake hose in which reinforcing yarn containing polyethylene terephthalate (PET), which has low adhesion to the rubber layer, is used for the reinforcing layer of the brake hose, and further, even when the hose is vulcanized without being coated with resin, the adhesion between the rubber layer and the reinforcing layer is good. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 2 is a partially cutaway perspective view of an example of a brake hose. [Figure 2] FIG. 1 is a perspective view of an example of a vulcanizing device. [Figure 3] FIG. 10 is a diagram showing the relationship between adhesive strength and vulcanization pressure when the first vulcanization step is performed under a variety of conditions. [Figure 4] FIG. 10 is a diagram showing the relationship between the 100% modulus of the outer rubber layer and the vulcanization temperature when the second vulcanization step is carried out under a variety of conditions. [Figure 5] FIG. 10 is a diagram showing the relationship between the 100% modulus of the inner rubber layer and the vulcanization temperature when the second vulcanization step is performed under a plurality of conditions. DETAILED DESCRIPTION OF THE INVENTION

[0014] Preferred embodiments of the present invention will be described below. Note that the embodiments described below are examples of specific embodiments of the present invention and are not intended to limit the present invention.

[0015] The method according to this embodiment is a method for manufacturing a brake hose. The brake hose has, from the inside out, an inner rubber layer, a reinforcing layer containing polyethylene terephthalate, and an outer rubber layer. Figure 1 shows an example of a brake hose.

[0016] The brake hose 100 shown in Fig. 1 has, in this order from the inside, an inner rubber layer 1, a first reinforcing layer (reinforcing layer) 2, an intermediate rubber layer 3, a second reinforcing layer (reinforcing layer) 4, and an outer rubber layer 5. These components are cylindrical. The brake hose 100 is used, for example, as a brake hose for a vehicle.

[0017] The inner rubber layer 1 is the innermost layer of the brake hose 100. The inner rubber layer 1 contains an ethylene propylene-based rubber. Examples of ethylene propylene-based rubber include ethylene propylene rubber (EPM) and ethylene propylene diene rubber (EPDM). The inner rubber layer 1 may contain one type of ethylene propylene-based rubber, or may contain two or more types of ethylene propylene-based rubber. The inner rubber layer 1 may also contain a material other than ethylene propylene-based rubber. The inner rubber layer 1 is obtained, for example, by extrusion molding.

[0018] The first reinforcing layer 2 is formed from reinforcing yarns containing polyethylene terephthalate (PET). The reinforcing yarns may contain materials other than PET. Examples of materials other than PET include polyvinyl alcohol (PVA) fibers, polyester fibers, polyamide fibers, aramid fibers, glass fibers, and metal fibers. The first reinforcing layer 2 is formed by winding reinforcing yarns around the inner rubber layer 1 and braiding them. The braiding method is not particularly limited, and examples include spiral braiding and braid braiding.

[0019] The intermediate rubber layer 3 is a layer between the first reinforcing layer 2 and the second reinforcing layer 4. The intermediate rubber layer 3 contains an ethylene propylene-based rubber, a butyl-based rubber, or a combination thereof. Examples of the ethylene propylene-based rubber are the same as those described for the inner rubber layer 1. The intermediate rubber layer 3 may contain one type of ethylene propylene-based rubber, or two or more types of ethylene propylene-based rubber. Examples of butyl-based rubber include butyl rubber (IIR) and halogenated butyl rubber (Br-IIR, Cl-IIR). The intermediate rubber layer 3 may contain one type of butyl-based rubber, or two or more types of butyl-based rubber. The intermediate rubber layer 3 may contain a material other than ethylene propylene-based rubber and butyl-based rubber. The intermediate rubber layer 3 is obtained, for example, by coating using extrusion molding or the like.

[0020] The second reinforcing layer 4 is formed from reinforcing yarns containing polyethylene terephthalate (PET). The reinforcing yarns may contain materials other than PET. Examples of materials other than PET include polyvinyl alcohol (PVA) fibers, polyester fibers, polyamide fibers, aramid fibers, glass fibers, and metal fibers. The second reinforcing layer 4 is formed by winding reinforcing yarns around the intermediate rubber layer 3 and braiding them. The braiding method is not particularly limited, and examples include spiral braiding and braid braiding.

[0021] The outer rubber layer 5 is the outermost layer of the brake hose 100. The outer rubber layer 5 contains an ethylene propylene-based rubber. Examples of the ethylene propylene-based rubber are the same as those described for the inner rubber layer 1. The inner rubber layer 1 may contain one type of ethylene propylene-based rubber, or two or more types of ethylene propylene-based rubber. The outer rubber layer 5 may contain a material other than ethylene propylene-based rubber. For example, the outer rubber layer 5 may contain one or more of chloroprene rubber (CR), isoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), halogenated butyl rubber, and acrylonitrile-butadiene copolymer rubber (NBR) in addition to ethylene propylene-based rubber. The outer rubber layer 5 is obtained, for example, by extrusion molding.

[0022] 1 has an intermediate rubber layer 3 between the first reinforcing layer 2 and the second reinforcing layer 4, but the brake hose may also have no intermediate rubber layer 3. Furthermore, when no intermediate rubber layer 3 is present, two reinforcing layers (first reinforcing layer 2 and second reinforcing layer 4) may be present between the inner rubber layer 1 and the outer rubber layer 5, or only one reinforcing layer may be present.

[0023] Next, a method for manufacturing a brake hose will be described, using the reference numerals of the brake hose 100 shown in FIG.

[0024] Figure 2 shows an example of equipment used to manufacture brake hoses.

[0025] The first vulcanizing device 20 shown in Figure 2 is a device for steam vulcanizing an object. The first vulcanizing device 20 has a first vulcanizing pipe 21, a second vulcanizing pipe 22, and a direction switching device 23. The first vulcanizing pipe 21 and the second vulcanizing pipe 22 are long in one direction. One end of the first vulcanizing pipe 21 and one end of the second vulcanizing pipe 22 are connected to the direction switching device 23. The direction switching device 23 is a device that changes the traveling direction of the object so that the object that has passed through the first vulcanizing pipe 21 enters the second vulcanizing pipe 22.

[0026] The inside of the first vulcanizing pipe 21 and the inside of the second vulcanizing pipe 22 are filled with water vapor. Due to the water vapor, the inside of the first vulcanizing pipe 21 and the inside of the second vulcanizing pipe 22 are at a temperature of 115°C or higher and 140°C or lower, and the gauge pressure is 0.07 MPaG or higher and 0.26 MPaG or lower. The inside of the first vulcanizing pipe 21 and the inside of the second vulcanizing pipe 22 are more preferably at a temperature of 130°C or higher and 140°C or lower, and the gauge pressure is even more preferably at a temperature of 0.17 MPaG or higher and 0.26 MPaG or lower. The first vulcanizing pipe 21 and the second vulcanizing pipe 22 steam vulcanize the object.

[0027] The inside of the direction switching device 23 may also be at the same temperature and pressure due to water vapor as the inside of the first vulcanizing pipe 21 and the inside of the second vulcanizing pipe 22. For example, the inside of the direction switching device 23 may be at 115°C or higher and 140°C or lower due to water vapor, and the gauge pressure may be at 0.07 MPaG or higher and 0.26 MPaG or lower.

[0028] The second vulcanizing device 30 shown in Fig. 2 is a device for vulcanizing an object using hot or warm air. The interior of the second vulcanizing device 30 is heated to 180°C or higher and 190°C or lower by the hot or warm air. It is more preferable that the interior of the second vulcanizing device 30 be heated to 183°C or higher and 188°C or lower. The second vulcanizing device 30 is, for example, an oven.

[0029] A method for manufacturing the brake hose 100 shown in FIG. 1 using the first vulcanizing device 20 and the second vulcanizing device 30 shown in FIG. 2 will be described below.

[0030] The laminate 110 shown in FIG. 2 has, in this order from the inside, an unvulcanized inner rubber layer 1, a first reinforcing layer 2, an unvulcanized middle rubber layer 3, a second reinforcing layer 4, and an unvulcanized outer rubber layer 5. A mandrel 10 is present inside the laminate 110. The mandrel 10 is used when producing the laminate 110. For example, the unvulcanized inner rubber layer 1 is extruded onto the outer surface of the mandrel 10, and a reinforcing thread is braided onto the outer surface of the inner rubber layer 1 to produce the first reinforcing layer 2. The unvulcanized middle rubber layer 3 is then coated onto the outer surface of the first reinforcing layer 2. The second reinforcing layer 4 is then braided onto the outer surface of the middle rubber layer 3 to produce the second reinforcing layer 4. The unvulcanized outer rubber layer 5 is then extruded onto the outer surface of the first reinforcing layer 2. The laminate 110 is not coated with a resin or the like.

[0031] With the mandrel 10 present on the laminate 110, the laminate 110 is placed in the first vulcanizing pipe 21. In conventional vulcanization methods, the laminate 110 is coated with resin and the resin-coated laminate 110 is placed in the first vulcanizing pipe 21, but in this embodiment, the laminate 110 is not coated with resin before vulcanization. The laminate 110 that is not coated with resin is placed in the first vulcanizing pipe 21.

[0032] While the laminate 110 passes through the first vulcanizing pipe 21, the inner rubber layer 1, the middle rubber layer 3, and the outer rubber layer 5 are vulcanized. After passing through the first vulcanizing pipe 21, the laminate 110 enters the direction changing device 23, changes its direction, and enters the second vulcanizing pipe 22. When the inside of the direction changing device 23 is at the same temperature and pressure as the inside of the first vulcanizing pipe 21 and the inside of the second vulcanizing pipe 22 due to water vapor, the laminate 110 is also vulcanized in the direction changing device 23. Thereafter, the laminate 110 passes through the second vulcanizing pipe 22. While the laminate 110 passes through the second vulcanizing pipe 22, the inner rubber layer 1, the middle rubber layer 3, and the outer rubber layer 5 are vulcanized. The lengths of the first vulcanizing pipe 21 and the second vulcanizing pipe 22 are, for example, 140 to 150 m. The laminate 110 advances through the pipe at a speed of, for example, 15 to 20 m / min. The laminate 110 is vulcanized in the first vulcanizing device 20 for, for example, 7 to 10 minutes.

[0033] The laminate 110 emerging from the second vulcanizing pipe 22 has the inner rubber layer 1, intermediate rubber layer 3, and outer rubber layer 5 in a semi-vulcanized state. "The inner rubber layer 1, intermediate rubber layer 3, and outer rubber layer 5 are in a semi-vulcanized state" means that the rubber contained in the inner rubber layer 1, the rubber contained in the intermediate rubber layer 3, and the rubber contained in the outer rubber layer 5 are in a semi-vulcanized state. "The rubber is in a semi-vulcanized state" means that the rubber is not in an unvulcanized state, but is not completely vulcanized, and is somewhere between an unvulcanized state and a completely vulcanized state.

[0034] In this way, the first vulcanizing device 20 brings the laminate 110 into a semi-vulcanized state (first vulcanization step).

[0035] Next, the semi-vulcanized laminate 110 is fully vulcanized in the second vulcanizer 30 (second vulcanization step). By fully vulcanizing the inner rubber layer 1, the intermediate rubber layer 3, and the outer rubber layer 5, the laminate 110 becomes the brake hose 100. Here, "fully vulcanizing the inner rubber layer 1, the intermediate rubber layer 3, and the outer rubber layer 5" means that the rubber contained in the inner rubber layer 1, the rubber contained in the intermediate rubber layer 3, and the rubber contained in the outer rubber layer 5 are fully vulcanized. In the second vulcanizer 30, the laminate 110 is vulcanized for, for example, 15 to 21 minutes.

[0036] After the inner rubber layer 1, the intermediate rubber layer 3, and the outer rubber layer 5 are completely vulcanized, the brake hose 100 is removed from the second vulcanizer 30, and the mandrel 10 is removed from the brake hose 100 (mandrel removal step).

[0037] The above method provides the following effects. The first reinforcing layer 2 and second reinforcing layer 4 shown in FIG. 1 use reinforcing yarns containing polyethylene terephthalate (PET), which has low adhesion to the inner rubber layer 1, intermediate rubber layer 3, and outer rubber layer 5. Furthermore, in the above method, the laminate 110 is vulcanized without being coated with resin. Despite the fact that conditions exist that tend to reduce the adhesion between these rubber layers (inner rubber layer 1, intermediate rubber layer 3, outer rubber layer 5) and the reinforcing layers (first reinforcing layer 2, second reinforcing layer 4), by subjecting the laminate 110 to two-stage vulcanization under the above vulcanization conditions, it is possible to produce a brake hose 100 that has good adhesion between the rubber layers (inner rubber layer 1, intermediate rubber layer 3, outer rubber layer 5) and the reinforcing layers (first reinforcing layer 2, second reinforcing layer 4).

[0038] When vulcanizing fluororubber, silicone rubber, or other rubbers that are difficult to vulcanize, two vulcanization processes, i.e., a primary vulcanization and a secondary vulcanization, are required. However, for rubbers other than these, it is common to vulcanize the rubber in a single vulcanization process, and two vulcanization processes are not performed. This is because performing two vulcanization processes on such rubbers may cause variations in the hose temperature, resulting in an unstable vulcanized state. In this embodiment, the inner rubber layer 1, the intermediate rubber layer 3, and the outer rubber layer 5 do not use rubbers that require two vulcanization processes, but rather use rubber layers that are normally vulcanized in a single vulcanization process. For example, ethylene propylene rubber is used for the rubber layers. In such cases, it has been found that by performing two-stage vulcanization of the laminate 110 under the above vulcanization conditions, the rubber layers (inner rubber layer 1, intermediate rubber layer 3, and outer rubber layer 5) can be vulcanized to a state equivalent to that achieved by performing a normal single vulcanization process.

[0039] In the above embodiment, the laminate 110 is vulcanized with the mandrel 10 present on the laminate 110 as shown in FIG. 2. This allows the hose shape to be maintained even during vulcanization. In particular, the first vulcanizing device 20 is prone to losing its shape due to high pressure. The laminate 110 is also prone to losing its shape due to the influence of water vapor, hot air, or warm air. However, the mandrel 10 allows the laminate 110 to be vulcanized while maintaining the hose shape, thereby producing a brake hose 100 in a hose shape.

[0040] On the other hand, the presence of the mandrel 10 inside the inner rubber layer 1 makes it difficult to vulcanize the inner rubber layer 1 and the intermediate rubber layer 3. However, in this embodiment, rubber that requires two vulcanization processes is not used, so even if the laminate 110 is vulcanized with the mandrel 10 present, all of the rubber layers, including the inner rubber layer 1, intermediate rubber layer 3, and outer rubber layer 5, can be completely vulcanized, and a brake hose 100 can be obtained that maintains its hose shape.

[0041] Next, the experiment that led to the above findings will be described.

[0042] (Experiment 1) In the brake hose manufacturing method described in the above embodiment, brake hoses were manufactured by changing the temperature and pressure conditions in the first vulcanization step. Table 1 shows the temperature and pressure conditions in the first vulcanization step. The conditions shown in Table 1 are conditions under which all rubber layers were semi-vulcanized in the first vulcanization step. In the first vulcanization step, two vulcanization pipes of 70 to 75 m in length were used, and the laminate progressed at a speed of 15 to 20 m / min inside the vulcanization pipes. In the second vulcanization step, the temperature inside the device was raised to 180°C to 190°C using hot air, and the laminate was vulcanized for 15 to 21 minutes.

[0043] In this experiment, the first and second vulcanization steps were carried out with the mandrel present in the laminate. After the second vulcanization step, the mandrel was removed from the brake hose.

[0044] [Table 1]

[0045] To examine the adhesion between the rubber layer and the reinforcing layer, the outer rubber layer of the manufactured brake hose was peeled off. The force required to peel off 1 cm of the outer rubber layer was defined as the adhesive strength [N / cm]. Experience has shown that adhesive strength of 35 N / cm or greater prevents the rubber layer and reinforcing layer from slipping apart, even when the hose is bent. Therefore, adhesive strength of 35 N / cm or greater was determined to be high, and is indicated by a "Good" in Table 2. Furthermore, adhesive strengths of less than 35 N / cm but greater than 30 N / cm also prevent the rubber layer and reinforcing layer from slipping apart, and are indicated by a "Good" in Table 1. Adhesive strengths of less than 30 N / cm are indicated by an "Poor" in Table 1. The evaluation results are shown in Table 1. Figure 3 also shows the relationship between adhesive strength and vulcanization pressure. The vulcanization pressure shown in Figure 3 is the vulcanization pressure used in the first vulcanization process.

[0046] From Table 1 and Figure 3, it can be seen that when the vulcanization temperature in the first vulcanization step is 115°C or higher and 140°C or lower, and the vulcanization pressure is a gauge pressure of 0.07 MPaG or higher and 0.26 MPaG or lower, the adhesion between the rubber layer and the adjacent reinforcing layer is high.

[0047] (Experiment 2) In the brake hose manufacturing method described in the above embodiment, brake hoses were manufactured by changing the vulcanization temperature in the second vulcanization step. Table 2 shows the temperature conditions for the second vulcanization step. The vulcanization time in the second vulcanization step was 15 to 21 minutes.

[0048] In the first vulcanization step, the laminate was vulcanized at a vulcanization temperature of 115°C to 140°C and a vulcanization pressure of 0.07 MPaG to 0.26 MPaG gauge pressure. Two vulcanization pipes of 70 to 75 m were used, and the laminate travel speed in the vulcanization pipes was 15 to 20 m / min. In this experiment, the laminate was vulcanized with the mandrel still present in the laminate. After the second vulcanization step, the mandrel was removed from the brake hose.

[0049] [Table 2]

[0050] To examine the state of vulcanization of the rubber layer, a sample of the outer rubber layer from the manufactured brake hose was pulled in the axial direction of the brake hose. The force at which the outer rubber layer was stretched 100% was recorded as the 100% modulus [N]. Similarly, a sample of the inner rubber layer from the manufactured brake hose was pulled in the axial direction of the brake hose. The force at which the inner rubber layer was stretched 100% was recorded as the 100% modulus [N]. Table 2 shows the 100% modulus [N] of the outer and inner rubber layers. Figure 4 shows the relationship between the 100% modulus [N] of the outer rubber layer and the vulcanization temperature. Figure 5 shows the relationship between the 100% modulus [N] of the inner rubber layer and the vulcanization temperature. The vulcanization temperatures shown in Figures 4 and 5 are those of the second vulcanization process.

[0051] For comparison, Table 2, Figures 4 and 5 show the 100% modulus [N] of the outer rubber layer and inner rubber layer of three types of brake hoses manufactured using a conventional vulcanization method. The conventional vulcanization method involves coating the laminate with resin before vulcanization, and then steam-vulcanizing the resin-coated laminate. The 100% modulus [N] of the outer rubber layer of these three types of brake hoses ranged from 35N to 42N, and the 100% modulus [N] of the inner rubber layer ranged from 67N to 75N. If the 100% modulus [N] falls within these three ranges, it can be said that the rubber layer is in the same state of vulcanization as when manufactured using a conventional vulcanization method.

[0052] From Table 2 and Figure 4, it can be seen that when the vulcanization temperature in the second vulcanization process is set to 180°C or higher and 190°C or lower, the 100% modulus [N] of the outer rubber layer falls within the range of the 100% modulus [N] of conventional vulcanization methods. Furthermore, Table 2 and Figure 5 show that when the vulcanization temperature in the second vulcanization process is set to 180°C or higher and 190°C or lower, the 100% modulus [N] of the inner rubber layer falls within the range of the 100% modulus [N] of the conventional vulcanization method. From this, it was found that by vulcanizing the laminate at 180°C or higher and 190°C or lower in the second vulcanization process after the first vulcanization process, it is possible to achieve a vulcanization state equivalent to that achieved by conventional vulcanization methods.

[0053] From the above, it was found that by steam-vulcanizing a laminate having, in order from the inside out, an inner rubber layer, a reinforcing layer containing polyethylene terephthalate (PET), and an outer rubber layer in the first vulcanization step at 115°C to 140°C and a gauge pressure of 0.07MPaG to 0.26MPaG, and then vulcanizing it using hot or warm air at 180°C to 190°C in the second vulcanization step, it is possible to produce a brake hose with high adhesion equivalent to that of brake hoses produced by conventional vulcanization methods, even when the hose is vulcanized without being coated with resin.It was also found that a brake hose with high adhesion between the rubber layer and reinforcing layer can be produced even when the reinforcing layer uses reinforcing yarn containing PET, which has low adhesion to the rubber layer.

[0054] Although the embodiments of the present invention have been described above with reference to the drawings, the specific configurations should not be considered to be limited to these embodiments. The scope of the present invention is defined not by the above description but by the claims, and includes all modifications within the meaning and scope of the claims.

[0055] For example, in the above embodiment and experiment, the laminate 110 was vulcanized in a state where the mandrel 10 was present in the laminate 110, as shown in Fig. 2. However, the laminate 110 may also be vulcanized in a state where the mandrel 10 is not present in the laminate 110. [Explanation of symbols]

[0056] 1 Inner rubber layer 2 First reinforcing layer (reinforcing layer) 3 Middle rubber layer 4 Second reinforcing layer (reinforcing layer) 5 outer rubber layer 10 mandrels 20 First vulcanizing device 21 1st vulcanized pipe 22 Second vulcanized tube 23 Directional switching device 30 Second vulcanizing device 100 brake hose 110 Laminate

Claims

1. A method for manufacturing a brake hose having, in order from the inside, an inner rubber layer, a reinforcing layer containing polyethylene terephthalate, and an outer rubber layer, comprising: a first vulcanization step of subjecting a laminate having, in order from the inside, an unvulcanized inner rubber layer, a reinforcing layer containing polyethylene terephthalate, and an unvulcanized outer rubber layer to steam vulcanization at a temperature of 115°C to 140°C and a gauge pressure of 0.07 MPaG to 0.26 MPaG, thereby bringing the inner rubber layer and the outer rubber layer into a semi-vulcanized state; a second vulcanization step in which, after the first vulcanization step, the laminate is vulcanized at 180°C or higher and 190°C or lower using hot air or warm air, thereby completely vulcanizing the inner rubber layer and the outer rubber layer; A method for manufacturing a brake hose, comprising:

2. The inner rubber layer and the outer rubber layer contain ethylene propylene rubber.

2. The method for manufacturing a brake hose according to claim 1.

3. a mandrel is present inside the laminate before the laminate is vulcanized in the first vulcanization step; In the first vulcanization step, the laminate is vulcanized by steam in a state where the mandrel is present in the laminate; In the second vulcanization step, the laminate is vulcanized in a state where the mandrel is present in the laminate, After the second vulcanization step, the method further includes a mandrel removal step of removing the mandrel from the laminate.

3. The method for manufacturing a brake hose according to claim 1 or 2.

Images