Reinforcement thread for heat-resistant hose and rubber hose reinforced therewith

Abstract

To provide a reinforcement yarn for heat-resistant hose that has good process passability while having tensile strength, adhesiveness, and fatigue resistance.SOLUTION: A reinforcement yarn used for reinforcing heat-resistant hose is obtained by twisting a spanized yarn formed of aromatic polyamide fibers. The spanized yarn is made of aromatic polyamide single filaments having average fiber length of 20 to 100 cm. The spanized yarn becomes a reinforcement yarn by being twisted in one direction at twist coefficient of 2 to 6 defined by the following formula. The tensile strength of the reinforcement yarn is 3 cN / dtex or higher. TM=T×√D / 1055 (where TM is twist coefficient, T is the number of twists (twists / m), D is total fineness of the spanized yarn (tex)).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a reinforcing yarn for heat-resistant hoses that require high heat resistance, such as air hoses for automobile engines, particularly air hoses for superchargers (turbochargers) and cooling hoses, and to a hose. [Background technology]

[0002] Due to the trend toward higher efficiency and higher power output of automobile engines and the downsizing of engine rooms, there is an increasing demand for improved heat resistance and durability of heat-resistant hoses such as air hoses for turbocharger systems and oil cooling hoses. At the same time, as engine rooms become more complex, there is also an increasing demand for improved flexibility to suit complex layouts.

[0003] Conventionally, aromatic polyamide (aramid) fibers, which have excellent heat resistance, have been used as reinforcing fibers for these high-heat-resistant and high-pressure-resistant hoses because general-purpose synthetic fibers such as ordinary polyamide and polyester are insufficient in terms of heat resistance. However, filament (long fiber) type reinforcing threads often lack sufficient adhesion to rubber due to their smooth surface, and there is a problem that the fibers peel off when subjected to repeated pressure fluctuations. On the other hand, spun (spun yarn) type reinforcing threads have excellent adhesion to rubber due to their fine fluff shape, but the strength of the fibers themselves is reduced, which means that durability is not improved and the hose is prone to breakage.

[0004] To address this problem, for example, a method has been proposed in which a stretch-break yarn made of meta-aromatic polyamide fiber is used in order to achieve both adhesion to rubber and strength (Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2008-163488 A Summary of the Invention [Problem to be solved by the invention]

[0006] In order to achieve both durability and flexibility in rubber hoses, reinforcing yarns are often used in the form of knitting. In this case, during the knitting process of the reinforcing yarn in hose molding, the knitting needles come into contact with the reinforcing yarn, causing the single fibers on the surface of the stretch-break processed yarn to fall off and accumulate on the guides of the process. In this case, frequent cleaning is required, and the process passability is significantly reduced. In addition, the fluff on the surface falls off during the process, preventing sufficient adhesion from being achieved.

[0007] An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a reinforcing yarn for a heat-resistant hose which has tensile strength, adhesiveness and fatigue resistance, and at the same time, has good processability. [Means for solving the problem]

[0008] That is, the present invention relates to a reinforcing yarn for use in reinforcing a heat-resistant hose, the reinforcing yarn being obtained by twisting a stretch-break processed yarn composed of an aromatic polyamide fiber, the stretch-break processed yarn being made of aromatic polyamide monofilaments having an average fiber length of 20 to 100 cm, the stretch-break processed yarn being twisted in one direction with a twist factor of 2 to 6 defined by the following formula to form a reinforcing yarn, and the tensile strength of the reinforcing yarn being 3 cN / dtex or more. TM=T×√D / 1055 (where TM is the twist coefficient, T is the number of twists (turns / m), and D is the total fineness (tex) of the stretch-break textured yarn.) Effect of the Invention

[0009] The present invention provides a reinforcing yarn for a heat-resistant hose that has tensile strength, adhesiveness and fatigue resistance, while also exhibiting good processability. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing an example of a manufacturing device for stretch-breaking textured yarn. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] [Aromatic polyamide fiber] The reinforcing yarn for a heat-resistant hose of the present invention is a reinforcing yarn obtained by twisting a stretch-break textured yarn made of aromatic polyamide fiber. The stretch-break textured yarn is obtained by stretch-breaking a long fiber bundle of aromatic polyamide, and entangling the fibers obtained, thereby bundling the fibers.

[0012] The aromatic polyamide long fibers constituting the long fiber bundle may be any of those conventionally known and may be produced by known methods, for example, those described in JP-A-49-100322, JP-A-47-10863, JP-A-58-144152, and JP-A-4-65513.

[0013] As the aromatic polyamide long fiber, either para-type aromatic polyamide fiber or meta-type aromatic polyamide fiber can be used, with meta-type aromatic polyamide fiber being preferred due to its excellent long-term heat resistance and fatigue resistance. Examples of para-type aromatic polyamide fiber include polyparaphenylene terephthalamide fiber and copolyparaphenylene-3,4'-oxydiphenylene-terephthalamide fiber. Specific examples of meta-type aromatic polyamide fiber include polymetaphenylene isophthalamide fiber (e.g., "Teijinconex" manufactured by Teijin Limited).

[0014] [Stretch-break processed yarn] The reinforcing yarn for heat-resistant hoses of the present invention is made of a stretch-break textured yarn obtained by stretch-breaking a long fiber bundle of aromatic polyamide, entangling the obtained fibers, and bundling them. This stretch-break textured yarn has fuzz on its surface, which gives it good adhesion to rubber, and by using this, a heat-resistant hose with excellent fatigue resistance can be obtained.

[0015] The average fiber length of the single fiber of the stretch-break processed yarn is 20 to 100 cm. If the average fiber length is less than 20 cm, the fluffing that improves adhesion is sufficient, but the intertwining of the fibers is insufficient, resulting in a decrease in tensile strength and therefore a decrease in fatigue resistance against repeated vibration. On the other hand, if the average fiber length exceeds 100 cm, the form of the reinforcing yarn is similar to that of a filament (long fiber), and not only is the fluffing effect of the fiber not obtained and adhesion is insufficient, but the uniformity of the reinforcing yarn deteriorates, causing variation in physical properties along the length of the reinforcing yarn, and as a result, sufficient rubber reinforcing properties cannot be obtained.

[0016] The reinforcing yarn for heat-resistant hoses of the present invention is made of stretch-break processed yarn produced by the stretch-break method, so that the fiber length of the single fibers constituting the reinforcing yarn is long, and the degree of fiber alignment is higher than that of conventional spun yarns, so that high strength can be obtained. Therefore, the reinforcing yarn for heat-resistant hoses of the present invention has a tensile strength of 3 cN / dtex or more. If the tensile strength is less than 3 cN / dtex, sufficient rubber reinforcing properties cannot be obtained.

[0017] [Fineness] The reinforcing yarn for a heat-resistant hose of the present invention preferably has a total fineness of 1000 to 6000 dtex, more preferably 2000 to 5000 dtex. The total fineness may be 1000 dtex or may be a total fineness consisting of a plurality of stretch-break processed yarns. If the total fineness is less than 1000 dtex, the reinforcing properties of the rubber are reduced, which is not preferable. On the other hand, if the total fineness exceeds 6000 dtex, it is difficult to obtain surface fluff corresponding to the strength improvement due to the thicker reinforcing yarn, and a sufficient reinforcing effect cannot be obtained, which is not preferable.

[0018] The single fiber fineness of the stretch-broken fibers constituting the stretch-broken yarn is preferably 0.5 to 5.0 dtex. If it is less than 0.5 dtex, each single fiber becomes weak, so that more fuzz falls off during the process, which deteriorates the processability, which is not preferable. On the other hand, if it exceeds 5.0 dtex, the number of single fibers becomes relatively small, so that it becomes difficult to bundle them in the stretch-broken processing step, and as a result, the strength of the stretch-broken yarn decreases, which is not preferable.

[0019] [Twisted Yarn] The reinforcing yarn for a heat-resistant hose of the present invention is twisted in one direction with a twist factor of 2 to 6. Here, the twist factor (TM) is defined by the following formula, where TM is the twist factor, T is the number of twists (turns / m), and D is the total fineness (tex) of the original yarn. TM=T×√D / 1055

[0020] In the application of the stretch-break processing step, the intertwining between the single fibers constituting the stretch-break processing step is insufficient for the application of the reinforcing thread for a heat-resistant hose, and it is necessary to twist the yarn in one direction within the above range. In the reinforcing thread for a hose of the present invention, the twist coefficient is 2 to 6, so that the fluff consisting mainly of the ends of each single fiber remains on the surface, but the single fibers constituting the fluff are strongly constrained within the twisted yarn, so that they do not easily fall off. As a result, for example, in the processing step of a heat-resistant hose, the falling off of the fluff when the reinforcing thread comes into contact with a guide or a jig at high speed is greatly suppressed, and excellent process passability and adhesion after passing through the process can be obtained. In addition, the stress applied to the single fiber is easily dispersed, and fatigue resistance is also improved.

[0021] In the present invention, the number of twists applied to the twisted yarn is preferably 160 to 600 times / m. By having a twist number of 160 times / m or more and the above-mentioned twist coefficient of 2 to 6, both excellent processability and fatigue resistance can be achieved. If the twist number exceeds 600 times / m, twisting becomes difficult. If the twist number is less than 160 times / m, the single fibers constituting the fluff are not sufficiently restrained within the twisted yarn, and they easily fall off due to friction with guides and the like during the process. The fluff accumulated on these guides further accelerates the friction, and if the amount of accumulation increases, the accumulated fluff clumps will eventually become entangled with the running yarn, becoming foreign matter or hindering the smooth running of the yarn, causing process defects, yarn breakage, etc., which is not preferable.

[0022] [Surface treatment] The hose reinforcing yarn of the present invention is preferably surface-treated to further improve adhesion, fatigue resistance and processability by adhering a surface treatment agent made of polyester resin, polyurethane resin, silicone resin, fluororesin, epoxy resin, acrylic resin, vinyl ester resin, polyurea resin, polyethylene resin, polypropylene resin, polyvinyl alcohol resin or polyamide resin to the surface of the heat-resistant hose reinforcing yarn.

[0023] From the viewpoint of adhesion and processability, polyester resin is preferred as the surface treatment agent. The polyester resin is attached to the surface of the reinforcing yarn for heat-resistant hoses in an amount of preferably 1 to 10% by weight based on 100% by weight of the aromatic polyamide stretch-break processed yarn constituting the reinforcing yarn for heat-resistant hoses. This surface treatment agent makes it possible to bundle the fiber bundles without reducing the anchoring effect due to the surface fluff, suppresses the shedding of fluff, and achieves both adhesion and processability. At the same time, the surface is protected by the soft resin, preventing abrasion of the fiber bundle surface and improving fatigue resistance. If the amount of the surface treatment agent attached is less than 1% by weight, the bundling of the fiber bundles will be insufficient, and will not contribute to improving the processability. On the other hand, if the amount of the surface treatment agent attached is more than 10% by weight, the fuzz on the surface of the fiber bundles will be covered with the resin, reducing the anchoring effect and therefore the adhesiveness.

[0024] When the surface treatment agent is a polyester resin, the components of the polyester include a dicarboxylic acid component such as terephthalic acid or isophthalic acid, and a diol component such as ethylene glycol, trimethylene glycol, or propylene glycol.

[0025] [Manufacturing method] The stretch-broken yarn made of aromatic polyamide fiber used in the present invention can be produced by the process described in JP-A-2008-163488, for example. That is, it can be produced by the process shown in Fig. 1, in which a continuous long fiber bundle 1 of aromatic polyamide is stretched between a nip roller 2 and a nip roller 4 to a breaking elongation or more of the continuous long fiber bundle and stretch-broken, and then the stretch-broken fiber (hereinafter sometimes referred to as stretch-broken fiber) is sucked from the nip roller 4 by a suction air nozzle 5 and taken up, and then the fibers are entangled and / or bound by winding the stretch-broken fiber ends by a conjugating air nozzle 6, and then wound as a stretch-broken yarn 8 through a nip roller 7. The conjugation of the stretch-broken fibers by the conjugating air nozzle 6 may be either entanglement of the fibers by an interlace type air nozzle or winding of the fiber ends by a swirl type air nozzle.

[0026] The stretch-break processed yarn thus obtained is twisted in one direction when used as a reinforcing yarn for a heat-resistant hose. The twisting can be performed by a conventionally known method. In this case, preferably 2 to 10 strands of the stretch-break processed yarn, more preferably 2 to 5 strands, are combined and twisted. The number of twists is preferably 160 to 600 times / m, more preferably 200 to 400 times / m.

[0027] The hose of the present invention is a hose reinforced with the reinforcing yarn. In this case, the hose is preferably a hose consisting of an inner rubber tube layer, a reinforcing yarn surrounding the inner rubber tube layer, and one or more outer tube layers joined thereto. The hose can be formed by a known method.

[0028] 〔hose〕 The reinforcing yarn for a heat-resistant hose of the present invention is used to reinforce a rubber hose. In this case, the reinforcing yarn for a heat-resistant hose of the present invention constitutes the heat-resistant hose together with the rubber.

[0029] Examples of the rubber used in this case include acrylic rubber, acrylonitrile-butadiene rubber, hydrogenated acrylonitrile-butadiene rubber, isoprene rubber, urethane rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber (EPDM), chloroprene rubber, silicone rubber, styrene-butadiene rubber, polysulfide rubber, natural rubber, butadiene rubber, and fluororubber. In particular, acrylic rubber, silicone rubber, and fluororubber, which have excellent heat resistance, are preferred. EXAMPLES

[0030] The present invention will now be described with reference to examples.

[0031] (1) Average fiber length From the stretch-break textured yarn, 200 single fibers were randomly selected without breaking them, and the lengths of the single fibers were stretched and measured, and the average value was calculated.

[0032] (2) Total fineness of reinforcing yarn The total fiber size (weight) including the attached resin was measured according to JIS L1017.

[0033] (3) Tensile strength and tensile strength The tensile strength of the reinforcing yarn was measured according to JIS L 1017. The tensile strength was calculated by dividing the tensile strength by the total fineness of the reinforcing yarn including the attached resin.

[0034] (4) Hook strength and hook strength The loop strength of the reinforcing yarn was measured according to JIS L 1013. The loop strength was calculated by dividing the loop strength by the fineness of the reinforcing yarn including the attached resin.

[0035] (5) Process passability The reinforcing yarn was rubbed against a pin guide having a diameter of 1 mm at a speed of 100 m / min, and the weight of the fluff that fell off in 10 minutes was measured.

[0036] (6) Adhesive strength This shows the adhesive strength between the reinforcing thread and rubber before and after the process. For the reinforcing thread before and after the process (5) above, 25 cords were embedded in a line near the surface of an unvulcanized rubber sheet whose main component was acrylic rubber, and the adhesive strength was measured at 150°C for 30 minutes with a test piece strength of 1N / mm 2 The specimen was vulcanized at a press pressure of 1000 MPa and the force required to peel it off at a speed of 200 mm / min in a direction at an angle of 90 degrees to the rubber sheet surface was measured.

[0037] (7) Fatigue resistance The reinforcing yarn was subjected to repeated loads of 0.3 to 1.5 cN / dtex at a rate of 10 Hz under a high temperature of 200° C. in a hooked state as described in JIS L1013, and then the hook strength was measured.

[0038] (8) Fineness of reinforcing thread The fineness (weight) was measured in accordance with JIS L 1017. When the water-soluble polyester was attached, the fineness was measured in that state.

[0039] Example 1 Using the device shown in Figure 1, a polymetaphenylene isophthalamide fiber tow (trade name Teijinconex: manufactured by Teijin Techno Products Co., Ltd.) having a total fineness of 33,000 dtex and 15,000 filaments was fed into the device as a continuous long fiber bundle (1), and the fiber bundle was stretch-broken at a stretch-break ratio of 11 times between nip rollers (2) and (4), and the stretch-broken fiber was subsequently taken out by a suction air nozzle (5), and the stretch-broken fiber was passed through an air-entrapping nozzle (6) having a swirling flow in a direction in which Z-twist is applied, whereby the stretch-broken fiber was entangled and bound, and then passed through a nip roller (7) and wound up by a winding device (9). The nip rollers (2) and (4) rotate at different rotation speeds, and the distance between them is 100 cm.

[0040] As a result, a stretch-break textured yarn was obtained with a total fineness of 1100 dtex and an average fiber length of the stretch-break fibers constituting the stretch-break textured yarn of 50 cm. Three of these stretch-break textured yarns were combined and further twisted in the Z direction with a twist factor of 3.4 (200 times / m) while being wound, and finally a twisted yarn with a total fineness of 3490 dtex was obtained due to the effect of twist shrinkage.

[0041] The obtained twisted yarn was dipped in a 10% by weight aqueous solution of water-soluble polyester (product name PLASCOAT Z-446, manufactured by GOO Chemical Co., Ltd.) in a separate process to obtain a surface-treated hose reinforcing yarn. The amount of water-soluble polyester attached was 3.0% by weight based on the fiber weight. The evaluation results of the obtained hose reinforcing yarn are shown in Table 1.

[0042] Example 2 A hose reinforcing yarn was obtained in the same manner as in Example 1, except that the stretch-break yarn was twisted in the Z direction with a twist coefficient of 5.2 (300 times / m). The total fineness of the twisted yarn was 3650 dtex, and the amount of the water-soluble polyester resin attached was 3.4% by weight based on the fiber weight. The evaluation results of the obtained hose reinforcing yarn are shown in Table 1.

[0043] Example 3 Except for not carrying out the surface treatment with the water-soluble polyester resin, a reinforcing yarn for a hose was obtained in the same manner as in Example 1. The evaluation results of the obtained reinforcing yarn are shown in Table 1.

[0044] Comparative Example 1 A hose reinforcing yarn was obtained in the same manner as in Example 1, except that the stretch-break textured yarn was twisted in the Z direction with a twist coefficient of 1.7 (100 times / m). The total fineness of the twisted yarn of the obtained hose reinforcing yarn was 3330 dtex, and the adhesion amount of the water-soluble polyester resin was 2.6% by weight based on the fiber weight. The evaluation results of the obtained hose reinforcing yarn are shown in Table 1.

[0045] [Table 1]

[0046] The hose reinforcing yarn obtained in the Examples was superior to the reinforcing yarn obtained in the Comparative Examples in terms of fatigue resistance, adhesion, and processability, and a hose reinforcing yarn with excellent durability and productivity was obtained. [Industrial Applicability]

[0047] The hose reinforcing yarn of the present invention is preferably used to reinforce heat-resistant hoses that require high heat resistance, such as air hoses for turbochargers, cooling hoses, etc. In these hoses, the reinforcing yarn is used in the form of a spiral, braid, woven fabric, or knitted fabric, and is preferably used in the form of a knitted fabric that has excellent elasticity. [Explanation of symbols]

[0048] 1. Aromatic polyamide continuous fiber bundle 2, 4, 7 Nip rollers 3. Guide to prevent disturbance of fiber bundle during stretch breaking 5 Suction Air Nozzle 6. Conjugate Air Nozzle 8. Draft-Break Thread 9 Winding device

Claims

1. A reinforcing yarn for a heat-resistant hose, comprising: a polyester resin adhered to a surface of the reinforcing yarn; the reinforcing yarn is obtained by doubling and twisting 2 to 10 stretch-break processed yarns made of aromatic polyamide fibers; the stretch-break processed yarn is made of aromatic polyamide single fibers having an average fiber length of 20 to 100 cm; the aromatic polyamide is a meta-type aromatic polyamide; the stretch-break processed yarn is twisted in one direction with a twist factor of 2 to 6 defined by the following formula to form a reinforcing yarn; and the tensile strength of the reinforcing yarn is 3 cN / dtex or more. TM=T×√D / 1055 (where TM is the twist coefficient, T is the number of twists (turns / m), and D is the total fineness (tex) of the stretch-break textured yarn.)

2. 2. The reinforcing yarn for a heat-resistant hose according to claim 1, wherein the stretch-break textured yarn is obtained by stretch-breaking a long fiber bundle of aromatic polyamide, entangling the resulting fibers, and bundling the fibers.

3. 3. The reinforcing yarn for a heat-resistant hose according to claim 1, having a total fineness of 1,000 to 6,000 dtex and a twist number of 160 to 600 turns / m.

4. A rubber hose reinforced with the knitted fabric of the reinforcing yarn for a heat-resistant hose according to any one of claims 1 to 3.

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